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Acta Mathematica Sinica,English Series 2024年第9期40卷 2091-2152页

作者： Qi An GUAN zhi Tong MI Zheng yuan School of Mathematical Sciences Peking UniversityBeijing 100871P.R.China School of Mathematics and Statistics Beijing Jiaotong UniversityBeijing 100044P.R.China Institute of Mathematics Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190P.R.China

In this article,we consider a modified version of minimal L^(2) integrals on sublevel sets of plurisubharmonic functions related to modules at boundary points,and obtain a concavity property of the modified *** applications,we give characterizations for the concavity degenerating to linearity on open Riemann surfaces and on fibrations over open Riemann surfaces.

关键词： Minimal L^(2)integrals plurisubharmonic functions boundary points weakly pseudoconvex Kähler manifold

Topological photonic states in gyromagnetic photonic crystals:Physics,properties,and applications

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Chinese Physics B 2022年第11期31卷 1-11页

作者： Jianfeng Chen zhi-yuan Li School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510640China

Topological photonic states(TPSs)as a new type of waveguide state with one-way transport property can resist backscattering and are impervious to defects,disorders and metallic *** photonic crystal(GPC)is the first artificial microstructure to implement TPSs,and it is also one of the most important platforms for generating truly one-way TPSs and exploring their novel physical properties,transport phenomena,and advanced ***,we present a brief review of the fundamental physics,novel properties,and practical applications of TPSs based on *** first examine chiral one-way edge states existing in uniformly magnetized GPCs of ordered and disordered lattices,antichiral one-way edge states in cross magnetized GPCs,and robust one-way bulk states in heterogeneously magnetized ***,we discuss the strongly coupling effect between two co-propagating(or counter-propagating)TPSs and the resulting physical phenomena and device ***,we analyze the key issues and prospect the future development trends for TPSs in *** purpose of this brief review is to provide an overview of the main features of TPSs in GPC systems and offer a useful guidance and motivation for interested scientists and engineers working in related scientific and technological areas.

关键词： topological photonic states gyromagnetic photonic crystal one-way edge states

Experimental investigation of surface roughness effects on flow behavior and heat transfer characteristics for circular microchannels

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Chinese Journal of Aeronautics 2016年第6期29卷 1575-1581页

作者： yuan Xing Tao zhi Li Haiwang Tian Yitu National Key Laboratory of Science and Technology on Aero-Engine Beihang University Collaborative Innovation Center for Advanced Aero-Engine of China of Aerodynamics Beihang University

This paper experimentally investigates the effect of surface roughness on flow and heat transfer characteristics in circular microchannels. All test pieces include 44 identical, parallel circular microchannels with diameters of 0.4 mm and 10 mm in length. The surface roughness of the microchannels is R= 0.86, 0.92, 1.02 lm, and the Reynolds number ranges from 150 to *** show that the surface roughness of the circular microchannels has remarkable effects on the performance of flow behavior and heat transfer. It is found that the Poiseuille and Nusselt numbers are higher when the relative surface roughness is larger. For flow behavior, the friction factor increases consistently with the increasing Reynolds number, and it is larger than the constant theoretical value for macrochannels. The Reynolds number for the transition from laminar to turbulent flow is about 1500, which is lower than the value for macrochannels. For the heat transfer property, Nusselt number also increases with increasing Reynolds number, and larger roughness contributes to higher Nusselt number.

关键词： Circular Flow behavior Heat transfer Microchannels Roughness

ABORT-like detector to combat active deceptive jamming in a network of LFM radars

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Chinese Journal of Aeronautics 2017年第4期30卷 1538-1547页

作者： yuan ZHAO zhi RAN Ying XIONG Bin TANG School of Electronic Engineering University of Electronic Science and Technology of China Chengdu 611731 China

This paper studies an electronic counter-counter measures（ECCM） scheme combating against deceptive electronic counter measure（ECM） techniques. An adaptive detector exploiting generalized likelihood ratio test（GRLT） criterion is applied to detect the presence of deceptive jamming in fractional Fourier transform（Fr FT） domain. First, the generating mechanism of spurious frequencies is analyzed based on the Volterra serial. The proposed nonlinear distortion model based on power amplifier behavior is robust in distortion analysis when the memory effect is ***, a modified adaptive beamformer orthogonal rejection test（ABORT） like detector in closed form is built. The proposed detector can discriminate the echo and deceptive jamming adaptively by exploiting primary data and secondary data. This ECCM scheme is capable of guaranteeing the performance without the restriction of orthogonality, which is essential for the ABORT detectors. The expansion to radar network is discussed as a special case at the final part of this paper. Numerical simulations demonstrate the effectiveness of the proposed method.

