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Self-heating Probe Instrument and Method for Measuring High Temperature Melting Volume Change Rate of Material

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 371-376页

作者： wang junwei wang Zhiping LU Yang CHENG Bo College of Materials Science and Engineering Lanzhou University of Technology State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials Lanzhou University of Technology Renewable Energy Laboratory Lanzhou University of Technology

The castings defects are affected by the melting volume change rate of material. The change rate has an important effect on running safety of the high temperature thermal storage chamber, too. But the characteristics of existing measuring installations are complex structure, troublesome operation and low precision. In order to measure the melting volume change rate of material accurately and conveniently, a self-designed measuring instrument, self-heating probe instrument, and measuring method are described. Temperature in heating cavity is controlled by PID temperature controller; melting volume change rate υ and molten density are calculated based on the melt volume which is measured by the instrument. Positive and negative υ represent expansion and shrinkage of the sample volume after melting, respectively. Taking eutectic LiF＋CaF2 for example, its melting volume change rate and melting density at 1 123 K are -20.6% and 2 651 kg/m–3 measured by this instrument, which is only 0.71% smaller than literature value. Density and melting volume change rate of industry pure aluminum at 973 K and analysis pure NaCl at 1 123 K are detected by the instrument too. The measure results are agreed with report values. Measuring error sources are analyzed and several improving measures are proposed. In theory, the measuring errors of the change rate and molten density which are measured by the self-designed instrument is nearly 1/20-1/50 of that measured by the refitted mandril thermal expansion instrument. The self-designed instrument and method have the advantages of simple structure, being easy to operate, extensive applicability for material, relatively high accuracy, and most importantly, temperature and sample vapor pressure have little effect on the measurement accuracy. The presented instrument and method solve the problems of complicated structure and procedures, and large measuring errors for the samples with high vapor pressure by existing installations.

关键词： high temperature volume expansion rate molten density measuring instrument measuring method

Synthesis,structural characterization and properties of a 3D infinitely extended structural rare earth coordination compound of K_3{[Sm(H_2O)_7]_2Na[α-SiW_(11)O_(39)Sm(H_2O)_4]_2}·14 H_2O

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Science China Chemistry 2005年第4期48卷 343-351页

作者： wang Jingping ZHAO junwei NIU Jingyang Institute of Molecule and Crystal Engineering School of Chemistry and Chemical EngineeringHenan UniversityKaifeng 475001China Institute of Molecule and Crystal EngineeringSchool of Chemistry and Chemical EngineeringHenan UniversityKaifeng 475001China Institute of Molecule and Crystal EngineeringSchool of Chemistry and Chemical EngineeringHenan UniversityKaifeng 475001China

A 3D infinitely extended structural rare earth coordination compound with a formula of K3{[Sm(H2O)7]2Na[a-SiW11O39Sm(H2O)4]2}·14H2O has been synthesized by reaction of Sm2O3,HClO4,NaOH with a-K8SiW11O39·nH2O,and characterized by IR,UV spectra,ICP,TG-DTA,cyclic voltammetry,variable-temperature magnetic susceptibility and X-ray single-crystal diffrac-tion.X-ray single-crystal diffraction indicates that the title compound crystallizes in a triclinic lat-tice,Pi space group,with a = 1.2462(3) nm,b = 1.2652(3) nm,c = 1.8420(4) nm,α = 87.45(3)°,β = 79.91(3)°,γ = 82.57(3)°,Z = 1,R1 = 0.0778,wR2 = *** analysis reveals that Sm3+(1) coordination cation has incorporated into the vacant site of [α-SiW11O39]8? entity,forming the [α-SiW11O39Sm(H2O)4]5? *** two adjacent [a-SiW11O39Sm(H2O)4]5? subunits are combined with each other through two Sm(1)-O-W bridges accompanying the formation of dim-mer structural unit [α-SiW11O39Sm(H2O)4]210? of the title *** neighboring dimmer structural units [α-SiW11O39Sm(H2O)4]210? are linked to form the 1D chainlike structure by means of two Sm3+(2) and a Na+(1) coordination *** K+(1) cations connect the 1D packing chains constructing the 2D netlike structure,and adjacent netlike layers are also grafted by K+(2) cations to build the novel 3D infinitely extended *** result of TG-DTA curves manifests that the decomposition temperature of the title polyanionic framework is 554℃.The cyclic volt-ammetry measurements show that the title polyanion has the two-step redox processes in aqueous solution with pH = *** temperature magnetic susceptibility indicates the title compound obeys the Cruie-Weiss Law in the higher temperature range from 110 to 300 K,while in the lower temperature range from 2 to 110 K the comparatively strong antiferromagnetism in-teractions can be observed.

关键词： silicotungstic acid, Keggin structure, crystal structure, polyoxometalates, rare earth metal.

