检索结果-南通市图书馆

Characterization of cytotoxicity of airborne particulates from urban areas of Lahore

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2012年第11期24卷 2028-2034页

作者： Badar Ghauri M.Mansha christian Khalil Institute of Space Technology Karachi 72500Pakistan School of Risk and Safety Sciences University of New South WalesAustralia

A number of species （organic and inorganic） in airborne particulates cause the toxicity to living being. The potential of in vitro test methods were explored for toxicity assessment of trace toxic elements （inorganic species） present in ambient air on human being （lungs）. A year long sampling of airborne particles （PM2.5） was carded （April 2008 to March 2009） in Lahore, Pakistan. A total of thirty nine samples were collected on 47 mm Zefiuor Teflon filter membranes and each was analysed to characterize for the elements： Sb, As, Be, Cd, Cr, Co, Pb, Mn, Hg using ICP-MS in water extract and total acid digestate. The samples cytotoxicity was also established using lung derived cells and MTS colorimetric assays. This generated dose response curves and IC50 values for the elemental mixtures identified on the Teflon filter membrane. The results indicated that even at low concentrations airborne elemental mixtures displayed an additive toxic effect.

关键词： particulate matter trace elements in vitro toxicity

A novel control solution for improved trajectory tracking and LVRT performance in DFIG-based wind turbines

在线全文

学校读者我要写书评

暂无评论

Control Theory and Technology 2020年第1期18卷 43-55页

作者： Ahmad HASHEMI christian CONFICONI Andrea TILLI The Center of Complex Automated Systems(CASY)at the Department of Electrical Electronic and Information Engineering(DEI)University of BolognaRisorgimento240136 BolognaItaly Sama Technical and Vocational training College Islamic Azad UniversityKermanshah BranchKermanshahIran

This paper presents a new control strategy for the rotor side converter of Doubly-Fed Induction Generator based Wind Turbine systems,under severe voltage *** main goal is to fulfill the Low Voltage Ride Through performance,required by modern grid *** this respect,the key point is to limit oscillations(particularly on rotor currents)triggered by line faults,so that the system keeps operating with graceful *** this aim,a suitable feedforward-feedback control solution is proposed for the DFIG rotor *** feedforward part exploits oscillation-free reference trajectories,analytically derived for the system internal *** feedback,designed accounting for control voltage limits,endows the system with robustness and further tame oscillations during ***,improved torque and stator reactive power tracking during faults is achieved,proposing an exact mapping between such quantities and rotor-side currents,which are conventionally used as controlled *** simulations are provided to validate the capability of the proposed approach to effectively cope with harsh faults.

关键词： Doubly-fed induction generator(DFIG) wind turbine(WT) feedforward-feedback control mapping solution low voltage ride through(LVRT)

Numerical modeling of cracking pattern's influence on the dynamic response of thickened tailings disposals: a periodic approach

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2018年第1期17卷 179-190页

作者： Gabriel Ferrer Esteban Sáez christian Ledezma School of Engineering Pontificia Universidad Católica de Chile National Research Center for Integrated Natural Disaster Management

Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials（tailings） are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal（TTD） is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with ＂fresh＂ tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings＇ behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.

关键词： Thickened tailings Liquefaction Periodic modeling

Rationality of quotients by linear actions of affine groups

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2011年第8期54卷 1521-1532页

作者： BOGOMOLOV Fedor BHNING christian GRAF VON BOTHMER Hans-christian Department of Mathematics Courant Institute of Mathematical Sciences New York University Mathematisches Institut University of Gottingen

LetG = SLn(C)Cn be the (special) affine group. In this paper we study the representation theory of G and in particular the question of rationality for V/G, where V is a generically free G-representation. We show that the answer to this question is positive (Theorem 6.1) if the dimension of V is sufficiently large and V is indecomposable. We explicitly characterize two-step extensions 0 → S → V → Q → 0, with completely reducible S and Q, whose rationality cannot be obtained by the methods presented here (Theorem 5.3).

关键词： rationality linear group quotients affine groups

Amorphous Polylactide Bead Foam–Effect of Talc and Chain Extension on Foaming Behavior and Compression Properties

在线全文

学校读者我要写书评

暂无评论

Journal of Renewable Materials 2021年第11期9卷 1859-1868页

作者： christian Brütting Julia Dreier christian Bonten Volker Altstädt Holger Ruckdäschel Department of Polymer Engineering University BayreuthBayreuth95447Germany Institut für Kunststofftechnik University of StuttgartStuttgart70569Germany

Polylactide(PLA)bead foams show a high potential regarding their applicability in packaging or consumer *** the comparable properties of PLA to Polystyrene(PS)and the good CO_(2) footprint it represents a potential alternative to petroleum-based polymer ***,foaming of PLA is challenging,due to its low melt strength,therefore chemical modifiers are often *** the bead foam technology regarding PLA,the available literature is limited so *** this study,the bead foaming behavior of neat and modified amorphous PLA was *** material was modified by talc and an epoxy-based chain *** compounds have been investigated regarding their sorption behavior in CO_(2) atmosphere and their foaming *** was conducted by using the batch foaming method based on a rapid temperature increase after saturation with CO_(2).In order to achieve welded bead foams,a one-step processing for foaming and welding has been ***,the compression properties of the PLA bead foams have been *** below 50 kg/m^(3) for single bead foams and 80 kg/m^(3) for molded foams were achieved,respectively.

关键词： Polylactide biofoam bead foam CO_(2) low density

Local Discontinuous-Galerkin Schemes for Model Problems in Phase Transition Theory

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 Computational Physics 2008年第9期4卷 860-893页

作者： Jenny Haink christian Rohde Fachbereich Mathematik-IANS Universitat StuttgartPfaffenwaldring 57D-70569 StuttgartGermany.

