Faculty Database Energy Initiative Office of the Provost Duke University |
||
HOME > Provost > Energy Initiative > Faculty | Search Help Login |
| Publications of Peter K. Haff :chronological alphabetical by type listing:%% @article{fds329153, Author = {Zalasiewicz, J and Waters, CN and Summerhayes, CP and Wolfe, AP and Barnosky, AD and Cearreta, A and Crutzen, P and Ellis, E and Fairchild, IJ and Gałuszka, A and Haff, P and Hajdas, I and Head, MJ and Ivar do Sul, JA and Jeandel, C and Leinfelder, R and McNeill, JR and Neal, C and Odada, E and Oreskes, N and Steffen, W and Syvitski, J and Vidas, D and Wagreich, M and Williams, M}, Title = {The Working Group on the Anthropocene: Summary of evidence and interim recommendations}, Journal = {Anthropocene}, Volume = {19}, Pages = {55-60}, Publisher = {Elsevier BV}, Year = {2017}, Month = {September}, url = {http://dx.doi.org/10.1016/j.ancene.2017.09.001}, Abstract = {Since 2009, the Working Group on the ‘Anthropocene’ (or, commonly, AWG for Anthropocene Working Group), has been critically analysing the case for formalization of this proposed but still informal geological time unit. The study to date has mainly involved establishing the overall nature of the Anthropocene as a potential chronostratigraphic/geochronologic unit, and exploring the stratigraphic proxies, including several that are novel in geology, that might be applied to its characterization and definition. A preliminary summary of evidence and interim recommendations was presented by the Working Group at the 35th International Geological Congress in Cape Town, South Africa, in August 2016, together with results of voting by members of the AWG indicating the current balance of opinion on major questions surrounding the Anthropocene. The majority opinion within the AWG holds the Anthropocene to be stratigraphically real, and recommends formalization at epoch/series rank based on a mid-20th century boundary. Work is proceeding towards a formal proposal based upon selection of an appropriate Global boundary Stratotype Section and Point (GSSP), as well as auxiliary stratotypes. Among the array of proxies that might be used as a primary marker, anthropogenic radionuclides associated with nuclear arms testing are the most promising; potential secondary markers include plastic, carbon isotope patterns and industrial fly ash. All these proxies have excellent global or near-global correlation potential in a wide variety of sedimentary bodies, both marine and non-marine.}, Doi = {10.1016/j.ancene.2017.09.001}, Key = {fds329153} } @article{fds328732, Author = {Haff, PK}, Title = {Being human in the Anthropocene}, Journal = {The Anthropocene Review}, Volume = {4}, Number = {2}, Pages = {103-109}, Publisher = {SAGE Publications}, Year = {2017}, Month = {August}, url = {http://dx.doi.org/10.1177/2053019617700875}, Abstract = {This essay aims to show how what is most intimately and essentially human – our ideas, personal purposes, feelings, and dreams – finds space for expression within the autonomous, unfeeling, physical dynamics of the technosphere – the defining system of the Anthropocene. The approach adopted is based on systems science and aims to avoid metaphysical assumptions about the nature and importance of human values. A non-humanistic analysis of human potential shows why the demands of the physical technosphere on human behavior leave space for nominally non-technospheric activities, such as the pursuit of personal purposes. The dynamical perspective also highlights the central role of humanistic pushback against technospheric encroachment on the human domain.}, Doi = {10.1177/2053019617700875}, Key = {fds328732} } @article{fds326651, Author = {Zalasiewicz, J and Williams, M and Waters, CN and Barnosky, AD and Palmesino, J and Rönnskog, AS and Edgeworth, M and Neal, C and Cearreta, A and Ellis, EC and Grinevald, J and Haff, P and Ivar do Sul, JA and Jeandel, C and Leinfelder, R and McNeill, JR and Odada, E and Oreskes, N and Price, SJ and Revkin, A and Steffen, W and Summerhayes, C and Vidas, D and Wing, S and Wolfe, AP}, Title = {Scale and diversity of the physical technosphere: A geological perspective}, Journal = {The Anthropocene Review}, Volume = {4}, Number = {1}, Pages = {9-22}, Publisher = {SAGE Publications}, Year = {2017}, Month = {April}, url = {http://dx.doi.org/10.1177/2053019616677743}, Abstract = {We assess the scale and extent of the physical technosphere, defined here as the summed material output of the contemporary human enterprise. It includes active urban, agricultural and marine components, used to sustain energy and material flow for current human life, and a growing residue layer, currently only in small part recycled back into the active component. Preliminary estimates suggest a technosphere mass of approximately 30 trillion tonnes (Tt), which helps support a human biomass that, despite recent growth, is ~5 orders of magnitude smaller. The physical technosphere includes a large, rapidly growing diversity of complex objects that are potential trace fossils or ‘technofossils’. If assessed on palaeontological criteria, technofossil diversity already exceeds known estimates of biological diversity as measured by richness, far exceeds recognized fossil diversity, and may exceed total biological diversity through Earth’s history. The rapid transformation of much of Earth’s surface mass into the technosphere and its myriad components underscores the novelty of the current planetary transformation.}, Doi = {10.1177/2053019616677743}, Key = {fds326651} } @article{fds325787, Author = {Zalasiewicz, J and Waters, CN and Wolfe, AP and Barnosky, AD and Cearreta, A and Edgeworth, M and Ellis, EC and Fairchild, IJ and Gradstein, FM and Grinevald, J and Haff, P and Head, MJ and do Sul, JAI and Jeandel, C and Leinfelder, R and McNeill, JR and Oreskes, N and Poirier, C and Revkin, A and Richter, DDB and Steffen, W and Summerhayes, C and Syvitski, JPM and Vidas, D and Wagreich, M and Wing, S and Williams, M}, Title = {Making the case for a formal Anthropocene Epoch: An analysis of ongoing critiques}, Journal = {Newsletters on Stratigraphy}, Volume = {50}, Number = {2}, Pages = {205-226}, Publisher = {Schweizerbart}, Year = {2017}, Month = {January}, url = {http://dx.doi.org/10.1127/nos/2017/0385}, Abstract = {A range of published arguments against formalizing the Anthropocene as a geological time unit have variously suggested that it is a misleading term of non-stratigraphic origin and usage, is based on insignificant temporal and material stratigraphic content unlike that used to define older geological time units, is focused on observation of human history or speculation about the future rather than geologically significant events, and is driven more by politics than science. In response, we contend that the Anthropocene is a functional term that has firm geological grounding in a well-characterized stratigraphic record. This record, although often lithologically thin, is laterally extensive, rich in detail and already reflects substantial elapsed (and in part irreversible) change to the Earth System that is comparable to or greater in magnitude than that of previous epoch-scale transitions. The Anthropocene differs from previously defined epochs in reflecting contemporary geological change, which in turn also leads to the term's use over a wide range of social and political discourse. Nevertheless, that use remains entirely distinct from its demonstrable stratigraphic underpinning. Here we respond to the arguments opposing the geological validity and utility of the Anthropocene, and submit that a strong case may be made for the Anthropocene to be treated as a formal chronostratigraphic unit and added to the Geological Time Scale.}, Doi = {10.1127/nos/2017/0385}, Key = {fds325787} } @article{fds323385, Author = {Haff, PK}, Title = {Purpose in the Anthropocene: Dynamical role and physical basis}, Journal = {Anthropocene}, Volume = {16}, Pages = {54-60}, Publisher = {Elsevier BV}, Year = {2016}, Month = {December}, url = {http://dx.doi.org/10.1016/j.ancene.2016.07.002}, Abstract = {The dynamics of the modern Earth-system is not explicable without reference to systems that have a purpose, i.e., that exhibit goal-seeking behavior. This paper develops the physical basis of agency or purposiveness in the technosphere—the human-technological system that defines the Anthropocene—as part of an analysis of the organizational requirements of energy-dissipating systems. The regulative, or framing, approach used here avoids reliance on reductive modeling and aims instead at establishing general properties of purposive systems. Establishment of purposiveness (the condition of having a purpose) as a physical system property, rather than a metaphysical concept or a purely biological phenomenon, enables a new look at the role of humans and human purpose in the Anthropocene. This approach can help avoid the misleading anthropocentric assumption that humans are independent authors of the Anthropocene they inhabit, rather than contingent actors whose purposes are not entirely their own.}, Doi = {10.1016/j.ancene.2016.07.002}, Key = {fds323385} } @article{fds323386, Author = {Williams, M and Zalasiewicz, J and Waters, CN and Edgeworth, M and Bennett, C and Barnosky, AD and Ellis, EC and Ellis, MA and Cearreta, A and Haff, PK and Ivar Do Sul and JA and Leinfelder, R and McNeill, JR and Odada, E and Oreskes, N and Revkin, A and Richter, DDB and Steffen, W and Summerhayes, C and Syvitski, JP and Vidas, D and Wagreich, M and Wing, SL and Wolfe, AP and Zhisheng, A}, Title = {The Anthropocene: A conspicuous stratigraphical signal of anthropogenic changes in production and consumption across the biosphere}, Journal = {Earth'S Future}, Volume = {4}, Number = {3}, Pages = {34-53}, Publisher = {American Geophysical Union (AGU)}, Year = {2016}, Month = {March}, url = {http://dx.doi.org/10.1002/2015EF000339}, Abstract = {Biospheric relationships between production and consumption of biomass have been resilient to changes in the Earth system over billions of years. This relationship has increased in its complexity, from localized ecosystems predicated on anaerobic microbial production and consumption to a global biosphere founded on primary production from oxygenic photoautotrophs, through the evolution of Eukarya, metazoans, and the complexly networked ecosystems of microbes, animals, fungi, and plants that characterize the Phanerozoic Eon (the last 541 million years of Earth history). At present, one species, Homo sapiens, is refashioning this relationship between consumption and production in the biosphere with unknown consequences. This has left a distinctive stratigraphy of the production and consumption of biomass, of natural resources, and of produced goods. This can be traced through stone tool technologies and geochemical signals, later unfolding into a diachronous signal of technofossils and human bioturbation across the planet, leading to stratigraphically almost isochronous signals developing by the mid-20th century. These latter signals may provide an invaluable resource for informing and constraining a formal Anthropocene chronostratigraphy, but are perhaps yet more important as tracers of a biosphere state that is characterized by a geologically unprecedented pattern of global energy flow that is now pervasively influenced and mediated by humans, and which is necessary for maintaining the complexity of modern human societies.}, Doi = {10.1002/2015EF000339}, Key = {fds323386} } @article{fds281143, Author = {UNGAR, JE and HAFF, PK}, Title = {Steady state saltation in air}, Journal = {Sedimentology}, Volume = {34}, Number = {2}, Pages = {289-299}, Publisher = {WILEY}, Year = {2016}, Month = {January}, url = {http://dx.doi.org/10.1111/j.1365-3091.1987.tb00778.x}, Abstract = {Coupled equations of motion for steady state saltation over an infinite plane are derived and solved for a simplified model of the grain‐surface impact process. Experimentally observed features of the wind velocity profile in saltation are qualitatively reproduced, including a diminution of the sub‐saltation layer mean wind speed, as the friction speed increases. In this model the surface impact velocity of the saltating grains remains relatively constant over a wide range of free‐stream shear stresses, and the grain mass flux increases with friction speed uf* less rapidly than uf3. Copyright © 1987, Wiley Blackwell. All rights reserved}, Doi = {10.1111/j.1365-3091.1987.tb00778.x}, Key = {fds281143} } @article{fds323387, Author = {Williams, M and Zalasiewicz, J and Haff, PK and Schwägerl, C and Barnosky, AD and Ellis, EC}, Title = {The anthropocene biosphere}, Journal = {The Anthropocene Review}, Volume = {2}, Number = {3}, Pages = {196-219}, Publisher = {SAGE Publications}, Year = {2015}, Month = {December}, url = {http://dx.doi.org/10.1177/2053019615591020}, Abstract = {The geological record preserves evidence for two fundamental stages in the evolution of Earth’s biosphere, a microbial stage from ~3.5 to 0.65 Ga, and a metazoan stage evident by c. 650 Ma. We suggest that the modern biosphere differs significantly from these previous stages and shows early signs of a new, third stage of biosphere evolution characterised by: (1) global homogenisation of flora and fauna; (2) a single species (Homo sapiens) commandeering 25-40% of net primary production and also mining fossil net primary production (fossil fuels) to break through the photosynthetic energy barrier; (3) human-directed evolution of other species; and (4) increasing interaction of the biosphere with the technosphere (the global emergent system that includes humans, technological artefacts, and associated social and technological networks). These unique features of today’s biosphere may herald a new era in the planet’s history that could persist over geological timescales.}, Doi = {10.1177/2053019615591020}, Key = {fds323387} } @article{fds281126, Author = {Zalasiewicz, J and Waters, CN and Williams, M and Barnosky, AD and Cearreta, A and Crutzen, P and Ellis, E and Ellis, MA and Fairchild, IJ and Grinevald, J and Haff, PK and Hajdas, I and Leinfelder, R and McNeill, J and Odada, EO and Poirier, C and Richter, D and Steffen, W and Summerhayes, C and Syvitski, JPM and Vidas, D and Wagreich, M and Wing, SL and Wolfe, AP and An, Z and Oreskes, N}, Title = {When did the Anthropocene begin? A mid-twentieth century boundary level is stratigraphically optimal}, Journal = {Quaternary International}, Volume = {383}, Pages = {196-203}, Publisher = {Elsevier BV}, Year = {2015}, Month = {October}, ISSN = {1040-6182}, url = {http://dx.doi.org/10.1016/j.quaint.2014.11.045}, Abstract = {We evaluate the boundary of the Anthropocene geological time interval as an epoch, since it is useful to have a consistent temporal definition for this increasingly used unit, whether the presently informal term is eventually formalized or not. Of the three main levels suggested - an 'early Anthropocene' level some thousands of years ago; the beginning of the Industrial Revolution at ~1800 CE (Common Era); and the 'Great Acceleration' of the mid-twentieth century - current evidence suggests that the last of these has the most pronounced and globally synchronous signal. A boundary at this time need not have a Global Boundary Stratotype Section and Point (GSSP or 'golden spike') but can be defined by a Global Standard Stratigraphic Age (GSSA), i.e. a point in time of the human calendar. We propose an appropriate boundary level here to be the time of the world's first nuclear bomb explosion, on July 16th 1945 at Alamogordo, New Mexico; additional bombs were detonated at the average rate of one every 9.6 days until 1988 with attendant worldwide fallout easily identifiable in the chemostratigraphic record. Hence, Anthropocene deposits would be those that may include the globally distributed primary artificial radionuclide signal, while also being recognized using a wide range of other stratigraphic criteria. This suggestion for the Holocene-Anthropocene boundary may ultimately be superseded, as the Anthropocene is only in its early phases, but it should remain practical and effective for use by at least the current generation of scientists.}, Doi = {10.1016/j.quaint.2014.11.045}, Key = {fds281126} } @article{fds323388, Author = {Edgeworth, M and Richter, DDB and Waters, C and Haff, P and Neal, C and Price, SJ}, Title = {Diachronous beginnings of the anthropocene: The lower bounding surface of anthropogenic deposits}, Journal = {The Anthropocene Review}, Volume = {2}, Number = {1}, Pages = {33-58}, Publisher = {SAGE Publications}, Year = {2015}, Month = {April}, url = {http://dx.doi.org/10.1177/2053019614565394}, Abstract = {Across a large proportion of Earth’s ice-free land surfaces, a solid-phase stratigraphic boundary marks the division between humanly modified ground and natural geological deposits. At its clearest, the division takes the form of an abrupt surface at the base of deposits variously called ‘artificial ground’, ‘anthropogenic ground’ or ‘archaeological stratigraphy’ - which together comprise a distinctive part of the geosphere called the ‘archaeosphere’. In other cases the bounding surface is more diffuse, gradational or mixed, due to action of non-human agencies and anthropedogenic forcings. It is alternately conformable and unconformable. Layers above typically contain artificial features, structures, artifacts and other material traces of human activity, in contrast to their relative absence in layers below. A fundamental characteristic of the boundary is that it is diachronous, still being formed and renewed today. In examining the boundary, this paper asks - does it reflect the diachronous onset and development of the Anthropocene itself?.