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Joint synchronization estimation based on genetic algorithm for OFDM/OQAM systems

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Journal of Systems Engineering and Electronics 2020年第4期31卷 657-665页

作者： LIU Yongjin CHEN Xihong zhao Yu Air and Missile Defense College Air Force Engineering UniversityXi’an 710051China

This paper investigates the problem of synchronization for offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) systems based on the genetic algorithm. In order to increase the spectrum efficiency,an improved preamble structure without guard symbols is derived at first. On this basis, instead of deriving the log likelihood function of power spectral density, joint estimation of the symbol timing offset and carrier frequency offset based on the preamble proposed is formulated into a bivariate optimization problem. After that, an improved genetic algorithm is used to find its global optimum solution. Conclusions can be drawn from simulation results that the proposed method has advantages in the joint estimation of synchronization.

关键词： offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) synchronization joint estimation genetic algorithm

Long-term adaptive evolution of Shewanella oneidensis MR-1 for establishment of high concentration Cr(Ⅵ) tolerance

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Frontiers of Environmental Science & Engineering 2020年第1期14卷 65-75页

作者： Yong Xiao Changye Xiao Feng zhao CAS key Laboratory of Urban Pollutant Conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China

Acclimation is the main method to enhance the productivity of microorganisms in environmental biotechnology,but it remains uncertain how microorganisms acquire resistance to high concentrations of pollutants during long-term *** oneidensis MR-1 was acclimated for 120 days with increasing hexavalent chromium(Cr(VI))concentrations from 10 to 190 mg/*** bacterium was able to survive from the highly toxic Cr(VI)environment due to its enhanced capability to reduce Cr(VI)and the increased cell membrane *** sequenced 19 complete genomes from 7 populations of MR-1,including the ancestral strain,the evolved strains in Cr(VI)environment on days 40,80 and 120 and their corresponding controls.A total of 27,49 and 90 single nucleotide polymorphisms were found in the Cr(VI)-evolved populations on days 40,80 and 120,*** substitutions were clustered according to gene functions,and the gene mutations related to integral components of the membrane,including efflux pumps and transporters,were the key determinants of chromate *** addition,MR-1 strengthened the detoxification of Cr(VI)through gene variations involved in adenosine triphosphate binding,electron carrier activity,signal transduction and DNA *** results provide an in-depth analysis of how Cr(VI)resistance of *** MR-1 is improved by acclimation,as well as a genetic understanding of the impact of longterm exposure of microorganisms to pollution.

关键词： Environmental biotechnology Acclimation Chromate resistance Efflux pumps Detoxification

面向SDN的脆弱性扩散形式化建模与扩散因素分析

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计算机研究与发展 2018年第10期55卷 2256-2268页

作者：王健赵国生赵中楠李可哈尔滨理工大学计算机科学与技术学院哈尔滨150080 哈尔滨师范大学计算机科学与信息工程学院哈尔滨150025

SDN将传统网络控制面与转发面解耦,在实施集中化管控的同时引入诸多新的安全和管理问题.脆弱点类型在SDN各层及南北向接口存在差异性,且传播趋势不同.针对脆弱性在SDN层内及层间的扩散效果及抑制策略问题,提出了一种基于Bio-PEPA的SDN... 详细信息

SDN将传统网络控制面与转发面解耦,在实施集中化管控的同时引入诸多新的安全和管理问题.脆弱点类型在SDN各层及南北向接口存在差异性,且传播趋势不同.针对脆弱性在SDN层内及层间的扩散效果及抑制策略问题,提出了一种基于Bio-PEPA的SDN脆弱性扩散形式化模型.1)对Bio-PEPA基础语义进行讨论,阐明其适用于具有明显分层架构的SDN及具有动态性的脆弱性扩散过程;2)探讨SDN中各层存在的脆弱性问题,并对SDN中存在的脆弱性以层为单位进行建模,通过对SDN层内及层间脆弱性扩散过程构建形式化模型,进而分析SDN内脆弱性在水平(层内)及垂直(层间)2个维度内的扩散机理,从而更好地抑制脆弱性在SDN内的扩散;3)通过仿真实验得出可以通过降低连接转化率、提升检测转化率及修复转化率来有效抑制SDN的脆弱性扩散.

