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Nearly degenerate ground states of a checkerboard antiferromagnet and their bosonic interpretation

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Science china(Physics,Mechanics & Astronomy) 2024年第1期67卷 84-89页

作者： Haiyuan Zou Fan yang wei Ku key Laboratory of Polar Materials and Devices(MOE) School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241China Department of Physics Beijing Institute of TechnologyBeijing 100081China Tsung-Dao Lee Institute Shanghai 200240China key Laboratory of Artificial Structures and Quantum control(Ministry of Education) Shanghai 200240China Shanghai Branch Hefei National LaboratoryShanghai 201315China

The spin-1/2.model system with antiferromagnetic(AF) couplings on a J1-J2.heckerboard lattice, known as the planar pyrochlore model, is strongly frustrated and associated with a two-to-one dimensional crossover. Using the Projected Entangled Simplex states tensor network ansatz, we identify a large number of nearly degenerate states in the frustrated region(J_(1)2.).Specifically, we find the long-sought crossed-dimer valence bond solid(VBS) state to be the ground state at J_(1)≤J_(2., while various 1D AF correlated states take over the rest. We verify the stability of the VBS state against nematic perturbation. The corresponding bosonic picture provides an intuitive understanding of the low-energy physics. Particularly, it predicts weaker VBS states in the easy-plane limit, which we confirm numerically. Our results clarify the most essential ground state properties of this interesting system and demonstrate the usefulness of bosonic picture in dealing with frustrated magnetism.

关键词： tensor networks frustrated magnetism dimensional crossover degenerate states

Solving the constrained shortest path problem using random search strategy

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Science china(Technological Sciences) 2010年第12期53卷 3258-3263页

作者： LI KePing, GAO ZiYou , TANG Tao & yang LiXing state {2. Laboratory of rail traffic control and safety, beijing jiaotong university, beijing 100044, china 1. state key Laboratory of {2. traffic control and safety Beijing Jiaotong University Beijing 100044 China

In this paper, we propose an improved walk search strategy to solve the constrained shortest path problem. The proposed search strategy is a local search algorithm which explores a network by walker navigating through the network. In order to analyze and evaluate the proposed search strategy, we present the results of three computational studies in which the proposed search algorithm is tested. Moreover, we compare the proposed algorithm with the ant colony algorithm and k shortest paths algorithm. The analysis and comparison results demonstrate that the proposed algorithm is an effective tool for solving the constrained shortest path problem. It can not only be used to solve the optimization problem on a larger network, but also is superior to the ant colony algorithm in terms of the solution time and optimal paths.

关键词： constrained shortest path deterministic random walk optimization

Urban expressway traffic state forecasting based on multimode maximum entropy model

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Science china(Technological Sciences) 2010年第10期53卷 2808-2816页

作者： SUN XiaoLiang1,2. JIA LiMin1, DONG HongHui1, QIN Yong1 & GUO Min3 1state key Laboratory of {2. traffic control and safety, beijing jiaotong university, beijing 100044, china 2.chool of traffic and Transportation, beijing jiaotong university, beijing 100044, china 3beijing traffic Management Bureau, beijing 100044, china 1. state key Laboratory of {2. traffic control and safety Beijing Jiaotong University Beijing 100044 China2. School of Traffic and Transportation Beijing Jiaotong University Beijing 100044 China3. Beijing Traffic Management Bureau Beijing 100044 China

The accurate and timely traffic state prediction has become increasingly important for the traffic participants,especially for the traffic managements. In this paper,the traffic state is described by Micro-LOS,and a direct prediction method is introduced. The development of the proposed method is based on Maximum Entropy (ME) models trained for multiple modes. In the Multimode Maximum Entropy (MME) framework,the different features like temporal and spatial features of traffic systems,regional traffic state are integrated simultaneously,and the different state behaviors based on 14 traffic modes defined by average speed according to the date-time division are also dealt with. The experiments based on the real data in beijing expressway prove that the MME models outperforms the already existing model in both effectiveness and robustness.

关键词： traffic state forecast maximum entropy model multimode

Optimization model and algorithm for mixed traffic of urban road network with flow interference

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Science china(Technological Sciences) 2008年第12期51卷 2213-2222页

作者： SI BingFeng,LONG JianCeng & GAO ZiYou state key Laboratory of {2. traffic control and safety,beijing jiaotong university,beijing 100044,china state key Laboratory of {2. traffic control and safety Beijing Jiaotong University Beijing 100044 China

In this paper,the problem of interferences between motors and non-motors in urban road mixed traffic network is considered and the corresponding link impedance function is presented based on travel *** the base of this,the main factors that influence travelers' traffic choices are all considered and a combined model including flow-split and assignment problem is *** a bilevel model with its algorithm for system optimization of urban road mixed traffic network is *** the application of the model and its algorithm is illus-trated with a numerical example.

