检索结果-南通市图书馆

Cr-catalyzed allylic C(sp^(3))–H addition to aldehydes enabled by photoinduced ligand-to-metal charge transfer

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第5期67卷 1589-1595页

作者： Xianrong Zeng Feng-hua Zhang Runchen Lai Xiaoyu Lin Zhaobin wang Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province Department of ChemistrySchool of Science and Research Center for Industries of the FutureWestlake UniversityHangzhou 310030China Institute of Natural Sciences Westlake Institute for Advanced StudyHangzhou 310024China Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province Instrumentation and Service Center for Molecular SciencesWestlake UniversityHangzhou 310024China

Photoinduced ligand-to-metal charge transfer(LMCT) has emerged as an effective strategy for synthesizing organic molecules in a sustainable manner. However, the majority of existing reports on selective C(sp^(3))–H bond functionalization via photoinduced LMCT focus on the use of late transition metals or rare-earth metals for radical additions or cross-couplings. In contrast, the utilization of photoinduced LMCT with 3d early transition metals poses a significant challenge. Herein, we describe an unprecedented approach to allylic C(sp^(3))–H addition to aldehydes, employing chromium(Cr) complexes as catalysts through visible-light-induced LMCT. By investigating the reaction pathway through various mechanistic studies, including radical trapping, kinetic isotope effect(KIE) analysis, and transient absorption spectroscopy, valuable insights have been gained. The proposed mechanism suggests the intermediacy of bromine radicals through homolysis of the Cr–Br bond. Notably, this protocol expands our understanding of the photochemical properties of earth-abundant Cr complexes.

关键词： Cr catalysis photoinduced ligand-to-metal charge transfer hydrogen-atom transfer carbonyl addition

Effect of Mo and cold forging deformation on strength and ductility of cobalt-based alloy L605

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第7期31卷 1811-1823页

作者： Zhong-lin wang Zhi-hua Gong Quan Li Han-sheng Bao School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou 014017Inner MongoliaChina Institute of Special Steels Central Iron and Steel Research Institute Co.Ltd.Beijing 100081China

Mo element was added to cobalt-based alloy L605,and cold forging deformation was *** effects of the addition and cold forging deformation on the microstructure and mechanical properties of the alloy were studied by thermodynamic calculation,electron backscatter diffraction,transmission electron microscopy,and X-ray *** stacking fault energy(SFE)of the alloy decreased after the addition,and the formation of stacking faults and intersections were promoted to improve the strength and *** tensile strength of the alloy with Mo increased from 1190 to 1702 MPa after 24%cold deformation,producing significant work *** strengthening mechanism is strain-induced martensitic transformation(SIMT)and deformation *** alloy,combined with Mo and after 24%deformation,had both high strength and ductility in comparison with the original cobalt-based alloy *** is attributed to the lower SFE which caused the increase in stacking fault *** the tensile process,theε-hcp phase was easily generated at the stacking fault to reduce the stress concentration and increase the *** SIMT by adjusting the density of stacking faults can improve the mechanical properties of cobalt-based ***ε-hcp phase,the interaction between deformation twins and dislocations,and the interaction between e-hcp phases during cold forging deformation caused local stress concentration,lowering ductility and toughness.

关键词： Cobalt-based alloy-Stacking fault energy Strain-induced martensitic transformation Deformation twin Cold forging deformation

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

特殊构造砖烟囱定向爆破拆除

爆破 2017年第2期34卷 96-99,147页

作者：王爱华宁夏天宏爆破有限公司银川750011

介绍了定向控制爆破技术拆除一座烟囱、水塔的结合体,拟爆结构物地坪以上27 m处设置钢筋混凝土结构水箱,致使重心高于一般烟囱,其外壁采用ф12 mm钢筋网箍和60 mm厚混凝土进行加固。周边环境复杂,距高压配电房仅1.4 m,为避免地坪处+0.5 ... 详细信息

介绍了定向控制爆破技术拆除一座烟囱、水塔的结合体,拟爆结构物地坪以上27 m处设置钢筋混凝土结构水箱,致使重心高于一般烟囱,其外壁采用ф12 mm钢筋网箍和60 mm厚混凝土进行加固。周边环境复杂,距高压配电房仅1.4 m,为避免地坪处+0.5 m烟道口对定向的影响,将爆破切口位置提高到+3.0 m处;为减小触地振动、防止倾倒过程中出现后座,采用梯形切口,爆破切口长度取其周长62%,爆破切口高度取1.4 m。为克服烟囱外壁加固层和圆拱墙体钻凿深度不准确的影响,同排相邻炮孔采用一深、一浅的布置方式,其炮眼深度差值2~3 cm,装药结构应用正、反向起爆综合技术。采用开挖减震沟、设置缓冲带控制爆破振动等措施,爆破效果理想,保证了邻近建筑物及设施安全。

