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An Optimal Control Problem of a Coupled Nonlinear Parabolic Population System

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Acta Mathematicae Applicatae Sinica 2007年第3期23卷 377-388页

作者： chao-hua jia De-xing Feng Department of Applied Mathematics LMIB of the Ministry of Education Beijing University of Aeronauticsand Astronautics Beijing 100083 China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

An optimal control problem for a coupled nonlinear parabolic population system is considered. The existence and uniqueness of the positive solution for the system is shown by the method of upper and lower solutions. An explicit prior bound of solutions to the system is given by considering an auxiliary coupled linear system. The existence of the optimal control is proved and the characterization of the optimal control is established.

关键词： Nonlinear parabolic systems optimal control upper and lower solutions

A Review on Flow Boiling of the Fluid with Lower Boiling Point in Micro-Channels

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Journal of Thermal Science 2024年第1期33卷 1-17页

作者： ZHANG Zhiqiang jia Li DANG chao Beijing Key Laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

With the advancement of micro machining technology,the high-heat-flux removal from miniature electronic devices and components has become an attractive *** boiling in micro-channels is an optimal form of heat transfer and has been widely employed in high-heat-flux cooling *** comprehensively-reviewed article focused on the available recent literatures of experimental investigation regarding the flow boiling heat transfer and unstable behaviors of the fluid with lower boiling point in *** thermal-fluid characteristics and potential heat transfer mechanisms of low-boiling-point fluids flow boiling in different narrow passages were summarized and *** literatures regarding the pressure drop and occurrence of the unstable phenomena existing in two-phase flow boiling process were also *** emphasis was given to the heat transfer enhancement methods as well as instability elimination,and various methods such as modification of surface and channel flow geometries were *** future researches in the field of micro-scale flow boiling were suggested.

关键词： flow boiling lower boiling point fluids mini/micro-channels instabilities enhancement suppression

Microstructure and property of laser additive manufactured alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si after aged at different temperatures

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Rare Metals 2024年第5期43卷 2275-2281页

作者： Guo-chao Li Xu Cheng hua-Ming Wang National Engineering Laboratory of Additive Manufacturing for Large Metallic Components and Engineering Research Center of Ministry of Education on Laser Direct Manufacturing for Large Metallic Components School of Materials Science and EngineeringBeihang UniversityBeijing 100191China

The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar *** this study,the influence of aging temperatures(600,700 and 800°C)on microstructure and mechanical properties of titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si was *** results indicate that after solid solution treatment at 970°C followed by water quenching,the alloy mainly consists of coarsening lamellar a phase in martensite α' *** at 600°C will not change the size of primary lamellar α phase but lead to huge amount of secondary a phases(α_(s))generating with very fine *** increasing the aging temperature,the number of α_(s) decreases but with coarsened *** aged at 800°C,the width of the asphase reaches 350 nm,almost 7 times wider than that aged at 600°*** changing size of α_(s) obviously influences the property of the *** fine α_(s) leads to high strength and microhardness but low plasticity,and specimen aged at 700°C with suitable assize has the best comprehensive properties.

关键词： α+βtitanium alloy Laser additive manufacturing Solid solution and aging treatment Microstructure Room temperature tensile property

Research on blade tip clearance cavitation and turbulent kinetic energy characteristics of axial flow pump based on the partially-averaged Navier-Stokes model

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Journal of Hydrodynamics 2024年第1期36卷 184-201页

作者： Xiao-qi jia Shuai-kang Zhang Zu-chao Zhu Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou310018China

To reveal the cavitation forms of tip leakage vortex(TLV)of the axial flow pump and the flow mechanism of the flow field,this research adopts the partially-averaged Navier-Stokes(PANS)model to simulate the cavitation values of an axial flow pump,followed by experimental *** experimental result shows that compared with the shear stress transport(SST)k-ωmodel,the PANS model significantly reduces the eddy viscosity of the flow field to make the vortex structure clearer and allow the turbulence scale to be more robustly *** cavitation area within the axial flow pump mainly comprises of TLV cavitation,clearance cavitation and tip leakage flows combined effect of triangular cloud cavitation *** formation and development of cavitation are accompanied by the formation and evolution of vortex,and variations in vortex structure also generate and promote the development of *** addition,an in-depth analysis of the relationship between the turbulent kinetic energy(TKE)transport equation and cavitation patterns was also conducted,finding that the regions with relatively high TKE are mainly distributed around gas/liquid boundaries with serious cavitation and evident gas-liquid *** phenomenon is mainly attributed to the combined effect of the pressure action term,stress diffusion term and TKE production term.

关键词： Cavitation axial flow pump tip leakage vortex(TLV) partially-averaged Navier-Stokes(PANS)model turbulent kinetic energy(TKE)

Side Information-Based Stealthy False Data Injection Attacks Against Multi-Sensor Remote Estimation

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1054-1056页

作者： Haibin Guo Zhong-hua Pang chao Li the Key Laboratory of Fieldbus Technology and Automation of Beijing North China University of TechnologyBeijing 100144China

Dear Editor,This letter investigates a novel stealthy false data injection(FDI)attack scheme based on side information to deteriorate the multi-sensor estimation performance of cyber-physical systems(CPSs).Compared with most existing works depending on the full system knowledge,this attack scheme is only related to attackers'sensor and physical process *** design principle of the attack signal is derived to diverge the system estimation ***,it is proven that the proposed attack scheme can successfully bypass the residual-based ***,all theoretical results are verified by numerical simulation.

