Modeling the environmental controls on tree water use at different temporal scales

Acknowledgements This study is part of the first author’s PhD projects in 2010–2014, co-funded by the National Centre for Groundwater Research and Training in Australia and the China Scholarship Council. We give thanks to Zijuan Deng and Xiang Xu for their assistance in the field. Constructive comments and suggestion from the anonymous reviewers are appreciated for significant improvement of the manuscript.Peer reviewedPostprin

Groundwater sapping channels: Summary of effects of experiments with varied stratigraphy

Experiments in the recirculating flume sapping box have modeled valley formation by groundwater sapping processes in a number of settings. The effects of the following parameters on sapping channel morphology were examined: surface slope; stratigraphic variations in permeability cohesion and dip; and structure of joints and dikes. These kinds of modeling experiments are particularly good for: testing concepts; developing a suite of distinctive morphologies and morphometries indicative of sapping; helping to relate process to morphology; and providing data necessary to assess the relative importance of runoff, sapping, and mass wasting processes on channel development. The observations from the flume systems can be used to help interpret features observed in terrestrial and Martian settings where sapping processes are thought to have played an important role in the development of valley networks

Improving the worthiness of the Elder problem as a benchmark for buoyancy driven convection models

An important trapping mechanism associated with the geosequestration of CO~2~ is that of dissolution into the formation water. Although supercritical CO~2~ is significantly less dense than water, experimental data reported in the literature show that the density of an aqueous solution of CO~2~ could be slightly greater. Under normal situations, the transfer of gas to solution is largely controlled by the relatively slow process of molecular diffusion. However, the presence of variable densities can trigger off gravity instabilities leading to much larger-scale convection processes. Such processes can potentially enhance rates of dissolution by an order of magnitude. Consequently there is a need for future performance assessment models to incorporate buoyancy driven convection (BDC). A major issue associated with BDC models is that of grid convergence when benchmarking to the Elder problem. The Elder problem originates from a heat convection experiment whereby a rectangular Hele-Shaw cell was heated over the central half of its base. A quarter of the way through the experiment, Elder (1967) observed six plumes, with four narrow plumes in the center and two larger plumes at the edges. As the experiment progressed, only four plumes remained. The issue is that depending on the grid resolution used when seeking to model this problem, modelers have found that different schemes yield steady states with either one, two or three plumes. The aim of this paper is to clarify and circumvent the issue of multiple steady state solutions in the Elder problem using a pseudospectral method

Suppression of low-frequency noise in two-dimensional electron gas at degenerately doped Si:P \delta-layers

We report low-frequency 1/f noise measurements of degenerately doped Si:P \delta-layers at 4.2K. The noise was found to be over six orders of magnitude lower than that of bulk Si:P systems in the metallic regime and is one of the lowest values reported for doped semiconductors. The noise was found to be nearly independent of magnetic field at low fields, indicating negligible contribution from universal conductance fluctuations. Instead interaction of electrons with very few active structural two-level systems may explain the observed noise magnitudeComment: 4 pages, 4 figure

Assessing Alternatives for Directional Detection of a WIMP Halo

The future of direct terrestrial WIMP detection lies on two fronts: new, much larger low background detectors sensitive to energy deposition, and detectors with directional sensitivity. The former can large range of WIMP parameter space using well tested technology while the latter may be necessary if one is to disentangle particle physics parameters from astrophysical halo parameters. Because directional detectors will be quite difficult to construct it is worthwhile exploring in advance generally which experimental features will yield the greatest benefits at the lowest costs. We examine the sensitivity of directional detectors with varying angular tracking resolution with and without the ability to distinguish forward versus backward recoils, and compare these to the sensitivity of a detector where the track is projected onto a two-dimensional plane. The latter detector regardless of where it is placed on the Earth, can be oriented to produce a significantly better discrimination signal than a 3D detector without this capability, and with sensitivity within a factor of 2 of a full 3D tracking detector. Required event rates to distinguish signals from backgrounds for a simple isothermal halo range from the low teens in the best case to many thousands in the worst.Comment: 4 pages, including 2 figues and 2 tables, submitted to PR

Optimal surface coating distribution on a femoral endoprosthesis

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994.Includes bibliographical references (leaves 112-117).by Craig A. Simmons.M.S

Hyper structures + visual programs = hyperprograms : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Computer Science at Massey University

This thesis describes an investigation into the integration of hyper-techniques with visual programming languages to support a multi-dimensional, minimally syntactic program representation. Programming involves two phases: first, forming a mental model of the problem solution; secondly, mapping the mental model onto a physical representation. The mental model is complex, syntax-free and multi-dimensional; in textual programming languages, the physical representation is complex, syntax-rich and single-dimensional. Performing the mapping is painstaking work which has more to do with easing compilation than with representing data manipulations. It is believed that a physical representation which better matches the programmer's mental model will significantly reduce the difficulty of generating programs. Modern computer systems combine powerful processors, and large memories with high-resolution graphics and powerful graphic input mechanisms. This ideally fits them for supporting the building and interpretation of complex multi-dimensional structures with minimal syntax. The Hyperprogramming paradigm exploits this capability. A hyperprogramming language uses different visual representations for different program dimensions - for example different visual vocabularies are appropriate for algorithms and subroutine nesting. Each view is carefully chosen to overlap the others minimally, and where overlap is essential, hyperlinks between views are provided to allow easy navigation between them, and to allow automatic updating of shared information. HyperPascal was developed using this philosophy, as a testbed for it. In creating a program, a HyperPascal programmer edits information in three separate views: the action window view, in which subroutines are each represented using a visual language based on structure diagrams the scope window view, in which declarations are stored in a nested structure corresponding to conventional subroutine nesting the forms window, in which the appearance of I/O can be designed using a WYSIWYG editor, free of the distractions of data processing specifications. A protoype of HyperPascal has been implemented, and a number of programs developed using it

Unstable density-driven flow in heterogenous porous media: A stochastic study of the Elder (1967b) "short heater" problem

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