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101.
Anita Saha Madhumangal Pal Tapan K. Pal 《Journal of Mathematical Modelling and Algorithms》2003,2(4):407-409
Volume Contents
Contents of Volume 2 (2003) 相似文献102.
A. Saha A. Ray S. Mukhopadhyay P.K. Datta P.K. Dutta S.M. Saltiel 《Applied physics. B, Lasers and optics》2007,87(3):431-436
An all-solid-state, side diode array pulse pumped Nd:YAG laser tunable for six wavelengths ranging from 1318.8 nm to 1356.0 nm
is developed. The tunability is obtained by using a grating in Littrow mode that also serves as an output coupler. The configuration
ensures a line width as low as 0.04 nm. Thermal effects limit the maximum average power to 250 mW for an average absorbed
pump power of 8.0 W in the free-running condition. An acousto-optic Q-switching of the laser provides pulses of width 251 ns
with peak power of 733 W for an average pump power of 11.5 W. The laser may find application in microsurgery and dermatology.
PACS 42.55.Xi; 42.60.-v; 42.60.Fc; 42.60.Gd; 42.62.Be 相似文献
103.
Paramita Saha Chowdhury 《Journal of luminescence》2007,124(2):327-332
Here, we have examined the role of capping agent on the optical properties of CdS nanoparticles by steady-state and time-resolved photoluminescence (PL) spectroscopy. The estimated particles sizes are 3.45, 2.5 and 2.39 nm for uncapped, capped with silica (SiO2) and thiosalicylic acid (TSA), respectively. The absorption and emission spectra show a clear blue shift to shorter wavelengths in presence of TSA- and SiO2-capped nanoparticles. It is found that the average decay time 〈τ〉 are 6.24, 4.54 and 2.84 ns for uncapped, capped with SiO2 and TSA nanoparticles, respectively. Our analysis suggests that the hole or the electron is trapped on thiol molecule of TSA or hydroxyl group of SiO2, then radiative recombination of the electron and hole is delayed, resulting in strong quenching of PL efficiency. 相似文献
104.
Rana Saha A.K. Bera Y. Sundarayya S.M. Yusuf A. Sundaresan C.N.R Rao 《Journal of solid state chemistry》2011,184(3):494-9532
Magnetic properties of the Al1−xGaxFeO3 family of oxides crystallizing in a non-centrosymmetric space group have been investigated in detail along with structural aspects by employing X-ray and neutron diffraction, Mössbauer spectroscopy and other techniques. The study has revealed the occurrence of several interesting features related to unit cell parameters, site disorder and ionic size. Using first-principles density functional theory based calculations, we have attempted to understand how magnetic ordering and related properties in these oxides depend sensitively on disorder at the cation site. The origin and tendency of cations to disorder and the associated properties are traced to the local structure and ionic sizes. 相似文献
105.
Surajit Saha Surjeet Singh R. Suryanarayanan A.K. Sood 《Journal of solid state chemistry》2011,184(8):2204-2208
Here we report a temperature-dependent Raman study of the pyrochlore “dynamic spin-ice” compound Pr2Sn2O7 and compare the results with its non-pyrochlore (monoclinic) counterpart Pr2Ti2O7. In addition to phonon modes, we observe two bands associated with electronic Raman scattering involving crystal field transitions in Pr2Sn2O7 at ∼135 and 460 cm−1 which couple strongly to phonons. Anomalous temperature dependence of phonon frequencies that are observed in pyrochlore Pr2Sn2O7 are absent in monoclinic Pr2Ti2O7. This, therefore, confirms that the strong phonon-phonon anharmonic interactions, responsible for the temperature-dependent anomalous behavior of phonons, arise due to the inherent vacant sites in the pyrochlore structure. 相似文献
106.
