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Numerical study of conduction and radiation heat losses from vacuum annulus in parabolic trough receivers

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Frontiers in Energy 2022年第6期16卷 1048-1059页

作者： Dongqiang lei Yucong ren Zhifeng WANG Key Laboratory of Solar Thermal Energy and Photovoltaic System Chinese Academy of SciencesBeijing 100190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing Engineering Research Center of Solar Thermal Power Beijing 100190China

Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar *** heat loss of the receiver has an important influence on the thermal efficiency and the operating cost of the power *** this paper,conduction and radiation heat losses are analyzed respectively to identify the heat loss mechanism of the receiver.A 2-D heat transfer model is established by using the direct simulation Monte Carlo method for rarefied gas flow and heat transfer within the annulus of the receiver to predict the conduction heat loss caused by residual *** numerical results conform to the experimental results,and show the temperature of the glass envelope and heat loss for various conditions in *** effects of annulus pressure,gas species,temperature of heat transfer fluid,and annulus size on the conduction and radiation heat losses are systematically ***,the main factors that cause heat loss are analyzed,providing a theoretical basis for guiding the improvement of receiver,as well as the operation and maintenance strategy to reduce heat loss.

关键词： parabolic trough receiver vacuum annulus rarefied gas DSMC(direct simulation Monte Carlo) heat loss

An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

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Energy Engineering 2022年第3期119卷 1179-1196页

作者： lei ren lei Zhang School of Electrical Engineering Nantong UniversityNantong226019China

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter(TSI),the second harmonic current(SHC)is generated in the frontend dc-dc converter(FDC).To reduce the SHC,optimizing the control strategy of the FDC is an effective and costless *** view of visual impedance,this paper conducts an intensive study on the SHC reduction *** of the SHC is illustrated ***,the equivalent circuit models of the FDC under different control strategies are proposed to analyse the SHC propagation *** derived model can offer a better insight into how the inductor SHC is affected by the control *** to the derived models,a synthesis of different control strategies is presented and the relevant parameters are listed for control design to achieve better suppression *** benefits and limitations of these control strategies are also *** on the proposed equivalent circuit models,several optimization methods are proposed to enhance the effect.A 1500 VA TSI prototype is built and simulated on MATLAB/Simulink,verifying the effectiveness of the proposed optimization *** paper is aimed to provide a guideline for the control design and control optimization of the TSIs.

关键词： Two-stage single-phase inverter(TSI) second harmonic current(SHC) equivalent circuit models optimization

Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 136-146页

作者： Chenjin Zhang Guangyu Yang lei Xiao Zhiyong Kan Jing Guo Qiang Li Wanqi Jie State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China College of Materials Science and Engineering Fuzhou UniversityFuzhou 350108China College of Chemistry and Environmental Science Qujing Normal UniversityQujing 655011China

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed *** dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)*** the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical-rare-earth(RE)*** alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening *** results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

关键词： Mg-rare earth alloys extrusion temperature extrusion ratio extrusion speed strengthening mechanisms

A parameter formula connecting PID and ADRC

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Science China(Information Sciences) 2020年第9期63卷 175-187页

作者： Sheng zhong Yi HUANG lei GUO Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

This paper presents a parameter formula connecting the well-known proportional-integralderivative(PID) control and the active disturbance rejection control(ADRC). On the one hand, this formula gives a quantitative lower bound to the bandwidth of the extended state observer(ESO) used in ADRC,implying that the ESO is not necessarily of high gain. On the other hand, enlightened by the design of ADRC, a new PID tuning rule is provided, which can guarantee both strong robustness and nice tracking performance of the closed-loop systems under the PID control. Moreover, it is proved that the ESO can be rewritten as a suitable linear combination of the three terms in PID, which can give a better estimate for the system uncertainty than the single integral term in the PID controller. Theoretical results are verified also by simulations in the paper.

关键词： nonlinear uncertain systems proportional-integral-derivative PID active disturbance rejection control ADRC extended state observer ESO

Set-Membership Filtering Approach to Dynamic Event-Triggered Fault Estimation for a Class of Nonlinear Time-Varying Complex Networks

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IEEE/CAA Journal of Automatica Sinica 2024年第3期11卷 638-648页

作者： Xiaoting Du lei Zou Maiying zhong the College of Electrical Engineering and Automation Shandong University of Science and TechnologyQingdao 266590China IEEE the College of Information Science and Technology Donghua UniversityShanghai 201620 the Engineering Research Center of Digitalized Textile and Fashion Technology Ministry of EducationShanghai 201620China

The present study addresses the problem of fault estimation for a specific class of nonlinear time-varying complex networks,utilizing an unknown-input-observer approach within the framework of dynamic event-triggered mechanism(DETM).In order to optimize communication resource utilization,the DETM is employed to determine whether the current measurement data should be transmitted to the estimator or *** guarantee a satisfactory estimation performance for the fault signal,an unknown-input-observer-based estimator is constructed to decouple the estimation error dynamics from the influence of fault *** aim of this paper is to find the suitable estimator parameters under the effects of DETM such that both the state estimates and fault estimates are confined within two sets of closed ellipsoid *** techniques of recursive matrix inequality are applied to derive sufficient conditions for the existence of the desired estimator,ensuring that the specified performance requirements are met under certain ***,the estimator gains are derived by minimizing the ellipsoid domain in the sense of trace and a recursive estimator parameter design algorithm is then ***,a numerical example is conducted to demonstrate the effectiveness of the designed estimator.

