Biomedical subjects

J D Noh

Publications and source records attributed to J D Noh.

4 recordsLinked to original sources

PubMed2005

Load distribution in weighted complex networks.

We study the load distribution in weighted networks by measuring the effective number of optimal paths passing through a given vertex. The optimal path, along which the total cost is minimum, crucially depends on the cost distribution function p(c) (c) . In the strong disorder limit, where p(c) (c) approximately c(-1) , the load distribution follows a power law both in the Erdös-Rényi (ER) random graphs and in the scale-free (SF) networks, and its characteristics are determined by the structure of the minimum spanning tree. The distribution of loads at vertices with a given vertex degree also follows the SF nature similar to the whole load distribution, implying that the global transport property is not correlated to the local structural information. Finally, we measure the effect of disorder by the correlation coefficient between vertex degree and load, finding that it is larger for ER networks than for SF networks.

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PubMed2004

Analytic study of the three-urn model for separation of sand.

We present an analytic study of the three-urn model for separation of sand, which can be regarded as a zero-range process. We solve analytically the master equation and the first-passage problem. We find that the stationary probability distribution obeys the detailed balance and is governed by the free energy. We find that the characteristic lifetime of a cluster diverges algebraically with exponent 1/3 at the limit of stability. We also give a general argument that the scaling behavior is robust with respect to different expressions of the flux.

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PubMed2002

Critical behavior of the frustrated antiferromagnetic six-state clock model on a triangular lattice.

We study the antiferromagnetic six-state clock model with nearest neighbor interactions on a triangular lattice with extensive Monte Carlo simulations. We find clear indications of two phase transitions at two different temperatures: Below T(I) a chirality order sets in and by a thorough finite-size-scaling analysis of the specific heat and the chirality correlation length we show that this transition is in the Ising universality class (with a nonvanishing chirality order parameter below T(I)). At T(KT) (<T(I)) the spin-spin correlation length as well as the spin susceptibility diverges according to a Kosterlitz-Thouless (KT) form and spin correlations decay algebraically below T(KT). We compare our results to recent x-ray diffraction experiments on the orientational ordering of CF3Br monolayers physisorbed on graphite. We argue that the six-state clock model describes the universal feature of the phase transition in the experimental system and that the orientational ordering belongs to the KT universality class.

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PubMed2001

Disorder-driven critical behavior of periodic elastic media in a crystal potential.

A lattice model of a three-dimensional periodic elastic medium at zero temperature is studied with exact combinatorial optimization methods. A competition between pinning of the elastic medium, representing magnetic flux lines in a superconductor or charge density waves in a crystal, by randomly distributed impurities and a periodic lattice potential gives rise to a continuous roughening transition from a flat to a rough phase. A finite size scaling analysis yields the critical exponents nu approximately 1.3, beta approximately 0.05, gamma/nu approximately 2.9 that are universal with respect to the periodicity of the lattice potential. The small order parameter exponent is reminiscent of the random field Ising critical behavior in 3D.

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