• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.905-908
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• 2008

시행 4년차를 맞이하는 BTL사업은 평가부문에서 일본의 PFI사업을 벤치마킹하여 도입되었는데 우선협상대상자 선정평가단계를 살펴보면, 기술적 요소는 시설사업별로 수정 보완되어 고시되는 반면 가격요소 부문은 여전히 최저가 낙찰제가 시행되고 있다. BTL사업의 가격부문은 임대형 사업이라는 특성을 감안해 볼 때 우선협상대상자 선정 방식에 대한 문제 제기와 더불어 향후 운영관리기간 동안 사업비 운용에 대한 우려가 높아지고 있다. 이에 본 연구에서는 계층분석기법을 활용하여 사업초기 우선협상 대상자 선정을 위한 우선순위 결정방법과 사업수행과정에서의 BTL사업비용 타당성 평가를 위한 평가모형을 정립하고자 한다. BTL사업 참여 경험이 있는 전문가 집단을 대상으로 평가 요소를 추출하였으며 평가요소 Levelling과 항목에 대한 Grouping을 통하여 3단계 평가모형을 정립하였다 ; 1단계 - LCC분석과 정부지급금 산출, 2단계 - 1단계 요인에 더하여 각각 분석기준 및 방법의 적정성, RFP요구조건 반영, 비용관련계획의 적정성, 산출비용의 적정성, 3단계 - 각각의 2단계 요인에 대하여 3개-5개의 요소.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.527-530
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• 2007

건설시장이 점차 전문화, 대형화되면서 건설요구품질수준이 높아지고 있다. 이러한 변화에 대응하기 위해 1960년대부터 프랑스, 영국, 미국, 일본 등은 목적물의 품질과 성능을 일정기간 보증하는 성능계약제도를 도입하여 요구품질을 확보하고 있다. 그러나 국내에서는 품질확보를 위해 하자담보책임제도를 강화하였으나, 하자 기준의 불명확성, 과도한 하자담보책임기간, 부실시공과 하자를 동일시하는 사회인식, 공사계약의 체결 및 이행과정에서 발주자 우위의 거래관행등의 문제가 제기되면서 시공자에게 과도한 책임문제가 발생하고 있다. 게다가 최근 FTA 협상에 따라 국내 BOT시장이 개방되면서 국제적인 경쟁이 불가피한 시점이다. 이러한 문제를 해결하기 위해서는 시공자의 기술혁신 유도와 명확한 책임이 규정된 성능보증계약제도를 도입하여 국제적인 경쟁력을 확보할 필요성이 있다. 따라서, 본 연구에서는 해외민간투자사업에 적용되고 있는 성능계약제도의 특성과 발주프로세스를 벤치마킹하여 국내 현황을 고려한 민간투자사업의 성능발주모델을 제안하였다.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• Earthquakes and Structures
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• 제20권4호
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• pp.377-388
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• 2021

Thin perforated Steel Plate Shear Walls (SPSWs) are among the most common types of seismic energy dissipation systems to protect the main boundary components of SPSWs from fatal fractures in the high-risk zones. In this paper, the cyclic behavior of the different circular hole patterns under cyclic loading is reported. Based on the experimental results, it can be concluded that a change in the perforation pattern of the circular holes leads to a change in the locations of the fracture tendency over the web plate, especially at the plate-frame interactions. Accordingly, the cyclic responses of the tested specimens were simulated by finite element method using the ABAQUS package. Likewise, perforated shear panels with a new perforation pattern obtained by implementing Topology Optimization (TO) were proposed. It was found that the ultimate shear strength of the specimen with the proposed TO perforation pattern was higher than that of the other specimens. In addition, theoretical equations using the Plate-Frame Interaction (PFI) method were used to predict the shear strength and initial stiffness of the considered specimens. The theoretical results showed that the proposed reduced coefficients relationships cannot accurately predict the shear strength and initial stiffness of the considered perforated shear panels. Therefore, the reduced coefficients should be adopted in the theoretical equations based on the obtained experimental and numerical results. Finally, with the results of this study, the shear strength and initial stiffness of these types of perforated shear panels can be predicted by PFI method.

