Biomedical subjects

Zhun-Zhi Jin

Publications and source records attributed to Zhun-Zhi Jin.

10 recordsLinked to original sources

PubMed2004

Particle-cluster aggregation on a small-world network.

To describe the aggregation behaviors on substrates with long-range jump paths, a model of particle-cluster aggregation on a two-dimensional small-world network is presented. This model is characterized by two parameters: the clustering exponent alpha and the long-range connection rate phi. The results show that there exists an asymptotic fractal dimension D(max)(f) that depends upon alpha. With decrement of alpha, D(max)(f) varies from 1.7 to 2.0, which corresponds to a crossover from diffusion-limited-aggregation-like to dense growth. The change of the aggregation pattern results from the long-range connection in the network, which reduces the effect of screening during the aggregation. When the system size is not large enough, the effective fractal dimension D(f) depends upon phi because of the finite-size effect. With primitive analysis, we obtain the expression of the effective fractal dimension D(f) with the network parameters alpha and phi.

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PubMed2004

Morphological evolution in the electrodeposition of the Pb-Sn binary system.

Morphological evolution in the electrodeposition of Pb-Sn binary system is studied. As the second component increases, the morphology of the codeposit changes from dendrite to ramification, to dense branch, and finally to fractal structure, respectively. The evolution arises from the influence of crystallographic texture, which leads to a splitting of dendritic tips and the formation of ramified morphology. This work provides direct evidence to explore the crystallographic influence on the morphological evolution in electrodeposition.

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PubMed2003

Critical behavior of efficiency dynamics in small-world networks.

Some dynamical processes in a small-world network shows a critical transition at a finite disorder phi(c) of the network, in contrast with the geometrical properties that exhibit the critical behavior at phi(c)=0. Although it has been pointed out in previous works that the transition is related to the structural properties of the network, it is still not very clear why the transition occurs at phi(c) not equal 0. In this paper we present a simple social model of efficiency dynamics in small-world networks, which also shows a transition at phi(c)>0. We obtain the critical point with phi(c) approximately equal 0.098 from the finite-size analysis. It is found that both the geometrical properties of the network and the specific dynamical characters of the model contribute to the critical transition. This work is useful for understanding this kind of transition occurring in many dynamical processes in small-world networks.

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PubMed2003

Network-induced nonequilibrium phase transition in the "game of Life".

A cellular automation model of the "game of Life" on a two-dimensional small-world network is presented in order to count in long-range interactions among living individuals in social or biological systems. The density of the life and its fluctuation are calculated, respectively. The present model exhibits a nonequilibrium phase transition from an "inactive-sparse" state to an "active-dense" one at a certain intermediate value of the network disorder. Employing finite-size scaling analysis, we estimate the location of the critical point with p(c)( infinity ) approximately 0.3685. The transition is of the "second-order" type with power-law diverging length. We obtain the critical exponents 1/nu approximately 1.70, beta approximately 0.50, and beta/nu approximately 0.85. The calculated results indicate that the present model may belong to the universality class of directed percolation.

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PubMed2002

Multiparticle random walks on a deformable medium.

Multiparticle random walks on a deformable medium have been investigated in (2+1) dimensions. The time evolution of the particle distribution is studied. The results show that the randomly distributed particles in the beginning will be self-organized into a cluster pattern in the intermediate stage, and then return to the random distribution pattern in the late stage. The dependence of the clustering degree on the stiffness parameter of medium alpha, stability parameter of systems beta, and average particle density rho(0) is also investigated. There exists an optimal clustering stability beta(p), at which the system has the strongest clustering ability and corresponds to a maximum clustering coefficient Gamma(*)(p). The dependence of the optimal clustering coefficient Gamma(*)(p) on the stiffness alpha and particle density rho(0) is obtained, and the landscape of the medium generated by particles is also investigated.

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PubMed2002

Patterns of particle distribution in multiparticle systems by random walks with memory enhancement and decay.

