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182.
The structure of the matrix of a two phase heavy alloy, 93W-4.9Ni-2.1Fe (wt%), was characterized. The matrix phase was not the expected face centred cubic Ni-Fe-W solid solution with a large grain size reported in the literature. Instead, an amorphous phase containing fine grained crystals as well as intermetallic compounds having different compositions were found. The partition of tungsten from the matrix toward the tungsten phase resulted in formation of different phases in the matrix. Under furnace cooling, the matrix phase was composed of an amorphous phase for the matrix phase remote from the tungsten grain-matrix interfaces, and a strained FeNi intermetallic phase near the interfaces. For specimens solution treated at temperatures between 1000–1400 °C followed by water quenching, an intermetallic phase rich in tungsten, (Ni, Fe) W, evolved and surrounded the tungsten grains in clusters. The relative abundance of this intermetallic phase was highest for a solution treatment temperature of 1400 °C, indicating that the formation of this phase was a result of supersaturation of tungsten in the matrix phase and retarded partition of tungsten from the matrix phase to tungsten grains under a rapid cooling condition. 相似文献
183.
184.
DR Offord MH Boyle D Campbell P Goering E Lin M Wong YA Racine 《Canadian Metallurgical Quarterly》1996,41(9):559-563
OBJECTIVE: To present the one-year prevalence of 14 psychiatric disorders in a community sample of Ontarians aged 15 to 64 years. METHOD: Data on psychiatric disorders were collected on 9953 respondents using the University of Michigan revision of the Composite International Diagnostic Interview (UM-CIDI). DSM-III-R criteria were used to define the psychiatric disorders. RESULTS: Almost 1 in 5 Ontarians (18.6%) had one or more of the disorders measured in the survey. Among 15-to 24-year-olds, 1 in 4 was affected. The distribution of individual disorders varied by sex and age. CONCLUSION: Because of the immense burden of suffering associated with psychiatric disorders, clinical and research efforts in this area should receive high priority within the health budget. 相似文献
185.
HM Chaung CH Hong CP Chiang SK Lin YS Kuo WH Lan CC Hsieh 《Canadian Metallurgical Quarterly》1996,95(7):545-550
This review reports the different genetic factors that have been identified either as risk factor for Alzheimer's disease (AD) or directly causing the disease. First are reviewed epidemiological data and biological mechanisms about the apoplipoprotein E gene allele epsilon 4 that is a major risk factor for Alzheimer's disease. The second part describes the mutations responsible for early-onset autosomal dominant AD found in three different genes. The gene located on chromosome 21 encodes the amyloid precusor protein (APP). The presenilin 1 and presenilin 2 genes, located on chromosome 14 and 1 respectively, encode not yet known membrane proteins. 相似文献
186.
Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern. 相似文献
187.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
188.
i-line光刻高均匀照明系统光能分布的计算模拟 总被引:5,自引:0,他引:5
叙述了i-line光刻高均匀照明系统的均匀照明原理,以及其具有特殊面形(非球面)、特殊结构(非共轴)、超光学表面(由多个非共轴光学表面组成)的光学系统的光能分布计算模拟的原理、方法。作为例子,用所编写的程序计算模拟了我们近来设计的一曝光系统几个重要光学表面上具有权重的点列图和光能分布曲线。 相似文献
189.
190.
锝化学研究 Ⅸ.脑显像剂Tc~(Ⅴ)ON_2S_2类配合物结构稳定性和价态的研究 总被引:1,自引:0,他引:1
采用改进的CNDO/2法模拟了BAT类脑显像剂Tc(Ⅴ)O配合物价态的转换过程,发现N2S2类配体与Tc(Ⅴ)O核配位时,可能存在配位平衡离子X。在溶液中由于X离子的优先解络,瞬间存在+1价对称性99Tcm配合物,并且,它又自动向相对稳定的0价不对称性99Tcm配合物转换,在动态转换过程中,将导致仅有一个配位N原子保留一个质子,这与实验结果一致。采用键级削弱百分数概念,表征配位过程的二个配位N原子上保留程度,解释了Tc(Ⅴ)O核、Tc(Ⅴ)≡N核N2S2类配合物两个N-H键上质子保留程度不同的原因,为今后设计不同价态锝配合物结构提供理论依据。 相似文献