振荡管流传质及其在呼吸问题上的应用

本文在分析呼吸系统几何特点和通气过程力学特性的基础上,根据振荡管流传质的原理,提出了一个适用于生理呼吸,常规呼吸和高频呼吸的统一通气模型,它有助于理解各类呼吸机的临床效果,它可以说明Fredberg模型和Slutsky模型不能说明的临床实验结果。     

金属团簇物理

即使已经有了更基本的复杂理论,科学家也经常在简单模型的基础上,建立起最富有前景的研究领域.建立这些模型是为了对实验观察结果进行必要的解释.如果这些模型是正确的,那么它不仅能满意地解释各种数据,还能成功地预言新的结果.这些“正确的”模型还应和已有的基本理论相吻合,或者可从基本理论导出.原子的玻尔模型是一典型的例子.最初汤姆孙提出了“葡萄干布丁式”的原子模型,即作为负电子的“葡萄干”浸没在正电荷的球形布丁内.卢瑟福的散射实验说明它应该被核式原子模型所取代,后来的光谱数据又导致了玻尔的壳层模型,它得到了量子力学的证…     

非线性超场和夸克禁闭

利用非线性超场技术,我们讨论了超对称的非线性场论模型.找到了超对称运动方程精确静态解的一般形式,它可以作为袋模型的出发点。作为一个特殊情形,我们重新得到了 SLAC 袋模型,也就是说,SLAC 袋是超对称的.文中还讨论了超对称的 Sine-Gordon 模型、Sinh 模型和 exp 模型.     

x^3振荡器及其周期

建立了ｘ＾３振荡器模型,导出了它的振动周期公式。     

Kagome晶格上混合自旋模型的自由费密近似解

本文考虑Kagome晶格上的混合自旋模型,运用decimation和对偶变换,证明它等价于一个八顶角模型。由八顶角模型的自由费密近似解给出了该模型的自由能及临界条件的近似表达式。 关键词：     

对磁通运动的扩展模型的评骘

本对磁通运动的扩展模型作了评骘，为此我们也对扩展模型的主要假设和它的主要结果作了介绍。     

原子核的空间结构

核模型的发现在卢瑟福研究原子散射α粒子时发現湯姆孙的原子模型不正确、正电荷不是按整个原子連续地分布,而是集中在它的中部——核之后,原子核物理学就产生了。这是一个革命的事件,它改变了物理科学发展的全部进程。电子——在它身上集中的全是負电的粒子——的发现只是推翻原子的旧概念的第一步。     

封面说明

1953年,沃森和克里克建立了生物细胞内的遗传信息载体DNA(去氧核糖核酸)结构的双螺旋模型,今年是60周年.DNA双螺旋模型的建立是20世纪科学的一件大事,它是20世纪自然科学四大模型之一(另外三个是宇宙学标准模型、粒子物理学标准模型和地壳的板块模型).它一方面将生命科学的基础置于分子水平之上,置于坚实的物理学、化学和信息科学的原理之上,使生命科学更多地得到数学、演绎和推理方法的支持,导致作     

(广义)BFOFW模型的Hamilton程式及其量子化

本文讨论了作为规范WZNW场论的BFOFW模型的Hamilton程式,并在此基础上研究了它的正则量子化及BFV-BRST量子化.另外,本文还在经典水平上提出了一种广义的BFOFW模型。     

x~3振荡器及其周期

建立了ｘ~３振荡器模型,导出了它的振动周期公式．     

Phase transition and bulk properties of some polonide compounds: a comparative study

In the present paper the structural and electronic properties of polonides of lead, barium and calcium polonide (PbPo, BaPo and CaPo) have been reported. These properties have been studied using first principles calculations as well as the interionic potential model modified with the covalency effect. Gibbs free energy and enthalpy calculations show that these compounds undergo a structural phase transition from NaCl-type structure to CsCl-type structure. The electronic band structure and density of states of the PbPo, BaPo and CaPo have also been reported. The calculated equilibrium structural parameters are in good agreement with the available experimental results.     

Electronic structural and bulk properties of ScSe: ab initio study

Electronic, structural and bulk properties of scandium selenide, ScSe have been reported in the present paper. These properties have been studied using first principle calculations as well as the interionic potential model modified with covalency effect. The Gibbs free energy and enthalpy calculations show that present compound undergoes a structural phase transition from the NaCl-type structure to the CsCl-type structure. The stability of the present compound is discussed in terms of electronic band structure and density of states. The calculated equilibrium structural parameters are in a good agreement with the available experimental results.     

Ab initio study of the structure of oriented films of linearly chain carbon

Ab initio study of oriented carbon films consisting of bent carbon chains closely packed into a hexagonal cell has been reported. A new structural model of films has been presented. It has been shown that hydrogen impurity is necessary for the stabilization of their structure. Interatomic distances in the film both between chains and along them, as well as the bending angle of carbon chains, have been determined. It has been shown that carbon atoms in the chains have a polyene bond. The distances between chains (5.0 Å) theoretically determined in this work are in excellent agreement with the previously reported experimental data. The analysis of the electronic density of states shows that these films have the dielectric properties with a band gap of about 0.43 eV. The distribution of the charge density along the chains in the film has been studied, which makes it possible to propose a model of the structural instability of such films.     

