检索结果-南通市图书馆

Key parameters for low temperature warm compaction of high density iron-based P/M materials

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第4期12卷 359-365页

作者：曹顺华林信平李炯义谢湛蔡志勇 State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China State

In order to reduce powder temperature to lower than 100℃ in warm compaction by changing polymer lubricant design, powder flowability, warm compacting behavior, lubricating mode as well as ultimate tensile strength after sinter-hardening and tempering were investigated systematically. By means of low temperature warm pressing and sintered hardening technique, samples with the sintered densities of 7.407.45g/cm3 and the strengths of 950 1390MPa are achieved as the early compacting pressure is 686735MPa.

关键词： iron-based P/M materials low temperature warm compaction lubricating mode

Effect of nucleating agents on microstructure and mechanical properties of SiO_2-Al_2O_3-ZrO_2 glass-ceramics

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第5期12卷 507-510页

作者：余丽萍肖汉宁胡鹏飞 School of Materials Science and Engineering Hunan University Changsha 410082 China School of Chemistry and Chemical Engineering Hunan Normal University Changsha 410081 China School of Materials Science and Engineering Hunan University Changsha 410082 China

SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength （120MPa） than others.

关键词： glass-ceramics SiO2-Al2O3-ZrO2 system microstructure mechanical property

Characteristics of magnetic Fe_3O_4 nanoparticles encapsulated with human serum albumin

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2006年第1期13卷 6-11页

作者：何捍卫刘红江周科朝王维容鹏飞 State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China The Third Xiangya Hospital Central South University Changsha 410013 China

Magnetic nanoparticles （Fe304） were prepared by chemical precipitation method using Fe^2＋ and Fe^3＋ salts with sodium hydroxide in the nitrogen atmosphere. Fe3O4 nanoparticles were coated with human serum albumin（HSA） for magnetic resonance imaging as contrast agent. Characteristics of magnetic particles coated or uncoated were carried out using scanning electron microscopy and X-ray diffraction. Zeta potentials, package effects and distributions of colloid particles were measured to confirm the attachment of HSA on magnetic particles. Effects of Fe3O4 nanoparticles coated with HSA on magnetic resonance imaging were investigated with rats. The experimental results show that the adsorption of HSA on magnetic particles is very favorable to dispersing of magnetic Fe3O4 particles, while the sizes of Fe3O4 particles coated are related to the molar ratio of Fe3O4 to HSA. The diameters of the majority of particles coated are less than 100 nm. Fe3O4 nanoparticle coated with HSA has a good biocompatibility and low toxicity. This new contrast agent has some effects on the nuclear magnetic resonance imaging of liver and the lowest dosage is 20μmol/kg for the demands of diagnosis.

关键词： Fe3O4 nanoparticle human serum albumin chemical precipitation method magnetic resonance imaging contrast agent

Preparation and antimicrobial ability of natural porous antibacterial materials

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第4期12卷 370-375页

作者：董发勤李国武孙志刚沈刚冯启明代群威 School of Materials Science and Engineering Southwest University of Science and Technology Mianyang 621010 China School

The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag^＋ , Cu^2＋ and Zn^2＋ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i.e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag^＋ is the bests the exchange capacities of materials with Cu^2＋ or Zn^2＋ are all higher, but the antimicrobial ability of Cu^2＋ is better than that of Zn^2＋ .

关键词： liquid ion exchange solid salt melt dry-wet circulation mineral antimicrobial material

Microscopic phase-field simulation for nucleation incubation time of Ni_(75)Al_xV_(25-x)alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第6期12卷 635-640页

作者：李永胜陈铮卢艳丽王永欣张建军 School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.

