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41.
Carolyn A. Eschenbach Frank J. Hall Deborah L. Harrell Zhongshan Li 《Czechoslovak Mathematical Journal》1999,49(2):255-275
By a sign pattern (matrix) we mean an array whose entries are from the set {+, –, 0}. The sign patterns A for which every real matrix with sign pattern A has the property that its inverse has sign pattern A
T are characterized. Sign patterns A for which some real matrix with sign pattern A has that property are investigated. Some fundamental results as well as constructions concerning such sign pattern matrices are provided. The relation between these sign patterns and the sign patterns of orthogonal matrices is examined. 相似文献
42.
The monomeric cobalt-phosphite-thiolato complex [ Co (mpt)2 {P (OCH3 )3 }2 ] BF4 (Hmpt = 2-mercaptothiazoline) has been prepared and characterized by X-ray crystallography. The complex crystallizes in the monoclinic space group C2/c with a= 0.8078(5), b=2.6020(18), c=1.2191(7) nm, β= 99.38 (1)°, V= 2.528(3) nm3, and Z = 4. The structure comprises discrete cations [Co(mpt)2{P(OCH3)3}2.] and anions BF4- , in which the cobalt (Ⅲ) atom is coordinated to two chelate mpt- and two as-oriented monodentate P(OCH3)3 ligands in a highly distorted octahedral geometry. The most distorted angles are S(2)-Co(1)-S(2a) of 162.23(10)° and N(1)-Co(1)-S(2) of 71. 47 (13)°, the latter is caused by the geometric constraint of the bidentate ligand mpt- . Cyclic voltammetry has been used to study the electrochemical behavior of the title complex on the R electrode in MeCN solution with 0.1 mol·L-1 of Bun4NBF4 as electrolyte. The results indicate that the title complex is unstable in MeCN. 相似文献
43.
PREPARATION AND THEIR ANTIBACTERIAL ACTIVITY OF ACTIVATED CARBON FIBER CONTAINING SILVER* 总被引:2,自引:0,他引:2
CHEN Shuixia** LUO Ying XU Ruimei LI Jian ZENG Hanmin Key Laboratory of Polymer Composite Functional Materials Education Ministry Materials Science Institute Zhongshan University Guangzhou 《Chinese Journal of Reactive Polymers》2000,(2)
1.INTRODUCTIONActivatedcarbonfibers(ACF)havehighspecificsurfaceareasorabundantmicropores,whichmakethemhavegreatadsorptionrateandlargeadsorptioncapacity.Nowtheymakeaveryimportantroleinenvironmentalcontrolandinresourcerecovery[1].Bytakingadvantageoftheactivatedcarbonfibers'adsorptionabilityagainstbacteriaandstenchsubstance,theycanalsobeusedinpurifyingblood,inmedicinebandageforpreventingthewoundbacteriafrompropagatingandforadsorbingandeliminatingthewoundstench.Theresultsbyotherworkersindica… 相似文献
44.
45.
二氧化锡反射光谱的气敏现象 总被引:4,自引:1,他引:3
作者发现二氧化锡薄膜的反射光谱具有气敏效应,在还原性气体中,其可见及近红外区反射率随气体浓度增加而减少。 相似文献
46.
Cantor集的自乘积集的Hausdorff测度的下界 总被引:1,自引:0,他引:1
证明了三分Cantor集C的自乘积集C×C的Hausdorff测度满足 H~(log_3)~4(C×C)≥1.48329。 相似文献
47.
The influences of residual chlorine ions and water on the performance of a Pd/Al2O3 catalyst in methane combustion have been studied. The results show that the catalyst containing Cl− exhibits a relatively low activity, and the addition of water to the reaction system accelerates the deactivation process. The catalyst has been characterized by N2 adsorption, X-ray fluorescence, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry (TG). The results show that the presence of Cl− appears to strongly inhibit the total oxidation of methane and hinder the dispersion of Pd on Al2O3. The formation of Pd(OH)2 during the reaction is the most likely reason for the inhibition effect of water, which is confirmed by FT-IR and TG analysis. The regeneration of the Pd/Al2O3 catalyst can be achieved by purging in nitrogen at 550 °C. 相似文献
48.
