• 제목/요약/키워드: Root Cause Analysis

검색결과 281건 처리시간 0.03초

고압 커패시터의 고장 분석을 통한 신뢰도 예측 (Reliability Estimation of High Voltage Ceramic Capacitor by Failure Analysis)

  • 양석준;김진우;신승우;이희진;신승훈;유동수;장석원
    • 비파괴검사학회지
    • /
    • 제21권6호
    • /
    • pp.618-629
    • /
    • 2001
  • 본 논문은 고압 커패시터의 고장분석과 신뢰성 예측 결과를 다루고 있다. 부품의 수명과 고장률을 예측하기 위해서 두 가지 방법으로 고장 모드와 고장 메커니즘을 연구하였다 에폭시 수지로 성형된 고압 커패시터가 절연내압 시험 하에서 저항이 제로로 되는 고장에 대하여, 근본원인 고장분석 체계를 효과적으로 수립함으로써 고장 메커니즘의 원인을 분석하였다. 특히 세라믹-에폭시 계면에서의 절연파괴 고장 현상이 강조되었으며, 본 연구에서 얻어진 결과의 타당성은 마그네트론에 장착된 고압 커패시터의 열사이클 시험 수행에 의한 가속시험 결과로부터 입증되었다. 시험 결과들은 결함이 있는 로트를 신속히 규명하고 $B_{10}$ 수명을 결정하는데 유용하게 사용할 수 있다. 또한, 유전체의 절연파괴에 대해서 부하-강도 간섭모델을 이용하여 고장률을 예측하였다.

  • PDF

The Association Among Individual and Contextual Factors and Unmet Healthcare Needs in South Korea: A Multilevel Study Using National Data

  • Lee, Seung Eun;Yeon, Miyeon;Kim, Chul-Woung;Yoon, Tae-Ho
    • Journal of Preventive Medicine and Public Health
    • /
    • 제49권5호
    • /
    • pp.308-322
    • /
    • 2016
  • Objectives: The objective of this study is to investigate associations between contextual characteristics and unmet healthcare needs in South Korea after accounting for individual factors. Methods: The present study used data from the 2012 Korean Community Health Survey (KCHS) of 228 902 adults residing within 253 municipal districts in South Korea. A multilevel analysis was conducted to investigate how contextual characteristics, defined by variables that describe the regional deprivation, degree of urbanity, and healthcare supply, are associated with unmet needs after controlling for individual-level variables. Results: Of the surveyed Korean adults, 12.1% reported experiencing unmet healthcare needs in the past. This figure varied with the 253 districts surveyed, ranging from 2.6% to 26.2%. A multilevel analysis found that the association between contextual characteristics and unmet needs varied according to the factors that caused the unmet needs. The degree of urbanity was associated with unmet need due to "financial burden" (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.42 to 0.66 for rural vs. metropolitan), but not unmet need due to "service not available when needed." There were no significant associations between these unmet need measures and regional deprivation. Among individual-level variables, income level showed the highest association with unmet need due to "financial burden" (OR, 5.63; 95% CI, 4.76 to 6.66), while employment status showed a strong association with unmet need due to "service not available when needed." Conclusions: Our finding suggests that different policy interventions should be considered for each at-risk population group to address the root cause of unmet healthcare needs.

한국 유통산업이 한국 경제에 미치는 상호영향력에 관한 실증적 연구 (An Empirical Study on Mutual Influence between Economic Index and Distribution Industry in Korean)

  • 임병진
    • 산경연구논집
    • /
    • 제10권9호
    • /
    • pp.53-60
    • /
    • 2019
  • Purpose - The objective of this paper is to discover if there exists a relationship between the economic index and distribution industry index in Korean. Because of the distribution industry boom in the recent years, a lot of interest in the relationship between the economic index and distribution industry index in Korean and the economy has been generated. This article examine on the mutual influence between economic index and distribution industry index in Korean. Research design, data, and methodology - For this purpose, we use the vector-auto regression model, impulse response function and variance decomposition of the economic index and distribution industry index, Granger causality test using weekly data on the economic index and distribution industry price index in korea. The sample period is covering from January 2, 2010 to August 31, 2019. The VAR model can also be linked to cointegration analysis. Cointegration Analysis makes possible to find a mechanism causing x and y to move around a long-run equilibrium (Engle and Granger, 1987). This equilibrium means that external shocks may separate the series temporarily at any particular time, but there will be an overall tendency towards some type of long-run equilibrium. If variables are found to have this tendency they are said to be cointegrated and a long-run relationship between these series is established. These econometric tools have been applied widely into economics and business areas to analyze intertemporal linkages between different time series. Results - This research showed following main results. First, from the basic statistic analysis of the economic index and distribution industry index in Korean, the economic index and the distribution industry index in korea have unit roots. Second, there is at least one cointegration between the economic index and distribution industry index in Korean. Finally, the correlation between of the economic index and the distribution industry index in korea is (+) 0.528876. Conclusions - We find that the distribution industry price index Granger cause the economic index in korea. As a consequence, the distribution industry index affect the economic index in Korean. The distribution industry index to the economic index is stronger than that from the economic index to the distribution industry index.

