检索结果-南通市图书馆

IGNITING ShS BY LASER AND ITS APPLICATION TO SELECTIVE LASER SINTERING OF METALLIC POWDER MATERIAL

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 694-704页

作者： Y.S.Shi S.C.Chen X.L.Lu S.h.huang StateKeyLaboratoryofPlasticFormingSimulationandDie＆MouldTechnology SchoolofMaterialScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China

how to directly fabricate metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are researching. Existent problems during directly fabricating metal part by use of SLS are analyzed. For the sake of solving the problems, a new idea of adding self-propagating high-temperature synthesis (ShS) material into metallic powder material to form new type of SLS metallic powder material is put forward. This powder material can release controllable amount of heat during its interaction with the laser beam energy to reduce the requirement to laser power during directly sintering metallic part, to prolong the time of metallic liquid phase existing, and to improve the intensity and accuracy of SLS part. For this reason, ShS material′s interaction with the CO2 laser beam energy is researched, which proves that CO2 laser beam energy may instantly ignite ShS reaction. On the basis of the above-mentioned researches, the effect of sintering the metal powder material mixing ShS material with CO2 laser is also researched, which shows: there is an optimal blending ratio of various material in the new metallic powder material. Under the optimal blending ratio and SLS process parameters, this new metallic powder material can indeed release amount of heat and ShS reaction may be controlled within the laser sintering. This research result makes it possible that the metallic part is directly sintered with small CO2 laser (less than 50W), which may greatly reduce the volume, cost and running expenditure of SLS machine, be propitious to application.

关键词： selective laser sintering (SLS) self-propagating high-temperaturesynthesis (ShS) ignition time metallic powder material,metallic part

LOW TEMPERATURE ThERMODYNAMIC STUDY OF ThE STABLE AND METASTABLE PhASES OF SILVER

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 355-362页

作者： X.B. Li Y.Q. Xie Y.Z. Nie h.J. Peng Research Center of Advanced Materials Xiangtan University Xiangtan 411105 China School of Material Science and Engineering University Changsha 410083 China Central South

The low temperature thermodynamics of the stable phase of silver was assessed by the polynomial model and Debye model from the experimental data available in the literature. By means of the constrained non-linear least squares curve fitting arithmetic, two sets of parameter values were determined. The expression of the thermodynamic functions cp（T） and G（T）-h （298.15K） at 0-298.15K were presented. Only the low temperature thermodynamics of the metastable phase of silver can be extrapolated by the Debye model The expression of the thermodynamic functions cp（T） at 0- 298.15K was presented.

关键词： silver thermodynamic heat capacity SGTE (Scientific Group Thermodata Europe)

Experimental results of the tribology of aluminum measured with a pin-on-disk tribometer: Testing configuration and additive effects

在线全文

学校读者我要写书评

暂无评论

Friction 2016年第2期4卷 124-134页

作者： S.M.h.AhMER L.S.JAN M.A.SIDDIG S.F.ABDULLAh Department of Physics GS Faculty Yanbu University College Yanbu al Sinayiah 41912 Kingdom of Saudi Arabia Department of Physics Faculty of Science and Technology al Neelain University Khartoum 11111 Sudan Mechanical Engineering Department UNITEN Kajang 43009 Malaysia

The friction coefficient, wear rate, and wear coefficient of the aluminum metal surface were measured at room temperature (≈300 K) with a pin-on-disk machine at a fixed load of 196.2 N. Two different testing configurations were adopted: (1) aluminum pin vs. helix oil-on-steel disk (AhS) and (2) aluminum pin vs. 10% Polytron plus 90% helix oil-on-steel disk (APS). In the AhS configuration, the wear of the aluminum surface was found to be approximately 70 μm; however, in the APS configuration the wear dropped to 20 μm, revealing a marked decrement of one-third of the wear of aluminum. The volume wear rate of the metal in the unaided helix oil was estimated to be 1.28×10–3 mm3/min. The additive minimized the volume wear rate of the aluminum metal by orders of magnitude to 6.08×10–5 mm3/min. Similarly, the wear coefficient of the aluminum pin, calculated in the AhS configuration, rendered a value of 1.27×10–10 m2/N. In the APS configuration, the same parameter was 4.22×10–11 m2/N, that is to say, an order of magnitude lower than the preceding value. The observed coefficient of friction for aluminum is 0.012 in helix oil and falls to a remarkably lower value of 0.004 through the Polytron additive. The experimental findings demonstrate that Polytron additive substantially lessens the wear of the aluminum surface; in effect, the wear coefficient and the wear rate decline linearly. This singularity may be linked to the ability of Polytron to impregnate the crystal structure of the metal due to its ionic character and the consequent adherence to the metallic surface as a hard surface layer.

