• 천문학회보
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• 제41권1호
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• pp.77.4-78
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• 2016

Binary interactions may have significant impact on Pop III stellar evolution. Pop III single star evolution indicates that for primary masses less than $20M_{\odot}$, no significant binary mass transfer would occur before core helium exhaustion. We perform binary system evolution for various primary masses ($20M_{\odot}$ < $M_1$ < $60M_{\odot}$) and initial periods under same mass ratio $M_2/M_1=0.9$, and follow the evolution and mass transfer of the primary star. If binary mass transfer occurs during post main sequence, the primary star does not evolve into naked helium star and still contain significant hydrogen in the envelope. During the post mass transfer phase, the primary star evolves redward, and does not become sufficiently hot to enhance the number of ionizing photons, compared to the case of single star evolution for a given initial mass. This result implies that primary stars of massive Pop III binary systems would have little contribution to the reionization in the early universe. Given the large hydrogen content ($0.326-1.793M_{\odot}$), the primary stars that underwent stable mass transfers would explode as a Type IIb supernova, and it would be difficult for Pop III binary stars to produce Type Ib/c supernovae that look similar to those found in the local universe.

• 천문학회보
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• 제39권1호
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• pp.83.1-83.1
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• 2014

Open clusters consisting of a co-spatial and coeval population with a similar chemical composition are a superb astrophysical test bed in both stellar and galactic astronomy. We introduce not only several scientific issues relating to these objects but also comprehensive studies of the two young open clusters Westerlund 1 and IC 1848 formed in extremely different star-forming conditions. Westerlund 1 is known as the most massive starburst cluster in the Galaxy. Located in the Scutum-Centaurus spiral arm, the cluster is relatively close to the Galactic Center. The apparent surface density is very high. On the other hand, IC 1848 is a core cluster within the large-scale star-forming region W5 lying in the Perseus arm. Unlike Westerlund 1, IC 1848 with a putatively low metallicity exhibits a low surface density. We present the fundamental parameters of those young clusters, such as reddening, distance, and age, obtained from the broadband photometric analysis. The stellar initial mass function (IMF) of the clusters is used to investigate the effects of the different star-forming conditions on the star formation activity. With the results of previous studies for several young open clusters, our preliminary results support a possibility that star formation activity may be affected by the environmental factors or the initial condition of natal clouds. In addition, we shortly discuss the age scale and spread of pre-main sequence stars to understand the formation processes of star clusters.

• 정보처리학회논문지A
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• 제15A권2호
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• pp.95-100
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• 2008

본 논문에서는 Folded 하이퍼-스타 연결망을 기반으로 하는 새로운 상호연결망, 계층적 Folded 하이퍼-스타 연결망 HFH($C_n,\;C_n$)을 제안한다. 그리고 본 논문에서 제안한 HFH($C_n,\;C_n$)가 Folded 하이퍼-스타 연결망과 기존에 제안된 계층적 연결망인 HCN(m,m), HFN(m,m)보다 망비용(지름${\times}$분지수) 측면에서 우수한 연결망임을 보인다. 또한 HFH($C_n,\;C_n$)의 여러 가지 망 성질(연결도, 라우팅 알고리즘, 지름, 방송)을 분석한다.

• 천문학회보
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• 제36권1호
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• pp.54.2-54.2
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• 2011

It is the conventional wisdom that the Poynting-Robertson effect is essentially the outcome of the interplay between absorption and reemission processes. For a better understanding of the motion of charged particles around a compact star with strong radiation, we reached an alternative interpretation for the Poynting-Robertson effect based on the covariant formalism and found that it is attributed to the combination of the aberration and the Lorentz transformation of the radiation stress-energy tensor. As a general relativistic application of the Poynting-Robertson effect, we studied the dynamics of test particles around the spinning relativistic star with strong radiation. We discovered that the combination of the angular momentum and the finite size of the star generates "radiation counter drag" which exerts on the test particle to enhance its specific angular momentum, contrary to the radiation drag. The balance of the radiation drag and the radiation counter drag renders the particle to hover around the spinning luminous star at the "suspension orbit". The radial position and the angular velocity of the particle on the "suspension orbit" are determined by the angular momentum, the luminosity, and the size of the central star only, and they are independent of the initial position and velocity of the particle.

• Journal of Microbiology and Biotechnology
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• 제22권10호
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• pp.1350-1358
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• 2012

Viral pathogens, alongside other pathogens, have major effects on crustacean aquaculture. Hepatopancreatic parvovirus (HPV) is an emerging virus in the shrimp industry and has been detected in shrimp farms worldwide. The HPV genome has greater diversity than other shrimp viruses owing to its wide host range and geographical distribution. Therefore, developing diagnostic tools is essential to detect even small copy numbers from the target region of native HPV isolates. We have developed two easy to use quantitative real-time PCR kits, called Green Star and Dual Star, which contain all of the necessary components for real-time PCR, including HPV primers, using the primers obtained from the sequences of HPV isolates from Korea, and analyzed their specificity, efficiency, and reproducibility. These two kits could detect from 1 to $1{\times}10^9$ copies of cloned HPV DNA. The minimum detection limits obtained from HPV-infected shrimp were $7.74{\times}10^1$ and $9.06{\times}10^1$ copies in the Green Star and Dual Star assay kits, respectively. These kits can be used for rapid, sensitive, and efficient screening for HPV isolates from Korea before the introduction of postlarval stages into culture ponds, thereby decreasing the incidence of early development of the disease.

