检索结果-南通市图书馆

Asymmetric Baylis-Hillman Reaction between Chiral Activated Alkenes and Aromatic Aldehydes in Me_(3)N/H_(2)O/Solvent Medium

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2005年第11期16卷 1427-1430页

作者： Ke HE Zheng Hong ZHOU Hong Ying tang guo Feng zhao Chu Chi tang State Key Laboratory of Elemento-Organic Chemistry Institute of Elemento-Organic Chemistry Nankai University Tianjin 300071

Chiral activated alkene, L-menthyl acrylate and （＋）-N-α-phenylethyl acrylamide, induced asymmetric Baylis-HiUman reaction of aromatic aldehydes was realized at 25℃ for 7 days in Me3N/H2O/solvent homogeneous medium. The corresponding Baylis-Hillman adducts were obtained in good chemical yield with moderate to excellent diastereoselectivity （up to 99% de）.

关键词： Chiral activated alkene asymmetric Baylis-Hillman reaction aromatic aldehyde,diastereoselectivity

Research progress on metal-organic framework compounds(MOFs)in electrocatalysis

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第7期141卷 261-276页

作者： Yutong guo Shunzheng zhao Xiaolong tang Honghong Yi Department of Environmental Science and Engineering School of Energy and Environmental EngineeringUniversity of Science and Technology BeijingBeijing 100083China Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants Beijing 100083China

Metal-organic frameworks(MOFs)have favorable characteristics such as large specific surface area,high porosity,structural diversity,and pore surface modification,giving them great potential for development and attractive prospects in the research area of modern materials ***,unsatisfactory catalytic activity and poor electronic conductivity are the main challenges facing *** review focuses on MOF-based materials used in electrocatalysis,based on the types of catalytic reactions that have used MOF-based materials in recent years along with their applications,and also looks at some new electrocatalytic materials and their future development prospects.

关键词： Metal-organic frame compounds Electrocatalysis Oxidation-reduction Nitrogen fixation to synthesize ammonia Carbon dioxide reduction

Time-domain model for wheel-rail noise analysis at high operation speed

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2017年第8期18卷 593-602页

作者： Jian HAN Shuo-qiao ZHONG Xin ZHOU Xin-biao XIAO guo-tang zhao Xue-song JIN State Key Laboratory of Traction Power Southwest Jiaotong University Chengdu 610031 China China Railway Corporation Beijing 100844 China

This paper develops a numerical model for wheel-rail noise analysis in the time-domain. This model for wheel-rail noise is based on vehicle-track coupling dynamics considering the effect of flexible wheelsets and track, and a transient wheel-rail noise prediction method. This model can approximatively characterize the components of vibration and noise in the frequency range up to 3.5 kHz. The wheel-rail forces are calculated and shown in both time and frequency domains by using the vehicle- track coupling dynamic model. Then the vibration and sound of the flexible wheelset are calculated by the transient finite element- boundary element （FE-BE） prediction model at 300 kin/h, in which the effects of random irregularity and discrete supporting excitation are considered. The numerical results calculated by using the present model are discussed. The present model is also used to calculate the effect of corrugation with wavelengths of 40 mm to 300 mm on wheel-rail noise. The numerical results can be useful for academic research and engineering application to railway noise and vibration.

关键词： Vibration and sound Wheel-rail Vehicle-track coupling dynamics Rigid wheelset Flexible wheelset High-speed operation

Conceptual design of a 714-MHz RFQ for compact proton injectors and development of a new tuning algorithm on its aluminium prototype

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第1期35卷 45-58页

作者： Yi-Xing Lu Wen-Cheng Fang Yu-Sen guo Zhen-tang zhao Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800China University of Chinese Academy of Sciences Beijing 101408China Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201204China Shanghai Key Laboratory of Cryogenics&Superconducting RF Technology Shanghai 201800China ShanghaiTech University Shanghai 201210China

