scholarly journals Shock Structure and Relaxation in the Multi-Component Mixture of Euler Fluids

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 955
Author(s):  
Damir Madjarević ◽  
Milana Pavić-Čolić ◽  
Srboljub Simić
Keyword(s):  
Relaxation Times ◽  
Thermal Relaxation ◽  
Collision Operator ◽  
Weak Form ◽  
Shock Structure ◽  
Theory Approach ◽  
Component Mixture ◽  
Single Temperature ◽  
The Difference ◽  
Euler Fluids

The shock structure problem is studied for a multi-component mixture of Euler fluids described by the hyperbolic system of balance laws. The model is developed in the framework of extended thermodynamics. Thanks to the equivalence with the kinetic theory approach, phenomenological coefficients are computed from the linearized weak form of the collision operator. Shock structure is analyzed for a three-component mixture of polyatomic gases, and for various combinations of parameters of the model (Mach number, equilibrium concentrations and molecular mass ratios). The analysis revealed that three-component mixtures possess distinguishing features different from the binary ones, and that certain behavior may be attributed to polyatomic structure of the constituents. The multi-temperature model is compared with a single-temperature one, and the difference between the mean temperatures of the mixture are computed. Mechanical and thermal relaxation times are computed along the shock profiles, and revealed that the thermal ones are smaller in the case discussed in this study.

scholarly journals Superior photo-carrier diffusion dynamics in organic-inorganic hybrid perovskites revealed by spatiotemporal conductivity imaging

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuejian Ma ◽  
Fei Zhang ◽  
Zhaodong Chu ◽  
Ji Hao ◽  
Xihan Chen ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cell ◽  
Relaxation Times ◽  
Charge Trapping ◽  
Free Carrier ◽  
Carrier Dynamics ◽  
Electron Hole ◽  
Inorganic Hybrid ◽  
Diffusion Dynamics ◽  
The Difference

AbstractThe outstanding performance of organic-inorganic metal trihalide solar cells benefits from the exceptional photo-physical properties of both electrons and holes in the material. Here, we directly probe the free-carrier dynamics in Cs-doped FAPbI3 thin films by spatiotemporal photoconductivity imaging. Using charge transport layers to selectively quench one type of carriers, we show that the two relaxation times on the order of 1 μs and 10 μs correspond to the lifetimes of electrons and holes in FACsPbI3, respectively. Strikingly, the diffusion mapping indicates that the difference in electron/hole lifetimes is largely compensated by their disparate mobility. Consequently, the long diffusion lengths (3~5 μm) of both carriers are comparable to each other, a feature closely related to the unique charge trapping and de-trapping processes in hybrid trihalide perovskites. Our results unveil the origin of superior diffusion dynamics in this material, crucially important for solar-cell applications.

The solution conformation of prostacyclin as determined by high field proton magnetic resonance techniques

1980 ◽  
Vol 58 (10) ◽  
pp. 974-983 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts ◽  
Tom T. Nakashima ◽  
Glen Bigam
Keyword(s):  
Magnetic Resonance ◽  
Correlation Time ◽  
Proton Magnetic Resonance ◽  
Double Resonance ◽  
Relaxation Times ◽  
Segmental Motion ◽  
Solution Conformation ◽  
Nmr Spectrum ◽  
H Nmr ◽  
The Difference

The proton magnetic resonance (1H nmr) spectrum at 400 MHz of prostacyclin at pH 10.4 in glycine buffer has been completely analyzed utilizing homonuclear double resonance, inversion recovery, and difference nOe experiments. The spectral analysis shows that the two protons at C-4 are non-equivalent even though they are removed from the asymmetric centres at C-8 and C-9 by five bonds. The difference nOe measurements verify the configuration at C-5.Proton longitudinal relaxation times (T1) were measured at 400 and 200 MHz. From the T1 frequency dependence, effective rotational correlation times ranging from 2.3 × 10−10 to 3.0 × 10−10 s were calculated for H-5, H-9, H-11, and H-15. This indicates that the portion of the molecule encompassed by these protons has a longer correlation time than is observed for the C-2 and the C-17 to C-19 protons, for which the average correlation time is 1.2 × 10−10 s. Hence the aliphatic side chains have more segmental motion.

scholarly journals Evolution Equation and Transport Coefficients of Swarms in Initial Relaxation Processes

1987 ◽  
Vol 40 (3) ◽  
pp. 367 ◽  
Author(s):  
Keiichi Kondo
Keyword(s):  
Evolution Equation ◽  
Transport Coefficients ◽  
Collision Operator ◽  
Operator Method ◽  
Time Dependent ◽  
Relaxation Processes ◽  
Projection Operator Method ◽  
Model Collision ◽  
The Difference ◽  
Dependent Transport

The problem of a swarm approaching the hydrodynamic regime is studied by using the projection operator method. An evolution equation for the density and the related time-dependent transport coefficient are derived. The effects of the initial condition on the transport characteristics of a swarm are separated from the intrinsic evolution of the swarms, and the difference from the continuity equation with time-dependent transport coefficients introduced by Tagashira et al. (1977, 1978) is discussed. To illustrate this method, calculations on the relaxation model collision operator have been carried out. The results are found to agree with the analysis by Robson (1975).

scholarly journals Applications of Cattaneo–Christov fluxes on modelling the boundary value problem of Prandtl fluid comprising variable properties

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Umar Nazir ◽  
Muhammad Sohail ◽  
Umair Ali ◽  
El-Sayed M. Sherif ◽  
Choonkil Park ◽  
...  
Keyword(s):  
Magnetic Parameter ◽  
Fluid Model ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Coupled System ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Variable Properties ◽  
Cartesian Coordinate ◽  
And Diffusion

