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Second-order schemes for solving decoupled forward backward stochastic differential equations

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Science China Mathematics 2014年第4期57卷 665-686页

作者： zhaO weidong LI Yang FU Yu School of Mathematics Shandong University College of Science University of Shanghai for Science and Technology

In this paper,by using trapezoidal rule and the integration-by-parts formula of Malliavin calculus,we propose three new numerical schemes for solving decoupled forward-backward stochastic differential *** theoretically prove that the schemes have second-order convergence *** demonstrate the effectiveness and the second-order convergence rate,numerical tests are given.

关键词： forward backward stochastic differential equations second-order scheme error estimate trape-zoidal rule Malliavin calculus

Frequency Offset Compensation for Satellite Communication System with CE-OFDM

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China Communications 2017年第8期14卷 93-104页

作者： Gaofeng Cui Cheng Wang weidong Wang Yinghai zhang Key Laboratory of Universal Wireless Communications Ministry of Education Information&Electronics Technology Lab School of Electronic EngineeringBeijing University of Posts and Telecommunications

Constant envelope orthogonal frequency division multiplexing(CE-OFDM) is a waveform that can achieve 0d B peak-to-average power ratio and avoid the signal distortion caused by the nonlinear power amplifi er. However, the carrier frequency offset(CFO) in CE-OFDM systems can cause errors at phase unwrapper module. In this paper, a CFO estimation scheme is proposed for CEOFDM in satellite communication system. As the null subcarrier is inherent in the conjugate symmetric symbol structure at the transmitter, the proposed scheme uses the null subcarrier as prior information to estimate the CFO at the receiver. The ideal estimation range of normalized CFO is obtained by mathematical analysis. Simulation results show that the proposed scheme can estimate the CFO accurately under additive white Gaussian noise(AWGN) channel and multipath fading channel, especially for moderate and high signal-to-noise ratio(SNR).

关键词： CE-OFDM carrier frequency offset null subcarrier satellite communication

A resilient trust management scheme for defending against reputation time-varying attacks based on BETA distribution

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Science China(Information Sciences) 2017年第4期60卷 60-70页

作者： weidong FANG Wuxiong zhaNG Yang YANG Yang LIU Wei CHEN Key Laboratory of Wireless Sensor Network & Communication Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai Research Center for Wireless Communication School of Computer Science and Technology China University of Mining and Technology

Compared with the encryption and the authentication which can prevent the external attacks,the trust management schemes are the better approaches for defending against the internal attacks in wireless sensor network(WSN). The reputation time-varying(RTV) attacks are internal attacks. In the reputation timevarying attacks, the reputation value of nodes is manipulated to adjust dynamically by the compromised nodes or malicious attackers. Hence, these attacks have greater covert and invasive. In this paper, we propose a Timewindow-based Resilient Trust Management Scheme(TRTMS) to defend against the reputation time-varying attacks in wireless sensor network. In this scheme, based on BETA distribution, the behaviors of compromised nodes are analyzed for a period of time, and then the difference judgment and the trend analysis are utilized to identify the abnormality of nodes’ reputation value, meanwhile, the control factor Fc and the time window are introduced to verify and remove the compromised modes from the suspected malicious nodes, which refer to those nodes’ reputation value changes are caused by the wireless channel changes. The result of simulation shows that our proposed scheme can defend reputation time-varying attacks effectively and it is convenient to implement.

关键词： wireless sensor network(WSN) reputation time-varying attack trust value trust management time window

EXTENDED CLUSTERING COEFFICIENTS：GENERALIZATION OF CLUSTERING COEFFICIENTS IN SMALL-WORLD NETWORKS

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Journal of Systems Science and Systems Engineering 2007年第3期16卷 370-382页

作者： Wenjun XIAO Wenhong WEI weidong CHEN Yong QIN Behrooz PARHAMI Department of Computer Science South China University of Technology Guangzhou 510641 China Department of Electrical & ComputerEngineering University of California Santa Barbara CA 93106-9560 USA

