Academic literature on the topic 'Liquide de Dufour'

This paper deals with the examination effect of Dufour and Soret Effect on MHD heat and mass transfer with radiative heat flux in a liquid over a rotating dick. The problem is solved by HAM (Homotopy Analysis Method). The arrangement of Non-Linear Partial Differential Equations (PDEs) which administer the stream, heat and mass exchange qualities is changed into Ordinary Differential Equations (ODEs). It is discovered from the current exploration that Dufour and radiation impacts cause diminishments in the liquid temperature. The effect of suction diminishes the speed, temperature, what’s more, focus profiles essentially in the limit layer.

This exploration examines the nonlinear effect of radiation on magnet flow consisting of hybrid alloy nanoparticles in the way of stream-wise and cross flow. Many experimental, as well as theoretical explorations, demonstrated that the thermal conductivity of the regular liquid increases by up to 15 to 40% when nanomaterials are mixed with the regular liquid. This change of the thermal conductivity of the nanoliquid depends on the various characteristics of the mixed nanomaterials like the size of the nanoparticles, the agglomeration of the particles, the volume fraction, etc. Researchers have used numerous nanoparticles. However, we selected water-based aluminum alloy (AA7075) and titanium alloy (Ti6Al4V) hybrid nanomaterials. This condition was mathematically modeled by capturing the Soret and Dufour impacts. The similarity method was exercised to change the partial differential equations (PDEs) into nonlinear ordinary differential equations (ODEs). Such nonlinear ODEs were worked out numerically via the bvp4c solver. The influences of varying the parameters on the concentration, temperature, and velocity area and the accompanying engineering quantities such as friction factor, mass, and heat transport rate were obtained and discussed using graphs. The velocity declines owing to nanoparticle volume fraction in the stream-wise and cross flow directions in the first result and augment in the second result, while the temperature and concentration upsurge in the first and second results. In addition, the Nusselt number augments due to the Soret number and declines due to the Dufour number in both results, whereas the Sherwood number uplifts due to the Dufour number and shrinks due to the Soret number in both results.

AbstractThis study reveals the characteristics of chemical reaction on Marangoni mixed convective stream towards a penetrable Riga surface. The heat and mass phenomena are analysed within the sight of Dufour and Soret impacts. The administering partial differential equations system is converted into three nonlinear ordinary differential equations utilizing appropriately adjusted transformations. The resultant system of highly nonlinear equations is analytically solved by invoking the homotopy analysis method. Thereafter, the convergence of series solutions is discussed. The impact of appropriate parameters on various flow fields is thoroughly explained with the help of graphs and tables. The wall drag coefficient and relevant flux rates are arranged and discussed for dimensionless parameters. The outcomes show that the stronger Dufour effect of liquid causes a notable incremental variation in heat and mass flux, whereas an opposite trend is noted in the heat flux rate for the Soret effect. However, the mass flux is still found increasing for the stronger Soret effect.

Present study addresses Soret and Dufour effects in mixed convection MHD flow of viscoelastic liquid with chemical reaction. Flow induced by an exponential stretching sheet is addressed in the presence of magnetic field. Energy expression is modelled by exponential space dependent internal heat source, thermal radiation, and convective condition. Relevant problems are modelled by employing boundary-layer concept. The partial differential systems are reduced to ordinary differential systems, and problem is solved by homotopic technique. Physical insight of results is arranged by graphs and tables.

Thermal-diffusion and diffusion-thermo effects on combined heat and mass transfer in mixed convection boundary layer flow with aiding and opposing external flows from a vertical plate embedded in a liquid saturated porous medium with melting are investigated. The resulting system of nonlinear ordinary differential equations is solved numerically using Runge Kutta-Fehlberg with shooting techniques. Numerical results are obtained for the velocity, temperature, and concentration distributions, as well as the Nusselt number and Sherwood number for several values of the parameters, namely, the buoyancy parameter, melting parameter, Dufour effect, Soret effect, and Lewis number. The obtained results are presented graphically and in tabular form and the physical aspects of the problem are discussed.