Rupankar PairaArindam Maity Shyamal MondalSubhendu Naskar Krishnendu B. SahuPritam Saha Abhijit HazraE. Padmanaban Sukdeb BanerjeeNirup B. Mondal 《Tetrahedron letters》2011,52(14):1653-1657
Basic alumina supported solvent-free one-pot synthesis of pyridine-fused polycyclic diazepaniums was achieved under microwave irradiation. The process was successfully extended to the synthesis of pyridine-fused bicyclic imidazolidiniums and tetrahydro-pyrimidiniums and also of tri- and tetracyclic diaza-heterocycle-fused quinoliniums. The dual characteristic of basic alumina, a solid support as well as a base, was successfully employed in the current investigation. The method emerged to be an effective route in terms of product yield, reaction time, and ease of purification and most importantly for environment friendly protocols. 相似文献
107.
A generalized single‐particle model for the prediction of combustion dynamics of a porous coal char in a fluidized bed is analyzed in the present work using a volume reaction model (VRM). A fully transient nonisothermal model involving both heterogeneous and homogeneous chemical reactions, multicomponent mass transfer, heat transfer with intraparticle resistances, as well as char structure evolution is developed. The model takes into account convection and diffusion inside the particle pores, as well as in the boundary layer. By addressing the Stefan flow originated due to nonequimolar mass transfer and chemical reactions, this work enables a more realistic analysis of the combustion process. The model, characterized by a set of partial differential equations coupled with nonlinear boundary conditions, is solved numerically using the implicit finite volume method (FVM) with a FORTRAN code developed in‐house. The use of a FVM for solving such an elaborate char combustion model, based on the VRM, was not reported earlier. Experiments consisting of fluidized‐bed combustion of a single char particle were carried out to determine the internal surface area of a partially burned char particle and to enable model validation. Predicted results are found to compare well with the reported experimental results for porous coal char combustion. The effects of various parameters (i.e., bulk temperature and initial particle radius) are examined on the dynamics of combustion of coal char. The phenomena of ignition and extinction are also investigated. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 299–315, 2010 相似文献
108.
Separation of lignosulfonate from its aqueous solution using supported liquid membrane 总被引:2,自引:1,他引:1
Kabita Chakrabarty Prabirkumar Saha Aloke Kumar Ghoshal 《Journal of membrane science》2009,340(1-2):84-91
This paper presents an experimental and theoretical study on facilitated transport of lignosulfonate (LS) through a flat sheet supported liquid membrane using trioctylamine (TOA) as carrier and dichloroethane as diluent. The studies were carried out with various support materials and operating conditions (viz. carrier concentration, strip phase concentration, salt concentration, etc.) and their effects on the transport of LS. The results were analyzed to identify a suitable combination of support and operating condition that would yield best performance of the supported liquid membrane (SLM) in terms of fast and efficient transport of LS. The stability of the SLM was assessed in terms of loss of liquid from the pores of membrane support. The SLM is found to be stable till 10 h. Co-transport mechanism has been adopted in this work by using NaOH as the strip phase. It was observed that extraction of LS is increased with increase in concentration of NaOH up to a limiting value of 0.5 M NaOH. Difference of salt concentration between feed and strip phase considerably affect the separation process. The diffusional resistances of organic membrane (Δorg) and aqueous solution (Δaq) calculated from the permeation model, which is again a combination of three unique mechanisms viz., diffusion through a feed aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier–complex through the organic membrane, are found to be 609.9 and 176.6 s cm−1, respectively. The values of the diffusion coefficient in the membrane (Dorg) and in the bulk organic phase (Dcomplex) are 1.67×10−9 and 6.68 × 10−8 m2s−1, respectively. The extraction of LS is about 90%. Nearly 43% of LS can be recovered at optimum condition. 相似文献
109.
Sumit Saha 《Tetrahedron letters》2008,49(41):5928-5930
A mild and efficient method for the preparation of acetonides from epoxides catalyzed by iron(III) chlorides has been developed. 相似文献
110.
Tapan Saha Charugopal Chakrabarti 《Journal of Mathematical Analysis and Applications》2009,358(2):389-1233
In this paper, a delayed Holling-Tanner predator-prey model with ratio-dependent functional response is considered. It is proved that the model system is permanent under certain conditions. The local asymptotic stability and the Hopf-bifurcation results are discussed. Qualitative behaviour of the singularity (0,0) is explored by using a blow up transformation. Global asymptotic stability analysis of the positive equilibrium is carried out. Numerical simulations are presented for the support of our analytical findings. 相似文献