大气环境对空间CCD相机成像的影响

分析了大气环境对空间CCD相机在轨成像的影响,应用计算软件对大气环境影响空间相机成像的传递函数进行了初步的计算。     

一种计算原子核能隙Δ的新方法

在传统的计算能隙Δ的三参数公式基础上, 通过曲线拟合, 消除了同位旋变化对结合能的影响, 得到了更为理想的能隙Δ计算方法。 计算发现, 粒子数越少, 同位旋的影响越大, 传统计算方法产生的偏差越大, 而新的计算方法, 无论是在轻核区还是在重核区, 得到的结果更接近于经验公式。     

ITER屏蔽包层屏蔽块热工水力分析

通过ANSYS CFX对ITER屏蔽块进行了热工水力分析,对同一计算模型给出了两套不同的网格,分析了网格对计算精度的影响,结果表明两套网格都有较好的计算精度。通过数值模拟分析了壁面粗糙度对流动及传热的影响,结果表明壁面粗糙度是影响传热的一个非常重要的因素。     

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通过ANSYS CFX对ITER屏蔽块进行了热工水力分析,对同一计算模型给出了两套不同的网格,分析了网格对计算精度的影响,结果表明两套网格都有较好的计算精度。通过数值模拟分析了壁面粗糙度对流动及传热的影响,结果表明壁面粗糙度是影响传热的一个非常重要的因素。     

自由参数对基于双流体模型水锤计算精度影响的研究

本文采用气液两相双流体模型,分析探讨了该种计算模型对于计算带有液柱分离现象的水锤瞬变过程的准确性,同时研究了计算模型中自由参数对计算结果的影响,通过计算分析及实验验证,得到以下结论:1.采用气液两相双流体模型,考虑相间的质量分布,并采用类NND的高精度数值解法,可以较为准确的计算带有液柱分离现象弥合性水锤的瞬变过程。2.通过分析比对发现,双流体模型中的自由参数对于计算结果的影响中,气相波速改变对于计算结果精度的影响较大。     

能量分辨率对EXAFS的影响

测量EXAFS谱时,系统的能量分辨率是影响其结果的重要因素。本文提出了分辨率影响结构参数的计算方法,以Ge,Ni样品为例,测量及计算了不同分辨率下的结构参数的差异。测量结果与计算结果符合得很好,讨论了分辨率如何影响EXAFS谱及结构参数,给出了修正方法。 关键词：     

太阳能热化学制氢反应腔的热性能分析

本文修正了反应腔吸热效率的计算公式,在已有碟式聚光器的基础上,设计了一个太阳能热化学制氢反应器。本文计算了各种热损失对吸热器吸热效率的影响,也计算了反应腔倾斜角度以及采光孔尺寸对吸热效率的影响。计算结果表明,反应腔倾斜角度对反应腔热效率影响不大;采光孔直径越大,吸热效率越低。     

高速摄影机的鉴别率

本文分析了影响高速摄影机鉴别率的因素,计算了高速摄影机的鉴别率,通过实验数据分析了计算的结果。     

高空核爆电磁脉冲穿透电离层数值计算

 电离层对电磁脉冲传播的影响可以用一个频域的电流密度来描述,在时域则等效为一附加的电流密度和电导率。推导了附加电流密度和电导率在时域的表达式,它们是电离层参数和作用电场的函数,并以差分方程的形式给出。高空核爆电磁脉冲(HEMP)的计算是在时域进行的,将该电流密度和电导率计算方法应用于HEMP产生和传播的自洽计算中。作为算例,计算了100 km高空核爆电磁脉冲产生和向上传播的3种情况,并对计算结果进行了比对分析。计算结果表明:电离层时域计算方法与核爆电磁脉冲计算方法的结合是合理有效的,爆点上方考虑电离层影响的HEMP要比不考虑电离层影响的结果小得多。     

向量裂变谱与矩阵裂变谱对临界计算的影响

用蒙特卡罗方法及可适应多种截面的三维多群P₃中子输运蒙特卡罗程序MCMG,计算比较了不同裂变材料使用向量裂变谱与矩阵裂变谱的计算结果,通过与MCNP程序结果的比较,确信两种裂变谱对计算结果的影响是存在的,但对计算结果不会带来本质影响.同时还比较了不同中子截面库计算结果.     

