12 research outputs found
Recommended from our members
Rarefied particle motions on hillslopes - Part 4: Philosophy
Theoretical and experimental work (Furbish et al., 2021a, b, c) indicates that the travel distances of rarefied particle motions on rough hillslope surfaces are described by a generalized Pareto distribution. The form of this distribution varies with the balance between gravitational heating due to conversion of potential to kinetic energy and frictional cooling by particle-surface collisions. The generalized Pareto distribution in this problem is a maximum entropy distribution constrained by a fixed energetic "cost"- the total cumulative energy extracted by collisional friction per unit kinetic energy available during particle motions. The analyses leading to these results provide an ideal case study for highlighting three key elements of a statistical mechanics framework for describing sediment particle motions and transport: the merits of probabilistic versus deterministic descriptions of sediment motions, the implications of rarefied versus continuum transport conditions, and the consequences of increasing uncertainty in descriptions of sediment motions and transport that accompany increasing length scales and timescales. We use the analyses of particle energy extraction, the spatial evolution of particle energy states, and the maximum entropy method applied to the generalized Pareto distribution as examples to illustrate the mechanistic yet probabilistic nature of the approach. These examples highlight the idea that the endeavor is not simply about adopting theory or methods of statistical mechanics "off the shelf"but rather involves appealing to the style of thinking of statistical mechanics while tailoring the analysis to the process and scale of interest. Under rarefied conditions, descriptions of the particle flux and its divergence pertain to ensemble conditions involving a distribution of possible outcomes, each realization being compatible with the controlling factors. When these factors change over time, individual outcomes reflect a legacy of earlier conditions that depends on the rate of change in the controlling factors relative to the intermittency of particle motions. The implication is that landform configurations and associated particle fluxes reflect an inherent variability ("weather") that is just as important as the expected ("climate") conditions in characterizing system behavior. © Copyright:Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
Hack distributions of rill networks and nonlinear slope length-soil loss relationships
Surface flow on rilled hillslopes tends to produce sediment yields that scale nonlinearly with total hillslope length. The widespread observation lacks a single unifying theory for such a nonlinear relationship.We explore the contribution of rill network geometry to the observed yield length scaling relationship. Relying on an idealized network geometry, we formally develop probability functions for geometric variables of contributing area and rill length. In doing so, we contribute towards a complete probabilistic foundation for the Hack distribution. Using deterministic and empirical functions, we then extend the probability theory to the hydraulic variables that are related to sediment detachment and transport. A Monte Carlo simulation samples hydraulic variables from hillslopes of different lengths to provide estimates of sediment yield. The results of this analysis demonstrate a nonlinear yield length relationship as a result of the rill network geometry. Theory is supported by numerical modeling, wherein surface flow is routed over an idealized numerical surface and a natural surface from northern Arizona. Numerical flow routing demonstrates probability functions that resemble the theoretical ones. This work provides a unique application of the Scheidegger network to hillslope settings which, because of their finite lengths, result in unique probability functions. We have addressed sediment yields on rilled slopes and have contributed towards understanding Hack s law from a probabilistic reasoning. © 2021 BMJ Publishing Group. All rights reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
Rarefied particle motions on hillslopes - Part 3: Entropy
