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Comparison of the RF MEMS switches with dielectric layers on the bridge’s lower surface and on the transmission line

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science china(Information sciences) 2011年第2期54卷 396-406页

作者： CHEN KenLe & ZHANG JinWen National key laboratory of Micro/Nano Fabrication Technology, Institute of Microelectronics, Peking university, beijing 100871, china 1. National key laboratory of Micro/Nano Fabrication Technology Institute of Microelectronics Peking University Beijing 100871 China

Previously, we proposed that the dielectric layer of RF MEMS switch can be fabricated either on the transmission line, as traditional switches, or on the lower surface of the bridge. This paper presents a detailed comparison of the RF MEMS switches with different positions of dielectric layer. Through theoretically analyzing the physical model of fringing capacitance, it is revealed that different positions of dielectric layer can result in different switch capacitances. Therefore, the change of dielectric-layer position can reduce the switch capacitance and insertion loss when the bridge is much wider than t-line. The theoretical analysis is demonstrated by Maxwell 3D and HFSS simulation, showing that the insertion loss is reduced by around 13% when the bridge width is three times of transmission line width. Further, the inffuence of switch’s structural parameters, such as dielectric material and dimensions of dielectric layer, on the differences between these two kinds of switches is discussed. To achieve high integration together with low-loss and low-actuation-voltage design, the novel switch with dielectric layer on bridge’s lower surface can be expected to have broad applications in the future.

关键词： RF MEMS switch insertion loss fringing capacitance dielectric layer

A new navigation approach of terrain contour matching based on 3-D terrain reconstruction from onboard image sequence

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science china(Technological sciences) 2010年第5期53卷 1176-1183页

作者： LI LiChun1,2,YU QiFeng2,SHANG Yang2,YUAN Yun2,LU HongWei3 & LIU XiaoLin4 1 beijing Aerospace Control Center,beijing 100094,china 2 College of Aerospace and material engineering,National university of Defense Technology,Changsha 410073,china 3 Equipment Research Institute of PLA’s Second Artillery,beijing 100085,china 4 College of Mechatronic engineering and Automation,National university of Defense Technology,Changsha 410073,china 1. beijing Aerospace Control Center Beijing 100094 China2. College of Aerospace and Material Engineering National University of Defense Technology Changsha 410073 China3. Equipment Research Institute of PLA’s Second Artillery Beijing 100085 China4. College of Mechatronic Engineering and Automation National University of Defense Technology Changsha 410073 China

This article presents a passive navigation method of terrain contour matching by reconstructing the 3-D terrain from the image sequence(acquired by the onboard camera).To achieve automation and simultaneity of the image sequence processing for navigation,a correspondence registration method based on control points tracking is proposed which tracks the sparse control points through the whole image sequence and uses them as correspondence in the relation geometry ***,a key frame selection method based on the images overlapping ratio and intersecting angles is explored,thereafter the requirement for the camera system configuration is *** proposed method also includes an optimal local homography estimating algorithm according to the control points,which helps correctly predict points to be matched and their speed ***,the real-time 3-D terrain of the trajectory thus reconstructed is matched with the referenced terrain map,and the result of which provides navigating *** digital simulation experiment and the real image based experiment have verified the proposed method.

关键词： terrain contour matching vision-based navigation 3-D reconstruction control points key frame registration optimal local homography

Unsteady-state Grinding Technology (I) Theoretical Generalization and Research on Grinding Mechanism

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厦门大学学报（自然科学版） 2002年第S1期41卷 46-47页

作者： LIN Bin, LI Zhi-chao, XU Yan-shen, HU Jun (The state Education Ministry key laboratory of High Temperature Structure ceramics and Machining Technology of engineering ceramics, Tianjin university, Tianjin 300072, china)