关键词：软件定义网络 Bio-PEPA 形式化建模脆弱性扩散抑制策略

Friction and wear behavior of different seal materials under water-lubricated conditions

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Friction 2021年第4期9卷 697-709页

作者： Weigang zhao Guoyuan ZHANG Guangneng DONG School of Astronautics Northwestern Polytechnical UniversityXi’an 710072China School of Mechano-Electronic Engineering Xidian UniversityXi'an 710071China key Laboratory of Modern Design and Rotor-bearing System of Ministry of Education Xi’an Jiaotong UniversityXi’an 710049China

The shaft mechanical face seal in a high-speed turbopump of a liquid rocket engine often operates under extremely harsh *** example,a low-temperature and low-viscosity fluid(such as liquid oxygen or liquid hydrogen)is used as a *** performance of the seal rings,especially the friction and wear behavior,directly determines whether the seal functions *** this study,the friction and wear behavior of several ring materials are tested using a pin-on-disk tribo-tester,and the wear morphology of the ring is *** friction coefficients(COFs)and mass-wear rates under dry-friction and water-lubricated conditions,which are used to simulate low-viscosity conditions,are *** results show that at a pressure-velocity(PV)value of 2.4 MPa-(m/s),the COF between the copper graphite(stator)and copper-chrome alloy disk(rotor)is low(with a value of 0.18)under the dry-friction conditions,and the 5-min wear mass of the copper graphite is approximately 2 *** the water-lubricated conditions,compared with other materials(such as copper-chrome alloy,S07 steel,alumina ceramic coating,and nickel-based calcium fluoride),the S07 steel with a diamond-like carbon film is preferred for use in a high-speed turbopump under extreme *** results of this study can provide theoretical and experimental guidance in the design of mechanical face seals in liquid rocket engines.

关键词： friction wear mechanical face seal water-lubricated high-speed turbopump

On PID Control Theory for Nonaffine Uncertain Stochastic Systems

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Journal of Systems Science & Complexity 2023年第1期36卷 165-186页

作者： ZHANG Jinke zhao Cheng GUO Lei key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Mathematical Science University of Chinese Academy of SciencesBeijing 100049China

PID(proportional-integral-derivative)control is recognized to be the most widely and successfully employed control strategy by ***,there are limited theoretical investigations explaining the rationale why PID can work so well when dealing with nonlinear uncertain *** paper continues the previous researches towards establishing a theoretical foundation of PID control,by studying the regulation problem of PID control for nonaffine uncertain nonlinear stochastic *** be specific,a three dimensional parameter set will be constructed explicitly based on some prior knowledge on bounds of partial derivatives of both the drift and diffusion *** will be shown that the closed-loop control system will achieve exponential stability in the mean square sense under PID control,whenever the controller parameters are chosen from the constructed parameter ***,similar results can also be obtained for PD(PI)control in some special cases.A numerical example will be provided to illustrate the theoretical results.

关键词： Asymptotically regulation global stability nonaffine PID control stochastic systems uncertain structure

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柔性直流配电系统高频突变量距离保护

电工技术学报 2020年第2期35卷 383-394页

作者：贾科赵其娟冯涛赵冠琨毕天姝新能源电力系统国家重点实验室(华北电力大学)

柔性直流配电系统可以高效、灵活地接入新能源电源与直流负荷,成为配电网研究热点之一。然而受电力电子装置控制影响,直流故障时换流器提供的短路电流非线性强,其故障等值阻抗时变,保护难以基于变化的阻抗识别故障区域。针对该问题,通... 详细信息

柔性直流配电系统可以高效、灵活地接入新能源电源与直流负荷,成为配电网研究热点之一。然而受电力电子装置控制影响,直流故障时换流器提供的短路电流非线性强,其故障等值阻抗时变,保护难以基于变化的阻抗识别故障区域。针对该问题,通过分析故障高频信号在换流器开关过程中的回路,建立不受控制策略影响的换流器高频恒定阻抗等效模型,为保护研究奠定基础。进而提出一种基于高频突变量的距离保护,该方法利用系统故障前后几ms内的电气量信息,通过提取电压高频分量映射故障区段,结合保护整定配合实现故障区域识别。在PSCAD/EMTDC电磁暂态仿真平台上搭建了六端柔性直流配电系统精细化模型,仿真结果表明,所提方法具有良好的速动性和选择性,能够可靠识别故障区域,并且有较好的耐受过渡电阻和抗噪声能力。

关键词：柔性直流配电系统换流器高频突变量故障识别距离保护

Post-collisional mafic magmatism:Record of lithospheric mantle evolution in continental orogenic belt

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Science China Earth Sciences 2020年第12期63卷 2029-2041页

