• Composites Research
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• 제29권2호
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• pp.60-65
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• 2016

본 연구에서는 Type IV 수소 압력용기 시제품의 충격하중 조건에 따른 구조 건전성을 분석하고자 유한요소해석과 FBG 센서 삽입을 통한 실시간 모니터링 실험을 수행하여 결과를 분석하였다. 플라이 모델링 기법을 활용한 유한요소해석을 통해 FBG 센서를 삽입할 수소 압력용기의 취약부 선정 및 가압 조건을 제시하였으며, 실험을 진행할 기초 정보를 확보하였다. 실제 용기제작에 앞서 시편 실험을 통해 FBG 센서의 삽입방식 신뢰성을 확보하였으며, 이후 해당 결과를 활용하여 필라멘트 와인딩 공정에 적용하였다. 비충격 가압 피로실험과 총 4회의 충격 피로실험을 수행하였다. 실험결과 비충격 가압 피로실험에서는 해석과 동일한 거동을 보였으며, 4회의 충격 피로실험에서는 용기의 충전 시간이 점진적으로 증가하고 충전률은 감소하는 것을 확인하였다.

• 한국항해항만학회지
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• 제32권3호
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• pp.215-221
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• 2008

구조물의 대표적 동적특성인 고유진동수 및 모드형상은 손상평가, 구조계추정기법 등과 결합한 구조건전성 평가분야에서 매우 중요한 기초 자료로 활용되고 있다. 그러나 해양구조물이나 대경간 교량과 같은 대형 구조물의 경우 진동원을 정확히 계측하기 힘들기 때문에 소규모의 구조물에 많이 쓰이는 기존의 모달 테스트 기법으로는 구조물의 진동특성을 구할 수 없다. 본 논문에서는 경간이 긴 대형 트러스 구조물을 대상으로 가속도 응답만으로 고유진동수 및 모드형상을 추출할 수 있는 방법을 연구하였다. 트러스 구조물의 수치해석 모델을 이용하여 가속도 응답 및 주파수 응답함수의 생성과정, 모드분석을 통한 고유진동수 및 모드형상 추출과정을 상세히 설명하였다. 제안한 방법으로 얻은 모드형상은 고유치 해석으로부터 계산된 모드형상과 비교하여 정확성을 검증하였으며, 모의 손상을 통한 손상평가기법에 적용하여 타당성을 입증하였다.

• 한국안전학회지
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• 제28권3호
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• pp.44-50
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• 2013

Process gas piping is one of the most basic components frequently used in the refinery and petrochemical plants. Many kinds of by-product gas have been used as fuel in the process plants. In some plants, natural gas is additionally introduced and mixed with the byproduct gas for upgrading the fuel. In this case, safety or design margin of the changed piping system of the plant should be re-evaluated based on a proper design code such as ASME or API codes since internal pressure, temperature and gas compositions are different from the original plant design conditions. In this study, series of piping stress analysis were conducted for a process piping used for transporting the mixed gas of the by-product gas and the natural gas from a mixing drum to a knock-out drum in a refinery plant. The analysed piping section had been actually installed in a domestic industry and needed safety audit since the design condition was changed. Pipe locations of the maximum system stress and displacement were determined, which can be candidate inspection and safety monitoring points during the upcoming operation period. For studying the effects of outside air temperature to safety the additional stress analysis were conducted for various temperatures in $0{\sim}30^{\circ}C$. Effects of the friction coefficient between the pipe and support were also investigated showing a proper choice if the friction coefficient is important. The maximum system stresses were occurred mainly at elbow, tee and support locations, which shows the thermal load contributes considerably to the system stress rather than the internal pressure or the gravity loads.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.255-260
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• 2006

Safety-critical navigation systems have to provide 'reliable' position solutions, i.e., they must detect and exclude measurement or system faults and estimate the uncertainty of the solution. To obtain more accurate and reliable navigation systems, various filtering methods have been employed to reduce measurement noise level, or integrate sensors, such as global navigation satellite system/inertial navigation system (GNSS/INS) integration. Recently, particle filters have attracted attention, because they can deal with nonlinear/non-Gaussian systems. In most GNSS applications, the GNSS measurement noise is assumed to follow a Gaussian distribution, but this is not true. Therefore, we have proposed a fault detection and exclusion method using particle filters assuming non-Gaussian measurement noise. The performance of our method was contrasted with that of conventional Kalman filter methods with an assumed Gaussian noise. Since the Kalman filters presume that measurement noise follows a Gaussian distribution, they used an overbounded standard deviation to represent the measurement noise distribution, and since the overbound standard deviations were too conservative compared to the actual distributions, this degraded the integrity-monitoring performance of the filters. A simulation was performed to show the improvement in performance of our proposed particle filter method by not using the sigma overbounding. The results show that our method could detect smaller measurement biases and reduced the protection level by 30% versus the Kalman filter method based on an overbound sigma, which motivates us to use an actual noise model instead of the overbounding or improve the overbounding methods.