关键词： microscopic phase-field nucleation incubation time order parameter simulation

Extension of Subjective Logic for Time-Related Trust

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2005年第1期10卷 56-60页

作者： HUANGChen-lin HUHua-ping SchoolofComputer NationalUniversityofDefenseTechnologyChangsha410073HunanChina

To describe the dynamic propcrty of trust relationship, wt propose atime-related trust model and extend Joang's subjective logic to fit for time-related trust *** extension includes prepositional conjunction, disjunction and negation for traditional logic anddiscounting and consensus operators that are evidential operators specially designed for thepropagation and computation of trust relationships. With the extension of subjective logic fortime-related trust, our time-related trust modelis suitable to model the dynamic trust relationshipin practice. Finally an example of reputation assessment is offered to demonstrate the usage of ourtrust model.

关键词： trust model lime-related trust relationship time-related trust model subjective logic

Analysis of Essential Oil from Stems of Schisandra Chinensis(Turc z.) Baill

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2004年第3期20卷 311-313页

作者： LIHong-jun MENGXiang-ying WUYin BAOYong-li LIYu-xin InstituteofGeneticsandCytology NortheastNormalUniversityChangchun130024P.R.China

The essential oil of Schisandra Chinensis(Turc z.) Baill was extracted and analyzed. The essential oil was obtained in a 1.8%(mL/100 g material) yield. Forty eight compounds were isolated and characterized from the oil. The results show that the content(20.42%) of β -pinene of naturally essential oil is the highest among the components of the oil,which has laid a foundation for the futher development and application of the stems of Schisandra Chinensis(Turc z.) Baill .

关键词： Schisandra Chinensis(Turc z.) Baill Essential oil GC-MS

Soft sensor modeling based on Gaussian processes

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第4期12卷 469-471页

作者：熊志化黄国宏邵惠鹤 Institute of Automation Shanghai Jiaotong University Shanghai 200030 China Institute

In order to meet the demand of online optimal running, a novel soft sensor modeling approach based on Gaussian processes was proposed. The approach is moderately simple to implement and use without loss of performance. It is trained by optimizing the hyperparameters using the scaled conjugate gradient algorithm with the squared exponential covariance function employed. Experimental simulations show that the soft sensor modeling approach has the advantage via a real-world example in a refinery. Meanwhile, the method opens new possibilities for application of kernel methods to potential fields.

关键词： Gaussian processes soft sensor modeling kernel methods

Preparation and properties of 4.25Cu-0.75Ni/NiFe_2O_4 cermet

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University of Technology 2005年第3期12卷 284-289页

作者：李劼张刚赖延清田忠良秦庆伟 School of Metallurgical Science and Engineering Central South University Changsha 410083China

4.25Cu-0.75Ni/NiFe2O4 cermets were prepared by doping NiFe2O4 ceramic matrix with the mixed powders of Cu and Ni or Cu-Ni alloy powder as the electrical conducting metallic elements. The effects of technological parameters, such as the adding modes of metallic elements, the ball milling time, the sintering time and the sintering temperature, on the relative density and resistivity of the cermets were studied. The results show that the resistivity of 4.25Cu-0.75Ni/NiFe2O4 cermets decreases with increasing temperature, and has a turning point at 590℃, which is similar to that of NiFe2O4 ceramic. The sintering temperature and adding modes of metallic elements have a great influence on the properties of 4.25Cu-0.75Ni/NiFe2O4 cermets. When the sintering temperature increases from 1200℃ to 1300℃, the relative density increases from 89.86% to 95.33%, and the resistivity at 960℃ decreases from 0.11Ω·cm to 0.03Ω·cm, respectively. When the metallic elements are added with the mixed powders of Cu and Ni, the cermets of finely and uniformly dispersed metallic phase, high density and electric conductivity are obtained. The relative density and resistivity at 960℃ are 90.23% and 0.04Ω·cm respectively for the cermet samples sintered at 1200℃ for 2h, which are both better than those of the cermets prepared under the same technique conditions but with the metallic elements added as 85Cu-15Ni alloy powders.

关键词： NiFe_2O_4 cermet preparation property inert anode