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12-bit 2.6 GS/s RF DAC based on return-to-zero technology

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The Journal of China Universities of Posts and Telecommunications 2019年第4期26卷 36-42页

作者： Li Xiaopeng Wang Zhigong zhang Yi zhang Youtao zhang mi Institute of RF and OE ICs Southeast UniversityNanjing 210096China Nanjing Guobo Electronics Company Limited Nanjing 210016China Nanjing Electronic Devices Institute Nanjing 210016China National and Local Joint Engineering Laboratory of RF Integration and micro-assembly Technology Nanjing 210046China College of microelectronics Nanjing University of Posts and TelecommunicationsNanjing 210046China State Key Laboratory of millimeter Waves Southeast UniversityNanjing 210096China Science and Technology on Monolithic Intergrated Circuits and Modules Laboratory Nanjing 210016China

A 12-bit 2.6 GS/s radio frequency digital to analog converter(RF DAC)based on 1 um GaAs heterojunction bipolar transistor(HBT)process is *** DAC integrates a 4:1 multiplexer to reduce the data rate of input ports,which greatly facilitates the *** core adopts 4+8 segmented current steering structure.R-2R ladder network is used for 8 least significant bit(LSB)to realize binary current weighting and thermometer coding is used for 4 most significant bit(MSB).Return-to-zero(RZ)technology is used to expand the effective bandwidth of DAC output to the third Nyquist *** proposed DAC has a better output power flatness and spurious-free dynamic range(SFDR).Compared to traditional DAC,measured results demonstrate that the output power of this RZ DAC is increased by 33 dB and the SFDR is enhanced by 27 dB near the second Nyquist band.

关键词： DAC RZ Nyquist band

Effect of Friction Stir Welding on Bulk Metallic Glasses

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Journal of Wuhan University of Technology(Materials Science) 2021年第5期36卷 624-628页

作者： zhang Xiangyun zhang mi CHEN Wenbin YUAN Zizhou State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China Wenzhou Engineering Institute of Pump&Valve Lanzhou University of TechnologyWenzhou 325105China

In order to enlarge the size of bulk metallic glasses(BMGs),two Cu_(36)Zr_(48)Al_(8)Ag_(8) BMGs plates were successfully welded by friction stir welding(FSW)without obvious *** effect of friction stir welding on microstructure and mechanical properties of the BMGs was investigated.X-ray diffraction(XRD)and scanning electron microscope(SEM)were used to evaluate the changes of the crystalline particles in the *** was applied to analyze the changes of the amorphous ***-hardness of the stir zone before and after FSW was tested to explore changes of the mechanical *** show that the original Al3Zr particles in the BMGs were refined and some cavities parallel to the rotating direction of the pin were observed in the amorphous matrix after ***,micro-hardness of the stirred zone rises approximately 50 Hv compared with the as-cast sample due to structure relaxation of the amorphous matrix.

关键词： bulk metallic glasses friction stir welding micro-hardness nanoindentation

Spray-coated electret materials with enhanced stability in a harsh environment for an MEMS energy harvesting device

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microsystems & Nanoengineering 2021年第1期7卷 151-159页

作者： Anxin Luo Yixin Xu Yulong zhang mi zhang Xiaoqing zhang Yan Lu Fei Wang School of microelectronics Southern University of Science and Technology518055 ShenzhenChina State Key Laboratory of AMS-VLSI Institute of MicroelectronicsUniversity of Macao(UM)999078 MacaoChina Department of Electrical and Computer Engineering FSTUM999078 MacaoChina Engineering Research Center of Integrated Circuits for Next-Generation Communications Ministry of EducationSouthern University of Science and Technology518055 ShenzhenChina Department of Mechanical Engineering Boston UniversityBostonMAUSA College of New Materials and New Energies Shenzhen Technology University518118 ShenzhenChina Shanghai Key Laboratory of Special Artificial School of Physics Science and Engineering Tongji University200092 ShanghaiChina

The charge stability of electret materials can directly affect the performance of electret-based devices such as electrostatic energy *** this paper,a spray-coating method is developed to deposit an electret layer with enhanced charge *** long-term stability of a spray-coated electret is investigated for 500 days and shows more stable performance than a spin-coated layer.A second-order linear model that includes both the surface charge and space charge is proposed to analyze the charge decay process of electrets in harsh environments at a high temperature(120°C)and high humidity(99%RH);this model provides better accuracy than the traditional deep-trap *** further verify the stability of the spray-coated electret,an electrostatic energy harvester is designed and fabricated with MEMS(micro-electromechanical systems)*** electret material can work as both the bonding interface and electret layer during fabrication.A maximum output power of 11.72μW is harvested from a vibrating source at an acceleration of 28.5 m/*** the energy harvester with the spray-coated electret is exposed to a harsh environment(100°C and 98%RH),an adequate amount of power can still be harvested even after 34 h and 48 h,respectively.