• 정보처리학회논문지A
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• 제15A권6호
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• pp.345-350
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• 2008

최근에 병렬처리를 위한 새로운 위상으로 하이퍼 스타 연결망 HS(2n,n)가 제안되었다. 하이퍼 스타 연결망은 하이퍼큐브와 스타 그래프의 성질을 가지고 있으면서, 같은 노드수를 갖는 하이퍼큐브보다 망비용이 우수한 연결망이다. 본 논문에서는 하이퍼스타 연결망 HS(2n,n)에서 에지 중복 없는 스패닝 트리를 구성하는 알고리즘을 제안한다. 그리고 제안한 알고리즘에 의해 구성된 에지 중복 없는 스패닝 트리가 에지 중복없는 최적 스패닝 트리임을 증명한다.

• 천문학회보
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• 제44권1호
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• pp.40.1-40.1
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• 2019

We utilize times since infall of cluster galaxies obtained from Yonsei Zoom-in Cluster Simulation (YZiCS), the cosmological hydrodynamic N-body simulations, and star formation rates from the SDSS data release 10 to study how quickly late-type galaxies are quenched in the cluster environments. In particular, we confirm that the distributions of both simulated and observed galaxies in phase-space diagrams are comparable and that each location of phase-space can provide the information of times since infall and star formation rates of cluster galaxies. Then, by limiting the location of phase-space of simulated and observed galaxies, we associate their star formation rates at z ~ 0.08 with times since infall using an abundance matching technique that employs the 10 quantiles of each probability distribution. Using a flexible quenching model covering different quenching scenarios, we find the star formation history of satellite galaxies that best reproduces the obtained relationship between time since infall and star formation rate at z ~ 0.08. Based on the derived star formation history, we constrain the quenching timescale (2 - 7 Gyr) with a clear stellar mass trend and confirm that the refined model is consistent with the "delayed-then-rapid" quenching scenario: the constant delayed phase as ~ 2.3 Gyr and the quenching efficiencies (i.e., e-folding timescale) outside and inside clusters as ~ 2 - 4 Gyr (${\propto}M_*^{-1}$) and 0.5 - 1.5 Gyr (${\propto}M_*^{-2}$), Finally, we suggest: (i) ram-pressure is the main driver of quenching of satellite galaxies for the local Universe, (ii) the quenching trend on stellar mass at z > 0.5 indicates other quenching mechanisms as the main driver.

• 유통과학연구
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• 제20권7호
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• pp.11-22
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• 2022

Purpose: Since the emergence of the Covid-19 pandemic, almost all the hospitality industry has experienced a decrease in the distribution of room occupancy. Therefore, this study aims to examine how to improve the performance of 5-star hotels in Bali by involving market orientation, revenue management orientation, competitive advantage, dynamic capability, and pricing capability. Research design, data and methodology: This study involved 127 managers in 62 five-star hotels in Bali. Analysis of this study using structural equation modelling (SEM) with SmartPLS software. Results: This study reveals that the performance of five-star hotels in Bali is influenced by factors such as market orientation, revenue management orientation, competitive advantage, dynamic capability, and pricing capability. In addition, revenue management orientation, competitive advantage, and dynamic capability have been shown to mediate the effect of market orientation on the performance of five-star hotels in Bali. Finally, pricing capability has been proven to have not been able to increase the revenue and performance of five-star hotels in Bali. Conclusions: Hotel performance is largely determined by several important factors which include market orientation, revenue management orientation, competitive advantage, dynamic capability, and pricing capability. This study provides important implications for hospitality practitioners to improve the distribution of hotel performance.

• 한국산업융합학회 논문집
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• 제24권6_2호
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• pp.891-897
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• 2021

In this paper, we propose a destination optimal route algorithm for providing route finding service for the transportation handicapped by using the multi-criteria decision-making technique and the modified A-STAR optimal route search algorithm. This is a method to set the route to the destination centering on safety by replacing the distance cost of the existing A-STAR optimal route search algorithm with the safety cost calculated through AHP/TOPSIS analysis. To this end, 10 factors such as road damage, curb, and road hole were first classified as poor road factors that hinder road driving, and then pairwise comparison of AHP was analyzed and then defined as the weight of TOPSIS. Afterwards, the degree of driving safety was quantified for a certain road section in Busan through TOPSIS analysis, and the development of an optimal route search algorithm for the transportation handicapped that replaces the distance cost with safety in the finally modified A-STAR optimal route algorithm was completed.

• 천문학회보
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• 제46권1호
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• pp.28.2-28.2
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• 2021

We investigate the impact of ram pressure stripping due to the intracluster medium (ICM) on star-forming disk galaxies with a multiphase interstellar medium maintained by strong stellar feedback. We carry out radiation-hydrodynamic simulations of an isolated disk galaxy embedded in a 1011 M⦿ dark matter halo with various ICM winds mimicking the cluster outskirts (moderate) and the central environment (strong). We find that both star formation quenching and triggering occur in ram pressure-stripped galaxies, depending on the strength of the winds. HI and H2 in the outer galactic disk are significantly stripped in the presence of moderate winds, whereas turbulent pressure provides support against ram pressure in the central region, where star formation is active. Moderate ICM winds facilitate gas collapse, increasing the total star formation rates by ~40% when the wind is oriented face-on or by ~80% when it is edge-on. In contrast, strong winds rapidly blow away neutral and molecular hydrogen gas from the galaxy, suppressing star formation by a factor of 2 within ~200 Myr. Dense gas clumps with nH≳10 M⦿ pc-2 are easily identified in extraplanar regions, but no significant young stellar populations are found in such clumps. In our attempts to enhance radiative cooling by adopting a colder ICM of T=106K only a few additional stars are formed in the tail region, even if the amount of newly cooled gas increases by an order of magnitude.