用测量法求平面封闭区域之面积及空间封闭区域之体积

怎样用测量的方法来分别求由无解析表达式或由积分法很难求面积或体积的已知表达式的平面封闭曲线或空间封闭曲面所围的面积或体积?本文分别给出了简单易行的求面积的“改进了的方格法”及求体积的“立方体分割法”,并且证明了对于满足一定条件的平面封闭曲线或空间封闭曲面,当测量所用单位(平面小正方形的边长或空间小立方体的边长)充分小时,所测得的面积或体积与实际的面积或体积之差的绝对值是所用单位的二阶无穷小.并且,当曲线或曲面的某些性质已知或至少可以估计出其范围的情况下,本文给出了为使测量结果达到任意精度,应当使用多大的测量单位.     

FULL DISCRETE NONLINEAR GALERKIN METHOD FOR THE NAVIER-STOKES EQUATIONS

This paper deals with the inertial manifold and the approximate inertial manifold concepts of the Navier-Stokes equations with nonhomogeneous boundary conditions and inertial algorithm. Furtheremore, we provide the error estimates of the approximate solutions of the Navier-Stokes Equations.     

重离子碰撞两体关联输运理论Ⅲ.半经典近似下的数值计算

为了验证由相干单粒子波函数和两体关联动力学所建立的非相对论条件下的重离子碰撞两体关联输运理论的有效性,利用没有碰撞项的量子分子动力学,即时间相关的Hartree-Fock方法的经典近似,实现了两体关联输运理论在半经典近似下的数值计算.计算结果表明:这种两体关联输运理论的确能够有效地描述重离子碰撞过程中的输运和耗散过程.     

几种特殊根

在本文中,我们首先借助于近似诸零根和广义诸零根的模刻划分别证明近似诸零根和广义诸零根为特殊根。然后,引进环的 PM-根和 PM-本原环的概念,PM-根是特殊根,最后讨论全矩阵环的 PM-根和 PM-本原性。     

不同倾角的脉管制冷机内自然对流影响的研究

本文通过对脉管内自然对流的数值模拟，讨论了当脉管冷端处在不同方向时，脉管内的自然对流对脉管制冷机性能的影响．数值模拟结果表明，当冷端在下时获得的制冷温度最低；当热端在下并与重力方向成３０°时制冷温度最高．结论与实验测量结果定性一致．所做的理论分析对实现脉管制冷机的良好运行有指导意义。     

A Simple Calculation Approach for the Second－Harmonic Sound Beam Generated by an Arbitrary Distribution Source

We present a simple calculation approach for the fundamental and second-harmonic sound beams with an arbitrary distribution source in the quasilinear approximation. The analysis is based on the assumption that the source function with an arbitrary geometry and distribution is expanded into the sum of a set of two-dimensional Gaussian functions. The two- and five-dimensional integral solutions for the fundamental and second-harmonic fields are, respectively, reduced in terms of Gaussian functions and simple one-dimensional integrals. The numerical evaluation of field distributions is then greatly simplified.     

双组元姿控发动机反流特性的DSMC模拟

为准确获得双组元姿控发动机的羽流及其反流特性,采用直接模拟蒙特卡罗(DSMC)方法结合可变软球(VSS)模型数值模拟以N2O4/MMH为推进剂的真空羽流。喷口参数由喷管流动的DSMC法计算得到。与文献比较表明本文计算程序可信。模拟结果表明,分子质量越小的气体越容易进入反流区;本文的计算条件下,在偏离X轴正向116°~140°范围内,组分数密度和质量流率以及温度均出现了最大值。     

An approach to the detection of underwater remote target

An approach to the detection of underwater remote target by estimating its backscattering coefficient is presented. The key to this approach is that the echo signal is represented in state-variable model and the back-scattering coefficients of target are contained in dynamic noise of this model, thus underwater target can be detected by estimating this dynamic noise, i.e., deconvolving this model. When all noise statistics are a priori known, an optimum deconvolution algorithm based on the optimum state filter is derived, or else, an adaptive deconvolution algorithm based on the adaptive state filter of alternatively estimating the vector state and the noise statistics is developed. In the final simulation test, an echo signal with SNR equal to -6.1 dB is proceeded using the aforementioned two deconvolution algorithms, respectively, and the results demonstrate good performance of the approach.     

在大学物理教材中引入计算机数值解的尝试

本文从普通物理教学现代化的要求出发,通过新编《普通物理学》中若干例题的求解,论述了在大学物理教学中适当引入计算机数值模拟的研究方法将有助于物理概念的深化,以及学生综合能力的培养.