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Effect of Kovar alloy oxidized in simulated N_2/H_2O atmosphere on its sealing with glass

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Journal of University of Science and Technology Beijing 2008年第3期15卷 267-271页

作者： dawei Luo Wenbo Leng Zhuoshen Shen School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The effect of Kovar alloy oxidized in simulated field atmosphere on its sealing with glass was studied in this article. After Kovar plates and pins were preoxidized in N2 with 0℃, 10℃ and 20℃ dew points at 1000℃ for different times, Fe304 and Fe203 existed in the oxidation products on Kovar surface, and the quantity of Fe203 increased with increasing dew point and oxidation time. Then they were sealed with borosilicate glass insulator at 1030℃ for 20 rain. The results indicated that the type and quantity of oxidation products would directly influence the quality of glass-to-metal seals. With the increase of oxidation products, gas bubbles in the glass insulator were more serious, the climbing height of glass along the pins was higher, and corrosion of Kovar pins caused from the molten glass was transformed from uniform to the localized.

关键词： Kovar alloy oxidation sealing glass microelectronic package

TOOTH CURVES AND ENTIRE CONTACT AREA IN PROCESS OF SPLINE COLD ROLLING

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Chinese Journal of Mechanical Engineering 2008年第6期21卷 94-97页

作者： ZHANG dawei LI Yongtang FU Jianhua School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072. China School of Materials Science and Engineering Taiyuan University of Science and Technology Taiyuan 030024 China

In spline rolling process, the contact area between roller and workpiece plays an important role in calculating rolling-force and rolling-moment. For the purpose of studying the contact area, contact state between roller and workpiece in process of spline cold rolling based upon cross rolling is analyzed. According to the suitable hypothesis, the mathematic model of roller-tooth-curve in optional position of rolling process is established. Combing the theory of conjugate curves with the theory of envelope curve, the corresponding mathematic model of workpiece-tooth-curve is established. By utilizing establishing mathematic models, the algorithm of entire contact area in rolling process is created. On the basis of the algorithm, calculation-program is compiled under MATLAB program language environment. The calculation-program actualizes quantitative analysis and quantitative calculation of contact areas. Utilizing the calculation-program, the influence of parameters on contact area is analyzed, and the tendency is consistent with the manufacturing experience. In consideration of rolling-force optimization, the primary process parameters may be selected according to results of calculation. The result of the present study may provide basis for research on rolling-force and rolling-moment.

关键词： Spline Cold rolling Contact area Mathematic model MATLAB

Emergence of charge density wave and Ising superconductivity in centrosymmetric monolayer 1T-HfTe_(2)

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Nano Research 2023年第8期16卷 11521-11527页

作者： dawei Wang Jizheng Wu Chen Si Department of Medical Engineering Medical Supplies Center of PLA General HospitalBeijing 100853China School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Understanding and control of many-body collective phenomena such as charge density wave(CDW)and superconductivity in atomically thin crystals remains a hot topic in material ***,using first-principles calculations,we find that 1T-HfTe_(2)possessing no CDWs in the bulk form,unexpectedly shows a stable 2×2 CDW order in the monolayer form,which can be attributed to the enhancement of electron–phonon coupling(EPC)in the ***,the CDW induces a metal-to-insulator transition in monolayer 1T-HfTe_(2)through the accompanying lattice ***,Ising superconductivity with a significantly enhanced in-plane critical field can emerge in centrosymmetric monolayer 1T-HfTe_(2)after the CDW is suppressed by electron *** Ising paring is revealed to be protected by the spin–orbital locking without the participation of the inversion symmetry breaking which is a must for conventional 2H-NbSe2-like Ising *** results open a new window for designing and controlling novel quantum states in two-dimensional(2D)matter.

