• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1999년도 추계학술대회논문집
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• pp.111-121
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• 1999

From the traffic analyses, and model constructions and verifications for speed prediction on the freeway ramp junctions with 70mph speed limit, the following results obtained: ⅰ) The traffic flow distribution showed a big difference depending on the time periods. Especially, more traffic flows were concentrated on the freeway junctions in the morning peak period when compared with the afternoon peak period. ⅱ) The occupancy distribution was also shown to be varied by a big difference depending on the time periods. Especially, the occupancy in the morning peak period showed over 100% increase when compared with the 24hours average occupancy, and the occupancy in the afternoon peak period over 25% increase when compared with the same occupancy.ⅲ) The speed distribution was not shown to have a big difference depending on the time periods. Especially, the speed in the morning peak period shown 10mph decrease when compared with the 24hours' average speed, but the speed did not show a big difference in the afternoon peak period.ⅳ) The analyses of variance showed a high explanatory power between the speed predictive models(SPM) constructed and the variables used, especially the upstream speed. ⅴ) The analysis of correlation for verifying the speed predictive models(SPM) constructed on the ramp junctions were shown to have a high correlation between observed data and predicted data. Especially, the correlation coefficients showed over 0.95 excluding the unstable condition on the diverge sectionⅵ) Speed predictive models constructed were shown to have the better results than the HCM models, even if the speed limits on the freeway were different between the HCM models and speed predictive models constructed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1999년도 추계학술대회논문집
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• pp.131-140
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• 1999

Today freeway is experiencing a severe congestion with incoming or outgoing traffic through freeway ramps during the peak periods. Thus, the objectives of this study is to identify the traffic characteristics, analyze the relationships between the traffic characteristics and finally construct the delay predictive models on the ramp junctions of freeway with 70mph speed limit. From the traffic analyses, and model constructions and verifications for delay prediction on the ramp junctions of freeway, the following results were obtained: ⅰ) Traffic flow showed a big difference depending on the time periods. Especially, more traffic flows were concentrated on the freeway junctions in the morning peak period when compared with the afternoon peak period. ⅱ) The occupancy also showed a big difference depending on the time periods, and the downstream occupancy(Od) was especially shown to have a higher explanatory power for the delay predictive model construction on the ramp junction of freeway. ⅲ) The speed-occupancy curve showed a remarkable shift based on the occupancies observed ; Od < 9% and Od$\geq$9%. Especially, volume and occupancy were shown to be highly explanatory for delay prediction on the ramp junctions of freeway under Od$\geq$9%, but lowly for delay predicion on the ramp junctions of freeway under Od<9%. Rather, the driver characteristics or transportation conditions around the freeway were through to be a little higher explanatory for the delay perdiction under Od<9%. ⅳ) Integrated delay predictive models showed a higher explanatory power in the morning peak period, but a lower explanatory power in the non-peak periods.

• 한국항만경제학회지
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• 제34권4호
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• pp.181-190
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• 2018

본 연구는 2012년 1월부터 2018년 5월까지의 주별 건화물선 운임과 원자재 가격 자료를 사용하여 두 변수간의 비대칭적인 관계를 다음의 두 가지를 중심으로 실증 분석한다. 첫째, 원자재가격의 거시경제지표에 대한 비대칭성을 2단계 경계(threshold) 공적분 검정모형으로 추정한다. 둘째, 기존의 원자재가격 변화의 무역수지에 대한 비대칭관계 검정을 보다 고빈도 건화물선 운임지수로 우회해서 검정한다. 추정결과 기존의 선형 분석과 대조적으로 하한과 상한에 대한 각각의 경계값이 상이한 비대칭성을 갖는 것으로 드러났다. 이는 불규칙적인 수익률 변동을 유발하는 급격한 잔차의 변동 구간이 원자재 가격과 건화물선 운임간의 선형의 장기균형관계가 성립하지 않도록 함을 의미한다. 따라서 이상의 추정결과는 급격한 가격 변화를 분석에 고려하기 위해서는 불규칙(irregular)적인 변동성을 제어하는 무반응(band of inaction)구간을 모형에 포함하는 것이 필요함을 의미하며 기존의 원자재가격의 무역수지에 대한 비대칭성과 일치하는 실증분석 결과다.

• 한국항해항만학회지
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• 제38권6호
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• pp.689-694
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• 2014

The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel's proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel's closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel's proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.98-101
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• 2009

최근에는 차량 진단을 위한 방법으로 차량 내 네트워크 방식이 사용되고 있으며, CAN(Controller Area Network), MOST, LIN, FlexRay와 같은 차량 프로토콜의 사용 증대로 인해 차량에 대한 분산 제어와 원하는 데이터를 실시간 모니터링 하기 위한 방법들이 모색되고 있다. 현재의 자동차의 경우 자가진단 점검단자인 OBD2(On Board Diagnostics)표준 DLC(Data Link Connector)커넥터를 이용한 진단용 모듈(스캐너)을 통해 차량을 진단 한다. 그러나 엔진과 동력전달 계통(Powertrain) 부분으로 진단이 국한되어 있고, 사용자 측면을 고려하지 못하였다. 따라서, 본 논문에서는 Ethernet port를 이용한 차량 진단 모니터링 시스템을 설계하여 CAN 프로토콜 차량 데이터를 송수신하고 PC를 이용하여 보다 간편하게 차량의 상태와 정보를 제공하고 진단할 수 있는 모니터링 시스템을 구현한다.

