• Journal of Korean Society for Quality Management
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• v.28 no.3
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• pp.11-17
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• 2000

This paper presents a model for determining the optimal number of general repairs and supplementary input cost limit rate in addition to minimal repair cost rate to implement preventive maintenance. The basic concept parallels the periodic replacement model with minimal repair at failure introduced by Barlow and Hunter(1960) and Park(1979), only difference being the replacement signalled by the number of previous general repairs performed on the system. A general repair brings the state of the system to a certain better state than before repaired. Numerical examples are provided.

• Journal of the Korean Statistical Society
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• v.30 no.1
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• pp.89-98
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• 2001

Brown and Proschan(1983) introduced a model for imperfect repair. At each failure of a device, with probability p, it is repaired completely or replaced with a new device(perfect repair), and with probability 1-p, it is returned to the functioning state, but it is only recovered to its condition just prior to failure(imperfect repair or minimal repair). In this paper, we limit the number of consecutive minimal repairs by n. We find some useful properties about $\mu$$_{k}$, the expected time between the k-th and the (k+1)-st repair under he assumption that only minimal repairs are performed. Then, we assign cost to each repair and find the value of n which minimized the long-run average cost for a fixed p under the condition that the life distribution F os the device is DMRL.L.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.63-70
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• 2000

Brown and Proschan(1983) introduced a model for imperfect repair. At each feilure of a device, with probability p, it is repaired completely or replaced with a new device(perfect repair), and with probability 1 - p, it is returned to the functioning state, but it is only recovered to its condition just prior to failure(imperfect repair or minimal repair). In this paper, we limit the number of consecutive minimal repairs by n. We find some useful properties about ${\mu}$$\_$k/, the expected time between the k-th and the (k + 1)-st repair under the assumption that only minimal repairs are performed. Then, we assign cost to each repair and find the value of n which minimizes the long-run average cost for a fixed p under the condition that distribution F of the device is DMRL.

• Journal of the Korean Institute of Rural Architecture
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• v.21 no.2
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• pp.1-10
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• 2019

This research aimed to identify characteristics of housing repairs for the weak class in rural area. Data are analyzed by the status according to year focusing on voluntary activity of the Korean Institute of Rural Architecture that is performing more than 10 years. The results are followings. First, approximately 63.3% of residents living in benefit houses are 70s and 80s in their age. They are weak in financial and physical and they have more than two weak points. Second, housing repairs were performed total 1,990 cases among 797 houses and average 2.5 cases per one house. Repair work in house interior is at the highest, the next is repair work in kitchen, repair work related to restroom, repair work for housing structure improvement, and repair work for insulation in order. Third, repair work required difficult work process and high cost is tend to decrease recently. However, work changing of wallpaper and papered floor and performing in outside is tend to increase because it has simple work process and low cost. Finally, barrier free needs to be more actively reflected for the weak class in rural area.

• Journal of Korean Institute of Industrial Engineers
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• v.4 no.1
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• pp.1-3
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• 1978

This paper presents a model for determining the optimal number of minimal repairs before replacement. The basic concept parallels the periodic replacement model with minimal repair at failure introduced by Barlow and Hunter, only difference being the replacement signalled by the number of previous minimal repairs performed on the unit. In the case of Weibull distribution, which is widely used as a general failure distribution, the optimal solution could be obtained numerically and seems more cost effective compared to the Barlow and Hunter's Policy II.

• The Journal of Fisheries Business Administration
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• v.13 no.1
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• pp.63-84
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• 1982

This study is an analysis of the growing trend from 1971 to 1980 on the four major fisheries in Korea; large powered purse seine, anchovy drag net, two boats large trawl and one boat large trawl. The main purpose of this study is to find some solutions against the problems which these fisheries are faced with, through the analysis of the growing trend of income, capital structure and main ratios of finance. According to the result of the analysis, the problems are as following: \circled1 Revenues per vessel was decreased when catches per vessel was decreased in 1979, 1980. therefore the increase ratio of the revenues per vessel was weakened from 1979. \circled2 Catches per vessel was decreased from 1979 in spite of the increase of gross cathes in its field. \circled3 Production costs in fishing, such as the cost of wages, fuels and repairs, was steadily up year by year. \circled4 Profitability was deteriorated from 1978. \circled5 productivity was lower from 1978. \circled6 Stability was lower from 1978. The solutions out of the above problems are as follows; \circled1 Fisheries resources must be fostered. \circled2 The numbers of vessels should be reduced according to the fisheries resources. \circled3 The precise amount of resources should be dynamically estimated. \circled4 The fishermen must be educated to reduce fishing cost such as the cost of fuels and repairs, etc. \circled5 The old vessels should be replaced. \circled6 The production efficiency should be promoted. \circled7 The rate of interest should be cut down to reduce financial cost.

• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.193-204
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• 2003

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate but remains the pattern of hazard rate unchanged. And the system undergoes only minimal repairs at failures between PM's. The expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Journal of Korean Society for Quality Management
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• v.22 no.3
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• pp.54-65
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• 1994

A hybrid warranty policy for a repairable item is considered. Assuming that minimal repairs ar e performed for failures during warranty period, present worth of warranty cost is derived from a supplier's viewpoint. An optimal preventive periodic replacement policy for the case is also derived from a user's viewpoint Numerical examples are presented in order to explain the results.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.25-35
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• 2011

Purpose: There are some advantages of the acrylic resin denture base ; appropriate strength, volume safety, simple processing apparatus, and low cost. But, it have a weakness for fracture by intense pressure or shock. However, the repairs for resin denture base are possible using various materials and techniques. There is a few studies in repairs for resin denture base, but not clinical researches. And there is no studies in absorbed saliva into the region of fracture and bond strength. This study is to observe re-bond strength of resin denture base after repairing under saliva absorption. Methods: The samples were made of heat curing resin and the rectangular parallelepiped specimens which were 50mm long, 10mm wide and 3mm high. The four different groups immersed in the artificial saliva for 2 weeks were prepared, 1) no repaired control samples, 2) immediately repaired samples, 3) repaired samples after 1 day dry, and 4) repaired samples after 3 days dry. The prepared samples were repaired by two different curing materials, self curing resin and heat curing resin method. Each groups composed of 10 specimens were experimented with the three point bending tests for bonding strength measuring Results: There were under condition absorbed in the artificial saliva and repaired by self curing resin method, repaired specimens after 1 day and 3 days dry groups had higher values of bonding strengths than control group, and bonding strengths of immediately repaired samples were similar to those of control samples (p<0.05). There were under condition immersed in the artificial saliva and repaired by heat curing resin method, immediately repaired samples showed similar values to bonding strengths of control groups, and repaired samples after 1 day and 3 days dry groups were lower than those of control group (p>0.05). Conclusion: In this study, the repairs for resin denture base were remarkably high values of bonding strengths than those of the past, and showed that have stable bonding strengths independent of saliva absorption of denture base, so present repairs for resin denture base can be performed, regardless of saliva conditions.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.287-288
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• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.