Modeling The X-ray Timing Properties Of Cygnus X-1 As Caused By Waves Propagating In A Transition Disk

We show that waves propagating in a transition disk can explain the short term temporal behavior of Cygnus X-1. In the transition disk model the spectrum is produced by saturated Comptonization within the inner region of the accretion disk where the temperature varies rapidly with radius. Recently, the spectrum from such a disk has been shown to fit the average broad band spectrum of this source better than that predicted by the soft-photon Comptonization model. Here, we consider a simple model where waves are propagating cylindrically symmetrical ly in the transition disk with a uniform propagation speed ($c_p$). We show that this model can qualitatively explain (a) the variation of the power spectral density (PSD) with energy, (b) the hard lags as a function of frequency and (c) the hard lags as a function of energy for various frequencies. Thus the transition disk model can explain the average spectrum and the short term temporal behavior of Cygnus X-1.Comment: accepted for publication in APJ letter

A Review of Models for Evaluating Quality in Open Source Software

Open source products/projects targeting the same or similar applications are common nowadays. This makes choosing a tricky task. Quality is one factor that can be considered when choosing among similar open source solutions. In order to measure quality in software, quality models can be used. Open source quality models emerged due to the inability of traditional quality models to measure unique features (such as community) of open source software. The aim of the paper therefore is to examine the characteristic features, unique strengths, and limitations of existing open source quality models. In addition, we compare the models based on some selected attributes

Development of Waste Management Culture

Development of any culture is a time consuming exercise. However, the civilized world has been developing different kinds of cultures depending upon the necessity of the time prevailing. The development of waste management/minization culture is the need of the day and the techniques opted are obviously of pollution prevention/control. Pollution generated by anthropogenic wastes has grown to horrifying levels. Though the subject is vast and general, the scope of the paper has been confined to the industrial sector only. Zones of improvements are varied and numerous like energy, raw materials, process conditions, waste genera-tion etc. Inculcation of waste minimization culture amon-gst workers and managers has been discussed. Since devel-opment of a relatively new culture is a prolonged process, it has to be introduced in the grass root level from the very beginning. However, it is never too late to introduce such waste management/minization techniques in to the present industries