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Building Simulation 2023年第11期16卷 2159-2176页

作者： Xianzhong Chen Rang Tu Ming Li Xu Yang Kun Jia School of Civil and Resources Engineering University of Science and Technology BeijingBeijing100083China School of Automation and Electrical Engineering University of Science and Technology BeijingBeijing100083China China Electronics Engineering Design Institute CO. LTD.Beijing100142China

In this paper,models to predict hot spot temperature and to estimate cooling air’s working parameters of racks in data centers were established using machine learning algorithms based on simulation data.First,simulation models of typical racks were established in computational fluid dynamics(CFD).The model was validated with field test results and results in literature,error of which was less than 3%.Then,the CFD model was used to simulate thermal environments of a typical rack considering different factors,such as servers’power,which is from 3.3 kW to 20.1 kW,cooling air’s inlet velocity,which is from 1.0 m/s to 3.0 m/s,and cooling air’s inlet temperature,which is from 16℃ to 26℃ The highest temperature in the rack,also called hot spot temperature,was selected for each case.Next,a prediction model of hot spot temperature was built using machine learning algorithms,with servers’power,cooling air’s inlet velocity and cooling air’s inlet temperature as inputs,and the hot spot temperatures as outputs.Finally,based on the prediction model,an operating parameters estimation model was established to recommend cooling air’s inlet temperatures and velocities,which can not only keep the hot spot temperature at the safety value,but are also energy saving.

关键词： data center CFD simulation hot spot temperature machine learning algorithm prediction and estimation models

International public opinion analysis of four olympic games:From 2008 to 2022

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Journal of Safety Science and Resilience 2022年第3期3卷 252-262页

作者： Kun Jia Yizhen Zhu Yuxin Zhang Feng Liu jiayin Qi Institute of Artificial Intelligence and Change Management Shanghai University of International Business and EconomicsShanghai 201620China School of Statistics and Information Shanghai University of International Business and EconomicsShanghai 201620China School of Computer Science and Technology East China Normal UniversityShanghai 200062China Shanghai Key Laboratory of Mental Health and Psychological Crisis Intervention other institutesSchool of Psychology and Cognitive ScienceEast China Normal UniversityShanghai 200062China

Since the rapid spread of the COVID-19 worldwide,the pandemic has led to a huge impact on global sporting events.As a major international event,the 2022 Beijing Winter Olympics has commonalities with the 2008 Beijing Olympics,the 2014 Sochi Winter Olympics,and the 2020 Tokyo Olympics in terms of international public opinion context and epidemiological background.In this study,over 1 million pieces of UGC(User Generated Contents)in Chinese and English languages were obtained from social media platforms such as Twitter,YouTube,as well as traditional mass media in various countries to compare the differences between the two languages in international public opinion.Using sentiment analysis,this study explores the evolution of international public opinion topics and sentiment differences among the above four Olympic Games.The analysis results show that:1)regardless of traditional mass media or online social media,there is a more obvious tendency of general politicization in the topics of the 2008 Beijing Olympics and 2022 Beijing Winter Olympics,and extreme emotional remarks of the 2022 Beijing Winter Olympics are more frequent;2)in the topic of political opinion involving China,international Chinese public opinion presents more negative sentiment than those in English;3)Among the topics involving COVID-19,the negative level of public opinion in Chinese and English is opposite for the 2020 Tokyo Olympics and the 2022 Beijing Winter Olympics;4)International public opinion on the topic of sports events is significantly more positive in Chinese than in English;5)YouTube’s Chinese opinion environment is better than English.

