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21.
We theoretically investigate the dynamics of dark solitons as well as their interaction in nonlocal media. Approximate equations describing the evolution of the beams are obtained via suitable trial functions of amplitude u and refractive index n in an averaged Lagrangian. Our results reveal that out-of-phase dark solitons can evolve into stable bound states in nonlocal materials. Moreover, it is found that the separations in the bound state monotonically increase with the degree of nonlocality in nonlocal limit. These results are in excellent agreement with the numerical simulations.  相似文献   
22.
Realistic representation of stochastic inputs associated with various sources of uncertainty in the simulation of fluid flows leads to high dimensional representations that are computationally prohibitive. We investigate the use of adaptive ANOVA decomposition as an effective dimension–reduction technique in modeling steady incompressible and compressible flows with nominal dimension of random space up to 100. We present three different adaptivity criteria and compare the adaptive ANOVA method against sparse grid, Monte Carlo and quasi-Monte Carlo methods to evaluate its relative efficiency and accuracy. For the incompressible flow problem, the effect of random temperature boundary conditions (modeled as high-dimensional stochastic processes) on the Nusselt number is investigated for different values of correlation length. For the compressible flow, the effects of random geometric perturbations (simulating random roughness) on the scattering of a strong shock wave is investigated both analytically and numerically. A probabilistic collocation method is combined with adaptive ANOVA to obtain both incompressible and compressible flow solutions. We demonstrate that for both cases even draconian truncations of the ANOVA expansion lead to accurate solutions with a speed-up factor of three orders of magnitude compared to Monte Carlo and at least one order of magnitude compared to sparse grids for comparable accuracy.  相似文献   
23.
In this paper, a phase field model is developed for vesicle adhesion involving complex substrate and vesicle geometries. The model takes into account an adhesion potential that depends on the distance of vesicle to the substrate. A variational problem is solved in a 3D computational domain by minimizing the contribution of bending elastic energy and the adhesion energy under the constraints of total surface area and volume, described via a phase function. An adaptive finite element method is used to efficiently compute the numerical solutions of the model. The computational results are validated through comparison of several axisymmetric shapes with the sharp-interface ODE solution. Moreover, we compute shapes for non-axisymmetric situations to support the observation that concave substrates favor adhesion.  相似文献   
24.
A Roe-average algorithm has been derived for a granular-gas model, proposed by Goldshtein and Shapiro [Goldshtein, Shapiro, Mechanics of collisional motion of granular materials: Part 1. General hydrodynamic equations, J. Fluid Mech. 282 (1995) 75–114], which contains non-conservative terms in the Euler-like hyperbolic governing equations apart from sink terms, which arise from inelastic collision of granules and are present only in the energy equation. The non-conservative terms introduce non-isentropic effects in acoustic-wave propagation within granular media and they also contribute to the Rankine–Hugoniot relations across a discontinuity. A Roe-average algorithm, based on the same granular-gas model, was derived in the literature [V. Kamenetsky, A. Goldshtein, M. Shapiro, D. Degani, Evolution of a shock wave in a granular gas, Phys. Fluids, 12 (2000) 3036–3049] which then required the implementation of a shock-fitting technique at a discontinuity. In the present work, Roe-averaged variables have been obtained from the Rankine–Hugoniot jump relations and the non-conservative terms have been incorporated in the numerical flux formula consistent with upwind principles associated with the granular speed of sound. Results for unsteady one-dimensional granular flows, colliding with a wall, demonstrate the capability of the proposed algorithm to capture strong shocks in addition to flow features not found in molecular gases, such as a fluidized region downstream of the shock and a compacted solid-block region adjacent to the wall.  相似文献   
25.
利用Hyperion数据进行环境星HSI红边参数真实性检验   总被引:2,自引:0,他引:2  
针对我国新发射运行的HJ-1A星HSI数据,利用高光谱分辨率的Hyperion数据进行了HJ-1A星HSI的光谱模拟,提取了红谷位置、红边位置、红边斜率和红边振幅等4个主要的红边参数,对真实与模拟环境星HSI数据的红边参数进行了对比分析,从而以Hyperion数据为参照检验了环境星HSI红边参数的真实性。研究结果显示,环境星HSI与模拟HSI的红边范围光谱反射率平均相关系数为0.946,标准差为0.011,为极显著相关,两种数据在红边范围内的光谱反射率变化高度一致;4个红边参数的相关系数分别为0.414,0.543,0.808和0.802,并且随植被覆盖度的变化呈现出明显的规律性,模拟与真实红边参数差值标准差分别为5.75,1.86,5.7e-4和0.024,认为环境星HSI的红边参数可以较好反映该区域植被变化所造成的红边光谱特征差异。  相似文献   
26.
红外辐射在水雾中衰减计算的修正方法研究   总被引:2,自引:0,他引:2  
Du YC  Yang L  Zhang XF  Wu MM 《光谱学与光谱分析》2010,30(10):2632-2635
水雾系统对红外光谱有着强烈的衰减作用,因此在军事目标的各种制导对抗中被予以高度的关注。以Mie散射理论为基础,分析了粒子对红外光谱前向散射的聚集特性,定义了近前向散射比,并确定了在应用朗伯比尔定律时需修正的粒子尺度和散射半角的范围。通过大量计算发现,单独将粒子尺度和散射半角的乘积作为独立变量计算的视消光系数不够精确。在中远红外波段,前向散射附近的小角度内散射强度积分与粒子尺度和散射角都成正比,若红外波长为定值,则与粒子半径成正比。最后根据前向散射规律给出了两个不单独以x.θ为变量的经验计算公式,使得对水雾消光的修正计算更加简便精确。  相似文献   
27.
The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency.  相似文献   
28.
静脉采血,分离并制备血红蛋白溶液,用拉曼光谱方法观察不同pH时H+对血红蛋白-氧结合状态与能力的影响。结果显示:在514.5nm激光的激发下,当pH为7.4时,随着氧分压降低,血红蛋白在1 375,1 562,1 585和1 638cm-1峰强均逐渐减弱,其中以1 375和1 638cm-1峰渐变最明显且相关性显著。以氧分压为横坐标,拉曼峰强为纵坐标,对pH为5.7,7.4和8.0时的血红蛋白在1 375和1 638cm-1峰的强度及其氧分压进行线性拟合,结果显示2处的拟合效果均良好,拉曼峰强度/氧分压的斜率关系表现为K8.0>K7.4>K5.7,表明pH越低血红蛋白的氧亲和力越低,越有利于向组织释放氧气。研究表明,应用拉曼光谱技术可检测血红蛋白与氧的亲和力,通过对血红蛋白-氧亲和力的量化检测,可以观察pH对血氧结合状态的影响,为血氧分压的监测以及氢离子和二氧化碳等血氧亲和力调节因子调节能力的研究提供新的研究方法与理论基础。  相似文献   
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