Request pattern change-based cache pollution attack detection and defense in edge computing

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Digital Communications and Networks 2023年第5期9卷 1212-1220页

作者： junwei wang Xianglin Wei Jianhua Fan Qiang Duan Jianwei Liu Yangang wang The 63rd Research Institute National University of Defense TechnologyNanjing210007China

Through caching popular contents at the network edge,wireless edge caching can greatly reduce both the content request latency at mobile devices and the traffic burden at the core ***,popularity-based caching strategies are vulnerable to Cache Pollution Attacks(CPAs)due to the weak security protection at both edge nodes and mobile *** CPAs,through initiating a large number of requests for unpopular contents,malicious users can pollute the edge caching space and degrade the caching *** paper firstly integrates the dynamic nature of content request and mobile devices into the edge caching framework,and introduces an eavesdroppingbased CPA ***,an edge caching mechanism,which contains a Request Pattern Change-based Cache Pollution Detection(RPC2PD)algorithm and an Attack-aware Cache Defense(ACD)algorithm,is proposed to defend against *** results show that the proposed mechanism could effectively suppress the effects of CPAs on the caching performance and improve the cache hit ratio.

关键词： Mobile edge computing Cache pollution attack Flash crowd

Feedback control design with vibration suppression for flexible air-breathing hypersonic vehicles

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Science China(Information Sciences) 2014年第3期57卷 249-262页

作者： GAO Yan WU HuaiNing wang junwei GUO Lei Science and Technology on Aircraft Control Laboratory School of Automation Science and Electrical EngineeringBeihang University

This paper investigates the problem of feedback control design with vibration suppression for a flexible air-breathing hypersonic vehicle(FAHV).FAHV includes intricate coupling between the engine and flight dynamics,as well as complex interplay between flexible and rigid modes,which results in an intractable system for the control *** this paper,a longitudinal model,which is described by a coupled system of ordinary diferential equations(ODEs)and partial diferential equations(PDEs),is ***,a linearized ODE model for the rigid part is established around the trim condition,while vibration of the fuselage is described by ***,based on the Lyapunov direct method,a control law via ODE state feedback and PDE boundary output feedback is designed for the system such that the closed-loop exponential stability is ***,simulation results are given to illustrate the efectiveness of the proposed design method.

关键词： flexible air-breathing hypersonic vehicle(FAHV) Euler-Bernoulli beam vibration suppression Lyapunov direct method boundary control

Theoretical Analysis of Annular Elliptic Finned Tube Evaporative Condenser Based on Field Measurement

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Journal of Thermal Science 2020年第5期29卷 1355-1369页

作者： GU Yaxiu wang junwei wang Xinru Ll Mohua PAN Song LIU Guangdong wang Wentao GING Zexiang Department of Building Environment and Energy Engineering School of Civil EngineeringChang'an UniversityXi'an 710061China Research Centre for Fluid and Thermal Engineering Department of Architectural and Built EnvironmentUniversity of Nottingham Ningbo ChinaNingbo 315100China College of Architecture and Civil Engineering Beijing University of TechnologyBeijing 100124China

In this article,a new evaporative condenser with an annular elliptic firmed tube heat exchanger that includes a round inner tube and elliptic outer finned tube was designed and *** refrigerant flows between the round inner tube and the elliptic outer tube,and it simultaneously exchanges heat with the cooling water in the inner tube,the spray water,and the cooling air flowing past the outer *** field measurement for the traditional round finned tube evaporative condenser in the Futong Metro Station of Line 14 in Beijing,China,the theoretical heat transfer performance of the annular elliptic finned tube evaporative condenser was analyzed and *** with a round finned tube heat exchanger,the heat exchange capacity of the annular elliptic finned tube increased by 2.34%to 9.28%;the total heat transfer coefficient increased by 47.42%,and the power consumption of the fan in the air-conditioning system with an annular elliptic finned tube heat exchanger decreased by 11.18%to 14.65%.Therefore,the energy-saving performance and the heat transfer performance of the new annular elliptic finned tube heat exchanger were enhanced compared to the round finned tube heat exchanger.

