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Cyclic Gradient Methods for Unconstrained Optimization

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Journal of the Operations Research Society of China 2024年第3期12卷 809-828页

作者： ya Zhang Cong sun School of Science Beijing University of Posts and TelecommunicationsBeijing100876China

Gradient method is popular for solving large-scale *** this work,the cyclic gradient methods for quadratic function minimization are extended to general smooth unconstrained optimization *** with nonmonotonic line search,we prove its global ***,the proposed algorithms have sublinear convergence rate for general convex functions,and R-linear convergence rate for strongly convex *** experiments show that the proposed methods are effective compared to the state of the arts.

关键词： Gradient method Unconstrained optimization Nonmonotonic line search Global convergence

Holographic topological semimetals

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Science China(Physics,Mechanics & Astronomy) 2020年第5期63卷 6-30页

作者： Karl Landsteiner yan Liu ya-Wen sun instiuto de Fisica Teorica UAM/CSiC C/Nicolas Cabrera 13-15Campus CantoblancoCantoblanco 28049Spain Center for Gravitational Physics Department of Space ScienceBeihang UniversityBejing 100191China Key Laboratory of Space Environment Monitoring and information Processing Ministry of Indusry and Information Technology.Beijing 100191China School of Physics&CAS Center for Excllence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100049China Kavli institute for Theoretical Sciences University of Chinese Academy of SciencesBeijing 100049China

The holographic duality allows to construct and study models of strongly coupled quantum matter via dual gravitational *** general such models are characterized by the absence of quasiparticles, hydrodynamic behavior and Planckian dissipation times. One particular interesting class of quantum materials are ungapped topological semimetals which have many interesting properties from Hall transport to topologically protected edge states. We review the application of the holographic duality to this type of quantum matter including the construction of holographic Weyl semimetals, nodal line semimetals, quantum phase transition to trivial states(ungapped and gapped), the holographic dual of Fermi arcs and how new unexpected transport properties,such as Hall viscosities arise. The holographic models promise to lead to new insights into the properties of this type of quantum matter.

关键词： gauge/gravity duality topological semimetal Weyl semimetal anomaly

Stochastic P-bifurcations of a noisy nonlinear system with fractional derivative element

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Acta Mechanica Sinica 2021年第3期37卷 507-515,I0004页

作者： ya-Hui sun Yong-Ge yang Wei Xu School of Applied Mathematics Guangdong University of TechnologyGuangzhou 510520China Department of Applied Mathematics Northwestern Polytechnical UniversityXi'an 710072China

This paper investigates the stochastic P-bifurcation(SPB)of a fractionally damped oscillator subjected to additive and multiplicative Gaussian white *** transformation and the stochastic averaging technique are applied to derive the expression of probability density function(PDF)of the system *** conditions of the stochastic bifurcation induced by system parameters are presented based on the change in the number of extreme points of the probability density *** results are given to show the effectiveness of the proposed *** P-bifurcations for additive and multiplicative noise are studied in detail according to the critical conditions.

关键词： Stochastic P-bifurcation Fractional derivative Stochastic averaging method Gaussian white noise

Regional Multi-Agent Cooperative Reinforcement Learning for City-Level Traffic Grid Signal Control

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iEEE/CAA Journal of Automatica Sinica 2024年第9期11卷 1987-1998页

作者： Yisha Li ya Zhang Xinde Li Changyin sun School of Automation Southeast UniversityNanjing 210096 Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of EducationSoutheast UniversityNanjing 210096China

This article studies the effective traffic signal control problem of multiple intersections in a city-level traffic system.A novel regional multi-agent cooperative reinforcement learning algorithm called RegionSTLight is proposed to improve the traffic *** a regional multi-agent Q-learning framework is proposed,which can equivalently decompose the global Q value of the traffic system into the local values of several regions Based on the framework and the idea of human-machine cooperation,a dynamic zoning method is designed to divide the traffic network into several strong-coupled regions according to realtime traffic flow *** order to achieve better cooperation inside each region,a lightweight spatio-temporal fusion feature extraction network is *** experiments in synthetic real-world and city-level scenarios show that the proposed RegionS TLight converges more quickly,is more stable,and obtains better asymptotic performance compared to state-of-theart models.

