Articles de revues : « Thermo-diffusion system »

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Krehel, Oleh, Toyohiko Aiki et Adrian Muntean. « Homogenization of a thermo-diffusion system with Smoluchowski interactions ». Networks & ; Heterogeneous Media 9, n^o 4 (2014) : 739–62. http://dx.doi.org/10.3934/nhm.2014.9.739.

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Sohail, Muhammad, Umair Ali, Fatema Tuz Zohra, Wael Al-Kouz, Yu-Ming Chu et Phatiphat Thounthong. « Utilization of updated version of heat flux model for the radiative flow of a non-Newtonian material under Joule heating : OHAM application ». Open Physics 19, n^o 1 (1 janvier 2021) : 100–110. http://dx.doi.org/10.1515/phys-2021-0010.

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Abstract This study reports the thermal analysis and species transport to manifest non-Newtonian materials flowing over linear stretch sheets. The heat transfer phenomenon is presented by the Cattaneo–Christov definition of heat flux. Mass transportation is modeled using traditional Fick’s second law. In addition, the contribution of Joule heating and radiation to thermal transmission is also considered. Thermo-diffusion and diffusion-thermo are significant contributions involved in thermal transmission and species. The physical depiction of the scenario under consideration is modeled through the boundary layer approach. Similar analysis has been made to convert the PDE model system into the respective ODE. Then, the transformed physical expressions are calculated for momentum, thermal, and species transport within the boundary layer. The reported study is a novel contribution due to the combined comportment of thermal relaxation time, radiation, Joule heating, and thermo-diffusion, which are not yet explored. Several engineering systems are based on their applications and utilization.

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Hamid, R. A., W. M. K. A. Wan Zaimi, N. M. Arifin, N. A. A. Bakar et B. Bidin. « Thermal Diffusion and Diffusion Thermo Effects on MHD Thermosolutal Marangoni Convection Boundary Layer Flow over a Permeable Surface ». Journal of Applied Mathematics 2012 (2012) : 1–14. http://dx.doi.org/10.1155/2012/750939.

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The problem of thermal diffusion and diffusion thermo effects on thermosolutal Marangoni convection flow of an electrically conducting fluid over a permeable surface is investigated. Using appropriate similarity transformations, the governing system of partial differential equation is transformed to a set of nonlinear ordinary differential equations, then solved numerically using the Runge-Kutta-Fehlberg method. The effects of thermal diffusion and diffusion thermo, magnetic field parameter, thermosolutal surface tension ratio, and suction/injection parameter on the flow field, heat transfer characteristic, and concentration are thoroughly examined. Numerical results are obtained for temperature and concentration profiles as well as the local Nusselt and Sherwood numbers are presented graphically and analyzed. It is found that these governing parameters affect the variations of the temperature and concentration and also the local Nusselt and Sherwood numbers.

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Martuzans, B., et Yu Skryl. « Numerical Simulation of Charge Transfer in Shocked Silicon at low Pressure ». Latvian Journal of Physics and Technical Sciences 45, n^o 4 (1 janvier 2008) : 33–46. http://dx.doi.org/10.2478/v10047-008-0018-2.

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Numerical Simulation of Charge Transfer in Shocked Silicon at low PressureA numerical method for simulation of electron and hole diffusion in silicon in the temperature gradient created by the shock load is developed. To analyze the transfer process, a complete system of electro-thermo-diffusion equations for charge carriers was solved based on the Poisson equation. The numerical solution was obtained using the difference methods developed for semiconductor devices. The comparison of the experimental results with the numerical calculation shows a good correlation, which means that the thermo-diffusion of charge carriers in the shock wave front is the main factor responsible for polarization in the shocked silicon.

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Khan, Sohail A., et Tasawar Hayat. « Entropy Analysis for Hydromagnetic Darcy–Forchheimer Flow Subject to Soret and Dufour Effects ». Mathematical and Computational Applications 27, n^o 5 (19 septembre 2022) : 80. http://dx.doi.org/10.3390/mca27050080.

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Here, our main aim is to examine the impacts of Dufour and Soret in a radiative Darcy–Forchheimer flow. Ohmic heating and the dissipative features are outlined. The characteristics of the thermo-diffusion and diffusion-thermo effects are addressed. A binary chemical reaction is deliberated. To examine the thermodynamical system performance, we discuss entropy generation. A non-linear differential system is computed by the finite difference technique. Variations in the velocity, concentration, thermal field and entropy rate for the emerging parameters are scrutinized. A decay in velocity is observed for the Forchheimer number. Higher estimation of the magnetic number has the opposite influence for the velocity and temperature. The velocity, concentration and thermal field have a similar effect on the suction variable. The temperature against the Dufour number is augmented. A decay in the concentration is found against the Soret number. A similar trend holds for the entropy rate through the radiation and diffusion variables. An augmentation in the entropy rate is observed for the diffusion variable.

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KHAN, SHEIKH IRFANULLAH, SYED TAUSEEF MOHYUD-DIN et BANDAR BIN-MOHSIN. « THERMO-DIFFUSION AND DIFFUSO-THERMO EFFECTS ON MHD SQUEEZING FLOW BETWEEN PARALLEL DISKS ». Surface Review and Letters 24, n^o 02 (30 janvier 2017) : 1750022. http://dx.doi.org/10.1142/s0218625x17500226.

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In this article, Magnetohydrodynamic (MHD) squeezing flow between two parallel disks is considered. The upper disk is taken to be solid and the lower one is permeable. Soret and Dufour effects are measured to explore the thermal-diffusion and diffusion-thermo effects. Governing PDEs are converted into system of ODEs with the support of suitable similarity transforms. Homotopy analysis method (HAM) has been employed to obtain the expressions for velocity, temperature and concentration profiles. Effects of different emerging parameters such as squeezing number [Formula: see text], Hartman number [Formula: see text], Prandtl number Pr, Eckert number Ec, dimensionless length [Formula: see text] and Schmidt number Sc on the flow are also discussed with the help of graphs for velocity, temperature and concentration. The local Nusselt and Sherwood numbers along with convergence of the series solutions are presented with the help of graphs. From the results obtained, we observed that the physical quantities like skin friction coefficient increases with increasing value of Hartmann number [Formula: see text] in the blowing case [Formula: see text] whereas a fall is observed in the suction case [Formula: see text]. However, the rate of heat transfer at upper wall increases with increasing values of Dufour number Du and Soret number Sr for both the suction [Formula: see text] and blowing flow [Formula: see text], whereas, for the larger values of Dufour number Du and smaller values of Soret number Sr, a rapid fall is observed in Sherwood number Sh for both the suction [Formula: see text] and blowing [Formula: see text] cases. A numerical solution is obtained by employing Runge–Kutta method of order four (RK-4) to check the validity and reliability of the developed algorithm. A well agreement is found between both the solutions.

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Pochiraju, K. V., et G. P. Tandon. « Modeling Thermo-Oxidative Layer Growth in High-Temperature Resins ». Journal of Engineering Materials and Technology 128, n^o 1 (1 août 2005) : 107–16. http://dx.doi.org/10.1115/1.2128427.

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This paper describes modeling of degradation behavior of high-temperature polymers under thermo-oxidative aging conditions. Thermo-oxidative aging is simulated with a diffusion-reaction model in which temperature, oxygen concentration, and weight-loss effects are considered. A parametric reaction model based on a mechanistic view of the reaction is used for simulating reaction-rate dependence on the oxygen availability in the polymer. Macroscopic weight-loss measurements are used to determine the reaction and polymer consumption parameters. The diffusion-reaction partial differential equation system is solved using Runge-Kutta methods. Simulations illustrating oxidative layer growth in a high-temperature PMR-15 polyimide resin system under isothermal conditions are presented and correlated with experimental observations of oxidation layer growth. Finally, parametric studies are conducted to examine the sensitivity of material parameters in predicting oxidation development.