}, Doi = {10.1177/2053019614565394}, Key = {fds323388} } @article{fds323389, Author = {Haff, P}, Title = {Humans and technology in the anthropocene: Six rules}, Journal = {The Anthropocene Review}, Volume = {1}, Number = {2}, Pages = {126-136}, Publisher = {SAGE Publications}, Year = {2014}, Month = {August}, url = {http://dx.doi.org/10.1177/2053019614530575}, Abstract = {Humans play an essential role in creating the technological systems of the Anthropocene, but, nonetheless, large-scale technology - the ‘technosphere’ - operates according to a quasiautonomous dynamics, summarized by six rules: (1) the rule of inaccessibility, that large components of the technosphere cannot directly influence the behavior of their human parts; (2) the rule of impotence, that most humans cannot significantly influence the behavior of large technological systems; (3) the rule of control, that a human cannot control a technological system that expresses a larger number of behaviors than he himself; (4) the rule of reciprocity, that a human can interact directly only with systems his own size; (5) the rule of performance, that most humans must perform at least some tasks that support the metabolism of the technosphere; and (6) the rule of provision, that the technosphere must provide an environment for most humans conducive to their survival and function.}, Doi = {10.1177/2053019614530575}, Key = {fds323389} } @article{fds323390, Author = {Zalasiewicz, J and Williams, M and Waters, CN and Barnosky, AD and Haff, P}, Title = {The technofossil record of humans}, Journal = {The Anthropocene Review}, Volume = {1}, Number = {1}, Pages = {34-43}, Publisher = {SAGE Publications}, Year = {2014}, Month = {April}, url = {http://dx.doi.org/10.1177/2053019613514953}, Abstract = {As humans have colonised and modified the Earth’s surface, they have developed progressively more sophisticated tools and technologies. These underpin a new kind of stratigraphy, that we term technostratigraphy, marked by the geologically accelerated evolution and diversification of technofossils - the preservable material remains of the technosphere (Haff, 2013), driven by human purpose and transmitted cultural memory, and with the dynamics of an emergent system. The technosphere, present in some form for most of the Quaternary, shows several thresholds. Its expansion and transcontinental synchronisation in the mid 20th century has produced a global technostratigraphy that combines very high time-resolution, great geometrical complexity and wide (including transplanetary) extent. Technostratigraphy can help characterise the deposits of a potential Anthropocene Epoch and its emergence marks a step change in planetary mode.}, Doi = {10.1177/2053019613514953}, Key = {fds323390} } @article{fds281127, Author = {Haff, PK}, Title = {Technology as a geological phenomenon: Implications for human well-being}, Journal = {Geological Society, London, Special Publications}, Volume = {395}, Number = {1}, Pages = {301-309}, Booktitle = {A Stratigraphical Basis for the Anthropocene, Waters, C. N., et al, (Eds), Geological Society, London, Special Publications SP 395-4}, Publisher = {Geological Society of London}, Year = {2014}, Month = {January}, ISSN = {0305-8719}, url = {http://dx.doi.org/10.1144/SP395.4}, Abstract = {The technosphere, the interlinked set of communication, transportation, bureaucratic and other systems that act to metabolize fossil fuels and other energy resources, is considered to be an emerging global paradigm, with similarities to the lithosphere, atmosphere, hydrosphere and biosphere. The technosphere is of global extent, exhibits large-scale appropriation of mass and energy resources, shows a tendency to co-opt for its own use information produced by the environment, and is autonomous. Unlike the older paradigms, the technosphere has not yet evolved the ability to recycle its own waste stream. Unless or until it does so, its status as a paradigm remains provisional. Humans are 'parts' of the technosphere-subcomponents essential for system function. Viewed from the inside by its human parts, the technosphere is perceived as a derived and controlled construct. Viewed from outside as a geological phenomenon, the technosphere appears as a quasi-autonomous system whose dynamics constrains the behaviour of its human parts. A geological perspective on technology suggests why strategies to limit environmental damage that consider only the needs of people are likely to fail without parallel consideration of the requirements of technology, especially its need for an abundant supply of energy. © The Geological Society of London 2014.}, Doi = {10.1144/SP395.4}, Key = {fds281127} } @article{fds340276, Author = {Haff, PK}, Title = {Biolevitation of pebbles on desert surfaces}, Journal = {Granular Matter}, Volume = {16}, Number = {2}, Pages = {275-278}, Year = {2014}, Month = {January}, url = {http://dx.doi.org/10.1007/s10035-013-0438-4}, Abstract = {Certain desert surfaces called desert pavements are characterized by a nearly stone-free layer of fine granular material, mostly silt (diameter of hundredths of mm) and sand (tenths of mm) capped by a monolayer of pebble-sized (few cm) stones. The fine granular material is deposited as dust from the air, so the stones must be levitated to accommodate emplacement of this material. In so-called "normal grading" of stratigraphic deposits of geologic material, as in many stream deposits, finer grained material tends to settle on top of coarser grains which have faster settling velocities. Anecdotal observations in the field suggested that the observed "reverse grading" of pavement surfaces is a consequence of the activity of small animals that provide through their activities sufficient input of energy to the surface to cause large particles to "float" on the accumulating fine sediment. To test this idea a laboratory experiment with a test organism, the large desert beetle Eleodes, was carried out to observe possible sorting process. Essentially random foraging motions of the beetles in an environment in which fine sediment was periodically added from above led to sorting of stones that were moveable by the organisms, burial of immovable stones, as well as burial and diffusion of marked grains that were comparable in size to the fine sediment. These results help explain the existence of a geologic deposit with an unusual layering of grain sizes. © 2013 Springer-Verlag Berlin Heidelberg.}, Doi = {10.1007/s10035-013-0438-4}, Key = {fds340276} } @article{fds281129, Author = {Haff, PK}, Title = {Prediction in geology versus prediction in engineering}, Journal = {Special Paper of the Geological Society of America}, Volume = {502}, Pages = {127-134}, Booktitle = {Rethinking the Fabric of Geology, Baker, V.R., ed., Geological Society of America Special Papers 502}, Publisher = {Geological Society of America}, Year = {2013}, Month = {January}, ISSN = {0072-1077}, url = {http://dx.doi.org/10.1130/2013.2502(06)}, Abstract = {As humans become increasingly dominant agents of geologic change, prediction of the reaction of natural systems to human intervention and of the performance of geoengineered structures assumes increasing importance. To help clarify the role of geological prediction in an anthropic world, we examine the end-member cases of prediction in natural geologic systems and engineered systems. The behavior of natural geologic systems tends to be less reliably predictable than the behavior of engineered systems. Engineered systems are designed, and their behavior is predictable in terms of the function and interaction of their parts. Geologic systems, although undesigned, also have parts. Natural analogs of engineered parts are the emergent structures arising from nonlinear interactions between small-scale constituents. The behavior of natural systems at a given scale follows directly from the dynamics of their parts as defi ned at similar scales; it is argued that application of same-scale dynamics, or scale matching, provides the best basis for prediction in such systems. Mathematical models of natural systems are also likely to be most effective for prediction when applied at scales matched to the scales of the phenomenon of interest. There are also systems that are intermediate between natural systems and engineered systems. A "peri-engineering" transition zone governed by large-scale interactions is always present between the parts of the engineered structure and the parts of the surrounding natural environment. This contact region between engineered structure and the natural environment is often partially engineered to improve predictability. The peri-engineering halo is only partly subject to human design, and consequently it is often a region of reduced predictability and increased probability of malfunction or failure compared to the engineered system itself. © 2013 Geological Society of America.}, Doi = {10.1130/2013.2502(06)}, Key = {fds281129} } @article{fds281130, Author = {Haff, PK}, Title = {Biolevitation of pebbles on desert surfaces}, Journal = {Granular Matter}, Volume = {16}, Number = {2}, Pages = {1-4}, Publisher = {Springer Nature}, Year = {2013}, ISSN = {1434-5021}, url = {http://dx.doi.org/10.1007/s10035-013-0438-4}, Abstract = {Certain desert surfaces called desert pavements are characterized by a nearly stone-free layer of fine granular material, mostly silt (diameter of hundredths of mm) and sand (tenths of mm) capped by a monolayer of pebble-sized (few cm) stones. The fine granular material is deposited as dust from the air, so the stones must be levitated to accommodate emplacement of this material. In so-called "normal grading" of stratigraphic deposits of geologic material, as in many stream deposits, finer grained material tends to settle on top of coarser grains which have faster settling velocities. Anecdotal observations in the field suggested that the observed "reverse grading" of pavement surfaces is a consequence of the activity of small animals that provide through their activities sufficient input of energy to the surface to cause large particles to "float" on the accumulating fine sediment. To test this idea a laboratory experiment with a test organism, the large desert beetle Eleodes, was carried out to observe possible sorting process. Essentially random foraging motions of the beetles in an environment in which fine sediment was periodically added from above led to sorting of stones that were moveable by the organisms, burial of immovable stones, as well as burial and diffusion of marked grains that were comparable in size to the fine sediment. These results help explain the existence of a geologic deposit with an unusual layering of grain sizes. © 2013 Springer-Verlag Berlin Heidelberg.}, Doi = {10.1007/s10035-013-0438-4}, Key = {fds281130} } @article{fds281160, Author = {Haff, PK}, Title = {Technology and human purpose: The problem of solids transport on the Earth's surface}, Journal = {Earth System Dynamics}, Volume = {3}, Number = {2}, Pages = {149-156}, Publisher = {Copernicus GmbH}, Year = {2012}, Month = {December}, ISSN = {2190-4979}, url = {http://dx.doi.org/10.5194/esd-3-149-2012}, Abstract = {Displacement of mass of limited deformability ("solids") on the Earth's surface is opposed by friction and (the analog of) form resistance - impediments relaxed by rotational motion, self-powering of mass units, and transport infrastructure. These features of solids transport first evolved in the biosphere prior to the emergence of technology, allowing slope-independent, diffusion-like motion of discrete objects as massive as several tons, as illustrated by animal foraging and movement along game trails. However, highenergy-consumption technology powered by fossil fuels required a mechanism that could support fast advective transport of solids, i.e., long-distance, high-volume, high-speed, unidirectional, slope-independent transport across the land surface of materials like coal, containerized fluids, minerals, and economic goods. Pre-technology nature was able to sustain regional- and global-scale advection only in the limited form of piggybacking on geophysical flows of water (river sediment) and air (dust). The appearance of a mechanism for sustained advection of solids independent of fluid flows and gravity appeared only upon the emergence of human purpose. Purpose enables solids advection by, in effect, simulating a continuous potential gradient, otherwise lacking, between discrete and widely separated fossil-fuel energy sources and sinks. Invoking purpose as a mechanism in solids advection is an example of the need to import anthropic principles and concepts into the language and methodology of modern Earth system dynamics. As part of the emergence of a generalized solids advection mechanism, several additional transport requirements necessary to the function of modern large-scale technological systems were also satisfied. These include spatially accurate delivery of advected payload, targetability to essentially arbitrarily located destinations (such as cities), and independence of structure of advected payload from transport mechanism. The latter property enables the transport of an onboard power supply and delivery of persistent-memory, high-information-content payload, such as technological artifacts ("parts"). ©Author(s)2012.}, Doi = {10.5194/esd-3-149-2012}, Key = {fds281160} } @article{fds281132, Author = {Furbish, DJ and Haff, PK and Roseberry, JC and Schmeeckle, MW}, Title = {A probabilistic description of the bed load sediment flux: 1. Theory}, Journal = {Journal of Geophysical Research: Earth Surface}, Volume = {117}, Number = {3}, Pages = {n/a-n/a}, Publisher = {American Geophysical Union (AGU)}, Year = {2012}, Month = {September}, ISSN = {0148-0227}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000309139300001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Abstract = {We provide a probabilistic definition of the bed load sediment flux. In treating particle positions and motions as stochastic quantities, a flux form of the Master equation (a general expression of conservation) reveals that the volumetric flux involves an advective part equal to the product of an average particle velocity and the particle activity (the solid volume of particles in motion per unit streambed area), and a diffusive part involving the gradient of the product of the particle activity and a diffusivity that arises from the second moment of the probability density function of particle displacements. Gradients in the activity, instantaneous or time-averaged, therefore effect a particle flux. Time-averaged descriptions of the flux involve averaged products of the particle activity, the particle velocity and the diffusivity; the significance of these products depends on the scale of averaging. The flux form of the Exner equation looks like a Fokker-Planck equation (an advection-diffusion form of the Master equation). The entrainment form of the Exner equation similarly involves advective and diffusive terms, but because it is based on the joint probability density function of particle hop distances and associated travel times, this form involves a time derivative term that represents a lag effect associated with the exchange of particles between the static and active states. The formulation is consistent with experimental measurements and simulations of particle motions reported in companion papers. © 2012. American Geophysical Union. All Rights Reserved.}, Doi = {10.1029/2012JF002352}, Key = {fds281132} } @article{fds281161, Author = {Peter, H and Jackson, R}, Title = {A reply to Holl and Loik}, Journal = {Frontiers in Ecology and the Environment}, Volume = {9}, Number = {6}, Pages = {318-319}, Publisher = {WILEY}, Year = {2011}, Month = {August}, ISSN = {1540-9295}, url = {http://dx.doi.org/10.1890/11.WB.015}, Doi = {10.1890/11.WB.015}, Key = {fds281161} } @article{fds281159, Author = {Jackson, R and Haff, P}, Title = {A "neoenvironmental" manifesto}, Journal = {Frontiers in Ecology and the Environment}, Volume = {9}, Number = {2}, Pages = {87}, Publisher = {WILEY}, Year = {2011}, Month = {March}, ISSN = {1540-9295}, url = {http://dx.doi.org/10.1890/1540-9295-9.2.87}, Doi = {10.1890/1540-9295-9.2.87}, Key = {fds281159} } @article{fds281162, Author = {Haff, PK}, Title = {Hillslopes, rivers, plows, and trucks: Mass transport on earth's surface by natural and technological processes}, Journal = {Earth Surface Processes and Landforms}, Volume = {35}, Number = {10}, Pages = {1157-1166}, Publisher = {WILEY}, Year = {2010}, Month = {August}, ISSN = {0197-9337}, url = {http://dx.doi.org/DOI:10.1002/esp.1902}, Abstract = {The surface of the earth is being transformed by a new force in the form of technological systems and processes that move significant quantities of mass large distances. Because movement of mass is perhaps the most basic geomorphic process, and because the continuing rise of technology appears to characterize a new epoch in earth evolution (the Anthropocene), it is of interest to compare technological and natural mass transport mechanisms. A purely dynamical 'mass-action' metric, representing the product of mass displaced, distance moved, and mean speed of displacement, is used to compare the transport effectiveness of selected systems. Systems with large mass-action tend to be advective, and systems with small mass-action diffusive. Local environments are conditioned by mass-action through the introduction of transport corridors, such as roads and rivers, which put constraints on mass transport by embedded diffusive systems. Advection also subjects local environments to externally determined time scales, such as the times for delivery of unit mass of water or sediment to a river mouth, and supports the emergence of associated dynamical processes there, for example those of human activity or delta construction, that are too rapid to be sustained by diffusion. Most of the world's mass-action is generated by the motion of fluids of global or continental extent, as in atmospheric circulation or river flow. Technological mass-action exceeds that of all land-based geomorphic systems except rivers. Technological systems with large mass-action tend to be comprised of discrete, self-powered units (e.g. trucks). Discretization of transported mass reflects the different locomotion strategy required for transport of solids on land, compared with the transport requirements of spatially extensive fluids in nature. The principle of maximum entropy production may provide a framework for understanding the emergence of advective, technological mass-transport systems. © 2010 John Wiley & Sons, Ltd.