Low-Temperature Dielectric Properties of Ceramic Potassium Tantalate (KTaO3)

Dielectric properties of KTaO₃ ceramic fabricated by both conventional sintering and sintering followed by isostatic hot pressing (HIP) were measured at T =4.2 to 300 K over a frequency range from 400 Hz to 4 MHz. The weak field response shows a faint peak near 10 K which has a clear relaxation character, as in high-purity single crystals. The general response is well reproduced by the Barrett function, but additional polarizability with relaxation character is also in evidence at higher temperatures. No dielectric hysteresis was observed at high fields for cycling frequencies down to 0.04 Hz anywhere in the temperature range.     

国外聚甲醛生产技术现状与发展

综述了国外主要甲醛生产厂商的工艺技术，树脂生产技术的发展和品种开发情况。     

从铁镜公主的扮相看旗装的发展变化

此文以京剧戏衣中的"旗装"为例,探讨了它演变的过程和演变背后的契因,目的在于通过服饰--这种无声的戏曲发展史--反思了京剧的审美进程,也辉映出其在20世纪--京剧真正意义的黄金时代--的发展历程.     

Effect of certain factors on the strength of ready-mixed concrete

Conclusion The strength of concrete was investigated. It was found that in the case of charging individual concrete components into TMs mounted on the chassis of KrAZ and KamAZ trucks, high-grade concrete cannot always be prepared with such a technological scheme.It was established that with a yield of various volumes of ready-mixed concrete from TMs, the strength of the concrete from the smaller volume (3.5 m³) was higher an age 1 day than of concrete from a volume of 4 m³.However, at age 28 days the strengths equalize. Furthermore, the concrete taken from 3.5 m³ was more uniform. In addition to this, an attempt was made to predict how the concrete strength would increase directly in structures during operation of tunnels constructed by the open method during the year.It was established that the maximum gain of strength of concrete will occur in the summer, in June and July. At the same time, in August there are great differences between the ambient temperature and humidity. This means that there will not be enough moisture for active hydration of cement, the concrete will have shrinkage and an increase of concrete strength may not only be markedly retarded but may stop entirely. In the winter, spring, and fall, the strength of concrete will increase, but apparently less intensely than in the summer.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 21–22, November, 1991.     

Infrared reflectance and transmission spectra of semiconducting non-stoichiometric CdGe x As2

The infrared reflectance and transmission spectra of amorphous CdGe _x As₂ were investigated to study the amorphous structure with varying Ge content. The mid-infrared optical absorption edges of amorphous CdGe _x As₂ with 0<x<1.2, were observed in the range 1.6–1.7 m, indicating a structural similarity in short-range order throughout. Comparing the reflectance and transmission spectra of amorphous and devitrified crystalline phases established that the structures of amorphous CdGe _x As₂ transformed from the CdAs₂ basic structure to the chalcopyrite (CdGeAs₂) structure, as one progressed fromx=0 tox=1.2. The infrared spectra were interpreted interactively with radial distribution function, magnetic susceptibility, density measurements, and crystallization studies. The crystallization behaviour of amorphous CdGe _x As₂ that was heat treated at different temperatures was investigated using far-infrared transmission spectra.     

Influence of strain rate on the nature of failure under prolonged static and cyclical loads. 2. Examples of calculation

Based on a physicomechanical model of intercrystallite failure in materials, such as presented in the previous communication, we have proposed a computational algorithm for the endurance of polycrystalline material under cyclical load. We have provided examples for the calculation of the cyclical strength in austenitic steel under various strain rates. Comparison of the theoretical results against the experimental data demonstrated the possibility of using the model developed here to describe the quantitative relationships governing intercrystallite failure of the material over a broad range of load regimes.Translated from Problemy Prochnosti, No. 8, pp. 42–47, August, 1991.