투자결정 모델을 활용한 개인정보유출의 기대손실 분석 (Analysis of Loss Expectancy on Personal Information leakage using Quantitative Invest Decision Model)

  • 김정연
    • 한국전자거래학회지
    • /
    • 제20권2호
    • /
    • pp.93-106
    • /
    • 2015
  • 전자상거래의 성립을 위해 온라인 정보시스템 상에서 거래 당사자의 정보를 제공하는 것은 필수적이다. 거래의 간편성을 위해 서비스 제공 기업이 이를 보관하고 개인정보와 거래 정보를 가공하여 추가 서비스를 제공하는 것이 전자상거래 분야에서 일반화 되고 있다. 그러나 해당정보의 임의적 보관은 거래의 간편화에 도움이 되는 반면 외부 유출로 인해 직접적 혹은 간접적 피해가 발생할 수 있는 가능성을 높인다. 본 연구는 시스템 운영 기업의 측면에서 정보유출 사고발생의 위험률과 이로 인해 발생할 수 있는 기대 손실을 분석하기 위해 정보보호 관리체계로 대표되는 정성적 정보보호 관리방식과 더불어 대표적인 정량적 분석 방법인 개인정보에 대한 수요공급 곡선과 Gordon and Loeb 모델을 소개한다. 또한 한국인터넷진흥원에서 실시한 개인정보보호 수준 실태조사 결과 중 개인정보 누출사고가 있었던 조사 대상 사업자의 분포가 핵심사업분야나 기업규모에 따라 큰 편차를 나타내는 원인을 제시하였다. 이를 통해 징벌적 손해배상으로 유출사고로 인한 기업의 금전적 손실이 일정 수준을 유지하는 것과 법률로 요구하는 개인정보보호 기준을 최상위등급으로 유지하는 것이 기업간 개인정보 취약점의 편차를 보완할 수 있는 방법으로 제시된다.

Predictive model for the shear strength of concrete beams reinforced with longitudinal FRP bars

  • Alzabeebee, Saif;Dhahir, Moahmmed K.;Keawsawasvong, Suraparb
    • Structural Engineering and Mechanics
    • /
    • 제84권2호
    • /
    • pp.143-154
    • /
    • 2022
  • Corrosion of steel reinforcement is considered as the main cause of concrete structures deterioration, especially those under humid environmental conditions. Hence, fiber reinforced polymer (FRP) bars are being increasingly used as a replacement for conventional steel owing to their non-corrodible characteristics. However, predicting the shear strength of beams reinforced with FRP bars still challenging due to the lack of robust shear theory. Thus, this paper aims to develop an explicit data driven based model to predict the shear strength of FRP reinforced beams using multi-objective evolutionary polynomial regression analysis (MOGA-EPR) as data driven models learn the behavior from the input data without the need to employee a theory that aid the derivation, and thus they have an enhanced accuracy. This study also evaluates the accuracy of predictive models of shear strength of FRP reinforced concrete beams employed by different design codes by calculating and comparing the values of the mean absolute error (MAE), root mean square error (RMSE), mean (𝜇), standard deviation of the mean (𝜎), coefficient of determination (R2), and percentage of prediction within error range of ±20% (a20-index). Experimental database has been developed and employed in the model learning, validation, and accuracy examination. The statistical analysis illustrated the robustness of the developed model with MAE, RMSE, 𝜇, 𝜎, R2, and a20-index of 14.6, 20.8, 1.05, 0.27, 0.85, and 0.61, respectively for training data and 10.4, 14.1, 0.98, 0.25, 0.94, and 0.60, respectively for validation data. Furthermore, the developed model achieved much better predictions than the standard predictive models as it scored lower MAE, RMSE, and 𝜎, and higher R2 and a20-index. The new model can be used in future with confidence in optimized designs as its accuracy is higher than standard predictive models.