ZnO nanoparticles favours heterogeneous nucleation in PET–ZnO nanocomposites

The structural and chemical properties with non-isothermal crystallization kinetics of PET–ZnO nanocomposites have been reported in this article. ZnO nanoparticles have been synthesized via chemical route with average diameter 19 nm which made confirm by transmission electron microscopy and X-ray diffractometer (XRD) techniques. PET–ZnO nanocomposites have been prepared by solution casting method. The structural and chemical changes occurred in poly (ethylene terephthalate) after inclusion of ZnO nanoparticles have been studied with the help of XRD and Fourier transform infrared spectroscopy, respectively. It was observed from differential scanning calorimeter that ZnO nanoparticles work as nucleating agent for heterogeneous nucleation in PET matrix under non-isothermal crystallization process. The combined Avrami and Ozawa models have been proved adequate to explain non-isothermal crystallization kinetics of PET–ZnO nanocomposites, and also, ZnO nanoparticles have been caused to reduce crystallization activation energy in pristine PET as per the applied Kissinger model.     

IMPROVEMENT OF A TAIL-PLANE STRUCTURAL MODEL USING VIBRATION TEST DATA

To achieve the best structural model improvement using vibration test data, a major effort has been made to identify poor modelling regions as a guideline for subsequent model updating. The method presented and used in this paper is the energy error estimation method. In the method the difference between analytical and test data based energies at element scale is estimated to indicate any poor structural mass and stiffness modelling. As a result, poor modelling regions can be distinguished from those modelled correctly and the improvement of the original structural model can be carried out effectively and accurately. To demonstrate the application of this method, a full-scale tail-plane structure has been studied by using simulated “test” modes as a simulated case and using measured modes as a practical case. In both cases poor modelling regions of the original structural model have been accurately located. Subsequently, a significant improvement of the structural model with a reduction of average frequency error from original 2·2% down to 0·1% for the simulated case and from 4·6 to 1·8% for the practical case has been achieved.     

Kinetics of migration (deposition) of fission products and interstitial impurities to sinks with different singularities

The initial stage of the phase transformation kinetics in the process of migration of fission products and interstitial impurities to sinks with different singularities has been studied. The following model sinks have been considered: edge dislocations, tops of microcracks, and wedge and stereo disclinations. Analytical dependences for kinetic regularities of phase transformations in the vicinity of the corresponding structural irregularities have been presented.     

高温高压下闪锌矿相GaN结构和热力学特性的分子动力学研究

利用分子动力学方法和Buckingham经验势模型对重要半导体材料GaN立方闪锌矿相的晶格常数、相变压力(从闪锌矿到岩盐结构)、热膨胀、等温体模量、定压热容等结构和热力学特性在300—3000K的温度范围和0—65GPa的压力范围内进行了研究.研究表明，闪锌矿相GaN常态下的结构和热力学参数的模拟结果与实验数据及其他理论结果相符.同时在所选作用势模型可靠性检验的基础上，对等温体模量、定压热容诸非谐性参量在高温高压下的热力学行为进行了预测.所得结果在材料科学等领域的研究中具有一定的应用背景和参考价值. 关键词： GaN Buckingham势 分子动力学模拟 高温高压     

Neutron diffraction studies on La2−x Dy x Ca2xBa2Cu4+2x Oz superconductors

Structural studies on Dy-substituted La-2125 type superconductors have been carried out by neutron diffraction experiments at room temperature using a monochromatic neutron beam of wavelength (λ) = 1.249 Å. A series of samples with La_2-xDy_xCa_2xBa₂Cu_4+2xO_z stoichiometric composition, forx = 0.1–0.5, have been studied for their structural properties. A tetragonal Y-123 unit cell was taken as the starting model for the Rietveld analysis. All the samples fit into the starting model, with no structural transition taking place with increasing dopant concentration. The results of Rietveld analysis and structural properties will be discussed in detail.

     

Vibrational characteristics of the niobium dichalcogenide. Bulk samples and nanofilms

A model of the niobium diselenide crystal lattice has been proposed. This model sufficiently describes the vibrational characteristics of both bulk samples and nanofilms with a thickness beyond one three-layered structural element. Calculation of the local Green functions and mean-squared atom amplitudes have been performed using the Jacobi-matrix method.Phonon density of states features stipulated by acoustic branches and low-frequency low-dispersion optical modes cross-over have been analyzed.     

A structural model of the orthorhombic Ga7Mn5 derived from its HREM image

The base-centered orthorhombic approximant Ga7Mn5 (a = 4.547(6) nm, b = 1.256(9) nm, c = 1.482(1) nm) consisting of flattened hexagon and concave octagon (called "crown" in this paper) subunits shown by high-resolution electron microscopy (HREM) was found to coexist with the Ga-Mn decagonal quasicrystal in the Ga58Mn42 alloy. The atomic sites in the flattened hexagon subunit have been deduced recently from a structural study of the orthorhombic Ga-Mn (1/1,1/1) approximant that consists only of the hexagon subunits. Similarly, the atomic sites in the crown subunit have been deduced from another orthorhombic Ga-Mn (2/1,1/1) approximant consisting only of the crown subunits. A structural model of the orthorhombic Ga7Mn5 can thus be constructed from these structural subunits. There are 332 Ga atoms and 232 Mn atoms in a unit cell, with a composition of Mn41.2Ga58.8, satisfying the symmetry of the space group Bmm2. The simulated electron diffraction patterns, [010] HREM images, and X-ray powder diffraction pattern based on this structural model agrees mainly with the experimental observations.