The clustering coefficient C of a network, which is a measure of direct connectivity between neighbors of the various nodes, ranges from 0 （for no connectivity） to 1 （for full connectivity）. We define extended clustering coefficients C（h） of a small-world network based on nodes that are at distance h from a source node, thus generalizing distance-1 neighborhoods employed in computing the ordinary clustering coefficient C = C（1）. Based on known results about the distance distribution Pδ（h） in a network, that is, the probability that a randomly chosen pair of vertices have distance h, we derive and experimentally validate the law Pδ（h）C（h） ≤ c log N / N, where c is a small constant that seldom exceeds 1. This result is significant because it shows that the product Pδ（h）C（h） is upper-bounded by a value that is considerably smaller than the product of maximum values for Pδ（h） and C（h）. Extended clustering coefficients and laws that govern them offer new insights into the structure of small-world networks and open up avenues for further exploration of their properties.

关键词： Clustering coefficient small-world extended clustering coefficient distance distribution

Yield anisotropy and tension/compression asymmetry of a Ni_3 Al based intermetallic alloy

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Chinese Journal of Aeronautics 2013年第3期26卷 801-806页

作者： Chen Lei Wen weidong Cui Haitao zhang Hongjian Xu Ying College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics

In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were cut from a sheet with different angles inclined from the solidification direction. The inclined angles were taken to be 0 , 22.5 , 45 , 67.5 and 90 . All experiments were conducted at room temperature except for orientation 0 , whose deformation temperatures ranged from 298 to 1273 K. Experimental results show that the yield strength of alloy IC10 has the anomalous behavior which has been observed for other Ll 2 -long-range ordered intermetallic alloys, but it is less pronounced. The abnormalities show the following characteristics：（i） the yield strength increases as the temperature is raised below the peak temperature, （ii） yield strength anisotropy, （iii） tension/compression asymmetry. Compared to Ni 3 Al single crystals, the polycrystalline exhibits some different yielding behaviors which may be due to the high volume fraction of c phase.

关键词： Alloy IC10 Critical resolved shear stress (CRSS) Intermetallics Ni 3 Al-based superalloy Plastic anisotropy t/c Asymmetry

Phase Structure and Electrochemical Properties of Rare Earth Based Hydrogen Storage Alloys

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Journal of Rare Earths 2004年第Z1期22卷 228-231页

作者： Chen weidong Liu Xiangdong Liu Xiao Che Guangdong School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China

The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this *** Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and then to change the phase structure, the influences of phase structure on the electrochemical properties were *** results indicate that the main phase of all alloys is LaNi5 with CaCu5 type structure and the crystal lattices constants of LaNi5 are changed with increasing x value, i.e, decreased a-axis, increased c-axis and axis ratio and nonlinear decreased crystal *** crystal volume of the alloy with x = 0.3 is larger than *** is second phase A1LaNi4 in alloys when x≥0.3, which decrease the discharge capacity, but increase the cycling stability and high rate discharge *** comprehensively, the alloy with x = 0.3 shows the higher discharge capacity and the better cycling stability.

关键词： rare earth based hydrogen storage alloy phase structure activation discharge capacity cycling stability high rate discharge ability

Photoluminescent properties of tunable green-emitting oxynitride （Baa-xSrx）Si6012N2 ：Eu2＋ phosphor and its application in white LEDs

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Journal of Rare Earths 2013年第10期31卷 944-949页

作者： Guantong CHEN weidong ZHUANG Ronghui LIU Yuanhong LIU Yunsheng HU Huaqiang HE National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous Metals Grirem Advanced Materials Co. Ltd. Beijing 100088 China

Green emitting Eu2＋-doped （Ba3_xSrx）Si6012N2 solid solutions were synthesized through solid state reaction at 1350 ℃ for 10 h under a N2/H2 atmosphere. The XRD patterns revealed that the solid solution series of （Ba3 x-ySrx）Si6Ol2N2：yEu2＋ with x value ranging from 0-0.6 were established. An efficient and intense tunable green light was observed by varying the cation Sr/Ba ratio. The emission spectra exhibited an entire shift towards long wavelength with increasing ofx value, which was caused by large crystal field splitting and Stokes shift. The x value dependence of emission intensity was discovered and explained by the enhanced probability of electron from excited 4f state to 5d ground state via nonradioactive transition. Highly thermal stability and feasible color coordinates were verified. White LEDs with excellent photochromic properties were fabricated by packing GaN based blue chips and （Ba Sr）3Si6012N2：Eu2＋ phosphors. All results indicated that the （Ba3_xSrx）SirO12N2：Eu2＋ phosphors were confirmed to be a promising candidate for pc-white LEDs in solid state lighting.