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Aouadi, Moncef, et Alberto Castejón. « Properties of global and exponential attractors for nonlinear thermo-diffusion Timoshenko system ». Journal of Mathematical Physics 60, n^o 8 (août 2019) : 081503. http://dx.doi.org/10.1063/1.5066224.

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Khan, Najeeb Alam, Shahnila Aziz et Saif Ullah. « Entropy Generation on MHD Flow of Powell-Eyring Fluid Between Radially Stretching Rotating Disk with Diffusion-Thermo and Thermo-Diffusion Effects ». Acta Mechanica et Automatica 11, n^o 1 (1 mars 2017) : 20–32. http://dx.doi.org/10.1515/ama-2017-0004.

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Abstract An investigation is performed for an alyzing the effect of entropy generation on the steady, laminar, axisymmetric flow of an incompressible Powell-Eyring fluid. The flow is considered in the presence of vertically applied magnetic field between radially stretching rotating disks. The Energy and concentration equation is taking into account to investigate the heat dissipation, Soret, Dufour and Joule heating effects. To describe the considered flow non-dimensionalized equations, an exact similarity function is used to reduce a set of the partial differential equation into a system of non-linear coupled ordinary differential equation with the associated boundary conditions. Using homotopy analysis method (HAM), an analytic solution for velocity, temperature and concentration profiles are obtained over the entire range of the imperative parameters. The velocity components, concentration and temperature field are used to determine the entropy generation. Plots illustrate important results on the effect of physical flow parameters. Results obtained by means of HAM are then compared with the results obtained by using optimized homotopy analysis method (OHAM). They are in very good agreement.

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Sheri, Siva Reddy, Chamkha Ali. J. et Anjan Kumar Suram. « Thermal-diffusion and diffusion-thermo effects on MHD natural convective flow through porous medium in a rotating system with ramped temperature ». International Journal of Numerical Methods for Heat & ; Fluid Flow 27, n^o 11 (6 novembre 2017) : 2451–80. http://dx.doi.org/10.1108/hff-09-2016-0349.

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Purpose The purpose of this paper is to analyze the thermal-diffusion and diffusion-thermo effects on magnetohydrodynamics (MHD) natural convective flow through porous medium in a rotating system with ramped temperature. Design/methodology/approach Using the non-dimensional variables, the flow governing equations along with corresponding initial and boundary conditions have been transformed into non-dimensional form. These non-dimensional partial differential equations are solved by using finite element method. This method is powerful and stable. It provides excellent convergence and flexibility in providing solutions. Findings The effects of Soret number, Dufour number, rotation parameter, magnetic parameter, Hall current parameter, permeability parameter, thermal Grashof number, solutal Grashof number, Prandtl number, thermal radiation parameter, heat absorption parameter, Schmidt number, chemical reaction parameter and time on the fluid velocities, temperature and concentration are represented graphically in a significant way and the influence of pertinent flow governing parameters on the skin frictions and Nusselt number are presented in tabular form. On the other hand, a comparison for validation of the numerical code with previously published work is performed, and an excellent agreement is observed for the limited case existing literature. Practical implications A very useful source of information for researchers on the subject of MHD flow through porous medium in a rotating system with ramped temperature. Originality/value The problem is moderately original, as it contains many effects like thermal-diffusion (Soret) and diffusion-thermo (Dufour) effects and chemical reaction.

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Aiki, Toyohiko, et Adrian Muntean. « Large-time behavior of solutions to a thermo-diffusion system with Smoluchowski interactions ». Journal of Differential Equations 263, n^o 5 (septembre 2017) : 3009–26. http://dx.doi.org/10.1016/j.jde.2017.04.024.

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Motsa, S. S., et S. Shateyi. « Successive Linearization Analysis of the Effects of Partial Slip, Thermal Diffusion, and Diffusion-Thermo on Steady MHD Convective Flow due to a Rotating Disk ». Mathematical Problems in Engineering 2012 (2012) : 1–15. http://dx.doi.org/10.1155/2012/397637.

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We proposed a general formulation of the successive linearization method for solving highly nonlinear boundary value problem arising in rotating disk flow. The problem was studied under the effects of partial slip, thermal diffusion, and diffusion-thermo. The governing fundamental conservation equations of mass, momentum, angular momentum, energy, and concentration are transformed into a system of ordinary differential equations by means of similarity transformations. A parametric study illustrating the influence of the magnetic field, slip factor, Eckert number, Dufour and Soret numbers was carried out.

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Magri, Luca, et Matthew P. Juniper. « Global modes, receptivity, and sensitivity analysis of diffusion flames coupled with duct acoustics ». Journal of Fluid Mechanics 752 (4 juillet 2014) : 237–65. http://dx.doi.org/10.1017/jfm.2014.328.

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AbstractIn this theoretical and numerical paper, we derive the adjoint equations for a thermo-acoustic system consisting of an infinite-rate chemistry diffusion flame coupled with duct acoustics. We then calculate the thermo-acoustic system’s linear global modes (i.e. the frequency/growth rate of oscillations, together with their mode shapes), and the global modes’ receptivity to species injection, sensitivity to base-state perturbations and structural sensitivity to advective-velocity perturbations. Some of these could be found by finite difference calculations but the adjoint analysis is computationally much cheaper. We then compare these with the Rayleigh index. The receptivity analysis shows the regions of the flame where open-loop injection of fuel or oxidizer will have the greatest influence on the thermo-acoustic oscillation. We find that the flame is most receptive at its tip. The base-state sensitivity analysis shows the influence of each parameter on the frequency/growth rate. We find that perturbations to the stoichiometric mixture fraction, the fuel slot width and the heat-release parameter have most influence, while perturbations to the Péclet number have the least influence for most of the operating points considered. These sensitivities oscillate, e.g. positive perturbations to the fuel slot width either stabilizes or destabilizes the system, depending on the operating point. This analysis reveals that, as expected from a simple model, the phase delay between velocity and heat-release fluctuations is the key parameter in determining the sensitivities. It also reveals that this thermo-acoustic system is exceedingly sensitive to changes in the base state. The structural-sensitivity analysis shows the influence of perturbations to the advective flame velocity. The regions of highest sensitivity are around the stoichiometric line close to the inlet, showing where velocity models need to be most accurate. This analysis can be extended to more accurate models and is a promising new tool for the analysis and control of thermo-acoustic oscillations.

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Alaa Jaber Abuiyada, Nabil Tawfik Eldabe, Mohamed Yahya Abou-zeid et Sami Mohamed El Shaboury. « Effects of Thermal Diffusion and Diffusion Thermo on a Chemically Reacting MHD Peristaltic Transport of Bingham Plastic Nanofluid ». Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 98, n^o 2 (29 septembre 2022) : 24–43. http://dx.doi.org/10.37934/arfmts.98.2.2443.

