• Corrosion Science and Technology
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• 제10권2호
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• pp.60-64
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• 2011

Lean duplex stainless steels have been developed in Korea for the purpose of being used in the seawater systems of industry. There are also many important seawater systems in nuclear power plants. These systems supply seawater to cooling water condenser tubes, heat exchanger tubes, related pipes and chlorine injection systems. The flow velocity of some part of seawater systems in nuclear power plants is high and damages of components from corrosion are severe. The considered lean duplex stainless steels are STS329LD (20.3Cr-2.2Ni-1.4Mo) and STS329J3L (22.4Cr-5.7Ni-3Mo) and PRENs of them are 29.4 and 37.3 respectively. Physical, mechanical and micro-structural properties of them are evaluated, and electrochemical corrosion resistance is measured quantitatively in NaCl solution. Critical Pitting Temperatures (CPT)s are measured on these alloys and pit depths are evaluated using laser microscope. Long period field tests on these alloys are now being performed, and some results are going to be presented in the following study.

• 동력기계공학회지
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• 제19권2호
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• pp.40-48
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• 2015

As advantages of LPG-DI engine, LPG is directly injected into combustion chamber during compression stroke to reduce compression temperature, prevent knock and spontaneous combustion, and adjust engine output using the amount of directly injected fuel, thereby reducing pumping loss caused by throttle valve. Stratified charge can be supplied nearby spark plugs to allow for overall lean combustion, which improves thermal efficiency and can cope with problems regarding emission regulations. In addition, it is characterized by free designing of intake manifold. Despite the fact that LPG-DI has many advantages as described above, there is lack of detailed investigation and study on spray characteristics, combustion flame characteristics, and ignition probability. In this study, a visualization experiment system that consists of visualization combustion chamber, air supply control system, emission control system, LPG fuel supply system, electronic control system and image data acquisition system was designed and manufactured. For supply of stratified charge in the combustion chamber, alignment of injector and spark plugs was made linear.

• 한국건설관리학회논문집
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• 제5권4호
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• pp.71-78
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• 2004

최근 우리나라의 건설 환경은 도심지 내 대형 건설공사가 증가하는 추세이며, 건설공사 관리 요소 중 기존 골조공사의 관리 중요성에 더하여 마감공사관리의 중요성이 부각되고 있다. 마감공사의 체계적인 관리를 위해서는 마감공사의 공정 중 자재 양중 측면, 공사기간 측면에서 많은 부분을 차지하고 있는 세대 내 가구공사의 관리체계 정립이 필수적이라 할 수 있다. 본 연구에서는 초고층 주거건축을 위한 마감공사 중 양중 측면에서 주 고려 대상이 되고 있는 가구공사의 관리체계를 정립하기 위하여, 적시생산(Just-In-Time)방식과 린건설(Lean Construction)의 개념을 도입하였다. 이를 바탕으로 가구공사의 프로세스를 분석하고 그에 따른 개선방안을 제시하였다. 이러한 분석과 개선방안의 제시는 마감공사의 원활한 흐름을 유도할 수 있으며, 또한 공사기간을 단축하고 공사비용을 절약함으로써 프로젝트의 성공에 기여할 수 있다.

• 한국건설순환자원학회논문집
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• 제6권4호
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• pp.75-81
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• 2012

콘크리트포장에서 린콘크리트 기층용 재료 생산을 위한 골재 파쇄시 골재의 입도조정을 위하여 세골재로 천연모래를 투입하고 있으며, 천연모래의 투입비는 혼합골재의 중량비로 30~40%를 투입하고 있다. 린콘크리트용 재료생산을 위한 세골재로 적용중인 천연모래는 골재원의 고갈추세로 골재를 공급하기가 어려워지고 있으며, 도로 건설비용에 천연모래 구입비가 포함되어 있다. 그러므로, 천연모래를 대체할 수 있는 방안으로 산업부산물인 스크리닝스를 적용하여 세골재원의 고갈해소와 아울러 공사원가의 절감에 기여하고자 본 연구를 실시하였다. 린콘크리트용 세골재로 스크리닝스를 사용한 경우와 모래를 사용한 경우를 비교 분석한 결과, 세골재로 스크리닝스를 적용한 경우가 모래를 사용한 경우보다 일축압축강도가 우수한 것으로 나타났다. 시험시공 및 평판재하, 비파괴 포장표면 처짐, 밀도, 강도 등을 추적조사를 실시한 결과, 스크리닝스를 사용한 경우가 천연모래를 사용한 경우에 비하여 일축압축강도 및 지지력 측면에서 높게 나타났다. 따라서, 스크리닝스를 린콘크리트에 현장적용시 건설예산절감 및 자원재활용, 환경보호에 기여할 것으로 기대된다.

• International Journal of Computer Science & Network Security
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• 제21권3호
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• pp.245-256
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• 2021

