Chiral plasma instability and primordial Gravitational wave

It is known that cosmic magnetic field, if present, can generate anisotropic stress in the plasma and hence, can act as a source of gravitational waves. These cosmic magnetic fields can be generated at very high temperature, much above electroweak scale, due to the gravitational anomaly in presence of the chiral asymmetry. The chiral asymmetry leads to instability in the plasma which ultimately leads to the generation of magnetic fields. In this article, we discuss the generation of gravitational waves, during the period of instability, in the chiral plasma sourced by the magnetic field created due to the gravitational anomaly. We have shown that such gravitational wave will have a unique spectrum. Moreover, depending on the temperature of the universe at the time of its generation, such gravitational waves can have a wide range of frequencies. We also estimate the amplitude and frequency of the gravitational waves and delineate the possibility of its detection by future experiments like eLISA.Comment: 8 pages, 2 figure

An efficient high-order Nystr\"om scheme for acoustic scattering by inhomogeneous penetrable media with discontinuous material interface

This text proposes a fast, rapidly convergent Nystr\"{o}m method for the solution of the Lippmann-Schwinger integral equation that mathematically models the scattering of time-harmonic acoustic waves by inhomogeneous obstacles, while allowing the material properties to jump across the interface. The method works with overlapping coordinate charts as a description of the given scatterer. In particular, it employs "partitions of unity" to simplify the implementation of high-order quadratures along with suitable changes of parametric variables to analytically resolve the singularities present in the integral operator to achieve desired accuracies in approximations. To deal with the discontinuous material interface in a high-order manner, a specialized quadrature is used in the boundary region. The approach further utilizes an FFT based strategy that uses equivalent source approximations to accelerate the evaluation of large number of interactions that arise in the approximation of the volumetric integral operator and thus achieves a reduced computational complexity of $O(N \log N)$ for an $N$-point discretization. A detailed discussion on the solution methodology along with a variety of numerical experiments to exemplify its performance in terms of both speed and accuracy are presented in this paper

Large Miscibility Gap in the Ba(Mn_xFe_{1-x})2As2 System

The compounds BaMn2As2 and BaFe2As2 both crystallize in the body-centered-tetragonal ThCr2Si2-type (122-type) structure at room temperature but exhibit quite different unit cell volumes and very different magnetic and electronic transport properties. Evidently reflecting these disparities, we have discovered a large miscibility gap in the system Ba(Mn_xFe_{1-x})2As2. Rietveld refinements of powder x-ray diffraction (XRD) measurements on samples slow-cooled from 1000 C to room temperature (RT) reveal a two-phase mixture of BaMn2As2 and Ba(Mn_{0.12}Fe_{0.88})2As2 phases together with impurity phases for x = 0.2, 0.4, 0.5, 0.6 and 0.8. We infer that there exists a miscibility gap in this system at 300 K with composition limits 0.12 < x < 1. For samples quenched from 1000 C to 77 K, the refinements of RT XRD data indicate that the miscibility gap at RT narrows at 1000 C to 0.2 < x < 0.8. Samples with x=0.4, 0.5 and 0.6 quenched from 1100-1400 C to 77 K contain a single 122-type phase together with significant amounts of Fe_{1-x}Mn_xAs and FeAs2 impurity phases. These results indicate that the system is not a pseudo-binary system over the whole composition range and that the 122-type phase has a significant homogeneity range at these temperatures. Magnetic susceptibility, electrical resistivity and heat capacity measurements versus temperature of the single-phase quenched polycrystalline samples with x = 0.2 and 0.8 and for lightly doped BaMn2As2 crystals are reported.Comment: 14 pages, 16 figures, 3 tables; published versio

Numerical Simulation of Compression Ignition Diesel Injection (CIDI) to investigate Performance parameters

This paper describes the requirement of the Numerical simulation of compression ignition diesel injection by the use of computer language and it also compares the performance parameter for the biodiesel such as jatropha and karanja. The Engine test was carried out in 512 Army base workshops for the experimental validations. It was carried out on SAJ dynamometer which was installed in Engine test house for testing of Engines. Performance parameters such as Brake power, Brake Torque, Mechanical efficiency, Thermal Efficiency, Pressure vs Crank angle and Heat release Rate vs Crank Angle was taken from the Engine test house. The Program code for the Performance parameter of Engine was developed in C++ language. Then the simulation was carried out. The simulation results were compared and analyzed with the experimental results. The final results was effective for compression ignition diesel injection. As we know that today&rsquo;s world is approaching towards computer simulated results, so the numerically simulated results will save time and money for engine testing house. Likewise we can approach towards numerical simulation for various types of Engines

