稀土掺杂注射成形AlN陶瓷的结构与性能

以自蔓延法合成的AlN粉末为原料,加入5%Y2O3为烧结助剂,选用PW∶PP∶SA=60∶35∶5的粘结剂体系,以注射成形的方法制备了具有高热导率的、形状复杂的AlN陶瓷制品。脱脂采用溶剂脱脂与真空热脱脂相结合的工艺,脱脂后的坯体在高温碳管炉中流动N2气氛下进行烧结。利用XRD进行物相分析,SEM观察断口形貌,排水法测烧结试样的密度,激光闪光法测烧结试样的热导率。结果表明:当烧结温度在1850℃,保温4 h,得到致密度为3.28 g.cm-3,热导率为200 W.m-1.K-1的AlN陶瓷制品。AlN中的晶界第二相主要为Al2Y4O9。     

江西省科技馆楼宇设备自动化系统设计概述

结合江西省科学技术馆楼宇设备自动化系统设计,阐述楼宇设备自动化系统基本概念及设计方法。     

Spin Injection Processes in ZnSe-Based Double Quantum Dots of Diluted Magnetic Semiconductors

Spin injection processes in the double quantum dots of ZnSe-based diluted magnetic semiconductors are discussed. Double quantum dots are fabricated from ZnSe-based double quantum wells by electron beam lithography and wet etching. In these samples, the photo-excited carriers in the magnetic dots are injected into the non-magnetic dots. The circular polarization degrees of photoluminescence from the non-magnetic dots are measured by micro-photoluminescence measurement system under the magnetic field up to 5 T. The maximum spin polarization degrees of injected carriers determined from our experiment are 10% for double quantum wells and 15% for double quantum dots. The spin injection efficiency was estimated both from the observed circular polarization degree and the diffusion length of carriers. We concluded that the spin injection efficiency is increased in the double quantum dots.     

Gas turbine disk-blade attachment crack

Evaluation of a gas turbine disk revealed a crack in the blade attachment area. The subsequent effort to understand the origin of this crack led to a series of analyses that included computing the stresses on the attachment, characterization of fatigue crack growth, and a model for fretting fatigue crack growth. These elements were brought together to simulate the conditions that led to the cracking. It is concluded that the crack was probably caused by fretting fatigue induced by the stresses related to normal takeoff and landing cycles and exacerbated by aircraft maneuvers, and that short periods of blade resonance may have contributed to the cracking. If material had not been removed from the attachment surface of the disk by service-induced wear, it is likely more cracks would have been found.     

Processing of Net‐shaped Nanocrystalline Fe‐Ni Material

Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. This paper provides an overview on our recent investigations on the processing of net‐shaped nanocrystalline Fe‐Ni powder and related material property such as mechanical property. The key‐processing concept is the synthesis of nanopowders and subsequent consolidation with controlled microstructure by using powder injection molding (PIM) process. Especially, the pressureless sintering process is inevitable for consolidation of the PIMed nanopowder. The present review focuses on the densification process and related mechanical property of the PIMed Fe‐Ni nanopowder in association with microstructural evolution and diffusion process.     

Influence of resonance tube length on performance of thermoacoustically driven pulse tube refrigerator

A resonance tube is an important component of a thermoacoustic engine, which has great influence on the performance of the thermoacoustically driven pulse tube refrigerator. A standing wave thermoacoustic engine is simulated with linear thermoacoustics. Computed results show that an appropriate accretion of the resonance tube length may lead to a decrease of the working frequency and an increase of the pressure amplitude, which will improve the match between the thermoacoustic engine and the pulse tube refrigerator. The theoretical prediction is verified by experiments. A refrigeration temperature as low as 88.6 K has been achieved with an optimized length of the resonance tube, helium as working gas, and 2200 W of heating power.     

一类矩阵方程的简便解法

对一类矩阵方程的解法进行了讨论，在一定条件下给出了一种简便快速的求解公式，并举例给予说明。     

直接转矩控制中一种磁链估计新方法

本文作者把直接转矩控制(DTC)与定子磁链定向矢量控制(SFOVC)相结合,利用DTC中电压矢量的空间位置角推导出SFOVC中的磁链定向角,然后根据旋转坐标系中的d轴和q轴电流分量建立定子磁链估计的数学模型.这样可使DTC中磁链的估计更简便易行也更精确.文章给出了一个7.5KW交流电机DTC的实验结果,它证明理论分析是正确和实用的.     

航天器电推进技术现状与发展趋势

航天器的发展趋势极大地促进了电推进技术在航天器入轨、离轨、状态保持、精确定位及复定位、姿态控制、行星探测一次、二次推进中的应用。概述了俄罗斯和美国当前的电推进活动，重点对霍尔发动机、离子发动机、脉冲等离子体发动机等进行了分析；对电推进相关的重要关键技术，如阴极技术、先进高功率概念、羽流效应、热效应、场效应及供应系统技术进行了介绍；对航天器电推进项目未来发展方向进行了分析展望。     

基于 ADuC812开发板的内燃机试验数据采集系统

介绍了一种基于ADuC812开发板的内燃机试验参数采集展统，给出了系统相关的电路图和程序框图，并就此系统中软件的关键部分予以说明。该系统具有体积小、价格低、使用方便等特点。