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101.
Xiangyang Zhou David Weise Shankar Mahalingam 《Proceedings of the Combustion Institute》2005,30(2):2287-2294
An extensive experimental and numerical study was completed to analyze the marginal burning behavior of live chaparral shrub fuels that grow in the mountains of southern California. Laboratory fire spread experiments were carried out to determine the effects of wind, slope, moisture content, and fuel characteristics on marginal burning in fuel beds of common chaparral species. Four species (Manzanita sp., Ceanothus sp., Quercus sp., and Arctostaphylos sp.), two wind velocities (0 and 2 m/s), two fuel bed depths (20 and 40 cm), and three slope percents (0%, 40%, or 70%) were used. Oven-dry moisture content M of fine fuels (<6.25 mm diameter) ranged from 29% to 105%. Sixty-five of 115 fires successfully propagated the length (2.0 m) of the elevated fuel bed. A previously derived empirical marginal burning criterion was assessed, and a suitable modification was proposed for live chaparral fuels. Based on the experimental data, a stepwise logistic regression model was developed to predict the probability of successful fire spread. This procedure resulted in the selection of wind speed, slope percent, fuel loading, fuel moisture content, and relative humidity as the primary variables. It correctly classified 96% of 115 fires. Finally, a multidimensional numerical model for vegetation fire spread using a porous media sub-model was developed to simulate the laboratory fires. Results are used to analyze the internal heat transfer and combustion processes that determine fire spread success in shrub fuel bed. 相似文献
102.
Z-scan studies on porphyrin derivative 总被引:2,自引:0,他引:2
K. Kandasamy K. Divakar Rao Rekha Deshpande P.N. Puntambekar Bhanu P. Singh Shankar J. Shetty T.S. Srivastava 《Applied physics. B, Lasers and optics》1997,64(4):479-484
Received: 10 January 1996 / Revised version: 15 June 1996 相似文献
103.
P. N. Shankar 《Pramana》2005,65(3):437-455
We consider in a frame fixed to a bubble translating with steady speedU, the inviscid, axisymmetric, irrotational motion of the liquid past it. If all speeds are normalized byU and lengths by {ie437-1}, whereT is the surface tension of the liquid-bubble interface, it can be shown that the unknown bubble shape and field depend on
a single parameter {ie437-2} alone, where the pressures are the ones in the bubble and far away respectively. WhenΓ is very large the bubble is almost spherical in shape while for Γ<- Γ* ≈ -0.315, bubbles whose exteriors are simply connected do not exist. We solve the non-linear, free boundary problem for the
whole range Γ* < Γ < ∞ by the use of an analytical representation for the bubble shape, a surface singularity method to compute potential
flows and a generalized Newton’s method to continue inΓ. Apart from providing explicit representations for bubble shapes and detailed numerical values for the bubble parameters,
we show that the classical linearized solution for largeΓ is a very good approximation, surprisingly, to as low values of Γ as 2. We also show that Miksiset al [1] is inaccurate over the whole range and in serious error for large and smallΓ. These have been corrected. 相似文献
104.
Susheel K. Verma Girja Shankar Deepak Singh 《International Journal of Infrared and Millimeter Waves》1994,15(3):559-566
A balanced upconverter circuit has been developed in planar transmission line configuration using NEC GaAs beam lead Schottky barrier diodes. RF power output of +1.6 dBm SSB is obtained at Ka-band when up converter is driven by +17 dBm IF and +20 dBm LO signal. 相似文献
105.
106.
Subramaniam Ramdas John M. Thomas Paul W. Betteridge Anthony K. Cheetham E. Keith Davies 《Angewandte Chemie (International ed. in English)》1984,23(9):671-679
The unique structural, adsorptive, and catalytic properties of zeolites are particularly amenable to illustration by computer (especially color) graphics. The siting of cations, the accommodation of guest reactant or product species, as well as the occurrence of various kinds of intergrowths (e.g. twin planes and coincidence boundaries) within these microporous solids can all be effectively portrayed by graphical means in such a manner as to emphasize the shape-selective character of the host zeolite. The dynamics of translational and angular motion of guest species (for example benzene) in a channel of molecular dimensions within a typical zeolitic solid (for example silicalite) can also be probed interactively using appropriate potential functions. 相似文献
107.
Substitution of coordinated chlorides in cis-α, and cis-β dichloro (triethylene tetramine) cobalt(III) chloride by thiocyanate was studied in aqueous medium in the pH range 3.8 to 4.0 at 25–26° C. Substitution, as in aquation, took place in two steps corresponding to the two chlorides, one step being faster than the other. Mechanisms have been discussed in the paper. 相似文献
108.
109.
Complexes having the general formula ML.HL, where M = Na, K, Rb or Cs and HL = quinaldinic acid, have been obtained. The isolation of adducts in the solid state appeared to be favoured by increase in atomic radius, and hence decrease in ionisation potential of the metal. Attempts to synthesise similar adducts of picolinic acid N-oxide and quinaldinic acid N-oxide did not succeed. Complexes have been characterised by elemental analyses, thermal, IR spectral and solution studies. Our findings suggest that pK value of the ligands cannot be regarded a dominant factor in the synthesis and isolation of alkali metal complexes. 相似文献
110.
After formulation of the various dynamical and kinematical relations connecting the flow quantities with the geometrical parameters of the stream line trajectories, the expressions for the tangent, principal normal and binormal vectors and the curvature and torsion of the stream line have been obtained in-terms of the velocity components, the pressure, the density, the magnetic field and the relaxation variable. This is followed by expressing the equations governing the flow in the intrinsic forms. It has been shown that the non-equilibrium character of the gas decreases the total pressure gradient along the streamlines, but the total pressure remains constant along the binormals and if the stream lines are straight lines, the trajectories of the principal normals lie on the surface of the constant total pressure. Further, the expressions for vorticity components in terms of curvature of the stream line and the velocity gradients along the stream line and their principal normals and binormals have been obtained. Finally, a class of circular helical flows have been discussed. 相似文献