Transcriptome Profiling of Differentially Expressed Genes in Cowpea (Vigna unguiculata L.) Under Salt Stress

  • Byeong Hee Kang;Woon Ji Kim;Sreepama Chowdhury;Chang Yeok Moon;Sehee Kang;Bo-Keun Ha
    • 한국작물학회:학술대회논문집
    • /
    • 한국작물학회 2022년도 추계학술대회
    • /
    • pp.261-261
    • /
    • 2022
  • Cowpea [Vigna unguiculata (L.) Walp] is one of the most important grain legumes that enhance soil fertility and is well-adapted to various abiotic stress. Also, it is cultivated worldwide as a tropical annual crop, and the semi-arid regions are known as the main cowpea-produced regions. However, accumulation of soil salinity induced by low rainfall in these regions is reducing crop yields and quality. In general, plants exposed to soil salinity cause an accumulation of high ion chloride, which leads to the degradation of root and leaf proteins. In this study, we identified candidate genes associated with salinity tolerance through an analysis of differentially expressed genes (DEGs) in four cowpea germplasms with contrasting salinity tolerance. A total of 553,776,035 short reads were obtained using the Illumina Novaseq 6000 platform for RNA-Seq, which were subsequently aligned to the reference genome of cowpea Vunguiculata v1.2. A total of9,806 DEGs were identified between NaCl treatment and control of four cowpea germplasms. Among these DEGs, functions related to salt stress such as calcium transporter and cytochrome-450 family were associated with salt stress. In GO analysis and KEGG analysis, these DEGs were enriched in terms such as the "phosphorylation", ''extracellular region", and "ion binding". These RNA-seq results will improve the understanding of the salt tolerance of cowpea and can be used as useful basic data for molecular breeding technology in the future.

  • PDF

State-of-the-Art in Cyber Situational Awareness: A Comprehensive Review and Analysis

  • Kookjin Kim;Jaepil Youn;Hansung Kim;Dongil Shin;Dongkyoo Shin
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • 제18권5호
    • /
    • pp.1273-1300
    • /
    • 2024
  • In the complex virtual environment of cyberspace, comprised of digital and communication networks, ensuring the security of information is being recognized as an ongoing challenge. The importance of 'Cyber Situation Awareness (CSA)' is being emphasized in response to this. CSA is understood as a vital capability to identify, understand, and respond to various cyber threats and is positioned at the heart of cyber security strategies from a defensive perspective. Critical industries such as finance, healthcare, manufacturing, telecommunications, transportation, and energy can be subjected to not just economic and societal losses from cyber threats but, in severe cases, national losses. Consequently, the importance of CSA is being accentuated and research activities are being vigorously undertaken. A systematic five-step approach to CSA is introduced against this backdrop, and a deep analysis of recent research trends, techniques, challenges, and future directions since 2019 is provided. The approach encompasses current situation and identification awareness, the impact of attacks and vulnerability assessment, the evolution of situations and tracking of actor behaviors, root cause and forensic analysis, and future scenarios and threat predictions. Through this survey, readers will be deepened in their understanding of the fundamental importance and practical applications of CSA, and their insights into research and applications in this field will be enhanced. This survey is expected to serve as a useful guide and reference for researchers and experts particularly interested in CSA research and applications.

치조골 흡수가 포오스트로 인한 치근내 응력에 미치는 영향에 관한 삼차원 유한요소법 분석 (THREE DIMENSIONAL FINITE ELEMENT ANALYSIS OF THE EFFECTS OF ALVEOLAR BONE LOSS ON STRESS DISTRIBUTION IN POST-RECONSTRUCTED TEETH)

