• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1103-1111
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• 2016

Korea Astronomy and Space Science Institute (KASI) has been operating SLR (Satellite Laser Ranging) system with 2kHz repetition rate for satellite precise orbit and spin determination as well as space geodesy. But the SLR system was improved to be capable of laser ranging with high repetition rate, up to 10kHz by developing new operation software and novel range gate generator, called HSLR-10. The HSLR-10 will contribute to the accurate spin rate determination of geodetic satellites and geodetic research due to its largest repetition rate in the world. In this study, the development methodology and configuration of operation software are addressed, and its validation results are also presented.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.93-102
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• 2011

Korea Astronomy and Space Science Institute (KASI) launched the development project of two satellite laser ranging (SLR) systems in early 2008 after the government fund approval of the SLR systems in 2007. One mobile SLR system and one permanent SLR station will be developed with the completion of the project. The main objectives of these systems will be focused on the Space Geodetic researches. A system requirement review was held in the second half of the same year. Through the following system design review meeting and other design reviews, many unsolved technical and engineering issues would be discussed and resolved. However, the design of the mobile SLR system is a corner stone of whole project. The noticeable characteristics of Korea's first SLR system are 1) use of light weight main mirror, 2) design of compact optical assembly, 3) use of KHz laser pulse, 4) use of commercial laser generator, 5) remote operation capability, 6) automatic tracking, 7) state of art operation system, etc. In this paper, the major user requirement and pre-defined specification are presented and discussed.

• The Optical Journal
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• v.13 no.5 s.75
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• pp.32-37
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• 2001

최근 인기몰이를 하고 있는 디지털카메라를 비롯해 고가의 콤팩트와 SLR카메라 밀수가 기승을 부리고 있는 것으로 나타났다. 지난 99년 수입선다변화 해제와 더불어 밀수문제가 심각해질 것이라는 업계의 우려가 현실로 나타난 것이다. 카메라 업계에서는 현재 시중에 유통되는 카메라가 10$\%$가 밀수이고, SLR의 경우 유통량의 절반이 밀수라고 추정할 만큼 밀수제품이 성행하면서 유통질서를 흐리고 있어 심각한 문제로 대두되고 있다.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.189-200
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• 2015

In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 - 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.27.5-28
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• 2010

The unexpected observation condition or insufficient measurement modeling can lead to uncertain measurement errors. The uncertain measurement error of orbit determination problem typically consists of noise, bias and drift. It must be removed by using a proper estimation process for better orbit accuracy. The estimation of noise and drift is not easy because of their random or unpredictable variation. On the other hand, bias is a constant difference between the mean of the measured values and the true value, so it can be simply removed. In this study, precision orbit determination with SLR observations considering range bias estimation is presented. The Yonsei Laser-ranging Precision Orbit Determination System (YLPODS) and SLR NP (Normal Point) observations of CHAMP satellite are used for this work. The SLR residual test is performed to estimate the range bias of each arc. The result shows that we can get better orbit accuracy through range bias estimation.

• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.227-233
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• 2018

This study presents the generation and accuracy assessment of predicted orbital ephemeris based on satellite laser ranging (SLR) for geostationary Earth orbit (GEO) satellites. Two GEO satellites are considered: GEO-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) for simulational validation and Compass-G1 for real-world quality assessment. SLR-based orbit determination (OD) is proactively performed to generate orbital ephemeris. The length and the gap of the predicted orbital ephemeris were set by considering the consolidated prediction format (CPF). The resultant predicted ephemeris of GK-2B is directly compared with a pre-specified true orbit to show 17.461 m and 23.978 m, in 3D root-mean-square (RMS) position error and maximum position error for one day, respectively. The predicted ephemeris of Compass-G1 is overlapped with the Global Navigation Satellite System (GNSS) final orbit from the GeoForschungsZentrum (GFZ) analysis center (AC) to yield 36.760 m in 3D RMS position differences. It is also compared with the CPF orbit from the International Laser Ranging Service (ILRS) to present 109.888 m in 3D RMS position differences. These results imply that SLR-based orbital ephemeris can be an alternative candidate for improving the accuracy of commonly used radar-based orbital ephemeris for GEO satellites.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4555-4571
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• 2019

