检索结果-南通市图书馆

High Temperature Deformation Behavior of 4340 Steel: Activation Energy Calculation and modeling of Flow Response

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 2013年第12期20卷 133-139页

作者： S V Sajadifar g g Yapici m Ketabchi B Bemanizadeh mechanical Engineering Department Ozyegin University mining and metallurgical Engineering Department Amirkabir University of Technology Islamic Azad University Karaj Branch

The 4340 steel is extensively utilized in several industries including automotive and aerospace for manufac- turing a large number of structural components. Due to the importance of thermo-mechanical processing in the pro- duction of steels, the dynamic recrystallization （DRX） characteristics of 4340 steel were investigated. Namely, hot compression tests on 4340 steel have been performed in a temperature range of 900-- 1200 ℃ and a strain rate range of 0.01--1 s-1 and the strain of up to 0.9. The resulting flow stress curves show the occurrence of dynamic recrys- tallization. The flow stress values decrease with the increase of deformation temperature and the decrease of strain rate. The microstrueture of 4340 steel after deformation has been studied and it is suggested that the evolution of DRX grain structures can be accompanied by considerable migration of grain boundaries. The constitutive equations were developed to model the hot deformation behavior. Finally based on the classical stress-dislocation relations and the kinematics of the dynamic recrystallization; the flow stress constitutive equations for the dynamic recovery period and dynamic reerystallization period were derived for 4340 steel, respectively. The validity of the model was demon- strated by demonstrating the experimental data with the numerical results with reasonable agreement.

关键词： 4340 steel hot deformation activation energy dynamic recrystallization, modeling strain rate sen- sitivity

ON THE IDENTIFICATION OF RESIDUAL ImPACT PROPERTIES OF mATERIALS BY ACOUSTO-ULTRASONICS——A PATTERN RECOgNITION APPROACH

在线全文

学校读者我要写书评

暂无评论

Acta mechanica Sinica 1995年第1期11卷 34-43页

作者： g.J.molina Y.m.Haddad Dept.of mechanical Engineering University of OttawaOttawaCanada K1N 6N5

This paper deals with the application of Acousto-ultrasonics,in con- junction with Pattern Recognition and Classification techniques,to the identification of residual impact properties of a class of polymeric material,namely,Polyvinylchlo- ride(PVC).PVC specimens of different low-energy repeated impact damage states are processed by Acousto-ultrasonics(AU)to retrieve AU signals in the form of dig- italized *** AU signals are grouped as distinct classes,each pertaining to a known level of repeated impact *** features of these AU signals are used to build Pattern Recognition(PR)*** classifiers are used to identify unknown damage states in other PVC specimens by classifying the re- trieved AU signals as belonging to one of the *** obtained results indicate that Acousto-ultrasonics in combination with Pattern Recognition and Classification techniques can be used for the quantitative non-destructive identification of damage states in PVC specimens of unknown low-energy repeated impact conditions.

关键词： pattern recognition acousto-ultrasonics impact damage quantitative non-destructive examination

Review:Resuspension of wall deposits in spray dryers

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第11期8卷 1762-1774页

作者： HANUS m.J. LANgRISH T.A.g. School of Chemical and Biomolecular Engineering University of Sydney Sydney NSW 2006 Australia

Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.

关键词： Wall deposition Spray dryers Dried particles Re-entrainment Adhesive forces

Dipole (hyper)polarizabilities of neutral silver clusters

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第12期25卷 217-222页

作者： Francisco E Jorge Luiz g m de macedo Departarnento de Fisica Universidade Fedoral do Espirito Santo 29060-900 Vitoria Brazil Unidade Academica de Fisica Universidade Federal de Campina Grande 58429-900 Campina Grande Brazil Faculdade de Biotecnologia ICB Universidade Federal do Para 66075-110 Belem Brazil

