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121.
In this paper, an analytical study about the effect of a falling gas–liquid absorption film temperature on entropy generation is carried out. Entropy generation formulations due to viscous effects and mass transfer are derived. Results in terms of viscous, mass transfer and total irreversibilities are graphically presented and discussed. 相似文献
122.
MOUSSAOUI Abdelkrim KHODJA Brahim 《偏微分方程(英文版)》2009,22(2):111-126
In this paper, we study the existence of nontrivial solutions for the problem
{-△u=f(x,u,v)+h1(x)in Ω
-△v=g(x,u,v)+h2(x)inΩ
u=v=0 onδΩ
where Ω is bounded domain in R^N and h1,h2 ∈ L^2 (Ω). The existence result is obtained by using the Leray-Schauder degree under the following condition on the nonlinearities f and g:
{lim s,|t|→+∞f(x,s,t)/s=lim |s|,t→+∞g(x,s,t)/t=λ+1 uniformly on Ω,
lim -s,|t|→+∞f(x,s,t)/s=lim |s|,-t→+∞g(x,s,t)/t=λ-,uniformly on Ω,
where λ+,λ-∈(0)∪σ(-△),σ(-△)denote the spectrum of -△. The cases (i) where λ+ = λ_ and (ii) where λ+≠λ_ such that the closed interval with endpoints λ+,λ_ contains at most one simple eigenvatue of -△ are considered. 相似文献
{-△u=f(x,u,v)+h1(x)in Ω
-△v=g(x,u,v)+h2(x)inΩ
u=v=0 onδΩ
where Ω is bounded domain in R^N and h1,h2 ∈ L^2 (Ω). The existence result is obtained by using the Leray-Schauder degree under the following condition on the nonlinearities f and g:
{lim s,|t|→+∞f(x,s,t)/s=lim |s|,t→+∞g(x,s,t)/t=λ+1 uniformly on Ω,
lim -s,|t|→+∞f(x,s,t)/s=lim |s|,-t→+∞g(x,s,t)/t=λ-,uniformly on Ω,
where λ+,λ-∈(0)∪σ(-△),σ(-△)denote the spectrum of -△. The cases (i) where λ+ = λ_ and (ii) where λ+≠λ_ such that the closed interval with endpoints λ+,λ_ contains at most one simple eigenvatue of -△ are considered. 相似文献
123.
S. Armagan Tarim Brahim Hnich Steven Prestwich Roberto Rossi 《Annals of Operations Research》2009,171(1):77-99
Real-life management decisions are usually made in uncertain environments, and decision support systems that ignore this uncertainty
are unlikely to provide realistic guidance. We show that previous approaches fail to provide appropriate support for reasoning
about reliability under uncertainty. We propose a new framework that addresses this issue by allowing logical dependencies
between constraints. Reliability is then defined in terms of key constraints called “events”, which are related to other constraints
via these dependencies. We illustrate our approach on three problems, contrast it with existing frameworks, and discuss future
developments. 相似文献
124.
A new formulation is presented for the modeling of immiscible compressible two-phase flow in porous media taking into account
gravity, capillary effects, and heterogeneity. The formulation is intended for the numerical simulation of multidimensional
flows and is fully equivalent to the original equations, contrary to the one introduced in Chavent and Jaffré (Mathematical
Models and Finite Elements for Reservoir Simulation, 1986). The main feature of this formulation is the introduction of a
global pressure. The resulting equations are written in a fractional flow formulation and lead to a coupled system which consists
of a nonlinear parabolic (the global pressure equation) and a nonlinear diffusion–convection one (the saturation equation)
which can be efficiently solved numerically. A finite volume method is used to solve the global pressure equation and the
saturation equation for the water and gas phase in the context of gas migration through engineered and geological barriers
for a deep repository for radioactive waste. Numerical results for the one-dimensional problem are presented. The accuracy
of the fully equivalent fractional flow model is demonstrated through comparison with the simplified model already developed
in Chavent and Jaffré (Mathematical Models and Finite Elements for Reservoir Simulation, 1986). 相似文献
125.
