• Journal of Fisheries and Marine Sciences Education
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• v.21 no.4
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• pp.523-542
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• 2009

The purpose of this study was to figure out the procedure of learning Korean for international students. A research question was set up as follows: What is the procedure of leaning Korean for international students in Korean universities? To achieve the research purpose, this study implemented a method of semi-constructed interviews. Nineteen international students participated in the interview. The collected data for this study included transcripts from each interview. The transcripts of 60 minutes of interviews with all the participants was audio-taped recorded. This study investigated the research question based on the grounded theory. The analysis of open coding, axial-coding, and selective coding was used in the study. Results indicated that international students learned Korean in a daily basis, and then they adapted to academic Korean in their majored fields. Both personality and mother tongue influenced Korean language learning positively and negatively. International students' improvement of Korean was related in studying with Korean mass media such as TV soap dramas, talk shows, and songs. International students think that TOPIK(Test Of Proficiency In Korean) is not much related with their Korean language fluency. In conclusion, the researchers suggested to give more emphasis on academic training courses for Korean language and to improve the TOPIK in general academic Korean.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.65.1-65.1
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• 2011

We built a simple Adaptive Optics (AO) system at laboratory. This AO system is a step toward developing AO system for astronomical use. In this step, the AO system consists of He-Ne laser as a artificial light source, wavefront sensor, MEMS (Micro electro mechanical system) type deformable mirror and several lenses. MEMS deformable mirror allows the compact system at low cost and the only several mm sized collimated beam. We made Shack-Hartmann wavefront sensor using a lenslet array and a fast frame CCD. Its performance is verified using an artificial phase disturber and noting the movement of spot images by the lenslet array. The frame rate of the driving software is about 70 fps, depending on the control parameters. The characteristics of MEMS deformable mirror was measured which includes the voltage-to-deflection relation, influence function, and cross-talk. The total system is operated under closed-loop control for the artificial phase disturber and the wavefront is found to be compensated successfully.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.59.1-59.1
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• 2019

Immediate vicinity of a supermassive black hole (SMBH) is an important place to test general relativity in strong gravity regime. Also, this is a place where mass accretion and jet formation actively occurs at the centers of active galaxies. Theoretical studies predict presence of bright ring-like emission encircling an accreting SMBH with a diameter of about 5 Schwarzschild radii, and a flux depression at the center (i.e., BH shadow). Direct imaging of the BH shadow is accordingly of great importance in modern astrophysics. However, the angular sizes of the horizon-scale structures are desperately small (e.g., ~40-50 microarcseconds (uas) diameter for the nearest best candidates). This poses serious challenges to observe them directly. Event Horizon Telescope (EHT) is a global network of sensitive radio telescopes operating at 230 GHz (1.3 mm), providing ultra-high angular resolution of 20 uas by cutting-edge very long baseline interferometry techniques. With this resolution, EHT aims to directly image the nearest SMBHs; M87 and the galactic center Sgr $A{\ast}$ (~40-50 uas diameters). In Spring 2017, the EHT collaboration conducted a global campaign of EHT and multiwavelength observations of M87 and Sgr $A{\ast}$, with addition of the phased ALMA to the 1.3mm VLBI array. In this talk, I review results from past mm-VLBI and EHT observations, provide updates on the results from the 2017 campaign, and future perspectives.

• Journal of Information Technology Applications and Management
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• v.19 no.4
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• pp.75-95
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• 2012

This study focuses on examining the determinants of smartphone-based social network services(SNS) use. That is, the study explores the key factors affecting the use of smartphone-based SNS. People who have been using online-based SNS such as Cyworld and Facebook for years are now using mobile-based SNS such as KakaoStory. Under the situation. the study attempts to draw key determinants of smartphone-based SNS use from the studies of TAM, hedonic information systems, and social perspectives. To test the hypotheses, we conducted partial least squares (PLS) analysis using a total of 233 data collected on the users of smartphone-based SNS including KakaoTalk and KakaoStory. The key findings are as follows : first, it is verified that both ease of use and usefulness, two main factors in TAM, had positive effects on smartphone-based SNS use. Second, for enjoyment and escapism considered as the two main factors of hedonic IS characteristics, only the effect of enjoyment on SNS use was significant. Finally, social ties as a factor of social characteristics had the most significant effect on smartphone-based SNS use. The result implies that smartphone-based SNS can be one of the major means of maintaining existing social ties.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.40.4-41
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• 2018

The current 'standard model' of cosmology provides a minimal theoretical framework that can explain the gaussian, nearly scale-invariant density perturbations observed in the CMB to the late time clustering of galaxies. However accepting this framework, requires that we include within our cosmic inventory a vacuum energy that is ~122 orders of magnitude lower than Quantum Mechanical predictions, or alternatively a new scalar field (dark energy) that has negative pressure. An alternative approach to adding extra components to the Universe would be to modify the equations of Gravity. Although GR is supported by many current observations there are still alternative models that can be considered. Recently there have been many works attempting to test for modified gravity using the large scale clustering of galaxies, ISW, cluster abundance, RSD, 21cm observations, and weak lensing. In this work, we compare various modified gravity models using cosmic shear data from the Deep Lens Survey as well as data from CMB, SNe Ia, and BAO. We use the Bayesian Evidence to quantify the comparison robustly, which naturally penalizes complex models with weak data support. In this talk we present our methodology and preliminary results that show f(R) gravity is mildly disfavoured by the data.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.53.1-53.1
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• 2016

