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由于Green应变具有单元翻转不变性,在大变形的仿真中有可能会出现单元的逆转,破坏模型网格的拓扑结构,导致仿真失败,因此提出一个新的有限单元模型,在采用Green应变度量变形同时把单元体积变化率和单元内压强关系引入到本构方程中,解决单元逆转问题;同时,模型导出的单元弹性势能是单元结点位移的多项式函数,有效地简化了共轭梯度法的求解,效率显著提高.实验结果表明,该模型可以应用于软组织大变形的实时仿真中. 相似文献
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《发光学报》2019,(10)
光机系统中支撑结构与光学元件的接触位置、接触面积、接触应力及支撑结构的柔度是光学系统成像质量的重要影响因素,为了降低因垂直方向支撑引起的几何像差,以像差指数PV值为优化目标,对单个透镜接触支撑结构进行了拓扑优化设计。首先建立接触拓扑优化模型,以采用Signorini接触条件建立的刚性支撑单向接触中的线弹性结构为例,验证了接触拓扑优化模型的正确性。用透镜变形函数来描述透镜的像差指数PV值,将其作为拓扑模型的优化目标。采用SIMP方法描述拓扑优化设计变量,采用扩展后的拉格朗日算子求解接触条件。采用MMA优化算法求解拓扑优化模型的最优解。通过拓扑优化设计变量的最优解,定义了满足几何畸变要求的支撑结构的最优拓扑结构。结果表明,该方法可使透镜PV值降低14%,面形RMS值降低13.8%。同时搭建实验平台,对透镜PV值和RMS值进行测试,得到的最佳接触支撑结构的支持试验结果表明,平面反射镜表面PV值分别降低了60.4%和42.9%,面形RMS值分别降低了74.3%和38.9%,优化后的接触支撑结构有效地提高了高精度单透镜支架的精度,具有很大的实际应用潜力。 相似文献
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传统的Zernike多项式在光机优化设计中存在着一定的局限性,如离散情况下正交性损失仅适用于与圆同胚的边界光滑平面单连通区域。利用Laplace方程得到的特征模态所具有的离散正交性和共形性质,在有限元数值离散的情况下,实现对光学曲面变形的近似表述,并对圆形光学反射镜支撑结构进行以特征基底系数极小为目标的结构拓扑优化。将特征模态的优化结果与Zernike多项式优化结果对比之后发现,特征模态可以取得和Zernike多项式近似的优化性能。在此基础上,进一步将特征模态应用于六边形曲面镜支撑结构的拓扑优化。 相似文献
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针对薄板弯曲大变形问题, 运用变分原理, 建立了薄板弯曲大变形问题的高阶非线性偏微分方程. 运用有限差分法和动态设计变量优化算法原理, 以离散坐标点的上未知挠度为设计变量, 以离散坐标点的差分方程组构建目标函数, 提出了薄板弯曲大变形挠度求解的动态设计变量优化算法, 编制了相应的优化求解程序. 分析了具有固定边界、均布载荷下的矩形薄板挠度的典型算例. 通过与有限元的结果对比, 表明了本文求解算法的有效性和精确性, 提供了直接求解实际工程问题的基础. 相似文献
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基于主观式测量人眼波前像差的眼模型研究 总被引:8,自引:8,他引:0
通过主观式光线追踪波前像差测量方法得到用Zernike系数描述的人眼波前像差;在Gullstrand-Le Grand眼模型的基础上,引入用医用角膜地形图仪测量并用高次非球面函数拟合的实际人眼角膜形状数据,又引入角膜、前房及玻璃体厚度等个体化的眼结构参数;在光学建模软件Zemax中用所测Zernike系数建立评价函数,并对用Zernike矢高面描绘的晶状体表面进行优化.由此建立了个体化眼模型,并由此模型中可以计算得到与实际测量的波前像差值完全相同的各项Zernike系数值,从而可用于描述实际人眼的光学特性. 相似文献
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20单元双压电片变形反射镜的影响函数有限元分析和实验测量 总被引:6,自引:3,他引:3
影响函数是分析双压电片变形反射镜像差校正能力的重要参量,通过建立有限元模型预测实际器件的影响函数,以有限元模型的不断优化替代实际器件的尝试性改进,可以减小构造的盲目性,从而节约研发成本,缩短双压电片变形镜的实用化进程.采用Veeco干涉仪测量了20单元双压电片变形反射镜的影响函数,同时建立有限元模型进行了相应计算,并将计算结果与实际器件的测量数据进行了对比分析.结果表明,相对于实测数据而言,有限元模型计算得出的影响函数在量值上略有偏小,但其形状和峰值位置与测量数据一致性好,两者对前35项泽尼克像差的拟合曲线也基本吻合,各项拟合误差系数之差皆小于0.1.这说明通过不断改进有限元模型实现对实际器件的优化设计是切实可行的. 相似文献
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An immune-motivated optimization method is proposed and applied to both spin glass and graph coloring problems. Also an immune-motivated modification for the numerical Euler method is proposed. 相似文献
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Narendra Chauhan Ankush Mittal Dietmar Wagner M. V. Kartikeyan M. K. Thumm 《International Journal of Infrared and Millimeter Waves》2008,29(8):792-798
In this paper the design and optimization of a nonlinear diameter taper, connecting the output section of a gyrotron cavity
to the uniform output waveguide section, is presented. The design of a nonlinear taper of a 42 GHz, 200 kW CW gyrotron operating
in the TE0,3 cavity mode with axial output collection has been taken as a case study. The taper synthesis has been carried out considering
a raised cosine type of nonlinear taper and the analysis is done using a dedicated scattering matrix code. In addition, an
improved particle swarm optimization - an evolutionary optimization - algorithm is used for the design optimization of this
nonlinear taper. The optimum design of the taper shows the effectiveness of the presented method. 相似文献
