检索结果-南通市图书馆

Crystal facet-dependent CO_(2)cycloaddition to epoxides over ZnO catalysts

在线全文

学校读者我要写书评

暂无评论

Frontiers of Chemical Science and Engineering 2024年第5期18卷 49-59页

作者： Yongjian Wei Ying Li Yunfei Xu Yinghui Sun Tong xu Haiou Liang Jie Bai Inner Mongolia Key Laboratory of Industrial Catalysis Hohhot 010051China College of Chemical Engineering Inner Mongolia University of TechnologyHohhot 010051China

With regard to green chemistry and sustainable development,the fixation of CO_(2)into epoxides to form cyclic carbonates is an attractive and promising pathway for CO_(2)utilization.Metal oxides,renowned as promising eco-friendly catalysts for industrial production,are often undervalued in terms of their impact on the CO_(2)addition reaction.In this work,we successfully developed ZnO nanoplates with(002)surfaces and ZnO nanorods with(100)surfaces via morphology-oriented regulation to explore the effect of crystal faces on CO_(2)cycloaddition.The quantitative data obtained from electron paramagnetic resonance spectroscopy indicated that the concentration of oxygen vacancies on the ZnO nanoplate surfaces was more than twice that on the ZnO nanorod surfaces.Density functional theory calculations suggested that the(002)surfaces have lower adsorption energies for CO_(2)and epichlorohydrin than the(100)surfaces.As a result,the yield of cyclochloropropene carbonate on the ZnO nanoplates(64.7%)was much greater than that on the ZnO nanorods(42.3%).Further evaluation of the reused catalysts revealed that the decrease in the oxygen vacancy concentration was the primary factor contributing to the decrease in catalytic performance.Based on these findings,a possible catalytic mechanism for CO_(2)cycloaddition with epichlorohydrin was proposed.This work provides a new idea for the controllable preparation of high-performance ZnO catalysts for the synthesis of cyclic carbonates from CO_(2)and epoxides.

关键词： carbon dioxide cycloaddition zinc oxide crystal face oxygen vacancy

Molecular chaperones in stroke-induced immunosuppression

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2023年第12期18卷 2638-2644页

作者： Haoduo Qiao Qing xu Yunfei Xu Yao Zhao Nina He Jie Tang Jie Zhao Ying Liu Department of Neurosurgery Xiangya HospitalCentral South UniversityChangshaHunan ProvinceChina Department of Pathophysiology Xiangya School of MedicineCentral South UniversityChangshaHunan ProvinceChina Sepsis Translational Medicine Key Laboratory of Hunan Province ChangshaHunan ProvinceChina National Medicine Functional Experimental Teaching Center ChangshaHunan ProvinceChina Department of Clinical Pharmacology Xiangya HospitalCentral South UniversityChangshaHunan ProvinceChina

Stroke-induced immunosuppression is a process that leads to peripheral suppression of the immune system after a stroke and belongs to the central nervous system injury-induced immunosuppressive syndrome.Stroke-induced immunosuppression leads to increased susceptibility to post-stroke infections,such as urinary tract infections and stroke-associated pneumonia,worsening prognosis.Molecular chaperones are a large class of proteins that are able to maintain proteostasis by directing the folding of nascent polypeptide chains,refolding misfolded proteins,and targeting misfolded proteins for degradation.Various molecular chaperones have been shown to play roles in stroke-induced immunosuppression by modulating the activity of other molecular chaperones,cochaperones,and their associated pathways.This review summarizes the role of molecular chaperones in stroke-induced immunosuppression and discusses new approaches to restore host immune defense after stroke.

关键词： Hsp70 Hsp72 Hsp90 HspB5 hypothalamic-pituitary-adrenal axis molecular chaperones neuroprotection stroke stroke-induced immunosuppression sympathetic nervous system

An Area Optimization Based Cooperative Localization Algorithm with Node Selection

在线全文

学校读者我要写书评

暂无评论

China Communications 2021年第12期18卷 178-195页

作者： Ke Han Chongyu Zhang Huashuai Xing Yunfei Xu School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications) Beijing 100876China

In recent years,position information has become a key feature to drive location and context aware services in mobile communication.Researchers from all over the world have proposed many solu-tions for indoor positioning over the past several years.However,due to weak signals,multipath or non-line-of-sight signal propagation,accurately and efficiently localizing targets in harsh indoor environments re-mains a challenging problem.To improve the perfor-mance in harsh environment with insufficient anchors,cooperative localization has emerged.In this paper,a novel cooperative localization algorithm,named area optimization and node selection based sum-product al-gorithm over a wireless network(AN-SPAWN),is de-scribed and analyzed.To alleviate the high compu-tational complexity and build optimized cooperative cluster,a node selection method is designed for the cooperative localization algorithm.Numerical experi-ment results indicate that our proposed algorithm has a higher accuracy and is less impacted by NLOS errors than other conventional cooperative localization algo-rithms in the harsh indoor environments.

