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The advection-dominated accretion flow+thin accretion disk model for two low-luminosity active galactic nuclei: M81 and NGC 4579

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Chinese Journal of Astronomy and Astrophysics 2009年第4期9卷 401-408页

作者： Ya-di xu Xin-Wu Cao Physics Department Shanghai Jiao Tong University Shanghai 200240 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030~ China

It was found that advection-dominated accretion flow （ADAF）＋thin disk model calculations can reproduce the observed spectral energy distributions （SEDs） of two low-luminosity active galactic nuclei （AGNs）, provided they are accreting at -0.01-0.03 Eddington rates and the thin disks are truncated to ADAFs at -100Rs （Rs is the Schwarzschild radius） for M81 and NGC 4579 （Quataert et al. 1999）. However, the black hole masses adopted in their work are about one order of magnitude lower than recent measurements on these two sources. Adopting the well estimated black hole masses, our ADAF＋thin disk model calculations can reproduce the observed SEDs of these two low- luminosity AGNs, if the black hole is accreting at 2.5×10^-4 Eddington rates with the thin disk truncated at Rtr=120Rs for M81（m= 3.3×10^-3 and Rtr=80Rs are required for NGC 4579）. The transition zones with temperature from the thin disk with ,-10^4- 10^5 to ,-10^9-10^10K in the ADAF will inevitably emit thermal X-ray lines, which provides a useful diagnosis of their physical properties. The observed widths of the thermal X-ray iron lines at -6.8 keV are consistent with Doppler broadening by Keplerian motion of the gases in the transition zones at ,-100Rs. We use the structure of the transition zone between the ADAF and the thin disk derived by assuming the turbulent diffusive heat mechanism to calculate their thermal X-ray line emission with the standard software package Astrophysical Plasma Emission Code （APEC）. Comparing them with the equivalent widths of the observed thermal X-ray iron lines in these two sources, we find that the turbulent diffusive heat mechanism seems to be unable to reproduce the observed thermal X-ray line emission. The test of the evaporation model for the accretion mode transition with the observed thermal X-ray line emission is briefly discussed.

关键词： accretion, accretion disks-black hole physics-galaxies active-radiation mechanisms thermal-galaxies individual (M81, NGC 4579)

Recent Progress in Electrospun Nanofibers for the Membrane distillation of Hypersaline Wastewaters

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Advanced Fiber Materials 2022年第6期4卷 1357-1374页

作者： di xu Zhigao Zhu Jiansheng Li Key Laboratory of New Membrane Materials Ministry of Industry and Information TechnologySchool of Environmental and Biological EngineeringNanjing University of Science and TechnologyNanjing 210094China

Membrane distillation(MD)utilizing low-grade thermal energy can be used to effectively desalinate hypersaline brines with a high freshwater recovery for water *** flux and durability are the two main indices used to evaluate MD membrane *** the past decade,electrospun nanofibrous distillation membranes(EFDMs)with a low mass transfer resistance have garnered increasing attention in MD research,owing to their high porosity and interconnected-pore ***,on the one hand,the pores of EFDMs compared to those of phase-inversion membranes are easily deformed and impacted by water flow,reducing membrane flux;on the other hand,the general hydrophobic interface is susceptible to being wetted,fouled and scaled during the desalination/concentration process,resulting in MD *** review will present a comprehensive discussion of the recent progress in electrospun nanofibers for the MD of hypersaline wastewaters with a focus on designing specially wettable membrane interfaces and welding-pore structured membranes to enhance MD distillation efficiency and durability ***,the challenges and perspectives of MD in treating hypersaline wastewaters are also provided as a guide for future research on sustainable and clean freshwater recovery.

关键词： Electrospinning Membrane distillation Flux and durability Wetting,fouling and scaling control Pore deformation

Gold/WO3 nanocomposite photoanodes for plasmonic solar water splitting

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Nano Research 2016年第6期9卷 1735-1751页

作者： dianyi Hu Peng diao di xu Qingyong Wu Key Laboratory of Aerospace Materials and Performance (Ministry of Education) School of Materials Science and EngineeringBeihang University Bei)ing 100191 China