Poor logistical infrastructure and agri-food supply chain management leads to significant food waste in logistic system. The concept of the sustainable value added agri-food chains requires defined approach to the analysis of the existing situation, possible improving strategies and also assessment of these changes impact on further development. The purpose of research is to provide scientific substantiation of theoretical and methodological principles and develop practical recommendations for the improvement of the agri-food logistics distribution system. A case study methodology is used in this article. The research framework is based on 4 steps: Value Stream Mapping (VSM), Gap and Process Analysis, Validation and Improvement Areas Definition and Imitation Modelling. This paper presents the appropriateness of LEAN logistics tools using, in particular, Value Stream Mapping (VSM) for minimizing logistic losses and Simulation Modeling of possible logistics distribution system improvement results. The algorithm of VSM analysis of the agri-food supply chain, which involves its optimization by implementing the principles of sustainable development at each stage, is proposed. The methodical approach to the analysis of possible ways for optimizing the operation of the logistics system of the agri-food distribution is developed. It involves the application of Value Stream Mapping, i.e. designing of stream maps of the creation of the added value in the agri-food supply chain for the current and future state based on the minimization of logistic losses. Simulation modeling of the investment project on time optimization in the agri-food supply chain and economic effect of proposed improvements in logistics product distribution system functioning at the level of the investigated agricultural enterprise has been determined. Improvement of logistics planning and coordination of operations in the supply chain and the innovative pre-cooling system proposed to be introduced have a 3-year payback period and almost 75-80% probability. Based on the conducted VSM analysis of losses in the agri-food supply chain, there have been determined the main points, where it is advisable to conduct optimization changes for the achievement of positive results and the significant economic effect from the proposed measures has been confirmed. In further studies, it is recommended to focus on identifying the synergistic effect of the agri-food supply chain optimization on the basis of sustainable development.

• 한국IT서비스학회지
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• 제13권1호
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• pp.87-101
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• 2014

This paper is a study on information Quality of Domestic Call Center Information System; recognized the importance of information quality and analyzed the impact on use and satisfaction of users following information quality which is a success element and ultimately the impact on user's performance by expanding information quality evaluating model by Jeong-Woo Lee et al.(2003) who reflected domestic special corporate culture based on information system success model by DeLone and McLean(2003). This is meaningful in providing theoretical foundation for efficient information quality supply and building quality management system at call center in future and provides hints to be considered in raising understanding of consultants on provided information and arranging ground that can utilize it in a timely manner.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.127-134
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• 2004

Three-dimensional numerical investigations are carried out to understand the combustion characteristics inside a DLN(dry low NOx) utility gas turbine combustor during the combustion mode change period by applying transient fuel flow rates in fuel supply system as numerical boundary conditions. The numerical solution domain comprises the complex combustor liner including cooling air holes, three types of fuel nozzles, a swirl vane, and a venturi. Detailed three-dimensional flow and temperature fields before and after combustion mode changeover have been analyzed. The results may be useful for further studies on the unfavorable phenomena, such as flashback or thermal damage of combustor parts when the combustion mode changes.

• 한국표면공학회지
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• 제49권6호
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• pp.477-485
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• 2016

As expensive and valuable metals being used in electronic and semiconducting industries are abandoned as industrial wastes after use of them, it is required to recover them from e-wasted electronics parts. Gold which is used for printed circuit boards or electronic equipments, accessories, etc., is one of e-Wasted materials and recently indium, gallium, zirconium, cobalt, molybdenum and lithium are bacome valuable metals to be recovered from the e-wastes. Since the amount of precious metals is now being faced with scarcity, lean too much on area and instability of supply, and industrial demands are rapidly increasing every year, it becomes more important to recover the valuable metals from the industrial wastes. In this review, we introduced technologies and research trend of the recovery processes of valuable metals from the e-wastes in high-tech devices over the world.

• 한국분무공학회지
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• 제28권1호
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• pp.24-31
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• 2023

In this study, characteristics of a propane-air premixed flame sin DC electric field was investigated. The stainless steel Bunsen burner and the stainless steel ring were used as electrode, and the high voltage supply was used for applying electric field. Flammability range increased significantly when the positive voltage was applied because of extension of LBO limit, while it shrank when the negative voltage was applied. The reason for this was not much related to the burning velocity, but the induced flow around the burner by electric field. withNOx production slightly increased after positive voltage was applied in identical equivalence ratio. Nevertheless, it was advantageous to apply the positive electric field to reduce the NOx since the extension of LBO limit makes the burner possible to operate in very low equivalence ratio.

• 대한안전경영과학회지
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• 제15권3호
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• pp.151-161
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• 2013

This paper proposes a strategic model of linkage between productivity metrics and financial accounting metrics to properly evaluate the financial effect of TPM activities and the business performance. This linkage strategy provides a connection tool for clear communication between factory-level and headquarters that the metrics proposed by this paper ultimately improves a quality of support from the management by receiving the factors required for productivity activities in the practical field. This factor includes such as equipment, raw materials and labors. Here, we propose that chain reaction models using break down structure of productivity metrics and financial metrics enhance the knowledge sharing of KPI (Key Performance Indicator) which generally tend to create oversimplified communication between management in headquarters and employees in the practical fields. The productivity metrics include OEE(Overall Equipment Effectiveness) of TPM (Total Productive Maintenance), OLE (Overall Labor Effectiveness) of PAC(Performance and Analysis and Control) activities, and OYE (Overall Yield Effectiveness) of TMM(Total Material Management) activities. The financial accounting metrics include ROE(Return on Equity), ROA(Return on Asset), and AVR(Added-Value Rate). The suggested chain reaction model selects the financial metrics as initial stage and branch down until final stage of productivity metrics. When demand exceeds supply, an ideal speed rate, the lean OEE strategy can be initially applied to reduce the gap between the demand and supply, then apply variable costing to estimate correct amount of operating profit. In addition, the paper presents a new type of model for linkage between financial accounting metrics including CAPEX(Capital Expenditure), OPEX(Operating Expenditure), EVA(Economic Added Value), DCL(Degree of Combined Leverage), and TPM productivity activities including AM(Autonomous Maintenance), PM(Preventive Maintenance), MP(Maintenance Prevention) and QM(Quality Maintenance). In order to support the evidence of proposed linkage strategy, a case analysis on 52 projects from national TPM contest from 2011 to 2012 is analyzed. The case presents the classification of CAPEX and OPEX activities from TPM, and proposes the correct implementation of financial effect for TPM projects.