At the Douglas-Kroll-Hess （DKI4） level, the B3PW91 functional along with the all-eleclron relativistic basis sets of valence triple and quadruple zeta qualities are used to determine the structure, stability, and electronic properties of the small silver clusters （Agn, n ≤ 7）. The results presented in this study are in good agreement with the experimental data and theoretical values obtained at a higher level of theory from the literature. Static polarizability and hyperpolarizability are also reported. It is verified that the mean dipole polarizability per atom exhibits an odd-even oscillation and that the polarizability anisotropy is directly related to the cluster shape. In this article, the first study of hyperpolarizabilities of small silver clusters is presented. Except for the monomer, the second hyperpolarizabilities of the silver clusters are significantly larger than those of the copper clusters.

关键词： B3PW91 functional all-electron basis sets non-relativistic and DKH2 calculations silver clusters,dipole (hyper)polarizabilities

The Jacobian Dual of Certain mixed Product Ideals

在线全文

学校读者我要写书评

暂无评论

Algebra Colloquium 2020年第2期27卷 263-280页

作者： m.La Barbiera m.Lahyane g.Restuccia Dipartimento di Scienze matematiche e Informatiche Scienze Fisiche e Scienze Della TerraUniversity of Messina98166 MessinaItaly Instituto de Fisica y matematicas(IFm)Universidad michoacana de San Nicolas de Hidalgo(UmSNH)Edificio C-3 Ciudad UniversitariaC.P.58040 MoreliaMichoacanMexico

We consider the symmetric algebra of a class of monomial ideals generated by *** these ideals with linear syzygies,we determine their Jacobian dual modules and study their duality properties.

关键词： graded algebra symmetric algebra monomial ideal Jacobian dual

mechanical properties and in vivo biodegradability of mg-Zr-Y-Nd-La magnesium alloy produced by a combined severe plastic deformation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare metals 2021年第3期40卷 651-662页

作者： A.Torkian g.Faraji m.S.Pedram School of mechanical Engineering College of EngineeringUniversity of TehranTehran 11155-4563Iran Department of Veterinary Surgery and Radiology Faculty of Veterinary MedicineUniversity of Tehran14199-63111Iran

Permanent implants are going to be replaced by the implementation of biodegradable magnesium-based implants in fixation of internal bone fractures because of many concerns associated with conventional ***,biodegradable magnesium-based biomaterials exhibit higher biodegradation rate and low mechanical properties which are the main *** work aims to almost overcome both disadvantageous by grain refining of a WE43 magnesium alloy containing 93.04 wt% mg,4.12 wt% Y,2.15 wt% Nd,0.43 wt% Zr,and 0.26 wt%*** this study,the consequences of combined severe plastic deformation(SPD) on the mechanical properties,microstructure,and in vivo degradation behavior of WE43 magnesium alloy were *** do so,WE43 magnesium alloy was chosen and processed through multipass equal channel angular pressing(ECAP) at 330℃ for up to four passes followed by an extrusion *** results showed that higher strength and hardness with minimum ductility less was obtained in the sample processed via two-pass ECAP followed by *** vivo biodegradation experiments showed higher degradation rate for the unprocessed coarse-grained(Cg) WE43 *** two-pass ECAP and extruded sample with ultrafine-grained(UFg) structure exhibited the lowest in vivo biodegradation rate besides appropriate mechanical *** may be concluded that the WE43 magnesium alloy processed via two-pass ECAP and extrusion could be a very promising candidate for biodegradable implants from both mechanical and biocorrosion viewpoints.

