• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.2
• /
• pp.252-261
• /
• 2014

A Bayesian network (BN) based fault diagnosis framework for semiconductor etching equipment is presented. Suggested framework contains data preprocessing, data synchronization, time series modeling, and BN inference, and the established BNs show the cause and effect relationship in the equipment module level. Statistically significant state variable identification (SVID) data of etch equipment are preselected using principal component analysis (PCA) and derivative dynamic time warping (DDTW) is employed for data synchronization. Elman's recurrent neural networks (ERNNs) for individual SVID parameters are constructed, and the predicted errors of ERNNs are then used for assigning prior conditional probability in BN inference of the fault diagnosis. For the demonstration of the proposed methodology, 300 mm etch equipment model is reconstructed in subsystem levels, and several fault diagnosis scenarios are considered. BNs for the equipment fault diagnosis consists of three layers of nodes, such as root cause (RC), module (M), and data parameter (DP), and the constructed BN illustrates how the observed fault is related with possible root causes. Four out of five different types of fault scenarios are successfully diagnosed with the proposed inference methodology.

• Journal of Applied Reliability
• /
• v.6 no.1
• /
• pp.93-103
• /
• 2006

Basic function of calorifier system is to supply warm water to the vessel. The heater used in the calorifier system plays a very important role in its reliability. The failure mechanism of heater are compared with accelerated life test. The main cause of failed heater is pitting corrosion occurred between the surface of heater and spacer. To prevent the corrosion failure from heater, material of spacer replaces metal(SUS 304) with polymer (Acryl). The life of redesigned heater can guarantee 2.47years of B10 life under the worst condition.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1349-1354
• /
• 2008

In this study, we try to find the root cause of water condensing failures in a headlamp using chemical and mechanical analysis. Through the surface inspection by OM, SEM and CT, it was found that water infiltrate into the headlamp through hotmelt adhesive debonding part caused by adhesion force degradation and poor quality. IR spectra shows that adhesion force degradation are characterized by increase of some functional group(1742, 1710, 1649, 1016). Through the ESPI measurement, it is turned out that bonding structural change by thermal expansion and degradation of adhesive can be the cause of void generation. So it is recommended that cooling passage and the bonding part should be redesigned to give a guarantee of less thermal stress and high adhesion quality.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.36 no.3
• /
• pp.34-42
• /
• 2013

In this study, we develop a method for analyzing business process based on the event-driven process chain (EPC) model. The method consists of five stages such as identifying abnormal events, finding causes for the abnormal events and problems caused by the abnormal events, making cause-and-effect chains, drawing root-cause map, and defining improvement areas. We illustrate how to apply the method with some examples for the domestic registered mail delivery process.

• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.627-628
• /
• 2015

Construction defect which can causes economic damage such as schedule delay, cost overrun is a considerably important factor in construction industry. In general, a construction defect features a difficulty to find out causes precisely because it occurs when several interrelated causes combine. Yet, studies have tried to understand the interrelationships between factors are limited. In addition, despite of a tremendous amount of construction data, it's not still enough to analyze them, but tends to depend on experience or know-how of practitioners. Thus, it is necessary to identify underlying causes in influential factors by utilizing related data. This paper analyses Interrelationships between causal factors using Association Rule Mining to discover root causes of construction defects. Confidence and Lift that can be used for presenting the interrelationships of the causes were extracted from 1241 cases in 30 projects in Korea. It is expected that this paper allows the construction managers to discover key factors and make right decisions to reduce occurrence of construction defects. Furthermore, analysis of interrelationships can improve understanding of structural patterns of construction defects.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.1
• /
• pp.1-12
• /
• 2021

