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101.
Computer simulations have shown a novel geodesic splitting on the paraboloid of revolution leading to a multiplicity of surface ray paths. Such a phenomenon would have wide ramifications for wave propagation problems in general, besides applications in target-detection problems and the computational requirements of ray-theoretic formulations such as the UTD, in computing the antenna characteristics in the high-frequency domain.<> 相似文献
102.
We describe a Java implementation of a policy based bandwidth management system using the standard policy protocols and an interface to the Linux Diffserv implementation. The useful features, such as extensibility and object orientation, of the Java implementation is illustrated by directly referring to the relevant programming codes. Through two practical experiments, we demonstrate the capability of our implementation in supporting policy‐based dynamic resource allocations in enterprise networks. Copyright © 2003 John Wiley &Sons, Ltd. 相似文献
103.
Srinivasan Srikanth Ajay Kumar Ray Amitava Bandopadhyay Bandari Ravikumar Animesh Jha 《Journal of the American Ceramic Society》2005,88(9):2396-2401
The phase constitution during the sintering of pure red mud and red mud–fly ash mixtures was studied in the temperature range of 900°–1250°C. The phases formed at different sintering temperatures were analyzed by X-ray powder diffraction. The phases that are likely to form at equilibrium at any isotherm were predicted using the Gibbs free energy minimization technique and the databases provided in the FactSage software. Although the thermodynamic prediction is in reasonable agreement with the experimental results for the major phases, there is some disagreement regarding the minor phases, especially the more complex phases. The major limitation of the thermodynamic approach presently is the non-availability of thermodynamic data for several complex and multi-component solution phases. 相似文献
104.
A higher-order shear and normal deformations plate theory is employed for stress analysis and free vibration of functionally graded (FG) elastic, rectangular, and simply (diaphragm) supported plates. Although functionally graded materials (FGMs) are highly heterogeneous in nature, they are generally idealized as continua with their mechanical properties changing smoothly with respect to the spatial coordinates. This idealization is required in order to obtain the closed-form solutions of some fundamental solid mechanics problems and also simplify the evaluation and development of numerical models of the structures made of FGMs. The material properties of FG plates such as Young’s moduli and material density are considered in this case to vary continuously in the thickness direction according to the volume fraction of constituents and mathematically modeled as exponential and power law functions. Poisson’s ratio is assumed to be constant. The effect of variation of material properties in terms of material grading index on the deformations, stresses, and natural frequency of FG plates is studied. The accuracy of the presented numerical solutions has been established with the solutions available of other models and the exact three-dimensional (3D) elasticity solutions. 相似文献
105.
F. Litimein R. Khenata Sanjeev K. Gupta G. Murtaza Ali. H. Reshak A. Bouhemadou S. Bin Omran Masood Yousaf Prafulla K. Jha 《Journal of Materials Science》2014,49(22):7809-7818
We performed ab initio calculations using the FPLAW method with the local density approximation (LDA) implemented in the WIEN2 k code for the orthorhombic (α) and triclinic (β) phases of BiNbO4. The modified Becke–Johnson exchange potential (mBJ)-LDA approach was also used to improve the electronic properties. The lattice constants calculated for both structures using the LDA are in good agreement with the experimental values. For the band structure calculations, the mBJ-LDA approach provides reasonable agreement for the band gap value compared with the LDA. The estimated (mBJ)-LDA band gap values are 2.89 eV (3.73 eV) and 2.62 eV (3.15 eV) for the α and β phases of BiNbO4, respectively. Significant optical anisotropy is clearly observed in the visible-light region. We also calculated and evaluated the electron energy loss spectrum for BiNbO4. This work provides the first quantitative theoretical prediction of optical properties and electron energy loss spectra for both the orthorhombic and triclinic phases of BiNbO4. 相似文献
106.
