• 대한수학회보
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• 제41권2호
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• pp.235-239
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• 2004

Vaughan proved that if X is countably compact, then the Alexandroff duplicate A(X) is acc. In this note, we give an example to show that the result can not be generalized to star-Lindelof spaces. Moreover, we give a positive result.

• 경영과정보연구
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• 제34권3호
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• pp.101-123
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• 2015

외부 환경의 불확실성이 점점 더 높아지는 가운데 조직의 경쟁우위를 달성하기 위한 방안으로 우수한 인적자원의 확보 및 보유가 점차 중요시되고 있다. 특히, 동료 직원들에 비해 몇 배나 높은 탁월한 성과를 창출할 수 있는 '스타 인재'는 지식과 정보가 중시되는 지식기반산업에서 점차 그 중요성이 강조되고 있어 이에 관련된 학계와 산업계의 관심이 증대되고 있다. 하지만 이처럼 스타 인재에 대한 관심이 증가하고 있음에도 불구하고 스타 인재의 보유가 조직성과에 미치는 영향을 실증적으로 분석한 선행연구는 부족한 편이다. 특히 스타 인재의 보유가 조직 내외부에 미치는 긍정적 부정적 영향력을 고려할 때, 조직 내 스타 인재의 비율(ratio of star employee)과 조직성과의 관계는 단순 선형 관계(simple linear relationship)의 가능성 뿐 아니라 비선형의 곡선형 관계(curvilinear relationship)가 존재할 가능성도 가지고 있다. 이에 본 연구에서는 스타 인재에 관한 선행 연구를 토대로, 스타 인재의 비율이 증가함에 따라 한계효과가 증가하는 체증관계(U자형 곡선)와 한계효과가 감소하는 체감관계(역U자형 곡선)의 두 가지 대립가설을 설정한 후 국내 34개 상장증권사의 2008~2013년 134개 관측수를 대상으로 실증분석을 진행하였다. 국내 경제전문지가 선정한 '베스트 애널리스트'(스타 인재)의 비율이 증권사의 재무성과에 미치는 영향을 불균형 패널모형으로 검증한 결과, 스타 인재의 비율이 증가할수록 조직성과는 증가하지만, 그 한계효과는 점차 감소하는 체감형 비선형 관계가 검증되었다. 이러한 연구결과는 지식기반 산업에서도 스타 인재를 활용하는 것이 중요함을 시사함과 동시에, 스타 인재에 대한 과도한 의존은 경계할 필요성이 있음을 시사한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.28.2-28.2
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• 2008

Recently, star sensors have been successfully used as main attitude sensors for attitude control in many satellites. This research presents the star visibility analysis for star trackers and the goal of this analysis is to make sure that the star tracker implementation is suitable to the mission profile and scenario and satisfies the requirement of attitude orbit control system. As a main optical attitude sensor imaging stars, accomodations of a star tracker should be optimized in order to improve the probability of the usage by avoiding the blinding (the unavailability) by the Sun and the Earth. For the analysis, a statistical approach and a time simulation approach are used. The statistical approach is based on the generation of numerous cases, to derive relevant statistics about Earth and Sun proximity probabilites for different lines of sight. The time simulation approach is performed for one orbit to check the statistical result and to refine the statistical result and accomodations of star trackers. In order to perform simulations first of all, an orbit and specific mission profiles of a satellite are set, next the earth proximity probability and the sun proximity probability are calculated by considering the attitude maneuvers and the geometry of the orbit, and then finally the unavailability positions are estimated. As a result, the optimized accomodations of two star trackers are suggested for the low earth orbit satellite.

• The Journal of Asian Finance, Economics and Business
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• 제5권3호
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• pp.73-80
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• 2018

The growth of Bandung's tourism industry has had a massive impact on the hotel sector. Most tourists visiting Bandung are domestic tourists and tend to be modest spenders fitting the profile of a mid-market (2/3 star) hotel guest. As competition has increased mid-market hotels have come under pressure from upmarket (4/5 star) and budget hotels committed to cutting prices. There is also competition with the mid-market hotel sector, which means that the 2/3 star hotels have to keep innovating in order to remain competitive. This study uses the Service Quality framework to describe customer expectations and identify gaps in hotel services. A questionnaire survey of 105 local tourists who had stayed in 2/3 star hotels in Bandung showed that the most important dimension is responsiveness, following by reliability, assurance, tangibles and empathy. Thus we conclude that local tourists' primary expectations are that hotels will deliver the service they have promised, be responsive to guests' needs and comply with service standards. Furthermore, these findings validate the earlier prediction that comparing 2/3 star hotel with 5/4 start hotel, the customers are having preliminary knowledge on facilities limitation and friendliness. Tourists using 2/3 star hotels tend to be prepared to accept limited facilities and less friendly staff service.

