728 research outputs found
Torsion, Chern-Simons Term and Diffeomorphism Invariance
In the approach of gravity Chern-Simons
modification has been considered here. It has been found that Chern-Simons
contribution to the bianchi identity has become cancelled from that of the
scalar field part. But "homogeneity and isotropy" consideration of present day
cosmology is a consequence of the "strong equivalence principle" and
vice-versa.Comment: 8 page
Beyond the Horizon
Cosmic horizons arise in general relativity in the context of black holes and
in certain cosmologies. Classically, regions beyond a horizon are inaccessible
to causal observers. However, quantum mechanical correlations may exist across
horizons that may influence local observations. For the case of de Sitter
space, we show how a single particle excitation behind the horizon changes the
density matrix governing local observables. As compared to the vacuum state, we
calculate the change in the average energy and entropy per unit volume. This
illustrates what may be a generic property allowing some features of spacetime
beyond a horizon to be inferred.Comment: 9 pages, 1 figur
Relation between Stochastic Resonance and Synchronization of Passages in a Double-Well System
We calculate, numerically, the residence times (and their distribution) of a
Brownian particle in a two-well system under the action of a periodic,
saw-tooth type, external field. We define hysteresis in the system. The
hysteresis loop area is shown to be a good measure of synchronization of
passages from one well to the other. We establish connection between this
stochastic synchronization and stochastic resonance in the system.Comment: To appear in PRE May 1997, figures available on reques
Effect of Silting Yield Index on Biomass and Carbon Sequestration Potential along an Altitudinal Gradient of Subtropical Chir Pine Forests and Grasslands in North Western Himalaya, India
Biomass is an important characteristic of vegetation and is regarded as an important indicator of ecological and management processes in the vegetation. Measures of standing crop also reflect the amount of energy stored in the vegetation, which can indicate the potential productivity at the site. Forests are important for carbon sequestration besides playing very important role in the global carbon cycle. They store about 80% of all aboveground and 40% of all belowground terrestrial organic carbon. This study comprises to estimate the biomass and carbon stock of chirpine forests at different altitudinal gradients
Aperiodic tumbling of microrods advected in a microchannel flow
We report on an experimental investigation of the tumbling of microrods in
the shear flow of a microchannel (40 x 2.5 x 0.4 mm). The rods are 20 to 30
microns long and their diameters are of the order of 1 micron. Images of the
centre-of-mass motion and the orientational dynamics of the rods are recorded
using a microscope equipped with a CCD camera. A motorised microscope stage is
used to track individual rods as they move along the channel. Automated image
analysis determines the position and orientation of a tracked rods in each
video frame. We find different behaviours, depending on the particle shape, its
initial position, and orientation. First, we observe periodic as well as
aperiodic tumbling. Second, the data show that different tumbling trajectories
exhibit different sensitivities to external perturbations. These observations
can be explained by slight asymmetries of the rods. Third we observe that after
some time, initially periodic trajectories lose their phase. We attribute this
to drift of the centre of mass of the rod from one to another stream line of
the channel flow.Comment: 14 pages, 8 figures, as accepted for publicatio
The layer disorders defect in coir fiber under thermal and chemical treatment
Natural coir fibers, subjectd to thermal treatments in the range of 0oC
to 200oC and alkali treatment with 5% to 30% concentration w/w, have been used in
the present investigation to determine the interlayer variability of the cellulose
planes (020), (110) and (110). Among the equatorial reflections (110), (110) and
(020), the extent of variability is found to be more with the proportion of such
affected planes less for (020) reflection in the native cellulose at lower
temperature while at higher temperature (110) and (110) become more affected by
variability defect. (110) and (1 10) planes are more affected also with alkali
treatment.The layer disorders defect in coir fiber under thermal and chemical treatment
D N Mahato*, B K Mathur and S Bhattacharjee
Department of Physics, Indian Institute of Technology,
Kharagpur-721 302, West Bengal, India
E-mail : [email protected] of Physics, Indian Institute of Technology,
Kharagpur-721 302, West Bengal, Indi
Flutter analysis of rotary laminated composite structures using higher-order kinematics
Abstract The flutter analysis of rotary laminated structures has been performed using Carrera Unified Formulation (CUF). CUF is a one-dimensional higher-order structural model, in which the displacement at the cross-section is the only unknown parameter. The cross-sectional displacement fields of the model are defined using the Lagrange- and Taylor expansion. The quasi-steady and unsteady theories (Theodorsen and Loewy) have been used to apply the aerodynamic force. Subsequently, the equation of motion is defined in 'fundamental nucleus' form using Hamilton's principle. The engineering solution of the flutter condition has been obtained by using p-k method. The computational studies of flutter analysis have been done for various rotor hub, lamination sequence, and structural models. The regular, irregular plies and arbitrary fiber orientation of the orthotropic structures have also been considered. The present study suggests that the proposed CUF model can obtain an aeroelastic solution of rotary structure in a computationally and economically efficient manner
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