关键词： Adaptive signal detector ECCM capability Power amplifier Radar discrimination Signal processing

Methodology to determine regional water demand for instream flow and its application in the Yellow River Basin

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Journal of Environmental Sciences 2006年第5期18卷 1031-1039页

作者： ZHANG yuan YANG zhi-feng Wang Xi-qin School of Environmental Sciences State Key Laboratory of Water Environment Simulation Beijing Normal University Beijing 100875 China Chinese Research Academy of Environmental Sciences Beijing 100012 China School of Natural Resources and Environment Renmin Universitiy of China Beijing 100872 China

In order to realistically reflect the difference between regional water demand for instream flow and river ecological water demand as well as to resolve the problem that water demand may be counted repeatedly, a concept of regional water demand for minimum instream flow have been developed. The concept was used in the process of determining river functions and calculating ecological water demand for a river. The Yellow River watershed was used to validate the calculation methodology for regional water demand. CaIculation results indicate that there are significant differences in water demands among the different regions. The regional water demand at the downstream of the Yellow River is the largest about 14.893 × 10^9 m^3/a. The regional water demand of upstream, Lanzhou-Hekou section is the smallest about -5.012 × 10^9 m^3/a. The total ecological water demand of the Yellow River Basin is 23.06 × 10^9 m^3/a, about the 39% of surface water resources of the water resources should not exceed 61% in the Yellow River Basin. Yellow River Basin. That means the maximum available surface The regional river ecological water demands at the Lower Section of the Yellow River and Longyangxia-Lanzhou Section exceed the surface water resources produced in its region and need to be supplemented from other regions through the water rational planning of watershed water resources. These results provides technical basis for rational plan of water resources of the Yellow River Basin.

关键词： regional water demand instream flow environmental flow methodology the Yellow River Basin

Effects of asymmetric rolling process on ridging resistance of ultra-purified 17%Cr ferritic stainless steel

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International Journal of Minerals,Metallurgy and Materials 2018年第2期25卷 216-225页

作者： Cheng-zhuang Lu Jing-yuan Li zhi Fang School of Materials Science and Engineering University of Science and Technology Beijing Institute for Advanced Materials and Technology University of Science and Technology Beijing

In ferritic stainless steels, a significant non-uniform recrystallization orientation and a substantial texture gradient usually occur, which can degrade the ridging resistance of the final sheets. To improve the homogeneity of the recrystallization orientation and reduce the texture gradient in ultra-purified 17%Cr ferritic stainless steel, in this work, we performed conventional and asymmetric rolling processes and conducted macro and micro-texture analyses to investigate texture evolution under different cold-rolling conditions. In the conventional rolling specimens, we observed that the deformation was not uniform in the thickness direction, whereas there was homogeneous shear deformation in the asymmetric rolling specimens as well as the formation of uniform recrystallized grains and random orientation grains in the final annealing sheets. As such, the ridging resistance of the final sheets was significantly improved by employing the asymmetric rolling process. This result indicates with certainty that the texture gradient and orientation inhomogeneity can be attributed to non-uniform deformation, whereas the uniform orientation gradient in the thickness direction is explained by the increased number of shear bands obtained in the asymmetric rolling process.

关键词： ferritic stainless steel asymmetric rolling surface ridging texture shear bands

Effect of long-term thermal exposure on microstructure of laser-welded UNS N10003 alloy

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Nuclear Science and Techniques 2024年第11期35卷 73-81页

作者： Kun Yu yuan Zhang Xiao-Dan yuan Li-Bin Zhao zhi-Jun Li Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Nuclear and Radiation Safety Center Beijing 100082China

The evolution of the microstructure and tensile rupture mechanism of laser welds in UNS N10003 alloy exposed to 700℃are *** M_(6)C carbides precipitate around the primary eutectic M_(6)C-γcarbides in the fusion zone after 100 h of *** long-term thermal exposure,the size of the fine M_(6)C carbides *** eutectic M_(6)C-γcarbides in the as-welded fusion zone transformed into spherical M_(6)C carbides as the exposure time extends to 10000 ***,the spherical M_(6)C particles exhibit size coarsening with increasing exposure *** tensile properties of the welded joints are not adversely affected by the evolution of eutectic M_(6)C-γcarbides and the coarsening of M_(6)C carbides.

