丙烯腈与丙烯酸乙酯乳液共聚合及其表征

用氧化还原引发体系在低温下研究了丙烯腈与丙烯酸乙酯的乳液共聚合。考察了聚合温度、乳化剂浓度和分子量调节剂浓度对聚合的影响 ,结果表明 ,随温度升高 ,乳化剂浓度增大 ,单体转化率和分子量增大 ,乳液更稳定 ;链转移剂十二烷基硫醇浓度增加 ,分子量显著降低 ,转化率有所降低 ,表明十二烷基硫醇在调节分子量的同时也起着缓聚剂的作用。用激光粒径分析仪考察了 2 0℃时聚合过程中乳胶粒子大小的变化 ,发现聚合过程的成核和增长均在胶束中进行的。用凝胶渗透色谱法研究了十二烷基硫醇对聚合物分子量的影响 ,发现聚合时加入分子量调节剂 ,活性链寿命较短并呈单峰分布 :聚合时不加入分子量调节剂 ,活性链寿命较长并呈双峰分布。 DSC结果表明 ,随聚合体系中软单体含量增加 ,共聚物的玻璃化温度降低。     

Phenylimidazole-based homoleptic iridium(III) compounds for blue phosphorescent organic light-emitting diodes with high efficiency and long lifetime

In order to obtain triplet emitters with high stability and efficiency, three homoleptic iridium(III) compounds — specifically, Ir(tpim)₃ (1), Ir(mtpim)₃ (2), and Ir(itpim)₃ (3), where tpim = 1-([1,1′:3′,1″-terphenyl]-2′-yl)-2-(4-fluorophenyl)-1H-imidazole, mtpim = 2-(4-fluorophenyl)-1-(5′-methyl-[1,1′:3′,1″-terphenyl]-2′-yl)-1H-imidazole, and itpim = 2-(4-fluorophenyl)-1-(5′-isopropyl-[1,1′:3′,1″-terphenyl]-2′-yl)-1H-imidazole — were prepared by one-pot reaction of the corresponding phenylimidazole ligand with an Ir(I) complex as a starting material. Compounds 1–3 emit bright sky-blue phosphorescence with λ_max = 459–463 nm and phosphorescent quantum efficiencies of 0.38–0.50. Multi-layer phosphorescent organic light-emitting diodes using compounds 1–3 as the triplet emitters and mCBP (3,3-di(9H-carbazol-9-yl)biphenyl) as the host have been fabricated. Compound 3 doped in the emissive layer demonstrate external quantum efficiency as high as 20.1% at 1000 cd/m². In addition, the device based on compound 1 as an emitter shows a stable lifetime greater than 300 h at 1000 cd/m², which is one of the best results concerning the device lifetime.     

Estimation of the impurity levels in polyimide foils and the life-time of the foils irradiated by charged projectiles

The life-time of thin polyimide foils (prepared by in-situ polymerisation) in beams of 2.0 MeV helium ions and 1.5 MeV protons has been studied, irradiating foils with beams of different intensities. The impurity levels of the foils measured by PIXE and RBS were found to be in order of ng/cm².     

Polymer anion-selective membrane for electrolytic water splitting: The impact of a liquid electrolyte composition on the process parameters and long-term stability

In the present study the impact of KOH replacement by a NaHCO₃ or Na₂CO₃ solution on the performance of alkaline water electrolysis and the life-time of an anion-selective polymer electrolyte was assessed. In the first instance, the impact of the electrolyte composition on the kinetics of the electrode reactions was studied. Subsequently the ionic conductivity of the membrane, in the form of individual anions, and the efficiency of the alkaline water electrolysis process were evaluated by means of electrochemical impedance spectroscopy and a laboratory single-cell alkaline water electrolyzer. The anion used was observed to make a significant impact both on the ionic conductivity as well as on the kinetics of the anode reaction, resulting in reduced electrolysis efficiency. A stability test revealed kinetics of chemical degradation of the polymer anion-selective membrane in a Na₂CO₃ solution similar to those in a KOH environment at 70 °C. An alternative approach of decreasing the temperature to 50 °C prolonged the chemical stability and made less impact on the process efficiency.     

