Investigation of nose bluntness and angle of attack effects on slender bodies in viscous hypersonic flows

Hypersonic flows over cones and straight biconic configurations are calculated for a wide range of free stream conditions in which the gas behind the shock is treated as perfect. Effect of angle of attack and nose bluntness on these slender cones in air is studied extensively. The numerical procedures are based on the solution of complete Navier-Stokes equations at the nose section and parabolized Navier-Stokes equations further downstream. The flow field variables and surface quantities show significant differences when the angle of attack and nose bluntness are varied. The complete flow field is thoroughly analyzed with respect to velocity, temperature, pressure, and entropy profiles. The post shock flow field is studied in detail from the contour plots of Mach number, density, pressure, and temperature. The effect of nose bluntness for slender cones persists as far as 200 nose radii downstream

Non-Gaussianity from extragalactic point-sources

The population of compact extragalactic sources contribute to the non-Gaussianity at Cosmic Microwave Background frequencies. We study their non-Gaussianity using publicly available full-sky simulations. We introduce a parametrisation to visualise efficiently the bispectrum and we describe the scale and frequency dependences of the bispectrum of radio and IR point-sources. We show that the bispectrum is well fitted by an analytical prescription. We find that the clustering of IR sources enhances their non-Gaussianity by several orders of magnitude, and that their bispectrum peaks in the squeezed triangles. Examining the impact of these sources on primordial non-Gaussianity estimation, we find that radio sources yield an important positive bias to local fNL at low frequencies but this bias is efficiently reduced by masking detectable sources. IR sources produce a negative bias at high frequencies, which is not dimmed by the masking, as their clustering is dominated by faint sources.Comment: 4pages, 2 figures, 2 tables. Contribution to the proceedings of the International Conference on Gravitation and Cosmology, Goa, December 201

CMB Lensing Power Spectrum Biases from Galaxies and Clusters using High-angular Resolution Temperature Maps

The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to ACT and SPT. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on sigma_8 and an uncertainty on the total neutrino mass of approximately 50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M_vir = 10^14 M_sun. To achieve such percent level bias, we find that only modes up to a maximum multipole of l_max ~ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.Comment: 14 pages, 14 figures, to be submitted to Ap

Evidence for Non-Hydrostatic Gas from the Cluster X-ray to Lensing Mass Ratio

Using a uniform analysis procedure, we measure spatially resolved weak gravitational lensing and hydrostatic X-ray masses for a sample of 18 clusters of galaxies. We find a radial trend in the X-ray to lensing mass ratio: at r2500 we obtain a ratio MX/ML=1.03+/-0.07 which decreases to MX/ML=0.78+/-0.09 at r500. This difference is significant at 3 sigma once we account for correlations between the measurements. We show that correcting the lensing mass for excess correlated structure outside the virial radius slightly reduces, but does not eliminate this trend. An X-ray mass underestimate, perhaps due to nonthermal pressure support, can explain the residual trend. The trend is not correlated with the presence or absence of a cool core. We also examine the cluster gas fraction and find no correlation with ML, an important result for techniques that aim to determine cosmological parameters using the gas fraction.Comment: 8 pages, minor modifications, accepted for publication in MNRA

A Methodology to Inter-Compare Brass and Such Alloys Manufactured at Different Geographical Locations

319-329This paper is about a method developed to normalize the Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) data counts of each constituent ion in a mass spectra, by dividing each ion count with the total ion count. So by comparing their statistical means, data of different samples of any alloy like brass etc. from different places around the world can be inter-compared using TOF-SIMS data collected using similar separate instruments under similar experimental conditions. Such a methodology can also be extended to analysis of constituents of other materials using TOF-SIMS as well. Here, all brass samples were chosen on a representative global basis and had similar end uses. Variations in normalized mean counts of major constituent ions suggest that brass produced in different parts of the world for similar uses can be a little different in composition and can be readily identified and distinguished using their normalized statistical mean ion counts using TOF-SIMS. Their performance does not drastically change due to variation in such constituents of the alloy as the thermal treatments used on them were possibly different. Based on these observations, it was felt that unless there is a drastic change in any alloys’ micro-structure or crystalline phase properties, there will be no drastic change in its properties with variation of its’ major or minor alloying constituents. Data from literature using different aluminum alloys as a representative example and using their available data on micro-hardness and noting their variation with alloying also suggests such a phenomena

A Methodology to Inter-Compare Brass and Such Alloys Manufactured at Different Geographical Locations

This paper is about a method developed to normalize the Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) data counts of each constituent ion in a mass spectra, by dividing each ion count with the total ion count. So by comparing their statistical means, data of different samples of any alloy like brass etc. from different places around the world can be inter-compared using TOF-SIMS data collected using similar separate instruments under similar experimental conditions. Such a methodology can also be extended to analysis of constituents of other materials using TOF-SIMS as well. Here, all brass samples were chosen on a representative global basis and had similar end uses. Variations in normalized mean counts of major constituent ions suggest that brass produced in different parts of the world for similar uses can be a little different in composition and can be readily identified and distinguished using their normalized statistical mean ion counts using TOF-SIMS. Their performance does not drastically change due to variation in such constituents of the alloy as the thermal treatments used on them were possibly different. Based on these observations, it was felt that unless there is a drastic change in any alloys’ micro-structure or crystalline phase properties, there will be no drastic change in its properties with variation of its’ major or minor alloying constituents. Data from literature using different aluminum alloys as a representative example and using their available data on micro-hardness and noting their variation with alloying also suggests such a phenomen

On CP Asymmetries in Two-, Three- and Four-Body D Decays

Indirect and direct CP violations have been established in K_L and B_d decays. They have been found in two-body decay channels -- with the exception of K_L to pi^+ pi^- e^+ e^- transitions. Evidence for direct CP asymmetry has just appeared in LHCb data on A_{CP}(D^0 to K^+ K^-) - A_{CP}(D^0 to pi^+ pi^-) with 3.5 sigma significance. Manifestations of New Dynamics (ND) can appear in CP asymmetries just below experimental bounds. We discuss D^{\pm}_{(s)}, D^0/\bar D^0 and D_L/D_S transitions to 2-, 3- and 4-body final states with a comment on predictions for inclusive vs. exclusive CP asymmetries. In particular we discuss T asymmetries in D to h_1 h_2 l^+ l^- in analogy with K_L to pi^+ pi^- e^+ e^- transitions due to interference between M1, internal bremsstrahlung and possible E1 amplitudes. Such an effect depends on the strength of CP violation originating from the ND -- as discussed here for Little Higgs Models with T parity and non-minimal Higgs sectors -- but also in the interferences between these amplitudes even in the Standard Model (SM). More general lessons can be learnt for T asymmetries in non-leptonic D decays like D to h_1h_2 h_3 h_4. Such manifestations of ND can be tested at LHCb and other Super-Flavour Factories like the projects at KEK near Tokyo and at Tor Vergata/Frascati near Rome.Comment: 27 pages, 6 figures. Revised with current results from LHCb and HFAG and further interpretation