A Two-Dimensional Random Walk Model for Polymers

1965 ◽  
Vol 20 (3) ◽  
pp. 423-427 ◽  
Author(s):  
V. D. Gupta ◽  
A. K. Gupta
Keyword(s):  
Random Walk ◽  
Random Walk Model ◽  
Two Dimensional

The spatial distribution of gyrotactic swimming micro-organisms in laminar flow fields

2011 ◽  
Vol 680 ◽  
pp. 602-635 ◽  
Author(s):  
R. N. BEARON ◽  
A. L. HAZEL ◽  
G. J. THORN
Keyword(s):  
Random Walk ◽  
Diffusion Model ◽  
Diffusion Models ◽  
Random Walk Model ◽  
Two Dimensional ◽  
Local Flow ◽  
Spatial And Temporal Scales ◽  
Advection Diffusion ◽  
Micro Organisms ◽  
Good Agreement

We compare the results of two-dimensional, biased random walk models of individual swimming micro-organisms with advection–diffusion models for the whole population. In particular, we consider the influence of the local flow environment (gyrotaxis) on the resulting motion. In unidirectional flows, the results of the individual and population models are generally in good agreement, even in flows in which the cells can experience a range of shear environments, and both models successfully predict the phenomena of gravitactic focusing. Numerical results are also compared with asymptotic expressions for weak and strong shear. Discrepancies between the models arise in two cases: (i) when reflective boundary conditions change the orientation distribution in the random walk model from that predicted by the long-term asymptotics used to derive the advection–diffusion model; (ii) when the spatial and temporal scales are not large enough for the advection–diffusion model to apply. We also use a simple two-dimensional flow containing a variety of flow regimes to explore what happens when there are localized regions in which the generalized Taylor dispersion theory used in the derivation of the population model does not apply. For spherical cells, we find good agreement between the models outside the ‘break-down’ regions, but comparison of the results within these regions is complicated by the presence of nearby boundaries and their influence on the random walk model. In contrast, for rod-shaped cells which are reorientated by both vorticity and strain, we see qualitatively different spatial patterns between individual and advection–diffusion models even in the absence of gyrotaxis, because cells are advected between regions of differing rates of strain.

Deterministic Random Walks on the Two-Dimensional Grid

2009 ◽  
Vol 18 (1-2) ◽  
pp. 123-144 ◽  
Author(s):  
BENJAMIN DOERR ◽  
TOBIAS FRIEDRICH
Keyword(s):  
Random Walk ◽  
Random Walks ◽  
Random Walk Model ◽  
Two Dimensional ◽  
Expected Number ◽  
Fixed Order ◽  
The Difference ◽  
Propp Machine

Jim Propp's rotor–router model is a deterministic analogue of a random walk on a graph. Instead of distributing chips randomly, each vertex serves its neighbours in a fixed order. We analyse the difference between the Propp machine and random walk on the infinite two-dimensional grid. It is known that, apart from a technicality, independent of the starting configuration, at each time the number of chips on each vertex in the Propp model deviates from the expected number of chips in the random walk model by at most a constant. We show that this constant is approximately 7.8 if all vertices serve their neighbours in clockwise or order, and 7.3 otherwise. This result in particular shows that the order in which the neighbours are served makes a difference. Our analysis also reveals a number of further unexpected properties of the two-dimensional Propp machine.

Availability analysis of periodically inspected systems with random walk model

2001 ◽  
Vol 38 (4) ◽  
pp. 860-871 ◽  
Author(s):  
Lirong Cui ◽  
M. Xie
Keyword(s):  
Random Walk ◽  
Random Walk Model ◽  
Two Dimensional ◽  
Availability Analysis ◽  
Periodic Inspection ◽  
Dimensional Plane ◽  
Inspection And Maintenance ◽  
The Relationship

In this paper, the instantaneous availability of a system maintained under periodic inspection is investigated using random walk models. Two cases are considered. In the first model, the system is repaired or modified and it is assumed to be as good as new upon periodic inspection and maintenance. In the second model, the system is not modified after the inspection if the system is still working, and the condition of the system is assumed to be the same as that before the inspection. For both models the failures only can be found through the inspection. Perfect repair or replacement of a failed system is assumed to be carried out, but the time it takes can be constant or of a random length. The relationship between this problem and the random walk model in a two-dimensional plane is described. Several new results are also shown.

Agglomeration kinetics of monodisperse systems — computer simulation of agglomeration by a two-dimensional random walk model

1984 ◽  
Vol 38 (3) ◽  
pp. 211-216 ◽  
Author(s):  
H. Sunada ◽  
A. Otsuka ◽  
Y. Yamada ◽  
Y. Kawashima ◽  
H. Takernaka ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Random Walk ◽  
Random Walk Model ◽  
Two Dimensional ◽  
Kinetics Of

Availability analysis of periodically inspected systems with random walk model

2001 ◽  
Vol 38 (04) ◽  
pp. 860-871 ◽  
Author(s):  
Lirong Cui ◽  
M. Xie
Keyword(s):  
Random Walk ◽  
Random Walk Model ◽  
Two Dimensional ◽  
Availability Analysis ◽  
Periodic Inspection ◽  
Dimensional Plane ◽  
Inspection And Maintenance ◽  
The Relationship

In this paper, the instantaneous availability of a system maintained under periodic inspection is investigated using random walk models. Two cases are considered. In the first model, the system is repaired or modified and it is assumed to be as good as new upon periodic inspection and maintenance. In the second model, the system is not modified after the inspection if the system is still working, and the condition of the system is assumed to be the same as that before the inspection. For both models the failures only can be found through the inspection. Perfect repair or replacement of a failed system is assumed to be carried out, but the time it takes can be constant or of a random length. The relationship between this problem and the random walk model in a two-dimensional plane is described. Several new results are also shown.

A Multi-Label Classification Algorithm Based on Random Walk Model

2010 ◽  
Vol 33 (8) ◽  
pp. 1418-1426 ◽  
Author(s):  
Wei ZHENG ◽  
Chao-Kun WANG ◽  
Zhang LIU ◽  
Jian-Min WANG
Keyword(s):  
Random Walk ◽  
Classification Algorithm ◽  
Random Walk Model
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