• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.847-851
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• 2016

Due to global warming it is estimated that the arctic ocean route will be avaliable and traffic will increase by approximately year 2030. However, most navigation in the arctic is based on the ice breaker captains'orders, there is no exact measurement of convoy speed and distance between ships. So, this research was conducted to find out the minimum safe separation distance and minimum breaking distance via ship controling simulations, and the results are as stated. For breaking distances, for ships that have a lead distance which is 2~4 times the width of the ship and traveling less than 7 knots, crash astern and crash astern & hard rudder showed no significant difference. But ships traveling at 10 knots there was a decrease in breaking distance of 1L, from 3.5L to 2.5L. By analyzing 10 subject ships by crash astern the breaking distance for 5 knots is 0.98L~1.8L, for 8 knots is 1.9L~4.0L. The minimum safe separation distance in narrow sea-ways is 6L, but as the arctic sea-way is only one-way 3L is required. As the result, it is found that in the arctic the safe escort speed is less than 5 knots, if the escort speed is 8knots or more and by using crash astern & hard rudder to break the safe distance should be kept at 3.4L.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.111-122
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• 2012

There has been a strong demand for providing diverse services to drivers utilizing existing ITS infrastructure. To this end, this study is aiming at improving the accuracy of a variable speed limit system by determining recommended speeds for the system utilizing the information from Urban Traffic Information System(UTIS) and Weather Information System(WIS). In order to determine appropriate speed limits under inclement weather conditions for the variable speed limit system, this study examined three methods: i) the method utilizing the information from WIS, ii) the method utilizing the information from UTIS, and iii) the method which combines the information from WIS and UTIS using different weights for diverse weather conditions. Finally, this study selected the third method which determines an appropriate speed limit using the relationship between the vehicle operating speed and the minimum stopping distance which is estimated using the existing speed limit, surface coefficient of friction and superelevation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.5-10
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• 2005

T.S. HANBADA will navigate to maintain the adequate distance between own ship and other ships safely for about 17 hours on the about 2 kts. On the above situation, M broadcasting station requires to maintain the distance from 100m to 500m between ships. This paper aims to calculate the minimum safe distance between ships, the distance is assessed by using ES Model which is a quantitative model for evaluating the difficulty of shiphandling. After marine traffic flow simulation, minimum safe distance for HANBADA on the 2kts is about 260m based ES value. On this paper, the result was compared about its distance to the actual navigating distance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.475-478
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• 2009

안개가 교통사고를 유발시키는 원인을 살펴보면 운전자의 시거와 밀접한 관련이 있다. 짙은 안개가 발생하게 되면 돌발상황이 발생하였을 때 도로를 주행하던 차량이 안전하게 정지하기 위해서 필요한 최소 정지거리가 증가하게 되나 안개로 인한 시정이 나빠지게 되어서 사고발생확률이 높은 것이다. 또한 안전한 시거가 확보되지 않기 때문에 단독사고 발생 후 뒤따르던 차량이 전방을 확인하지 못한 상황에서 연쇄 충돌하게 되어 사고가 대형화된다. 이에 본 연구에서는 IT기술인 RFID와 USN을 이용하여 안개로 인한 시정거리에 따라 도로에 있는 과속카메라가 도로주행 한계속도를 자기 스스로 판단하여 자동조절하게 만들고 변경된 한계속도를 그 도로를 이용하는 차량운전자 휴대폰에 문자로 전송해주고 도로전광판에서도 정확하게 주행속도정보를 볼 수 있게 한다. 그리하여 도로주행 한계속도를 어기는 차량에는 범칙금을 부과하게 만든다. 본 연구를 통해 안개에 대한 교통사고의 위험을 줄이고 사회적 경제적으로 이익이 되도록 하기위해 기상상태 변화에 따른 USN 기반의 도로주행 한계속도 지능적 조정 관리시스템을 제안하고자 한다.

• Proceedings of the KOR-KST Conference
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• 2007.05a
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• pp.300-309
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• 2007

