检索结果-南通市图书馆

Third-Order Nonlinear Optical Responses of Bis(15-crown-5)-stilbenes Binding to One-or Two-Alkali Metal Cation(li^(+),Na^(+)and K^(+))

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Physics 2023年第5期36卷 601-612,I0002页

作者： hai-ling Yu Tong Zhang Tian-liang ma Bo Hong zhi-qiang Cheng College of Resources and Environmental Science Jilin Agricultural UniversityChangchun 130118China

Bis(15-crown-5)-stilbenes containing crown ether parts have been widely used in a variety of chemical applications,such as cation detectors,because of their ability to selectively bind to alkali metal cations,Bis(15-crown-5)-stilbenes and its derivatives with complexation of one-or two-alkali metal cation(li^(+),Na^(+)and K^(+))have been theoretically investigat-ed by quantum chemistry *** coordination of alkali cations results in partial shrinkage of crown ethers,which directly affected natural distribution analysis charges and molecular orbital energy *** number of alkali metal ions has significant effects on absorption spectra and mean second *** one alkali metal ion was added to the anticonformer of bis(15-crown-5)-stilbene,the absorption spectra were obvious-ly redshifted and the mean second hyperpolarizability values were slightly increased;while two alkali metal ions were added to bis(15-crown-5)-stilbene,the absorption spectra were ob-viously blue shifted and the mean second hyperpolarizability values *** the other hand,as the radius of the alkali ions increased,the mean second hyperpolarizability values of the compounds increased *** is indicated that the mean second hyperpolarizability value is sensitive to the number and radius of the alkali metal cations,thus the third order nonlinear optical response can be used as a signal to detect the number and type of alkali met-al ions.

关键词： Bis(crown)-stilbene Cation detector Metal cation Quantum chemistry Sec-ond hyperpolarizability

Effect of Niobium and Titanium on Dynamic Recrystallization Behavior of Low Carbon Steels

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

Journal of Iron and Steel Research International 2008年第3期15卷 31-36页

作者： ma li-qiang liU Zhen-yu JIAO Si-hai yuan xiang-qian WU Di Shenyang Metrology Testing Institution Shenyang 110179 Liaoning China State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 Liaoning China Institute of Research and Development Baosteel Co Shanghai 201900 China

Using a Gleeble 3800 thermo-mechanical simulator, the effect of niobium and titanium on the dynamic recrystallization （DRX） behavior of low carbon steels was investigated. Isothermal single compression tests were performed in the temperature range of 850 to 1 150 ℃ at constant strain rates of 0.1 to 5 s-1. The experimental results showed that the addition of niobium and titanium to the low carbon steels significantly increased both the peak stress and steady state stress. The activation energy of deformation Qd was larger than the activation energy associated with the steady state stress Qss. Furthermore, the difference between Qd and Qss became significant because of the addition of niobium and titanium. DRX is effectively retarded because of solute dragging and dynamic precipitate pinning of niobium and titanium, resulting in higher values of the peak strain and steady state strain. Finally, the influence of niobium and titanium on the DRX kinetics and steady state grain size was determined.

关键词： peak strain activation energy dynamic recrystallization

Improvement of impact properties of Al-Si-Mg alloy via solution treatment and joint modification with Sr and La

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第7期43卷 3301-3313页

作者： Xiong-ling Zheng Shao-xiang li Jia-Le ma Qing-Yan Xu hai-Dong Zhao zhi-qiang Han Key Laboratory for Advanced materials Processing Technology Ministry of EducationSchool of Materials Science and EngineeringTsinghua UniversityBeijing 100084China National Engineering Research Center of Near-Net Shape Forming for Metallic materials South China University of TechnologyGuangzhou 510641China

An effort to obtain superior impact properties for Al-7Si-0.35 Mg alloy is presented,where modification with 0.02 wt% Sr and 0.1 wt% La as well as solution treatment was jointly *** samples were solution treated at 535℃ for 15 min to 12 *** microstructure,fracture mechanism,and their correlation with the impact properties of the alloy were studied in detail mainly through optical microscopy(OM),scanning electron microscopy(SEM) and oscillography impact *** results show that the addition of Sr and La refined the eutectic Si particles significantly from~ 2.05 μm(modified with Sr alone) to~ 0.75 μm in as-cast microstructure,leading to a very homogeneous distribution of spheroidized Si particles in the alloy solution treated at 535℃ for 8 *** alloy exhibits excellent impact toughness up to 75 J·cm^(-2),which is much higher than the maximum impact toughness of the alloys modified by Sr alone(~ 46 J·cm^(-2)).The major reason for this remarkable increase in the impact property is the dramatic increase in crack initiation *** dispersoid-free zones(DFZs)near the eutectic regions mainly consist of the ductile Al-matrix,which exhibits excellent *** ductile Al-matrix of the DFZs hinders the crack propagation,resulting in a significant increase in crack propagation energy.

