• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.119-120
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• 2015

We report results of the measurement of the trigonometric parallax of an $H_2O$ maser source in IRAS 22555+6213 with the VLBI Exploration of Radio Astrometry (VERA). The annual parallax was determined to be $0.278{\pm}0.019$ mas, corresponding to a distance of $3.66^{+0.30}_{-0.26}kpc$. Our results confirm that IRAS 22555+6213 is located in the Perseus arm. We computed the peculiar motion of IRAS 22555+6213 to be ($U_{src}$, $V_{src}$, $W_{src}$) = ($0{\pm}1$, $-32{\pm}1$, $9{\pm}1$) $km\;s^{-1}$, where $U_{src}$, $V_{src}$, and $W_{src}$ are directed toward the Galactic center, in the direction of Galactic rotation and toward the Galactic north pole, respectively. IRAS 22555+6213, NGC7538 and Cepheus A lie along the same line of sight, and are within $2^{\circ}$ on the sky. Their parallax distances, with which we derived their absolute position in the Milky Way, show that IRAS 22555+6213 and NGC7538 are associated with the Perseus arm, while Cepheus A is located in the Local arm. We compared the kinematic distances of IRAS 22555+6213 derived with flat and non-flat rotation curve with its parallax distance and found the kinematic distance derived from the non-flat rotation assumption ($-32km\;s^{-1}$ lag) to be consistent with the parallax distance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.1011-1017
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• 2004

Ultra Wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as Korean Cellular CDMA and WCDMA. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum CDMA(DS-CDMA) UWB source and an impulse radio UWB source, to a Cellular CDMA and WCDMA digital transmission system. The average frame error rate degradation of each system are presented. From these experimental results, the interference effects of DS-CDMA UWB source is not severe compared to the Impulse UWB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.10
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• pp.966-982
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• 2014

This paper presents recent trends in system-level EMC investigation and countermeasure technology for radio frequency interference (RFI) influenced by noise generated in high-speed digital system. Recently, as the only digital device can perform various roles, there are a variety of EMI/EMC problems between systems. Especially, RFI is now recognized as a major problem, which occurs by EMI caused by the digital system. Therefore, in this paper, recent trends of RFI investigation from component-level to system-level are introduced and analyzed. Furthermore, in order to solve the RFI problem, recent researches are presented and investigated for the occurrences and suppression methods of common-mode noise which is one of the major noise sources in high-speed digital system. Lastly, this paper suggested future research of system-level EMC analysis and countermeasure technology for RFI problems.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.

• Korean Journal of Community Nutrition
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• v.5 no.2
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• pp.280-288
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• 2000

This study was undertaken to compare the obesity related dietary factors among rural middle school students living in Korea. Anthropometric data showed that mean height and weigh were 161.7$\pm$13.0 and 49.8$\pm$10.3kg in 226 male students and 158.3$\pm$6.1 and 48.2$\pm$7.5kg in 212 female students. Mean BMIs for boys and girls were 19.10$\pm$2.47 and 19.26$\pm$2.35, respectively. 71.68% of male students and 72% of female students were underweight by the BMI index. The BMI of older students was higher than young ones in both sexes. Most nutrient intakes of the subjects were below the RDA. In particular Ca and Fe intakes were extremely low in both sexes. 66.88% of the students skipped breakfast and it was found that the reasons for missing a meal for both sexes were significantly different. Compared to males, more female respondents felt guilty and depressed related to eating. Furthermore, females were more significantly concerned with body image, diet, and body weight(p〈0.001), and they were not satisfied with their weight. The sources of information on obesity and diet were from radio and TV in males while females got information from magazines and friends. In male students their ideal body weight was higher was higher than actual body weight. In contrasting, female students desired a thin body shape. A different approach for nutrition education for adolescents should be developed and implemented based on sex.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.35.4-35.4
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• 2019

