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1.
We consider an initial boundary value problem for a nonlinear differential system of two equations. Such a system is formed by the equations of compressible miscible flow in a one-dimensional porous medium. No assumption about the mobility ratio is involved. Under some reasonable assumptions on the data, we prove the existence of a global weak solution. Our basic approach is the semi-Galerkin method. We use the technique of renormalized solutions for parabolic equations in the derivation ofa prioriestimates. 相似文献
2.
The goal of this paper is twofold : at first, to present the stochastic timed Pétri nets model by emphasizing its ability to express the main characteristics of real time distributed systems (parallelism, synchronization by message exchange, time attributes and in particular time constraints) and to allow both qualitative and quantitative analysis (concept of randomized states graph); second, to show a modeling methodology based on this model that allows a rigorous modeling of theDqdb protocol (Qa access, bwb mechanism role,Pa access influence). A new contribution to theQa mechanism has been done (1). 相似文献
3.
Fayçal Boukhari Nacéra Tigrine‐Kordjani Brahim Youcef Meklati 《Helvetica chimica acta》2013,96(6):1168-1175
Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non‐insulin‐dependent diabetics. In recent years, the type‐II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwave‐assisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC‐FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050±0.001% (w/w)) than by HD (0.030±0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with β‐caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with β‐pinene and eucalyptol, respectively, as major components. 相似文献
4.
We study the equations of flow of an electrically conductive magnetic fluid, when the fluid is subjected to the action of an external applied magnetic field. The system is formed by the incompressible Navier–Stokes equations, the magnetization relaxation equation of Bloch type and the magnetic induction equation. The system takes into account the Kelvin and Lorentz force densities. We prove the local-in-time existence of the unique strong solution to the system equipped with initial and boundary conditions. We also establish a blow-up criterion for the local strong solution. 相似文献
5.
This paper presents a method for designing fullband and non-fullband IIR digital integrators with linear phase that has been used to approximate fractional-order integrators with IIR filters. Several numerical integration rules have been considered in this study, namely, Euler, Simpson, Schneider, bilinear, and F012. The main idea in our design is based on interpolating the well-known integration rules (Euler, Bilinear and Simpson) proposed by Al-Alaoui combined with deterministic signal modeling techniques. Numerical examples are presented to illustrate the performance of the proposed integrators. It was found that the Euler–Simpson integrator gives better approximation accuracy than existing integrators. 相似文献
6.
Hamida Maachou Kheireddine Bal Youcef Bal Alexandre Chagnes Gerard Cote Djamel Aliouche 《Applied biochemistry and biotechnology》2012,168(6):1459-1475
Chitosan/hydroxyapatite composite microparticles were prepared by a solid-in-water-in-oil emulsification cross-linking method. The characteristics and activity in presence of simulated body fluid for 14 and 21?days were investigated. The size distribution, surface morphology, and microstructure of these biomaterials were evaluated. The scanning electron microscopy revealed an aggregate of microparticles with a particle size, ranged from 4 to 10???m. The deposited calcium phosphate was studied using X-ray diffraction analysis, Fourier transform infrared spectroscopy, and inductively coupled plasma/atomic emission?spectroscopy analysis of phosphorus. These results show that the mineral, formed on microparticles, was a mixture of carbonated hydroxyapatite and calcite. Scanning electron microscopy revealed that calcium phosphate crystals growth was in form of rods organized as concentric triangular packets interconnected to each other by junctions. Interaction between chitosan and growing carbonated hydroxyapatite and calcite crystals are responsible for a composite growth into triangular and spherical shapes. The results demonstrated that these microparticles were potential materials for bone repair. 相似文献
7.
Youcef Amirat Vladimir Shelukhin 《Journal of Mathematical Analysis and Applications》2008,342(2):1227-1245
By the homogenization approach we justify a two-scale model of ion transport in porous media for one-dimensional horizontal steady flows driven by a pressure gradient and an external horizontal electrical field. By up-scaling, the electroosmotic flow equations in horizontal nanoslits separated by thin solid layers are approximated by a homogenized system of macroscale equations in the form of the Poisson equation for induced vertical electrical field and Onsager's reciprocity relations between global fluxes (hydrodynamic and electric) and forces (horizontal pressure gradient and external electrical field). In addition, the two-scale approach provides macroscopic mobility coefficients in the Onsager relations. 相似文献
8.
The theory of resolution optimization by isochronal analysis is further extended to the cases involving simultaneous changes in mobile phase velocity and column temperature, and in mobile phase composition and temperature. In each case, the resolution equation, when written in terms of isochronal conditions, shows that improvements can be obtained without sacrificing analysis time. Several subcases, which relate to the dependence of the selectivity factors on the changed parameters, are described. For each system, the contributions of the various parameters to the resolution are examined. The results of these discussions are plotted as resolution surfaces, on which lines of constant analysis time are indicated. The experimental routes that chromatographers must take in order to apply isochronal analysis are described. 相似文献
9.
Heru Kuswanto Franois Goutaland Abdennacer Yahya Aziz Boukenter Youcef Ouerdane 《Journal of Non》2001,280(1-3):277-280
The effects of heat-treatment and ultraviolet (UV) light at 325 nm on virgin and hydrogen loaded germanosilicate optical fibers have been investigated by using laser spectroscopy technique. The luminescence band around 650 nm is sensitive to heat treatment. The hydrogen reloading of the hydrogen loaded fibers subsequent to heat treatment showed a new emission band around 570 nm. The irradiated fibers have an emission band around 383 nm which was not detected in hydrogen loaded fibers. 相似文献
10.