关键词： evaporative condenser finned tube heat exchanger annular elliptic tube heat transfer enhancement air-conditioning system metro station

Modeling of the resilient supply chain system from a perspective of production design changes

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Frontiers of Engineering Management 2023年第1期10卷 96-106页

作者： Shuangshuang ZHANG Hongfeng wang Guo LI junwei wang College of Information Science and Engineering Northeastern UniversityShenyang 110819China School of Management and Economics Beijing Institute of TechnologyBeijing 100081China Department of Industrial and Manufacturing System Engineering The University of Hong KongHong KongChina

Building an effective resilient supply chain system (RSCS) is critical and necessary to reduce the risk of supply chain disruptions in unexpected scenarios such as COVID-19 pandemic and trade wars. To overcome the impact of insufficient raw material supply on the supply chain in mass disruption scenarios, this study proposes a novel RSCS considering product design changes (PDC). An RSCS domain model is first developed from the perspective of PDC based on a general conceptual framework, i.e., function-context-behavior-principle-state-structure (FCBPSS), which can portray complex systems under unpredictable situations. Specifically, the interaction among the structure, state and behavior of the infrastructure system and substance system is captured, and then a quantitative analysis of the change impact process is presented to evaluate the resilience of both the product and supply chain. Next, a case study is conducted to demonstrate the PDC strategy and to validate the feasibility and effectiveness of the RSCS domain model. The results show that the restructured RSCS based on the proposed strategy and model can remedy the huge losses caused by the unavailability of raw materials.

关键词： resilient supply chain supply chain disruption domain modeling product design changes

Building a Cloud-Based Energy Storage System through Digital Transformation of Distributed Backup Battery in Mobile Base Stations

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China Communications 2020年第4期17卷 42-50页

作者： Song Ci Yanglin Zhou Yuan Xu Xingjian Diao junwei wang Department of Electrical Engineering Tsinghua UniversityBeijing 100084China Shanghai Institute of Microsyst&Information Technology CASShanghai 200050China Guangzhou Power Supply Bureau Guangdong Power Grid Co.LtdGuangzhou 510620China Department of Computer Science University of PittsburghPA15260USA China Tower Company Limited Guangzhou518000China School of Information Science&Technology ShanghaiTech UniversityShanghai 200210China University of Chinese Academy of Sciences Beijing100039China

Battery energy storage systems(ESS) have been widely used in mobile base stations(BS) as the main backup power source. Due to the large number of base stations, massive distributed ESSs have largely stayed in idle and very difficult to achieve high asset utilization. In recent years, the fast-paced development of digital energy storage(DES) technology has revolutionized the traditional operation and maintenance of ESSs by transforming them into digital assets, further enabling battery energy storage services, raising up a new way to achieve a much higher utilization of such kind of largely idle ESS resources. In this paper, the disruptive DES technology will be introduced and its application under the context of mobile BSs will be studied, and then a cloud-based energy storage(CES) platform is proposed based on a large scale distributed DESs to provide a new cyber-enabled energy storage service to the local utility company. A real-world case study shows the effectiveness and efficiency of the CES platform.

关键词： digital energy storage dynamic reconfigurable battery network energy digitization software-defined battery system cloud energy storage

A proof of image Euler Number formula

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Science in China(Series F) 2006年第3期49卷 364-371页

作者： LIN Xiaozhu SHA Yun JI junwei wang Yanmin Information Engineering School Beijing Institute of Petrochemical Technology Beijing 102617 China

Euler Number is one of the most important characteristics in topology. In twodimension digital images, the Euler characteristic is locally computable. The form of Euler Number formula is different under 4-connected and 8-connected conditions. Based on the definition of the Foreground Segment and Neighbor Number, a formula of the Euler Number computing is proposed and is proved in this paper. It is a new idea to locally compute Euler Number of 2D image.

关键词： topology Euler Number binary image 4-connected 8-connected.

Propane Aromatization over Mo/HZSM-5 Catalysts

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Journal of Natural Gas Chemistry 2002年第1期11卷 43-50页

作者： junwei wang Maoqing Kang Zhixin Zhang Xinkui wang Institute of Coal Chemistry Chinese Academy of SciencesTaiyuan 030001China

Impregnation, mechanical mixing and hydrothermal treatment methods were used to introduce molybdenum species into the HZSM-5 zeolite. The structure and surface acidity of the catalysts were studied by means of XRD, FT-IR, NH3-TPD, TPR and XPS. The effects of Mo content and reaction time on stream on the aromatization of propane were investigated. It was found that the performance of the Mo/HZSM-5 catalyst prepared by the hydrothermal treatment method was much better than that of the other two catalysts. For example, under the reaction conditions of 823 K and 600 h-1, propane conversion and aromatics selectivity over the catalyst prepared by hydrothermal pretreatment could reach 89.17% and 78.56%, respectively. XRD and XPS results showed that the Mo species in the catalysts prepared by hydrothermal treatment were highly dispersed on the surface of the HZSM-5, and larger amounts of them could penetrate into the HZSM-5 channel, as compared with the other two kinds of catalysts. These factors may be responsible for their high activities for propane aromatization. IR and NH3-TPD studies indicated that the number of Bronsted acid centers decreased and the Lewis acid centers increased after Mo was introduced into the HZSM-5 zeolite.

关键词： Mo/HZSM-5 propane aromatization preparation hydrothermal treatment