关键词： Public opinion Sentiment analysis Olympic games COVID-19 pandemic Computational affection

Numerical study on the electromechanical behavior of dielectric elastomer with the influence of surrounding medium

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International Journal of Smart and Nano Materials 2016年第1期7卷 52-68页

作者： Kun Jia Tongqing Lu State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi’an Jiaotong UniversityXi’anChina

The considerable electric-induced shape change,together with the attributes of lightweight,high efficiency,and inexpensive cost,makes dielectric elastomer,a promising soft active material for the realization of actuators in broad applications.Although,a number of prototype devices have been demonstrated in the past few years,the further development of this technology necessitates adequate analytical and numerical tools.Especially,previous the-oretical studies always neglect the influence of surrounding med-ium.Due to the large deformation and nonlinear equations of states involved in dielectric elastomer,finite element method(FEM)is anticipated;however,the few available formulations employ homemade codes,which are inconvenient to implement.The aim of this work is to present a numerical approach with the commercial FEM package COMSOL to investigate the nonlinear response of dielectric elastomer under electric stimulation.The influence of surrounding free space on the electric field is analyzed and the corresponding electric force is taken into account through an electric surface traction on the circumstances edge.By employ-ing Maxwell stress tensor as actuation pressure,the mechanical and electric governing equations for dielectric elastomer are coupled,and then solved simultaneously with the Gent model of stain energy to derive the electric induced large deformation as well as the electromechanical instability.The finite element imple-mentation presented here may provide a powerful computational tool to help design and optimize the engineering applications of dielectric elastomer.

关键词： Dielectric elastomer electromechanical coupling finite element method Maxwell stress tensor

Assessment of land degradation in Inner Mongolia between 2000 and 2020 based on remote sensing data

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Geography and Sustainability 2023年第2期4卷 100-111页

作者： Linlin Zhao Kun Jia Xin Liu Jie Li Mu Xia State Key Laboratory of Remote Sensing Science Faculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China Beijing Engineering Research Center for Global Land Remote Sensing Products Faculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China Geological Survey of Inner Mongolia HohhotInner Mongolia 010020China

Achieving land degradation neutrality(LDN)worldwide is a significant target of the Sustainable Development Goal(SDG15.3).Inner Mongolia,as a typical dryland region in northern China,has carried out several large-scale ecological restoration programs to combat land degradation.However,there is a lack of comprehensive assess-ment of its land degradation situation after ecological programs implementation,which is of great significance to supporting SDG15.3 in China.This study analyzed the land degradation situation using the improved SDG15.3.1 calculation framework based on fine resolution data in Inner Mongolia from 2000 to 2020,and finally compre-hensively evaluated the land status of the whole region and those subject to ecological programs.The results show that net land restoration proportion of various ecological project regions and whole region continues to increase.The scope of the Grain for Green Program(GGP)had the largest proportion of net land restoration while the Natural Reserve Program(NRP)had the lowest proportion from 2000 to 2020.The net land restoration area of Inner Mongolia during 2000-2010 and 2010-2020 was 35,800 km 2 and 65,300 km 2,respectively.Overall,Inner Mongolia has achieved statistically zero growth in land degradation under the governance of ecological restora-tion programs.Therefore,reasonable planning,well monitoring,and timely assessment of ecological restoration programs are crucial to support SDG15.3.

关键词： SDG15.3 Land degradation neutrality(LDN) Land degradation Ecological programs Inner Mongolia

A lightweight DDoS detection scheme under SDN context

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Cybersecurity 2023年第1期6卷 75-89页

作者： Kun Jia Chaoge Liu Qixu Liu Junnan Wang jiazhi Liu Feng Liu State Key Laboratory of Information Security Institute of Information EngineeringBeijingChina School of Cyber Security University of Chinese Acad emy of SciencesBeijing 100049China The Sixth Research Offce Institute of Information EngineeringChinese Academy of SciencesBeijing 100093China

