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Open-loop Phase Synchronization Method of Positive and Negative Sequences for Three-phase Asymmetric Grid

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CSEE Journal of Power and Energy Systems 2023年第5期9卷 1973-1979页

作者： jian he Shanxu Duan State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Currently,a grid-connected inverter is required to inject a dual-sequence current during asymmetric grid sags,which means both positive and negative sequence phases should be *** paper proposes an open-loop phase synchronization(OLS)method of positive and negative sequences for an asymmetric grid based on the moving average filter(MAF),which does not need to separate the positive and negative sequence fundamental components of grid *** a benefit,there is no double-frequency oscillation in the estimated phases at offnominal frequencies since the positive and negative sequence phases are obtained *** proposed method not only has the inherent advantages of OLS,but also further improves the dynamic response since the window length of MAF is only 1/6 of the fundamental *** effectiveness of the proposed OLS is verified by experimental results.

关键词： Asymmetric grid open-loop synchronization positive and negative sequence phases

n-exact Categories Arising from n-exangulated Categories

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Acta Mathematica Sinica,English Series 2023年第9期39卷 1781-1794页

作者： jian he Pan Yue Zhou Department of Applied Mathematics Lanzhou University of TechnologyLanzhou730050P.R.China School of Mathematics and Statistics Changsha University of Science and TechnologyChangsha410114P.R.China

Let l be a Krull-Schmidt n-exangulated category and A be an n-extension closed subcategory of *** A inherits the n-exangulated structure from the given n-exangulated category in a natural *** construction gives n-exangulated categories which are neither n-exact categories in the sense of Jasso nor(n+2)-angulated categories in the sense of Geiss-Keller-Oppermann in ***,we also give a sufficient condition on when an n-exangulated category A is an n-exact *** results generalize work by Klapproth and Zhou.

关键词： (n+2)-angulated categories n-exact categories n-extension closed subcategories n-exangulated categories

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Impact of Si addition on high-temperature oxidation behavior of NiAlHf alloys

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Journal of Materials Science & Technology 2019年第9期35卷 2038-2047页

作者： JingJing jian he Hongbo Guo School of Materials Science and Engineering Beihang University (BUM)Beijing 100191China Frontier Research Institute of Innovative Science and Technology Beihang University (BUM)Beijing 100191China Key Laboratory of High-temperature Structural Materials & Coatings Technology (Ministry o f Industry and Information Technology) Beihang University (BUM)Beijing 100191China

Silicon (Si) and reactive elements (REs) like hafnium (Hf) have favorable effects on improving the high-temperature oxidation resistance. To reveal the interaction effect between them, Si with different contents was added into P-NiAlHf alloy in this study. Cyclic oxidation behavior at 1200℃ was investigated. Results show that Si can increase the Hf-rich precipitates and suppress Hf outward diffusion, thus inhibit the RE effect leading to worse oxidation resistance. However, NiAlHf-5Si alloy exhibited a lower oxidation rate and better spallation resistance mainly because of the existence of micro-cracks and Ni2 Al3 phases which provided more rapid diffusion paths for Al^3+.

关键词： Intermetallic NiAl Rare earth element Thermal cycling Oxidation Segregation

Gravitational Equivalence Theorem and Double-Copy for Kaluza-Klein Graviton Scattering Amplitudes

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Research 2022年第4期2022卷 411-420页

作者： Yan-Feng Hang Hong-jian he Tsung-Dao Lee Institute and School of Physics and Astronomy Key Laboratory for Particle Astrophysics and Cosmology(MOE)Shanghai Key Laboratory for Particle Physics and CosmologyShanghai Jiao Tong UniversityShanghaiChina Institute of Modern Physics and Department of Physics Tsinghua UniversityBeijingChina Center for High Energy Physics Peking UniversityBeijingChina

