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Bi Layer Formation at the Anode Interface in Cu/Sn-58Bi/Cu Solder Joints with High Current Density

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Journal of Materials Science & Technology 2012年第1期28卷 46-52页

作者： Hongwen He Haiyan Zhao Fu Guo Guangchen xu Department of Mechanical Engineering Tsinghua University Beijing 100084 China College of Materials Science and Engineering Beijing University of Technology Beijing 100124 China

Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was the main diffusing species migrating from the cathode to the anode. The electromigration force and Joule heating took on the main driving forces for Bi diffusion and migration. In addition, two appearance types of Bi layers, planar-type and groove-type, were found during current stressing. The morphology and thickness of Bi layers were affected by current density and current stressing time.

关键词： Bi layer formation Current density Electromigration Joule heating

WARRANTY STRATEGY IN A SUPPLY CHAIN WHEN TWO RETAILER'S EXTENDED WARRANTIES BUNDLED WITH THE PRODUCTS

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Journal of Systems Science and Systems Engineering 2015年第3期24卷 364-388页

作者： Yiwen Bian Shuai Yan Wei Zhang Hao xu SHU-UTS SILC(Sydney Institute of Language & Commerce) Business School Shanghai University School of Management Zhejiang University School of Business Anhui University

We in this paper examine warranty strategy in a two-stage supply chain consisting of a manufacturer and two competing retailers. The manufacturer produces two substitute products and markets them through the two retailers to a group of consumers, respectively. For each type of products, the manufacRtrer＇s base warranty and a retailer＇s extended warranty are bundled with the product. We use game theoretic models to explore the interactions between the two types of warranties and the competition between the retailers. For this purpose, two scenarios are considered： no retailer and both the two retailers providing the extended warranties, respectively. In each scenario, the manufacturer＇s base warranties are assumed to be offered. Our results show that when the retailers offer their extended warranties, the manufacturer has no incentive to offer the base warranties; otherwise, the manufacturer has to provide the base warranties. The competition between retailers in terms of the product substitutability has no impact on warranty decisions, but affects all players＇ profits in the supply chain. The manufacturer can provide a longer warranty length and higher customer welfare to a customer than the retailers do, if it is more efficient than the retailers in warranty cost-efficiency, and vice versa.

关键词： Base warranty extended warranty supply chain competition.

Numerical Simulation of 2D Supersonic Magnetohydrodynamic Channel and Study on Hall Effect

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Chinese Journal of Aeronautics 2011年第2期24卷 136-144页

作者： ZHENG Xiaomei LU Haoyu xu Dajun CAI Guobiao School of Astronautics Beihang University Beij'ing 100191 China

In this research effort,numerical simulation of two-dimensional magnetohydrodynamic（MHD） channel is performed and Hall effect is *** computational model consists of the Navier-Stokes（N-S） equations coupled with electrical-magnetic source terms,Maxwell equations and the generalized Ohm＇s *** conditions for the electrical potential equation considering Hall effect are *** start with,the MHD channel with single-pair electrodes is studied and flow of the electric current is in accordance with physical *** the MHD channel with five-pair electrodes is numerically *** results show that the electrical current concentrates on the downstream of the anode and the upstream of the cathode due to Hall effect,and the flow field becomes *** the current value of the magnetic interaction parameter,the electrical-magnetic force affects the flow remarkably,decreasing the outlet Mach number and increasing the outlet pressure;what＇s more,the flow structure in the channel becomes extremely *** of MHD channels with continual electrodes and segmented electrodes are *** results show that performance of the MHD channel with segmented electrodes is better than that with continual electrodes with the increase of Hall parameter.

关键词： hypersonic vehicles scramjet magnetohydrodynamics Hall effect numerical simulation

BACH： A Bandwidth-Aware Hybrid Cache Hierarchy Design with Nonvolatile Memories

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Journal of Computer Science & Technology 2016年第1期31卷 20-35页

作者： Jishen Zhao Cong xu Tao Zhang Yuan Xie Department of Computer Engineering University of California at Santa Cruz Santa Cruz CA 95064 U.S.A. Hewlet-Packard Labs Palo Alto CA 94304 U.S.A. NVIDIA Corporation Santa Clara CA 95050 U.S.A. Department of Electrical and Computer Engineering University of California at Santa Barbara Santa Barbara CA 93106 U.S.A.

