• Journal of Fisheries and Marine Sciences Education
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• v.21 no.1
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• pp.52-58
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• 2009

With the increase of marine traffic capacity, marine accidents have also been increased for recent several years. Especially watch officer must maneuver not entering into the safety minimum approaching distances when two power-driven vessels are crossing. The author calculated the safety minimum approaching distances to provide a navigator with them based on zig-zag motion by experimental ship. The obtained results are summarized as follows : 1. The greatest distance is to be kept by the give way vessel to avoid collision when the crossing course angle is $90^{\circ}$. In this case the safety minimum approaching distance must be more than from 5 times to 11 times of her own length according to her size. 2. The watch officer of the give way vessel must always take an action to avoid collisions outside of the safety minimum approaching distance. 3. When the navigator used rudder to small angle than to large angle to avoid other vessel he must take action outside the sufficient safety minimum outside distances in advance. 4. Risk of collision in crossing situation is more greater in obtuse situation than in acute one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.10
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• pp.867-873
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• 2013

Competition policy for growth and activation of market should consider structural nature of relevant industry closely. In this viewpoint, whether domestic MNOs(mobile network operators) are competing while securing the effect of scale economies and maximum production efficiency is an important element when looking for competition policy means of domestic mobile communication market. With this, present study analyzed level of MES (Minimum Efficient Scale) and whether achieving them or not through investigating the relation between the cost per minute and call traffic of domestic MNOs. This analysis is differentiated from existing econometric studies entailing several assumptions by enhancing a reality reflection through directly deducing of cost curve using verified data(cost per minute and call traffic). As a result of analysis, the levels of minimum efficient scale were different from each other between domestic MNOs, and an incumbent MNO(SKT) accomplished minimum efficient scale while entrant MNOs(KT and LGU+) could not yet reach minimum efficient scale level. This result demonstrates a gap exists in production efficiency level among domestic MNOs and implies that the policy to alleviate the gap among operators is required when establishing competitive policy in the future.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.155-163
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• 2012

At present the letter sizes of traffic sign are variously designated as 22 cm through 60 cm, however the basis for determination has not been found so far. Driver's visual acuity for getting a driver licence is required higher than 0.5. In order to interpret the information of traffic signs effectively, the minimum requirement of driver's visual acuity must be applied to determine the letter size of traffic sign. Therefore we reviewed that a driver with visual acuity of 0.5 could read the current letter sizes of traffic sign. In addition, a methodology was developed to determine the letter size of traffic sign satisfied with the driver's visual acuity of 0.5. This study established scenarios that were composed of visual acuity, reaction time, the number of lane and the letter sizes of traffic sign for each scenario were proposed. Current letter size of traffic sign would not be difficult for drivers with minimum visual acuity of 0.5 to recognize the contents or information of traffic signs. The method developed in this research has an advantage that can consider a human factor like driver's visual acuity for the design of traffic signs. There is also a meaning of making a basis for the letter size of traffic sign.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.1
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• pp.33-44
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• 2001

In this paper, we address a problem of traffic grooming and wavelength routing in all optical WDM ring networks. Given a traffic demand for each node pair, we should aggregate the traffic onto lightpaths between pairs of nodes to transport the demand, and set up the routing path for each lightpath with minimum number of wavelengths to be assigned to lightpaths. In this paper, we formulate our problem as a mixed Integer Programming model. Owing to the problem complexity, it is hard to find an optimal solution for our problem. hence, we develop a heuristic algorithm to solve our problem efficiently. From the computational experiments, we can find the proposed heuristic is very satisfactory in both the computation time and the solution quality generated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2191-2201
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• 2012

Traffic classification seeks to assign packet flows to an appropriate quality of service (QoS) class based on flow statistics without the need to examine packet payloads. Classification proceeds in two steps. Classification rules are first built by analyzing traffic traces, and then the classification rules are evaluated using test data. In this paper, we use self-organizing map and K-means clustering as unsupervised machine learning methods to identify the inherent classes in traffic traces. Three clusters were discovered, corresponding to transactional, bulk data transfer, and interactive applications. The K-nearest neighbor classifier was found to be highly accurate for the traffic data and significantly better compared to a minimum mean distance classifier.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.3
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• pp.63-80
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• 2007

