检索结果-南通市图书馆

Ferroelectric properties of Bi_(3.4)Ho_(0.6)Ti_3O_(12) thin films prepared by sol-gel method

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Technological sciences) 2008年第9期51卷 1439-1444页

作者： FU ChengJu1, HUANG ZhiXiong1, LI Jie2 & GUO DongYun3 1 school of Materials science and technology, Wuhan university of technology, Wuhan 430070, china 2 school of Mechanical engineering, Chongqing university of science and technology, Chongqing 400050, china 3 Department of Physics, Wuhan university, Wuhan 430072, china school of Materials science and technology Wuhan University of Technology Wuhan 430070 China school of Mechanical engineering Chongqing University of Science and Technology Chongqing 400050 China Department of Physics Wuhan University Wuhan 430072 China

We have prepared the Ho-substituted bismuth titanate (Bi3.4Ho0.6Ti3O12, BHT) thin films on Pt/Ti/SiO2/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm2 and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×109 switching cycles at 1 MHz frenquency, and the BHT film shows good in-sulating behavior according to the test of leakage current.

关键词： Bi3.4Ho0.6Ti3O12 thin film sol-gel method ferroelectric property fatigue dielectric constant

FORMING PRINCIPLE OF TWO SIDE-DIRECTION BURR AND IT'S PREDICTION IN METAL CUTTING

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2001年第4期14卷 300-304页

作者： Wang Guicheng (school of Machinery engineering,Jiangsu university of science and technology) 江苏理工大学江苏

The burr is one of the common phenomena occurring i n metal cutting operations The mathematical mechanical model of two side dir ection burr formation and transformation is established with plane stress strain theory,based on the orthogonal cutting The main laws of formation and change of the burr are revealed,and it is confirmed by experiment result,which first realizes prediction of the forming and changing of the two side direction burr in metal cutting operation.

关键词： Metal cutting Two side direction burr Mathe matical mechanical model Prediction Precision and ultraprecision machining

A new heuristic algorithm for the circular packing problem with equilibrium constraints

在线全文

学校读者我要写书评

暂无评论

science china(Information sciences) 2011年第8期54卷 1572-1584页

作者： LIU JingFa 1,2,LI Gang 3 & GENG HuanTong 1 1 school of computer and Software,Nanjing university of Information science & technology,Nanjing 210044,china 2 Network Information Center,Nanjing university of Information science & technology, Nanjing 210044,china 3 school of Mathematics and Physics,Nanjing university of Information science & technology,Nanjing 210044,china 1. school of computer and Software Nanjing University of Information Science & Technology Nanjing 210044 China2. Network Information Center Nanjing University of Information Science & Technology Nanjing 210044 China3. School of Mathematics and Physics Nanjing University of Information Science & Technology Nanjing 210044 China

The circular packing problem with equilibrium constraints is an optimization problem about simplified satellite module layout design.A heuristic algorithm based on tabu search is put forward for solving this *** algorithm begins from a random initial configuration and applies the gradient method with an adaptive step length to search for the minimum energy *** jump out of the local minima and avoid the search doing repeated work,the algorithm adopts the strategy of tabu *** the process of tabu search,we improve the traditional neighboring solutions,tabu objects and the acceptance criteria of the current solution *** test two sets of benchmarks consisting of 11 representative instances from the current *** numerical results show that the proposed algorithm breaks the records in seven out of 11 instances,and obtains the optimal solutions for the other four instances.

关键词： equilibrium constraints packing problem heuristic algorithm tabu search layout optimization

Corner occupying theorem for the two-dimensional integral rectangle packing problem

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Information sciences) 2012年第11期55卷 2466-2472页

作者： HUANG WenQi1,YE Tao1 & CHEN DuanBing2 1school of computer science and technology,Huazhong university of science and technology,Wuhan 430074,china 2Web sciences Center,school of computer science,university of Electronic science and technology of china,Chengdu 611731,china 1. school of computer science and technology Huazhong University of Science and Technology Wuhan 430074 China2. Web Sciences Center School of Computer Science University of Electronic Science and Technology of China Chengdu 611731 China

This paper proves a corner occupying theorem for the two-dimensional integral rectangle packing problem,stating that if it is possible to orthogonally place n arbitrarily given integral rectangles into an integral rectangular container without overlapping,then we can achieve a feasible packing by successively placing a rectangle onto a bottom-left corner in the *** on this theorem,we might develop e?cient heuristic algorithms for solving the integral rectangle packing *** fact,as a vague conjecture,this theorem has been implicitly mentioned with different appearances by many people for a long time.

