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SPECTRAL CHARACTERIZATION OF TISSUES MICROSTRUCTURE BY ULTRASOUNDS - A STOCHASTIC APPROACH

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 1990年第5期37卷 448-456页

作者： LANDINI, L VERRAZZANI, L UNIV PISA INST ELECTR & TELECOMMUNI-56100 PISAITALY

A model of the echo formation process from tissues is suggested, in order to relate microstructural features to ultrasonic spectral signatures. The tissue is modeled as a collection of ideal randomly distributed scatterers, filtered by a time-invariant system representing the measurement apparatus and the average properties of the scattering medium, to obtain the backscattered signal. The gamma distribution has been assumed to describe the process, because it offers a flexible approach to approximating the parametric regularity of the scatterers. According to the model the spectral characteristics of the backscattered signal are strictly correlated with the spatial architecture and can be related to the gamma distribution parameters, i.e. interdistance and order. The model has been tested by simulating practical situations, in order to prove its validity and to test the procedure for estimating model parameters from actual data. The correspondence of experimental results obtained from tissues of different degrees of regularity with the simulated results confirms the effectiveness of the model for tissue characterization studies.

关键词： average performance tissue characterization Ultrasonic Waves model parameters stochastic approach measurement apparatus Time invariant systems distributed parameter Gamma Distribution order

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ASSESSING THE INVERSE GAUSSIAN DISTRIBUTION ASSUMPTION

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IEEE TRANSACTIONS ON RELIABILITY 1990年第3期39卷 352-355页

作者： EDGEMAN, RL Colorado State University Fort Collins USA

Two easily applied goodness-of-fit tests for the inverse Gaussian distribution are discussed. One of these tests is the familiar Kolmogorov-Smirnov one-sample test that is applied when the form of a probability distribution is completely specified. When the parameters of the distribution are unknown, as is more typical, the Kolmogorov-Smirnov test cannot be directly applied. In this instance, a transformation that uses a distributional result relating the Student-t distribution to the inverse Gaussian distribution allows the Lilliefors test of normality to be adapted to test the inverse Gaussian distribution assumption.

关键词： Inverse Student's t-distribution Gaussian distribution Probability distribution distributed parameter

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Nonlinear Analysis of Dynamics and Control of Interconnected Systems with distributed parameters

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IFAC Proceedings Volumes 1989年第4期22卷 419-426页

作者： V.M. Matrosov Irkutsk Computing Centre of the Siberian Brunch of the USSR Academy of Sciences USSR

The paper presents some results on development and application of the method of vector Lyapunov functions to the nonlinear analysis of different dynamical properties of interconnected control systems with distributed parameters. These results were obtained by the author and his coworkers at the Irkutsk Computing Centre of the Siberian Branch of the USSR Academy of Sciences.

关键词： Interconnected system vector Lyapunov function comparison method optimal control distributed parameter nonlinear dynamics

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THE COMPUTATION OF VISIBLE-SURFACE REPRESENTATIONS

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1988年第4期10卷 417-438页

作者： TERZOPOULOS, D Schlumberger Palo Alto Res. CA USA

A computational theory of visible-surface representations is developed. The visible-surface reconstruction process that computes these quantitative representations unifies formal solutions to the key problems of: (1) integrating multiscale constraints on surface depth and orientation from multiple-visual sources; (2) interpolating dense, piecewise-smooth surfaces from these constraints; (3) detecting surface depth and orientation discontinuities to apply boundary conditions on interpolation; and (4) structuring large-scale, distributed-surface representations to achieve computational efficiency. Visible-surface reconstruction is an inverse problem. A well-posed variational formulation results from the use of a controlled-continuity surface model. Discontinuity detection amounts to the identification of this generic model\'s distributed parameters from the data. Finite-element shape primitives yield a local discretization of the variational principle. The result is an efficient algorithm for visible-surface reconstruction.

关键词： efficient algorithm representations Interpolation Surface reconstruction discontinuities distributed parameter

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MATHEMATICAL-MODELING OF 3-PHASE ELECTRODE SALT-BATH FURNACE WITH THE TWO-DIMENSIONAL ELECTRIC-FIELD

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ARCHIV FUR ELEKTROTECHNIK 1988年第1期71卷 19-25页

作者： JANDA, S KALIC, D Tehnicki fakultet

After a short historical survey of the attempts to solve the problem of designing and determining the dimensions of a three-phase electrode salt-bath furnace, the authors apply the theory of the three-phase transmission line with uniformly distributed parameters to the phenomena in the electrode furnace. Taking all necessary boundary conditions and permissible simplifications, formulae for most widely sprcad types of the furnaces are derived, which allow the calculation of input admittance and input power of the furnace, as well as other important electric quantities.

