589 research outputs found
Percolation in deposits for competitive models in (1+1)-dimensions
The percolation behaviour during the deposit formation, when the spanning
cluster was formed in the substrate plane, was studied. Two competitive or
mixed models of surface layer formation were considered in (1+1)-dimensional
geometry. These models are based on the combination of ballistic deposition
(BD) and random deposition (RD) models or BD and Family deposition (FD) models.
Numerically we find, that for pure RD, FD or BD models the mean height of the
percolation deposit grows with the substrate length according to
the generalized logarithmic law , where
(RD), (FD) and (BD).
For BD model, the scaling law between deposit density and its mean height
at the point of percolation of type are observed, where is a scaling
coefficient. For competitive models the crossover, %in versus
corresponding to the RD or FD -like behaviour at small and the BD-like
behaviour at large are observed.Comment: 8 pages,4 figures, Latex, uses iopart.cl
Locally Frozen Defects in Random Sequential Adsorption with Diffusional Relaxation
Random sequential adsorption with diffusional relaxation, of two by two
square objects on the two-dimensional square lattice is studied by Monte Carlo
computer simulation. Asymptotically for large lattice sizes, diffusional
relaxation allows the deposition process to reach full coverage. The coverage
approaches the full occupation value, 1, as a power-law with convergence
exponent near 1/2. For a periodic lattice of finite (even) size , the final
state is a frozen random rectangular grid of domain walls connecting
single-site defects. The domain sizes saturate at L**0.8. Prior to saturation,
i.e., asymptotically for infinite lattice, the domain growth is power-law with
growth exponent near, or possibly somewhat smaller than, 1/2.Comment: 16 pages of text in plain TeX + 6 figures in PostScrip
Crossover effects in a discrete deposition model with Kardar-Parisi-Zhang scaling
We simulated a growth model in 1+1 dimensions in which particles are
aggregated according to the rules of ballistic deposition with probability p or
according to the rules of random deposition with surface relaxation (Family
model) with probability 1-p. For any p>0, this system is in the
Kardar-Parisi-Zhang (KPZ) universality class, but it presents a slow crossover
from the Edwards-Wilkinson class (EW) for small p. From the scaling of the
growth velocity, the parameter p is connected to the coefficient of the
nonlinear term of the KPZ equation, lambda, giving lambda ~ p^gamma, with gamma
= 2.1 +- 0.2. Our numerical results confirm the interface width scaling in the
growth regime as W ~ lambda^beta t^beta, and the scaling of the saturation time
as tau ~ lambda^(-1) L^z, with the expected exponents beta =1/3 and z=3/2 and
strong corrections to scaling for small lambda. This picture is consistent with
a crossover time from EW to KPZ growth in the form t_c ~ lambda^(-4) ~ p^(-8),
in agreement with scaling theories and renormalization group analysis. Some
consequences of the slow crossover in this problem are discussed and may help
investigations of more complex models.Comment: 16 pages, 7 figures; to appear in Phys. Rev.
No self-similar aggregates with sedimentation
Two-dimensional cluster-cluster aggregation is studied when clusters move
both diffusively and sediment with a size dependent velocity. Sedimentation
breaks the rotational symmetry and the ensuing clusters are not self-similar
fractals: the mean cluster width perpendicular to the field direction grows
faster than the height. The mean width exhibits power-law scaling with respect
to the cluster size, ~ s^{l_x}, l_x = 0.61 +- 0.01, but the mean height
does not. The clusters tend to become elongated in the sedimentation direction
and the ratio of the single particle sedimentation velocity to single particle
diffusivity controls the degree of orientation. These results are obtained
using a simulation method, which becomes the more efficient the larger the
moving clusters are.Comment: 10 pages, 10 figure
Percolation in Models of Thin Film Depositions
We have studied the percolation behaviour of deposits for different
(2+1)-dimensional models of surface layer formation. The mixed model of
deposition was used, where particles were deposited selectively according to
the random (RD) and ballistic (BD) deposition rules. In the mixed one-component
models with deposition of only conducting particles, the mean height of the
percolation layer (measured in monolayers) grows continuously from 0.89832 for
the pure RD model to 2.605 for the pure RD model, but the percolation
transition belong to the same universality class, as in the 2- dimensional
random percolation problem. In two- component models with deposition of
conducting and isolating particles, the percolation layer height approaches
infinity as concentration of the isolating particles becomes higher than some
critical value. The crossover from 2d to 3d percolation was observed with
increase of the percolation layer height.Comment: 4 pages, 5 figure
Moving In and Moving Up? Labor Conditions and China’s Changing Development Model
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138267/1/pad1800.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138267/2/pad1800_am.pd
Multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering
A multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering is presented. The design was first theoretically optimized using the optical constants, refractive index and extinction coefficient, of thin single layers. The spectral optical constants in the wavelength range from 0.3 to 27 µm were calculated from the transmittance and reflectance data of thin single layers deposited on silicon and glass substrates. The samples were characterized by Scanning Electron Microscopy, X-ray diffraction, Fourier-transform Infrared Spectroscopy and UV–VIS–NIR spectroscopy. It is shown that the TiO2 layer presents a partially rutile phase polycrystalline structure and a higher refractive index than amorphous SiO2 and SiNx layers in the spectral range from 0.3 to 2.5 μm. The cooling device was deposited on copper substrates and a thin low-density polyethylene foil with high transmittance in the 8 to 13 µm spectral range was used as convection cover material. The device is characterized by both low reflectance (high emittance) in the sky atmospheric window (wavelength range from 8 to 13 µm) and high hemispherical reflectance elsewhere, allowing for temperature drops of average 7.4 °C at night-time in winter, which corresponds to a net cooling power of ~43 W m−2. Further, a temperature drop of 2.5 °C was obtained during winter daytime.FCT in the framework of the Strategic Funding UID/FIS/04650/2013 and the financial support of FCT, POCI and PORL operational programs through the project POCI-01-0145-FEDER-016907 (PTDC/CTM-ENE/2892/2014), co-financed by European community fund FEDE
High Out-Of-Pocket Medical Spending Among the Poor and Elderly in Nine Developed Countries
Objective: The design of health insurance, and the role out-of-pocket (OOP) payments play in it, is a key policy issue as rising health costs have encouraged greater cost-sharing measures. This paper compares the percentage of Americans spending large amounts OOP to meet their health needs with percentages in eight other developed countries. By disaggregating by age and income, the paper focuses on the poor and elderly populations within each. Data Source: The study uses nationally representative household survey data made available through the Luxembourg Income Study. It includes nations with high, medium, and low levels of OOP spending. Study Design: Households have high medical spending when their OOP expenditures exceed a threshold share of income. I calculate the share of each nation\u27s population, as well as subpopulations within it, with high OOP expenditures. Principal Findings: The United States is not alone in exposing large numbers of citizens to high OOP expenses. In six of the other eight countries, one-quarter or more of low-income citizens devoted at least 5 percent of their income to OOP expenses, and in all but two countries, more than 1 in 10 elderly citizens had high medical expenses. Conclusions: For some populations in the sample nations, health insurance does not provide adequate financial protection and likely contributes to inequities in health care delivery and outcomes. © Health Research and Educational Trus
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