Chemical Evolution of Strongly Magnetized Quark Core in a Newborn Neutron Star

The chemical evolution of nascent quark matter core in a newborn compact neutron star is studied in presence of a strong magnetic field. The effective rate of strange quark production in degenerate quark matter core in presence of strong magnetic fields is obtained. The investigations show that in presence of strong magnetic fields a quark matter core becomes energetically unstable and hence a deconfinement transition to quark matter at the centre of a compact neutron star under such circumstances is not possible. The critical strength of magnetic field at the central core to make the system energetically unstable with respect to dense nuclear matter is found to be $\sim 4.4\times 10^{13}$G. This is the typical strength at which the Landau levels for electrons are populated. The other possible phase transitions at such high density and ultra strong magnetic field environment are discussed.Comment: 18 pages, latex, eight EPS figures not included, available under request, REVTEX forma

Broadband DOA estimation using Convolutional neural networks trained with noise signals

A convolution neural network (CNN) based classification method for broadband DOA estimation is proposed, where the phase component of the short-time Fourier transform coefficients of the received microphone signals are directly fed into the CNN and the features required for DOA estimation are learnt during training. Since only the phase component of the input is used, the CNN can be trained with synthesized noise signals, thereby making the preparation of the training data set easier compared to using speech signals. Through experimental evaluation, the ability of the proposed noise trained CNN framework to generalize to speech sources is demonstrated. In addition, the robustness of the system to noise, small perturbations in microphone positions, as well as its ability to adapt to different acoustic conditions is investigated using experiments with simulated and real data.Comment: Published in Proceedings of IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA) 201

Selection of Dominant Characteristic Modes

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The theory of characteristic modes is a popular physics based deterministic approach which has found several recent applications in the fields of radiator design, electromagnetic interference modelling and radiated emission analysis. The modal theory is based on the approximation of the total induced current in an electromagnetic structure in terms of a weighted sum of multiple characteristic current modes. The resultant outgoing field is also a weighted summation of the characteristic field patterns. Henceforth, a proper modal measure is an essential requirement to identify the modes which play a dominant role for a frequency of interest. The existing literature of significance measures restricts itself for ideal lossless structures only. This paper explores the pros and cons of the existing measures and correspondingly suggests suitable alternatives for both radiating and scattering applications. An example is presented in order to illustrate the proposed modal method for approximating the shielding response of a slotted geometry

Validation of measurement setup for assessing complex dielectric constant

Abstract. Electromagnetic waves interact with different obstacles or materials. The propagation of electromagnetic waves depends on how they interact with different materials. Understanding the transmission and reflection characteristics of various media leads to understanding the propagation of electromagnetic waves. The transmission and reflection of radio waves are dictated by the dielectric properties of the material. The estimation of dielectric properties of a material is acquired by proper measurement techniques and methods. In this thesis, a measurement setup for assessing complex dielectric constant is verified. The measurement setup is designed with two high frequency horn antennas and a two-port vector network analyzer, controlled by a computer via a GPIB interface. Various measurement scenarios and results needed to achieve the goal are presented in the thesis. All measurements are done in an anechoic chamber. The measurement data is collected in frequency ranges of 1–9.5 GHz and 9.5–18 GHz. Furthermore, reflection measurements are taken from the side wall absorbers in the same anechoic chamber for checking the wall absorption characteristics. The key findings of this experiment are dielectric constant, Brewster angle and the reflection coefficient. The obtained value of the dielectric constant can be further used for similar type of environments or measurement setup

A Search for Fallback Disks in Four Young Supernova Remnants

We report on our search for the optical/infrared counterparts to the central compact objects in four young supernova remnants: Pup A, PKS 1209-52, RCW 103, and Cas A. The X-ray point sources in these supernova remnants are excellent targets for probing the existence of supernova fallback disks, since irradiation of a disk by a central X-ray source should lead to an infrared excess. We used ground-based optical and near-infrared imaging and Spitzer Space Telescope mid-infrared imaging to search for optical/infrared counterparts at the X-ray point source positions measured by the Chandra X-Ray Observatory. We did not detect any counterparts, and hence find no evidence for fallback disks around any of these sources. In PKS 1209-52, we are able to exclude a nearby optical/infrared candidate counterpart. In RCW 103, a blend of 3 faint stars at the X-ray source position prevents us from deriving useful limits. For the other targets, the upper limits on the infrared/X-ray flux ratio are as deep as (1.0--1.7)$\times 10^{-4}$. Comparing these limits to the ratio of $\approx 6\times10^{-5}$ measured for 4U 0142+61 (a young pulsar recently found with an X-ray irradiated dust disk), we conclude that the non-detection of any disks around young neutron stars studied here are consistent with their relatively low X-ray luminosities, although we note that a similar dust disk around the neutron star in Pup A should be detectable by deeper infrared observations.Comment: 9 pages, 5 figures, revised to address referee's comments, and accepted for publication in Ap