• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.516-523
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• 2020

Since the aging of coastal structures have been increased, the researches about the reinforcements of the existing aged structures are needed. Especially, the existing armor units placed on rubble mound structures should satisfy the stability against the increased design wave conditions. However the researches about these design problems have not been performed. In this study, the hydraulic model tests to investigate the stability number about the additionally placed armor unit were conducted. The main armor unit is a Tetrapod. The test results showed that the stability number (Kd) for additionally placed armor units(Tetrapod) increased up to maximum 10% comparing with that for 2 layers tetrapod (Kd = 8) within these test conditions with the pattern placing for existing armor layers and the stable armor layer slope for the non overtopping condition.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.73-73
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• 2004

KOMPSAT-2 위성에서 사용되는 원격명령어와 텔레메트리는 국제표준규격인 CCSDS format을 따르고 있다. 이들 원격명령어와 텔레메트리는 KOMPSAT-1의 heritage에 따라 구성되었으나 테스트 단계를 거치는 동안 여러 가지 형식의 원격명령어와 텔레메트리가 추가되었으며 각 유닛의 프로세서와 탑재컴퓨터간의 충돌을 피하기 위해 그 구현 및 전달 방식도 보다 복잡해졌다. 본 논문에서는 KOMPSAT-2에서 사용되고 있는 원격명령어와 텔레메트리의 각 타입을 분석하고 유닛 별로 구현 및 전달 방식이 어떻게 달라지는 지 보여준다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.160.2-160.2
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• 2012

Unified State Model(이후 USM)은 Altman(1972)에 의해 처음 제안된 이후 Chodas(1981), Raol & Sinha(1985), Vittaldev et al.(2012) 등을 거치며 연구 발전되어 왔다. 이 모델은 공간상 6개 성분의 위치, 속도 벡터를 이용해 위성의 운동을 기술하는 기존 계산 방법과 달리 4개의 Quaternion 변수를 도입하여 위성의 위치를, 3개의 Hodograph 변수를 도입하여 위성의 속도를 각각 기술한다. USM의 장점은 직교좌표계로 표현된 위성의 위치, 속도 변수에 비해 USM 변수의 변화량이 상대적으로 작기 때문에 수치 계산 시 계산의 안정도가 높다. 또한 원궤도(${\omega}$ : undefined)와 적도면 궤도(i = 0, ${\Omega}$ : undefined) 계산 시에 나타나는 특이성(singularity) 문제가 발생하지 않는다. 본 연구에서는 USM 계산방법과 기존 방법에 의한 위성궤도 계산결과의 차이를 비교 분석하였다. 지구궤도 위성의 정밀계산을 위해 이체항 이외에 지구타원체 섭동항과 대기 항력에 의한 섭동항을 추가 적용하였다. 비구형 지구 중력 포텐셜에 의한 섭동은 J4항까지 고려하였으며, 대기 항력은 간단한 exponential 모델을 적용하였다. 또한 수치계산 시 적분 간격과 정밀도 차수를 조절하여 각 모델의 계산 안정성을 테스트하였다. 본 연구의 궤도계산 결과 USM 모델을 이용한 계산방법은 그 정밀성과 계산효율성이 매우 우수한 것으로 검증되었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.1445-1447
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• 2012

팀으로 구성된 개발 조직은 주어진 시간 안에 가용할 수 있는 인력으로 고객에게 전달될 최종 산출물인 소프트웨어를 개발한다. 개발과 통합을 거친 소프트웨어는 테스트를 거치며 발생되는 결함에 대해 수정 조치한다. 하지만 결함 수정과 병행하여 초기 요구사항은 변경되고 추가되어 개발되는 소프트웨어에 반영되야 함으로 팀에서는 메일, 전화, 또는 게시판 방식으로 결함 사항을 알리고 최종 소프트웨어를 개발해 나간다. 본 논문은 이러한 환경에 결함추적도구를 사용하여 결함 발견 시 등록하고, 해결된 소프트웨어의 버전을 관리하기 위한 방법에 대해 오픈소스 기반의 형상관리도구와 결함추적도구를 활용한 환경을 연구해 나가고자 한다.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.279-285
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• 2012

