120 research outputs found
Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes
Comparative classical and ab initio Molecular Dynamics study of molten and glassy germanium dioxide
A Molecular Dynamics (MD) study of static and dynamic properties of molten
and glassy germanium dioxide is presented. The interactions between the atoms
are modelled by the classical pair potential proposed by Oeffner and Elliott
(OE) [Oeffner R D and Elliott S R 1998, Phys. Rev. B, 58, 14791]. We compare
our results to experiments and previous simulations. In addition, an ab initio
method, the so-called Car-Parrinello Molecular Dynamics (CPMD), is applied to
check the accuracy of the structural properties, as obtained by the classical
MD simulations with the OE potential. As in a similar study for SiO2, the
structure predicted by CPMD is only slightly softer than that resulting from
the classical MD. In contrast to earlier simulations, both the static structure
and dynamic properties are in very good agreement with pertinent experimental
data. MD simulations with the OE potential are also used to study the
relaxation dynamics. As previously found for SiO2, for high temperatures the
dynamics of molten GeO2 is compatible with a description in terms of mode
coupling theory.Comment: 27 pages, 16 figure
New method to characterize a machining system: application in turning
Many studies simulates the machining process by using a single degree of
freedom spring-mass sytem to model the tool stiffness, or the workpiece
stiffness, or the unit tool-workpiece stiffness in modelings 2D. Others impose
the tool action, or use more or less complex modelings of the efforts applied
by the tool taking account the tool geometry. Thus, all these models remain
two-dimensional or sometimes partially three-dimensional. This paper aims at
developing an experimental method allowing to determine accurately the real
three-dimensional behaviour of a machining system (machine tool, cutting tool,
tool-holder and associated system of force metrology six-component
dynamometer). In the work-space model of machining, a new experimental
procedure is implemented to determine the machining system elastic behaviour.
An experimental study of machining system is presented. We propose a machining
system static characterization. A decomposition in two distinct blocks of the
system "Workpiece-Tool-Machine" is realized. The block Tool and the block
Workpiece are studied and characterized separately by matrix stiffness and
displacement (three translations and three rotations). The Castigliano's theory
allows us to calculate the total stiffness matrix and the total displacement
matrix. A stiffness center point and a plan of tool tip static displacement are
presented in agreement with the turning machining dynamic model and especially
during the self induced vibration. These results are necessary to have a good
three-dimensional machining system dynamic characterization
EMImCl-AlCl 3
This work studied the electro-polymerisation of 3,4-ethylenedioxythiophene (EDOT) and its electrochemical behavior in Lewis acidic, neutral and basic chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) by cyclic voltammetry. It was found that the electro-polymerisation on vitreous carbon only occurs in Lewis neutral EMImCl-AlCl3 as a dark blue-violet film whereas the electro-polymerisation in a Lewis acidic or basic compositions is not possible due to the interactions between the conductive polymer and the ionic liquid as well as the potential stability limits of the electrolyte. PEDOT films synthesised in Lewis neutral ionic liquid were tested in monomer-free Lewis acidic, basic and neutral EMImCl-AlCl3 and show different doping and de-doping behavior for chloride ionic species. The PEDOT films in a Lewis neutral composition showed higher doping levels due to the higher potential stability window, up to 2.6 V vs. Al|Al(III) than in a Lewis acidic and basic solutions. Furthermore, it was shown that the doping and de-doping levels are predefined during the electro-polymerisation of PEDOT. The anion doping and de-doping reaction reached 97% reversibility in the neutral composition, which suggests that PEDOT is a suitable electrode material to store charged species in this media and could be used in rechargeable energy storage devices
Computational Modeling of Silicate Glasses: A Quantitative Structure-Property Relationship Perspective
This article reviews the present state of Quantitative Structure-Property
Relationships (QSPR) in glass design and gives an outlook into future developments.
First an overview is given of the statistical methodology, with particular emphasis
to the integration of QSPR with molecular dynamics simulations to derive informative
structural descriptors. Then, the potentiality of this approach as a tool for
interpretative and predictive purposes is highlighted by a number of recent inspiring
applications
Injection system used into SI engines for complete combustion and reduction of exhaust emissions in the case of alcohol and petrol alcohol mixtures feed
Berechnung des potentialtheoretischen Einflusses in der instationären, reibungsfreien und inkompressiblen Strömung durch ebene Gitterstufen von axialen Turbomaschinen
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