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An Approximation Algorithm for the Generalized Prize-Collecting Steiner Forest Problem with Submodular Penalties

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Journal of the Operations Research Society of China 2022年第1期10卷 183-192页

作者： Xiao-dan jia Bo Hou Wen Liu School of Mathematical Sciences Hebei Normal UniversityShijiazhuang 050024HebeiChina

In this paper,we consider the generalized prize-collecting Steiner forest problem with submodular penalties(GPCSF-SP problem).In this problem,we are given an undirected connected graph G=(V,E)and a collection of disjoint vertex subsets V={V_(1),V_(2),…,V_(l)}.Assume c:E→R_(+)is an edge cost function andπ:2^(V)→R_(+)is a submodular penalty *** objective of the GPCSF-SP problem is to find an edge subset F such that the total cost including the edge cost in F and the penalty cost of the subcollection S containing these Vi not connected by F is *** using the primal-dual technique,we give a 3-approximation algorithm for this problem.

关键词： Generalized prize-collecting Steiner forest problem Submodular function Primal-dual algorithm

Nanostructured lubricant additives for titanium alloy:Lubrication by the solid-liquid interface with Coulomb repulsion

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Friction 2024年第7期12卷 1564-1579页

作者： Linlin DUAN dan jia jian LI jianfang LIU Haitao DUAN State Key Laboratory of Special Surface Protection Materials and Application Technology Wuhan Research Institute of Materials ProtectionWuhan 430030China Hubei Longzhong Laboratory Xiangyang 441000China College of Life Science and Technology Wuhan Polytechnic UniversityWuhan 430030China

In this work,the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid–liquid nanosized contact interface is taken,and the superior friction-reducing property of Cu_(3)(PO_(4))2·3H_(2)O(CuP)oil-based additives has been confirmed for titanium ***-dimensional(3D)CuP nanoflowers(CuP-Fs)with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating *** by CuP-Fs additives for titanium alloy,friction coefficient(COF)can be reduced by 73.68%,and wear rate(WR)reduced by 99.69%.It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid–liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil ***,any steric hindrance or connection between this repulsive solid–liquid interface will trigger the adhesion and increase the viscous shear force,for example,dispersant,hydrogen bondings,and shaky adsorbed water ***,the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological *** the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.

关键词： lubrication nanomaterial additive solid-liquid interface wear

Multiple Mobile Sinks Data Dissemination Mechanism for Large Scale Wireless Sensor Network

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China Communications 2014年第A01期11卷 1-8页

作者： XIE Dongliang WU Xiaojie LI dan SUN jia StateKeyLaboratoryofNetworkingandSwitchingTechnology BeijingUniversityofPostsandTelecommunicationsBeijing100876China.

WSN has been developing from traditional environment monitoring applications to the ubiquitous information services such as the Congestion-oriented Intelligent Transportation System （ColTS）. However, the mobility of nodes makes data dissemination a hard nut to crack. In this paper, we propose MSDD, a multiple mobile sinks data dissemination mechanism for solving the dissemination problem. The main ideas of MSDD are constructing a two-tier grid structure by a designated sink, exploiting a hierarchical monitoring mechanism, and employing a global agent to track the sink locations in order to make the emergencies reported to the sinks immediately, In addition, MSDD supports the query-driven data dissemination. Being compared with TTDD, MSDD is theoretically proved to have less communication overhead. We also validate MSDD outperforms TTDD in reliability and the emergency delivery latency bv simulations.

