• Wind and Structures
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• 제15권6호
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• pp.481-494
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• 2012

The greenhouse type metal structures are increasingly used in modern construction of livestock farms because they are less laborious to construct and they provide a more favorable microclimate for the growth of animals compared to conventional livestock structures. A key stress factor for metal structures is the wind. The external pressure coefficient ($c_{pe}$) is used for the calculation of the wind effect on the structures. A high pressure coefficient value leads to an increase of the construction weight and subsequently to an increase in the construction cost. The EC1 in conjunction with EN 13031-1:2001, which is specialized for greenhouses, gives values for this coefficient. This value must satisfy two requirements: the safety of the structure and a reduced construction cost. In this paper, the Navier - Stokes and continuity equations are solved numerically with the finite element method (Galerkin Method) in order to simulate the two dimensional, incompressible, viscous air flow over the vaulted roofs of single span and twin-span with eaves livestock greenhouses' structures, with a height of 4.5 meters and with length of span of 9.6 and 14 m. The simulation was carried out in a wind tunnel. The numerical results of pressure coefficients, as well as, the distribution of them are presented and compared with data from Eurocodes for wind actions (EC1, EN 13031-1:2001). The results of the numerical experiment were close to the values given by the Eurocodes mainly on the leeward area of the roof while on the windward area a further segmentation is suggested.

• 대한교통학회지
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• 제35권4호
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• pp.292-306
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• 2017

교통 소음비용은 피해비용 접근법 또는 회피비용 접근법으로 평가할 수 있다. 본 연구는 피해비용 접근법을 바탕으로 소음의 외부비용을 산정하는 방안을 제시하였다. 이를 위하여 네 가지를 검토하였다. 첫째, 한국의 실정에 맞는 소음피해 비용 원단위 41,737-601,910 원/(인 년)를 도출하였다. 둘째, 소음도 예측식을 이용하여 소음 영향권을 설정하였다. 셋째, 소음 영향권 내에서 소음에 노출된 인구와 실제 피해인구 비율의 곱으로 소음피해 인구를 추산하였다. 마지막으로 소음의 피해비용을 산출하는 과정을 간소하게 하는 소음 피해비용과 소음도간 관계식을 제시하였다. 이를 바탕으로 피해비용 접근법과 회피비용 접근법으로 소음저감 편익을 산출하고 비교함으로써 피해비용 접근법이 회피비용 접근법보다 이론적 정합성과 정책적 신뢰성이 높은 방법론임을 확인하였다.

• 청정기술
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• 제28권2호
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• pp.182-192
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• 2022

This study provides an overview of the production costs of methane and hydrogen via water electrolysis-based hydrogen production followed by a methanation based methane production technology utilizing CO₂ from external sources. The study shows a comparative way for economic optimization of green methane generation using excess free electricity from renewable sources. The study initially developed the overall process on the Aspen Plus simulation tool. Aspen Plus estimated the capital expenditure for most of the equipment except for the methanation reactor and electrolyzer. The capital expenditure, the operating expenditure and the feed cost were used in a discounted cash flow based economic model for the methane production cost estimation. The study compared different reactor configurations as well. The same model was also used for a hydrogen production cost estimation. The optimized economic model estimated a methane production cost of $11.22/mcf when the plant is operating for 4000 hr/year and electricity is available for zero cost. Furthermore, a hydrogen production cost of $2.45/GJ was obtained. A sensitivity analysis was performed for the methane production cost as the electrolyzer cost varies across different electrolyzer types. A sensitivity study was also performed for the changing electricity cost, the number of operation hours per year and the plant capacity. The estimated levelized cost of methane (LCOM) in this study was less than or comparable with the existing studies available in the literature.

