819 research outputs found
The origin of interparticle potential of electrorheological fluids
The particles of electrorheological fluids can be modelled as dielectric
spheres (DS) immersed in a continuum dielectric. When an external field is
applied, polarization charges are induced on the surfaces of the spheres and
can be represented as point dipoles placed in the centres of the spheres. When
the DSs are close to each other, the induced charge distributions are distorted
by the electric field of the neighbouring DSs. This is the origin of the
interaction potential between the DSs. The calculation of this energy is very
time consuming, therefore, the DS model cannot be used in molecular
simulations. In this paper, we show that the interaction between the point
dipoles appropriately approximates the interaction of DSs. The polarizable
point dipole model provides better results, but this model is not pair-wise
additive, so it is not that practical in particle simulations.Comment: 10 pages, 5 figure
The mean spherical approximation for a dipolar Yukawa fluid
The dipolar hard sphere fluid (DHSF) is a useful model of a polar fluid. However, the DHSF lacks a vapor-liquid transition due to the formation of chain-like structures. Such chains are not characteristic of real polar fluids. A more realistic model of a polar fluid is obtained by adding a Lennard-Jones potential to the intermolecular potential. Very similar results are obtained by adding a Yukawa potential, instead of the Lennard-Jones potential. We call this fluid the dipolar Yukawa fluid (DYF). We show that an analytical solution of the mean spherical approximation (MSA) can be obtained for the DYF. Thus, the DYF has many of the attractive features of the DHSF. We find that, within the MSA, the Yukawa potential modifies only the spherically averaged distribution function. Thus, although the thermodynamic properties of the DYF differ from those of the DHSF, the MSA dielectric constant of the DYF is the same as that of the DHSF. This result, and some other predictions, are tested by simulations and are found to be good approximations. © 1999 American Institute of Physics.published_or_final_versio
Magnetization and susceptibility of ferrofluids
A second-order Taylor series expansion of the free energy functional provides
analytical expressions for the magnetic field dependence of the free energy and
of the magnetization of ferrofluids, here modelled by dipolar Yukawa
interaction potentials. The corresponding hard core dipolar Yukawa reference
fluid is studied within the framework of the mean spherical approximation. Our
findings for the magnetic and phase equilibrium properties are in quantitative
agreement with previously published and new Monte Carlo simulation data.Comment: 8 pages including 4 figure
Thermodynamics and structural properties of the dipolar Yukawa fluid
We report computer simulations and a theoretical study of the thermodynamics and structure of a dipolar Yukawa system. A comparison between the analytical mean spherical approximation (MSA) solution, perturbation theory and Monte Carlo simulation data of pressure, internal energy and dielectric constant is given. In the perturbation theory, the MSA solution of hard core Yukawa fluid is used as a reference system. It was found that the MSA solution is reasonable only at lower dipole moments, while the perturbation theory gives good results at low and high values of dipole moment. Liquid-vapor coexistence data of dipolar Yukawa fluid are also obtained by Monte Carlo simulation and by both MSA and perturbation theory. It was found that at high dipole moments the liquid-vapor equilibrium disappears while chain-like structures appear in the low density fluid phase. The appearance of chain-like structures of dipolar Yukawa fluid is discussed in comparison with the Stockmayer fluid. © 1999 American Institute of Physics.published_or_final_versio
Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission
We report the first results from our long-term observational survey aimed at
discovering late-time interaction between the ejecta of hydrogen-poor Type I
supernovae and the hydrogen-rich envelope expelled from the progenitor star
several decades/centuries before explosion. The expelled envelope, moving with
a velocity of ~10 -- 100 km s, is expected to be caught up by the
fast-moving SN ejecta several years/decades after explosion depending on the
history of the mass-loss process acting in the progenitor star prior to
explosion. The collision between the SN ejecta and the circumstellar envelope
results in net emission in the Balmer-lines, especially in H-alpha. We look for
signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having
hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha
emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia
events. Thirty-eight SN sites were observed on at least two epochs, from which
three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal
variation in the strength of their H-alpha emission in our DIAFI data. This
suggests that the variable emission is probably not due to nearby H II regions
unassociated with the SN, and hence is an important additional hint that
ejecta-CSM interaction may take place in these systems. Moreover, we
successfully detected the late-time H-alpha emission from the Type Ib SN 2014C,
which was recently discovered as a strongly interacting SN in various (radio,
infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap
Frank Lloyd Wright és a tokiói Imperial Hotel
Frank Lloyd Wright is one of the most prominent architects of the first half of the twentieth century. Wright's architecture was given a name organic, also known as organic architecture, which means the effort to harmonize the buildings and the surrounding natural environment. During his life he designed a lot of buildings, but perhaps one of the most important buildings which received the biggest negative and positive response is the Imperial Hotel in Tokyo.Frank Lloyd Wright egyike a XX. század első felének legkiemelkedőbb építészeinek. Wright építészete az organikus vagy más néven szerves építészet nevet kapta, amely az épületek és azt körülvevő természetes környezet messzemenő harmonizációjára való törekvést jelenti. Élete során rengeteg épületet tervezett, de talán egyik legmeghatározóbb, és legnagyobb negatív és pozitív visszhangot kapó épülete a tokiói Imperial Hotel volt
Phase transitions and ordering of confined dipolar fluids
We apply a modified mean-field density functional theory to determine the
phase behavior of Stockmayer fluids in slitlike pores formed by two walls with
identical substrate potentials. Based on the Carnahan-Starling equation of
state, a fundamental-measure theory is employed to incorporate the effects of
short-ranged hard sphere - like correlations while the long-ranged
contributions to the fluid interaction potential are treated perturbatively.
The liquid-vapor, ferromagnetic liquid - vapor, and ferromagnetic liquid -
isotropic liquid first-order phase separations are investigated. The local
orientational structure of the anisotropic and inhomogeneous ferromagnetic
liquid phase is also studied. We discuss how the phase diagrams are shifted and
distorted upon varying the pore width.Comment: 15 pages including 8 figure
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