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51.
A. K. Sen R. Bera P. K. Karmakar 《International Journal of Infrared and Millimeter Waves》1997,18(11):2233-2257
The use of Ka Band (20/30 GHz) for future satellite communications has been addressed. The exploitation of Ka band with a
bandwidth of 2500 MHz seems to represent the largest significant achievement in satellite communications potential, so far.
The problems associated with the use of this frequency band such as attenuation and receiver noise temperature (floor) variation
with rain has been addressed. The receiver noise floor variation with rain has so far been ignored. Therefore, in view of
propagation and noise study over this Ka Band, both signal attenuation and receiver noise floor variations with rain rate
are estimated using dual frequency radiometers operating at 22.235 and 31.4 GHz over a tropical station, Calcutta, India. 相似文献
52.
Subhendu K. Datta 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1961,12(6):558-563
Zusammenfassung Es werden die Transversalwellen untersucht, welche in einem viskoelastischen Halbraum unter einem plötzlich an der Grenzebene angebrachten Moment entstehen. Insbesondere werden die Verschiebungen an der Grenzfläche für kleine und grosse Distanzen vom Störungszentrum angegeben. Das Medium wird als isotroper Kelvin-Stoff angenommen. 相似文献
53.
S. N. Karmakar R. K. Moitra P. Chaudhuri 《Zeitschrift für Physik B Condensed Matter》1985,58(2):133-140
In this paper we present a new theory for including both short range order and long range order simultaneously in the well known cluster Bethe lattice method for binary alloys. We have used this theory for obtaining the Friedel criterion for the appearance of magnetic moments in disordered states using the single band Hubbard model. This is followed by a study of this criterion in a two-bands-d hybridised Hubbard model, which is considered as a simulation of real transition metals. A new technique for solving this problem in the Bethe lattice network is presented, which yields an analytic solution for the critical correlation strength in the presence of hybridisation and short range order. It is found that in all cases hybridisation tends to diminish the tendency for magnetisation, which is in accord with physical expectations. 相似文献
54.
Dattatray J. Late Soumen Karmakar Mahendra A. More Sudha V. Bhoraskar Dilip S. Joag 《Journal of nanoparticle research》2010,12(7):2393-2403
Lanthanum hexaboride (LaB6) nanocrystallites/nanowires have been successfully synthesized using gas phase condensation in arc plasma. Our results show
that the LaB6 nanowires have ~20 nm diameter and length of several micrometers. The as-synthesized LaB6 nanocrystallites and nanowires are crystalline in nature. Field emission studies were carried out on as synthesized LaB6 nano-powder deposited on W and Re tips and foils, and also on Si foil substrates under ultra high vacuum. The Fowler–Nordheim
plots obtained from the current–voltage characteristics are found to be linear in accordance with the quantum mechanical tunneling
phenomenon. High value of field enhancement factor (8177) is observed for LaB6 on Re substrate, indicating that the electron emission is from the nanometric features of the LaB6. Our results show that the arc plasma synthesized LaB6 nanocrystalline film exhibits good emission stability as emitter without severe deviations from the initial set value and
also a strong ability to withstand the ion bombardment, which is useful for low operation voltage vacuum micro/nano electronic
devices. 相似文献
55.
J. Chowdhury S. Sil S. N. Karmakar B. Bhattacharyya 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):435-444
We have presented the role of the Coulomb interaction (U) and the magnetic
field [(B)\vec]\vec{B} on the ground state properties of the quasi-one dimensional
graphite ribbon structures at half-filling. Mean field Hartree-Fock
Approximation is used to study the systems. To understand the boundary effects
in graphite structures, we have compared the results of these systems
with those of the square lattice ribbon structures. Studying the density of
states, the Drude weight and the charge gap, we have drawn the U – B phase
diagrams for the zigzag and the armchair graphite ribbons. 相似文献
56.
An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green. 相似文献
57.
Tining Su Tong Ju Baojie Yan Jeffrey Yang Subhendu Guha P. Craig Taylor 《Journal of Non》2008,354(19-25):2231-2234
We studied the stability and light-induced paramagnetic centers in hydrogenated nanocrystalline silicon thin films (nc-Si:H) by electron-spin-resonance (ESR) and photothermal-deflection-spectroscopy (PDS). There is no measurable change in defect density upon illumination with white light with a light intensity of 300 mW cm?2 for 300 h. At low temperatures, upon illumination with sub-bandgap light, a light-induced ESR signal appears. This signal is similar to that in hydrogenated micro-crystalline silicon (μc-Si:H). 相似文献
58.
Sutapa Sen Manas K. Saha Tarakranjan Gupta Aswini K. Karmakar Parimal Kundu Samiran Mitra Michael B. Hursthouse K. M. Abdul Malik 《Journal of chemical crystallography》1998,28(10):771-777
The compound [Cu(phen)(O2CCF3)2]n (phen = 1,10-phenanthroline) has been synthesized and its crystal structure determined. It crystallizes in monoclinic space group C2/c, with a = 19.229(7), b = 11.281(5), c = 7.621(2) Å, = 104.305(12)°, and Z = 4. The crystal structure is polymeric, being built from infinite zigzag chains of trifluoroacetate bridged copper(II), with the phenanthroline ligands being stacked between the chains. The variable-temperature (13–300 K) magnetic susceptibility and ESR data are reported and a weak ferromagnetic exchange interaction is observed with the exchange parameter estimated as J = 2.9 cm–1. 相似文献
59.
Ananta Karmakar Mushkin Basha G.T. Venkatesh Babu Murali Botlagunta Noormohamed Abdul Malik Richard Rampulla Arvind Mathur Arun Kumar Gupta 《Tetrahedron letters》2018,59(48):4267-4271
A number of cyanomethyl esters of natural/unnatural aminoacids with un-protected amino functionality were synthesized because of their synthetic and medicinal importance. Critical N-Boc deprotection methods in the presence of labile (hydrolytic sensitivity) cyanomethyl functionality were screened thoroughly and it was found that readily available 4M HCl in 1,4-dioxane solution (2–4 equiv); acetonitrile, 0?°C, 2–4?h was a suitable condition. This condition was generalized and successfully applied to a variety of alkyl, alkynyl, aryl, heteroaryl, benzyl, azido, spiro amino acid cyanomethylesters irrespective of the nature of the amine (primary or secondary) and the distance between the amine and ester group to achieve final deprotected amino esters with high yield, and purity compared to other commonly known N-protecting groups (Cbz, Fmoc, Ac, Bn, Bz etc.). It was also demonstrated that N-Boc protected aminoacid cyanomethylesters are stable enough to carry out further functionalization compared to N-unprotected counterparts. 相似文献
60.
Saito Y Bag SS Kusakabe Y Nagai C Matsumoto K Mizuno E Kodate S Suzuka I Saito I 《Chemical communications (Cambridge, England)》2007,(21):2133-2135
A novel FRET based strategy for DNA sequence analysis utilising base-discriminating fluorescence (BDF) nucleoside, (Py)U/(2-Ant)U, as donor in the dual-labelled oligonucleotide probe is reported; a selective/specific emission from acceptor, was observed upon excitation at the donor, only when the opposite base of the "smart" fluorescently labeled BDF nucleoside, (Py)U/(2-Ant)U, is adenine on the complementary target sequence. 相似文献