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The dependence of the high-harmonic conversion efficiency in noble gases on experimental parameters is analyzed. The results presented here supply a guideline for the optimization of HHG. The most striking finding of our analysis is the dependence of the harmonic yield on the laser pulse duration. It is generally accepted that the harmonic yield increases for shorter pulse durations. Calculations in neon show that this is only true for harmonics close to the cutoff. Away from the cutoff however, the harmonic yield increases approximately linearly with the pulse duration. 相似文献
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Net current free toroidal ("stellarator") confinement is studied with a combination of several methods: a complete set of analytical vacuum fields for finding favorable vacuum field configurations; three-dimensional MHD codes for finite-?, equilibrium computations; the expansion of a general toroidal equilibrium around its magnetic axis as guideline for the computational search in configurational space and for finite-?, MHD stability; Monte Carlo simulations for particle containment; continuous modular coil systems generating the configurations considered. Results are: vacuum field configurations with sizeable Q = 0, 1, 2, 3 helical fields, substantial twist number (? 1/2), significant reduction of the parallel current density, and vacuum magnetic well exist for a toroidal aspect ratio of 15-20 and can be generated by modular coils whose excursions from meridional planes are small compared to the toroidal period length. In these configurations, the finite-? toroidal shift is strongly reduced, so that a larger ? value (factor 2-4) than in the equivalent Q = 2 stellarator can be achieved. Stability calculations do not exclude the possibility of stable equilibria of this kind with (?) ? 0.05-0.1; transport calculations without electrical field show improvement-as compared to the Q = 2 stellarator-in the collisional and plateau regimes. 相似文献
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《Infrared physics》1990,30(6):489-497
The optimized operating parameters of SPRITE detector working band in the 8–14 μm region have been calculated by computer modeling based on one dimensional theory. The results suggest the length of filaments should be 700 μm; the width 50 μm; the thickness 7 μm; the length of read-out area 50 μm and the bias voltage 2.8 V. The optimized outline curve of the read-out area has also been obtained by use of a variational method: Y = 7.5 cosh (0.04211X). This results in a significant reduction of transit time and transit time dispersion from 0.26 to 0.20 μs and 0.13 to 0.045 μs, respectively. 相似文献
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云计算可以通过即付即用的方式向用户工作流提供资源。为了解决资源服务代价异构环境下的云工作流任务调度代价问题,提出一种基于改进粒子群算法的云工作流任务调度算法WSA-IPSO。通过综合考虑任务的执行代价和依赖任务间发生数据传输时的通信代价,算法将总代价优化问题形式化为有向无环图DAG中的任务调度模型,并提出基于改进粒子群算法的优化模型对其进行求解。通过改进传统粒子群算法的粒子速度更新策略和惯性权重更新策略,算法可以以更快的收敛速度得到代价最小化的调度方案。通过仿真实验,与MCT算法及标准粒子群算法进行性能比较。实验结果表明,WSA-IPSO算法在降低总代价、任务分布的负载均衡以及算法收敛性方面比较同类算法均表现出更好的性能。 相似文献
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The generation of ozone under homogeneous conditions is described by a system of kinetic equations. We supposed a certain time dependence of electric field intensity inside a discharge gap. We computed the dependence of efficiency of the ozone generation on both the width and the maximum intensity of electric pulse. 相似文献