Software-defined networking(SDN),a novel network paradigm,separates the control plane and data plane into dif-ferent network equipment to realize the flexible control of network traffic.Its excellent programmability and global view present many new opportunities.DDoS detection under the SDN context is an important and challenging research field.Some previous works attempted to collect and analyze statistics related to flows,usually recorded in switches,to address DDoS threats.In contrast,other works applied machine learning-based solutions to identify DDos and achieved promising results.Generally,most previous works need to periodically request flow rules or packets to obtain flow statistics or features to detect stealthy exceptions.Nevertheless,the request for flow rules is very time-consuming and CPU-consuming;moreover may congest the communication channel between the controller and the switches.Therefore,we present FORT,a lightweight DDoS detection scheme,which spreads the rule-based detection algorithm at edge switches and determines whether to start it by periodically retrieving the ports state.A time-series algorithm,ARIMA,is utilized to determine the port statistics adaptively,and an SVM algorithm is applied to detect whether a DDoS attack does occur.Representative experiments demonstrate that FORT can significantly reduce the controller load and provide a reliable detection accuracy.Referring to the false alarm rate of 1.24%in the comparison scheme,the false alarm rate of this scheme is only 0.039%,which significantly reduces the probability of false alarm.Besides,by introducing the alarm mechanism,this scheme can reduce the load of the southbound chan-nel by more than 60%in the normal state.

关键词： DDoS Port monitoring Flow rule Software defined network MiniNet RYU controller Detection

3D confined self-assembling of QD within super-engineering block copolymers as biocompatible superparticles enabling stimulus responsive solid state fluorescence

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Nano Research 2021年第1期14卷 285-294页

作者： Xiaohong He Kun Jia Robert Marks Yiguo Hu Xiaobo Liu School of Materials and Energy University of Electronic Science and Technology of ChinaChengdu 611731China The Avram and Stella Goldstein-Goren Department of Biotechnology Engineering Bert-Gurion University of the NegevBeer-Sheva 8410501Israel State Key Laboratory of Biotherapy Sichuan UniversityChengdu 610051China

Eliminating colloidal toxicity and enabling its intrinsic fluorescence in aggressive environmental conditions are the key challenges for commercializing hydrophobic cadmium based quantum dots(QD).Polyarylene ether nitriles(PEN)are an example of super-engineering thermoplastics that possess a unique combination of thermal stability,intrinsic fluorescence,biocompatibility and distinct emulsion self-assembly feature.Herein,the co-self-assembly of amphiphilic PEN with hydrophobic CdSe@ZnS QD,confined in the three-dimensional(3D)oil-in-water emulsion droplets,has been explored tofabricate fluorescent microparticles(FMP).It was found that these FMP demonstrated good biocompatibility(cell viability above 90%),while exhibiting a fluorescence emission in aqueous solution that was retained(intensity retention ratio above 80%)within the whole pH range of 1-14,as well as,after being subjected to autoclaving at 120℃for 1 h.Interestingly,it was discovered that introduction of calcium ions in the emulsion self-assembly contributed to in-situ generation of phase changing nanoplates inside the FMP,which led to the photo-thermal modulated solid state fluorescence from drop-casted FMP film.Thanks to their versatile fluorescence,these FMP colloids were exploited as fluorescent probes for macrophages imaging,while micro-patterns with reversible changing of emission color were induced via thermal treatment and direct laser lithography.

关键词： three-dimensional(3D)confinement self-assembly quantum dots amphiphilic polyarylene ether nitrile stimulus responsive fluorescence

Pressure evolution in shock-compacted granular media

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Petroleum Science 2023年第6期20卷 3736-3751页

作者： jia-Rui Li Jun-Sheng Zeng kun Xue State Key Laboratory of Explosive Science and Technology Beijing Institute of TechnologyBeijing100081China Institute of Applied Physics and Computational Mathematics Beijing100094China

The pressure evolution associated with the transient shock-induced infiltration of gas flow through granular media consisting of mobile particles is numerically investigated using a coupled Eulerian–Lagrangian approach.The coupling between shock compaction and interstitial flow has been revealed.A distinctive two-stage diffusing pressure field with deflection occurring at the tail of the compaction front is found,with corresponding spikes in both gaseous velocity and temperature profiles emerging within the width of the compaction front.The compaction front,together with the deflection pressure,reaches a steady state during the later period.An analytical prediction of the steady deflection pressure that considers the contributions of porosity and the non-isothermal effect is proposed.The isothermal single-phase method we developed,combining the porosity jump condition across the compaction front,shows consistent pressure evolution with the non-isothermal CMP-PIC one under weak shock strength and low column permeability.Lastly,the microscale mechanism governing the formation of not only pressure deflection but also gaseous velocity and temperature spikes within the width of the compaction front has been described.These aforementioned evolutions of the flow field are shown to arise from the nozzling effects associated with the particle-scale variations in the volume fraction.

