A COMPARISON OF COHERENT POTENTIAL AND RANDOM WALK METHODS FOR CALCULATING THE TRANSPORT PROPERTIES OF AMORPHOUS SEMICONDUCTORS

1981 ◽  
Vol 42 (C4) ◽  
pp. C4-119-C4-122 ◽  
Author(s):  
V. Halpern
Keyword(s):  
Random Walk ◽  
Transport Properties ◽  
Amorphous Semiconductors

Quantitative Evaluation of Transport Properties of SOFC Porous Anode by Random Walk Process

2019 ◽  
Vol 25 (2) ◽  
pp. 1887-1896 ◽  
Author(s):  
Masashi Kishimoto ◽  
Hiroshi Iwai ◽  
Motohiro Saito ◽  
Hideo Yoshida
Keyword(s):  
Random Walk ◽  
Transport Properties ◽  
Quantitative Evaluation ◽  
Random Walk Process ◽  
Porous Anode

scholarly journals Comb Model: Non-Markovian versus Markovian

2019 ◽  
Vol 3 (4) ◽  
pp. 54 ◽  
Author(s):  
Alexander Iomin ◽  
Vicenç Méndez ◽  
Werner Horsthemke
Keyword(s):  
Wave Function ◽  
Random Walk ◽  
Transport Properties ◽  
Power Law ◽  
Continuous Time ◽  
Schrodinger Equation ◽  
Quantum Particle ◽  
Continuous Time Random Walk ◽  
Slow Diffusion ◽  
Branched Structures

Combs are a simple caricature of various types of natural branched structures, which belong to the category of loopless graphs and consist of a backbone and branches. We study two generalizations of comb models and present a generic method to obtain their transport properties. The first is a continuous time random walk on a many dimensional m + n comb, where m and n are the dimensions of the backbone and branches, respectively. We observe subdiffusion, ultra-slow diffusion and random localization as a function of n. The second deals with a quantum particle in the 1 + 1 comb. It turns out that the comb geometry leads to a power-law relaxation, described by a wave function in the framework of the Schrödinger equation.

scholarly journals Characterization of the Structure and Transport Properties of Alginate/Chitosan Microparticle Membranes Utilized in the Pervaporative Dehydration of Ethanol

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 411
Author(s):  
Gabriela Dudek ◽  
Przemysław Borys ◽  
Anna Strzelewicz ◽  
Monika Krasowska
Keyword(s):  
Random Walk ◽  
Transport Properties ◽  
Experimental Studies ◽  
Transport Parameters ◽  
Void Space ◽  
Fractal Parameters ◽  
Dehydration Processes ◽  
Average Size ◽  
High Resolution Microscopy

The structure and transport properties of alginate/chitosan microparticle membranes used in ethanol dehydration processes were investigated. The membranes were characterized based on images obtained from high-resolution microscopy. The following parameters were determined: the observed total amount of void space, the average size of the void domains, their length and diameter, the fractal dimension, and the generalized stochastic fractal parameters. The total amount of void space was determined to be between 54% and 64%. The average size of the void domains is smaller for alginate membranes containing neat (CS) and phosphorylated (CS-P) chitosan particles when compared to those membranes filled with glycidol-modified (CS-G) and glutaraldehyde crosslinked (CS-GA) chitosan particles. Furthermore, the transport of ethanol and water particles through the studied membranes was modelled using a random walk framework. It was observed that the results from the theoretical and experimental studies are directly correlated. The smallest values of water to ethanol diffusion coefficient ratios (i.e., 14) were obtained for Alg (sodium alginate) membranes loaded with the CS and CS-P particles, respectively. Significantly larger values (27 and 19) were noted for membranes filled with CS-G and CS-GA particles, respectively. The simulation results show that the size of channels which develop in the alginate matrix is less suited for ethanol molecules compared to water molecules because of their larger size. Such a situation facilitates the separation of water from ethanol. The comparison of the structural analysis of the membranes and random walk simulations allows one to understand the factors that influence the transport phenomena, in the studied membranes, and comment on the effect of the length, diameter, number of channels, and variations in the pore diameters on these transport parameters.

The Impact of a Long-Ranged Random Potential on the Transport Properties of Amorphous Semiconductors

1992 ◽  
Vol 258 ◽  
Author(s):  
Harald Overhof
Keyword(s):  
Activation Energy ◽  
Transport Properties ◽  
Random Potential ◽  
Amorphous Semiconductors ◽  
Random Potentials ◽  
Detailed Model ◽  
Model Calculations ◽  
Undoped Material ◽  
Dc Current ◽  
The Impact

ABSTRACTWe discuss electrostatic random potentials in doped and in compensated amorphous semiconductors. These potentials are caused by the residual inhomogeneity of a random distribution of charged dopants and their compensating charges. Random potentials are also present in undoped material with negative-U defects. A high density of positive-U defects can also give rise to a random potential in undoped material.We demonstrate with the help of detailed model calculations the effect of such random electrostatic potentials on the transport properties. For transport in extended states the random potential does not give rise to a mere shift of the mobility edge. Instead several new features are observed: the activation energy of the resulting Ohmie dc conductivity is virtually unaffected by the random potential in contrast to the activation energy of the thermoelectric power and that of the Hall effect, respectively. The Ohmie dc current changes at high fields into a superlinear current. The random potential contributes to the dispersion of the transients in time-of-flight experiments but leaves the field dependence of the TOF mobility unaltered. Comparing our results with experimental data we discuss under which circumstances the effect of random potentials can be identified.

Sign in / Sign up

Export Citation Format

Share Document