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781.
Multi-Material Arbitrary Lagrangian–Eulerian (ALE) finite element methods can solve large deformations in fast dynamic problems like explosions because the mesh motion can be independent of the material motion. However materials must flow between elements and this advection involves numerical dissipations. The rezoning mesh method presented in this paper was designed to reduce these numerical errors for shock wave propagation. The mesh moves to refine the elements near the shock front. This refinement limits the advection fluxes and so the numerical diffusion. This technique is applied to the numerical simulations of airblast problems for which a parameter controlling the mesh refinement is studied. 相似文献
782.
Pressure response of human cells was investigated. Various proteins in the human promyelocytic cells (HL-60), compressed for 30 minutes at a pressure of 100 MPa and at a temperature of 37 °C, were detected by 2-dimensional gel electrophoresis (2-DE). The amount of f - and g -tubulin decreased appreciably immediately after decompression. It suggests that the decrease of tubulin promotes the pressure-induced apoptosis. The amount of heat shock proteins, HSP60 and HSP70 increased immediately after decompression on 2-DE. These proteins may increase to correct the pressure-induced disorder in folding of protein molecules. 相似文献
783.
The dynamics of fronts, or kinks, in dispersive media with gain and losses is considered. It is shown that the front parameters, such as the velocity and width, depend on initial conditions. This result is not typical for dissipative systems. For exponentially decreasing initial conditions, the relations for the front parameters are found. A presence of the global bifurcation, when a soliton solution is replaced by the front solution, is demonstrated. It is also shown that in order to observe fronts, the front velocity should be larger than the characteristic velocity of the modulational instability. 相似文献
784.
AbstractA comprehensive review of important progress achieved over the last 30 years regarding knowledge of laser-induced plasmas generated by CO2 and Nd:YAG lasers in a variety of ambient gases is presented in this article, as well as research results on the extension of laser-induced breakdown spectroscopy (LIBS) for quantitative analysis of light elements, especially hydrogen and deuterium. First, the formation of shock wave–induced expanding secondary plasma in low-pressure ambient gases is discussed along with the dynamic characteristics of the secondary plasma expansion process. The unique advantages of low-pressure gas plasma are explained in relation to the successful detection of the sharp H and D emission lines. The experimental results using helium ambient gas are presented with emphasis on the role of He gas plasma in introducing an additional delayed excitation mechanism involving the helium metastable excited state, which resulted in the complete resolution of H and D emission lines, separated by only 0.18 nm. The development of a laser precleaning treatment and special double-pulse techniques further produced a linear calibration line with zero intercept applicable to quantitative H and D analyses of zircaloy sample, with either low- or high-pressure ambient He gas. More recent use of a transversely excited atmospheric (TEA) CO2 laser in place of an Nd:YAG laser has demonstrated the much desired larger excited helium plasma and thereby resulted in significant emission enhancement and improved detection sensitivity. 相似文献
785.
We demonstrate here a laser-driven shock wave in a hydrogen sample, pre-compressed in a diamond anvil cell. The compression factors of the dynamic and static techniques are multiplied. This approach allows access to a family of Hugoniot curves which span the P–T phase diagram of fluid hydrogen to high density. In this first-of-its-kind experiment, two hydrogen Hugoniot curves have been partially followed starting from pre-compression at pressures of 0.7?GPa and 1.2?GPa. Optical reflectance probing at two wavelengths reveals the onset of the conducting fluid state. The boundary line to conducting fluid hydrogen is suggested. 相似文献
786.
Ken-Ichi Kondo 《高压研究》2013,33(5-6):747-757
Abstract Both the heterogeneous deformation and the localization of heat in the shock compressed materials are supported by in situ measurements and textural observations. Additional shock-induced radiation measurements on diamond powder aggregates confirm such a current aspect and the proposed model, namely the skin model, that allows us to estimate quantitatively both the amount of localized heat and the subsequent thermal diffusion process. The parameter, ratio of the skin thickness to the cube size or particle size, is a convenient, universal parameter to representthe shock state of powder and is independent of particle size but dependent on shock pressures. The skin temperatures are approximately constant and equal to the melting temperature. The shock processing, especially shock consolidation of powders, effectively utilizes these phenomena and can be designed based on the skin model. 相似文献
787.
Chen Shuxing 《数学年刊B辑(英文版)》1996,17(4):445-456
Inthispaperwecontinueourdiscussionin[5].Mainlywewillestablishaprioriestimatesforthelinearizedproblem(G),andthenprovetheexistenceofthesolutiontononlinearproblem.In§5wegivesometechnicalpreparations.Thenthewhole§6isdevotedtotheestablishmentofenergyestimates.I… 相似文献
788.
789.
Jiˇí Fürst 《Flow, Turbulence and Combustion》2006,76(4):331-342
The article describes the development of a high order finite volume method for the solution of transonic flow problems. The method is based on a reconstruction procedure similar to the weighted essentially non-oscillatory scheme (WENO). The analysis of accuracy and stability of the method is carried out for the case of smooth data and for simple discontinuity. The computational results demonstrate the performance of the WLSQR method for the solution of several flow problems in 2D and 3D using both structured and unstructured meshes. 相似文献
790.
Zhonghai Xu 《Journal of Mathematical Analysis and Applications》2006,322(2):712-728
The problem of shock reflection by a wedge in the flow dominated by the unsteady potential flow equation is an important problem. In weak regular reflection, the flow behind the reflected shock is immediately supersonic and becomes subsonic further downstream. The reflected shock is transonic. Its position is a free boundary for the unsteady potential equation, which is degenerate at the sonic line in self-similar coordinates. Applying the special partial hodograph transformation used in [Zhouping Xin, Huicheng Yin, Transonic shock in a nozzle I, 2-D case, Comm. Pure Appl. Math. LVII (2004) 1-51; Zhouping Xin, Huicheng Yin, Transonic shock in a nozzle II, 3-D case, IMS, preprint, 2003], we derive a nonlinear degenerate elliptic equation with nonlinear boundary conditions in a piecewise smooth domain. When the angle between incident shock and wedge is small, we can see the weak regular reflection as the disturbance of normal reflection as in [Chen Shuxing, Linear approximation of shock reflection at a wedge with large angle, Comm. Partial Differential Equations 21(78) (1996) 1103-1118]. By linearizing the resulted nonlinear equation and boundary conditions with the above viewpoint in [Chen Shuxing, Linear approximation of shock reflection at a wedge with large angle, Comm. Partial Differential Equations 21(78) (1996) 1103-1118], we obtain a linear degenerate elliptic equation with mixed boundary conditions in a curved quadrilateral domain. By means of elliptic regularization techniques, a delicate a priori estimate and compact arguments, we show that the solution of the linearized problem is smooth in the interior and Lipschitz continuous up to the degenerate boundary. 相似文献