关键词： charge density wave(CDW) Ising superconductivity two-dimensional(2D)materials HfTe_(2) first-principles calculations

Theoretical Predition of Two-dimensional SiGeP_(2)by the Global Optimization Method

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Journal of Wuhan University of Technology(Materials Science) 2023年第5期38卷 1010-1016页

作者： XUE Xiao YU Jiahui ZHOU dawei PU Chunying School of Information Engineering Nanyang Institute of TechnologyNanyang 473004China School of Mathematics and Physics Nanyang Institute of TechnologyNanyang 473004China School of Physics and Electronic Engineering Nanyang Normal UniversityNanyang473061China

The well-developed particle-swarm optimization method together with density functional theory calculations were employed to search lowest-energy geometric structures of two-dimensional(2D)SiGeP_(2).Two newly found structures(P3m1 and Pmm2)are *** unbiased global search reveals that the two lowest-energy structures are honeycomb lattices with robust dynamical stabilities.A more accurate Heyd-Scuseria-Ernzerhof(HSE06)hybrid functional is used to estimate the band structures of SiGeP_(2),which indicates that both the structures are semiconductors with indirect band-gap energies 1.80 e V for P3m1 and1.93 e V for Pmm^(2),*** the deformation potential theory,the P3m1-SiGeP_(2)is predicted to have high electron mobilities(6.4×10^(4)along zigzag direction and 2.9×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively)and hole electron mobilities(1.0×10^(3)along zigzag direction and 2.5×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively),which can be comparable with that of phosphorene and show anisotropic character *** addition,to estimate the elastic limit of SiGeP_(2),we also calculated the surface tension of SiGeP_(2)as a function of tensile *** results show that the 2D SiGeP_(2)may be good candidaticates for applications in nanoelectronic devices.

关键词： two dimensional SiGeP_(2) the first-principles carrier mobility

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大舾装可视化虚拟装配DAP技术应用

造船技术 2021年第2期49卷 65-69页

作者：刘森峻翁戍生鲍雨晖张宝民郑晓光杨利春臧大伟徐建军高飞大连船舶重工集团有限公司辽宁大连116011

依托车间现场可视化平台,通过制订装配编码规则、转换轻量化装配模型、集成模型与图纸和文件信息、设定装配信息发布规则,实现面向生产车间的大舾装可视化虚拟装配分段装配规划(Detailed Assembly Planning,DAP)技术应用。以某超大型油... 详细信息

依托车间现场可视化平台,通过制订装配编码规则、转换轻量化装配模型、集成模型与图纸和文件信息、设定装配信息发布规则,实现面向生产车间的大舾装可视化虚拟装配分段装配规划(Detailed Assembly Planning,DAP)技术应用。以某超大型油船(Very Large Crude Carrier,VLCC)的典型分段为对象,进行实例应用。通过实例,大舾装可视化虚拟装配DAP技术的有效性和先进性得到验证,为更深入的船舶智能制造研究打下基础。

关键词：船舶大舾装 DAP 虚拟装配可视化

Jet dispersion and deposition of charged particles in confined chambers

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Particuology 2010年第1期8卷 28-36页

作者： Chao Zhu dawei Wang Chao-Hsin Lin Department of Mechanical Engineering NewJersey Institute of Technology Newark NJ 07102 USA Environmental Control Systems Boeing Commercial Airplanes Seattle WA 98124 USA

Dispersion and surface deposition of charged particles by gas-solids jets in confined chambers are constantly encountered in many industrial applications such as in electrostatic precipitation and dry powder coating processes. Understanding and control of flow patterns and trajectories of charged particles are important to the optimal design and operation of such devices. In this study, modeling of flow fields and particle trajectories of dilute gas-solid two-phase flows with charged particles in confined chambers is performed. The dilute gas-solid two-phase flows are simulated by use of a hybrid Eulerian-Lagrangian approach with the one-way coupling between the gaseous phase and particle phase. The space charge distribution is included as a source term in equations of motion or Lagrangian equation of charged particles, which in turn depends on the particle trajectories that determine the space charge distribution. Our modeling predictions suggested that the electrostatic charge plays a significant role in particle radial dispersion. Effect of voltage has limited influence on particle trajectories however it can have a big impact on the residence time. Cone angle has a significant effect on the structure of flow field. For cone with a larger cone angle （typically over 15°）, there will be a flow separation along the side wall near the flow entrance region. By comparing with the conical chamber, the cylindrical chamber has a big vortex and three smaller vortexes in the lower part of the chamber, which would complicate the particle dispersion with or without the coupling of charging.

