检索结果-南通市图书馆

Selection Principles and Sierpinski Sets

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

Acta Mathematica Sinica,English Series 2007年第7期23卷 1153-1162页

作者： marion SCHEEPERS Department of Mathematics Boise State University

We show that a set of real numbers is a Sierpinski set if, and only if, it satisfies a selection property similar to the familiar Menger property.

关键词： Sierpinski set selection principle infinite game partition relation L-space

Investigation of Influencing Parameters for Tribological Conditions in Dry Forming Processes

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第12期28卷 1435-1441页

作者： Jennifer Steiner marion Merklein Institute of Manufacturing Technology Friedrich-Alexander-Universitat Erlangen-Nürnberg

Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge about the changing tribological conditions and to identify the relevant influencing parameters. The commonly used flat strip drawing test was selected to investigate the tribological conditions in the flange area of deep drawing processes. The influencing factors of contact pressure and varying drawing velocities were analyzed under dry and lubricated conditions. Additionally,the tool and workpiece surfaces were characterized. Besides lubrication, the contact pressure mainly determines the tribological conditions. In lubricated tests higher normal pressure reduces friction, whereas without lubrication higher pressure results in slightly increasing friction. A changing drawing velocity affects the friction when lubricant is applied. In dry experiments, no influence of velocity was found. Results of surface characterization reveal adhesion as main wear mechanism under dry conditions. Based on the investigated influence of the process parameters, an increase in process understanding for dry forming operations is derived.

关键词： Deep drawing Tribology Friction Dry forming

Thermal response of steel framing members in open car park fires

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2022年第9期16卷 1071-1088页

作者： Xia YAN marion CHARLIER Thomas GERNAY Department of Civil and Systems Engineering Johns Hopkins UniversityBaltimoreMD 21218USA ArcelorMittal Steligence Esch-sur-Alzette 4221Luxembourg

For open car park structures,adopting a performance-based structural fire design is often justified and allowed because the fire does not reach ***,this design approach requires an accurate assessment of temperatures in structural members exposed to car *** paper describes a numerical study on the thermal exposure on steel framing members in open car park *** temperatures are computed by the coupling of computational fluid dynamics and finite element modeling,and by analytical models from the *** addition,the influence of galvanization on the steel temperature evolution is *** show that temperatures in unprotected beams and columns are influenced by the section geometry,car fire scenario,modeling approach,and use of *** slightly delays and reduces peak *** the different models,CFD-FEM(CFD:computational fluid dynamics,FEM:finite-element method)coupled models predict lower temperatures than the Hasemi model,because the latter conservatively assumes that the fire flame continuously touches the ***,the Hasemi model cannot account for the effect of reduced emissivity from galvanization on the absorbed heat *** temperature distributions obtained in the steel members can be used to complete efficient structural fire designs based on the member sections,structure layout,and use of galvanization.

关键词： open car park localized fire steel frame numerical modeling computational fluid dynamics

NUMERICAL RECONSTRUCTION OF SMALL PERTURBATIONS IN THE ELECTROMAGNETIC COEFFICIENTS OF A DIELECTRIC MATERIAL

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2014年第1期32卷 21-38页

作者： marion Darbas Stephanie Lohrengel LAMFA UMR CNRS 7252 - Universitd de Picardie Jules Verne Amiens France LMR EA 4535 - Universitd de Reims Champagne-Ardenne Reims France

The aim of this paper is to solve numerically the inverse problem of reconstructing small amplitude perturbations in the magnetic permeability of a dielectric material from partial or total dynamic boundary measurements. Our numerical algorithm is based on the resolution of the time-dependent Maxwell equations, an exact controllability method and Fourier inversion for localizing the perturbations. Two-dimensional numerical experiments illustrate the performance of the reconstruction method for different configurations even in the case of limited-view data.

关键词： Maxwell's equations Inverse problems Numerical reconstruction Exact boundary controllability Fourier inversion.

Precipitation of metal oxide nanoparticles using a miniemulsion technique

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

Particuology 2011年第5期9卷 502-505页

作者： marion Winkelmann Heike Petra Schuchmann Institute of Process Engineering in Life Sciences Section I: Food Process Engineering Karlsruhe Institute of Technology

A method to precipitate nanoparticles using a miniemulsion technique is described, in which miniemulsion droplets between 100 and 1000 nm in size serve as nanoreactors enabling both the control of particle formation and particle growth. The application of miniemulsion droplets to synthesise nanoparticles comprises three advantages： first, the size of the precipitated particles is limited by the reactant concentration within the emulsion droplet; second, particle agglomeration is prevented as nanoparticle collision outside the nanoreactor is avoided; and third, easy technical scale up can be realized by increasing emulsion volume and thus the number of nanoreactors, while local conditions within the reactors are not changed, The miniemulsion technique is an easy scalable process which allows defined synthesis of particles by precipitation reactions. The miniemulsion technique involves first the preparation of a stable water-in- oil miniemulsion by high pressure homogenisation. Whereas a water soluble reactant is provided within the aqueous droplets, another oilas well as water-soluble reactant can be introduced to the emulsion after homogenisation. The precipitation reaction is induced by the diffusion of the second reactant into the emulsion droplet. Together with this contribution, a method is described and discussed which uses a high pressure homogenisation process to produce stable water-in-oil miniemulsions serving as a reaction medium to precipitate metal oxides.

