Electrical Properties and Electroluminescence of 4H-SiC p-n Junction Diodes

Homoepitaxial growth of 4H-SiC on off-oriented Si-face(0001 ) substrates was performed by using the step-controlled epitaxy technique in a newly developed low-pressure hot-wall CVD (LP-HWCVD) system with a horizontal aircooled quartz tube at around 1500 ℃and 1.33 × 104 Pa by employing SiH4 C2H4 H2. In-situ doping during growth was carried out by adding NH3 gas into the precursor gases. It was shown that the maximum Hall mobility of the undoped 4H-SiC epilayers at room temperature is about 430 cm2 ·V -1 ·s -1 with a carrier concentration of ～ 1016 cm-3 and the highest carrier concentration of the N-doped 4H-SiC epilayer obtained at NH3 flow rate of 3 sccm is about 2.7 × 1021 cm-3 with a mobility of 0.75 cm2 ·V -1 ·S -1. SiC p-n junctions were obtained by epitaxially growing N-doped 4H-SiC epilayers on Aldoped 4H-SiC substrates. The C-V characteristics of the diodes were linear in the 1/C3-V coordinates indicating that the obtained p-n junctions were graded with a built-in voltage of 2.7 eV. The room temperature electroluminescence spectra of 4H-SiC p-n junctions are studied as a function of forward current. The D-A pair recombination due to nitrogen donors and the unintentional, deep boron center is dominant at low forward bias, while the D-A pair recombination due to nitrogen donors and aluminum acceptors are dominant at higher forward biases. The p-n junctions could operate at temperature of up to 400 ℃, which provides a potential for high-temperature applications.     

Challenges and R&D opportunities of smart distribution grids in China

In this paper, 5 investigations on the current states of power distribution grids in China have been introduced that cover the surveys of the practical distribution asset utilization, the simultaneity factor of feeder loading, the load compositions and characteristics, the urban reliability and the integration of distributed generations of renewable resources. Based on the survey results in the investigations, 12 Facts are clearly presented. It shows that the challenges to modernize the distribution grids in China are to improve the asset utilization rates, the electricity efficiencies and the reliability of distribution systems, as well as to integrate increasing amount of variable distributed renewable resources. Furthermore based on the challenges, 8 R&D opportunities have been identified.     

电测技术在人体骨骼力学性能分析中的应用

用电测实验应力分析方法,对人体管状长骨的力学性质,以及骨折的钢板皮外固定治疗中的力学问题,进行测量与分析。其结果对于推进力学理论在医学方面的应用,以及临床治疗骨折,具有实用价值。     

湖南省土壤中天然放射性核素含量调查研究

本文报道湖南省土壤中天然放射性核素含量的调查结果。布点方法与环境陆地γ辐射剂量率调查相同,全省共布25×25km 网格点309个,土类加密点5个,特殊加密点7个,共采集土壤样品321个。土壤样品中天然放射性核素含量的测定采用放化分析方法。调查结果表明,湖南省土壤中~(23(?))U、~(232)Th、~(226)Ra 和~(40)K 含量按样品数的加权均值分别为48.05、54.82、59.36和447.75Bq/kg。零陵地区土壤中~(238)U、~(232)Th 和~(226)Ra 含量最高,郴州地区次之,湘西自治州地区居三。湖南省6类主要土壤中~(40)含量较为接近,而红壤中~(238)U、~(232)Th 和~(226)Ra 含量较高。     

矿热炉把持器的传热分析

以矿热炉电极把持器的传热计算为核心,研究把持器的结构设计和参数选用。通过对冷却水流量、壁面厚度、水垢厚度、烟气温度等影响因素的研究,结合把持器传热边界条件,分析了在不同参数条件下传热变化趋势,为电极把持器的设计和应用提供了参考依据。     

微机控制的感应电动机特性测试系统

采用单片机作为下位机,PC机作为上位机,联合组成了感应电动机特性的微机测试系统。单片机对被测电量波形进行同步采样,对被测电机的运行状态进行控制。PC机控制单片机的运行,对测量数据进行快速处理,打印试验报告,绘制图形曲线,实现了测试过程的自动化。     

同步沉淀除磷在污水生物处理中的应用

在同步沉淀工艺的基础上,综述了同步沉淀在不同的污水生物处理工艺中的除磷效果、化学试剂用量的控制、除磷过程模拟的研究进展,并重点讨论了同步沉淀中的化学试剂对生物处理系统性能的影响.最后,展望了同步沉淀在污水生物处理中的应用前景和研究方向.     

Invariant Deformation Element Model Interpretation to the Crystallography of Diffusional Body-Centered-Cube to Face-Centered-Cube Phase Transformations

The crystallography of body-centered-cube to face-centered cube (bcc-to-fcc) diffusion phase transformations in a duplex stainless steel and a Cu-Zn alloy, including long axis, orientation relationship (OR), habit plane (HP), and dislocation spacing, is successfully interpreted with one-step rotation from the Bain lattice relationship by applying a simplified invariant line (IL) analysis. It is proposed that the dislocation slipping direction in the matrix plays an important role in controlling the crystallography of precipitation.     

基于Jack的虚拟环境中一种防止穿越的实现

在虚拟环境下虚拟人手和虚拟物体的交互中,会发生穿越现象。为了解决穿越问题,在人体模型系统Jack的虚拟环境中,根据约束Constraint对象的特点,利用Constraint对象来模拟物体对人手阻挡作用,并利用约束队列实现了对场景中Constraint对象的管理,达到防穿越的效果。     

壳聚糖负载稀土化合物催化环氧乙烷与环氧丙烷共聚合反应研究

研究以壳聚糖(Cs)作为高分子金属催化剂载体,制得负载稀土金属化合物的高分子金属催化剂,应用于环氧乙烷(BO)和环氧丙烷(PO)的共聚合反应.研究发现以三异丁基铝(Al(i-Bu)3)为助催化剂,乙酰丙酮(Acac)为第三组分时,该体系的催化活性高达192 kg*copolymer/mol*Y,比非负载型稀土催化体系活性提高1个数量级以上.环氧乙烷和环氧丙烷的竞聚率r 1(EO)、r 2(PO)分别为2.75±0.02和0.55±0.01;并用13C-NMR谱和DSC谱对共聚物结构进行了表征.