• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.115-121
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• 2017

This paper is to introduce the main modeling assumptions and data structures associated with right-censored data to describe the successful methodological ideas for analyzing such a field-failure-data when components operating in different environments. The Kaplan - Meier method is the most popular method used for survival analysis. Together with the log-rank test, it may provide us with an opportunity to estimate survival probabilities and to compare survival between groups. An important advantage of the Kaplan - Meier curve is that the method can take into account some types of censored data, particularly right-censoring. The above non-parametric method was used to verify the equality of parts life used in different environments. After that, we performed the life distribution analysis using the parametric method. We simulated data from three distributions: exponential, normal, and Weibull. This allowed us to compare the results of the estimates to the known true values and to quantify the reliability indices. Here we used the Akaike information criterion to find a suitable life time distribution. If the Akaike information criterion is the smallest, the best model of failure data is presented. In this paper, no-nparametrics and parametrics methods are analyzed using R program which is a popular statistical program.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.12
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• pp.54-59
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• 2011

LED lightings typically do not fail catastrophically during use. However, over time the light output will gradually depreciate. Even if there are same LED lighting, they are so different at all. because of dissimilar the use and environment of each LED lighting. In this paper, we make a description of reliability analysis procedures for the degradation data using collected field data. Reliability analysis procedures are consisted of estimating degradation models and failure time, verification of distribution and parameters of the distribution, and reliability measures estimation. At some point in time, the light emitted from an LED lightings depreciates to a level where it is no longer considered adequate for a specific application.

• Smart Structures and Systems
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• v.5 no.4
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• pp.397-413
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• 2009

Composite bridges offer many advantages compared to current steel and aluminum bridges. This paper presents the results of a comprehensive on-going research program to develop innovative Diagnostic Prognostic System (DPS) and a structural evaluation of Composite Army Bridge (CAB) system. The DPS is founded on three technologies: optical fiber sensing, remote data transmission, and virtual testing. In developing this system, both laboratory and virtual test were used in different damage scenarios. Health monitoring with DPS entailed comparing live strain data to archived strained data in various bridge locations. For field repairs, a family of composite chords was subjected to simple ramp loads in search of ultimate strength. As such, composite bridge specimens showcased their strengths, heralded the viability of virtual testing, highlighted the efficacy of field repair, and confirmed the merits of health monitoring.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.35
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• pp.115-122
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• 1995

This paper is developed with software system for the construction of periodic maintenance. The system includes records of equipment, maintenance work, failure mode analysis and work standards of maintenability, inspection & repair to establish periodic maintenance system. And the software program is designed with user-oriented to analyze maintenance data and maintenance system of periodic interval times. Also machine operator can easily apply maintenance management system in production & manufacturing field. Visual Basic in the environment of Window system is used as computer program language for graphics and data base management in IBM PC.

• Korean Journal of Adult Nursing
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• v.17 no.5
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• pp.709-718
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• 2005

Purpose: The research aims to understand the lived experience of the caregivers of chronic renal failure(CRF) patients and its essential meaning. The results of the study can be used as basic materials for developing comprehensive intervention methods of care givers of CRF patients. Method: The research used van Manen's hermeneutic and phenomenological research methods in order to describe the lived experience and to understand its meaning. It concentrates on the understanding the essence of experience and consists of existential survey, hermeneutic and phenomenological reflection and hermeneutic writings. Participants in this research were five women care givers of CRF patients who had hemolysis at C university hospital in a metropolitan city, the period of data collection was from July 27 to Sep. 4, 2004 and major data of results in the following 5 essential themes. "sole responsibility for the patient enduring everything", "creating their own field", "heavy and painful life without hope of their private life", "wishing not to be inherited and consoling each other". Conclusion: The above findings point out that the experience of care givers of CRF patient affected and changed all parts of an individual life and his or her family life. Therefore, it suggests that total family nursing care must be considered in order to provide the holistic caring for CRF patients and their care givers.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.397-406
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• 2003

Several sensor systems are used to estimate the reinforcing effect of stabilizing pile in slopes, and to find a failure surface in slopes effectively. FBG(Fiber Brags Crating) sensor, V/W(Vibrating Wire) sensor and inclinometer have shown a great potentiality to serve real time health monitoring of the reinforcing structures. Field tests and test results have shown great solutions for sensor systems of Smart Structures. The purpose of this research is to seek for the relationships among the slope movement and the reinforcing effect of stabilizing pile, and the strain distribution of stabilizing pile in a active zone by analyzing the data from the in-situ measurement so that the possible failure surface should be well defined based on the relationships. The field test results have shown that the data by FBG sensor are well coincided with those of V/W sensor and inclinometer, and the reinforcing effect of the stabilizing pile is good enough.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.17-23
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• 2015