}, Doi = {10.1002/esp.1902}, Key = {fds281162} } @article{fds328733, Author = {Furbish, DJ and Haff, PK}, Title = {From divots to swales: Hillslope sediment transport across divers length scales}, Journal = {Journal of Geophysical Research}, Volume = {115}, Number = {F3}, Publisher = {American Geophysical Union (AGU)}, Year = {2010}, Month = {July}, url = {http://dx.doi.org/10.1029/2009jf001576}, Doi = {10.1029/2009jf001576}, Key = {fds328733} } @misc{fds185790, Author = {J. C. Roseberry and M. W. Schmeeckle and D. J. Furbish and P. K. Haff}, Title = {A probabilistic definition of the bedload sediment flux: Experiments}, Journal = {AGU abstract}, Year = {2010}, Key = {fds185790} } @article{fds281158, Author = {Ellis, EC and Haff, PK}, Title = {Earth science in the anthropocene: New Epoch, new Paradigm, new responsibilities}, Journal = {Eos}, Volume = {90}, Number = {49}, Pages = {473}, Publisher = {American Geophysical Union (AGU)}, Year = {2009}, Month = {December}, ISSN = {0096-3941}, url = {http://dx.doi.org/10.1029/2009EO490006}, Doi = {10.1029/2009EO490006}, Key = {fds281158} } @article{fds281163, Author = {Furbish, DJ and Haff, PK and Dietrich, WE and Heimsath, AM}, Title = {Statistical description of slope-dependent soil transport and the diffusion-like coefficient}, Journal = {Journal of Geophysical Research: Earth Surface}, Volume = {114}, Number = {4}, Publisher = {American Geophysical Union (AGU)}, Year = {2009}, Month = {September}, ISSN = {2169-9011}, url = {http://dx.doi.org/DOI:10.1029/2009JF001267}, Abstract = {[1] For hillslopes undergoing "diffusive" soil transport, it is often assumed that the soil flux is proportional to the local land-surface gradient, where the coefficient of proportionality is like a diffusion coefficient. Inasmuch as transport involves quasirandom soil particle motions related to biomechanical mixing and similar dilational processes, a slope-dependent relation arises from a balance between particle fluxes that tend to loft a soil and gravitational settling of particles into available pore space. A specialized form of the Fokker-Planck equation adapted to such particle motions clarifies how the particle flux involves advective and diffusive parts. This in turn contributes to a kinematic description of the diffusion-like coefficient. Ingredients of this coefficient include an active soil thickness, a characteristic particle size, the porosity in excess of a consolidated porosity, and the rate of particle activation as a function of depth. These last two ingredients, vertical porosity structure and activation rate, in effect characterize the magnitude and frequency of settling particle motions related to biological activity and thereby set the rate constant of the transport process. The significance of land-surface slope is that it is a measure of the downslope component of slope-normal lofting that is balanced by settling. Because the diffusion-like coefficient contains the soil thickness, the analysis suggests that the soil flux is proportional to the "depth-slope" product. The analysis is consistent with published profiles of soil creep displacement and with published estimates of soil flux obtained by downslope integration of soil production rates for hillslopes in California and Australia. Copyright 2009 by the American Geophysical Union.}, Doi = {10.1029/2009JF001267}, Key = {fds281163} } @article{fds281128, Author = {Haff, P}, Title = {Not a chance}, Journal = {Nature}, Volume = {459}, Number = {7246}, Pages = {606}, Publisher = {Springer Nature}, Year = {2009}, Month = {May}, ISSN = {0028-0836}, url = {http://dx.doi.org/DOI:10.1038/459606a}, Doi = {10.1038/459606a}, Key = {fds281128} } @article{fds281157, Author = {Jon Furbish and D and Childs, EM and Haff, PK and Schmeeckle, MW}, Title = {Rain splash of soil grains as a stochastic advection-dispersion process, with implications for desert plant-soil interactions and land-surface evolution}, Journal = {Journal of Geophysical Research: Solid Earth}, Volume = {114}, Number = {3}, Publisher = {American Geophysical Union (AGU)}, Year = {2009}, Month = {March}, ISSN = {2169-9356}, url = {http://dx.doi.org/DOI:10.1029/2009JF001265}, Abstract = {We formulate soil grain transport by rain splash as a stochastic advection-dispersion process. By taking into account the intermittency of grain motions activated by raindrop impacts, the formulation indicates that gradients in raindrop intensity, and thus grain activity (the volume of grains in motion per unit area) can be as important as gradients in grain concentration and surface slope in effecting transport. This idea is confirmed by rain splash experiments and manifest in topographic roughening via mound growth beneath desert shrubs. The formulation provides a framework for describing transport and dispersal of any soil material moveable by rain splash, including soil grains, soil-borne pathogens and nutrients, seeds, or debitage. As such, it shows how classic models of topographic "diffusion" reflect effects of slope-dependent grain drift, not diffusion, and it highlights the role of rain splash in the ecological behavior of desert shrubs as "resource islands." Specifically, the growth of mounds beneath shrub canopies, where differential rain, splash initially causes more grains to be splashed inward beneath the protective canopy than outward, involves the "harvesting" of nearby soil material, including nutrients. Mounds thus represent temporary storage of soil derived from areas surrounding the shrubs. As the inward grain flux associated with differential rain splash is sustained over the shrub lifetime, mound material is effectively sequestered from erosional processes that might otherwise move this material downslope. With shrub death and loss of the protective canopy, differential rain splash vanishes and the mound material is dispersed to the surrounding area, again subject to downslope movement. Copyright 2009 by the American Geophysical Union.}, Doi = {10.1029/2009JF001265}, Key = {fds281157} } @article{fds281156, Author = {Murray, AB and Lazarus, E and Ashton, A and Baas, A and Coco, G and Coulthard, T and Fonstad, M and Haff, P and McNamara, D and Paola, C and Pelletier, J and Reinhardt, L}, Title = {Geomorphology, complexity, and the emerging science of the Earth's surface}, Journal = {Geomorphology}, Volume = {103}, Number = {3}, Pages = {496-505}, Publisher = {Elsevier BV}, Year = {2009}, Month = {February}, ISSN = {0169-555X}, url = {http://dx.doi.org/DOI:10.1016/j.geomorph.2008.08.013}, Abstract = {The following is a white paper (adapted here for print) for the U.S. National Research Council's committee on Challenges and Opportunities in Earth Surface Processes, drafted at a National Science Foundation sponsored workshop associated with the 38th Binghamton Geomorphology Symposium, "Complexity in Geomorphology," held at Duke University in October 2007. © 2008 Elsevier B.V. All rights reserved.}, Doi = {10.1016/j.geomorph.2008.08.013}, Key = {fds281156} } @article{fds167759, Author = {E. C. Ellis and P.K. Haff}, Title = {Earth Science in the Anthropocene: New Era, New Paradigm, New Responsibilities}, Journal = {EOS 40, 473}, Year = {2009}, Key = {fds167759} } @article{fds281154, Author = {Haff, PK}, Title = {The landscape Reynolds number and other dimensionless measures of Earth surface processes}, Journal = {Geomorphology}, Volume = {91}, Number = {3-4}, Pages = {178-185}, Publisher = {Elsevier BV}, Year = {2007}, Month = {November}, ISSN = {0169-555X}, url = {http://dx.doi.org/10.1016/j.geomorph.2007.04.010}, Abstract = {An analogy between turbulent fluid systems and landscape drainage systems [Parker, G., Haff, P.K., Murray, A.B., 2001, EOS, Transactions of the American Geophysical Union, 82, pp. F564.] is suggested by the observation that transport in both systems can be approximated by diffusion with size-proportional effective diffusivities, with a cross-over at small scales to Fickian diffusion. The "landscape" Reynolds number of a typical fluvial landscape is estimated to be of order ReL ∼ 106 to 109, these large values reflecting the relative efficiency of fluvial transport compared to creep. ReL is the ratio of the large-scale effective diffusivity of rivers to the small-scale diffusivity of creep processes on hillslopes. The spatial dependence of the effective diffusivity produces rivers with logarithmic long-profiles, similar to the profiles of many rivers in nature, and analogous to the logarithmic dependence of mean fluid velocity on distance from a wall in turbulent flow. The landscape example suggests how other generalized "Reynolds numbers" can be constructed as ratios of large-scale to small-scale diffusivities to measure the efficiencies of complex processes that affect the surface. As an example, the global airline transportation network is estimated to have an efficacy relative to that of direct human mechanisms for transport of similar goods and materials of about 108 as measured by a corresponding "technology" Reynolds number. The appearance of such large dimensionless numbers, pertaining to the consequences of human invention and design, reflects the emergence of the technosphere as an increasingly efficient overlay on the historical domain of biology and surficial geology. © 2007 Elsevier B.V. All rights reserved.}, Doi = {10.1016/j.geomorph.2007.04.010}, Key = {fds281154} } @article{fds281155, Author = {Chan, KMA and Pringle, RM and Ranganathan, J and Boggs, CL and Chan, YL and Ehrlich, PR and Haff, PK and Heller, NE and Al-Khafaji, K and Macmynowski, DP}, Title = {When agendas collide: human welfare and biological conservation.}, Journal = {Conservation Biology : the Journal of the Society for Conservation Biology}, Volume = {21}, Number = {1}, Pages = {59-68}, Year = {2007}, Month = {February}, ISSN = {0888-8892}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17298511}, Abstract = {Conservation should benefit ecosystems, nonhuman organisms, and current and future human beings. Nevertheless, tension among these goals engenders potential ethical conflicts: conservationists' true motivations may differ from the justifications they offer for their activities, and conservation projects have the potential to disempower and oppress people. We reviewed the promise and deficiencies of integrating social, economic, and biological concerns into conservation, focusing on research in ecosystem services and efforts in community-based conservation. Despite much progress, neither paradigm provides a silver bullet for conservation's most pressing problems, and both require additional thought and modification to become maximally effective. We conclude that the following strategies are needed to make conservation more effective in our human-dominated world. (1) Conservation research needs to integrate with social scholarship in a more sophisticated manner. (2) Conservation must be informed by a detailed understanding of the spatial, temporal, and social distributions of costs and benefits of conservation efforts. Strategies should reflect this understanding, particularly by equitably distributing conservation's costs. (3) We must better acknowledge the social concerns that accompany biodiversity conservation; accordingly, sometimes we must argue for conservation for biodiversity's sake, not for its direct human benefits.}, Doi = {10.1111/j.1523-1739.2006.00570.x}, Key = {fds281155} } @article{064310191589, Author = {Strudley, MW and Murray, AB and Haff, PK}, Title = {Emergence of pediments, tors, and piedmont junctions from a bedrock weathering-regolith thickness feedback}, Journal = {Geology}, Volume = {34}, Number = {10}, Pages = {805-808}, Publisher = {Geological Society of America}, Year = {2006}, Month = {October}, ISSN = {0091-7613}, url = {http://dx.doi.org/10.1130/G22482.1}, Keywords = {Landforms;Sediment transport;Weathering;Erosion;Geomorphology;Lithology;}, Abstract = {Sediment erosion laws form the basis for most landscape evolution models and guide geomorphologists in the pursuit of understanding how landscapes evolve. This focus on the alluvial surface, however, ignores the role of intrinsic feedbacks between sediment transport and bedrock weathering in shaping Earth's landforms. Here, we present a new, parsimonious explanation for the origin and maintenance of pediments, piedmont junctions, and tors, which emerge spontaneously in a numerical model coupling bedrock weathering and sediment transport. The spatial uniformity of the thin regolith mantle that often characterizes pediments is a manifestation of a negative feedback between bedrock weathering and regolith thickness: if regolith thins (thickens) by sediment transport, the regolith production rate will increase (decrease), maintaining an equilibrium regolith thickness on the piedmont. We propose that high infiltration capacities and the instability of ephemeral channel banks in and and semiarid environments suppress fluvial incision and promote the smoothness of pediments. A positive feedback between bedrock weathering and regolith thickness causes tor growth: if regolith thins locally below a critical value, regolith production slows while surrounding areas continue to weather and erode more rapidly. We suggest that many pedimented and tor-studded landscapes may therefore be a consequence of intrinsic sediment transport-weathering feedbacks mediated by climatic and tectonic conditions, not by lithologic templates. © 2006 Geological Society of America.}, Doi = {10.1130/G22482.1}, Key = {064310191589} } @article{fds281152, Author = {Strudley, MW and Muray, AB and Haff, PK}, Title = {Regolith thickness instability and the formation of tors in arid environments}, Journal = {Journal of Geophysical Research: Earth Surface}, Volume = {111}, Number = {3}, Pages = {n/a-n/a}, Publisher = {American Geophysical Union (AGU)}, Year = {2006}, Month = {September}, ISSN = {2169-9011}, url = {http://dx.doi.org/10.1029/2005JF000405}, Abstract = {We present model results suggesting that a physical erosion-bedrock weathering feeback is responsible for the development of isolated bedrock knobs (tors/inselbergs) that often punctuate otherwise smooth pediments of homogeneous basement lithology. Tors and larger, more heavily jointed and morphologically complex exposures, inselbergs, may arise as a consequence of fluctuations in rainfall and sediment transport conditions combined with a bedrock weathering mechanism that depends on regolith thickness. Hydrogeochemical considerations and field observations in arid, granitic environments suggest that the relationship between weathering rate and regolith thickness exhibits a maximum for a finite thickness of cover. We have encapsulated this simple erosion-weathering feedback in a numerical model simulating arid/ semiarid landscape evolution that produces low-sloping pediments punctuated by tors. Tors form during periods of higher effective moisture, resulting in local base level incision and regolith thinning on pediments, invoking a transition in which mantled surfaces lower at rates exceeding the bare bedrock weathering rate. This condition favors the emergence and growth of tors in areas covered by regolith thickness less than a threshold value. Subsequent shifts in climate or local base level that restore sediment surface lowering rates less than the bare bedrock weathering rate will lead to a progressive decrease in tor height and, ultimately, their disappearance. Thus, according to this model, tors in and environments represent possibly transient features related to fluctuations in climate or local transport conditions rather than palimpsests of an ancient landscape derived from differential subsurface weathering followed by regolith stripping. Copyright 2006 by the Americal Geophysical Union.