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71.
To facilitate molecular spectroscopic observation of the mysterious transition of dissolved sodium silicate molecules into
nanoparticles of desired silica gel and zeolite structures, the IR and Raman spectra of Na2H2SiO4 monomers are studied here in details. It is demonstrated that the 3–0.2 mol/L aqueous solutions of Na2SiO3 and Na2SiO3 × 9H2O contain mostly Na2H2SiO4 monomers dissociated about 30%–80%, respectively. In contrast to the common belief the Si–O vibrations of these monomers
depend on their dissociation level generating FTIR and Raman bands which are frequently associated with polymer silica structures
in the current literature. To stay consistent with the molweight and dissociation measurements, these vibrational assignments
are revised in this paper. Some unique and unexpected effects of D2O used instead of H2O as solvent are also reported. 相似文献
72.
N.D. Dahale Meera Keskar R. Agarwal K.D. Singh Mudher 《Journal of Nuclear Materials》2007,362(1):26-35
In the Na-U-Mo-O system, five compounds with composition Na2UMo2O10, Na2U2Mo2O13, Na2U2Mo3O16, Na2UMo4O16 and Na2U2Mo4O19 were prepared by solid state reaction of Na2MoO4, UO3 and MoO3 in the required stoichiometric ratio. The compounds were characterized by X-ray powder diffraction, infrared and thermal analysis techniques. The XRD data of all the above-mentioned compounds were indexed on the orthorhombic system. All the compounds showed thermal stability up to 600 °C in air and decomposed at 950 °C to form Na2U2O7. Infrared spectra of all the compounds show strong spectral bands in the range 700-950 cm−1 due to tetrahedra and the group. A pseudo-ternary phase diagram of Na2O-UO3-MoO3 was drawn using the quaternary compounds and information available on Na-U-O, Mo-U-O and Na-Mo-O ternary systems. The various phase fields prepared during this work were established by XRD analysis. 相似文献
73.
The fracture behavior of glass-cloth-reinforced composites has been studied. Fracture of these composites proceeds by tensile failure of fibers rather than by the shear failure of the matrix or the interface. Although the spread of damage in these composites is restricted to small distances away from the crack path due to the interweaving of the fibers, this distance is found to be appreciably larger for the samples with smaller initial crack lengths. Characteristic distances associated with the Whitney-Nuismer criteria are, in turn, found to be smaller for these composites than for the angle ply laminates or randomly oriented short-fiber composites reported in literature in which the spread of the damage is much greater. Analysis through the crack growth resistance also supports this correlation with the extent of damage spread and indicates that the critical crack length for these composites may be equal to the best fit value of the characteristic distance of the average stress criterion. 相似文献
74.
Abstract We propose an experimental scheme utilizing the different travelling speed of photons at different frequencies to ‘erase’ the time sequential distinguishability of photons emitted from the two steps of an atomic cascade. Interference in joint detection requires not only the overlapping of the same photon in time through different paths, but also the presence of both photons simultaneously. 相似文献
75.
Remote Sensing and GIS Based Approach for Identification of Artificial Recharge Sites 总被引:2,自引:1,他引:1
The main aim of this paper is to demonstrate the capabilities of Remote Sensing (RS) and Geographic Information System (GIS) techniques for the demarcation of suitable sites for artificial recharge of groundwater aquifers, in the Loni watershed, located in Unnao and Raebareli districts, Uttar Pradesh, India. In this study, the SCS-CN model, groundwater depth data and morphological parameters (bifurcation ratio, elongation ratio, drainage density, ruggedness number, relief ratio, and circulatory ratio) have been used to delineate the recharge sites for undertaking water conservation measures. Augmentation of water resource is proposed in the watershed by constructing runoff storage structures, like check dam, percolation tank and nala bund. The site suitability for these water harvesting structures is determined by considering spatially varying parameters, like runoff potential, slope, groundwater fluctuation data and morphometric information of the watershed. GIS has been used as an effective tool to store, analyse and integrate spatial and attribute information pertaining to runoff, slope, drainage, groundwater fluctuation and morphometric characteristics for such studies. 相似文献
76.