关键词： UNS N10003 alloy Laser welding M_(6)C Long-term thermal exposure

Automatic liver and tumor segmentation based on deep learning and globally optimized refinement

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Applied Mathematics(A Journal of Chinese Universities) 2021年第2期36卷 304-316页

作者： HONG yuan MAO Xiong-wei HUI Qing-lei OUYANG Xiao-ping PENG zhi-yi KONG de-xing School of Mathematical Science Zhejiang UniversityHangzhou 310058China department of Radiology Zhejiang University HospitalHangzhou 310058China department of Radiology The First Afiliated HospitalZhejiang University School of MedicineHangzhou 310003China School of Mechanical Engineering Zhejiang UniversityHangzhou 310058China

Automatic segmentation of the liver and hepatic lesions from abdominal 3D comput-ed tomography(CT)images is fundamental tasks in computer-assisted liver surgery ***,due to complex backgrounds,ambiguous boundaries,heterogeneous appearances and highly varied shapes of the liver,accurate liver segmentation and tumor detection are stil-1 challenging *** address these difficulties,we propose an automatic segmentation framework based on 3D U-net with dense connections and globally optimized ***-ly,a deep U-net architecture with dense connections is trained to learn the probability map of the *** the probability map goes into the following refinement step as the initial surface and prior *** segmentation of liver tumor is based on the similar network architecture with the help of segmentation results of *** order to reduce the infuence of the surrounding tissues with the similar intensity and texture behavior with the tumor region,during the training procedure,I x liverlabel is the input of the network for the segmentation of liver *** do-ing this,the accuracy of segmentation can be *** proposed method is fully automatic without any user *** qualitative and quantitative results reveal that the pro-posed approach is efficient and accurate for liver volume estimation in clinical *** high correlation between the automatic and manual references shows that the proposed method can be good enough to replace the time-consuming and non-reproducible manual segmentation method.

关键词： liver segmentation tumor segmentation CT deep learning

Potential for Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy Cosmic-radiation detection Facility on Board China's Space Station

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Research in Astronomy and Astrophysics 2023年第8期23卷 290-296页

作者： zhi-Hui Xu Qiang yuan zhi-Cheng Tang Xiao-Jun Bi Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Precise measurements of the spectra of secondary and primary cosmic rays are crucial for understanding the origin and propagation of those energetic *** High Energy Cosmic-radiation detection(HERD)facility on board China's Space Station,which is expected to operate in 2027,will push the direct and precise measurements of cosmic-ray fluxes up to PeV *** this work,we investigate the potential of HERD for studying the propagation of cosmic rays using measurements of boron,carbon,and oxygen *** find that,compared with the current results,the new HERD measurements can improve the accuracy of the propagation parameters by 8%–40%.The constraints on the injection spectra at high energies will also be improved.

关键词： (ISM:)cosmic rays-instrumentation detectors-The Galaxy

Single-atom Ag-loaded carbon nitride photocatalysts for efficient degradation of acetaminophen:The role of Ag-atom and O_(2)

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Journal of Environmental Sciences 2024年第5期139卷 12-22页

作者： Yi yuan Wen-Long Wang zhi-Wei Wang Jin Wang Qian-yuan Wu Key Laboratory of Microorganism Application and Risk Control of Shenzhen Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental SafetyInstitute of Environment and EcologyShenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China Shenzhen Environmental Science and New Energy Technology Engineering Laboratory Tsinghua-Berkeley Shenzhen InstituteShenzhen 518055China College of Materials Science and Engineering Shenzhen UniversityShenzhen 518071China

Carbon nitride has been extensively used as a visible-light photocatalyst,but it has the disadvantages of a low specific surface area,rapid electron-hole recombination,and relatively low light *** this study,single-atom Ag was successfully anchored on ultrathin carbon nitride(UTCN)via thermal polymerization,the catalyst obtained is called *** Ag hardly changed the carbon nitride's layered and porous physical *** exhibited efficient visible-light photocatalytic performances in the degradation of various recalcitrant pollutants,eliminations of 85% were achieved by visible-light irradiation for *** with Ag improved the photocatalytic performance of UTCN by narrowing the forbidden band gap from 2.49 to 2.36 e V and suppressing electron-hole pair *** addition,Ag doping facilitated O_(2) adsorption on UTCN by decreasing the adsorption energy from -0.2 to -2.22 e V and favored the formation of O_(2)^(·-).Electron spin resonance and radical-quenching experiments showed that O_(2)^(·-)was the major reactive species in the degradation of Acetaminophen(paracetamol,APAP).

关键词： Ag single atom Carbon nitride Photocatalysis Visible light Adsorption energy Reactive species