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The Minimax Estimator of Stochastic Regression Coefficients and Parameters in the Class of All Estimators

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Acta Mathematica Sinica,English Series 2007年第3期23卷 497-506页

作者： Li wen xu Song Gui WANG Department of Mathematics Tsinghua University Beijing 100084 P. R. China College of Applied Sciences Beijing University of Technology Beijing 100022 P. R. China College of Applied Sciences Beijing University of Technology Beijing 100022. P. R. China

In this paper, the authors address the problem of the minimax estimator of linear combinations of stochastic regression coefficients and parameters in the general normal linear model with random effects. Under a quadratic loss function, the minimax property of linear estimators is investigated. In the class of all estimators, the minimax estimator of estimable functions, which is unique with probability 1, is obtained under a multivariate normal distribution.

关键词： minimax estimator stochastic regression coefficients quadratic loss function normal linear model

Optimizing Photovoltaic Performance by Kinetic Quenching of Layered Heterojunctions

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Chinese Journal of Polymer Science 2022年第1期40卷 29-37页

作者： Li-Feng xu Zhan-wen xu Jia-Ping Lin Li-Quan Wang Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials of Ministry of EducationSchool of Materials Science and EngineeringEast China University of Science and TechnologyShanghai 200237China

The mixing morphology control plays a crucial role in photovoltaic power generation,yet this specific effect on device performances remains ***,we employed computational approaches to delineate the photovoltaic properties of layered heterojunction polymer solar cells with tunable mixing ***-step quench and two-step quench strategies were proposed to adjust the mixing morphology by thermodynamic and kinetic *** computation for the one-step quench revealed that modulating interfacial widths and interfacial roughness could significantly promote the photovoltaic performance of layered heterojunction polymer solar *** two-step quench can provide a buffer at a lower temperature before the kinetic quenching,leading to the formation of small-length-scale islands connected to the interface and a further increase in photovoltaic *** discoveries are supported by recent experimental evidence and are anticipated to guide the design of photovoltaic materials with optimal performance.

关键词： Dissipative particle dynamics Drift-diffusion model Polymer solar cells Quench

Subcarrier assignment considering path loss for multiuser OFDM systems with proportional fairness

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The Journal of China Universities of Posts and Telecommunications 2008年第2期15卷 12-17,25页

作者： xu wen-jun HE Zhi-qiang School of Information Engineering Beijing University of Posts andTelecommunications Beijing 100876 China

This article studies downlink subcarrier assignment problem to maximize rate-sum capacity subject to total power and proportional rate constraints in orthogonal frequency division multiplexing （OFDM） systems. Previous algorithms assume that the initial power is equally distributed over all subcarriers. The presence of path loss makes the assumption not correct any more. This article proposes a novel subcarrier assignment algorithm which makes full use of path loss and rate proportionality information to improve rate-sum capacity. The proposed algorithm determines optimal initial power allocation according to path losses and rate proportionalities of different users, assigns subcarriers to users in a greedy fashion, and then exchanges subcarfiers between users to obtain fairer rate distribution. Simulation results show that the proposed algorithm approximately achieves double the capacity of static assignment schemes, such as fixed frequency band approach, and obtains better performance than previous subcarrier assignment algorithms in the presence of different path losses and proportional rate requirements..

关键词： OFDM subcarrier assignment path loss

Temporal Skewness of Electromagnetic Pulsed Waves Propagating Through Random Media with Ebedded Irregularity slab

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Chinese Physics Letters 2003年第3期20卷 370-373页

作者： xu Zheng-wen Wu Jian Huo wen-Ping Wu Zhen-Sen School of Science Xidian University Xi'an 710071 National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave Propagation Beijing 102206

Electromagnetic pulsed waves can be distorted in the propagation through random media, and their energy distributions change along the leading and trailing edge of the waveform, which can be presented by the temporal skewness. The skewness presents asymmetry and is treated by the third-order temporal moment, in which an analytic solution for the two-frequency mutual coherence function is obtained recently. Then, transionospheric pulses are discussed in details. Both theoretical analysis and numerical computation indicate that the contributions from scattering and dispersion of irregularities dominate over those of background, so the latter can be neglected in most cases. Also, the temporal skewness of a transionospheric pulse is negative and energy is shifted to the leading edge.

