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661.
Pramod?R.?WatekarEmail author M.?L.?N.?Goswami J.?C.?Biswas H.?N.?Acharya B.?P.?Pal 《Optical and Quantum Electronics》2005,37(4):377-390
Erbium-doped dispersion-compensating optical fiber (EDCF) has been theoretically simulated and experimentally fabricated using Modified Chemical Vapor Deposition (MCVD) for optimum operation at 5.0km. It is optimized for both gain as well as negative dispersion. The erbium has been doped into the cladding region while the core of the optical fiber is chosen to be narrow so as to have a high negative dispersion. Measured gain of 3.1 dB at 200 m using 100 mW pumping power (980 nm wavelength) at 1550 nm has been obtained and the gain of 32 dB at 5.0 km using same pumping scheme has been predicted. The chromatic dispersion of this EDCF has been also measured to be –43.5 ps/km-nm at 1550 nm and thus, providing the dispersion of –217.5 ps/nm at 5 km. The bend-induced losses are found to be negligible. We are the first to report the experimental realization of EDCF. 相似文献
662.
A Goswami B K Srivastava Alok Srivastava S B Manohar Satya Prakash M V Ramaniah 《Pramana》1986,26(3):179-189
Fractional independent yields of fission products in the thermal neutron-induced fission of233U,235U,239Pu,241Pu and in the spontaneous fission of252Cf have been correlated with the neutron-to-proton ratio of the fission products. The yields of the products from a fissioning
system, when plotted as a function of neutron-to-proton (N/Z) ratio of fission preducts, fall on two Gaussian distribution corresponding to light and heavy fission products. The centroids
of the distribution or the most probable value of neutron-to-proton ratio is found to be very close to theN/Z of the fissioning nucleus. From the most probable value ofN/Z the various parameters of charge distribution e.g. most probable massA
p, most probable chargeZ
p, the mass dispersionσ
Aand the charge dispersionσ
Zhave been obtained and are in good agreement with the experimental values ofA
pandZ
p. 相似文献
663.
The current-voltage characteristics of a quasi one-dimensional organic system having asymmetric donor molecule like Qn-(TCNQ)2 pellet with stoichiometry 1:2 grown from acetonitrile as a solvent have been studied atT=69 K. The characteristic curves show a pronounced deviation from ohmicity beyond a certain value of current. For higher values
of currents a negative differential resistance region is observed. 相似文献
664.
Two categories of model have been developed to describe the mass transfer process in emulsion liquid membrane extraction of phenols/amines from waste water. In the first the reaction between the transferred solutes and the trapping agent in the internal phase is assumed to be irreversible while in the second a reversible reaction is involved. Generally the various authors have tested the proposed models against their own experimental data. The present study is an attempt to investigate the efficacy of the reversible reaction model of Bunge and Noble, which is simpler to use and requires input of less parameters to predict the experimental data reported by different authors. It is shown that by introducing a shape factor into the model for the effective diffusivity of solute within the macrodrop, it is possible to use this model to simulate experimental data of other groups reasonably well. 相似文献
665.
The quantum confined Stark effect causes a strong wavelength and voltage dependence of photocurrent near excitonic resonances which is used to study the wavelength selectivity of p-i(MQW)-n photodiode. For a parallel input of optical bits each coming at a different wavelength, the selectivity is considered good if the state of a λi wavelength bit can be detected regardless of the λj (j ≠ i) state of the bits. Photocurrent is found to have very good selectivity if λj bits are all zero, i.e. the optical information is serial. However, we find that differential photocurrent (Δ Iph/ΔV) provides a good selectivity for random states of λj bits (i.e. parallel input). Four channel selectivity is demonstrated at 200K. Specially designed quantum well structures can greatly improve this selectivity. 相似文献
666.
667.
The return current induced in a plasma by a relativisitc electron beam generates a new electron-ion two-stream instability
(return current instability). Although the effect of these currents on the beam-plasma e-e instability is negligible, there
exists a range of wave numbers which is unstable only to return current (RC) instability and not to e-e instability. The electromagnetic
waves propagating along the direction of the external magnetic field, in which the plasma is immersed, are stabilized by these
currents but the e.m. waves with frequencies,ω
2≪Ω
e
2
≪ω
pe
2
(Ω
e andω
pe being cyclotron and plasma frequency for the electrons of the plasma respectively) propagating transverse to the magnetic
field get destabilized. Heuristic estimates of plasma heating, due to RC instability and due to decay of ion-acoustic turbulence
generated by the return current, are made. The fastest time scale on which the return current delivers energy to the plasma
due to the scattering of ion-sound waves by the electrons can be ∼ω
pi
−1
(ω
pi being the plasma frequency for the ions). 相似文献
668.
B. C. Giri A. Goswami K. S. Chaudhuri 《The Journal of the Operational Research Society》1996,47(11):1398-1405
A generalized EOQ model for deteriorating items is considered here in which the demand rate, deterioration rate, holding cost and ordering cost are all assumed to be continuous functions of time. Shortages are also allowed and are completely backlogged. The planning horizon is finite and the replenishment periods are assumed to be constant. The optimal replenishment policy and the decision rule which minimizes the total system cost are derived. A numerical example is given to illustrate the developed model. Sensitivity analysis is also presented for the given model. 相似文献
669.
This study is aimed at attempting to improve both the selectivity and the permeation rates for the separation of 1-methylnaphthalene from dodecane using aqueous surfactant membranes. This enhancement is achieved by adding various water-soluble chemical compounds (“additives”) to the water phase. Seven different additives were tried in this study and their efficacy was determined by carrying out mass transfer permeation experiments to determine both the rates of transfer and the selectivity of separation. In line with our previous work (Sharma et al. [5]; Krishna et al. [6]), we have corrected the mass transfer coefficients for emulsion breakage, and found these coefficients, and the selectivity, to correlate well with the work of transfer of the additive-containing surfactant system. The increase in selectivity in the presence of the additive has been shown to be due to the relative increase in the activity coefficient of 1-methylnaphthalene in the aqueous solution with respect to that of dodecane. The presence of the additive increases the selectivity by about one order of magnitude, and the present study should aid in the development of a viable liquid membrane separation process for the selective removal of aromatics from kerosene, a process which is required for the production of aviation turbine fuel from crudes having a high aromatic content in the lighter distillates. 相似文献
670.
L. Chatterjee G. Das R. Goswami 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,32(1):73-78
Cross sections for radiative Coulomb capture of muons in hydrogen are shown to be enhanced by two orders of magnitude for muon energies in the neighbourhood of 2.8 keV. This effect has not been recognised earlier and has important consequences for negative muon physics as shown. 相似文献