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(K,Na)NbO_(3)-based lead-free ceramics with enhanced temperature-stable piezoelectricity and efficient red luminescence

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Journal of Advanced Ceramics 2023年第2期12卷 373-385页

作者： Qing LIU Er PAN Fucai LIU jing-feng LI School of Optoelectronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

There has been a surge of research interest in the promising lead-free potassium-sodium niobate(KNN)-based ceramics,applications of which could be significantly promoted by improving thermal stability of ***,endowing the KNN-based ceramics with photoluminescence property by rare-earth-ion doping can make them more completive lead-free counterparts in potential applications such as novel multifunctional sensing ***,a novel KNN-based ceramic material doped with Eu was elaborately designed to simultaneously obtain enhanced temperaturestable piezoelectricity and good luminescence *** the introduction of diffused phase transition and the modulation of unit cell distortion,a large piezoelectric strain coefficient(d^(*)_(33))with a small variation(590±59 pm/V)over a wide temperature range(from room temperature to 110℃)was *** optimal composition also exhibited a considerable piezoelectric coefficient(d_(33))with small fluctuation(330±33 pC/N)from 20 to 80℃.In addition to the enhanced temperature-stable piezoelectricity,the luminescence of these ceramics was slightly enhanced with the elevation of BaZrO_(3)(BZ)doping contents,which could be attributed to the increased compositional disorder and the decreased unit cell distortion of the matrix ***,an optical characteristic was more prominent at ultra-low *** work unprecedentedly provides a novel paradigm for the design of multifunctional KNN-based ceramics with enhanced temperature-stable piezoelectricity and good luminescence property,revealing the great potential of the rare-earth-element-doped KNN material for future applications in the novel multifunctional devices.

关键词： piezoelectric thermal stability rare-earth lead-free potassium-sodium niobate(KNN)

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High-intensity focused ultrasound with large scale spherical phased array for the ablation of deep tumors

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2009年第9期10卷 639-647页

作者： Xiang JI jing-feng BAI Guo-feng SHEN Ya-zhu CHEN Department of Biomedical Engineering Shanghai Jiao Tong University Shanghai 200240 China Biomedical Instrument Institute Med-X Research Institute Shanghai Jiao Tong University Shanghai 200030 China

Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound （HIFU） is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements （diameter=1.4 cm and frequency=l MHz） were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume （a 2 cm×2 cm×3 cm volume） at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.

关键词： High-intensity focused ultrasound (HIFU) Spherical phased array Large scale Deep tissue ablation

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Detecting Agro-Droughts in Southwest of China Using MODIS Satellite Data

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Journal of Integrative Agriculture 2013年第1期12卷 159-168页

作者： ZHANG feng ZHANG Li-wen WANG Xiu-zhen HUNG jing-feng Institute of Agricultural Remote Sensing & Information Application Zhejiang University Key Laboratory of Environmental Remediation and Ecological Health Ministry of Education/College of Natural Resources and Environmental Science Zhejiang University Institute of Remote Sensing and Earth Sciences Hangzhou Normal University The Provinical Key Laboratories of Agricultural Remote Sensing and Information System Zhejiang Province

The normalized difference vegetation index （NDVI） has proven to be typically employed to assess terrestrial vegetation conditions. However, one limitation of NDVI for drought monitoring is the apparent time lag between rainfall deficit and NDVI response. To better understand this relationship, time series NDVI （2000-2010） during the growing season in Sichuan Province and Chongqing City were analyzed. The vegetation condition index （VCI） was used to construct a new drought index, time-integrated vegetation condition index （TIVCI）, and was then compared with meteorological drought indices-standardized precipitation index （SPI）, a multiple-time scale meteorological-drought index based on precipitation, to examine the sensitivity on droughts. Our research findings indicate the followings：（1） farmland NDVI sensitivity to precipitation in study area has a time lag of 16-24 d, and it maximally responds to the temperature with a lag of about 16 d. （2） We applied the approach to Sichuan Province and Chongqing City for extreme drought monitoring in 2006 and 2003, and the results show that the monitoring results from TIVCI are closer to the published China agricultural statistical data than VCI. Compared to VCI, the best results from TIVCI3 were found with the relative errors of -4.5 and 6.36% in 2006 for drought affected area and drought disaster area respectively, and 5.11 and -5.95% in 2003. （3） Compared to VCI, TIVCI has better correlation with the SPI, which indicates the lag and cumulative effects of precipitation on vegetation. Our finding proved that TIVCI is an effective indicator of drought detection when the time lag effects between NDVI and climate factors are taken into consideration.