Due to increasing interest in distributed agile software development, there is a need to systematically review the literature on challenges encountered in the agile software development environment. Using the Systematic Literature Review (SLR) approach, 32 relevant publications, dated between 2013 and 2018 were selected from four electronic databases. Data from these publications were extracted to identify the key challenges across the system development life cycle (SDLC) phases, which essentially are short phases in each agile-based iteration. 5 types of key challenges were identified as impacting the SDLC phases; these challenges are Communication, Coordination, Cooperation, Collaboration and Control. In the context of the SLDC phases, the Communication challenge was discussed the most often (79 times, 33%). The least discussed challenges were Cooperation and Collaboration (26 times, 11% each). The 5 challenges occur because of distances which occur in distributed environment. This SLR identified 4 types of distances which contribute to the occurrence of these key challenges - physical, temporal, social-cultural and knowledge/experience. Of the 32 publications, only 4 included research which proposed new solutions to address challenges in agile distributed software development. The authors of this article believe that the findings in this SLR are a resource for future research work to deepen the understanding of and to develop additional solutions to address the challenges in distributed agile software development.

• Journal of the Korean housing association
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• v.26 no.6
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• pp.35-42
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• 2015

The Brazilian Federal Housing Program "Minha Casa Minha Vida" -PMCMV (My House My Life) is part of a large housing policy to eradicate the housing deficit, estimated at around five million homes in the country. The Ministry for Cities created a network of independent research organizations to evaluate the program, and the PMCMV has attracted many studies. Despite the inherent worth of these individual studies, there is a need for a holistic evaluation. A Systematic Literature Review (SLR) is seen as an important contribution to focus research efforts on the problems identified, to avoid the repetition of studies and to provide novel insights. This article carried out a SLR to map and quantify the types of research and represent a graphic panorama of published studies. Gap spotting was part of the study. In the five-year period from 2010-2014, the SLR identified 1489 bibliographic items. The panorama is categorised according to types of publications, and the analysis of items shows that most studies are concentrated on housing policies, financial questions, urban impacts and Brazilian social development. The results of this SLR raise some new research questions and show opportunities to reduce errors in the housing projects themselves.

• Journal of Korean Medicine Rehabilitation
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• v.23 no.4
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• pp.159-167
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• 2013

Objectives In this study, we wanted to find out the characteristics - gender, SLR test, valsalva test, duration, ESR, CRP and night pain - of lumbar disc herniation being classified as blood stasis and phlegm-retained fluid. Methods We surveyed 42 patients suffering from lumbar disc herniation using the diagnosis blood stasis syndrome, water retention syndrome of the comprehensive diagnosis of QI blood water. Blood stasis and phlegm-retained fluid are identical with blood stasis syndrome, water retention syndrome. Then we analyzed the characteristics - gender, SLR test, valsalva test, duration, ESR, CRP and night pain - of the patients suffering from lumbar disc herniation who were diagnosed as blood stasis and phlegm-retained fluid. Results Patients were sorted into two groups: 18 blood stasis patients and 30 phlegm-retained fluid patients. Gender (Woman), acute phase and night pain are related to blood stasis. Acute phase, positive of SLR test is related to phlegm-retained fluid. There was no correlation between blood stasis and SLR test, valsalva test, duration, ESR, CRP. Also no correlation between phlegm-fluid and gender, valsalva test, duration, ESR, CRP and night pain. Conclusions By Considering the characteristics - gender, SLR test, valsalva test, duration, ESR, CRP and night pain - of lumbar disc herniation patients, it can help to analyze the pattern of its symptoms.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.24 no.1
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• pp.7-14
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• 2018

Background: The purpose of this study is to investigate the effects of Mulligan's bent leg raise (BLR), two leg rotation (TLR) and straight leg raise with traction (traction SLR) technique on the change of shortened hamstring length. Methods: Sixty subjects participated in this study. The subjects were randomly assigned to either the BLR group (n=20) or TLR group (n=20) or traction SLR group (n=20). 90-90 SLR test was performed for evaluation of hamstring shortening at initial time of study. After intervention, immediate effect(immediately after intervention) and effect of maintenance (after 60 minutes from intervention) were assessed. Results: All three groups showed significant differences in the immediate evaluation and the post evaluation after 60 minutes on the change of shortened hamstring length compared to the initial evaluation. When three groups were compared, in the immediate effect, BLR and traction SLR groups were higher than TLR group (p<.05). And the effect after 60 minutes, BLR group was higher than the other two groups (p<.05). Conclusion: In the results of this study, three groups showed immediately and lasting effectiveness in flexibility of shortened hamstring. In addition, BLR and traction SLR groups were more flexible than TLR group in the immediate evaluation and BLR group had better maintenance of flexibility than the other two groups in the post evaluation after 60 minutes.