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In this work we investigated the solution of the peristaltic motion of Bingham plastic nanofluid through a vertical symmetric channel. The system is stressed by an external strong magnetic field to produce a hall currents. Moreover, we involved effects of Joule heating, radiation, chemical reaction and couple stresses. Further, we considered Soret and Dufour effects. This phenomenon is represented mathematically by a system of non-linear equations which describe the problem. We used the approximation of low Reynolds number and long-wavelength approximation to simplify the governing equations. Then, we used Homotopy perturbation method (HPM) to solve the equations. We sketched a graph for the influence of various parameters on velocity, temperature and nanoparticles concentration profiles and then discussed them physically. Finding revealed that an increase of Bingham number and the regularization parameter of Bingham fluid decreases the velocity and increases the temperature, but radiation parameter has an opposite relative to them. Also, we found that increasing of chemical reaction parameter reduces the nanoparticles concentration, whereas the reverse is the case when the reaction order is increased.

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Zenkour, Ashraf M. « Thermo-diffusion of solid cylinders based upon refined dual-phase-lag models ». Multidiscipline Modeling in Materials and Structures 16, n^o 6 (23 avril 2020) : 1417–34. http://dx.doi.org/10.1108/mmms-12-2019-0213.

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PurposeThe thermo-diffusion analysis of an isotropic cylinder under thermal flux and chemical potential impacts has been discussed. Improvements of Green and Naghdi generalized thermoelasticity theory have been proposed.Design/methodology/approachSome models with and without energy dissipation have been presented as well as the simple forms of Green–Naghdi (G–N) theories. These novel multi- and single-/dual-phase-lag models are presented to investigate the thermo-diffusion of the solid cylinder. The closed-form solution of thermo-diffusion governing equations of solid cylinder has been obtained to deduce all field variables.FindingsA comparison study between the simple G–N II and III models and their improved models has been presented. The validations of outcomes are acceptable and so benchmarks are reported to help other investigators in their future comparisons.Originality/valueThe modified Green and Naghdi theories of types II and III are presented to get novel and accurate models of single- and dual-phase-lag of multiterms. The heat of mass diffusion equation as well as the constitutive equations for the stresses and chemical potential of a solid cylinder is added to the present formulation. The system of three differential coupled equations is solved, and all field variables are obtained for the thermal diffusion of the solid cylinder. Some validation examples and applications are presented to compare the simple and modified Green and Naghdi theories of types II and III. Sample plots are illustrated along the radial direction of the solid cylinder. Some results are tabulated to serve as benchmark results for future comparisons with other investigators. The reported and illustrated results show that the simple G–N II and III models yield the largest values of all field quantities. The single-phase-lag models give the smallest values. However, the dual-phase-lag model yields results that are intermediate between those of the simple and single-phase-lag G–N models.

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Liu, Ying Ying, Ying Jie Qiao, Ai Dong Liu et Yan Wang. « Binder System Removal from Laminated Boron Carbide Ceramics ». Applied Mechanics and Materials 151 (janvier 2012) : 388–91. http://dx.doi.org/10.4028/www.scientific.net/amm.151.388.

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The binder system removal was studied in a laminated B4C ceramics prepared by tape casting and lamination with castor oil, polyvinyl butyral(PVB) and di-n-butyl phthalate (DBP) as dispersant, binder and plasticizer, respectively. Thermo gravimetric analysis and Fourier transform infrared spectromer was used to examine the degradation of the binder system. The degradation behavior of the pure organics, single sheet and laminated B4C body were investigated. The results indicate that nitrog4en was selected as the binder system removal atmosphere and two decomposition temperature ranges was obtained for organics. A model based on diffusion can be used to predict the binder system removal time for a certain thickness of laminated B4C.

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Bykov, V., et A. Koksharov. « Study of internal flame front structure of accelerating hydrogen/oxygen flames with detailed chemical kinetics and diffusion models ». Mathematical Modelling of Natural Phenomena 13, n^o 6 (2018) : 53. http://dx.doi.org/10.1051/mmnp/2018079.

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The problem of Detonation to Deflagration (DDT) is revisited. A stoichiometric hydrogen/oxygen combustion system is considered. The study focuses on the investigation of the system solution in the thermo-chemical state space of the system. The Σ model is implemented to study the flame acceleration and DDT in 1D formulation. The model was suggested to take into account wrinkling of the flame surface. In this way, the problem becomes treatable numerically even with the detailed mechanism of chemical kinetics and with detailed models for molecular diffusion. In order to treat and integrate the model a recently developed numerical scheme to deal with very stiff systems both in time and in space is introduced and applied. Typical system solution profiles of the ignition, quasi-deflagration, flame acceleration, DDT and detonation stages are considered to study the structure of the flame front in the system thermo-chemical state space. The results of computations show that at the stages of the ignition, deflagration and acceleration the flame structure in the state/composition space moderately depends on Σ, however, significant influence shows up during later stages of the flame acceleration and DDT. Moreover, the path of the solution in the detonation regime significantly deviates from that of deflagration. This means that accurate and quantitative study of the DDT is not possible without reliable mechanisms of chemical kinetics able to describe the system state space during the transient.

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JOU, DAVID, JOSé CASAS-VáZQUEZ, JUSTINO R. MADUREIRA, ÁUREA R. VASCONCELLOS et ROBERTO LUZZI. « ENERGY TRANSPORT IN A MESOSCOPIC THERMO-HYDRODYNAMICS ». International Journal of Modern Physics B 15, n^o 32 (30 décembre 2001) : 4211–22. http://dx.doi.org/10.1142/s021797920100783x.

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We analyse the question of transport of energy in fluids, done, for specificity, for the case of a system of fermions interacting with a boson system. Resorting to a generalized thermo-hydrodynamics based on a nonequilibrium ensemble formalism, the so-called MaxEnt-NESOM, we derive the equations of evolution for the energy density and its first and second fluxes in a truncated description. We obtain a generalized Fourier's law, relating the flux of energy with extended thermodynamic forces which include contributions of the Guyer–Krumhansl–type. An extended evolution equation for the density of energy is derived, and the conditions when it goes over restricted forms of the type of the telegraphist equation and the traditional Fourier heat diffusion equation are discussed.

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Sun, Yu Ping, et Neng Zhu. « Study on Assessment of High Temperature and Humidity in Working Environment on Human Health ». Advanced Materials Research 610-613 (décembre 2012) : 739–42. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.739.

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In this study, a series of references on human physiology and psychology response to hot and humid environments were analyzed. On basis of the thermo metabolism system, energy metabolism system, cardiovascular system and respiratory system, impact mechanism of high temperature and humidity on human health was presented. The results indicate that the high temperature and humidity in working environment have significant impact on human health. The high temperature and humidity cause the reducing of temperature difference in vitro and in vivo, the difficult of metabolic heat diffusion, the significant increasing of energy metabolism and oxygen consumption, heart failure, hypoxia and other physiological responses.

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Payá, J., A. Freni, J. M. Corberán et V. Compañ. « Hydriding kinetics of LaNi₅ using Nucleation-growth and Diffusion Models ». Journal of New Materials for Electrochemical Systems 15, n^o 4 (22 février 2012) : 293–300. http://dx.doi.org/10.14447/jnmes.v15i4.50.

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In this paper, the hydriding kinetics of a LaNi5 alloy have been measured with a thermo-gravimetric system. The rate controlling steps have been analyzed. In the α + β phase, a first order Johnson-Mehl-Avrami model provides a good agreement with the measurements. In the ? phase, the previous approach shows that the reaction becomes progressively controlled by the diffusion of hydrogen atoms through the hydride. In order to support this hypothesis, a Crank-Nicholson diffusion model has also been applied and achieved good results. The results show that the transition in the rate controlling mechanism takes place before the static pressure-composition isotherms are reached.

