345 research outputs found
Characteristics of Vehicular Traffic Flow at a Roundabout
We construct a stochastic cellular automata model for the description of
vehicular traffic at a roundabout designed at the intersection of two
perpendicular streets. The vehicular traffic is controlled by a self-organized
scheme in which traffic lights are absent. This controlling method incorporates
a yield-at-entry strategy for the approaching vehicles to the circulating
traffic flow in the roundabout. Vehicular dynamics is simulated within the
framework of the probabilistic cellular automata and the delay experienced by
the traffic at each individual street is evaluated for specified time
intervals. We discuss the impact of the geometrical properties of the
roundabout on the total delay. We compare our results with traffic-light
signalisation schemes, and obtain the critical traffic volume over which the
intersection is optimally controlled through traffic light signalisation
schemes.Comment: 10 pages, 17 eps figures. arXiv admin note: text overlap with
arXiv:cond-mat/040107
The incidence of prostate cancer in Iran: Results of a population-based cancer registry
Background: Little is known about the epidemiology of prostate cancer in Iranian men. We carried out an active prostate cancer surveillance program in five provinces of Iran. Methods: Data used in this study were obtained from population-based cancer registries between 1996 and 2000. Results: The age-standardized incidence rate of prostate carcinoma in the five provinces was 5.1 per 100,000 person-years. No significant difference was seen in the age-standardized incidence rate of prostate cancer within the provinces studied. The mean±SD age of patients with prostate cancer was 67±13.5 years. Conclusion: The incidence of prostate cancer in Iran is very low as compared to the Western countries. This can partly be explained by lack of nationwide screening program, younger age structure and quality of cancer registration system in Iran
Diffusive transport of light in two-dimensional granular materials
We study photon diffusion in a two-dimensional random packing of monodisperse
disks as a simple model of granular material. We apply ray optics approximation
to set up a persistent random walk for the photons. We employ Fresnel's
intensity reflectance with its rich dependence on the incidence angle and
polarization state of the light. We present an analytic expression for the
transport-mean-free path in terms of the refractive indices of grains and host
medium, grain radius, and packing fraction. We perform numerical simulations to
examine our analytical result.Comment: 9 pages, 3 figure
Study of Thermodynamic Quantities in Generalized Gravity Theories
In this work, we have studied the thermodynamic quantities like temperature
of the universe, heat capacity and squared speed of sound in generalized
gravity theories like Brans-Dicke, Hoava-Lifshitz and
gravities. We have considered the universe filled with dark matter and dark
energy. Also we have considered the equation of state parameters for open,
closed and flat models. We have observed that in all cases the equation of
state behaves like quintessence. The temperature and heat capacity of the
universe are found to decrease with the expansion of the universe in all cases.
In Brans-Dicke and gravity theories the squared speed of sound is found
to exhibit increasing behavior for open, closed and flat models and in
Hoava-Lifshitz gravity theory it is found to exhibit
decreasing behavior for open and closed models with the evolution of the
universe. However, for flat universe, the squared speed of sound remains
constant in Hoava-Lifshitz gravity.Comment: 15 pages, 12 figure
Statefinder and Om Diagnostics for Interacting New Holographic Dark Energy Model and Generalized Second Law of Thermodynamics
In this work, we have considered that the flat FRW universe is filled with
the mixture of dark matter and the new holographic dark energy. If there is an
interaction, we have investigated the natures of deceleration parameter,
statefinder and diagnostics. We have examined the validity of the first
and generalized second laws of thermodynamics under these interactions on the
event as well as apparent horizon. It has been observed that the first law is
violated on the event horizon. However, the generalized second law is valid
throughout the evolution of the universe enveloped by the apparent horizon.
When the event horizon is considered as the enveloping horizon, the generalized
second law is found to break down excepting at late stage of the universe.Comment: 9 pages, 13 figure
On thermodynamics second law in the modified Gauss Bonnet gravity
The second law and the generalized second law of thermodynamics in cosmology
in the framework of the modified Gauss-Bonnet theory of gravity are
investigated. The conditions upon which these laws hold are derived and
discussed.Comment: 9pages, typos corrected, references adde
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