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。     

A general solution to the Schrödinger–Poisson equation for a charged hard wall: Application to potential profile of an AlN/GaN barrier structure

A general, system-independent, formulation of the parabolic Schrödinger–Poisson equation is presented for a charged hard wall in the limit of complete screening by the ground state. It is solved numerically using iteration and asymptotic boundary conditions. The solution gives a simple relation between the band bending and sheet charge density at an interface. Approximative analytical expressions for the potential profile and wave function are developed based on properties of the exact solution. Specific tests of the validity of the assumptions leading to the general solution are made. The assumption of complete screening by the ground state is found be a limitation; however, the general solution provides a fair approximate account of the potential profile when the bulk is doped. The general solution is further used in a simple model for the potential profile of an AlN/GaN barrier structure. The result compares well with the solution of the full Schrödinger–Poisson equation.     

Determinants of the structured and structureless green emissions of ZnO

Green emission can be identified as either a structured or a structureless emission. In the downward surface band bending region, the influence of defects on the continuous change in the 0-0 electronic transition was found to be a dominating factor that differentiates the characteristics of green emission. Such a change in the 0-0 electronic transition gives rise to the structureless green emission at higher energy, while the 0-0 electronic transition in the bulk of ZnO plays an important role resulting in structured green emission with lower energy.     

从几何的角度看微分中值定理

从平面几何中曲线之间的相切关系不依赖于坐标轴的选取这一基本事实去看数学分析中Rolle中值定理、Lagrange中值定理以及Cauchy中值定理.     

Geometric and topological rigidity for compact submanifolds of odd dimension

We investigate rigidity problems for odd-dimensional compact submanifolds.We show that if Mn(n 5)is an odd-dimensional compact submanifold with parallel mean curvature in Sn+p,and if RicM(n-2-1n)(1+H2)and Hδn,whereδn is an explicit positive constant depending only on n,then M is a totally umbilical sphere.Here H is the mean curvature of M.Moreover,we prove that if Mn(n 5)is an odd-dimensional compact submanifold in the space form Fn+p(c)with c 0,and if RicM(n-2-εn)(c+H2),whereεn is an explicit positive constant depending only on n,then M is homeomorphic to a sphere.     

Coarse equivalences of Euclidean buildings

We prove the following rigidity results. Coarse equivalences between metrically complete Euclidean buildings preserve spherical buildings at infinity. If all irreducible factors have dimension at least two, then coarsely equivalent Euclidean buildings are isometric (up to scaling factors); if in addition none of the irreducible factors is a Euclidean cone, then the isometry is unique and has finite distance from the coarse equivalence.     

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.     

基于视频图像测量的母线折弯技术研究

现有折弯机在母线的角度测量中一般采用光栅尺或编码器,针对这种接触式检测方法存在的局限性,提出了基于视频技术的角度检测方法,这种非接触式测量方法不仅使角度的检测更加方便,而且增加了折弯机机头机械设计的灵活性.分析了母线在进行边缘检测时角度存在跳动的原因,提出了一种通过抑制伪边缘的方法来控制检测角度的不稳定性.以铜、铝母线...