}, Doi = {10.1029/2005JF000405}, Key = {fds281152} } @article{fds281153, Author = {Haff, PK}, Title = {Response of desert pavement to seismic shaking, Hector Mine earthquake, California, 1999}, Journal = {Journal of Geophysical Research: Earth Surface}, Volume = {110}, Number = {2}, Publisher = {American Geophysical Union (AGU)}, Year = {2005}, Month = {June}, ISSN = {2169-9011}, url = {http://dx.doi.org/10.1029/2003JF000054}, Abstract = {[1] The October 1999 M<inf>w</inf> 7.1 Hector Mine earthquake in the Mojave Desert, California, generated characteristic surface disturbances on nearby desert pavements. These disturbances included (1) zones of wholesale gravel displacement interspersed with zones of intact pavement, (2) displaced and .rotated cobbles, (3) moats around loosened, embedded boulders, (4) filling of abandoned cobble sockets, boulder moats, and other depressions with gravel, and (5) formation of narrow, subparallel, linear strips of exposed fine-grained subpavement matrix (matrix lineations). Clasts displaced from matrix lineations and from cobble sockets tended to move downslope. Sharp boundaries of matrix lineations and slope-controlled displacement directions on slopes of only a few degrees indicated that clasts remained close to the pavement surface during shaking. The regular, few decimeter spacing of matrix lineations suggests the presence of standing waves during seismic shaking. Boulder moats probably have good preservation potential and, at some desert pavement locations, might provide information on paleoseismic shaking. Although readily produced by coseismic shaking, displaced cobbles are unreliable indicators of past earthquake activity because of potential multiple origins. For an assumed earthquake recurrence interval of 10 ka, seismically driven sediment fluxes similar to those generated by the Hector Mine earthquake at the Lavic Siding pavement study site may be marginally competitive with aseismic smoothing mechanisms driven by bioturbation, rainbeat, and wash. For a 1 ka recurrence interval, seismic smoothing is likely to play a significant role in pavement evolution. Copyright 2005 by the American Geophysical Union.}, Doi = {10.1029/2003JF000054}, Key = {fds281153} } @article{fds281151, Author = {Haff, PK}, Title = {Neogeomorphology}, Journal = {Eos}, Volume = {83}, Number = {29}, Pages = {310-310}, Publisher = {American Geophysical Union (AGU)}, Year = {2002}, Month = {July}, ISSN = {0096-3941}, url = {http://dx.doi.org/10.1029/2002EO000223}, Doi = {10.1029/2002EO000223}, Key = {fds281151} } @article{fds281164, Author = {Haff, PK}, Title = {Desert pavement: An environmental canary?}, Journal = {The Journal of Geology}, Volume = {109}, Number = {5}, Pages = {661-668}, Publisher = {University of Chicago Press}, Year = {2001}, Month = {January}, url = {http://dx.doi.org/10.1086/321960}, Abstract = {Ongoing disruption of ancient, varnished desert pavement surfaces near Death Valley National Park is inferred to be the result of unusually intense animal foraging activity. Increased levels of bioturbation are associated with enhanced vegetation growth stimulated by recent El Nino precipitation. The occurrence of abundant, recently overturned, varnished clasts suggests that the pavement disturbances reported here are rare on the millennial time scale of desert varnish formation. These observations suggest the possibility that changes in desert pavement surfaces may provide early hints of future changes in desert ecology and environment.}, Doi = {10.1086/321960}, Key = {fds281164} } @misc{fds49955, Author = {P. K. Haff}, Title = {Response of Desert Pavement to Seismic Shaking, Hector Mine Earthquake, California}, Year = {2001}, Key = {fds49955} } @misc{fds49957, Author = {P.K. Haff}, Title = {Neogeomorphology, Prediction, and the Anthropic Landscape}, Year = {2001}, Key = {fds49957} } @article{fds281150, Author = {Haff, PK}, Title = {Rivers, blood and transportation networks.}, Journal = {Nature}, Volume = {408}, Number = {6809}, Pages = {159-160}, Year = {2000}, Month = {November}, ISSN = {0028-0836}, url = {http://www.ncbi.nlm.nih.gov/pubmed/11089962}, Doi = {10.1038/35041633}, Key = {fds281150} } @misc{fds49951, Author = {P.K. Haff}, Title = {Rivers and Blood - Allometric Scaling in Biology and River Networks}, Journal = {Nature}, Volume = {408}, Pages = {159-2000}, Year = {2000}, Key = {fds49951} } @misc{fds49952, Author = {Haff and Furbish}, Title = {Upslope Transport and Other Oddities of Landscape Diffusion}, Year = {2000}, Key = {fds49952} } @misc{fds49953, Author = {Furbish and Haff}, Title = {The Master Equation Applied to Landscape Evolution}, Year = {2000}, Key = {fds49953} } @misc{fds49950, Author = {Boring and Haff}, Title = {An Empirical Model of Large Scale Sediment Transport in Arid Terrain: Application to Basalt Flow Erosion and Pediment Evolution near the Cima Volcanic Field, Mojave Desert, California}, Year = {1998}, Key = {fds49950} } @article{fds281131, Author = {Jyotsna, R}, Title = {Microtopography as an indicator of modern hillslope diffusivity in arid terrain}, Journal = {Geology}, Volume = {25}, Number = {8}, Pages = {695-698}, Publisher = {Geological Society of America}, Year = {1997}, Month = {January}, ISSN = {0091-7613}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1997XR32200006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Abstract = {Diffusion of topography is normally considered a smoothing process, but at the scale of the diffusive disturbance, diffusion becomes a roughening process. Roughening is exemplified by topographic features associated with disturbances such as animal burrows, hoof prints of grazing animals, and small landslides (here called large-scale processes). Diffusive processes that make small or indistinct topographic landmarks, such as rain splash and rhcological creep (here called small-scale processes), tend to erase these roughness elements. The ratio of the small-scale diffusion coefficient to the large-scale diffusion coefficient can be estimated by a measurement of the areal density of large-scale disturbances. In lightly vegetated, arid terrain, small-scale diffusion is dominant unless large-scale roughness elements cover a large fraction of the surface. The values of large-scale and small-scale modern diffusion coefficients can be estimated if the rate of generation of large-scale disturbances is known. Such estimates are performed for a burrowed fault scarp in Nevada.}, Doi = {10.1130/0091-7613(1997)025<0695:MAAIOM>2.3.CO;2}, Key = {fds281131} } @misc{fds328734, Author = {Haff, PK}, Title = {Why prediction of grain behavior is difficult in geological granular systems}, Journal = {Powders & Grains 97}, Pages = {61-64}, Publisher = {A A BALKEMA}, Editor = {Behringer, RP and Jenkins, JT}, Year = {1997}, Month = {January}, ISBN = {90-5410-884-3}, Key = {fds328734} } @misc{fds49947, Author = {P.K. Haff}, Title = {Why prediction of grain behavior is difficult for geological granular systems}, Year = {1997}, Key = {fds49947} } @misc{fds49949, Author = {Boring and Haff}, Title = {Landscape Evolution Using Digital Elevation Models of the Cima Dome Area, Mojave Desert, California}, Year = {1997}, Key = {fds49949} } @article{96063204446, Author = {Raghuraman, J and Haff, PK}, Title = {Scaling-up of small-scale granular sediment transport laws}, Journal = {Proceedings of Engineering Mechanics}, Volume = {1}, Pages = {262-264}, Address = {Fort Lauderdale, FL, USA}, Year = {1996}, Month = {January}, Keywords = {Granular materials;Mechanics;Computer simulation;Erosion;Runoff;Soils;Mathematical models;Channel flow;Sediments;Shear stress;}, Abstract = {Practical applications of laboratory sediment transport studies include the attempt to predict erosion of soil on hillslopes subject to rainfall-induced runoff. Most scientific studies of the mechanics of sediment transport have been performed at laboratory-scale, or in limited reaches of streams where bed and flow conditions are relatively well-known. The study reported here examines the application of basic sediment transport laws to prediction of large-scale sediment fluxes on hillslopes where topographic details of the slope are unknown at scales below the cell-size of the simulation. In particular, the situation in which small channels or rills on the hillslope are not resolved is examined. It is shown that empirical power-law sediment transport rules may generate systematic errors in their prediction of erosion and deposition rates.}, Key = {96063204446} } @article{96110389582, Author = {Haff, PK and Werner, BT}, Title = {Dynamical Processes on Desert Pavements and the Healing of Surficial Disturbances}, Journal = {Quaternary Research}, Volume = {45}, Number = {1}, Pages = {38-46}, Publisher = {Cambridge University Press (CUP)}, Year = {1996}, Month = {January}, ISSN = {0033-5894}, url = {http://dx.doi.org/10.1006/qres.1996.0004}, Abstract = {Mature desert pavements are traditionally regarded as hallmarks of stability, but their stability is dynamic, not static. In a study aimed at documenting this dynamic stability and its role in healing surface disturbances, experiments were performed over a 5-yr period on small cleared patches, or plats, on pavement surfaces in Panamint Valley, California. These experiments show that stones from plat edges begin to resurface the clearing at rates of about 1% per year on 40-cm-square plats and 10% per year on 10-cm-square plats. Stones contributing to the regenerated pavement have smaller average diameters than stones on the surrounding pavement. Cavities 5-10 cm deep, formed in mature pavement by removal of embedded boulders, fill by ravel and slope failure. After five years, cavity depth has been reduced by as much as 60%. Forty-year-old boulder cavities are nearly completely refilled and have been repaved by smaller than average pavement stones. Gaps caused by removal of small stones (2-3 cm) have completely healed in 5 yr. Displacement of surface stones by small animals is a major component of the healing process. © 1996 University of Washington.}, Doi = {10.1006/qres.1996.0004}, Key = {96110389582} } @misc{fds328735, Author = {Haff, PK}, Title = {Limitations on predictive modeling in geomorphology}, Journal = {Scientific Nature of Geomorphology}, Pages = {337-358}, Publisher = {JOHN WILEY & SONS LTD}, Editor = {Rhoads, BL and Thorn, CE}, Year = {1996}, Month = {January}, ISBN = {0-471-96811-0}, Key = {fds328735} } @article{194276, Author = {Haff, PK and Eisenberg, JM}, Title = {Dynamic nuclear effects in pionic and kaonic atoms}, Journal = {Phys. Lett. B (Netherlands)}, Volume = {33B}, Number = {2}, Pages = {133-136}, Year = {1996}, Keywords = {mesic and muonic atoms;}, Abstract = {Corrections have been calculated to adsorption widths in pionic and kaonic atoms due to the admixture of excited nuclear states. Effects as large as 12% and 27% are indicated for pionic and kaonic atoms, respectively}, Key = {194276} } @article{95062731563, Author = {Haff, PK}, Title = {Constitutive laws and prediction in granular systems}, Journal = {Proceedings of Engineering Mechanics}, Volume = {2}, Pages = {786-789}, Address = {Boulder, CO, USA}, Year = {1995}, Month = {January}, Keywords = {Mathematical models;Composition effects;Large scale systems;}, Abstract = {Constitutive properties of large-scale granular systems are likely to be unique or ill-defined as the result of history effects, compositional variation, and absence of suitable averaging volumes. In consequence, fundamental physical studies of granular systems at laboratory scale can contribute in only a limited way to quantitative numerical prediction of the behavior of large-scale granular systems.}, Key = {95062731563} } @article{95062731599, Author = {Haff, PK and Jiang, Z}, Title = {Vertical mixing of grains during bedload transport}, Journal = {Proceedings of Engineering Mechanics}, Volume = {2}, Pages = {931-933}, Address = {Boulder, CO, USA}, Year = {1995}, Month = {January}, Keywords = {Mixing;Sediments;Traction (friction);Diffusion;Granular materials;Mathematical models;}, Abstract = {Simulations of bedload transport predict that the active layer of transported grains on a sediment bed is a zone of vertical diffusion of sediment particles. Shallow exhumation and burial of grains is possible in the absence of either erosion or deposition. The thickness of the diffusion layer is predicted to be proportional to the applied surface traction.}, Key = {95062731599} } @article{fds281147, Author = {Jiang, Z and Haff, PK}, Title = {Multiparticle simulation methods applied to the micromechanics of bed load transport}, Journal = {Water Resources Research}, Year = {1993}, Month = {January}, Abstract = {We solve the Newtonian equations of motion to follow the trajectories of each of a large number of two-dimensional circular bed load particles as they move in response to stresses exerted by an overlying fluid. The fluid is modeled as a moving layer or 'slab' which exerts a velocity-dependent drag force on embedded particles and satisfies its own momentum balance equation. Bed load mass flux and hop length and hop height statistics of simulated beds resemble those observed in the laboratory. By marking particles originally residing on the surface, vertical mixing of sediment is investigated. An injection of fine particles into a bed load system of coarse particles under traction illustrates the early stages of the evolution of sedimentary stratigraphy. Friction angles and their distribution are investigated as a function of bed transport history and particle size. The main thrust of the paper, however, is to describe and test a microscopic bed load model which engineers, geologists, and biologists may find useful for applications where particle arrangement and relative particle motion are important. (Authors)}, Key = {fds281147} } @article{fds281148, Author = {Jiang, Z and Haff, PK}, Title = {Multiparticle simulation methods applied to the micromechanics of bed load transport}, Journal = {Water Resources Research}, Volume = {29}, Number = {2}, Pages = {399-412}, Publisher = {American Geophysical Union (AGU)}, Year = {1993}, Month = {January}, url = {http://dx.doi.org/10.1029/92WR02063}, Abstract = {We solve the Newtonian equations of motion to follow the trajectories of each of a large number of two‐dimensional circular bed load particles as they move in response to stresses exerted by an overlying fluid. The fluid is modeled as a moving layer or “slab” which exerts a velocity‐dependent drag force on embedded particles and satisfies its own momentum balance equation. Bed load mass flux and hop length and hop height statistics of simulated beds resemble those observed in the laboratory. By marking particles originally residing on the surface, vertical mixing of sediment is investigated. An injection of fine particles into a bed load system of coarse particles under traction illustrates the early stages of the evolution of sedimentary stratigraphy. Friction angles and their distribution are investigated as a function of bed transport history and particle size. The main thrust of the paper, however, is to describe and test a microscopic bed load model which engineers, geologists, and biologists may find useful for applications where particle arrangement and relative particle motion are important. Copyright 1993 by the American Geophysical Union.}, Doi = {10.1029/92WR02063}, Key = {fds281148} } @article{fds281149, Author = {HAFF, PK and ANDERSON, RS}, Title = {Grain scale simulations of loose sedimentary beds: the example of grain‐bed impacts in aeolian saltation}, Journal = {Sedimentology}, Volume = {40}, Number = {2}, Pages = {175-198}, Publisher = {WILEY}, Year = {1993}, Month = {January}, url = {http://dx.doi.org/10.1111/j.1365-3091.1993.tb01760.x}, Abstract = {Sediment transport by wind is one of many processes of interest to the geomorphologist in which grain to grain contacts play an important role. In order to illustrate the modelling of collections of frictional, inelastic sedimentary grains with the particle dynamics method (PDM), we use the grain impact process in aeolian saltation as a specific example. In PDM, all the forces on each particle are evaluated at a sequence of small time‐steps, and the Newtonian equations of motion are integrated forward in time. Interparticle forces at grain contacts are treated as springs with prescribed stiffness (normal force) and by a Coulomb friction law (tangential force); particle inelasticity is represented by spring damping. The granular splash resulting from saltation impacts is assessed for sensitivity to the choice of grain properties, and the integration time‐step. We find that for the range of impact speeds and impactor masses relevant to aeolian settings, grain splashes are relatively insensitive to grain stiffness, grain inelasticity and grain friction, and that the pattern of ejection from the bed is largely controlled by bed microtopography. A large set of impact realizations involving a variety of impact points on a small set of target beds is used to collect the appropriate statistics for describing the stochastic splash process. The splash function representing these statistics is then available for use in calculations over longer time‐scales, such as the evolution of the saltation curtain. The details given here will enable the interested reader to adapt PDM modelling to other types of clastic sedimentary systems. Copyright © 1993, Wiley Blackwell. All rights reserved}, Doi = {10.1111/j.1365-3091.1993.tb01760.x}, Key = {fds281149} } @article{93091081163, Author = {Haff, PK and Jiang, Z and Forrest, SB}, Title = {Transport of granules by wind and water: Micromechanics to macromechanics in geology and engineering}, Journal = {Mechanics of Materials}, Volume = {16}, Number = {1-2}, Pages = {173-178}, Publisher = {Elsevier BV}, Address = {Potsdam, NY, USA}, Year = {1993}, Month = {January}, ISSN = {0167-6636}, url = {http://dx.doi.org/10.1016/0167-6636(93)90040-X}, Keywords = {Transport properties;Fluid mechanics;Flow of fluids;Mixing;Water;Wind;Sand;Sediments;Shear stress;Microstructure;Mathematical models;}, Abstract = {We present two examples of micromechanical simulations and show how the calculations can be used to draw useful conclusions at the macroscopic leve. In bedload transport by water we examine the mixing depth of sediments undergoing shear traction. In transport of dry sand grains by wind we examine the development of periodic bedforms and the burial and preservation of bedding surfaces. © 1993.}, Doi = {10.1016/0167-6636(93)90040-X}, Key = {93091081163} } @article{fds328737, Author = {HAFF, PK and FORREST, S}, Title = {WIND RIPPLES FORM AND STRATIGRAPHY}, Journal = {Geotimes}, Volume = {37}, Number = {7}, Pages = {12-14}, Publisher = {AMER GEOLOGICAL INST}, Year = {1992}, Month = {July}, Key = {fds328737} } @article{92041264888, Author = {Forrest, SB and Haff, PK}, Title = {Mechanics of wind ripple stratigraphy.