关键词： cooperative localization node selection PDR indoor localization

DFF-EDR:An Indoor Fingerprint Location Technology Using Dynamic Fusion Features of Channel State Information and Improved Edit Distance on Real Sequence

在线全文

学校读者我要写书评

暂无评论

China Communications 2021年第4期18卷 40-63页

作者： Ke Han Yunfei Xu Zhongliang Deng Jiawei Fu School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

Positioning technology based on wireless network signals in indoor environments has developed rapidly in recent years as the demand for locationbased services continues to increase.Channel state information(CSI)can be used as location feature information in fingerprint-based positioning systems because it can reflect the characteristics of the signal on multiple subcarriers.However,the random noise contained in the raw CSI information increases the likelihood of confusion when matching fingerprint data.In this paper,the Dynamic Fusion Feature(DFF)is proposed as a new fingerprint formation method to remove the noise and improve the feature resolution of the system,which combines the pre-processed amplitude and phase data.Then,the improved edit distance on real sequence(IEDR)is used as a similarity metric for fingerprint matching.Based on the above studies,we propose a new indoor fingerprint positioning method,named DFF-EDR,for improving positioning performance.During the experimental stage,data were collected and analyzed in two typical indoor environments.The results show that the proposed localization method in this paper effectively improves the feature resolution of the system in terms of both fingerprint features and similarity measures,has good anti-noise capability,and effectively reduces the localization errors.

关键词： channel state information indoor positioning edit distance on real sequence dynamic parameters feature resolution

A Three-phase Integrated Power Electronic Transformer with the Capability of DC Fault Clearance

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2021年第4期7卷 785-796页

作者： Yunfei Xu Guangfu Tang Weiguo Li Guoliang Zhao Zhanfeng Deng State Key Laboratory of Advanced Transmission Technology(Global Electricity Interconnection Research Institute Co.Ltd.) Changping DistrictBeijing 102211China

This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC side.Finally,this paper verifies the proposed PET through an EMT simulation and experimental prototype.

关键词： DC fault clearing experimental verification power electronic transformer three phase integration

Periodic atomization characteristics of simplex swirl injector induced by klystron effect

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2018年第5期31卷 1066-1074页

作者： Anlong YANG Shangrong YANG Yunfei Xu Longfei LI Science and Technology on Liquid Rocket Engine Laboratory Xi'an Aerospace Propulsion Institute

The atomization dynamic characteristics of a simplex swirl injector was investigated experimentally by using a hydrodynamic mechanical pulsator and the shadow photography technique. The frequency response characteristics of the fluid film and atomization fluctuations and their correlations with pressure fluctuations were obtained by using an in-house code of image processing. It is demonstrated that the klystron effect induced by periodic pressure fluctuations results in periodic liquid film fluctuation with large amplitudes, periodic superposition of droplets and reduction of the breakup length. It was found that the atomization of the simplex swirl injector only responds to the pressure fluctuation in frequency range approximately from 0 to 300 Hz, and it is particularly sensitive to pressure fluctuations at frequencies from 100 to 200 Hz. According to this experiment, the responsive frequency limitation is merely affected by injector configuration, rather than the supply line.

