Magnetic behavior of single crystalline Ho2_2PdSi3_3

The magnetic behavior of single-crystal Ho$_2$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure, is investigated by magnetic susceptibility ($\chi$) and electrical resistivity ($\rho$) measurements along two directions. There is no dramatic anisotropy in the high temperature Curie-Weiss parameter or in the $\rho$ and isothermal magnetization data, though there is a noticeable anisotropy in the magnitude of $\rho$ between two perpendicular orientations. The degree of anisotropy is overall less prominent than in the Gd (which is an S-state ion!) and Tb analogues. A point of emphasis is that this compound undergoes long range magnetic ordering below 8 K as in the case of analogous Gd and Dy compounds. Considering this fact for these compounds with well-localised f-orbital, the spin glass freezing noted for isomorphous U compounds in the recent literature could be attributed to the role of the f-ligand hybridization, rather than just Pd-Si disorder.Comment: Physical Review B, in pres

Persistence of Manifolds in Nonequilibrium Critical Dynamics

We study the persistence P(t) of the magnetization of a d' dimensional manifold (i.e., the probability that the manifold magnetization does not flip up to time t, starting from a random initial condition) in a d-dimensional spin system at its critical point. We show analytically that there are three distinct late time decay forms for P(t) : exponential, stretched exponential and power law, depending on a single parameter \zeta=(D-2+\eta)/z where D=d-d' and \eta, z are standard critical exponents. In particular, our theory predicts that the persistence of a line magnetization decays as a power law in the d=2 Ising model at its critical point. For the d=3 critical Ising model, the persistence of the plane magnetization decays as a power law, while that of a line magnetization decays as a stretched exponential. Numerical results are consistent with these analytical predictions.Comment: 4 pages revtex, 1 eps figure include

Time dependent spectral modeling of Markarian 421 during a violent outburst in 2010

We present the results of extensive modeling of the spectral energy distributions (SEDs) of the closest blazar (z=0.031) Markarian 421 (Mrk 421) during a giant outburst in February 2010. The source underwent rapid flux variations in both X-rays and very high energy (VHE) gamma-rays as it evolved from a low-flux state on 2010 February 13-15 to a high-flux state on 2010 February 17. During this period, the source exhibited significant spectral hardening from X-rays to VHE gamma-rays while exhibiting a "harder when brighter" behavior in these energy bands. We reproduce the broadband SED using a time-dependent multi-zone leptonic jet model with radiation feedback. We find that an injection of the leptonic particle population with a single power-law energy distribution at shock fronts followed by energy losses in an inhomogeneous emission region is suitable for explaining the evolution of Mrk 421 from low- to high-flux state in February 2010. The spectral states are successfully reproduced by a combination of a few key physical parameters, such as the maximum $\&$ minimum cutoffs and power-law slope of the electron injection energies, magnetic field strength, and bulk Lorentz factor of the emission region. The simulated light curves and spectral evolution of Mrk 421 during this period imply an almost linear correlation between X-ray flux at 1-10 keV energies and VHE gamma-ray flux above 200 GeV, as has been previously exhibited by this source. Through this study, a general trend that has emerged for the role of physical parameters is that, as the flare evolves from a low- to a high-flux state, higher bulk kinetic energy is injected into the system with a harder particle population and a lower magnetic field strength.Comment: 13 pages, 5 figures, accepted for publication in MNRA

Statistical Properties of Functionals of the Paths of a Particle Diffusing in a One-Dimensional Random Potential

We present a formalism for obtaining the statistical properties of functionals and inverse functionals of the paths of a particle diffusing in a one-dimensional quenched random potential. We demonstrate the implementation of the formalism in two specific examples: (1) where the functional corresponds to the local time spent by the particle around the origin and (2) where the functional corresponds to the occupation time spent by the particle on the positive side of the origin, within an observation time window of size $t$. We compute the disorder average distributions of the local time, the inverse local time, the occupation time and the inverse occupation time, and show that in many cases disorder modifies the behavior drastically.Comment: Revtex two column 27 pages, 10 figures, 3 table