关键词： mathematical modeling input admittance Electrodes Furnaces Electric fields Boundary conditions distributed parameter PHENOMENON

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VERTICAL MOTION DIAGNOSTICS RELATED TO Q-VECTORS, AND THE REORGANIZATION OF A COLD FRONTAL SYSTEM

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METEOROLOGY AND ATMOSPHERIC PHYSICS 1988年第2期39卷 65-73页

作者： TAPP, RG 1. Bureau of Meteorology Research Centre Gr-O Box 1289K 3001 Melbourne Australia

Estimates of vertical motion obtained by explicit solution of the quasi-geostrophic omega equation expressed in terms of Q-vectors (Hoskins et al., 1978) were compared with qualitative estimates based on the divergence of Q-vectors. The horizontal distributions of each were broadly similar, but differed in their detail. At any level, the relative magnitudes of centres of vertical motion varied between the parameters. The precise locations of the main centres also differed. Greater differences existed in the vertical distributions of the parameters. The divergence ofQ andF _Q of Hoskins et al. (1978) both reached maximum values in upper levels, whereas peak values of ω occurred in middle levels. A vertical distribution similar to ω was achieved ifF _Q was divided by a stability parameter. The diagnosed vertical velocities appeared consistent with the restructuring of a summertime cold front as it crossed waters south of Australia.

关键词： Diagnosis divergence Reorganisation Explicit Solution Divergence Divergence vertical motion cold front maximum value divergence Vertical distribution distributed parameter

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CALCULATION OF THE HEAT-TRANSFER COEFFICIENT FOR FREE LAMINAR CONVECTION ON VERTICAL CYLINDERS USING THE INTEGRAL METHOD

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WARME UND STOFFUBERTRAGUNG-THERMO AND FLUID DYNAMICS 1988年第3-4期22卷 147-150页

作者： SUPPANZ, N 1. Fachbereich Versorgungs- und Energietechnik Luxemburger Str. 10 1000 Berlin 65

Solutions of the momentum and energy boundary-layer equations for heat transfer on vertical cylinders are presented. The velocity and temperature distribution as developed by Eckert have been applied. The parameters of the distributions on the cylinder are related to those of an equivalent wall having corresponding height and similar boundary conditions. With such assumptions the boundary-layer equations can be solved. The Nusselt Number as determined corresponds well with that calculated using numerical methods.

关键词： Cylinders Heat transfer Momentum Boundary conditions distributed parameter speed Equation Temperature distribution Solutions Vertical cylinder Cylinders Numerical methods Nusselt number

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ELASTIC-SCATTERING OF POLARIZED ELECTRONS FROM MERCURY AND XENON

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JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 1986年第21期19卷 3539-3557页

作者： BERGER, O KESSLER, J Phys. Inst. Munster Univ. West Germany

Polarised electrons have been scattered elastically from mercury and xenon. The angular distribution of the parameters that describe the change in the electron polarisation caused by the scattering process has been measured in the energy range from 25 to 150 eV for mercury and from 40 to 350 eV for xenon. With these parameters, in conjunction with the absolute differential cross section, a complete analysis of the scattering amplitudes with respect to their magnitudes and their relative phase is performed for xenon.

关键词： Scattering elastic scattering ENERGY RANGE Electrons Xenon electron polarization distributed parameter mercury

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DISTRIBUTION OF THE HEAT AND CURRENT FLUXES IN GAS TUNGSTEN ARCS

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METALLURGICAL TRANSACTIONS B-PROCESS METALLURGY 1985年第4期16卷 841-846页

作者： TSAI, NS EAGAR, TW MIT DEPT MAT SCI & ENGNCAMBRIDGEMA 02139

The distribution of heat flux on a water-cooled copper anode as a function of welding process parameters has been determined experimentally following an experimental technique developed previously. The results indicate that arc length is the primary variable governing heat distribution and that the distribution is closely approximated by a gaussian function. The half width of the heat flux is defined by a distribution parameter, σ, which was determined from the experimental data and is expressed as a function of arc length, current, and electrode tip angle. The distribution parameter, σ, increases from 1.5 mm to 3.6 mm as the arc length increases from 2 mm to 9 mm for a 100 A arc. The experimental data also show that arc energy transfer efficiency is greater than 80 pct on the water-cooled anode which is much higher than has been measured in the presence of a molten metal pool. For this reason, it is believed that the distribution of the heat flux and not the magnitude is the most useful information obtained in this study. The effect of helium additions to the argon on the heat distribution is also reporte

关键词： ELECTRIC ARC Arc length welding process parameters Heat flux copper anode half-value width flux arcs distributed parameter liquid metals arc heat chip angle TUNGSTEN INERT GAS WELDING Heat distribution

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ADDITION OF A LARGE NUMBER OF IDENTICAL ANGULAR MOMENTA - STATISTICAL DISTRIBUTIONS

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JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL 1979年第12期12卷 2329-2335页

作者： MIKHAILOV, VV Kazan Phys.&Tech. Inst. Acad. of Sci. Kazan USSR

The quantum mechanical addition of an arbitrary (very large) number of identical angular momenta is considered. The resulting states jm usually occur many times. The corresponding multiplicities Pjand Qmare investigated. Several explicit formulae for Qmare given. The asymptotic approximations for multiplicities Pjand Qm, which are the Wigner and Gauss distributions respectively, are derived. All parameters of the distributions are explicitly obtained. A comparison of theoretical multiplicities with the exact ones is made when the number of angular moments is relatively small.

关键词： Explicit formula Angle law of large numbers Gauss equation Gauss Moment of force Arbitrary Graham's number Angular momentum asymptotic distributed parameter

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