The preparation and magnetic properties of Fe-Ag granular solid using a sol-gel method

The Fe-Ag granular metal solid samples with 10% and 30% weight iron have been successfully fabricated using a sol-gel method, which are characterized by X-ray diffraction and transmission electron micrography. The average diameters of iron particles are from about a few nanometres to a few tens of nanometres controlled by the reducing temperature. The evolution of magnetic properties and microstructure during heat treating are described in detail and explained by using the superparamagnetism, single domain and multi domain theories. The magnetic anisotropy of the Fe-Ag granular solid is studied by using the law of approach to saturation. It is found that the magnetic anisotropy constant is in the order of 10⁵ J m^–3 which is higher than the value of the bulk iron and increases with the increase of reducing temperature.     

The influence of the alloying elements upon the transformation kinetics and morphologies of ferrite plates in alloy steels

A series of Fe-C-X and Fe-C-X₁-X₂ alloys in which X, X₁ and X₂ either raise or depress the activity of C iny were investigated by autodilatometer, optical microscopy, and transmission electron microscopy (TEM) to reveal the relations among the chemical composition, transformation kinetics, and morphology of ferrite plates. The incubation time of austenite decomposition at the nose temperature in the time-temperature-transformation (TTT) diagrams, the concentration of C in y in contact with theα/gg boundary, and the growth rate of ferrite were evaluated to estimate the magnitude of the solute drag-like effect (SDLE) for the different alloying elements used. All the results are consistent qualitatively with the SDLE hypothesis. This article is based on a presentation made at the Pacific Rim Conference on the “Roles of Shear and Diffusion in the Formation of Plate-Shaped Transformation Products,” held December 18-22, 1992, in Kona, Hawaii, under the auspices of ASM INTERNATIONAL’S Phase Transformations Committee.     

用于生产甲基丙烯酸的杂多酸催化剂的研究

以异丁烯为原料的两段直接氧化生产甲基丙烯酸最新工艺有许多优点。其技术关键在于研制出高效的甲基丙烯醛选择性氧化催化剂。本文报道P-Mo-As-Cu杂多化合物催化剂的组成、制备条件对催化剂活性的影响。经优化后获得高选择性、高活性的二段氧化催化剂，其甲基丙烯酸收率达60％以上。     

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本文通过对在用钻机井架的现场实际测试,建立数据库、测评模型,对实测的数据用计算机技术进行分析,提出了初始弯曲应力;数据正态分布检验——x～2检验;建立回归方程;在给定置信度下测评当前承载能力的技术概念。解决了在用钻机A型井架的安全性评估问题,是一种较为合理、可靠、科学的测评技术和方法。     

Curvilinear fatigue crack reliability analysis by stochastic boundary element method

In this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 with the first-order reliability method, is developed to study probabilistic fatigue crack growth. Due to the high degree of complexity and non-linearity of the response, direct differentiation coupied with the response-surface method is employed to determine the response gradient. Three random processes, the mode I and mode II. stress intensity factors and the crack direction angle, are included in the expression of the response gradient. The sensitivity of these random processes is determined using a first-order response model. An iteration scheme based on the HL-RF method² is applied to locate the most probable failure point on the limit-state surface. The accuracy and efficiency of the stochastic boundary element method are evaluated by comparing the cumulative distribution function of the fatigue life obtained with Monte Carlo simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with randomness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variable at the design point is determined to show its role in the fatigue failure. The variation of each primary random variable at the design point with the change of probability of failure is also presented in numerical examples.     

超细铁粉和氧化铁颗粒的研究

用透射电镜和图像分析仪等研究了超细铁粉和γ-Fe_2O_3粉末的结构、形貌、粒子的平均尺寸以及粒度分布。研究结果表明,多数超细铁粉粒子近似呈球形,并且,铁粉粒子由两相组成,粒子的核心部分是金屑a-Fe,表面的包裹层为氧化物层,它由Fe_3O_4和7-Fe_O_3的混合物组成。氧化层的平均厚度大约占整个粒子直径的20％左右。羰基铁粉粒子(含氧化层)的平均直径为16nm。直径在4～24nm范围的粒子数占总粒子数的91％,而7-Fe_2O_3粉末既有雪茄状粒子,也有小球状粒子。分析表明,球状粒子的平均直径为113nm,雪茄状粒子的平均直径(按<长 宽>/2计算)为148nm。由于超细铁粉粒子很细,且有磁性,制备电镜试样时分散比较困难。本文比较了几种分散方法后,使用了一种较好的分散方法——超声喷管分散法。     

基于GIS技术的安徽省重大农业气象灾害测评系统总体设计

对《基于GIS技术的安徽省重大农业气象灾害测评系统》的总体设计方法作了概要介绍。该系统的建立主要是采用GIS技术，综合气候分析、遥感监测、地理环境影响评判等方法，提高对安徽省干旱、洪涝、低温冻害等重大农业气象灾害实时监测、趋势预测，以及对农业生产影响的分析评价结果的准确性。     

Ce,Eu双掺BSO晶体光折变效应研究

在ＢＳＯ晶体中同时掺入Ｃｅ和Ｅｕ离子，生长了Ｃｅ：Ｅｕ：ＢＳＯ晶体，对晶体的二波耦合和四波混频性能了测试。结果表明，Ｃｅ和Ｅｕ离子对晶体的光折变效应起到了增强的作用。     

Uptake characteristics of loracarbef and cephalexin in the Caco-2 cell culture model: effects of the proton gradient and possible presence of a distinctive second component

The mechanisms of apical (AP) uptake of cephalexin (CEPH) and loracarbef (LOR) in the absence or presence of an (extemally imposed) proton gradient were determined using well-stirred diffusion chambers that minimize the effects of the unstirred water layer. The results indicated that, compared to AP uptake in the presence of an imposed proton gradient, AP uptake in the absence of an imposed proton gradient had higher K(m) values and lower Jmax values. Furthermore, when inhibition studies were performed in the absence of a proton gradient, only natural peptides were effective, whereas the peptide analogs (e.g., enalapril) were not. In addition to the effects of concentration and competitive inhibitors, the results also indicated that (1) the AP uptake of both drugs was decreased more than 60% by FCCP, regardless of whether the proton gradient was present or absent; (2) effects of protein kinase C promoter were dependent upon the presence of a proton gradient; and (3) AP uptake in the presence of an imposed proton gradient was not affected by feeding restriction, whereas AP uptake in the absence of an imposed proton gradient was. These results showed for the first time that two substrates with similar AP uptake characteristics in the presence of an imposed proton gradient may not share those characteristics in the absence of an imposed proton gradient. Taken together, these results suggest that the AP uptake component that functions in the absence of an imposed proton gradient is distinctly different from the one that functions in the presence of an imposed proton gradient. Data generated from the present study and those in the literature lend support to the hypothesis that this distinctive component represents the second binding site on the AP peptide transporter. However, an alternative hypothesis that there are two AP peptide transporters remains to be disapproved.