• Journal of Korean Institute of Industrial Engineers
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• v.36 no.1
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• pp.69-77
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• 2010

The failure rate model of External Environment Maintenance(EEM) for a system under severe environment is investigated. EEM, which is recently introduced concept, is a maintenance activity controlling external environment factors that potentially cause system failure such as cleaning equipment, controlling temperature (humidity) and removing dust inside of electronic appliances. EEM can not have any influence on the inherent failure rate of a system but reduce the severity of the external environment causing failure since it deals with only external environment factors. Therefore, we propose two failure rate models to express the improvement effect of EEM: The intensity reduction model and age reduction model. The intensity and age reduction models of EEM are developed assuming the quality of improvement effect is proportioned to an extra intensity or age respectively. The validation of proposed failure rate models is performed in order of data generation, parameter estimation and test for goodness-of-fit.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.779-791
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• 2023

Long-termly used in water supply, an underground concrete pipe is easily subjected to the coupled action of pressure loading and flowing water, which can cause the chemo-mechanical damage of the pipe, resulting in its premature failure and lifetime reduction. Based on the leaching characteristics and damage mechanism of concrete pipe, this paper proposes a coupled chemo-mechanical damage and failure model of underground concrete pipe for water supply, including a calcium leaching model, mechanical damage equation and a failure criterion. By using the model, a numerical simulation is performed to analyze the failure process of underground concrete pipe, such as the time-varying calcium concentration in concrete, the thickness variation of pipe wall, the evolution of chemo-mechanical damage, the distribution of concrete stress on the pipe and the lifetime of the pipe. Results show that, the failure of the pipe is a coupled chemo-mechanical damage process companied with calcium leaching. During its damage and failure, the concentrations of calcium phase in concrete decrease obviously with the time, and it can cause an increase in the chemo-mechanical damage of the pipe, while the leaching and abrasion induced by flowing water can lead to the boundary movement and wall thickness reduction of the pipe, and it results in the stress redistribution on the pipe section, a premature failure and lifetime reduction of the pipe.

• Journal of Drive and Control
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• v.18 no.1
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• pp.24-30
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• 2021

There is an increasing interest in condition-based maintenance for the prevention of economic loss due to failure. Moreover, immense research is being carried out in related technologies in the field of construction machinery. In particular, data-based failure diagnosis methods that employ AI (machine & deep learning) algorithms are in the spotlight. In this study, we have focused on the failure diagnosis and mode classification of reduction gear of excavator's travel device by using the AI algorithm. In addition, a remote monitoring system has been developed that can monitor the status of the reduction gear by using the developed diagnosis algorithm. The failure diagnosis algorithm was performed in the process of data acquisition of normal and abnormal under various operating conditions, data processing and analysis by the wavelet transformation, and learning. The developed algorithm was verified based on three-evaluation conditions. Finally, we have built a system that can check the status of the reduction gear of travel devices on the web using the Edge platform, which is embedded with the failure diagnosis algorithm and cloud.

• Advances in pediatric surgery
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• v.19 no.2
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• pp.66-72
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• 2013

Intussusception is common cause of intestinal obstruction in children. Most of intussusceptions can be treated with non-operative reduction using air or barium. However, about 10% patients need operative treatment due to failure of reduction, peritonitis, and recurrence after reduction. We introduce our experience of laparoscopic surgery for intussusception. From April 2010 to March 2013, we reviewed 57 children who diagnosed intussusception. Twelve patients underwent an operation. The cause of operation was 7 of failure of air reduction and 5 of recurrence after air reduction. Median age was 21.5 months (range: 5.0~57.7 months) and 11 children (91.7%) underwent successful laparoscopic reduction. Median operating time was 50 minutes (range: 30~20 minutes) and median hospital days was 4.5 days (range: 3~8 days). One patient had a leading point as a heterotopic pancreas and underwent bowel resection through conversion. There was neither intra-operative nor postoperative complication. Laparoscopic reduction for intussusception can bring an excellent cosmetic effect with high success rate.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.434-443
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• 2009

Slope stability analysis is an essential part of rock slope design. For highly fractured rock, the limit equilibrium method (LEM) based slope stability analysis with a circular failure surface is often carried out assuming the rock mass behaves more or less as a continuum. This paper examines first, the applicability of the finite-element method (FEM) based shear strength reduction (SSR) technique for highly fractured rock slope, and second the use of Mohr-Coulomb (MC) failure criterion in conjunction with generalized Hoek-Brown (HB) failure criterion. The numerical results on a number of cases are compared in terms of the factor of safety (FS). The results indicated that the FEM-based SSR technique yields almost the same FSs from LEM, and that the MC and HB failure criteria yield almost identical FSs when the strength parameters for MC failure criterion are obtained based on the modified HB failure criterion if and only if value of the Hoek-Brown constant $m_i$ is smaller than 10 and slope angle is smaller than 1:1, otherwise MC failure criteria over-estimate the factor of safety.