关键词： antiwear Polytron additive aluminum metal lubrication friction

Stabilization for Equal-Order Polygonal Finite Element Method for high Fluid Velocity and Pressure Gradient

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2020年第3期62卷 1109-1123页

作者： T.Vu-huu C.Le-Thanh h.Nguyen-Xuan M.Abdel-Wahab Department of Electrical energy MetalsMechanical Constructions and SystemsFaculty of Engineering and ArchitectureGhent UniversityGhentBelgium Faculty of Civil Engineering Vietnam Maritime UniversityHai PhongVietnam Faculty of Civil Engineering and Electricity Ho Chi Minh City Open UniversityHo Chi MinhVietnam CIRTech Institute Ho Chi Minh City University of Technology(HUTECH)Ho Chi MinhVietnam Division of Computational Mechanics Ton Duc Thang UniversityHo Chi MinhVietnam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi MinhVietnam

This paper presents an adapted stabilisation method for the equal-order mixed scheme of finite elements on convex polygonal meshes to analyse the high velocity and pressure gradient of incompressible fluid flows that are governed by Stokes equations *** technique is constructed by a local pressure projection which is extremely simple,yet effective,to eliminate the poor or even non-convergence as well as the instability of equal-order mixed polygonal *** this research,some numerical examples of incompressible Stokes fluid flow that is coded and programmed by MATLAB will be presented to examine the effectiveness of the proposed stabilised method.

关键词： Polygonal finite element method fluid computation stokes equation mixed method local projection

Progress in neutron activation analysis for uranium

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 1996年第2期39卷 219-224页

作者：杜鸿善李贵群董桂芝李俊兰 K.h.Chiu C.M.Wai China Institute of Atomic Energy Beijing 102413 China Department of Chemistry University of Idaho USA

A new type of extractant, sym-dibenzo-16-crown-5-oxyhydroxamic acid (hL) is introduced. The extractions of UO22+, Na+, K+, Sr2+, Ba2+ and Br- were studied with hL in chloroform. The results obtained show that UO22+ can be quantitatively extracted at ph values above 5, whereas the extractions of K+, Na+, Sr2+, Ba2+ and Br- are negligible in the ph range of 2 - 7. The dependence of the distribution ratio of U(VI) on both the concentration of the hL and ph are linear, and they have the same slope of 2. This suggests that U(VI) appears to form a 1:2 complex with ligand. Uranium(VI) can be selectively separated and concentrated from interfering elements such as Na, K, Sr and Br by solvent extraction with hL under specific conditions. The recovery of uranium is nearly 100% and the radionudear purity of uranium is greater than 99.99%. Therefore, neutron activation analysis has greatly improved the sensitivity and accuracy for the detection of trace uranium from seawater.

关键词： uranium preconcentration neutron activation analysis.

Early osteoimmunomodulation by mucin hydrogels augments the healing and revascularization of rat critical-size calvarial bone defects

在线全文

学校读者我要写书评

暂无评论

Bioactive Materials 2023年第7期25卷 176-188页

作者： Song Chen huan Wang Dachuan Liu Jianzhong Bai håvard Jostein haugen Bin Li hongji Yan Orthopedic Institute Department of Orthopedic SurgeryThe First Affiliated HospitalSchool of Biology&Basic Medical SciencesSuzhou Medical CollegeSoochow UniversitySuzhouJiangsuChina Department of Biomaterials Institute for Clinical DentistryUniversity of OsloPO Box 1109 BlindernOslo0376Norway AIMES-Center for the Advancement of Integrated Medical and Engineering Sciences at Karolinska Institute and KTh Royal Institute of Technology 17177StockholmSweden Department of Neuroscience Karolinska Institute17177StockholmSweden Division of Glycoscience Department of ChemistrySchool of Engineering Sciences in ChemistryBiotechnology and HealthKTH Royal Institute of TechnologyAlbaNova University Center10691StockholmSweden

The design principle of osteogenic bone grafts has shifted from immunological inertness to limiting foreign body response to combined osteoimmunomodulatory activity to promote high-quality endogenous bone *** developed immunomodulatory mucin hydrogels have been shown to elicit very low complement activation and suppress macrophage release and activation after implantation in ***,their immunoregulatory activity has not yet been studied in the context of tissue ***,we synthesized mucin-monetite composite materials and investigated their early osteoimmunomodulation using a critical-size rat bone defect *** demonstrated that the composites can polarize macrophages towards the M2 phenotype at weeks 1 and *** early osteoimmunomodulation enhanced early osteogenesis and angiogenesis and ultimately promoted fracture healing and engraftment(revascularization of the host vasculature)at weeks 6 and ***,we demonstrated the applicability of mucin-based immunomodulatory biomaterials to enhance tissue repair in tissue engineering and regenerative medicine.

