Spiral waves in driven strongly coupled Yukawa systems

Spiral wave formations are ubiquitous in nature. In the present paper, the excitation of spiral waves in the context of driven two-dimensional dusty plasma (Yukawa system) has been demonstrated at particle level using molecular dynamics simulations. The interaction amidst dust particles is modeled by Yukawa potential to take account of the shielding of dust charges by the lighter electron and ions species. Spatiotemporal evolution of these spiral waves has been characterized as a function of frequency and amplitude of the driving force, dust neutral collisions etc. The effect of strong coupling has been studied which show that the excited spiral wave structures get clearer as the medium gets more strongly coupled. The radial propagation speed of the spiral wave is observed to remain unaltered with the coupling parameter. However, it is found to depend on the screening parameter of the dust medium and decreases when it is increased. In the crystalline phase (with screening parameter \k{appa} > 0.58), spiral wavefront are shown to be hexagonal in shape. This shows that the radial propagation speed depends on the interparticle spacing

Experimental Research Work to Optimize Process Parameters into Electro Chemical Abrasive Flow Machining using Taguchi Methodology

Electrochemical assisted abrasive flow finishing is a newly developed hybrid finishing process which is used to finish the internal parts of work piece having complicated geometry to large extent. In electrochemical assisted abrasive flow machining higher abrasion of the material was detected due to the combine effect of ECM and AFF processes. In Electrochemical aided abrasive flow machining a electrolyte is added to the prepared media .This media consist a kind of polymeric carrier and abrasive particles that are hydrocarbon gel, Al2O3, Silicon based polymer, and NaI Sodium iodide as electrolytic salt. In this experimental research different process parameters such as voltage, abrasive concentration, Number of cycle, molal concentration and diameter of rod were considered at different levels for response characteristic of surface roughness Ra and material removal MR based on Taguchi method using standard L27 orthogonal array OA for the plan of experimentation. To determine the contribution of each parameter analysis of variance was used. Sandeep Singh | Sunil kumar "Experimental Research Work to Optimize Process Parameters into Electro Chemical Abrasive Flow Machining using Taguchi Methodology" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-4 , June 201

A Study of the Effect of Bulges on Bar Formation in Disk galaxies

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disk instabilities that evolve by transferring angular momentum from the inner to outer disks and to the dark matter halo. It is well known that a massive spherical component such as halo in a disk galaxy can make it bar stable. In this study we explore the effect of another spherical component, the bulge, on bar formation in disk galaxies. In our models we vary both the bulge mass and concentration. We have used two sets of models, one that has a dense bulge and high surface density disk. The second model has a less concentrated bulge and a lighter disk. In both models we vary the bulge to disk mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cutoff in bulge to disk mass ratio M b /M d above which bars cannot form; the cutoff is smaller for denser bulges( M b /M d = 0.2) compared to less denser ones (M b /M d = 0.5). We define a new criteria for bar formation in terms of bulge to disk radial force ratio (F b /F d ) at the disk scale lengths above which bars cannot form. We find that if F b /F d > 0.35, a disk is stable and a bar cannot form. Our results indicate that early type disk galaxies can still form strong bars in spite of having massive bulges.Comment: Accepted at MNRAS,12 pages, 19 figure