This research deals with the mathematical model for the development of the peristaltic principle of the combination of the pressure and electroosmotic flow (EOF) of ionic liquid across microchannels with electrokinetic effects. For thermomechanical dynamics, the convective conditions on the boundary for mass and heat transfer at the walls of the channel are quantified. For the microchannel, a porous structure is presumed. Soret, Dufour, and Joule heating are also listed in the scope of the problem addressed. The corresponding equations for the ionic fluid flow, mass, and heat transfer along with the Poisson–Boltzmann equation within the electrical double layer (EDL) are studied. The exact solution has been obtained based on lubrication theory (i.e., low Reynolds number and long wavelength approximations). The channel height is therefore believed to be much higher than the electrical double layer (EDL) thickness. Various dimensionless pertinent parameters illustrate the important aspects of electroosmotically controlled flow and subsequent convective mass/heat transfer attributes in a microchannel. A linear dependency on the fluid flow rate is exhibited by the pressure drop. The analysis shows that the electroosmotic parameter gives a reducing effect on the channel permeability. The distribution of temperature and concentration is greatly affected by convective heat and mass parameters, respectively. In biomedical engineering, the application areas of the study proposed are for the design of the devices such as a microfluidic pump to pump a small amount of ionic liquids by regulating the variation in temperature and concentration.

Abstract In the present study we aim to model and examine the impact of melting and double stratification on MHD flow of Carreau liquid over a stretching sheet. Incompressible non-Newtonian liquid is electrically conducting and exposed to a constant magnetic field. The exponential space dependent internal heat source effect is incorporated in the energy expression. Mass transfer is characterized in terms of activation energy and a binary chemical reaction. In addition, Soret and Dufour phenomena are included. The boundary layer concept is utilized to simplify the governing equations. A system of ordinary differential equations is obtained through proper transformations. The coupled non-linear system is then computed by the NDSolve technique. Plots and tabulated values are arranged for interpretation of different variables. The obtained results show that the flow field is influenced appreciably by melting, the heat source, the reaction rate and the activation energy. Moreover, Nusselt and Sherwood numbers are increased by the activation energy.

Abstract In this paper, triple diffusive natural convection under Darcy flow over an inclined plate embedded in a porous medium saturated with a binary base fluid containing nanoparticles and two salts is studied. The model used for the nanofluid is the one which incorporates the effects of Brownian motion and thermophoresis. In addition, the thermal energy equations include regular diffusion and cross-diffusion terms. The vertical surface has the heat, mass and nanoparticle fluxes each prescribed as a power law function of the distance along the wall. The boundary layer equations are transformed into a set of ordinary differential equations with the help of group theory transformations. A wide range of parameter values are chosen to bring out the effect of buoyancy ratio, regular Lewis number and modified Dufour parameters of both salts and nanofluid parameters with varying angle of inclinations. The effects of parameters on the velocity, temperature, solutal and nanoparticles volume fraction profiles, as well as on the important parameters of heat and mass transfer, i.e., the reduced Nusselt, regular and nanofluid Sherwood numbers, are discussed. Such problems find application in extrusion of metals, polymers and ceramics, production of plastic films, insulation of wires and liquid packaging.