关键词：定向倒塌控制爆破砖混结构后坐倒梯形切口正、反起爆法

Effect of titanium on the sticking of pellets based on hydrogen metallurgy shaft furnace:Behavior analysis and mechanism evolution

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2024年第2期31卷 282-291页

作者： Jinge Feng Jue Tang Zichuan Zhao Mansheng Chu aijun Zheng Xiaobing Li Xiao’ai wang School of Metallurgy Northeastern UniversityShenyang 110819China Institute for Frontier Technologies of Low-carbon Steelmaking Northeastern UniversityShenyang 110819China Liaoning Low-carbon Steelmaking Technology Engineering Research Center Northeastern UniversityShenyang 110819China Engineering Research Center of Frontier Technologies for Low-carbon Steelmaking(Ministry of Education Shenyang 110819China Zhang Xuan Technology of HBIS Group Co. Ltd.Shijiazhuang 050000China Xuanhua Iron and Steel Group Co. Ltd.Shijiazhuang 050000China Iron and Steel Research Institute of HBIS Group Co. Ltd.Shijiazhuang 050000China

Direct reduction based on hydrogen metallurgical gas-based shaft furnace is a promising technology for the efficient and low-carbon smelting of vanadium-titanium ***,in this process,the sticking of pellets occurs due to the aggregation of metal-lic iron between the contact surfaces of adjacent pellets and has a serious negative effect on the continuous *** paper presents a detailed experimental study of the effect of TiO2 on the sticking behavior of pellets during direct reduction under different *** showed that the sticking index(SI)decreased linearly with the increasing TiO2 *** phenomenon can be attributed to the increase in unreduced FeTiO3 during reduction,leading to a decrease in the number and strength of metallic iron interconnections at the sticking *** the TiO2 addition amount was raised from 0 to 15wt%at 1100°C,the SI also increased from 0.71%to 59.91%.The connection of the slag phase could be attributed to the sticking at a low reduction temperature,corresponding to the low sticking ***,the interconnection of metallic iron became the dominant factor,and the SI increased sharply with the increase in re-duction ***2 had a greater effect on SI at a high reduction temperature than at a low reduction temperature.

关键词： titanium sticking index hydrogen metallurgy direct reduction pellets

在线全文

学校读者我要写书评

暂无评论

基于FPGA的高精度高斯白噪声产生方法

北京理工大学学报 2010年第4期30卷 474-477页

作者：汪春霆李修国王爱华西安电子科技大学通信工程学院陕西西安710071 北京理工大学信息与电子学院北京100081

提出一种基于非均匀量化思想的高精度高斯白噪声产生方法.该方法在利用均匀分布与高斯分布之间的映射关系产生高斯白噪声时,通过将映射曲线分区化,不同分区的均匀噪声的量化精度不同,可产生高精度高斯白噪声.实测数据表明,该方法在满足... 详细信息

提出一种基于非均匀量化思想的高精度高斯白噪声产生方法.该方法在利用均匀分布与高斯分布之间的映射关系产生高斯白噪声时,通过将映射曲线分区化,不同分区的均匀噪声的量化精度不同,可产生高精度高斯白噪声.实测数据表明,该方法在满足噪声精度要求的同时极大地减少了硬件资源占用.

关键词：非均匀量化高精度高斯白噪声曲线分区化

A Secure Mutual Authentication Protocol Based on Visual Cryptography Technique for IoT-Cloud

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2024年第1期33卷 43-57页

作者： Brou Bernard Ehui Chen CHEN Shirui wang hua GUO Jianwei LIU School of Cyber Sciences and Technology Beihang University State Key Laboratory of Software Development Environment Beihang University Sino-French Engineering School Beihang University Beihang Hangzhou Innovation Institute Yuhang

Because of the increasing number of threats in the IoT cloud, an advanced security mechanism is needed to guard data against hacking or attacks. A user authentication mechanism is also required to authenticate the user accessing the cloud services. The conventional cryptographic algorithms used to provide security mechanisms in cloud networks are often vulnerable to various cyber-attacks and inefficient against new attacks. Therefore,developing new solutions based on different mechanisms from traditional cryptography methods is required to protect data and users’ privacy from attacks. Different from the conventional cryptography method, we suggest a secure mutual authentication protocol based on the visual cryptography technique in this paper. We use visual cryptography to encrypt and decrypt the secret images. The mutual authentication is based on two secret images and *** user requests the ticket from the authentication server(AS) to obtain the permission for accessing the cloud services. Three shared secret keys are used for encrypting and decrypting the authentication process. We analyze the protocol using the Barrows-Abadi-Needham(BAN)-logic method and the results show that the protocol is robust and can protect the user against various attacks. Also, it can provide a secure mutual authentication mechanism.