关键词： mixed traffic impedance function user equilibrium optimization

Decoding algorithms for shortened-extended turbo product codes in WiMAX systems

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Science in china(Series F) 2009年第12期52卷 2415-2423页

作者： XU ChangLong1,3,4, yang wei1,2.& YE {2.Chen4 1 state key Laboratory of Networking and Switching Technology, beijing university of Posts and Telecommunications, beijing 100044, china 2.state key Laboratory of rail {12. control and safety, beijing jiaotong university, beijing 100044, china 3 National Mobile Communications Research Laboratory, Southeast university, Nanjing 2.0096, china 4 Intel Corporation, beijing Kerry Center, Guanghua Road 1, beijing 10002., china state key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100044 China state key Laboratory of {2. traffic control and safety Beijing Jiaotong University Beijing 100044 China National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China Intel Corporation Beijing Kerry Center Guanghua Road 1 Beijing 100020 China

The component codes of turbo product codes in WiMAX systems are extended Hamming codes and single parity check codes as well as their shortened forms, In this paper, three novel iterative decoding algorithms based on Chase, MAP algorithms and their combination are proposed for shortened-extended turbo product codes. The iterative decoding algorithm based on Chase algorithm is proposed to reduce the decoding complexity without any performance loss. An efficient MAP algorithm is then proposed to decode the component codes of shortened single parity check codes and shortened-extended Hamming codes. A comprehensive performance comparison of the proposed decoding schemes is conducted for three typical classes of turbo product codes in WiMAX OFDMA systems. The suitable decoding algorithms are recommended for different classes based on the simulation results.

关键词： block code product code iterative decoding

Dynamic-based model for calculating the boulder impact force in debris flow

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Journal of Mountain Science 2024年第6期21卷 1930-1940页

作者： yang Chaoping ZHANG Shaojie YIN Yueping yang Hongjuan {2. Fangqiang state key Laboratory of Mountain Hazards and Engineering Resilience Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610299China university of Chinese Academy of Sciences Beijing 100049China china Institute of Geological Environment Monitoring Beijing 100081China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China Chongqing School University of Chinese Academy of SciencesChongqing 400714China

The boulder impact force in debris flow is generally calculated by static methods such as the cantilever beam ***,these methods cannot describe the dynamic scenario of boulder collision on structures,so the inertia and damping effects of the structures are not involved causing an overestimation on the boulder impact *** order to address this issue,a dynamic-based model for calculating the boulder impact force of a debris flow was proposed in this study,and the dynamic characteristics of a cantilever beam with multiple degrees of freedom under boulder collision were *** using the drop-weight method to simulate boulders within debris flow,seven experiments of drop-weight impacting the cantilever beam were used to calibrate the error of the dynamicbased *** indicate that the dynamic-based model is able to reconstruct the impact force history on the cantilever beam during impact time and the error of dynamic-based model is 15.3%in calculating boulder impact force,significantly outperforming the cantilever beam model’s error of 2.5%.Therefore,the dynamic-based model can overcome the drawbacks of the static-based models and provide a more reliable theoretical foundation for the engineering design of debris flow {2. structures.

关键词： Debris flow Impact force Boulder collision Dynamic-based model Engineering design

Superior piezoelectric performance with high operating temperature in bismuth ferrite-based ternary ceramics

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Journal of Materials Science & Technology 2024年第2期169卷 172-181页

作者： Yunyao Huang Leiyang Zhang Ruiyi Jing yang yang Vladimir Shur Xiaoyong wei Li Jin Electronic Materials Research Laboratory Key Laboratory of the Ministry of EducationSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Faculty of Materials and Manufacturing Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaBeijing University of TechnologyBeijing 100124China School of Natural Sciences and Mathematics Ural Federal UniversityEkaterinburg620000Russia

Due to the thermal depolarization effect,adequate piezoelectric performance with high operating temperature is regarded to be challenging to accomplish concurrently in piezoceramics for applications in specific piezoelectric *** this work,we synthesized(0.8−x)BiFeO_(3)-x PbTi_(3)-0.2.a(Zr_(0.2.)Ti_(0.75))O_(3)(abbreviated as BFO-x PT-BZT)ternary solid solutions with 0.15≤x≤0.30 by conventional solid-state reaction *** MPB composition with a coexisting state of rhombohedral-tetragonal phases exhibits enhanced electromechanical properties,including Curie temperature of 380℃,large-signal equivalent piezoelectric coefficient d^(∗)_(33)of 395 pm V^(-1),small-signal piezoelectric coefficient d_(33)of 302.pC N^(-1),and electromechanical coupling factor k_(p)of 50.2.,which is comparable to commercial PZT-5A ceramics,indicating potential in high-temperature ***,in-situ X-ray diffraction(XRD)and piezoelectric force microscopic(PFM)techniques demonstrate that multiphase coexistence and complex nanodomains promote piezoelectric response via *** x=0.2. composition exhibits the highest in-situ d_(33)of 577 pC N^(-1)and good temperature stability in 30−2.0℃,indicating that BZT-modified BFO-PT ceramics are promising candidates for high-temperature piezoelectric devices.

