Information Rich GIS Dissemination in Disconnected Environments

Information‐rich maps are today rendered from powerful back‐end servers. Unfortunately, there may be circumstances in which access to such Internet‐resident web services is infeasible or unreliable. These disconnected environments can theoretically occur during major power outages, malicious attacks on communications infrastructure, natural disasters, or in remote operating environments. One might also envision applications in which a disconnected service is preferred over Internet‐resident services, such as when the local internet service is overloaded with traffic, making communication though it difficult. To this end, this article presents a software stack (a map stack) that can serve GIS information from low power embedded nodes. The system combines a spatially enabled SQL database, location‐based routing, and multi‐scale map rendering to serve information‐rich GIS data on common hand‐held devices at minimal energy consumption. The maps are rendered on browsers on off‐the‐shelf mobile devices such as smart phones and tablets. The system also provides a crowd sourced capability where end users can annotate maps with up‐to‐date information on the scene of the natural disaster. We have prototyped a fully functional map stack on a battery powered Gumstix Overo air platform. We show that the map stack is a highly extensible platform that provides low latency, and low energy dissemination of maps during a natural disaster.     

Acceleration of the universe in f(R) gravity models

A general formalism for the investigation of the late time dynamics of the universe for any analytic f(R) gravity model, along with a cold dark matter, has been discussed in the present work. The formalism is then elucidated with two examples. The values of the parameters of the models are chosen in such a way that they are consistent with the basic observational requirement.     

Spintessence: A Possible Candidate as a Driver of the Late Time Cosmic Acceleration

In this paper, it is shown completely analytically that a spintessence model in the dust dominated universe can very well serve the purpose of providing an early deceleration and a present day acceleration.     

De Sitter type of cosmological model with a self-gravitating nonlinear scalar field

Homogeneous isotropic cosmological solutions are obtained for a de Sitter type of metric in the presence of a self-gravitating scalar field with cubic nonlinearity. Unlike the usual de Sitter case which is indefinitely expanding it is here interestingly found that in the presence of a nonlinear scalar field the model gives a bounce from a maximum of spatial volume. The possibility of bounce from a maximum, however, disappears when a linear scalar field is considered instead.     

Thermodynamics of a system of leptons,photons and interacting nucleons

The thermodynamics of matter composed of interacting nucleons with an admixutre of leptons and photons is investigated in the density-temperature region relevant to the problem of supernova explosion. A quantum mechanical calculation is carried out using Skyrme effective interaction between nucleons. The equation of state is shown to soften below the nuclear density and suddenly stiffen in the transnuclear density region, a condition which is suitable for producing a strong bounce shock that is needed for effective supernova explosion and leaving a remnant neutron star behind.