理想流体球的爱因斯坦场方程内部严格解研究

当静态的具有球对称性的理想流体的密度是径向坐标的函数时，Oppenheimer-Volkoff(OV) 方程成为Riccati方程-根据OV方程的一个已知特解，能将它变换成可积分的Bernoulli方程 ，严格地求得OV方程的通解和另一特解，进一步得到理想流体球的爱因斯坦场方程的内部严 格解，即度规分量的解析表示式- 关键词： 爱因斯坦场方程 OV方程 理想流体球内部严格解     

(2+1)维Camassa-Holm方程的相似约化与解析解

将Clarkson和Krushal引入的直接约化方法推广并应用到(2+1)维CamassaHolm方程组,获得了该方程的若干相似约化和解析解,其中包括Logistic方程和Bernoulli方程.约化结果得到了Peakon解、Cuspon解和关于时间t的奇异解.该方法也适用于其他有重要物理背景的非线性演化方程 关键词： Camassa-Homl方程 相似约化 直接方法 解析解     

由刘维尔方程推导玻尔兹曼方程

刘维尔方程是统计物理中基本方程，因而原则上统计物理中许多重要方程都可以由刘维尔方程导出，本文尝试由刘维尔方程推导玻尔兹曼方程．     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程（昂内斯气态方程的简称）的几点讨论。一是昂氏气态方程收缩为范式气态方程的讨论;二是昂氏气态方程温度昂T 和理想气态方程温度T理相等的压强（下面简称等温压强）的讨论;三是昂氏气态方程压强昂P 和理想气态方程压强P理相等的温度（下面简称等压温度）的讨论。     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程(昂内斯气态方程的简称)的几点讨论.一是昂氏气态方程收缩为范式气态方程的讨论;二是昂氏气态方程温度T昂和理想气态方程温度T理相等的压强(下面简称等温压强)的讨论;三是昂氏气态方程压强P昂和理想气态方程压强P理相等的温度(下面简称等压温度)的讨论.     

有关昂氏气态方程的几点讨论

本文叙述了有关昂氏气态方程(昂内斯气态方程的简称)的几点讨论.一是昂氏气态方程收缩为范式气态方程的讨论；二是昂氏气态方程温度T昂和理想气态方程温度T理相等的压强(下面简称等温压强)的讨论；三是昂氏气态方程压强P昂和理想气态方程压强P理相等的温度(下面简称等压温度)的讨论.     

几个典型的数学物理方程的物理解读

拉普拉斯方程、 泊松方程、 热传导方程( 扩散方程)和波动方程是大学物理教学中常见的几个典型的微 分方程, 分别涉及到了流体力学、 电磁学、 热学和波动等重点教学内容. 探索了如何用直观明确而容易理解的物理 语言解读这些方程. 从拉普拉斯方程的物理本质出发, 通过改变该方程右端的形式, 分别引出泊松方程、 热传导方 程( 扩散方程)和波动方程, 详细阐述了上述方程与相关物理现象之间的内在联系, 提出了一种关于以上方程的纵 向对比讲授法, 为学生深入理解典型的数学物理微分方程的物理含义提供了可行的思路     

三类非线性演化方程新的Jacobi椭圆函数精确解

应用修正影射法分别求解三类非线性演化方程,即非线性Klein-Gordon方程,mKdV方程和广义Boussinesq方程,得到了一些新的Jacobi椭圆函数展开解,包括Jacobi椭圆函数解、混合Jacobi椭圆函数解、孤子解和三角函数解. 关键词： Klein-Gordon方程 mKdV方程 广义Boussinesq方程 Jacobi椭圆函数     

广义Birkhoff系统的一类积分

将Birkhoff方程添加一附加项成为广义Birkhoff方程.将Birkhoff方程的一类积分推广并应用于广义Birkhoff方程.举例说明结果的应用. 关键词： Birkhoff方程 广义Birkhoff方程 积分     

轴流压气机转子内流数值模拟及叶顶间隙泄漏分析

本文数值求解N—S方程和Euler方程对比分析单转子轴流压气机内部流场、计算较好地预测了压气机的平均流场及叶尖泄漏涡的生成演化过程。为分析泄漏流动的成因，本文采用简化模型计算泄漏速度。计算与实验结果的时比表明，泄漏流动是无私流动，粘性主要表现为对涡的衰减；泄漏流动由叶片两侧的转了静压控制，粘性在叶片两侧作用持平；给定叶片两侧的转子静压即可由Bernoulli方程求出泄漏速度。     