We have conducted a 22 GHz very long baseline interferometry (VLBI) survey of 281 local (z < 0.05) active galactic nuclei (AGNs) selected from the Swift Burst Alert Telescope (BAT) 70-month ultra hard X-ray (14-195 keV) catalog. The main goal is to investigate the relation between the strengths of black hole accretion and the parsec-scale nuclear jet, which is expected to tightly correlate but has not been observationally confirmed yet. The BAT AGN Spectroscopic Survey (BASS) provides the least biased AGN sample against obscuration including both Seyfert types, hence it makes an ideal parent sample for studying the nuclear jet properties of an overall AGN population. Using the Korean VLBI Network (KVN), the KVN and VERA Array (KaVA), and the Very Long Baseline Array (VLBA), we observed 281 objects with a 22 GHz flux > 30 mJy, detecting 11 targets (~4% of VLBI detection rate). This implies that the fraction of X-ray AGNs which are currently ejecting a strong nuclear jet is very small. Although our 11 sources span a wide range of pc-scale morphological types, from compact to complex, they lie on a tight linear relation between accretion luminosity and nuclear jet luminosity. Our finding may indicate that the power of nuclear jet is directly responsible for the amount of black hole accretion. We also have probed the fundamental plane of black hole activity in VLBI scale (e.g., few milli-arcsecond). The results from our high-frequency VLBI radio study support that the change of jet luminosity and size follows what is predicted by the AGN evolution scenario based on the Eddington ratio (ƛ$_{Edd}$) - column density ($N_H$) plane, proposed by a previous study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.8
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• pp.1222-1230
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• 2022

As the number of signal sources with low detectability by using various modulation techniques increases, research to classify signal modulation methods is steadily progressing. Recently, a Convolutional Neural Network (CNN) deep learning technique using FFT as a preprocessing process has been proposed to improve the performance of received signal classification in signal interference or noise environments. However, due to the characteristics of the FFT in which the window is fixed, it is not possible to accurately classify the change over time of the detection signal. Therefore, in this paper, we propose a CNN model that has high resolution in the time domain and frequency domain and uses wavelet transform as a preprocessing process that can express various types of signals simultaneously in time and frequency domains. It has been demonstrated that the proposed wavelet transform method through simulation shows superior performance regardless of the SNR change in terms of accuracy and learning speed compared to the FFT transform method, and shows a greater difference, especially when the SNR is low.

• Journal of Christian Education in Korea
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• v.65
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• pp.103-131
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• 2021

The purpose of this study is to identify the direction of future Christian ministry by examining the educational/pastoral ministries of Korean churches during the COVID-19 period. The study used the case study method, where pastors from four different churches were the primary sources of data. Although each church has its own unique ministry, special early morning prayer meetings, family worship services, family Vacation Bible Schools, Bible writing and reading programs, and on-line discipleship training programs were common. In addition, each church implemented special programs that reflected the characteristics and needs of the church, like a talk show, visible radio, surfing meeting, and book-making of Bible manuscripts. Based on these results, ministry programs reflecting the church's pastoral philosophy, strengthening community consciousness, restoring the spiritual function of the family, utilizing online teaching methods, and psychological support for the underprivileged are proposed. In addition, the recovery of Christian publicity and the help from denomination or specialized institutions to develop the programs and online materials were suggested. Through this study, the direction of educational/pastoral ministry in a time of COVID-19 and post-COVID-19 is proposed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.143-150
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• 2023

Underwater wireless communication is a challenging issue for realizing the smart aqua-farm and various marine activities for exploring the ocean and environmental monitoring. In comparison to acoustic and radio frequency technologies, the visible light communication is the most promising method to transmit data with a higher speed in complex underwater environments. To send data at a speedier rate, high-performance photodetectors are essentially required to receive blue and/or cyan-blue light that are transmitted from the light sources in a light-fidelity (Li-Fi) system. Here, we fabricated high-performance organic phototransistors (OPTs) based on P-type donor polymer (PTO2) and N-type acceptor small molecule (IT-4F) blend semiconductors. Bulk-heterojunction (BHJ) PTO2:IT-4F photo-active layer has a broad absorption spectrum in the range of 450~550 nm wavelength. Solution-processed OPTs showed a high photo-responsivity >1,000 mA/W, a large photo-sensitivity >10³, a fast response time, and reproducible light-On/Off switching characteristics even under a weak incident light. BHJ organic semiconductors absorbed photons and generated excitons, and efficiently dissociated to electron and hole carriers at the donor-acceptor interface. Printed and flexible OPTs can be widely used as Li-Fi receivers and image sensors for underwater communication and underwater internet of things (UIoTs).

