VRc Photometry of Dwarf Cepheids

Kim, Chulhee,Michael-D.Joner 한국우주과학회 1993 한국우주과학회보 Vol.2 No.2

The Objective-Prism Search of Emission-Line Galaxies Towards Hydra Void

Chulhee Kim 한국천문학회 1996 天文學會報 Vol.21 No.-

SoxF Transcription Factors Are Positive Feedback Regulators of VEGF Signaling

Kim, Kangsan,Kim, Il-Kug,Yang, Jee Myung,Lee, Eunhyeong,Koh, Bong Ihn,Song, Sukhyun,Park, Junseong,Lee, Sungsu,Choi, Chulhee,Kim, Jin Woo,Kubota, Yoshiaki,Koh, Gou Young,Kim, Injune Grune & Stratton 2016 Circulation research Vol.119 No.7

<P>Rationale: Vascular endothelial growth factor (VEGF) signaling is a key pathway for angiogenesis and requires highly coordinated regulation. Although the Notch pathway-mediated suppression of excessive VEGF activity via negative feedback is well known, the positive feedback control for augmenting VEGF signaling remains poorly understood. Transcription factor Sox17 is indispensable for angiogenesis, but its association with VEGF signaling is largely unknown. The contribution of other Sox members to angiogenesis also remains to be determined. Objective: To reveal the genetic interaction of Sox7, another Sox member, with Sox17 in developmental angiogenesis and their functional relationship with VEGF signaling. Methods and Results: Sox7 is expressed specifically in endothelial cells and its global and endothelial-specific deletion resulted in embryonic lethality with severely impaired angiogenesis in mice, substantially overlapping with Sox17 in both expression and function. Interestingly, compound heterozygosity for Sox7 and Sox17 phenocopied vascular defects of Sox7 or Sox17 homozygous knockout, indicating that the genetic cooperation of Sox7 and Sox17 is sensitive to their combined gene dosage. VEGF signaling upregulated both Sox7 and Sox17 expression in angiogenesis via mTOR pathway. Furthermore, Sox7 and Sox17 promoted VEGFR2 (VEGF receptor 2) expression in angiogenic vessels, suggesting a positive feedback loop between VEGF signaling and SoxF. Conclusions: Our findings demonstrate that SoxF transcription factors are indispensable players in developmental angiogenesis by acting as positive feedback regulators of VEGF signaling.</P>

Optical Microvariability of Blazers

Chulhee Kim,K.K. Ghosh,B.D. Ramsey,S. Soundararajaperumal 한국천문학회 2000 天文學會報 Vol.25 No.2

VR_C PHOTOMETRY OF DWARF CEPHEIDS (Ⅱ)

KIM, CHULHEE,JONER, MICHAEL D. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-

In this paper, we derived the empirical relationship between stellar surface brightness parameter(F_v) and (V-R_c) colour in Cousins system appropriate to dwarf cepheids. Also theoretical counterpart to this relation has been calculated from model atmospheres. The theoretical relation is in reasonable agreement with the empirical relation but reveals small sensitivities to surface gravity and metallicity. Both relations were used to apply the surface brightness method to estimate the radius of four dwarf cepheids of YZ Boo, AD CMi, XX Cyg, and EH Lib which were observed with V and R band in Cousins photometric system by Kim and Joner (1994). We could obtain the reliable result for AD CMi and it was fund that, for three other variables, there are large phase shifts between angular diameter variation and radial displacements.

PULSATIONAL CHARACTERISTICS OF V1719 CYGNI WITH PECULIAR LIGHT CURVE

KIM CHULHEE,KIM SEUNG-LI,SADAKANE KOZO The Korean Astronomical Society 1993 Journal of The Korean Astronomical Society Vol.26 No.2

The light curve and radial velocity curve of multiperiodic dwarf cepheid VI719 Cyg (HD200925) with peculiar light curve have been reanalyzed in order to identify the oscillation modes to confirm the helium settling within the envelope. To do these, through the period search for the photometric and radial velocity data from the literature, two different periods were determined and the oscillation modes corresponding to the first and second periods were identified as the fundamental and first radial overtones. Hence the helium settling within the envelope was confirmed from the period ratio. The color excess, metallicity, effective temperature, and surface gravity corresponding to two different modes were determined and it was found that these parameters almost do not depend upon different oscillation mode. By utilizing the surface brightness method, we investigated the variation of angular diameter and radial displacement and it was found that the angular variation is very peculiar. Also by referring to the stellar models, mass and age were determined as $2.7M_{\bigodot}$ and 0.42 Gyr respectively which make this variable star heavier and younger than other multimode dwarf cepheids. Preliminary spectroscopic CCD observations were carried out and it was found that Mg in VI719 Cygni is nearly solar abundent according to the analysis of $5172.68{\AA}MgI$ line which is inconsistent with the photometric result. It was suggested that VI719 Cyg may be classified as a $\rho$ Pup stars according to the photometric characteristics.

