Studying Three Phase Supply in School

The power distribution of nearly all major countries have accepted 3-phase distribution as a standard. With increasing power requirements of instrumentation today even a small physics laboratory requires 3-phase supply. While physics students are given an introduction of this in passing, no experiment work is done with 3-phase supply due to the sheer possibility of accidents while working with such large powers. We believe a conceptual understanding of 3-phase supply would be useful for physics students with hands on experience using a simple circuit that can be assembled even in a high school laboratorys

Optical flow: a curve evolution approach

©1995 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.DOI: 10.1109/ICIP.1995.537569Presented at the 1995 International Conference on Image Processing, October 23-26, 1995, Washington, DC, USA.A novel approach for the computation of optical flow based on an L 1 type minimization is presented. It is shown that the approach has inherent advantages since it does not smooth the flow-velocity across the edges and hence preserves edge information. A numerical approach based on computation of evolving curves is proposed for computing the optical flow field and results of experiments are presented

Chiral plasma instability and primordial Gravitational wave

It is known that cosmic magnetic field, if present, can generate anisotropic stress in the plasma and hence, can act as a source of gravitational waves. These cosmic magnetic fields can be generated at very high temperature, much above electroweak scale, due to the gravitational anomaly in presence of the chiral asymmetry. The chiral asymmetry leads to instability in the plasma which ultimately leads to the generation of magnetic fields. In this article, we discuss the generation of gravitational waves, during the period of instability, in the chiral plasma sourced by the magnetic field created due to the gravitational anomaly. We have shown that such gravitational wave will have a unique spectrum. Moreover, depending on the temperature of the universe at the time of its generation, such gravitational waves can have a wide range of frequencies. We also estimate the amplitude and frequency of the gravitational waves and delineate the possibility of its detection by future experiments like eLISA.Comment: 8 pages, 2 figure

Throughput Analysis of Primary and Secondary Networks in a Shared IEEE 802.11 System

In this paper, we analyze the coexistence of a primary and a secondary (cognitive) network when both networks use the IEEE 802.11 based distributed coordination function for medium access control. Specifically, we consider the problem of channel capture by a secondary network that uses spectrum sensing to determine the availability of the channel, and its impact on the primary throughput. We integrate the notion of transmission slots in Bianchi's Markov model with the physical time slots, to derive the transmission probability of the secondary network as a function of its scan duration. This is used to obtain analytical expressions for the throughput achievable by the primary and secondary networks. Our analysis considers both saturated and unsaturated networks. By performing a numerical search, the secondary network parameters are selected to maximize its throughput for a given level of protection of the primary network throughput. The theoretical expressions are validated using extensive simulations carried out in the Network Simulator 2. Our results provide critical insights into the performance and robustness of different schemes for medium access by the secondary network. In particular, we find that the channel captures by the secondary network does not significantly impact the primary throughput, and that simply increasing the secondary contention window size is only marginally inferior to silent-period based methods in terms of its throughput performance.Comment: To appear in IEEE Transactions on Wireless Communication

Exclusion Principle for Quantum Dense Coding

We show that the classical capacity of quantum states, as quantified by its ability to perform dense coding, respects an exclusion principle, for arbitrary pure or mixed three-party states in any dimension. This states that no two bipartite states which are reduced states of a common tripartite quantum state can have simultaneous quantum advantage in dense coding. The exclusion principle is robust against noise. Such principle also holds for arbitrary number of parties. This exclusion principle is independent of the content and distribution of entanglement in the multipartite state. We also find a strict monogamy relation for multi-port classical capacities of multi-party quantum states in arbitrary dimensions. In the scenario of two senders and a single receiver, we show that if two of them wish to send classical information to a single receiver independently, then the corresponding dense coding capacities satisfy the monogamy relation, similar to the one for quantum correlations.Comment: v2: 6 pages, RevTeX 4, title changed, previous results unchanged, new results adde

(SI10-057) Effect of Time-delay on an SIR Type Model For Infectious Diseases with Saturated Treatment

This study presents the complex dynamics of an SIR epidemic model incorporating a constant time-delay in incidence rate with saturated type of treatment rate. The system is studied to observe the effect of time lag in the asymptotic stability of endemic equilibrium states. We also establish global asymptotic stability of both disease-free and endemic equilibrium states by Lyapunov direct method with the help of suitable Lyapunov functionals. The existences of periodic solutions are ensured for the suitable choice of delay parameter. Finally, we perform numerical simulations supporting the analytical findings as well as to observe the effect of time-delay. The theoretical and numerical results together show delay can have both stabilizing and destabilizing effects on the system. Moreover, we observe that infection may die out from the population when the corresponding system without delay has two endemic equilibrium for appropriate choice of time-delay

Viscosity in cosmic fluids

The effective theory of large-scale structure formation based on $\Lambda$CDM paradigm predicts finite dissipative effects in the resulting fluid equations. In this work, we study how viscous effect that could arise if one includes self-interaction among the dark-matter particles combines with the effective theory. It is shown that these two possible sources of dissipation can operate together in a cosmic fluid and the interplay between them can play an important role in determining dynamics of the cosmic fluid. In particular, we demonstrate that the viscosity coefficient due to self-interaction is added inversely with the viscosity calculated using effective theory of $\Lambda$CDM model. Thus the larger viscosity has less significant contribution in the effective viscosity. Using the known bounds on $\,\sigma/m$ for self-interacting dark-matter, where $\,\sigma\,$ and $m$ are the cross-section and mass of the dark-matter particles respectively, we discuss role of the effective viscosity in various cosmological scenarios.Comment: 7 pages, Updated to match with the published versio