Coal Washing Pilot Plants at Central Fuel Research Institute, Jealgora, India

The plan, design and selection of industrial coal washers require the proper assessment of a number of factors which can be summarised as follows: (1) Methods of Mining, mode of transport and handling at the collieries as well as inside the washery and their resultant effect on the size of the coal fed to the washery. (2) Requirement of the consumers as regards size, quality and moisture content of the washed products. (3) Washability characteristics of the deals to be cleaned. (4) Limitations and efficiency of the different types of washing plants. (5) Capital and recurring expenses etc. etc

Global Persistence Exponent for Critical Dynamics

A `persistence exponent' $\theta$ is defined for nonequilibrium critical phenomena. It describes the probability, $p(t) \sim t^{-\theta}$, that the global order parameter has not changed sign in the time interval $t$ following a quench to the critical point from a disordered state. This exponent is calculated in mean-field theory, in the $n=\infty$ limit of the $O(n)$ model, to first order in $\epsilon = 4-d$, and for the 1-d Ising model. Numerical results are obtained for the 2-d Ising model. We argue that $\theta$ is a new independent exponent.Comment: 4 pages, revtex, one figur

Can Hydrocyclone be an Alternative in solid-liquid Separation Process?

In mineral processing industry, most of the separation processes involve substantial quantities of water. The final concentrate generated has to be with low moisture content and recovery of water from the tailing stream has to be recycled. So dewatering i.e., separation of liquid from solid is an important step in mineral processing. As dewatering processes are expensive and inefficient in general, these need focused attention. In case of fine and ultra-fine particles, (fine <100µm, ultra-fine < 5 µm) screening, even if in wet condition, is not effective. As there are many limitations associated with thickeners and filtration units, hydrocyclone can be thought of as an alternative in the solid-liquid separation process. Because of the design and operational simplicity, high capacity, low maintenance and operating cost, hydrocyclone is found to be very attractive for dewatering purpose. So, if hydrocyclones can be used efficiently at this stage, then the load on filtration units or thickeners can be reduced. This paper is aimed at understanding the most important factors that are affecting the separation of solid and liquid in a hydrocyclone for dewatering application i.e., recovering maximum solid and minimum water in the underflow which means maximum water recovery in the overflow. In this study the effect of three parameters on dewatering efficiency was studied in a 2″ hydrocyclone keeping at maximum pressure to achieve the objective. From the experimental results on silica sand, it was found that maximum 98.6 % solid can be recovered with 42.6 % water in the underflow

Image Exploitation-A Forefront Area for UAV Application

Image exploitation, an innovative image utilisation program uses high revisit multisensor, multiresolution imagery from unmanned air vehicle or other reconnaissance platform for intelligent information gathering. This paper describes the imagc exploitation system developed at the Aeronautical Dcvclopment Establishment, Bangalore, for the remotely piloted vehicle (RPV) Nishonr and highlights two major areas (i) In-flight imagc exploitation, and (ii) post-flight imagc cxploitatlon. In-flight imagc study includes real-timeenhancement of images frames during RPV flight. target acquisition. calculation of geo-location of targets, distance and area computation, and image-to-map correspondence. Post-flight image exploitation study includes image restoration, classtfication of terrain, 3-D depth computation using stereo vision and shape from shading techniques. The paper shows results obtained in each of these areas from actual flight trials

Mass and Scalar Cross-sections for Neutralino Dark Matter in Anomaly Mediated Supersymmetry Breaking Model

We have considered neutralino to be the lightest supersymmetric particle (LSP) in the framework of minimal Anomaly Mediated Supersymmetric (mAMSB) model. We have studied variation of neutralino mass with the supersymmetric parameters. Considering these neutralinos to be the candidates for weakly interacting massive particle (WIMP) or cold dark matter (CDM), we have calculated the neutralino nucleon scalar cross-sections and compared them with DAMA-NaI neutralino direct detection search results. From this study we observe that the mAMSB model results cannot explain the allowed region in WIMP mass and WIMP-nucleon scalar cross-section space obtained from annual modulation signature in DAMA-NaI experiment.Comment: 7 Pages LaTeX, 4 figures, J. Phys. G., to appea