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81.
Byron P. Brassel Sunil D. Maharaj Rituparno Goswami 《General Relativity and Gravitation》2017,49(8):101
We establish the result that the standard Boulware–Deser spacetime can radiate. This allows us to model the dynamics of a spherically symmetric radiating dynamical star in five-dimensional Einstein–Gauss–Bonnet gravity with three spacetime regions. The local internal region is a two-component system consisting of standard pressure-free, null radiation and an additional string fluid with energy density and nonzero pressure obeying all physically realistic energy conditions. The middle region is purely radiative which matches to a third region which is the vacuum Boulware–Deser exterior. Our approach allows for all three spacetime regions to be modeled by the same class of metric functions. A large family of solutions to the field equations are presented for various realistic equations of state. A comparison of our solutions with earlier well known results is undertaken and we show that Einstein–Gauss–Bonnet analogues of these solutions, including those of Husain, are contained in our family. We also generalise our results to higher dimensions. 相似文献
82.
P. Majee G. Goswami M. K. Sen B. C. Bag 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(3):435-439
In this paper we have studied the directed motion of a Brownian particle
in a multiplicative noise
driven flashing ratchet system. Our investigation shows
the current (j) is either maximum or minimum
in the super-diffusion (SPD) region depending on the asymmetric character of the ratchet potential.
But the optimum behavior disappears for the symmetric
ratchet potential and there is a current inversion around the normal diffusion (ND). With increase of
half cycle period(tp/2) (which controls the on-off operation
mechanism of the potential), j
passes through a maximum and the peak height is the highest for the SPD. Also
at low asymmetry in the system, the mobility is more dominating for
the normal and the super-diffusion cases than the sub-diffusion.
For large asymmetry in the ratchet potential,
the diffusion control positive current
is larger for the ND compared to the other cases.
Finally, we observe that there is a maximum in the variation of current as a function of noise correlation time for
SPD. But it disappears for the other cases. 相似文献
83.
This presentation reports some novel examples of organic ring amination reactions via metal mediation. The organic transformations
are highly regioselective and can be controlled by the proper selection of the mediator complex. The two isomeric organic
ligands viz. HL1 and HL2 were isolated in their pure states by the removal of the metal ions. These were fully characterized. The ligand HL1 has lowpKa, 8.5. Upon deprotonation, it behaves as a potentialbis chelating N,N,N-donors. The coordination chemistry of the HL1 ligand involving some 3d-metal ions is described. Two unusual low-spin complexes of manganese(II) and iron(III) are reported. The ferric complex displayed a rhombic EPR while, the corresponding manganese compound showed a complex pattern
due to hyperfine coupling. All the complexes displayed large number of redox responses. A brief mention about the future projection
of this work is noted. 相似文献
84.
Watekar P.R. Goswami M.L.N. Biswas J.C. Acharya H.N. 《Optical and Quantum Electronics》2004,36(5):405-411
The Er-doped double-core dispersion compensating fiber (EDDCF) has been fabricated using modified chemical vapor deposition
(MCVD) technique. We have obtained 14 dB gain at 1550 nm (using a diode laser of 980 nm wavelength which provides 100 mW of
pump power) with dispersion of about −165 ps/km nm. It is useful for the optical fiber network where amplification as well
as negative dispersion is necessary. We are the first to report the experimental realization and characterization of the EDDCF. 相似文献
85.
Goswami J.C. Hoefel A.E. Schwetlick H. 《Geoscience and Remote Sensing, IEEE Transactions on》2005,43(10):2332-2339
Measurement, evaluation, and monitoring of subsurface objects often require wireless data transmission between an embedded sensor and an exterior host system. Such technologies find applications in many areas-medical imaging, space exploration, earth formation evaluation in oilfield industries, for example. This paper describes a complete wireless data acquisition system that includes design of a transceiver unit, as well as communication protocols for data encoding and decoding. Although the application considered in this paper pertains to the oilfield industry, the method is applicable to other areas as well. The transceiver design is highly constrained due to requirements on physical size, mechanical stability, and low-power consumption. The host antenna generally consists of ferrite-backed coils wound on a metallic cylinder. A critical requirement in the design of these coils is to produce a desired spatial variation of the magnetic field in a specified region. A genetic algorithm is used to optimize the location and excitation of each coil. A combination of finite-element method and superposition principle is used to speed up the solution of forward problem. The data measured by an embedded sensor are encoded with seven-bit cyclic redundancy code concatenated with Manchester code for error detection/correction and bit synchronization. Coded data are finally transmitted by binary frequency-shift keying modulation scheme. Numerical and experimental results for magnetic field, signal-to-noise ratio, and data demodulation are presented. 相似文献
86.