关键词： ubiquitous information services multiple-mobile sink hierarchical monitoring two-tier grid global agent query-driven

Vacuum joints of dispersion-strengthened copper and its applications in synchrotron radiation front end

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Nuclear Science and Techniques 2016年第6期27卷 74-78页

作者： Yong-Jun Li Song Xue Min Zhang dan-dan jia Dong-Bai Dou Yu Gao Shanghai Institute of Applied Physics Chinese Academy ofSciencesZhangJiangShanghai 201204China University of Chinese Academy of Sciences Beijing 100049China SKY Technology Development Co. LtdChinese Academyof SciencesShenyang 110179China

Masks are critical elements of synchrotron radiation front end that are exposed to high temperature and *** absorber material is typically comprised of dispersion-strengthened copper,which can retain high performance at elevated *** processes under vacuum,including brazing and electron beam welding,are novel approaches for prolonging the absorber and for reducing power *** mechanical properties of brazed joints and electron beam welded joints of dispersion-strengthened copper workpieces are evaluated by tensile testing at 20,100,and 200 *** testing results indicate that the tensile strength and elongation of both vacuum joints decrease with increasing *** to brazed joints,electron beam welded joints have higher tensile strength,better ductility,and more stable performance.A novel welded mask with a total length of 600 mm is presented and shown to be practical for use in the highest heat load front end in the Shanghai synchrotron radiation facility phase-Ⅱ beamline project.

关键词：上海同步辐射装置弥散强化铜焊接接头前端真空电子束焊接应用钎焊接头

New embedded DDSCR structure with high holding voltage and high robustness for 12-V applications

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Chinese Physics B 2020年第10期29卷 550-555页

作者： Jie-Yu Li Yang Wang dan-dan jia Wei-Peng Wei Peng Dong School of Physics and Optoelectronics Xiangtan UniversityXiangtan 411105China Hunan Engineering Laboratory for Microelectronics Optoelectronics and System on A ChipXiangtan 411105China SuperESD Microelectronics Technology CO. LTD.Changsha 410100China

A new dual directional silicon-controlled rectifier based electrostatic discharge (ESD) protection device suitable for 12-V applications is proposed in this paper. The proposed device (NPEMDDSCR) is based on the embedded DDSCR (EMDDSCR) structure, in which the P+ electrode and P+ injection are removed from the inner finger. Compared with the conventional modified DDSCR (MDDSCR), its high holding voltage meets the requirements for applications. Compared with the embedded DDSCR (EMDDSCR), it has good conduction uniformity. The MDDSCR, EMDDSCR, and NPEMDDSCR are fabricated with an identical width in a 0.5-μm CDMOS process. In order to verify and predict the characteristics of the proposed ESD protection device, a transmission line pulse (TLP) testing system and a two-dimensional device simulation platform are used in this work. The measurements demonstrate that the NPEMDDSCR provides improved reliability and higher area efficiency for 12 V or similar applications. The measurement results also show that the NPEMDDSCR provides higher robustness and better latch-up immunity capability.

关键词： DDSCR holding voltage failure current conduction uniformity

Minority carrier lifetime evaluation of periphery edge region in high-performance multicrystalline ingot produced by seed-assisted directional solidification

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Frontiers of physics 2017年第5期12卷 91-97页

作者： Zhong Li jia-dan Li Lin Zhuang Rui-jiang Hong College of Physics and Electronic Information Engineering Qinghai Nationalities University Xining 810007 China Guangdong Provincial Key Laboratory of Photovoltaic Technology School of Physics Sun Yat-sen University Guangzhou 510006 China

A high-performance multicrystalline silicon （mc-Si） ingot was produced by seed-assisted directional solidification, and the minority carrier lifetime of the periphery edge region was evaluated. The defects and impurities in the periphery edge region of the silicon wafers were systematically studied with photoluminescence （PL） imaging, minority carrier lifetime mapping, and Fourier transform infrared （FTIR） spectroscopy. Their relationships with the minority carrier lifetime were investigated. The concentration of substitutional carbon, interstitial oxygen, and dislocation clusters is not directly correlated with the low minority carrier lifetime of the edge zone of the mc-Si ingot. Inhomogeneous grain size distribution and contamination with iron impurities were demonstrated to be the main factors affecting the low minority carrier lifetime. By controlling the impurities and improving the grain size distribution, a modified furnace was designed and a higher-quality mc-Si ingot was manufactured.