}, Journal = {Science (New York, N.Y.)}, Volume = {255}, Number = {5049}, Pages = {1240-1243}, Year = {1992}, Month = {March}, ISSN = {0036-8075}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17816833}, Abstract = {Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The simulations show that climbing strata can be produced by impact alone; direct action of fluid shear is unnecessary. The model provides a means for evaluating the connection between mechanical processes occurring in the paleoenvironment during deposition and the resulting stratigraphy preserved in the geologic column: vertical compression of small laminae above a planar surface indicates nascent ripple growth; supercritical laminae are associated with unusually intense deposition episodes; and a plane erosion surface separating sets of well-developed laminae is consistent with continued migration of mature ripples during a hiatus in deposition.}, Doi = {10.1126/science.255.5049.1240}, Key = {92041264888} } @article{92060512809, Author = {Haff, PK}, Title = {Discrete mechanics of sediment transport}, Journal = {Proceedings of Engineering Mechanics}, Pages = {756-759}, Address = {College Station, TX, USA}, Year = {1992}, Month = {January}, Keywords = {Flow of Fluids - Granular Materials;Fluid Mechanics;Mathematical Techniques - Differential Equations;}, Abstract = {Usually a granular medium is being represented by a continuous approximation in which the degrees of freedom of individual grains are averaged away in favor of a partial differential equation (PDE). To do this we need a constitutive equation. This paper describes an impact process which is slove sensitive, since unit surface elements oriented into the wind receive more impact per unit time than surface elements oriented downwind. Although the systems simulated in the paper are small compared to the expanse of a sand dune surface, the stratigraphic patterns generated in each small sample are diagnostic of mechanical conditions (wind velocity etc.) prevailing at deposition, and therefore may serve as indicators of}, Key = {92060512809} } @article{fds327857, Author = {Haff, PK and Jiang, Z and Forrest, SB}, Title = {Transport of Granules by Wind and Water: Micromechanics to Macromechanics in Geology and Engineering}, Journal = {Studies in Applied Mechanics}, Volume = {31}, Number = {C}, Pages = {373-380}, Publisher = {Elsevier}, Year = {1992}, Month = {January}, url = {http://dx.doi.org/10.1016/B978-0-444-89213-3.50044-4}, Abstract = {We present two examples of micromechanical simulations and show how the calculations can be used to draw useful conclusions at the macroscopic level. In bedload transport by water we examine the mixing-depth of sediments undergoing shear-traction. In transport of dry sand grains by wind we examine the development of periodic bedforms and the burial and preservation of bedding surfaces. © 1992, Elsevier B.V.}, Doi = {10.1016/B978-0-444-89213-3.50044-4}, Key = {fds327857} } @article{fds328736, Author = {HAFF, PK}, Title = {WIND RIPPLES AS TIMES MEMORY}, Journal = {Recherche}, Volume = {23}, Number = {247}, Pages = {1186-1188}, Year = {1992}, Key = {fds328736} } @article{91110333088, Author = {Haff, PK}, Title = {Basic physical models in sediment transport}, Journal = {Coastal Sediments '91}, Pages = {1-14}, Address = {Seattle, WA, USA}, Year = {1991}, Month = {January}, Keywords = {Flow of Fluids--Sediment Transport;Coastal Zones;Flow of Solids--Granular Materials;Soils--Sediments;Sedimentation--Models;}, Abstract = {Basic particle dynamics and cellular automata micromodels of clastic sediments are described and applications are illustrated in the areas of aeolian saltation, bedload transport, size segregation in shear flows, dry granular flows and aeolian bedform generation.}, Key = {91110333088} } @article{4026704, Author = {Gutt, GM and Haff, PK}, Title = {Boundary conditions on continuum theories of granular flow}, Journal = {International Journal of Multiphase Flow}, Volume = {17}, Number = {5}, Pages = {621-634}, Publisher = {Elsevier BV}, Year = {1991}, Month = {January}, ISSN = {0301-9322}, url = {http://dx.doi.org/10.1016/0301-9322(91)90028-2}, Keywords = {Couette flow;granular materials;kinetic theory of gases;two-phase flow;}, Abstract = {Continuum theories of highly agitated granular flows have recently been developed based on ideas from the kinetic theory of gases, with the fluctuation velocity of the grains corresponding to the temperature of the gas. Most often the boundary conditions for a granular system at a wall have been taken to be the same as the boundary conditions for a gas (i.e. the "no-slip" boundary conditions on the average flow velocity and the temperature). However, it is clear from experimental observations that a significant slip can exist in the average flow velocity and temperature at a wall. In this paper, a model of boundary conditions on granular flows will be presented which incorporates the following points: 1. 1. The average flow velocity of the grains at the wall does not equal the wall velocity, with the shear stress at the wall being proportional to the difference in these velocities (the "slip velocity"). 2. 2. Small-amplitude vibrations of the wall can be regarded as one factor in an effective wall "temperature". The other factor is the effect of the roughness of the wall coupled with the slip velocity. The flux of "thermal" energy between the granular system and the wall is determined by the relative values of this effective wall "temperature" and the granular system "temperature". 3. 3. Due to differences between grain-grain and grain-wall collisions, the density of the granular system may exhibit a "jump" at the wall. 4. 4. For walls of insufficient roughness, measured angles of effective internal friction may reflect more the effect of shearing at the wall than in the bulk. These boundary conditions are illustrated by solving a problem in Couette flow. © 1991.}, Doi = {10.1016/0301-9322(91)90028-2}, Key = {4026704} } @misc{fds344724, Author = {Gutt, GM and Haff, PK}, Title = {An automata model of granular materials}, Journal = {Proceedings of the 5th Distributed Memory Computing Conference, Dmcc 1990}, Volume = {1}, Pages = {522-529}, Year = {1990}, Month = {January}, ISBN = {0818621133}, url = {http://dx.doi.org/10.1109/DMCC.1990.555429}, Abstract = {A new modeling technique (the Lattice Grain Model) is presented for the simulation of two-dimensional granular systems involving large numbers (- lo4 to 10') of grains. These granular systems (e.g., rock slides, planetary rings, industrial powders, etc.) may include both high shear rate regions as well as static plugs of grains and cannot easily be handled within the framework of existing continuum theories such as soil mechanics. The Lattice Grain Model (LGrM) is similar to the Lattice Gas Model (LGM), which was introduced as a discrete model of fluids, in that the computation is carried out by means of cellular automata which evolve according to a simple set of rules based on local interactions. This allows large simulations to be programmed onto a hypercube concurrent processor in a straightforward manner. However, it differs from LGM in that it includes the inelastic collisions and volume-filling properties of macroscopic grains. Examples to be presented will include Couette flow, flow through an hourglass, and gravity-driven flows around obstacles.}, Doi = {10.1109/DMCC.1990.555429}, Key = {fds344724} } @misc{fds331186, Author = {Werner, BT and Haff, PK}, Title = {Dynamical sinulations of granular naterials using the caltech hypercuee}, Journal = {Proceedings of the 3rd Conference on Hypercube Concurrent Computers and Applications: Architecture, Software, Computer Systems, and General Issues, C3p 1988}, Volume = {2}, Pages = {1313-1318}, Publisher = {ACM Press}, Year = {1989}, Month = {January}, ISBN = {0897912780}, url = {http://dx.doi.org/10.1145/63047.63085}, Abstract = {A technique for simulating the motion of granular materials using the Caltech Hypercube is described, We demonstrate that grain dynamics simulations run efficiently on the Hypetcube and therefore that they offer an opportunity for greatly expanding the use of parallel simulations in studying granular materials. Several examples, which illustrate how the simulations can be used to extract information concerning the behavior of granular materials, are discussed.}, Doi = {10.1145/63047.63085}, Key = {fds331186} } @article{3275657, Author = {Anderson, RS and Haff, PK}, Title = {Simulation of eolian saltation.}, Journal = {Science (New York, N.Y.)}, Volume = {241}, Number = {4867}, Pages = {820-823}, Year = {1988}, Month = {August}, ISSN = {0036-8075}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17829176}, Keywords = {atmospheric boundary layer;dust;sand;wind;}, Abstract = {Saltation is important in the transport of sand-sized granular material by wind and in the ejection of dust from the bed both on Earth and on Mars. The evolution of the saltating population and all its characteristic profiles is calculated from inception by pure aerodynamic entrainment through to steady state. Results of numerical simulations of single-grain impacts into granular beds are condensed into analytic expressions for the number and speeds of grains rebounding or rejected (splashed) from the bed. A model is combined with (i) this numerical representation, (ii) an expression for the aerodynamic entrainment rate, and (iii) the modification of the wind velocity profile by saltating grains. Calculated steady state mass fluxes are within the range of mass fluxes measured in wind tunnel experiments; mass flux is nonlinearly dependent on the shear velocity. Aerodynamically entrained grains in the system are primarily seeding agents; at steady state, aerodynamic entrainment is rare. The time for the entire system to reach steady state is roughly 1 second, or several long-trajectory hop times.}, Doi = {10.1126/science.241.4867.820}, Key = {3275657} } @article{fds281144, Author = {WERNER, BT and HAFF, PK}, Title = {The impact process in aeolian saltation: two‐dimensional simulations}, Journal = {Sedimentology}, Volume = {35}, Number = {2}, Pages = {189-196}, Publisher = {WILEY}, Year = {1988}, Month = {January}, url = {http://dx.doi.org/10.1111/j.1365-3091.1988.tb00944.x}, Abstract = {ABSTRACT A critical event in the trajectory of a sand grain saltating in air is its interaction with the surface. We examine the phenomenon of grain‐bed impacts in two dimensions using a combination of dynamical computer simulations, analytical models and physical reasoning. The results indicate that the grain‐bed collisions can be treated as two‐body collisions with the bed particle assuming an effective mass greater than its true mass. Also, the presence of geometrical surface irregularities has a strong bearing on the interaction between saltating and surface grain populations, as well as on the formation of small‐scale bedforms. Copyright © 1988, Wiley Blackwell. All rights reserved}, Doi = {10.1111/j.1365-3091.1988.tb00944.x}, Key = {fds281144} } @article{3819590, Author = {Werner, B.T. and Haff, P.K.}, Title = {Dynamical simulations of granular materials using the Caltech Hypercube}, Journal = {Third Conference on Hypercube Concurrent Computers and Applications}, Pages = {1313 - 18}, Address = {Pasadena, CA, USA}, Year = {1988}, Keywords = {digital simulation;granular materials;hypercube networks;mechanical engineering computing;physics computing;}, Abstract = {A technique for simulating the motion of granular materials using the Caltech Hypercube is described. The authors demonstrate that grain dynamics simulations run efficiently on the Hypercube and therefore that they offer an opportunity for greatly expanding the use of parallel simulations in studying granular materials. Several examples, which illustrate how the simulations can be used to extract information concerning the behavior of granular materials, are discussed}, Key = {3819590} } @article{88020028942, Author = {Haff, PK and Werner, BT}, Title = {COLLISIONAL INTERACTION OF A SMALL NUMBER OF CONFINED, INELASTIC GRAINS.}, Volume = {3}, Pages = {483-501}, Address = {Miami Beach, FL, USA}, Year = {1987}, Month = {December}, Keywords = {SOLIDS - Velocity Measurement;FLOW OF FLUIDS - Granular Materials;}, Abstract = {In some grain systems of practical interest, however, the dispersed grains, although playing an important role in the system dynamics, are not numerous enough to justify a continuum description a priori. We have studied a computer model of one such system, in which a small number of inelastic spheres driven by a localized energy source are confined to an enclosed three dimensional space. Grain inelasticity exerts a dominant influence on these systems. With respect to the Maxwellian velocity distribution which elastic particles with the same average 'temperature' would show, the simulated velocity distribution exhibits a peak at lower energy, with a significant high energy tail.}, Key = {88020028942} } @article{87060093996, Author = {Mitha, S and Tran, MQ and Werner, BT and Haff, PK}, Title = {The grain-bed impact process in aeolian saltation}, Journal = {Acta Mechanica}, Volume = {63}, Number = {1-4}, Pages = {267-278}, Publisher = {Springer Nature}, Address = {Interlaken, Switz}, Year = {1986}, Month = {November}, ISSN = {0001-5970}, url = {http://dx.doi.org/10.1007/BF01182553}, Keywords = {SAND AND GRAVEL;MATERIALS TESTING - Impact;WIND EFFECTS;}, Abstract = {We report the results of impact experiments in which high velocity steel spheres (BBs) were directed against a loose bed of similar particles. The purpose of these experiments is to shed some light on the collision processes which occur when saltating sand grains driven by the wind strike the bed. The scattered particles fall into two categories: a single high energy rebound which scatters quasi-specularly, and a number of low energy recoils. The high energy rebound is identified with the "successive saltation" particle of Rumpel, and the low energy recoils are interpreted as creeping, or reptating particles. These observations provide information on the "splash function" of Ungar and Haff, which describes the response of a bed to grain impact and which plays a central role in the theory of saltation. © 1986 Springer-Verlag.}, Doi = {10.1007/BF01182553}, Key = {87060093996} } @article{2681610, Author = {Shapiro, MH and Lo, DY and Haff, PK and Tombrello, TA}, Title = {Simulation of sputtering from liquid Cu targets}, Journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions With Materials and Atoms}, Volume = {13}, Number = {1-3}, Pages = {348-352}, Publisher = {Elsevier BV}, Address = {Washington, DC, USA}, Year = {1986}, Month = {March}, ISSN = {0168-583X}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1986A702600066&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {copper;liquid metals;molecular dynamics method;sputtering;}, Abstract = {The sputtering of Cu atoms from liquid targets by normally incident 5 keV Ar+ ions was simulated using the multiple interaction molecular dynamics technique. Yields, energy distributions, and angular distributions of sputtered atoms were obtained at several temperatures slightly above and below the experimental melting point of copper. In all cases the resulting angular distributions of ejected atoms peaked more sharply than the cos θ behavior predicted by linear cascade theory. The ratio of yields from individual layers of the liquid targets, and the energy and angular distributions of ejected atoms generally were found to be similar to those obtained in previous simulations with solid Cu targets. Our results also are in qualitative agreement with Dumke's measurements of angular distributions and layer yield ratios of sputtered atoms from liquid Ga-In eutectic alloy targets. In particular, no marked changes in yields or energy distributions were observed when the temperature of the target was lowered below the nominal melting point of copper. The angular distributions were found to broaden with increasing temperature. © 1986.}, Doi = {10.1016/0168-583X(86)90525-2}, Key = {2681610} } @article{88020024200, Author = {Haff, PK}, Title = {A Physical Picture of Kinetic Granular Fluids}, Journal = {Journal of Rheology}, Volume = {30}, Number = {5}, Pages = {931-948}, Publisher = {Society of Rheology}, Address = {Blacksburg, VA, USA}, Year = {1986}, Month = {January}, url = {http://dx.doi.org/10.1122/1.549875}, Keywords = {KINETICS - Mathematical Models;}, Abstract = {We give a physical and heuristic discussion of the kinetic model of granular fluids, wherein the grain plays the role of a molecule. A consideration of the details of grain—grain and grain—wall interactions leads naturally to the equations of motion and to suitable boundary conditions. Examples from a Couette flow geometry are used to support the argument that the energy and momentum equations must be treated on an equal footing. The introduction of the energy equation leads to the appearance of a new length scale A, the conduction length, which describes the competition between viscous heating and collisional energy absorption and whose value determines the distribution of “granular temperature” and hence the flow field in the fluid. © 1986, The Society of Rheology. All rights reserved.