关键词： Atomization Combustion stability Klystron effect Liquid rocket engine Simplex swirl injector

A Simplified Model for Buckling and Post-Buckling Analysis of Cu Nanobeam Under Compression

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2020年第11期125卷 611-623页

作者： Jiachen Guo Yunfei Xu Zhenyu Jiang Xiaoyi Liu Yang Cai Department of Engineering Mechanics South China University of TechnologyGuangzhou510640China The Peac Institute of Multiscale Sciences Chengdu610031China

Both of Buckling and post-buckling are fundamental problems of geometric nonlinearity in solid mechanics.With the rapid development of nanotechnology in recent years,buckling behaviors in nanobeams receive more attention due to its applications in sensors,actuators,transistors,probes,and resonators in nanoelectromechanical systems(NEMS)and biotechnology.In this work,buckling and post-buckling of copper nanobeam under uniaxial compression are investigated with theoretical analysis and atomistic simulations.Different cross sections are explored for the consideration of surface effects.To avoid complicated high order buckling modes,a stressbased simplified model is proposed to analyze the critical strain for buckling,maximum deflection,and nominal failure strain for post-buckling.Surface effects should be considered regarding critical buckling strain and the maximum post-buckling deflection.The critical strain increases with increasing nanobeam cross section,while themaximumdeflection increases with increasing loading strain but stays nearly the same for different cross sections,and the underlying mechanisms are revealed by our model.The maximum deflection is also influenced by surface effects.The nominal failure strains are captured by our simulations,and they are in good agreement with the simplified model.Our results can be used for helping design strain gauge sensors and nanodevices with self-detecting ability.

关键词： Nanobeam buckling post-buckling simplified model atomistic simulation

Periodic atomization characteristics of an impinging jet injector element modulated by Klystron effect

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2018年第10期31卷 1973-1984页

作者： Anlong YANG Bin LI Shangrong YANG Yunfei Xu Longfei LI Science and Technology on Liquid Rocket Engine Laboratory Xi'an Aerospace Propulsion Institute

An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter images are captured by using the high speed camera. It is found that periodicity of forced atomization relies on pressure drop fluctuation amplitude and phase differences between atomization and pressure drop fluctuations relate to fluctuation frequencies. This feature of periodic atomization induced by Klystron effect corresponds to periodicities and high amplitudes of pressure fluctuations in unstable combustion chambers and chaos and low amplitudes of pressure fluctuations in stable combustions chambers. Drastically periodic varying of gross surface area of droplets with time was shown in Mie scatter images. The importance of periodic impinging jet atomization modulated by pressure drop fluctuations for acoustic liquid propellant combustion instabilities is illustrated.

关键词： Atomization Combustion stability Impinging jet injector Klystron effect Liquid rocket engine Mie scatter

Design of Novel and Low Cost Triple-node Upset Self-recoverable Latch

在线全文

学校读者我要写书评

暂无评论

原子能科学技术 2023年第12期57卷 2326-2336页

作者： BAI Na MING Tianbo xu Yaohua WANG Yi LI yunfei LI Li Information Materials and Intelligent Sensing Laboratory of Anhui Province Anhui UniversityHefei 230601China Shanxi Key Laboratory of Advanced Semiconductor Optoelectronic Devices and Integrated Systems Jincheng 048000China Jincheng Research Institute of Opo-mechatronics Industry Jincheng 048000China

With the development of semiconductor technology,the size of transistors continues to shrink.In complex radiation environments in aerospace and other fields,small-sized circuits are more prone to soft error(SE).Currently,single-node upset(SNU),double-node upset(DNU)and triple-node upset(TNU)caused by SE are relatively common.TNU’s solution is not yet fully mature.A novel and low-cost TNU self-recoverable latch(named NLCTNURL)was designed which is resistant to harsh radiation effects.When analyzing circuit resiliency,a double-exponential current source is used to simulate the flipping behavior of a node’s stored value when an error occurs.Simulation results show that the latch has full TNU self-recovery.A comparative analysis was conducted on seven latches related to TNU.Besides,a comprehensive index combining delay,power,area and self-recovery—DPAN index was proposed,and all eight types of latches from the perspectives of delay,power,area,and DPAN index were analyzed and compared.The simulation results show that compared with the latches LCTNURL and TNURL which can also achieve TNU self-recoverable,NLCTNURL is reduced by 68.23%and 57.46%respectively from the perspective of delay.From the perspective of power,NLCTNURL is reduced by 72.84%and 74.19%,respectively.From the area perspective,NLCTNURL is reduced by about 28.57%and 53.13%,respectively.From the DPAN index perspective,NLCTNURL is reduced by about 93.12%and 97.31%.The simulation results show that the delay and power stability of the circuit are very high no matter in different temperatures or operating voltages.

关键词： circuit reliability latch design self-recoverability soft error radiation hardening triple-node upset