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Investigating jet physical properties of Fermi blazars with broad-line emissions

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中国科学:物理学、力学、天文学英文版 2023年第10期66卷 138-154页

作者： lixia Zhang Jianghe Yang Yi liu Junhui Fan Center for Astrophysics Guangzhou UniversityGuangzhou 51006China Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province Guangzhou 510006China Key Laboratory for Astronomical Observation and Technology of Guangzhou Guangzhou 510006China Great Bay Center National Astronomical Data CenterGuangzhou 510006China Department of Physics and Electronics Science Hunan University of Arts and ScienceChangde 415000China

Relativistic outflows often exhibit extreme observational characteristics due to beaming effects, which makes measuring their jet power a challenging task. Although the spectral energy distribution(SED) obtained from multi-wavelength data can constrain the physical parameters of these jets, accurately estimating the Doppler factor remains difficult. To address this challenge, we assemble a comprehensive sample containing available SEDs of synchrotron and inverse Compton(IC) components, monochromatic luminosity, and broad-line region(BLR) emissions. We employ a parabolic equation to fit the synchrotron radiation SEDs,constraining jet physical parameters within the framework of a one-zone leptonic model. Our study delves into the jet properties and Doppler factor estimations, yielding the following key findings:(1) The fitting results of SED data for the entire sample reveal normal distributions of jet physical parameters for two subclasses of blazars.(2) Correlation analysis demonstrates that synchrotron peak luminosity exhibits a proportional relationship with both the radio and the γ-ray luminosities.(3) We introduce a novel method for estimating Doppler factors, which uncovers discrepancies between Doppler factors from this work and others from different techniques.

关键词： active galactic nuclei blazars jets spectral energy distribution

Hybrid Beamforming for Terahertz Wireless Communications with Beam Squint:A Survey

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Chinese Journal of Electronics 2022年第6期31卷 1043-1052页

作者： WU Yezeng XIAO lixia liu Guanghua JIANG Tao Research Center of 6G Mobile Communications School of Cyber Science and EngineeringHuazhong University of Science and Technology Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology

Benefiting from the ultra-wide bandwidth, terahertz(THz) communication is considered one of the core technologies of the 6G mobile communication.However, high path loss is a severe issue for THz band,which needs to be solved by the ultra-massive multiple-input multiple-output(MIMO) technology. For the sake of reducing the hardware cost and power comsumption, the hybrid beamforming technology is required, which has been adopted in the 5G communication. In the hybrid beamforming for the THz wideband system, the enormous antenna and ultra-wide bandwidth cause the spatialand frequency-wideband effect, resulting in acute beam squint. Eliminating beam squint is the key to the engineering realization of ultra massive MIMO for the THz band. To circumvent this issue, this paper presents a comprehensive overview of the hybrid beamforming technology including the channel model, the traditional phase shifter based and the true time delay based architectures,the 3D hybrid beamforming for the uniform planar array.Finally, multiple significant open issues and potential challenges are pointed out and elaborated.

关键词： Terahertz Ultra-massive MIMO Hybrid beamforming Beam squint True time delay

Synthesis of flexible heat exchanger networks:A review

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Chinese Journal of Chemical Engineering 2019年第7期27卷 1485-1497页

作者： lixia Kang Yongzhong liu Department of Chemical Engineering Xi’an Jiaotong UniversityXi’an 710049China Key Laboratory of Thermo-Fluid Science and Engineering Ministry of EducationXi’an 710049China

Dealing with uncertainty is one of practical issues in design and operation of heat exchanger networks(HENs),arising the problem of flexible HEN synthesis.This paper addresses the state-of-the-art methods for flexible HEN synthesis based on sensitivity analysis,resilience analysis,flexibility analysis and multiperiod synthesis techniques as well.Each of these methods is summarized by presenting their general procedures and recent developments on modeling,solving strategies and applications.Some current topics related to flexible process synthesis have been briefly presented to provide several future research possibilities.