AbstractStretched flows have numerous applications in different industrial, biomedical and engineering processes. Current research is conducted to examine the flow phenomenon of Prandtl fluid model over a moveable surface. The phenomenon of mass and thermal transportation is based on generalized theory of Cattaneo–Christov which considers the involvement of relaxation times. In addition to these, variable characteristics of thermal conductivity and diffusion coefficient are considered as a function of temperature. The physical problem in Cartesian coordinate system is modeled via boundary layer theory which yields a coupled system of partial differential equations. Group scaling transportation is applied to model these PDEs system. The converted equations have been approximated via optimal homotopic scheme. The efficiency and validity of used approach has been shown by computing the error analysis and establishing a comparative study. It is noted that the enhancement in magnetic parameter plays a controlling role for velocity field and it augment the concentration and temperature fields. Furthermore, increase in thermal relaxation parameter and Prandtl number maintains the fluid temperature.

scholarly journals Analyzing 3D Advection-Diffusion Problems by Using the Improved Element-Free Galerkin Method

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Heng Cheng ◽  
Guodong Zheng
Keyword(s):  
Penalty Method ◽  
Weak Form ◽  
Singular Matrix ◽  
Element Free Galerkin Method ◽  
Element Free Galerkin ◽  
Advection Diffusion ◽  
Computational Speed ◽  
The Difference ◽  
Element Free ◽  
Diffusion Problems

In this paper, the improved element-free Galerkin (IEFG) method is used for solving 3D advection-diffusion problems. The improved moving least-squares (IMLS) approximation is used to form the trial function, the penalty method is applied to introduce the essential boundary conditions, the Galerkin weak form and the difference method are used to obtain the final discretized equations, and then the formulae of the IEFG method for 3D advection-diffusion problems are presented. The error and the convergence are analyzed by numerical examples, and the numerical results show that the IEFG method not only has a higher computational speed but also can avoid singular matrix of the element-free Galerkin (EFG) method.

Bootstrap-current computations for a stellarator-reactor plasma

1990 ◽  
Vol 44 (3) ◽  
pp. 431-453 ◽  
Author(s):  
W. D. D'Haeseleer ◽  
W. N. G. Hitchon ◽  
C. D. Beidler ◽  
J. L. Shohet
Keyword(s):  
Distribution Function ◽  
Kinetic Equation ◽  
Physical Interpretation ◽  
Collision Operator ◽  
Numerical Code ◽  
Parallel Flows ◽  
Bootstrap Current ◽  
The Difference ◽  
Rotational Transform ◽  
The Impact

Numerical results for the bootstrap current in a stellarator-reactor plasma are presented. The distribution function f is computed numerically from a kinetic equation that is averaged over the helical ripple. The parallel flows and the current are obtained as v‖ moments of f. The physics issues embedded in the code are discussed concisely, concentrating on the justification as to why the bootstrap current can be estimated from an averaged scheme. Results are presented for typical stellarator-reactor parameters. The numerical code FLOCS predicts that the momentum-restoring terms in the collision operator have no significant impact on the value of the bootstrap current (the difference being about 10%). The results obtained are related to the equilibrium flows, and a physical interpretation based on the kinetic picture is presented. Finally, an estimate for the impact of J‖ on the rotational transform is given.

scholarly journals Recovery of Galilean invariance in thermal lattice Boltzmann models for arbitrary Prandtl number

2014 ◽  
Vol 25 (10) ◽  
pp. 1450046 ◽  
Author(s):  
Hudong Chen ◽  
Pradeep Gopalakrishnan ◽  
Raoyang Zhang
Keyword(s):  
Prandtl Number ◽  
Lattice Boltzmann ◽  
Relaxation Times ◽  
Collision Operator ◽  
Lattice Boltzmann Model ◽  
Operator Form ◽  
Prandtl Numbers ◽  
Lattice Boltzmann Models ◽  
Thermal Lattice Boltzmann ◽  
Boltzmann Model

In this paper, we demonstrate a set of fundamental conditions required for the formulation of a thermohydrodynamic lattice Boltzmann model at an arbitrary Prandtl number. A specific collision operator form is then proposed that is in compliance with these conditions. It admits two independent relaxation times, one for viscosity and another for thermal conductivity. But more importantly, the resulting thermohydrodynamic equations based on such a collision operator form is theoretically shown to remove the well-known non-Galilean invariant artifact at nonunity Prandtl numbers in previous thermal lattice Boltzmann models with multiple relaxation times.

Analysis of Deep Levels in GaAs Detector Diodes Using Impedance Spectroscopy

1993 ◽  
Vol 302 ◽  
Author(s):  
C Eiche ◽  
M Fiederle ◽  
J Weese ◽  
D Maier ◽  
D Ebling ◽  
...  
Keyword(s):  
Cross Section ◽  
Regularization Method ◽  
Capture Cross Section ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Simulated Data ◽  
Deep Levels ◽  
Admittance Spectroscopy ◽  
Thermal Relaxation Times ◽  
Level 2

ABSTRACTImpedance or admittance spectroscopy has been shown to be a very convenient tool for the investigation of deep levels in semiconductor junctions. At constant temperature a frequency sweep is performed. After that the impedance signal is analysed by a regularization method based on Tikhonov regularization in order to obtain the thermal relaxation times of the deep levels present in the junction. The high resolution of the regularization method in comparison to conventional techniques is demonstrated using simulated data. The temperature dependence of the thermal relaxation times provides information about the properties of the deep levels such as activation energy or capture cross section. Two donor levels with activation energies dE1 =0.58 eV and dE2 =0.68 eV are observed in our detector diodes. It can be shown that the concentration of level 2 is increased after irradiation.

Sign in / Sign up

Export Citation Format

Share Document