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41.
42.
Alok Kumar Rai N. K. Singh Sang-Kwon Lee K. D. Mandal D. Kumar Om Parkash 《Journal of Materials Science: Materials in Electronics》2011,22(9):1286-1289
Dielectric properties of iron doped CaCu3Ti4O12 (CCTO), viz. CaCu3Ti3.9Fe0.1O12 (CCTFO) prepared by a novel semi-wet route have been investigated. X-ray diffraction of powder sintered at 900 °C show formation
of single phase solid solution. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of CuO rich phase at grain
boundaries of CCTFO. Nature of dielectric relaxation observed above room temperature is studied using complex plane impedance
analysis and modulus spectroscopy. It has been found that out of the two relaxations reported earlier above room temperature,
one occurring at lower temperature is due to grainboundaries interfacial polarization. 相似文献
43.
Hidetoshi Somekawa Tadanobu Inoue Alok Singh Toshiji Mukai 《Metallurgical and Materials Transactions A》2011,42(8):2475-2480
The deformation mechanism in the crack-tip region of a fine-grained Mg-2.4 at. pct Zn binary alloy was investigated by focused
ion beam (FIB) and transmission electron microscopy (TEM) observation and finite element analysis (FEA) at the beginning of
the fracture toughness test. The deformed microstructure observations showed the formation of subgrains instead of deformation
twins in the fracture toughness tested sample, which was performed at a conventional crosshead speed of 1 mm/min. By preventing
the formation of deformation twins at the beginning of the test, the crack tip of the fine-grained magnesium alloys became
blunted, and thus, the alloys obtained high fracture toughness. Finite element results showed that the temperature increased
50 to 110 K, and the strain rate became two orders of magnitude higher; however, this temperature increment was not sufficient
to form high-angle grain boundaries, i.e., a complete occurrence of dynamic recrystallization. On the other hand, the deformed microstructure observations in the sample,
which was tested at a crosshead speed of 50 mm/min, showed the formation of nano-order {10-12} deformation twins and subgrains.
The formation of deformation twins was caused, in part, by the severe strain from the operation of a high strain rate in the
crack-tip region. 相似文献
44.
Alok Gupta Boris Jukic Mingzhi Li Dale O. Stahl Andrew B. Whinston 《Computational Economics》2001,17(2-3):203-218
We investigate two parametric approaches and one non-parametric approach toestimating Internet users' value-of-time, an important characteristic ofdemand for Internet services. The advantages of these approaches are madeclear and their limitations discussed. The models are tested with datagenerated from our similation model of the Internet economy. Given thecharacteristics of the data, we investigate parametric count-data modelsfirst. While reasonably good results are obtained on all medium- andlarge-sized jobs, the method fails on small-sized ones. Second, we develop anonparametric quasi-Bayesian update algorithm for retrieving the underlyingdistribution function of Internet users' value-of-time purely fromobservations on their choices. Compared with the parametric count-data models,good results are obtained in every case. 相似文献
45.
Alok Choudhury 《真空研究与实践》1990,2(2):114-120
The growing demands for better quality of metallic materials can only be met by the application of vacuum during the production of these metals and alloys and their field of application. 相似文献
46.
47.
Influence of Interfacial LSMO Nanoparticles/Layer on the Vortex Pinning Properties of YBCO Thin Film
Alok K. Jha Neeraj Khare R. Pinto 《Journal of Superconductivity and Novel Magnetism》2014,27(4):1021-1026
YBa2Cu3O7?δ (YBCO) thin films have been deposited on bare and La0.67Sr0.33MnO3 (LSMO) modified single crystal SrTiO3 (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field. 相似文献
48.
Sorption and extractability of naphthol and naphthol polymerization products (NPP) were evaluated in two surface soils. NPP were generated by the addition of horseradish peroxidase and H2O2 to naphthol solutions in contact with the surface soils. While NPP retention on the forest soil was lower compared to the parent naphthol, no difference in sorption of naphthol and NPP was observed in the agricultural soil. The agricultural soil retained more naphthol and NPP than the forest soil. The NPP sorption behavior noted in this study was in contrast to that of phenol polymerization products observed by other researchers. The presence of phenol and 2,4-dichlorophenol as cosolutes had no significant impact on naphthol or NPP retention on the two soils, and naphthol was more easily extracted from both soils whenever phenol was present as a cosolute. Characterization of the naphthol polymerization products using reverse-phase high-pressure liquid chromatography and octanol-water partitioning indicated that significant fractions of the water-soluble and insoluble NPP were comprised of oligomers that were more polar than the parent 1-naphthol. This decrease in polarity upon polymerization is believed to have been responsible for the NPP retention and binding behavior observed in this study. 相似文献
49.
In this paper, we report the reactive ion etching (RIE) of trenches in 6H-silicon carbide using SF6/O2. The plasma parameters: etchant composition, gas flow rate, chamber pressure, and radio frequency power were optimized to obtain a maximum etch rate of 360Å/min. The etch rate of SiC was found to exhibit a direct correlation with the dc self bias except when the O2 percentage was varied. Trenches were fabricated using the optimized conditions. It was found that the trench surface was extremely rough due to the aluminum micromasking effect. To overcome this effect, a TeflonTM sheet was used to cover the cathode during the experiment. The trenches fabricated using this modification were found to have smooth etched surfaces and sidewalls. The angle of anisotropy of these trenches was approximately 80° which is suitable for device applications. 相似文献
50.
K AnanthasivanS Anthonysamy Alok SinghP.R Vasudeva Rao 《Journal of Nuclear Materials》2002,306(1):1-9
Thorium oxalate was obtained by precipitation in water and in non-aqueous solvents and de-agglomerated by ultrasonication in both aqueous as well as non-aqueous media. Sinteractive thoria (crystallite size 6-20 nm) obtained from the de-agglomerated thorium oxalate was characterised for residual carbon, crystallite size, specific surface area, particle size distribution and bulk density. Microstructure of the precursor and the product was studied using TEM and HRTEM. The morphology of the sintered pellets was studied using SEM. The reactivity of the calcined powders was determined by measuring the density of the sintered compacts. The solvent used for de-agglomeration was found to have significant influence on the microstructure of the powders. Thoria derived through aqueous precipitation route could be sintered to a density of 9.7 Mg m−3 at 1673 K. It was demonstrated that ultrasonic de-agglomeration could be a useful method for obtaining sinteractive thoria. 相似文献