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181.
The influence of lattice structure on the dynamic performance of metal hollow sphere agglomerates 总被引:1,自引:0,他引:1
This paper addresses the dynamic performances of partially bonded or unbonded metallic hollow sphere structure (MHSS). Under the condition that the densities of MHSS are the same, three morphologies, that is, simple cubic (SC), body-centered cubic (BCC) and face-centered cubic (FCC) are investigated to see the topological effect of lattice structure on the dynamic performance of MHS agglomerates. 相似文献
182.
Hypersonic aerospace vehicles are exposed to extreme flight conditions with heavy contour loads during their mission. Especially
at ridges and sharp corners, the wall heat flux and pressure may cause serious damage to the body. Sometimes, the surface
material cannot resist the high loading and fails completely.
In this work the laminar hypersonic flow over forward and backward facing steps is investigated by CFD techniques and the
results are compared with experimental data. The selected flow conditions correspond to cold hypersonic flow according to
the availability of experimental data. The Navier-Stokes equations in the high temperature gas approximation of a thermally
perfect gas in local equilibrium serve as the model for the physical problem. A multiblock finite-volume method is used to
discretize consistently all spatial derivatives appearing in the balance equations. A second order in space Godunov-type method
is utilized for the non-diffusive part of the governing equations whereas centered differences are used for the diffusive
part. Time integration is performed by a second order implicit scheme. In each time step, the resulting nonlinear system of
equations is solved by Newton's method employing a relaxation scheme based on conjugate gradients for the linear equation
system.
The results obtained permit a close insight into the physics of the flow problems under consideration and by this provide
valuable information for construction concepts of hypersonic vehicles. Besides a careful comparison of the numerical results
with experimental data, numerical aspects like the grid influence are addressed.
Received 9 November 1998 / Accepted 2 December 1999 相似文献
183.
184.
Hyoung Gwon Choi 《国际流体数值方法杂志》2012,68(7):887-904
In this paper, a least‐square weighted residual method (LSWRM) for level set (LS) formulation is introduced to achieve interface capturing in two‐dimensional (2D) and three‐dimensional (3D) problems. An LSWRM was adopted for two semi‐discretized advection and reinitialization equations of the LS formulation. The present LSWRM provided good mathematical properties such as natural numerical diffusion and the symmetry of the resulting algebraic systems for the advection and reinitialization equations. The proposed method was validated by solving some 2D and 3D benchmark problems such as those involving a rotating slotted disk, the rotation of a slotted sphere, and a time‐reversed single‐vortex flow and a deformation problem of a spherical fluid. The numerical results were compared with those obtained from essentially non‐oscillatory type formulations and particle LS methods. Further, the proposed LSWRM for the LS formulation was coupled with a splitting finite element method code to solve the incompressible Navier–Stokes equations, and then, the collapse of a 3D broken dam flow was well simulated; in the simulation, the entrapping of air and the splashing of the surge front of water were reproduced. The mass conservation of the present method was found to be satisfactory during the entire simulation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
185.
Tuo Zhao Kathryn Roeder Han Liu 《Journal of computational and graphical statistics》2013,22(4):895-922
Many statistical methods gain robustness and flexibility by sacrificing convenient computational structures. In this article, we illustrate this fundamental tradeoff by studying a semiparametric graph estimation problem in high dimensions. We explain how novel computational techniques help to solve this type of problem. In particular, we propose a nonparanormal neighborhood pursuit algorithm to estimate high-dimensional semiparametric graphical models with theoretical guarantees. Moreover, we provide an alternative view to analyze the tradeoff between computational efficiency and statistical error under a smoothing optimization framework. Though this article focuses on the problem of graph estimation, the proposed methodology is widely applicable to other problems with similar structures. We also report thorough experimental results on text, stock, and genomic datasets. 相似文献
186.
In this paper, the super-linearly and quadratically convergent strong sub-feasible method [J.L. Li, J.B. Jian, A superlinearly and quadratically convergent strongly subfeasible method for nonlinear inequality constrained optimization, OR Transactions, 7 (2) (2003) 21-34] for nonlinear inequality constrained optimization is improved, such that the iterative points can get into the feasible region after a finite number of iterations. As a result, a strict restricted condition can be overcome. Another two contributions of this paper are that a new bidirectional Armijo line search is presented and a lot of numerical comparison results are reported. 相似文献
187.
An integral approach for large deflection cantilever beams 总被引:1,自引:0,他引:1
Li Chen 《International Journal of Non》2010,45(3):301-305
A new integral approach is proposed to solve the large deflection cantilever beam problems. By using the moment integral treatment, this approach can be applied to problems of complex load and varying beam properties. This versatile approach generally requires only simple numerical techniques thus is easy for application. Treatment for typical loading and beam property conditions are presented to demonstrate the capability of this approach. 相似文献
188.
The paper presents several cost-effective modeling strategies that can be used by structural engineers in practice to determine the stresses in the spliced members. The computational efficiency and the modeling effort required for the several modeling options are also discussed. The deformation mechanisms and load transfer for several types of connections are illustrated. Optimization techniques are also presented to economize the computer time for connections with large number of bolts. Results are presented to compare the accuracy of several modeling strategies commonly used in practice. It is shown that for eccentric connections, the flexural bending largely affect the maximum tensile and compressive stresses within the joint. The difference may reach up to 54%. Finally, Experimental comparisons are made with the numerical procedures for typical connection model. 相似文献
189.
Raymond Ross 《Applied Mathematical Finance》2013,20(2):83-106
Using number-theoretic methods, we investigate low-discrepancy sequences and weighted-sum estimators which outperform standard low-discrepancy techniques for pricing multi-asset European options on up to 5 underlying factors. The sequences used are simpler to implement than most low-discrepancy sequences, and computation time is considerably faster. 相似文献
190.