In conventional grinding theory, it is obvious that there must be a very high hardness difference between grains of the grinding wheel and workpieces. The best grinding wheels are those giving the lowest "natural limiting surface roughness" while cutting at appreciable plunge velocities. With the development of new materials and new machining processes, conventional theories of grinding techniques are no longer suitable to explain many phenomena in the course of grinding procedures. In dealing with precision or ultra-precision grinding processes of advanced ceramics, many results of experiments and practical production have shown that grinding with super hard materials wheels is not the only method to machine advanced ceramics. This paper is intended to propose a new grinding theory named as unsteady-state grinding technique evolved from some phenomena that can not be explained by conventional grinding theory. Unsteady-state grinding technique means the technique which can make the surface roughness of the materials, especially hard and brittle, be up to the standard of ultra-precision machining by utilizing common wheels characteristic of inferior self-sharpening and wear-resistance. In the process of machining, the common wheel need to be redressed about 3～5 times and the time between two redressings is about 3～5 minutes. As a validation of the new grinding technology, experimental work was performed to prove the existence of the unsteady state in the process of ultra-precision grinding with common abrasive wheel-pink fused alumina wheel. From the results of the observation of the wheel topography, the whole grinding process in unsteady state was separated into three stages namely cutting by grains peaks, micro-cutting by micro edges of the broken grains and rubbing without material removal, which is different from conventional grinding theory. For the difference of hardness between grinding wheel and workpiece material is not so apparent, some people have doubts

关键词： unsteady state grinding theory grinding mechanism common abrasive wheel ceramic

STUDIES ON ION BEAM APPLICATION TO IMPROVE AQUATIC MACROPHYTE REMEDIATION CAPACITY IN EUTROPHIC WATERS

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水生生物学报 2006年第6期30卷 711-717页

作者： LI Miao1, WU Yue-Jin 1, ZHANG Jun 1, YU Han-Qing 2, WU Xiao-Lei 3 and YU Zeng-Liang 1 (1. key laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, the Chinese Academy of sciences, Hefei, china 230031 2. School of Chemistry and material science, the university of science and Technology of china, Hefei, china 230026 3. department of Environmental science and engineering, tsinghua university, beijing, china 100084 ) Institute of Plasma Physics the Chinese Academy of Sciences Key Laboratory of Ion Beam Bioengineering CAS Hefei 230031 School of Chemistry and material science the University of Science and Technology of China Hefei 230026 department of Environmental science and engineering Tsinghua University Beijing 100084

Using ion beam biotechnology in combination with soil-less plant cultivation on artificial substratum (floating beds), the experiments were conducted with Ipomoea aquatica Forsk. Plants were attached to floating-beds which were placed on the surface of artificially nutrient-enriched tank water, in order to study the purification and remediation efficiency of ion beam-treated I. aquatica cultivars. The results show that N + ion beams with 25keV energy and dosages of 0, 2.6, 3.9, 5.2, 6.5, 7.8, 9.1×10 13N +(ions)/cm 2 affected I. aquatica dry seeds differently, with the dose of 3.9×10 13N + (ions)/cm 2 improving effectively the performance as expressed by various biological indices. After ion beam application, I. aquatica cultivars grew well in nutrient-enriched water bodies, increasing the growth of leaves and stem, number of leaves, length and area of roots, plant height, and weight more remarkably than observed in the control. The net removing rates of TN, TP were as high as 75% and 82%, respectively. Especially under the dose of 3.9×10 13N +(ions)/cm 2, the net removing rates of TN, TP were highest, for 77% and 85%, respectively. It was proved that ion beam application improves phytoremediation and may be used to purify nutrient rich water bodies.

关键词： Ion beam treatment Aquatic macrophyte Ipomoea aquatica Forsk Nutrient-enriched waters Remediation capacity

Optimization of processing Parameters for Laser Powder Deposition using Finite Element Method

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Journal of Wuhan university of Technology(materials science) 2010年第5期25卷 832-837页

作者：付垚 state key laboratory of Non-ferrous Metals and Processes General Research Institute for Non-ferrous Metals

In order to investigate the effects of powder materials and processing parameters on thermal and stress field during laser powder deposition （LPD）, a finite element model was developed with the help of ANSYS software. The finite element model was verified by the comparison between the experimental results and computed results. Then LPD processes with different powder materials and processing parameters were simulated by using the FE model. The results show that less difference of thermal conductivity and thermal expansion coefficient between powder material and substrate material produces lower residual stress; higher laser power, laser scanning speed and smaller laser beam diameter can lead higher peak temperature and higher residual stress. The research opens up a way to rational selection of the powder materials and processing parameters for ensured quality.