This study is a generalization of 'stable dynamics' recently suggested by Nesterov and de Palma[29]. Stable dynamics is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with user equilibrium model that is common in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on the congestion. Therefore it is expected to be an useful analysis tool for transportation planners. An equilibrium in stable dynamics needs only maximum flow in each arc and Wardrop[33] Principle. In this study, we generalize the stable dynamics into the model with multiple traffic classes. We classify the traffic into the types of vehicle such as cars, buses and trucks. Driving behaviors classified by age, sex and income-level can also be classes. We develop an equilibrium with multiple traffic classes. We can find the equilibrium by solving the well-known network problem, multicommodity minimum cost network flow problem.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.33-39
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• 1997

In this paper we proposed a new traffic load shedding scheme which maximizes the throughput of traffic control by decreasing the load of the hot-spot cell using minimum load cell selection (MLCS) algorithm and deployed control flow of calls to define characteristic for hadoff region. we compared the performance of the random shedding approach with that of the proposed algorithm. The results of simulation show that MLCS algorithm minimizes the cal blocking rate under a high-density traffic compared to the random shedding scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.12
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• pp.520-528
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• 2002

The ATM Forum recently introduced the Guaranteed Frame Rate(GFR) service category GFR service has been designed to support classical best effort traffic such as TCP/IP based traffic. The GFR service not only guarantees a minimum throughput, but also supports fair distribution of available bandwidth to completing VCs. In this paper, we proposed a new buffer management algorithm based on leaky bucket to provide minimum cell rate guarantee and improve fairness. The proposed algorithm reduces complexity and processing overhead of leaky-bucket algorithm to implement easily.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.117-126
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• 2009

The recent interest in sensor networks has led to a number of routing schemes that use the limited resources available at sensor nodes more efficiently. These schemes typically try to find the minimum energy path to optimize energy usage at a node. Some schemes, however, are prone to unbalance of the traffic and energy. To solve this problem, we propose a novel solution: a gradient-field approach which takes account of the minimum cost data delivery, energy consumption balancing, and traffic equalization. We also modify the backoff-based cost field setup algorithm to establish our gradient-field based sensor network and give the algorithm. Simulation results show that the overhead of routing establishment obtained by our algorithm is much less than the one obtained by Flooding. What's more, our approach guarantees the basic Quality of Service (QoS) without extra spending.

• Proceedings of the KOR-KST Conference
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• 1998.10a
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• pp.236-244
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• 1998

When the capacity and traffic operation at signalized intersections are analyzed in Korea, the unprotected left-turn saturation flow rate, which is an important parameter for the analysis, is estimated form the USHCM model. thus, exact analysis of the left-turn is not possible because of the difference of traffic environments between two contries. In order to improve this problem, it is undertaken in this study to develop techniques for the estimation of unprotected left-turn saturation flows based on Korean drivers' data. As study intersections, signalized or unsignalized intersections on the 6, 4 and 2 lane streets are selected. the data for the saturation flow measurement and gap-acceptance behavior analysis are inputed in a notebook computer on the sites. The critical acceptance gaps of the 6, 4, and 2 lane streets are analyzed to be 6.0 secs, 4.6 secs, and 4.3 secs respectively. the average minimum headway of the left-turn vehicle was observed to be 2.6 secs. As the model to estimate unportected left-turn saturation flows, the drew model is recommended for 6 and 4 lane streets, and a graph is suggested for the 2-lane street. As the values of the parameters of the Drew model, the 2.6 secs of this study is recommended for the average minimum headway of the left-turn. But, the critical acceptance gap varies according to the approach speed of opposing traffic and driver population, it requires field survey to measure the gap of an intersection; however, the values of the gaps studied in this study may be used for the general intersections in urban area in Korean.