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Search Results: 1 - 10 of 27896 matches for " Sang Chul Lee "
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Bertrand-Cournot Comparison in a Mixed Duopoly with Advertisement  [PDF]
Chul-Hi Park, Dmitriy Li, Sang-Ho Lee
Theoretical Economics Letters (TEL) , 2016, DOI: 10.4236/tel.2016.62017
Abstract: We examine the Bertrand-Cournot comparison with advertisement in a differentiated mixed duopoly market, and compare with the social optimum. We show that not only both firms’ quantities but also both firms’ advertisements are higher (lower) in Cournot (Bertrand) than the social optimum. Thus, both firms engage in excessive (insufficient) advertisement in Cournot (Bertrand). We also show that despite lower both firms’ prices in Cournot, both firms’ profits and social welfare are strictly higher in Bertrand and thus, both firms prefer Bertrand to Counrnot.
Prevalence of depression and correlates of depressive symptoms among residents in urban area of Jeju Island
Kim Moon,Chul Seong,Lee Sang
Annals of General Psychiatry , 2006, DOI: 10.1186/1744-859x-5-s1-s177
Abstract:
Stellar Populations of the Sagittarius Dwarf Irregular Galaxy
Myung Gyoon Lee,Sang Chul Kim
Physics , 1999, DOI: 10.1086/301211
Abstract: We present deep BVRI CCD photometry of the stars in the dwarf irregular galaxy SagDIG. The color-magnitude diagrams of the measured stars in SagDIG show a blue plume which consists mostly of young stellar populations, and a well-defined red giant branch (RGB). The foreground reddening of SagDIG is estimated to be E(B-V)=0.06. The tip of the RGB is found to be at I_(TRGB)=21.55 +/- 0.10 mag. From this the distance to this galaxy is estimated to be d = 1.18 +/- 0.10 Mpc. This result, combined with its velocity information, shows that it is a member of the Local Group. The mean metallicity of the red giant branch is estimated to be [Fe/H] < -2.2 dex. This shows that SagDIG is one of the most metal-poor galaxies. Total magnitudes of SagDIG (< r_H (= 107 arcsec)) are derived to be B^T=13.99 mag, V^T=13.58 mag, R^T=13.19 mag, and I^T=12.88 mag, and the corresponding absolute magnitudes are M_B=-11.62 mag, M_V=-11.97 mag, M_R=-12.33 mag, and M_I=-12.60 mag. Surface brightness profiles of the central part of SagDIG are approximately fit by a King model with a core concentration parameter c = log (r_t / r_c) ~ 0.6, and those of the outer part follow an exponential law with a scale length of 37 arcsec. The central surface brightness is measured to be mu_B (0) = 24.21 mag arcsec^(-2) and mu_V (0) =23.91 mag arcsec^(-2). The magnitudes and colors of the brightest blue and red stars in SagDIG (BSG and RSG) are measured to be, respectively, _BSG = 19.89 +/- 0.13 mag, <(B-V)(3)>_BSG = 0.08 +/- 0.07 mag, _RSG = 20.39 +/- 0.10 mag, and <(B-V)(3)>_RSG = 1.29 +/- 0.12 mag. The corresponding absolute magnitudes are derived to be _BSG = -5.66 mag and _RSG = -5.16 mag, which are about one magnitude fainter than those expected from conventional correlations with galaxy luminosity.
Nonequilibrium Quantum Dynamics of Second Order Phase Transitions
Sang Pyo Kim,Chul H. Lee
Physics , 2000, DOI: 10.1103/PhysRevD.62.125020
Abstract: We use the so-called Liouville-von Neumann (LvN) approach to study the nonequilibrium quantum dynamics of time-dependent second order phase transitions. The LvN approach is a canonical method that unifies the functional Schr\"{o}dinger equation for the quantum evolution of pure states and the LvN equation for the quantum description of mixed states of either equilibrium or nonequilibrium. As nonequilibrium quantum mechanical systems we study a time-dependent harmonic and an anharmonic oscillator and find the exact Fock space and density operator for the harmonic oscillator and the nonperturbative Gaussian Fock space and density operator for the anharmonic oscillator. The density matrix and the coherent, thermal and coherent-thermal states are found in terms of their classical solutions, for which the effective Hamiltonians and equations of motion are derived. The LvN approach is further extended to quantum fields undergoing time-dependent second order phase transitions. We study an exactly solvable model with a finite smooth quench and find the two-point correlation functions. Due to the spinodal instability of long wavelength modes the two-point correlation functions lead to the $t^{1/4}$-scaling relation during the quench and the Cahn-Allen scaling relation $t^{1/2}$ after the completion of quench. Further, after the finite quench the domain formation shows a time-lag behavior at the cubic power of quench period. Finally we study the time-dependent phase transition of a self-interacting scalar field.
Emergence of Classicality in Quantum Phase Transitions
Sang Pyo Kim,Chul H. Lee
Physics , 2000, DOI: 10.1103/PhysRevD.65.045013
Abstract: We show that classicality emerges during quantum phase transitions due to parametric interactions without coupling to environments. The Wigner functions are explicitly calculated for the Gaussian vacuum, number, and thermal states of a free scalar field that describes the spinodal instability regime. The Wigner functions are sharply peaked around their classical trajectories during the phase transition and exhibit classical correlation only for unstable long wavelength modes but retain quantum coherence for short wavelength modes. Thus classicality emerges from the quantum evolution of phase transitions without a classical order parameter. We define a quantal ordering parameter that is linear in the field variable and satisfies the classical field equation.