We analyze the structure of scattering amplitudes of the Kaluza-Klein (KK) gravitons and of the KK gravitational Goldstone bosons in the compactified 5d general relativity (GR). Using a general Rξ gauge fixing, we study the geometric Higgs mechanism for the massive spin-2 KK gravitons. We newly propose and prove a gravitational equivalence theorem (GRET) to connect the scattering amplitudes of longitudinal KK gravitons to that of the KK gravitational Goldstone bosons, which formulates the geometric gravitational Higgs mechanism at the scatteringS-matrix level. We demonstrate that the GRET provides a general energy cancellation mechanism guaranteeing the N-point longitudinal KK graviton scattering amplitudes to have their leading energy dependence cancelled down by a large power factor of E^(2N)(N≥4) up to any loop level. We propose an improved double-copy approach to construct the massive KK graviton (Goldstone) amplitudes from the KK gauge boson (Goldstone) amplitudes. With these, we establish a new correspondence between the two types of energy cancellations in the four-point longitudinal KK amplitudes at tree level: E^(4)→E0 in the KK gauge theory and E^(10)→E^(2) in the KK GR theory.

关键词： theory gauge guarantee

Wavelet Transform and Radon Transform on the Quaternion heisenberg Group

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Acta Mathematica Sinica,English Series 2014年第4期30卷 619-636页

作者： jian Xun he he Ping LIU School of Mathematics and Information Sciences Guangzhou University Key Laboratory of Mathematics and Interdisciplinary Sciences of Guangdong Higher Education Institutes Guangzhou University LMAM School of Mathematical SciencesPeking University

Let be the quaternion heisenberg group, and let P be the affine automorphism group of . We develop the theory of continuous wavelet transform on the quaternion heisenberg group via the unitary representations of P on L2（）. A class of radial wavelets is constructed. The inverse wavelet transform is simplified by using radial wavelets. Then we investigate the Radon transform on . . A Semyanistyi-Lizorkin space is introduced, on which the Radon transform is a bijection. We deal with the Radon transform on both by the Euclidean Fourier transform and the group Fourier transform. These two treatments are essentially equivalent. We also give an inversion formula by using wavelets, which does not require the smoothness of functions if the wavelet is smooth. In addition, we obtain an inversion formula of the Radon transform associated with the sub-Laplacian on .

关键词： Quaternion heisenberg group wavelet transform Radon transform inverse Radon transform

Study of primordial deuterium abundance in Big Bang nucleosynthesis

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Nuclear Science and Techniques 2024年第3期35卷 208-215页

作者： Zhi-Lin Shen jian-Jun he Key Laboratory of Beam Technology of Ministry of Education College of Nuclear Science and TechnologyBeijing Normal UniversityBeijing 100875China Institute of Radiation Technology Beijing Academy of Science and TechnologyBeijing 100875China

Big Bang nucleosynthesis(BBN)theory predicts the primordial abundances of the light elements^(2) H(referred to as deuterium,or D for short),^(3)he,^(4)he,and^(7) Li produced in the early *** these,deuterium,the first nuclide produced by BBN,is a key primordial material for subsequent *** date,the uncertainty in predicted deuterium abundance(D/H)remains larger than the observational *** this study,the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium *** found that the reaction rate uncertainties of the four reactions d(d,n)^(3)he,d(d,p)t,d(p,γ)^(3)he,and p(n,γ)d had the largest influence on the calculated D/H ***,the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p,γ)^(3) he *** the nuclear physics aspect,there is still room to largely reduce the reaction-rate uncertainties;hence,further measurements of the important reactions involved in BBN are still necessary.A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source Facility to precisely study the deuterium production reaction of p(n,γ)d.