Local Discontinuous Galerkin(LDG)schemes in the sense of[5]are a flexible numerical tool to approximate solutions of nonlinear convection problems with complicated dissipative *** terms frequently appear in evolution equations which describe the dynamics of phase changes in ***-vapour mixtures or in elastic *** report on results for one-dimensional model problems with dissipative terms including third-order and convolution *** entropy inequalities and L2-stability results are proved for those model *** is common in phase transition theory the solution structure sensitively depends on the coupling parameter between viscosity and *** avoid spurious solutions due to the counteracting effect of artificial dissipation by the numerical flux and the actual dissipation terms we introduce Tadmors’entropy conservative *** numerical experiments underline the reliability of our approach and also illustrate interesting and(partly)new phase transition phenomena.

关键词： Conservation laws discontinuous-Galerkin method dynamical phase boundaries Tadmor flux convolution operator.

Efficient Algorithm forMany-Electron Angular Momentum and Spin Diagonalization on Atomic Subshells

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 Computational Physics 2016年第1期19卷 192-204页

作者： christian B.Mendl Zentrum Mathematik Technische Universitat MunchenBoltzmannstraße 385748 Garching bei MunchenGermany

We devise an efficient algorithm for the symbolic calculation of irreducible angular momentum and spin(LS)eigenspaces within the n-fold antisymmetrized tensor product∧^(n)V_(u),where n is the number of electrons and u=s,p,d,…denotes the atomic *** is an essential step for dimension reduction in configurationinteraction(CI)methods applied to atomic many-electron quantum *** algorithm relies on the observation that each Lz eigenstate with maximal eigenvalue is also an L2 eigenstate(equivalently for Sz and S2),as well as the traversal of LS eigenstates using the lowering operators L−and S−.Iterative application to the remaining states in∧^(n)V_(u)leads to an implicit simultaneous diagonalization.A detailed complexity analysis for fixed n and increasing subshell number u yields run time O(u^(3n−2)).A symbolic computer algebra implementation is available online.

关键词： Angular momentum and spin symmetry atomic many-electron quantum systems symbolic computation

Event-Based Semantics of UML 2.X Concurrent Sequence Diagrams for Formal Verification

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 Computer Science & Technology 2022年第1期37卷 4-28页

作者： Inès Mouakher Fatma Dhaou J.christian Attiogbé Faculty of Sciences of Tunis University of Tunis El Manar1068TunisTunisia Institute of Technology University of Nantes44322NantesFrance

UML 2.X sequence diagrams(SD)are among privileged scenarios-based approaches dealing with the complexity of modeling the behaviors of some current ***,there are several issues related to the standard semantics of UML 2.X SD proposed by the Object Management Group(OMG).They mainly concern ambiguities of the interpretation of SDs,and the computation of causal relations between events which is not specifically laid ***,SD is a semi-formal language,and it does not support the verification of the modeled *** justifies the considerable number of research studies intending to define formal semantics of UML *** proposed in our previous work semantics covering the most popular combined fragments(CF)of control-flow ALT,OPT,LOOP and SEQ,allowing to model alternative,optional,iterative and sequential behaviors *** proposed semantics is based on partial order theory relations that permit the computation of the precedence relations between the events of an SD with nested *** also addressed the issue of the evaluation of the interaction constraint(guard)for guarded CFs,and the related synchronization *** this paper,we first extend our semantics,proposed in our previous work;indeed,we propose new rules for the computation of causal relations for SD with PAR and STRICT CFs(dedicated to modeling concurrent and strict behaviors respectively)as well as their ***,we propose a transformational semantics in *** modeling approach emphasizes computation of causal relations,guard handling and transformational semantics into *** transformation of UML 2.X SD into the formal method Event-B allows us to perform several kinds of verification including simulation,trace acceptance,verification of properties,and verification of refinement relation between SDs.

关键词： UML 2.X sequence diagram formal semantics nested combined fragment partial order theory Event-B

Tribological mechanisms of slurry abrasive wear

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2023年第6期11卷 1079-1093页

作者： Yulong LI Paul SCHREIBER Johannes SCHNEIDER christian GREINER Institute for Applied Material(IAM) Karlsruhe Institute of Technology(KIT)Karlsruhe76131Germany KIT IAM-ZM MicroTribology Center(μTC) Karlsruhe76131Germany

Abrasive wear mechanisms—including two-body and three-body abrasion—dominate the performance and lifespan of tribological systems in many engineering fields,even of those operating in lubricated *** steel(100Cr6)pins and discs in a flat-on-flat contact were utilized in experiments together with 5 and 13 μm Al_(2)O_(3)-based slurries as interfacial media to shed light on the acting *** results indicate that a speed-induced hydrodynamic effect occurred and significantly altered the systems'frictional behavior in tests that were performed using the 5 μm *** experiments revealed that a speed-dependent hydrodynamic effect can lead to a 14% increase in film thickness and a decrease in friction of around 2/3,accompanied by a transition from two-body abrasion to three-body abrasion and a change in wear mechanism from microcutting and microploughing to fatigue ***,no correlation could be found between the total amount of wear and the operating state of the system during the experiment;however,the wear distribution over pin and disc was observed to change *** paper studies the influence of the hydrodynamic effect on the tribological mechanism of lubricated abrasive wear and also highlights the importance to not only consider a tribological systems'global amount of wear.

关键词： abrasive wear two-body abrasion three-body abrasion hydrodynamic effect steel