关键词： Random processes

Dynamic Positioning Capability Analysis for Marine Vessels Based on A DPCap Polar Plot Program

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China Ocean Engineering 2018年第1期32卷 90-98页

作者： WANG Lei YANG Jian-min xu Sheng-wen State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Shipand Deep-Sea Exploration(CISSE) Shanghai 200240China

Dynamic positioning capability(DPCap) analysis is essential in the selection of thrusters, in their configuration, and during preliminary investigation of the positioning ability of a newly designed vessel dynamic positioning *** analysis can help determine the maximum environmental forces, in which the DP system can counteract in given headings. The accuracy of the DPCap analysis is determined by the precise estimation of the environmental forces as well as the effectiveness of the thrust allocation logic. This paper is dedicated to developing an effective and efficient software program for the DPCap analysis for marine vessels. Estimation of the environmental forces can be obtained by model tests, hydrodynamic computation and empirical formulas. A quadratic programming method is adopted to allocate the total thrust on every thruster of the vessel. A detailed description of the thrust allocation logic of the software program is given. The effectiveness of the new program DPCap Polar Plot(DPCPP)was validated by a DPCap analysis for a supply vessel. The present study indicates that the developed program can be used in the DPCap analysis for marine vessels. Moreover, DPCap analysis considering the thruster failure mode might give guidance to the designers of vessels whose thrusters need to be safer.

关键词： DPCap analysis thrust allocation logic quadratic programming method

Trace Semantics and Algebraic Laws for Total Store Order Memory Model

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Journal of Computer Science & Technology 2021年第6期36卷 1269-1290页

作者： Li-Li Xiao Hui-Biao Zhu Qi-wen xu Shanghai Key Laboratory of Trustworthy Computing East China Normal UniversityShanghai 200062China Department of Computer and Information Science Faculty of Science and TechnologyUniversity of Macao MacaoChina

Modern multiprocessors deploy a variety of weak memory models(WMMs).Total Store Order(TSO)is a widely-used weak memory model in SPARC implementations and x86 *** omits the store-load constraint by allowing each core to employ a write *** this paper,we apply Unifying Theories of Programming(abbreviated as UTP)in investigating the trace semantics for TSO,acting in the denotational semantics style.A trace is expressed as a sequence of snapshots,which records the changes in registers,write buffers and the shared *** the valid execution results containing reorderings can be described after kicking out those that do not satisfy program order and modification *** paper also presents a set of algebraic laws for *** study the concept of head normal form,and every program can be expressed in the head normal form of the guarded choice which is able to model the execution of a program with *** the linearizability of the TSO model is ***,we consider the linking between trace semantics and algebraic *** linking is achieved through deriving trace semantics from algebraic semantics,and the derivation strategy under the TSO model is provided.

关键词： weak memory model Total Store Order(TSO) trace semantics algebraic law Unifying Theories of Programming(UTP)

Novel hydrophobically associative polyacrylamide with tunable viscosity

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Chinese Chemical Letters 2009年第11期20卷 1361-1365页

作者： xu Feng Zhang wen Hui Wu School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 China

Hydrophobically associative polyacrylamide （HAPAM） were prepared in aqueous solution by radical copolymerization of novel cationic surface-active monomer, dimethylhexadecyl（3-acrylamidopropyl）ammonium bromide （DMHAB）, with acrylamide （AM） in the presence of DMHAB/CTAB mixed micelles. The length of hydrophobic microblock （NH） in HAPAM is controlled by the molar fraction of DMHAB in mixed micelles, which can be mediated by the ratio of CTAB to DMHAB. The results of steady-state fluorescence probe and viscometry experiments showed the ability of HAPAM association was determined by the length of the hydrophobic microblock. HAPAM with tunable association ability are promising materials for thickening agent.

