100,574 research outputs found
Joshua Davis: Author of Spare Parts
No full textCitation: K-State First (2016). Joshua Davis: Author of Spare Parts [Flier]. Manhattan, Kansas: K-State First.Flyer advertising Joshua Davis's author talk at Kansas State University
Group Theoretic Methods and Similarity Solutions of the Savage-Hutter Equations
No full textWe consider the spatially one-dimensional time dependent system of equations, obtained by Savage and Hutter, which describes the gravity-driven free surface flow of granular avalanches. All similarity solutions of this system are found by means of group analysis. The family of solutions which are invariant to stretching transformations is investigated in greater detail. Explicit solutions are constructed in three cases and their physical interpretation is given. © Springer-Verlag Berlin Heidelberg 2003
Steven Johnson Author Talk Poster
No full textK-State Book NetworkA poster advertising an author talk by Steven Johnson at Kansas State University on September 3, 2014. Steven Johnson's book "The Ghost Map" was the 2014-2015 common book
Group Theoretic Methods and Similarity Solutions of the Savage-Hutter Equations
No full textWe consider the spatially one-dimensional time dependent system of equations, obtained by Savage and Hutter, which describes the gravity-driven free surface flow of granular avalanches. All similarity solutions of this system are found by means of group analysis. The family of solutions which are invariant to stretching transformations is investigated in greater detail. Explicit solutions are constructed in three cases and their physical interpretation is given. © Springer-Verlag Berlin Heidelberg 2003
Weather and Climate
No full textEighty Years of Weather and Climate at Toledo, Ohio by Harry K. Hutter. Reprinted from The Ohio Journal of Science Vol. LII, No. 2, March, 1952
Variations of porosity in a sheared pressurized layer of saturated soil induced by vertical drainage of water
No full textInternational audienceWe use the mixture model of soil saturated by a fluid, as developed by dell'Isola & Hutter and applied to an isothermal steady simple shear flow pressed and drained by a steady flow of water from above. The governing equations are reduced to a single second-order ordinary differential equation (ODE) for the solid-volume fraction; its coefficients depend on the fluid viscosity and the thermodynamic pressure. The coefficients of this ODE give rise to the application of perturbation techniques; the solutions constructed in this way demonstrate that when the thermodynamic pressure is ignored, the solid-volume profile varies unrealistically largely over the layer thickness. Furthermore, when the vertical fluid convective acceleration terms are incorporated, they give rise to a 'destabilizing' mechanism in the sense that a boundary layer over which large changes of the solid-volume fraction arise and which is located where the draining fluid enters may flip to the exit boundary, and so make effective fluidities against shear deformations large. So, depending on the amount of water flow through the layer, the horizontal shearing to prescribed shear tractions may be small or large. For ice-sheet flow situations on soft beds, the flow rates achieving this flip are of the order of a few tens of centimetres per year and are, thus, fairly realistic
Methods of similitude in granular avalanche flows
No full textSnow avalanches are relatively dry and dense granular hows for which the Savage-Hutter (SH) equations have been demonstrated to be an adequate mathematical model. We review these equations and point out for which cases the equations have been tested against laboratory experiments. Since the equations are scale invariant and because agreement with experiments is good, laboratory experiments can be used to test realistic flows. This is detailed in this paper. We demonstrate how shocks are formed when dilatational how states merge into compacting states and show that shock formation is an essential mechanism in flows against obstructions. We finally apply the theory of similitude to the design of a projected avalanche protection structure of the Schneefernerhaus at the Zugspitze
Natural variation in Drosophila melanogaster
No full textThis work is dedicated to studying natural variation in D. melanogaster at the DNA sequence and gene expression level. In addition I present a new version of the DNA polymorphism analysis program VariScan, which includes significant improvements.
