A new minimum zone method for evaluating flatness errors

A new minimum zone method for flatnes error analyis is proposed in this article. Based on the criteria for the minimum zone solution and strict rules for data exchange, a simple and rapid algorithm, called the control plane rotation scheme, is developed for the flatness analysis of a flat surface. Experimental work was performed, and some examples are given in terms of the minimum zone and least-squares solutions.     

粘土作为高放废物处置回填材料的可行性研究

本文以西北粘土为对象,对其压实行为、热传导、膨胀特性,以及吸附和渗透性能进行了初步研究,借以探讨西北粘土在高放废物处置中用作回填材料的可行性。试验表明,以西北粘土为基材,经过适当的热改性和吸附改性,在初始含水量约为9%,于70MPa 下成型,用作高放废物处置中的回填材料是可行的。     

硫氰酸钠湿纺腈纶设备的孔蚀与防护

本文重点讨论了硫氰酸钠湿纺腈纶设备因钝化膜缺陷和Cl-侵入而产生孔蚀的机理及环境因素对孔蚀的影响,并针对产生孔蚀的主要原因提出了防护措施。     

Synthesis, characteristics and oxygen-sensitive properties of SrMgxTi 1 − xO3 nanocrystals

SrMg_xTi_{1 - x}O₃ nanocrystals (x = 0.1–0.6) were synthesized by the stearic acid gel method. Powder samples were characterized by X-ray diffraction and X-ray photoelectron (XP) spectroscopy. The results showed that the lattice parameter a and the O 1s XP spectrum changed not only with the Mg content x but also with the grain size d of the samples. The conductivity of a thick film specimen fabricated on an aluminium oxide wafer was investigated in a nitrogen—oxygen atmosphere.     

A bench-scale study on biodegradation and volatilization of ethylbenzoate in aquifers

Experiments were conducted to investigate the fate of ethylbenzoate and soil microorganisms in shallow aquifers. Biodegradation and volatilization have been identified as the major mechanisms in attenuating ethylbenzoate in contaminated soils. The rate of volatilization was experimentally found to be limited by gas-phase diffusion. The parameters of an available model, i.e., the maximum specific growth rate and the saturation constant, have been estimated by fitting the model to the experimental data obtained with ethylbenzoate as the carbon source; the former was 0.49 h⁻¹, and the latter was 62 mg L⁻¹. Various facets of biodegradation, including the effects of mass-transfer resistance and initial distribution of microorganisms, have been numerically analyzed on the basis of the model.     

Microstructures of high-J c melt-textured YBa2Cu3O7−x /Ag superconductors

Silver has been previously added to the melt-textured YBa₂Cu₃O_7?x in order to increase the critical current density (J _c ) of these materials. However, the effect of this addition on theJ _c is presently unclear. The purpose of this study is to investigate the effect of silver on both critical current density and the microstructure of the melt-textured YBa₂Cu₃O_7?x superconductors by means of X-ray diffraction, optical polarized microscopy, and transmission electron microscopy (TEM). TheJ _c of the MTG YBCO/Ag samples is more than 10⁴A/cm² under the 5 kOe magnetic field. It has been shown that as the concentration of silver increases, the fraction of the 211 phase dispersed within the 123 matrix decreases. Therefore, theJ _c slightly decreases. These results, together with the effect of the 211 phase, dislocations, and other structure defects on flux pinning, are described in this paper.     

各种状态的液体通过核孔膜的规律

介绍了液体通过核孔膜规律方面取得的新认识，包括：（１）纯净液体通过核孔膜的规律；（２）核孔膜测定液体粘滞系数的各种方法；（３）各种物质溶液浓度的核孔膜测定；（４）液相混合物快速分离和化学分离；（５）流体中固体微粒对核孔膜的堵塞及其公式；（６）用核孔膜滤除液中各各斩规律。     

排列互比法用于超精测角的研究

作者分析了我互比法现行的两种数据处理方法的缺点，提出了应用最小二乘法原理推导出合理的数据处理方法。本文还首次从理论上阐明了排列互比法测量结果中出现一次谐波系统误差的原因，提出了减少和消除这一些系统误差的方法，并给实验验证。     

ⅡB型LBO光参量振荡器

二极管泵浦的Nd:YAG激光器美国加州圣克拉拉的Continuum公司推出的HPO-300型高功率二极管泵浦Nd:YAG激光器,在1064nm波长输出3mJ.该激光器重复率在1～300Hz可产生接近衍射极限的脉冲。     

Patterning of mammalian somites by surface ectoderm and notochord: evidence for sclerotome induction by a hedgehog homolog

An early step in the development of vertebrae, ribs, muscle, and dermis is the differentiation of the somitic mesoderm into dermomyotome dorsally and sclerotome ventrally. To analyze this process, we have developed an in vitro assay for somitic mesoderm differentiation. We show that sclerotomal markers can be induced by a diffusible factor secreted by notochord and floor plate and that heterologous cells expressing Sonic hedgehog (shh/vhh-1) mimic this effect. In contrast, expression of dermomyotomal markers can be caused by a contact-dependent signal from surface ectoderm and a diffusible signal from dorsal neural tube. Our results extend previous studies by suggesting that dorsoventral patterning of somites involves the coordinate action of multiple dorsalizing and ventralizing signals and that a diffusible form of Shh/Vhh-1 mediates sclerotome induction.