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71.
Garg BS Sharma RK Kumar V Reddy MJ Mittal S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(12):2789-2794
Novel complexes of Co(II), Ni(II), Cu(II) and Pd(II) with the new ligand [N,N'-bis(2-carboxy-1-oxo-phenelenyl)ethylenediamine] (H2L) have been synthesized and characterized on the basis of elemental analyses, magnetic susceptibility, thermal, infrared, electronic, 1H NMR and EPR spectral studies. Infrared and 1H NMR spectra show that H2L acts as a binegative tetradentate ligand. Coordination occurs through deprotonated carboxylate oxygens and nondeprotonated amido nitrogens in all the complexes. Electronic spectral studies and magnetic moment values suggest N2O2 coordination around each metal centre with strong field square planar chromophores. The probable structures of the complexes have been assigned on the basis of spectral studies. The complex formation between M(II) [M(II) = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)] and (L2-) has also been studied potentiometrically in 75% aqueous DMF at 25 degrees C in 0.1 M NaClO4. The stability constants were found to follow the order: Mn(II) < Co(II) < Ni(II) < Cu(II) > Zn(II). 相似文献
72.
R. S. Karve A. K. Nayak S. K. Sarlar K. V. S. Rama Rao J. P. Mittal 《Applied physics. B, Lasers and optics》1989,49(6):571-576
Isotope separation of tritium by multiple photon dissociation process in multiple frequency fields of a TEA-CO2 laser is reported for the first time. A ten-fold improvement in the bulk selectivity was obtained in 8.5 Torr CTF3/CHF3 in the presence of buffer gas at room temperature using 9R(8) to 9R(14) CO2 laser lines compared to single frequency excitation. Investigations of various process parameters such as exciting laser frequencies, pulse energy, sample and buffer gas pressure indicate that this is a promising technique for the separation of tritium. 相似文献
73.
A. K. Nayak S. K. Sarkar R. S. Karve V. Parthasarathy K. V. S. Rama Rao J. P. Mittal S. L. N. G. Krishnamachari T. V. Venkitachalam 《Applied physics. B, Lasers and optics》1989,48(5):437-443
Infrared laser multiple photon excitation/dissociation of Thiophene (Th) was studied as a function of Th pressure, laser pulse energy, pulse duration and added buffer gas. While the excitation process was probed via optoacoustic technique, the stable reaction products were analyzed by IR spectroscopy and mass spectrometry. Although C2H2 and CH3CCH were the major hydrocarbon products under all experimental conditions, the distribution of these, as well as higher hydrocarbons of lower yield, was found to be very much dependent upon the experimental conditions. The laser induced reaction under dielectric breakdown conditions with either high substrate pressure or laser energy produced significant amount of CS2 and unidentified polymer as well. We propose a mechanism involving breakage of the C–S bond in Th to form an unstable 1,5-diradical which further decomposed via different channels. However, at higher substrate pressures, radical-Th reactions complicated the overall chemistry of the system. Evidences for collisional energy-pooling and rotational hole-filling were also obtained. 相似文献
74.
75.
V. Parthasarathy S. K. Sarkar K. V. S. Rama Rao J. P. Mittal 《Applied physics. B, Lasers and optics》1986,39(3):187-190
Selective decomposition of CDF3 at natural abundance level (150ppm) in fluoroform has been achieved by infra-red multiple-photon excitation at moderate substrate pressure using 100 ns FWHM CO2 laser pulses. Effects of energy fluence, number of laser pulses, buffer gas pressure and substrate pressure on decomposition yield and bulk selectivity are reported and discussed. 相似文献
76.
A. C. Bhasikuttan A. V. Sapre K. V. S. Rama Rao J. P. Mittal 《Photochemistry and photobiology》1995,62(2):245-250
Abstract— Laser flash photolysis studies were carried out on a triphenylmethane dye, crystal violet (CV+ ), at 248 nm in aqueous solutions. The results show that CV+ undergoes photoionization and the resulting transients CV-2+ , hydrated electrons (e- aq ) and CV+ radical formed by the reaction of e- aq with CV+ have been characterized. Studies using suitable scavengers were done to support the characterization of the transient species. Laser intensity effects show that the ionization is biphotonic. Two mechanisms are proposed to explain the observed photoionization involving higher excited singlet state and/ or another long-lived excited state of the dye. 相似文献
77.
The Lorenz model has been widely used for exploring many real world problems. In this paper we obtain, with the help of an invariant manifold technique, the return map for the maximum value of the variable x of the model and use this return map to derive the simple, empirically obtained, regime transition rules for forecasting regime changes and length in the new regime for the model. The probability distribution for number of cycles between successive regime transitions of the Lorenz model may be of interest in many disciplines. We apply the Perron-Frobenius algorithm over the return map to estimate the probability distribution for the number of cycles between successive regime transitions. These probabilities are also estimated for the forced Lorenz model, which is a conceptual model to explore the effects of sea surface temperature on seasonal rainfall. 相似文献
78.
A new method for shape optimization for unsteady viscous flows is presented. It is based on the continuous adjoint approach using a time accurate method and is capable of handling both inverse and direct objective functions. The objective function is minimized or maximized subject to the satisfaction of flow equations. The shape of the body is parametrized via a Non-Uniform Rational B-Splines (NURBS) curve and is updated by using the gradients obtained from solving the flow and adjoint equations. A finite element method based on streamline-upwind Petrov/Galerkin (SUPG) and pressure stabilized Petrov/Galerkin (PSPG) stabilization techniques is used to solve both the flow and adjoint equations. The method has been implemented and tested for the design of airfoils, based on enhancing its time-averaged aerodynamic coefficients. Interesting shapes are obtained, especially when the objective is to produce high performance airfoils. The effect of the extent of the window of time integration of flow and adjoint equations on the design process is studied. It is found that when the window of time integration is insufficient, the gradients are most likely to be erroneous. 相似文献
79.
Imran Akhtar Rajat Mittal George V. Lauder Elliot Drucker 《Theoretical and Computational Fluid Dynamics》2007,21(3):155-170
Numerical simulations have been used to analyze the effect that vortices, shed from one flapping foil, have on the thrust
of another flapping foil placed directly downstream. The simulations attempt to model the dorsal–tail fin interaction observed
in a swimming bluegill sunfish. The simulations have been carried out using a Cartesian grid method that allows us to simulate
flows with complex moving boundaries on stationary Cartesian grids. The simulations indicate that vortex shedding from the
upstream (dorsal) fin is indeed capable of increasing the thrust of the downstream (tail) fin significantly. Vortex structures
shed by the upstream dorsal fin increase the effective angle-of-attack of the flow seen by the tail fin and initiate the formation
of a strong leading edge stall vortex on the downstream fin. This stall vortex convects down the surface of the tail and the
low pressure associated with this vortex increases the thrust on the downstream tail fin. However, this thrust augmentation
is found to be quite sensitive to the phase relationship between the two flapping fins. The numerical simulations allows us
to examine in detail, the underlying physical mechanism for this thrust augmentation.
相似文献
80.