Crack Branching in All-Oxide Ceramic Composites

The existence of oxidation embrittlement in previously developed ceramic-matrix composite (CMC) systems at intermediate temperatures (500–900°C) has motivated the development of all-oxide CMCs. Studies of the damage tolerance of an all-oxide CMC suggest that it relies on distributing fiber bundles heterogeneously in a porous matrix with a thin matrix-only region surrounding each bundle. For such composites, loading in the direction of the fibers causes cracks to first commence in the fiber bundles, breaching both the matrix and fibers within each bundle. These fiber-bundle cracks then branch in the matrix-rich region, parallel to the load, forming stable H-shaped cracks. The mechanics behind one mechanism controlling the competition between branching and continued extension of a preexistent fiber-bundle crack in a unidirectional all-oxide CMC are provided in this paper. Both plane-strain and axisymmetric cases are studied using an integral equation method as well as a numerical method based on finite elements. With no elastic mismatch assumed between the fiber and matrix, a single nondimensional combination, E Ω/σ_∞, emerges as the key parameter that governs the tendency of the crack to branch (where E is Young's modulus, Ω is the thermal misfit strain between the fiber bundle and matrix, and σ_∞ is the stress applied parallel to the fiber axis). Quantitative estimates of the conditions under which the branching of the bundle crack is favored are presented.     

不同品位高钛渣对沸腾氯化工艺的影响

分别以94％品位高钛渣和90％品位高钛渣为原料，采用沸腾氯化工艺制备粗TiCl4，分析了两种品位高钛渣对沸腾氯化工艺的影响。结果表明：94％品位高钛渣由于其活性低而对沸腾氯化工艺的影响较大。     

A new ordered bed modular reactor concept

The Ordered Bed Modular Reactor (OBMR) is an advanced modular HTGR design in which the annular reactor core is filled with an ordered bed of fuel spheres. This arrangement allows fuel elements to be poured into the core cavity which is shaped so that an ordered bed is formed and to be discharged from the core through the opening holes in the reactor top. These operations can be performed in a shorter shutdown time.     

经历双重还原

大约在2002年的年底,我受邀参与湖滨项目的建筑设计。在此之前,美国JERDE与SWA作了这一地区的较大范围的详细规划(西起湖滨路,东到浣沙路,北起庆春路,南到解放路)。JERDE的规划商业气氛浓厚,有狂欢节式的城市空间感,但其中关于沿湖滨路区域并未得到杭州市政府的认可,根据市政府     

InGaAsP／InP PFBH激光器

采用Ｎ－ＩｎＰ衬底研制ＩｎＧａＡｓＰ／ＩｎＰ激光器和ＤＦＢ激光器在国内已报导过多次，本文介绍用Ｐ－ＩｎＰ衬底研制ＩｎＧａＡｓＰ／ＩｎＰ平面埋层异质结构激光器和ＤＦＢ－ＰＦＢＨ激光器，同时利用晶体生长和晶向的依赖关系，改进埋区的结构，使器件最高激射温度大于１００℃。     

NUMERICAL SIMULATION OF PARTICLE SEPARATION IN AN OIL-SAND SEPARATOR

ＮＯＴＡＴＩＯＮＳＡ　Ａｒｅａｏｆｉｎｌｅｔ ,ｍ2ａ　Ｃｅｎｔｒｉｆｕｇａｌａｃｃｅｌｅｒａｔｉｏｎ ,ｍ2 /ｓｉ　Ｇｒｉｄｏｆａｘｉａｌｄｉｒｅｃｔｉｏｎｍｌ 　ＭａｘｉｍｕｍｇｒｉｄｎｕｍｂｅｒｏｆｒａｄｉａｌｄｉｒｅｃｔｉｏｎＱ　Ｆｌｕｉｄｍａｓｓｒａｔｅ ,ｍ3/ｓＲｃ 　Ｍａｘｉｍｕｍｒａｄｉｕｓｏｆｃｙｃｌｏｎｅ ,ｍＲｅ　Ｒｅｙｎｏｌｄｓｎｕｍｂｅｒｒ　Ｄｉｍｅｎｓｉｏｎｌｅｓｓｒａｄｉａｌｄｉｓｔａｎｃｅｔ　Ｄｉｍｅｎｓｉｏｎｌｅｓｓｔｉｍｅｕ　Ｄｉｍｅｎｓｉｏｎｌｅｓｓａｘｉａｌｖｅｌｏｃ…     

《联合国气候变化框架公约》与我国水电资源开发

《联合国气候变化框架公约》旨在将大气中的温室气体浓度稳定在防止气候系统受到危险的人为干扰的水平上，使生态系统能够自然地适应气候变化，确保粮食生产免受威胁并使经济发展能够可持续地进行。该公约对我国控制高污染煤炭能源的生产消费，发展清洁可持续利用的替代能源，特别是发展水电资源，制订国家中长期能源战略将产生深远的影响。     

乙烯直接氧化合成乙酸

用常规固定床反应器考察了Pd-SiW12/SiO2催化剂还原条件对乙烯直接氧化合成乙酸催化性能的影响。催化剂用H2在200－300℃还原后Pd 的分散度较高，其催化活性远高于肼在液相中还原的催化剂，在乙烯气相氧化合成乙酸反应的原料气中，适量1，2－二氯乙烷的存在有助于提高乙酸的选择性和时空产率，初步考察了Pd-Se-SiW12/SiO2催化剂连续206h运转的稳定性，结果表明，催化剂中Pd晶粒的长大和硅钨酸的流失是造成催化剂失活的主要原因。