• Journal of The Korean Astronomical Society
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• v.30 no.1
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• pp.27-70
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• 1997

The brightest stars in galaxies have been used as distance indicators since Hubble. However, the accuracy of the brightest stars for distance estimates has been controversial. Recently, Rozanski & Rowan-Robinson [1994 : MNRAS, 271, 530] argued large errors of this method for the distance determination : 0.58 mag and 0.90 mag, respectively, for the brightest red stars and the brightest blue stars, while Karachentsev & Tikhonov [1994 : A&A, 286, 718] suggested much smaller errors in the distance determination than the former: 0.37 mag for the brightest red stars and 0.46 mag for the brightest blue stars. The reasons for these conflicting results are not yet known. In this study we have investigated the accuracy of this method using a sample of 17 galaxies for which Cepheid distances are known and reliable photometry of the brightest stars are available. We have obtained the calibrations of the relations between the mean luminosities of the three blue and red brightest supergiants (BSGs and RSGs, respectively) and the total luminosities of the parent galaxies: $= 0.21M_B^T- 3.84, \sigma(M_v) = 0.37 mag,\;and\;\delta_{\mu0}=0.47$ mag for the brightest red supergiants, and $= 0.30M_B^T -3.02, \sigma(M_B)\;=\;0.55 mag,\;and\; \delta_{\mu0}=0.79mag$ for the brightest blue supergiants. Also it is found that the errors in the distance determination are reduced by a factor of two, as the observing wavelengths increase from B-band to K-band. In conclusion, the brightest red supergiants are considered to be useful for determining the distances to resolved late-type galaxies.

• Advanced Composite Materials
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• v.18 no.4
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• pp.351-364
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• 2009

The thermal stability and elevated temperature mechanical properties of $SiC_P$/Al-11.7Fe-1.3V-1.7Si (Al-11.7Fe-1.3V-1.7Si reinforced with SiC particulates) composites sheets prepared by spray deposition (SD) $\rightarrow$ hot pressing $\rightarrow$ rolling process were investigated. The experimental results showed that the composite possessed high ${\sigma}_b$ (elevated temperature tensile strength), for instance, ${\sigma}_b$ was 315.8 MPa, which was tested at $315^{\circ}C$, meanwhile the figure was 232.6 MPa tested at $400^{\circ}C$, and the elongations were 2.5% and 1.4%, respectively. Furthermore, the composite sheets exhibited excellent thermal stability: the hardness showed no significant decline after annealing at $550^{\circ}C$ for 200 h or at $600^{\circ}C$ for 10 h. The good elevated temperature mechanical properties and excellent thermal stability should mainly be attributed to the formation of spherical ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase particulates in the aluminum matrix. Furthermore, the addition of SiC particles into the alloy is another important factor, which the following properties are responsible for. The resultant Si of the reaction between Al matrix and SiC particles diffused into Al matrix can stabilize ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase; in addition, the interface (Si layer) improved the wettability of Al/$SiC_P$, hence, elevated the bonding between them. Furthermore, the fine $Al_4C_3$ phase also strengthened the matrix as a dispersion-strengthened phase. Meanwhile, load is transferred from Al matrix to SiC particles, which increased the cooling rate of the melt droplets and improved the solution strengthening and dispersion strengthening.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.43-47
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• 2008

The nickel and cobalt resistance of Cupriavidus metallidurans CH34 is mediated by the CnrCBA efflux pump encoded by the cnrYHXCBAT metal resistance determinant. The products of the three genes cnrYXH transcriptionally regulate expression of cnr. CnrY and CnrX are membrane-bound proteins, probably functioning as anti-sigma factors, whereas CnrH is a cnr-specific extracytoplasmic functions (ECF) sigma factor. The periplasmic domain of CnrX (residues 29-148) was cloned as a N-terminal His-tagged protein, expressed in Escherichia coli, and purified using affinity chromatography and gel filtration. The molecular mass was estimated to be about 13.6kDa by size exclusion chromatography, corresponding to a monomer. The tetragonal bipyramid crystals were obtained by mixing an equal volume of protein in 50mM Tris-HCl, pH 7.5, 1% glycerol, 100mM NaCl, 1mM DTT, and the reservoir solution of 15% w/v PEG 2000, 100mM lithium chloride at 277K in 2-4 days using hanging drop vapor diffusion. The protein concentration was 24mg/ml. The crystal that diffracted to $2.42{\AA}$ resolution belongs to space group $P4_1\;or\;P4_3$ with unit cell parameters of $a=b=32.14{\AA},\;c=195.31{\AA},\;{\alpha}={\beta}={\gamma}=90^{\circ}$, with one molecule of CnrX in the asymmetric unit.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.4
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• pp.75-82
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• 2001

Static loadings on ship structure induced either by water pressure before service such as a tank test and ballasting or by cargo pressure during first laden voyage cause relatively much greater stress than dynamic loadings induced by wave. With these static pre-loadings, the initial residual stresses around welded joint, where fatigue strength is concerned(in most cases, where stress concentration occurs) are expected to be shaken-down in a great extent by the elasto-plastic deformation behavior of material. Therefore, it is more resonable to assess the fatigue strength of ship structure with S-N data which have taken into account the effect of shaken-down residual stresses(re-distributed stresses) on the fatigue strength. In this research work, the re-distribution of residual stresses by the tensile pre-loading is measured using an ordinary sectioning method for specimens of padding plate weldment. Fatigue tests are performed also to evaluate the fatigue strength of the both as-welded and pre-loaded specimens.