The International Maritime Organization (IMO) is promoting the introduction of e-Navigation that prevents maritime accidents by fusion of Information & Communication Technology (ICT) with ship operation technology. In Korea, Korean e-Navigation is also being developed for fishing vessels and small vessels sailing offshore, which are vulnerable to maritime accidents. However, for the successful development of Korean e-Navigation, it is necessary to develop an indicator that can evaluate the development performance so that the development performance that has been progressed so far can be evaluated and the development direction can be re-established. Therefore, this study attempted to develop an evaluation index tailored to the development goal of e-Navigation service centering on the collision accident, which is a major maritime accident. In this study, a collision accident evaluation index for e-Navigation service was developed by deriving and quantifying the root cause of maritime collision accidents using Root cause analysis(RCA) and fault tree analysis (FTA) techniques. This indicator is considered to be helpful in reducing maritime accidents as it is used as a development indicator for e-Navigation and an indicator for maritime collision accident analysis.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.617-621
• /
• 2003

The purpose of this paper is to analyze piping failure trend of safety pipings In domestic nuclear power plants. First, database for the piping failure was constructed with 105 data fields. The database includes plant population data, event data, and service history data. 7 kinds of piping failures in domestic NPPs were investigated. Among the 7 cases, detailed root causes were investigated for 3 cases. The first one is pipe wall thinning in main feedwater pipings of Westinghouse 3 loop type plants. The root cause of the wall thinning was flow accelerated corrosion near welding area. The next one is leak event in chemical and volume control system(CVCS) due to vibration. Some cracks occurred in socket welding area. The events showed that the integrity or socket weld is very vulnerable to vibration. The last one is also a leak event in primary sampling line in Korean standard reactor due to thermal fatigue. Although the structural integrity was not maintained by the events, there was no effect on nuclear safety in the above 3 piping failure eases.

• 열병합발전
• /
• s.30
• /
• pp.21-25
• /
• 2002

According to recent Korea Electric Power Company report, yearly distribution line brass cramp bolts failure summed up to 4,400 cases emerging as one of main local break-down causes. Naturally, the need for the investigation was proposed To determine the root cause of the cramp bolt failures, mechanical and metallurgical investigation were performed for 90 samples which collected from various sites. For the understanding of the geometric characteristics, stress distribution was evaluated by CAE program and proof load of each bolts was tested. The SEM&EDS was used for metallurgical investigation. Through the investigation, the root causes of failures were confirmed. All damaged bolts showed intergrannular fracture mode and the all fractured bolt showed ß phase morphology contrast to the a&ß mixture morphology of the non-damaged samples. Additionally, EDS analysis confirmed the existence of lead rich layer on grain boundaries.

• Safety and Health at Work
• /
• v.1 no.1
• /
• pp.43-50
• /
• 2010

Objectives: The objective of this study was to investigate the effect of chain installation condition on stress distribution that could eventually cause disastrous failure from sudden deformation and geometric rupture. Methods: Fractographic method used for the failed chain indicates that over-stress was considered as the root cause of failure. 3D modeling and finite element analysis for the chain, used in a crane hook, were performed with a three-dimensional interactive application program, CATIA, commercial finite element analysis and computational fluid dynamic software, ANSYS. Results: The results showed that the state of stress was changed depending on the initial position of the chain that was installed in the hook. Especially, the magnitude of the stress was strongly affected by the bending forces, which are 2.5 times greater (under the simulation condition currently investigated) than that from the plain tensile load. Also, it was noted that the change of load state is strongly related to the failure of parts. The chain can hold an ultimate load of about 8 tons with only the tensile load acting on it. Conclusion: The conclusions of this research clearly showed that a reduction of the loss from similar incidents can be achieved when an operator properly handles the installation of the chain.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.650-653
• /
• 2002

The increaseing speeds are accompanied by decreases in pulse rise and fall time in VLSI circuits. These accenturate the high frequency spectral contents of the signals and cause the frequency dependent loss of the conductors which interconnect the various sub-circuits composing of VLSI circuit. The lossy effect is approximated by the square root of frequency dependence of the per unit length resistance. In the practical applications, several problems may arise along with this approximation, so we extend our investigation of the lossy effect by numerical Laplace inversion method.