关键词： minority carrier lifetime periphery edge seed-assisted directional solidification defects impurity

Fluorescence Emission from Small Molecules Containing Amino Group

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Chinese Chemical Letters 2006年第4期17卷 502-504页

作者： Dong Jun WANG dan dan jia Yong Guang ZHAO Xi Hai SHEN Yue Dong YANG Hebei Normal University of Science and Technology Department of Chemistry Qinhuangdao 066600

After the treatment of oxygen gas, the small molecules containing amine group could emit fluorescence. Oxidation was believed to play an important role in the formation of fluorescence centers. Compared to previous re... 详细信息

关键词： Fluorescence amine oxidation oxygen.

Motor oil degradation during urban cycle road tests

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Friction 2021年第5期9卷 1002-1011页

作者： Lei WEI Haitao DUAN Yongliang JIN dan jia Bingxue CHENG jianfang LIU jian LI State Key Laboratory of Special Surface Protection Materials and Application Technology Wuhan Research Institute of Materials ProtectionWuhan 430030China College of Mechanical Engineering Hunan Institute of Science and TechnologyYueyang 414006China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China College of Biological and Pharmaceutical Engineering Wuhan Polytechnic UniversityWuhan 430023China

Several civilian vehicles in China operate in urban traffic conditions and have their motor oil changed every 5,000 *** study investigates the variations in oil properties after servicing at 5,000 km,based on systematic road tests(including a repeated test,a parallel test,and a new vehicle test).The physicochemical properties,changes in components,oxidation stability,detergent‐dispersant performance,and tribological properties of motor oils were *** results showed that the total acid number(TAN)of oils increased with the operation mileage,by up to 1.41 mgKOH/*** total base number(TBN)decreased after the road tests were completed,and the decrease was less than 44.6%.The kinematic viscosity(KV)of most oils decreased initially and then stabilized in the middle stage,before starting to increase later in the *** change in KV at 100℃was less than 15.96%.The oxidation onset temperature(OOT)of the oils diminished gradually with the operation *** OOT values of the used oils were higher than 210℃.A spot test indicated that the used oils retained their detergentdispersant performance to an appropriate *** four‐ball wear scar diameters and friction coefficient of the used oils did not increase significantly after the road tests were *** study can serve as a reference for end‐users when changing motor oils.

关键词： motor oil urban vehicles oil degradation road test oil analysis

Experimental investigation of propagation mechanisms and fracture morphology for coalbed methane reservoirs

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Petroleum Science 2018年第4期15卷 815-829页

作者： Chi Ai Xiao-Xuan Li Jun Zhang dan jia Wen-Jing Tan College of Petroleum Engineering Northeast Petroleum University College of Geoscience and Technology China University of Petroleum (East China)

Fracture propagation mechanisms in coalbed methane(CBM) reservoirs are very complex due to the development of the internal cleat system. In this paper, the characteristics of initiation and propagation of hydraulic fractures in coal specimens at different angles between the face cleat and the maximum horizontal principal stress were investigated with hydraulic fracturing tests. The results indicate that the interactions between the hydraulic fractures and the cleat system have a major effect on fracture networks. "Step-like’’ fractures were formed in most experiments due to the existence of discontinuous butt cleats. The hydraulic fractures were more likely to divert or propagate along the butt cleat with an increase in the angles and a decrease in the horizontal principal stress difference. An increase in the injection rate and a decrease in the fracturing fluid viscosity were more conducive to fracture networks. In addition, the influence on fracture propagation of the residual coal fines in the wellbore was also studied. The existence of coal fines was an obstacle in fracturing, and no effective connection can be formed between fractures. The experimental investigation revealed the fracture propagation mechanisms and can provide guidance for hydraulic fracturing design of CBM reservoirs.

关键词： Coalbed methane reservoir Butt cleat Propagation mechanisms Fracture morphology Step-like fractures