Effect of microstructure on the coercivity of HDDR Nd-Fe-B permanent magnetic alloy

The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations of the structure defect factors based on the nucleation and pinning mechanism with 2r ₀/lex (where r ₀ and lex are the defect thickness and the length of exchange coupling, respectively) were calculated. The results show that the coercivity mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary. For a fixed lex, when 2r ₀/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r ₀/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r ₀/lex = 1.67. The calculation result is consistent well with the experimental result given by Morimoto et al. Supported by the National Natural Science Foundation of China (Grant No. 50671055)     

Fabrication of nano-structured polythiophene nanoparticles in aqueous dispersion

The synthetic route of unsubstituted polythiophene (PT) nanoparticles was investigated in aqueous dispersion via Fe³⁺-catalyzed oxidative polymerization. With this new synthetic method, high conversion of thiophene monomers was obtained with only a trace of FeCl₃. The dispersion state showed that the PT nanoparticles were well dispersed in many polar solvents, compared to non-polar solvents, such as acetone, chloroform, hexane, and ethyl acetate. To compare the photoluminescence properties between PT nanoparticle dispersion and PT bulk polymers, the PL intensities were measured in the same measuring conditions. Further, core–shell poly(styrene/thiophene) (poly(St/Th)) latex particles were successfully prepared by Fe³⁺-catalyzed oxidative polymerization during emulsifier-free emulsion polymerization. The different polymerization rates of each monomer resulted in core–shell structure of the poly(St/Th) latex particles. The PL data of the only crumpled shells gave evidence that the shell component of core–shell poly(St/Th) latex particles is indeed PT, which was corroborated by SEM data. PL intensity of the core–shell poly(St/Th) nanoparticle dispersion was much higher than that of the PT nanoparticle dispersion, due to its thin shell layer morphology, which was explained by the self-absorption effect.     

Calculation of electron wave functions and refractive index of Ne

The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered. Supported by the New Star Program of Beijing Science and Technology, China (Grant No. 952870400), the Beijing Municipal Commission of Education, and the Excellent Young Teachers Program of Ministry of Education, China     

On the Denseness of Rational Systems

This note characterizes the denseness of rational systems

Full-size image

in C[−1, 1], where the nonreal poles in {a_k}^∞_k=1 \[−1, 1] are paired by complex conjugation. This extends an Achiezer's result.     

电偏转扫描法测量高电荷态ECR源发射度

成功地研制了一套适合于低能离子束流发射度测量的电偏转扫描探测器.对该探测器的原理和结构作了较详细的描述,并给出该探测器对兰州近代物理研究所高电荷态ECR源LECR3引出离子束流发射度的测量结果.典型结果为:在引出高压为15.97kV,引出束流为190μA时,O⁴⁺水平发射度(x方向)为137πmm·mrad,垂直发射度(y方向)为120πmm·mrad(包括90%束流).最后,对测量结果作了一些分析和讨论.     

Fringe skeletonizing using an improved derivative sign binary method

A modified derivative sign binary method is proposed to extract fringe skeletons from interferometric fringe patterns. A fringe direction map ranging from 0° to 360° is obtained with an unambiguous relationship between the grayscale and fringe tangent direction. Using this approach, the derivative sign binary map is detected without a fringe direction jump. The dark (light) fringe intensity minimum (maximum) can be extracted automatically to define fringe skeletons. In addition, two different anisotropic one-dimensional filters are described that can be used for further improving the fringe quality. Examples are provided for a holographic interferogram and a Moiré fringe pattern to illustrate applications and benefits of the approach.     

基于PC机的虚拟现实技术研究

本文利用所需额外硬件很少的立体显示技术,研制了一种基于微机平台的虚拟现实系统。这个系统利用最新推出的微机版的三维图形标准Open GL建模,以实时动画形式实现了真正的交互性,立体视觉效果明显,可以给观赏者提供真实的临场感和亲自控制的参与感。与已研制出的“三维立体显示系统”相比,有了实质性的进步。     

离子交换法在净水剂制备中的应用研究

本文进行了Ａｌ２（ＳＯ４）３＋ＲＣｌ＋Ｈ２Ｏ体系的理论分析和跟踪测试，确认该体系的主要交换反应是：该交换反应促进了铝离子的水解，提高了硫酸铝的盐基度和混凝沉降速度，制得性能优于精制硫酸铝的聚硫氯化铝净化剂。     

液相外延制备InGaAsP/InP掩埋异质结若干工艺问题的讨论

本文对InGaAsP/InP(DC-PBH)激光器掩埋异质结液相外延生长中的几个关键工艺问题进行了研究,提出了获得有利于沟道掩埋生长的理想沟道几何图形的新的腐蚀配方(Br_2/HBr),对二次外延再生长光刻腐蚀面损伤层和有害杂质的去除采用了阳极氧化工艺,同时探索了利用二次外延过程中Zn扩散来控制限制层(3)掺杂的新方法,在研究基础上制造了重现性好且性能良好的1.3μm激光二极管,室温时,阈值电流最低小于25mA,典型值为30mA,在60mA直流电流的驱动下,光输出功率高达12.5mW.