关键词： rectangle packing bottom-left corner occupying theorem NP hard

Irradiation Damage of Oxide Dispersion Strengthened Ferritic Steel after Recrystallization

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 160-164页

作者： Benfu Hu Shunmi Peng H Takahashi(Material science and engineering school, university of science and technology Beijing, Beijing 100083, china)(Faculty of engineering, Hokkado university, Sapporo 060, Japan) Material science and engineering school University of Science and Technology Beijing Beijing 100083 China Faculty of engineering Hokkado University Sapporo 060 Japan

The evolution of secondary defects and the characteristics of the void swelling of electrons irradiated Oxide Dispersion Strengthened Ferritic Steels (ODS steels) after recrystallization were studied. It was found that recrystallization increases the void swelling of ODS steel as compared with solution and injected He+ + D+ *** are two size ranges of voids formed in recrystallized ODS steel during irradiation, and bubbles can be preferential sites for the void formation. Polycrystal with low density of defects is formed, and sites where point defects disappear by irradiation decrease. This is the main reason for the increase of void swelling of ODS steel after recrystallization.

关键词： ODS steel recrystallization, electron irradiation

Wear characteristics of spheroidal graphite roll WC-8Co coating produced by electro-spark deposition

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2010年第2期29卷 174-179页

作者： WANG Jiansheng, MENG Huimin, YU Hongying, FAN Zishuan, and SUN Dongbai school of Materials science and engineering, university of science and technology Beijing, Beijing 100083, china school of Materials science and engineering University of Science and Technology Beijing

Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll *** microstructure and properties of the coating were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） with energy dispersive X-ray（EDX） and ball-disc configuration wear *** results show that nanosized particles and amorphous structures prevail in the coating which is metallurgically bonded to the *** microstructures of the transition zone include columnar structure and equiaxed *** primary phases of the coating contain W2C, W6C2.54, Fe3W3C, and *** results of abrasive test show that the coating has low friction coefficients（μaverage = 0.18） and the wear mechanisms are mainly abrasive wear, fatigue wear, and oxidation *** maximum microhardness value of the coating is about 17410 N/*** study reveals that the electro-spark deposition process has better coating quality and the coating has high wear resistance and hardness.

关键词： electro-spark deposition WC/Co coatings wear resistance microstructure

Powder injection molding of pure titanium

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2009年第3期28卷 261-265页

作者： GUO Shibo DUAN Bohua HE Xinb QU Xuanhui Advanced Materials Synthesis and Applied technology Laboratory College of Electromechanical Engineering Hunan University of Science and Engineering Xiangtan 411201 China school of Materials science and engineering University of Science and Technology of Beijing Beijing 100083 China

An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.

关键词： powder injection molding titanium debinding sintering mechanical properties

Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating

在线全文

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2006年第8期16卷 874-878页

作者： LIU Junbo, WANG Limei and HUANG Jihua (Weifang university, Weifang 261061, china school of Materials science and engineering, university of science and technology, Beijing 100083, china) Weifang university Weifang 261061 China school of Materials science and engineering University of Science and Technology Beijing 100083 China

A wear resistant Cr7C3/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr7C3 primary particles uniformly distributed in theγ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr7C3/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr7C3/γ-Fe ceramal composite coating is attributed to the coating's high hardness, strong covalent atomic bonding and refined microstructure.

关键词： PTA clad Cr7C3/γ-Fe composite coating microstructure wear resistance.

Simulation of the Backward Flow of the Melted Pool into the Laser Keyhole

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

稀有金属材料与工程 2011年第S4期40卷 35-38页

作者： Wang Hong,Huo Houzhi,Wang Lingyun school of Material science and engineering,Taiyuan university of science and technology,Taiyuan 030024,china Taiyuan Univ Sci & Technol Sch Mat Sci & Engn Taiyuan 030024 Peoples R China

When laser beam is ceased,the melt metal flows downward to fill the keyhole during keyhole *** models and VOF(volume of fluid)techniques have been developed to study the refilling *** simulation results show that the surface tension pressure plays more important role than the total pressure of fluid flow in the molten pool,and the violent interaction between liquid metal and keyhole air and whirlpool in the fluid flow influence the dimension of keyhole air region and the velocity of molten pool.

关键词： laser welding molten pool simulation