• 한국신뢰성학회지:신뢰성응용연구
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• 제15권4호
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• pp.241-247
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• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• 기술혁신학회지
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• 제16권1호
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• pp.346-366
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• 2013

최근 도전적이고 창의적인 연구의 중요성이 증가함에 따라, 모험적 연구가 요구되고 있으나 이에 따른 실패의 경우, 이를 보호할 수 있는 제도적 장치가 미비하여 그 정착이 시급한 실정이다. 이러한 문제점을 해소할 수 있도록 '국가연구개발사업의 관리 등에 관한 규정'에서 성실실패제도가 명시되어 있으나, 그 기준이 명확하지 않고 세부적인 규정이 마련되어 있지 않았으며 이로 인해 각 전문기관들이 상이하게 운영하고 있어 연구자들의 혼란이 가중되고 있다. 이에 따라 본 연구는 현재의 성실실패제도와 관련하여 현행 실태와 해외사례 등을 검토하여, 성실여부 판정기준, 평가주체의 상이성, 실패의 인정 및 그에 따른 해당연구 결과의 활용방안의 미비점, 제재감면 범위의 불명확성, 반복적 성실실패에 대한 검증 및 방지 방안의 부족으로 요약되는 문제점들을 도출하여 분석하고, 그에 대한 개선점을 국내외 사례를 비교분석하여 그 안을 제시하였다.

• 복식문화연구
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• 제18권3호
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• pp.526-540
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• 2010

Due to fierce competition, many domestic fashion businesses are suffering difficulty in securing and maintaining customers. Accordingly, fashion companies are devoting all their energy to secure customers by using high quality and diverse strategies for distribution and promotion, and to secure loyalty by satisfying customers with the offer of excellent service. Thus, it is very important to provide systematic service recovery strategy available for handling service failure effectively. Therefore, the purpose of this study is comprehensively analyzing influences of expectation dis-confirmation and perceived justice for service recovery upon consumers' satisfaction and loyalty. The findings are as follows. First, as for the service failure that customers experienced, the more consumers who expect it to be recovered led to the higher formation of expectation-compensation dis-confirmation. Second, it was indicated that the higher seriousness in service failure that customers experienced led to the lower satisfaction and loyalty to service recovery. Third, as a result of examining influence of expectation-compensation dis-confirmation for service-failure recovery upon consumer satisfaction and loyalty, the customers who showed more positive dis-confirmation to expectation-compensation were indicated to form the more satisfaction and loyalty. Fourth, as a result of examining the influence of the perceived justice in the process of service-failure recovery upon customer satisfaction, all in 3 dimensions of justice had effect on customer satisfaction.

• 콘크리트학회논문집
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• 제12권5호
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• pp.35-46
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• 2000

In this paper, an analytical model is proposed to predict the shear strenth of RC beams strengthened by FRP. This predictional model is composed of two basic models-the upper bound theorem for shear failure (shear tension or shear compression criteria) and a truss model based on the lower bound theorem for diagonal tension creteria. Also, a simple flexural theory based on USD is used to explain flexural failure. The major cause of destruction of RC beams shear strengthened by FRP does not lie in FRP fracture but in the loss of load capacity incurred by rip-off failure of shear strengthening material. Since interfacial shear stree between base concrete and the FRP is a major variable in rip-off failure mode, it is carefully analyzed to derive the shear strengthening effect of FRP. The ultimate shear strength and failure mode of RC beams, using different strengthening methods, estimated in this predictional model is then compared with the result derived from destruction experiment of RC beams shear strengthened using FRP. To verify the accuracy and consistency of the analysis, the estimated results using the predictional model are compared with various other experimental results and data from previous publications. The result of this comparative analysis showed that the estimates from the predictional model are in consistency with the experimental results. Therefore, the proposed shear strength predictional model is found to predict with relative accuracy the shear strength and failure mode of RC beams shear strengthened by FRP regardless of strengthening method variable.

• Journal of Electrical Engineering and Technology
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• 제4권1호
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• pp.43-48
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• 2009

The purpose of the this paper is to make decision of the maintenance priority of power distribution system using Time-Varying Failure Rate(TVFR) with interruption cost. This paper emphasizes the practical use of the reliability indices and interruption cost. To make a decision of maintenance priority on power distribution system equipment, the quantification of the reliability level should be represented as a cost. In this paper, the TVFR of power distribution system equipment applied in this paper utilizes analytic method to use the historical data of KEPCO. From this result, the sensitivity analysis on TVFR of equipment was done for the priority, which represents that high priority of the equipment has more effect on system reliability, such as SAIDI or SAIFI, than other equipment. By this priority, the investment plan is established. In this result, customer interruption cost(CIC) could be extracted, and CIC is used as weighting factor to consider a importance of customer. After that, the result calculated the proposal method in this paper is compared with other priority method, such as lifetime, failure rate or only sensitivity.

