1,076 research outputs found
Lifetime of dynamical heterogeneity in a highly supercooled liquid
We numerically examine dynamical heterogeneity in a highly supercooled
three-dimensional liquid via molecular-dynamics simulations. To define the
local dynamics, we consider two time intervals, and
. is the relaxation time, and
is the time at which non-Gaussian parameter of the van Hove
self-correlation function is maximized. We determine the lifetimes of the
heterogeneous dynamics in these two different time intervals,
and
, by calculating the time correlation
function of the particle dynamics, i.e., the four-point correlation function.
We find that the difference between and
increases with decreasing
temperature. At low temperatures, is
considerably larger than , while
remains comparable to
. Thus, the lifetime of the heterogeneous dynamics depends
strongly on the time interval.Comment: 4pages, 6figure
Dynamical heterogeneity in a highly supercooled liquid: Consistent calculations of correlation length, intensity, and lifetime
We have investigated dynamical heterogeneity in a highly supercooled liquid
using molecular-dynamics simulations in three dimensions. Dynamical
heterogeneity can be characterized by three quantities: correlation length
, intensity , and lifetime . We evaluated
all three quantities consistently from a single order parameter. In a previous
study (H. Mizuno and R. Yamamoto, Phys. Rev. E {\bf 82}, 030501(R) (2010)), we
examined the lifetime in two time intervals
and , where is the
-relaxation time and is the time at which the
non-Gaussian parameter of the Van Hove self-correlation function is maximized.
In the present study, in addition to the lifetime , we
evaluated the correlation length and the intensity from
the same order parameter used for the lifetime . We
found that as the temperature decreases, the lifetime
grows dramatically, whereas the correlation length and the intensity
increase slowly compared to or plateaus.
Furthermore, we investigated the lifetime in more
detail. We examined the time-interval dependence of the lifetime
and found that as the time interval increases,
monotonically becomes longer and plateaus at the
relaxation time of the two-point density correlation function. At the large
time intervals for which plateaus, the heterogeneous
dynamics migrate in space with a diffusion mechanism, such as the particle
density.Comment: 12pages, 13figures, to appear in Physical Review
Comparing technical efficiency of organic and conventional coffee farms in Nepal using data envelopment analysis (DEA) approach
Data Envelopment Analysis (DEA) approach used to estimate technical efficiency and followed by regressing the technical efficiency scores to farm specific characters under tobit regression model. Primary data was collected from random samples of 240 (120 from each) coffee famers. Mean technical efficiency score was 0.89 and 0.83 in organic and conventional coffee farming respectively. Farms operating under CRS, DRS and IRS were 31.67, 3.83 and 37.5% respectively in organic coffee and 29.17, 25 and 45.83% respectively in conventional farming areas. Tobit regression showed the variation in technical efficiency was related education, farm experience and training/extension services and excess to credit.Production frontier, Resource use, Technical efficiency, Organic, Altitude, Productivity Analysis,
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