• Title/Summary/Keyword: 건전성 모니터링

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A Study on the Rainwater Quality Monitoring and the Improvement, Collection and Storage System (빗물 집수 및 저장 시스템 개선과 수질 분석 모니터링)

  • Kim, Chul-Kyung
    • Clean Technology
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    • v.17 no.4
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    • pp.353-362
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    • 2011
  • In our nature, the utilization of rainwater is essential for healthy water recirculation. This is one of the solutions of the increment of impermeability surface according to the development of new cities; this study of the improvement of rainwater quality has been carried on through the improvement of collecting and restoring system of rainwater. The southwestern region of Daejeon City, the rainwater coefficient of run off was 0.40 and this number had computed to 0.59 after the development. After filtration of rainwater, the heavy metal (Cu, As, Cr, Fe, Mn) contents level were lower than underground water. Moreover, collected rainwater showed better quality than underground water in following criteria; hardness, permanganate consumption quality, chloride, evaporation residue, sulfates and nitrate nitrogen. This water quality met the gray water quality standards. The rainwater quality was still suitable to use as bathroom flushing and gardening after 100 days of storage. This study proved that modification (installation of cover with gutter to existing rainwater collection system, proper filtering, and installation of underground storage tank) of collection system could improve quality of water and maintain this approximately 100 days.

Source Location on Full-Scale Wind Turbine Blade Using Acoustic Emission Energy Based Signal Mapping Method (음향방출 에너지 기반 신호 맵핑 기법을 이용한 실물 풍력 블레이드 손상 검출)

  • Han, Byeong-Hee;Yoon, Dong-Jin;Huh, Yong-Hak;Lee, Young-Shin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.5
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    • pp.443-451
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    • 2013
  • Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. In this study, the activities of AE signals generated from external artificial sources was evaluated and located by new developed signal mapping source location method and this test is conducted by 750 kW full-scale blade. And a new source location method was applied to assess the damage in the wind turbine blade during step-by-step static load test. In this static loading test, we have used a full scale blade of 100 kW in capacity. The results show that the acoustic emission activities give a good agreement with the stress distribution and damage location in the blade. Finally, the applicability of the new source location method was confirmed by comparison of the result of source location and experimental damage location.

A Study on the Strength Characteristics and Failure Detection of Single-lap Joints with I-fiber Stitching Method (I-fiber 스티칭 공법이 적용된 Single-lap Joint의 강도 특성 및 파손 신호 검출 연구)

  • Choi, Seong-Hyun;Song, Sang-Hoon;An, Woo-Jin;Choi, Jin-Ho
    • Composites Research
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    • v.34 no.5
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    • pp.317-322
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    • 2021
  • When a complex load such as torsion, low-speed impact, or fatigue load is applied, the properties in the thickness direction are weakened through microcracks inside the material due to the nature of the laminated composite material, and delamination occurs. To prevent the interlaminar delamination, various three-dimensional reinforcement methods such as Z-pinning and stitching, and structural health monitoring techniques that detect the microcrack of structures in real time have been continuously studied. In this paper, the single-lap joints with I-fiber stitching process were manufactured by a co-curing method and their strengths and failure detection capability were evaluated. AE and electric resistance method were used for detection of crack and failure signal and electric circuit for signal analysis was manufactured, and failure signal was analyzed during the tensile test of a single-lap joint. From the experiment, the strength of the single lap joint reinforced by I-fiber stitching process was improved by about 44.6% compared to the co-cured single lap joint without reinforcement. In addition, as the single-lap joint reinforced by I-fiber stitching process can detect failure in both the electrical resistance method and the AE method, it has been proven to be an effective structure for failure monitoring as well as strength improvement.