Wei Fang Wei Gao Yubin Gao Fei Gong Guangming Jing Zhongshan Li Yanling Shao Lihua Zhang 《Czechoslovak Mathematical Journal》2016,66(3):895-911
A sign pattern matrix (or nonnegative sign pattern matrix) is a matrix whose entries are from the set {+,?, 0} ({+, 0}, respectively). The minimum rank (or rational minimum rank) of a sign pattern matrix A is the minimum of the ranks of the matrices (rational matrices, respectively) whose entries have signs equal to the corresponding entries of A. Using a correspondence between sign patterns with minimum rank r ≥ 2 and point-hyperplane configurations in Rr?1 and Steinitz’s theorem on the rational realizability of 3-polytopes, it is shown that for every nonnegative sign pattern of minimum rank at most 4, the minimum rank and the rational minimum rank are equal. But there are nonnegative sign patterns with minimum rank 5 whose rational minimum rank is greater than 5. It is established that every d-polytope determines a nonnegative sign pattern with minimum rank d + 1 that has a (d + 1) × (d + 1) triangular submatrix with all diagonal entries positive. It is also shown that there are at most min{3m, 3n} zero entries in any condensed nonnegative m × n sign pattern of minimum rank 3. Some bounds on the entries of some integer matrices achieving the minimum ranks of nonnegative sign patterns with minimum rank 3 or 4 are established. 相似文献
49.
Wubin Weng Shen Li Mário Costa Zhongshan Li 《Proceedings of the Combustion Institute》2021,38(3):3949-3958
This work investigated the combustion characteristics of single pulverized biomass-derived char particles. The char particles, in the size range 224–250 µm, were prepared in a drop tube furnace at pyrolysis temperatures of 1273 or 1473 K from four types of biomass particles – wheat straw, grape pomace, kiwi branches and rice husk. Subsequently, the char particles were injected upward into a confined region of hot combustion products produced by flat flames stabilized on a McKenna burner, with mean temperatures of 1460, 1580 and 1670 K and mean O2 concentrations of 4.5, 6.5 and 8.5 vol%. The data reported include particle temperature, obtained using a two-color pyrometry technique, and potassium release rate, measured using a laser-induced photofragmentation fluorescence imaging technique. In addition, particle ignition delay time and burning time, obtained from the temporal evolution of the thermal radiation intensity of the burning char particles, are also reported. The results indicated that ignition of the char particles occurs simultaneously with the starting of the potassium release, then the particle burning intensity increases rapidly until it reaches a maximum, after which both the particle temperature and the potassium release rate remain approximately constant until the end of the char oxidation process. The char ignition process is temperature controlled, and the char oxidation process is oxygen diffusion controlled, with the total potassium release being independent of the oxygen concentration and the temperature of the combustion products. The combustion behavior of the chars studied is more affected by the char type than by the conditions used to prepare them. 相似文献
50.
Xiao Cai Jinhua Wang Zhijian Bian Haoran Zhao Zhongshan Li Zuohua Huang 《Proceedings of the Combustion Institute》2021,38(2):2013-2021
The propagation of laminar and turbulent expanding flames subjected to Darrieus–Landau (DL), hydrodynamic instability was experimentally studied by employing stoichiometric H2/O2/N2 flames under quiescent and turbulent conditions performed in a newly developed medium-scale, fan-stirred combustion chamber. In quiescent environment, DL unstable laminar flame exhibits three-stage propagation, i.e. smooth expansion, transition acceleration, and self-similar acceleration. The self-similar acceleration is characterized by a power-law growth of acceleration exponent, α, with normalized Peclet number, which is different from the usually suggested self-similar propagation with a constant α. The imposed turbulence advances the onset of both transition acceleration and self-similar acceleration stages and promotes the strength of flame acceleration as additional wrinkles are invoked by turbulence eddies. A DL–turbulent interaction regime is confirmed to be the classical corrugated flamelets regime. Furthermore, the DL instability significantly facilitates the propagation of expanding flames in medium and even intense turbulence. The development of DL cells is not suppressed by turbulence eddies, and it needs to be considered in turbulent combustion. 相似文献