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Search Results: 1 - 10 of 2962 matches for " Hyung Yoon "
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Equilibrium and Dynamical Evolution of Self-Gravitating System Embedded in a Potential Well
Ilsang Yoon,Hyung Mok Lee,Jongsuk Hong
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.18589.x
Abstract: Isothermal and self-gravitating systems bound by non-conducting and conducting walls are known to be unstable if the density contrast between the center and the boundary exceeds critical values. We investigate the equilibrium and dynamical evolution of isothermal and self-gravitating system embedded in potential well, which can be the situation of many astrophysical objects such as the central parts of the galaxies, or clusters of galaxies with potential dominated by dark matter, but is still limited to the case where the potential well is fixed during the evolution. As the ratio between the depth of surrounding potential well and potential of embedded system becomes large, the potential well becomes effectively the same boundary condition as conducting wall, which behaves like a thermal heat bath. We also use the direct N-body simulation code, NBODY6 to simulate the dynamical evolution of stellar system embedded in potential wells and propose the equilibrium models for this system. In deep potential well, which is analogous to the heat bath with high temperature, the embedded self-gravitating system is dynamically hot, and loosely bound or can be unbound since the kinetic energy increases due to the heating by the potential well. On the other hand, the system undergoes core collapse by self-gravity when potential well is shallow. Binary heating can stop the collapse and leads to the expansion, but the evolution is very slow because the potential as a heat bath can absorb the energy generated by the binaries. The system can be regarded as quasi-static. Density and velocity dispersion profiles from the N-body simulations in the final quasi-equilibrium state are similar to our equilibrium models assumed to be in thermal equilibrium with the potential well.
Recent progress in staggered chiral perturbation theory
Bailey, Jon;Kim, Hyung-Jin;Lee, Weonjong;Yoon, Boram
High Energy Physics - Phenomenology , 2013,
Abstract: We present a review on recent progress in staggered chiral perturbation theory (SChPT). In the last decade, the scope of the application of SChPT has been extended beyond the level of calibration into the region of prediction with high precision. SChPT becomes an essential tool to do the data analysis reliably for physical observables calculated using improved staggered fermions. Here, we focus on the following examples: pion spectrum, pion decay constants, $\varepsilon_K$, and $\pi-\pi$ scattering amplitudes. In each subject, we review the recent progress and future prospects.
A novel walking speed estimation scheme and its application to treadmill control for gait rehabilitation
Yoon Jungwon,Park Hyung-Soon,Damiano Diane
Journal of NeuroEngineering and Rehabilitation , 2012, DOI: 10.1186/1743-0003-9-62
Abstract: Background Virtual reality (VR) technology along with treadmill training (TT) can effectively provide goal-oriented practice and promote improved motor learning in patients with neurological disorders. Moreover, the VR + TT scheme may enhance cognitive engagement for more effective gait rehabilitation and greater transfer to over ground walking. For this purpose, we developed an individualized treadmill controller with a novel speed estimation scheme using swing foot velocity, which can enable user-driven treadmill walking (UDW) to more closely simulate over ground walking (OGW) during treadmill training. OGW involves a cyclic acceleration-deceleration profile of pelvic velocity that contrasts with typical treadmill-driven walking (TDW), which constrains a person to walk at a preset constant speed. In this study, we investigated the effects of the proposed speed adaptation controller by analyzing the gait kinematics of UDW and TDW, which were compared to those of OGW at three pre-determined velocities. Methods Ten healthy subjects were asked to walk in each mode (TDW, UDW, and OGW) at three pre-determined speeds (0.5 m/s, 1.0 m/s, and 1.5 m/s) with real time feedback provided through visual displays. Temporal-spatial gait data and 3D pelvic kinematics were analyzed and comparisons were made between UDW on a treadmill, TDW, and OGW. Results The observed step length, cadence, and walk ratio defined as the ratio of stride length to cadence were not significantly different between UDW and TDW. Additionally, the average magnitude of pelvic acceleration peak values along the anterior-posterior direction for each step and the associated standard deviations (variability) were not significantly different between the two modalities. The differences between OGW and UDW and TDW were mainly in swing time and cadence, as have been reported previously. Also, step lengths between OGW and TDW were different for 0.5 m/s and 1.5 m/s gait velocities, and walk ratio between OGS and UDW was different for 1.0 m/s gait velocities. Conclusions Our treadmill control scheme implements similar gait biomechanics of TDW, which has been used for repetitive gait training in a small and constrained space as well as controlled and safe environments. These results reveal that users can walk as stably during UDW as TDW and employ similar strategies to maintain walking speed in both UDW and TDW. Furthermore, since UDW can allow a user to actively participate in the virtual reality (VR) applications with variable walking velocity, it can induce more cognitive activities during the