Surface Photometry of the Dwarf Elliptical Galaxies NGC 185 and NGC 205
Sang Chul Kim,Myung Gyoon Lee
Physics , 1998,
Abstract: We present BVRI CCD surface photometry for the central (6'.35 X 6'.35) regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R < 225") and NGC 205 (R < 186") show excess components in the central regions. The colors of NGC 185 get bluer inward at R < 25", while they remain constant at R >= 25". The colors of NGC 205 get bluer inward at 1" < R < 50", and remain flat outside. Our photometry, supplemented by the photometry based on the far-ultraviolet and visual images of the HST archive data, shows that there is an inversion of color at the very nucleus region (at about 1"). The implications of the redder color of the core part of the nucleus compared with neighboring regions are discussed. The amount of the excess components in the central regions of these galaxies is estimated to be ~10^5 solar luminosity. Distributions of dust clouds in the central regions of the two galaxies are also investigated.
Optical spectral classification of southern ultraluminous infrared galaxies
Jong Chul Lee,Ho Seong Hwang,Myung Gyoon Lee,Minjin Kim,Sang Chul Kim
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.18437.x
Abstract: We present a study of the optical spectral properties of 115 ultraluminous infrared galaxies (ULIRGs) in the southern sky. Using the optical spectra obtained at CTIO 4 m and provided by the 2dF Galaxy Redshift Survey and the 6dF Galaxy Survey, we measure emission line widths and fluxes for spectral classification. We determine the spectral types of ULIRGs with H_alpha measurement using the standard diagnostic diagrams. For ULIRGs without H_alpha measurement, we determine their spectral types using the plane of flux ratio between [OIII]_lambda5007 and H_beta versus [OIII] line width based on our new empirical criterion. This criterion is efficient to distinguish active galactic nuclei (AGNs) from non-AGN galaxies with completeness and reliability of about 90 per cent. The sample of 115 ULIRGs is found to consist of 8 broad-line AGNs, 49 narrow-line AGNs, and 58 non-AGNs. The AGN fraction is on average 50 per cent and increases with infrared luminosity and IRAS 25-60 micron colour, consistent with previous studies. The IRAS 25-60 micron colour distributions are significantly different between AGN and non-AGN ULIRGs, while their IRAS 60-100 micron colour distributions are similar.
Electrogastrography associated with symptomatic changes after prokinetic drug treatment for functional dyspepsia
Hyun Chul Lim,Sang In Lee,Jiande DZ Chen,Hyojin Park
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i41.5948
Abstract: AIM: To evaluate the effect of prokinetic drugs on electrogastrography (EGG) parameters according to symptomatic changes in patients with functional dyspepsia (FD). METHODS: Seventy-four patients with FD were prospectively enrolled in this study between December 2006 and December 2010. We surveyed the patients using a questionnaire on dyspeptic symptoms before and after an 8-wk course of prokinetic drug treatment. We also measured cutaneous pre-prandial and post-prandial EGG recordings including percentage of gastric waves (normogastria, bradygastria, tachygastria), dominant frequency (DF), dominant power (DP), dominant frequency instability coefficient (DFIC), dominant power instability coefficient (DPIC), and the ratio of post-prandial to fasting in DP before and after the 8-wk course of prokinetic drug treatment. RESULTS: Fifty-two patients (70%) achieved symptomatic improvement after prokinetic drug treatment. Patients who had normal gastric slow waves showed symptom improvement group after treatment. Post-prandial DF showed a downward trend in the symptom improvement group, especially in the itopride group. Post-prandial DP was increased regardless of symptom improvement, especially in the itopride group and mosapride group. Post-prandial DFIC and DPIC in the symptom improvement group were significantly increased after the treatment. The EGG power ratio was increased after treatment in the symptom improvement group (0.50 ± 0.70 vs 0.93 ± 1.77, P = 0.002), especially in the itopride and levosulpiride groups. CONCLUSION: Prokinetics could improve the symptoms of FD by regulating gastric myoelectrical activity, and EGG could be a useful tool in evaluating the effects of various prokinetics.
Accuracy Evaluation for Region Centroid-Based Registration of Fluorescent CLSM Imagery
Lee Sang-Chul,Bajcsy Peter,Lin Amy,Folberg Robert
EURASIP Journal on Advances in Signal Processing , 2006,
Abstract: We present an accuracy evaluation of a semiautomatic registration technique for 3D volume reconstruction from fluorescent confocal laser scanning microscope (CLSM) imagery. The presented semiautomatic method is designed based on our observations that (a) an accurate point selection is much harder than an accurate region (segment) selection for a human, (b) a centroid selection of any region is less accurate by a human than by a computer, and (c) registration based on structural shape of a region rather than based on intensity-defined point is more robust to noise and to morphological deformation of features across stacks. We applied the method to image mosaicking and image alignment registration steps and evaluated its performance with 20 human subjects on CLSM images with stained blood vessels. Our experimental evaluation showed significant benefits of automation for 3D volume reconstruction in terms of achieved accuracy, consistency of results, and performance time. In addition, the results indicate that the differences between registration accuracy obtained by experts and by novices disappear with the proposed semiautomatic registration technique while the absolute registration accuracy increases.
Effects of Ru Doping on the Transport Behavior and Superconducting Transition Temperature of NdFeAsO0.89F0.11
Sang Chul Lee,Erika Satomi,Yoshiaki Kobayashi,Masatoshi Sato
Physics , 2009, DOI: 10.1143/JPSJ.79.023702
Abstract: The transport behavior and superconducting transition temperature Tc of NdFe1-yRuyAsO0.89F0.11 have been studied for various y values. Because Ru impurities are isoelectronic to host Fe atoms, we basically expect that the number of electrons does not change with y, at least in the region of small y values. The results indicate that the rate of Tc suppression by Ru atoms is too small to be explained by the pair breaking effect of nonmagnetic impurities expected for the S+- symmetry, confirming our previous results for Co doping.
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