关键词： Human-machine cooperation mixed domain attention mechanism multi-agent reinforcement learning spatio-temporal feature traffic signal control

内蒙古农牧交错区典型黑土坡耕地土壤侵蚀空间分布特征

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水土保持研究 2025年第1期32卷 13-20页

作者：邹惠杰刘刚舒成博孙波刘亚张琼郭珍中国科学院教育部水土保持与生态环境研究中心黄土高原土壤侵蚀与旱地农业国家重点实验室中国科学院水利部水土保持研究所中国科学院大学西北农林科技大学黄土高原土壤侵蚀与旱地农业国家重点实验室四川华标测检测技术有限公司

[目的]定量了解内蒙古典型黑土区土壤侵蚀速率，探究该区域土壤侵蚀空间分布特征，阐明土壤侵蚀坡面和区域空间分布规律，以期为区域水土流失治理提供参考。[方法]采集内蒙古农牧交错区（海拉尔区、额尔古纳市和牙克石市）典型黑土坡耕... 详细信息

[目的]定量了解内蒙古典型黑土区土壤侵蚀速率，探究该区域土壤侵蚀空间分布特征，阐明土壤侵蚀坡面和区域空间分布规律，以期为区域水土流失治理提供参考。[方法]采集内蒙古农牧交错区（海拉尔区、额尔古纳市和牙克石市）典型黑土坡耕地的土壤样品，利用137Cs示踪技术计算各采样点土壤侵蚀速率，结合小波分析的方法研究土壤侵蚀在坡面的分布特征。[结果]（1） 3个坡面所有采样点137Cs含量均小于背景值（1 984.24 Bq/m2）,表现为所有坡面土壤流失。（2） 3个地区的采样坡面平均侵蚀速率表现为：海拉尔[6 533.37 t/（km2·a）]>额尔古纳[4 174.35 t/（km2·a）]>牙克石[2 765.87 t/（km2·a）]。相同坡面的3个纵向断面的平均侵蚀速率相近，同一断面侵蚀速率的变异程度较高。（3）土壤侵蚀速率沿坡长呈强弱交替的周期性变化，但周期长度并不固定。大部分纵向断面存在周期长度为80～160 m和160～200 m的大小两个周期。部分纵向断面只存在一个周期长度为100～120 m的周期。[结论]该地区土壤侵蚀在坡面尺度表现为全坡面侵蚀且在纵向呈现周期性特征，在区域尺度呈现从东到西逐渐增加趋势。

关键词：土壤侵蚀典型黑土农牧交错带小波分析

Trusted GPSR protocol without reputation faking in VANET

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The Journal of China Universities of Posts and Telecommunications 2015年第5期22卷 22-31 55,55页

作者： Xiao ya Zheng Shihui sun Bin School of Computer Science Beijing University of Posts and Telecommunications

in vehicular ad hoc network(VANET), misbehaviors of internal nodes, such as discarding packets, may lead to a rapid decline in packet delivery ratio. To solve this problem, an improvement of greedy perimeter stateless routing(GPSR) protocol is presented. in the new protocol, trustworthiness is considered in the route selection process. The trustworthiness is measured by an objective trust model based on the subjective trust model Dy Trust. And the reputation value which reflects the trustworthiness of each node is calculated and broadcasted by the intersection nodes. Specially, besides resisting the packet-discarding behavior of selfish nodes, this protocol also includes a location detection process to resist the location-faking behavior of malicious nodes. As a result, the selfish nodes and the malicious nodes can be excluded from the network. in addition, compared with improved GPSR protocol, the presented one is able to resist one kind of reputation-faking attack and has better performance in simulation.

