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991.
992.
对数梯度材料泊松比不为零时的裂纹尖端场 总被引:1,自引:0,他引:1
严格地求出了当泊松比不为零时对数梯度材料的裂纹尖端场.
虽然在本构方程中对数项为\exp(ax), 但严格地证明了在最后应力的表达式中,
它却变为\exp(ax/2+ak_{1}^{1 / 2}y/2-kr/2) 与\exp(ax/2-ak_{1}^{1/2}
y/2-kr/2). 对于数值解法, 若考虑了此种严格关系, 将会很容易地解释其结果. 相似文献
993.
瞬态光谱法确定环氧丙烷DDT过程中起主导作用的基团 总被引:1,自引:1,他引:0
解决了燃料爆燃转爆轰(DDT)过程初始阶段弱辐射瞬态光谱测试问题、反应中间产物辐射相对强度定标问题和瞬态光谱测试系统同步控制问题后,从爆炸激波管的6个不同侧窗,拍摄了环氧丙烷DDT过程不同距离处的曝光时间为2~8 μs、分辨率达到0.2 nm的瞬态发射光谱。对所测光谱进行相对强度定标后,得到了主要反应中间产物光辐射强度随燃烧波阵面传播距离的变化曲线, 此曲线反映出DDT过程中反应中间产物的发展过程和其相应的浓度变化。结果显示,在爆燃阶段,燃烧气体的化学反应速率平缓增加,反应中间产物浓度逐渐增大;但在爆燃转爆轰的瞬间,反应急剧增快,反应中间产物的浓度突跃式地成倍增大。其中CO分子和CHO,OH自由基的浓度增幅显著大于其他反应产物,表明这几个基团是环氧丙烷爆燃转爆轰过程中起主导作用的重要基团。 相似文献
994.
Based on generalized the variation method, by introducing Hamilton function andLagrange multiplier, this paper proposed a linear quadratic optimal control strategy for an in-complete controllable system with fixed terminal state and time. Applying the proposed optimalcontrol to the simple two-input dual-stage actuator magnetic head positioning system with threedegrees-of-freedom, the simulation results show that the system has no residual vibration at theterminal position and time,which can reduce the total access time during head positioning process.To verify the validation of the optimal control strategy of three degrees-of-freedom spring-massmodels in actual magnetic head positioning of hard disk drives, a finite element model of an actualmagnetic head positioning system is presented. Substituting the optimal control force from simplethree degrees-of-freedom spring-mass models into the finite element model, the simulation resultsshow that the magnetic head also has no residual vibration at the end of track-to-track travel.That is to say, the linear quadratic optimal control technique based on simple two-input dual-stage actuator system with three degrees-of-freedom proposed in this paper is of high reliabilityfor the industrial application of an actual magnetic head positioning system. 相似文献
995.
996.
997.
Starting from the solutions of soliton equations and corresponding eigenfunctions obtained by Darboux transformation, we present a new method to solve soliton equations with self-consistent sources (SESCS) based on method of variation of parameters. The KdV equation with self-consistent sources (KdVSCS) is used as a model to illustrate this new method. In addition, we apply this method to construct some new solutions of the derivative nonlinear Schrödinger equation with self-consistent sources (DNLSSCS) such as phase solution, dark soliton solution, bright soliton solution and breather-type solution. 相似文献
998.
Let be a sequence of negatively associated random variables with a common distribution function and finite expectation and let τ be a nonnegative integer-valued random variable independent of . In this paper we give unified form for the asymptotic behavior of the random sums in the case of . The results extend the earlier results of Aleškevi?iené et al. (2008) [2]. 相似文献
999.
1000.
The kinetics of a monolayer growth is studied using the two-dimensional lattice gas model by means of the path-probability method (PPM) for nonequilibrium phenomena. Kinetic equations for the combined processes of relaxation (adsorption and desorption) and diffusion are derived analytically and solved for the first time in the square approximation of the PPM. Comparison of the square approximation with the point and pair approximations along with Monte Carlo simulation shows the effect of using a larger basic cluster than in the previous studies. When the square approximation is used, the growth rate results are much improved in both cases with and without diffusion and agree well with the Monte Carlo simulations results, except for very small values of the driving forceL=/k
b
T where is the chemical potential difference between the vapor and the solid phase. In the range where the agreement is good, there exists a region where the growth rateR is proportional to exp(–c/L with a constantc. This is the feature which is characteristic of two-dimensional nucleation-limited growth. 相似文献