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排序方式: 共有399条查询结果,搜索用时 359 毫秒
131.
Mustapha Raïssouli 《Linear and Multilinear Algebra》2019,67(2):213-220
Let T and S be two self-adjoint positive invertible operators of a complex Hilbert space H. In this paper, we investigate some inequalities involving the quadratic forms of the weighted arithmetic and harmonic means of T and S. Application for operator entropies is also discussed. 相似文献
132.
Mustapha Hellou 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,25(1):642-657
The positive inversion transformation applied to a
two-dimensional Stokes flow around bodies leads alike to a Stokes
flow. This fact can be exploited to find new two-dimensional
Stokes flow solutions around inverse bodies. Some features of this
method, such as the relations between the reference and inverse
fluid velocity fields, are presented followed by an application to
examples of cellular flow between two parallel plates induced by
rotating or translating cylinder. Thus hydrodynamic
characteristics of flow around circular bodies obtained by
inversion of the plates are straightforward deduced. Typical fluid
flow patterns around two circular cylinders in contact placed in
the centre of a rotating or a translating circular cylinder are
thus illustrated. 相似文献
133.
We show that the electrically charged wormhole soliton solution of sourceless five-dimensional general relativity is classically stable against radial perturbations, except in the special case of a massless soliton.On leave of absence from: Département de Physique Théorique, Université de Constantine, Constantine, Algeria 相似文献
134.
This paper studies a stochastic linear quadratic (LQ) control problem in the infinite time horizon with Markovian jumps in parameter values. In contrast to the deterministic case, the cost weighting matrices of the state and control are allowed to be indinifite here. When the generator matrix of the jump process – which is assumed to be a Markov chain – is known and time-invariant, the well-posedness of the indefinite stochastic LQ problem is shown to be equivalent to the solvability of a system of coupled generalized algebraic Riccati equations (CGAREs) that involves equality and inequality constraints. To analyze the CGAREs, linear matrix inequalities (LMIs) are utilized, and the equivalence between the feasibility of the LMIs and the solvability of the CGAREs is established. Finally, an LMI-based algorithm is devised to slove the CGAREs via a semidefinite programming, and numerical results are presented to illustrate the proposed algorithm. 相似文献
135.
Tewfik Bouchaour Fr d rick Roussel Jean-Marc Buisine Xavier Coqueret Mustapha Benmouna Ulrich Maschke 《Liquid crystals》2003,30(4):487-491
The thermophysical properties of mixtures of poly (2-phenoxyethylacrylate) and 4-cyano-4'-pentyl-biphenyl, 5CB, are investigated using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The polymer has a molar mass M w = 181 000 g mol -1 ; the low molecular mass liquid crystal exhibits a nematic to isotropic transition at 35.3°C and crystallizes below 23°C. The phase diagram exhibits miscibility gaps in certain regions of temperature and composition where coexisting nematic and isotropic phases are found. From a practical point of view when considering the electro-optical applications of these systems, it proves to be useful to know precisely the amount of small liquid crystal molecules dissolved in the polymer matrix and the concentration of polymer in the nematic phase. The former quantity has a mechanical impact due to a plasticizing effect, an optical impact since it changes the polymer refractive index, while the polymer in the nematic phase shifts the transition temperatures influencing the electro-optical response of the liquid crystal. The present work addresses these important aspects using POM and DSC. 相似文献
136.
Nan Huang Tiansheng Wang Mustapha Soukri Rakesh Ganorkar Bruce Deker Jose Madalengoitia 《Tetrahedron》2008,64(42):9850-9856
Condensation of methyl 3-benzyl-1,2,3,4,5,6-hexahydroazepino[4,5-b]indole-5-carboxylate (3) with methyl Z-4-formylhex-3-enoate (6) gave cis-fused dimethyl 5-benzyl-4-ethyl-2,4a,5,6,7,12-hexahydro-1H-benzo[2,3]azepino[4,5-b]indole-2,12b-dicarboxylate and its trans-fused diastereomer. Selective reduction of the less hindered ester group with sodium borohydride to an alcohol ester, tosylation, debenzylation, and cyclization gave racemic catharanthine (1). 相似文献
137.
Mustapha Mokhtar-Kharroubi 《Journal of Evolution Equations》2008,8(2):327-352
We deal with streaming operators T
H
defined in L
1 spaces by the directional derivative with positive boundary operator H of norm 1 relating the incoming and outgoing fluxes. It is known that T
H
need not be a generator but there exists a contraction semigroup generated by an extension A of T
H
. This paper deals with the total mass carried by individual trajectories {e
tA
f; t ≥ 0} for nonnegative initial data f and related topics. In particular, our analysis covers the problem of (the lack of) stochasticity of {e
tA
; t ≥ 0} for conservative boundary operator H.
相似文献
138.
Tatiana Campos-Malpartida Ferenc Joó Ágnes Kathó Mustapha Saoud 《Journal of organometallic chemistry》2008,693(3):468-474
The process of catalytic isomerisation of various allylic alcohols (alk-1-en-3-ols) into saturated ketones under mild conditions is reported. The water-soluble Na4[{RuCl2(mtppms)2}2] complex, previously reported by us as a precursor to very active hydrogenation catalysts was also found an active catalyst of the redox isomerisation of allylic alcohols in aqueous media. The new Na[Ru(CO)Cp(mtppms)2] as well as Na4[{RuCl(μ-Cl)(CCCPh2)(mtppms)2}2] and Na2[RuClCp(mtppms)2] also showed good to excellent catalytic activities for redox isomerisations in aqueous systems at 50-80 °C under inert atmosphere. 相似文献
139.
Christian Ruby Mustapha Abdelmoula Ghouti Medjahdi Michel François 《Journal of solid state chemistry》2008,181(9):2285-2291
The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula (OH)12 SO4, 8H2O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO42−), i.e. y=0, in which a bilayer of sulphate anions points to the Fe3+ species. A cationic order is proposed to occur in both GR(SO42−) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO42−) is preceded by the successive precipitation of FeIII and AlIII (oxy)hydroxides. Adsorption of more soluble AlIII species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y∼0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive FeII species of the material. 相似文献
140.
Mustapha Mourragui Enza Orlandi 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2007,43(6):677-715
We consider a lattice gas in a periodic d-dimensional lattice of width γ−1, γ>0, interacting via a Kac's type interaction, with range and strength γd, and under the influence of a random one body potential given by independent, bounded, random variables with translational invariant distribution. The system evolves through a conservative dynamics, i.e. particles jump to nearest neighbor empty sites, with rates satisfying detailed balance with respect to the equilibrium measures. In [M. Mourragui, E. Orlandi, E. Saada, Macroscopic evolution of particles systems with random field Kac interactions, Nonlinearity 16 (2003) 2123–2147] it has been shown that rescaling space as γ−1 and time as γ−2, in the limit γ→0, for dimensions d3, the macroscopic density profile ρ satisfies, a.s. with respect to the random field, a non-linear integral partial differential equation, having the diffusion matrix determined by the statistical properties of the external random field. Here we show an almost sure (with respect to the random field) large deviations principle for the empirical measures of such a process. The rate function, which depends on the statistical properties of the external random field, is lower semicontinuous and has compact level sets. 相似文献