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71.
Sk.F. Ahmed P.K. Ghosh S. Khan M.K. Mitra K.K. Chattopadhyay 《Applied Physics A: Materials Science & Processing》2007,86(1):139-143
We have observed low-macroscopic field electron emission from wide bandgap nanocrystalline Al doped SnO2 thin films deposited on glass substrates. The emission properties have been studied for different anode-sample spacings and for different Al concentrations in the films. The turn-on field and approximate work function were calculated and we have tried to explain the emission mechanism from this. The turn-on field was found to vary in the range 5.6–7.5 V/μm for a variation of anode sample spacing from 80–120 μm. The turn-on field was also found to vary from 4.6–5.68 V/μm for a fixed anode-sample separation of 80 μm with a variation of Al concentration in the films 8.16–2.31%. The Al concentrations in the films have been measured by energy dispersive X-ray analysis. Optical transmittance measurement of the films showed a high transparency with a direct bandgap ∼3.98 eV. Due to the wide bandgap, the electron affinity of the film decreased. This, along with the nanocrystalline nature of the films, enhanced the field emission properties. PACS 81.20.Fw; 61.10.-i; 79.70.+q 相似文献
72.
Construction of 6/7 fused bicycles featuring C/D rings of micrandilactone C and rubrifloradilactone B is reported through IMDA reaction of properly designed substrates. Also a route to the construction of a tricycle having A/B ring of nortriterpenoids of schisandra family is reported using RCM and a bromonium ion initiated cycloetherification reaction as the key steps. 相似文献
73.
A convenient protocol for the synthesis of chiral pyran and piperidine ring-fused anthraquinone derivatives has been developed from (R)-2,3-O-cyclohexylidene-glyceraldehyde using sequential applications of enyne metathesis, Diels–Alder reaction and aromatization as key steps. 相似文献
74.
Reduction of ketone 3 derived from (R)-2,3-cyclohexylideneglyceraldehyde 1 with some common hydrides took place with syn-selectivity. The resulting major product 4a has been exploited as a common chiral template to prepare both enantiomers Ia,b of disparlure. 相似文献
75.
Samrat Chatterjee Ezio Venturino Subhendu Chakraborty Joydev Chattopadhyay 《Mathematical Methods in the Applied Sciences》2009,32(13):1738-1750
We show how the inclusion of the defense strategy by different species can alter the prediction of simple models. One of the defense strategy by the phytoplankton population against their grazer is the release of toxic chemicals. In turn the zooplankton population reduces there predation rate over toxin producing phytoplankton (TPP) to protect themselves from those toxic chemicals. Thus, when the level of toxicity is high, the grazing pressure is low and when the level of toxicity is low or when the toxin is absent, the grazing pressure is high. Here we have considered a TPP–zooplankton system where the rate of toxin liberation and the predation rate vary with zooplankton abundance. We observe that our proposed model has the potential to show different dynamical behaviour that are similar to that seen in real‐world situations. Further, we consider three different functional forms for the distribution of the toxins and compare them using latin hypercube sampling technique and found that the functional forms seem to have no effect in determining the final outcome of the system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
76.
We have developed a gold-catalyzed intramolecular cyclization of variously substituted acetylenic amines under mild conditions, which yields pyrrolopyridines and 2-substituted indoles, quantitatively. The cycloisomerization of acetylenic amines was achieved with AuCl3 as catalyst without the use of base, acid or N-protecting group. 相似文献
77.
Chih-Wei Chiang Subrata Kumar Das 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(7):1187-1195
The aerosol optical thickness (AOT) is an important parameter for understanding the radiative impact of aerosols. AOT based on lidar measurements is often limited by its finite detection range. In this paper, we have reported a method of fitting and iterative calculation to derive the extinction profile of background aerosols from 0 to 30 km at 532 nm, which is virtually the AOT of the entire atmosphere. The mean extinction derived from this method at the ground level tallies with visibility measurement and it is also consistent with the sun-photometer data, within experimental error. These data have been further treated to study the dust cases. For most of the cases, transmission losses were determined to estimate the extinction as well as lidar ratio. The result of the analysis shows that for background aerosols, a mean lidar ratio of 47±15 sr was found. For dust layers, a mean lidar ratio of 44±19 sr and an optical thickness of 0.53±0.49 were determined at 532 nm. 相似文献
78.
79.
80.
A. Chattopadhyay G. A. Rogerson 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(4-5):307-316
Summary In this paper, the reflection of a plane wave at an incrementally traction-free boundary of a half-space composed of nearly
incompressible elastic material is considered. It is shown that two distinct cases exist, these being dependent on the underlying
primary deformation. In the first case, the appropriate slowness sections are each approximately elliptical, and the corresponding
reflection phenomena closely mirrors that associated with the corresponding linear isotropic theory. Specifically, an angular
range of direction of incident wave exists, for which both a quasi-longitudinal and quasi-shear wave are reflected, the former
being replaced by a surface wave outside this angular range. In the second case, the outer slowness section is re-enrant and,
in addition to the scenarios previously mentioned, it is possible for two quasi-shear waves to be reflected. Numerical illustrations
of reflection coefficients are presented in respect of a modified Varga material and the case of increasing bulk modulus is
investigated.
Received 17 January 2000; accepted for publication 22 February 2000 相似文献