• Steel and Composite Structures
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• 제21권5호
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• pp.1145-1156
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• 2016

To study the effects of foam core density and face-sheet thickness on the mechanical properties and failure modes of aluminum foam sandwich (AFS) beam, especially when the aluminum foam core is made in aluminum alloy and the face sheet thickness is less than 1.5 mm, three-point bending tests were investigated experimentally by using WDW-50E electronic universal tensile testing machine. Load-displacement curves were recorded to understand the mechanical response and photographs were taken to capture the deformation process of the composite structures. Results demonstrated that when foam core was combined with face-sheet thickness of 0.8 mm, its carrying capacity improved with the increase of core density. But when the thickness of face-sheet increased from 0.8 mm to 1.2 mm, result was opposite. For AFS with the same core density, their carrying capacity increased with the face-sheet thickness, but failure modes of thin face-sheet AFS were completely different from the thick face-sheet AFS. There were three failure modes in the present research: yield damage of both core and bottom face-sheet (Failure mode I), yield damage of foam core (Failure mode II), debonding between the adhesive interface (Failure mode III).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.322-324
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• 2004

Up to the present, digital replantation patients has appealed different symptoms due to blood circulatory failure. But, the level of blood circulatory failure has been evaluated only by clinical symptoms, or angiography. According to the cases of digit replantation is increasing, then objective evaluation methods of the level of blood circulation failure is needed other than patient's subjective symptoms and complaints. Although angiography, doppler, electromagnetic flowmeter, laser blood flowmeter, mechanical blood flowmeter has been used for the evaluation of the blood circulatory failure, the result was affected by time, place, surrounding temperature, patient's body temperature, and even emotion. Therefore, it is pointed out with lack of availability, feasibility and reproducibility. Thus, we compared digital blood flow of dominant hand to non dominant hand, and replanted fingers to opposite normal fingers from developed photo-plethysmography. The average digital blood flow showed no difference in normal digits each other, but, replanted digits showed average of 53% (9 - 100 %) compare to opposit normal digits. As it measure relative blood flow for circulatory failure of tissue such as fingers and toes more sensitively, reliably. In conclusion, it is expected that photo- plethysmography will be very useful for diagnosis, curative effect, prognosis of blood circulatory failure in digital replantation patient.

• 복식
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• 제63권3호
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• pp.46-60
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• 2013

With a goal of establishing a marketing strategy which allows businesses to hold a dominant position in beauty service industry, this study has attempted to investigate causal relations among behavioral intentions by customer satisfaction once service recovery strategy is recovered depending on customers' emotional responses against service failure. In order to provide relevant data to make correct decisions during management and marketing planning so that better customer satisfaction can be achieved in the beauty service industry, the results of the previous studies on service failure and recovery strategy in the beauty service industry have been examined. Then after selecting i) the efforts to recover service failure, ii) satisfaction after recovery and iii) behavioral intention after satisfaction as causal variables, the relation among these variables were verified using a structural equation model. As a result, an appropriate recovery strategy which is developed after service failure makes customers have positive behavioral intentions when customer satisfaction is achieved just as described in previous studies. Furthermore, it is a critical fact which helps businesses keep their customers in a mature market, where it is hard to attract new customers and create long-term profit. This study empirically supports information on how service failure and related variables occur in the beauty service industry. It is significant in that it has helped beauty service providers build service recovery-related strategies.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권3호
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• pp.250-259
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• 2018

Purpose: Previously, missile reliability prediction is based on theoretical failure prediction model. It has shown that the predicted reliability is inadequate to real field data. Although an MTTF based reliability prediction method using real field data has recently been studied to overcome this issue. In this paper, we present a more realistic method, considering MTBF concept, to predict missile reliability. Methods: In this paper we proposed a modified survival model. This model is considering MTBF as its core concept, and failed missiles in the model are to be repaired and redeployed. We compared the modified model (MTBF) and the previous model (MTTF) in terms of fitness against the real failure data. Results: The reliability prediction result of MTBF based model is closer to fields failure data set than that of MTTF based model. Conclusion: The proposed MTBF concept is more fitted to real failure data of missile than MTTF concept. The methodology of this study can be applied to analyze field failure data of other similar missiles.

• Smart Structures and Systems
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• 제22권2호
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• pp.151-159
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• 2018

Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.