• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.535-544
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• 2016

This paper aims at examining the effects of sustained load and elevated temperature on the time-dependent deformation of a carbon fiber reinforced polymer (CFRP) sheets bonded to concrete as well as the pull-off strength of single-lap shear specimens after the sustained loading period using digital images. Elevated temperature during the sustained loading period resulted in increased slip of the CFRP composites, whereas increased curing time of the polymer resin prior to the sustained loading period resulted in reduced slip. Pull-off tests conducted after sustained loading period showed that the presence of sustained load resulted in increased pull-off strength and interfacial fracture energy. This beneficial effect decreased with increased creep duration. Based on analysis of digital images, results on strain distributions and fracture surfaces indicated that stress relaxation of the epoxy occurred in the 30 mm closest to the loaded end of the CFRP composites during sustained loading, which increased the pull-off strength provided the failure locus remained mostly in the concrete. For longer sustained loading duration, the failure mode of concrete-CFRP bond region can change from a cohesive failure in the concrete to an interfacial failure along the concrete/epoxy interface, which diminished part of the strength increase due to the stress relaxation of the adhesive.

• Journal of Applied Reliability
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• v.11 no.4
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• pp.433-445
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• 2011

Duty cycle is determined as the ratio of operating time to total time. Duty cycle in reliability prediction is one of the significant factors to be considered. In duty cycle application, non-operating time failure rate has been easily ignored even though the failure rate in non-operating period has not been proved to be small enough. Ignorance of non-operating time failure rate can result in over-estimated system reliability calculation. Furthermore, utilization of duty cycle in reliability prediction has not been evaluated in its effectiveness. In order to address these problems, two reliability models, such as MIL-HDBK-217F and RIAC-HDBK-217Plus, were used to analyze non-operating time failure rate. This research has proved that applying duty cycle in 217F model is not reasonable by the quantitative comparison and analysis.

• Journal of Chest Surgery
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• v.26 no.12
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• pp.915-919
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• 1993

The management of Patent Ductus Arteriosus[PDA] with heart failure and cardiac cachexia in premature infants have been a disturbing and controversial problem in the field of pediatric cardiovascular surgery.We analysed our experiences to determine the rationale of surgical closure of PDA in infants . During a period of 7 years from January 1986 to December 1992, 12 infants under 2 months of age underwent operations for "hemodynamically significant" PDA which had caused severe heart failure.There were 6 male and 6 female patients. Their mean gestational age was 33.8 weeks and their mean body weight was 1990 g. ranged from 710 g. to 2900 g. Mean age at operation was 28.5days. Seven patients had history of Indomethacin trial. All patients were operated with double ligation technique under general anesthesia.There was no mortality and blood transfusion was not necessary in any patient during the operation.In all cases, we could confirm the complete closure of PDA after operation by follow-up echocardiography.Two patients died during their hospital stay and 1 patient died at 6 months after operation. The causes of death were sepsis with congestive heart failure, necrotizing entero colitis and pneumonia respectively.We can not detect any operation related complication which resulted in permanent sequelae as well as delayed complications related to nerve damage. These results indicate that surgical ligation of PDA in infants with severe heart failure is relatively safe and effective.effective.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.143-148
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• 2010

A Statistical methods are used to determine the reliability of a Fuel Boost Pump for aviation. Failures are referenced from failure reports. The failure-free periods between successive failure events are evaluated in the form of weibull distribution. The results of analysis were calculated shape factor, scale parameter and mean time to failure. It found that the reason of failure is wear-out period.

• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.1-6
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• 2003

In this work, procedure evaluating failure modes such as pipe rupture, large scale leak, and small scale leak was suggested using equations to assess remaining strength by corrosion failure. Additionally, the method to predict probability of failure was suggested according to the aforementioned failure modes, and by combining data on corrosion rate, probability of long-term failure can be induced. This work will be very useful in predicting lifetime or exchanging period of pipeline.

• Archives of Craniofacial Surgery
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• v.24 no.4
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• pp.159-166
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• 2023

Background: Free tissue transfer is the preferred method of reconstructing head and neck defects, with a success rate of approximately 95%. Although flap failure is uncommon, it has a major impact on patient morbidity and diminishes quality of life, making it is important to investigate the causes of flap failure. Methods: This retrospective chart review analyzed patients who underwent free tissue transfer during head and neck reconstruction at a single institution between 2016 and 2021. Results: During the study period, 58 patients underwent 60 free flap procedures. Revision surgery was needed in 14 patients. Subsequent free flap surgery was performed in one patient, and three free flaps (5%) could not be salvaged. Cardiovascular disease was significantly associated with flap failure, and venous congestion (thrombosis) was the most common reason for revision surgery. Conclusion: Cardiovascular disease clearly emerged as a factor related to the failure of free flap surgery, and this issue warrants particular attention in patients for whom free tissue transfer is planned.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.174-182
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• 2007