Statistical properties of sampled networks by random walks
Sooyeon Yoon,Sungmin Lee,Soon-Hyung Yook,Yup Kim
Physics , 2006, DOI: 10.1103/PhysRevE.75.046114
Abstract: We study the statistical properties of the sampled networks by a random walker. We compare topological properties of the sampled networks such as degree distribution, degree-degree correlation, and clustering coefficient with those of the original networks. From the numerical results, we find that most of topological properties of the sampled networks are almost the same as those of the original networks for $\gamma \lesssim 3$. In contrast, we find that the degree distribution exponent of the sampled networks for $\gamma>3$ somewhat deviates from that of the original networks when the ratio of the sampled network size to the original network size becomes smaller. We also apply the sampling method to various real networks such as collaboration of movie actor, world wide web, and peer-to-peer networks. All topological properties of the sampled networks show the essentially same as the original real networks.
Recent progress in staggered chiral perturbation theory
Jon Bailey,Hyung-Jin Kim,Weonjong Lee,Boram Yoon
Physics , 2013,
Abstract: We present a review on recent progress in staggered chiral perturbation theory (SChPT). In the last decade, the scope of the application of SChPT has been extended beyond the level of calibration into the region of prediction with high precision. SChPT becomes an essential tool to do the data analysis reliably for physical observables calculated using improved staggered fermions. Here, we focus on the following examples: pion spectrum, pion decay constants, $\varepsilon_K$, and $\pi-\pi$ scattering amplitudes. In each subject, we review the recent progress and future prospects.
Mesoscopic model for mechanical characterization of biological protein materials
Gwonchan Yoon,Hyung-Jin Park,Sungsoo Na,Kilho Eom
Quantitative Biology , 2008,
Abstract: Mechanical characterization of protein molecules has played a role on gaining insight into the biological functions of proteins, since some proteins perform the mechanical function. Here, we present the mesoscopic model of biological protein materials composed of protein crystals prescribed by Go potential for characterization of elastic behavior of protein materials. Specifically, we consider the representative volume element (RVE) containing the protein crystals represented by alpha-carbon atoms, prescribed by Go potential, with application of constant normal strain to RVE. The stress-strain relationship computed from virial stress theory provides the nonlinear elastic behavior of protein materials and their mechanical properties such as Young's modulus, quantitatively and/or qualitatively comparable to mechanical properties of biological protein materials obtained from experiments and/or atomistic simulations. Further, we discuss the role of native topology on the mechanical properties of protein crystals. It is shown that parallel strands (hydrogen bonds in parallel) enhances the mechanical resilience of protein materials.
Modeling the effects of constructed wetland on nonpoint source pollution control and reservoir water quality improvement

Ham Jonghwa,Yoon Chun G,Kim Hyung-Joong,Kim Hyung-Chul,

环境科学学报(英文版) , 2010,
Abstract: This article describes the integrated modeling approach for planning the size and the operation of constructed wetlands for maximizing retention of nonpoint source pollutant loads and reservoir water-quality improvement at a catchment scale. The experimental field-scale wetland systems (four sets, 0.88 ha each) have been in operation since 2002, where water depth was maintained at 30-50 cm and hydraulic loading rate was at 6.3-18.8 cm/day. The wetland system was found to be adequate for treating polluted stream water with stable removal efficiency even during the winter. The integrated modeling system (modified-BASINS) was applied to the Seokmoon estuarine reservoir watershed and calibrated with monitoring data from constructed wetland, stream, and reservoir. The calibrated integrated modeling system estimated that constructing wetlands on 0.5% (about 114 ha) of the watershed area at the mouth of reservoir could reduce 11.61% and 13.49% of total external nitrogen and phosphorus loads, respectively. It also might improve the nitrogen and phosphorus concentration of the reservoir by 9.69% and 16.48%, respectively. The study suggested that about 0.1 %-1 .0% of the watershed area should be allocated for constructed wetland to meet specified water-quality standards for the estuarine reservoir at the polder area where land use planning is relatively less complicated.