• Journal of Construction Engineering and Project Management
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• 제6권2호
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• pp.8-15
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• 2016

Cost planning practices in the construction industry worldwide has gained much popularity in recent times due to economic recession and stringent measures that various procurement laws prescribe in most developed and developing countries. Nevertheless, these practices in developing countries such as Ghana are constrained with the existence of critical barriers that render them non-effective and hence, accounting for the numerous abandonment of both private and public projects. Consequently, this study was enunciated with the aim to examine the critical barriers to the practice of effective cost planning in the Ghanaian construction industry. Through an in-depth literature review and a pilot survey, questionnaires were designed and administered to quantity surveyors. Data generated from the field survey was subjected to principal component analysis. The findings of the study revealed weak cost planning knowledge base, poor cost databases and understanding, inadequate designs and planning and external conditions are the major barriers to cost planning practices in the Ghanaian construction industry. The need for this study cannot be doubted since it provides an insight for experts in the construction industry on the barriers of the practice of cost planning in the industry. The awareness of these barriers will therefore facilitate efficient and effective efforts to resolve them. A future study is thereby proposed by this study to explore effective cost planning practices in the Ghanaian construction industry that will ensure private and public stakeholders get value for their money invested.

• 한국콘텐츠학회논문지
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• 제18권1호
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• pp.132-142
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• 2018

본 연구는 기업 외부와 내부 환경요소들이 외부주체와의 협력 추진에 미치는 영향을 기업의 해외직접투자로서의 해외생산법인의 유무에 따른 차이와 함께 규명하고자 한다. 본 연구는 지금까지 협력(제휴)과 관련하여 그 결정요인에 대한 연구는 다양하게 분석이 이루어 졌으나, 해외직접투자의 유무에 따라 외부와 내부환경요소로 나뉘어 복합적 분석을 한 연구는 거의 찾아보기 어렵기 때문에 이를 규명하고자 하였다. 분석 결과로는 해외직접투자를 한 기업은 내부요인 중 설비투자의 효율, 가격경쟁력, 3년간 투자실적이 각각 유효한 제휴의 동기로 나타났고, 해외직접투자를 하지 않은 기업은 외부요인인 비용구조의 불확실성, 내부요인인 가격경쟁력, 투자실적이 유효한 결과로 나타났다. 결국, 본 연구에서는 해외직접투자를 한 기업과 해외직접투자를 하지 않는 기업은 모두 내부역량인 가격경쟁력과 3년간의 투자실적이 중요한 협력의 동기가 된다는 것과, 해외투자를 한 기업과 해외투자를 하지 않는 기업의 차이는 해외직접투자를 한 기업은 내부요인에서 설비투자의 효율이, 해외직접투자를 하지 않는 기업은 외부요인 중 비용구조의 불확실성이 각각 주요한 환경요인이 된다는 것을 규명하였다. 종합하여 보면, 본 연구의 시사점은 기업의 내부역량은 협력의 중요한 동기가 된다는 동시에 내부역량 강화는 또한 기업이 다른 기업과의 협력의 기회를 넓혀준다는 것이다.

• 한국공간구조학회논문집
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• 제7권3호
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• pp.133-140
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• 2007

대공간 구조물은 힘의 흐름을 자연스럽게 하고, 휨모멘트의 영향을 가능한 저감 시켜 면내력만으로 외부하중에 저항하는 역학 개념을 기초로, 구조 시스템의 효율성을 극대화시키는 형태저항형 구조이다. 구조물의 경제성 분석은 그 프로젝트의 실행을 결정할 수 있는 중요한 요소이다. 대공간 건설에는 일반 건물에 비해 많은 기술적 고려가 요구된다. 프로젝트의 성공적인 수행을 위해 타당성 검토 단계에서 구조물의 전 생애의 필수적인 요소에 대한 분석이 요구된다. 본 논문에서는 기존 대공간 구조물의 사례를 조사하며, 이를 통해 자료를 수집하고 공사비를 분석하였다. 본 연구는 대공간 구조의 데이터 베이스 구축을 위한 기본적인 데이터 제공을 목적으로 한다.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1005-1014
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• 2009