关键词： trusted routing protocol reputation model vehicula

Preparation of high-purity tellurium powder by hydrometallurgical method

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Rare Metals 2014年第4期33卷 479-484页

作者： Yuan Liu ya-Jie Zheng Zhao-Ming sun School of Metallurgy and Environment Central South University

This hydrometallurgical method consists of oxidation leaching, sulfide impurities removing, and sulfur dioxide reduction. The crude tellurium powder was treated by H2Oa oxidation for 2.0 h at pH 2.5 when adding 50 ml H2O2 （30 %） per 100 g raw material, a tellurium recover rate around 91% is achieved. The tellurium leaching ratio can reach 98.9 % under 3.75 mol.L-1 NaOH concentration in liquid-solid ratio of 5：1 at 80 ℃ for 1.5 h. The overall separation of tellurium and other heavy metals is optimum at sulfide dosages of about 1.1 times of the theoretical values. The removal rates of Ag, Ni, Pb, and Cu from the solution are greater than 99.8 %, and As and Se removal rates are 98.6 % and 97.2 %, respectively. Over 99.5 % tellurium can be recovered by SOu reaction when the operation is conducted at 85 ℃ in 6 mol.L-1 HC1 solution. The tellurium powder with size of 〈5 μm and purity of 〉99.999 % is obtained.

关键词： High purity Tellurium powder Hydrometallurgical method

Effect of wide-spectrum pulsed magnetic field on grain refinement of pure aluminium

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China Foundry 2023年第1期20卷 40-48页

作者： ya-ming Bai Gang Li ya-wei sun Yong-yong Gong Qi-jie Zhai College of Science Shanghai University99 Shangda RoadShanghai 200444China Center for Advanced Solidification Shanghai University99 Shangda RoadShanghai 200444China School of Materials Science and Engineering Shanghai University99 Shangda RoadShanghai 200444China

A wide-spectrum pulsed magnetic field(WSPMF)was obtained by adjusting the number of current pulses and the pulse interval between adjacent *** effect of WSPMF on the grain refinement of pure aluminium was *** distribution of electromagnetic force and flow field in the melt under the WSPMF was simulated to reveal the grain refining *** show that the grain refinement is attributed to the combined effect of the melt flow and oscillation under a *** the pulse interval is 5 ms,the extreme value of electromagnetic force is the highest,and the size of the crystal nucleus is 0.35 *** the case of similar flow rates,the grain size gradually decreases as the pulse interval *** range of the harmonic frequency of the magnetic field gradually expands with the increase of the pulse interval,which can provide more energy for nucleation at the solid-liquid interface and promote nucleation.

关键词： wide-spectrum pulsed magnetic field forced flow grain refinement frequency components

Pore Engineering for Covalent Organic Framework Membranes

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Chemical Research in Chinese Universities 2022年第2期38卷 364-372页

作者： yaO Jin LU ya sun Huihui ZHAO Xin Key Laboratory of Synthetic and Self-assembly Chemistry for Organic Functional Molecules Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032P.R.China School of Chemistry and Materials Science Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024P.R.China College of Chemistry and Materials Science Shanghai Normal UniversityShanghai 200234P.R.China

Membrane technology is of particular significance for the sustainable development of society owing to its potential capacity to tackle the energy shortage and environmental *** materials are the core part of membrane *** have always been pursuing predictable structures of advanced membrane materials,which provides a possibility to fully unlock the potential of *** organic frameworks(COFs),with the advantage of controllable pore microenvironment,are considered to be promising candidates to achieve this design *** customizable function of COF membranes through pore engineering does well in the enhancement of selective permeability performance,which offers COF membranes with great application potentials in separation and transportation *** this context,COF-based membranes have been developed rapidly in recent ***,we present a brief overview on the strategies developed for pore engineering of COF membranes in recent years,including skeleton engineering,pore surface engineering,host-guest chemistry and membrane ***,the features of transmission or separation of molecules/ions based on COF membranes and corresponding applications are also *** the last part,the challenges and prospects of the development of COF membranes are discussed.

关键词： Membrane technology Covalent organic framework(COF) Pore engineering Separation ion transportation