32,965 research outputs found
Shape Instabilities in the Dynamics of a Two-component Fluid Membrane
We study the shape dynamics of a two-component fluid membrane, using a
dynamical triangulation monte carlo simulation and a Langevin description.
Phase separation induces morphology changes depending on the lateral mobility
of the lipids. When the mobility is large, the familiar labyrinthine spinodal
pattern is linearly unstable to undulation fluctuations and breaks up into
buds, which move towards each other and merge. For low mobilities, the membrane
responds elastically at short times, preferring to buckle locally, resulting in
a crinkled surface.Comment: 4 pages, revtex, 3 eps figure
A Novel Monte Carlo Approach to the Dynamics of Fluids --- Single Particle Diffusion, Correlation Functions and Phase Ordering of Binary Fluids
We propose a new Monte Carlo scheme to study the late-time dynamics of a
2-dim hard sphere fluid, modeled by a tethered network of hard spheres.
Fluidity is simulated by breaking and reattaching the flexible tethers. We
study the diffusion of a tagged particle, and show that the velocity
autocorrelation function has a long-time tail. We investigate the
dynamics of phase separation of a binary fluid at late times, and show that the
domain size grows as for high viscosity fluids with a
crossover to for low viscosity fluids. Our scheme can accomodate
particles interacting with a pair potential ,and modified to study
dynamics of fluids in three dimensions.Comment: Latex, 4 pages, 4 figure
Initial stages of cavitation damage and erosion on copper and brass tested in a rotating disk device
In view of the differences in flow and experimental conditions, there has been a continuing debate as to whether or not the ultrasonic method of producing cavitation damage is similar to the damage occurring in cavitating flow systems, namely, venturi and rotating disk devices. In this paper, the progress of cavitation damage during incubation periods on polycrystalline copper and brass tested in a rotating disk device is presented. The results indicate several similarities and differences in the damage mechanism encountered in a rotating disk device (which simulates field rotary devices) and a magnetostriction apparatus. The macroscopic erosion appears similar to that in the vibratory device except for nonuniform erosion and apparent plastic flow during the initial damage phase
Size scale effect in cavitation erosion
An overview and data analyses pertaining to cavitation erosion size scale effects are presented. The exponents n in the power law relationship are found to vary from 1.7 to 4.9 for venturi and rotating disk devices supporting the values reported in the literature. Suggestions for future studies were made to arrive at further true scale effects
Application to rotary wings of a simplified aerodynamic lifting surface theory for unsteady compressible flow
A general method of predicting airloads is applied to helicopter rotor blades on a full three-dimensional basis using the general theory developed for a rotor blade at the psi = pi/2 position where flutter is most likely to occur. Calculations of aerodynamic coefficients for use in flutter analysis are made for forward and hovering flight with low inflow. The results are compared with values given by two-dimensional strip theory for a rigid rotor hinged at its root. The comparisons indicate the inadequacies of strip theory for airload prediction. One important conclusion drawn from this study is that the curved wake has a substantial effect on the chordwise load distribution
Profitability of Cotton on a Pest Management Continuum in Guntur District of Andhra Pradesh
The plant protection response of farmers in the Guntur district of Andhra Pradesh has been examined with particular reference to the adoption of Bt cotton varieties and IPM components. The farmers have been found to follow a wide range of practices to manage the insect pests in cotton. The use of chemical insecticides has accounted for, about 37 per cent of the total variable costs. No significant reduction in plant protection expenditure has been recorded on adoption of Bt varieties without IPM practices. The adoption of IPM practices, however, has led to reduced use of insecticides and increased profitability. The saving on plant protection chemicals has more than compensated the cost of adopting IPM components. Consequently, the net returns have been found increased considerably from cotton cultivation.Crop Production/Industries,
X-ray properties of the microquasar GRS 1915+105 during a variability class transition
We present a detailed X-ray study of the microquasar GRS 1915+105 during a
variability class transition observed in 2000 June with the PPCs of the Indian
X-ray Astronomy Experiment. We supplement this observation with data from the
RXTE archives. The source made a transition from a steady low-hard state to a
regular oscillatory behaviour in the light curve known as bursts or class `rho'
(Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the
low-hard state on 2000 June 27. A gradual change in the burst recurrence time
from about 75 s to about 40 s was observed which then increased to about 120 s
during the ~ 40 days of class `rho'. The regular bursts disappeared from the
X-ray light curves and the class transition was observed to occur within 1.5
hours on 2000 June 27 with the PPCs. A correlation is found between the
observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray
intensity of the source during the class `rho'. We notice a strong similarity
between the properties of the source during the class `rho' and those during
the oscillatory phase of the observations of class `alpha'. From the timing and
spectral analysis, it is found that the observed properties of the source over
tens of days during the class `rho' are identical to those over a time scale of
a few hundreds of seconds in the class `alpha'. Examining the light curves from
the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the
change of state from radio-quiet low-hard state to high state occurs through
the X-ray classes `rho' and `alpha' which appear together during the state
transition. It is further inferred that the source switches from low-hard state
to the class `rho' through the intermediate class `alpha'.Comment: 10 pages with 9 figures, LaTex. To be appeared in MNRA
A double peaked pulse profile observed in GX 1+4
The hard X-ray pulsar GX 1+4 was observed several times in the last few years
with a pair of balloon-borne Xenon filled Multi-cell Proportional Counters
(XMPC). In a balloon flight made on 22 March 1995, the source was detected in a
bright state, the average observed source count rate being per
detector. X-ray pulsations with a period of s were detected in
the source with a broad double peak pulse feature. When observed in December
1993 with the same instrument, the pulse profile of GX 1+4 showed a single
peak. This change in the pulse profile to a double pulse structure in about 15
months indicates either activation of the opposite pole of the neutron star if
the magnetic field is asymmetric or possibly a change in the beam pattern, from
a pencil beam to a fan beam. Assuming a fan beam configuration, the pulse
profile is used to find the inclinations of the magnetic axis and the viewing
axis with the spin axis. The derived angles support the GINGA observations of a
dip in the pulse profile which was resolved to have a local maximum in one of
the observations and was explained with resonance scattering of cyclotron line
energy photons by the accretion column (Makishima et al., \markcite{maki1988},
Dotani et al., \markcite{dotani1989}.). Compared to our previous observation of
the same source with the same telescope (Rao et al., \markcite{rao1994}) a
period change rate of is obtained which is the lowest rate
of change of period for this source since its discovery. Average pulse fraction
in the hard X-ray range is low (30%), consistent with its anti correlation with
luminosity as reported by us earlier (Rao et al., \markcite{rao1994}) and the
observed spectrum is very hard (power law photon index ).Comment: 10 pages, to appear in A&
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