Stochastic backgrounds of gravitational waves are intrinsic fluctuations of spacetime which lead to an unavoidable decoherence mechanism. This mechanism manifests itself as a degradation of the contrast of quantum interferences. It defines an ultimate decoherence border for matter-wave interferometry using larger and larger molecules. We give a quantitative characterization of this border in terms of figures involving the gravitational environment as well as the sensitivity of the interferometer to gravitational waves. The known level of gravitational noise determines the maximal size of the molecular probe for which interferences may remain observable. We discuss the relevance of this result in the context of ongoing progresses towards more and more sensitive matter-wave interferometry. 相似文献
126.
Jazia Sriti Iness Bettaieb Olfa Bachrouch Thierry Talou Brahim Marzouk 《Arabian Journal of Chemistry》2019,12(7):1765-1773
This study was designed to examine the effect of operating conditions on essential oil composition and antioxidant activity of coriander cakes. Twenty-nine components were determined in essential oils, which were mostly alcohol monoterpenes. The highest essential oil yields (0.11%) were obtained by the nozzle diameter of 5 mm. The main components of cake essential oil linalool, γ-terpinene, geranyl acetate, linalyl acetate and camphor showed significant variations with different nozzle diameter.The total phenol contents and condensed flavonoid contents varied between different nozzle diameters; the highest values obtained of small diameters (5 and 6 mm). Significant differences were also found in total tannin contents among different nozzle diameters. The total phenol contents decreased significantly (p < 0.05) when increased the nozzle diameter to 9 mm and reached 9.11 mg GAE/g.The screening of antioxidant activity of the different coriander cakes using the di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium radical (DPPH) assay showed an appreciable reduction of the stable radical DPPH, although small nozzle diameter was the most efficient method with an IC50 reached of 55 μg/ml as compared with bigger diameter (IC50 = 88 μg/ml).All the extracts had lower β-carotene bleaching activity than that of synthetic antioxidant BHA and BHT. Coriander cake extracts presented a very low reducing power ability (EC50 ≈ 700 μg/ml) compared to ascorbic acid (EC50 = 40 μg/ml). 相似文献
127.
Bla Bakalar Brahim Heddi Emmanuelle Schmitt Yves Mechulam Anh Tun Phan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2353-2357
Recently, we observed the first example of a left‐handed G‐quadruplex structure formed by natural DNA, named Z‐G4. We analysed the Z‐G4 structure and inspected its primary 28‐nt sequence in order to identify motifs that convey the unique left‐handed twist. Using circular dichroism spectroscopy, NMR spectroscopy, and X‐ray crystallography, we revealed a minimal sequence motif of 12 nt (GTGGTGGTGGTG) for formation of the left‐handed DNA G‐quadruplex, which is found to be highly abundant in the human genome. A systematic analysis of thymine loop mutations revealed a moderate sequence tolerance, which would further broaden the space of sequences prone to left‐handed G‐quadruplex formation. 相似文献
128.
Exchanging light pulses to perform accurate space-time positioning is a paradigmatic issue of physics. It is ultimately limited by the quantum nature of light, which introduces fluctuations in the optical measurements and leads to the so-called standard quantum limit (SQL). We propose a new scheme combining homodyne detection and mode-locked femtosecond lasers that lead to a new SQL in time transfer, potentially reaching the yoctosecond range (10(-21)-10(-24) s). We demonstrate that this already very low SQL can be overcome using appropriately multimode squeezed light. Benefitting from the large number of photons and from the optimal choice of both the detection strategy and of the quantum resource, the proposed scheme represents a significant potential improvement in space-time positioning. 相似文献
129.
The direction of propagation followed by a monochromatic beam in a periodic structure is generally deduced from the isofrequency diagram, which is related to the group velocity. However, the group velocity is the derivative of omega with respect to the wavenumber, while the behavior of the beam should depend on omega only. In the subwavelength regime, a method for choosing the relevant branch of the isofrequency diagram and relying on the behavior of the system at omega only is described. 相似文献
130.
El Antri A Messouri I Tlemçani RC Bouktaib M El Alami R El Bali B Lachkar M 《Molecules (Basel, Switzerland)》2004,9(7):568-573
The known flavonoid chrysin-7-O-(beta-D-glycopyranoside) (chrysin glucoside,1) as a major fraction and a new glycoside flavone, chrysin-7-O-beta-D-[(6"-acetyl)glycopyranoside] (2) were isolated from the flowers and leaves of Calycotome Villosa Subsp. Intermedia, They were identified by UV-Vis, 1R, (1)H-, (13)C-NMR and ESI-MS. 相似文献