  • 이기영;장익태
    • 대한치과보철학회지
    • /
    • 제35권4호
    • /
    • pp.674-696
    • /
    • 1997
  • There're many cases that should be reconstructed with post and core when clinical crown is destructed. But this post and core restoration may cause damaging stress on the teeth. Previous finite element study was restricted to normal bone model relatively close to cemen-toenamel junction. Moreover, the test of a model with diminished bone support was rare. The purpose of this study is to test the effects of alveolar bone loss on the magnitude, stress distribution and displacement of post reconstructed teeth. In this study, it was assumed that the coronal portion of upper incisor was severely destructed. After conventional endodontic treatment, it was restored with post and core. The PFM restoration was made on it. This crown was cemented with ZPC. Alveolar bone was classified by 4 types of bone, such as normal, 2 mm, 4 mm, 6 mm bone, according to the bone loss. Meanwhile, the material of post are divided into 2 types of materials, such as gold, co-cr. Force was applied to two directions. One was fuctional maximum bite force (300 N) applied to the spot just lingual to the incisal edge with the angle of 45 degree to the long axis of the tooth, and the other one was horizontal force (300 N) applied to the labial surface. The results analyzed with three dimensional finite element method were as follows : 1. Stress was concentrated on the adjacent dentin of the post apex, one third portion of the post apex and the labial & lingual mid-portion of the root in all case. The stress of middle third of the root was apparently concentrated on the labial aspect. 2. The stress on adjacent dentin of the post apex and one third of the post apex increased as alveolar bone height moved apically. This increase was dramatic beyond 4 mm bone loss model. 3. The stress of the post apex was spreaded to the middle third of the post and greater than gold post in the case of metal post. 4. The displacement of the neck of post was the greatest in one of the post-cement interface and this increased as alveolar bone height moved apically. Besides the displacement of the metal post is slightly lower than one of the gold post.

  • PDF

Effects of High-harmonic Components on the Rayleigh Indices in Multi-mode Thermo-acoustic Combustion Instability

  • Song, Chang Geun;Yoon, Jisu;Yoon, Youngbin;Kim, Young Jin;Lee, Min Chul
    • International Journal of Aeronautical and Space Sciences
    • /
    • 제17권4호
    • /
    • pp.518-525
    • /
    • 2016
  • This paper presents the characteristics of non-fundamental multi-mode combustion instability and the effects of high-harmonic components on the Rayleigh criterion. Phenomenological observations of multi-harmonic-mode dynamic pressure waves regarding the intensity of harmonic components and the source of wave distortion have been explained by introducing examples of second- and third-order harmonics at various amplitudes. The amplitude and order of the harmonic components distorted the wave shapes, including the peak and the amplitude, of the dynamic pressure and heat release, and consequently the temporal Rayleigh index and its integrals. A cause-and-effect analysis was used to identify the root causes of the phase delay and the amplification of the Rayleigh index. From this analysis, the skewness of the dynamic pressure turned out to be a major source in determining whether multi-mode instability is driving or damping, as well as in optimizing the combustor design, such as the mixing length and the combustor length, to avoid unstable regions. The results can be used to minimize errors in predicting combustion instability in cases of high multi-mode combustion instability. In the future, the amount of research and the number of applications will increase because new fuels, such as fast-burning syngases, are prone to generating multi-mode instabilities.

항공기엔진용 1단계 터빈블레이드에 대한 파손 연구 (The Study for Fracture in the First Stage Blade of Aircraft Engine)

  • 윤영웅;박형규;김정
    • 한국항공우주학회지
    • /
    • 제46권10호
    • /
    • pp.806-813
    • /
    • 2018
  • 항공기 엔진을 구성하는 부품 중 하나인 블레이드의 파손에 대해 분석하였다. 블레이드의 파손원인과 그 거동은 다양하지만 크게 일시파단과 피로파손의 두가지 형태로 나뉘어진다. 이 논문에서는 전체 거동은 일시파단으로 진행되고 일부 피로 파손된 블레이드에 대해 기술하였고, 특히 고온에서의 블레이드 손상거동을 분석하므로써 사례의 하나로 제시하고자 한다. 분석한 블레이드는 니켈기 초내열 합금으로 외관, 재질, 미세조직, 고온 크리프 특성, 파단면 형상을 각각의 분석장비를 활용하여 손상원인과 거동을 확인하였고, 원재질에서 재현하였다. 고온에서 니켈 합금은 ${\gamma}^{\prime}$ 형상이 변형되고 조직변형(Alloy Depletion)구간이 관찰되며 재질의 기계적 성질, 물성치 등이 저하되고 연화되어 장시간 운용 시 파손될 수 있다. 니켈합금은 고온특성이 좋으나 함유되는 미량원소에 따라 그 물성치가 다양하므로 니켈합금이라 하여도 그 목적에 맞는 세분화된 소재를 사용해야한다.