大功率半导体激光器腔面氮钝化的研究

针对980 nm大功率半导体激光器腔面离子铣氮钝化处理工艺进行了研究,发现腔面离子铣氮钝化可以提高激光器的输出特性及COD功率,器件输出功率提高了32.14%;老化实验后,经过氮钝化的半导体激光器没有明显退化,而未经氮钝化处理的激光器退化严重;使用俄歇谱测试仪(AES)对钝化处理后的半导体激光器试验片进行测试,发现有部分的氮离子遗留在腔面处;氮元素含量由原有的0%上升到20%,与此同时,氧元素的含量由原来的61%降至30%。结果表明,该技术能够改善半导体激光器的腔面特性,器件的可靠性和使用寿命可望得到提高。     

Synthesis and gas transport properties of polypentafluorostyrene

Polypentafluorostyrene (PPFS) (M _w = 1.7 × 10⁵ Da, M _w /M _n = 1.6, and Т _g = 110°С) has been synthesized by radical polymerization of pentafluorostyrene. The chemical structure of the polymer has been confirmed by ¹H and ¹⁹F NMR data. The permeability and diffusion coefficients of gases (He, H₂, O₂, N₂, CO₂, and CH₄) have been measured on a barometric setup. The permeability, diffusion, and solubility coefficients of gases have been shown to increase with the increases in the fluorine content in the repeat unit of the polymer in the polystyrene–poly(p-fluorostyrene)–PPFS series. Such behavior of transport parameters in the polymer series is associated with the growth in the fractional free volume and decrease in the cohesive energy density. The investigated polymers on the basis of styrene and its derivatives including PPFS are located in the middle of clouds of Robeson diagrams for N₂/CH₄, CO₂/CH₄, and O₂/N₂ and are not of interest for their separation.     

Deformation properties of modified polyacrylonitrile fibres

Conclusions Deformation properties of polyacrylonitrile fibres modified with alkali metal salts have been studied.The introduction of alkali metals by treatment of freshly spun gel-fibre with solutions of the appropriate salts aids in loosening fibre structure.Both the form of cation and also of the anion in the salt introduced affect the deformability of the modified fibres.Translated from Khimicheskie Volokna, No. 4, pp. 40–41, July–August, 1989.     

Chemical cross-linking of carboxymethylated viscose yarns

Conclusions The parameters of chemical cross-linking of yarns based on carboxymethylcellulose (CMC) and their physicomechanical properties depend on the concentration of the cross-linking agent — formaldehyde — the catalyst concentration, and also on the reaction temperature and time.A bound formaledhyde content of 0.5% by wt., in the form of methylene bridges in the make-up of CMC yarns, leads to a 31% increase in their strength in the wet state.Chemical cross-linking of CMC fibres with formaldehyde helps increase their resistance to biodegradation and correspondingly leads to a larger strength retention in living organisms.Translated from Khimicheskie Volokna, No. 5, pp. 18–20, September–October, 1989.     

Development and study of robast control system for dc thyristor electric drive using polynomial techniques

Possibilities of polynomial techniques for synthesizing and analyzing a robast control system of dc thyristor electric drivers are considered. It is shown that the use of the suggested techniques makes it possible to decrease the sensitivity of a controlled electric drive to parametric, structural, and external disturbances by about an order of magnitude. A technique for optimizing the parametric sensitivity of the quality factors is suggested.     

Mathematical modelling of perorally induced immunological tolerance

A mathematical model of the mechanism of development of orally induced immunologic tolerance has been suggested. The model presents a system of differential non-linear equations, and it is realized as a program in FORTRAN. The model describes primary and secondary immune responses, reflects the main features of the immune system response to antigen intake with food. The immune system model response to varying doses and frequency of the antigen intake with food has been studied. It has been established that repeated administration of small doses of the food antigen leads to a deeper tolerance due to lower stimulation of the immune system. The existence of optimal tolerogenic doses of the food antigen has been proved. Qualitative changes in the immune system response to the food antigen have been recorded in case of increased permeability of the intestinal wall.     

复杂环境下砖砌烟囱的爆破拆除

本文介绍了采用定向爆破拆除一座砖砌烟囱的施工设计方法,包括爆破方案选择、爆破切口设计和爆破安全验算等内容,对类似工程有一定的参考意义。