关键词： Precipitation Miniemulsion Nanoparticles Metal oxide High pressure homogenisation

Finite Volume Multilevel Approximation of the Shallow Water Equations

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,Series B 2013年第1期34卷 1-28页

作者： Arthur BOUSQUET Martine marion Roger TEMAM The Institute for Scientific Computing and Applied Mathematics Indiana University Département Mathématique Informatique Université de LyonEcole Centrale de Lyon

The authors consider a simple transport equation in one-dimensional space and the linearized shallow water equations in two-dimensional space, and describe and implement a multilevel finite-volume discretization in the context of the utilization of the incremental unknowns. The numerical stability of the method is proved in both cases.

关键词： Finite-volume methods Multilevel methods Shallow water equations Stability analysis

Residual force enhancement due to active muscle lengthening allows similar reductions in neuromuscular activation during position-and force-control tasks

在线全文

学校读者我要写书评

暂无评论

Journal of Sport and Health Science 2020年第6期9卷 670-676页

作者： Rhiannon marion Geoffrey A.Power Department of Human Health and Nutritional Sciences College of Biological SciencesUniversity of GuelphGuelphOntarioN1G 2W1Canada

Background:Residual torque enhancement(rTE)is the increase in torque observed during the isometric steady state following active muscle lengthening when compared with a fixed-end isometric contraction at the same muscle length and level of neuromuscular *** the rTE state,owing to an elevated contribution of passive force to total force production,less active force is required,and there is a subsequent reduction in *** vivo studies of rTE reporting an activation reduction are often performed using a dynamometer,where participants contract against a rigid restraint,resisting a torque *** has yet to be investigated during a position task,which involves the displacement of an inertial load with positional ***:A total of 12 participants(6 males,6 females;age=22.8±1.1 years,height=174.7±8.6 cm,mass=82.1±37.7 kg;mean±SD)completed torque-and position-matching tasks at 60%maximum voluntary contraction for a fixed-end isometric contraction and an isometric contraction following active lengthening of the ankle ***:There were no significant differences in activation between torque-and position-matching tasks(p=0.743),with^27%activation reduction following active lengthening for both task types(p<0.001).Conclusion:These results indicate that rTE is a feature of voluntary,position-controlled *** findings support and extend previous findings of isometric torque-control conditions to position-controlled contractions that represent different tasks of daily living.

关键词： Eccentric Electromyography History dependence of force Position tasks Residual force enhancement

How a membrane agent buys goods in a membrane store

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第4期17卷 442-448页

作者： Rudolf Freund marion Oswald Thomas Schirk Institute of Computer Languages Vienna University of Technology Favoritenstr. 9 WienAustria

In this paper we consider a specific model of membrane systems, i. e. membrane systems with attributes. In these systems, the information is placed at the membranes in form of attributes, no objects are considered inside the membranes except for other membranes. The membrane system with attributes evolves according to rules that compute new values for the attributes from the attributes assigned to the membranes involved in the rule. The model of membrane systems with attributes allows us to specify business transactions in a precise way and to simulate different models for such transactions with a suitable tool for membrane systems with attributes.

关键词： model membrane systems with attributes.

PTEN in liver diseases and cancer

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2010年第37期16卷 4627-4633页

作者： marion Peyrou Lucie Bourgoin Michelangelo Foti Department of Cellular Physiology and Metabolism Geneva Medical Faculty Centre Médical Universitaire

The phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt axis is a key signal transduction node that regulates crucial cellular functions, including insulin and other growth factors signaling, lipid and glucose metabolism, as well as cell survival and apoptosis. In this pathway, PTEN acts as a phosphoinositide phosphatase, which terminates PI3Kpropagated signaling by dephosphorylating PtdIns(3,4)P2 and PtdIns(3,4,5)P3. However, the role of PTEN does not appear to be restricted only to PI3K signaling antagonism, and new functions have been recently discovered for this protein. In addition to the well-established role of PTEN as a tumor suppressor, increasing evidence now suggests that a dysregulated PTEN expression and/or activity is also linked to the development of several hepatic pathologies. Dysregulated PTEN expression/activity is observed with obesity, insulin resistance, diabetes, hepatitis B virus/hepatitis C virus infections, and abusive alcohol consumption, whereas mutations/deletions have also been associated with the occurrence of hepatocellular carcinoma. Thus, it appears that alterations of PTEN expression and activity in hepatocytes are common and recurrent molecular events associated with liver disorders of various etiologies. These recent f indings suggest that PTEN might represent a potential common therapeutic target for a number of liver pathologies.

关键词： Phosphatase and tensin homolog Obesity Insulin resistance Non-alcoholic fatty liver diseases Steatosis Steatohepatitis Fibrosis Hepatocellular carcinoma Viral hepatitis Alcohol