• 한국분무공학회지
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• 제24권2호
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• pp.51-57
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• 2019

In this study, the spray atomization characteristics of urea injector used in SCR system for construction machinery was analyzed, and the uniformity index at the front of mixer and NOx conversion efficiency were evaluated through numerical analysis. Spray visualization and droplet size/velocity measurement were performed and the measured results were used to verify the spray analysis model to calculate the uniformity index in the exhaust gas after-treatment system. For the flow analysis, STAR-CCM, a three-dimensional CFD, was used and the uniformity index of the SCR system at the front of the mixer was calculated using the droplet dissociation model and the wall collision model. Finally, the DeNOx performance for the average condition of the NRTC driving mode was calculated to understand the NOx conversion efficiency reflecting the exhaust gas temperature. The simulation results show that the uniformity index at the front of mixer was calculated as 0.862 and DeNOx efficiency was 75.9%.

• Biotechnology and Bioprocess Engineering:BBE
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• 제4권1호
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• pp.51-58
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• 1999

A mathematical model for a three phase fluidized bed bioreactor (TFBBR) was proposed to describe oxygen utilization rate, biomass concentration and the removal efficiency of Chemical Oxygen Demand (COD) in wastewater treatment. The model consisted of the biofilm model to describe the oxygen uptake rate and the hydraulic model to describe flow characteristics to cause the oxygen distribution in the reactor. The biofilm model represented the oxygen uptake rate by individual bioparticle and the hydrodynamics of fluids presented an axial dispersion flow with back mixing in the liquid phase and a plug flow in the gas phase. The difference of setting velocity along the column height due to the distributions of size and number of bioparticle was considered. The proposed model was able to predict the biomass concentration and the dissolved oxygen concentration along the column height. The removal efficiency of COD was calculated based on the oxygen consumption amounts that were obtained from the dissolved oxygen concentration. The predicted oxygen concentration by the proposed model agreed reasonably well with experimental measurement in a TFBBR. The effects of various operating parameters on the oxygen concentration were simulated based on the proposed model. The media size and media density affected the performance of a TFBBR. The dissolved oxygen concentration was significantly affected by the superficial liquid velocity but the removal efficiency of COD was significantly affected by the superficial gas velocity.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 공동학술발표회
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• pp.244-244
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• 2017

최근 4차 산업혁명의 주요 변화동인 중 하나인 "빅데이터" 기술을 활용하여 다양한 산업에 적용하기 위한 연구가 활발히 이루어지고 있다. 선박이 운항 하면서 발생되는 데이터에는 1해리 당 소모연료량, 엔진출력, 대지속력, 대수속력, Main Engine RPM, FOC, SFOC, DFOC 등의 여러 지표가 있다. 본 논문에서는 Gathering 데이터간의 민감도를 분석 하여 각 변수들간의 영향력을 판단하여 선박 운항 관련 에너지효율에 대한 주요 변수를 분석 하고, 분석 기법 중 수학 모델을 이용한 근사 모델을 생성 하여, 실측 데이터와 예측결과를 비교분석 하였다. 이를 통해 빅데이터 분석 기술을 활용하여 운항 선박의 에너지효율 관련 변수 간 민감도 확인, 근사모델을 이용한 연비 관련 지표 예측에 활용 할 수 있는 가능성을 확인 하였다.

• 한국유체기계학회 논문집
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• 제7권6호
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• pp.7-14
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• 2004

A new electrostatic rotary atomizing painting equipment using air turbine was developed for high transfer efficiency. Based on the overall design requirements of painting equipment, basic design specifications of the equipment parts such as air turbine and atomizing disk ate defined from the present conceptual design model. Air turbine is designed with the section profile of NACA airfoil, and its internal flow field is analyzed by commercial CFD code. Atomizing disk is designed to achieve the ligament type spray of paint with the use of visualization technique. Various experiments and tests are conducted to investigate the spray and the transfer characteristics of newly-designed painting equipment, and the measurement results are compared with the those of conventional painting equipments. The comparison results show the present painting equipment is superior to the conventional ones in the aspects of transfer efficiency and coating surface characteristics.

• 한국항해항만학회지
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• 제30권4호
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• pp.267-275
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• 2006

Due to the growth of container traffic and port competition, ports have increasingly been under pressure to improve their efficiency in port operation and port management for competitive edge. The purpose of this study is to compare the technical efficiency among major container terminals in China, Korea and Singapore using Data Envelopment Analysis (DEA). This paper analyses the returns-to-scale using the output orientation of VRS and CRS model. The benefits of this study examining the relative performance of container terminals will enable container terminal operating companies or port policy makers in those countries to identify current slacks and to set up a proper port management and operation plan to improve their productivity.

