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  • 1
    Electronic Resource
    Electronic Resource
    Interpretation of slingram conductivity mapping in near-surface geophysics: using a single parameter fitting with 1D model (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 44 (1996), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Electrical conductivity mapping is a prerequisite tool for hydrogeological or environmental studies. Its interpretation still remains qualitative but advantages can be expected from a quantitative approach. However a full 3D interpretation is too laborious a task in comparison with the limited cost and time which are involved in the majority of such field studies. It is then of value to define the situations where lateral variations are sufficiently smooth for a 1D model to describe correctly the underlying features.For slingram conductivity measurements, criteria allowing an approximate 1D inversion are defined: these mainly consist of a limited rate of variation over three times the intercoil spacing.In geological contexts where the weathering has generated a conductive intermediate layer between the underlying sound rock and the soil, this processing can be applied to determine the thickness of the conductive layer from the apparent resistivity map when the other geoelectrical parameters are known. The examples presented illustrate this application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1996.tb00148.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Pattern study in the 2-D solutal convection above a Bridgman-type solidification front (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3149-3161 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We numerically investigate the two-dimensional (2-D) convective flow developing in the liquid phase above an alloy growing in the upward Bridgman configuration of directional solidification. Using a time-dependent approach, we are able to describe the various cycles of hysteresis that connect the different branches of stable steady solutions. The main trends of the present results show that the bifurcation diagram, composed of the branches, found in previous works for the partition coefficient k=0.3, remains qualitatively valid for k=1.1: for a small frontal width the leading primary bifurcation is subcritical, while a transcritical bifurcation occurs for larger front. We bring the new complementary feature that the subcritical bifurcation becomes supercritical when the front width tends to zero. Furthermore, for an intermediate frontal width, we address the question of the nature of upper stability limits on various stable steady branches. We show that the limit occurs via either a steady secondary bifurcation or a Hopf bifurcation that initiates an unsteady solution branch which is followed up to chaos. The related route is a subharmonic cascade. When following this chaotic branch, a striking relaminarization process towards a steady secondary branch occurs. Finally we shortly investigate the case of a twice larger frontal width, for which several cycles of hysteresis are equally reported. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869432
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Anilinium Hydrogen Monofluorophosphate, C6H8N+.HPO3F− (1995)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 1359-1361 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010827019401214X
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of traffic shaping in efficiently providing end-to-end performance guarantees (1996)
    Springer
    Telecommunication systems 5 (1996), S. 71-83 
    Details
    ISSN: 1572-9451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper reports new results concerning the capabilities of a family of service disciplines aimed at providing per-connection end-to-end delay (and throughput) guarantees in high-speed networks. This family consists of the class of rate-controlled service disciplines, in which traffic from a connection is reshaped to conform to specific traffic characteristics, at every hop on its path. When used together with a scheduling policy at each node, this reshaping enables the network to provide end-to-end delay guarantees to individual connections. The main advantages of this family of service disciplines are their implementation simplicity and flexibility. On the other hand, because the delay guarantees provided are based on summing worst case delays at each node, it has also been argued that the resulting bounds are very conservative which may more than offset the benefits. In particular, other service disciplines such as those based on Fair Queueing or Generalized Processor Sharing (GPS), have been shown to provide much tighter delay bounds. As a result, these disciplines, although more complex from an implementation point-of-view, have been considered for the purpose of providing end-to-end guarantees in high-speed networks. In this paper, we show that through “proper” selection of the reshaping to which we subject the traffic of a connection, the penalty incurred by computing end-to-end delay bounds based on worst cases at each node can be alleviated. Specifically, we show how rate-controlled service disciplines can be designed to outperform the Rate Proportional Processor Sharing (RPPS) service discipline. Based on these findings, we believe that rate-controlled service disciplines provide a very powerful and practical solution to the problem of providing end-to-end guarantees in high-speed networks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109727
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  • 5
    Electronic Resource
    Electronic Resource
    Cell versus message level performances in ATM networks (1996)
    Springer
    Telecommunication systems 5 (1996), S. 223-239 
    Details
    ISSN: 1572-9451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The goal of this paper is to provide some insight into the relations that exist between cell level and message level performance guarantees in the context of ATM networks. Cell level guarantees are typically what the network is capable of providing, while message level guarantees are the ones of interest to users. It is, therefore, important to understand how the two are related, and which factors influence this relation. There are many different performance measures that are of importance, and in this paper we try to touch on the (three) most relevant ones. This includes comparing cell and message loss probabilities, average cell and message delays, and cell and message jitter. Specifically, we show that cell and message loss probabilities can exhibit significant differences, which strongly depend on traffic characteristics such as peak rate and burst size, i.e., for a fixed cell loss probability, the message loss probability can greatly vary when peak rate and burst size change. One reason for this sensitivity, is that message loss depends on what happen toall the cells in a message. For delay and jitter, we also find that peak rate and burst size play a role in determining the relation between cell and message performance. However, this sensitivity is not as acute as with losses since message delay and jitter are typically determined by the performance seen by onlyone cell, the last cell in a message. In the paper, we provide quantitative examples that illustrate the range of behaviors and identify the impact of different parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109735
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  • 6
    Electronic Resource
    Electronic Resource
    COLLOCATION METHOD FOR CONVECTIVE FLOW INDUCED BY DIRECTIONAL SOLIDIFICATION IN A CYLINDER (1996)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 393-409 
    Details
    ISSN: 0271-2091
    Keywords: generalized Stokes problem ; Chebyshev spectral method ; thermosolutal convection ; directional solidification ; vertical Bridgman problem ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The paper presents a Chebyshev-Fourier collocation method for solving the unsteady 3D Navier-Stokes equations in a cylindrical domain. The numerical scheme uses primitive variables and the incompressibility constraint is satisfied by applying iteratively a correction to the pressure field. The method, due to Cahouët and Chabard (Int. j. numer. methods fluids,8, 869-895 (1988)) and originally developed in the framework of finite elements, is checked with respect to the present high-order approach. Several tests are carried out in Cartesian geometries, successively 2D and 3D, then a comparison is performed in a cylindrical domain with two different sets of radial collocation nodes: Gauss-Lobatto nodes and Gauss-Radau points. Although quite acceptable results are obtained with the latter chain, a general decrease in efficiency is noticeable in the collocation method. This is interpreted as the consequence of two factors: the collocation formulation is not symmetric and the Fourier analysis, used as heuristic guide by CahouMt and Chabard, loses its efficiency in a non-equidistant grid, especially in a cylindrical geometry.We present an application to the study of thermosolutal convection induced by unidirectional solidification of a binary alloy. The latter grows from a Pb-30%Tl liquid phase in a cylindrical crucible corresponding to the vertical Bridgman upward configuration. We study the influence of the flow patterns on the crystal composition.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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