排序方式: 共有6条查询结果,搜索用时 15 毫秒
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Mohammed Boutayeb Soufiane El Imadi El Mokhtar Essassi Nour-Eddine Es-Safi Lahcen El Ammari 《合成通讯》2013,43(14):2130-2137
New pyrazolo[1.5.4-de]quinoxaline derivatives were prepared by the action of 7-aminoindazole 1 on diethyl and dimethyl acetylene dicarboxylates. The structures of the obtained compounds and the direction of cyclization were investigated through a crystallographic study of compound 2. Further alkylation, hydrogenation, and bromination were also explored. The action of potassium thiocyanate on the obtained halo product led to a tetracyclic compound of 1.3-thiazolo[3.4-a]pyrazolo[1.5.4-de]quinoxaline series. 相似文献
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On doubling metric measure spaces endowed with a strongly local regular Dirichlet form, we show some characterisations of pointwise upper bounds of the heat kernel in terms of global scale-invariant inequalities that correspond respectively to the Nash inequality and to a Gagliardo–Nirenberg type inequality when the volume growth is polynomial. This yields a new proof and a generalisation of the well-known equivalence between classical heat kernel upper bounds and relative Faber–Krahn inequalities or localised Sobolev or Nash inequalities. We are able to treat more general pointwise estimates, where the heat kernel rate of decay is not necessarily governed by the volume growth. A crucial role is played by the finite propagation speed property for the associated wave equation, and our main result holds for an abstract semigroup of operators satisfying the Davies–Gaffney estimates. 相似文献
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In this paper, we address the problem of observer design for a class of Lipschitz nonlinear discrete-time systems with time-delay. The main contribution lies in the use of a new structure of the proposed observer with a novel Lyapunov-Krasovskii functional. Thanks to these designs, new nonrestrictive synthesis conditions, expressed in terms of linear matrix inequalities (LMIs), are obtained. Indeed, the obtained LMIs contain more degree of freedom than those established by the approaches available in the literature which consider a simple Luenberger observer with a simple Lyapunov function for the stability analysis. An extension of the presented result to H∞ performance analysis is given in order to take into account the noise (if it exists) affecting the considered system. 相似文献
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A. Boutayeb A. Chetouani A. Achouyab E. H. Twizell 《Journal of Applied Mathematics and Computing》2006,21(1-2):127-139
A mathematical study of the size of a population ofdiabetes mellitus patients is carried out in this paper. The study also monitors the number of patients with complications. By appropriate definition of a parameter, the mathematical model may be classified as linear or non-linear. The non-linear case is discussed and the critical values of the population are analysed for stability. Numerical methods are developed for solving the model equations and the results of numerical simulations are reported. 相似文献
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Second-order finite-difference methods are developed for the numerical solutions of the eighth-, tenth- and twelfth-order
eigenvalue problems arising in the study of the effect of rotation on a horizontal layer of fluid heated from below. Instability
setting-in as overstability may be modelled by an eighth-order ordinary differential equation. When a uniform magnetic field
also acts across the fluid in the same direction as gravity, instability setting-in as ordinary convection may be modelled
by a tenth-order differential equation, while instability setting-in as overstability may be modelled by a twelfth-order differential
equation. The numerical methods are developed by making direct replacements of the derivatives in the differential equations
and then by computing the eigenvalues, which may incorporate Rayleigh number, horizontal wave speed and a time constant, from
the resulting algebraic eigenvalue problem. The eigenvalues are also computed by writing the differential equations as systems
of second-order differential equations and then using second- and fourth-order methods to obtain the eigenvalues. Numerical
results obtained using the two approaches are compared with estimates appearing in the literature. 相似文献
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Moulay Taïb Belghiti Boutayeb El Ammari Laurent P. Gendre 《Comptes Rendus Mathematique》2018,356(11-12):1125-1130
We study the problem of global approximation by polynomials in Whitney -flat jet classes on irregular compacts of . 相似文献
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