}, Doi = {10.1122/1.549875}, Key = {88020024200} } @article{87030040511, Author = {Haff, PK and Werner, BT}, Title = {Computer simulation of the mechanical sorting of grains}, Journal = {Powder Technology}, Volume = {48}, Number = {3}, Pages = {239-245}, Publisher = {Elsevier BV}, Year = {1986}, Month = {January}, ISSN = {0032-5910}, url = {http://dx.doi.org/10.1016/0032-5910(86)80048-1}, Keywords = {CLASSIFIERS - Computer Simulation;GRANULAR MATERIALS - Friction;FLOW OF FLUIDS - Granular Materials;}, Abstract = {A two-dimensional system of inelastic frictional disks all of equal diameter save one was studied by computer simulation. A single large disk was placed on the bottom of a container and covered by 30 smaller disks. When the container was agitated to induce a shear motion in the disk assembly, the large particle showed a tendency to rise toward the surface. This sorting process was mediated by shear-driven rotational motion, the large grain rolling up on top of neighboring small grains. The grain-grain friction coefficient μ is a critical parameter in this kind of sorting process, since if μ is too small, the large grain cannot get sufficient purchase to roll without slipping. © 1986.}, Doi = {10.1016/0032-5910(86)80048-1}, Key = {87030040511} } @article{86060026161, Author = {Hui, K and Haff, PK}, Title = {Kinetic grain flow in a vertical channel}, Journal = {International Journal of Multiphase Flow}, Volume = {12}, Number = {2}, Pages = {289-298}, Publisher = {Elsevier BV}, Year = {1986}, Month = {January}, ISSN = {0301-9322}, url = {http://dx.doi.org/10.1016/0301-9322(86)90031-5}, Keywords = {FLUID DYNAMICS;MATHEMATICAL MODELS;}, Abstract = {A self-consistent kinetic grain flow model proposed earlier has been applied in detail to the description of rapid flow in a verticad channel. The equations of motion reduce to an ordinary differential equation for the fluctuation velocity ν, which is solved numerically. Boundary conditions on ν are derived which incorporate the nature of grain-wall collisions. The overall flow pattern is found to depend significantly upon the grain inelasticity parameter γ (γ = 0 for elastic grains) and upon the grain diameter d. The flow velocity profile is rounded for very elastic grains and for large grains, but becomes more blunt as grain diameter decreases or γ increases. For large enough γ, a region of plug flow develops in the central region of the channel, corresponding to a vanishing grain fluctuation velocity. In this case the region of dispersed or "thermalized" grains, within which all shearing occurs, is restricted to a thin layer near each wall. © 1986.}, Doi = {10.1016/0301-9322(86)90031-5}, Key = {86060026161} } @article{2754696, Author = {Haff, PK and Eviatar, A}, Title = {Micrometeoroid impact on planetary satellites as a magnetospheric mass source}, Journal = {Icarus}, Volume = {66}, Number = {2}, Pages = {258-269}, Publisher = {Elsevier BV}, Year = {1986}, Month = {January}, ISSN = {0019-1035}, url = {http://dx.doi.org/10.1016/0019-1035(86)90156-9}, Keywords = {meteoroids;micrometeorites;planetary atmospheres;planetary satellites;planets;}, Abstract = {Planetary satellites are an important source of mass for planetary magnetospheres. Meteoroid impact vaporization is a supply mechanism which can potentially compete with charged-particle sputtering. Recent estimates of impact fluxes in the outer solar system vary by several orders of magnitude. For the larger flux values impact vaporization will play a role both at Jupiter and Saturn, although for the most part it will not dominate sputtering. At the small end of the flux range, sputtering dominates magnetospheric mass-loading everywhere. © 1986.}, Doi = {10.1016/0019-1035(86)90156-9}, Key = {2754696} } @article{fds281142, Author = {Werner, BT and Haff, PK and Livi, RP and Anderson, RS}, Title = {Measurement of eolian sand ripple cross-sectional shapes.}, Journal = {Geology}, Volume = {14}, Number = {9}, Pages = {743-745}, Publisher = {Geological Society of America}, Year = {1986}, ISSN = {0091-7613}, url = {http://dx.doi.org/10.1130/0091-7613(1986)14<743:MOESRC>2.0.CO}, Abstract = {Measures shapes by casting a shadow perpendicular to the ripple crests.-from Authors}, Doi = {10.1130/0091-7613(1986)14<743:MOESRC>2.0.CO}, Key = {fds281142} } @article{fds319907, Author = {Shapiro, MH and Lo, DY and Haff, PK and Tombrello, TA}, Title = {Simulation of sputtering from liquid Cu targets}, Journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions With Materials and Atoms}, Volume = {13}, Number = {1-3}, Pages = {348-352}, Year = {1986}, Abstract = {The sputtering of Cu atoms from liquid targets by normally incident 5 keV Ar+ ions was simulated using the multiple interaction molecular dynamics technique. Yields, energy distributions, and angular distributions of sputtered atoms were obtained at several temperatures slightly above and below the experimental melting point of copper. In all cases the resulting angular distributions of ejected atoms peaked more sharply than the cos θ behavior predicted by linear cascade theory. The ratio of yields from individual layers of the liquid targets, and the energy and angular distributions of ejected atoms generally were found to be similar to those obtained in previous simulations with solid Cu targets. Our results also are in qualitative agreement with Dumke's measurements of angular distributions and layer yield ratios of sputtered atoms from liquid Ga-In eutectic alloy targets. In particular, no marked changes in yields or energy distributions were observed when the temperature of the target was lowered below the nominal melting point of copper. The angular distributions were found to broaden with increasing temperature. © 1986.}, Key = {fds319907} } @article{fds328738, Author = {HAFF, PK}, Title = {BOOMING DUNES}, Journal = {American Scientist}, Volume = {74}, Number = {4}, Pages = {376-381}, Year = {1986}, Key = {fds328738} } @article{2543525, Author = {Shapiro, MH and Haff, PK and Tombrello, TA and Harrison, DE}, Title = {Simulation of isotopic mass effects in sputtering}, Journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions With Materials and Atoms}, Volume = {12}, Number = {1}, Pages = {137-145}, Publisher = {Elsevier BV}, Year = {1985}, Month = {January}, ISSN = {0168-583X}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1985APU1900017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {copper;digital simulation;isotope effects;molecular dynamics method;sputtering;}, Abstract = {The multiple interaction, molecular dynamics code SPUT1 has been used to simulate the effects of isotopic mass differences on atoms sputtered from single crystal Cu targets by normally incident Ar ions. Calculations were carried out for 1 keV and 5 keV ions incident on natural Cu targets (69.1% 63Cu, 30.9% 65Cu). and for 5 keV ions incident on pseudo-Cu targets composed of mixtures of natural Cu (63.546 amu) and "very light" Cu (50.837 amu) in the abundance ratios 1:3, 1:1, and 3:1. In all cases the sputtered ejecta showed an overall enrichment in the light isotope relative to the isotopic composition of the target. Preferential enrichment of the light isotope in the normal direction was pronounced. Material ejected at oblique angles was either depleted in the light isotope or had a much lower enrichment of the light isotope compared to material ejected normal to the target. Studies with the pseudo-Cu targets showed that smaller enrichments were obtained when the incident ion recoiled immediately back through the first layer of the target, while larger enrichments were associated with deeper penetration of the incident ion into the target crystallite. In both cases, the average energy of the light atoms in the collision cascade was found to be higher than that of the heavy atoms. However, this effect was enhanced with deeper penetration of the incident ion into the target. The preferential enrichment of the light ejected atoms normal to the target is largely the result of a strong momentum asymmetry in the collision cascades. Light atoms in the cascades, on average, carry far greater momentum towards the surface of the target than do the heavy atoms. A limited number of simulation runs also were carried out with heavy ions (74 amu) incident on pseudo-Cu targets. Overall enrichment of the light atoms in the sputtered material was reduced, but the angular variation of the isotopic yields persisted. © 1985.}, Doi = {10.1016/0168-583X(85)90709-8}, Key = {2543525} } @article{2563514, Author = {Shapiro, MH and Haff, PK and Tombrello, TA and Jr, HDE and Webb, RP}, Title = {Computer-simulated energy and angular distributions of sputtered Cu atoms}, Journal = {Radiat. Eff. (Uk)}, Volume = {89}, Number = {3-4}, Pages = {234-255}, Year = {1985}, Keywords = {copper;molecular dynamics method;sputtering;}, Abstract = {The energy and angular distributions of copper atoms ejected by 5 keV incident Ar ions have been simulated using the multiple interaction molecular dynamics technique. Calculations carried out with two independently written computer codes yielded essentially identical results. As in previous simulation studies of low to medium energy sputtering, virtually all ejected atoms came from the first layer or second layer. Two different ion-atom potentials were used in the simulations. Absolute sputtering yields depended strongly on the choice of potential; relative yields and angular distributions were found to be insensitive to the choice of potential. For Ar ions normally incident on the (100), (110), and (111) faces of a FCC Cu crystallite, ejected atoms from the second layer of the crystallite exited preferentially in the forward direction compared to those sputtered from the first layer. The energy spectra of atoms ejected from the second layers were harder than those of the first layer atoms}, Key = {2563514} } @article{fds319908, Author = {Shapiro, MH and Haff, PK and Tombrello, TA and Jr, DEH}, Title = {Simulation of isotopic mass effects in sputtering}, Journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions With Materials and Atoms}, Volume = {12}, Number = {1}, Pages = {137-145}, Year = {1985}, Abstract = {The multiple interaction, molecular dynamics code SPUT1 has been used to simulate the effects of isotopic mass differences on atoms sputtered from single crystal Cu targets by normally incident Ar ions. Calculations were carried out for 1 keV and 5 keV ions incident on natural Cu targets (69.1% 63Cu, 30.9% 65Cu). and for 5 keV ions incident on pseudo-Cu targets composed of mixtures of natural Cu (63.546 amu) and "very light" Cu (50.837 amu) in the abundance ratios 1:3, 1:1, and 3:1. In all cases the sputtered ejecta showed an overall enrichment in the light isotope relative to the isotopic composition of the target. Preferential enrichment of the light isotope in the normal direction was pronounced. Material ejected at oblique angles was either depleted in the light isotope or had a much lower enrichment of the light isotope compared to material ejected normal to the target. Studies with the pseudo-Cu targets showed that smaller enrichments were obtained when the incident ion recoiled immediately back through the first layer of the target, while larger enrichments were associated with deeper penetration of the incident ion into the target crystallite. In both cases, the average energy of the light atoms in the collision cascade was found to be higher than that of the heavy atoms. However, this effect was enhanced with deeper penetration of the incident ion into the target. The preferential enrichment of the light ejected atoms normal to the target is largely the result of a strong momentum asymmetry in the collision cascades. Light atoms in the cascades, on average, carry far greater momentum towards the surface of the target than do the heavy atoms. A limited number of simulation runs also were carried out with heavy ions (74 amu) incident on pseudo-Cu targets. Overall enrichment of the light atoms in the sputtered material was reduced, but the angular variation of the isotopic yields persisted. © 1985.}, Key = {fds319908} } @article{2346371, Author = {Hui, K and Haff, PK and Ungar, JE}, Title = {Boundary conditions for high-shear grain flows}, Journal = {Journal of Fluid Mechanics}, Volume = {145}, Number = {EM1}, Pages = {223-233}, Publisher = {Cambridge University Press (CUP)}, Year = {1984}, Month = {January}, url = {http://dx.doi.org/10.1017/S0022112084002883}, Keywords = {boundary-value problems;Couette flow;fluctuations;shear flow;two-phase flow;}, Abstract = {Boundary conditions are developed for rapid granular flows in which the rheology is dominated by grain–grain collisions. These conditions are [formula-omitted] and u0 = const du0/dy, where [formula-omitted] and u are the thermal (fluctuation) and flow velocities respectively, and the subscript indicates that these quantities and their derivatives are to be evaluated at the wall These boundary conditions are derived from the nature of individual grain–wall collisions, so that the proportionality constants involve the appropriate coefficient of restitution ew for the thermal velocity equation, and the fraction of diffuse (i.e. non-specular) collisions in the case of the flow-velocity equation. Direct application of these boundary conditions to the problem of Couette-flow shows that as long as the channel width h is very large compared with a grain diameter d it is permissible to set [formula-omitted] at the wall and to adopt the no-slip condition. Exceptions occur where d/h is not very small, when the wall is not rough, and when the grain–wall collisions are very elastic. Similar insight into other flows can be obtained qualitatively by a dimensional analysis treatment of the boundary conditions. Finally, the more difficult problem of self-bounding fluids is discussed qualitatively. © 1984, Cambridge University Press. All rights reserved.}, Doi = {10.1017/S0022112084002883}, Key = {2346371} } @article{fds328739, Author = {HAFF, PK}, Title = {SPUTTERING BY PARTICLE BOMBARDMENT, PT 2, SPUTTERING OF ALLOYS AND COMPOUNDS, ELECTRON AND NEUTRON SPUTTERING, SURFACE-TOPOGRAPHY - BEHRISCH,R}, Journal = {American Scientist}, Volume = {72}, Number = {5}, Pages = {510-510}, Year = {1984}, Key = {fds328739} } @article{2136743, Author = {Summers, ME and Yung, YL and Haff, PK}, Title = {A two-stage mechanism for escape of Na and K from Io}, Journal = {Nature}, Volume = {304}, Number = {5928}, Pages = {710-712}, Publisher = {Springer Nature}, Year = {1983}, Month = {December}, ISSN = {0028-0836}, url = {http://dx.doi.org/10.1038/304710a0}, Keywords = {Jupiter;planetary atmospheres;planetary satellites;}, Abstract = {It is generally accepted that Io is the source of S, O, Na and K which, after ionization, form the constituents of the Io plasma torus. The escape of S and O from Io can be understood in terms of the photochemistry of a predominantly SO2 atmosphere created by the high vapour pressure of SO2 (refs 1,15). However, the vapour pressures of Na2S, K2S and other common compounds containing Na and K are negligible at the surface temperatures of Io. This has given rise to the suggestion that over part of Io's surface (the nightside) the atmosphere is thin enough so that surface sputtering by co-rotating ions can eject Na and K directly into the Io torus2,3. The main objection to this idea is that it implies a 'Sun-locked' source for Na and K, while observations of the Na and K clouds around Io indicate a 'Jupiter-locked' ejection mechanism. We propose here that Na and K escape from Io in two stages. Atoms of Na and K are first sputtered into the atmosphere from the surface by high-energy magnetospheric ions. Atmospheric sputtering4 by low-energy co-rotating ions then removes these constituents (along with others present) out of Io's gravitational field. We suggest that the observed Na and K ejection asymmetry is due to preferential sputtering of atmospheric particles on the hemisphere of Io facing Jupiter. The estimated injection rates are sufficiently large to maintain the observed K, Na, and O clouds observed around Io5-7,18. © 1983 Nature Publishing Group.}, Doi = {10.1038/304710a0}, Key = {2136743} } @article{2150608, Author = {Haff, PK}, Title = {Grain flow as a fluid mechanical phenomenon}, Journal = {Journal of Fluid Mechanics}, Volume = {134}, Number = {-1}, Pages = {401-430}, Publisher = {Cambridge University Press (CUP)}, Year = {1983}, Month = {January}, url = {http://dx.doi.org/10.1017/S0022112083003419}, Keywords = {fluid dynamics;}, Abstract = {The behaviour of granular material in motion is studied from a continuum point of view. Insofar as possible, individual grains are treated as the ‘molecules’ of a granular ‘fluid'. Besides the obvious contrast in shape, size and mass, a key difference between true molecules and grains is that collisions of the latter are inevitably inelastic. This, together with the fact that the fluctuation velocity may be comparable to the flow velocity, necessitates explicit incorporation of the energy equation, in addition to the continuity and momentum equations, into the theoretical description. Simple ‘microscopic’ kinetic models are invoked for deriving expressions for the ‘coefficients’ of viscosity, thermal diffusivity and energy absorption due to collisions. The ‘coefficients’ are not constants, but are functions of the local state of the medium, and therefore depend on the local ‘temperature’ and density. In general the resulting equations are nonlinear and coupled. However, in the limits ≪d, wheres is the mean separation between neighbouring grain surfaces and is a grain diameter, the above equations become linear and can be solved analytically. An important dependent variable, in this formulation, in addition to the flow velocity u, is the mean random fluctuation ('thermal') velocity v of an individual grain. With a sufficient flux of energy supplied to the system through the boundaries of the container, v can remain non zero even in the absence of flow. The existence of a non uniform v is the means by which energy can be ‘conducted’ from one part of the system to another. Because grain collisions are inelastic, there is a natural (damping) lengthscale, governed by the value of d, which strongly influences the functional dependence of v on position. Several illustrative examples of static (u = 0) systems are solved. As an example of grain flow, various Couette type problems are solved analytically. The pressure, shear stress, and ‘thermal’ velocity function v are all determined by the relative plate velocity U (and the boundary conditions). If v is set equal to zero at both plates, the pressure and stress are both proportional to U2i.e. the fluid is non-Newtonian. However, if sufficient energy is supplied externally through the walls (v ≠ 0 there), then the forces become proportional to the first power of U. Some examples of Couette flow are given which emphasize the large effect on the grain system properties of even a tiny amount of inelasticity in grain—grain collisions. From these calculations it is suggested that, for the case of Couette flow, the flow of sand is supersonic over most of the region between the confining plates. © 1983, Cambridge University Press. All rights reserved.