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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4169-4176 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A synchrotron x-ray diffraction method is presented for structural investigations of interfaces between low-Z substrates and heavier liquids. The method, similar to methods used in neutron scattering, is based on illuminating the interface through the solid substrate. The backgrounds arising from bulk scattering and the signal-to-background ratio are estimated and compared with experimental results. An ultrahigh vacuum (UHV) setup is described in which the atomic arrangement and roughness of clean interfaces can be studied in situ. Our first results illustrate the possibilities for both out-of-plane and in-plane diffraction studies. The specular reflectivity of the Ga/diamond(111)-2×1 interface was measured for perpendicular momentum transfers up to 2.2 Å−1. In an in-plane study of Ga/Si(111)-7×7 the in-plane structure factor of Ga liquid within a depth of ∼50 Å was compared to the structure factor of the bulk liquid. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Boston, USA and Oxford, UK : Blackwell Publishers Inc
    Computational intelligence 17 (2001), S. 0 
    ISSN: 1467-8640
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: This paper introduces an application of a particular form of rough neural computing in signal analysis. The form of rough neural network used in this study is based on rough sets, rough membership functions, and decision rules. Two forms of neurons are found in such a network: rough membership function neurons and decider neurons. Each rough membership function neuron constructs upper and lower approximation equivalence classes in response to input signals as an aid to classifying inputs. In this paper, the output of a rough membership function neuron results from the computation performed by a rough membership function in determining degree of overlap between an upper approximation set representing approximate knowledge about inputs and a set of measurements representing certain knowledge about a particular class of objects. Decider neurons implement granules derived from decision rules extracted from data sets using rough set theory. A decider neuron instantiates approximate reasoning in assessing rough membership function values gleaned from input data. An introduction to the basic concepts underlying rough membership neural networks is briefly given. An application of rough neural computing in classifying the power system faults is considered.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 100 (1993), S. 79-93 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary It has long been recognized that fabric, i.e., the grain configuration in a domain, plays a significant role in the constitutive response of granular media. Here we establish that this effect has bearing on the suitability of non-associative plasticity laws that describe the observed deviation of the plastic strain rate, from the normal to the yield surface. It is known that when non-associated plasticity laws are used, uniqueness of the solution of the initial value problem cannot be proved. Here it is shown that the introduction of configurational entropy and temperature into the theory, gives rise to a thermodynamic framework, specifically athermoplastic potential, with respect to which the plasticity law is associative. However, the inelastic strain is the sum of a plastic and a configurational strain. While the plastic strain rate is still normal to the potential (yield) surface, the inelastic strain rate,which is what is measured in the laboratory, is not. It is further shown that despite the non-normality of the inelastic strain rate to the plastic potential surface, the solution of the coupled initial value — configurational diffusion problem is unique. In the process of development of the underlying configurational thermodynamics, the concept of configurational flux is introduced and a time indifferent configurational diffusion law is inferred on the basis of uniqueness requirements. Thus the foundation is laid for the mode of propagation of chaos in granular media.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 114 (1996), S. 1-25 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Associative plasticity theories do not predict correctly the volumetric plastic strain, in the course of plastic deformation, in the case of materials where the position and conformation of the yield surface are functions of the prevailing hydrostatic stress. Non-associative theories have been proposed and used to correct this deficiency. Such theories, however, lead to other serious difficulties. In this paper we establish clear criteria for the well-posedness of the initial, boundary/initial and boundary value problems when the plasticity theory is associative as well as non-associative. We further show cases where non-associativity leads to ill-posedness of these problems even when the material is not at failure. Specifically we demonstrate that the initial/boundary and boundary value problems either have no solution, or if they do, the solution is not unique. We also show by specific examples that the banding condition, i.e., the vanishing of the determinant of the acoustic tensor, is tantamount (a) to loss of hyperbolicity of the equation of motion and (b) lack of existence or loss of uniqueness of the solution of the boundary value problem, in certain situations. Finally, we show the existence of a fundamental criterion that governs the stability of infinitesimal as well as finite elastoplastic domains.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 15 (1991), S. 77-102 
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Thermodynamic and physical principles are applied in conjunction with the concepts of endochronic plasticity to develop a theory of constitutive behaviour of soils with dilatant capability. Three separate constitutive models are derived within the framework of the proposed theory, all capable of accounting for shear-volume coupling of soil within the context of endochronic plasticity. One specific model is singled out as the most appropriate on the basis of its analytical simplicity and the plausibility of its thermodynamic and physical foundations. A simple example is worked out for the purposes of illustration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2012-02-28
    Description: Finding explosive threats in complex environments is a challenge. Benign objects (e.g. rocks, plants and rubbish), ground surface variation, heterogeneous soil properties and even shadows can create anomalies in remotely sensed imagery, often triggering false alarms. The overarching goal is to dissect these complex sensor images to extract clues for reducing false alarms and improve threat detection. Of particular interest is the effect of soil properties, particularly hydrogeological properties, on physical temperatures at the ground surface and the signatures they produce in infrared imagery. Hydrogeological variability must be considered at the scale of the sensor's image pixels, which may be only a few centimetres. To facilitate a deeper understanding of the components of the energy distribution, a computational testbed was developed to produce realistic, process-correct, synthetic imagery from remote sensors operating in the visible and infrared portions of the electromagnetic spectrum. This tool is being used to explore near-surface process interaction at a fine scale to isolate and quantify the phenomena behind the detection physics. The computational tools have confirmed the importance of hydrogeology in the exploitation of sensor imagery for threat detection. However, before this tool's potential becomes a reality, several technical and organizational problems must be overcome.
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  • 7
    Publication Date: 1997-11-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
    Publication Date: 1999-02-22
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 9
    Publication Date: 1990-05-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2013-02-22
    Description: Due to the dynamic nature of the shallow subsurface, knowledge of soil thermal properties across a wide range of soil moisture and temperature conditions is necessary to accurately describe heat transport in many settings. Soil thermal properties are difficult to measure at high temperatures, however, due to the lack of suitable measurement devices and the potential for measurement-induced changes. Therefore, thermal property data are often scarce and incomplete and very often limited to specific soils. Due to this scarcity of accurate experimental data, empirical relationships often do not accurately predict the thermal properties of soils as a function of both soil moisture and temperature. In this study, thermal conductivity and diffusivity were measured for silica sands under loose and tight packing conditions and a field sand under varied water saturation and temperature. Several recent sensor-based technologies were integrated into a small cell modified to have a network of sampling ports, continuously monitoring water saturation, temperature, and soil thermal properties. For the test sands studied, data showed that the thermal conductivity and diffusivity increased noticeably for sample temperatures 〉50°C. At sample temperatures between 30 and 50°C, any change in thermal properties with temperature was small. Thermal conductivities measured in this study were compared with independent estimates made using empirical models from the literature. In general, good agreement was observed for most thermal conductivity data when proper fitting parameters were established, except at intermediate saturation values.
    Electronic ISSN: 1539-1663
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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