关键词： stability. stability electrostatic

Fabrication of Al-Coated Mg-Li Alloy Sheet and Investigation of Its Properties

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Acta Metallurgica Sinica(English Letters) 2019年第2期32卷 169-177页

作者： Tian-Long zhang Toko Tokunaga Munekazu Ohno mi-Lin zhang Kiyotaka Matsuura Graduate School of Engineering Hokkaido University Faculty of Engineering Hokkaido University College of Materials Science and Chemical Engineering Harbin Engineering University

An Al-coated Mg-8 mass% Li alloy rectangular bar was fabricated by hot extrusion, and then, it was hot-rolled into a thin sheet. The Al coating was uniform in thickness and had good bonding with the substrate during all the processing. This Alcoated Mg–Li alloy exhibited a good corrosion resistance in a 0.5 mass% HCl aqueous solution. No intermetallic compound was observed at the Al/Mg–Li interface after the extrusion and the rolling. The Al-coated Mg–Li alloy sheet exhibited an elongation to fracture of 35% at room temperature at a strain rate of 0.001 s(-1)without any debonding between the coating and the substrate. When tensile tested at 573 K at 0.001 s(-1)in the air, the Al coating remained undamaged even until an elongation of about 150%. Further elongation generated cracks on the coating and the specimen fractured at an elongation of about 200%. In an Ar atmosphere, the specimen exhibited a fracture elongation of over 400% under the same conditions at 573 K at 0.001 s(-1), although a large number of cracks generated on the Al coating.

关键词： Mg–Li alloy Composite material Coating Mechanical properties Superplasticity

Impacts of Roof/Ground mitigation Strategies on Improving the Urban Thermal Environment and Human Comfort over the Yangtze River Delta, China

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Journal of Meteorological Research 2024年第1期38卷 108-125页

作者： Hongyun MA mi zhang Haishan CHEN Yan WANG Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)/Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)Nanjing University of Information Science&TechnologyNanjing 210044 School of Atmospheric Sciences Nanjing UniversityNanjing 210023 Experimental Teaching Center for Meteorology and Environment Nanjing University of Information Science&TechnologyNanjing 210044

The combined effects of global warming and the urban heat islands exacerbate the risk of urban heat stress. It is crucial to implement effective cooling measures in urban areas to improve the comfort of the thermal environment. In this study, the Weather Research and Forecasting Model(WRF), coupled with a single-layer Urban Canopy Model(UCM), was used to study the impact of heat mitigation strategies. In addition, a 5-km resolution land-cover dataset for China(ChinaLC), which is based on satellite remote sensing data, was adjusted and used, and 18 groups of numerical experiments were designed, to increase the albedo and vegetation fraction of roof/ground parameters. The experiments were conducted for four heatwave events that occurred in the summer of 2013 in the Yangtze River Delta urban agglomeration of China. The simulated results demonstrated that, for the single roof/ground schemes, the mitigation effects were directly proportional to the albedo and greening. Among all the experimental schemes, the superposed schemes presented better cooling effects. For the ground greening scheme, with similar net radiation flux and latent heat flux, its storage heat was lower than that of the roof greening scheme, resulting in more energy flux into the atmosphere, and its daytime cooling effect was not as good as that of the roof greening scheme. In terms of human thermal comfort(HTC), the improvement achieved by the ground greening scheme was better than any other single roof/ground schemes, because the increase in the relative humidity was small. The comprehensive evaluation of the mitigation effects of different schemes on the thermal environment presented in this paper provides a theoretical basis for improving the urban environment through rational urban planning and construction.

关键词： urban heat island human thermal comfort urban canopy mitigation strategies Yangtze River Delta Weather Research and Forecasting Model(WRF) Urban Canopy Model(UCM)

Projection of residential and commercial electricity consumption under SSPs in Jiangsu province, China

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Advances in Climate Change Research 2020年第2期11卷 131-140页

作者： zhang mi CHENG Chin-Hsien MA Hong-Yun Key Laboratory of Meteorological Disaster Ministry of Education(KLME)Nanjing University of Information Science and TechnologyNanjing210044China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD) Nanjing University of Information Science and TechnologyNanjing210044China Institute for Climate and Application Research(ICAR) Nanjing University of Information Science and TechnologyNanjing210044China

Future electricity consumption may increase due to climate change,but the amplitude depends on the interaction between many uncertain *** on the linear model and policy model,the residential and commercial electricity consumption in Jiangsu province are projected under the shared socioeconomic pathways(SSPs).The linear model considers climate and socioeconomic factors,and the policy model also takes policy factors into *** find that the cooling degree days(CDD)coefficient is about 3 times of heating degree days(HDD),which reflects that the cooling demand is much larger than heating,and also shows in the *** results of the policy model are generally lower than the linear model,which is the impact of policy *** example,the SSP1 and SSP2 of the policy model are 320 TW h and 241.6 TW h lower than the linear model in 2100,*** the end of the 21st century,the residential and commercial electricity consumption in Jiangsu province will reach 107.7–937.9 TW h per year,1.3–11.6 times of *** SSP1 scenario under the policy model is based on feasible assumptions,and can be used as the target scenario for policymakers to establish energy intensity reduction targets.

