On the electrical transport in nickel telluride

Journal of Materials Science Letters -     

The effect of internal pressure on a penny-shaped crack at the interface of two bonded dissimilar micropolar elastic half-spaces

In the linear theory of micropolar elasticity, the problem of a penny-shaped crack at the interface of two bonded dissimilar micropolar elastic half spaces is studied. The problem is first reduced to a system of dual integral equations which are further reduced to the solution of Riemann-Hilbert problem. Further stresses at the rims of cracks and in the vicinity have been evaluated.     

A spatial procedure to spectral subtraction for speech enhancement

Multimedia Tools and Applications - The major drawback of the most widely used spectral subtraction (SS) algorithm is, it fails to reduce musical noise. In addition to this in SS, the subtraction...     

Rare-Earth Barium Stannates: Synthesis, Characterization, and Potential Use as Substrates for YBa2Cu3O7-δ Superconductor

A new group of complex perovskites, REBa₂SnO_5.5 (where RE = Pr, Sm, Eu, and Gd) have been synthesized and sintered as single-phase materials with high sintered density and stability by the solid-state reaction method. The structure of REBa₂SnO_5.5 was studied by the X-ray diffraction technique, and all of them were found to be isostructural and have a cubic perovskite structure. The dielectric constant and loss factor values of these materials are in a range suitable for substrate applications. The X-ray diffraction and resistivity measurements have shown that there is no detectable reaction between YBa₂Cu₃O_7-δ and REBa₂SnO_5.5, even when the substances are mixed thoroughly and sintered at 950°C for 15 h. Thick films of YBa₂Cu₃O_7-δ fabricated on polycrystalline REBa₂SnO_5.5 substrates gave superconducting zero resistivity transition T _C(0)= 92 K, indicating the suitability of these new materials as substrates for YBa₂Cu₃O_7-δ films.     

Condition monitoring of electric motor ball bearings for the detection of grease contaminants

Grease used in the ball bearings of electric motors often get contaminated either from external particles or particles generated within these bearings. The effectiveness of vibration, stator current, acoustic emission and shock pulse measurements in detecting the presence of contaminant particles in bearing grease has been investigated. Silica and ferric oxide particles were used to contaminate grease. The levels of vibration, stator current, acoustic emission and shock pulse appreciably increased as contaminant level and contaminant size increased. Acoustic emission peak amplitude proved to be the best condition monitoring technique for the detection of grease contaminants in motor bearings. It is followed by shock pulse maximum value and carpet value in terms of effectiveness.     

Simulation for the prediction of surface roughness in magnetic abrasive flow finishing (MAFF)

The final machining (or finishing) of precision parts with high level of surface finish and close tolerance is making the application of magnetic abrasive finishing technology increasingly important. Magnetic abrasive flow finishing (MAFF) is a new abrasive finishing process combining the features of abrasive flow finishing (AFF) and magnetic abrasive finishing (MAF). MAFF provides a high level of surface finish and close tolerances for wide range of industrial application. This paper focuses on the modeling and simulation for the prediction of surface roughness on the workpiece surface finished by MAFF process. A finite element model is developed to find the magnetic potential distribution in the magnetic abrasive brush formed during finishing action and then it is used to evaluate machining pressure, surface finish and material removal. The simulation results are compared with the experimental results available in the literature. The simulated workpiece surface roughness shows features similar in nature to the experimental results.     

Theoretical Analysis of Thermal Stresses in Electro-discharge Diamond Grinding

Excessive heat generated at the machining zone, during Electro-discharge diamond grinding (EDDG), is the major cause of thermal stresses, untempered martensite, overtempered martensite, and cracks. Therefore, the key to achieve good surface integrity in a machined part is to prevent excessive temperature and thermal stresses generated during machining process. A finite element model has been developed to estimate thermal stresses during EDDG when the current is switched-off. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. Computations were carried out in plane strain condition for different down feeds of the grinding wheel. The effects of time of grinding and feed on thermal stress distribution have been reported. The thermal stresses are found to be higher near top surface at initial time of grinding but shifted away towards bottom after some grinding time.     

Effect of storage period on provitamin-A carotenoids retention in biofortified maize hybrids

Vitamin A-rich maize hybrids provide sustainable solutions to malnutrition. However, significant loss of carotenoids during storage reduces its efficacy. Grains of nine sub-tropically adapted crtRB1-based biofortified hybrids along with six normal hybrids were stored under conventional storage for five months. PVAC (β-carotene and β-cryptoxanthin) among crtRB1-based hybrids degraded from initial level of 18.77 to 3.24 µg g⁻¹, while NPVAC (lutein and zeaxanthin) reduced to 10.79 µg g⁻¹ from 19.00 µg g⁻¹ during storage. Among PVAC, β-cryptoxanthin (21.8%) possessed more stability than β-carotene (16.4%). For NPVAC, lutein (61.2%) showed the highest retention than zeaxanthin (50.4%). Majority of the PVAC loss occurred within first three months of storage. Retention for PVAC among crtRB1-based hybrids varied from 14% to 23% indicating the role of favourable genetic factors. APQH1, APQH7 and APH2 were the promising hybrids with higher retention (>20%) of PVAC. This is the first report on identification of provitamin A-rich crtRB1-based biofortified maize hybrids with higher retention during sub-tropical storage.     

Diamond face grinding of WC-Co composite with spark assistance: Experimental study and parameter optimization

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 μs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.     

Precipitation in CdTe crystals studied through mie scattering

Below gap optical losses in as-grown n-type CdTe crystals were analyzed in terms of free carrier absorption and Mie extinction due to Te precipitates. Experimental absorption spectra measured between 2 to 20 μm exhibited the well-known free carrier absorption behavior α_FCA∼λ^x with x=3 due to scattering by polar optical phonons. In shorter wavelength regions below 6 μm, however, additional contributions to the light loss due to absorption and scattering by precipitates were also observed. Assuming a log-normal size distribution, the precipitate extinction spectra were calculated according to Mie theory within the electric and magnetic dipole and electric quadrupole approximation. A comparison with the experimental spectra identifies the precipitates and enables estimation of their sizes and total number density. In this investigation, both undoped and In-doped CdTe crystals grown from stoichiometric melts by vertical asymmetric Bridgman method were used. It was found that In doping, in general, suppresses Te precipitation. At high doping level (melt containing∼10¹⁹ In atoms cm⁻³), the formation of In₂Te₂ is also indicated. It is demonstrated that the Mie extinction analysis offers an, expedient method to rapidly analyze the precipitates in CdTe and in similar other wide gap materials in a nondestructive manner.