• 센서학회지
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• 제10권1호
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• pp.42-51
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• 2001

본 연구에서는 복합재료에 삽입된 광섬유센서의 인장하중하에서의 정적 물성치와 피로하중하에서의 동적 물성치를 실험적인 방법과 유한요소해석을 통하여 고찰하였다. 결과에 의하면 삽입된 광섬유센서는 인접한 강화섬유에 수직한 방향으로 삽입된 피로하중의 경우를 제외하고 복합재료의 기계적인 물성치에 큰 영향을 끼치지 않는다고 결론지을 수 있다. 광강도형 광섬유센서를 복합재료 적층판에 삽입하여 복합재 적층판의 강성저하를 측정함으로써 직교적층판 피로손상을 검출하였다. 이 실험의 결과에 의하면 광강도형 광섬유센서는 간단하고 저렴한 장치와 측정된 신호의 복잡한 후처리 과정이 필요 없다는 장점으로 인하여 구조물의 강성저하를 측정하여 피로손상을 감시하는데 있어서 큰 잠재력을 가진다고 할 수 있다. 또한 삽입된 광강도형 광섬유센서는 우수한 내 피로성과 넓은 강성측정 범위를 보였다.

• Journal of Positioning, Navigation, and Timing
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• 제8권2호
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• pp.79-85
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• 2019

The mission tasks of polar exploration utilizing unmanned systems such as glacier monitoring, ecosystem research, and inland exploration have been expanded. To facilitate unmanned exploration mission tasks, precise and robust navigation systems are required. However, limitations on the utilization of satellite navigation system are present due to satellite orbital characteristics at the polar region located in a high latitude. The orbital inclination of global positioning system (GPS), which was developed to be utilized in mid-latitude sites, was designed at $55^{\circ}$. This means that as the user is located in higher latitudes, the satellite visibility and vertical precision become worse. In addition, the use of satellite-based wide-area augmentation system (SBAS) is also limited in higher latitude regions than the maximum latitude of signal reception by stationary satellites, which is $70^{\circ}$. This study proposes a local-area augmentation system that additionally utilizes Global Navigation Satellite System (GLONASS) considering satellite navigation system environment in Polar Regions. The orbital inclination of GLONASS is $64.8^{\circ}$, which is suitable in order to ensure satellite visibility in high-latitude regions. In contrast, GLONASS has different system operation elements such as configuration elements of navigation message and update cycle and has a statistically different signal error level around 4 m, which is larger than that of GPS. Thus, such system characteristics must be taken into consideration to ensure data integrity and monitor GLONASS signal fault. This study took GLONASS system characteristics and performance into consideration to improve previously developed fault detection algorithm in the local-area augmentation system based on GPS. In addition, real GNSS observation data were acquired from the receivers installed at the Antarctic King Sejong Station to analyze positioning accuracy and calculate test statistics of the fault monitors. Finally, this study analyzed the satellite visibility of GPS/GLONASS-based local-area augmentation system in Polar Regions and conducted performance evaluations through simulations.

• Animal Bioscience
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• 제35권4호
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• pp.527-532
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• 2022

Objective: In this study, we aimed to investigate the recent changes such as allele frequencies and total probability of exclusion (PE) in Thoroughbred horses in Korea using short tandem repeat (STR) parentage panels between 2006 and 2016. Methods: The genotype was provided for 5,988 horse samples with 15 microsatellite markers (AHT4, AHT5, ASB2, ASB17, ASB23, CA425, HMS1, HMS2, HMS3, HMS6, HMS7, HTG4, HTG10, LEX3 and VHL20). Results: In our study, the observed number of alleles per locus ranged from 3 (HMS1) to 9 (ASB17) in 2006 and 4 (HMS1) to 9 (ASB2) in 2016, with a mean value of 6.28 and 6.40, respectively. Of the 15 markers, HMS2, HTG4, and CA425 loci had relatively low polymorphism information content (<0.5000) in the Thoroughbred population. Mean levels of genetic variation in 2006 and 2016 were observed heterozygosity (H_O) = 0.708, and expected heterozygosity (H_E) = 0.685, as well as and H_O = 0.699 and H_E = 0.682, respectively. The PE was calculated for each group based on the allele frequencies of 14 or 15 STRs. The 2006 survey analyzed that PE was 0.9998, but it increased to 0.9999 in 2016 after the HMS2 marker was added in 2011. The current STR panel is still a powerful tool for parentage verification that contributes to the maintenance of integrity in the Thoroughbred population. Conclusion: The current STR panel is still a powerful tool for parentage verification that contributes to the maintenance of integrity in the Thoroughbred horses. However, continuous monitoring genetic variability is necessary.

