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A new resource-rich carbonate luminescent host KNa_(5)Ca_(5)(CO_(3))_(8):A case study activated by Eu^(3+) for red-phosphor purpose

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Journal of Rare Earths 2021年第8期39卷 913-920页

作者： Yunjian Wang Song Chen Lei geng College of Chemistry and Materials Science Huaibei Normal UniversityHuaibei 235000China College of Physics and Engineering Qufu Normal UniversityQufu 273100China

Exploring and designing new luminescent host with rich resource is beneficial to reducing the cost and the large-scale application of luminescent ***,a series of novel Eu^(3+)-activated KNa5-Ca5(CO3)8 red-emitting phosphors with different Eu^(3+) concentrations were successfully synthesized under mild hydrothermal *** and SEM characterizations show that all as-prepared KNa_(5)Ca_(5)(CO_(3))_(8):Eu^(3+) samples crystallize in a hexagonal structure,P63 mc(No.186) space group,and show monodispersed hexagonal sheet mo rphologies,within a side length interval about of 2-3μm and a thickness of about 0.6 μm,Eu^(3+) doping within 6 mol% concentration has little influence on the crystal structure of the host,as indicated by XRD,and FT-IR results,but thermal stability changes as shown by the ***_(5)Ca_(5)(CO_(3))_(8) phosphors with different Eu^(3+) concentrations can emit red-light under effectively excitation by near-UV *** chromaticity coo rdinates of all KNa_(5)Ca_(5)(CO_(3))_(8):Eu^(3+) phosphors were calculated to locate in red region,and CCT of each sample is the range from 2815 to 3650 K,very close to the tungsten lamp ***,concentration quenching phenomenon appearing at 5 mol% is found to be the result of electric multipolar interaction of Eu^(3+)activators,and the decay lifetime is about1.63 ms,which almost unchanges with Eu^(3+) doping ***,thermal quenching analysis reveals good thermal stability with thermal activation energy of about 0.216 *** results reported here demonstrate that KNa_(5)Ca_(5)(CO_(3))_(8) is a promising fluorescent host for LEDs applications.

关键词： Carbonates KNa_(5)Ca_(5)(CO_(3))_(8) Hydrothermal synthesis Eu^(3+)doping Photoluminescence Rare earths

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NOx Emission Reduction Technology for Marine Engine Based on Tier-Ⅲ:A Review

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Journal of Thermal Science 2020年第5期29卷 1242-1268页

作者： LU Xiuwei geng Peng CHEN Yunyue Merchant Marine College Shanghai Maritime UniversityShanghai 201306China Tianjin Research Institute of Water Transport Engineering Tianjin 300456China

The development of maritime trade has greatly promoted the development of diesel ***,with the increasingly serious environmental problems,more and more attention has been paid to the exhaust emissions of high-power marine diesel *** restrictions on SOx have been implemented globally,and the limitation of the NO,will be the next *** paper illustrates(a)Principle and research progress of NOx emissions-reduction technology of marine diesel engine;(b)Summary of advantages and disadvantages among various reduction technologies and their reduction effects;(c)The application effect of mainstream technology on ***,since exhaust gas recirculation(EGR)can achieve Tier-Ⅲ directly from Tier-Ⅰ without considering the increased fuel *** is deemed as the most promising technology to reduce emissions by controlling combustion ***,EGR has shortcomings of excessive increase in ftiel consumption and generation of waste water,which need to be solved ***,selective catalytic reduction(SCR)is the most effective and straightforward means to achieve Tier-Ⅲ.Despite of the continuous optimization of SCR unit volume,the problem of scrap catalyst seriously limits its wide *** to match the supercharger more efficiently is a key factor in choosing between high and low pressure ***,nature gas(NG)engines are capable of achieving a reduction in NOx,but in order to meet the requirements of Tier-Ⅲ,it still needs to be assisted by other *** emissions of hydrocarbon(HC)and CO in NG engines are huge defects that must be ***,technologies such as the Miller cycle,Two-stage supercharging and mixed-water combustion can also reduce emissions but were rarely used *** technologies can be combined with EGR,SCR and NG engines to optimize the enginesJ economy and emission characteristics.