Limited main memory bandwidth is becoming a fundamental performance bottleneck in chipmultiprocessor （CMP） design. Yet directly increasing the peak memory bandwidth can incur high cost and power consumption. In this paper, we address this problem by proposing a memory, a bandwidth-aware reconfigurable cache hierarchy, BACH, with hybrid memory technologies. Components of our BACH design include a hybrid cache hierarchy, a reconfiguration mechanism, and a statistical prediction engine. Our hybrid cache hierarchy chooses different memory technologies with various bandwidth characteristics, such as spin-transfer torque memory （STT-MRAM）, resistive memory （ReRAM）, and embedded DRAM （eDRAM）, to configure each level so that the peak bandwidth of the overall cache hierarchy is optimized. Our reconfiguration mechanism can dynamically adjust the cache capacity of each level based on the predicted bandwidth demands of running workloads. The bandwidth prediction is performed by our prediction engine. We evaluate the system performance gain obtained by BACH design with a set of multithreaded and multiprogrammed workloads with and without the limitation of system power budget. Compared with traditional SRAM-based cache design, BACH improves the system throughput by 58% and 14% with multithreaded and multiprogrammed workloads respectively.

关键词： memory bandwidth hybrid cache reconfigurable cache nonvolatile memory

Interannual modulation of intraseasonal sea level variability along the southern coast of Java

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Science China Earth Sciences 2018年第1期61卷 1-12页

作者： CAO GuoJiao HE YiJun WEI Zexun xu TengFei School of Marine Sciences Nanjing University of Information Science & Technology Nanjing 210044 China First Institute of Oceanography State Oceanic Administration Qingdao 266061 China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Qingdao 266237 China jiangsu Research Center for Ocean Survey and Technology Nanjing 210044 China

The intraseasonal variability(ISV) of sea level anomalies(SLAs) along the southern coast of Java and its interannual modulation were studied based on a gridded SLA product produced from the Archiving, Validation, and Interpretation of Satellite Oceanography dataset. This ISV is induced by the propagation of intraseasonal Kelvin waves derived from the central equatorial Indian Ocean(EIO). Wavelet analysis and empirical mode decomposition of intraseasonal SLAs along the southern coast of Java showed interannual variability, with weaker ISV events during El Ni years and positive Indian Ocean Dipole(IOD) years than during normal years. This interannual modulation of the ISV is influenced by the El Ni-Southern Oscillation teleconnection via the Walker Circulation and eastern Indian Ocean upwelling connected to IOD events. The anomalously weaker Walker Circulation during El Ni events generates anomalous surface easterlies over the central-eastern tropical Indian Ocean that produce upwelling Kelvin waves in the EIO and offshore water transport along the southern coasts of Sumatra and Java, resulting in negative SLAs along the southern coast of Java. These negative SLAs damp the positive SLAs induced by the eastward propagation of downwelling Kelvin waves from the central EIO during the following March–May of El Ni years. Similar features of SLAs and sea surface wind anomalies also occur during positive IOD years. Consequently, the sea level ISV along the southern coast of Java is weaker in El Ni and positive IOD years.

关键词： Intraseasonal variability Sea level Interannual variability Kelvin waves Indian Ocean

Fault detection of flywheel system based on clustering and principal component analysis

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Chinese Journal of Aeronautics 2015年第6期28卷 1676-1688页

作者： Wang Rixin Gong xuebing xu Minqiang Li Yuqing Deep Space Exploration Research Center Harbin Institute of Technology

Considering the nonlinear, multifunctional properties of double-flywheel with closed- loop control, a two-step method including clustering and principal component analysis is proposed to detect the two faults in the multifunctional flywheels. At the first step of the proposed algorithm, clustering is taken as feature recognition to check the instructions of ＂integrated power and attitude control＂ system, such as attitude control, energy storage or energy discharge. These commands will ask the flywheel system to work in different operation modes. Therefore, the relationship of parameters in different operations can define the cluster structure of training data. Ordering points to identify the clustering structure （OPTICS） can automatically identify these clusters by the reachability-plot. K-means algorithm can divide the training data into the corresponding operations according to the teachability-plot. Finally, the last step of proposed model is used to define the rela- tionship of parameters in each operation through the principal component analysis （PCA） method. Compared with the PCA model, the proposed approach is capable of identifying the new clusters and learning the new behavior of incoming data. The simulation results show that it can effectively detect the faults in the multifunctional flywheels system.