In CHAPTER 1 I describe a genome scan of single nucleotide polymorphism in two natural D. melanogaster populations (from Africa and Europe) on the third chromosome. Together with polymorphism data previously published for the X chromosome of the same populations, this allows a comparative study of the polymorphism patterns of the X chromosome and an autosome. The frequency spectrum of mutations and the patterns of linkage disequilibrium are investigated. The observed patterns indicate that there is a significant difference in the behavior of the two chromosomes, as has already been suggested by previous studies. To uncover the reasons for this a coalescent based maximum likelihood method is applied that incorporates the effects of demographic history and unequal sex ratios. For the African population the differential behavior of the chromosomes can be explained by its demographic history and an excess of females. In Europe, a population bottleneck and an excess of males alone cannot explain the patterns we observe. The additional action of positive selection in this population is proposed as a possible explanation.
In CHAPTER 2 I investigate the variation in gene expression of the two aforementioned populations. Whole-genome microarrays are used to study levels of expression for 88% of all known genes in eight adult males from both populations. The observed levels of expression variation are equal in Africa and Europe, despite the fact that DNA sequence variation is much higher in Africa. This is evidence for the action of stabilizing selection governing levels of expression polymorphism. Supporting this view, genes involved in many different functions, and are therefore on strong selective constraint, show less variation than do genes with only few functions. The experimental design allows the search for genes which differ in their expression patterns between Europe and Africa and might therefore have undergone adaptive evolution. Detected candidates include genes putatively involved in insecticide resistance and food choice. Surprisingly, many genes over-expressed in Africa are involved in the formation and function of the flying apparatus.
In CHAPTER 3 I present version 2 of the program VariScan. This program was designed to analyse patterns of DNA sequence polymorphism on a chromosomal scale. The functionality of the core analysis tool, the wavelet decomposition, is described. In addition, multiple improvements to the previous version are presented. The program now supports the “pairwise deletion” option. This is essential for analysing data at the chromosome scale, since such data often contains incomplete information. It is now possible to add outgroup information, which allows the calculation of additional statistics. Furthermore, the separate analysis of different predefined chromosomal regions is added as an option. To increase the user friendliness, a graphical user interface is now included as part of the software package. Finally, VariScan is applied to published and computer-generated data and the ability of the wavelet-based analysis to uncover chromosomal regions with interesting DNA polymorphism patterns is demonstrated
Dilatancy and compaction around a cylindrical cavern leached-out in a fluid saturated salt rock
No full textAfluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formation under a hydrostatic stress is set under internal pressure that differs from the confining pressure. The fluid in the cavern and in the mixture is treated as ideal and the solid as elastic. The initial state of stress is a consequence of the outside pressure and the cavern pressure. Perturbing the cavern pressure induces small changes in the solid and fluid densities.We compute these fields as functions of the radial distance from the cavern centre and show that depending on the relative stress levels the (salt) formation experiences either a dilatation or a compaction that is concentrated in a boundary layer near the cavern wall. © 2005 Taylor & Francis Group, London
A numerical study of anisotropic, low Reynolds number, free surface flow for ice sheet modeling
No full textFew ice sheet flow models have been developed that solve the complete set of mechanical equations. Until now, these models were limited to isotropic conditions. We present here a two-dimensional, finite difference method capable of solving the equations for the steady flow of a viscous, incompressible, anisotropic fluid with a free surface under isothermal conditions. It is not a standard method, especially with respect to the time discretization of the numerical scheme, and converges for very low Reynolds numbers. This method is applied here to the planar flow of anisotropic ice over flat or irregular bedrock, with no-slip boundary conditions at the ice-bedrock interface. The results are presented here for Newtonian behavior in the vicinity of an ice divide. The ice is assumed to be isotropic at the ice sheet surface, with continuous and prescribed development of anisotropy with increasing depth. Going from isotropic to anisotropic situations, our results indicate that the free surface becomes flatter and the shear strain rates larger and more concentrated near the bedrock. The flow is less sensitive to variations of the bedrock topography in the anisotropic case than in the isotropic case. Furthermore, a new phenomenon appears in the anisotropic case: the partial stagnation of ice in the holes of the bedrock. These effects have significant consequences when dating the; ice. The isochrones obtained in the anisotropic case are flatter and the anisotropic ice is more than 10% younger above the bumps and more than 100% older within the holes than for the isotropic ice
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