The dependence of transverse and longitudinal resolutions on incident Gaussian beam widths in the illumination part of optical scanning microscopy
Hyung-Su Chon,Gisung Park,Sang-Bum Lee,Seokchan Yoon,Jaisoon Kim,Jai-Hyung Lee,Kyungwon An
Physics , 2004,
Abstract: We studied both theoretically and experimentally the intensity distribution of a Gaussian laser beam when it was focussed by an objective lens with its numerical-aperture (NA) up to 0.95. Approximate formulae for full widths at half maximum (FWHM) of the intensity distribution at focus were derived for very large and very small initial beam waists with respect to the entrance pupil radius of the objective lens. In experiments the energy flux through a 0.5 micron pinhole was measured for various pinhole positions. We found that the FWHM's at focus in the transverse and the longitudinal directions do not increase much from the ultimate FWHM's until the input beam waist is reduced below the half of the entrance pupil radius. In addition, we observed significance of the spatial distribution of the input beam against a true Gaussian beam profile in the case of small initial beam waist. For high NA with resulting focal beam waists comparable to or smaller than the wavelength of the laser, the interaction between the electric field and the conducting surface of the pinhole caused the transverse FWHM to be measured slightly smaller than FWHM of the unperturbed intensity distribution convoluted with the pinhole opening.
Differential Expression of Programmed Cell Death on the Follicular Development in Normal and Miniature Pig Ovary
Sang Hwan Kim, Kwan Sik Min, Nam Hyung Kim, Jong Taek Yoon
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046194
Abstract: Follicles are important in oocyte maturation. Successful estrous cycle requires remodeling of follicular cells, and proper execution of programmed cell death is crucial for normal follicular development. The objectives of the present study were to understand programmed cell death during follicle development, to analyze the differential follicle development patterns, and to assess the patterns of apoptosis and autophagy expression during follicle development in normal and miniature pigs. Through the analysis of differential patterns of programmed cell death during follicular development in porcine, MAP1LC3A, B and other autophagy-associated genes (ATG5, mTOR, Beclin-1) were found to increase in normal pigs, while it decreased in miniature pigs. However, for the apoptosis-associated genes, progression of genes during follicular development increased in miniature pigs, while it decreased in normal pigs. Thus, results show that normal and miniature pigs showed distinct patterns of follicular remodeling manifesting that programmed cell death largely depends on the types of pathway during follicular development (Type II or autophagy for normal pigs and Type I or apoptosis for miniature pigs).
Lower Salinomycin Concentration Increases Apoptotic Detachment in High-Density Cancer Cells
Ju-Hwa Kim,Tae Young Kim,Hyung Sik Kim,Suntaek Hong,Sungpil Yoon
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms131013169
Abstract: The present study identified a novel salinomycin (Sal) sensitization mechanism in cancer. We tested whether Sal reduced proliferation in a high-density population by counting attached cell numbers after Sal treatment. Sal reduced proliferation in high-density cell populations. Longer exposure to Sal further reduced proliferation. Sal concentrations of 0.1 and 5 μM had similar sensitization effects, suggesting that Sal toxicity was minimal with longer exposure to a high-density cell population. The results suggest that Sal can be applied at a relatively low concentration for a longer time to overcome drug-resistant solid tumors. The 0.5 μM Sal treatment resulted in fewer attached cells than that of the 5 μM Sal treatment with a longer exposure. The lower Sal concentration mainly increased the number of easily detachable cells on the surface. In particular, 0.5 μM Sal increased cellular detachment of newly produced daughter cells. The easily-detachable cells were undergoing apoptosis. It seems that the 0.5 μM Sal treatment also increased cellular toxicity. These novel findings may contribute to the development of Sal-based therapy for patients with drug-resistant cancer or a high-density solid tumor.
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