본 연구는 신호교차로에서의 딜레마 죤 범위를 산정하고 신호위반 단속의 허용 범위를 분석하는데 있다. 각 교차로 접근로별 조사 자료를 토대로 딜레마 죤의 범위를 산정하였고, 이를 토대로 신호위반 단속에 있어 딜레마 죤의 영향을 최소화 할 수 있는 방안을 제시하고자 하였다. 기존의 딜레마 죤에 관한 연구에서는 인지-반응 시간과 황색신호시간을 초기값으로 적용하였으나 본 연구에서는 해당 교차로의 조사치를 적용하였다. 조사 방법으로 속도조사는 스피드 건을 이용하여 각각의 대상 교차로별 접근로에서 접근 속도 및 통과 속도를 조사하였으며, 운전자의 인지-반응 시간 및 황색신호시간에 교차로를 통과하는 차량조사는 비디오 촬영을 통하여 조사하였다. 이러한 조사된 자료를 토대로 신호위반 단속기준에 맞추어 딜레마 죤에 관하여 분석하였다. 본 연구에서 딜레마 죤은 최소정지거리($d_0$)가 최대통과거리($d_c$)보다 클 때 존재하는 것으로 보았으며, 그 차이만큼의 딜레마 죤이 발생하는 것으로 정의하였다. 이에 신호위반 단속을 함에 있어딜레마 죤의 영향을 최소화 할 수 있는 방안 등을 제시하였다. 그러나 각각의 방안을 개별적으로 적용시킬 경우 문제점이 발생하였다. 이러한 문제점을 해결하기 위해서 자기감응식 루프검지기의 위치를 재조정함에 있어 하나의 루프 검지기를 정지선 이후에 존재함과 동시에 황색신호시간을 재조정하거나, 자기감응식 루프검지기의 작동시간을 재조정하는 방안을 제시하고자 하였다. 본 연구에서는 3개의 교차로를 비교대상으로 선정하여 각각의 교통환경에 따른 접근로별 딜레마죤의 범위를 최소화하기 위한 대안을 제시하였다.

• Journal of Korean Society of Transportation
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• v.26 no.4
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• pp.111-121
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• 2008

Using variable speed limits (VSL) is a key strategy for preventing traffic accidents and alleviating traffic congestion. This study proposes an algorithm to operate VSLs on freeways for traffic safety. The proposed algorithm consists of two components based on accident likelihood estimation and analysis of safe stopping distance under various environmental conditions. A binary logistic regression technique is used for estimating accident likelihood. It is expected that the proposed algorithm would be successfully applied in practice in support of an integrated traffic and environmental condition monitoring system. Technical issues associated with the field implementation are also discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.65-72
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• 2011

When an expressway intersects another expressway, a unique connector needs to be designed between the two consecutive exit ramps. In such a case, it is important to design a connector such that there is enough distance for drivers to find their way safely. A current design manual in Korea prescribes the minimum length of the connector as 240 m. In this research, we have suggested a method for calculating the minimum length of a connector in order to check the feasibility of the currently prescribed length. For this purpose, we have attempted to determine the total perception-reaction time and lane-changing time required by a driver. For determining the driver's perception-reaction time, we have used the driver's decision time in addition to the conventional 2.5 s of perception-reaction time for stopping sight distances. We have considered both the design speed and the average travel speed for the calculation of the length. To evaluate the accuracy of the new method, we have chosen four sites on expressways for which relatively high accident rates were recorded. As a result, we could verify that the current limit (240 m) was sufficient for drivers to be able to change lanes in the given specific geometry. However, the prescribed limit should be revised in case the drivers' decision time is considered to be their perception-reaction time. All new approaches for calculating the ideal length of a connector have been carried out by taking into account the design speed as well as the average travel speed. Owing to the characteristics of the specific geometry for two consecutive exit ramps and the large difference between the design speed and the average travel speed in the objective areas, it is more realistic to use the proposed method by keeping the decision time equal to a driver's perception-reaction time, in order to determine the ideal distance that should be maintained between two consecutive exit ramps.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.385-385
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• 2006

• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.153-162
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• 1999

In this study, mixing and dilution characteristics of vertical multijet discharged by multiport diffuser into stagnant water are investigated. The results obtained from the experiment of multiport diffuser performed in the three dimensional flume are as follows. As far as merging process of multiport diffuser is concerned, merging starts at about z/l = 3 although merging length is dependent upon stability condition and thereafter lateral temperature distribution becomes gradually uniform which is typical distribution of plane jet. Analyses of experimental data for minimum dilution show that characteristics of minimum dilution are described based on three regions which are jet region where momentum is dominated, intermediate region, and plume region where buoyancy is dominated. Minimum dilution coefficient in plume region of multiport diffuser obtained in this study is 15% higher than that of plane diffuser. This is because individual jet of multiport diffuser entrains more ambient water before merging is occurred, and therefore dilution increases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1142-1155
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• 2014

The classical PCM/PSK/PM scheme has been commonly used for TC & R applications between satellites and ground stations in the S-band. We analyzed TC & R link performance between ground station and the geostationary satellite which employs PCM/PSK/PM, when the satellite are particularly on the Super Synchronous Transfer Orbit(SSTO). The satellite parameters on SSTO are assumed to be those operating on the geostationary orbit, considering heritage aspect. In the uplink, the results shown indicate that sufficient margins over 3 dB are obtained when the EIRP of ground station is greater than 65 dBW. The down link performance is of great interest. By adjusting the telemetry modulation index and ranging modulation index, we could obtain the required margin of 3.0 dB in the down link, and find out the minimum G/T of ground station. In conclusion, the previously operated ground stations during LEOP at COMS launch, can be operational when GEO injection is made using SSTO(65,000 km and 70,000 km).