The first official shift in communication systems from fixed-location devices to portable/mobile devices happened in 1973 when Martin Cooper, general manager of Motorola's Communications Systems Division at the time, placed the first mobile call from a New York street using AT&T's network. Four years later, the first cell phone was made in Chicago with free trials offered to more than 2,000 people. The first commercial handset to receive FCC approval was Motorola's DynaTAC in 1983 [1], which was made available to the public a year later. This 1.13 kg (2.5 lb) phone that cost consumers US$3,500 was only able to achieve approximately 35 minutes of talk time and took almost 15 years to develop with the cost totaling US$100 million. 相似文献
77.
Agarwal V. Jin Sun Wang J.M. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2009,56(4):295-299
Traditional timing-variation reduction techniques are only able to decrease gate delay variation by incurring a delay overhead. In this brief, we propose a novel and effective splitting-based variation reduction technique for gates. We developed a new tool called Timing Uncertainty Reduction by Gate Splitting (TURGS), which reduces the timing variations of a circuit and presents little delay overhead at the primary output. Our experimental results show that TURGS achieves up to 20% improvement in timing variation for gates. 相似文献
78.
Devendra Vyas Pragya JainGarima Agarwal Ankur JainI.P. Jain 《International Journal of Hydrogen Energy》2012
The effect of Cr as a catalyst in different proportions was investigated to monitor the hydrogen storage properties of Mg2Ni including their thermodynamic aspects. The P–C–T isotherms for absorption/desorption were measured at 225 °C, 250 °C, 275 °C and 300 °C temperatures. A significant increment in the plateau pressures at different temperature was observed, which shows the positive impact of Cr content in the formation of less stable hydrides. The active sites produced by the ball milling may be the reason for the formation of less stable hydrides. Decrements in the storage capacity with the Cr content were attributed to the formation of MgNi2 phase which does not absorb hydrogen at the employed temperature-pressure conditions. XRD and SEM technique were used to identify the structural and morphological changes induced by the hydrogenation cycles. 相似文献
79.
Existing perspiration-based liveness detection algorithms need two successive images (captured in certain time interval),
hence they are slow and not useful for real-time applications. Liveness detection methods using extra hardware increase the
cost of the system. To alleviate these problems, we propose new curvelet-based method which needs only one fingerprint to
detect liveness. Wavelets are very effective in representing objects with isolated point singularities, but fail to represent
line and curve singularities. Curvelet transform allows representing singularities along curves in a more efficient way than
the wavelets. Ridges oriented in different directions in a fingerprint image are curved; hence curvelets are very significant
to characterize fingerprint texture. Textural measures based on curvelet energy and co-occurrence signatures are used to characterize
fingerprint image. Dimensionalities of feature sets are reduced by running Pudil’s sequential forward floating selection (SFFS)
algorithm. Curvelet energy and co-occurrence signatures are independently tested on three different classifiers: AdaBoost.M1,
support vector machine and alternating decision tree. Finally, all the aforementioned classifiers are fused using the “Majority
Voting Rule” to form an ensemble classifier. A fingerprint database consisting of 185 real, 90 Fun-Doh and 150 Gummy fingerprints
is created by using varieties of artificial materials for casts and moulds of spoof fingerprints. Performance of the new liveness
detection approach is found very promising, as it needs only one fingerprint and no extra hardware to detect vitality. 相似文献
80.
Kantesh Balani Flavia C. Brito Lidia Kos Arvind Agarwal 《Journal of the Royal Society Interface》2009,6(40):1097-1102
Pigmentation of murine cardiac tricuspid valve leaflet is associated with melanocyte concentration, which affects its stiffness. Owing to its biological and viscoelastic nature, estimation of the in situ stiffness measurement becomes a challenging task. Therefore, quasi-static and nanodynamic mechanical analysis of the leaflets of the mouse tricuspid valve is performed in the current work. The mechanical properties along the leaflet vary with the degree of pigmentation. Pigmented regions of the valve leaflet that contain melanocytes displayed higher storage modulus (7–10 GPa) than non-pigmented areas (2.5–4 GPa). These results suggest that the presence of melanocytes affects the viscoelastic properties of the mouse atrioventricular valves and are important for their proper functioning in the organism. 相似文献