关键词： Dynamic event-triggered mechanism(DETM) fault estimation nonlinear time-varying complex networks set-member-ship filtering unknown input observer

The nanohertz stochastic gravitational wave background from cosmic string loops and the abundant high redshift massive galaxies

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Science China(Physics,Mechanics & Astronomy) 2023年第12期66卷 11-19页

作者： Ziwei Wang lei lei Hao Jiao lei Feng Yi-zhong Fan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Department of Physics McGill UniversityMontreal H3A 2T8Canada

Recently,pulsar timing array(PTA)experiments have provided compelling evidence for the existence of the nanohertz stochastic gravitational wave background(SGWB).In this work,we demonstrated that cosmic string loops generated from cosmic global strings offer a viable explanation for the observed nanohertz SGWB data,requiring a cosmic string tension parameter of log(Gμ)~-12 and a loop number density of log N~***,we revisited the impact of cosmic string loops on the abundance of massive galaxies at high ***,our analysis revealed challenges in identifying a consistent parameter space that can concurrently explain both the SGWB data and observations from the James Webb Space *** indicates the necessity for either extending the existing model employed in this research or acknowledging distinct physical origins for these two phenomena.

关键词： nanohertz stochastic gravitational-wave background cosmic string loop JamesWebb Space Telescope galaxy formation

Advanced engineering and biomimetic materials for bone repair and regeneration

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Frontiers of Materials Science 2013年第4期7卷 313-334页

作者： lei YANG Chao zhong Institute of Orthopaedics Department of Orthopaedic Surgery at the First Affiliated Hospital Soochow University Suzhou 215006 China Research Laboratory of Electronics (RLE) Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139-4307 USA Synthetic Biology Center Massachusetts Institute of Technology Cambridge Massachusetts 02139-4307 USA

Over the past decade, there has been tremendous progress in developing advanced biomaterials for tissue repair and regeneration. This article reviews the frontiers of this field from two closely related areas, new engineering materials for bone substitution and biomimetic mineralization for bone-like nanocomposites. Rather than providing an exhaustive overview of the literature, we focus on several representative directions. We also discuss likely future trends in these areas, including synthetic biology-enabled biomaterials design and multifunctional implant materials for bone repair and regeneration.

关键词： bone engineering material biomimetic material implant biomineralization

Compatibility of Beauveria bassiana with Neoseiulus barkeri for Control of Frankliniella occidentalis

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Journal of Integrative Agriculture 2015年第1期14卷 98-105页

作者： WU Sheng-yong GAO Yu-lin XU Xue-nong Mark S Goettel lei zhong-ren State Key Laboratory for Biology of Plant Diseases and Insect Pests I nstitute of Plant ProtectionChinese Academy of Agricultural Sciences Lethbridge Research Centre Agriculture and Agri-Food Canada

The entomopathogenic fungus Beauveria bassiana （Balsamo） Vuillemin and predatory mite Neoseiulus barked Hughes are effective biological control agents of Frankliniella occidentalis Pergande （Thysanoptera： Thripidae）, one of the most important pests of ornamentals and vegetables world-wide. Combined application of both may enhance control efficiency. The functional response for N. barked on the first instar larvae of western flower thrips which were infected by B. bassiana for 12 and 24 h in the laboratory （（25＋1）℃, （70＋5）% RH, L：D=16 h：8 h） was determined. The virulence of B. bassiana against the second instar and pupae of the thrips attacked by N. barked were also tested. The results showed that N. barked exhibited a Holling type II functional response on treated thrips. After having been treated with the fungus for 12 h and then offered to the predator, thrips were more vulnerable to be killed by N. barked. The second instar larvae and pupae of the thrips which had been attacked by predatory mites were markedly more susceptible to B. bassiana infection than normal thrips; the cumulative corrected mortality of B. bassiana of the second instar and pupae which were attacked by N. barked were 57 and 94%, respectively, compared to 35 and 80% in controls on the day 8. These findings highlight the potential use of B. bassiana in combination with N. barkeri to control F. occidentalis.

关键词： Beauveria bassiana Neoseiulus barkeri Frankfiniella occidentalis functional response virulence

Computation of the stability derivatives via CFD and the sensitivity equations

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Acta Mechanica Sinica 2011年第2期27卷 179-188页

作者： Guo-Dong lei Yu-Xin ren Department of Engineering Mechanics Tsinghua University 100084 Beijing China

The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is ex- tended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agree- ment with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.

关键词： Aerodynamic stability derivatives Non-inertial frame of reference unstructured-grid Finite volume scheme Sensitivity equations