• International Journal of Reliability and Applications
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• v.15 no.1
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• pp.51-64
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• 2014

This paper develops a warranty cost model for complex systems with imperfect repair within a warranty period by addressing a practical case that the first inter-failure interval is longer than any other inter-failure intervals. The product is in its best condition before the first failure if repair is imperfect. After the imperfect repair, other inter-failure intervals which are explained by renewal processes, are stochastically smaller than the first inter-failure interval. Based on this idea, we suggest the failure-interval-failure-criterion model. In this model, we consider two random variables, X and Y where X represents failure intervals and Y represents failure criterion. We also obtain the distribution of the number of failures and conduct the warranty cost analysis. We investigate different types of warranty cost models, reliabilities and other measures for various systems including series-parallel configurations. Several numerical examples are discussed to demonstrate the applicability of the methodologies derived in the paper.

• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.571-582
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• 2019

Purpose: To develop a risk metric for failure cause that can help determine the action priority of each failure cause in FMEA considering time sequence of cause- failure- detection. Methods: Assuming a quadratic loss function the unfulfilled mission period, a risk metric is obtained by deriving the failure time distribution. Results: The proposed risk metric has some reasonable properties for evaluating risk accompanied with a failure cause. Conclusion: The study may be applied to determining action priorities among all the failure causes in the FMEA sheet, requiring further studies for general situation of failure process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.583-594
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• 1994

One of the major elements of a natural landslide is the increase of the pore water pressure in a weakened layer. Therefore, the measurement of the pore water pressure in the layer is important. This work is a laboratory model study of the measurement of the pore water pressure with regard to the confined groundwater level, the permeability of the crack zone and the weathering degree of the weakened layer. By the model of the Tertiary period failure type and the Colluvium failure type, the reactions of the pore air pressure and the pore water pressure were measured in the weakened layer according to the permeability of the filter on the condition of the confined groundwater states. On the reaction phase of the pore pressure according to the during time, the Tertiary period failure type proved to be a step type and the Colluvium failure type turned out to be a wave type. The reaction ratios of the pore water pressure in the Tertiary period failure type are higher than the Colluvium failure type, decrease according to increasing of the weathering degree of the weakened layer.

• 전기의세계
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• v.21 no.2
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• pp.20-24
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• 1972

The transient stability of the synchronous motor is generally improved by damper winding or flywheel. However the synchronous motor at full load will be pulled out from normal operation state when the period of power failure exceeds approximately ten cycle per second. This paper studies the method of improving the stability of synchronous motor by equipping the phase slipping switch between the motor and power source. This paper shows the motor does not pull out, which results from the decrease of power angle to about 30 electrical degrees by means of the switch even when the relatively long period of power failure brings the power angle to some 150 electrical degrees.

• Journal of Korean Institute of Industrial Engineers
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• v.15 no.2
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• pp.87-91
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• 1989

A warranty is a contractual obligation incurred by a producer in connection with the sale of a product. The warranty specifies that producer agrees to remedy certain failures in the product sold. There have been many articles dealing with warranties, but they have studied about optimal warranty cost for the warranty period. In this study, an optimal preventive maintenance time interval is computed. The optimal preventive maintenance time interval minimizing warranty cost for the warranty period is discussed. It is assumed that failure rate is increasing and the failure rate after preventive maintenance or corrective maintenance lies between good as new and bad as old.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.13 no.21
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• pp.19-24
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• 1990

This paper deals with a problem of choosing an optimum inspection period for an equipment with two stages of failures. Stage I failure which can be detected only through inspection detenorates the equipment and causes critical stage II failure after a random period of time. The expected average cost function is obtained and an optimum inspection policy is discussed. A numerical example is also worked out.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.283-290
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• 2021

Survival analysis was used to determine whether there are differences in the impact of trade payables on business failure according to the size of the company. A total of 41,781 firms from 1999 to 2019 were analyzed. The analysis period was divided into the entire period and before and after the financial crisis. The trade payable ratio is a proxy variable. The increase in trade payables over the entire period increases the possibility of business failure of Small and Medium Enterprises (SMEs). However, in large firms, a significant relationship between the increase in the trade payable ratio and the possibility of corporate failure could not be confirmed. Second, in SMEs during the sub-periods of 1999-2007 and 2009-2019, it was found that an increase in trade payables acts as a factor that increases the possibility of corporate failure. However, in large corporations, the increase in trade payables in the period from 2009 to 2019 has been shown to reduce the rate of failure. An increase in trade payables is recognized as the active development of business activities or the active use of interest-free debt. Therefore, it was confirmed that the impact of trade payables on corporate failure differs depending on the size of the company.

• Knowledge Management Research
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• v.12 no.4
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• pp.121-132
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• 2011

Failure, the research object, means situations when goals and their results are different, which has developed presenting various aspects from ancient times and modern times. Failure is a complex concept which essentially requires judgement, and also a relative concept which can be changed depending on how you set up time base and standard. There are four stages for failure study to have been developed from studying failure through historical facts to the approach of organizational theory and it has been studied by looking at the failure of an organization according to different categories such as a developmental stage, a type of business, a period and a course. Compared with success science, failure study has not been studied sufficiently and also the level of its analysis is low. Thus, since lessons of failure tend to repeat themselves instead of being didactically accumulated, there need more studies on this. This thesis identified the main cause of the failure through various studies regarding failure which have been conducted at home and abroad. What the main cause of the failure that more than three studies mentioned have in common was that it occurred because organizations concentrated on the inside without communicating with external environment. The key point of failure study is to analyze failure, utilize it as assets, and create a frame of failure management. This thesis focused on delivering fragmentary knowledge on failure study, but case studies regarding this subject should be done in the future.

• Communications for Statistical Applications and Methods
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• v.18 no.3
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• pp.277-286
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• 2011

Global companies can sell their products with dierent warranty periods based on location and times. Customers can select the length of warranty on their own if they pay an additional fee. In this paper, we consider the warranty period and the repair time limit as random variables. A two-dimensional warranty policy is considered with repair times and failure times. The repair times are considered within the repair time limit and the failure times are considered within the warranty period. Under the non-renewable warranty policy, we obtain the expected number of warranty services and their variances in the censored area by warranty period and repair time limit to conduct a warranty cost analysis. Numerical examples are discussed to demonstrate the applicability of the methodologies and results using field data based on the proposed approach in the paper.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.23 no.1
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• pp.169-181
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• 2010

Objective : The purpose of this study was to investigate the effects of Combination therapy with Gwakhyangjeonggisangamibang and Sojangjeonggyeok on patients with verucca plana. Methods : Sixty-five patients(male 19, female 46) with verruca plana were treated with Gwakhyangjeonggisangamibang and Sojangjeonggyeok for at least 3 months. After treatment, a clearance rate was divided into 4 scales such as; complete clearance / partial clearance-good / partial clearance-poor / no change. Statistical analysis was performed by using Independent-sample t-test. Results : Mean age of patients was 30.3 and mean period of disease duration was 64.6 months. Fifty-eight patients(73.8%) showed complete clearance, nine(13.8%) partial clearance-good, and eight(12.3%) partial clearance-poor. Complete clearance group(CC group) was statistically younger than failure group and disease duration of CC group was shorter than failure group. Although treatment period of failure group was statistically longer than CC group and dosage(貼) of herbal medicine of failure group was more than CC group, failure group showed partial clearance. Conclusion : This data demonstrates that combination therapy with Gwakhyangjeonggisangamibang and Sojangjeonggyeok could be an effective and safe treatment for the verucca plana.