Assessment of the Health of Fish Species Collected in Agricultural Reservoirs, AsanHo and NamyangHo (농업용저수지 아산호와 남양호에 서식하는 어류의 건전성 평가)

  • Kim, Byung-Seok;Park, Kyung-Hun;Park, Yoen-Ki;Joeng, Mi-Hye;You, Are-Sun;Yang, Yu-Jung;Choi, Ju-Byun;Kwon, Ok-Kyung;Ahn, Young-Joon
    • The Korean Journal of Pesticide Science
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    • v.12 no.1
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    • pp.57-66
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    • 2008
  • The purpose of this study was to establish biomonitoring method for the assessment of the health of fish species in agricultural reservoirs polluted from various environmental contaminants. The ichthyofauna and fish community were investigated in the AsanHo and NamyangHo from September to November 2007. We measured abundance, size distribution, biomass, the number of fish with external and internal lesions, organosomatic index of the fishes collected in the AsanHo and NamyangHo. Dominant species were Lepomis macrochirus, Carassius auratus and the highest biomass were found in Cyprinus carpio, Carassius auratus in the AsanHo and NamyangHo, respectively. The composition of age in the population of Carassius auratus in the AsanHo and NamyangHo was stabled by size distribution analysis. The sex ratio of Carassius auratus were 1:0.36, 1:0.52 as female: male ratio in AsanHo and NamyangHo, respectively. The GSI of were 4.30, 1.69 of female and 1.45, 1.70 of male in AsanHo and NamyangHo, respectively. Most carp were 10-70 cm long in the AsanHo and 20-50 cm in the NamyangHo. The sex ratio of Cyprinus carpio were 1:0.42, 1:0.59 as female: male ratio in AsanHo and NamyangHo, respectively. The GSI of were 0.16, 3.46 of female and 0.93, 2.37 of male in AsanHo and NamyangHo, respectively. Of the 227 fish examined, 1.8% had some type of external lesion in AsanHo and 10% in NamyangHo. Overall, HAI scores ranged from 10-60 and HAI scores of AsanHo relatively lower than that of NamyangHo.

ANN-Based Real-Time Damage Detection Technique Using Acceleration Signals in Beam-Type Structures (보 구조물의 가속도 신호를 이용한 인공신경망 기반 실시간 손상검색기법)

  • Park, Jae-Hyung;Lee, Yong-Hwan;Kim, Jeong-Tae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.3
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    • pp.229-237
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    • 2007
  • In this study, an artificial neural network (ANN)-based damage detection algorithm using acceleration signals is developed for real-time alarming locations of damage in beam-type structures. A new ANN-algorithm using output-only acceleration responses is designed tot damage detection in real time. The cross-covariance of two acceleration-signals measured at two different locations is selected as the feature representing the structural condition. Neural networks are trained lot potential loading Patterns and damage scenarios of the target structure for which its actual loadings are unknown. The feasibility and practicality of the proposed method are evaluated from laboratory-model tests on free-free beams for which accelerations were measured before and after several damage cases.

Regularization Method by Subset Selection for Structural Damage Detection (구조손상 탐색을 위한 부 집합 선택에 의한 정규화 방법)

  • Yun, Gun-Jin;Han, Bong-Koo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.1
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    • pp.73-82
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    • 2008
  • In this paper, a new regularization method by parameter subset selection method is proposed based on the residual force vector for damage localization. Although subset selection using the fundamental modal characteristics as a residual function has been successful in detecting a single damage location, this method seems to have limited capabilities in the detection of multiple damage locations and typically requires cumbersome weighting values. The method is presented herein and considers cases in which damage detection must be achieved using incomplete measurements of the structural responses. Model expansion is incorporated to deal with this challenge. The unique advantage of employing the new regularization method is that it can reliably identify multiple damage locations. Through an illustrative example, the proposed damage detection method is demonstrated to be a reliable tool for identifying multiple damage locations for a planar truss structure.

