• KIEAE Journal
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• 제13권1호
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• pp.159-165
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• 2013

Recently buildings are being constructed on the downtown area. In most building construction sites on the downtown area, the need for adequate material inventories are critical in order to avoid project delays and cost increases due to inappropriate deliveries of key materials. However immoderate material inventories cause increasing inventory cost. Therefore, we need a proper management material inventories. This research re-establishes the existing safety stock and analyzes relationship between safety stock and service level. It suggests an economical re-order point based on safety stock considering service level, various demand and delivery time.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.402-406
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• 1995

The purpose of this paper is to decrease shotcrete rebound losses and to produce economic effectiveness at the same time in construction. The mechanical properties and quick acceleration of various shoterete mixes were analyzed, which were intuenced by several accelerators and their amouts used. And the application and construction in the felds were evaluated. The shotcrete rebounds relied on the condition of construction rather than on the quality of materials, but it is found that the decreasing of the cost and time in shotcreting under the same condition was based on the rebounds which were affected by the accelerating capability of the accelerators. The application of the accelerator was limited by the condition of tunnel construction ; such as ground water, anti-corrosive, or anti-chemistry. It is important to choose a proper accelerator. Therefore, it is necessary that better accelerators which satisfly mechanical characteristics and economy are developed. Optimal working conditions should be announced to the workers and workers' skill be improved in the shotcrete construction feld as well.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.71-74
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• 2006

The introduction of materials and methods of construction which are appropriated to property of green roofs could be a decisive factor in a long-range durability and economical maintenance cost, moreover, it support to variety construction system and organization. In this paper I focused to assure the basic system for waterproofing materials and root barrier apply to green roof as searching the application of field condition. And I suggest proper waterproofing and root barrier as considering the mutual connection and plant growth. and it can be a standard model to adopt to domestic green roof system.

• 한국철도학회논문집
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• 제9권6호
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• pp.766-771
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• 2006

Railway stations are important facilities for transport of passengers and freights. The location of station have an effect on the efficiency of railway transport and operation. In this study, an inspection of the primary factors for station spacing in urban railway has been performed and a review for the propriety of the present states and further improvement has been carried. It may be helpful for proper decisions on the route planning in urban railway. Primary factors for station spacing are 1)train capacity, 2)competitiveness with other transportation, 3)accessibility and 4)construction cost, which is out of consideration in the inspection. From the result of this study, the proper station spacing is about 600m for the accessibility, more over 1.03km for the train capacity and more over 1.4km for the competitiveness with other transportation.

• 한국건설관리학회논문집
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• 제8권2호
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• pp.59-67
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• 2007

2001년 이후 주택가격의 상승에 따라 저소득층의 주거비 부담이 가중되고 있다. 이러한 문제를 해결하기 위해서 정부에서는 국민임대주택의 지속적인 공급과 더불어 민간주도의 공공임대주택의 확대공급을 적극 장려하고 있다. 주거비 보조제도는 선진복지국가에서 저소득층 세입자의 주거문제해결을 원조하는 방법의 하나로서 임대료 통제 및 공공임대주택의 공급과 더불어 3대 정책수단으로 인식되고 있다. 국내에서도 국민기초생활보장법에 임대료와 수선비 지원이 가능한 주거급여가 제한적으로 포함되어 있으나, 공공임대주택사업의 경우 아직 뚜렷하게 제시된 수익률에 관한 명확한 기준이나 체계가 없어 본격적인 제도발전을 위한 연구가 필요한 단계이다. 따라서 본 연구에서는 공공임대주택사업의 적정 수익률의 산정과 더불어 저소득층의 주거 비 지불능력을 고려한 주거비 보조금액의 기준 제시를 목적으로 한다.

• 소성∙가공
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• 제27권1호
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• pp.28-36
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• 2018

Electromagnetic forming is a type of high-speed forming process to deform a workpiece through a Lorentz force. As the high strain rate in an electromagnetic-forming simulation causes infeasibility in determining constitutive parameters, we employed inverse parameter estimation in the previous study. However, the inverse parameter estimation process required us to spend considerable time, which leads to an increase in computational cost. To overcome the computational obstacle, in this research, we applied two types of surrogate modeling methods and compared them to each other to evaluate which model is best for the electromagnetic-forming simulation. We exploited an artificial neural network and we reduced-order modeling methods. During the construction of a reduced-order model, we extracted orthogonal bases with proper orthogonal decomposition and predicted basis coefficients by utilizing an artificial neural network. After the construction of the surrogate models, we verified the artificial neural network and reduced-order models through training and testing samples. As a result, we determined the artificial neural network model is slightly more accurate than the reduced-order model. However, the construction of the artificial neural network model requires a considerably larger amount of time than that of the reduced-order model. Thus, a reduced order modeling method is more efficient than an artificial neural network for estimating the electromagnetic forming and for the rapid approximation of structural simulations which needs repetitive runs.