关键词： estimation scheme system

Correlation between carbon emissions,fuel consumption of vehicles and speed limit on expressway

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第4期11卷 631-642页

作者： chao Gao Jinliang Xu Miao jia Zhenhua Sun School of Highway Chang'an UniversityXi'an 710064China Shaoxing Communications Investment Group Co. Ltd.Shaoxing 312000China

This paper aimed to investigate the correlation between carbon emissions,fuel consumption,and speed limit.A theoretical model was derived based on the energy conservation law,which expresses the relationship between vehicle's fuel consumption and ***,a total of 40 sets of fuel consumption data were collected through field tests to verify the accuracy of the theoretical model at different speeds and different road longitudinal slope *** fuel consumption was then converted to carbon emissions according to the carbon emission factors specified by Intergovernmental Panel on Climate Change(IPCC).In the field experiment,two types of cars and trucks,which are most common on the expressways in China,were ***,the travel speed under different posted speed limits was obtained through the previously established model,and the carbon emission changes of different vehicle types at different limited speeds are *** results show that the speed limit has a significant impact on fuel consumption and carbon *** the speed limit increased from 80 to 120 km/h,average vehicle speeds increased about 21%-27%,and fuel consumption and carbon emissions increased from approximately 33%-38%.Another interesting result was that the vehicle's fuel consumption and carbon emissions are only affected by *** results of the study explore the effect of speed limits on carbon emissions and provide evidence for road managers to set reasonable speed limits.

关键词： Vehicle carbon emission Vehicle fuel consumption Posted speed limit Average speed Road longitudinal slope

Dynamic Multi-Physics Behaviors and Performance Loss of Cylindrical Batteries Upon Low-Velocity Impact Loading

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Energy & Environmental Materials 2024年第6期7卷 184-192页

作者： Qingdan huang Yang Bai Han Luo Yikai jia chao Zhang School of Civil Aviation Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory on the Impact Protection and Safety Assessment of Civil Aviation Vehicle Taicang 215400China School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China EVE Energy Co. Ltd.Huizhou 516006C

In challenging operational environments,Lithium-ion batteries(LIBs)inevitably experience mechanical stresses,including impacts and extrusion,which can lead to battery damage,failure,and even the occurrence of fire and explosion ***,it is imperative to investigate the safety performance of LIBs under mechanical *** study is grounded in a more realistic coupling scenario consisting of electrochemical cycling and low-velocity *** systematically and experimentally uncovered the mechanical,electrochemical,and thermal responses,damage behavior,and corresponding mechanisms under various *** study demonstrates that higher impact energy results in increased structural stiffness,maximum temperature,and maximum voltage ***,heightened impact energy significantly influences the electrical resistance parameters within the internal *** also examined the effects of State of Charge(SOC)and *** methodology and experimental findings will offer insights for enhancing the safety design,conducting risk assessments,and enabling the cascading utilization of energy storage systems based on LIBs.

关键词： cycling performance damaged battery lithium-ion battery low-velocity impact mechanical safety

Structure engineering of cathode host materials for Li-S batteries

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Rare Metals 2024年第4期43卷 1370-1389页

作者： jia-Jun Long hua Yu Wen-Bo Liu School of New Energy and Materials Southwest Petroleum UniversityChengdu610500China School of Mechanical Engineering Sichuan UniversityChengdu610065China

Although lithium-sulfur batteries are one of the favorable candidates for next-generation energy storage devices,a few key challenges that have not been addressed have limited its *** challenges include lithium dendrite growth in the anode side,volume change of the active material,poor electrical conductivity,dissolution and migration of poly sulfides,and slow rate of solid-state reactions in the cathode *** the electrochemical performance of lithium-sulfur batteries is greatly affected by the design of the cathode host material,it has also been widely discussed in addressing the abovementioned *** this paper,three design ideas of cathode host materials in terms of microstructure,crystal structure and electronic structure are introduced and ***,the current progress of these three structural design strategies and their effects on the electrochemical performance of lithium-sulfur batteries are discussed in ***,future directions in the structural design of cathode materials for lithium-sulfur batteries are discussed and further perspectives are provided.

关键词： Lithium-sulfur batteries Structure engineering Cathode Host materials

Advances of biomarkers in nasopharyngeal carcinoma’s early detection

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Science Bulletin 2024年第2期69卷 141-145页

作者： Xiao-Hui Zheng Allan Hildesheim Wei-hua jia State Key Laboratory of Oncology in South China Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and TherapyGuangdong Provincial Clinical Research Center for CancerSun Yat-sen University Cancer CenterGuangzhou 510060China Costa Rican Agency for Biomedical Investigation INCIENSA FoundationSan Jose 10108Costa Rica

Nasopharyngeal carcinoma(NPC),a highly invasive and metastatic cancer,is widely prevalent in South China,Southeast Asia,and North *** patients with stages I and II are often ***,NPC patients are usually diagnosed with advanced-stage(stages III and IV)at their first *** of NPC at early stage is the key to improve the survival of ***-Barr virus(EBV)plays an essential role in NPC occurrence in endemic ***-based biomarkers,including EBV antibody in serum and EBV DNA in plasma,have been specifically proposed for NPC early ***,we summarize recent advances in biomarkers for the early detection of NPC.

关键词： patients nasopharyngeal Nasopharyngeal