关键词： oxynitride phosphor solid solution white LEDs rare earths

Phase Equilibrium Characteristics of CO_(2)and Ionic Liquids with[FAP]-Anion Used for Absorption-Compression Refrigeration Working Pairs

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Journal of Thermal Science 2021年第1期30卷 165-176页

作者： WU weidong WANG Li LI Xiang LIU Hui zhaNG Hua DOU Binlin School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

The study of the phase equilibrium characteristics of CO_(2)-ionic liquids(ILs)as new absorption-compression type refrigeration working pairs is of great *** kinds of ILs,i.e.,[emim][FAP],[bmim][FAP]and[hmim][FAP],were chosen as potential *** solubility of CO_(2)in these ILs was measured experimentally within 0 to 5.0 MPa at temperatures of 293.15 K to 333.15 K,and the effects of temperature,pressure,IL anion and cation structure and stirring action on CO_(2)solubility were also discussed and *** results showed that the longer alkyl chains in an identical IL family,the alkyl fluoride group in IL anions and the stirring action by a magnetic stirrer had positive effects on the solubility of CO_(2).In the three ILs,[hmim][FAP]possessed the best performance for CO_(2)absorption;the solubility of CO_(2)reached 0.7641 at a pressure of 5 MPa and temperature of 293.15 K,the maximum solubility measured in this *** CO_(2)-[hmim][FAP]binary mixture is recommended as a potentially applicable working pair for CO_(2)absorption-compression refrigeration systems.

关键词： CO_(2) ionic liquids(ILs) absorption-compression refrigeration working pair phase equilibrium tris(perfluoroalkyl)trifluorophosphate anions([FAP]^(-))

Diagenesis of shale and its control on pore structure, a case study from typical marine, transitional and continental shales

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Frontiers of Earth Science 2021年第2期15卷 378-394页

作者： weidong XIE Meng WANG Hua WANG Ruying MA Hongyue DUAN School of Earth Resources China University of GeosciencesWuhan 430074China Low Carbon Energy Institute China University of Mining and TechnologyXuzhou 221008China College of Geology and Mining Engineering Xinjiang UniversityUrumqi 830000China

Due to discrepancies in pore structure,the productivity of shale gas reservoirs under different diagenesis stages varies *** study discussed the controlling of sedimentation and diagenesis on shale pore structure in typical marine,transitional,and continental shales,*** shale samples from the Shuinan Formation,Jiaolai Basin,transitional shale samples from the Taiyuan,Shanxi and Xiashihezi Formations,Ordos Basin,and marine shale samples from the Longmaxi Formation,Sichuan Basin,were *** electron microscope with argon ion polishing,high-pressure mercury injection,and low-temperature nitrogen adsorption experiments were conducted to acquire pore structure *** the diagenetic stage of the reservoir was classified according to thermal maturity,organic geochemical parameters,and mineral *** results exhibit that continental,transitional,and marine shales are period A,period B of the middle diagenetic stage,and the late diagenetic stage,*** pore structure,micropore(0–2 nm)and mesopore(2–50 nm)controlled pore volume and specific surface area of transitional and marine shales,and specific surface area of continental shale have similar results,while micropore,mesopore,and macropore(>50 nm)all have a significant proportion of pore volume in continental *** pore structure characteristics and controlling factors exhibit a pronounced difference in different diagenesis stages,the compaction and cementation in period A of the middle diagenesis stage is relatively weak,intergranular pore and interlayer pore of clay minerals are well preserved,and moldic pore and dissolved pore developed as well;organic matter is in high maturity in period B of the middle diagenesis stage,organic matter pore developed correspondingly,while the intergranular pore developed poorly affected by compaction,notably,the carbonate is negligible in transitional shale,and the interlayer pore of clay minerals are well preserved

关键词： shale gas reservoirs diagenesis stage pore structure controlling factors