关键词： Implant Severe plastic deformation WE43 grain refinement Hardness mechanical properties

mineralogical, REE-geochemical and fluid inclusion studies on some uranium occurrences, gabal gattar, Northeastern Desert, Egypt

在线全文

学校读者我要写书评

暂无评论

Chinese Journal Of geochemistry 2011年第4期30卷 430-443页

作者： El-Feky m.g. Nuclear materials Authority

Altered granite occurrences (gII and gV) at gabal (g.) gattar are the most important mineralized rocks hosting U-mineralization in Egypt. This mineralized granite is affected by multi-stage hydrothermal alteration proc-esses along brittle structures. This alteration comprises pre-ore alkali-metasomatism and ore-stage hydrothermal hematitization, silicification, kaolinitization, fluoritization, carbonatization and episyenitization. Autoradiographic examination indicates that primary uranium mineralization is present as massive or disseminated ores along tectonic fractures, interstitially in granular minerals, and as cements of breccias. Uraninite, pitchblende and coffinite are the main primary minerals, while uranophane and kasolite are the secondary ones. galena, chalcopyrite, pyrrohtite and pyrite are the most abundant sulphides in association with uranium mineralizations. Hydrothermal alterations at the gII occurrence exhibit an increase in Ni, Cu, Zn, Pb, mo, Nb, Rb beside HREEs and a decrease in Ba, Co, Sr, and V, while alterations at the gV occurrence show enrichment in Ni, Cu, Pb, mo, Nb, Y, HREEs and depletion in Zn, Ba, Co, Rb, Sr, and V. Hydrothermal alteration during the late magmatic stage is also identified through the development of unusual REE patterns and fractionation of ratios like Zr/Hf and Y/Ho out of the CHARAC (Charge Radius Con-trolled) range. Non-chondritic Y/Ho ratio at gV is of larger value than chondritic one which may result from wa-ter-rock interaction or print from the encompassing sedimentary rocks. Fluid inclusion studies on quartz and fluorite revealed that temperatures of the mineralizing fluids range between 126 and 240℃ at pressure ≤0.5×108 Pa and give salinity values ranging between 1 wt% and 7.8 wt% NaCl equivalent.

关键词：稀土元素地球化学流体包裹体铀矿化矿物学埃及全球信息基础设施东北部沙漠

Quinpi:Integrating Conservation Laws with CWENO Implicit methods

在线全文

学校读者我要写书评

暂无评论

Communications on Applied mathematics and Computation 2023年第1期5卷 343-369页

作者： g.Puppo m.Semplice g.Visconti Dipartimento di matematica UniversitàLa SapienzaP.le Aldo Moro500185 RomaItaly Dipartimento di Scienza e Alta Tecnologia Universitàdell'InsubriaVia Valleggio1122100 ComoItaly

many interesting applications of hyperbolic systems of equations are stiff,and require the time step to satisfy restrictive stability *** way to avoid small time steps is to use implicit time *** integration is quite straightforward for first-order *** order schemes instead also need to control spurious oscillations,which requires limiting in space and time also in the linear *** propose a framework to simplify considerably the application of high order non-oscillatory schemes through the introduction of a low order implicit predictor,which is used both to set up the nonlinear weights of a standard high order space reconstruction,and to achieve limiting in *** this preliminary work,we concentrate on the case of a third-order scheme,based on diagonally implicit Runge Kutta(DIRK)integration in time and central weighted essentially non-oscillatory(CWENO)reconstruction in *** numerical tests involve linear and nonlinear scalar conservation laws.

关键词： Implicit schemes Essentially non-oscillatory schemes Finite volumes WENO and CWENO reconstructions

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis:An update

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of gastroenterology 2014年第23期20卷 7260-7276页

作者： gülsüm ?zlem Elpek Department of Pathology Akdeniz University Medical School07070 AntalyaTurkey

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver *** data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even ***,efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver *** of hepatic stellate cells(HSCs)remains a central event in fibrosis,complemented by other sources of matrix-producing cells,including portal fibroblasts,fibrocytes and bone marrow-derived *** cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent *** the interaction of different cell types,revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic ***,the characterization of different pathways associated with different etiologies aid in the development of disease-specific *** article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future *** pathogenesis of liver fibrosis associated with alcoholic liver disease,non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

关键词： Liver Liver fibrosis Cirrhosis Fibrogenesis Hepatic stellate cells myofibroblast Extracellular matrix