• Smart Structures and Systems
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• 제26권2호
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• pp.227-239
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• 2020

Despite proven effectiveness and accuracy in laboratories, the existing damage assessment based on guided ultrasonic waves (GUWs) or acoustic emission (AE) confronts challenges when extended to real-world structural health monitoring (SHM) for railway tracks. Central to the concerns are the extremely complex signal appearance due to highly dispersive and multimodal wave features, restriction on transducer installations, and severe contaminations of ambient noise. It remains a critical yet unsolved problem along with recent attempts to implement SHM in bourgeoning high-speed railway (HSR). By leveraging authors' continued endeavours, an SHM framework, based on actively generated diffuse ultrasonic waves (DUWs) and a benchmark-free condition contrast algorithm, has been developed and deployed via an all-in-one SHM system. Miniaturized lead zirconate titanate (PZT) wafers are utilized to generate and acquire DUWs in long-range railway tracks. Fatigue cracks in the tracks show unique contact behaviours under different conditions of external loads and further disturb DUW propagation. By contrast DUW propagation traits, fatigue cracks in railway tracks can be characterised quantitatively and the holistic health status of the tracks can be evaluated in a real-time manner. Compared with GUW- or AE-based methods, the DUW-driven inspection philosophy exhibits immunity to ambient noise and measurement uncertainty, less dependence on baseline signals, use of significantly reduced number of transducers, and high robustness in atrocious engineering conditions. Conformance tests are performed on HSR tracks, in which the evolution of fatigue damage is monitored continuously and quantitatively, demonstrating effectiveness, adaptability, reliability and robustness of DUW-driven SHM towards HSR applications.

• 한국안전학회지
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• 제25권1호
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• pp.32-37
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• 2010

When back-out & firing Process applies heat, hume is piled up in exhaust duct by organic compound and it have high dangerousness. There by, the process is happening a lot of damage that is exhaust duct fire. However we do not have certain fire dangerousness estimation and digestion countermeasure. So we need preventive measure. Back-out & firing is a process which has fine structure, electrical and mechanical characteristics, such as firing kiln and back-out kiln which has pipe line and box type. The box oven is made of heating coil, fan motor and control panel. Back-out & firing process has air circulation institution of quick ventilation type. When we operate this process for long time, fire can break out easily. Duct is made by zinc shredder. If fire breaks out in duct inside, fire by deposit fume can be dispersed easily. Accordinglym, This project estimate danger for back-out & firing process exhaust duct through real fire test. And there is purpose of study to establish preventive measure.

• Smart Structures and Systems
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• 제29권1호
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• pp.129-140
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• 2022

The effectiveness of system identification, damage detection, condition assessment and other structural analyses relies heavily on the accuracy and reliability of the measured data in structural health monitoring (SHM) systems. However, data anomalies often occur in SHM systems, leading to inaccurate and untrustworthy analysis results. Therefore, anomalies in the raw data should be detected and cleansed before further analysis. Previous studies on data anomaly detection mainly focused on just single type of data anomaly for denoising or removing outliers, meanwhile, the existing methods of detecting multiple data anomalies are usually time consuming. For these reasons, recognising multiple anomaly patterns for real-time alarm and analysis in field monitoring remains a challenge. Aiming to achieve an efficient and accurate detection for multi-type data anomalies for field SHM, this study proposes a pattern-recognition-based data anomaly detection method that mainly consists of three steps: the feature extraction from the long time-series data samples, the training of a pattern recognition neural network (PRNN) using the features and finally the detection of data anomalies. The feature extraction step remarkably reduces the time cost of the network training, making the detection process very fast. The performance of the proposed method is verified on the basis of the SHM data of two practical long-span bridges. Results indicate that the proposed method recognises multiple data anomalies with very high accuracy and low calculation cost, demonstrating its applicability in field monitoring.

• 콘크리트학회논문집
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• 제18권3호
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• pp.389-395
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• 2006

