• Journal of Astronomy and Space Sciences
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• v.33 no.1
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• pp.37-44
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• 2016

This paper presents an algorithm for Real-Time Orbit Determination (RTOD) of navigation satellites for the Korean Regional Navigation Satellite System (KRNSS), when the navigation satellites generate ephemeris by themselves in abnormal situations. The KRNSS is an independent Regional Navigation Satellite System (RNSS) that is currently within the basic/preliminary research phase, which is intended to provide a satellite navigation service for South Korea and neighboring countries. Its candidate constellation comprises three geostationary and four elliptical inclined geosynchronous orbit satellites. Relative distance ranging between the KRNSS satellites based on Inter-Satellite Ranging (ISR) is adopted as the observation model. The extended Kalman filter is used for real-time estimation, which includes fine-tuning the covariance, measurement noise, and process noise matrices. Simulation results show that ISR precision of 0.3-0.7 m, ranging capability of 65,000 km, and observation intervals of less than 20 min are required to accomplish RTOD accuracy to within 1 m. Furthermore, close correlation is confirmed between the dilution of precision and RTOD accuracy.

• Journal of Environmental Science International
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• v.20 no.12
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• pp.1635-1646
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• 2011

This April 5th dam and Hwanggang dam, which are located in Imjin river, North Korea, become the main causes of water shortages and damages in Imjin river downstream. April 5th dam is assumed a small or medium-sized dam, its total storage volume reaches about 88 million $m^3$. And Hwanggang dam, multi-purposed dam of total storage volume approximately 0.3 billion $m^3$ to 0.4 billion $m^3$ is used as source of residental or industrial water in Gaeseong Industrial Complex. North Korea, which has April 5th dam and Hwanggang dam in Imjin river, manages water of approximately 0.39 billion $m^3$ to 0.49 billion $m^3$ directly. As water is storaged or discharged through dam, it causes a severe damage to areas in Yeoncheon-gun and Paju city, South Korea. Therefore, this study intends to analyze and estimate runoff through dam construction by using hydrological observation data and artificial data such as service water supply and agricultural water in Imjin river, water shortage and damage correctly.

• Journal of Korean Elementary Science Education
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• v.29 no.1
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• pp.56-68
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• 2010

The purpose of this study was to investigate the elementary school teachers' perceptions about the science subject exclusive system. For this study, we developed the questionnaire to investigate teachers' perceptions and 43 elementary school teachers participated in the questionnaire test. And we used participation observation method to investigate characteristics the exclusive elementary science teacher and the elementary school homeroom teacher's science classes. After participation observation, we had interviews with exclusive elementary school science teacher and elementary school homeroom teacher. The results showed that elementary school teachers thought the science subject exclusive system was very necessary. And elementary school teachers thought that the exclusive elementary science teacher had higher professionality about teaching science subject than the homeroom teacher. Then, they expected that the strong points of science subject exclusive system would be some solution to the weak points of homeroom teachers' science classes. We suggested that it must be to enlarge the science subject exclusive system and develope in-service teacher program for the exclusive elementary science teachers.

• English Language & Literature Teaching
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• v.16 no.3
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• pp.339-363
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• 2010

The purpose of this paper is to investigate how the English classes in secondary schools in Korea are in terms of communicative nature. After literature study, COLT parts A and B were used to analyze three kinds of English classes: a common class type taught by a school teacher who had won 1st prize at TEE contest, a team teaching class taught by NNS and NS, and a model class taught by a pre-service English teacher. Their communicative English classes were videotaped and transcribed for analysis by COLT. The results of the study revealed that students participated in the classes mostly as a unit and, therefore, did not get many meaningful chances to speak English. Second, creative language-use opportunities were barely found during classes. Third, the group work seemed to be prepared before the class, not to be done during the class. Therefore it is likely to be learned from memorization rather than meaningful communication. These results suggest English classes in schools be more communicatively oriented for successful English learning. Further study should be conducted in order to make English classes more communicative to help students communicate their genuine messages in English and to help teachers teach English efficiently.

• International journal of advanced smart convergence
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• v.8 no.3
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• pp.161-166
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• 2019

Viewed in the rate of change in the web environment, it is very difficult to remain the initial planning at the time until the time of launch, and there is a need for a method to accommodate changes and satisfy market demands during the development process. Unlike the traditional waterfall approach of maintaining initial planning, scrum is one of the agile methodologies that enables flexibility to respond to changes in the market and customers' needs and drive customer satisfaction and business success. However, to apply the scrum to a project in actual, the practice method itself is relatively simple but not easy to apply. The reason is that the members of the organization need to understand and participate in scrum's philosophy and principles and the continuous observation and change management should be carried out. Therefore, in this paper, we presented the feature dashboard and customized scrum methodology to enable continuous observation and change management using visibility, and we shared the case that periodically reflected inspection and adaptation with the explanation of the main points. Also, based on the experience with participants, the strengths and weakness of the feature dashboard and the customized scrum methodology are summarized.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.101-107
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• 2022

