Fault Detection Method for Steam Boiler Using Mahalanobis Distance

Jungwon Yu,Jaeyel Jang,Jaeyeong Yoo,Sungshin Kim 한국지능시스템학회 2016 한국지능시스템학회 학술발표 논문집 Vol.26 No.1

Bagged Auto-Associative Kernel Regression-Based Fault Detection and Identification Approach for Steam Boilers in Thermal Power Plants

Jungwon Yu,Jaeyel Jang,Jaeyeong Yoo,June Ho Park,Sungshin Kim 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4

In complex and large-scale industries, properly designed fault detection and identification (FDI) systems considerably improve safety, reliability and availability of target processes. In thermal power plants (TPPs), generating units operate under very dangerous conditions; system failures can cause severe loss of life and property. In this paper, we propose a bagged auto-associative kernel regression (AAKR)-based FDI approach for steam boilers in TPPs. AAKR estimates new query vectors by online local modeling, and is suitable for TPPs operating under various load levels. By combining the bagging method, more stable and reliable estimations can be achieved, since the effects of random fluctuations decrease because of ensemble averaging. To validate performance, the proposed method and comparison methods (i.e., a clustering-based method and principal component analysis) are applied to failure data due to water wall tube leakage gathered from a 250 MW coal-fired TPP. Experimental results show that the proposed method fulfills reasonable false alarm rates and, at the same time, achieves better fault detection performance than the comparison methods. After performing fault detection, contribution analysis is carried out to identify fault variables; this helps operators to confirm the types of faults and efficiently take preventive actions.

A Clustering-Based Fault Detection Method for Steam Boiler Tube in Thermal Power Plant

Jungwon Yu,Jaeyel Jang,Jaeyeong Yoo,June Ho Park,Sungshin Kim 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.4

System failures in thermal power plants (TPPs) can lead to serious losses because the equipment is operated under very high pressure and temperature. Therefore, it is indispensable for alarm systems to inform field workers in advance of any abnormal operating conditions in the equipment. In this paper, we propose a clustering-based fault detection method for steam boiler tubes in TPPs. For data clustering, k-means algorithm is employed and the number of clusters are systematically determined by slope statistic. In the clustering-based method, it is assumed that normal data samples are close to the centers of clusters and those of abnormal are far from the centers. After partitioning training samples collected from normal target systems, fault scores (FSs) are assigned to unseen samples according to the distances between the samples and their closest cluster centroids. Alarm signals are generated if the FSs exceed predefined threshold values. The validity of exponentially weighted moving average to reduce false alarms is also investigated. To verify the performance, the proposed method is applied to failure cases due to boiler tube leakage. The experiment results show that the proposed method can detect the abnormal conditions of the target system successfully.

One-Dimensional Assembly on Two-Dimensions: AuCN Nanowire Epitaxy on Graphene for Hybrid Phototransistors

Jang, Jeongsu,Lee, Yangjin,Yoon, Jun-Yeong,Yoon, Hoon Hahn,Koo, Jahyun,Choe, Jeongheon,Jeon, Sungho,Sung, Jongbaek,Park, Jungwon,Lee, Won Chul,Lee, Hoonkyung,Jeong, Hu Young,Park, Kibog,Kim, Kwanpyo American Chemical Society 2018 Nano letters Vol.18 No.10

<P>The van der Waals epitaxy of functional materials provides an interesting and efficient way to manipulate the electrical properties of various hybrid two-dimensional (2D) systems. Here we show the controlled epitaxial assembly of semiconducting one-dimensional (1D) atomic chains, AuCN, on graphene and investigate the electrical properties of 1D/2D van der Waals heterostructures. AuCN nanowire assembly is tuned by different growth conditions, although the epitaxial alignment between AuCN chains and graphene remains unchanged. The switching of the preferred nanowire growth axis indicates that diffusion kinetics affects the nanowire formation process. Semiconducting AuCN chains endow the 1D/2D hybrid system with a strong responsivity to photons with an energy above 2.7 eV, which is consistent with the bandgap of AuCN. A large UV response (responsivity ∼10<SUP>4</SUP> A/W) was observed under illumination using 3.1 eV (400 nm) photons. Our study clearly demonstrates that 1D chain-structured semiconductors can play a crucial role as a component in multifunctional van der Waals heterostructures.</P> [FIG OMISSION]</BR>

Nanotopography-based engineering of retroviral DNA integration patterns

Jang, Yoon-ha,Park, Yi-seul,Nam, Jung-soo,Yang, Yeji,Lee, Ji-eun,Lee, Kwang-hee,Kang, Minho,Chialastri, Alex,Noh, Hohsuk,Park, Jungwon,Lee, Jin Seok,Lim, Kwang-il The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.12

