Publications by authors named "Chul Koo Kim"

An active particle can convert its internal energy into mechanical work. We study a generalized energy-depot model of an overdamped active particle in a ratchet potential. Using well-known biological parameters for kinesin-1 and modeling ATP influx as a pulsed energy supply, we apply our model to the molecular motor system.

View Article and Find Full Text PDF

We amplified acoustic evanescent waves using metamaterial slabs with a negative effective density. For the amplifying effect of the slab to overcome the dissipation, it is necessary that the imaginary part of the effective density is much smaller than the real part, a condition not satisfied so far. We report the construction of membrane-based two-dimensional negative-density metamaterials which exhibited remarkably small dissipation.

View Article and Find Full Text PDF

We propose a unified theoretical scheme to calculate genotype frequencies of polymorphic populations with biological and social inheritance. This scheme is used to simulate the effects of social non-random mating on the population's evolution in the general situation of multiple biological gene loci and allele inheritance with natural selection and mutation. We study the case of hemophilia in several diverse situations when there exists non-random mating due to inheritance of social status.

View Article and Find Full Text PDF

We fabricated an acoustic composite structure consisting of a periodic array of interspaced membranes and side holes. Experimental data on the transmission, effective density, and phase velocity are presented. The system exhibits two critical frequencies, omega{SH} and omega{c}.

View Article and Find Full Text PDF

We present a particle-based simulation study on two-component swarms where there exist two different types of groups in a swarm. Effects of different parameters between the two groups are studied systematically based on Langevin's equation. It is shown that the mass difference can introduce a protective behavior for the lighter members of the swarm in a vortex state.

View Article and Find Full Text PDF

We present experimental and theoretical results on an acoustic metamaterial that exhibits a negative effective modulus in a frequency range from 0 to 450 Hz. A one-dimensional acoustic metamaterial with an array of side holes on a tube was fabricated. We observed that acoustic waves above 450 Hz propagated well in this structure, but no sound below 450 Hz passed through.

View Article and Find Full Text PDF

Elastic wave propagation along the structure of hollow cylinders in a linear isotropic medium is investigated. The multipole method for modeling elastic waves propagation in such structures is formulated and implemented. Using the multipole method, dispersion dependencies of the structures (microstructured fibers) containing 3, 6, and 7 hollow cylinders are calculated.

View Article and Find Full Text PDF

The cochlea is an important auditory organ in the inner ear. In most mammals, it is coiled as a spiral. Whether this specific shape influences hearing is still an open problem.

View Article and Find Full Text PDF

Motivation: With complete knowledge of the human genome sequence, one of the most interesting tasks remaining is to understand the functions of individual genes and how they communicate. Using the information about genes (locus, allele, mutation rate, fitness, etc.), we attempt to explain population demographic data.

View Article and Find Full Text PDF