Measurement and Analysis of Low Flow in the Cheonggecheon Watershed (청계천 유역 갈수량 측정 및 분석)

  • Noh, Seong Jin;Kim, Hyeon Jun;Jang, Cheol Hee;Kim, Dong Pil;Hong, Il Pyo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.1067-1071
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    • 2004
  • 도시 유역의 물순환 특성을 종합적으로 이해하기 위해서는 갈수량 자료의 구축이 필수적이다. 하지만 지금까지의 인구는 주로 치수분야에 한정되어 대부분의 자료 또한 홍수기에 대해서만 자료가 구축되어 있으며 상대적으로 갈수기에 내한 자료와 관련 연구는 부족한 편이다. 본 연구에서는 청계천 유역의 기존 수문자료를 이용하여 유역의 유출 특성을 분석하고 갈수량을 측정하여 청계천 유역의 물순환 특성을 파악하기 위한 기초자료를 구축하였다. 청계천은 서울의 서북쪽에 위치한 인왕산과 북한산의 남쪽 기슭, 남산의 북쪽 기슭에서 시작하여 서에서 동으로 종로, 세운상가, 동대문 등 서울의 도심부를 흐르는 유로연장 13.75 km, 유역 면적 $50.96 km^2$의 도시하천으로 중량천의 제1지류인 지방2급 하천이며, 정릉친, 성북천을 제1지류, 월곡천을 제2지류로 포함한다. 청계천은 도시화로 인해 1950년대부터 1970년대까지 점차 복개되었다가 2003년 7월부터 5.9 km의 본류구간에 대한 복원공사가 진행 중이다. 청계천은 홍수기 이후 유량이 급격히 줄어 11월 이후에는 다음 홍수기까지 강바닥이 완전히 들어나는 일종의 간헐천으로 홍수기를 제외한 시기의 자료는 전무한 실정이다. 본 연구에서는 유역내 8개의 모니터링 지점을 선정하여 2003년 9월 이후, 월 2회 이상 갈수량 자료를 현장 측정${\cdot}$분석하였다. 청계천 유역은 복원공사 완공 후에는 유역의 물순환 특성이 대폭 바뀔 것이 예상되는 지역으로 본 연구에서 구축된 갈수량 자료는 청계천 유역의 물순환계 변화를 분석하고 건전한 물순환 체계의 유지${\cdot}$관리를 위한 기본 자료가 될 것으로 판단된다., 바늘꽃과, 속새과, 십자화과, 장미과, 사초과, 삼과, 현삼과, 닭의장풀과가 각 1종씩 조사되었으며, 조사지점(II)인 1km지점에서는 15과 26종으로, 벼과가 4종, 마디풀과, 국화과가 3종, 버드나무과, 십자화과, 콩과가 2종씩, 바늘꽃과, 속새과, 자라풀과, 장미과, 사초과, 백합과, 현삼과, 골풀과, 닭의장풀과가 각 1종씩으로, 조사지점( I )보다 좀 더 많은 종이 분포하는 것으로 조사되었다. 또한 어류는 조사지점( I )에서 3회에 걸쳐 총 396개체가 채집되어 3목 8과 21종이었다. 이 중 한국 고유종은 11종이었고, 외래 어종은 검정우럭과 2종이 조사되었으며, Zacco platypus(피라미), Zacco temmincki(갈겨니), Acheilongnathus koreanus(칼납자루), Odontobutis platycephala(동사리), Coreoleuciscus splendidus(쉬리) 순으로 분포하고 있었고, Acheilognathus signifer(묵납자루)는 댐 건설 전에는 많이 분포하였으나 현장조사에서 서식을 확인 할 수 언어 개체수의 큰 감소내지 멸종된 것으로 추정되었다.에서 동시에 시행하였다. 수술 후 1년 내 시행한 심초음파에서 모든 환아에서 단지 경등도 이하의 승모판 폐쇄 부전 소견을 보였다. 수술 후 조기 사망은 없었으며, 합병증으로는 유미흉이 한 명에서 있었다. 술 후 10개월째 허혈성 확장성 심근증이 호전되지 않아 Dor 술식을 시행한 후 사망한 예를 제외한 나머지 6명은 특이 증상 없이 정상 생활 중이다 결론: 좌관상동맥 페동맥이상 기시증은 드물기는 하나, 영유아기에 심근경색 및 허혈성 심근증 또는 선천성 승모판 폐쇄 부전등을 초래하는 심각한 선천성 심질환이다