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.213-219
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• 1985

The relative stability as a function of geometry in rigid cyclopropylcarbinyl cations was examined by $^{19}$F-nmr spectroscopy. 8-p-Fluorophenyl-tricyclo[3.3.1.0$^{2,7}$]octane-8-yl-(I), 9-p-fluorophenyl-tricyclo[3.3.1.0$^{2,8}$]nonane-9-yl (II), and 10-p-fluorophenyl-tricyclo[4.3.1.0$^{2,9}$]decane-10-yl cation(Ⅲ) were prepared from the corresponding carbinols in FSO$_3$H-SO$_2$ClF solution at -120$^{\circ}C$. $^{19}$F-nmr data indicate that the symmetrical bisected geometry of cyclopropane ring for ${\sigma}$-conjugation is a very impotant factor in charge delocalization. However, varied orientation of the bond angle ${\theta}$ within the bisected conformation does not affect the charge delocalization into the cyclopropane ring.

• Steel and Composite Structures
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• v.33 no.4
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• pp.489-507
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• 2019

In order to obtain high bearing capacity and good ductility simultaneously, a structural column with hybrid normal and high strength steel (HNHSS) welded box section has been developed. Residual stress is an important factor that can influence the behaviour of a structural member in steel structures. Accordingly, the magnitudes and distributions of residual stresses in HNHSS welded box sections were investigated experimentally using the sectioning method. In this study, the following four box sections were tested: one normal strength steel (NSS) section, one high strength steel (HSS) section, and two HNHSS sections. Based on the experimental data from previous studies and the test results of this study, the effects of the width-to-thickness ratio of plate, yield strength of plate, and the plate thickness of the residual stresses of welded box sections were investigated in detail. A unified residual stress model for NSS, HSS and HNHSS welded box sections was proposed, and the corresponding simplified prediction equations for the maximum tensile residual stress ratio (${\sigma}_{rt}/f_y$) and average compressive residual stress ratio (${\sigma}_{rc}/f_y$) in the model were quantitatively established. The predicted magnitudes and distributions of residual stresses for four tested sections in this study by using the proposed residual stress model were compared with the experimental results, and the feasibility of this proposed model was shown to be in good agreement.

• Journal of Climate Change Research
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• v.4 no.4
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• pp.317-330
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• 2013

The yield of rice production is affected severely by abnormal weather events, such as flood, drought, high temperature etc. The objective of this paper is to assess impacts of abnormal weather events on rice production, using a panel model which analyzes both cross-section data and ti- me series data. Abnormal weather is defined as the weather event which goes beyond the range of ${\pm}2{\sigma}$ from the average of a weather factor. The result of an analysis on impacts of high temperature on rice production showed that the yield of rice was decreased 5.8% to 16.3% under the conditions of extremely high temperature, and it was decreased 8.8 to 20.8% under the conditions of both extremely high and heavy rain. Adaptation strategies, development of new varieties enduring high temperature and heavy rain, adaptation of crop insurance, modernization of irrigation facilities are needed to minimize the impacts of abnormal weather on rice production, and to stabilize farmers' income.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.355-356
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• 2000

Three 'stress probe' plasmids were constructed and characterized which utilize a green fluorescent protein (CFP) as a non-invasive reporter to elucidate Escherichia coli cellular stress responses in quiescent or 'resting' cells. Facile detection of cellular stress levels was achieved by fusion of three heat shock stress protein promoter elements, those of the heat shock transcription factor ${\sigma}^{32}$, pretense subunit ClpB, and chaperone DnaK, to the reporter gene $gfp_{uv}$. When perturbed by chemical or physical stress (such as heat shock, nutrient (amino acid) limitation, addition of IPTG, acetic acid, ethanol, phenol, antifoam, and salt (osmotic shock), the E. coli cells produced GFPuv which was easily detected from within the cells as emitted green fluorescence. A temporal and amplitudinal mapping of these responses was performed, demonstrating regions where quantitative delineation of cell stress was afforded.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.11a
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• pp.404-410
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• 2006

6시그마 프로세스는 정의(Define), 측정(Measure), 분석(Analyze), 개선(Improve), 관리(Control) 라는 다섯 Step을 통하여 문제를 해결하고 성과를 달성한다. 이 다섯 단계 중에서 측정 단계는 6시그마로는 길에서 매우 중요한 전이 단계로서 문제점을 정교하게 다듬고 근원적 원인 규명을 시작하는 데 도움을 준다. 즉 개선 하고자 하는 영역에 대한 사실적 근거를 제공 받기 위해 프로세스를 숫자로 전환 할 때 무엇을 측정하고 어떻게 측정 할 것인가를 결정한다. 측정단계는 주로 3 Step으로 이루어진다. Step 1 은 CTQ 특성치의 선정, Step 2는 성과기준의 정의, Step 3은 측정시스템의 분석이다. F사의 6시그마 발표자료 중 측정 부분만을 집중 분석하여 문제점 및 그 개선 방향을 제시하려한다.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.11a
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• pp.114-118
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• 2006

시그마경영은 1997년 국내에 도입된 이후 많은 기업이 생존 전략과 경영혁신의 방법으로 활용 하고 있다. 도입 초기에는 대기업과 제조업을 중심으로 적용되었으나 이후 서비스업과 R&D에 이르는 전 분야에서 운영되고 있다. 다양한 업종에서의 적용으로 각 분야에 따른 성공요소가 연구 발표되었다. 현재는 철도청을 비롯하여 우정사업 본부, 환경부에 이르기까지 다양한 공공기업과 관공서도 혁신의 방법으로 6시그마 경영을 도입하여 활용하고 있다 그러나 아직까지 공공부문의 특성이 고려된 성공요소에 대한 연구는 미진하였다. 본 논문은 이윤 추구를 중심으로 하는 일반기업과 다른 공익성을 강조해야 하는 공공기업의 특성과 공무원에 특징을 고려한 6시그마경영의 성공요소에 대하여 연구하였다.