• 천문학회보
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• 제39권2호
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• pp.71.2-71.2
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• 2014

processes at the origin of the star formation in the galaxies over the last 10 billions years. While it was proposed in the past that merging of galaxies has a dominant role to explain the triggering of the star formation in the distant galaxies having high star formation rates. In the opposite, more recent studies revealed scaling laws linking the star formation rate in the galaxies to their stellar mass or their gas mass. The small dispersion of these laws seems to be in contradiction with the idea of powerful stochastic events due to interactions, but rather in agreement with the new vision of galaxy history where the latter are continuously fed by intergalactic gas. I was especially interested in one of this scaling law, the relation between the star formation (SFR) and the stellar mass (M*) of galaxies, commonly called the main sequence of star forming galaxies. I have studied this main sequence, SFR-M*, in function of the morphology and other physical parameters as the radius, the colour, the clumpiness. The goal was to understand the origin of the sequence's dispersion related to the physical processes underlying this sequence in order to identify the main mode of star formation controlling this sequence. This work needed a multi-wavelength approach as well as the use of galaxies profile simulation to distinguish between the different galaxy morphological types implied in the main sequence.

• 대한원격탐사학회지
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• 제31권4호
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• pp.353-360
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• 2015

Earth's gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite's star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth' gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth's gravity field maps, the new Earth's gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth's gravity field maps.

• 천문학논총
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• 제30권2호
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• pp.169-171
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• 2015

NGC147 and NGC185, paired satellites of the Andromeda galaxy, possess the same order of mass and analogous structures, but they show different star formation and different amounts of interstellar gas and dust. Therefore, we present the first reconstruction of the star formation history of NGC147 and NGC185. Asymptotic Giant Branch stars are highly evolved stars that are brightest in K-band. This maximum K-band magnitude is related to the birth mass of stars. As a result, we have found a 9.9 Gyr old single star formation epoch for NGC185 followed by relatively continuous star formation. NGC147, however, has passed through two star formation episodes; one is as old as ~6 Gyr and the other is as recent as ~850 Myr. Asymptotic Giant Branch stars are also important dust factories; by fitting Spectral Energy Distributions to observed near and mid infrared data for each star, we were able to measure the dust production rates of individual stars; on order of $10^{-5}M_{\odot}yr^{-1}$. Hence, we estimate the total mass entering the interstellar medium to be $1.06{\times}10^{-4}M_{\odot}yr^{-1}$ and $2.89{\times}10^{-4}M_{\odot}yr^{-1}$ for NGC147 and NGC185.

• 정보처리학회논문지A
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• 제11A권5호
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• pp.341-346
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• 2004

최근에 병렬처리를 위한 새로운 위상으로 하이퍼-스타 그래프 HS(m, k)가 제안되었다. 하이퍼-스타 그래프는 하이퍼큐브와 스타 그래프의 성질을 가지고 있으면서, 같은 노드수를 갖는 하이퍼큐브 보다 망비용이 우수한 그래프이다 본 논문에서는 하이퍼-스타 그래프 HS(m, k)가 하이퍼큐브의 서브그래프임을 증명한다. 그리고 정규형 그래프인 하이퍼-스타 HS(2n, n)가 제안된 매핑 기법에 의해 노드 대칭임을 보이며, 최소 높이를 갖는 스패닝 트리를 이용한 일-대-다 방송 기법을 제안하고, 방송 수행 시간이 2n-1임을 보인다.

• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.105-113
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• 2019

Spectroscopic observations of barium star ${\zeta}$ Capricornus (HD204075) obtained at the 8.2 m telescope of the European Southern Observatory, with a spectral resolving power R = 80,000 and signal to noise ratio greater than 300, were used to refine the atmospheric parameters. We found new values for effective temperature ($T_{eff}=5,300{\pm}50K$), surface gravity ($log\;g=1.82{\pm}0.15$), micro-turbulent velocity ($v_{micro}=2.52{\pm}0.10km/s$), and iron abundance ($log\;N(Fe)=7.32{\pm}0.06$). Previously published abundances of chemical elements in the atmosphere of HD204075 were analyzed and no correlations of these abundances with the second ionization potentials of these elements were found. This excludes the possible influence of accretion of hydrogen and helium atoms from the interstellar or circumstellar environment to the atmosphere of this star. The accretion of nuclear processed matter from the evolved binary companion was primary cause of the abundance anomalies. The young age of HD204075 allows an estimation of the time-scale for the creation of the abundance anomalies arising from accretion of interstellar hydrogen and helium as is the case of stars with low magnetic fields; which we estimate should exceed $10^8$ years.

• 한국추진공학회지
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• 제27권1호
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• pp.17-26
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• 2023

Star 형상을 갖는 추진제 그레인은 다양한 면적 선도가 가능하고, 제작이 용이하여 실제 고체 추진제 로켓에 유용하게 적용될 수 있다. 그러나, 설계와 관련한 형상 변수가 많고 연소 말기 슬리버가 존재하므로, 해석 비용이 저렴한 일반적인 단일 최적화 기법으로는 최적 설계가 성공하기 어렵다. 본 연구에서는 활용성과 설계 성공률을 높이기 위해 데이터베이스를 사용하여 star 그레인을 설계하는 기법을 제안하였다. 제안된 방법에서는 성능 변수를 정의하고, 데이터베이스를 구축한 후 요구조건을 만족하는 해를 탐색한다. 제안된 방법을 적용하여 다양한 종류의 연소 면적 선도를 갖는 star 그레인의 설계를 수행하고, 설계 방법의 타당성을 검증하였다.