This study classified the categorization process of convergence products as a rule-based and a similarity-based categorization process. And we examined that how the categorization process was determined according to information types(visual vs. visual + verbal) about the components of two prototypes before convergence and thinking styles(holistic vs. analytic). The result of this study showed: (1) The rule-based categorization process appeared more in case of visual information with verbal information than only visual information. (2) Analytic thinkers chose a rule-based categorization process more than holistic thinkers. These findings provide the theoretical and practical implications to comprehend the categorization process of convergence products and the judgement for consideration set from various convergence products.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.135-144
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• 2009

The purpose of this study is to develop a simple and rational crack evaluation system using Marshall tester. Fracture energy were used as a parameter to evaluate the crack resistance of asphalt mixtures. Marshall tester basically measures the vertical deformation obtained from the linear variable differential transformer(LVDT) attached on the specimen's exterior, which can cause a measurement error due to the local deformation near the loading head. Therefore, the validity of the measurement system of Marshall tester should be tested to use it in calculation of fracture energy. Two types of indirect tensile strength tests were performed using four types of asphalt mixtures at two temperature conditions. From the tests, it was shown that local deformation near the loading head had not occurred before a specimen was fractured, so that it did not cause the measurement error of fracture energy. And also from the statistic analysis, the coefficient of variation of vertical deformation measurements obtained on specimen's exterior is less than 15%. Thus, vertical deformation measurements obtained on the specimen's exterior can be used in crack evaluation system using Marshall tester.

• Journal of KIISE
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• v.44 no.1
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• pp.57-62
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• 2017

Traditional Korean morphological analysis and POS tagging methods usually consist of two steps: 1 Generat hypotheses of all possible combinations of morphemes for given input, 2 Perform POS tagging search optimal result. require additional resource dictionaries and step could error to the step. In this paper, we tried to solve this problem end-to-end fashion using sequence-to-sequence model convolutional features. Experiment results Sejong corpus sour approach achieved 97.15% F1-score on morpheme level, 95.33% and 60.62% precision on word and sentence level, respectively; s96.91% F1-score on morpheme level, 95.40% and 60.62% precision on word and sentence level, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2289-2296
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• 2016

The password rules to be applied for the user account creation are often different by websites. Thus we often forget the password to sign in website and it creates waste of time for frequent password reset. In order to solve this problem we propose a new authentication method in this paper. When user forget the password to sign in, the existing methods require a password reset step but our proposed method provides new sign in scheme through the additional authentication step with base password and personal information registered at the member sign up stage. From the result of performance comparison the proposed method is considered to be more efficient than others because it provides not only an equivalent level of security with others but also requires only a half of the number of transactions and the time required for password reset step.

• Convergence Security Journal
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• v.19 no.3
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• pp.13-19
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• 2019

MANET has many security vulnerabilities because it consists of only mobile nodes using wireless. In particular, it is a very important factor determining network performance that excludes the participation of malicious nodes through accurate reliability measurements and authentication of nodes participating in the network. In this paper, we proposed a technique applied with blockchain technology in order to prevent forgery of authentication information for nodes participating in the network. And, an area-based hierarchical structure was applied to increase the efficiency of authentication for nodes and apply the optimal technique of block generation and exchange protocol. In addition, four data payloads were added to the block header in order to add authentication information for nodes in block. To improve the reliability by applying the blockchain technique to the hop-by-hop data transfer method between mobile nodes, blockchain exchange protocol through transaction creation, block packaging and verification processes were implemented. We performed the comparative experiment with the existing methods to evaluate the performance of the proposed method and confirmed the excellent performance by the experiment results.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.8
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• pp.901-906
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• 2015

We presented a method for Vad(Voice Activity Detection) using Bi-level HMM. Conventional methods need to do an additional post processing or set rule-based delayed frames. To cope with the problem, we applied to VAD a Bi-level HMM that has an inserted state layer into a typical HMM. And we used posterior ratio of voice states to detect voice period. Considering MFCCs(: Mel-Frequency Cepstral Coefficients) as observation vectors, we performed some experiments with voice data of different SNRs and achieved satisfactory results compared with well-known methods.