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Bai, Weimin, Guanglong Xu, Mingyue Tan, Zhijie Yang, Lijun Zeng, Di Wu, Libin Liu et Ligang Zhang. « Diffusivities and Atomic Mobilities in bcc Ti-Mo-Zr Alloys ». Materials 11, n^o 10 (8 octobre 2018) : 1909. http://dx.doi.org/10.3390/ma11101909.

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β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand and manipulate the phase transformation and microstructure evolution during homogenization and precipitation. In this work, diffusion couple technique was employed to investigate the diffusion behaviors in bcc Ti-Mo-Zr alloys. The diffusion couples were prepared and annealed at 1373 K for 72 h and 1473 K for 48 h, respectively. The composition-distance profiles were obtained via electron probe micro-analysis (EPMA). The chemical diffusion coefficients and impurity diffusion coefficients were extracted via the Whittle-Green method and Hall method. The obtained diffusion coefficients were assessed to develop a self-consistent atomic mobility database of bcc phase in Ti-Mo-Zr system. The calculated diffusion coefficients were compared with the experimental results. They showed good agreement. Simulations were implemented by Dictra Module in Thermo-Calc software. The predicted composition-distance profiles, inter-diffusion flux, and diffusion paths are consistent with experimental data, confirming the accuracy of the database.

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Рабчинский, М. К., Е. Д. Эйдельман, А. Я. Виноградов, С. А. Грудинкин et А. Т. Дидейкин. « Углеродная наноструктура для термоэлектрического генератора ». Письма в журнал технической физики 45, n^o 7 (2019) : 33. http://dx.doi.org/10.21883/pjtf.2019.07.47534.17630.

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AbstractWe demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed technology ensures uniformity and rather small thickness of these films and allows them to be formed on a diamond-like film substrate with deposited contacts at acceptable interface. Measurements show that the electron-phonon drag effect in this system ensures thermo-emf values about 100 times as large as those provided by the diffusion process. Arrangement of the graphite-like material on a diamond-like film substrate also favors increase in the thermo-emf, which is a manifestation of the electron–ballistic phonon drag. It is established that conditions necessary for the creation of a thermoelectric generator can be achieved based on the proposed carbon nanostructures.

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Jha, Basant K., Umaru Mohammed et Abiodun O. Ajibade. « Dufour and Soret Effects on Melting from a Vertical Plate Embedded in Saturated Porous Media ». Journal of Applied Mathematics 2013 (2013) : 1–9. http://dx.doi.org/10.1155/2013/182179.

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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.

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Ali, Farhan, Cherlacola Srinivas Reddy, A. Zaib, M. Faizan, Khaled Al-Farhany et Alphonsa Mathew. « 3D flow of MHD tangent hyperbloic nanoliquid with the combined effect of soret and dufour effect past a heated convective stretching sheet ». International Journal of Hydrology 6, n^o 4 (5 juillet 2022) : 108–16. http://dx.doi.org/10.15406/ijh.2022.06.00315.

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Convective heat transport gives the remarkable behaviour in the many industrial procedure owing it mechanical behaviours of the system. A study has been obtained to analyse thermal radiative flow on unsteady MHD tangent hyperbolic nanoliquid near a stagnation point under viscous dissipation and chemical reaction. Also, thermal-diffusion and thermo-diffusion have been considered. The nonlinear PDE’s are altered into a set of ODE’s through suitable transformation and which are then numerically utilized. Further, numerical outputs for friction factor, Nusselt number and Sherwood are produced in table. Moreover, velocity distribution is increasing for a larger value of We and reduces for n. Moreover, similar behaviour is noted for temperature profile. A comparison with accessible outcomes for limited case is obtained with tremendous achievement.

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Gao, Xin-Yi, Yong-Jiang Guo et Wen-Rui Shan. « Scaling and hetero-/auto-Bäcklund transformations with solitons of an extended coupled (2+1)-dimensional Burgers system for the wave processes in hydrodynamics and acoustics ». Modern Physics Letters B 34, n^o 34 (16 novembre 2020) : 2050389. http://dx.doi.org/10.1142/s0217984920503893.

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The Burgers-type equations are applied to oceanography, hydrodynamic turbulence, gas dynamics, shock-wave formation, acoustic transmission structure, boundary-layer behavior, continuum-traffic simulation, convection-dominated diffusion, wave formation in the thermo-elastic media, vorticity transport, dispersion in the porous media, particle sedimentation in fluid suspension, colloid evolution, and so forth. Hereby, taking into account the wave processes in hydrodynamics and acoustics, we investigate an extended coupled (2+1)-dimensional Burgers system, and with symbolic computation, work out a scaling transformation, two hetero-Bäcklund transformations and two auto-Bäcklund transformations, with the soliton solutions. Our results are dependent on the coefficients in the system.

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Sengupta, Sanjib, et Nazibuddin Ahmed. « MHD free convective mass transfer flow of radiative uniform heat generation (absorption) fluid through a wavy permeable channel in the presence of Soret and Dufour effects ». Canadian Journal of Physics 95, n^o 1 (janvier 2017) : 44–58. http://dx.doi.org/10.1139/cjp-2014-0599.

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The paper aims to present analytically the parametric effect of thermo-diffusion (Soret) and diffusion-thermo (Dufour) effects on a two-dimensional steady magnetohydrodynamic (MHD) free convective heat and mass transfer flow of a reasonably viscous incompressible electrically conducting fluid in the presence of thermal radiation and zeroth-order heat generation (absorption) effects. The governing system of partial differential equations with favorable boundary conditions is first non-dimensionalized and then solved by splitting the solution into a mean part and a perturbed part. Ostrach’s static fluid model is used to solve the mean part of the solution, while long wave approximations are employed to deal with the perturbed part of the solution. It is observed that an increase in parametric values of Soret and Dufour numbers as well as wall temperature and wall concentration parameters increase the primary velocity, while the cross flow velocity is found to be decreasing because of the increase in values of Soret and Dufour numbers. The primary and the cross flow velocities are both found to be increasing because of the increase in the thermal radiation parameter. The Nusselt number at the plates decreases because of the increase in the wall temperature parameter. It is also interesting to observe that the temperature and concentration of fluid particles near a plate are regulated by the influence of wall temperature and wall concentration parameters.

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Степаненко, В. М., А. И. Медведев, И. А. Корпушенков, Н. Л. Фролова et В. Н. Лыкосов. « A river routing scheme for an Earth system model ». Numerical Methods and Programming (Vychislitel'nye Metody i Programmirovanie), n^o 4 (10 septembre 2019) : 396–410. http://dx.doi.org/10.26089/nummet.v20r435.

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Представлена новая версия модели ИВМ РАНМГУ деятельного слоя суши с описанием термогидродинамики речных потоков. Динамика рек представлена уравнениями диффузионной волны, термика одномерным уравнением притока тепла. Объектноориентированная реализация блока речной сети позволяет использовать произвольные решатели одномерных задач речной динамики, например уравнений СенВенана. В описание термодинамики снежного покрова добавлены эффекты просачивания жидкой влаги и ее замерзания. Совокупность усовершенствований модели позволила существенно улучшить расчет годового расхода воды и удовлетворительно воспроизвести термический режим крупной равнинной реки Северная Двина. A new version of the INM RASMSU land surface scheme is presented which includes a module for the thermo and hydrodynamics of rivers. The river dynamics is described by the diffusion wave equations, whereas the river thermodynamics is simulated by the onedimensional heat equation. The objectoriented implementation of the river routing scheme allows one to use arbitrary solvers of onedimensional river dynamics problems, for example, the SaintVenant equations. The snow cover thermodynamics is supplemented by the effects of liquid moisture percolation and freezing. The set of model updates significantly improved simulation of the annual cycle of water discharge and temperature for Severnaya Dvina river.

