• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.443-445
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• 2003

매년 증가하는 컨테이너 물동량의 효율적인 처리를 위해서 수출 컨테이너의 처리과정인 반입, 장치 적하의 과정중 배에 싣는 적하작업시 재취급이 발생하게 된다. 재취급이란 컨테이너 야드장에 장치되어 있는 수출 컨테이너를 적하하기 위해 배로 이동할 때 옮겨야 할 수출 컨테이너 위에 다른 수출 컨테이너가 있을 경우 상위의 수출 컨테이너를 다른 곳으로 이동시킨후 해당 컨테이너를 배로 옳기는 것을 말한다. 이와같은 재취급이 발생할 경우 선박의 적하시간이 늘어나고 장비의 이용률이 증가함으로서 컨테이너 터미널의 운영의 효율성이 떨어진다. 적하작업시 발생하는 재취급의 횟수를 최소화하기 위해 수출 컨테이너를 장치할 때 수출 컨테이너를 적하순서의 역순으로 장치를 하는 것이다. 그러나 수출컨테이너가 터미널에 도착하는 순서는 일정하지 않기 때문에 장치되어져 있는 컨테이너를 여러번 재장치하여 일방적으로 역순의 형태로 장치할 경우 재취급의 횟수는 줄일 수 있으나 장비의 사용량은 늘어나므로 결과적으로 효율적이지 못하다. 그래서 본 논문에서는 일정하지 않게 반입되는 수출컨테이너의 위치를 유전자 알고리즘(genetic algorithm)을 이용하여 결정함으로서 수출컨테이너 장치시 재조작횟수를 증가시키지 않고 재 취급을 최소화할 수 있는 방법을 제시한다.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.103-110
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• 2003

In this paper, we propose and evaluate the performance distance-based registration considering call arrival. We propose the mobility model, which can be used to analyze the performance of proposed registration schemes. Numerical results show that zone-based registration needs less number of registration than distance-based registration. On the other hand, the registration load of the distance-based registration is equally distributed to all cells in a location area. However, the registration load of the distance-based registration considering cail arrival is similar to that of zone-based registration and equally distributed to all cells in a location area. Therefore, the proposed scheme can be effectively used restricted radio resources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.854-861
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• 2003

In this paper, we proposed the fuzzy control algorithm for efficient buffer control about traffic that is connected in ATM networks. The proposed Fuzzy control algorithm has total traffic arrival ratio, buffer occupancy ratio and Fuzzy set to search for dynamic service rates in server. That is, is based on Fuzzy logic according to the arrival ratio of total traffic and buffer occupancy ratio that is happened and reasoning. Then, made reasoning result control service rates in server about traffic that is connected with defuzzification value. Performance analysis result: it was confirmed that with the proposed scheme, performance improves at cell loss rate, when compared with the existing PBS scheme.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.149-155
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• 2009

The frequency is widely used to measure the distance. In the warehouse, however, the frequency is apt to be interrupted by various unmade stuffs and cannot be easily applied to that kind of environment. This study will suggest the method to localize a worker in the warehouse exactly with calculating the time difference of arrival from the base position to a node or between each node and with 3-points pin pointer. This study will propose the localizing method using RFID tag and analyze the result using the suggested method. Also, the efficiency of suggested method will be increased with the simulation based on the information from the RFID tag.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.989-998
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• 1993

In a bursty user traffic mode, ALOHA random multiple access protocol achieves higher performance than any conventional fixed assignment technique. One of central problems in slotted ALOHA is synchronization. Because of the long propagation delay in satellite mobile communication, packet may be spilt over into adjacent slots and thus guard time may be included between packet intervals. In conventional ALOHA channels, simultaneous transmission by two or more users results in a collision : the unsuccessful packets have to be retransmitted according to some retransmission algorithm. However, in a radio environment, users are often at different distances from the receiver : therefore, their received signals have substantially different power levels. The packet arriving with the highest energy now has a good chance of being detected accurately. Similarly, in some spread-spectrum random access systems, the earliest arriving packet dominates later arriving packets and thus captures the channel. In this paper slotted ALOHA channel with non zero guard time and capture probability is studied. Using the Markovian model, the performance of slotted ALOHA with guard time and capture effects is derived and compared with that of the conventional ALOHA via numerical analysis.

