Magnetohydrodynamics equilibrium of a self-confined elliptic plasma ball

A variational principle is applied to the problem of magnetohydrodynamics (MHD) equilibrium of a self-contained elliptical plasma ball, such as elliptical ball lightning. The principle is appropriate for an approximate solution of partial differential equations with arbitrary boundary shape. The method reduces the partial differential equation to a series of ordinary differential equations and is especially valuable for treating boundaries with nonlinear deformations. The calculations conclude that the pressure distribution and the poloidal current are more uniform in an oblate self-confined plasma ball than that of an elongated plasma ball. The ellipticity of the plasma ball is obviously restricted by its internal pressure, magnetic field, and ambient pressure. Qualitative evidence is presented for the absence of sighting of elongated ball lightning.

Magnetohydrodynamic equilibrium of plasma ball lightning

Thin foil observations using transmission electron microscopy reveal that the density of dislocations within the band is extremely high and the tangled arrangement of dislocations tends to align along the length of the shear band. The grains in the band were also elongated along the shear band and clearly exhibited a crystallographic nature.

Statistical Simulation of Thin-Film Bearings

The information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method are used to simulate the gas flows between the write/read head and the platter of the disk drive (the slider bearing problem). The results of both methods are in good agreement with numerical solution of the Reynolds equation in the cases studied. However, the DSMC method owing to the problem of large sample size demand and the difficulty in regulating boundary conditions at the inlet and outlet was able to simulate only short bearings, while IP simulates the bearing of authentic length ~1000 m ? and can provide more detailed flow information.

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Coupling with bionic principles, an attempt to improve the wear resistance of ball bearing steel (GCr15) with biomimetic units on the surface was made using a pulsed Nd: YAG laser. Air and water film was employed as processing medium, respectively. The microstructures of biomimeitc units were examined by scanning electron microscope and X-ray diffraction was used to describe the microstructure and identify the phases as functions of different mediums as well as water film with different thicknesses. The results indicated that the microstructure zones in the biomimetic specimens processed with water film were more refined and had better wear resistance increased by 55.8% in comparison with that processed in air; a significant improvement in microhardness was achieved by laser surface melting. The application of water film provided considerable microstructural changes and much more regular grain shape in biomimetic units, which played a key role in improving the wear resistance of ball bearing steel. (c) 2010 Elsevier B.V. All rights reserved.

Crystallographic and electrochemical characteristics of TiZrNiCu quasicrystal ball-milled with La0.9Zr0.1Ni4.5Al0.5 alloy

Icosahedral quasicrystalline Ti45Zr35Ni17Cu3 alloy was ball-milled with 30 mass% La0.9Zr0.1Ni4.5Al0.5 alloy (LaNi5 phase), the effect of the milling time on crystallographic and electrochemical characteristics of the alloy powder was investigated. The amount of amorphous phase increased with increasing milling time from 60 to 360 min, and the LaNi5 phase cannot be observed when milling time was 240 min or more. The maximum discharge capacity and high-rate dischargeability of milled alloy electrodes were obviously higher than those of the alloy electrode before milling. The cycling capacity retention rate after 40 cycles increased from 52.8% (t = 60 min) to 62.9% (t = 360 min).

Crystallographic and electrochemical characteristics of Ti45Zr35Ni17Cu3 quasicrystalline alloy ball-milled with nickel powder

Crystallographic and electrochemical characteristics of ball-milled Ti45Zr35Ni17Cu3 +xNi (x = 0, 5, 10, 15 and 20 mass%) composite powders have been investigated. The powders are composed of amorphous, I- and Ni-phases when x increases from 5 to 20. With increasing x, the amount of Ni-phase increases but the quasi-lattice constant decreases. The maximum discharge capacity first increases as x increases from 0 to 15 and then decreases when x increases further from 15 to 20. The high-rate dischargeability and cycling stability increase monotonically with increasing x. The improvement of the electrochemical characteristics is ascribed to the metallic nickel particles highly dispersed in the alloys, which improves the electrochemical kinetic properties and prevents the oxidation of the alloy electrodes, as well as to the mixed structure of amorphous and icosahedral quasicrystal line phases, which enhances the hydrogen diffusivity in the bulk of the alloy electrodes and efficiently inhibits the pulverization of the alloy particles.

Crystallographic and electrochemical properties of ball-milled quasicrystalline Ti45Zr35Ni17Cu3 alloy with 20 mass% Ni

Icosahedral quasicrystalline Ti45Zr35Ni17Cu3 alloy powder was ball-milled with 20 mass% Ni, and the effect of the ball-milling time (t) on crystallographic and electrochemical characteristics were investigated. The amounts of icosahedral quasicrystalline and Ni phases decreased when ball-milling time increased from 30 to 180 min. The powder consisted of amorphous and (Ni and Ti) phases after 360 min of ball-milling. The maximum discharge capacity of the powder electrodes first increased from 89 (t = 0 min) to 192 mAh g(-1) (t = 180 min), and then decreased to 138 mAh g(-1) (t = 360 min). The high-rate dischargeability and the discharge capacity after 15 cycles increased with increasing ball-milling time.