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Kwak, Jae B., et Seungbae Park. « Integrated hygro-swelling and thermo-mechanical behavior of mold compound for MEMS package during reflow after moisture preconditioning ». Microelectronics International 32, n^o 1 (5 janvier 2015) : 8–17. http://dx.doi.org/10.1108/mi-04-2014-0014.

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Purpose – The purpose of this paper was to study the combined effect of hygro and thermo-mechanical behavior on a plastic encapsulated micro-electro-mechanical systems (MEMS) package during the reflow process after exposed to a humid environment for a prolonged time. Plastic encapsulated electronic packages absorb moisture when they are subjected to humid ambient conditions. Design/methodology/approach – Thus, a comprehensive stress model is established for a three-axis accelerometer MEMS package, with detailed considerations of fundamentals of mechanics such as heat transfer, moisture diffusion and hygro-thermo-mechanical stress. In this study, the mold compound is considered to be the most critical plastic material in MEMS package. Other plastic components of thin film materials can be disregarded due to their small sizes such as die attach and Bismaleimide Triazine (BT) core, even though they are also susceptible to moisture. Thus, only the moisture-induced properties of mold compound were obtained from the proposed experiments. From the desorption measurement after preconditioning at 85°C/85 per cent relative humidity (RH), the saturated moisture content and diffusivity were obtained by curve fitting the data to Fick’s equation. In addition, a new experimental setup was devised using the digital image correlation system together with a precision weight scale to obtain the coefficient of hygroscopic swelling (CHS) at different temperatures. Findings – The experimental results show that the diffusion coefficient of mold compound material follows Arrhenius equation well. Also, it is shown that the CHS of mold compound increases as temperature increases. Experimentally obtained moisture properties were then used to analyze the combined behavior (thermo-hygro-mechanical) of fully saturated MEMS package during the reflow process using a finite element analysis (FEA) with the classical analogy method. Finally, the warpage and stresses inside the MEMS package were analyzed to compare the effects of hygroscopic, thermal and hygro-thermo-mechancal behaviors. Originality/value – In this study, unlike the other researches, the moisture effects are investigated specifically for MEMS package which is relatively smaller in scale than conventional electronic packages. Also, as a conjugated situation, MEMS package experiences both humid and temperature during the moisture resistance test. Thus, major objective of this study is to verify stress state inside MEMS package during the reflow process which follows the preconditioning at 85°C/85 per cent RH. To quantify the stresses in the package, accurate information of material properties is experimentally obtained and used to improve modeling accuracy.

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Usman, Auwalu Hamisu, Usa Wannasingha Humphries, Poom Kumam, Zahir Shah et Phatiphat Thounthong. « Double Diffusion Non-Isothermal Thermo-Convective Flow of Couple Stress Micropolar Nanofluid Flow in a Hall MHD Generator System ». IEEE Access 8 (2020) : 78821–35. http://dx.doi.org/10.1109/access.2020.2986021.

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Hayat, Tasawar, Meraj Mustafa et Said Mesloub. « Mixed Convection Boundary Layer Flow over a Stretching Surface Filled with a Maxwell Fluid in Presence of Soret and Dufour Effects ». Zeitschrift für Naturforschung A 65, n^o 5 (1 mai 2010) : 401–10. http://dx.doi.org/10.1515/zna-2010-0505.

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This article looks at the heat and mass transfer characteristics in mixed convection boundary layer flow about a linearly stretching vertical surface. An incompressible Maxwell fluid occupying the porous space takes into account the diffusion-thermo (Dufour) and thermal-diffusion (Soret) effects. The governing partial differential equations are transformed into a set of coupled ordinary differential equations, by invoking similarity transformations. The involved nonlinear differential system is solved analytically using the homotopy analysis method (HAM) to determine the convergent series expressions of velocity, temperature, and concentration. The physical interpretation to these expressions is assigned through graphs and tables for the Nusselt number θ '(0) and the Sherwood number φ '(0). The dependence of suction parameter S, mixed convection parameter λ, Lewis number Le, Prandtl number Pr, Deborah number β , concentration buoyancy parameter N, porosity parameter γ , Dufour number Df, and Soret number Sr is seen on the flow quantities.

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Yakubov, K., M. Latipova et A. Qodirov. « Features of Obtaining Films MnXSiY on Silicon by Solid-phase Reaction ». Bulletin of Science and Practice 7, n^o 4 (15 avril 2021) : 251–57. http://dx.doi.org/10.33619/2414-2948/65/28.

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Recently, in the development of new device structures, structures with various metals on silicon have been used. Numerous studies have shown that as a result of solid-phase reactions of Mn and Si, it is possible to create heterophase systems from various manganese silicide. Such films possessing a unique set of thermoelectric properties. At the present time, obtaining a film with high values of a sufficient thermo-EMF, the maximum thermoelectric figure of merit of these materials of the pack has not yet been achieved. In this regard, there is a need for a detailed study of the structure and perfection of manganese silicide – silicon films obtained on a silicon substrate. In this work, we study the solid-phase reaction in the Mn-Si diffusion system and the process of the formation of manganese silicide phases on a silicon substrate.

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OYELAKIN, Ibukun Sarah, Sabyasachi MONDAL, Precious SIBANDA et Sandile Sydney MOTSA. « A Multi-Domain Bivariate Approach for Mixed Convection in a Casson Nanofluid with Heat Generation ». Walailak Journal of Science and Technology (WJST) 16, n^o 9 (16 juillet 2018) : 681–99. http://dx.doi.org/10.48048/wjst.2019.3049.

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We study the mixed convection flow of a Casson nanofluid past a permeable moving flat plate with heat generation, chemical reaction and viscous dissipation effects in the presence of thermo and thermal diffusion effects. The fluid model described assumes the nanoparticle flux at the boundary is zero, and suction effects on the velocity boundary are accounted for. The system of partial differential equations obtained is solved using a multi-domain bivariate quasi-linearization method with a detailed description of the numerical method of solution. The effects of various fluid parameters on the velocity, temperature, and nanoparticle concentration profiles, as well as on the local skin friction, and heat and mass transfer coefficients, are discussed in detail.

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Wróbel, Marek, et Andriy Burbelko. « A Diffusion Model of Binary Systems Controlled by Chemical Potential Gradient ». Journal of Casting & ; Materials Engineering 6, n^o 2 (27 avril 2022) : 39–44. http://dx.doi.org/10.7494/jcme.2022.6.2.39.

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The paper presents a model of diffusion in a single phase with chemical potential gradient as the driving force of the process. Fick’s laws are strictly empirical and the assumption that the concentration gradients are the driving forces of diffusion is far from precise. Instead, the gradient of chemical potential μi of component i is the real driving force. The matter of governing equations of models that incorporate this approach will be raised and discussed in this article. One of more important features is the ability to acquire results where diffusion against the concentration gradient may occur. The presented model uses the Finite Difference Method (FDM) and employs the CALPHAD method to obtain chemical potentials. The calculations of chemical potential are carried out for instant conditions – temperature and composition – in the entire task domain by Thermo-Calc via a TQ-Interface. Then the heterogeneity of chemical potentials is translated into mass transfer for each individual element. Calculations of two modelling tasks for one-dimension diffusion field were carried out. First: isothermal conditions with linear initial composition distribution and second: constant temperature gradient with uniform chemical composition in the specimen. Results for two binary solid solutions: Fe-C and Fe-Si, in the FCC phase for the given tasks will be presented. Modelling allows us to estimate the time needed to reach a desired state in a particular equilibrium or quasi-equilibrium state. It also shows the path of the composition change during the process. This can be used to determine whether the system at some point is getting close to the formation of another phase due to significant deviation from its initial conditions.