In Korea, the military has been conducting counseling forthe preemptive detection of psychologically unstable soldiers to prevent unexpected accidents and to help them adapt to military life. However, several soldiers feel anxious about face-to-face counseling with military officers and they have difficulty expressing themselves. Video See-Through HMD is a state-of-the-art mixed reality device that converts the user's real view into a digital view, which leads users to feel the actual situation as the virtual. To validate its usefulness as a new psychological counseling aid, we investigated 11 army soldiers who are under the counseling program in barracks. During the counseling conversation, participants were asked to wear or take off the Video See-Through HMD repeatedly. All conversations were recorded for behavioral observation. As a result, 80% of the soldiers showed a relatively stable state of mind when wearing the Video See-Through HMD, which leads them to be innocent and frank about their concerns. This method could improve the effectiveness of counseling to prevent unexpected accidents caused by unnoticeable psychological instabilities of the clients.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.199-206
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• 2024

The GEO-KOMPSAT-2A (GK2A) satellite, which was launched in December 2018, carries weather observation payloads and uses the image navigation and registration system to calibrate the observation images. The calibration system requires accurate orbit prediction data and depends on the accuracy of the orbit determination accuracy. In order to find a possible way to improve the current orbit determination accuracy of the GK2A flight dynamic subsystem module, orbit determination software was developed to independently evaluate the orbit determination accuracy. A comprehensive satellite dynamic model is applied for a batch-type least squares filter. When determining the orbit, thrust firing during station-keeping maneuvers and wheel-off loading maneuvers is taken into account. One month of GK2A ranging data were processed to estimate the satellite position on a daily basis. The orbit determination error was evaluated by comparing estimates during overlapping estimation intervals.

• Korean Journal of Remote Sensing
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• v.36 no.5_4
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• pp.1139-1151
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• 2020

The National Disaster Management Research Institute(NDMI) has been developed technologies for disaster management applicability as well as disaster monitoring and damage analysis based on various earth observation platforms such as satellites, drones, and disaster field investigation vehicles. In this special issue, recent research results related to the disaster site investigation, satellite-based disaster management technology, and disaster information analysis using GIS conducted by NDMI are described in detail. Based on such achievements in the research of earth observation, we will continue to make efforts to improve the integrated national disaster investigation, analysis, and monitoring technology by connecting with the existing geo-spatial information service technology and various information collected at the disaster site.

• Current Optics and Photonics
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• v.1 no.4
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• pp.263-270
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• 2017

Solar radiation data measured by pyranometers is of fundamental use in various fields. In the field of atmospheric optics, the measurement of solar energy must be precise, and the equipment needs to be maintained frequently. However, there seem to be many errors with the existing type of pyranometer, which is an element of the solar-energy observation apparatus. In particular, the error caused by the thermal dome effect occurs because of the thermal offset generated from a temperature difference between outer dome and inner casing. To resolve the thermal dome effect, intensive observation was conducted using the method and instrument designed by Ji and Tsay. The characteristics of the observed global solar radiation were analyzed by classifying the observation period into clear, cloudy, and rainy cases. For the clear-weather case, the temperature difference between the pyranometer's case and dome was highest, and the thermal dome effect was $0.88MJ\;m^{-2}\;day^{-1}$. Meanwhile, the thermal dome effect in the cloudy case was $0.69MJ\;m^{-2}\;day^{-1}$, because the reduced global solar radiation thus reduced the temperature difference between case and dome. In addition, the rainy case had the smallest temperature difference of $0.21MJ\;m^{-2}\;day^{-1}$. The quantification of this thermal dome effect with respect to the daily accumulated global solar radiation gives calculated errors in the cloudy, rainy, and clear cases of 6.53%, 6.38%, and 5.41% respectively.

• Journal of The Korean Association For Science Education
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• v.23 no.5
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• pp.484-493
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• 2003

This case study exemplifies science classroom observation and analysis. Data from two-day classroom observation, pre- and post-instruction interviews with the teacher and instructional materials were used to analyse the features of a science classroom. A teacher's classroom practices were examined in terms of the following six categories: (1)curriculum and science content, (2)teaching and learning methods, (3) teacher' s knowledge about learners, (4)classroom environment, (5)assessment, and (6)teacher's efforts for professional development. The teacher in this case study not only improved his own classroom practices, but also took an active role in teachers' in-service education to share his practical knowledge with others. Implications that valid evaluation(or observation) frameworks of classroom practices have on teacher education and teachers' inservice education are also discussed. These evaluation frameworks should provide teachers with a vision of highly accomplished practices.