关键词： Heat exchanger network Sensitivity analysis Resilience analysis Flexibility analysis Multiperiod synthesis

A systematic strategy for multi-period heat exchanger network retrofit under multiple practical restrictions

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Chinese Journal of Chemical Engineering 2017年第8期25卷 1043-1051页

作者： lixia Kang Yongzhong liu Department of Chemical Engineering Xi'an Jiaotong University Key Laboratory of Thermo-Fluid Science and Engineering Ministry of Education

A systematic strategy for retrofit of the multi-period heat exchanger network (HEN) on the basis of the multi-objective optimization is developed. In this three-stage procedure, a simplified multi-objective optimization model of the multi-period HEN is first established and then solved to target the retrofit, aiming to minimizing the total annual cost and total annual CO_2 emissions. The obtained Pareto front represents series of retrofit targets under different emission limitations, from which the most desirable one can be selected. The matching of the existing and the required heat exchangers is further implemented to finalize the retrofit, which will meet the practical retrofit requirements and matching restrictions. The application of the proposed procedure is illustrated through a case study of a HEN in a vacuum gas oil hydro-treating unit.

关键词：网络改造换热器系统多目标优化模型多工况二氧化碳排放量多段水处理装置

Digital-to-analog converter free architecture for digital reconfigurable intelligent surface

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Frontiers of Information Technology & Electronic Engineering 2023年第12期24卷 1752-1762页

作者： Miaoran PENG Jinhao KAN lixia XIAO Guanghua liu Tao JIANG Research Center of 6G Mobile Communications Huazhong University of Science and TechnologyWuhan430074China School of Cyber Science and Engineering Huazhong University of Science and TechnologyWuhan430074China School of Electronic Information and Communications Huazhong University of Science and TechnologyWuhan430074China

This research investigates the digital-to-analog converter(DAC)free architecture for the digital reconfigurable intelligent surface(RIS)system,where the transmission lines are implemented for reflection coefficient(RC)control to reduce power consumption.In the proposed architecture,the radio frequency(RF)switch based phase shifter is considered.By using a single-pole four-throw(SP4T)switch to simultaneously control the RCs of a group of elements,a 2-bit phase shifter is realized for passive beam steering.A novel modulation scheme is developed to explore the cost effectiveness,which approaches the performance of traditional quadrature amplitude modulation(QAM).Specifically,to overcome the limitation of the phase shift bits,joint frequency-shift and phase-rotation operations are applied to the constellation points.The simulation and experimental results demonstrate that the proposed architecture is capable of providing an ideal transmission performance.Moreover,64-and 256-QAM modulation schemes could be implemented by expanding the elements and phase bits.

关键词： Reconfigurable intelligent surface Hardware implementation High-order modulation

Influence of Blocking-Stressors on Post-90s Employees’ Occupational Mobility: The Chain Mediating Effect of Psychological Contracts and Negative Emotion

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International Journal of Mental Health Promotion 2022年第4期24卷 527-538页

作者： lixia Niu Ying liu Jie liu Rui Zhao School of Business and Management Liaoning Technical UniversityHuludao125100China School of Economics and Management Beijing University of Posts and TelecommunicationsBeijing100876China

To clarify the mechanism of blocking-stressors,psychological contracts,and negative emotions on post-90s employees’occupational mobility,based on the literature study,a hypothetical model of the relationship was established.Using the blocking-stressor,psychological contract,negative emotion,and occupational mobility scales,317 post-90s employees were selected to investigate their status.It used correlation analysis and intermedi-ary effect tests to verify the hypothesis model.The results showed that:ﬁrst,there were signiﬁcant positive cor-relations between blocking-stressors,negative emotions,and occupational mobility,while indicating a signiﬁcant negative correlation with the psychological contract;second,blocking-stressors can directly and signiﬁcantly pre-dict occupational mobility;and third,blocking-stressors can indirectly affect occupational mobility through the mediating role of negative emotions and the chain-mediating role of psychological contracts and negative emo-tions.The effective intervention of blocking-stressors,psychological contracts,and negative emotions can reduce the rate of occupational mobility and provide some guidance for enterprises in making rational use of human resources.

