烧结NdFeB永磁合金的边界显微结构与磁硬化SCIEI

用TEM观察了烧结NdFeB永磁合金的内边界显微结构,发现该合金存在4种类型的边界。回火前后前三类边界的形貌没有变化,而第4类边界的显微结构发生了显著的变化。用SAED和AES分析了第4类边界的成分与结构,该边界由两个区域组成,即富Nd相区和Nd_2Fe_(14)B晶粒的外延层。回火时,由于原子的扩散和物质迁移,Nd_2Fe_(14)B晶粒的外延层发生了磁硬化,因而合金的矫顽力得到提高。     

氢作用下Nd14Fe73Co6B7的相转变

利用X射线衍射、透射电子显微镜、扫描电镜及磁测量技术观察和分析了Nd_(14)Fe_(73)Co_6B_7合金于770℃吸氢后相结构组成与变化发现铸锭中的Nd_2Fe_(14)B基体吸氢后分解成约为0.1μm的NdH_2,α-Fe和Fe_2B三相混合物,脱氢后重新结合的Nd_2Fe_(14)B相尺寸约为0.3μm;铸锭中分布在基体相周围的富Nd边界相在吸氢时扩散入Nd_2Fe_(14)B基体,在脱氢过程中保留下来,均匀地分布在由若干Nd_2Fe_(14)B细小晶粒组成的晶粒团周围     

定向凝固NiAl多相合金的高温超塑性研究

本文研究了Ni-30Al-5Mo-0.5Hf金属间化合物的显微组织及其超塑性变形行为.该合金是由NiAl/Ni3Al/Mo三相组成,在NiAl中分散着大量的条状Ni3Al.在1050-1100℃,应变速率为5.2X10-4-6.24X10-3s-1拉伸变形时,合金呈现超塑性行为;1050℃,5.2X10-4s-1时的最大延伸率达160％,此时对应的应变速率敏感指数为0.46.超塑性变形的机理主要是由于变形过程中的动态回复和再结晶,同时合金中的NiAl和Ni3Al两相在高温下可以协调变形.     

黄铜表面多层化学转化膜特性研究

黄铜经苯并三氮唑(BTA)和络合钝化剂PVA溶液钝化处理后,表面耐蚀性明显提高,椭圆偏振法和X射线光电子能谱法(XPS)研究表明,PVA能在Cu(I)BAT薄膜上继续外延生长成膜,BTA—PVA混合液钝化处理效果与先用BTA、后用PVA溶液钝化处理效果基本相同、钝化处理后的化学转化膜大体上为三层结构,即Cu_2O/Cu(I)BTA/PVA膜     

Convective heat transfer in channels with high wall ribs

The features of the convective heat transfer intensified by the turbulization caused by high ribs are experimentally studied using laboratory tube-in-tube heat exchangers.     

LDPC codes for fading Gaussian broadcast channels

In this work, we study coding over a class of two-user broadcast channels (BCs) with additive white Gaussian noise and multiplicative fading known at the receivers only. Joint decoding of low-density parity-check (LDPC) codes is analyzed. The message update rule at the mapping node linking the users' codes is derived and is found to exhibit an interesting soft interference cancellation property. High performance codes are found using the differential evolution optimization technique and extrinsic information transfer analysis adapted to our multiuser setting. The optimized codes have rates very close to the boundary of the achievable region for binary constrained input for both faded and unfaded channels. Simulation results for moderate block lengths show that our codes operate within less than 1 dB of their respective threshold.     

Web site based safety program development for the undergraduate chemistry laboratory environment

In order to develop a top notch laboratory safety Web site one needs to have a clear vision of the purpose and potential audience that it is intended to serve. It is prudent to conduct open discussions involving all interested or affected groups about the structure and content of the Web site. Include those who have the necessary resources such as time, talent, and hardware. Explore documents now being used before beginning, and take what is useful for your project. In order to establish and maintain a world-class project, dedicate enough time and resources to actively maintain and upgrade the site.     

Plug-Flow Tubular Turbulent Reactors: A New Type of Industrial Apparatus

Chemical apparatuses of a new type, specifically, quasi-isothermal plug-flow divergent–convergent tubular turbulent continuous reactors, are considered. These apparatuses combine the merits of plug-flow tubular reactors and stirred continuous reactors and have some technical and technological advantages.