• 융합보안논문지
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• 제11권1호
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• pp.39-48
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• 2011

QoS(Quality of Service)는 ITU-T Rec. E.800에 의해 서비스를 사용하는 형태, 특성 그리고 요구 수준에 따라 사용자의 요구에 부응하여 제공할 수 있는 네트워크 서비스의 성능지표로 표현된다. 네트워크를 활용하는 정보시스템에서 최종적인 목표는 요구되는 시간내에 목적하는 성능을 확보하는 것이다. 본 연구에서 제안하는 보안 QoS 프레임워크는 측정 메트릭스, 측정스케쥴, 측정도구, 측정의순서, 측정 결과분석에 관련된 사항으로 구성된다. 보안 QoS에서 네트워크보안의 정보보호기능과 시스템기능을 분리하여 관리하지 않고 연계하여 종합 메커니즘으로 구성 및 적용할 경우 종합적인 정보보호 효율은 시너지효과로 나타난다. 본 연구는 정보보호기능과 제반 시스템기능을 연계하여 정보보호기능을 적용했을 경우의 연동메커니즘 구현방법 개발과 그 성과를 측정하기 위한 것이다. 본 연구에서 제안한 네트워크 보안 효율성 제고를 위한 보안 QoS측정방안 연구 방법론을 통해 체계적인 측정환경을 설계할 경우 운용시스템상에서 보안 효율성 측정이 가능함이 입증되었고 측정 메커니즘을 통해서 개선된 네트워킹기능과 정보시스템 기능을 위한 효율성제고 방법론 개발이 가능함을 보여주고 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.51-56
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• 2012

본 논문은 고파워 전자소자의 폐열로부터 에너지 수확을 목적으로 하는 열전생성기의 생성효율과 열적 성능에 대하여 논한다. 열경계저항을 포함하는 열전모델이 적용되어 생성효율과 고전력 전자소자의 junction 온도를 예측하였고 그 결과는 실험치로 검증되어진다. 검증결과는 예측치와 계측치의 오차가 작음을 보인다. 검증후 열전모델은 다양한 로드저항과 열원의 열율에서 생성효율, 열전생성기 양면의 온도차, 소자의 junction 온도를 예측한다. 본 연구는 로드저항이 생성효율, 열전생성기 양면의 온도차, junction 온도에 미치는 영향에 대해서도 탐구한다.

• 한국항해항만학회지
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• 제44권2호
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• pp.119-127
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• 2020

In this study, the current state of management efficiency of ocean carriers in Korea and the factors affecting them were analyzed. The purpose of this research is to enhance global competitiveness of ocean carriers by presenting suggestions that can improve management efficiency based on the analysis results. The measurement of management efficiency was made using the DEA model. The results of testing the adequacy of the input and output variables used are as follows. Appropriate inputs are total assets, cost of goods sold, charter expenses, sales and general management expenses, and interest expenses. Appropriate variables are sales, operating income, and operating cash flow. According to the analysis results of the DEA model by these variables, inefficient carriers (78%) are nearly four times more than efficient carriers(22%). However, container carriers have the most improved management efficiency compared to 2016 and 2017. According to the panel regression analysis, the charter rate has the greatest negative impact on efficiency (CRS), and the debt rate has a significant negative impact. Thus, it appears that reducing the charter size and the debt-to-sale rate facilitate improvement of the management efficiency of ocean carriers. Additionally, the pre-sales tax return rate, value added rate, total asset turnover rate, and the scale variable and interest coverage rate have a positive (+) effect. Thus ocean carriers should restore their global competitiveness by improving management efficiency by securing stable cargoes increasing sales profitability from the cost management perspective, increasing productivity, and enhancing the efficiency of their total assets through efficient fleet management.

• 한국소음진동공학회논문집
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• 제24권6호
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• pp.452-461
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• 2014

Two stroke low speed diesel engines that have many advantages such as high thermal efficiency and durability have been widely used for marine engine. However, it is also true that many problems have occurred due to the high explosion pressure and severe operating environment. Especially problems of shaft damage etc. intensively occurred due to the phenomenon of crankshaft exceeding the allowable stress, including the shaft vibration of the engine model in the early stage. In this study, the crankshaft fracture phenomenon of early engine model was evaluated and analyzed by using up-to-date torsional vibration calculation program and measurement instrument. And this was numerically shown.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.423-428
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• 2005

If the load of constructing vehicles during the construction work acts on the road or the ground surface on the soft ground, due to the excess stresses in soils the trafficability of the vehicles influences the constructing efficiency, constructing period and so on. Stress distribution in soils is the very important element to design and to solve the problems of settlement, safety of foundations and trafficability of constructing vehicle in civil engineering. This research represents the comparative estimation of the actual and theoretical measurement on the underground stress of outer layer for each soil after the observation of each top soil layer for its vertical and horizontal stress in (1)homogeneous sand ground (2) weak stratum with the sand soil (3) weak stratum with gravel of the soil model, and it also investigates the effect of subsidence of ground by the repeated load. The underground stress turn out to be different in the value of theoretical and actual measurement after the trial examination of model.