基于Hough变换的金刚石颗粒测量方法研究

针对金刚石颗粒图像分析时的颗粒边缘非闭合性问题,本文提出了一种基于Hough变换的金刚石颗粒测量新方法。该方法首先对图像进行形态学去噪、平滑滤波和Canny边缘检测等预处理,得到金刚石颗粒图像的初始边缘曲线,然后采用Hough变换提取边缘曲线的直线特征,并通过极径和极角对多个直线特征进行判断和图形识别,得到确定的金刚石颗粒边缘轮廓,最后对得到的边缘轮廓进行拟合,测量出金刚石颗粒的粒径、椭圆度和圆度等参数大小。该方法在VC+ 环境下,用OpenCV编程技术对其进行了实验验证,结果表明：该方法可以准确快速地测量出金刚石颗粒特征参数,为金刚石颗粒的等级评定提供了技术支持。     

基于远程控制的六足搜救机器人系统的设计

针对灾后现场环境的危险性与复杂性,设计了一套搜救机器人系统。在基于仿生学的基础上设计机器人六足式移动平台,以Atmega128型单片机为控制核心,通过步态与动作控制,使之具有强大的越障能力和机体灵活性。整个搜救系统分为机器人系统和控制中心系统两大部分。机器人系统配有完备的传感器模块以及高清摄像头,通过无线传输技术,可在0-1000米范围内实现向控制中心系统上位机的数据与图像传输,并接受上位机控制指令,控制中心根据采集到的信息,可以有效指挥现场搜救人员,大大提高了搜救速度与效率。     

全势能线性Muffin-Tin轨道组合分子动力学方法及其在半导体团簇结构计算中的应用

研究原子团簇的结构及其与之相关的物理和化学的性质是当前国际上一个活跃的研究前沿。全势能线性Muffin Tin轨道组合法是目前国际上最先进的第一性原理分子动力学方法之一。本文简要地阐述了全势能线性Muffin Tin轨道组合法的原理 ,以及本研究小组用此方法在半导体原子团簇结构研究中的部分结果。     

SeX(X=H,C,N,O)的结构与势能函数

用密度泛函B3LYP方法对SeX(X=H,C,N,O) 分子体系进行了理论研究,得到SeX(X=H,C,N,O) 分子体系的基态电子状态的平衡几何Re和离解能De,并在计算出来的一系列单点势能基础上,用正规方程组拟合Murrell-Sorbie(M-S)势能函数,得到相应态的解析势能函数,光谱参数Be、αe、ωe、和ωeχe为:HSe:7.74786cm-1、0.22000cm-1、2425.33344cm-1 and 39.51563cm-1;SeC:0.56678cm-1、0.00370cm-1、1021.70315cm-1、5.10000cm-1;NSe:0.45528cm-1、0.00375cm-1、946.30895cm-1、4.98923cm-1;OSe:0.45296cm-1、0.00001cm-1、889.77025cm-1、4.55983cm-1.由此计算对应的光谱参数和力学性质.结果表明SeX(X=H,C,N,O) 分子体系是可稳定存在的.     

Nd:GdVO4 self-Raman laser using double-end polarised pumping at 880 nm for high power infrared and visible output

We report and evaluate a novel double-end polarised 880?nm pumping scheme for a Nd:GdVO₄ self-Raman laser, aimed at efficiently generating high output powers in the near-infrared and visible. Compared to conventional single-end pumping, this pump scheme has significant benefits in terms of absorption efficiency, temperature effects in the crystal, and mode-matching between the pumping beam and TEM₀₀ resonator mode. The maximum first-Stokes output powers were 4.1?W for CW operation and 5.63?W for quasi-CW (50?% duty-cycle) operation, with the diode-Stokes conversion efficiency of 11.2?% and 10.3?%, respectively. Visible emission was also realised by intra-cavity frequency-doubling (586.5?nm) or sum-frequency-generation (559?nm) using BBO or LBO crystals. For CW operation, the maximum output power was 3.46?W at 586.5?nm and 4.05?W at 559?nm, with diode-visible conversion efficiency of 10.7?% and 12.5?%; while for quasi-CW operation (50?% duty-cycle), the maximum output peak power was 6.5?W at 586.5?nm and 9.2?W at 559?nm, corresponding to 13.1?% and 18.9?% diode-visible conversion efficiency.     

Crystalline Cr²⁺:ZnSe/chalcogenide glass composites as active mid-IR materials

We propose new transition metal (TM)-doped ZnSe/As?S?:As?Se? composite materials for mid-IR fiber lasers. The composites are the suspension of crystalline micro- and nanosized TM2?:ZnSe or TM2?:ZnS powders in chalcogenide glasses with the refraction index matching. Mid-IR room-temperature lasing of Cr2?:ZnSe/As?S?:As?Se? microcomposite material is demonstrated at the 2.4 μm wavelength.     