关键词： High-temperature piezoelectrics Morphotropic phase boundary In-situ technique Domain structure BFO

Micromechanism and mathematical model of stress sensitivity in tight reservoirs of binary granular medium

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Petroleum Science 2024年第3期21卷 1780-1795页

作者： Jian-Bang Wu Sheng-Lai yang Qiang Li Kun yang Can Huang Dao-Ping Lv {2. Zhou state key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing2249China Laboratoire de G eologie Ecole Normale Sup erieure/CNRS UMR8538PSL Research UniversityParis75005France Research Institute of Exploration and Development Xinjiang Oilfield CompanyKaramay834000XinjiangChina

Research on reservoir rock stress sensitivity has traditionally focused on unary granular structures,neglecting the binary nature of real reservoirs,especially tight *** the stresssensitive behavior and mathematical characterization of binary granular media remains a challenging *** this study,we conducted online-NMR experiments to investigate the permeability and porosity evolution as well as stress-sensitive control mechanisms in tight sandy conglomerate *** results revealed stress sensitivity coefficients between 0.042.and 0.098 and permeability damage rates ranging from 65.6%to 90.9%,with an average pore compression coefficient of 0.0168—0.02.8 MPa ***-scale compression occurred in three stages:filling,compression,and compaction,with matrix pores playing a dominant role in pore *** stress sensitivity of binary granular media was found to be influenced by the support structure and particle *** stress sensitivity was associated with small fine particle size,high fines content,high uniformity coefficient of particle size,high plastic deformation,and low Young's ***-supported samples exhibited a high irreversible permeability damage rate(average=74.2.)and stress sensitivity coefficients(average=0.089),with pore spaces more *** contrast,grain-supported samples showed low stress sensitivity coefficients(average=0.02.)at high stress *** on the experiments,we developed a mathematical model for stress sensitivity in binary granular media,considering binary granular properties and nested interactions using Hertz contact deformation and Poiseuille *** describing the change in activity content of fines under stress,we characterized the non-stationary state of compressive deformation in the binary granular structure and classified the reservoir into three *** model was applied for production prediction using actual data from the Mahu reservoir in {2.,showing that the e

关键词： Stress sensitivity Binary granular medium Tight reservoir Online-NMR Reservoir energy retention rate

A review on Bi_(2.WO_(6)-based photocatalysts synthesis, modification, and applications in environmental remediation, life medical, and clean energy

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Frontiers of Environmental Science & Engineering 2024年第7期18卷 87-108页

作者： wei Mao Xuewu Shen Lixun Zhang yang Liu Zehao Liu Yuntao Guan Guangdong Provincial Engineering Technology Research Center for Urban Water Cycle and Water Environment safety Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China state Environmental Protection key Laboratory of Microorganism Application and Risk {2. School of EnvironmentTsinghua UniversityBeijing 100084China

Photocatalysis has emerged a promising strategy to remedy the current energy and environmental crisis due to its ability to directiy convert clean solar energy into chemical *** tungstate(Bi_(2.WO_(6))has been shown to be an excellent visible light response,a well-defined perovskite crystal structure,and an abundance of oxygen atoms(providing efficient channels for photogenerated carrier transfer)due to their suitable band gap,effective electron migration and separation,making them ideal *** has been extensively applied as photocatalyst in aspects including pollutant removal,carbon dioxide reduction,solar hydrogen production,ammonia synthesis by nitrogen photocatalytic reduction,and cancer *** this review,the fabrication and application of Bi_(2.WO_(6) in photocatalysis were comprehensively *** photocatalytic properties of BizwO-based materials were significantly enhanced by carbon modification,the construction of heterojunctions,and the atom doping to improve the photogenerated carrier migration rate,the number of surface active sites,and the photoexcitation ability of the *** addition,the potential development directions and the existing challenges to improve the photocatalytic performance of Bi_(2.WO_(6)-based materials were discussed.

关键词： Bismuth tungstate Synthesis and modification Photocatalytic application Environmental remediation Clean energy Medical science