关键词： Aluminum alloys Modification Solution treatment Microstructure Impact properties Fracture mechanism

An Objective Measure to Evaluate Actual Body Shape among Children and Adolescents in China

在线全文

学校读者我要写书评

暂无评论

Biomedical and Environmental Sciences 2014年第8期27卷 582-593页

作者： FU lian Guo WANG hai Jun li Xiao Hui WANG zhi qiang Patrick WC Lau YANG Yi De meng xiang Kun ma Jun Institute of Child and Adolescent Health School of Public Health Peking University Health Science Center Centre for Chronic Disease School of Medicine University of Queensland Department of Physical Education Hong Kong Baptist University

Objective The purpose of this study was to explore an objective measure to assess actual body shape of children and adolescents in China. Methods Based on the Chinese National Survey on Student＇s Constitution and Health （CNSSCH） in 2005, 210 927 children and adolescents＇（7-18 years） body height, body weight, chest circumference, sitting height, chest circumference-height ratio, chest circumference-sitting height ratio, chest circumference-low limb ratio, and sitting height-low limb ratio measurements were used to develop an objective measure by using transformation variables and explored factor analysis （EFA）. Discrimination power of the objective measure was evaluated based on BMI reference and Receiver Operating Characteristic curves （ROC）. Results The objective measure included four dimensions scores：transverse dimension （TD） indicating weight and chest circumference; length dimension （LD） indicating height and sitting height;transverse-length ratio dimension （TLD） indicating chest circumference-height ratio, chest circumference-sitting height and chest circumference-low limb ratio; proportion dimension （PD） indicating sitting height-low limb ratio. The whole dimension （WD） indicating the whole body shape was showed by the average of four dimensions scores. Four dimensions and WD scores were approximately 80 in children and adolescents with normal weight, and higher than those of overweight, obesity, and underweight （all P-values〈0.001）. Areas under ROC of overweight and obesity compared with normal weight ranged from 0.88 to 1.00 for scores of TD, TLD, and WD. Conclusion The objective measure which included four dimensions was explored, and TD, TLD, and WD had significant discrimination power.

关键词： Objective measure Body shape Children and adolescents

Microstructures and mechanical properties of a commercial Mg-Al-Zn-Mn alloy with various hot-extrusion processes

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第3期43卷 1329-1336页

作者： He ma Fan-zhi meng qiang Yang Ze-Feng Xie yuan-Ding Huang Xin Qiu State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China School of materials Science and Engineering Changchun University of Science and TechnologyChangchun130022China magIC-magnesium Innovation Center Helmholtz-Zentrum Geesthacht21502GeesthachtGermany Engineering Research Center of Optoelectronic Functional materials Ministry of EducationChangchun University of Science and TechnologyChangchun130022China

Mg-Al-Zn-Mn(AZ)system alloys have become widely used due to their good castability,excellent formability and outstanding corrosion resistance[1-6].However,their strength is still much lower than that of traditional Mg... 详细信息

关键词： alloys alloy corrosion

在线全文

学校读者我要写书评

暂无评论

多目标粒子群优化的复合型组播拥塞控制

应用科学学报 2011年第5期29卷 459-466页

作者：麻海圆孟相如马志强马森空军工程大学电讯工程学院中国人民解放军94303部队

为提高异构环境下大规模动态组播的吞吐量并减小速率抖动,提出一种复合型组播拥塞控制机制(composite multicast congestion control,CMCC).该机制在基层和增强层使用不同的速率调节方案:基层使用单速率机制控制发送速率,防止接收能力... 详细信息

为提高异构环境下大规模动态组播的吞吐量并减小速率抖动,提出一种复合型组播拥塞控制机制(composite multicast congestion control,CMCC).该机制在基层和增强层使用不同的速率调节方案:基层使用单速率机制控制发送速率,防止接收能力较弱的接收端被"排挤"出组;增强层使用最优化的方法分配速率以提高组播吞吐量并平滑发送速率.CMCC以最大化全局满意度和最小化速率抖动为目标将增强层速率的分配归纳为多目标优化问题,并选用收敛速度快、参数少且计算量小的多目标粒子群优化算法搜索最优解.仿真结果表明,CMCC能有效提高组播吞吐量,平滑发送速率,且计算量小,实时性高,适用于具有异质接收端的大规模组播.