Les venins animaux, par leur richesse biochimique et la diversité de leurs cibles moléculaires, sont une source importante de molécules dont les applications potentielles sont nombreuses. La recherche de nouveaux médicaments pour remplacer certains antibiotiques devenus inefficaces face à l'apparition de résistances, est un axe fort de la recherche pharmacologique. Depuis plus de 40 ans, la découverte de toxines animales montre que les animaux venimeux peuvent être les « pharmaciens du futur ». Le venin de fourmis est encore peu étudié. Seul celui de quelques espèces a été exploré, avec à chaque fois la mise en évidence de toxines originales. L'objectif de cette thèse a été l'étude du venin de fourmis exotiques sur la base d'une approche pluridisciplinaire qui combine l'analyse biochimique et la toxinologie. Les travaux se sont articulés autour de deux axes principaux : (1) Recherche d'activités biologiques sur insectes et bactéries ; (2) Fractionnement des venins par des techniques séparatives et analyse biochimique des peptides isolés par spectrométrie de masse. Deux espèces de fourmis ont été choisies en fonction de leur mode de vie : Crematogaster striatula, une espèce arboricole et Tetramorium bicarinatum, une espèce terricole. Les différentes activités biologiques de leurs sécrétions venimeuses ont été conduites par test MTT. Le liquide de Dufour de C. striatula en plus de sa capacité à éloigner les espèces concurrentes montre une capacité à paralyser les termites de manière irréversible. Concernant le venin de T. bicarinatum, deux peptides ont été isolés et identifiés par spectrométrie de masse. La bicarinaline, peptide de 20 acides aminés et amidé à son extrémité C-terminale, s'est démarqué par son action antibactérienne à large spectre. Testée sur deux souches de staphylocoques, ce peptide se révèle aussi efficace voire plus puissant que la méllitine, peptide antimicrobien du venin d'abeille. La bicarinaline apparaît comme un candidat potentiel pour la conception de nouveaux traitements antibiotiques
Animal venoms, by their biochemical richness and diversity of molecular targets, are a highly significant source of new molecules, with numerous potential applications. A major thrust of present pharmacological research now concerns drugs to replace certain antibiotics, proven ineffective due to the appearance of resistant strains. And discoveries of animal toxins over the past 40 years or more, have shown that venomous species could be the « pharmacists of the future », with only a few species of ants' venoms having been studied, but each time resulting in the description of original toxins. The aim of this thesis has been to study the venom of tropical ants using a multidisciplinary approach combining biochemical analysis and toxinology, centred on two main areas: (1) Research into their biological activity on insects and bacteria; (2) Fractionation of venoms using separative techniques, plus biochemical analysis of the peptides isolated using mass spectrometry. Two species of ant have been chosen based on their lifestyles: Crematogaster striatula is arboricolous and Tetramorium bicarinatum, terricolous, and the different biological activities of their crude venoms have been investigated using the MTT test. The Dufour liquid of C. striatula, in addition to its ability to scare away competitors, can definitively paralyse termites. For the venom of T. bicarinatum, two peptides have been isolated, and identified using mass spectrometry. Bicarinalin, a short 20 amino acid residues C-terminally amidated peptide, was notable for its wide spectrum antibacterial activity which, when tested on two Staphylococcus strains, proved to be at least if not more potent than mellitin, the antimicrobial peptide from bee venom. Bicarinalin would thus appear to be a good candidate for the development of new antibiotic drugs

"The main objective of the paper was the pharmacognostic analysis of the microscopic and chemical species of the aerial part of the species Cerastium bulgaricum Uechtr. sin. Cerastium gracile Dufour, to establish the chemical composition and especially to identify active principles that scientifically substantiate the traditional use of the plant product. The microscopic analyses of the vegetative organs (stem and leaf) the species Cerastium bulgaricum Uechtr led to the conclusion that its histo-anatomical structure is specific to Caryophyllaceae. Following the global chemical analysis, active principles known in the literature for the antioxidant potential were identified. Following the preliminary quantitative determinations (drying loss, determination of soluble substances) results comparable to those in the literature on the content of volatile substances and soluble substances were obtained. The separation, identification and quantification of poliphenols compounds were made through high performance of liquid chromatography (HPLC), standardized method according to USP30-NF25 Monograph"

This work deals with a numerical study of simultaneous heat and mass transfer with phase change in an inclined channel formed by two parallel plates. The lower one is covered by a thin liquid water film and the upper one is considered impermeable. The plates are maintained at a constant temperature TW. Ambient air with uniform dry bulb temperature Tin and relative humidity φin enters the channel with a uniform upward velocity Uin. The liquid film is assumed to be extremely thin and its temperature is equal to the wall temperature. Steady state conditions are considered and the flow is assumed to be laminar. Viscous dissipation, radiation heat transfer and other secondary effects (pressure work, energy transport by the inter-diffusion of species, Dufour and Soret effects) are neglected. The physical properties are taken constant except for the density in the body forces, which is considered to be a linear function of temperature and mass fraction. Results show that buoyancy forces have an important effect on the hydrodynamic, thermal and mass fraction fields and this effect depends on the channel inclination. A flow reversal chart and analytical correlations for the corresponding critical values of the thermal and solutal Grashof numbers are presented for different channel inclinations.