• 한국지반환경공학회 논문집
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• 제23권11호
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• pp.13-18
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• 2022

본 연구는 항만 중력식 구조물에 대한 내진보강을 분석하여, 그라우팅공법 적용의 적정성을 평가하고자 한다. 평가항목은 액상화, 활동, 전도 및 원호활동 등으로 공법의 적정성을 비교하기 위하여 그라우팅공법인 저유동성 모르타르 주입공법과 말뚝벽체식 보강공법인 SPC 파일 및 GRB 공법을 각각 평가하여 비교하였으며, 평가대상은 포항 구항 중력식 구조물로 선정하였다. 평가결과, 그라우팅공법과 말뚝벽체식 보강공법 모두 평가항목에 대하여 안정성을 충분히 확보하는 것으로 검토되었다. 따라서 중력식 항만 구조물의 경우 시공성, 경제성 및 유지관리 부분과 유사 시공사례 등을 고려 시 내진보강 공법으로 그라우팅공법이 보다 효율적임을 알 수 있었다.

• Journal of Korea Trade
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• 제26권3호
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• pp.23-44
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• 2022

Purpose - Recent issues such as vessel enlargement, strengthening of environmental regulations, and port smartization are expected to increase costs and intensify competition in the port industry. In the new normal era, when external growth has reached its limit, the efficient operation of ports is becoming indispensable for achieving sustainable growth. This study aims to identify the determinants of inefficiency by examining the cost structure and efficiency of container terminals in Korea and furthermore propose the political implications to derive the maximization of efficiency. Design/methodology - This study estimates the cost function of container terminal operators and identifies the efficiency of container terminals using stochastic cost frontier (SCF) in the first stage. In the second step, the SCF results are compared with the data envelopment analysis (DEA). Last, this paper proposes efficiency determinants on container terminal operation to establish appropriate strategies. Out of the 29 container terminal operators in South Korea, 13 operators participated in the survey. The translog cost function was estimated utilizing a total of 116 observations collected over the 2007-2017 period. Findings - Empirical analysis shows that economies of scale exist in Korea's container ports, which provides a rationale for the government's policy to establish the global terminal operator by integrating small terminal operators to enhance competitiveness. In addition, as a result of the determinants analysis, container throughput, weight of direct employment costs, and labour cost share have positive effects on improving cost efficiency, while inefficiency increases as the length of quay increases. More specifically, cost efficiency improves as the proportion of direct employment costs to outsourcing service costs increases. Originality/value - This study contributes to analyzing the inefficiency factors of container terminals through efficiency analysis with respect to a cost function. In addition, this study proposes the practical and political implications, such as establishing a long-term manpower pool, the application of the hybrid liner terminal system, and the construction of a statistical data system, to improve the cost inefficiency of terminal operators.

• 한국항해항만학회지
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• 제30권10호
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• pp.779-785
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• 2006

선박의 충돌회피 방법을 제시하는 관점에 있어, 두 선박의 조우각도에 따라 속력이 충분히 고려되어야 할 것이다. 하지만 선박의 충돌회피를 위해 새롭게 연구된 근접상황 선박충돌회피지원 모델의 안전경계영역(Safe-Guard Ring) 설정은 본선과 상대선박의 속력비가 약 1.7이하로 제한되어 있으므로 제한된 범위 이외의 경우에서 충돌 위험이 존재 할 수 있다. 따라서 본 연구에서는 두 선박이 조우하는 각도 및 속력을 고려한 안전경계영역 설정을 연구함으로써 안전한 충돌회피 조종을 위한 선박충돌회피모델을 제시하고자 한다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.51-58
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• 2003

A cycle simulation method is developed by coupling a commercial code, Ricardo's WAVE, with the SENKIN code from CHEMKIN packages to predict combustion characteristics of an HCCI engine. By solving detailed chemical kinetics the SENKIN code calculates the combustion products in the combustion chamber during the valve closing period, i.e. from IVC to EVO. Except the combustion chamber during the valve closing period the WAVE code solves thermodynamic status in the whole engine system. The cycle simulation of the complete engine system is made possible by exchanging the numerical solutions between the codes on the coupling positions of the intake port at IVC and of the exhaust port at EVO. This method is validated against the available experimental data from recent literatures. Auto ignition timing and cylinder pressure are well predicted for various engine operating conditions including a very high ECR rate although it shows a trend of sharp increase in cylinder pressure immediate after auto ignition. This trend is overpredicted especially for EGR cases, which may be due to the assumption of single-zone combustion model and the limit of the chemical kinetic model for the prediction of turbulent air-fuel mixing phenomena. A further work would be needed for the implementation of a multi-zone combustion model and the effect of turbulent mixing into the method.

• 한국항해항만학회지
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• 제29권10호
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• pp.827-832
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• 2005

본 연구는 근접상황 선박충돌회피지원시스템 개발을 위한 기초연구로써, 근거리 조우상황에서 항해사의 부적절한 조선으로 발생하는 선박충돌사고를 감소시키기 위한 선박충돌회피지원모델을 제시한다. 이 모델은 선박의 다양한 조우상황을 비교하고, 자선의 선회특성을 이용하여 상대선박의 침로, 속도 유지에 대한 충돌회피 가능영역과 방법을 나타냄으로써 근접상황에서도 신속한 피항동작 검토 및 결정을 가능케 하며 효과적인 충돌회피 조선을 지원할 것이다.