关键词：组播分层组播拥塞控制多目标优化粒子群优化

pH-Sensitive assembly/disassembly gold nanoparticles with the potential of tumor diagnosis and treatment

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2019年第1期62卷 105-117页

作者： jinlong ma Xiaomin li Zhenpeng Hu Xinyu Wang Yapei Zhang Wei Wang qiang Wu zhi yuan Key Laboratory of Functional Polymer materials of Ministry of Education Institute of Polymer Chemistry College of Chemistry Nankai University Collaborative Innovation Center of Chemical Science and Engineering Nankai University

Due to the ability to combine the separately unique characteristics of assembled and disassembled nanoparticles(NPs), the stimuli-responsive self-assembly of NPs has attracted considerable interest in functional material applications especially biomaterials. Here we demonstrate a facile and versatile approach to regulate the self-assembly process and transition pH of Au NPs by fine-tuning the co-modified pH-responsive compounds and poly(ethylene glycol)(PEG). Importantly the transition pH(ΔpH=0.4) of the system can be predetermined in the range of 8.2–5.8(assembled to disassembled) and 8.2–4.2(disassembled to assembled), which ideally covers the pH of normal tissue, tumor tissue milieu and organelles. The results of fluorescence imaging, Raman spectroscopy and photothermal conversion of the stimuli-responsive Au NPs shows the potential application for tumor specificity theranostics. In a nutshell this study provides a useful toolkit to design tumor-activatable self-assembled NPs with high specificity and universality.

关键词： pH-sensitive assemble disassemble gold nanoparticles transition pH

In-situ synchrotron high energy X-ray diffraction study of spontaneous reorientation of R phase upon cooling in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2022年第6期41卷 1948-1954页

作者： zhi-yuan ma Yu-Xuan Chen Yang Ren Kai-yuan Yu Da-qiang Jiang Yi-Nong liu li-Shan Cui Department of materials Science and Engineering China University of Petroleum(Beijing)Beijing 102249China Department of Physics City University of Hong KongHong Kong 999077China Centre for Neutron Scattering City University of Hong KongHong Kong 999077China Department of Mechanical Engineering The University of Western AustraliaPerthWA 6009Australia

This study investigated a peculiar phenomenon of self-reorientation of thermally formed R phase in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)by means of in-situ syn-chrotron high energy X-ray diffraction(HE-XRD).Two samples with different average grain sizes of 40 and 90 nm were investigated.R phase in the 40-nm grain size sample was found to self-reorient gradually upon cooling,whereas the same phenomenon did not occur in the 90-nm grain size *** self-reorientation process is attributed to the development and evolution of an internal stress anisotropy caused by the second order continuous lattice distortion of R phase upon further cooling in the small nanograined matrix,which lacks the self-accommodation mechanism for internal stress cancellation.

关键词： TiNiFe martensitic transformation R phase reorientation Synchrotron diffraction Nanocrystalline material

Boost VS_(2) electrochemical reactive kinetics by regulating crystallographic planes and coupling carbon matrix for high performance sodium-ion storage

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第1期43卷 98-112页

作者： Min Zeng Ming-Shan Wang lin Chen En-zhi li Zhen-liang Yang Dan Zhou hai-Jiao Xie Jun-Chen Chen zhi-yuan ma Bing-Shu Guo Bo Yu Xing li School of New Energy and materials Southwest Petroleum UniversityChengdu 610500China Energy Storage Research Institute Southwest Petroleum UniversityChengdu 610500China Institute of materials China Academy of Engineering PhysicsMianyang 621908China Beijing Advanced Innovation Center for materials Genome Engineering University of Science and TechnologyBeijingBeijing 100083China Hangzhou Yanqu Information Technology Co. Ltd.Hangzhou 310003China

Vanadium disulfide(VS_(2)) as a typical two-dimensional transition metal chalcogenide has excellent competitiveness for sodium-ion storage due to its wide layer spacing(0.575 nm),high theoretical capacity of 932mah·g^(-1) originating from multi-electron electrochemical ***,continuous sodiation process accompanied by crystal structural evolution and collapse cause rapid capacity ***,novel few-layer VS_(2)nanosheets with open(001) crystal planes are in-situ constructed on reduced graphene oxide to solve these issues mentioned *** indicates that few-layer VS_(2)provides more Na^(+) storage activity due to the low Na^(+)surface migration energy barrier on exposed crystal(001)*** flexible and high electronic conductivity of carbon matrix also effectively builds multi-level buffer structure and electron transport kinetics to boost the Na^(+)insertion/conversion reactive activity on VS_(2) as well as Na^(+) pseudocapacitance storage kinetics on edges and defects of nano *** coupling effects result in high rate capability and long cycling stability as a battery/capacitor *** delivers conspicuous high energy density of 81 and 40 Wh·kg^(-1) at power density of 118 and 10,286W·kg^(-1),as well as 80% energy retention rate after 5000cycles,confirming its great application potential in sodiumbased storage devices.

关键词： Vanadium disulfide Reduced graphene oxide Anode Sodium-ion battery Sodium-ion capacitor