AlGaN-GaN double-channel HEMTs

We present the design, fabrication, and characterization of AlGaN-GaN double-channel HEMTs. Two carrier channels are formed in an AlGaN-GaN-AlGaN-GaN multilayer structure grown on a sapphire substrate. Polarization field in the lower AlGaN layer fosters formation of a second carrier channel at the lower AlGaN-GaN interface, without creating any parasitic conduction path in the AlGaN barrier layer. Unambiguous double-channel behaviors are observed at both dc and RF. Bias dependent RF small-signal characterization and parameter extraction were performed. Gain compression at a high current level was attributed to electron velocity degradation induced by interface scattering. Dynamic IV measurement was carried out to analyze large-signal behaviors of the double-channel high-electron mobility transistors. It was found that current collapse mainly occurs in the channel closer to device surface, while the lower channel suffers minimal current collapse, suggesting that trapping/detrapping of surface states is mainly responsible for current collapse. This argument is supported by RF large-signal measurement results.     

Study on the protection of Er-doped phosphate glass waveguide surface in ion-exchange processing

A novel method, sputtering K9 glass film, is proposed to solve the surface corrosion of Er-doped phosphate glass during ion-exchange processing for optical waveguide fabrication. The corrosion causes are analyzed to be the intrinsically weak stabilization of phosphate glass structure, hydrophile and weakly acidic property of phosphate radical. Experimental results show that the K9 glass film could not only protect the Er-doped phosphate glass surface from being corroded but also give no influence on the waveguide fabrication. The effect of thickness of K9 glass film on the optical property of waveguide is also investigated and the optimal thickness is found to be 60–80 nm. It provides a good base for further fabrication of active phosphate glass optical waveguide devices. Supported by the Optical Science and Technology Foundation of Shanghai Technology Committee (Grant No. 022261009), the Young Teacher Cultivation Foundation of Dalian University of Technology (Grant No. 893210), and the Doctor Startup Foundation of Dalian University of Technology (Grant No. 893322)     

"情景共享模型"在淮河干流水量分配中的应用

为适应水资源管理理念和管理方法的转变,提出情景共享模型及其建模思想和方法,对淮河干流及其主要支流2010规划水平年的水资源分配情景进行了模拟。结果证明该模型性能良好,效率较高,可为不同利益相关者共同参与水资源管理决策提供理想的分析工具。     

A mobile teletrauma system using 3G networks

This paper introduces a cost-effective portable teletrauma system that assists health-care centers in providing prehospital trauma care. Simultaneous transmission of a patient's video, medical images, and electrocardiogram signals, which is required throughout the prehospital procedure, is demonstrated over commercially available 3G wireless cellular data service. Moreover, the physician can remotely control the information sent from the patient side. Such a technology will allow a trauma specialist to be virtually present at the remote location and participate in prehospital care, which improves the quality of trauma care and can potentially reduce mortality and morbidity. To alleviate the limited and fluctuant bandwidth barriers of the wireless cellular link, the system adapts to network conditions through media transformations, data prioritization, and application-level congestion control methods. Experimental evaluation of the system prototype over real network conditions, transmitting different media types between the trauma patient and hospital unit, is encouraging. The teletrauma system reported in this paper is the first of its kind and it provides a basis for future enhancements.     

Application of computational fluid dynamics analysis for improving performance of commercial scale selective catalytic reduction

The performance of commercial scale selective catalytic reduction (SCR) system is strongly dependant upon the degree of mixing between NH₃ and NOx or NH₃ concentration distribution at the catalyst layer according to the reaction kinetics of SCR catalysts. Insufficient mixing of the reduction agent and NOx mass flow necessitates an uneconomically large catalyst volume and high NH₃ slip to meet the required NOx emission values. The effective methodology which can increase the performance of commercial scale SCR through improving NH₃ concentration distribution at the catalyst layer using computational fluid dynamics (CFD) analysis was suggested and applied to the real operations. The operation results have shown that the performance of commercial SCR was improved from 54.4% to 74.8% as NH₃ concentration deviation at the catalyst layer was reduced from 23.6% to 8.6%. It is established that the increase of NH₃ concentration uniformity at the catalyst layer contributes to improvement of performance of commercial scale SCR.     

多层旧工房成套改造的几点体会

上海在上世纪七八十年代计划经济时建造了大量低标准住宅,设计是按照市民用建筑设计院上海市职工住宅定型图纸,建有上百万平方米的居民住宅小区。当时所谓福利房都为五六层砖混结构,面积小,功能不全,即没有独用厨卫设施,仅每层设公用卫生间约4m2,十户共用倒便池,居住质量很差,给居民生活带来极大不便。随着社会经济的发展,人民生活水平不断提高,居民强烈希望改善居住条件。如果全部拆除重建是不现实的,因此从通过成套改造、增加厨卫设施这一举措解决住户“上厕难”的问题,适当改善旧小区居民的居住条件,是当地房管部门正常的房屋修缮行为。…     

Accelerating the Development of Hydrogenation Process and Technology in China

The crude oils processed at refineries worldwide are becom ing heavier with the contents of sulfur and heavy metals increasing since the 1990s. The environmental regulations promulgated by the governments of many countries are tight ening and there is an urgent need which calls the refiners'attention to adopt clean production processes and make clean fuels.     

压电行波马达的孤极反馈频率跟踪技术

提出利用定子陶瓷的孤极反馈来完成行波马达的闭环控制，减少了频率漂移所引起的速度波动问题。     

A statistical description of stimulated Brillouin scattering beamcombination efficiency

The mutual coherence between two stimulated Brillouin signals produced by undepleted pump beams that are partially overlapped is studied. The mutual coherence of the stimulated-Brillouin-scattered beams determines the efficiency with which the two beams can be combined. The statistical properties of the mutual coherence are calculated. The mechanism for coupling of two stimulated-Brillouin-scattering outputs is four-wave mixing. Mutual coherence is found to depend on the pump beam's pulse duration, the medium's phonon lifetime, and the degree of overlap between the laser pump beams