关键词： time-integrated vegetation condition index (TIVCI) time lag normalized difference vegetation index (NDVI) drought monitor standardized precipitation index (SPI)

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Enhancing hydrogen sorption in MgH_(2) by controlling particle size and contact of Ni catalysts

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Rare Metals 2021年第4期40卷 995-1002页

作者： Ting-Zhi Si Xue-Yang Zhang jing-jing feng Xiao-Li Ding Yong-Tao Li School of Materials Science and Engineering Anhui University of TechnologyMaanshan 243002China

A comparative study based on MgH2 ball-milled with altered Ni particle sizes under different conditions was conducted to reveal the effect of close contact between hydrides and metal catalysts on their hydrogen sorption *** is found that the Mg+nano-Ni(5 at%)composites not only exhibit a substantial decreased onset desorption temperature by approximately 180℃ but also dramatically enhance the absorption kinetics by sixteen times in comparison with those of pure MgH_(2).This remarkable kinetics enhancement can be explained by the superior catalytic effect of Ni present in composites that highly depends on its particle size and its close contact with MgH2.

关键词： Hydrogen storage Magnesium hydride Nickel Sorption properties Catalytic effect

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High-entropy perovskite RETa_(3)O_(9) ceramics for high-temperature environmental/thermal barrier coatings

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Journal of Advanced Ceramics 2022年第4期11卷 556-569页

作者： Lin CHEN Baihui LI Jun GUO Yuke ZHU jing feng Faculty of Material Science and Engineering Kunming University of Science and TechnologyKunming 650093China

Four high-entropy perovskite(HEP)RETa_(3)O_(9) samples were fabricated via a spark plasma sintering(SPS)method,and the corresponding thermophysical properties and underlying mechanisms were investigated for environmental/thermal barrier coating(E/TBC)*** prepared samples maintained low thermal conductivity(1.50 W·m^(−1)·K^(−1)),high hardness(10 GPa),and an appropriate Young’s modulus(180 GPa),while the fracture toughness increased to 2.5 MPa·m^(1/2).Nanoindentation results showed the HEP ceramics had excellent mechanical properties and good component *** analysed the influence of different parameters(the disorder parameters of the electronegativity,ionic radius,and atomic mass,as well as the tolerance factor)of A-site atoms on the thermal *** thermal expansion coefficients,combined with a high melting point and extraordinary phase stability,expanded the applications of the HEP RETa_(3)O_(9).The results of this study had motivated a follow-up study on tantalate high-entropy ceramics with desirable properties.

关键词： high-entropy ceramics(HECs) tantalates thermal conductivity nanoindentation fracture toughness

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Mechanical and thermal properties of RETaO4(RE=Yb,Lu,Sc)ceramics with monoclinic-prime phase

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Journal of Materials Science & Technology 2020年第17期52卷 20-28页

作者： Lin Chen Mingyu Hu Jun Guo Xiaoyu Chong jing feng Faculty of Material Science and Engineering Kunming University of Science and TechnologyKunming 650093People's Republic of China School of Engineering Brown UniversityProvidenceRl02912USA

As candidate thermal/environmental barrier coatings(T/EBCs),the structure characteristics and comprehensive properties of monoclinic-prime(m')RETaO4(RE=Yb,Lu,Sc)with excellent Al2O3/SiO2 chemical compatibility are *** thermal insulation protection will be provided by m'RETaO4 due to their low thermal conductivity(~1.6 Wm^-1 K^-1,900℃)and prominent thermal radiation resistance,which is much better than those of YSZ(~2.5 Wm^-1 K^-1,1000℃)and La-12 Zr2O7(~2.0 Wm^-1 K,900℃).The thermal expansion coefficients(TECs)are 3.0–8.0×10^-6 K^-1(200-1200℃),which is suitable for T/EBCs ***,absence of phase transition and extraordinary chemical compatibility with Al2O3/SiO2 up to 1500℃indicate the potential application *** documented governing mechanisms of m'RETaO4 properties will enable researchers to promote their application in the future investigation.

关键词： Ceramics Thermal/environmental barrier coatings Rare earth tantalates Mechanical property Thermal conductivity Chemical compatibility

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Interface structure of Ag(111)/SnO_(2)(200)composite material studied by density functional theory

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Science China(Technological Sciences) 2009年第5期52卷 1258-1263页

作者： feng jing CHEN jingChao XIAO Bing YU Jie Key Laboratory of Advanced Materials of Precious-Nonferrous Metals Ministry of Education of Chinaand Key Laboratory of Advanced Materials of Yunnan ProvinceKunming University of Science and TechnologyKunming 650093China School of Materials Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China

Electric contact material of Ag/SnO2 was successfully synthesized by in situ process *** in-terface structure was characterized by high-resolution transmission electron microscopy(HTEM) and simulated at atomic scale on *** mean-square displacements of atoms near the interface were calculated,and the results showed that near the interface both Ag side and SnO2 were mis-matched and this effect decays rapidly far from the *** inspecting the calculated density of states(DOS),we found that the electric-conductivity of this composite material was decreased because of the localized 4d and 2p electrons of Ag and O near the Fermi surface,*** density changed acutely across the interface,so that there was no extra compound precipitated.A mi-cro-electric field also formed in the whole material due to the interface structure,and this may affect the electron conduction and the related electric-conductivity of the *** is found that the interface cohesive energy of Ag(111)/SnO2(200) was-3.50 J/m2,which is higher than the experimental results.