실존하는 콘크리트 구조체를 평가할 때, 그 콘크리트의 강도를 알아내는 것이 매우 중요하다. 콘크리트의 강도를 알아내기 위하여 재하시험이나 코어시험을 하는 것은 시험비용, 편의성, 시간, 구조체에 대한 손상, 신뢰성등 많은 문제점이 있다. 그러므로 이러한 문제점들을 극복하기 위하여 여러 가지 비파괴 시험과 통게적 해석을 통한 구조해석법이 발전해 오고 있다. 본 연구에서는 재령 3, 7, 14, 28, 90, 180, 365, 730일에 대하여 28일 표준실린더 압축강도 65.0MPa인 고강도 콘크리트 구조체의 실제강도를 알기 위한 일련의 실험을 하였고, 각 실험결과를 SPSS 프로그램으로 회귀분석 하였다. 회귀분석에 의한 강도추정식과 코어강도값을 비교하여 오차율을 계산하고, 기존식과 비교하여 추정식의 유의성을 검토한 결과 기존식들은 보통강도 콘크리트에는 적용할 수 있지만 고강도 콘크리트에는 적용에 한계가 있음이 밝혀졌다. 따라서 40MPa 이상의 고강도 콘크리트의 슈미트 해머 시험에 의한 강도 추정을 위해 다음과 같은 강도식을 제안하였다.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.589-603
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• 2014

Expressions for determining the value of the impact force as reported in the literature and incorporated into code provisions are essentially quasi-static forces for emulating deflection. Quasi-static forces are not to be confused with contact force which is generated in the vicinity of the point of contact between the impactor and target, and contact force is responsible for damage featuring perforation and denting. The distinction between the two types of forces in the context of impact actions is not widely understood and few guidelines have been developed for their estimation. The value of the contact force can be many times higher than that of the quasi-static force and lasts for a matter of a few milli-seconds whereas the deflection of the target can evolve over a much longer time span. The stiffer the impactor the shorter the period of time to deliver the impulsive action onto the target and consequently the higher the peak value of the contact force. This phenomenon is not taken into account by any contemporary codified method of modelling impact actions which are mostly based on the considerations of momentum and energy principles. Computer software such as LS-DYNA has the capability of predicting contact force but the dynamic stiffness parameters of the impactor material which is required for input into the program has not been documented for debris materials. The alternative, direct, approach for an accurate evaluation of the damage potential of an impact scenario is by physical experimentation. However, it can be difficult to extrapolate observations from laboratory testings to behaviour in real scenarios when the underlying principles have not been established. Contact force is also difficult to measure. Thus, the amount of useful information that can be retrieved from isolated impact experiments to guide design and to quantify risk is very limited. In this paper, practical methods for estimating the amount of contact force that can be generated by the impact of a fallen debris object are introduced along with the governing principles. An experimental-calibration procedure forming part of the assessment procedure has also been verified.

• 한국방재학회 논문집
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• 제4권1호
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• pp.65-75
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• 2004

자연재해에 기인한 철도노반의 유실 및 파괴는 유실된 선로복구를 위한 공사가 장기간 소요됨으로써 정상적인 철도운행에 지장을 초래하여 사회적, 경제적으로 많은 비용 및 시간의 손실을 유발시키고 있다. 본 연구에서는 자연재해로 인해 유실된 철도노반에 대한 신속하고 안전한 복구대책으로서 토목섬유로 제조된 Soilbag의 적용성을 평가하고자 정적하중 및 모사반복 열차하중 재하 실대형시험을 수행하였다. 실대형시험을 통해 심도별 연직토압과 침하량을 계측한 결과, 하중분산효과에 기인한 토압 및 침하 저감 효과를 확인할 수 있었으며 시공성과 장기적 안정성을 고려할 때 Soilbag 공법의 현장적용성은 가능할 것으로 판단된다.

• 한국지반환경공학회 논문집
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• 제17권9호
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• pp.47-52
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• 2016

최근 사회기반시설의 안전설계 용량을 초과하는 잦은 위험기상 등으로 자연재난의 빈도가 증가하고 피해규모도 대형화되고 있으며, 도시화 진전에 따른 시설의 고층화 노후건축물 증가와 세계화에 따른 유동인구 및 물류 증가 등이 신종 복합 재난을 가중시키는 요인으로 작용하고 있다. 첨단 과학기술을 활용하여 재난위험 사전 감지, 실시간 정보분석, 재난현장에 대한 신속한 대응이 가능하지만, 매몰자 긴급구호에 필요한 시공에서는 반드시 검증된 기술을 활용해야 함에도 불구하고 현장 시험시공을 통한 검증은 미흡하다. 본 연구에서는 도심지 시설물 붕괴 재난 사고 발생 시 매몰지점에 고립된 피구호자를 대상으로 골든타임인 72시간 이내에 식수 및 구호품을 신속하게 공급하기 위한 1차 생명선 설치와 철근 콘크리트 구조체 굴착 성능을 평가하는 데 목적이 있다.