作者： wenliang Xu Zifu zhao Liqun Dai College of Earth Sciences Jilin UniversityChangchun130061China CAS key Laboratory of Crust-Mantle Materials and Environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei230026China Center for Excellence in Comparative Planetology Chinese Academy of Sciences(CAS)Hefei230026China

In order to better understand the role of post-collisional mafic magmatism at convergent plate boundaries in revealing the earth’s evolution,this paper has systematically summarized the research history of post-collisional mafic magmatism,different types of collision and their influence on the nature of orogenic mantle,the concept and implication of post-collisional magmatism,and the relationship between post-collisional mafic magmatism and orogenic mantle evolution and ***-collisional mafic igneous rocks are not only the direct records for studying the nature and evolution of orogenic mantle,but also the important carriers for regional ***,the type and quantity of the crustal materials involved in modifying the overlying lithospheric mantle during collisional orogeny,the process and mechanism of such modification,and the major control factors and mechanism of mafic magmatism-related mineralization during the post-collisional period are the main contents and direction of future researches in this ***,the study of post-collisional mafic magmatism is of significant implications for developing the theory of plate tectonics.

关键词： Orogenic belt Types of collision Post-collisional mafic magmatism Orogenic mantle evolution Mineralization

Improved Coordinated Control Approach for Evolved CCC-HVDC System to Enhance Mitigation Effect of Commutation Failure

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Journal of Modern Power Systems and Clean Energy 2021年第2期9卷 338-346页

作者： Chunyi Guo Bo Liu Chengyong zhao State key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(North China Electric Power University) BeijingChina

The evolved capacitor commutated converter(ECCC),embedded with anti-parallel thyristors based dual-directional full-bridge modules(APT-DFBMs),can effectively reduce commutation failure(CF)risks of line-commutated converter-based high voltage direct current(HVDC)and improve the dynamic responses of capacitor-commutated converterbased *** paper proposes an improved coordinated control strategy for ECCC with the following improvements:(1)under normal operation state,series-connected capacitors can accelerate the commutation process,thereby reducing the overlap angle and increasing the successful commutation margin;(2)under AC fault conditions,the ability of ECCC to mitigate the CF issue no longer relies on the fast fault detection,since the capacitors inside the APT-DFBMs can consistently contribute to the commutation process and further reduce the CF probability;(3)the inserted capacitors can output certain amount of reactive power,increase the power factor,and reduce the required reactive power compensation ***,the proposed coordinated control approach is presented in detail,and the extra commutation voltage to mitigate the CFs provided by the proposed control approach and an existing approach is ***,the mechanism of the improved control approach to accelerate commutation process and improve the power factor is analyzed ***,the detailed electromagnetic transient(EMT)simulation in PSCAD/EMTDC is conducted to validate the effectiveness of the proposed coordinated *** results show that the proposed approach can present a further substantial improvement for ECCC,especially enhancing the CF mitigation effect.

关键词： Evolved capacitor commutated converter(ECCC) coordinated control commutation failure power factor

Controlled rocking pile foundation system with replaceable bar fuses for seismic resilience

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Earthquake Engineering and Engineering Vibration 2022年第3期21卷 683-696页

作者： Cheng zhao Li Shuai Wang Jingquan Bridge Engineering Research Center of Southeast University School of Civil EngineeringSoutheast UniversityNanjing 210096China

Bridges designed following a conventional approach minimize the risk of collapse,but often require challenging,costly,and time-consuming restoration after an earthquake *** new seismic design philosophy requires bridges to maintain functionality even after severe *** this context,this paper proposes a controlled rocking pile foundation(CRPF)system and numerically evaluates bridges′degree of seismic *** CRPF system allows a pile cap to rock on a pile foundation and dissipate seismic energy through inelastic deformations of replaceable bar fuses that connect a pile cap and *** the conceptual design of the CRPF system,two analytical models were developed for a bridge pier utilizing the CRPF system and a pier designed to develop a plastic hinge in its *** analytical results indicate that,after experiencing a severe earthquake,a conventionally designed bridge pier sustained substantial damage in its column and exhibited significant residual *** contrast,a pier using the CRPF system showed negligible residual displacement and maintained elastic behavior except,as expected,for bar *** damaged fuses can be rapidly replaced to recover bridge seismic resistance following an ***,the CRPF system helps to achieve the desired postearthquake performance objectives.

关键词： seismic resilience bridges pier controlled rocking pile foundation repairable bar fuse