Summary. The objective of this paper is to introduce a fast algorithm for computing the integral wavelet transform (IWT) on a dense
set of points in the time-scale domain. By applying the duality principle and using a compactly supported spline-wavelet as
the analyzing wavelet, this fast integral wavelet transform (FIWT) is realized by applying only FIR (moving average) operations,
and can be implemented in parallel. Since this computational procedure is based on a local optimal-order spline interpolation
scheme and the FIR filters are exact, the IWT values so obtained are guaranteed to have zero moments up to the order of the
cardinal spline functions. The semi-orthogonal (s.o.) spline-wavelets used here cannot be replaced by any other biorthogonal
wavelet (spline or otherwise) which is not s.o., since the duality principle must be applied to some subspace of the multiresolution
analysis under consideration. In contrast with the existing procedures based on direct numerical integration or an FFT-based
multi-voice per octave scheme, the computational complexity of our FIWT algorithm does not increase with the increasing number
of values of the scale parameter.
Received March 3, 1994 相似文献
87.
The problem of the diffraction of surface waves, obliquely incident on a partially immersed fixed vertical barrier in deep water, is solved approximately by reducing it to the solution of an integral equation, for small angle of incidence of the incident wave. The corrections to the reflection and transmission coefficients over their normal incidence values for small angle of incidence are obtained and presented graphically for some intermediate values of wave numbers. 相似文献
88.
Joshi P Ethirajan M Goswami LN Srivatsan A Missert JR Pandey RK 《The Journal of organic chemistry》2011,76(21):8629-8640
In this report, we present a regioselective oxidation of a series bacteriochlorins, which on reacting with either ferric chloride (FeCl(3)) or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) yielded the corresponding ring-B or ring-D reduced chlorins. The effect of the number of electron-withdrawing groups present at the peripheral position, with or without a fused isocyclic ring (ring-E), did not make any significant difference in regioselective oxidation of the pyrrole rings. However, depending on the nature of substituents, the intermediate bis-dihydroxy bacteriochlorins on subjecting to pinacol-pinacolone reaction conditions gave various ketochlorins. The introduction of the keto-group at a particular position in the molecule possibly depends on the stability of the intermediate carbocation species. The newly synthesized bacteriochlorins show strong long-wavelength absorption and produced significant in vitro (Colon26 cells) photosensitizing ability. Among the compounds tested, the bacteriochlorins containing a keto-group at position 7 of ring-B with cleaved five-member isocyclic ring showed the best efficacy. 相似文献
89.
Bhattacharjee CR Goswami P Pramanik HA Paul PC Mondal P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(5):1408-1415
Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)~5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level. 相似文献
90.
Rotational spectra of five isotopologues of the title complex, C(6)H(5)CCH···H(2)O, C(6)H(5)CCH···HOD, C(6)H(5)CCH···D(2)O, C(6)H(5)CCH···H(2)(18)O and C(6)H(5)CCD···H(2)O, were measured and analyzed. The parent isotopologue is an asymmetric top with κ = -0.73. The complex is effectively planar (ab inertial plane) and both 'a' and 'b' dipole transitions have been observed but no c dipole transition could be seen. All the transitions of the parent complex are split into two resulting from an internal motion interchanging the two H atoms in H(2)O. This is confirmed by the absence of such doubling for the C(6)H(5)CCH···HOD complex and a significant reduction in the splitting for the D(2)O analog. The rotational spectra, unambiguously, reveal a structure in which H(2)O has both O-H···π (π cloud of acetylene moiety) and C-H···O (ortho C-H group of phenylacetylene) interactions. This is in agreement with the structure deduced by IR-UV double resonance studies (Singh et al., J. Phys. Chem. A, 2008, 112, 3360) and also with the global minimum predicted by advanced electronic structure theory calculations (Sedlack et al., J. Phys. Chem. A, 2009, 113, 6620). Atoms in Molecule (AIM) theoretical analysis of the complex reveals the presence of both O-H···π and C-H···O hydrogen bonds. More interestingly, based on the electron densities at the bond critical points, this analysis suggests that both these interactions are equally strong. Moreover, the presence of both these interactions leads to significant deviation from linearity of both hydrogen bonds. 相似文献