关键词： laser powder deposition thermal field stress field powder material processing parameters

Effect of Tool Geometry in Nanometric Cutting

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厦门大学学报（自然科学版） 2002年第S1期41卷 16-17页

作者： HAN Xue-song, LIN Bin, YU Si-yuan, LIN Mon-xia (The state Education Ministry key laboratory of High Temperature Structure ceramics and Machining Technology of engineering ceramics, Tianjin university, Tianjin 300072, china)

With the development of science and technology, the ultra-precision manufacturing of the brittle and hard materials with superior quality have become a new attractive subject. Brittle materials (such as engineering ceramics, optical glass, semiconductor and so on) are widely used in electronics, optics, aeronautics and other high technology fields, so there are important theory significance and practical value to systematically study its machining mechanism and technology. Single crystal silicon is one of the typical brittle materials. Single crystal silicon wafer is a basic component of large and ultralarge integrated the circuit, its surface roughness and flatness are the key factor of improving its integration. With the successfully producing of the large diameter single crystal silicon wafer, its manufacturing technology became attractive subject again. This paper carries out computer simulation of nanometer cutting on single crystal silicon. Molecular Dynamics method which is different from continuous mechanics is employed to investigate the features of grinding energy dissipation, grinding force, stress state and grinding temperature, constructs the atom model of tool and work piece, and explains the microscale mechanism of material remove and surface generation of nanometer(subnanometer) manufacturing. This paper also investigates the variation of cutting force, thrust force, specific energy and surface deformation with different tool edge radius, different depth of cut.

关键词： single crystal silicon ultraprecision machining manufacturing mechanism molecular dynamics computer simulation

稀土Gd^(3+)的掺杂对Sr_2CeO_4∶Eu中Eu^(3+)发光的影响

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四川大学学报（自然科学版） 2005年第S1期42卷 311-313页

作者：石士考周济栗俊敏清华大学材料科学与工程系新型陶瓷和精细工艺国家重点实验室北京100084 河北师范大学化学与材料科学学院石家庄050016

采用共沉淀方法,合成了Gd3+和Eu3+共掺杂的Sr2CeO4荧光体.当Eu3+浓度较小(掺杂浓度为2%)时,Gd3+离子对Sr2CeO4的蓝带发射及附着在其上面的Eu3+的特征跃迁起猝灭作用;而当Eu3+的浓度较高(掺杂浓度为8%)时,Gd3+离子对Sr2CeO4的蓝带发射及... 详细信息

采用共沉淀方法,合成了Gd3+和Eu3+共掺杂的Sr2CeO4荧光体.当Eu3+浓度较小(掺杂浓度为2%)时,Gd3+离子对Sr2CeO4的蓝带发射及附着在其上面的Eu3+的特征跃迁起猝灭作用;而当Eu3+的浓度较高(掺杂浓度为8%)时,Gd3+离子对Sr2CeO4的蓝带发射及附着在其上面的Eu3+的特征跃迁起敏化作用,尤其是当Gd3+离子的掺杂浓度为3%时,Eu3+的5D0-7F2跃迁发射(615nm)增强为原来的132%.

关键词：发光 Sr_2CeO_4 Eu^(3+) Gd^(3+)

Photocatalytic degradation kinetics of Rhodamine B cata- lyzed by nanosized TiO_2 film

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Chinese science Bulletin 2003年第1期48卷 49-52页

作者： WEI Gang, ZHANG Yuanjing & XIONG Rongchun College of material science and engineering, beijing university of Chemical Technology, beijing 100029, china Correspondence should be addressed to Xiong Rongchun (e-mail: xiongrongchun@***) College of material science and engineering Beijing University of Chemical Technology Beijing 100029 China

A fixed bed photocatalytic reactor was de-signed, and dynamic fast scan of UV-Vis adsorption spec-trum was adopted to study the photocatalytic degradation dynamic behavior of Rhodamine B, a kind of dye generally recognized as to be degraded difficultly, on the surface of nanosized TiO2 thin film. The results indicate that the photocatalytic degradation process of Rhodamine B does not comply with the first-order reaction kinetic process. As a result, a kinetic model of Rhodamine B photocatalytic deg-radation reaction is brought forward, and the model is proved by the theoretical deduction and experiment.

关键词：若丹明B 光催化降解动力学含染料废水固定床光催化反应器纳米级二氧化钛薄膜 TiO2

Sintering time influences on microstructure and electrical properties of scandium doped zinc oxide varistor ceramics

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Sintering time influences on microstructure and electrical p...