• Asian-Australasian Journal of Animal Sciences
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• 제28권11호
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• pp.1649-1656
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• 2015

Gene expression profiling has offered new insights into postmortem molecular changes associated with meat quality. To acquire reliable transcript quantification, high quality RNA is required. The objective of this study was to analyze integrity of RNA isolated from chicken skeletal muscle (pectoralis major) and its capability of serving as the template in quantitative real-time polymerase chain reaction (qPCR) as a function of postmortem intervals representing the end-points of evisceration, carcass chilling and aging stages in chicken abattoirs. Chicken breast muscle was dissected from the carcasses (n = 6) immediately after evisceration, and one-third of each sample was instantly snap-frozen and labeled as 20 min postmortem. The remaining muscle was stored on ice until the next rounds of sample collection (1.5 h and 6 h postmortem). The delayed postmortem duration did not significantly affect $A_{260}/A_{280}$ and $A_{260}/A_{230}$ ($p{\geq}0.05$), suggesting no altered purity of total RNA. Apart from a slight decrease in the 28s:18s ribosomal RNA ratio in 1.5 h samples (p<0.05), the value was not statistically different between 20 min and 6 h samples ($p{\geq}0.05$), indicating intact total RNA up to 6 h. Abundance of reference genes encoding beta-actin (ACTB), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), hypoxanthine-guanine phosphoribosyltransferase (HPRT), peptidylprolylisomerase A (PPIA) and TATA box-binding protein (TBP) as well as meat-quality associated genes (insulin-like growth factor 1 (IGF1), pyruvate dehydrogenase kinase isozyme 4 (PDK4), and peroxisome proliferator-activated receptor delta (PPARD) were investigated using qPCR. Transcript abundances of ACTB, GAPDH, HPRT, and PPIA were significantly different among all postmortem time points (p<0.05). Transcript levels of PDK4 and PPARD were significantly reduced in the 6 h samples (p<0.05). The findings suggest an adverse effect of a prolonged postmortem duration on reliability of transcript quantification in chicken skeletal muscle. For the best RNA quality, chicken skeletal muscle should be immediately collected after evisceration or within 20 min postmortem, and rapidly preserved by deep freezing.

• 융합보안논문지
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• 제24권1호
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• pp.51-57
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• 2024

최근 산업제어시스템은 정보기술과 운영기술을 융합하는 Industrial IoT의 도입과 함께 진화를 계속하고 있지만, 과거에는 경험하지 못한 다양한 사이버 공격 역시 증가하고 있다. 제어센터에서 전송되는 다양한 명령어 메시지를 통해 시스템을 구성하는 필드 디바이스들에 대한 모니터링 및 운영 제어가 행해지기에 명령어 메시지에 대한 무결성과 더불어 제어센터에 대한 인증은 필수 요구사항이 되고 있다. 기존의 대칭키 기반의 메시지인증코드 방식 또는 공개키 기반의 서명 방식은 제어센터 그리고 자원 제약적 필드 디바이스의 비대칭성에 따른 적용상의 제약들이 존재한다. 특히, 대칭키 방식에서는 필드 디바이스에 설치된 대칭키가 공격자에게 노출되면 시스템 전반적인 보안 문제점이 발생한다. 본 논문에서는 명령어 메시지를 구성하는 구성 필드들이 취할 수 있는 데이터 값들이 제한적(낮은 엔트로피)이라는 점에 착안하여 암호해시함수로 구축된 이중 해시체인을 통한 메시지 인증기법을 제안한다. 한 쌍의 이중 해시체인은 오직 한 개의 명령어 메시지에 적용되기에 다중 사용을 위한 Merkle 트리에 기반을 둔 확장 기법 역시 제안한다. 메시지 인증을 위해 암호해시함수 이외의 암호 프리미티브는 사용이 안되기에 계산 복잡도는 매우 낮게 유지될 수 있음을 성능평가를 통해 확인한다.

• 환경영향평가
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• 제20권6호
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• pp.845-856
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• 2011

In order to establish fundamental data for stream restoration and environmental flow, we investigated inhabitation and species diversity of fish to substrate size in the typical streams of Geum River Basin. Field monitoring including fish sampling was conducted from October 2007 to October 2009. Substrate size was determined according to six different : silt (Si), sand (Sa), fine gravel (Fg), coarse gravel (Cg), cobbles (Co) and boulders (Bo). A total number of fish caught in the 18 sites was 7,649 representing 10 families 50 species, and Si, Sa, Fg, Cg, Co and Bo stations occupied 30, 29, 38, 30, 27 and 17 species, respectively. The most frequently found species in number was pale chum (Zacco platypus, 29.7%, n=2,275) followed by Z. koreanus (22.5%, n=1,720) in total stations. Biological diversity with increase of substrate size from the dominance of part species showed higher values as dominance index, lower and diversity, richness and evenness index. Index of biological integrity (IBI) and qualitative habitat evaluation index (QHEI) scores decreased with increase of substrate size. Therefore, it is necessary to make an effort on stream rehabilitation with evaluation of physical habitat condition by indicator species in order to maintain biodiversity and perform ecological restoration.