关键词： Charged particle deposition Confined chamber Electric field Jet dispersion

Weakly magnetic field-assisted synthesis of magnetite nano-particles in oxidative co-precipitation

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Particuology 2009年第5期7卷 363-367页

作者： dawei Hu Yanmin Wang Qi Song College of Materials Science and Engineering South China University of Technology 510640 Guangzhou China Key Laboratory of Special Functional Materials under Ministry of Education 510640 Guangzhou China

This paper presents experimental results on weakly magnetic field-assisted synthesis of magnetite （Fe3O4） nano-particles in an oxidative co-precipitation method, in comparison to the case without magnetic induction. The XRD results show that a weakly magnetic induction below 220 Gs could accelerate the phase transformation from goethite （α-FeOOH） to magnetite （Fe3O4）, and affect the crystal structure, the particle size/morphology and magnetic response of the magnetite nano-particles synthesized. In addition, a higher concentration of the FeCl2 solution in the synthesis reaction led to finer particles, both with and without magnetic induction.

关键词： Magnetic field Oxidative co-precipitation Nano-particle Magnetite Morphology

Analysis of an Axial-flux Slotted Limited-angle Torque Motor with Quasi-Halbach Array for Torque Performance Improvement

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CES Transactions on Electrical Machines and Systems 2023年第3期7卷 266-274页

作者： Mingjie Wang dawei Li Ronghai Qu State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074China IEEE

Better torque performance and higher reliability have long been the focus of research for slotted limited-angle torque motors(LATMs),which are primarily used to position first-stage valves in electrohydraulic *** paper presents a high reliability axial-flux slotted LATM with quasi-Halbach array for torque performance improvement including constant torque range(CTR)and output ***,the structure with two sets of windings and the operation principle of the proposed slotted LATM is ***,a brief design procedure is presented,the structure selections of open slot and double-stator single-rotor(DSSR)interior rotor with surface mounted quasi-Halbach permanent magnet(PM)array are illustrated,and the geometric parameters are optimized to obtain the optimal design of the proposed slotted ***,3-D finite-element method(FEM)is employed to compare the proposed slotted LATM with the conventional surface mounted PM slotted LATM in terms of cogging torque,no-load back EMF,and output torque,and the results show that the proposed LATM with quasi-Halbach array has a 10%improvement in output torque and a 25%improvement in ***,the flux linkages and torque performance of the two sets of windings under various conditions verify good magnetic ***,prototypes of two different rotor types are manufactured and a series of experiments are performed to validate the analysis.

关键词： Limited-angle torque motor(LATM) Axial-flux machine Quasi-Halbach array Finite-element method(FEM) Cogging torque Torque performance

Certificateless designated verifier proxy signature scheme for unmanned aerial vehicle networks

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Science China(Information Sciences) 2021年第1期64卷 79-93页

作者： Lei HE Jianfeng MA Limin SHEN dawei WEI School of Computer Science and Technology Xidian University School of Computer and Communication Engineering Zhengzhou University of Light Industry School of Cyber Engineering Xidian University School of Computer Science and Technology Nanjing Normal University

Unmanned aerial vehicle(UAV) technologies have a promising application prospect. It is necessary to use digital signature schemes to protect the integrity and authentication of messages in the UAV networks. According to the characteristics of UAV networks, digital signature schemes should solve the problems of digital certificate management and key escrow, guarantee the real-time performance of UAV executing commands, and ensure that only the designated verifier can verify the signature. Therefore, we proposed a certificateless designated verifier proxy signature(CLDVPS) scheme which meets the requirements. We proved our signature scheme is existentially unforgeable under an adaptive chosen message attack in the random oracle model and compared the efficiency of our signature scheme with other signature *** implemented these signature schemes in jPBC to obtain the computing time and theoretically analyzed signature length of these signature schemes. The analysis results indicate that our CLDVPS scheme is more efficient than most of other related signature schemes on computation costs and also efficient on communication costs.

关键词： certificateless designated verifier proxy digital signature unmanned aerial vehicle