Residual life assessment of steam turbine casing containing crack defect

In steam turbine casing made of cast steel of type 0.6Cr0.5Mo0.25V ( SN 42 2744), which run about 25% over designed life, several crack defects were found. The most serious case was represented by a crack in valve chest, which reached nearly up to one half of wall thickness. In spite of this it was necessary to operate the turbine for some time. The aim of this contribution is to describe procedures used for assessment of safe residual life.Material data necessary for this life assessment were evaluated during research of material properties of another steam turbine casing made of the same type steel whose operating time was finished after 1.23×10⁵ h. The mentioned material data are also presented.     

论红外变像管积分灵敏度的标准（上）

主动式红外夜视仪的可靠性主要决定于红外变像管,而红外变像管的可靠性和工作寿命则决定于红外光电阴极——半透明银氧铯光电阴极的性能和寿命。本文从银氧铯阴极光谱特性的稳定性出发,阐述了光谱特性与红外积分灵敏度S之间的有机联系,并得出结论:S≥8μm/lm的光电阴极是稳定的,具有较一致的光谱特性;S<7μm/lm的光电阴极不稳定,其光谱特性不断变化。因此,合格变像管光电阴极的红外积分灵敏度S>8μm/lm。同时,从寿命试验证实,S=8μm/lm的变像管有超过技术条件一倍以上的工作寿命,性能稳定,从而能确保红外夜视仪的寿命,增加其可靠性。因此,银氧铯光电阴极红外积分灵敏度标准的确定对红外夜视仪的视距和可靠性是十分重要的。     

Stability loss of thin-walled cylindrical tubes, subjected to longitudinal compressive forces and external corrosion

The paper is devoted to investigation of stability loss of thin-walled elastic circular cylindrical pipes subjected to simultaneous action of longitudinal compressive forces and uniform corrosion from outside. The pipe is treated as a thin closed elastic circular cylindrical shell which can be described within Kirchhoff–Love approximation. The critical time of stability loss of the pipe is found, using the upper critical load value for static stability loss of the pipe, not subjected to corrosion, and the law of corrosion rate. Numerical results were obtained for pipes, made from steel and aluminum with different initial wall thickness.     

Stability of thin-walled high-pressure vessels subjected to uniform corrosion

The stressed state in real metal constructions changes in the process of operation even under permanent external loading. It takes place due to changes in the cross-sections of the loaded elements, resulting from the surface corrosion. This paper proposes a method for determining the critical time of stability loss in thin-walled high-pressure vessels subjected to uniform corrosion from the inside. The method is based upon the model of a thin elastic cylindrical shell. It is shown that this critical time can be established if the solution of the respective problem of the static stability loss for the vessel, not subjected to corrosion, and the law of corrosion rate change are known. Several special cases of the law of corrosion rate are examined.     

Micromechanical modeling of short fatigue cracks

This paper gives an overview over the micromechanical modeling approaches of short fatigue cracks. Until now many approaches have been presented in the literature, which differ significantly in their degree of complexity ranging from simple empirical or analytical models to complex models based on numerical solutions. In recent years different trends were observed: On the one hand detailed models are presented, which describe the propagation of a microstructurally short fatigue crack in a physically sound way based on discrete dislocations. However, their application is somewhat limited due to their complexity regarding the application in real microstructures. Thus, another trend is to develop models closely related to experimental research work to identify and focus on the main aspects of short fatigue crack growth.     

宇宙线μ轻子寿命测量实验和电子学设计

采用可编程逻辑器件,设计了一种新的读出电子学和逻辑电路,仅使用一个闪烁探测器配合该读出电路,实现对宇宙线μ子寿命测量。实验证明该读出方法不仅简便,而且有着很好的测量精度,可用于一些粒子寿命及时间测量的科学实验中。