Similarity rules for collisionless hot‐filament discharges

The plasma parameters of a collisionless hot‐filament discharge are investigated theoretically and experimentally as functions of a dimensionless variable called the discharge efficiency, which is a product of several relevant external parameters. It is found that the main plasma parameters, as measured in plasma chambers that are either geometrically different or filled with different working gases, depend on this variable in approximately the same way. Consequently, the number of experimental data necessary for discharge characterization may be drastically reduced.     

火焰原子吸收光谱法测定温泉矿泉水中微量元素

用火焰原子吸收光谱仪对乌鲁木齐市水磨沟区温泉矿泉水中的铜、钾、锌、钙、镁等微量元素进行了分析测定,并探讨了酸度、干扰离子对测定的影响.同时用吸光光度法测定了矿泉水中铁,用容量分析法测定了矿泉水中硫化氢,取得较好的结果.     

Modelling particle formation and growth in a plasma synthesis reactor

A model for particle nucleation and growth in a thermal plasma reactor is discussed. A nondimensional form of the aerosol general dynamic equation is derived under a set of simplifying assumptions which are appropriate to plasma powder synthesis, and the resulting set of equations is solved numerically. The results are converted to dimensional form for the case of iron powder, for which experimental data are available, and for silicon carbide. Calculated particle sizes increase significantly with increasing reactant concentrations and with decreasing cooling rate, although the influence of cooling rate is mainly a residence time effect.     

Fundamental problems in brittle fracture: unstable cracks and delayed breaking

This presents a short review on two problems where brittle fracture is involved. In the first one, a hot glass plate is subject to a local stress when drowned into a cold bath. In the region of transition between the cold and hot side, large stresses build up, that can be related accurately to the various coefficients typical of the plate material, heat dilation coefficient, heat conductivity, Young's modulus, etc. Thanks to thais, one can compare well the experimental results and the theoretical predictions based on the Griffith criterion for the propagation of a straight crack, and for its instability against an undulating mode. In the other problem, one looks at the delay before a bent 2D crystal breaks: this (very long) delay is interpreted as the time required for homogeneous nucleation of a critical Griffith nucleus in a region of the crystal under extension. Although it agrees fairly well with some experimental data, other experimental facts are required to complicate the model by considering a multistep nucleation process. To cite this article: Y. Pomeau, C. R. Mecanique 330 (2002) 249–257.     

Absence of screening in certain lattice gauge and plasma models

We discuss some Abelian lattice gauge models of the noncompact variety, including models of relativistic and nonrelativistic plasmas. For all these models we show absence of exponential clustering for some observables in some domains in parameter space. We comment on the physical meaning of these results, in particular with respect to Debye screening of static electric charges.     

弱相对论等离子体横向扰动下的离子声孤波

在低阶近似下，得到了描述无磁场相对论热离子等离子体的KP(Kadomtsev-Petviashvilli) 方程.研究表明，相对论热离子等离子中的非线性离子声孤波在高阶横向拢动下是稳定的， 且在相对论热离子等离子体中仅存在压缩型孤波. 关键词： 离子等离子体 孤波 声波 约化摄动法     

On the phenomenology of tachyon radiation

We present a brief overview of the different kinds of electromagnetic radiations expected to come from (or to be induced by) space-like sources (tachyons). New domains of radiation are here considered, and the possibility of experimental observation of tachyons via electromagnetic radiation is discussed.     

Tomographic reconstruction of volume emission coefficients from line integral data

The technique of reconstructive tomography (RT) is a powerful method of obtaining local, spatially resolved volumetric emission coefficients from line integral data. The applicability of this technique as a diagnostic for nonuniform sources is studied using simulated data with and without noise. The major advantage of RT techniques is that they may be applied, without restriction, to highly asymmetric data as well as symmetric data. When applied to symmetric data, the technique appears to be less susceptible to noise than Abel inversion techniques. Also examined is a method of accounting for self-absorption under certain circumstances.     

累托石粘土/热塑性聚氨酯弹性体纳米复合材料的热性能研究

以十二烷基季铵盐与累托石 (REC)进行阳离子交换得到有机粘土 (OREC) ,以OREC与热塑性聚氨酯弹性体 (TPUR)采用熔融挤出共混法制备了OREC TPUR纳米复合材料 .用透射电子显微镜 (TEM)表征了复合材料的微相结构 ,测试了复合材料动态热机械性能 (DMA)及热失重 (TG) ,讨论了复合材料的耐热空气老化性能及耐油介质性能等 .结果表明 ,累托石粘土在聚氨酯热塑性弹性体中以纳米尺寸分散 ,纳米复合材料具有较高的动态热机械性能 ,其储能模量最大可提高 7倍多 ,损耗模量最大可提高 4倍多 .复合材料的其他性能均有不同程度的提高 ,特别是OREC添加量为 2 %时 ,复合材料TG、耐油性及耐空气老化性能最高 .其初始分解温度提高 1 5℃ ,在 40 #机油中浸泡 1 68h后拉伸强度保持率达到 86 4% ,1 2 0℃热空气老化箱中老化 72h后拉伸强度保持率达到 87 0 % .     

Reactions of O(3P) with secondary C-H bonds of saturated hydrocarbons in nonequilibrium plasmas

The functionalization of three n-alkanes by means of a low-pressure oxygen plasma has been achieved. The plasma was generated by applying a low-Frequency high-voltage glow discharge through an oxygen flow. bit, activated species so produced have been allowed to interact with the surface of each one of the liquid compounds at a time. The hydrocarbon has been cooled down to a temperature low enough so that its vapor pressure is about 20–100 times lower than the O₂ pressure, this heing of the order of 0.1–0.4 torr. Under these conditions the main products of the reactions have been the alcohols, except for the primary ones, and the corresponding ketones. A remarkable result we have arrived at is that for the first time secondary carbon hydrogen bonds have shown to possess different reactivities withO(³P). The latter has proved to he the most relevant active species of the plasma. A discussion is given to explain this novel result under two theoretical bases recently published: (i) a conformational analysis of the hydrocarbons according to molecular mechanics calculations, and (ii) an analysis of properties of the molecules based on calculations with charge distributions derived from 6–31G^* wave functions.