Long-range chemical interactions in solid-state reactions: effect of an inert Ag interlayer on the formation of L10-FePd in epitaxial Pd(0 0 1)/Ag(0 0 1)/Fe(0 0 1) and Fe(0 0 1)/Ag(0 0 1)/Pd(0 0 1) trilayers

The effect of 0, 0.5, and 1?μm-thick Ag interlayers on the chemical interaction between Pd and Fe in epitaxial Pd(0?0?1)/Ag(0?0?1)/Fe(0?0?1)/MgO(0?0?1) and Fe(0?0?1)/Ag(0?0?1)/Pd(0?0?1)/MgO(0?0?1) trilayers has been studied using X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and magnetic structural measurements. No mixing of Pd and Fe occurs via the chemically inert Ag layer at annealing temperatures up to 400?°C. As the annealing temperature is increased above 400?°C, a solid-state synthesis of an ordered L1₀-FePd phase begins in the Pd(0?0?1)/Ag(0?0?1)/Fe(0?0?1) and Fe(0?0?1)/Ag(0?0?1)/Pd(0?0?1) film trilayers regardless of the thickness of the buffer Ag layer. In all samples, annealing above 500?°C leads to the formation of a disordered Fe_xPd_1?x(0?0?1) phase; however, in samples lacking the Ag layer, the synthesis of Fe_xPd_1?x is preceded by the formation of an ordered L1₂-FePd₃ phase. An analysis of the X-ray photoelectron spectroscopy results shows that Pd is the dominant moving species in the reaction between Pd and Fe. According to the preliminary results, the 2.2?μm-thick Ag film does not prevent the synthesis of the L1₀-FePd phase and only slightly increases the phase’s initiation temperature. Data showing the ultra-fast transport of Pd atoms via thick inert Ag layers are interpreted as direct evidence of the long-range character of the chemical interaction between Pd and Fe. Thus, in the reaction state, Pd and Fe interact chemically even though the distance between them is about 10⁴ times greater than an ordinary chemical bond length.     

Configuration-Space Faddeev Calculation for Proton�CDeuteron Elastic Scattering Observables

A new computational method for solving the nucleon?Cdeuteron breakup scattering problem has been applied to study the elastic nucleon?Cdeuteron scattering on the basis of the configuration-space Faddeev?CNoyes?CNoble?CMerkuriev equations. The Merkuriev?CGignoux?CLaverne approach has been generalized for arbitrary nucleon?Cnucleon potentials and with an arbitrary number of partial waves. The nucleon?Cdeuteron observables at the incident nucleon energy 3?MeV have been calculated using the charge-independent AV14 nucleon?Cnucleon potential including the Coulomb force for the proton?Cdeuteron scattering. Results have been compared with those of other authors and with experimental proton?Cdeuteron scattering data.     

Surface passivation effects in silicon nanowires

We report first-principles simulation results for the electronic band structure of Si nanowires (SiNWs) aligned along the ?100? and ?110? directions with H, OH, and CH₃ substituents passivating the surfaces. The ?100? wires studied have {110} faces and square cross-sections with diameters up to 1.73 nm, while the ?110? wires have {111} faces and diamond cross-sections with diameters up to 1.46 nm. We found that passivation using OH or CH₃ groups reduced the band gaps compared to H-terminated ?100? SiNWs, and passivation using CH₃ groups produced systems with indirect gaps for all ?100? SiNWs studied. All band gaps were direct in the ?110? SiNWs independent of passivation. The near-gap orbitals are greatly affected by the different substituents. We also found that the carrier effective masses of ?100? SiNWs are sensitive to the diameter and passivation, while those of ?110? SiNWs are not.     

Simultaneous measurements of indoor radon and thoron and inhalation dose assessment in Douala City,Cameroon

ABSTRACT

Radon, thoron and associated progeny measurements have been carried out in 71 dwellings of Douala city, Cameroon. The radon–thoron discriminative detectors (RADUET) were used to estimate the radon and thoron concentration, while thoron progeny monitors measured equilibrium equivalent thoron concentration (EETC). Radon, thoron and thoron progeny concentrations vary from 31?±?1 to 436?±?12 Bq?m^–3, 4?±?7 to 246?±?5 Bq?m^–3, and 1.5?±?0.9 to 13.1?±?9.4 Bq?m^–3. The mean value of the equilibrium factor for thoron is estimated at 0.11?±?0.16. The annual effective dose due to exposure to indoor radon and progeny ranges from 0.6 to 9?mSv?a^–1 with an average value of 2.6?±?0.1?mSv?a^–1. The effective dose due to the exposure to thoron and progeny vary from 0.3 to 2.9?mSv?a^–1 with an average value of 1.0?±?0.4?mSv?a^–1. The contribution of thoron and its progeny to the total inhalation dose ranges from 7 to 60?% with an average value of 26?%; thus their contributions should not be neglected in the inhalation dose assessment.