关键词： electric contact material reactive synthesis interface energy structure relaxation electron structure Ab initio

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The Distribution and Uncertainty Quantification of Wind Profile in the Stochastic General Ekman Momentum Approximation Model

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Journal of Meteorological Research 2019年第2期33卷 336-348页

作者： Bing YAN Sixun HUANG jing feng Yu WANG College of Meteorology and Oceanography National University of Defense Technology Center for Computational Science and Finance Shanghai University of Finance and Economics

The general Ekman momentum approximation boundary-layer model(GEM) can be effectively used to describe the physical processes of the boundary layer. However, eddy viscosity, which is an approximated value, can lead to uncertainty in the solutions. In this paper, stochastic eddy viscosity is taken into consideration in the GEM, and generalized polynomial chaos is used to quantify the uncertainty. The goal of uncertainty quantification is to investigate the effects of uncertainty in the eddy viscosity on the model and to subsequently provide reliable distribution of simulation results. The performances of the stochastic eddy viscosity and generalized polynomial chaos method are validated based on three different types of eddy viscosities, and the results are compared based on the Monte Carlo method. The results indicate that the generalized polynomial chaos method can be accurately and efficiently used in uncertainty quantification for the GEM with stochastic eddy viscosity.

关键词： generalized polynomial chaos Monte Carlo method general Ekman momentum approximation model Ekman spiral

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Gauss Sum of Index 4:(1)Cyclic Case

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Acta Mathematica Sinica,English Series 2005年第6期21卷 1425-1434页

作者： Ke Qin feng jing YANG Shi Xin LUO Department of Mathematical Science Tsinghua University Beijing 100084 P. R. China

Let p be a prime, m ≥ 2, and （m,p（p - 1）） = 1. In this paper, we will calculate explicitly the Gauss sum G（X） = ∑x∈F＊qX（x）ζ^Tp^（x） in the case of [（Z/mZ）＊：（p）] = 4, and -1 （不属于）（p）, wher... 详细信息

Let p be a prime, m ≥ 2, and （m,p（p - 1）） = 1. In this paper, we will calculate explicitly the Gauss sum G（X） = ∑x∈F＊qX（x）ζ^Tp^（x） in the case of [（Z/mZ）＊：（p）] = 4, and -1 （不属于）（p）, where q P^f, f =φ（m）/4, X is a multiplicative character of Fq with order m, and T is the trace map for Fq/Fp. Under the assumptions [（Z/mZ）＊：（p）] = 4 and 1（不属于）（p）, the decomposition field of p in the cyclotomic field Q（ζm） is an imaginary quartic （abelian） field. And G（X） is an integer in K. We deal with the case where K is cyclic in this oaDer and leave the non-cvclic case to the next paper.

关键词： Gauss sum Stickelberger theorem Davenport-Hasse formula cyclic quartic number field

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A tasseled cap transformation for CBERS-02B CCD data

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第9期12卷 780-786页

作者： Li SHENG jing-feng HUANG Xiao-lu TANG Institute of Agricultural Remote Sensing and Information Application Zhejiang UniversityHangzhou 310029China Key Laboratory of Agricultural Remote Sensing and Information System of Zhejiang Province Hangzhou 310029China Yuhang Branch Bureau of Planning Hangzhou Urban Planning BureauHangzhou 311100China

The tasseled cap transformation of remote sensing data has been widely used in agriculture,forest,ecology,and *** this paper,tasseled cap transformation coefficients appropriate for data from a new sensor(China & Brazil Earth Resource Satellite(CBERS-02B)) are *** first three components after transformation captured 98% of the four-band variance,and represent the physical characteristics of brightness(coefficients:0.509,0.431,0.330,and 0.668),greenness(coefficients:0.494,0.318,0.324,and 0.741),and blueness(coefficients:0.581,0.070,0.811,and 0.003),*** hope these results will enhance the application of CBERS-02B charge-coupled device(CCD) data in the areas of agriculture,forest,ecology,and landscape.

关键词： Tasseled cap transformation CBERS-02B CCD Reflectance factor

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