}, Doi = {10.1017/S0022112083003419}, Key = {2150608} } @article{2235268, Author = {Haff, PK and Eviatar, A and Siscoe, GL}, Title = {Ring and plasma: The enigmae of Enceladus}, Journal = {Icarus}, Volume = {56}, Number = {3}, Pages = {426-438}, Publisher = {Elsevier BV}, Year = {1983}, Month = {January}, ISSN = {0019-1035}, url = {http://dx.doi.org/10.1016/0019-1035(83)90164-1}, Keywords = {planetary atmospheres;planetary rings;planetary satellites;plasma;Saturn;sputtering;}, Abstract = {The E ring associated with the Kronian moon Enceladus has a lifetime of only a few thousand years against sputteringly by slow corotating O ions. The existence of the ring implies the necessity for a continuous supply of matter. Possible particle source mechanisms on Enceladus include meteoroidal impact ejection and geysering. Estimates of ejection rates of particulate debris following small meteoroid impact are on the order of 3 × 10-18 g cm-2 sec-1, more than an order of magnitude too small to sustain the ring. A geyser source would need to generate a droplet supply at a rate of approximately 10-16 g cm-2 sec- in order to account for a stable ring. Enceladus and the ring particles also directly supply both plasma and vapor to space via sputtering. The absence of a 60 eV plasma at the Voyager 2 Enceladus L-shell crossing, such as might have been expected from sputtering, cannot be explained by absorption and moderation of plasma ions by ring particles, because the ring is too diffuse. Evidently, the effective sputtering yield in the vicinity of Enceladus is on the order of, or smaller than, 0.4, about an order of magnitude less than the calculated value. Small scale surface roughness may account for some of this discrepancy. © 1983.}, Doi = {10.1016/0019-1035(83)90164-1}, Key = {2235268} } @article{fds281139, Author = {Haff, PK and Seiberling, LE}, Title = {Anomalous sputtering at high energy}, Journal = {Nature}, Volume = {290}, Number = {5807}, Pages = {544-545}, Publisher = {Springer Nature}, Year = {1981}, Month = {December}, ISSN = {0028-0836}, url = {http://dx.doi.org/10.1038/290544a0}, Doi = {10.1038/290544a0}, Key = {fds281139} } @article{1825595, Author = {Haff, PK and Watson, CC and Tombrello, TA}, Title = {Possible isotopic fractionation effects in materials sputtered from minerals.}, Journal = {Journal of Geophysical Research}, Volume = {86}, Number = {B10}, Pages = {9553-9561}, Publisher = {American Geophysical Union (AGU)}, Year = {1981}, Month = {January}, url = {http://dx.doi.org/10.1029/JB086iB10p09553}, Keywords = {isotope relative abundance;isotope separation;lunar rocks and minerals;meteorites;minerals;oxygen;sputtering;}, Abstract = {A mathematical model is given which predicts fractionation of isotopes during sputtering. -K.A.R.}, Doi = {10.1029/JB086iB10p09553}, Key = {1825595} } @article{1809592, Author = {Haff, PK and Watson, CC and Yung, YL}, Title = {Sputter ejection of matter from Io}, Journal = {J. Geophys. Res. (Usa)}, Volume = {86}, Number = {A8}, Pages = {6933-6938}, Year = {1981}, Keywords = {Jupiter;planetary atmospheres;planetary satellites;}, Abstract = {The direct collisional interaction of magnetospheric particles with Io will lead to sputtering of atoms and molecules from the satellite into circum-Jovian space. The ~520-eV S (and ~260-eV O) ions composing the Io torus are the most effective agents for net sputter removal of matter from the satellite. An incident flux of ~1010 cm-2 s-1 is estimated to provide ~5×1010 S atoms cm-2 s-1 from sputtering of a (dayside) atmosphere with an exobase at a few hundred kilometers and up to ~1012 S atoms cm-2 s-1 from an atmosphere at 1500K with an exobase at ~2.2 RIo. The supply of S (and O) required to stabilize the torus has been estimated. If Na and K are present in the atmosphere at a concentration level of 1%, the corresponding sputtering rates are calculated. Sputtering can also remove heavy molecules, like Sn, from the atmosphere. All atomic species residing on the surface must be ejected into circum-Jovian space at a rate approximately proportional to their (surface) abundances, if direct surface sputtering occurs, so that the particle content of the inner Jovian magnetosphere should map rather faithfully all species present on Io's surface}, Key = {1809592} } @article{fds328740, Author = {Haff, PK and Watson, CC and Yung, YL}, Title = {Sputter ejection of matter from Io}, Journal = {Journal of Geophysical Research}, Volume = {86}, Number = {A8}, Pages = {6933-6933}, Publisher = {American Geophysical Union (AGU)}, Year = {1981}, url = {http://dx.doi.org/10.1029/ja086ia08p06933}, Doi = {10.1029/ja086ia08p06933}, Key = {fds328740} } @article{81020001625, Author = {Watson, CC and Haff, PK}, Title = {Sputter-induced isotopic fractionation at solid surfaces}, Journal = {Journal of Applied Physics}, Volume = {51}, Number = {1}, Pages = {691-699}, Publisher = {AIP Publishing}, Year = {1980}, Month = {December}, url = {http://dx.doi.org/10.1063/1.327327}, Keywords = {SPUTTERING;}, Abstract = {Elemental and isotopic mass fractionation in both binary and multicomponent media are investigated within the framework of the familiar collision-cascade model for sputtering. Some of the most salient features of the phenomenon are explicable on this basis. It is found that the partitioning of beam-deposited energy among the various target components can account for differentiations in the secondary recoil fluxes only on the order of one part per thousand, indicating the importance of the surface potentials when large enrichment effects occur. A mechanism governing the translation of internal recoil fluxes into external sputtered fluxes is proposed in order to account for isotopic fractionation, for which the surface binding effects are assumed to be negligible. The predicted initial fractionations are δf( 40Ca : 44Ca) =33 parts per thousand in the calcium-containing mineral plagioclase and δf(40Ca : 44Ca) =24 parts per thousand in CaF2, in reasonable agreement with recent data on isotopic fractionation.}, Doi = {10.1063/1.327327}, Key = {81020001625} } @article{fds281138, Author = {Watson, CC and Haff, PK and Tombrello, TA}, Title = {Solar wind sputtering effects in the atmospheres of Mars and Venus.}, Journal = {Geochimica Et Cosmochimica Acta, Supplement}, Volume = {14}, Number = {3}, Pages = {2479-2502}, Year = {1980}, Month = {January}, Abstract = {The consequences of the direct collisional interaction of an energetic particle flux with the neutral components of a planetary atmosphere were investigated. A combination of Monte Carlo simulations and analytical analysis suggests that solar wind sputtering could provide an important exospheric mass sink on both Mars and Venus under appropriate conditions. Sputtering of the venusian atmosphere may result in loss of He at the rate of approx 105 atoms/cm2-sec, and sputtering of the martian atmosphere could remove C, N, and O at the rates of 1 X 106 C atoms/cm2-sec, 5 X 105 N atoms/cm2-sec, and 3 X 106 O atoms/cm2-sec. Calculations based on a model martian atmosphere suggest that 99% of the N2 and 43% of the CO2 originally present could have been sputtered away over 4.5 X 109 yr. -P.Br.}, Key = {fds281138} } @misc{fds328741, Author = {WATSON, CC and HAFF, PK}, Title = {MOMENTUM TRANSPORT IN A DENSE HARD-SPHERE GAS}, Journal = {Bulletin of the American Physical Society}, Volume = {25}, Number = {4}, Pages = {531-531}, Year = {1980}, Key = {fds328741} } @article{1541656, Author = {Haff, PK and Watson, CC}, Title = {The erosion of planetary and satellite atmospheres by energetic atomic particles}, Journal = {Journal of Geophysical Research}, Volume = {84}, Number = {B14}, Pages = {8436-8436}, Publisher = {American Geophysical Union (AGU)}, Address = {Pasadena, TX, USA}, Year = {1979}, ISSN = {0148-0227}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1979JH89800048&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {Jupiter;Mars;planetary atmospheres;planetary satellites;solar wind;}, Abstract = {Analytic expressions are presented which may be used to compute the sputter-erosion yield from any unimolecular gravitationally bound gas by any atomic charged particle of energy. A calculation of solar wind proton and alpha particle induced erosion of the CO<sub>2</sub> atmosphere of Mars predicts molecular sputtering yields <i>S</i><sub>p</sub>≈0.029 and <i>S</i><sub>α</sub>≈0.21. These numbers are comparable to the results of earlier Monte Carlo simulations. An expression for the emission yield of energetic molecular fragments produced in primary knock-on events is also given in closed form. Such fragment emission is of secondary importance for mass loss compared to the molecular yield itself. Erosion by radiation belt protons of a hypothetical thin O<sub>2</sub> atmosphere associated with the Jovian satellite. Ganymede is considered. Molecular sputtering yields for proton energies at 1 keV and 1 MeV are 0.115 and 6.4×10<sup>-4</sup>, respectively. The yield at the lower energy can have significant effects on atmospheric equilibrium should keV proton fluxes equal or exceed about 10<sup>8</sup> cm<sup>-2</sup> s<sup>-1</sup>}, Doi = {10.1029/jb084ib14p08436}, Key = {1541656} } @misc{fds328742, Author = {HAFF, PK}, Title = {GROWTH AND MAINTENANCE OF A MINERAL ARMOR ON THE ICY SATELLITES OF JUPITER}, Journal = {Journal of the Electrochemical Society}, Volume = {126}, Number = {8}, Pages = {C342-C343}, Year = {1979}, Key = {fds328742} } @misc{fds328743, Author = {WATSON, CC and HAFF, PK}, Title = {SPUTTERING OF A MOLECULAR GAS}, Journal = {Bulletin of the American Physical Society}, Volume = {24}, Number = {4}, Pages = {660-660}, Year = {1979}, Key = {fds328743} } @article{1205543, Author = {Haff, PK and Switkowski, ZE and Tombrello, TA}, Title = {Solar-wind sputtering of the martian atmosphere}, Journal = {Nature}, Volume = {272}, Number = {5656}, Pages = {803-804}, Publisher = {Springer Nature}, Year = {1978}, Month = {December}, ISSN = {0028-0836}, url = {http://dx.doi.org/10.1038/272803a0}, Keywords = {Mars;planetary atmospheres;solar wind;}, Abstract = {In the sputtering process an incident particle beam loses part of its energy to recoil motion of target atoms, some of which may escape through a nearby surface. The sputtering yield is defined as the number of atoms ejected per incident particle. In the solar system, sputtering will occur whenever the solar wind, consisting mainly of 1 keV AMU<sup>-1</sup> hydrogen and helium ions, strikes a material body. Wehner et al. (1963) suggested that solar wind-induced sputtering of the lunar surface should be an important cause of erosion; recently, analyses of returned lunar material have been interpreted quantitatively in terms of such solar-wind sputtering. Mars provides another example of the interaction of the solar wind with a planetary body. However, in contrast to the lunar surface, the Martian surface is largely protected from direct solar wind bombardment by its atmosphere. The primarily CO<sub>2</sub> atmosphere is thin by terrestrial standards but still opaque to the solar wind. The authors discuss whether solar-wind sputtering of the Martian atmosphere is a mechanism leading to significant mass loss}, Doi = {10.1038/272803a0}, Key = {1205543} } @misc{fds328744, Author = {HAFF, PK}, Title = {SPALLATION SPUTTERING BY FAST PROTONS}, Journal = {Bulletin of the American Physical Society}, Volume = {23}, Number = {4}, Pages = {564-564}, Year = {1978}, Key = {fds328744} } @misc{fds328745, Author = {CREWTHER, DP and HAFF, PK and KELLOGG, WK}, Title = {ENERGY SHARING IN SLOW ATOMIC-COLLISIONS IN BINARY MATERIALS}, Journal = {Bulletin of the American Physical Society}, Volume = {23}, Number = {1}, Pages = {101-102}, Year = {1978}, Key = {fds328745} } @article{1127815, Author = {Haff, PK}, Title = {A model for surface layer composition changes in sputtered alloys and compounds}, Journal = {Applied Physics Letters}, Volume = {31}, Number = {4}, Pages = {259-260}, Publisher = {AIP Publishing}, Year = {1977}, Month = {December}, ISSN = {0003-6951}, url = {http://dx.doi.org/10.1063/1.89652}, Keywords = {sputtering;surface structure;}, Abstract = {Under the assumption that extracted beam energy is quickly shared among secondary cascade members of all masses, we present a model which accounts quantitatively for recently observed equilibrium surface enrichments in heavy atoms following ion bombardment of alloys and compounds. Assuming strong radiation-driven diffusion, effects of which are directly observed, and given the time required to reach equilibrium, we can calculate the thickness Δx of the enriched layer. Alternatively, knowing Δx, a calculation of the equilibration time constant is possible.}, Doi = {10.1063/1.89652}, Key = {1127815} } @article{77120003324, Author = {Haff, PK and Switkowski, ZE}, Title = {Ion-beam-induced atomic mixing}, Journal = {Journal of Applied Physics}, Volume = {48}, Number = {8}, Pages = {3383-3386}, Publisher = {AIP Publishing}, Year = {1977}, Month = {December}, url = {http://dx.doi.org/10.1063/1.324179}, Keywords = {SURFACES;MICROANALYSIS;}, Abstract = {Calculations based on the diffusion model are presented of atomic mixing by ion bombardment. This mixing is assumed to have its basis, as does sputtering, in the collision cascades generated by the primary beam. Sharp interfaces within a target are seen to be smoothed by ion bombardment. Mixing may place fundamental limits on the resolution of ion microprobes.}, Doi = {10.1063/1.324179}, Key = {77120003324} } @article{1124904, Author = {Scalo, JM and Haff, PK and Switkowski, ZE and Tombrello, TA}, Title = {Sputtering by fast electrons}, Journal = {Physics Letters B}, Volume = {70}, Number = {1}, Pages = {137-140}, Publisher = {Elsevier BV}, Year = {1977}, Month = {September}, ISSN = {0370-2693}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1977DV04400034&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {carbon;electron impact;iron;sputtering;}, Abstract = {Calculations are presented of collision cascade and knockon contributions to sputtering induced by fast electrons. The sputtering yield for MeV electrons bombarding carbon and iron is found to be ≈10-7 to 10-6. Important erosion effects on astrophysical grains are possible. © 1977.}, Doi = {10.1016/0370-2693(77)90362-8}, Key = {1124904} } @article{1202092, Author = {Switkowski, ZE and Haff, PK and Tombrello, TA and Burnett, DS}, Title = {Mass fractionation of the lunar surface by solar wind sputtering}, Journal = {Journal of Geophysical Research}, Volume = {82}, Number = {26}, Pages = {3797-3804}, Publisher = {American Geophysical Union (AGU)}, Year = {1977}, Month = {September}, ISSN = {0148-0227}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1977DW03900013&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {isotope relative abundance;Moon;solar wind;}, Abstract = {The sputtering of the lunar surface by the solar wind is examined as a possible mechanism of mass fractionation. Simple arguments based on current theories of sputtering and the ballistics of the sputtered atoms suggest that most ejected atoms will have sufficiently high energy to escape lunar gravity. However, the fraction of atoms which falls back to the surface is enriched in the heavier atomic components in relation to the lighter ones. This material is incorporated into the heavily radiation-damaged outer surfaces of grains, where it is subject to resputtering. Calculations predict that an equilibrium surface layer, enriched in heavier atoms, will form with δ(<sup>18</sup>O)≈+20<sup>0</sup>/<sub>00</sub>≈δ(<sup>30</sup>Si) and that oxygen will be depleted on the surface layers of grains relative to the bulk composition by about 12.5%. These results are in fair agreement with experiment}, Doi = {10.1029/jb082i026p03797}, Key = {1202092} } @article{1112600, Author = {Haff, PK}, Title = {Low energy muonic hydrogen reactions with heavy atoms}, Journal = {Physics Letters A}, Volume = {62}, Number = {5}, Pages = {301-302}, Publisher = {Elsevier BV}, Year = {1977}, Month = {September}, ISSN = {0375-9601}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1977DT60000007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {muon capture;muonic atoms;}, Abstract = {Average s-wave cross-sections appropriate for liquid hydrogen temperatures are calculated with the aid of an in-coming wave boundary condition for the muon transfer process μ-p + Z → (μ-Z)* + p on heavy atoms. The surface-correlated nature of the heavy atom X-rays is emphasized. © 1977.