Time-dependent diffusion models of the annihilation of low energy positrons implanted in solids

1994 ◽  
Vol 445 (1923) ◽  
pp. 57-67 ◽  
Keyword(s):  
Single Crystal ◽  
Diffusion Model ◽  
Diffusion Models ◽  
Low Energy ◽  
Experimental Results ◽  
Time Dependent ◽  
Group Model ◽  
Single Group ◽  
Thermal Distribution

Two different models for positron transport in solids after implantation are presented. In the simplest model positrons are assumed to be implanted thermally and diffuse to the surface. In the second, two group model, the epithermal distribution acts as time-dependent source for the thermal distribution. Using experimental results from single crystal aluminium, silver and gold, it is shown that for deeply implanted positrons a single group diffusion model can be applied. At lower incident energies, neither model is applicable. In particular, a single epithermal state does not satisfactorily describe the intermediate stages of thermalization.

Time-dependent diffusion model for sea clutter dynamics

2021 ◽  
Vol 42 (18) ◽  
pp. 6818-6836
Author(s):  
Pirouz Majdolashrafi ◽  
Mehrdad Ardebilipour ◽  
Yalda Rajabzadeh
Keyword(s):  
Diffusion Model ◽  
Time Dependent ◽  
Sea Clutter

Random Forces Resulting From Internal Two-Phase Flow on Bends and Tees

2006 ◽  
Author(s):  
E. de Langre ◽  
J. L. Riverin ◽  
M. J. Pettigrew
Keyword(s):  
Two Phase Flow ◽  
Experimental Results ◽  
Time Dependent ◽  
Phase Flow ◽  
Water Mixture ◽  
Dimensionless Form ◽  
Two Phase ◽  
Practical Applications ◽  
Random Forces

The time dependent forces resulting from a two-phase air-water mixture flowing in an elbow and a tee are measured. Their magnitudes as well as their spectral contents are analyzed. Comparison is made with previous experimental results on similar systems. For practical applications a dimensionless form is proposed to relate the characteristics of these forces to the parameters defining the flow and the geometry of the piping.

A study of time-dependent, low energy (2 × 10-4 eV

1996 ◽  
Vol 31 (2) ◽  
pp. 117-125 ◽  
Author(s):  
Sanjay Gupta ◽  
Feroz Ahmed ◽  
Suresh Garg
Keyword(s):  
Fusion Reactor ◽  
Low Energy ◽  
Time Dependent ◽  
Tritium Breeding ◽  
Neutron Spectra

Catalytically Transformed Low Energy Intensive 2D-Layered and Single Crystal-Graphitic Renewable Carbon Cathode Conductors

Carbon ◽  
2021 ◽  
Author(s):  
Maria Semeniuk ◽  
Zahra Sarshar ◽  
Sossina Gezahegn ◽  
Zhishan Li ◽  
Abisola Egbedina ◽  
...  
Keyword(s):  
Single Crystal ◽  
Low Energy ◽  
Carbon Cathode

scholarly journals A generalized perspective of Fourier and Fick’s laws: Magnetized effects of Cattaneo-Christov models on transient nanofluid flow between two parallel plates with Brownian motion and thermophoresis

2020 ◽  
Vol 9 (1) ◽  
pp. 201-222 ◽  
Author(s):  
Usha Shankar ◽  
Neminath B. Naduvinamani ◽  
Hussain Basha
Keyword(s):  
Brownian Motion ◽  
Joule Heating ◽  
Concentration Field ◽  
Double Diffusion ◽  
Diffusion Models ◽  
Time Dependent ◽  
Parallel Plates ◽  
Nanofluid Flow ◽  
Casson Nanofluid ◽  
Highly Nonlinear

AbstractPresent research article reports the magnetized impacts of Cattaneo-Christov double diffusion models on heat and mass transfer behaviour of viscous incompressible, time-dependent, two-dimensional Casson nanofluid flow through the channel with Joule heating and viscous dissipation effects numerically. The classical transport models such as Fourier and Fick’s laws of heat and mass diffusions are generalized in terms of Cattaneo-Christov double diffusion models by accounting the thermal and concentration relaxation times. The present physical problem is examined in the presence of Lorentz forces to investigate the effects of magnetic field on double diffusion process along with Joule heating. The non-Newtonian Casson nanofluid flow between two parallel plates gives the system of time-dependent, highly nonlinear, coupled partial differential equations and is solved by utilizing RK-SM and bvp4c schemes. Present results show that, the temperature and concentration distributions are fewer in case of Cattaneo-Christov heat and mass flux models when compared to the Fourier’s and Fick’s laws of heat and mass diffusions. The concentration field is a diminishing function of thermophoresis parameter and it is an increasing function of Brownian motion parameter. Finally, an excellent comparison between the present solutions and previously published results show the accuracy of the results and methods used to achieve the objective of the present work.

scholarly journals Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2851
Author(s):  
Huanqiang Liu ◽  
Linhua Jiang
Keyword(s):  
Diffusion Coefficient ◽  
Hydrostatic Pressure ◽  
Diffusion Model ◽  
Coupling Effect ◽  
Experimental Results ◽  
Chloride Diffusion ◽  
Concrete Durability ◽  
Chloride Diffusion Coefficient ◽  
Diffusion Behavior ◽  
Diffusion Source

The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions.

A model for the time-dependent thermal distribution within an iceball surrounding a cryoprobe

1998 ◽  
Vol 43 (12) ◽  
pp. 3519-3534 ◽  
Author(s):  
John C Rewcastle ◽  
George A Sandison ◽  
Leszek J Hahn ◽  
John C Saliken ◽  
J Gregory McKinnon ◽  
...  
Keyword(s):  
Time Dependent ◽  
Thermal Distribution

Molecular Dynamics Simulation of Sputtering with Mmany-Body Interactions

1988 ◽  
Vol 100 ◽  
Author(s):  
Davy Y. Lo ◽  
Tom A. Tombrello ◽  
Mark H. Shapiro ◽  
Don E. Harrison
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Single Crystal ◽  
Low Energy ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Many Body ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Small Single Crystal

ABSTRACTMany-body forces obtained by the Embedded-Atom Method (EAM) [41 are incorporated into the description of low energy collisions and surface ejection processes in molecular dynamics simulations of sputtering from metal targets. Bombardments of small, single crystal Cu targets (400–500 atoms) in three different orientations ({100}, {110}, {111}) by 5 keV Ar+ ions have been simulated. The results are compared to simulations using purely pair-wise additive interactions. Significant differences in the spectra of ejected atoms are found.

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