• 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.

• Steel and Composite Structures
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• 제43권3호
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• pp.375-388
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• 2022

Nibellen structural system is a novel resilient bracing system based on the application of Bellville disks and Nitinol rods. The cyclic behavior of Nibellen assembly was obtained, and the design equations were developed based on the available literature. Seismic performance of the system was then studied analytically. Two groups of buildings with different lateral force resisting systems were designed and studied: one group with the Nibellen system, and the other with the special concentrically braced frame system. Each building group consisted of 5-, 10-, and 15-story buildings. The Design-Base-Event (DBE) and Maximum Considered Event (MCE) were considered as the seismic hazard, and a suite of seven ground motions were scaled accordingly for response history analyses. Finally, the resiliency of the buildings was studied by obtaining the functionality curve of the buildings before and after the seismic event. The construction cost of the 5-story building with Nibellen bracing system increased but the post-earthquake cost decreased significantly. The application of Nibellen system in the 10- and 15-story buildings reduced both the construction and repair costs, considerably. Resiliency of all the buildings was improved when Nibellen system was used as the lateral force resisting system.

• 현장농수산연구지
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• 제25권4호
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• pp.67-77
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• 2024

This study analyzed the profitability and diagnosed business performance of fruit and vegetable (cherry tomatoes, tomatoes, strawberries, cucumbers) businesses targeting young farmers participating in the youth business incubation center of A Smart Farm Innovation Valley. The purpose of this is to provide basic data for decision-making by prospective young entrepreneurs. As a result of the analysis, Smart Farm Innovation Valley had the advantage of having a fixed rental fee. As a result, it was analyzed that various costs such as depreciation of large farm equipment, depreciation of farming facilities, repair and maintenance costs, land rent, floating capital service cost, fixed capital service cost, and land capital service cost are being reduced. However, excessive input of labor, water, electricity, other materials, and fertilizer costs was being made. Guidance to reduce these costs is expected to make a significant contribution to expanding the influx of young farmers.

• 한국주거학회논문집
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• 제23권5호
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• pp.9-18
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• 2012

For the quality of life and independent living of the disabled, government has provided financial supports for housing renovation and improvement projects for the disabled. However, there is a limited budget which should be properly distributed for a number of disabled families. Therefore, it is important to decide which parts should be improved for housing renovation for the disabled. Financial and administrative supports for the renovation should improve housing conditions in terms of accessibility (barrier free) and should bring the better comfort for the disabled. The purpose of this study was to describe the characteristics of the housing renovation projects, to investigate whether the renovation influence occupants' satisfaction, and to examine which factor such as renovation cost and renovation elements would influence the degree of satisfaction for residents with disabilities. Participants of this study are limited to the recipients of financial supports for housing renovation and refurbishment from City of Seoul and Ministry of Health and Welfare. A total of 153 cases were analyzed using post occupancy survey and the project cost data for the participants' housing were collected. Overall, more cost were used for modification for housing condition than for removal of architectural barriers. Housing type and physical condition of the housing affects cost for renovation more significantly. Overall the improvement cost is positively related to resident's satisfaction using regression analysis. In addition, it is important to meet the residents specific needs for repair, refurbishment, and renovation of housing.

• 한국농촌건축학회논문집
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• 제13권1호
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• pp.37-44
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• 2011

The maintenance works for brick-structured buildings are a new field in Korea, and practical cases are yet inadequate so that such works may cause adverse effects of damaging the buildings after all. Therefore, this study has extracted a preservation technology believed to be most desirable in minimizing the damage to the original state of the buildings and preserving the value as the cultural assets through maintenance work details from 1986 to 2010 regarding brick-structured buildings designated as cultural properties. Firstly, a brick replacement method of using the brick used at the time of construction is efficient in replacement and repair of brick material for preserving value of cultural assets and minimizing damage of the original form. Secondly, use of lime mortar through material analysis is effective in repair of masonry joint and mortar but it is not used often due to high experimental cost. Finally, reinforcement of structure using a form for a building with severe damage is most efficient when considering additional problems. However, damage on the original form of a building can be minimized and value of a building can be preserved only when consideration on sufficient case analysis, materials to be used, and conditions of a building is supported.

