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991.
992.
建立有限元模型,通过求解瞬态辐射传输方程模拟短脉冲激光在半透明介质中的传输.针对散射占优性半透明介质内辐射传输求解效率较差的问题,采用扩散综合加速迭代算法,提高计算效率,缩短计算时间.结果表明:采用精确解析式描述脉冲激光散射源项的求解策略可以获得准确的计算结果,精确地模拟快速变化的波前,不会产生数值扩散和数值振荡.此外,扩散综合迭代算法的计算时间仅为源项迭代的50%~60%. 相似文献
993.
In this paper, the dynamic surface control (DSC) algorithm is proposed for a class of stochastic nonlinear systems with nonminimum
phase and the standard output-feedback form. The proposed algorithm is a stochastic vision by combining the traditional back-stepping
together with the DSC technique, which can overcome the problem of ‘explosion of complexity’ in the back-stepping designing
procedure for the stochastic nonlinear systems. Thus, it can reduce the computation complexity and is easy to be used in the
actual implementation. It is shown that all the signals of the resulting closed-loop system are uniformly ultimately bounded. 相似文献
994.
The problem of globally exponential stability of stochastic neutral-type delayed neural networks with impulsive perturbations and Markovian switching is studied in this paper. By using the Lyapunov?CKrasovskii method and the stochastic analysis approach, a sufficient condition to ensure globally exponential stability for the stochastic neutral-type delayed neural networks with impulsive perturbations and Markovian switching is derived. Finally, a numerical example is given to illustrate the effectiveness of the result proposed in this paper. 相似文献
995.
Feimin?Huang Yi?Wang Tong?YangEmail author 《Archive for Rational Mechanics and Analysis》2012,203(2):379-413
We study the vanishing viscosity limit of the compressible Navier–Stokes equations to the Riemann solution of the Euler equations
that consists of the superposition of a shock wave and a rarefaction wave. In particular, it is shown that there exists a
family of smooth solutions to the compressible Navier–Stokes equations that converges to the Riemann solution away from the
initial and shock layers at a rate in terms of the viscosity and the heat conductivity coefficients. This gives the first
mathematical justification of this limit for the Navier–Stokes equations to the Riemann solution that contains these two typical
nonlinear hyperbolic waves. 相似文献
996.
This paper presents a new water retention curve (WRC) model for the simulation of coupled thermo-hydro-mechanical processes
in geological porous media. The model simultaneously considers the impact of porosity and temperature on suction, for both
wetting processes and drying processes. The model is based on an idealization of porous geological media as having an isotropic
and homogeneous microscopic pore structure. Suction is expressed as a function of degree of saturation, porosity, surface
tension of the water–air interface, and the length of air bubble perimeter of the pores per unit area on a random 2D cross-section
of the medium. The tension of water–air interface is written as a function of temperature, and the length of perimeter of
the water–air interface of the pores becomes a function of porosity and degree of saturation. The final equation of the new
WRC is a function of suction, effective degree of saturation, temperature, porosity, pore-gas pressure, and the rate of degree
of saturation change with time for both wetting and drying processes. The model was used to fit experimental data of the FEBEX
bentonite, with good agreements between measured and calculated results. 相似文献
997.
This article presents analytic solutions of energy release rates of a cracked laminate by using a global–local method. Deformations of a cracked laminate subjected to pure bending moments are analyzed and then a new mode partition equation is proposed. By using this partition equation, closed-form solutions of energy release rates GI and GII are derived by using a global method. For a cracked laminate subjected to axial forces and bending moments, a local method based on the crack-tip force model is used and the unknown coefficient is solved by combining the present analytic solutions for the bending moment loading case. Numerical results of the mode mixity predicted by the present closed-form formulations correlate well with those numerically calibrated on the basis of the singular field and crack-tip force models. 相似文献
998.
Uniform nano-sized calcium hydroxide (Ca(OH)2) monocrystal powder was synthesized from calcium oxide in a surfactant solution via a digestion method by decreasing the surface tension of the reaction system to control the growth of crystalline Ca(OH)2. The Ca(OH)2 monocrystal powder samples were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and Fourier transform-infrared spectroscopy (FT-IR). The NOx adsorption ability of the samples was evaluated, and the influence of various types and concentrations of surfactants on powder agglomeration and then the specific surface area in the precipitation process were studied. The specific surface area of the samples was found as high as 58 m2/g and 92 m2/g and the particle size, 300–400 nm and 200–300 nm in the presence of 10 wt% PEG600 and 0.086 mL/L SDS at a reaction time of 5 h, respectively. The product has an exceptionally strong adsorption ability for NOx, which makes it a highly promising adsorbent for emission control and air purification. 相似文献
999.
可见/近红外漫透射光谱结合CARS变量优选预测脐橙可溶性固形物 总被引:11,自引:0,他引:11
可溶性固形物(SSC)是脐橙重要内部品质之一。采用QualitySpec型光谱仪在350~1000 nm波段范围采集脐橙的可见/近红外漫透射光谱,采用CARS(competitive adaptive reweighted sampling)变量选择方法筛选出与脐橙SSC相关的重要变量,并与无信息变量消除(UVE)及连续投影算法(SPA)比较。最后,对选择的38个重要波长变量应用偏最小二乘(PLS)回归建立脐橙SSC预测模型,并对未参与建模的75个样品进行预测。研究结果表明,CARS方法优于UVE及SPA变量选择方法,能有效地筛选出重要波长变量。CARS-PLS建立的SSC预测模型优于全光谱的PLS模型,其校正集及预测集的相关系数分别为0.948和0.917,均方根误差分别为0.347%和0.394%。因此,可见/近红外漫透射光谱结合CARS方法可以预测脐橙可溶性固形物,CARS变量选择方法能有效简化预测模型和提高模型的预测精度。 相似文献
1000.
根据Beer-Lambert定律可知,增加气体池的有效光程是提高气体监测灵敏度最直接而有效的途径.通过实验研究和分析,漫反射立方腔作为气体池能显著地增加有效光程,因此研究其内部的光线传播规律具有重要意义.基于对漫反射立方腔内光线传播规律的理论分析,得到了单次反射平均光程的理论值,建立了漫反射立方腔内光线传播的理论近似模型,并通过有限元法仿真获得了单次反射平均光程的模拟值.利用可调谐二极管激光吸收光谱技术得到了立方腔的有效光程,间接求得了单次反射平均光程的实验值.对理论值、模拟值和实验值进行比较分析,验证了理论近似模型和有限元法仿真的准确性和稳定性. 相似文献