With the official start of the operations of the three 1.6 m KMTNet telescope systems from 2015 October, we have initiated a program named KMTNet Supernova Program (KSP) from 2015 to 2019 aiming at searching for supernovae (SNe), other optical transients and related sources. Taking advantage of the 24-hour coverage, high cadence and multi-color monitoring observations, this is optimal for discovering early SNe and peculiar ones. From the start of the previous test observing runs of ~half a year, we have performed observations on several nearby galaxy groups and nearby galaxies with short separations on the sky. We have developed data reduction/variable object search pipelines, meanwhile we have discovered some interesting transient objects. We also stacked all the images for given fields, searched for new objects/galaxies, and discovered several new dwarf galaxies, e.g., in the NGC 2784 galaxy group field (H. S. Park et al.'s talk). We will report the current project status and the results obtained.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.238.2-238.2
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• 2012

We report the results of KVN-VERA('KAVA'; KVN and VERA Arrary) AGN WG test observation in 2011 and 2012. The results from these commisioning years show that 'KAVA' is able to produce noble images of radio loud AGNs at 22 and 43GHz. This dedicated high frequency VLBI facility will be especially competitive for the regions where conventional low freuquency facilities see the optically thick part of synchrotron radiation. In the second part of this talk, we report the early science activities of the AGN WG. Sgr A*, Jet acceleration zone of M87, extremely young radio galaxies are the prime cadidates of the joint activities. Lastly we will stress how the phase-referencing 'KAVA' does enhance the imaging sensitivity and open new era of VLBI AGN researches.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.14 no.4
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• pp.524-535
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• 2007

Purpose: The purpose was to identify the risk of drug use by adolescents. Method: The participants were 933 male students in the first grade of a high school in D city. The data were collected from Aug. 5th to Oct. 30th, 2004. The instrument was the High Risk Group Adolescent Drug User Screening Test(HIRIGADUST) developed by the Korea Adolescent Society(1996). The data were analyzed using SPSS. Results: For substance use, 64.5% of the students answered that they had drunk, 40.3% that they had smoked, and 2.0% that they had tried drug use. For scores on HIRIGADUST regarding socio-demographic characteristics, there were significant differences depending on school type, personality, academic performance, economic status, and ability to talk with parents. For scores on HIRIGADUST regarding drug using-related characteristics, there were significant differences depending on drinking experience, frequency of drinking, amount of alcohol intake, smoking experience and number of cigarettes smoked. Of the students 27.2% students were in the high risk group. Conclusion: In schools, systematic and intensive assessment of drug use should be done, and if needed, a service system connected to clinics specializing in drug addiction should be established. Prevention education should be carried out continuously.

• Korean Journal of Childcare and Education
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• v.19 no.6
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• pp.79-95
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• 2023

Objective: This study examines the relationships among four-year-olds' counting skills, their use of number words, and their mothers' use of number words during mother-child free play. Specifically, we assess whether children's use of number words mediates the relationship between their counting skills and their mothers' use of number words during play. Methods: Forty-two 4-year-old children and their mothers were asked to play freely with a given set of toys at their home for 10 minutes. Children also completed a counting skill test. Frequencies of number word use were calculated for mothers and children from transcriptions of the free play. Results: Children's counting skills, the frequency of their number word use, and their mothers' frequency of number word use were positively correlated with each other. Additionally, the frequency of children's number-word use completely mediated the relationship between their counting skills and their mothers' frequency of number-word use. Conclusion/Implications: The results suggest that children's use of number language may play a crucial role in the provision of number-related language input by parents, based on their children's math skills. Practical implications of the findings are discussed.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.32.3-32.3
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• 2008

Solar and Space Weather Research Group in Korea Astronomy & Space Science Institute (KASI) has been funded for "Construction of Korean Space Weather Prediction Center" from Korean government. It has started since 2007 February and is planed as a 5-year project. The goal of this project is to develop a space weather warning and prediction system by the next solar maximum. KASI installed a magnetometer at Mt. Bohyun, which is about 200 km south-east apart from KASI, in 2007 September. After finishing test observations of the magnetometer for the period from September 2007 to January 2008, KASI has operated the magnetometer to monitor geomagnetic field variations associated with space weather effect. Ground-based magnetometers are critical for understanding geomagnetic disturbances in the near-Earth space environment, which are caused by solar wind variations. In this talk, we introduce science topics to be done with the data from KASI magnetometer and also discuss how they are related to space weather phenomena.