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Lengauer, Walter, et Marcel Bohn. « Thermochemical Basis of the Preparation of Well-Defined Transition Metal Carbide, Nitride and Carbonitride Reference Materials for Electron-Probe Microanalysis (EPMA) ». Solid State Phenomena 274 (mai 2018) : 20–42. http://dx.doi.org/10.4028/www.scientific.net/ssp.274.20.

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A common and straightforward method for the standardisation in electron-probe microanalysis (EPMA) is the use of homogeneous reference materials prepared by various techniques such as by melting, sintering, high-temperature annealing and hot-pressing. The reference materials have to be analysed by independent methods accurately in order to define their “true” composition. For some compounds the preparation techniques are difficult because of their specific thermo-chemical properties (e.g. low diffusivities, high equilibrium nitrogen pressure, incongruent melting). In addition, many compounds show large homogeneity ranges with an a priori existing uncertainty in composition, contrary to what is generally preferred: to use compounds with a narrow homogeneity range (“line compounds”). For the latter, diffusional preparation techniques can be applied to yield diffusion layers instead of massive samples for standardisation. However, also single-phase samples with narrow homogeneity ranges can be prepared by diffusion, depending on the phase equilibria in the corresponding system. The presentation summarises efforts that have been made in order to prepare various reference materials for carbon and nitrogen standardisation of EPMA by various techniques. The boundary conditions such as phase stabilities, phase compositions and diffusion kinetics, which are important for their preparation to obtain well-defined reference samples are discussed. These samples were applied to various WDS/EPMA-based studies of phase diagrams and diffusion kinetics by means of Cameca SX 50 and SX 100 microprobes.

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Sheng, Can, Gai Wu, Xiang Sun et Sheng Liu. « Molecular Dynamics Investigation of the Thermo-Mechanical Properties of the Moisture Invaded and Cross-Linked Epoxy System ». Polymers 14, n^o 1 (28 décembre 2021) : 103. http://dx.doi.org/10.3390/polym14010103.

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In spite of a high market share of plastic IC packaging, there are still reliability issues, especially for the effects of moisture. The mechanism between moisture and epoxy polymer is still obscure. A multi-step cross-linking approach was used to mimic the cross-linking process between the DGEBA resin and JEFFAMINE®-D230 agent. Based on the molecular dynamics method, the thermo-mechanical properties and microstructure of epoxy polymer were analyzed. In this paper, the degree of cross-linking ranged from 0% to 85.4% and the moisture concentration ranged from 0 wt.% to 12 wt.%. The hydrogen bonds were investigated in the moisture invaded epoxy polymer. Although most of the hydrogen bonds were related to water molecules, the hydrogen bonds between the inside of epoxy polymer were reduced only a little as the concentration of moisture increased. The diffusion coefficient of the water molecules was found to increase with the increase of moisture concentration. When the moisture concentration was larger than 12 wt.% or smaller than 1.6 wt.%, the diffusion coefficient was less affected by the epoxy polymer. In addition, the free volume and the thermal conductivity of the epoxy polymer were considered. It was found that the moisture could increase the thermal conductivity from 0.24 to 0.31 W/m/K, identifying a coupling relationship between moisture and thermal properties. Finally, the mechanical properties of epoxy polymer were analyzed by uniaxial tensile simulation. The COMPASS and DREIDING force fields were used during the uniaxial tensile simulation. A better result was achieved from the DREIDING force field compared with the experiment. The degree of cross-linking was positively correlated with mechanical properties. For the system with the largest degree of cross-linking of 85.4%, the Young’s modulus was 2.134 ± 0.522 GPa and the yield strength was 0.081 ± 0.01 GPa. There were both plasticizing and anti-plasticizing effects when the water molecules entered the epoxy polymer. Both the Young’s moduli and yield strength varied in a large range from 1.38 to 2.344 GPa and from 0.062 to 0.128 GPa, respectively.

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Ariza, M. P., K. G. Wang et M. Ortiz. « Atomistic Models of Long-Term Hydrogen Diffusion in Metals ». Advances in Science and Technology 93 (octobre 2014) : 118–23. http://dx.doi.org/10.4028/www.scientific.net/ast.93.118.

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The effective and efficient storage of hydrogen is one of the key challenges in developing a hydrogen economy. Recently, intensive research has been focused on developing and optimizing metal-based nanomaterials for high-speed, high-capacity, reversible hydrogen storage applications. Notably, the absorption and desorption of hydrogen in nanomaterials is characterized by an atomic, deformation-diffusion coupled process with a time scale of the order of seconds to hours--far beyond the time windows of existing simulation technologies such as Molecular Dynamics (MD) and Monte Carlo (MC) methods. In this work, we present a novel deformation-diffusion coupled computational framework, which allows the long-term simulation of such slow processes and at the same time maintains a strictly atomistic description of the material. Specifically, we first propose a theory of non-equilibrium statistical thermodynamics for multi-species particulate solids based on Jayne's maximum entropy principle and the meanfield approximation approach. This non-equilibrium statistical thermodynamics model is then coupled with novel discrete kinetics laws, which governs the diffusion of mass--and possibly also conduction of heat--at atomic scale. Finally, this thermo-chemo-mechanical coupled system is solved numerically using a staggered procedure. The salient features of this computational framework are demonstrated in the simulation of a specific hydrogen diffusion problem using palladium nanofilms, which comes with a simulation time of one second. More generally, the proposed computational framework can be considered as an ideal tool for the study of many deformation-diffusion coupled phenomena in hydrogen-storage-related applications including, but not limited to, hydrogen embrittlement, grain boundary diffusion, and various cyclic behaviors.

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Jayakar, R., B. Rushi Kumar et Oluwole Daniel Makinde. « Thermo Diffusion Effects on MHD Chemically Reacting Fluid Flow Past an Inclined Porous Plate in a Slip Flow Regime ». Defect and Diffusion Forum 387 (septembre 2018) : 587–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.387.587.

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The investigation is undertaken to study the thermal diffusion and radiation effects on unsteady MHD heat and mass transfer flow past a semi-infinite inclined porous plate embedded in a porous medium in a slip flow regime with variable suction in the presence of first order chemically reaction. The analytical solutions for velocity, temperature and concentration fields are obtained by reducing the governing nonlinear coupled partial differential equations in dimensionless form into a system of ordinary differential equations, using perturbation method. The effect of pertinent flow parameters on velocity, temperature, concentration, the skin friction, the rate of heat transfer and the rate of mass transfer are studied graphically.

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Rana, G. C., et R. C. Thakur. « THE ONSET OF DOUBLE-DIFFUSIVE CONVECTION IN A LAYER OF NANOFLUID UNDER ROTATION ». Revista de Engenharia Térmica 15, n^o 1 (30 juin 2016) : 88. http://dx.doi.org/10.5380/reterm.v15i1.62153.