关键词： marine engine NOx emission Tier-Ill exhaust gas recirculation(EGR) selective catalytic reduction(SCR) dual-fuel

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An APD-Based Evaluation on the Effect of Transient Disturbance over Digital Transmission

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Chinese Journal of Electronics 2020年第1期29卷 57-65页

作者： geng Xin WEN Yinghong ZHANG Jinbao Institute of Electromagnetic Compatibility Beijing Jiaotong University Beijing Engineering Research Center of EMC and GNSS Technology for Rail Transportation

In railway electromagnetic environment,transient disturbances usually degenerate the function of railway wireless communication systems, thus may cause severe security issues. To protect communication services,measurement methodology to characterize disturbances keeps evolving. Nowadays, the statistical characteristics of disturbances, such as Amplitude probability distribution(APD), have been proven more efficient to assess the degradation of digital transmission than Quasipeak detection in most Electromagnetic Compatibility standards. To demonstrate the impact of disturbances on error performance more precisely, a more refined method to estimate Bit error probability(BEP) of digital modulation is necessary. The APD value is ideally obtained with the equivalent bandwidth of the radio service under threat, which means specific apparatus of certain radio service is consequently indispensable. This paper proposes a novel method to estimate the maximum BEP of multilevel amplitude modulations based on APD acquired by standard apparatus. The calculated BEP also provides reference for APD emission restriction.

关键词： APD BEP Digital transmission Transient disturbance

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Practical age estimation using deep label distribution learning

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Frontiers of Computer Science 2021年第3期15卷 75-80页

作者： Huiying ZHANG Yu ZHANG Xin geng Pujiang Institute Nanjing Tech UniversityNanjing 211200China School of Computer Science and Engineering Southeast UniversityNanjing 211189China

Age estimation plays an important role in human-computer interaction *** lack of large number of facial images with definite age label makes age estimation al-gorithms *** label distribution learning(DLDL)which employs convolutional neural networks(CNN)and label distribution learning to learn ambiguity from ground-truth age and adjacent ages,has been proven to outperform current state-of-the-art ***,DLDL assumes a rough label distribution which covers all ages for any given age *** this paper,a more practical label distribution paradigm is proposed:we limit age label distribution that only covers a reasonable number of neighboring *** addition,we explore different label distributions to improve the performance of the proposed learning *** employ CNN and the improved label distribution learning to estimate *** results show that compared to the DLDL,our method is more effective for facial age recognition.

关键词： deep learning convolutional neural networks label distribution learning facial age estimation

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Experimental investigation on the yield behavior of metal foam under shear-compression combined loading

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Science China(Technological Sciences) 2021年第7期64卷 1412-1422页

作者： LUO geng XUE Pu LI YuLong School of Automobile Chang’an UniversityXi’an710064China School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China Joint International Research Laboratory of Impact Dynamics and its Engineering Applications Northwestern Polytechnical UniversityXi’an710072China

Metal foams are typically subjected to quasi-static or dynamic shear-compression combined loading in applications such as energy absorbers and structure protectors. The yield behavior of a metal foam under dynamic and quasi-static shear-compression combined loadings is investigated in this study. First, quasi-static and dynamic compression-shear combined tests at different loading angles are conducted using a universal testing machine and a rotatable Hopkinson bar system, respectively. Shear deformation reduces the plateau stress as the loading angle increases. Subsequently, the yield modes of the metal foam under combined loadings are investigated. Only one yield band occurs under a combined loading with large loading angles(mode I),whereas several yield bands occur under a combined loading with small loading angles(mode II). Finally, the yield surface plot of metal foam indicates significant enhancement in terms of normal stress and shear stress under dynamic loading. Quasi-static and dynamic phenomenological yield criteria for a shear-normal stress space are established to provide a brief and precise prediction of the behavior of metal foam under quasi-static and dynamic combined loadings.

关键词： metal foam yield behavior shear-compression combined loading yield mode yield criterion

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Research on Piezoelectric Driving Microminiature Three-Legged Crawling Robot

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Journal of Bionic Engineering 2023年第4期20卷 1481-1492页

作者： Zhongyuan Zheng Yanru Zhao geng Wang School of Mechanical and Power Engineering Henan Polytechnic UniversityJiaozuo454000China Key Laboratory of Testing Technology for Manufacturing Process of Ministry of Education Southwest University of Science and TechnologyMianyang621010China