• Journal of the Economic Geographical Society of Korea
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• v.14 no.4
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• pp.540-552
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• 2011

Freight travel pattern has been less studied comparing with the field of passenger travel. Nonetheless, the importance of the freight travel has been increasing in urban travel sector, and the research needs on the freight travel demand hence is increasing. The current paper aims to identify, by tons of freight trucks and cargos, the characteristics of mean travel pattern, efficiency or performance, and the characteristics of freight trip chain regarding destination location, destination type and freight type. The study analyzed the nation-wide data of freight travel behavior survey. This study intended to set the starting framework of decision-making principle in freight travel, which has already been popular in passenger travel study. Findings suggest that those characteristics are clearly distinguished among trucks and cargos of different sizes of tons. The results are expected to provide important insight to the development of relevant transportation policy measures.

• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.502-508
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• 2005

This paper proposes a dynamic hybrid patching technique that can improve the performance of VOD systems by adopting the advantages of both greedy patching and grace patching to use a VOD server's limited network-I/O bandwidth. The proposed technique uses grace patching to the requests for the videos, arrival intervals of which are smaller than the size of patching window, and uses greedy patching to the rest requests. In addition, proposed patching technique expands the latest particular patching multicast into a regular multicast for a new request. In result, the patching multicast data for the new request can be the data from the beginning to the skew point of the video and the holding time of a dispatched channel can exceedingly decrease. Simulation results confirm that the proposed technique is better than grace patching in terms of defection rate and average service latency.

• The KIPS Transactions:PartD
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• v.15D no.3
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• pp.297-304
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• 2008

Due to the proliferation of the Internet and intranet, new application domains such as stream data processing have emerged. Stream data is real-timely and continuously generated. In stream data environments, a lot of queries are registered, and then, the arrived data item is evaluated by registered queries. Thus, to accelerate the query performance, diverse continuous query index schemes have been proposed for stream data processing systems. In this paper, we focus on the query index technique for stream data. In general, a stream query contains the range condition. Thus, by using range conditions, the queries can be indexed. In this paper, we propose an efficient query index scheme, called QUISIS, using a modified Interval Skip Lists to accelerate search time. QUISIS utilizes a locality where a value which will arrive in near future is similar to the current value. Through the experimental study, we show the efficiency of our proposed method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.2 s.29
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• pp.133-140
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• 2007

Since early times, captain have been sailing to select the optimum route considering the weather, ship loading status condition and operational scheduling empirically. However, it is rare to find digitalized onboard route support system whereas weather facsimile or wave and swell chart are utilized for the officer, based on captain's experience. In this paper, optimal route safety assessment system which is composed of voyage efficiency and safety component is introduced. Optimum route minimizea ETA(estimated time of arrival) and fuel consumption that shipping company and captain are requiring to evaluate for efficient voyage considering speed loss and power increase based on wave added resistance of ship. In the view point of safety, seakeeping prediction is performed based on 3 dimensional panel method. Finally, It is assistance measure for ship's optimum navigation route safety planning & assessment.

• Journal of KIISE:Databases
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• v.37 no.1
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• pp.1-11
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• 2010

Recently, there has been a growing interest in the processing of continuous queries over multiple data streams. When the arrival rates of tuples exceed the memory capacity of the system, a load shedding technique is used to avoid the system becoming overloaded by dropping some subset of input tuples. In this paper, we propose an effective load shedding algorithm for multi-way windowed joins over multiple data streams. Most previous load shedding algorithms estimate the productivity of each tuple, i.e., the number of join output tuples produced by the tuple, based on its "join attribute value" and drop tuples with the lowest productivity. However, the productivity of a tuple cannot be accurately estimated from its join attribute value when the join attribute values are unique and do not repeat, or the distribution of the join attribute values changes over time. For these cases, we estimate the productivity of a tuple based on its "arrival order" on data streams, rather than its join attribute value. The proposed method can effectively estimate the productivity of a tuple even when the productivity of a tuple cannot be accurately estimated from its join attribute value. Through extensive experiments and analysis, we show that our proposed method outperforms the previous methods in terms of effectiveness and efficiency.