关键词： Occupational mobility post-90s blocking-stressors psychological contract negative emotion

Error Probability Analysis for Ultra-Massive MIMO System and Near-Optimal Signal Detection

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China Communications 2023年第5期20卷 1-19页

作者： lixia Xiao Shuo Li Yangyang liu Guanghua liu Pei Xiao Tao Jiang Research Center of 6G Mobile Communications School of Cyber Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China 5G&6G Center of University of Surrey SurreyGU27XHUnited Kingdom

In this paper,average bit error probability(ABEP)bound of optimal maximum likelihood(ML)detector is first derived for ultra massive(UM)multiple-input-multiple-output(MIMO)system with generalized amplitude phase modulation(APM),which is confirmed by simulation results.Furthermore,a minimum residual criterion(MRC)based lowcomplexity near-optimal ML detector is proposed for UM-MIMO system.Specifically,we first obtain an initial estimated signal by a conventional detector,i.e.,matched filter(MF),or minimum mean square error(MMSE)and so on.Furthermore,MRC based error correction mechanism(ECM)is proposed to correct the erroneous symbol encountered in the initial result.Simulation results are shown that the performance of the proposed MRC-ECM based detector is capable of approaching theoretical ABEP of ML,despite only imposing a slightly higher complexity than that of the initial detector.

关键词： average bit error probability(ABEP) ultra-massive MIMO(UM-MIMO) minimum residual criterion(MRC) maximum likelihood(ML) matched filter(MF)

Performance Analysis for Orthogonal Time Frequency Space Modulation Systems with Generalized Waveform

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China Communications 2023年第4期20卷 57-72页

作者： Shuo Li lixia Xiao Yangyang liu Guanghua liu Pei Xiao Tao Jiang Research Center of 6G Mobile Communications School of Cyber Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China School of Electronic Information and Communications Huazhong University of Science and TechnologyWuhan 430074China 5G & 6G Center of University of Surrey SurreyGU27XHUnited Kingdom

Orthogonal time-frequency space(OTFS),which exhibits beneficial advantages in high-mobility scenarios,has been considered as a promising technology in future wireless communication systems.In this paper,a universal model for OTFS systems with generalized waveform has been developed.Furthermore,the average bit error probability(ABEP)upper bounds of the optimal maximum likelihood(ML)detector are first derived for OTFS systems with generalized waveforms.Specifically,for OTFS systems with the ideal waveform,we elicit the ABEP bound by recombining the transmitted signal and the received signal.For OTFS systems with practical waveforms,a universal ABEP upper bound expression is derived using moment-generating function(MGF),which is further extended to MIMO-OTFS systems.Numerical results validate that our theoretical ABEP upper bounds are concur with the simulation performance achieved by ML detectors.

关键词： orthogonal time frequency space(OTFS) average bite error rate(ABEP) maximum likelihood(ML) moment generating-function(MGF)

All-metallic metasurfaces towards high-performance magneto-plasmonic sensing devices

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Photonics Research 2020年第11期8卷 1742-1748页

作者： lixia Li Xueyang Zong Yufang liu Henan Key Laboratory of Infrared Materials&Spectrum Measures and Applications School of PhysicsHenan Normal UniversityXinxiang 453007China

Magneto-plasmonic sensors based on surface plasmon resonance have been studied considerably in recent years,as they feature high sensitivity and ultrahigh resolution.However,the majority of such investigations focus on prism-based sandwich architectures that not only impede the miniaturization of devices but also have a weak transverse magneto-optical Kerr effect(TMOKE)in magnitude.Herein,we theoretically demonstrate a magneto-plasmonic sensor composed of Au/Co bilayer nanodisk arrays on top of optically thick metallic films,which supports a narrow surface plasmon resonance(SPR)with a bandwidth of 7 nm and allows for refractive index sensitivities as high as 717 nm/RIU.Thanks to the high-quality SPR mode,a Fano-like TMOKE spectrum with a subnanometer bandwidth can be achieved in the proposed structure,thereby giving rise to ultrahigh sensing of merit values as large as 7000 in water.Moreover,we demonstrate a large TMOKE magnitude that exceeds 0.6.The value is 1 order of magnitude larger than that of magneto-plasmonic sensors reported.We also demonstrate that the behavior of TMOKE spectra can be controlled by tuning the geometrical parameters of the device including the diameter and thickness of nanodisk arrays.This work provides a promising route for designing magneto-plasmonic sensors based on metasurfaces or metamaterials.

关键词： metallic magneto thereby