Time of flight spectra in thermal desorption of helium

Time of flight spectra are calculated within the cascade model of phonon-mediated desorption for helium desorbing from graphite, sapphire and Nichrome. One and three-dimensional theories are compared. Deviations from Knudsen's cosine law are traced to dynamical effects. The spectra are — as a function of time — narrower than a Maxwellian distribution and their maxima are generally shifted to shorter times indicating that the desorbed molecules are hotter than the solid temperature. Relevant experiments are discussed. Experimental geometries are analysed.     

Parametric excitation of subharmonic oscillations

Subharmonic oscillations of order one-half for a single-degree-of-freedom system with quadratic, cubic, and quartic nonlinearities under parametric excitation are investigated. Two approximate methods (multiple scales and generalized synchronization) are used for comparison. The modulation equations (reduced equations) of the amplitudes and the phases are obtained. Steady-state solutions (periodic solutions) and their stability are determined. Numerical solutions are carried out, and graphical representations of the results are presented and discussed. The results obtained by the two methods are in excellent agreement.     

Faithful quantum secure direct communication protocol against collective noise

An improved quantum secure direct communication (QSDC) protocol is proposed in this paper.Blocks of entangled photon pairs are transmitted in two steps in which secret messages are transmitted directly.The single logical qubits and unitary operations under decoherence free subspaces are presented and the generalized Bell states are constructed which are immune to the collective noise.Two steps of qubit transmission are used in this protocol to guarantee the security of communication.The security of the protocol against various attacks are discussed.     

Radar cross sections of a random medium layer

Analytic expressions are derived for the normalized radar cross sections (NRCS) of a random medium layer. These are calculated from the first-order solutions for diffuse intensities which are based on a multiple-scattering wave theoretical analysis. The permittivity fluctuations are assumed to be small and to obey stationary Gaussian statistics. On studying the expressions for the NRCS, some of their characteristics are pointed out. Three different correlation functions are considered and expressions for the coherent propagation constants are provided. Numerical examples are used to verify theoretical results and highlight some interesting characteristics of NRCS.     

Predicting rogue waves

Observational data regarding anomalously high waves on the sea’s surface (freak or rogue waves) are reviewed. The objectives of the research are identified, and the difficulties encountered are noted. The main physical mechanisms employed in explaining rogue waves are listed, and possible approaches to predicting marine hazards are discussed. Principles for ongoing short-term forecasting of extreme waves (within tens of wave periods or wavelengths) are proposed. Some preliminary results are presented.     

Effect of magnetic field on freely moving superconductors in the audio band

The results of studying the magnetomechanical effects in classical superconductors are analyzed. The energy losses are determined, and a number of macroscopic parameters are calculated using a developed model. The studies of superconductors by the method of rotation of a body suspended without contact are described. The results obtained are analyzed, and the values of some parameters are determined.     

Radar cross sections of a random medium layer

Abstract

Analytic expressions are derived for the normalized radar cross sections (NRCS) of a random medium layer. These are calculated from the first-order solutions for diffuse intensities which are based on a multiple-scattering wave theoretical analysis. The permittivity fluctuations are assumed to be small and to obey stationary Gaussian statistics. On studying the expressions for the NRCS, some of their characteristics are pointed out. Three different correlation functions are considered and expressions for the coherent propagation constants are provided. Numerical examples are used to verify theoretical results and highlight some interesting characteristics of NRCS.     

Parameter design of a liquid-filled sloshing system

<正>The nonlinear governing equations of the liquid sloshing modals in a cylindrical storage tank are established. Through analytical analysis,the analytical expressions of the solutions of this kind of system are obtained.With different parameters,the dynamical behaviors of the solutions are different from the trivial ones.To prevent system instability,two selection principles that the stiffness equations are positive-definite and the nonlinear terms of the system are not regenerative elements are given.Meanwhile,numerical simulations are also given,which confirm the analytical results.     

Advanced research in millimeter-wave vacuum electronics

Selected basic research efforts currently sponsored by the U.S. Department of Defense (DOD) and the National Science Foundation (NSF) are reviewed. Major achievements are highlighted and remaining obstacles are discussed. Future advances are suggested. Opinions expressed are solely those of the author.