Galactic cosmic ray induced radiation dose on terrestrial exoplanets

This past decade has seen tremendous advancements in the study of extrasolar planets. Observations are now made with increasing sophistication from both ground and space-based instruments, and exoplanets are characterized with increasing precision. There is a class of particularly interesting exoplanets, falling in the habitable zone, which is defined as the area around a star where the planet is capable of supporting liquid water on its surface. Theoretical calculations also suggest that close-in exoplanets are more likely to have weaker planetary magnetic fields, especially in case of super earths. Such exoplanets are subjected to a high flux of Galactic Cosmic Rays (GCRs) due to their weak magnetic moments. GCRs are energetic particles of astrophysical origin, which strike the planetary atmosphere and produce secondary particles, including muons, which are highly penetrating. Some of these particles reach the planetary surface and contribute to the radiation dose. Along with the magnetic field, another factor governing the radiation dose is the depth of the planetary atmosphere. The higher the depth of the planetary atmosphere, the lower the flux of secondary particles will be on the surface. If the secondary particles are energetic enough, and their flux is sufficiently high, the radiation from muons can also impact the sub-surface regions, such as in the case of Mars. If the radiation dose is too high, the chances of sustaining a long-term biosphere on the planet are very low. We explore the dependence of the GCR induced radiation dose on the strength of the planetary magnetic field and its atmospheric depth, finding that the latter is the decisive factor for the protection of a planetary biosphere.Comment: Accepted for publication in Astrobiolog

Enabling Radiative Transfer on AMR grids in CRASH

We introduce CRASH-AMR, a new version of the cosmological Radiative Transfer (RT) code CRASH, enabled to use refined grids. This new feature allows us to attain higher resolution in our RT simulations and thus to describe more accurately ionisation and temperature patterns in high density regions. We have tested CRASH-AMR by simulating the evolution of an ionised region produced by a single source embedded in gas at constant density, as well as by a more realistic configuration of multiple sources in an inhomogeneous density field. While we find an excellent agreement with the previous version of CRASH when the AMR feature is disabled, showing that no numerical artifact has been introduced in CRASH-AMR, when additional refinement levels are used the code can simulate more accurately the physics of ionised gas in high density regions. This result has been attained at no computational loss, as RT simulations on AMR grids with maximum resolution equivalent to that of a uniform cartesian grid can be run with a gain of up to 60% in computational time.Comment: 19 pages, 17 figures. MNRAS, in pres

Polynomial disaggregation procedures

January 1991.Includes bibliographical references.In air quality monitoring, often aerosol samples are collected using various filter methods in regular sampling cycles. Some aerosol species samples may be collected at 12 hour cycles while others may be collected at 6 hour cycles or 24 hour cycles, etc. If some species are collected at 6 hour intervals and others at 12 hour intervals, then a statistical analysis of these data are often carried out after aggregating the 6 hour data to produce 12 hour data so that all data correspond to the same time cycle. It is of some interest to investigate the alternative possibility of disaggregating the 12 hour data to obtain "6 hour (pseudo) data" and then performing statistical analyses on the 6 hour scale. In this report we investigate this possibility by studying how well a certain class of disaggregation procedures is able to disaggregate aggregated data. The performance of the methods considered are evaluated using real data collected as part of the WHITEX study.Research supported by the National Oceanic Atmospheric Administration under Grant no. NA90RAH00077

Information-theoretic significance of the Wigner distribution

A coarse grained Wigner distribution p_{W}(x,u) obeying positivity derives out of information-theoretic considerations. Let p(x,u) be the unknown joint PDF (probability density function) on position- and momentum fluctuations x,u for a pure state particle. Suppose that the phase part Psi(x,z) of its Fourier transform F.T.[p(x,u)]=|Z(x,z)|exp[iPsi(x,z)] is constructed as a hologram. (Such a hologram is often used in heterodyne interferometry.) Consider a particle randomly illuminating this phase hologram. Let its two position coordinates be measured. Require that the measurements contain an extreme amount of Fisher information about true position, through variation of the phase function Psi(x,z). The extremum solution gives an output PDF p(x,u) that is the convolution of the Wigner p_{W}(x,u) with an instrument function defining uncertainty in either position x or momentum u. The convolution arises naturally out of the approach, and is one-dimensional, in comparison with the two-dimensional convolutions usually proposed for coarse graining purposes. The output obeys positivity, as required of a PDF, if the one-dimensional instrument function is sufficiently wide. The result holds for a large class of systems: those whose amplitudes a(x) are the same at their boundaries (Examples: states a(x) with positive parity; with periodic boundary conditions; free particle trapped in a box).Comment: pdf version has 16 pages. No figures. Accepted for publ. in PR

