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Global well-posedness of coupled parabolic systems

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Science China Mathematics 2020年第2期63卷 321-356页

作者： Runzhang xu Wei lian Yi Niu College of Automation Harbin Engineering UniversityHarbin 150001China College of Science Harbin Engineering UniversityHarbin 150001China The Institute of Mathematical Sciences The Chinese University of Hong KongHong KongChina School of Information Science and Engineering Shandong Normal UniversityJinan 250014China

The initial boundary value problem of a class of reaction-diffusion systems(coupled parabolic systems)with nonlinear coupled source terms is considered in order to classify the initial data for the global existence,finite time blowup and long time decay of the *** whole study is conducted by considering three cases according to initial energy:the low initial energy case,critical initial energy case and high initial energy *** the low initial energy case and critical initial energy case the sufficient initial conditions of global existence,long time decay and finite time blowup are given to show a sharp-like *** addition,for the high initial energy case the possibility of both global existence and finite time blowup is proved first,and then some sufficient initial conditions of finite time blowup and global existence are obtained,respectively.

关键词： reaction-diffusion systems coupled parabolic systems global existence asymptotic behavior finite time blowup

Noise Reduction of an Axial Piston Pump by Valve Plate Optimization

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Chinese Journal of Mechanical Engineering 2018年第3期31卷 85-100页

作者： Shao-gan Ye Jun-Hui Zhang Bing xu State Key Laboratory of Fluid Power and Mechatronics Systems Zhejiang University Ocean College Zhejiang University

Current researches mainly focus on the investigations of the valve plate utilizing pressure relief grooves. However,air?release and cavitation can occur near the grooves. The valve plate utilizing damping holes show excellent perfor?mance in avoiding air?release and cavitation. This study aims to reduce the noise emitted from an axial piston pump using a novel valve plate utilizing damping holes. A dynamic pump model is developed,in which the fluid properties are carefully modeled to capture the phenomena of air release and cavitation. The causes of di erent noise sources are investigated using the model. A comprehensive parametric analysis is conducted to enhance the understanding of the e ects of the valve plate parameters on the noise sources. A multi?objective genetic algorithm optimization method is proposed to optimize the parameters of valve plate. The amplitudes of the swash plate moment and flow rates in the inlet and outlet ports are defined as the objective functions. The pressure overshoot and undershoot in the piston chamber are limited by properly constraining the highest and lowest pressure values. A comparison of the various noise sources between the original and optimized designs over a wide range of pressure levels shows that the noise sources are reduced at high pressures. The results of the sound pressure level measurements show that the optimized valve plate reduces the noise level by 1.6 d B(A) at the rated working condition. The proposed method is e ective in reducing the noise of axial piston pumps and contributes to the development of quieter axial piston machines.

关键词： Axial piston pump Noise reduction Fluid?borne noise Structure?borne noise Parametric analysis Multi?objective optimization

Hot deformation behavior and microstructure evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment

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Rare Metals 2013年第4期32卷 338-346页

作者： Yan xu lian-Xi Hu Yu Sun School of Materials Science and Engineering Harbin Institute of Technology School of Mechanical Engineering Beihua University

The deformation behavior and the microstruc-ture evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment were systematically inves-tigated. The flow stress behavior was studied by com-pression tests in strain rate range of 0.001-1.000 s^-1 and deformation temperature range of 220-380 ℃ with a maximum deformation strain of 60 %. The dependence of flow stress on deformation temperature and strain rate was described by hyperbolic sine constitutive equation. Through regression analysis, the average apparent activa- tion energy and coefficient of strain rate sensitivity were estimated to be 181.98 ***^-1 and 0.14, respectively. The results also reveal that the variation of peak stress depends on strain rate and deformation temperature. Microstructure observation shows that, at temperatures higher than 300 ℃ and strain rates lower than 0.01 s^-1, DRX developed extensively at the grain boundaries and in the core of coarse grains, resulting in a more homogeneous microstructure. Furthermore, the effects of strain, defor-mation temperature, strain rate, and eutectic β phase on the microstructure evolution of as-cast AZ91D magnesium alloy were discussed.

