共查询到20条相似文献,搜索用时 15 毫秒
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A new and general approach is proposed to analyze the dynamics of a colloidal particle interacting with a nearby wall. This
analysis can be used to determine the acting forces even when the system is non-stationary. As an illustration, we use total
internal reflection microscopy to investigate the forces acting on a polystyrene sulfate latex particle as it is receding
from a charged glass surface.
Received 10 October 2002 Published online: 16 April 2003
RID="a"
ID="a"Present address: Department of Polymer Physics, BASF Aktiengesellschaft, 67056 Ludwigshafen, Germany
RID="b"
ID="b"Present address: Arryx. Inc., Chicago, IL 60601, USA 相似文献
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Pica Ciamarra M Coniglio A Nicodemi M 《The European physical journal. E, Soft matter》2007,22(3):227-234
We overview the physics of a granular mixture subject to horizontal oscillations,
recently investigated via experiments and molecular dynamics simulations.
First we discuss the rich phenomenology exhibited by this system, which encompasses
both segregation and dynamical instabilities.
Then we show that the phenomenology can be explained
via an effective interaction approach, by which the driven,
non-thermal, granular mixture in mapped into a monodispersed thermal
system of particles interacting via an effective potential.
After determining the effective interaction we discuss its
microscopic origin and investigate how it induces the observed
phenomenology. Finally, as much as in thermal fluids, from the
effective interaction we derive a Cahn-Hilliard dynamics equation,
which appears to capture the essential characteristics of the dynamics
of the granular mixture. 相似文献
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S. Xiao W. Hu W. Luo Y. Wu X. Li H. Deng 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(4):479-484
In the present paper, the surface and size effects on the
alloying ability and phase stability of immiscible alloy
nanoparticles have been studied with calculating the heats of
formation of Au-Pt alloy nanoparticles from the single element
nanoparticles of their constituents (Au and Pt) with a simple
thermodynamic model and an analytic embedded atom method. The
results indicated that, besides the similar compositional dependence
of heat of formation as in bulk alloys, the heat of formation of
alloy nanoparticles exhibits notable size-dependence, and there
exists a competition between size effect and compositional effect on
the heat of formation of immiscible system. Contrary to the positive
heat of formation for bulk-immiscible alloys, a negative heat of
formation may be obtained for the alloy nanoparticles with a small
size or dilute solute component, which implies a promotion of the
alloying ability and phase stability of immiscible system on a
nanoscale. The surface segregation results in an extension of the
size range of particles with a negative heat of formation. The
molecular dynamics simulations have indicated that the structurally
and compositionally homogeneous AuPt nanoparticles tend to form a
core-shell structure with temperature increasing. 相似文献
6.
The avalanche mixing of granular solids in a slowly rotated 2D upright drum is studied. We demonstrate that the account of
the difference δ between the angle of marginal stability and the angle of repose of the granular material leads to a restricted
value of the mixing time τ for a half filled drum. The process of mixing is described by a linear discrete difference equation.
We show that the mixing looks like linear diffusion of fractions with the diffusion coefficient vanishing when δ is an integer
part of π. Introduction of fluctuations of δ suppresses the singularities of τ(δ) and smoothes the dependence τ(δ).
Received 27 October 2000 and Received in final form 13 March 2001 相似文献
7.
N. Clarke 《The European physical journal. E, Soft matter》2001,4(3):327-336
We study the early stages of phase separation in a mixture of a polydisperse and a monodisperse polymer within the Cahn-Hilliard
framework. We model the polydisperse component using a finite, but arbitrarily large, number of components, and show that
the number of components required for convergent behaviour to be achieved is computationally undemanding. We study the growth
rate of fluctuations following a quench into the two-phase region of the phase diagram. The q-dependence of the growth rate is shown to be commensurate with the behaviour of a monodisperse-monodisperse mixture, with
the major difference being an effective mobility that is dependent on the quench depth. We also study the deviation of the
time dependence of the scattering function from single exponential behaviour.
