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Experimental Investigations on the Out-of-Plane Sub-harmonic Vibration of a Circular Dielectric Elastomer Actuator

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Acta Mechanica Solida Sinica 2019年第5期32卷 591-598页

作者： Cheng Ma Meng Yang kun jia Tongqing Lu State Key Laboratory for Strength and Vibration of Mechanical Structure Department of Engineering MechanicsXi'an Jiaotong UniversityXi'an 710049China

Dielectric elastomers have found interesting applications in soft loudspeakers,where vibrations subject to alternating electrical excitations are the key *** there are many t heore tical studies on the nonlinear vibrations of dielec trie elasto mers subject to electromechanical coupling loads,the systematic experimental research is *** this work,we design a simple experimental setup to observe the out-of-plane vibrations of a circular dielec trie elastomer *** find that the dielec trie elastomer has different response modes including the harmonic,super-harmonic and sub-harmonic responses at different excitation *** analyze the responses by using the short-time Fourier *** find that the equivalent voltage and the AC/DC ratio are the main parameters affecting the occurrence of sub-harmonic *** phenomenon of mode shift is also observed in our *** experimental observations provide a deeper unders tanding of the dynamic responses of dielec trie elasto mer subject to electromechanical loads.

关键词： Dielectric elastomer Nonlinear vibration Harmonic response Sub-harmonic response

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

Hot spot temperature prediction and operating parameter estimation of racks in data center using machine learning algorithms based on simulation data

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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 ***,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 ***,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 ***,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

Flow-Induced Vibration Fatigue Damage of A Pair of Flexible Cylinders in A Staggered Array

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China Ocean Engineering 2021年第6期35卷 878-890页

作者： XU Wan-hai LI Yu-han jia kun LAI jiang State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Nuclear Power Institute of China Chengdu 610041China

Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and *** a substantial number of studies have been devoted to assessing FIV response behaviours,fatigue damage features of staggered flexible cylinders are not fully ***,the wake-induced flutter constitutes an intricate hydrodynamic behaviour that frequently occurs when one cylinder is in the vicinity of another ***,existing studies on the fatigue damage caused by wake-induced flutter are incapable of achieving better *** paper,therefore,estimates the FIV fatigue damage of two staggered flexible cylinders with an aspect ratio of 350 and a mass ratio of 1.90 based on normal S−N curves according to Det Norske Veritas(DNV)*** staggered cases(cross-flow spacing ratios of 2.0,3.0,4.0,and 6.0 and in-line spacing ratios of 4.0,6.0,and 8.0)are discussed for comparison,and fatigue damage caused by wake-induced flutter is thoroughly *** damage results indicate that the variation of the cross-flow(CF)spacing ratio has a greater influence than that of the in-line(IL)spacing ratio on the CF fatigue damage of the upstream *** IL fatigue damages of the upstream cylinder are observed when reduced velocity V_(r)≥15.03 due to the wake flow patterns with different IL spacing ***,wake interference,especially wake-induced flutter,predominates the fatigue damage characteristics of the downstream *** V_(r)=8.77−11.27,wake-induced flutter enhances the IL fatigue damage of the downstream cylinder and slightly affects that of the upstream ***,wake-induced flutter causes considerable IL fatigue damage disparity between the two staggered cylinders by suppressing the IL fatigue damage of the upstream cylinder when V_(r)≥20.04.

关键词： flow-induced vibration fatigue damage flexible cylinder staggered arrangement wake-induced flutter

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 ***,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 ***,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 *** 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

Evaluation of Mining Titles Based on Option-Pricing Model

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Journal of China University of Mining and Technology 2006年第1期16卷 33-36页

作者： CHAO kun jia Jin-ling School of Management China University of Mining ＆ Technology Beijing 100083 China

Limitations exist in applying discounted cash flow and analogy sales methods to evaluate mining titles. In order to find a more appropriate way of evaluating mining titles, the Black-Scholes model is discussed in this paper. The authors pay particular attention to the determination of the time to maturity of the option on the basis of characteristics of the mining industry, pointing out that a reasonable time to maturity of the option should be the remaining time after deducting the essential time, needed by exploitation of the mineral resources within the mining property, from the life of the mining title. Several conclusions, related to the exercise of mineral resource management, are drawn from a case study analysis; extending the life of a mining title within a certain range could increase the revenue to the seller of the mining title. Application of the Black-Scholes model to evaluate mining titles would encourage an expansion of the scale of production.

关键词： Mining titles Option evaluation method Time to maturity of option

Crevice Corrosion Behaviors Between CFRP and Stainless Steel 316L for Automotive Applications

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Acta Metallurgica Sinica(English Letters) 2019年第10期32卷 1219-1226页

作者： Xia-Yu Wu jia-kun Sun jia-Ming Wang Yi-Ming jiang Jin Li Department of Materials Science Fudan University

Carbon fiber reinforced plastics (CFRP) are promising lightweight materials for vehicle applications. 316L is one of the most widely used types of austenite stainless steels and applied in lots of automotive applications. The existence of crevices will result in galvanic corrosion and crevice corrosion when CFRPs and 316L are directly connected. A crevice former for the galvanic system was therefore designed and applied to evaluate the crevice corrosion behaviors and study the mechanism of galvanic crevice corrosion through several electrochemical techniques in this research. The results showed that the crevice corrosion of galvanic systems grew from crevice mouth to the inside crevice and could be divided into four steps, metastable pitting corrosion at the crevice mouth, initiating step of crevice corrosion, propagating step and ending step of crevice corrosion. Because of the influences of the galvanic system, electrode reaction rates were speeded up and the passivation region was shortened at the initiating stage of crevice corrosion. Corrosion rate was observed to be higher in the galvanic system than that in normal crevice systems.

关键词： Crevice corrosion Galvanic system Carbon fiber reinforced plastics 316L stainless steels

Vortex-Induced Vibration Response Features of A Submarine Multi-Span Pipeline via Towing Tank Experimental Tests

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China Ocean Engineering 2023年第2期37卷 175-189页

作者： XU Wan-hai jia kun MA Ye-xuan SONG Zhi-you State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the structural vibration characteristics more complex, which may change the fatigue characteristics of the pipeline and affect the safety of the structure. In this paper, model tests were designed to explore the vortex-induced vibration(VIV) characteristics of multi-span pipelines and investigate the multi-span interaction mechanism. The experimental study mainly focused on the dynamic response of double-span pipelines, and further extended to triple-span pipelines, hoping that the results can be applied to more complex environment. The effects of span-length ratio, buried depth and axial force on VIV of the pipeline were investigated and discussed. The dynamic response of the pipeline varied with the span length. There was obvious interaction between different spans of multi-span pipelines, and the pipe-sediment interaction obviously affected the vibration characteristics of pipeline. The differences of pipeline burial depth and axial force changed the structural stiffness. With the increase of buried depth, the response amplitude presented a downward trend. The spanwise evolutions were asymmetric caused by the pipe-sediment interaction and multi-span interaction. The results can help to identify multi-span pipelines in engineering, and realize the prevention and control of free spans.

关键词： vortex-induced vibration submarine pipeline pipe-sediment interaction multi-span interaction

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 *** 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 *** 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 *** sentiment analysis,this study explores the evolution of international public opinion topics and sentiment differences among the above four Olympic *** 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