关键词： AZ91D magnesium alloy Isothermalcompression Constitutive equation Peak stress Microstructure evolution

An Experimental Study on the Performance of a Hybrid Photovoltaic/Thermal Solar System

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Energy Engineering 2022年第6期119卷 2319-2345页

作者： Xin xu lian Zhang School of Energy Engineering Tianjin Sino-German University of Applied SciencesTianjin300350China Tianjin Sino-German and Cambodia Intelligent Motion Device and Communication Technology Promotion Center Tianjin“The Belt and Road”Joint LaboratoryTianjin300350China

Considered as the widespread renewable energy,solar energy is used to produce the electricity and heat for carbon peaking and carbon ***,the photo-electric conversion efficiency will decrease with the increase of cells *** solve this problem,a water-type hybrid photovoltaic/thermal(PV/T)solar system has been designed and tested in Hong *** outdoor experiment proceeded all days in 6 months with three different operating *** data of selected 33 days were used to analyze the performance of the *** results showed that the thermal efficiencies were 33.6%,52%,and 48.3%at zero reduced temperature,corresponding to three ***,the overall efficiencies were 43.2%,60.9%,and 55.2%accordingly,which are higher than those of the conventional flat-plate solar *** average water temperature in the storage tank could reach 39.9°C,and the system could produce 0.07 kWh electric power after one-day operation,when the collector with 96 kg/m2 M/Ac installed vertically combining with external wall for each *** is realizable to utilize the developed building integrated water-type photovoltaic/thermal(BIPVT)solar system for residential-intensive high-rise buildings in Hong Kong,satisfying the needs of hot water,and eventually reducing energy consumption of the buildings.

关键词： The water-type hybrid PV/T system operating modes the performance of the system

Performance Analysis of Multi-Energy Hybrid System Based on Molten Salt Energy Storage

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Energy Engineering 2021年第6期118卷 1905-1920页

作者： Xin xu lian Zhang School of Energy Engineering Tianjin Sino-German University of Applied SciencesTianjin300350China

This paper briefly summarizes the current status of typical solar thermal power plant system,including system composition,thermal energy storage medium and *** thermo-physical properties of the storage medium are some of the most important factors that affect overall efficiency of the system,because some renewable energy sources such as solar and wind are unpredictable.A thermal storage system is therefore necessary to store energy for continuous *** on the form of storage or the mode of system connection,heat exchangers of a thermal storage system can produce different temperature ranges of heat transfer fluid to realize energy cascade *** upon the review,a small hybrid energy system with a molten-salt energy storage system is proposed to solve the problems of heating,cooling,and electricity consumption of a 1000 m2 training hall at *** system uses molten-salt storage tank,water tank and steam generator to change the temperature of heat transfer fluid,in order to realize thermal energy cascade *** to the existing heating and cooling system,the proposed system needs more renewable energy and less municipal energy to achieve the same results according to simulation ***,by improving the original heating and cooling system,PMV has been *** comprehensive efficiency of solar energy utilization has been increased to 83%.

关键词： Solar thermal power thermal energy storage storage medium energy cascade utilization

Optimizing bedroom thermal environment:A review of human body temperature,sleeping thermal comfort and sleep quality

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Energy and Built Environment 2024年第6期5卷 829-839页

作者： Xinbo xu Zhiwei lian Department of Architecture Shanghai Jiao Tong UniversityShanghai 200240China

Thermal environment may affect sleep quality and sleeping thermal comfort at the same *** to now,there is no direct evidence or physiological theory can prove the idea that thermal comfort equal to good sleep quality,but how to balance the relationship between them is often ignored when designing thermal *** review took body temperature distribution as a bridge for the connection of sleep quality and sleeping thermal *** first,we reviewed the quantitative relationships among thermal environment,body temperature,sleep quality and sleeping thermal comfort,and then based on the idea of reverse derivation,a recommended design process for bedroom thermal environment was *** step of the process corresponded to the impact mechanism described *** review results showed that,body temperature distribution was closely related to both sleep quality and thermal comfort,and thus it was suitable to be used as a bridge between them;body temperatures fluctuated dynamically during sleep,and thus heat transfer and thermal regulation models should be used to describe them;most current sleep researches regarded skin temperature as the representative value of body temperature distribution,yet core body temperature needs to be paid more attention on in the future because it was more closely related to sleep rhythm;furthermore,in addition to young people,subjects of more age groups should be tested to enrich China’s sleep research *** general,it’s theoretically possible to guarantee both sleep quality and sleeping thermal comfort,and this review can be used as a reliable reference for bedroom thermal environment design.

