可见/红外宽光谱分色片偏振调控的设计

针对光学系统中可见/红外宽光谱分色片的偏振特性,采用诱导透射法设计了满足偏振遥感光学系统能量要求的可见/红外宽光谱分色片,并对其偏振特性进行了分析.通过计算获得了透射带400～900 nm可见/红外宽光谱分色片的偏振情况,采用等效层理论在其基底背面设计了偏振调控膜系,对分色片透射带的偏振度加以调控.使用needle优化...     

Synthesis and characterization of thermoluminescent Li2B4O7 nanophosphor

Lithium borate (Li₂B₄O₇) is a low Z_eff, tissue equivalent material that is commonly used for medical dosimetry using the thermoluminescence (TL) technique. Nanocrystals of lithium borate were synthesized by the combustion method for the first time in the laboratory. TL characteristics of the synthesized material were studied and compared with those of commercially available microcrystalline Li₂B₄O₇. The optimum pre-irradiation annealing condition was found to be 300 °C for 10 min and that of post-irradiation annealing was 300 °C for 30 min. The synthesized Li₂B₄O₇ nanophosphor has very poor sensitivity for low doses of gamma up to 10¹ Gy whereas from 10¹ to 4.5×10² Gy this phosphor exhibits a linear response and then from 4.5×10² to 10³ Gy it shows supralinearity. Thermoluminescence properties of Li₂B₄O₇ nanophosphor doped with Cu has also been investigated in this paper. It shows low fading and a linear response over a wide range of gamma radiation from 1×10² to 5×10³ Gy. Therefore the synthesized lithium borate nanophosphor doped with Cu may be used for high dose measurements of gamma radiations.     

一阶速度-应力Biot双相各向同性介质弹性波

提出一种等价的一阶双曲型速度一应力Biot双相各向同性介质弹性波波动方程,以实现双相介质混合波场中纯快慢纵波和纯横波波场分离的问题.应用散度和旋度理论证明双相介质等价方程波场分离的可行性,采用高阶交错网格有限差分法构建高精度正演算子,推导其PML吸收边界条件和稳定性条件,并对均匀双相介质和层状非均匀双相介质模型进行数值...     

基于压电探测判定激光支持燃烧波和爆轰波的点燃阈值

为了获得激光支持燃烧波和爆轰波的点燃阈值,采用压电探测器检测波长为1 064 nm的Nd:YAG激光作用在铝靶表面所产生的应变和冲压。从实验结果观察到压电信号的变化分为3个阶段,分别为光热弹性应变阶段、等离子体增强耦合阶段和激光支持爆轰波对靶表面的压力阶段,并从理论上研究了这3个阶段的激光与靶材料相互作用的机理,从而可以从压电信号是否发生跃变判断出激光支持燃烧波和激光支持爆轰波的点燃阈值,与其它方法所得到结果基本吻合。     

近红外消偏振分光膜设计近红外消偏振分光膜设计

大角度倾斜入射时,光学薄膜表现出强烈的偏振效应。入射光S分量和P分量的反射率和透射率曲线,以及反射或透射引起的两个分量的相位变化都不再相同,彼此有一定的偏振分离。通过对产生偏振效应内在原因的分析,采用一个在近红外波段对于45倾斜入射光的S分量和P分量等效导纳非常接近的膜系结构,结合单纯形法优化算法,设计得到一个1 500～1 600 nm范围内反射率都是50％的近红外消偏振分光膜。结果显示,在45入射时,S分量和P分量的反射率曲线偏振分离小,反射和透射引起的相位变化也控制在很小范围。     

微蜂窝环境中无线接收信号的特性分析

以微蜂窝系统为背景,研究了以测试射线法和虚拟源射线跟踪法为代表的射线跟踪技术,并用这两种方法对射线跟踪进行建模,分析比较两种模型的优缺点.利用这两种模型对实际情况进行计算,精确地找出所有给定情况的传播路径并可视化;对多波干涉的振幅进行了统计学分析,对宽带多波干涉现象进行了数学建模,并分析了合成波的包络统计特性.     

双向粘弹性节理岩体时域等效分析

以双向粘弹性节理岩体为研究对象,基于一种简单等效假定和自适应算法,并结合有限元方法,得到递推格式的等效本构模型和等效粘弹性场计算模型.通过算例,将等效解与基于ANSYS的非均质解进行比较.从计算精度和效率平衡的角度而言,等效模型的结果是令人满意的.     

Viscoelastic plate-fluid interactive vibration and liquid sloshing suppression

The viscoelastic plate-fluid interaction problem was studied. Forced vibration of the interactive system was investigated, and the equivalent mechanical models were obtained. The conclusion is that, for some case, the inner damping of the viscoelastic baffle will play a major role for liquid sloshing suppression. The project supported by National Natural Science Foundation of China and Astronautics Ministry.     

随机市场系数的M-V最优投资组合选择:一个鞅方法

通过引进凹函数U(x)以及等价鞅测度p^-，应用鞅的性质得到了随机市场系数情形下的M—V模型的最优投资策略以及有效前沿．