关键词： Hydrophobically associative polyacrylamide Surface-active monomer Mixed micelles Hydrophobic association

Preparation and Electrochemical Performance of Cobalt-free Cathode Material Ba0.5Sr0.5Fe0.9Nb0.1O3-δ for Intermediate-temperature Solid Oxide Fuel Cells

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Chemical Research in Chinese Universities 2014年第5期30卷 806-810页

作者： LONG wen xu Huawei HE Tianmin Key Laboratory of Physics and Technology for Advanced Batteries Ministry of Education College of Physics Jilin University Changchun 130012 P. R. China

Perovskite oxide Ba0.5Sr0.5Fe0.9Nb0.1O3-δ（BSFN） as a cobalt-free cathode for intermediate-temperature solid oxide fuel cells（IT-SOFCs） on the Ce0.5Sm0.2O1.9（SDC） and La0.9Sr0.1Ga0.8Mg0.23O3-δ（LSGM） electrolytes was prepared and investigated. The single phase BSFN oxide with a cubic perovskite structure and relatively high elec- trical conductivities was obtained after sintering at 1250℃ for 10 h in air. The BSFN cathode exhibited excellent chemical stability on the SDC and LSGM electrolytes at temperatures below 950 ℃. The area specific resistance of the BSFN cathode on the SDC and LSGM electrolytes were 0.024 and 0.021 Ω·cm2 at 800℃, respectively. The maximum power densities of the single cell with BSFN cathode in 300 μm-thick SDC and LSGM electrolytes achieved 414 and 516 mW/cm2 at 800℃, respectively. These results show that the BSFN material is a promising co- bait-free cathode candidate to be used in IT-SOFCs. A combination of the BSFN cathode and LSGM electrolyte is preferred owing to its excellent electrochemical performance.

关键词： Solid oxide fuel cell Cathode Phase formation Chemical stability Electrochemical performance

Adipose-derived mesenchymal stem cells accelerate nerve regeneration and functional recovery in a rat model of recurrent laryngeal nerve injury

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Neural Regeneration Research 2017年第9期12卷 1544-1550页

作者： Yun Li wen xu Li-yu Cheng Department of Otorhinolaryngology-Head Neck Surgery Beijing Tong Ren Hospital Capital Medical University Key Laboratory of Otorhinolaryngology-Head Neck Surgery Ministry of Education

Medialization thyroplasty or injection laryngoplasty for unilateral vocal fold paralysis cannot restore mobility of the vocal fold. Recent studies have shown that transplantation of mesenchymal stem cells is effective in the repair of nerve injuries. This study investigated wheth- er adipose-derived stem celt transplantation could repair recurrent laryngeal nerve injury. Rat models of recurrent laryngeal nerve injury were established by crushing with micro forceps. Adipose-derived mesenchymal stem cells （ADSCs; 8 ×105） or differentiated Schwann-like adipose-derived mesenchymal stem cells （dADSCs; 8×105） or extracellular matrix were injected at the site of injury. At 2, 4 and 6 weeks post-surgery, a higher density of myelinated nerve fiber, thicker myelin sheath, improved vocal fold movement, better recovery of nerve conduction capacity and reduced thyroarytenoid muscle atrophy were found in ADSCs and dADSCs groups compared with the extracellu- lar matrix group. The effects were more pronounced in the ADSCs group than in the dADSCs group. These experimental results indicated that ADSCs transplantation could be an early interventional strategy to promote regeneration after recurrent laryngeal nerve injury.

关键词： nerve regeneration mesenchymal stem cell transplantation adipose-derived mesenchymal stem cells recurrent laryngeal nerve larynx nerve injury functional recovery vocal fold cell differentiation neural regeneration