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7th International Conference on Recent Advances in Space Technologies (RAST)

作者： Chelaru, Teodor-Viorel Chelaru, Adrian Enache, Vasile Univ Politehn Bucuresti Res Ctr Aeronaut & Space Ghe Polizu 1 Bucharest Romania INCAS Natl Inst Aerosp Res Elie Carafoli Bucharest 061126 Romania SC Electromecania Ploiesti SA Ploiesti Romania

ISBN: (纸本)9781479976973

This paper develop a calculus model based on dedicated experiment for an innovative Reaction Control System (RCS) using hybrid rocket engine technology. Our RCS uses several hybrid micro-thrusters with their thrust modulated by a separate control system. For RCS, each of the thrusters is able to burn a few minutes and its thrust is modulated within certain limits by controlling the oxidizer flow. These studies were presented in RAST 2013 and are based on our own experiments performed in Electromecanica Ploiesti. Based on this concept we achieve a calculation of the performances of the RCS and make a comparison between theoretical and experimental results. Conclusions and discussions will be focused on technological possibilities to improve RCS performance and possible areas of application of it.

关键词： reaction control system hybrid rocket motor nozzle vehicle numerical algorithm computation model combustion

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Electric potential arising from a point-source near a cylinder in layered earth structures: Design criteria for a modified marine heat-flow probe

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Exploration Geophysics 2001年第1期32卷 64-69页

作者： Yang, Jianwen Edwards, R.N. Centre for Ore Deposit Research University of Tasmania Hobart TAS 7001 GPO Box 252-79 Australia Geophysics Division Department of Physics University of Toronto Toronto ON M5S 1A7 Canada

A modified marine heat-flow probe has been proposed to conduct simultaneous measurements of thermal and electric properties of seafloor sediments. A major concern in the electric aspect is the shielding effect caused by an extremely conductive solid steel strength-member of the probe. To appraise the feasibility of the proposed probe in electric measurements, we develop a novel numerical algorithm to calculate potential and hence apparent resistivities arising from a point-source of current near a cylinder situated in layered earth structures. The scheme is validated against an analytical solution with respect to a uniform whole-space in the presence of the cylinder. Image theory is employed to transform the layered earth structures into the whole-space models. Model parameters are taken from the design blueprint. numerical computations for varieties of electrode configurations reveal that the dipole?dipole array suffers the smallest disturbance, and can be employed to directly measure the true electric properties of seafloor sediments as long as its electrode spacing is less than 10 cm. The electric properties are also measurable when the pole?dipole array or the Wenner array is used with the electrode spacing less than 5 cm. The pole?pole array is however not applicable. © 2001, CSIRO. All rights reserved.

关键词： Cylinder Electric potential Image theory Layered earth numerical algorithm Point source Resistivity

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A time-discretization scheme for coupled thermomechanical evolutions of Shape Memory Alloys

A time-discretization scheme for coupled thermomechanical ev...

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Smart Structures and Materials 2006 Conference

作者： Peigney, Michael Lab Cent Ponts & Chaussees Paris France

ISBN: (纸本)0819462233

In this Paper is introduced a time-discretization scheme for the numerical simulation of coupled thermomechanical. evolutions of SMA structures. A particular feature of this time-discretized problem is that its solutions can be expressed as the solutions of a variational problem. This variational formulation allows one to study the existence and unicity of solutions. The approach presented is applied to simulate the propagation of a martensitic zone in a circular cylinder under traction.

关键词： shape memory alloys thermomechanical coupling numerical algorithm

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The Coupled Model for Surface Modification of Titanium Nickelide

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LOBACHEVSKII JOURNAL OF MATHEMATICS 2023年第6期44卷 2317-2325页

作者： Kryukova, O. N. Knyazeva, A. G. Russian Acad Sci Siberian Branch Inst Strength Phys & Mat Sci Tomsk 634055 Russia

In this paper, a coupled model of coating modification placed on a substrate is proposed. The model takes into account the different channels of stress effect on the evolution of coating and transition zone composition. The coupled model of coated material modification by pulsed electron beam is formulated for the first time, with particular attention paid to the mutual influence of stresses arising from composition changes and diffusion transport. Examples of calculations for the Ta-TiN system are presented which demonstrate both qualitative and quantitative differences between coupled and uncoupled problems.

关键词： coupled model reaction rates residual stresses numerical algorithm

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Computation of Carson Formulas Using Piecewise Quadratic Approximation 25

Computation of Carson Formulas Using Piecewise Quadratic App...

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25th International Conference on Software, Telecommunications and Computer Networks (SoftCOM)

作者： Krolo, Ivan Vujevic, Slavko Modric, Tonci Univ Split FESB Dept Elect Power Engn Split Croatia

ISBN: (纸本)9781538632123

In this paper, an existing numerical algorithm for high-accurate computation of exact Carson formulas based on piecewise linear approximation is improved. Carson formulas are used for computing of per-unit-length (pul) self and mutual impedances of infinitely long parallel conductors. The proposed algorithm is based on piecewise quadratic approximation of kernel function and analytical integrations of approximated kernel function multiplied by the rest of two integrands. Using proposed algorithm, high-accurate results with desired computer machine n-digit accuracy can be easily obtained. Total number of sample points is significantly decreased with proposed algorithm in comparison with piecewise linear approximation. Results computed by two approximation methods are compared with high-accurate results computed by proposed numerical algorithm for large frequency range.