关键词： Big Bang nucleosynthesis Abundance of deuterium Reaction cross section Reaction rate Monte Carlo method

Sintering behavior and thermal conductivity of Y_(2)O_(3) fully stabilized HfO_(2) ceramics

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Rare Metals 2021年第5期40卷 1255-1266页

作者： Chun Li jian he Yue Ma School of Materials Science and Engineering Beihang UniversityBeijing 100191China School of Energy and Power Engineering Beihang UniversityBeijing 100191China Key Laboratory of High-Temperature Structural Materials and Coatings Technology(Ministry of Industry and Information Technology) Beihang UniversityBeijing 100191China

A series of Y_(2)O_(3) fully stabilized HfO2 ceramics(Hf_(1-x)Y_(x)O_(2-0.5x),x=0.20,0.24,0.28,0.32,0.36 and 0.40)were synthesized by solid-state reaction at 1500℃.The phase composition,thermal conductivity and sintering behavior at 1400℃ of the ceramic bulks were *** Hf_(1-x)Y_(x)O_(2-0.5x) ceramics were comprised of pure cubic phase with disordered fluorite *** phase transformation occurred in the ceramics with Y3+doping concentration ranging from 0.24 to *** Hf_(0.64)Y_(0.36)O_(1.82) and Hf_(0.6)Y_(0.4)O_(1.8) samples revealed the lowest grain growth rate when sintered at 1400℃,indicating good resistance to ***,the Vicker’s hardness and Young’s modulus after annealed for 96 h at 1400℃ for the Hf_(0.64)Y_(0.36)O_(1.82) sample were 8.97 and 200 GPa,respectively,much lower than those of the Hf_(0.6)Y_(0.4)O_(1.8)(14.51 and 237 GPa,respectively).The thermal conductivity of Hf_(1-x)Y_(x)O_(2-0.5x) first decreased and then increased slowly as the Y3+content increased,and the associated mechanism was discussed.

关键词： Yttria fully stabilized hafnia Sintering Mechanical properties Thermal conductivity

A Portable Fall Detection and Alerting System Based on k-NN Algorithm and Remote Medicine

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China Communications 2015年第4期12卷 23-31页

作者： he jian HU Chen School of Software Engineering Beijing University of Technology

This paper presents information on a portable fall detection and alerting system mainly consisting of a custom vest and a mobile smart phone. A wearable motion detection sensor integrated with tri-axial accelerometer, gyroscope and Bluetooth is built into a custom vest worn by elderly. The vest can capture the reluctant acceleration and angular velocity about the activities of daily living(ADLs) of elderly in real time. The data via Bluetooth is then sent to a mobile smart phone running a fall detection program based on k-NN algorithm. When a fall occurs the phone can alert a family member or health care center through a call or emergent text message using a built in Global Positioning System. The experimental results show that the system discriminates falls from ADLs with a sensitivity of 95%, and a specificity of 96.67%. This system can provide remote monitoring and timely help for the elderly.

关键词： telemedicine fall detection k-NN smart phone bluetooth

Poly(ethylene carbonate)-based electrolytes with high concentration Li salt for all-solid-state lithium batteries

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Rare Metals 2018年第6期37卷 488-496页

作者： Zi-jian he Li-Zhen Fan Beijing Advanced Innovation Center for Materials Genome Engineering Institute of Advanced Materials and Technology University of Science and Technology Beijing

High-performance solid polymer electrolyte （SPE） has long been desired for the next-generation high energy density and safe rechargeable lithium batteries. A SPE composed of 80 wt% lithium bis（trifluo-romethanesulfonyl）imide （LiTFSI）, 20% poly（ethylene carbonate）（PEC） and a polyamide （PA） fiber membrane backbone was prepared by solution-casting method. This solid electrolyte exhibits quite high ionic conductivity and lithium ion transference number （t＋）, and excellent mechanical strength. The as-prepared solid electrolyte shows good wettability to porous electrodes during cycles, which is beneficial to form ionically conductive phase throughout porous electrodes. All-solid-state LiFePO4lLi cells assembled with the as-prepared solid electrolyte deliver a high initial discharge specific capacity of 125.7 mAh·g^-1 and good cycling stability at 55 ℃ （93.4% retention at 1C after 200 cycles）, and superior cycle performance. Outstanding electrochemical performance can be mainly ascribed to the improved ionic conductivity in the entire porous electrodes due to the good wettability of SPE.

关键词： Solid polymer electrolyte All-solid-state lithium batteries Poly(ethylene carbonate) Wettability Porous electrodes