关键词： Attitude control Cluster analysis Energy storage Fault detection Flywheels

HIGHLY DISPERSED MULTI-WALLED CARBON NANOTUBES IN WATER/ETHANOL AND ITS APPLICATION FOR PVA COMPOSITE

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 389-396页

作者： X.Y.Tao J.M.xu F.Liu G.L.xu InstituteofMaterialsPhysicsandMicrostructures DepartmentofMaterialsScienceandEngmeeringZhejiangUniversityHangzhou310027China CollegeofElectronicInformation HangzhouDianziUniversityHangzhou310018China

Two carboxylation processes were carried out to modify multi-walled carbon nanot ube bundles (m-MWNTs). The results showed that both of the m-MWNTs could be high ly dispersed in water with the concentration up to 25 and 15mg/mL in ethanol wit hout obvious deposition or conglomeration over 6 months. FTIR, Raman, TGA and TE M characterizations of the m- MWNTs showed that hydroxyl and carboxyl groups hav e been attached with MWNTs, and that the nanotube structure was only damaged a l ittle after modification treatments in mixed acids over 24h. Above prepared nano tube suspensions in water were successfully used as a filler of thermoplastic PV A composite to enhance its electrical conductivity. The results showed that the addition of m-MWNTs greatly improved the conductivity and the threshold of mass fraction was about 5wt%. The results also proved that purification process was n ot needed because of high purity of the raw MWNTs prepared in our group.

关键词： carbon nanotube polyvinylalcohol composite conductivity

Vehicle height control of electronic air suspension system based on mixed logical dynamical modelling

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Science China(Technological Sciences) 2015年第11期58卷 1894-1904页

作者： SUN XiaoQiang CHEN Long WANG ShaoHua xu Xing School of Automotive and Traffic Engineering Jiangsu University Automotive Engineering Research Institute Jiangsu University

Due to the coexistence and coupling of continuous variables and discrete events, the vehicle height adjustment process of electronic air suspension system can be regarded as a typical hybrid system. Therefore, the hybrid system theory was applied to design a novel vehicle height control strategy in this paper. A nonlinear mechanism model of the vehicle height adjustment system was established based on vehicle system dynamics and thermodynamic theory for variable-mass gas charge/discharge system. In order to model both the continuous/discrete dynamics of vehicle height adjustment process and the on-off statuses switching of solenoid valves, the framework of mixed logical dynamical(MLD) modelling was used. On the basis of the vehicle height adjustment control strategy, the MLD model of the adjustment process was built by introducing auxiliary logical variables and auxiliary continuous variables. Then, the co-simulation of the nonlinear mechanism model and the MLD model was conducted based on the compiling of HYSDEL. The simulation and experimental results show that the proposed control strategy can not only adjust the vehicle height effectively, but also achieve the on-off statuses direct control of solenoid valves.

关键词： electronic air suspension system vehicle height adjustment hybrid system mixed logical dynamical experiment

Multi-dimensional ambiguity function for subarray-based space-time coding radar

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Journal of Systems Engineering and Electronics 2019年第5期30卷 886-896页

作者： LAN Lan LIAO Guisheng xu Jingwei WANG Hanbing National Laboratory of Radar Signal Processing Xidian University

Space-time coding radar has been recently proposed and *** is a radar framework which can perform transmit beamforming at the ***,the range resolution decreases when the number of the transmit element increases.A subarray-based space-time coding(sub-STC)radar is explored to alleviate the range resolution *** the proposed radar configuration,an identical waveform is transmitted and it introduces a small time offset in different *** multidimensional ambiguity function of sub-STC radar is defined by considering resolutions in multiple domains including the range,Doppler,angle and probing *** on properties of the multi-dimensional ambiguity function of the sub-STC radar with regard to the spatial coverage,resolution performance and low sidelobes are also *** reveal that the range resolution and low sidelobes performance are improved with the proposed approach.

关键词： space-time coding radar multi-dimensional ambiguity function range resolution wide spatial coverage subarray sidelobe