Received 29 June 2000 and Received in final form 20 November 2000 相似文献
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T. Van Hoof A. Dzhurakhalov M. Hou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):159-163
Molecular Dynamics is used to study the formation of an interface between a
single crystalline Ag matrix and core-shell AgCo nanoclusters deposited with
energies ranging from 0.25 eV to 1.5 eV per atom. As a consequence of the
slowing down, clusters deform, may become epitaxial with the substrate and
keep their core-shell structure. The consequences of the cluster-surface
interaction are studied in detail for a realistic size and energy range and
the accumulation of clusters is modelled. It is found that the interface
formed is no more than a few atomic layers thick and that both the cobalt
cluster cores and the silver shells display limited epitaxy with the
substrate. The effect is not much energy dependent and is larger for the Ag
shells that for the Co cores. 相似文献
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M.?Beránek I.?Richterová Z.?Něme?ek J.?Pavl? J.??afránková 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):299-304
Surfaces in contact with a plasma can influence its characteristics and, on the other hand, the impact of plasma particles
can change surface properties of materials immersed in a plasma. Carbon is often present in plasma systems either as a building
material or a product of technological processes, thus its behavior is an important factor of these applications. The paper
deals with investigations of secondary emission of 1–6 μm spherical grains from amorphous carbon under the electric field
of the order of 108 V/m. We have found that the secondary emission yield increases with the electric field at the sample surface nearly linearly
and does not depend on the grain diameter. Long-lasting (hours) electron irradiation of the sample surface leads to a significant
decrease of the yield that was attributed to the removal of an absorbed layer from the grain surface. This conclusion is supported
by the fact that a similar effect was achieved after several minutes of simultaneous electron and ion treatments. 相似文献
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Satoshi Ninomiya Kazuya Ichiki Yoshiro Honda Takaaki Aoki Jiro Matsuo 《Applied Surface Science》2008,255(4):880-882
Si was bombarded with size-selected 40 keV Ar cluster ions and positive secondary ions were measured using the time-of-flight technique under high and ultra-high vacuum (HV and UHV respectively) conditions. Si+ ions were main species detected under the incidence of 40 keV Ar cluster ions, and the yields of Si cluster ions such as Si4+ were also extremely high under both conditions. On the other hand, oxidized secondary ions such as SiO+ were detected with high intensity only under the HV condition. The yield ratios of oxidized ions decreased in UHV to less than 1% of their values in HV. The effect of residual gas pressure on Si cluster ion yields is relatively low compared to oxidized ions, and the UHV condition is required to obtain accurate secondary ion yields. 相似文献
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We have used a modified surface force apparatus (SFA) to study adsorption onto mica surfaces from near-saturated vapours of
n-hexane and n-perfluorohexane, and mixtures thereof. For relative vapour pressures in the range 0.9-0.998 the films adsorbed from vapours
of the pure liquids range in thickness from 1 to 4 nm, in crude agreement with the predictions of non-retarded van der Waals-Lifshitz
theory. The observed deviations from theory show a qualitative difference between the two liquids, which may reflect differences
in the significance of structural contributions to the disjoining pressure. Under the same experimental conditions, adsorption
from vapours of (one-phase) liquid mixtures gives rise to films which are significantly thicker, over a broad range of intermediate
compositions, than those adsorbed from the pure vapours, with a broad maximum in thickness observed near the critical composition
of the bulk liquid mixture.
Received 30 July 2001 相似文献
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This paper calculates the transition wavelengths and probabilities
of the two-electron and one-photon (TEOP) transition from the
$(3{\rm s}^{-1}_{1/2}4{\rm d}_{j})_{J=1,2}$ to $(3{\rm
p}^{-1}_{3/2}4{\rm s}_{1/2})_{J=1}$ and the $(3{\rm
p}^{-1}_{1/2}4{\rm s}_{1/2})_{J=1}$ to $(3{\rm d}^{-1}_{j}4{\rm
d}_{j'})_{J=1,2}$ for highly charged Ni-like ions with atomic number
$Z$ in the range $47\leq Z\leq92$. In the calculations, the
multi-configuration Dirac--Fock method and corresponding program
packages GRASP92 and REOS99 were used, and the relativistic effects,
correlation effects and relaxation effects were considered
systematically. It is found that the TEOP transitions are very
sensitive to the correlation of electrons, and the probabilities
will be enhanced sharply in some special $Z$ regions along the
isoelectronic sequence. The present TEOP transition wavelengths are
compared with the available data from some previous publications,
good agreement is obtained. 相似文献
13.
Ghaouar N Benhamou M Derouiche A Gharbi A 《The European physical journal. E, Soft matter》2005,16(4):409-413
We present here a theoretical study of kinetics of phase separation within a mixture made of two chemically incompatible ramified polymers. For simplicity, we assume that they have the same topology. We are interested in the variation of the relaxation rate, q, versus the wave number q, in the vicinity of the spinodal temperature. The kinetics is governed by local (Rouse) and reptation motions (faster and slower modes). For qRG 1 (RG being the gyration radius), kinetics is entirely controlled by local motions where each chain moves inside its own tube, and we show that the corresponding characteristic frequency, {-1}q, scales as {-1}q
Gq6, where G is a known topological factor. For qRG 1, however, kinetics is rather dominated by long-wavelength (reptation) motions where unlike ramified polymers creep inside a long tube. For this case, we find that {-1}q
( 0 )q2 (c - ), where ( 0 ) is another known topological factor that represents the total mobility of free monomers belonging to connected chains and reticulation points, and c accounts for the critical value of the segregation parameter. Finally, the derived relaxation rate must be compared to that relative to a linear polymer mixture. 相似文献
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T. Schenkel A.V. Barnes A.V. Hamza D.H. Schneider 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):297-302
Cluster ion emission from a variety of surfaces upon impact of highly charged ions is investigated by time-of-flight secondary
ion mass spectrometry. The yield of cluster ions as a function of cluster size for and surface follow a power law decline with exponent approaching the -2 limit of the ”equilibrium” and ”shock wave” cluster emission
models. While the decline of the cluster ion emission with cluster size is an exponential decay for highly oriented pyrolytic
graphite upon impact, the decline is more gradual than for impact, such that at the relative cluster yield is 1000 times higher.