Radio frequency quadrupoles(RFQs),which are crucial components of proton injectors,significantly affect the performance of proton accelerator *** RFQ with a high frequency of 714 MHz dedicated to compact proton injectors for medi-cal applications is designed in this *** RFQ is designed to accelerate proton beams from 50 keV to 4 MeV within a short length of 2 m and can be matched closely with the downstream drift tube linac to capture more particles through a preliminary *** develop an advanced RFQ,challenging techniques,including fabrication and tuning method,must be evaluated and verified using a *** aluminium prototype is derived from the conceptual design of the RFQ and then redesigned to confirm the radio frequency performance,fabrication procedure,and feasibility of the tuning ***,a new tuning algorithm based on the response matrix and least-squares method is developed,which yields favorable results based on the prototype,i.e.,the errors of the dipole and quadrupole components reduced to a low level after several tuning *** from the conceptual design and techniques obtained from the prototype,the formal mechanical design of the 2-m RFQ is ready for the next manufacturing step.

关键词： Compact proton injector RFQ IH-DTL High gradient Tuning

Authenticated Digital Currency Redaction with Stronger Privacy and Usability

在线全文

学校读者我要写书评

暂无评论

China Communications 2024年第6期21卷 219-236页

作者： tang Yongli Li Ying zhao Zongqu Li Yuanhong guo Rui School of Computer Science and Technology Henan Polytechnic UniversityJiaozuo 454000China School of Cyberspace Security Xi’an University of Posts and TelecommunicationsXi’an 710121China

With the promotion of digital currency,how to effectively solve the authenticity,privacy and usability of digital currency issuance has been a key *** signature scheme(RSS)can provide the verification of the integrity and source of the generated sub-documents and solve the privacy problem in digital currency by removing blocks from the signed ***,it has not realized the consolidation of signed documents,which can not solve the problem of merging two digital ***,we introduce the concept of weight based on the threshold secret sharing scheme(TSSS)and present a redactable signature scheme with merge algorithm(RSS-MA)using the quasi-commutative *** scheme can reduce the communication overhead by utilizing the merge algorithm when transmitting multiple digital currency ***,this can effectively hide the scale of users’private monetary assets and the number of transactions between *** meeting the three properties of digital currency issuance,in order to ensure the availability of digital currency after redacting,editors shall not remove the relevant identification information block form digital ***,our security proof and the analysis of efficiency show that RSS-MA greatly improves the communication and computation efficiency when transmitting multiple signatures.

关键词： authenticity verification digital currency privacy protection RSS-MA TSSS usability

Suppression of low-frequency ultrasound broadband vibration using star-shaped single-phase metamaterials

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第4期34卷 217-224页

作者： Rui zhao Jian Zheng Jin guo Yunbo Shi Hengzhen Feng Jun tang Jun Liu Science and Technology on Electronic Test&Measurement Laboratory North University of ChinaTaiyuan 030051ShanxiChina School of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China

In order to suppress the low-frequency ultrasound vibration in the broadband range of 20 k Hz—100 k Hz,this paper proposes and discusses an acoustic metamaterial with low-frequency ultrasound vibration attenuation properties,which is configured by hybrid arc and sharp-angle convergent star-shaped *** effect of the dispersion relation and the bandgap characteristic for the scatterers in star-shaped are simulated and *** target bandgap width is extended by optimizing the geometry parameters of arc and sharp-angle convergent *** proposed metamaterial configured by optimized hybrid lattices exhibits remarkable broad bandgap characteristics by bandgap complementarity,and the simulation results verify a 99%vibration attenuation amplitude can be obtained in the frequency of20 k Hz—100 k *** the fabrication of the proposed hybrid configurational star-shaped metamaterial by 3D printing technique,the transmission loss experiments are performed,and the experimental results indicate that the fabricated metamaterial has the characteristics of broadband vibration attenuation and an amplitude greater than 85%attenuation for the target *** results demonstrate that the hybrid configurational star-shaped metamaterials can effectively widen the bandgap and realize high efficiency attenuation,which has capability for the vibration attenuation in the application of highprecise equipment.

