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141.
Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature 总被引:1,自引:0,他引:1
Osamu Ohtaka Hiroshi Fukui Taichi Kunisada Tomoyuki Fujisawa Kenichi Funakoshi Wataru Utsumi Tetsuo Irifune Koji Kuroda Takumi Kikegawa 《Journal of the American Ceramic Society》2001,84(6):1369-1373
Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO2 under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO2 , above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials. 相似文献
142.
The problem of how to develop a mathematical model of the heat processes that take place in the rotor of a spherical asynchronous motor under the influence of internal heat sources is considered. An analytic model of the process is suggested that makes it possible to solve the problems of determination of the extreme thermal modes of a motor and is well suitable for the searching procedures of the construction optimization problems. 相似文献
143.
R
R Chirumamilla R Marchant P Nigam 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2001,76(2):123-127
Captopril is an antihypertensive agent that inhibits the angiotensin‐converting enzyme of the renin–angiotensin system. Chiral intermediates are used in the synthesis of the drug. These intermediates are obtained by resolution of racemic compounds or by chemical, biocatalytic methods and or by asymmetric synthesis by biocatalytic process. This article reviews the various chemical and biochemical processes involved in the synthesis of the chiral drug, including the pharmacological action of captopril. © 2001 Society of Chemical Industry 相似文献
144.
采用万能拉伸试验机、冲击试验机、光学显微镜、XRD、SEM和TEM等对高氮不锈轴承钢Cronidur 30不同回火温度下的显微组织和力学性能进行了研究和分析。结果表明:高氮不锈轴承钢Cronidur 30在150~500 ℃回火时的显微组织为回火马氏体+碳氮化物+残留奥氏体,高于550 ℃回火后基体逐渐转变为回火索氏体,同时析出相逐渐聚集、长大;随着回火温度的升高,强度和硬度总体上呈现先下降后升高再下降的过程,而冲击性能反之,在450 ℃回火时,碳化物M23C6和氮化物Cr2N析出明显,此时产生二次硬化现象,其抗拉强度可达2133 MPa。400 ℃回火试样发现有极少量富Cr-Fe-Mo的析出相(σ相),显著降低其冲击性能,500 ℃回火时残留奥氏体分解、转变导致冲击性能略有降低。 相似文献
145.
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147.
结合提升静态小波和灰色关联分析的图像融合算法 总被引:2,自引:1,他引:1
本文针对多聚焦图像,提出了一种基于提升静态小波变换(lifting stationary wavelet transform,LSWT)和灰色关联度相结合的图像融合算法。首先将待融合的两幅图像分别进行提升静态小波变换,低频分量采用平均法融合,其次再针对低频分量和各个方向的高频分量,分别计算以每个像素为中心的方块的能量和均值,然后计算低频分量的能量和均值构成的序列与高频分量的能量和均值构成的序列之间的灰色欧几里德关联度。按照一定的融合规则,分别得到高频分量融合后的值,最后进行提升小波逆变换,得到融合后的图像。实验结果显示,该方法融合效果较好,优于传统算法。 相似文献
148.
Solar stills have been designed to produce water for use in teaching and research laboratories. Various designs and configurations have been constructed and tested over the past 10 years. The original double-surfaced cascade stills (stills A and B) were constructed in aluminium and were rather expensive. Later models termed Series D and E were of galvanised mild steel with stainless steel distillate drains and safety overflow drains. These galvanised steel units suffered from severe corrosion after a few years of operation. The latest design series F, is built in aluminium with stainless steel distillate drains and automatic feed valves. All of the stills produce very pure distilled water (conductance ~1.5 × 10?6 Ω?1 cm?1; pH 6.8–7.4) at a cost which is below that of conventional electrically heated stills. 相似文献
149.
Kinetics study on the reactive extraction of homophenylalanine enantiomers with BINAP-copper complex
This paper reports on the kinetics study of the reactive extraction of homophenylalanine (Hph) enantiomers with BINAP (2,2’-Bis(diphenylphosphino)-1,1’-binaphthalene)-copper complex (BINAP-Cu) as the chiral selector. The kinetic model was established based on the theory of interfacial chemical reactive extraction. Simultaneously, the effects of agitation speed, interface area, pH value of the aqueous phase, initial concentration of Hph enantiomers and initial concentration of BINAP-Cu on the specific rate of extraction were investigated. The forward rate constants of the reactions in reactive extraction process were found to be 6.16 × 10?4 m2.5mol?0.5s?1 for D-Hphe and 7.303 × 10?4 m2.5mol?0.5s?1 for L-Hphe. 相似文献
150.