关键词： Electricity consumption Residential and commercial Climate change Projection SSP

LuoJiaAI:A cloud-based artificial intelligence platform for remote sensing image interpretation

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Geo-Spatial Information Science 2023年第2期26卷 218-241页

作者： Zhan zhang mi zhang Jianya Gong Xiangyun Hu Hanjiang Xiong Huan Zhou Zhipeng Cao State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhanChina School of Remote Sensing and Information Engineering Wuhan UniversityWuhanChina Department of Land-Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHong KongChina

The rapid processing,analysis,and mining of remote-sensing big data based on intelligent interpretation technology using remote-sensing cloud computing platforms(RS-CCPs)have recently become a new *** existing RS-CCPs mainly focus on developing and optimizing high-performance data storage and intelligent computing for common visual representation,which ignores remote sensing data characteristics such as large image size,large-scale change,multiple data channels,and geographic knowledge embedding,thus impairing computational efficiency and *** construct a LuoJiaAI platform composed of a standard large-scale sample database(LuoJiaSET)and a dedicated deep learning framework(LuoJiaNET)to achieve state-of-the-art performance on five typical remote sensing interpretation tasks,including scene classification,object detection,land-use classification,change detection,and multi-view 3D *** details of the LuoJiaAI application experiment can be found at the white paper for LuoJiaAI industrial *** addition,LuoJiaAI is an open-source RS-CCP that supports the latest Open Geospatial Consortium(OGC)standards for better developing and sharing Earth Artificial Intelligence(AI)algorithms and products on benchmark *** narrows the gap between the sample database and deep learning frameworks through a user-friendly data-framework collaboration mechanism,showing great potential in high-precision remote sensing mapping applications.

关键词： Artificial intelligence cloud computing platform remote-sensing intelligent interpretation sample database deep learning framework

Progress in preparation of rare earth metals and alloys by electrodeposition in molten salts

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Rare Metals 2016年第11期35卷 811-825页

作者： Wei Han Mei Li mi-Lin zhang Yong-De Yan Key Laboratory of Superlight Materials and Surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering University

Rare earth（RE） metals and their alloys have attracted considerable practical interests due to their functional properties. Because of their negative deposition potentials, RE metals cannot be electrochemically deposited from aqueous media. Using molten salt as medium provides a unique opportunity for the electrowinning and electrorefining of high-purity RE metals, as well as for the electrochemical formation of their alloys and intermetallic compounds. Certainly, the electrochemical behaviors of RE metals and their alloys have been investigated in a number of different molten salts comprising all-fiuorides,all-chlorides and mixed chloride-fiuoride media. Based on the results, RE and their alloys were produced by molten salt electrolysis. In this paper, the developments of preparation of RE metals and their alloys by electrolysis in molten salts in recent years were systematically summarized on both the local and international levels. Attention was paid mainly to the electrodeposition of RE metals and their alloys, including RE-Mg, RE-Al, RE-Ni, RE-Co,RE-Cu, RE-Fe and RE-Zn alloys.

关键词： Electrochemical formation Molten salts Electrolysis Rare earth Alloys

Preparation and characterization of LiAl_xMn_(2-x)O_4 for a supercapacitor in aqueous electrolyte

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International Journal of minerals,Metallurgy and Materials 2009年第1期16卷 112-118页

作者： Yun Xue Ye Chen mi-lin zhang Yong-de Yan College of Materials Science and Chemical Engineering Harbin Engineering University Harbin 150001 China

LiAlxMn2-xO4 （0≤x≤0.5） was synthesized by high temperature solid-state reaction. The structure and morphology of LiAlxMn2-xO4 were investigated by X-ray diffraction and scanning electron microscopy （SEM）. The results indicate that all samples show spinel phase. The polyhedral particles turn to club-shaped, then change to small spherical, and finally become agglomerates with increasing Al content. The supercapacitive performances of LiAlxMn2-xO4 were studied by means of galvanostatic charge-discharge, cyclic voltammetry, and alternating current （AC） impedance in 2 mol·L^-1 （NH4）2SO4 aqueous solution. The results show that LiAlxMn2-xO4 represents rectangular shape performance in the potential range of 0-1 V. The capacity and cycle performance can be improved by doping Al. The composition of x=0.1 has the maximum special capacitance of 160 F·g^-1, which is 1.37 times that of LiMn2O4 electrode. The capacitance loss of LiAlxMn2-xO4 with x=0.1 is only about 14% after 100 cycles.

关键词： supercapacitor electrode materials aqueous electrolyte spinel