<P>Controlling the interactions between cells and viruses is critical for treating infected patients, preventing viral infections, and improving virus-based therapeutics. Chemical methods using small molecules and biological methods using proteins and nucleic acids are employed for achieving this control, albeit with limitations. We found, for the first time, that retroviral DNA integration patterns in the human genome, the result of complicated interactions between cells and viruses, can be engineered by adapting cells to the defined nanotopography of silica bead monolayers. Compared with cells on a flat glass surface, cells on beads with the highest curvature harbored retroviral DNAs at genomic sites near transcriptional start sites and CpG islands during infections at more than 50% higher frequencies. Furthermore, cells on the same type of bead layers contained retroviral DNAs in the genomic regions near cis-regulatory elements at frequencies that were 2.6-fold higher than that of cells on flat glass surfaces. Systems-level genetic network analysis showed that for cells on nanobeads with the highest curvature, the genes that would be affected by cis-regulatory elements near the retroviral integration sites perform biological functions related to chromatin structure and antiviral activities. Our unexpected observations suggest that novel engineering approaches based on materials with specific nanotopography can improve control over viral events.</P>

Establishment of hepatocyte differentiation in pig stem cells

Jungwon Yang,Eunjung Kim,Keunhye Jang,Hanbyul Lee,Borim An,Heung-Myong Woo,Seok-Ho Hong,Se-Ran Yang,Sung-Min Park 한국실험동물학회 2013 한국실험동물학회 학술발표대회 논문집 Vol.2013 No.2

일부 남성 금속제품 조립작업자들의 피로에 영향을 미치는 작업관련요인

장준호,강동묵,고상백,김정원,조병만,이수일 大韓産業醫學會 2004 대한직업환경의학회지 Vol.16 No.2

목적 : 남성 금속제품 조립 작업자들의 피로에 영향을 미치는 작업관련요인을 파악하고자 한다. 방법 : 작업자의 일반적 특성 및 작업관련 특성, 육체적 부하, 직무 스트레스 등을 조사 항목으로 하여 자동차 부품 조립업 1개소(476명), 자동차 엔진 조립업 1개소(610명), 대형 선박 엔진 조립업 1개소(454명)의 작업자(1,540명)를 대상으로 수거된 설문지 중 부실하게 응답한 38부를 제외한 1,136부(총연구대상의 73.8%)를 분석하였고, 피로도와의 연관성을 다중선형회귀분석으로 살펴보았다. 조사는 자기 기입식 설문지를 사용하였다. 육체적 부하를 측정하기 위해서는 Borg의 scale이 사용되었다. 격무 스트레스를 측정하기 위해서는 Karasek의 Job content questionnaire가 사용되었다. 피로의 측정은 전반적 피로도(sum of fatigue), 일상생활 기능장애(daily dysfunctioning), 상황적 피로(situational fatigue), 피로점수의 총합(sum of fatigue)으로 구성되어 있는 다면적 피로척도를 사용하였다. 피로점수의 분포는 본 연구에 응답한 피로점수의 총합을 사분위수로 나누어서 4등급으로 나누었다. 결과 : 피로점수의 분포는 피로점수의 총합을 사분위수로 나누었을 때, 0≤1등급≤73, 74≤2등급≤82, 83≤3등급≤93, 94≤4등급≤133이었다. 다중선형회귀분석에서 피로점수의 총합과 유의한 관계를 보인 경우는 주간근무, 긴 주당 노동시간, 높은 육체적 부하, 높은 직무요구도, 낮은 직무자율성, 낮은 상사의 지지 등이었고, 전반적 피로도와 유의한 관계를 보인 경우는 주간근무, 높은 육체적 부하, 높은 직무요구도, 낮은 직무자율성, 낮은 상사의 지지 등이었다. 일상생활 기능장애와 유의한 관계를 보인 경우는 주간근무, 긴 주당 노동시간, 높은 육체적 부하, 낮은 직무자율성 등이었다. 상황적 피로와 유의한 관계를 보인 경우는 높은 연령, 주간근무, 긴 주당 노동시간, 낮은 직무자율성 등이었다. 결론 : 피로관련 요인은 긴 주당노동시간, 높은 직무요구도, 높은 육체적 부하, 낮은 직무자율성, 낮은 상사의 지지로 생각된다. Objectives: To find work related factors affecting perceived fatigue among male metal product assemblers. Methods: The study subjects were metal product assemblers from three metal product companies (476 car parts assemblers, 610 car engine assemblers, 454 ship engine assemblers). From the total of 1,540 subjects, 1,136 (73.8%) were included and 38 respondents with insufficient replies were excluded. Associations between fatigue score and other variables (general characteristics, job related factors, workload, job stresses) were investigated in terms of the concept of multidimensional fatigue construct by self administered questionnaire. Using MFS (Multidimensional Fatigue Scale), JCQ (Job Content Questionnaire), and Borg's scale, we estimated the fatigue, job stress, and workload, respectively. Fatigue score was estimated by 'sum of fatigue' in MFS. Associations were tested by linear regression analysis using SAS v.8.0. Results: In this study, the fatigue related factors were older age, longer working hours per week, higher workload, higher job demand, lower decision latitude, and lower supervisor support. Conclusions: Prolonged working hours, higher workload, higher job demand, poor supervisor support and lower decision latitude were fatigue related factors among the male metal product assemblers of this study.