关键词： Mucin hydrogels Monetite osteoimmunomodulation Bone Revascularization

Finite Difference Analysis of Time-Dependent Viscous Nanofluid Flow Between Parallel Plates

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2019年第11期71卷 1293-1300页

作者： Salman Ahmad T.hayat A.Alsaedi Z.h.Khan M.Waleed Ahmed Khan Department of Mathematics Quaid-I-Azam University 45320Islamabad 44000Pakistan Nonlinear Analysis and Applied Mathematics(NAAM)Research Group Department of MathematicsFaculty of ScienceKing Abdulaziz UniversityP.O.Box 80257Jeddah 21589Saudi Arabia State Key Laboratory of hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China Key Laboratory of Advanced Reactor Engineering and Safety Ministry of EducationTsinghua UniversityBeijing 100084China

This article computes effect of uniform magnetic field on nanofluid flow filling porous medium inside parallel sheets. Darcy's law is used to characterize porous medium. Flow is caused by stretching of the lower sheet. The governing systems are computed using Finite difference technique. This scheme is used due to its more general and powerful nature to solve nonlinear problems. Results are obtained and discussed graphically. Nusselt number, skin friction, streamlines,velocity and temperature are emphasized.

关键词： finite difference scheme porous medium magnetic field nanofluid parallel stretchable sheets

Synthesis and Antimicrobial Activity of New 2,5-Disubstituted 1,3,4-Oxadiazoles and 1,2,4-Triazoles and Their Sugar Derivatives

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2012年第1期30卷 77-83页

作者： EI-Sayed, Wael A. Ali, Omar M hendy, hend A AbdeI-Rahman, Adel A.-h.t Department of Photochemistry National Research Centre Cairo Egypt Chemistry Department Northern Border University Afar Saudi Arabia Department of Chemistry Faculty of Science Menoufia University Shebin El-Koam Egypt

A series of new 2,5-disubstituted-l,3,4-oxadiazole and 1,2,4-triazole derivatives were synthesized by hetero- cyclization of acid hydrazide I and thiosemicarbazide derivative 2. Furthermore, the acyclic C-nucleoside analogs were prepared by cyclization of their corresponding sugar hydrazones by reaction with acetic anhydride. The antimicrobial activity of the prepared compounds was evaluated and some of the synthesized compounds revealed good activities against fungi.

关键词： 1,3,4-oxadiazoles 1,2,4-triazoles sugar hydrazones acyclic nucleosides antimicrobial activity

NUCLEATION BEhAVIOR OF Al_8Fe_4Nd PhASE IN RAPIDLY SOLIDIFIED Al-Fe-V-Si-Nd ALLOY

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2002年第5期15卷 453-459页

作者： h. Pang, Z.h. Jin, J.N. Deng, and M.G.ZengShenyang National Laboratory for Material Science, Institute of Metal Research, CAS, Shenyang 110016, ChinaCollege of Science, Northeastern University, Shenyang 110004, China Lab. for Mat. Sci. Shenyang Natil. Inst. of Metal Res. Chinese Acad. of Sci. Shenyang 110016 China Coll. of Sci. Northeastern Univ. Shenyang 110004 China

The microstructure of Al-Fe-V-Si-Nd alloy prepared by rapid solidification (RS) processing was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (hREM). The phase selection of the alloy during solidification and the nucleation behavior of Al8Fe4Nd phase were analyzed within the framework of time-dependent nucleation theory. The incubation time for Al8Fe4Nd phase was found shorter and the nucleation rate higher than those of α-Al. The results indicate the nucleation of Al8Fe4Nd phase is heterogeneous and the dispersoids of Al8Fe4Nd form as primary particles from the liquid, which is consistent with experimental observation.

关键词： Al-Fe based alloy rapid solidification phase selection nucleation behavior