scholarly journals Effects of time and diffusion phase-lags in a thin circular disc with axisymmetric heat supply

2017 ◽  
Vol 4 (1) ◽  
pp. 1369848
Author(s):  
Rajneesh Kumar ◽  
Lajvinder Singh Reen ◽  
S.K. Garg ◽  
Timothy Marchant
Keyword(s):  
Heat Supply ◽  
Circular Disc ◽  
Diffusion Phase ◽  
Phase Lags ◽  
And Diffusion

Effects of thermal and diffusion phase-lags in a plate with axisymmetric heat supply

2016 ◽  
Vol 12 (2) ◽  
pp. 275-290 ◽  
Author(s):  
Rajneesh Kumar ◽  
Nidhi Sharma ◽  
Parveen Lata
Keyword(s):  
Heat Supply ◽  
Mass Concentration ◽  
Chemical Potential ◽  
Phase Lag ◽  
Dual Phase ◽  
Content Type ◽  
Thermal Phase ◽  
Diffusion Phase ◽  
Phase Lags ◽  
And Diffusion

Purpose – The purpose of this paper is to depict the effect of time and thermal and diffusion phase-lags due to axisymmetric heat supply in a ring. The problem is discussed within the context of dual-phase-lag heat transfer and dual-phase-lag diffusion models. The upper and lower surfaces of the ring are traction free and subjected to an axisymmetric heat supply. Design/methodology/approach – The solution is found by using Laplace and Hankel transform technique and a direct approach without the use of potential functions. The analytical expressions of displacements, stresses and chemical potential, temperature and mass concentration are computed in transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically. The effect of time and diffusion and thermal phase-lags are shown on the various components. Some particular cases of result are also deduced from the present investigation. Findings – It is observed that change in time changes the behaviour of deformations of the various components of stresses, displacements, chemical potential function, temperature change and mass concentration. The authors find that for t=0.2, trends are oscillatory in all the cases whereas for t=0.1, trends are quite different. A sound impact of diffusion and thermal phase-lags on the various quantities is observed. A lot of difference in the trends of single phase lag and dual phase lag is observed. The use of diffusion phase-lags in the equation of mass diffusion gives a more realistic model of thermoelastic diffusion media as it allows a delayed response between the relative mass flux vector and the potential gradient. Originality/value – This problem is totally new because dual phase lag is applied in heat conduction and diffusion equation while considering the problem of plate in axisymmetric heat supply.

scholarly journals Nonequilibrium evolution thermodynamic of poly- and two-components alloys affected by severe plastic deformation

2021 ◽  
Vol 2052 (1) ◽  
pp. 012026
Author(s):  
L Metlov ◽  
M Gordey
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Kinetic Equations ◽  
Copper Matrix ◽  
Structural Defects ◽  
Two Component ◽  
Diffusion Phase ◽  
Qualitative Phase ◽  
And Diffusion

Abstract The nonequilibrium evolutionary thermodynamics approach is generalized to the case of alloys prone to structural martensitic and diffusion phase transitions in them. A system of kinetic equations is written out to describe the evolution of the density of structural defects, grain boundaries, dislocations and point defects, as well as for the order parameter in the processing of these alloys by the severe plastic deformation way. The approach is illustrated by the numerical experiments results on a specific example of two-component copper-based alloys. Kinetic curves of the evolution of the grain boundaries, dislocations and atoms dissolved in a copper matrix are obtained, qualitative phase diagrams are constructed.

Plane wave propagation in an anisotropic dual-phase-lag thermoelastic diffusion medium

2014 ◽  
Vol 10 (4) ◽  
pp. 562-592 ◽  
Author(s):  
Rajneesh Kumar ◽  
Vandana Gupta
Keyword(s):  
Mass Flux ◽  
Potential Gradient ◽  
Transversely Isotropic ◽  
Mass Diffusion ◽  
Phase Lag ◽  
Dual Phase ◽  
Thermoelastic Diffusion ◽  
Content Type ◽  
Diffusion Phase ◽  
Phase Lags

Purpose – The purpose of this paper is to depict the effect of thermal and diffusion phase-lags on plane waves propagating in thermoelastic diffusion medium with different material symmetry. A generalized form of mass diffusion equation is introduced instead of classical Fick's diffusion theory by using two diffusion phase-lags, one phase-lag of diffusing mass flux vector, represents the delayed time required for the diffusion of the mass flux and the other phase-lag of chemical potential, represents the delayed time required for the establishment of the potential gradient. The basic equations for the anisotropic thermoelastic diffusion medium in the context of dual-phase-lag heat transfer (DPLT) and dual-phase-lag diffusion (DPLD) models are presented. The governing equations for transversely isotropic and isotropic case are also reduced. The different characteristics of waves like phase velocity, attenuation coefficient, specific loss and penetration depth are computed numerically. Numerically computed results are depicted graphically for anisotropic, transversely isotropic and isotropic medium. The effect of diffusion and thermal phase-lags are shown on the different characteristic of waves. Some particular cases of result are also deduced from the present investigation. Design/methodology/approach – The governing equations of thermoelastic diffusion are presented using DPLT model and a new model of DPLD. Effect of phase-lags of thermal and diffusion is presented on different characteristic of waves. Findings – The effect of diffusion and thermal phase-lags on the different characteristic of waves is appreciable. Also the use of diffusion phase-lags in the equation of mass diffusion gives a more realistic model of thermoelastic diffusion media as it allows a delayed response between the relative mass flux vector and the potential gradient. Originality/value – Introduction of a new model of DPLD in the equation of mass diffusion.