Electrode characteristics and microstructure of AB(2)-AB(5) composite hydrogen storage alloy formed by ball-milling process

For improving the electrode characteristics of the Zr-based AB(2)-type alloy, a new kind of composite hydrogen Zr0.9Ti0.1(Ni0.50Mn0.35V0.15)(2)(represented as AB(2)) with a rare storage alloy was successfully prepared by ball-milling I earth-based AB(5)-type alloy (represented as AB(5)) which worked as a surface modifier. Effects of ball-milling on the electrode characteristics and microstructure of Zr0.9Ti0.1(Ni0.50Mn0.35V0.15)(2) alloy and mixtures of AB(2) with AB(5) alloy were investigated. After milling the mixed AB(2) and AB(5) powders (9: 1 in mass ratio) for 10min, XRD and SEM analysis showed that AB(2) and AB(5) maintained their original crystalline states, respectively, some AB(5) particles were adhered onto the surface of AB(2), and some fresh surfaces were formed. It was found that the activation cycles of AB(2)-AB(5) composite alloy was shortened from 14 to 7 and the maximum discharge capacity was increased from 330mAh . g(-1) to 347mAh . g(-1) as compared with AB(2) alloy. The discharge rate capability of AB(2) alloy was also improved by ball milling AB(2) with AB(5) alloy process. The combined effect of ball-milling and mixing with AB(5) alloy is superior to that of sole treatment. It was believed that AB(5) alloy works not only as a regular hydrogen storage alloy, but also as a surface modifier to catalyze the hydriding/ dehydriding process of AB(2) alloy.

Friction and Wear Studies of Octadecyltrichlorosilane SAM on Silicon

A self-assembled monolayer of octadecyltrichlorosilane (OTS) was prepared on a single-crystal silicon wafer (111) and its tribological properties were examined with a one-way reciprocating tribometer. The worn surfaces and transfer film on the counterface were analyzed by means of scanning electron microscopy and X-ray photoelectron spectroscopy. The results show that, due to the wear of the OTS monolayer and the formation of the transfer film on the counterpart ball, the friction coefficient gradually increases from 0.06 to 0.13 with increasing sliding cycles and then keeps stable at a normal load of 0.5N. The transfer film is characterized by deposition, accumulation, and spalling at extended test duration. Though low friction coefficients of the monolayer in sliding against steel or ceramic counterfaces are recorded, poor load-carrying capacity and antiwear ability are also shown. Moreover, the monolayer itself or the corresponding transfer film on the counterface fails to lubricate even at a normal load of 1.0 N. Thus, the self-assembled monolayer of octadecyltrichlorosilane can be a potential boundary lubricant only at very low loads.

Temperature Dependence of the Tribological Properties of Laser Re-Melted Al-Cu-Fe Quasicrystalline Plasma Sprayed Coatings

The aim of this study was to investigate the effect of temperature on tribological properties of plasma-sprayed Al-Cu-Fe quasicrystal (QC) coating after laser re-melting treatment. The laser treatment resulted in a more uniform, denser and harder microstructure than that of the as-sprayed coatings. Tribological experiments on the coatings were conducted under reciprocating motion at high frequency in the temperature range from 25 to 650 degreesC. Remarkable influence of temperature on the friction behavior of the coating was recorded and analyzed. Microstructural analysis indicated that the wear mechanisms of the re-melted QC coatings changed from abrasive wear at room temperature, to adhesive wear at 400 degreesC and severe adhesive wear at 650 degreesC owing to the material transfer of the counterpart ball. It was also observed that the ratio of the icosahedral (i)-phase to beta-Al-50(Fe,CU)(50) phase in the coating was higher after test at 400 'C than that at 650 'C. The variation of the ratio UP of coating and of the property of the counterpart ball and coating with the temperature are the two main factors influencing the wear mechanisms and value of the friction coefficient.

IP Simulation of Micro Gas Flows under 3-D Head Sliders

Gas film lubrication of a three-dimensional flat read-write head slider is calculated using the information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method, respectively. The pressure distributions on the head slider surface at different velocities and flying heights obtained by the two methods are in excellent agreement. IP method is also employed to deal with head slider with three-dimensional complex configuration. The pressure distribution on the head slider surface and the net lifting force obtained by the IP method also agree well with those of DSMC method. Much less (of the order about 10(2) less) computational time (the sum of the time used to reach a steady stage and the time used in sampling process) is needed by the IP method than the DSMC method and such an advantage is more remarkable as the gas velocity decreases.

