Polycrystalline diamond MESFETs by Au-mask technology for RF applications

Metal-semiconductor field effect transistors (MESFETs) were fabricated on H-terminated polycrystalline diamond.The DC characteristics of the p-channel MESFET showed a maximum drain current density of 204 mA/mm at a gate-source voltage of 6 V,and a maximum transconductance of 20 mS/mm at a gate-source voltage of 1.5 V.The small signal S-parameters of MESFET with 2 100 m gate width and 2 m gate length were measured.An extrinsic cut-off frequency (fT) of 1.7 GHz and the maximum oscillation frequency (fmax) of 2.5 GHz were obtained,which was the first report on diamond MESFETs with RF characteristics in China.     

Experimental research on air film formation behavior of air cushion belt conveyor with stable load

In this paper, the air film formation behavior of air cushion belt conveyor with stable load is studied. The air cushion field is analyzed by means of theoretical derivation, numerical simulation and experimental research. An intelligent experiment platform is developed. Three dimensional pressure distribution of air film and the air film thickness distribution along the conveyor belt in the width direction are obtained. The experimental result is analyzed by comparing with theoretical calculation and numerical simulation. The numerical and theoretical results are in good agreement with those obtained from experiments. The air film formation behavior pattern of air cushion belt conveyor with stable load is presented. The optimized film thickness and pore distribution are obtained based on the comprehensive energy consumption. This study provides a basis for the optimization design of air cushion belt conveyor.     

基于ANSYS的钢模台车顶模架拓扑优化设计

以江坪河溢洪道钢模台车为例,在用ANSYS软件对顶模架初始设计方案进行有限元分析的基础上,利用ANSYS拓扑优化理论对顶模架进行了结构拓扑优化设计,并对拓扑优化后的结构设计方案进行了有限元分析。对比分析结果显示,拓扑优化后的顶模架结构刚度、强度均有一定的提高,且未增加制造难度。     

云南某磷肥厂球磨机钢球配比的优化

针对云南某磷肥厂因钢球配比不合理、大球过多而造成的磨矿细度不高,不能很好地适应磷酸生产要求的问题,分析了入磨矿石的粒度组成.根据矿石的粒度组成采用昆明理工大学段希祥教授的精确化装补球方法,提出了一套针对该磷肥厂球磨机的精确化装球方案,同时提出了一个偏大方案和一个偏小方案,并和现厂的装球方案进行对比.针对四种装球方案进行了实验室扩大试验,研究结果表明:最佳装球方案为精确化装球方案,该方案与现厂的装球方案相比,可以使球磨机的生产能力提高14.44%;根据新方案的粒度特性曲线给出了补加钢球的方案,按此方案补加钢球可以使球磨机中的球荷组成始终保持近似于推荐的初装球组成.     

创新型经济发展对会计人才培养的影响

通过对2l世纪区域经济发展模式的调查,阐述了创新型经济的概念和特征,分析了创新型经济对企业会计业务的影响,研究了创新型经济对会计人员提出的新要求,从而提出了会计人才培养的改革设想。     

大岗山拱坝建基面质量标准及评价

大岗山拱坝是我国目前抗震设防烈度最高的拱坝,其基岩水平峰值加速度为0.557 5 g,在设计地震荷载作用下,建基面最大压应力达12.43 MPa,要求建基面的质量必须与之相适应。建基面质量评价包括开挖质量和岩体质量两方面,开挖质量评价按照有关规范的单元工程质量等级评定标准进行,岩体质量评价以地质鉴定岩类为主,声波纵波速度为辅。按事先拟定的开挖方案,建基面开挖平顺,开挖质量达到优良标准。     

大学生英语口语的组织单位使用分析

组织单位即组织性词块在话语组织中起着重要作用.通过COLSEC和BNC的对比研究,观察我国大学生英语口语组织单位的使用情况,结果表明大学生在口语中更常使用一小部分的组织单位,并且在单位词块内,学习者比本族语者更多重复使用了某些组织单位等现象.这些不同可能主要受母语迁移和外语焦虑等因素的影响.     

Accurate mirror-based camera pose estimation with explicit geometric meanings

An accurate closed form solution is proposed to estimate camera pose by several mirrored reference object images acquired via a planar mirror under different unknown poses. Compared with state-of-the-art methods, our method is more accurate when there are more than three images and has explicit geometric meanings. This method also properly handles cases in which some of the mirror poses are parallel. The central idea is to minimize an error metric based on all reflections of rotation, which enables the camera rotation to be estimated directly by SVD of sum of mirrored camera rotations. After that, the camera translation is computed by solving a large system of linear equations to minimize object space collinearity error. Both synthesized data and real data experiments show the advantages of our approach.     

The influence of oleic acid on the hydration and mechanical properties of portland cement

To investigate the effects of OA on the portland cement using oleic acid （OA） as grinding aid and the effects of OA on the portland cement, we characterized the different perfermances of the cement, discussed the characteristics of properties. The results reveal that the OA can reduce the water requirement of normal consistency. With the content of OA added, setting time was extended. The OA can significantly improve the rheological properties of cement-based materials, while the compressive strength decreases.     

钓鱼网站的鉴别方法与防范策略研究

文章从钓鱼网站的种类和传播途径入手,重点分析了钓鱼网站的鉴别方法和防范措施,最后指出了打击钓鱼网站的难度.