Theoretical and experimental work (Furbish et al., 2021a, b) indicates that the travel distances of rarefied particle motions on rough hillslope surfaces are described by a generalized Pareto distribution. The form of this distribution varies with the balance between gravitational heating, due to conversion of potential to kinetic energy, and frictional cooling, due to particle-surface collisions; it varies from a bounded form associated with rapid thermal collapse to an exponential form representing isothermal conditions to a heavy-tailed form associated with net heating of particles. The generalized Pareto distribution in this problem is a maximum entropy distribution constrained by a fixed energetic "cost"- the total cumulative energy extracted by collisional friction per unit kinetic energy available during particle motions. That is, among all possible accessible microstates - the many different ways to arrange a great number of particles into distance states where each arrangement satisfies the same fixed total energetic cost - the generalized Pareto distribution represents the most probable arrangement. Because this idea applies equally to the accessible microstates associated with net cooling, isothermal conditions and net heating, the fixed energetic cost provides a unifying interpretation for these distinctive behaviors, including the abrupt transition in the form of the generalized Pareto distribution in crossing isothermal conditions. The analysis therefore represents a novel generalization of an energy-based constraint in using the maximum entropy method to infer non-exponential distributions of particle motions. Moreover, the energetic costs of individual particle motions follow an extreme-value distribution that is heavy-tailed for net cooling and light-tailed for net heating. The relative contribution of different travel distances to the total energetic cost is reflected by the product of the travel distance distribution and the cost of individual particle motions - effectively a frequency-magnitude product. © Copyright:Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Oriented responses of carrot fly larvae, Psila rosae, to plant odours, carbon dioxide and carrot root volatiles
Sensitivity and photopigments of R1-6, a two-peaked photoreceptor, inDrosophila, Calliphora andMusca
Desempenho, características de carcaça e resultado econômico de cordeiros criados em creep feeding com silagem de grãos úmidos de milho Live weight gain, carcass traits and economic results on lambs fed with high moisture corn silage in creep feeding
Objetivou-se, com este trabalho, estudar níveis de substituição (0; 50 e 100%) do milho grão seco moído pela silagem de grãos úmidos de milho na ração de cordeiros alimentados em creep feeding. Vinte e quatro cordeiros Suffolk foram avaliados quanto ao desempenho, pesos e rendimentos das carcaças. Também foi realizada uma análise econômica. As rações foram fornecidas ad libitum, sendo suas sobras pesadas para o cálculo do consumo médio por animal. Ao atingirem 28 kg de peso vivo, os cordeiros foram submetidos a jejum por 16 horas e, então, novamente pesados para se obter o peso vivo ao abate. Após o abate, os animais foram eviscerados para se obterem os pesos e rendimentos de carcaça quente. As carcaças permaneceram por 24 horas em câmara de refrigeração, sendo novamente pesadas para se obterem os rendimentos de carcaça fria e as perdas por resfriamento. Os resultados revelaram que não houve efeito dos níveis de substituição sobre ganho médio diário de peso vivo, idade ao abate, pesos e rendimentos das carcaças quentes e frias, indicando que a silagem de grãos úmidos de milho pode ser utilizada em substituição ao milho moído na alimentação de cordeiros. Como o peso ao abate foi pré-fixado, as variações nas idades ao abate fizeram com que essa variável exercesse influência sobre os desempenhos, pesos e rendimentos e, quanto maiores essas idades, piores os resultados dos parâmetros avaliados. O tratamento com 50% de silagem de grãos úmidos apresentou os melhores resultados econômicos e o tratamento sem silagem de grãos úmidos foi o de menor rentabilidade.<br>The experiment was carried to study three levels (0, 50 e 100%) of high moisture corn silage replacing dry corn grain in rations of lambs fed in creep feeding. Twenty four Suffolk lambs were evaluated to live weight (LW) gain and carcasses dressing-outs percentage. It was performed an economical analysis too. Rations in creep feeding were fed ad libitum, and rests were weighed to obtain mean intake by treatment. When lambs reached 28 kg LW, lambs were submitted to 16 h fasting, and so were weighted again to check live weight at slaughter. After that, animals were eviscerated to obtain hot carcasses weights and dressing-out. After 24 h cooling, cold carcasses weight, dressing-out, and cooling loss were registered. Results showed that replacing levels did not affect lambs daily live weight gain, slaughter age, and hot and cool carcasses dressing-outs, showing that high moisture corn silage can replace dry corn grain in lambs feeding. Nevertheless, as slaughter weight was pre-established, individual variation of slaughter age caused that this variable affected animal performance, weights and dressing-outs. So, as later slaughter age, worst results of all studied parameters. Ration with 50% of high moisture corn silage showed better economical results and ration without high moisture corn silage showed less economical return