A PHOTOMETRIC AND SPECTROGRAPHIC STUDY OF BP PEGASI

KIM, CHULHEE,McNAMARA, D. H.,JONER, MICHEL D. 全北大學校 基礎科學硏究所 1991 基礎科學 Vol.14 No.1

New photometric(uvbyβ)and spectrographic observations of the dwarf Cepheid BP Peg are described. A reddening value, E(b-y) = 0^m.067, is derived from the photometry. Intrinsic(b-y), m_1 and c_1 values used in conjunction with a model-atmosphere grid yield a mean effective temperature, <T_eff> = 7470 K, a mean surface gravity, <log g> = 3.85, and [Fe/H] = -0.08. The pulsation theory and stellar model sequences yield M_bol = 1^m.4, a mass = 1.85?? , and age of 1.3 × 10^9yrs. The radial-velocity data indicate a mean radial velocity of -30㎞ s^-1 and a total velocity range of 36㎞ s^-1.

VR_C PHOTOMETRY OF DWARF CEPHEIDS (Ⅰ) : Observation

KIM, CHULHEE,JONER, MICHAEL D. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-

In this paper, we present VRc photometric observations of four dwarf cepheids: YZ Boo (P=0^d.104, ΔV=0^m.5), AD CMi (P=0^d.123, ΔV=0^m.5), XX Cyg (P=0^d.135, ΔV=0^m.5), EH Lib (P=0^d.088, ΔV=0^m.7). The light curves were obtained at West Mountain Observatory, Provo, Utah on 14 nights from 1983 through 1986 and contain 589 data points in each of the V and R bands in the Cousin photometric system. A detailed study of these stars, based on the present light curves, will be published separately.

PULSATIONAL CHARACTERISTICS OF V1719 CYGNI WITH PECULIAR LIGHT CURVE

KIM, CHULHEE,KIM, SEUNG-LI,SADAKANE, KOZO 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

The light curve and radial velocity curve of multiperiodic dwarf cepheid V1719 Cyg(HD200925) with peculiar light curve have reanalyzed in order to identify the oscillation modes to confirm the hellium sattling within the envelope. To do these, through the period search for the photmetric and radial velocity data from the literature, two different periods were determined and the oscillation modes corresponding to the first and second periods were identifed as the fundamental and first radial overtones. Hence the helium settling within the envelope was confirmed from the period ratio. The color excess, metallicity, effective temperature, and surface gravity corresponding to two different modes were determined and it was found that these parameters almost do not depend upon different oscillation mode. By utilizing the surface brightness method, we investigated the variation of angular diameter and radial displacement and it was found that the angular variation is very peculiar. Also by referring to the stellar models, mass and age were dtermined as 2.7M_?? and 0.42 Gyr respectively which make this variable star heavier and younger than other multimode dwarf cepheids. Preliminary spectroscopic CCD observations were carried out and it was found that Mg in V1719 Cygni is nearly solar abundent according to the analysis of 5172.68ÅMgI line which is inconsistent with the photometric result. It was suggested that V1719 Cyg may be classified as a ρ Pup stars according to the photometric characteristics.

Reliability estimation for ultrasonic transducer by voltage accelerated life test

Chulhee Kim,Bochul Kang,Byeongsuk Song 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1

As the income level was improved, the demand of humidifiers is increased. So the reliability of ultrasonic transducer which is the main part of humidifiers is very important too. To verify the reliability of ultrasonic transducers which were made of two kinds of material (TiN anodizing and Cr plating), voltage accelerated life test was performed . According to the data of failure time, PDF(Probability Density Function) and B10 life time were derived. As a result, TiN Anodizing material has better reliability than Cr plating material. Also failure analysis was performed using optical microscope and SEM. By the proper implementation, it is assumed that the same failure in field will be not occurred