关键词： Visualization Cloud computing Data privacy Protocols Biometrics (access control) Authentication Resists

碳包覆Zn_2SnO_4锂电池负极材料的制备及电化学性能研究

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

人工晶体学报 2014年第6期43卷 1535-1539页

作者：姬晓旭赵庆怀王丽王爱华南阳师范学院物理与电子工程学院南阳473061

利用Zn2SnO4纳米颗粒和葡萄糖为反应物,通过简单的水热法制备了碳包覆的Zn2SnO4纳米颗粒。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、热重分析(TG)和拉曼光谱对样品的结构、形貌和性质进行了表征。XRD和SEM结果表明制备了立... 详细信息

利用Zn2SnO4纳米颗粒和葡萄糖为反应物,通过简单的水热法制备了碳包覆的Zn2SnO4纳米颗粒。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、热重分析(TG)和拉曼光谱对样品的结构、形貌和性质进行了表征。XRD和SEM结果表明制备了立方尖晶石型Zn2SnO4纳米颗粒。TEM、TG和Raman结果表明制备了碳包覆的Zn2SnO4。电化学性能测试结果表明在200 mA/g的较大电流密度下,碳包覆Zn2SnO4纳米颗粒首次充放电容量分别为1429.2 mAh/g和737.7 mAh/g,库伦效率为51.6%。经过50次循环后放电容量保持374.8 mAh/g,表现出良好的循环性能,优于纯Zn2SnO4纳米颗粒。碳材料的引入抑制电极材料体积膨胀同时提高了其导电性能。

关键词：碳包覆 Zn2SnO4纳米颗粒负极材料锂离子电池

Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene:Efficient accessibility of active sites and suitable acidity

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 654-666页

作者： Ke Yu Wei-Min Kong Zhen Zhao ai-Jun Duan Lian Kong Xi-Long wang State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing102249China Institute of Catalysis for Energy and Environment College of Chemistry and Chemical EngineeringShenyang Normal UniversityShenyang 110034LiaoningChina

Yolk-shell SiO2 particles(YP)with center-radial meso-channels were fabricated through a simple and effective ***-containing YP-supported NiMo catalysts with different Al amounts(NiMo/AYP-x,x=Si/Al molar proportion)were prepared and dibenzothiophene(DBT)and 4,6-dimethyl-dibenzothiophene(4,6-DMDBT)were employed as the probes to evaluate the hydrodesulfurization(HDS)catalytic *** as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS *** average pore sizes of series AYP-x supports are above 6.0 nm,which favors the mass transfer of organic *** cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active *** embedded into the silica framework could facilitate the formation of Lewis(L)and Brønsted(B)acid sites and adjust the metal-support interaction(MSI).Among all the as-synthesized catalysts,NiMo/AYP-20 catalyst shows the highest HDS *** improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica,enhanced acidity,moderate MSI,and good accessibility/dispersion of active components.

关键词： Al-containing yolk-shell silica particles Accessibility Acidity Metal-support interaction Hydrodesulfurization

Improved nuclear mass formula with an additional term from the Fermi gas model

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第5期35卷 131-138页

作者： Xiao-Yu Xu Li Deng ai-Xi Chen Hang Yang Amir Jalili Han-Kui wang School of Science Zhejiang Sci-Tech UniversityHangzhou 310018China

Nuclear mass is a fundamental property of nuclear physics and a necessary input in nuclear *** to the complexity of atomic nuclei and nonperturbative strong interactions,conventional physical models cannot completely describe nuclear binding *** this study,the mass formula was improved by considering an additional term from the Fermi gas *** nuclear masses in the Atomic Mass Evaluation Database were reproduced with a root-mean-square deviation(RMSD)of -1.86 MeV(1.92 MeV).The new mass formula exhibits good performance in the neutron-rich nuclear *** RMSD decreases to 0.393 MeV when the ratio of the neutron number to the proton number is≥1.6.

关键词： Nuclear mass formula Neutron-rich nuclei Fermi-gas model