Micro-robots have the characteristics of small size,light weight and flexible *** design a micro three-legged crawling robot with multiple motion directions,a novel driving scheme based on the inverse piezoelectric effect of piezoelectric ceramics was *** three legs of the robot were equipped with piezoelectric bimorphs as drivers,*** motion principles were analyzed and the overall force analysis was carried out with the theoretical mechanics *** natural frequency,mode shape and amplitude were analyzed with simulation software COMSOL Multiphysics,the optimal size was determined through parametric analysis,and then the micro three-legged crawling robot was *** effects of different driving voltages,different driving frequencies,different motion bases and different loads on the motion speed of the robot were *** is shown that the maximum speed of single-leg driving was 35.41 cm/s,the switching ability between different motion directions was measured,and the movements in six different directions were *** is demonstrated the feasibility of multi-directional motion of the *** research may provide a reference for the design and development of miniature piezoelectric three-legged crawling robots.

关键词： Three-legged crawling robot Piezoelectric drive Mechanical property analysis Kinematic features analysis

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Modeling framework of voltage-source converters based on equivalence with synchronous generator

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Journal of Modern Power Systems and Clean Energy 2018年第6期6卷 1291-1305页

作者： Shulong TAN Hua geng geng YANG Huai WANG Frede BLAABJERG Department of Automation Tsinghua University Department of Energy Technology Aalborg University

Along with the increasing penetration of distributed generation with voltage-source converters(VSCs),there are extensive concerns over the potential virtual rotor angle stability, which is characterized by oscillations of power and frequency during the dynamic process of synchronization in the grid. Several control strategies have been developed for VSCs to emulate rotating inertia as well as damping of oscillations. This paper classifies these strategies and provides a small-signal modeling framework including all kinds of VSCs in different applications for virtual rotor angle stability. A unified perspective based on the famous Phillips–Heffron model is established for various VSCs. Thus, the concepts of equivalent inertia and the synchronizing and damping coefficients in different VSCs are highlighted, based on the similarities with the synchronous generator(SG) system in both physical mechanisms and mathematical models. It revealed the potentiality of various VSCs to achieve equivalence with the SG. This study helps promote the unity of VSCs and traditional SGs in both theories and methods for analyzing the dynamic behavior and enhancing the stability. Finally,future research needs and new perspectives are addressed.

关键词： Voltage-source converter(VSC) Synchronous generator Virtual rotor angle stability Inertia Synchronizing Damping

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Defect agglomeration in ferroelectric ceramics under cyclic electric field

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Science China(Technological Sciences) 2008年第8期51卷 1296-1305页

作者： geng LiMing YANG Wei Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

The agglomeration of point defects in ferroelectric ceramics could be driven by repeated domain switching under cyclic electric field. The evolution equation of pore concentration under cyclic electric field is derived, with the help of a relation between the pore concentration and the extent of pore agglomeration. The results of the simulation agree quantitatively with the experimental data. An integrated framework about the mechanisms of electrically induced fatigue is proposed, which links the mechanisms at different scales.

关键词： point defect domain switch ferroelectric ceramics structural evolution

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Singularity radius gradient-based rapid singularity-escape steering law for SGCMGs

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Chinese Journal of Aeronautics 2020年第10期33卷 2728-2742页

作者： Tao YI Yunhai geng Baolin WU Research Center of Satellite Technology Harbin Institute of TechnologyHarbin 150080China

In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is *** a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary,and quickly escape elliptic ***,simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.

关键词： Gaussian curvature Rapid singularity escape Single gimbal control moment gyroscope Singularity-escape steering law Singularity parameter Singularity type

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CRACK GROWTH BEHAVIOR AND FRACTURE FEATURE OF GH2132 UNDER CREEP-FATIGUE CONDITIONS

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Acta Metallurgica Sinica(English Letters) 1997年第6期10卷 495-500页

作者： geng, M.F. Luoyang Ship Material Research Inst Luoyang China

The superalloy GH2132 is equivalent to A286. The tests were carried out at 550°C under various cyclic frequencies (hold time) and load levels, and the fracture surfaces were examined by using a scanning electron microscope. It was shown that the fracture mode of creep-fatigue and the effect of cyclic loading on crack growth change with the growth of crack and the increase of net-section stress, and both are reversed when the net-section stress is up to the yield stress of material. When σn0.2, cracking is predominantly cyclic-dependent transgranular and cyclic loading accelerates creep crack growth, whereas when σn>σ0.2, the case is reversed.

关键词： Chromium alloys Crack propagation Creep Fracture Nickel alloys Rotating disks Superalloys

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