• 농업과학연구
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• 제38권1호
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• pp.95-100
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• 2011

In the present study, effects of autohydrolysis treatment on the properties of rice hull were investigated. Two temperature condition such as $160^{\circ}C$ and $180^{\circ}C$ and thee treatment time such as 15 min, 30 min and 45 min were applied for autohydrolysis treatment. The pH of extract after autohydrolysis treatment decreased as increasing of the temperature and the treatment time. The ash content and the lignin content of rice hull were not decreased by the autohydrolysis treatment. The structure of rice hull after autohydrolysis treatment became more weak, the better efficiency of the fiberization with PFI-Mill was shown for the autohydrolysis treated rice hull with the higher temperature and the longer treatment time.

• 한국연소학회지
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• 제18권1호
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• pp.7-12
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• 2013

A quasidimensional program is developed for a four stroke cycle homogeneous GDI (Gasoline Direct Injection) engine. It includes models for spray, burning rate and chemistry to predict knock and emissions. With early injection a homogeneous GDI engine goes through spark ignited, turbulent premixed combustion as in PFI (Port Fuel Injection) engines. The cylinder charge is divided into unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and RPM conditions. Comparison is made between an empirical knock model and predictions by the chemistry model in this work.

• 펄프종이기술
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• 제33권1호
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• pp.38-44
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• 2001

The effects of refining load on the paper properties were investigated. HwBKP, SwBKP and SwUKP were refined with PFI mill at the load of 3.33 N/mm and 6.00 N/mm. Higher Scott bond was obtained at the higher refining load for three pulp used in this study. However any changes in the light scattering coefficient with the change of refining load were not observed. Although the effect of refining load on the formation index for SwUKP was not observed, higher refining load gave the better formation for HwBKP and SwBKP. The fiber mass and fiber crowding factor were not affected by the refining load. Higher apparent density and tensile index were obtained with the higher refining load. However, the higher refining load did not improve the tensile index at the same apparent density. The tear index was decreased with the increase of refining load.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.65-71
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• 1999

Recently new engine system is being required to cope with intensive emission restriction . For this reason, GDI(Gasoline direct injection) engine system which can satisfy both as good fuel economy as diesel engine and the performance to surpass PFI gasoline engine is being development . Since fuel injection system plays a significant role in GDI engine performance, the investigation of the spray characteristics injected from GDI injector above all is indispensable for GDI system development. In this study , spray developing shape was visualized using laser sheet with Nd : YAG laser and atomization characteristics was analyzed by measuring velocities and droplet size with PDA. Utilizing these results , the basic design factor of GDI injector can be offered.

• 교육녹색환경연구
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• 제6권1호
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• pp.25-48
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• 2007

Korean government implemented the Build-Transfer-Lease (BTL) mechanism since 2005 as one of the privatization methods to procure the social infrastructure with private investment. The mechanism was originally prepared 10 provide such public properties as education facilities, child-care facilities, old generation recuperation facilities, medical welfare facilities, military personnel's apartments, environment facilities, and lease apartments. Since 2005, a total of 13.5 trillion won-valued private fund has been directed to the public educational facilities, which occupies 58% of the total private investment in the facilities of the seven categories. However, many officials in the local public entities have anticipated that the local entities need to be restructured or downsized because of the privatization in stead of providing the educational facilities by governmental finance. The main objective of this study is to identify the appropriate technocrat organization structures to manage the privatization procedures.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.28-35
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• 2005

Fuel injection rate of an injector is affected by various injection conditions such as injection duration, fuel temperature, injection pressure, and voltage in LPG liquid injection systems for either a port-fuel-injection(PFI) or a direct injection(DI) in a cylinder. Even fuel injection conditions are changed, the air-fuel ratio should be accurately controlled to educe exhaust emissions. In this study, correction factor for the fuel injection rate of an injector is derived from the density ratio and the pressure difference ratio. A voltage correction factor is researched from injection test results on an LPG liquid injection engine. A compensation method of the fuel injection rate is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI-engine show that this system works well on experimental range of engine speed and load conditions. And the fuel injection rate is accurately controlled by the proposed compensation method.