Interface Response Functions for multicomponent alloy solidification- An application to additive manufacturing

The near-rapid solidification conditions during additive manufacturing can lead to selection of non-equilibrium phases. Sharp interface models via interface response functions have been used earlier to explain the microstructure selection under such solidification conditions. However, most of the sharp interface models assume linear superposition of contributions of alloying elements without considering the non-linearity associated with the phase diagram. In this report, both planar and dendritic Calphad coupled sharp interface models have been implemented and used to explain the growth-controlled phase selection observed at high solidification velocities relevant to additive manufacturing. The implemented model predicted the growth-controlled phase selection in multicomponent alloys, which the other models with linear phase diagram could not. These models are calculated for steels and a Nickel-based superalloy and the results are compared with experimental observations.Comment: 33 pages, 11 figures, preprin

MULTI-PURPOSE EMBEDDED VOICE ASSISTANCE GADGET

One of the important problems that our society faces is that people with disabilities are finding it hard to cope up with the fast growing technology. In the recent years, there has been a rapid increase in the number of hearing impaired and speech disabled victims due to birth defects, oral diseases and accidents. When a deaf-dumb person speaks to a normal person, the normal person seldom understands and asks the deaf-dumb person to show gestures for his/her needs. Dumb persons have their own language to communicate to us; the only thing is that we need to understand their language. So, we need a translator to understand what they speak and communicate to us. In order to achieve this, we have proposed a system that can provide basic communication needs for a deaf-dumb person and also aid him in many ways. In the proposed system, we have used a speech recognition unit along with audio pre recorder and embedded controllers which will be helpful for deaf and dumb persons to express their needs to normal person. The frequently spoken words are stored in audio pre recorder which can be easily retrieved and also displayed using Liquid Crystal Display. The proposed device is also helpful for born deaf children to learn the basics of any language. In addition, voice based home automation system is also proposed for elderly and disabled people. Home automation system is achieved by wireless RF transmission and reception techniques integrated with our Embedded Voice Translator Kit. The proposed system along with text to speech converter and language translators as future enhancements will provide great assistance to deaf and dumb persons to portray their needs to society. Our system can also be incorporated for various applications like personal security, wireless TV remote control etc

FPM: Fine Pose Parts-Based Model with 3D CAD Models

We introduce a novel approach to the problem of localizing objects in an image and estimating their fine-pose. Given exact CAD models, and a few real training images with aligned models, we propose to leverage the geometric information from CAD models and appearance information from real images to learn a model that can accurately estimate fine pose in real images. Specifically, we propose FPM, a fine pose parts-based model, that combines geometric information in the form of shared 3D parts in deformable part based models, and appearance information in the form of objectness to achieve both fast and accurate fine pose estimation. Our method significantly outperforms current state-of-the-art algorithms in both accuracy and speed

Colloidal electrophoresis: Scaling analysis, Green-Kubo relation, and numerical results

We consider electrophoresis of a single charged colloidal particle in a finite box with periodic boundary conditions, where added counterions and salt ions ensure charge neutrality. A systematic rescaling of the electrokinetic equations allows us to identify a minimum set of suitable dimensionless parameters, which, within this theoretical framework, determine the reduced electrophoretic mobility. It turns out that the salt-free case can, on the Mean Field level, be described in terms of just three parameters. A fourth parameter, which had previously been identified on the basis of straightforward dimensional analysis, can only be important beyond Mean Field. More complicated behavior is expected to arise when further ionic species are added. However, for a certain parameter regime, we can demonstrate that the salt-free case can be mapped onto a corresponding system containing additional salt. The Green-Kubo formula for the electrophoretic mobility is derived, and its usefulness demonstrated by simulation data. Finally, we report on finite-element solutions of the electrokinetic equations, using the commercial software package COMSOL.Comment: To appear in Journal of Physics: Condensed Matter - special issue on occasion of the CODEF 2008 conferenc