We investigate the pattern of particle distribution and its evolution with time in multiparticle systems using the model of random walks with memory enhancement and decay. This model describes some biological intelligent walks. With decrease in the memory decay exponent alpha, the distribution of particles changes from a random dispersive pattern to a locally dense one, and then returns to the random one. Correspondingly, the fractal dimension D(f,p) characterizing the distribution of particle positions increases from a low value to a maximum and then decreases to the low one again. This is determined by the degree of overlap of regions consisting of sites with remanent information. The second moment of the density rho(2) was introduced to investigate the inhomogeneity of the particle distribution. The dependence of rho(2) on alpha is similar to that of D(f,p) on alpha. rho(2) increases with time as a power law in the process of adjusting the particle distribution, and then rho(2) tends to a stable equilibrium value.

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PubMed2002

Directed random walks in continuous space.

The investigation on diffusion with directed motion in a two-dimensional continuous space is completed by using the model of the continuous directed random walks. The average square end-to-end distance approximately t(2nu) is calculated. The results show that this type of walks belongs asymptotically to the same class (nu=1.0) as the ballistic motions. For short time, we observe a crossover from purely random walks (nu=0.5) to ballistic motions (nu=1.0). The dependence of the crossover on the direction parameter theta is studied. There exists a scaling relation of the form approximately tf(t/theta(-2)). The return probability P00(t) is also investigated and the scaling form similar to is obtained.

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PubMed2002

Pattern formation on nonuniform surfaces by correlated random sequential absorptions.

The pattern formation on nonuniform surfaces by correlated-random sequential absorption (CRSA) process has been investigated by computer simulations. The nonuniform surfaces are represented by percolation clusters with probabilities p(s) and p(s) stands for the nonuniform degree of surfaces. The interactions between the particles and the defects in surfaces are involved by introducing a sticking coefficient s. When s-->0, the CRSA process is controlled by the absorption of surfaces and the correlation between particles. With the correlation increasing from a weak limit to a strong one, the cluster consisting of absorbed particles changes from the dispersed pattern of site percolation to correlated percolation, and then to Leath percolation clusters. When s-->1 and p(s)-->p(c), the CRSA process is dominated by the absorption of the defects, where p(c) is the threshold of percolations. The patterns appear randomly dispersed in spite of the correlation. With the decrease of s and increase of p(s), the interaction controlling the CRSA process changes from the absorption of defects to that of surface and the correlation between particles gradually. For the system s-->0, the transition correlation exponent alpha(c)=d(s), where d(s) is the fractal dimension of the percolation surfaces.

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PubMed2002

Random walk with memory enhancement and decay.

A model of random walk with memory enhancement and decay was presented on the basis of the characteristics of the biological intelligent walks. In this model, the movement of the walker is determined by the difference between the remaining information at the jumping-out site and jumping-in site. The amount of the memory information s(i)(t) at a site i is enhanced with the increment of visiting times to that site, and decays with time t by the rate e(-beta(t)), where beta is the memory decay exponent. When beta=0, there exists a transition from Brownian motion (BM) to the compact growth of walking trajectory with the density of information energy u increasing. But for beta>0, this transition does not appear and the walk with memory enhancement and decay can be considered as the BM of the mass center of the cluster composed of remembered sites in the late stage.

Animals↗

PubMed2002

Random walks on a ( 2+1)-dimensional deformable medium.

A model of random walks on a deformable medium is proposed in 2+1 dimensions. The behavior of the walk is characterized by the stability parameter beta and the stiffness exponent alpha. The average square end-to-end distance l approximately equals (2nu) and the average number of visited sites approximately equals (k) are calculated. As beta increases, for each alpha there exists a critical transition point beta(c) from purely random walks ( nu = 1/2 and k approximate to 1) to compact growth ( nu = 1/3 and k = 2/3). The relationship between beta(c) and alpha can be expressed as beta(c) = e(alpha). The landscape generated by a walk is also investigated by means of the visit-number distribution N(n)(beta). There exists a scaling relationship of the form N(n)(beta)approximately n(-2)f(n/beta(z)).

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