• 한국산업융합학회 논문집
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• 제10권4호
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• pp.207-211
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• 2007

The durable lifetime of RC structures is shortened by various reasons, which are the generation of cracks in construction and service term, the exterior deterioration according to climatic condition, the surface damage due to chloride attack and the corrosion of reinforced bars. The durability of concrete structures is nevertheless able to be increased by the method and the material of reinforcement and repair. The epoxy resin is widely used for reinforment and repair of concrete because of the superiority in mechanical property, adhesive property, abrasion resistance, impact resistance and chemical resistance. The epoxy cement mortar with hardening agent has a lot of disadvantages that are troublesome mixing work, weakened weatherability and high cost for hardening agent. In this study, the mix proportion of mortar is presented just only with epoxy resin and some admixtures, and the test result of mortar without hardening agent shows the higher strength than the mortar with hardening agent. In the mix proportion, the weight of epoxy resin must be less than 15% of the unit weight of cement, and 10% of unit weight of cement is adequate for the weight of admixtures.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2000-2006
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• 2000

The enhancement of service life of damaged or cracked structures is currently major issue to the researchers and engineers. In order to improve the life of cracked aging aircraft structures, the repair technique which uses adhesively bonded boron/epoxy composite patches is being widely considered as a cost-effective and reliable method. This paper is to study the performance of the bonded composite patch repair of a plate containing an inclined central through-crack. A 3-dimensional finite element method having three layers to the cracked plate, composite patch and adhesive layer, is used to compute the stress intensity factor. In this paper, the reduction of stress intensity factors near the crack-tip are determined to evaluate the effects of various non-dimensional design parameter including composite patch thickness, and material properties of the composite patch and thickness of the adhesive layer, materials of patch etc., and the crack length, Finally, The problem of how to optimize the patch geometric configurations has been discussed.

• Geomechanics and Engineering
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• 제20권6호
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• pp.497-503
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• 2020

In the Kingdom of Saudi Arabia, the shallower depth of the earth's crust is composed of loose dune or beach sand with soluble salts. The expansive behavior of salt bearing soil, fluctuation of ground water table and extreme environmental conditions offer a variety of geotechnical problems affecting safety and serviceability of the infrastructure built on it. Despite spending money, time and other resources on repair and rehabilitation, no significant attention is paid to explore the root causes of excessive differential settlement and cracking to these facilities. The scientific solution required to ensure safety and serviceability of the constructed infrastructure is to improve the strength and durability properties of the supporting ground. In this study, shredded plastic is employed as a low cost and locally available additive to improve strength characteristics of the desert sand. The study shows a remarkable increase in the shear strength and normal settlement of the soil. A seven (07) degree increase in angle of internal friction is achieved by adding 0.4 percent of the shredded plastic additive. The effect of different proportions and sizes of the plastic strips is also investigated to obtain optimum values. Such a long-lived solution will seek to reduce maintenance and repair costs of the infrastructure facilities laid on problematic soil along with reduction of environmental pollutants.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제27권3호
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• pp.137-155
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• 2020

Redundancy is commonly employed to improve system reliability. In most situations, components in the standby configurations are assumed statistically similar but independent. In many realistic models, all parts in standby are not treated as identical as they have different failure possibilities. The operational structure of the system has subsystem-1 with five identical components working under 2-out-of-5: G; policy, and the subsystem-2 has two units and functioning under 1-out-of-2: G; policy. Failure rates of units of subsystems are constant and assumed to follow an exponential distribution. Computed results give a new aspect to the scientific community to adopt multi-dimension repair in the form of the copula.

• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.203-212
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• 2007

지금까지 재 제조에 필요한 자동차 중고부품은 주로 정비업체에서 회수하여 사용하였으나, 회수체계가 정비되어 있지 않아 자동차 중고부품 수집에 많은 시간과 경비가 소요되었으며, 폐차업체에서 생산되는 많은 자동차 중고부품은 재 제조에 활용되지 못하고 있는 실정이다. 본 시스템은 폐차장, 정비업체 등에서 자동차 중고부품 정보를 입력하고, 재 제조업체에서는 이들 정보를 이용하여 재 제조에 필요한 자동차 중고부품을 회수할 수 있게 함으로써 자동차 중고부품 회수체계를 확립하고 자동차 중고부품의 안정적 수급 방안을 마련할 수 있도록 설계하였다. 본 시스템은 자동차 부품 재 제조에 필요한 자동차 중고부품을 수집 관리하기 위한 물류정보시스템으로 DISRMPA(Distribution Information System for Recovery and Management of used Parts of an Automobile)라고 부른다.