• Arvind Kumar

      Articles written in Sadhana

    • InGaAsp-i-n photodiodes for fibre-optic communication

      D N Bose Arvind Kumar

      More Details Abstract Fulltext PDF

      High purity layers of In1 −xGaxAs have been grown by liquid phase epitaxy using a novel impurity gettering technique with rare earth atoms. The electron concentration could thus be decreased from 3 × 1018 cm−3 to 2·4 × 1015 cm−3 and the mobility increased from 7 110 cm2/Vs to 18,981 cm2/Vs (100 K). The excellent quality of the layers has been evidenced by X-ray diffraction and photoluminescence measurements. The fabrication ofp-i-n photodiodes using this technique is described and reliability aspects addressed.

    • Design, simulation, fabrication and testing of LIM for EML


      More Details Abstract Fulltext PDF

      Electromagnetic Launchers (EML) are being developed to accelerate various projectiles to high velocities. Technologically matured EMLs may find wide use in defence applications like aircraft launching from naval ships and in industry for rock pulverizing in mines. As part of a sanctioned project in IPR, a LinearInduction Motor (LIM) which can produce a maximum thrust and velocities of ~180 N and ~7.5 m/s respectively at ~35 A input rms current is developed. After obtaining the simulation results, a LIM has been fabricated from local industry, tested and results are compared to benchmark the design of the LIM. This paperdescribes a LIM based EML design, simulation, fabrication, testing and comparison of simulation and experimental results.

    • Experimental and numerical analysis of constitutive characteristics in bituminous coal


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      Characterization of bituminous coal is carried out to evaluate the behaviour of coal when it is subjected to different loading or stress conditions such as tensile stress, shear stress and normal stress. Index properties such as microstructure of geomaterial, density, porosity, specific gravity, water absorption, colour andformation that form a set of intrinsic properties have been evaluated and used to classify the bituminous coal. Mechanical properties have been evaluated based on strength characteristics such as quasi-static uniaxial compressive strength, shear strength, and tensile strength and other derived parameters such as normal stress, shear stress, deformation, elastic modulus, shear modulus, maximum stretching hydrostatic pressure, normalized cohesive strength, internal angle of friction, normalized pressure hardening coefficient, pressure hardeningindex, strain rate coefficient, maximum normalized intensity and damage parameters. Numerous material characterisation tests have been performed on bituminous coal to determine the above-mentioned parameters such as triaxial shear tests, large direct shear tests, uniaxial compression tests, split tensile strength tests, water absorption tests, porosity test and X-ray diffraction. Numerical methods have proven to be an important tool in the design and evaluation of safety in mines without involving cumbersome experimental analysis procedures. Finite element-based Software Abaqus has been employed using Holmquist Johnson and Cook model to validate and characterize the constitutive characteristics of bituminous coal. Numerical results of different strength aspects obtained through the study have been found in good agreement with the experimental results having an overall variation in results of less than 15%.

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