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Double-diffusive convection in a horizontal layer of nanofluid under rotation heated from below is studied. The nanofluid describes the effects of thermophoresis and Brownian diffusion. Based upon perturbations and linear stability theory, the normal mode analysis method is applied to obtain the dispersion relation characterizing the effect of different parameters when both the boundaries are free. Due to thermal expansion, the nanofluid at the bottom will be lighter than the fluid at the top. Thus, this is a top heavy arrangement which is potentially unstable. In this paper we discuss the influences of various non-dimensional parameters such as rotation, solute gradient, thermo- nanofluid Lewis number, thermo-solutal Lewis number, Soret and Dufour parameter on the stability of stationary convection for the case of free-free boundaries. It is observed that rotation and solute gradient have stabilizing influence on the system. Rotation and solute gradient play important role in the thermal convection of fluid layer and has applications in rotating machineries such as nuclear reactors, petroleum industry, biomechanics etc. and solute gradient finds applications in geophysics, food processing, soil sciences, oil reservoir modeling, oceanography etc. A very good agreement is found between the present paper and earlier published results.

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FAN, HONG-YI, et LI-YUN HU. « OPERATOR-SUM REPRESENTATION OF DENSITY OPERATORS AS SOLUTIONS TO MASTER EQUATIONS OBTAINED VIA THE ENTANGLED STATE APPROACH ». Modern Physics Letters B 22, n^o 25 (10 octobre 2008) : 2435–68. http://dx.doi.org/10.1142/s0217984908017072.

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We solve various master equations to obtain density operators' infinite operator-sum representation via a new approach, i.e., by virtue of the thermo-entangled state representation that has a fictitious mode as a counterpart mode of the system mode. The corresponding Kraus operators from the point of view of quantum channel are derived, whose normalization conditions are proved. Miscellaneous characters possessed by different quantum channels, such as decoherence, phase diffusion, damping, and amplification, can be shown explicitly in the entangled state representation of the density operators. Squeezing transformation is applied to the density operator for decoherence to generate a master equation for describing the phase sensitive process. Partial trace method for deriving new density operators is also introduced. Throughout our discussion, the technique of integration within an ordered product (IWOP) of operators is fully used.

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Kairi, Rishi Raj, Ch RamReddy et Santanu Raut. « Influence of viscous dissipation and thermo-diffusion on double diffusive convection over a vertical cone in a non-Darcy porous medium saturated by a non-Newtonian fluid with variable heat and mass fluxes ». Nonlinear Engineering 7, n^o 1 (26 mars 2018) : 65–72. http://dx.doi.org/10.1515/nleng-2016-0054.

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Abstract This paper emphasizes the thermo-diffusion and viscous dissipation effects on double diffusive natural convection heat and mass transfer characteristics of non-Newtonian power-law fluid over a vertical cone embedded in a non-Darcy porous medium with variable heat and mass flux conditions. The Ostwald–de Waele power-law model is employed to describe the behavior of non-Newtonian fluid. Local non-similarity procedure is applied to transform the set of non-dimensional partial differential equations into set of ordinary differential equations and then the resulting system of equations are solved numerically by Runge-Kutta fourth order method together with a shooting technique. The influence of pertinent parameters on temperature and concentration, heat and mass transfer rates are analyzed in opposing and aiding buoyancy cases through graphical representation and explored in detail.

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Jithender Reddy, G., R. Srinivasa Raju, P. Manideep et J. Anand Rao. « Thermal diffusion and diffusion thermo effects on unsteady MHD fluid flow past a moving vertical plate embedded in porous medium in the presence of Hall current and rotating system ». Transactions of A. Razmadze Mathematical Institute 170, n^o 2 (septembre 2016) : 243–65. http://dx.doi.org/10.1016/j.trmi.2016.07.001.

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Conceição, Eusébio, João Gomes, M. Manuela Lúcio, M. Inês Conceição, André Ramos et Hazim Awbi. « Coupling of differential CFD and integral human thermophysiology numerical models applied in indoor ventilated spaces ». E3S Web of Conferences 321 (2021) : 03002. http://dx.doi.org/10.1051/e3sconf/202132103002.

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This work presents the development of the coupling of differential Computer Fluid Dynamics and integral human thermo-physiology numerical models applied in indoor ventilated spaces. The study is performed in a virtual chamber, similar to an existing experimental chamber, with dimensions of 4.50×2.55×2.50 m3. The chamber, occupied with twelve virtual manikins, is equipped with six tables, twelve chairs, one exhaust system and one inlet system, based on confluents jets system. In the exhaust system, they are considered six air ducts, located above the head level, connected to the ceiling area. The inlet system, based in four vertical ducts, with 0.15 m diameter, located on the corners of the chamber, is equipped with consecutive holes, that promotes horizontal jets near the wall. The results demonstrate that when the airflow rate increases the air quality number increases, the thermal comfort number decreases, and the Air Diffusion Index increases slightly. The predicted percentage of dissatisfied index values show that the thermal comfort level of occupants is acceptable, the dioxide carbon concentration values show that the indoor air quality is near the acceptable value and the Draught Risk is acceptable.

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Bityurin, V. A., A. N. Bocharov, A. S. Dobrovolskaya, T. N. Kuznetsova, N. A. Popov et E. A. Filimonova. « Numerical Modeling of Pulse-Periodic Nanosecond Discharges ». Journal of Physics : Conference Series 2100, n^o 1 (1 novembre 2021) : 012032. http://dx.doi.org/10.1088/1742-6596/2100/1/012032.

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Abstract The first results of the numerical simulation of the Pulse-Periodic Nanosecond discharge in pin-to-pin configuration in 2Dt approximation of the full self-consist system of Navier-Stocks equation for real thermo-chemically non-equilibrium gases, drift-diffusion approximation of the low temperature plasma evolution in external electric and magnetic field and, alternative – arc (spark) discharge model of high-density energy input discharge. The intuitive criteria of the alternative discharge models re-switch are proposed and tested. The pin-to-pin the pulse-periodic nanosecond 5-MHz discharge has been considered for 1 microsecond interval. It was found that rather strong longitudinal non-uniformities of main physical parameters are created at the first corona stage of the interelectrode conducting channel. These nonuniformities reveal long-lived features that have define strong effect on the discharge performance

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Dychtoń, Kamil, Paweł Rokicki, Andrzej Nowotnik, Marcin Drajewicz et Jan Sieniawski. « Process Temperature Effect on Surface Layer of Vacuum Carburized Low-Alloy Steel Gears ». Solid State Phenomena 227 (janvier 2015) : 425–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.227.425.

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Gears, due to their complex shape, carried load and required accuracy are ones of most complex aircraft engine parts. Single tooth damage usually breaks the power transmission and causes failure of the entire gear system. Adequate sustainability and guarantees of transmission is therefore a condition for secure operation of whole device. Particularly high requirements for reliability are put to transmissions used in the aerospace industry. Due to the loads which are transmitted through the gears, the materials used by the manufacturer must have not only high strength but also show the abrasion resistance of the surface layer and the ductility of the core. Thermo-chemical treatment of industrial gears is a fundamental process, which gives them adequate mechanical properties regarding loads they carry and the surface conditions of work. The most promising method in the discussed field is vacuum carburizing, which by its specification of work significantly reduce the emission of CO2and the duration of the process, without reducing the quality of the final product. The main aim of the paper is to present criteria for selection of carburizing parameters (mainly temperature increase) as a part of thermo-chemical treatment process performed using vacuum methods. Proper (higher to compare with conventional methods) carburizing process temperature is crucial in programming of carbon diffusion process meaning in process time and final carburized layer characteristics as carbon profile and homogeneity of the carburized layer.

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Fazlalipour, F., M. Niki Nushari, N. Shakib et Ali Shokuhfar. « Comparative Tribological Behavior of V(N,C) and VC Diffusion Coatings ». Defect and Diffusion Forum 297-301 (avril 2010) : 1183–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.1183.