关键词： Sleep health Sleep quality Thermal comfort Thermal environment Body temperature distribution

Biomimetic Superlyophobic Metallic Surfaces: Focusing on Their Fabrication and Applications

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Journal of Bionic Engineering 2020年第1期17卷 1-33页

作者： Zhongxu lian Jinkai xu Zuobin Wang Huadong Yu Ministry of Education Key Laboratory for Cross-Scale Micro and Nano Manufacturing Changchun University of Science and TechnologyChangchun 130022China International Research Centre for Nano Handling and Manufacturing of China Changchun University of Science and TechnologyChangchun 130022China

Metals are indispensable engineered materials for day-to-day *** focused on metallic surfaces with superlyophobicity(superhydrophobicity,superoleophobicity,underwater superoleophobicity and slippery characteristic)have attracted much attention *** is a magician that gives each organic life a unique *** have created a large number of biomimetic superlyophobic metallic surfaces through various *** biomimetic superlyophobic metallic surfaces exhibit advantages in many applications,such as self-cleaning,corrosion resistance,anti-icing,and drag *** this review,the specific fabrication and applications of biomimetic superlyophobic metallic surfaces were *** remaining challenges and future outlook of biomimetic superlyophobic metallic surfaces were preliminarily *** is hoped that the review will be essential for broadening the scope of potential applications of metals and providing a powerful reference for future research on metal-based advanced functional materials.

关键词： biomimetic metallic surfaces superhydrophobicity superoleophobicity underwater superoleophobicity slippery characteristic

The effect of noise exposure on sleep quality of urban residents:A comparative study in Shanghai,China

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Building Simulation 2023年第4期16卷 603-613页

作者： Xinbo xu Li Lan Yuxiang Sun Zhiwei lian School of Design Shanghai Jiao Tong UniversityShanghai 200240China China Institute of Urban Governance Shanghai Jiao Tong UniversityShanghai 200030China

Noise exposure is becoming extremely common in urban area,but its specific impact on sleep remains *** the limitations of previous researches,a field study which can conduct both horizontal and longitudinal analysis was *** participants were tested during two weeks in their homes,and the noise level of bedroom was artificially regulated by changing the status of window and *** the 1050 test nights in 75 households,noise exposure was reflected from both instrument monitoring at night and perception questionnaire in the morning,and sleep quality was accessed from actigraphy and *** analysis results showed that,92.3%of the bedroom acoustic environment did not meet the minimum requirements of Chinese standards,and 87.9%of subjects had ever experienced harmful noise during the test ***,sleep quality was affected by noise exposure from the perspective of both physiological and psychological;the duration of rapid eye movement(REM)sleep was significantly(p<0.05)shortened with the increase of sound intensity,the duration of deep sleep shortened and subjective sleep quality worsened significantly(p<0.05)with the increase of acoustic sensation *** addition,females were more sensitive to noise exposure and their subjective sleep quality was more likely to be influenced by *** study has important implications for acoustic environment design of bedrooms in cities,and suggested more attention should be paid to the anxiety caused by noise exposure.

关键词： noise exposure sleep quality sound intensity subjective perception urban governance

A non-myopic scheduling method of radar sensors for maneuvering target tracking and radiation control

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Defence Technology（防务技术） 2020年第1期16卷 242-250页

作者： gan-lin Shan Gong-guo xu Cheng-lin Qiao Department of Electronic and Optical Engineering Army Engineering UniversityShijiazhuang 050003China

In decades,the battlefield environment is becoming more and more complex with plenty of electronic ***,in order to improve the survivability of radar sensors and satisfy the requirement of maneuvering target tracking with a low probability of intercept,a non-myopic scheduling is proposed to minimize the radiation cost with tracking accuracy *** first,the scheduling problem is formulated as a partially observable Markov decision process(POMDP).Then the tracking accuracy and radiation cost over the future finite time horizon are predicted by the posterior carmer-rao lower bound(PCRLB) and the hidden Markov model filter,***,the proposed scheduling is implemented efficiently by utilizing the branch and bound(B&B) pruning *** results show that the performance of maneuvering target tracking was improved by the improved interacting multiple model(IMM),and the scheduler time and maximum memory consumption were significant reduced by the present B&B pruning algorithm without losing the optimal solution.

关键词： Non-myopic scheduling Radiation control PCRLB POMDP Branch and bound