种子植物的起源和早期演化

本项研究工作是在“种子植物的起源和早期演化”的题目下由六个主要的研究部分构成 基本上是根据产自中国的化石所提供的形态学上的证据来探讨与现代植物类群之间的关系。 1)早二迭世山西组松柏类及相关类群的研究 2)山西省上石千峰组晚二迭世种子植物的研究 3)煤核植物科达类在演化上的意义 4)晚泥盆世植物Polypetalophyton wufengensis的研究 5)种子植物起源和早期演化的化石证据的研究 6)早泥盆世似种子植物的研究。

我国重要成煤植物的解剖学研究

本研究工作在研究华夏植物区重要成煤植物的解剖学特征的基础上，重点讨论了华夏植物区科达植物的地质地理分布特征以及科达植物的起源和演化问题，并根据煤巾植物残体研究成果，讨论了我国不同地质时代几种特殊煤的成因问题，把古植物学研究与国民经济的发展联系起来。 本研究工作的主要成果概括如下： 1 华夏植物区的科达植物主要分布于华北植物地理区，其起源时间可能与欧美植物区的科达植物一样早，但其繁盛期却比欧美植物区的要晚、而且其生存的历程要长. 2 华夏植物区的科达植物除了Mesoxylon和Pennsylvanioxylon(=Cordaixylon)二个自然属外，还有第三个自然属存在，即Shanxioxylon属。其茎和生殖器官的解剖构造与前二个属明显不同。 在茎的解剖构造上，Shanxioxylon介于Mesoxylon和Pennsylvanioxylon之间，但在生殖器官的构造上Shanxioxylon显然要比后二者进化。 3 山西太原西山煤田早二叠世早期太原组上部7号煤层煤核中的一种观音座莲目生殖器官一山西虫囊蕨（新种）Scolecopteris shanxiensis sp．nov.是华夏植物区目前发现的第二种具解剖构造的晚古生代观音座莲目生殖器官化石，与虫囊蕨属已有的29个具解剖构造的种相比，本新种具有较进化特征。 4 产于华南晚二叠世的举世闻名的“乐平煤”巾的“树皮体”组分不是来源于鳞木类周皮或辉木类小根皮层，而可能是来源于一种裸子植物的根的木栓组织，这种根很有可能是大羽羊齿类的根一刺根茎。 5 我国北方侏罗纪煤中，主要由银杏类植物形成的煤具有形成石油的很大潜力，而主要由松杉类或苏铁类植物形成的煤形成石油的希望不大。 6 我国云南晚第三纪特殊煤种一浅色褐煤（白泡煤）的主要成煤植物不是泥炭藓植物，而是草本被子植物。

小类心籽（新命名）和波缘靓籽（比较种）的结构与个体发育研究

本文报道了在中国山西太原晚石炭世煤核中发现的两种不同类型种子：小类心籽（新命名）Nucellangium minor nom. nov. 和波缘靓籽（比较种）Callospermarion cf. undulatum, 它们分别属于心籽目（Cardiocarpales)的类心籽属（Nucellangium）和靓籽属（Callospermarion）。 小类心籽为科达类植物种子，两侧对称，厚心形，主切面长约4-6mm，宽3-4mm，次切面厚约2.5-3.0mm。成熟种子的珠被由肉质层、硬质层组成，内表层由7-10层大型薄壁细胞组成，只存在于未成熟种子。肉质层外有一角质层和表皮层，肉质层分为两个亚层;外层细胞扁长，有深色内含物，内层无内含物，由薄壁细胞组成，越往内越小，硬质层外缘光滑无刺突，分为两个纤维细胞亚层，外层细胞壁厚直径小，内层细胞直径增大细胞壁变薄，沿纵切方向伸长。珠心除基部外游离于珠被。双维管系统由分布在肉质层的珠被维管束和呈套状分布的珠心维管束组成，组成珠心维管束的管胞为梯纹状加厚。文章对类心籽属的特征作了修正，并以小类心籽的形态、大小和珠被结构等特征为依据，就它的个体发育进行了探讨，证明晚出同名的小心籽（Cardiocarpus minor Wang 1987）为当前小类心籽个体发育的早期阶段。 波缘靓籽（比较种）（Callospermarion cf. undulatum)为靓羊齿植物（Callistophytales）种子，两侧对称，三层珠被，肉质层占据珠被的大部分，有分泌腔分布，肉质层外缘呈波缘状。珠心除了在基部外，游离于珠被。维管束分布在翼部肉质层内侧。首次在太原的靓籽属种子中发现了具有重要意义的特征性结构——分泌腔。还就山西太原发现的波缘靓籽所代表的个体发育阶段进行了讨论。 文中还分别讨论了这两类种子各自的亲缘关系。