}, Doi = {10.1016/0375-9601(77)90422-4}, Key = {1112600} } @article{1073512, Author = {Haff, PK and Vogel, P}, Title = {Transport properties of negative muons in matter}, Journal = {Physical Review A}, Volume = {15}, Number = {3}, Pages = {1336-1337}, Publisher = {American Physical Society (APS)}, Year = {1977}, Month = {January}, ISSN = {1050-2947}, url = {http://dx.doi.org/10.1103/PhysRevA.15.1336}, Keywords = {energy loss of particles;muon capture;muon probes;radiation chemistry;}, Abstract = {In deriving a formula for atomic capture ratios involving negative muons, Daniel postulates a model leading to a muon energy spectrum of a different character from that indicated by a more complete analysis. In this Comment we emphasize the dependence of the energy spectrum on both inelastic and capture processes, and suggest several experiments which may distinguish between different theoretical models. © 1977 The American Physical Society.}, Doi = {10.1103/PhysRevA.15.1336}, Key = {1073512} } @article{1055719, Author = {Haff, PK and Rodrigo, E and Tombrello, TA}, Title = {Muon transfer in gas targets}, Journal = {Annals of Physics}, Volume = {104}, Number = {2}, Pages = {363-379}, Publisher = {Elsevier BV}, Year = {1977}, Month = {January}, ISSN = {0003-4916}, url = {http://dx.doi.org/10.1016/0003-4916(77)90336-0}, Keywords = {atomic inelastic collisions;energy loss of particles;muonic atoms;nuclear bombardment targets;}, Abstract = {The transfer of a negative muon from a proton to a heavy atom Q, μ-p + Q → p + μ-Q, is treated in terms of a classical description of the μp trajectory. We discuss the muon transfer rate itself, the subsequent population of states in the atom Q, and the effects of electron screening. The polarizability of the μp atom emerges as a crucial factor in the transfer process. © 1977.}, Doi = {10.1016/0003-4916(77)90336-0}, Key = {1055719} } @article{fds281136, Author = {Haff, PK}, Title = {Low energy muonic hydrogen reactions with heavy atoms}, Journal = {Physics Letters A}, Volume = {62}, Number = {5}, Pages = {301-302}, Year = {1977}, ISSN = {0375-9601}, Abstract = {Average s-wave cross-sections appropriate for liquid hydrogen temperatures are calculated with the aid of an in-coming wave boundary condition for the muon transfer process μ-p + Z → (μ-Z)* + p on heavy atoms. The surface-correlated nature of the heavy atom X-rays is emphasized. © 1977.}, Key = {fds281136} } @article{fds281137, Author = {Scalo, JM and Haff, PK and Switkowski, ZE and Tombrello, TA}, Title = {Sputtering by fast electrons}, Journal = {Physics Letters B}, Volume = {70}, Number = {1}, Pages = {137-140}, Year = {1977}, ISSN = {0370-2693}, Abstract = {Calculations are presented of collision cascade and knockon contributions to sputtering induced by fast electrons. The sputtering yield for MeV electrons bombarding carbon and iron is found to be ≈10-7 to 10-6. Important erosion effects on astrophysical grains are possible. © 1977.}, Key = {fds281137} } @misc{fds328746, Author = {HAFF, PK and SWITKOWSKI, ZE and TOMBRELLO, TA and BURNETT, DS}, Title = {SOLAR-WIND SPUTTERING OF LUNAR-SURFACE}, Journal = {Bulletin of the American Physical Society}, Volume = {22}, Number = {4}, Pages = {538-538}, Year = {1977}, Key = {fds328746} } @misc{fds328747, Author = {HAFF, PK}, Title = {SURFACE ENRICHMENT INDUCED BY ION-BOMBARDMENT}, Journal = {Journal of the Electrochemical Society}, Volume = {124}, Number = {8}, Pages = {C291-C291}, Year = {1977}, Key = {fds328747} } @article{1004301, Author = {Haff, PK and Switkowski, ZE}, Title = {On the sputtering of binary compounds}, Journal = {Applied Physics Letters}, Volume = {29}, Number = {9}, Pages = {549-551}, Publisher = {AIP Publishing}, Year = {1976}, Month = {December}, ISSN = {0003-6951}, url = {http://dx.doi.org/10.1063/1.89180}, Keywords = {copper alloys;gold alloys;nickel alloys;platinum alloys;silicon alloys;sputtering;}, Abstract = {A simple physical model is presented to describe some aspects of the sputtering of compound targets. In particular, expressions are developed for the partial sputtering yields for binary systems in terms of the elemental sputtering rates, the stoichiometric concentrations, and surface binding energy. The partial yields depend nonlinearly on the bulk target concentrations. Comparison of the theoretical predictions with the data on sputtering of PtSi, NiSi, and Cu3Au indicates that the general features are well described.}, Doi = {10.1063/1.89180}, Key = {1004301} } @article{993008, Author = {Haff, PK}, Title = {Possible new sputtering mechanism in track registering materials}, Journal = {Applied Physics Letters}, Volume = {29}, Number = {8}, Pages = {473-475}, Publisher = {AIP Publishing}, Year = {1976}, Month = {December}, ISSN = {0003-6951}, url = {http://dx.doi.org/10.1063/1.89126}, Keywords = {energy loss of particles;ion beam effects;particle track visualisation;sputtering;}, Abstract = {The "ion explosion" model of track production in dielectric materials in investigated as a possible source of sputtered particles at high bombarding energies.}, Doi = {10.1063/1.89126}, Key = {993008} } @article{893235, Author = {Wilets, L and Tuerpe, DR and Haff, PK}, Title = {Calculation of the mass parameter in the theory of self-cranked generator coordinates}, Journal = {Physical Review C}, Volume = {12}, Number = {6}, Pages = {2088-2093}, Publisher = {American Physical Society (APS)}, Year = {1975}, Month = {January}, ISSN = {0556-2813}, url = {http://dx.doi.org/10.1103/PhysRevC.12.2088}, Keywords = {nuclear mass;nuclear shape;nuclear theory;nuclei with 90⩽a⩽149;}, Abstract = {The self-cranked generator coordinate (SCGC) method of Haff and Wilets, together with constrained Hartree-Fock-Bogoliubov wave functions, has been used to calculate the mass parameter BQ for quadrupole deformations. A simple ansatz reduces the required integrals to a form similar to that required in Hartree-Fock calculations, and the same matrix elements of the Hamiltonian occur in both cases. The results are sensitive to numerical approximations and care must be exercised to maintain accuracy. Since the SCGC method adds another variational function, the energy is lowered relative to the usual generator coordinate method, and hence BQ is increased. For a particular sample calculation, the correction more than doubled BQ. NUCLEAR STRUCTURE Self-cranked generator coordinate method employed to calculate quadrupole mass parameter and potential energy. Constrained Hartree-Fock-Bogoliubov wave functions. Ru108. © 1975 The American Physical Society.}, Doi = {10.1103/PhysRevC.12.2088}, Key = {893235} } @article{864882, Author = {Vogel, P and Haff, PK and Akylas, V and Winther, A}, Title = {Muon capture in atoms, crystals and molecules}, Journal = {Nuclear Physics A}, Volume = {254}, Number = {2}, Pages = {445-479}, Publisher = {Elsevier BV}, Year = {1975}, ISSN = {0375-9474}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1975AZ72200017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92}, Keywords = {energy loss of particles;mesic and muonic atoms;muon capture;}, Abstract = {The slowing down and capture of negative muons in solids is discussed on the basis of classical equations of motion where the energy dissipation is described in terms of frictional forces. Transport equations determining the energy distribution of the muons in the target are formulated and solved for various models. Using a statistical model of the atom it is shown that the muons are captured typically at energies of a few tens of electron volts, that the angular momentum distribution of the muons at capture is almost statistical, and that this distribution is not expected to be qualitatively changed by the subsequent cascade to the tightly bound orbits. In mixtures of atoms with atomic numbers Z1 and Z2 the capture ratio is to a good approximation proportional to the atomic concentration and, in the statistical model, proportional to ( Z1 Z2) 7 6. Calculations are also performed with more accurate atomic models, and it is shown that capture ratios as well as angular momentum distributions are influenced by the ionicity of the atomic bonds and the atomic shell structure. No systematic study of these effects has been made but the few results obtained seem to be in reasonable agreement with experiments. © 1975.}, Doi = {10.1016/0375-9474(75)90230-4}, Key = {864882} } @misc{fds328748, Author = {HAFF, PK and VOGEL, P and AKYLAS, V and WINTHER, A}, Title = {MUON-CAPTURE IN GASES, GAS-MIXTURES, AND CRYSTALS}, Journal = {Bulletin of the American Physical Society}, Volume = {20}, Number = {1}, Pages = {91-91}, Year = {1975}, Key = {fds328748} } @misc{fds328749, Author = {HAFF, PK and GRIFFITH, JE and TOMBRELLO, TA}, Title = {QUANTUM CASCADE IN HIGHLY EXCITED MUONIC ATOMS}, Journal = {Bulletin of the American Physical Society}, Volume = {20}, Number = {4}, Pages = {702-702}, Year = {1975}, Key = {fds328749} } @article{686747, Author = {Haff, PK and Wilets, L}, Title = {Mass parameter in nuclear quadrupole motion}, Journal = {Physical Review C}, Volume = {10}, Number = {1}, Pages = {353-365}, Publisher = {American Physical Society (APS)}, Year = {1974}, Month = {January}, ISSN = {0556-2813}, url = {http://dx.doi.org/10.1103/PhysRevC.10.353}, Keywords = {BCS theory;nuclear collective model;nuclear mass;}, Abstract = {The self-cranked generator coordinate (SCGC) formalism described earlier for computing the mass parameter for collective nuclear motion is cast into a form containing no explicit reference to the Hamiltonian. The expression is then specialized to the nuclear model of deformed harmonic oscillators. The usual Gaussian overlap approximation is eschewed in favor of direct evaluation of the appropriate matrix elements. Exchange terms are handled by a diagrammatic technique. The validity of certain assumptions made in the derivation of the mass formula is tested numerically. The effects of pairing and of short-range Jastrow correlations are investigated. The SCGC mass parameter is computed for several N=Z nuclei and found to be smaller than either the cranking or the irrotational values, if no correlations are included. The inclusion of short-range correlations is shown to lead to important changes in the value of the mass parameter. NUCLEAR STRUCTURE Quadrupole mass parameter calculated. Self-cranked generator coordinate formalism. Correlations included. Compared to irrotational flow values. © 1974 The American Physical Society.}, Doi = {10.1103/PhysRevC.10.353}, Key = {686747} } @article{695562, Author = {Griffith, JE and Haff, PK and Tombrello, TA}, Title = {Energy levels of highly excited muonic atoms}, Journal = {Annals of Physics}, Volume = {87}, Number = {1}, Pages = {1-16}, Publisher = {Elsevier BV}, Year = {1974}, Month = {January}, ISSN = {0003-4916}, url = {http://dx.doi.org/10.1016/0003-4916(74)90444-8}, Keywords = {angular momentum theory;atomic structure;mesic and muonic atoms;}, Abstract = {Energy levels of muonic atom states with high principal quantum number are examined. A Thomas-Fermi type treatment is used in all but the lightest atoms to take account of the effects of electron shielding. Transition energies of the muon are compared to electron binding energies, and implications for muon lifetimes are discussed. The splitting of angular momentum substates is explicitly studied; transitions with no change in principal quantum number are unlikely to be important. Effective charges for the muon are computed. The possibility of an absorptive component of the muon potential is raised. © 1974.}, Doi = {10.1016/0003-4916(74)90444-8}, Key = {695562} } @article{687073, Author = {Haff, PK and Tombrello, TA}, Title = {Negative muon capture in very light atoms}, Journal = {Annals of Physics}, Volume = {86}, Number = {1}, Pages = {178-192}, Publisher = {Elsevier BV}, Year = {1974}, Month = {January}, ISSN = {0003-4916}, url = {http://dx.doi.org/10.1016/0003-4916(74)90435-7}, Keywords = {helium atoms;hydrogen neutral atoms;lithium;mesic and muonic atoms;muon capture;}, Abstract = {The transition rates for unbound muons to be captured into atomic bound states are calculated as functions of (1) incident muon center-of-mass energy, (2) muon principal quantum number n, and (3) muon (final) angular momentum l, for the hydrogen, helium, and lithium atoms. These rates reflect differences in electron binding energies. At muon energies of several hundred electron volts, lithium K-shell electrons are more likely to be ejected than the L-shell electron, while this behavior is reversed for energies ≲ 10 eV. However, in each case when the capture rate is folded with a muon stopping power function, the result is that more than half of the unbound muons are absorbed above 75 eV. Implications for experiments which look at muon transfer processes are noted. © 1974.}, Doi = {10.1016/0003-4916(74)90435-7}, Key = {687073} } @article{fds304958, Author = {Haff, PK and Vogel, P and Winther, A}, Title = {Capture of negative muons in atoms}, Journal = {Physical Review A}, Volume = {10}, Number = {4}, Pages = {1430-1432}, Publisher = {American Physical Society (APS)}, Year = {1974}, Month = {January}, ISSN = {1050-2947}, url = {http://dx.doi.org/10.1103/PhysRevA.10.1430}, Abstract = {The frictional force derived from the stopping power of an electron gas is used in the classical equation of motion for the negative muons. We calculate the energy spectrum of the captured muons and the angular momentum distribution of muons at the energy of the electronic K orbit. The resulting P(l) distribution closely resembles the statistical 2l+1 distribution. © 1974 The American Physical Society.}, Doi = {10.1103/PhysRevA.10.1430}, Key = {fds304958} } @article{724100, Author = {Haff, PK and Vogel, P and Winther, A}, Title = {Capture of negative muons in atoms}, Journal = {Phys. Rev. A, Gen. Phys. (Usa)}, Volume = {10}, Number = {14}, Pages = {1430-1432}, Year = {1974}, ISSN = {1050-2947}, url = {http://dx.doi.org/10.1103/PhysRevA.10.1430}, Keywords = {mesic and muonic atoms;}, Abstract = {The effect of the collisions experienced by a muon moving through an atom may be described by introducing a frictional force in the classical equations of motion. In the region of the electronic K shell, the Auger transitions should be treated quantum-mechanically. This calculation of the energy spectrum of the captured muons and the angular momentum distributions of muons at the electronic K orbit includes the interrelation between the stopping power of the electron gas and capture. There is a close resemblance between the P(L) distribution of angular momentum and the statistical 2L+1 distribution}, Doi = {10.1103/PhysRevA.10.1430}, Key = {724100} } @article{510640, Author = {Haff, PK and Wilets, L}, Title = {Microscopic theory of nuclear collective motion}, Journal = {Physical Review C}, Volume = {7}, Number = {3}, Pages = {951-968}, Publisher = {American Physical Society (APS)}, Year = {1973}, Month = {January}, ISSN = {0556-2813}, url = {http://dx.doi.org/10.1103/PhysRevC.7.951}, Keywords = {nuclear collective model;}, Abstract = {A generalization of the Hill-Wheeler generator coordinate method is applied to collective deformations. The intrinsic wave function is constrained (as in constrained Hartree-Fock) to be characterized not only by a given deformation, but also by a deformation velocity. This is effected by a simple ansatz which involves operation on the singly constrained wave function by an exponentiated single-particle deformation operator containing an arbitrary function β(α), where α is the collective variable. The expectation value of the energy is minimized with respect to both β(α) and the Hill-Wheeler projection function f(α). This leads to an integral equation for f which, upon invoking the collective nature of the intrinsic states, may be approximated by a second-order differential equation in the deformation coordinate αQ. In order to reduce this equation to the Schrödinger form, certain assumptions are introduced with regard to the approximate form of f. This procedure leads to two different differential equations for f and to two mass parameters. One is valid in the classical region and one in the classically inaccessible tunneling region. This is to be contrasted to the cranking model where sufficient energy must always be available to drive the system. The expressions for the mass parameter are given in terms of expectation values of few-body operators. The case of uniform translation of the nucleus as a whole is studied in detail. The generalized Hill-Wheeler method as described above produces the correct mass (= total nuclear mass). This rigorous reproduction of a known result allows the study of approximations which become necessary for the general case of deformations. Comments are made about the potential energy of deformation surface, which is expected to lie lower than the expectation value of the Hamiltonian. © 1973 The American Physical Society.}, Doi = {10.1103/PhysRevC.7.951}, Key = {510640} } @article{fds281133, Author = {Haff, PK and Eisenberg, JM}, Title = {Dynamic nuclear effects in pionic and kaonic atoms}, Journal = {Physics Letters B}, Volume = {33}, Number = {2}, Pages = {133-136}, Publisher = {Elsevier BV}, Year = {1970}, Month = {September}, ISSN = {0370-2693}, url = {http://dx.doi.org/10.1016/0370-2693(70)90281-9}, Abstract = {Corrections have been calculated to absorption widths in pionic and kaonic atoms due to the admixture of excited nuclear states. Effects as large as 12% and 27% are indicated for pionic and kaonic atoms, respectively. © 1970.}, Doi = {10.1016/0370-2693(70)90281-9}, Key = {fds281133} } | |
Duke University * Faculty * Staff * Reload * Login |