scholarly journals Effects of two temperatures and thermal phase-lags in a thick circular plate with axisymmetric heat supply

2016 ◽  
Vol 3 (1) ◽  
pp. 1129811 ◽  
Author(s):  
Rajneesh Kumar ◽  
Nidhi Sharma ◽  
Parveen Lata ◽  
Xiao-Jun Yang
Keyword(s):  
Circular Plate ◽  
Heat Supply ◽  
Thermal Phase ◽  
Thick Circular Plate ◽  
Phase Lags ◽  
Two Temperatures

scholarly journals Cryptanalysis of Permutation–Diffusion-Based Lightweight Chaotic Image Encryption Scheme Using CPA

2019 ◽  
Vol 9 (3) ◽  
pp. 494
Author(s):  
Ming Li ◽  
Kanglei Zhou ◽  
Hua Ren ◽  
Haiju Fan
Keyword(s):  
Image Encryption ◽  
Encryption Scheme ◽  
Secret Key ◽  
Chosen Plaintext Attack ◽  
Image Communication ◽  
Diffusion Phase ◽  
Chaotic Image Encryption ◽  
Differential Attacks ◽  
And Diffusion ◽  
Attack Strategy

In order to meet the requirement of secure image communication in a resource-constrained network environment, a novel lightweight chaotic image encryption scheme based on permutation and diffusion has been proposed. It was claimed that this scheme can resist differential attacks, statistical attacks, etc. However, the original encryption scheme is found to be vulnerable and insecure to chosen-plaintext attack (CPA). In this paper, the original encryption scheme is analyzed comprehensively and attacked successfully. Only by choosing a full zero image as the chosen-plaintext of the diffusion phase, the encrypted image can be restored into permutation-only phase, and by applying the other chosen images as the chosen-plaintexts of the permutation phase, the map matrix which is equivalent to the secret key of the permutation phase can be further revealed. Experiments and analysis verify the feasibility of our proposed attack strategy.

Development of hybrid model for modeling of diffusion phase transformation

2020 ◽  
Vol 37 (8) ◽  
pp. 2761-2783
Author(s):  
Łukasz Łach ◽  
Dmytro Svyetlichnyy
Keyword(s):  
Phase Transformation ◽  
Heat Flow ◽  
Phase Transformations ◽  
Hybrid Model ◽  
Content Type ◽  
One Dimensional ◽  
Wide Range ◽  
Diffusion Phase ◽  
Simulation Results ◽  
And Diffusion

Purpose Some functional properties of engineering materials, i.e. physical, mechanical and thermal ones, depend directly on the microstructure, which is a result of processes occurring in the material during the forming and thermomechanical processing. The proper microstructure can be obtained in many cases by the phase transformation. This phenomenon is one of the most important processes during hot forming and heat treatment. The purpose of this paper is to develop a new comprehensive hybrid model for modeling diffusion phase transformations. A problem has been divided into several tasks and is carried out on several stages. The purpose of this stage is a development of the structure of a hybrid model, development of an algorithm used in the diffusion module and one-dimensional heat flow and diffusion modeling. Generally, the processes of phase transformations are studied well enough but there are not many tools for their complex simulations. The problems of phase transformation simulation are related to the proper consideration of diffusion, movement of phase boundaries and kinetics of transformation. The proposed new model at the final stage of development will take into account the varying grain growth rate, different shape of growing grains and will allow for proper modeling of heat flow and carbon diffusion during the transformation in many processes, where heating, annealing and cooling can be considered (e.g. homogenizing and normalizing). Design/methodology/approach One of the most suitable methods for modeling of microstructure evolution during the phase transformation is cellular automata (CA), while lattice Boltzmann method (LBM) suits for modeling of diffusion and heat flow. Then, the proposed new hybrid model is based on CA and LBM methods and uses high performing parallel computations. Findings The first simulation results obtained for one-dimensional modeling confirm the correctness of interaction between LBM and CA in common numerical solution and the possibility of using these methods for modeling of phase transformations. The advantages of the LBM method can be used for the simulation of heat flow and diffusion during the transformation taking into account the results obtained from the simulations. LBM creates completely new possibilities for modeling of phase transformations in combination with CA. Practical implications The studies are focused on diffusion phase transformations in solid state in condition of low cooling rate (e.g. transformation of austenite into ferrite and pearlite) and during the heating and annealing (e.g. transformation of the ferrite-pearlite structure into austenite, the alignment of carbon concentration in austenite and growth of austenite grains) in carbon steels within a wide range of carbon content. The paper presents the comprehensive modeling system, which can operate with the technological processes with phase transformation during heating, annealing or cooling. Originality/value A brief review of the modeling of phase transformations and a description of the structure of a new CA and LBM hybrid model and its modules are presented in the paper. In the first stage of model implementation, the one-dimensional LBM model of diffusion and heat flow was developed. The examples of simulation results for several variants of modeling with different boundary conditions are shown.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Sign in / Sign up

Export Citation Format

Share Document