关键词： numerical algorithm Carson formulas self impedance mutual impedance piecewise quadratic approximation

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A New Saint-Venant Solver for SWMM 11th

A New Saint-Venant Solver for SWMM

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11th International Conference on Urban Drainage Modelling (UDM)

作者： Hodges, Ben R. Liu, Frank Rowney, A. Charles Univ Texas Austin Ctr Infrastruct Modeling & Management Austin TX 78712 USA IBM Res Austin TX USA

ISBN: (纸本)9783319998671;9783319998664

The next generation of the public domain Storm Water Management Model (SWMM) code needs to be able to effectively use parallelization of 1000 + threads for high-resolution simulation of large urban drainage systems. We propose a new explicit solution technique using a "no-neighbour" finite-volume algorithm. A no-neighbour algorithm is strictly limited in the design of its time/space discretization stencil to limit the communication bandwidth issues that typically cause codes to lose efficiency when applied over large numbers of parallel threads. Returning SWMM to an explicit solver creates a number of challenges for implementing the solution technique, but also raises some new possibilities for how the model can be used. In this work, we briefly describe the proposed algorithm and examine its performance in simulating a steep urban stream.

关键词： numerical algorithm Multi-threading parallel Saint-Venant equations

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An Operational Matrix Method for Solving a Class of Nonlinear Volterra Integro-Differential Equations by Operational Matrix Method

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International Journal of Applied and Computational Mathematics 2017年第4期3卷 3279-3294页

作者： Öztürk, Yalçın Gülsu, Mustafa Ula Ali KoÇman Vocational School Muğla Sıtkı Koçman University Muğla Turkey Department of Mathematics Faculty of Science Muğla Sıtkı Koçman University Muğla Turkey

In this paper, the improved Chebyshev operational matrix method is proposed to solve a class of nonlinear Volterra integro-differential equation. The main characteristic behind this approach is that it reduces such problems to ones of solving systems of algebraic equations. Some examples are included to demonstrate the validity and applicability of the this techinque. The only a small number of shifted Chebyshev polynomials is needed to obtain a satisfactory result. © 2017, Springer India Pvt. Ltd.

关键词： Approximation method Chebyshev polynomials Nonlinear Volterra integro-differential equations numerical algorithm Operational matrix method

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Solution of working space about the 4-DOF parallel mechanism by ADAMS

Solution of working space about the 4-DOF parallel mechanism...

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2nd International Conference on Advanced Materials Design and Mechanics (ICAMDM 2013)

作者： Zhang Ruihua Lishui Univ Lishui 323000 Zhejiang Peoples R China

ISBN: (纸本)9783037857977

This article is based on ADAMS software platform to solve working space of the 4-DOF parallel mechanism. Design a kind of 4-DOF parallel mechanism and establish virtual prototype on ADAMS software platform. Then through enumeration three branched chain parameters combination, even without the premise of kinematics positive solution, we can solve it working space using the forward solving method and get the branched chain parameter with the reference point position corresponding numerical relations. It greatly simplifies the solution of the working space of parallel mechanism, is more advantageous to parameter optimization and trajectory planning of parallel mechanism.

关键词： ADAMS 4-DOF parallel mechanism Working space Enumeration algorithms numerical algorithm Direct kinematics

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Improving Density Functional Theory: General Computation of Exact Exchange Holes and a New algorithm for Fast Gaussian Transform

Improving Density Functional Theory: General Computation of ...

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作者： Wang, Yiting Middle Tennessee State University

学位级别：Ph.D., Doctor of Philosophy

Exchange and correlation holes are unique quantum concepts for understanding the nature of electron interactions based on quantum conditional probabilities. Among those, the exact exchange hole is of special interest since it is derived rigorously from first principles without approximations and is often modeled by approximate exchange expressions of density functional theory. In this work, the algorithm for the computation of the exact exchange hole for a given reference point is developed and implemented for molecular orbitals in Gaussian basis functions. The formulas include the spherical surface integral of a Gauss function. A computationally concise algorithm is proposed for obtaining the expansion coefficients of polynomial terms when the coordinate system is transformed from Cartesian to spherical. The result expression includes a number of cases of elementary integrals, the most difficult integral can be formed by linearly combining modified Bessel functions of the first kind. Direct applications of the standard approach using Mathematica and GSL are found to be inefficient and limited in the range of the parameters for the Bessel function. We propose an asymptotic function for the Bessel function. The relative error of the asymptotic function is in the order of 1e-16 with the first five terms of the asymptotic expansion. This new capability is used to explore the extent to which current popular model exchange holes resemble or differ from the exact exchange hole. Point-wise accuracy of the exchange holes for isolated atoms is important in local hybrid schemes, real-space models of static correlation and other. We find in this vein that among the models tested here only the BR89 exchange hole seems more or less suitable for that purpose, while better approximations are still very much on demand. Analyzing the deviations of model exchange holes from the exact exchange hole in molecules like H2 and Cr2 upon bond stretching reveals new aspects of the left-right

关键词： Cardinal B-spline Density functional theory Exchange hole Fast Gaussian Transform numerical algorithm Modified Bessel function of the first kind

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Laminar flow stability in a mass force field

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Fluid Dynamics 1968年第5期3卷 26-29页

作者： Gol'dshtik, M.A. Sapozhnikov, V.A. Novosibirsk

A study is made of the stability of a certain class of velocity profiles in a two-dimensional channel on the basis of a new numerical algorithm for the solution of the Orr-Sommerfeld equation. A profile is found which has (in a certain sense) the property of maximum stability. In form this profile is very similar to the averaged velocity profile of turbulent flow in a two-dimensional pipe. © 1972 Consultants Bureau.

关键词： Velocity Profile Force Field Laminar Flow Average Velocity numerical algorithm

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