Molecular dynamics simulation of microcrack healing in aluminium

The molecular dynamics method is used to simulate microcrack healing during heating or under compressive stress. A center microcrack in an Al crystal could be sealed under a critical compressive stress or by heating it over a critical temperature. During microcrack healing, dislocation and vacancy are generated and moved, and sometimes twin appears. The critical temperature necessary for microcrack healing depends upon the orientation of the crack plane. For example, the critical temperature of the crack along the ( 111 ) plane is the lowest. When there are pre-existing dislocations around the microcrack, the critical temperature necessary for microcrack healing will decrease. The energy condition for crack healing is б2π a ( 1-v2 ) / E + UT/ A ≥ 2 γ + γp, where б is the applied compressive stress, a the length of the crack, γ the Poisson' s ratio, E the Young' s modulus, UT heat energy driving crack healing, A the area of the crack, γ the surface energy, and γp the plastic deformation work. Pre-existing dislocations can reduce γp.     

不同种群灰飞虱(Laodelphax striatellus)的RAPD分析

用RAPD技术对9个不同的灰飞虱地理种群的DNA多态性进行了研究。按Neighbor-joining聚类法构建了这9个种群灰飞虱的分子系统树。该系统树分为2簇,簇1包括我国北京、福建、海南、辽宁、四川、上海、云南地区的灰飞虱种群,簇2包括宁夏地区和日本东京地区的2个灰飞虱种群。研究表明,不同地区灰飞虱种群的遗传距离与其地理距离不呈相关性。     

中国东部"冷槽”和"热脊”形成机制分析

中国东部（青藏高原以东）冬季形成低温的“冷槽”,而夏季形成高温的“热脊”冷槽、热脊形成的机制是不同时空尺度的环流和青藏高原的动力和热力作用,冷槽、热脊的形成对中国东部气候产生重大影响。     

一类离散模型的稳定性和持续生存性

讨论了时滞差分方程ｘｎ＋１－ｘｎ＝－δｘｎ＋ｐｘｎ－ｋｆ（ｘｎ－ｋ）ｔ,ｎ＝０,１,２,…得到了该方程零解的一致渐进稳定的充分条件,且每一个非负解都趋近于零,并且获得了该系统一致持存在的充要条件。     

In situ time-resolved FTIR investigation on the reaction mechanism of partial oxidation of methane to syngas over supported Rh and Ru catalysts

In situ time-resolved FTIR spectroscopy was used to study the reaction mechanism of partial oxidation of methane (POM) to synthesis gas and the reaction of CH4/O2/He (2/1/45, molar ratio) gas mixture with adsorbed CO species over Rh/SiO2, Ru/γ-Al2O3 and Ru/SiO2 catalysts at 500-600℃. It was found that CO is the primary product of POM reaction over reduced and working state Rh/SiO2 catalysts. Direct oxidation of CH4 is the main pathway of synthesis gas formation over Rh/SiO2 catalyst. CO2 is the primary product of POM over Ru/γ-Al2O3 and Ru/SiO2 catalysts. The dominant reaction pathway for synthesis gas formation over Ru/γ-Al2O3 catalyst is via the reforming reactions of CH4 with CO2 and H2O. For the POM reaction over Rh/SiO2 and Ru/γ-Al2O3 catalysts, consecutive oxidation of surface CO species is an important pathway of CO2 formation.     

越桔色素的性质研究

从越桔中提取了一种天然红色素,对越桔色素的可溶性、光谱特性进行了研究,并对色素的实用性能及耐热性、耐光性、耐酸碱性等进行了探讨。     

功能性高分子果树涂膜的应用研究与进展

概述了国内外关于果树保护用高分子乳液保护膜的研究进展.利用高分子保护膜特有的性质及配合适当添加剂来达到对果树多方面的保护并取得了理想效果.     

海南叶下株属植物资源种类和开发现状

表文介绍海南叶下株属植物14种的资源分布、药用情况和开发现状.     

载体盐助分散Ni/Al2O3催化剂上甲烷部分氧化制合成气

用ＴＰＲ,ＴＰＤ,ＴＰＭＣ（程序升温甲烷解离积炭）和活性评价等方法研究载体盐助分散浸渍法与普通浸渍法制备的Ｎｉ基催化剂对ＣＨ４部分氧化制合成气性能的影响,结果表明载体盐助分散浸渍法制备的催化剂其Ｎｉ－Ｏ－Ａｌ间作用较强,分散度增加２６％,抗积炭能力增加４．４倍。     

紫外辐照在PET膜表面接枝氨基酸的研究

生物材料的表面性能是影响材料血液相容性的重要原因,生物材料的表面改性对提高其血上容性有重要意义,目前国内外公认的材料表面内皮细胞化是提高生物材料血液相容性最为理想的途径。