• 한국축산식품학회지
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• 제34권6호
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• pp.829-835
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• 2014

Inflammatory bowel disease (IBD) is caused by dysregulation of colon mucosal immunity and mucosal epithelial barrier function. Recent studies have reported that lipoteichoic acid (LTA) from Lactobacillus plantarum K8 reduces excessive production of pro-inflammatory cytokine. In this study, we investigated the preventive effects of lysate of Lb. plantarum K8 in dextran sulfate sodium (DSS)-induced colitis. Male Sprague-Dawley rats were orally pretreated with lysate of Lb. plantarum K8 (low dose or high dose) or live Lb. plantarum K8 prior to the induction of colitis using 4% DSS. Disease progression was monitored by assessment of disease activity index (DAI). Histological changes of colonic tissues were evaluated by hematoxylin and eosin (HE) staining. Tumor necrosis factor-alpha (TNF-${\alpha}$), interleukin-6 (IL-6) levels were measured using enzyme-linked immunosorbent assay (ELISA). The colon mRNA expressions of TNF-${\alpha}$, IL-6, and toll like receptor-2 (TLR-2) were examined by quantitative real-time-transcription polymerase chain reaction (qPCR). Lysate of Lb. plantarum K8 suppressed colon shortening, edema, mucosal damage, and the loss of DSS-induced crypts. The groups that received lysate of Lb. plantarum K8 exhibited significantly decreased levels of the pro-inflammatory cytokines TNF-${\alpha}$ and IL-6 in the colon. Interestingly, colonic expression of toll like receptor-2 mRNA in the high-dose lysate of Lb. plantarum K8 group increased significantly. Our study demonstrates the protective effects of oral lysate of Lb. plantarum K8 administration on DSS-induced colitis via the modulation of pro-inflammatory mediators of the mucosal immune system.

• 드라이브 ㆍ 컨트롤
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• 제21권2호
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• pp.53-64
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• 2024

Global population growth has resulted in an increased demand for food production. Simultaneously, aging rural communities have led to a decrease in the workforce, thereby increasing the demand for automation in agriculture. Drones are particularly useful for unmanned pest control fields. However, the current method of uniform spraying leads to environmental damage due to overuse of pesticides and drift by wind. To address this issue, it is necessary to enhance spraying performance through precise performance evaluation. Therefore, as a foundational study aimed at optimizing drone-based pest control technologies, this research evaluated water-sensitive paper (WSP) via density map estimation using convolutional neural networks (CNN) with a encoder-decoder structure. To achieve more accurate estimation, this study implemented multi-task learning, incorporating an additional classifier for image segmentation alongside the density map estimation classifier. The proposed model in this study resulted in a R-squared (R²) of 0.976 for coverage area in the evaluation data set, demonstrating satisfactory performance in evaluating WSP at various density levels. Further research is needed to improve the accuracy of spray result estimations and develop a real-time assessment technology in the field.

• 한국화재소방학회논문지
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• 제30권3호
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• pp.73-78
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• 2016

'화재예방, 소방시설 설치유지 및 안전관리에 관한 법률'에 의하면 지하층 포함 30층 이상 고층 건축물에 대해 화재발생에 따른 위험성을 사전에 과학적으로 평가하여 재난발생 시 인명피해 및 재산피해를 최소화시킬 수 있도록 성능위주 설계를 실시해야 한다. 이에 따라 설계자는 컴퓨터 시뮬레이션 모델링 등 과학적인 분석 기법을 활용하여 거주자의 화재 및 피난 안전성을 평가하고 있다. 이 때, 인명안전성 평가를 위해 가용피난안전시간(ASET)과 소요피난안전시간(RSET) 을 산정하게 되는데 RSET 중에서도 가장 중요한 '반응시간(Response Time)'을 산정함에 있어 우리나라 사람들에 대한 실측 데이터에 기반한 명확한 법적 기준이 제시되지 못하고 있는 것이 현실이다. 이에 '소방시설 등의 성능위주설계 방 법 및 기준, 별표1'을 토대로 설계자별로 각각 상이한 값을 선택, 입력하거나 일본건축센터의 '건축방재계획지침'에 따라 계산하고 있는 경향을 보이고 있다. 따라서 본 연구에서는 최근 5년간 부산지역에서 성능위주 설계대상으로 지정된 고층 특정소방대상물을 대상으로 총 6명의 설계자가 실시한 성능위주 설계안 13건을 중심으로 RSET의 계산방법에 대해 비교 분석하였고, 특히 RSET 계산 시 결과값에 가장 큰 영향을 미치는 반응시간의 계산방법에 대한 결과를 비교하여 오차값을 산정하였다.