• Journal of Trauma and Injury
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• v.25 no.1
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• pp.7-16
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• 2012

Purpose: Cervical dislocations with locked facets account for more than 50% of all cervical injuries. Thus, investigating a suitable management of cervical locked facets is important. This study examined factors of close reduction failure in traumatically locked facets of the subaxial cervical spine patients to determine suitable surgical management. Methods: We retrospectively analyzed of the case histories of 28 patients with unilateral/bilateral cervical locked facets from Nov. 2004 to Dec. 2010. Based on MRI evaluation of disc status at the injury level, we found unilateral dislocations in 9 cases, and bilateral dislocations in 19 cases, The patients were investigated for neurologic recovery, closed reduction rate, factors of the close reduction barrier, fusion rate and period, spinal alignment, and complications. Results: The closed reduction failed in 23(82%) patients. Disc herniation was an obstacle to closed reduction (p=0.015) and was more frequent in cases involving a unilateral dislocation (p=0.041). The pedicle or facet fracture was another factor, although some patients showed aggravation of neurologic symptoms, most patients had improved by the last follow up. The kyphotic angle were statistically significant (p=0.043). Sixs patient underwent anterior decompression/fusion, and 15 patients underwent circumferential fusion, and 7 patients underwent posterior fusion. All patients were fused at 3 months after surgery. The complications were 1 case of CSF leakage and 1 case of esphageal fistula, 1 case of infection. Conclusion: We recommend closed reduction be performed as soon as possible after injury to maximize the potential for neurological recovery. Patients fot whom closed reduction of the cervical locked facets have a higher incidence of anatomic obstacles to reduction, including facet fractures and disc herniation. Immediate direct open anterior reduction or circumferential fixation/fusion of locked cervical facets is recommended as a treatment of choice for traumatic locked cervical facet patients after closed reduction failure.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.608-616
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• 2010

Seoul Metropolitan Rapid Transit Corporation, managing the line number 5,6,7 and 8 has inspected and maintained for the maintenance of the facilities spread in the extended 152km and 148 stations. Despite the thorough inspection for prevention of the facility failure, the failure has continuously occurred, due to the environmental factors of the underground, mechanical worn-out caused by frequent use, aging facilities, system error, negligence on use, etc. We have achieved a 53.4% reduction in the number of failure by the end of June, 2010 by breaking the conventional way of inspections and maintenance and by adopting quantitative goal management and new way of work. In this paper, we will analyze the problems of inspections and maintenance of the railway facilities, the failure reduction strategy and the performance of each strategy.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.9-11
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• 2006

This paper suggests a revision method for historical fault data using Proportional Aging Reduction(PAR) to consider maintenance effect in time-varying failure rate. In order to product time-varying failure rate, the historical fault data are necessary. However, the maintenance record could be left out in historical data by spot operator's mistake. In this case, the failure rate is produced less than the average failure rate for increasing equipments' life-time by maintenance effect. Hence, it is necessary for new time-varying failure rate to extract maintenance effect from the existing fault data. In this paper, the revision method to reduce equipments' life-time, adversely using PAR among three techniques to consider maintenance effect.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.61-65
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• 2005

Existing test methods for thick-section specimens ( 4mm) have not provided precise compressive properties to date for the analysis and design of thick structure. A survey of the failure behaviour of such thick specimens revealed that the failure initiated at the top corner of the specimen and propagated down and across the width of the specimen as premature failure, not typically reported for thin compression specimens. In the current study, the premature failure was successfully avoided during compressive testing and the failure mode was quite similar regardless of increasing specimen thickness and specimen volume. Failure mode was similar regardless of increasing specimen thickness and specimen volume, i.e. brooming failure mode combined with longitudinal splitting, interlaminar cracking, fibre breakage and kinkband formation (fibre microbuckling). Nevertheless, average failure strengths of the specimens decreased with increasing specimen thicnkiness from 2mm to 8mm with the T800/924C system (36% strength reduction) and specimen volumes from scaling factor I to scaling factor 4 with the IM7/8552 system (46% strength reduction). It was revealed from the literature$^{11}$ that the thickness effect and scaling effect arc caused by manufacturing defects such as void content and fibre waviness.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.643-650
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• 2002

The large planar failure has occurred in a rock cut slope of highway construction site in Boeun. This area is considered as unstable since the discontinuities whose orientations are similar to the orientation of the failure plane, are observed in many areas. Therefore, several analysis techniques such as SMR, stereographic analysis, limit equilibrium, numerical analysis, which are commonly used in rock slope stability analysis, are adopted in this area. In order to analyze the stress redistribution and nonlinear displacement caused by cut, which are not obtained in limit equilibrium method, the UDEC and shear strength reduction technique were used in this study Then the factors of safety evaluated by shear strength reduction technique and limit equilibrium were compared. In addition, the factor of safety under fully saturated slope condition was calculated and subsequently, the effect of the reinforcement was evaluated.