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Hard coatings show various tribological behaviors against different contact materials (counter-faces) during dry sliding depended on their microstructure, surface morphology and encountered tribological systems and condition. In this work, the tribological and wear mechanisms of vanadium carbide (VC) and vanadium nitrocarbide (V(N,C)) layers were examined against WC/Co cemented tungsten carbide pin during pin-on-disk sliding wear testing. The V(N,C) layer was produced by a duplex surface treatment involving the gas pre-nitrocarburising followed by thermo-reactive diffusion (TRD) vanadizing technique. The coating layers were characterized by a cross sectional and morphological examination methods and X-ray diffraction analysis to identify damages of the coating’s surface. Wear mechanisms were determined by SEM microscope in BSI and SE mode accompanied by EDS analysis. Results revealed that the surface morphology of the V(N,C) coating consist of dense and smooth layer in comparison with the VC coating surface which reveals a non-uniform structure with chasms. It was determined that the activation of tribo-chemical system and oxidizing of the coating layer together with minor plastic deformation are the dominant wear mechanism in the V(N,C) coated steel. In the case of the VC coating, combination of abrasive wear and adhesion of pin material to coating and vice versa are the major impairing mechanisms.

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Faraz, Faraz, Syed Muhammad Imran, Bagh Ali et Sajjad Haider. « Thermo-Diffusion and Multi-Slip Effect on an Axisymmetric Casson Flow over a Unsteady Radially Stretching Sheet in the Presence of Chemical Reaction ». Processes 7, n^o 11 (14 novembre 2019) : 851. http://dx.doi.org/10.3390/pr7110851.

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The objective of this article is to investigate the impacts of thermo-diffusion effect on unsteady axisymmetric Casson flow over a time-dependent radially stretching sheet with a multi-slip parameter and the force of chemical reaction. We employed an established similarity transformation to this non-linear partial differential system to convert it into a system of ordinary differential equations. The numerical results are attained for this system by using KELLER-BOX implicit finite difference scheme. It has great reliability and accuracy even a very short time period for computational simulation. The impacts of influential flow parameters on fluid flow are sketched through graphs and the numerical results are thoroughly argued. The temperature, velocity and wall concentration control parameters are analyzed. (i) It is witnessed that chemical reaction is not favorable to enhance the velocity profile. (ii) Multi-slip parameters vary inversely with velocity profile. (iii) The fluid concentration in its boundary layer decreases with the increase of heavier species, the parameter of the reaction rate and the exponent of power law for fluids having Prandtl number = 10.0, 15.0, 20.0 and 25.0. Moreover, the skin-friction-coefficient factor and Nusselt-number are compared with the published work. A strong numerical solution agreement is being observed.

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Prabhakar Reddy, Bijjula. « THERMOâ€”DIFFUSION AND HALL EFFECT ON RADIATING AND REACTING MHD CONVECTIVE HEAT ABSORBING FLUID PAST AN EXPONENTIALLY ACCELERATED VERTICAL POROUS PLATE WITH RAMPED TEMPERATURE ». Journal of the Serbian Society for Computational Mechanics 14, n^o 1 (30 juin 2020) : 12–28. http://dx.doi.org/10.24874/jsscm.2020.14.01.02.

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Numerical investigation is undertaken to study the effects of thermo-diffusion and Hall current on unsteady magneto-hydrodynamic convective flow of a viscous, incompressible, electrically conducting, radiating and heat absorbing fluid past an exponentially accelerated infinite vertical porous plate with ramped temperature in the presence of chemical reaction. A uniform magnetic field is applied transversely in the direction of the flow. The governing system of partial differential equations along with initial and boundary conditions is transformed to dimensionless form and then solved by employing finite element method. The impact of various flow parameters on the primary and secondary fluid velocities, fluid temperature and fluid concentration as well as shear stress, rate of heat and mass transfer at the plate are displayed through the graphs and tables. It can be observed that the temperature profiles are slower in case of ramped temperature plate than that of isothermal plate.

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Rosato, Antonio, Antonio Ciervo, Renata Concetta Vigliotti, Roxana Adina Toma, Rossana Pellegrino, Giovanni Ciampi, Michelangelo Scorpio et Sergio Sibilio. « Influence of Climatic Conditions on Dynamic Performance of Solar Hybrid Heating and Cooling Systems Integrating Seasonal Borehole Thermal Energy Storages : Application to School Buildings in the Campania Region of Italy ». Tecnica Italiana-Italian Journal of Engineering Science 65, n^o 2-4 (30 juillet 2021) : 187–95. http://dx.doi.org/10.18280/ti-ijes.652-407.

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In this paper 5 different case studies of solar hybrid heating and cooling networks serving 5 different school buildings assumed as representative of the 5 provinces of the Campania region (southern Italy) have been modelled, dynamically simulated and analyzed by means of the software TRNSYS over a 5-year period. The plants are based on the operation of solar thermal collectors coupled with a seasonal borehole thermal energy storage; the solar field is also integrated with photovoltaic panels coupled with an electric energy storage; a solar-powered adsorption system is used for covering the cooling requirements. Specific weather data files have been developed for each city based on 1-year in-situ hourly measurements to accurately take into account the influence of climatic conditions on systems’ performance; the effects of thermo-physical properties of underground associated to the different locations have also been taken into consideration according to measured data available in the literature. The proposed systems have been compared with conventional Italian heating and cooling plants from energy, environmental and economic points of view in order to assess the potential benefits, highlight the effects of both weather data and characteristics of underground as well as promote the diffusion of solar systems for Italian applications.

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Narita, Toshio, Stewart Ford, Takayuki Yoshioka, Takumi Nishimoto, Takeshi Izumi et Shigenari Hayashi. « Formation of Pt-Modified γ’-Ni₃Al and Re-Based σ-Alloy Coating System and Cyclic Oxidation Behavior of Coated Superalloy ». Materials Science Forum 595-598 (septembre 2008) : 135–41. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.135.

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A duplex layer, outer Pt-modified γ’-Ni3Al + γ-Ni and inner multi-barrier σ- Re(Cr,Ni,W), coating system was formed on a Ni-based single crystal 4th generation superalloy. Oxidation behavior of the coated alloy was investigated under thermo-cycling conditions, and analyzed by EPMA and XRD. During cyclic oxidation 1hr at 1100°C and 20 min at room temperature, a slow growing α-Al2O3 formed for up to 400 cycles and its spallation was rare. The parabolic rate constant of mass change was 6.3x10-16 kg2m-4s-1. The Pt-modified γ’-Ni3Al + γ-Ni contained 19Al, 12Pt, 4Cr, and 3Co in at%, and their concentration profiles were almost flat across the outer layer. The multi-barrier, σ-Re(Cr,Ni,W) contained 40Re, 23Cr, 17Ni, 7Al, 4W, 3.5Mo, and 3Co in at%. Furthermore, the γ’-Ni3Al containing Pt was newly formed between the multibarrier and bulk alloy substrate. It was concluded that the σ-Re(Cr,Ni,W) is compatible with the Ptmodified γ’-Ni3Al in the multi-diffusion barrier coating on Ni-based single crystal, 4th generation superalloy at high temperatures.

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Ma, Huan, Fengqi Si et Junshan Wang. « Internal flow reconstruction strategies to improve both thermo-flow performance and flue gas diffusion characteristic of the integrated dry-cooling tower and stack system ». Applied Thermal Engineering 166 (février 2020) : 114675. http://dx.doi.org/10.1016/j.applthermaleng.2019.114675.

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