Electrical door system is one of the most essential items for the successful commercial operation of the railway vehicles. Nowadays, reliability values of electrical door system have a tendency to be included in technical requirements for design and manufacturing of rolling stocks. Manufacturer shall meet the reliability target values of electrical door system which is proposed by railway operator in procurement contract book. Railway operator shall approve the supplier's the reliability target values based on maintenance operation data. Railway operators are in the transition stage from the framework of maintenance interval based on time to the framework of maintenance interval based on distance. In this study, failure rates of the electrical door system currently used in railway vehicles are collected from maintenance field data. Failure rates are analyzed by using Minitab. Several kinds of plan for improving reliability are also suggested. It is necessary to keep studying on reliability prediction methodology, applying it in the field and implementing on improvement of reliability through feedback as well. Further, it will be useful for determining new maintenance policies or changing maintenance intervals for existing railway vehicles.

• Structural Engineering and Mechanics
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• v.37 no.4
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• pp.427-442
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• 2011

In fatigue life design of mechanical components, uncertainties arising from materials and manufacturing processes should be taken into account for ensuring reliability. A common practice is to apply a safety factor in conjunction with a physics model for evaluating the lifecycle, which most likely relies on the designer's experience. Due to conservative design, predictions are often in disagreement with field observations, which makes it difficult to schedule maintenance. In this paper, the Bayesian technique, which incorporates the field failure data into prior knowledge, is used to obtain a more dependable prediction of fatigue life. The effects of prior knowledge, noise in data, and bias in measurements on the distribution of fatigue life are discussed in detail. By assuming a distribution type of fatigue life, its parameters are identified first, followed by estimating the distribution of fatigue life, which represents the degree of belief of the fatigue life conditional to the observed data. As more data are provided, the values will be updated to reduce the credible interval. The results can be used in various needs such as a risk analysis, reliability based design optimization, maintenance scheduling, or validation of reliability analysis codes. In order to obtain the posterior distribution, the Markov Chain Monte Carlo technique is employed, which is a modern statistical computational method which effectively draws the samples of the given distribution. Field data of turbine components are exploited to illustrate our approach, which counts as a regular inspection of the number of failed blades in a turbine disk.

• Journal of the Korean Society of Safety
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• v.26 no.1
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• pp.1-7
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• 2011

When the pumps stopped in the operation by the power failure, the hydraulic transients take place in the sudden change of a velocity of pipe line. Each and every water hammer problem shows the critical stage to be greatly affected the facts of safety and reliability in case of power failure. The field tests of the water hammer executed at Cheong-Yang booster pump station having an air chamber. The effects were studied by both the practical experiments and the CFD(Computational Fluid Dynamics : Surge 2008). The result states that the system with water hammering protection equipment was much safer when power failure happens. The following data by a computational fluid dynamic analysis are to be shown below, securing the system stability and integrity. (1) With water hammering protection equipment. (1) Change of pressure : Up to $15.5\;kg/cm^2$ in contrary to estimating $16.88\;kg/cm^2$. (2) Change rate of water level : 52~33% in contrary to estimating 55~27%. (3) Note that the operational pressure of pump runs approx. 145 m, lowering 155 m of the regularity head of pump. (4) Note that the cycle of water hammering delays from 80 second to 100 second, together with easing the function of air value at the pneumatic lines. (2) Change of pressure without water hammering protection equipment : Approximate $22.86\;kg/cm^2$. The comprehensive result says that the computational fluid dynamics analysis would match well with the practical field-test. It was able to predict Max. or Min. water hammering time in a piping system. This study aims effectively to alleviate water hammering in a pipe line to be installed with air chamber at the pumping station and results in making the stability of pump system in the end.

• Earthquakes and Structures
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• v.17 no.4
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• pp.355-363
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• 2019

Masonry structures in the rural areas of Turkey often damaged due to moderate and big earthquakes. After every earthquake many scientists made field investigations on the earthquake performance of these structures and gave many useful information on construction techniques. However, the newly constructed masonry buildings are still not suitable for the suggested techniques, and they are still in danger against future earthquakes. Five moderate earthquakes of moment magnitude Mw 5.3, 5.3, 5.2, 5.0, and 5.3 struck the Ayvacik-Çanakkale District of Turkey between 6 and 12 February, 2017. More than a thousand of aftershocks were occurred and most of the masonry buildings in the villages nearby main shock epicenter were affected. The author went to the earthquake field and investigated the earthquake performances of masonry structures. This paper presents the recorded acceleration data, acceleration response spectra, and the seismological aspects of these earthquakes. Besides, case studies of damaged stone masonry buildings, and failure mechanisms are discussed with illustrated photos which were taken during the field investigations. It is concluded that the damaged masonry buildings were not designed and constructed properly in accordance with the Turkish building codes or similar specifications.