Priyanka A. Jha A. K. Jha 《Journal of Materials Science: Materials in Electronics》2014,25(2):797-804
Nano-structuring of various ferroic materials has tailored the existing properties in their bulk counterpart. Keeping this fact in view, nano-crystalline barium zirconate titanate (BaZr0.05Ti0.95O3) ferroelectric ceramics were prepared by mechanical activation process using high-energy planetary ball milling followed by the sintering process. In the present work, effect of milling duration (15, 30 and 45 h) on structural and microstructural properties has been observed with the help of X-ray diffraction, scanning electron microscopy and transmission electron microscopy (for optimized milling duration). The crystallite size of the milled specimen decreases to 14.17 nm on increasing the milling duration from 15 to 45 h. A comparison with its bulk counterpart showed significant enhancement in di-, ferro-, piezo- and pyro-electric properties with strong blue emission in UV light (265 nm). The blue emission in UV light makes it a potential candidate for LEDs and optical devices. 相似文献
107.
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
108.
Studies were carried out to assess the effects of stabilized (i.e., coated with organic polyacrylic stabilizer) and nonstabilized forms of zero-valent nanoiron (nZVI) on the development of Mytilus galloprovincialis embryos following 2 h exposure of the sperm prior to in vitro fertilization. Both forms of nZVI caused serious disruption of development, consisting of 30% mortality among spermatozoa with subsequent 20% decline in fertilization success, and delay in development, i.e., over 50% of the larvae were suspended in the trochophore stage. Significant DNA damage was also detected in sperm exposed to the highest exposure concentrations (10 mg L(-1)). Distinct dose response to the two different types of nZVI observed are linked to aggregation behavior that is controlled by the surface stabilizers. This work reports on conventional biomarkers (for membrane integrity, genotoxicity, and developmental toxicity) applied for the rapid assessment of toxicity of nZVI, which are able to detect surface property-related effects to meet the requirements of risk assessments for nanotechnology. The study highlights the potential ecotoxicological impact of an environmentally relevant engineered nanoparticle. Implications of the NOM-nZVI interactions regarding soil and groundwater remediation and wastewater treatment are discussed. 相似文献
109.
A simple chemical route for the synthesis of PbS nanoparticle coated amorphous carbon nanotubes (aCNTs) was described. The nanocomposite was prepared from an aqueous suspension of acid functionalized aCNTs, lead acetate (PbAc), and thiourea (TU) at room temperature. The phase formation and composition of the samples were characterized by X-ray diffraction and energy dispersive analysis of X-ray studies. The Fourier transformed infrared spectra analysis revealed the attachment of PbS nanoparticles on the acid functionalized aCNT surfaces. Morphology of the samples was analyzed with a field emission scanning electron microscope. UV-Vis study also confirmed the attachment of PbS nanoparticles on the walls of aCNTs. Thermal gravimetric analysis showed that the PbS coated aCNTs are more thermally stable than functionalized aCNTs. The PbS coated aCNTs showed enhanced field emission properties with a turn-on field 3.34 V μm−1 and the result is comparable to that of pure crystalline CNTs. 相似文献
110.
D. Munoz-MartinJ.M. Fernandez-Navarro J. Gonzalo G. JoseA. Jha J.L.G. FierroC. Domingo J. Garcia-Lopez 《Thin solid films》2011,520(1):131-137
Tellurite (TeO2-TiO2-Nb2O5) thin film glasses have been produced by pulsed laser deposition at room temperature at laser energy densities in the range of 0.8-1.5 J/cm2 and oxygen pressures in the range of 3-11 Pa. The oxygen concentration in the films increases with laser energy density to reach values very close to that of the bulk glass at 1.5 J/cm2, while films prepared at 1.5 J/cm2 and pressures above 5 Pa show oxygen concentration in excess of 10% comparing to the glass. X-ray photoelectron spectroscopy shows the presence of elementary Te in films deposited at O2 pressures ≤ 5 Pa that is not detected at higher pressures, while analysis of Raman spectra of the samples suggests a progressive substitution of TeO3 trigonal pyramids by TeO4 trigonal bipyramids in the films when increasing their oxygen content. Spectroscopic ellipsometry analysis combined with Cauchy and effective medium modeling demonstrates the influence of these compositional and structural modifications on the optical response of the films. Since the oxygen content determines their optical response through the structural modifications induced in the films, those can be effectively controlled by tuning the deposition conditions, and films having large n (2.08) and reduced k (< 10− 4) at 1.5 μm have been produced using the optimum deposition conditions. 相似文献