关键词： Shock compaction Pressure evolution Transport in porous media Transient gas infiltration Mobile granular column

The binding energy parameter for common envelope evolution

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Research in Astronomy and Astrophysics 2016年第8期16卷 71-78页

作者： Chen Wang Kun Jia Xiang-Dong Li Department of Astronomy Nanjing University Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of Education

Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it has been erroneously adopted as a constant in most population synthesis calculations. We have system- atically calculated the values of A for stars of masses 1 - 60 M by use of an updated stellar evolution code, taking into account the contribution from both gravitational energy and internal energy to the binding energy of the envelope. We adopt the criterion for the core-envelope boundary advocated by Ivanova. A new kind of A with an enthalpy prescription is also investigated. We present fitting formulae for the calculated values of various kinds of A, which can be used in future population synthesis studies.

关键词： binaries： general -- stars： evolution -- stars： mass-loss

Wind farm active power dispatching algorithm based on Grey Incidence

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Global Energy Interconnection 2023年第2期6卷 175-183页

作者： Binbin Zhang Mengxin jia Chaobo Chen kun Wang Jichao Li School of Electronic and Information Engineering Xi’an Technological UniversityXi’an 710021P.R.China

This study proposes a wind farm active power dispatching(WFAPD) algorithm based on the grey incidence method, which does not rely on an accurate mathematical model of wind turbines. Based on the wind turbine start-stop data at different wind speeds, the weighting coefficients, which are the participation degrees of a variable speed system and a variable pitch system in power regulation, are obtained using the grey incidence method. The incidence coefficient curve is fitted by the B-spline function at a full range of wind speeds, and the power regulation capacity of all wind turbines is obtained. Finally, the WFAPD algorithm, which is based on the regulating capacity of each wind turbine, is compared with the wind speed weighting power dispatching(WSWPD) algorithm in MATLAB. The simulation results show that the active power fluctuation of the wind farm is smaller, the rotating speed of wind turbines is smoother, and the fatigue load of highspeed turbines is effectively reduced.

关键词： Wind farm Active power dispatching Grey incidence B-spline function

Numerical Study on the Pulsation Characteristics of An Attached Air Bubble Under A Nearby Oscillating Bubble

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China Ocean Engineering 2023年第2期37卷 299-311页

作者： jiaNG Ming-zuo LIU kun WANG jia-xia WEN Xiao-hu College of Automation Jiangsu University of Science and TechnologyZhenjiang 212003China School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

Numerical simulations of the non-spherical evolution of a pulsating bubble interacting with a stationary air bubble attached to a fixed structure were performed using a three-dimensional boundary integral method by implementing the mirror image method to simplify the processing of the numerical model. Code validation was accomplished by comparing the numerical results with the laboratory experimental data obtained in our previous study. Complex phenomena were observed, including three types of bubble jet forms, which depended strongly on the distance parameter with respect to the initial location of the bubble from the plate, the bubble strength parameter and the initial air bubble radius parameters. The results of the simulations provide detail insight into interesting bubble jetting phenomena,such as bubble splitting, jets moving away from the plate, and bubble shedding. The dimensionless distance parameter and the initial air bubble radius parameter play a major role in determining the shapes of two bubbles and the jetting direction. The air bubble strength parameter did not change the bubble jet direction but influenced the bubble shape.The detachment of the attached air bubble under oscillating bubble suction was easily observed for a small initial air bubble. These results showed that bubble jetting toward the plate was manipulated through the effect of attached air bubble, and that cavitation-based applications and underwater explosion bubble may benefit from this erosion mitigation approach.

关键词： bubble dynamics attached air bubble bubble collapse liquid jet