关键词： Star-shaped metamaterials Broadband Vibration attenuation Low-frequency ultrasound vibration Transmission loss

On the low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2024年第1期168卷 227-238页

作者： Guangyi guo guofu Xu Yuan tang Zhihao zhao Zhihao Yi Haoran Li Ruohan Wang Xiaoyan Peng School of Materials Science and Engineering Central South UniversityChangsha 410083China Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education Changsha 410083China

The low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing(NIA)was examined at different strain *** showed that NIA improved the low cycle fatigue life(more than 7000 cycles)by optimising the precipitate configuration within 5.5 h while maintaining comparable mechanical properties(570 MPa for tensile strength)and conductivity(nearly 39%IACS)to conventional isothermal ageing,*** observation combined with molecular dynamic simula-tion revealed that precipitation configuration manipulated by NIA had a crucial effect on fatigue resis-tance.A great number of repeatedly sheared and locally destructed GP zones enhanced co-planar slip and slip localisation in the under-aged alloy during the early stage of NIA,responsible for the dramatic displacement steps on the surface and resultant poor fatigue *** the NIA further proceeded,moderately coarsened precipitates with an average dimension of 6.0 nm and elevated number density ef-fectively impeded the dislocation movement and weaken the slip localisation to a great extent,improving the fatigue performance within a few hours.

关键词： Non-isothermal ageing Fatigue Al-Zn-Mg-Cu alloy Precipitate manipulation Slip localization

Blautia producta displays potential probiotic properties against dextran sulfate sodium-induced colitis in mice

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

Food Science and Human Wellness 2024年第2期13卷 709-720页

作者： Bingyong Mao Weiling guo Shumao Cui Qiuxiang Zhang Jianxin zhao Xin tang Hao Zhang State Key Laboratory of Food Science and Resources Jiangnan UniversityWuxi 214122China School of Food Science and Technology Jiangnan UniversityWuxi 214122China National Engineering Research Center for Functional Food Jiangnan UniversityWuxi 214122China

Blautia has attracted attention because of its potential efficacy in ameliorating host energy metabolism and *** study aims to investigate the influences of Blautia producta D4 on colitis induced by dextran sulfate sodium(DSS)and to reveal the underlying *** showed that *** D4 intervention significantly relieved body weight loss,and suppressed the elevation of pro-inflammatory cytokines(including interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),and interleukin-1β(IL-1β))and excessive oxidative stress(myeloperoxidease(MPO)activity,superoxide dismutase(SOD)activity,glutathione peroxidase(GSH-Px)activity,and malondialdehyde(MDA)level)in colitis ***,the concentrations of tight junction proteins(occludin,claudin-1,and ZO-1)related to the intestinal barrier were obviously elevated,and colitis-related TLR4/NF-κB pathway activation was remarkably inhibited after *** D4 *** intestinal microbial disorder was evidently ameliorated by increasing the relative abundance of Clostridium sensu stricto 1,Bifidobacterium,GCA-900066225,Enterorhabdus,and reducing the relative abundance of Lachnospiraceae NK4A136 *** conclusion,oral administration of *** D4 could ameliorate DSS-induced colitis by suppressing inflammatory responses,maintaining the intestinal barrier,inhibiting TLR4/NF-κB pathway,and regulating intestinal microbiota *** results are conducive to accelerate the development of *** D4 as a functional probiotic for colitis.

关键词： Blautia producta D4 Colitis Intestinal mechanical barrier TLR4/NF-κB pathway Intestinal microbiot

Advances in ice avalanches on the Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2024年第6期21卷 1814-1829页

作者： tang Minggao LI Guang zhao Huanle XU Qiang WU Guangjian YANG Wei guo Daojing State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China College of Environment and Civil Engineering Chengdu University of TechnologyChengdu 610059China Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing 100101China

As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains *** summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st *** distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to *** highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing *** failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure ***,we deliver recommendations concerning the risk assessment and prediction of *** results provide important scientific value for addressing climate change and resisting glacier-related hazards.

关键词： Ice avalanche Global warming Genetic mechanism Risk assessment Tibetan Plateau