• Journal of Society of Preventive Korean Medicine
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• v.6 no.1
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• pp.95-95
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• 2002

This study was conducted to examine housewives' knowledge level of herb medicine and its related factors in Korea. Data were collected from 667 housewives from April 1, 1999 to June 30, 1999. The results of this study are summarized as follows. 1. According to general characteristics of the subjects, 29.1$\%$ of the subjects was over fifties. 28.6$\%$ was primary school graduate. while 25.5$\%$ was high school graduate. In case of job, the unemployed was 67.0$\%$ and professional／clerical worker was 19.6$\%$. 82.0$\%$ had spouses and 45.7$\%$ believed in Buddha. 50.8$\%$ of the subjects lived in big cities and 76.7$\%$ was the middle class. In case of their health condition, 33.4$\%$ was in good health, while 5 1.1$\%$ suffered from certain diseases and 43.9$\%$ was not satisfied with health conditions. 2. The proportion of experience in taking herb medicine was 86.4$\%$. The marital status and health condition were significantly related to the experience in taking herb medicine. When the respondents took diseases, 68.0$\%$ of them were experienced in folk remedy. The variables of age and religion were significantly related to experience in folk remedy. 3. According to the respondents opinions of the effect of the folk remedy, 'effective' was 78.5$\%$ and 'common' was 17.6$\%$, while 'not effective' was 3.9$\%$. 59.3$\%$ of the respondents thought that the folk remedy had scientific basis. 4. In case of information sources on herb medicine, 59.7$\%$ of the respondents obtained the information from TV or Radio. 13.7$\%$ of them got it from magazines related to Oriental medicine and 13.3$\%$ of them obtained it from newspapers or related books. The information sources were significantly related to age and health condition. The knowledge level of herb medicine was 20.76${\pm}$2.66 point on the basis of 30 points. The knowledge level was significantly related to age, occupation, health condition, information sources, experience in taking herb medicine, and opinions of scientific basis of the folk remedy. 5. The respondents marked 2.23${\pm}$0.64 points on the basis of 3.0 points in the question of the effect of taking herb medicine in summer, 2.30${\pm}$0.61 points in the question of the relationship between taking deer antlers and becoming clear-headed, 2.72${\pm}$0.56 points in the question of ginseng, 2.51${\pm}$0.56 points in the question of the relationship between taking herb medicine and being harmful to the liver, 1.94${\pm}$0.74 points in the question of taking herb medicine during the period of pregnancy, 1.84${\pm}$0.78 points in the question of the relationship between menstrual irregularity and motherwort, 2.00${\pm}$0.83 points in the question of the relationship between taking herb medicine and getting fat, 1.76${\pm}$0.89 points in the question of the relationship between Ssanghwatang and cold, 2.15${\pm}$0.76 points in the question of taking honey, and 1.45${\pm}$0.77 points in the question of selecting foods during the period of taking herb medicine. 6. The factors influencing decision of taking herb medicine were experience of taking herb medicine, intention of receiving treatment by folk remedy, occupation, health condition, and age. As seen in the above results, the knowledge level of taking herb medicine during the period of pregnancy, the relationship between menstrual irregularity and motherwort, Ssanghwatang, honey, and selecting foods during the period of taking herb medicine was very low. Therefore, it is necessary to develop education programs in order to provide community residents with basic knowledge of herb medicine. In doing so, the government, Oriental medical doctors, and associations related to herb medicine must make great efforts.