Prediction of Initial and Striking Velocity of Primary Fragments from Cased Spherical Explosive inside Steel Cubical Structure

Usually, energy generated from an explosive’s detonation is transferred partly in the form of the blast impulse and some in the form of the kinetic energy of casing fragments. When detonation occurs in an explosive casing, it breaks the casing into fragments of different weights with varying velocities. The extent of destruction by these energized fragments depends upon the initial velocity they gain after an explosion. The momentum gained by the fragments decides the capability to perforate a barrier or propagate an explosion. A three-dimensional non-linear FEA method is used to model a box-shaped steel structure. This box-shaped structure is subjected to an internal cased explosion for estimating the initial and striking velocities of primary fragments. The effect of varying charge weight and the effect of the sacrificial wall on the initial and striking velocity of fragments via numerical simulations are also carried out. The initial and striking velocity values obtained through simulation are compared with the design guidelines of the code-based approach, and a good agreement is reported

Fabrication of a Resonant Photoacoustic Cell for Samples Study

Nondestructive treatment of a sample in photoacoustic spectroscopy is helpful in the study of thermal and optical properties of ice and snow. In the present study, a  low-temperature resonant photoacoustic cell, based on Helmholtz resonator model, has been designed and fabricated for the study of samples like ice or snow. Its performance has also been studied using carbon black as a standard sample and various other samples like water, ice, glass, plexi-glass, polycarbonate, etc. Thermal diffusivity of ice, water, and many other transparent materials has been determined by varying chopping frequency and recording corresponding phase changes in the photoacoustic signal. The results obtained are in good agreement with those predicted by Rosencwaig-Gersho (R-G)' theory

Tensile Strength of Snow using Centrifugal Technique

Tensile strength of snow was determined using indigenously developed automated centrifugalmachine. Processed snow (sintered at 20 °C for 4 days) samples of dia: 65 mm andheight:130 mm were tested using this machine.The experiments were conducted on sieved snowat four temperature levels of 0 °C, 3 °C,6 °C and 9 °C at density ranging from 200-460 kg/m3.Results of these experiments have been compared with the earlier  suggested models. Probabilitydistribution of snow strength on the basis of current experimental data has also been presented

Effect of Marma Therapy on Sandhigata Vata w.s.r. to Osteoarthritis

The principal aim of Ayurveda is to maintain and promote positive physical and mental health as well as ensure the prevention of diseases. Sandhigata Vata is the commonest form of articular disorder. It is a type of Vatavyadhi which mainly occurs in Vriddhavastha due to Dhatukshaya, which limits everyday activities such as walking, dressing, bathing etc. It occurs due to change in lifestyle like unsuitable sitting, sleeping, standing and look upwards or obliquely in various professions. Osteoarthritis (OA) is degenerative joint disorder, represents failure of the diarthrodial (movable, synovial lined) joint. OA of the joints comes under the inflammatory group which is almost identical to Sandhigata Vata described in Ayurveda with respect to etiology, pathology, and clinical features. Marma therapy is one which gives instant relief from pain by balancing local Vata and Kapha Dosha without any untoward effects. In the present research work, total 15 diagnosed case of Sandhigata Vata were randomly selected from OPD and IPD of department of Shalya Tantra, Rishikul Campus, Uttarakhand Ayurveda University, Haridwar (U.K.) India, all these patients were treated with the application of Marma therapy. Result was observed on the basis of subjective and objective parameters and analysed statistically. No complications were observed in this clinical study

Magnetization studies on superconducting MgB2_2 - lower and upper critical fields and critical current density

Magnetization studies have been carried out on superconducting MgB$_2$ (T$_c$=37K) in the temperature range of 2-50K and in magnetic field up to 5 Tesla. From these measurements, values of the lower critical field H$_c1$(0), upper critical field H$_c2$(0) at zero K are estimated to be ~300 Oe and ~12.5 Tesla, respectively, which yield a value of ~26 for the Ginzburg-Landau parameter, k. Magnetization hysteresis loops have been obtained at various temperatures from which the magnetization critical current density is estimated using Bean's critical state model.Comment: 7 pages, 6 figures, to be publihed in Solid State Communications (2001) [in press

Crystal Growth and Anisotropic Magnetic Properties of RAg2_2Ge2_2 (R = Pr, Nd and Sm) Single Crystals

We report the single crystal growth and anisotropic magnetic properties of the tetragonal RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) compounds which crystallize in the ThCr$_2$Si$_2$ type crystal structure with the space group \textit{I4/mmm}. The single crystals of RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) were grown by self-flux method using Ag:Ge binary alloy as flux. From the magnetic studies on single crystalline samples we have found that PrAg$_2$Ge$_2$ and NdAg$_2$Ge$_2$ order antiferromagnetically at 12 K and 2 K respectively, thus corroborating the earlier polycrystalline results. SmAg$_2$Ge$_2$ also orders antiferromagnetically at 9.2 K. The magnetic susceptibility and magnetization show a large anisotropy and the easy axis of magnetization for PrAg$_2$Ge$_2$ and NdAg$_2$Ge$_2$ is along the [100] direction where as it changes to [001] direction for SmAg$_2$Ge$_2$. Two metamagnetic transitions were observed in NdAg$_2$Ge$_2$ at $H_{\rm m1}$ = 1.25 T and $H_{\rm m2}$ =3.56 T for the field parallel to [100] direction where as the magnetization along [001] direction was linear indicating the hard axis of magnetization.Comment: 4 pages, 4 figures, submitted to SCES-2008 Proceedings. Submitted to SCES - 2008 Proceeding

Magnetocrystalline anisotropy in RAu_{2}Ge_{2} (R = La, Ce and Pr) single crystals

Anisotropic magnetic properties of single crystalline RAu_{2}Ge_{2} (R = La, Ce and Pr) compounds are reported. LaAu_{2}Ge_{2} exhibit a Pauli-paramagnetic behavior whereas CeAu_{2}Ge_{2} and PrAu_{2}Ge_{2} show an antiferromagnetic ordering with N\grave{e}el temperatures T_{N} = 13.5 and 9 K, respectively. The anisotropic magnetic response of Ce and Pr compounds establishes [001] as the easy axis of magnetization and a sharp spin-flip type metamagnetic transition is observed in the magnetic isotherms. The resistance and magnetoresistance behavior of these compounds, in particular LaAu_{2}Ge_{2}, indicate an anisotropic Fermi surface. The magnetoresistivity of CeAu_{2}Ge_{2} apparently reveals the presence of a residual Kondo interaction. A crystal electric field analysis of the anisotropic susceptibility in conjunction with the experimentally inferred Schottky heat capacity enables us to propose a crystal electric field level scheme for Ce and Pr compounds. For CeAu_{2}Ge_{2} our values are in excellent agreement with the previous reports on neutron diffraction. The heat capacity data in LaAu_{2}Ge_{2} show clearly the existence of Einstein contribution to the heat capacity.Comment: Submitted to PRB 11 Pages 13 Figure

Enhanced Joule Heating in Umbral Dots

We present a study of magnetic profiles of umbral dots (UDs) and its consequences on the Joule heating mechanisms. Hamedivafa (2003) studied Joule heating using vertical component of magnetic field. In this paper UDs magnetic profile has been investigated including the new azimuthal component of magnetic field which might explain the relatively larger enhancement of Joule heating causing more brightness near circumference of UD.Comment: 8 pages, 1 figure, accepted in Solar Physic