A facile electron-charging and reducing method was developed to prepare Au/＇VVO3 nanocomposites for plasmonic solar water splitting. The preparation method involved a charging step in which electrons were charged into WO3 under negative bias, and a subsequent reducing step in which the stored electrons were used to reductively deposit Au on the surface of WO3. The electron-charged WO3 （c-WO3） exhibited tunable reducibility that could be easily controlled by varying the charging parameters, and this property makes this method a universal strategy to prepare metalAVO3 composites. The obtained Au/VVO3 nanocomposite showed greatly improved photoactivity toward the oxygen evolution reaction （OER） when compared with WO3. After Au decoration, the OER photocurrent was improved by a percentage of over 80% at low potentials （〈0.6 V vs. SCE）, and by a percentage of over 30% at high potentials （〉1.0 V vs. SCE）. Oxygen evolution measurements were performed to quantitatively determine the Faraday efficiency for OER, which reflected the amount of photocurrent consumed by water splitting. The Faraday efficiency for OER was improved from 74% at the WO3 photoanode to 94% at the Au-8/＇vVO3 composite photoanode, and this is the first direct evidence that the Au decoration significantly restrained the anodic side reactions and enhanced the photoelectrochemical （PEC） OER efficiency. The high photoactivity of the composite photoanode toward OER was ascribed to the plasmon resonance energy transfer （PRET） enhancement and the catalytic enhancement of Au nanoparticles （NPs）.

关键词： tungsten trioxide gold nanoparticle surface plasmon resonance electron-charging plasmonic solar waterspitting

Prescribed Performance Tracking Control of Time-Delay Nonlinear Systems With Output Constraints

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IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1557-1565页

作者： Jin-Xi Zhang Kai-di xu Qing-Guo Wang IEEE the State Key Laboratory of Synthetical Automation for Process Industries Northeastern UniversityShenyang 110819China Institute of Artificial Intelligence and Future Networks Beijing Normal UniversityZhuhai 519087 Guangdong Key Laboratory of Artificial Intelligence and Multi-Modal Data Processing Beijing Normal University-Hong Kong Baptist University United International CollegeZhuhai 519087

The problem of prescribed performance tracking control for unknown time-delay nonlinear systems subject to output constraints is dealt with in this paper. In contrast with related works, only the most fundamental requirements, i.e., boundedness and the local Lipschitz condition, are assumed for the allowable time delays. Moreover, we focus on the case where the reference is unknown beforehand, which renders the standard prescribed performance control designs under output constraints infeasible. To conquer these challenges, a novel robust prescribed performance control approach is put forward in this ***, a reverse tuning function is skillfully constructed and automatically generates a performance envelop for the tracking error. In addition, a unified performance analysis framework based on proof by contradiction and the barrier function is established to reveal the inherent robustness of the control system against the time delays. It turns out that the system output tracks the reference with a preassigned settling time and good accuracy,without constraint violations. A comparative simulation on a two-stage chemical reactor is carried out to illustrate the above theoretical findings.

关键词： Nonlinear systems output constraints prescribed performance reference tracking time delays

Stability analysis in an AVQ model of Internet congestion control algorithm

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The Journal of China Universities of Posts and Telecommunications 2012年第4期19卷 22-28页

作者： ZHAN Zhen-qiu ZHU Jie xu di Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai 200240China

This paper focuses on the local stability of a classical congestion control model in the Intemet, namely adaptive virtual queue （AVQ） algorithm with feedback delay. Firstly, necessary and sufficient stability conditions in terms of key tuning parameters are given, which can provide exact guidelines for setting system parameters. Furthermore, by computing the rightmost characteristic root, the optimal parameter configuration for AVQ is derived, which can guarantee superior stability performance. Finally, some simulation examples are given to illustrate the correctness of the theoretical analysis.

关键词： congestion control AVQ stability time delay system

Progress in application of rare metals in superalloys

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Rare Metals 2014年第2期33卷 111-126页

作者： Kuang-di xu Zhong-Ming Ren Chuan-Jun Li Laboratory of Modern Metallurgy and Material Processing Shanghai University

Rare metals play an important role in development of superalloys. Over the last two decades, the application of the rare metals in superalloys has achieved progress significantly. They present multi-beneficial effects for strengthening the matrix and the cophase, increasing the lattice misfit, cleaning the grain boundary, improving the carbides and eutectics, refining the grain, stabilizing the oxidation film, etc., so that the elevated temperature rupture life and elevated temperature oxidation resistance are improved significantly, leading to a broad application in the superalloys. In order to meet the higher demand for better superalloys in the future, more intensive research is necessary on the effects of the rare metals on the superalloy, and especially on the combination effect of various rare metals and mutual influence among them. Utilization of the computational materials science and combinatorial high throughput experiment will be of importance in application of rare metals in superalloys.