Received: 22 April 1997 / Revised: 29 December 1997 / Accepted: 19 January 1998 相似文献
15.
Near-field flow and flame dynamics of LOX/methane shear-coaxial injector under supercritical conditions 总被引:2,自引:0,他引:2
The mixing and combustion of liquid oxygen (LOX) and gaseous methane of a shear coaxial injector operating under supercritical pressures have been numerically investigated. The near-field flow and flame dynamics are examined in depth, with emphasis placed on the flame-stabilization mechanisms. The model accommodates the full conservation laws and real-fluid thermodynamics and transport phenomena over the entire range of fluid states of concern. The injector flowfield is characterized by the evolution of the three mixing layers originating from the trailing edges of the two concentric tubes of the injector. As a consequence of the strong inertia of the oxygen stream and light density of methane, a diffusion-dominated flame is anchored in the wake of the LOX post and propagates downstream along the boundary of the oxygen stream. The large-scale vortices shedding from the outer rim of the LOX postengulf methane into the wake recirculation region to react with gasified oxygen. The frequencies of vortex shedding match closely those of the flow over a rear-facing step, mainly due to the large density disparity between LOX and gaseous methane. The effects of the momentum-flux ratio of the two streams are also examined. A higher-momentum methane stream enhances mixing and shortens the potential cores of both the LOX and methane jets. 相似文献
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Chambon B. Drain D. Pastor C. Dauchy A. Giorni A. Morand C. 《Zeitschrift für Physik A Hadrons and Nuclei》1983,312(1-2):125-133
Zeitschrift für Physik A Hadrons and nuclei - Angular correlations between neutrons and projectile-like fragments detected near the grazing angle were analysed by assuming two incoherent... 相似文献
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报道用 15 0keV的高电荷态离子1 2 6 Xeq + (6≤q≤ 30 )轰击Ti固体表面产生 2 0 0— 10 0 0nm波段发射光谱的实验结果 .结果显示 ,用电荷态足够高的离子作光谱激发源 ,无需很强的束流强度 (nA量级 ) ,便可激发起样品表面的原子和离子在可见光波段的特征谱线 .当入射离子剥离度q >qc≈ 2 0时 ,Ti原子及其离子的特征谱线强度突然显著增强 ;不同金属靶 ,特征谱线突然增强的qc值不同 .理论分析表明 ,这与q大于此临界值后 ,单电子转移释放能量激发靶材料传导电子气体的表面等离激元密切相关 . 相似文献
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Magneto-vibratory separation of glass and bronze granular mixtures immersed in a paramagnetic liquid
López-Alcaraz P Catherall AT Hill RJ Leaper MC Swift MR King PJ 《The European physical journal. E, Soft matter》2007,24(2):145-156
A fluid-immersed granular mixture may spontaneously separate when subjected to vertical vibration, separation occurring when
the ratio of particle inertia to fluid drag is sufficiently different between the component species of the mixture. Here,
we describe how fluid-driven separation is influenced by magneto-Archimedes buoyancy, the additional buoyancy force experienced
by a body immersed in a paramagnetic fluid when a strong inhomogeneous magnetic field is applied. In our experiments glass
and bronze mixtures immersed in paramagnetic aqueous solutions of MnCl2 have been subjected to sinusoidal vertical vibration. In the absence of a magnetic field the separation is similar to that
observed when the interstitial fluid is water. However, at modest applied magnetic fields, magneto-Archimedes buoyancy may
balance the inertia/fluid-drag separation mechanism, or it may dominate the separation process. We identify the vibratory
and magnetic conditions for four granular configurations, each having distinctive granular convection. Abrupt transitions
between these states occur at well-defined values of the magnetic and vibrational parameters. In order to gain insight into
the dynamics of the separation process we use computer simulations based on solutions of the Navier-Stokes' equations. The
simulations reproduce the experimental results revealing the important role of convection and gap formation in the stability
of the different states. 相似文献
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Weikl TR Andelman D Komura S Lipowsky R 《The European physical journal. E, Soft matter》2002,8(1):59-66
Biomimetic membranes in contact with a planar substrate or a second membrane are studied theoretically. The membranes contain
specific adhesion molecules (stickers) which are attracted by the second surface. In the absence of stickers, the trans-interaction
between the membrane and the second surface is assumed to be repulsive at short separations. It is shown that the interplay
of specific attractive and generic repulsive interactions can lead to the formation of a potential barrier. This barrier induces
a line tension between bound and unbound membrane segments which results in lateral phase separation during adhesion. The
mechanism for adhesion-induced phase separation is rather general, as is demonstrated by considering two distinct cases involving:
i) stickers with a linear attractive potential, and ii) stickers with a short-ranged square-well potential. In both cases,
membrane fluctuations reduce the potential barrier and, therefore, decrease the tendency of phase separation.
Received 24 January 2002 and Received in final form 24 April 2002 相似文献