Structural basis of inactivation of Ras and Rap1 small GTPases by Ras/Rap1-specific endopeptidase from the sepsis-causing pathogen <i>Vibrio vulnificus</i>

Jang, Song Yee,Hwang, Jungwon,Kim, Byoung Sik,Lee, Eun-Young,Oh, Byung-Ha,Kim, Myung Hee American Society for Biochemistry and Molecular Bi 2018 The Journal of biological chemistry Vol.293 No.47

<P>Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are secreted by Gram-negative bacteria and function as primary virulence-promoting macromolecules that deliver multiple cytopathic and cytotoxic effector domains into the host cytoplasm. Among these effectors, Ras/Rap1-specific endopeptidase (RRSP) catalyzes the sequence-specific cleavage of the Switch I region of the cellular substrates Ras and Rap1 that are crucial for host innate immune defenses during infection. To dissect the molecular basis underpinning RRSP-mediated substrate inactivation, we determined the crystal structure of an RRSP from the sepsis-causing bacterial pathogen <I>Vibrio vulnificus</I> (<I>Vv</I>RRSP). Structural and biochemical analyses revealed that <I>Vv</I>RRSP is a metal-independent TIKI family endopeptidase composed of an N-terminal membrane-localization and substrate-recruitment domain (N lobe) connected via an inter-lobe linker to the C-terminal active site–coordinating core β-sheet–containing domain (C lobe). Structure-based mutagenesis identified the 2His/2Glu catalytic residues in the core catalytic domain that are shared with other TIKI family enzymes and that are essential for Ras processing. <I>In vitro</I> KRas cleavage assays disclosed that deleting the N lobe in <I>Vv</I>RRSP causes complete loss of enzymatic activity. Endogenous Ras cleavage assays combined with confocal microscopy analysis of HEK293T cells indicated that the N lobe functions both in membrane localization via the first α-helix and in substrate assimilation by altering the functional conformation of the C lobe to facilitate recruitment of cellular substrates. Collectively, these results indicate that RRSP is a critical virulence factor that robustly inactivates Ras and Rap1 and augments the pathogenicity of invading bacteria via the combined effects of its N and C lobes.</P>

다운사이즈 된 부품의 용접 분리력과 안정성 검토

박중원(Jungwon Park),전상훈(Sanghoon Jeon),장지환(Jihwan Jang),손표영(Pyoyoung Son),이수아(Suah Lee),김형익(Hyungik Kim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11

마할라노비스 거리를 이용한 증기보일러 튜브의 고장탐지방법

유정원(Jungwon Yu),장재열(Jaeyel Jang),유재영(Jaeyeong Yoo),김성신(Sungshin Kim) 한국지능시스템학회 2016 한국지능시스템학회논문지 Vol.26 No.3

화력발전소의 설비들은 매우 높은 온도와 압력의 환경에서 운전되므로, 설비고장은 상당한 인적·물적 손실로 이어진다. 그러므로 발전설비의 비정상정인 동작 상태를 사전에 확인할 수 있는 고장탐지 시스템이 필수적이다. 본 연구에서는, 화력발전소 증기보일러의 고장탐지를 위해서 마할라노비스 거리(Mahalanobis distance, MD)를 이용하였다. MD 기반의 고장탐지방법에서는, 비정상샘플은 정상샘플들로부터 멀리 떨어져 있다고 가정한다. 정상상태로 동작중인 대상시스템으로부터 수집된 다변량 샘플을 이용하여 평균벡터와 공분산행렬을 계산하고, MD값의 문턱값을 설정한다. 검증단계에서는, 평균벡터와 검증샘플들 간의 MD를 구한 후, 계산된 MD 값이 미리 설정된 문턱값보다 높으면 알람신호가 발생하게 된다. MD 기반의 고장탐지방법의 성능을 검증하기 위해서, 200MW 유연탄 화력발전소의 증기보일러 튜브누설로 인해서 발전정지 된 사례를 사용하였다. 실험결과는 MD 기반의 고장탐지기법이 발전정지가 발생하기 이전의 이상징후를 성공적으로 탐지할 수 있음을 보여준다. Since thermal power plant (TPP) equipment is operated under very high pressure and temperature, failures of the equipment give rise to severe losses of life and property. To prevent the losses, fault detection method is, therefore, absolutely necessary to identify abnormal operating conditions of the equipment in advance. In this paper, we present Mahalanobis distance (MD) based fault detection method for steam boiler tube in TPP. In the MD-based method, it is supposed that abnormal data samples are far away from normal samples. Using multivariate samples collected from normal target system, mean vector and covariance matrix are calculated and threshold value of MD is decided. In a test phase, after calculating the MDs between the mean vector and test samples, alarm signals occur if the MDs exceed the predefined threshold. To demonstrate the performance, a failure case due to boiler tube leakage in 200MW TPP is employed. The experimental results show that the presented method can perform early detection of boiler tube leakage successfully.