There are not many studies on the maintenance and replacement for the ITS equipments. Most of ITS center has no comprehensive regulation on the equipment replacement. This study was focusing on estimation of equipment replacement period and the number of spare parts in stock using the actual failure data of Road Side Equipment (RSE) by Dedicated Short Range Communication (DSRC). The failure data showed a type of bath-tub curves. The data, however, did not fit to any probability distribution curve, which means that the preventive replacement cannot be strongly applied for the RSE. In the aspect of practical strategy, this study suggest that repairing cost and failure frequency be used for decision of replacement of RSE after the 1 or 2 year warrant period. The future study needs to include more RSE failure data as well as other equipments of the ITS.

• Smart Structures and Systems
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• v.22 no.2
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• pp.185-192
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• 2018

Participants in the Asia Pacific Conference of the Prognostics and Health Management Society 2017 (PHMAP 2017) Data Challenge were given measured vibration signals from motor-driven gearboxes used in pulverizers. Using this information, participants were requested to predict failure dates and the faulty components. The measured signals were affected by significant noise and disturbance, as the pulverizers in the provided data worked under actual operating conditions. This paper thus presents a fault prediction method for a motor-driven gearbox in a pulverizer system that can perform under external noise and disturbance conditions. First, two fault features, an RMS value in the higher frequency zones (HRMS) and an amplitude of a period for high-speed shaft in the quefrency domain ($QA_{HSS}$), were extracted based on frequency analysis using the higher and lower sampling rate data. The two features were then applied to each pulverizer based on results of frequency responses to impact loadings. Then, a regression analysis was used to predict the failure date using the two extracted features. A weighted regression analysis was used to compensate for the imbalance of the features in the given period. In addition, the faulty components in the motor-driven gearboxes were predicted based on the modulated frequency components. The score predicted by the proposed approach was ranked first in the PHMAP 2017 Data Challenge.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1291-1296
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• 2013

Risk-based inspection (RBI) is a well-known method that is used to optimize inspection activities based on risk analysis in order to identify the high-risk components of major facilities such as power plants. RBI, when implemented and maintained properly, improves plant reliability and safety while reducing unplanned outages and repair costs. Risk is given by the product of the probability of failure (POF) and the consequence of failure (COF). A semi-quantitative method is generally used for risk assessment. Semi-quantitative risk assessment complements the low accuracy of qualitative risk assessment and the high expense and long calculation time of quantitative risk assessment. The first step of RBI is to identify important failure modes and causes in the equipment. Once these are defined, the POF and COF can be assessed for each failure. During POF and COF assessment, an effective inspection method and range can be easily found. In this paper, the calculation of the POF is improved for accurate risk assessment. A modified semi-quantitative risk assessment was carried out for boiler facilities of thermal power plants, and the next maintenance schedules for the equipment were decided.

• Korean Journal of Health Education and Promotion
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• v.26 no.3
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• pp.25-34
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• 2009

Objectives: This study has longitudinally analyzed male smokers in order to find out the trend rate of re-smoking after smoking cessation. Methods: The study was conducted with 800 male smokers who were provided with smoking cessation services for 3 years at public health centers from July 16, 2005 to July 15, 2008. Results: The results can be summarized as follows: First, the success rate of smoking cessation for at least 6 months during 3-year period was 54.4%. The failure rate of smoking cessation at the second year was 47.5% and the third 27.2%, which indicates that the failure rate diminishes as the period of smoking cessation extends. Second, the success rate of smoking cessation at the first trial was 35.0%, the second 24.3%, and the third 16.4%. The success rate diminished as the number of trial increased. Third, the continuation rate of smoking cessation for a year was 18.3%, for 2 years 13.4%. For the success group, the continuation rate of smoking cessation for a year was 52.5%, for 2 years 38.2%. For the failure group, the rate for a year was 21.5%. Fourth, in this longitudinal analysis, the most crucial variables that affect the success rate of smoking cessation are total number of consultation and the past experience of successful smoking cessation. Conclusion: This study shows that success of smoking cessation and the continuance of smoking cessation are both difficult, and that the past experience of smoking cessation plays an important role determining the present success of smoking cessation and continuance of smoking cessation. Thus, it is necessary to divide people into success group and failure group based on the results of the past experience of smoking cessation when they consult at smoking cessation clinics at public health centers. Further, in order to increase the continuation rate of smoking cessation, this study suggests that we need to consider ways to take care of those who successfully abstained from smoking for 6 months.