Estimation of leakage power and delay in CMOS circuits using parametric variation

SummaryWith the advent of deep-submicron technologies, leakage power dissipation is a major concern for scaling down portable devices that have burst-mode type integrated circuits. In this paper leakage reduction technique HTLCT (High Threshold Leakage Control Transistor) is discussed. Using high threshold transistors at the place of low threshold leakage control transistors, result in more leakage power reduction as compared to LCT (leakage control transistor) technique but at the scarifies of area and delay. Further, analysis of effect of parametric variation on leakage current and propagation delay in CMOS circuits is performed. It is found that the leakage power dissipation increases with increasing temperature, supply voltage and aspect ratio. However, opposite pattern is noticed for the propagation delay. Leakage power dissipation for LCT NAND gate increases up to 14.32%, 6.43% and 36.21% and delay decreases by 22.5%, 42% and 9% for variation of temperature, supply voltage and aspect ratio. Maximum peak of equivalent output noise is obtained as 127.531nV/Sqrt(Hz) at 400mHz

Ba{1-x}KxMn2As2: An Antiferromagnetic Local-Moment Metal

The compound BaMn2As2 with the tetragonal ThCr2Si2 structure is a local-moment antiferromagnetic insulator with a Neel temperature TN = 625 K and a large ordered moment mu = 3.9 mu_B/Mn. We demonstrate that this compound can be driven metallic by partial substitution of Ba by K, while retaining the same crystal and antiferromagnetic structures together with nearly the same high TN and large mu. Ba_{1-x}K_xMn2As2 is thus the first metallic ThCr2Si2-type MAs-based system containing local 3d transition metal M magnetic moments, with consequences for the ongoing debate about the local moment versus itinerant pictures of the FeAs-based superconductors and parent compounds. The Ba_{1-x}K_xMn2As2 class of compounds also forms a bridge between the layered iron pnictides and cuprates and may be useful to test theories of high Tc superconductivity.Comment: 5 two-column typeset pages, 5 figures, 20 references; v2: minor revisions, 4 new references, published versio

Improved convergence of fast integral equation solvers for acoustic scattering by inhomogeneous penetrable media with discontinuous material interface

In recent years, several fast solvers for the solution of the Lippmann-Schwinger integral equation that mathematically models the scattering of time-harmonic acoustic waves by penetrable inhomogeneous obstacles, have been proposed. While many of these fast methodologies exhibit rapid convergence for smoothly varying scattering configurations, the rate for most of them reduce to either linear or quadratic when material properties are allowed to jump across the interface. A notable exception to this is a recently introduced Nystr\"{o}m scheme [J. Comput. Phys., 311 (2016), 258--274] that utilizes a specialized quadrature in the boundary region for a high-order treatment of the material interface. In this text, we present a solution framework that relies on the specialized boundary integrator to enhance the convergence rate of other fast, low order methodologies without adding to their computational complexity of $O(N \log N)$ for an $N$-point discretization. In particular, to demonstrate the efficacy of the proposed framework, we explain its implementation to enhance the order to convergence of two schemes, one introduced by Duan and Rokhlin [J. Comput. Phys., 228(6) (2009), 2152--2174] that is based on a pre-corrected trapezoidal rule while the other by Bruno and Hyde [J. Comput. Phys., 200(2) (2004), 670--694] which relies on a suitable decomposition of the Green's function via Addition theorem. In addition to a detailed description of these methodologies, we also present a comparative performance study of the improved versions of these two and the Nystr\"{o}m solver in [J. Comput. Phys., 311 (2016), 258--274] through a wide range of numerical experiments

Flank Wear Measurement of Al-based Metal Matrix Composite Materials (MMC)

Metal based Composite’s are the advanced materials possessing properties that make them useful in applications where high strength to weight ratio and ability to operate at elevated temperatures are required. MMC’s are difficult to machine, however, consisting of hard abrasive reinforcing medium set within a more ductile matrix material. This paper  results from a series of turning tests in which a number of  different cutting tool materials were used to machine an  Al(6063)/5 vol% SiCp Metal Matrix Composite. The influence of the cutting speed on tool wear was established for each tool material. It was found that carbide tools, both coated and uncoated sustained significant levels of tool wear after a short period of machining. The best overall performance was achieved using a titanium coated carbide insert. Keywords: Metal matrix composite, MMC’