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Dynamic Characteristics of Seohae Cable-stayed Bridge Based on Long-term Measurements (장기계측에 의한 서해대교 사장교의 동특성 평가)

  • Park, Jong-Chil;Park, Chan-Min;Kim, Byeong-Hwa;Lee, Il-Keun;Jo, Byung-Wan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.6 s.52
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    • pp.115-123
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    • 2006
  • This paper presents long-term dynamic characteristics of a cable-stayed bridge where installed SHM (Structural Health Monitoring) system. Modal parameters such as natural frequencies and mode shapes are identified by modal analysis using three dimensional finite element model. The developed baseline model has a good correlation with measured natural frequencies identified from field ambient vibrations. By statistical data processing between measured natural frequencies and temperatures, it is demonstrated that the natural frequency is in linearly inverse proportion to the temperature. The estimation of temperature effects against frequency variations is performed. Mode shapes are identified from the TDD (Time Domain Decomposition) technique for ambient vibration measurements. Finally, these results demonstrate that the TDD method can apply to identify modal parameters of a cable-stayed bridge.

Study on the Characteristics of Wavelet Decomposed Details of Low-Velocity Impact Induced AE Signals in Composite Laminaes (저속충격에 의해 발생한 복합적층판 음향방출신호의 웨이블릿 분해 특성에 관한 연구)

  • Bang, Hyung-Joon;Kim, Chun-Gon
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.308-315
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    • 2009
  • Because the attenuation of AE signal in composite materials is relatively higher than that of metallic materials, it is required to develop a damage assessment technique less affected by the attenuation property of composite materials in order to use AE sensing as a damage detection method. In the signal processing procedure, it is profitable to use the leading wave that arrives first because the leading wave is less influenced by the boundary conditions. Using wavelet transform, we investigated the frequency characteristics of impact induced AE signals focused on the leading wave in advance and chose the key factors to discriminate the damaged condition quantitatively. In this research, we established a damage assessment technique using the sharing percentage of the wavelet detail components of AE signal, and conducted a low-velocity impact test on composite laminates to confirm the feasibility of the proposed signal processing method.

Risk Analysis of Household Debt in Korea: Using Micro CB Data (개인CB 자료를 이용한 우리나라 가계의 부채상환위험 분석)

  • Hahm, Joon-Ho;Kim, Jung In;Lee, Young Sook
    • KDI Journal of Economic Policy
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    • v.32 no.4
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    • pp.1-34
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    • 2010
  • We conduct a comprehensive risk analysis of household debt in Korea for the first time using the whole sample credit bureau (CB) data of 2.2 million individual debtors. After analysing debt service capacity profiles of debtor groups classified by the borrower characteristics such as income, age, occupation, credit scoring, and the type of creditor business companies, we investigate the impact of interest rate and income changes on debt service-to-income ratios (DTIs) and default rates of respective debtor groups. Empirical results indicate that debt service burdens are relatively high for low income wage earners, high income self-employed, low income capital and card loan holders, and high income mutual savings loan holders. We also find that debtors from multiple financial companies are particularly weak in their debt service capacity. The scenario analysis indicates that financial companies, with the current level of capital buffers, may be able to absorb negative consequences arising from the increase in DTIs and loan default rates if the interest rate and income changes remain modest. However, the negative consequences may fall disproportionately on non-bank financial companies such as capital, credit card, and mutual savings banks, whose debtors' DTIs are already high. We also find that the refinancing risk of household debt is relatively high in Korea as more than half of household mortgage debts are bullet loans. As the DTIs of mortgage loan holders are already high, under the current DTI regulation, mortgage loans may not be readily refinanced especially when the interest rate rises. Disruptions in mortgage loan refinancing may put downward pressure on housing prices, which may in turn magnify refinancing risk under the current loan-to-value (LTV) regulation. Overall our analysis suggests that, for more effective monitoring of household debt risk, it is necessary to combine existing surveillance schemes based on macro aggregate indicators with more comprehensive and detailed risk analyses based on micro individual data.

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