关键词： Superalloys Rare metals Strengthening Carbide Intermetallics Elevated temperature mechnical property Oxidation resistance Rupture life Creep resistance

Particle collision behavior and heat transfer performance in a Na_(2)SO_(4) circulating fluidized bed evaporator

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Chinese Journal of Chemical Engineering 2022年第6期35卷 40-52页

作者： Feng Jiang di xu Ruijia Li Guopeng Qi Xiulun Li School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology Tianjin UniversityTianjin 300350China School of Biological and Environmental Engineering Tianjin Vocational InstituteTianjin 300410China

The particle collision behavior and heat transfer performance are investigated to reveal the heat transfer enhancement and fouling prevention mechanism in a Na_(2)SO_(4) circulating fluidized bed *** particle collision signals are analyzed with standard deviation by varying the amount of added particles ε(1%–3%),circulation flow velocity u(0.37–1.78 m·s^(-1)),and heat flux q(7.29–12.14 kW·m^(-2)).The results show that the enhancement factor reach up to 14.6%by adding polytetrafluoroethylene particles at ε=3%,u=1.78 m·s^(-1),and q=7.29 kW·m^(-2).Both the standard deviation of the particle collision signal and enhancement factor increase with the increase in the amount of added *** standard deviation increases with the increase in circulation flow velocity;however,the enhancement factor initially decreases and then *** standard deviation slightly decreases with the increase in heat flux at low circulation flow velocity,but initially increases and then decreases at high circulation flow *** enhancement factor decreases with the increase in heat *** enhancement factor in Na_(2)SO_(4) solution is superior to that in water at high amount of added *** empirical correlation for heat transfer is established,and the model results agree well with the experimental data.

关键词： Heat transfer enhancement Particle collision behavior Circulating fluidized bed Evaporation Na2SO4 Standard deviation

Contributions in renewable energy systems:A perspective from the latest publications of FCSE

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Frontiers of Chemical Science and Engineering 2019年第4期13卷 632-635页

作者： Xiaowen Zhu di xu Jing-Kang Wang School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China College of Chemistry and Chemical Engineering Chongqing University of Science&TechnologyChongqing 401331China

The Chinese Academy of Engineering(CAE)has been conducting Engineering Fronts Projects for three years since 2017,which aim of the future development directions of engineering science and *** potential Research Fronts topics were obtained by Clarivate Analytics,which based on the cocitation clustering method and clustered the top 10%highly cited papers in the Web of Science Core Collection.“Renewable Energy System”got voWng No.1 in this project in 2019 in the field group of Chemical,Metallurgical,and Materials Engineering[1].Among all 190 papers on this topic there are 8 papers got more than 100 citations in the Web of Science Core Collection[2-9].

关键词： technology. FCS Collection

Use of Intensity Analysis to Measure Land Use Changes from 1932 to 2005 in Zhenlai County, Northeast China

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Chinese Geographical Science 2017年第3期27卷 441-455页

作者： YANG Yuanyuan LIU Yansui xu di ZHANG Shuwen Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences College of Resources Science and Technology Beijing Normal University Urban Development Research Institute Shanghai Normal University Northeast Institute of Geography and Agroecology Chinese Academy of Sciences

Analyzing spatiotemporal dynamics of land use and land cover over time is widely recognized as important to better understand and provide solutions for social, economic, and environmental problems, especially in ecologically fragile region. In this paper, a case study was taken in Zhenlai County, which is a part of farming-pastoral ecotone of Northeast China. This study seeks to use multi-temporal satellite images and other data from various sources to analyze spatiotemporal changes from 1932 to 2005, and applied a quantitative methodology named intensity analysis in the time scale of decades at three levels: time interval, category, and transition. The findings of the case study are as follows: 1) the interval level of intensity analysis revealed that the annual rate of overall change was relatively fast in 1932–1954 and 1954–1976 time intervals. 2) The category level showed that arable land experienced less intensively gains and losses if the overall change was to have been distributed uniformly across the landscape while the gains and losses of forest land, grassland, water, settlement, wetland and other unused land were not consistent and stationary across the four time intervals. 3) The transition level illustrated that arable land expanded at the expense of grassland before 2000 while it gained intensively from wetland from 2000 to 2005. Settlement targets arable land and avoids grassland, water, wetland and other unused land. Besides, the loss of grassland was intensively targeted by arable land, forest land and wetland in the study period while the loss of wetland was targeted by water except for the time interval of 1976–2000. 4) During the early reclamation period, land use change of the study area was mainly affected by the policy, institutional and political factors, followed by the natural disasters.

关键词： intensity analysis land use and land cover change pattern driving forces Northeast China