• 한국도로학회논문집
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• 제18권3호
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• pp.33-45
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• 2016

PURPOSES : Concrete pavement has been used in the construction of the Jungbu expressway in 1987. More than 60% of the pavement on the expressway is currently made of concrete, but most has been used far beyond their design life. Pavement life has been extended through routine maintenance or overlay. However, the structural capacity of the pavement has reached its limit, and extensive rehabilitation/reconstruction with long time traffic blocking should be considered. The three following issues on concrete rehabilitation/reconstruction will be discussed: (1) economic comparison of asphalt inlay and asphalt overlay, (2) economic comparison preventive overlay on a section which is currently good and routine overlay on the section which will be poor, and (3) economic analysis of early-strength concrete when it is used in concrete reconstruction. METHODS : First, various life cycle cost analysis tools were compared, and the proper tool for the extensive rehabilitation/reconstruction was selected. Second, a sensitivity analysis of the selected tool was performed to find the influential input variables, which should be carefully selected in the analysis. Third, three case studies, which can be issues in the rehabilitation/reconstruction of the expressway concrete pavement in Korea, were performed. RESULTS : Asphalt overlay without milling the deteriorated concrete showed 18~25% lower life cycle cost than the current asphalt inlay with milling. The good current preventive overlay on the section was economically justified within the scope of this study. The construction cost limit of the early strength concrete was suggested to be economical for 1, 3, and 7 days of construction alternative opening. CONCLUSIONS : CA4PRS was a viable tool for comparing various rehabilitation/reconstruction issue alternatives. Several concrete issues associated with the rehabilitation/reconstruction of the deteriorated concrete pavement were discussed as mentioned above.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.42-43
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• 2013

Nowadays, Precast Concrete is adopted on most of construction, because of shortening construction period and good quality. In precast concrete, steam curing is necessary for getting proper strength, but it causes much CO₂ and economc. Therefore, on this study, by using type III cement and hardening accelerator, early compressive strength was shown 13MPa for 6hr. From the result, removal form could be shorten. Furthermore, annual CO₂ was reduced as much as 24% and also annual cost was decreased as much as 12%.

• 설비공학논문집
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• 제20권3호
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• pp.167-174
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• 2008

Cost related to building equipment accounts for about 85% of the life cycle cost of buildings. Therefore proper selection of air-conditioning system is important for reducing the overall cost of buildings. In this study, medium capacity EHP and GHP for air-conditioning a building with a floor area of 1,200 $m^2$ are compared economically. To consider all the factors of initial and operation costs effectively, an annual equal payment method is proposed. For the initial cost, cost of equipment, construction, installation, electric facility, financial subsidy and tax cut is considered. Cost of basic electricity, energy(electricity and gas), space charge, labor, insurance and repair is considered for the operation cost. Under the assumptions made in this study, overall cost of EHP is less than that of GHP, but this is not absolute and different outcome may result if different assumptions are made. This study is useful for those who are interested in choosing an air-conditioning system that costs less for mid-size buildings with simple calculations.

• Journal of Communications and Networks
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• 제14권3호
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• pp.319-335
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• 2012

In this study, we design an applicable model enabling internet protocol television (IPTV) service providers to use a virtual network (VN) for IPTV service delivery. The model addresses the guaranteed service delivery, cost effectiveness, flexible control, and scalable network infrastructure limitations of backbone or IP overlay-based content networks. There are two major challenges involved in this research: i) The design of an efficient, cost effective, and reliable virtual network topology (VNT) for IPTV service delivery and the handling of a VN allocation failure by infrastructure providers (InPs) and ii) the proper approach to reduce the cost of VNT recontruction and reallocation caused by VNT allocation failure. Therefore, in this study, we design a more reliable virtual network topology for solving a single virtual node, virtual link, or video server failure. We develop a novel optimization objective and an efficient VN construction algorithm for building the proposed topology. In addition, we address the VN allocation failure problem by proposing VNT decomposition and reconstruction algorithms. Various simulations are conducted to verify the effectiveness of the proposed VNT, as well as that of the associated construction, decomposition, and reconstruction algorithms in terms of reliability and efficiency. The simulation results are compared with the findings of existing works, and an improvement in performance is observed.