The Dual Unit Optimizer 2000 MWe (DUO2000) is put forward as a new design concept for large power nuclear plants to cope with economic and safety challenges facing the $21^{st}$ century green and sustainable energy industry. DUO2000 is home to two nuclear steam supply systems (NSSSs) of the Optimized Power Reactor 1000 MWe (OPR1000)-like pressurized water reactor (PWR) in single containment so as to double the capacity of the plant. The idea behind DUO may as well be extended to combining any number of NSSSs of PWRs or pressurized heavy water reactors (PHWRs), or even boiling water reactors (BWRs). Once proven in water reactors, the technology may even be expanded to gas cooled, liquid metal cooled, and molten salt cooled reactors. With its in-vessel retention external reactor vessel cooling (IVR-ERVC) as severe accident management strategy, DUO can not only put the single most querulous PWR safety issue to an end, but also pave the way to very promising large power capacity while dispensing with the huge redesigning cost for Generation III+ nuclear systems. Five prototypes are presented for the DUO2000, and their respective advantages and drawbacks are considered. The strengths include, but are not necessarily limited to, reducing the cost of construction by decreasing the number of containment buildings from two to one, minimizing the cost of NSSS and control systems by sharing between the dual units, and lessening the maintenance cost by uniting the NSSS, just to name the few. The latent threats are discussed as well.

• 산업경영시스템학회지
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• 제26권1호
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• pp.7-16
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• 2003

At present, company has to produce a product that consumer like with a competitive price, a good quality, and a fitting time to supply. Process control and quality control are very important to supply with a product uniformly and inexpensively. Process control is given much weight in the quality control in manufacturing system. Statistical process controls(SPC) that are used in process generally have major impact on manufacturing, product design activities, and process development potentially. Control charts in statistical process control method can be interpreted the data from quality characteristics in production process and discriminated between chance variation and assignable variation in process. In addition, control chart can be used to monitor the process output and detect when changes in the inputs are required to bring the process back to an in-control state. The models that relate the influential inputs to process outputs help determine the nature and magnitude of the adjustments required. In this paper, the characteristic of product quality is monitored by control chart during the machining process and construction of quality control cycle is considered to divide into two types in this case that different assignable causes lead to shifts having different magnitudes. Then we are intended to find a process shift magnitude which has economical quality cost policy and are considered to quality cost functions to find a process shift magnitude. Those costs are categorized into the well-known categories of prevention, appraisal, and internal failure and external failure. This paper ends with numerical examples that demonstrate the usefulness of the model.

• Asia pacific journal of information systems
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• 제33권2호
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• pp.298-317
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• 2023

This study is about the attitudes and intentions of consumers considering the usage of O2O application (app) under the COVID-19 situation. By integrating TAM and TPB as a theoretical background, we selected VPC (various product choice) and PII (product information intensity) as new functional external variables that have a positive effect on new system called O2O commerce. We also applied the transaction cost theory to investigate the obstacle of O2O business. We conducted a survey of consumers in large cities in the Korean market. As a result of this study, it was found that the more O2O app users recognized the influence of SN (subject norms), the more useful O2O app was, the more it led to a change in attitude and usage intention was positively significant. In addition, as the O2O app was easy to use and useful, and the SN was recognized, the user's attitude was positive. On the other hand, it was also found that the transaction cost that consumers have to pay had a negative effect on usage intention. Additionally, VPC and PII have been shown to positively influence on usefulness of O2O apps.

• 한국시스템다이내믹스연구
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• 제10권1호
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• pp.77-95
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• 2009

The ever-increasing government budget constraints have led to a continued decline in the increase rate for defense spending, and the government's 5-year National Fiscal Management Plan has served to reinforce the verification and validation procedures for the Force Improvement Programs (FIP) budget requirements and performance. Additionally, as large programs are controlled in accordance with the Total Program Cost Management Guidelines, timely and credible feasibility study and performance measurement need to be conducted. Due to these internal and external circumstances, needs have surged for feasibility and economic effectiveness study for big ticket projects in the FIP sector, with an increasing number of studies conducted by external research institutes. However, questions have been raised regarding the credibility and thoroughness of the program analyses performed by these research institutes due to various restrictions. This paper analyzes and identifies the structural limitations and problems using a systems thinking approach, and examines the systemic characteristics of the program analysis system. It also presents policy intervention recommendations based on the theory of systems thinking, a method to regularize and reinforce the program analysis system. Policy interventions recommended to ensure alignment of the external studies to the clear analysis objectives and resolve the bottlenecks in the external analysis include training those in charge of external study commissioning for a short term intervention, and increasing the number of research institutes and consulting agencies utilizing analysis and evaluation experts who transition to the private sector from the military for a long term intervention. additionally presented are strategies and policy alternatives to best utilize these policy interventions. They will contribute to the stable funding of Force Improvement Programs and efficient utilization of defense budget.