• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8B
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• pp.535-540
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• 2005

This paper presents a scalable caching algorithm of proxy server with the finite storage size minimizing client's buffer size and constant-bit-rate channel bandwidth. Under the general video traffic condition, it is observed that the amount of decreased client's buffer size and channel bandwidth after caching a video frame depends on the relative frame position in the time axis as the frame size. Based on this fact, we propose an effective caching algorithm to select the cached frames by using the normalized buffer size. Finally, experimental results are provided to show the superior performance of the proposed alghrithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7A
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• pp.987-995
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• 1999

The handoff is a distinctive characteristic of the mobile networks. In the CDMA systems, if base stations support multiple Frequency Assignment (FA), they provide both soft handoff and hard handoff. Under the CDMA environments, the soft handoff guarantees the favorable service quality and the continuity of call connection without interruption, and increases the service capacity of the base stations. This paper proposes call connection control schemes with handoff queue for supporting efficient handoff processing. The proposed schemes are divided into two categories: single handoff queue scheme and multiple handoff queue scheme. We analyze the performance of the proposed call connection control schemes using numerical analysis. From the analysis results, we can say that it is more desirable to avoid hard handoff as long as handoff queues are used. When a single handoff queue used, adaptive scheme that properly mixes avoidable and avoidable hard handoff method under the given traffic condition is more desirable. In case that multiple handoff queues are used, the suitable trade-off needs to be developed between handoff blocking probability and hard handoff probability to guarantee a given blocking probability threshold.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.1 s.28
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• pp.55-60
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• 2007

Many electric power cables span the sea in Korean archipelago. Lots of shipping routes were established between the islands in the same area and ships frequently sail under the cable which cross the seas. Sometimes electric power cables were accidently broken by sailing ships and catastrophic damage of island industry followed thereby. If navigators have detailed knowledge about the height of electric power cable, the ship's sailing condition will be greatly improved. But at the present time, navigators have limited data about the electric power cable. Those are the horizontal distance between pylons, the height of pylons and minimum height of electric power cable. This study introduced the calculating methodology to find out the height of cable at any position between pylons. The ship's tracks were recorded and traffic safety was assessed by statistical method in relation to cable height.

• Journal of Digital Contents Society
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• v.16 no.3
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• pp.365-371
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• 2015

In wireless network, the amount of video streaming packet information in receiver replay buffer can be varied according tothe wireless network condition. By the effect, unforeseeable delay and jitter are generated and then busty video traffics can be made. If the amount of buffer information coming in receiver replay buffer is larger than the amount of a specific buffer information, buffer overflow is generated. Such a problem makes the image skip effect and packet loss, and then causes the quality degradation and replay discontinuity of the video streaming service in destination receiver. To solve the buffer overflow problem, this paper applies the token bucket for the busty traffic to the receiver terminal and analyzes the effect of the token bucket. The simulation result using NS-2 and JSVM shows that the proposed scheme with the token bucket has significantly better performance than the conventional scheme without the token bucket in terms of overflow generation number, packet loss rate and PSNR.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.693-702
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• 2002

The aim of this study is to develop a 3-dimensional dynamic analysis model, capable of considering the interaction between vehicles and bridges more accurately. The dynamic analysis model is developed with the high-speed train (KTX) and a 2-span continuous prestressed concrete box girder bridge with a double track. The 20-car model is developed using the moving vehicle model for the regular trainset. Three-dimensional frame elements are used for the bridge model. Using the developed models, a dynamic behavior analysis program is coded. The analytical results are compared with the dynamic field test results and found to be valid to yield quite accurate dynamic responses. Based on the results of this study, the hybrid model, made up of the moving vehicle model for the heaviest power car and the moving force model for the other cars, is quite simple and effective without loosing the accuracy that much. Under the coincidence condition of two trains traveling with resonance velocity in the opposite directions, it is necessary to check not only the dynamic responses of the bridge with one-way traffic but those with two- way coincidence.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.351-358
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• 2012

This study is aimed at suggesting optical communication equipment that can deliver high quality video information in high speed, to efficiently handle the flood and water pollution in the river basin. This system is cheaper than existing equipment, and can monitor optical Internet as well as the condition of equipment. Generally, the communication equipment to prevent flood is installed in an unmanned control box and operated by the flood control office situated at the fiver mouth in a long distance section. Therefore, it is hard to promptly cope with communication interruptions, which occur by the cutting or aging of the optical cable. Under the circumstances, this study suggested an efficient system that can deliver high quality video information in high speed (Optical Transmission Convert System) by using optical fiber. The system also solves problems by making use of automatic protection switching (APS) when an accident happens. Its real-time monitoring function gives notice of the problem-occurring points. The system is expected to be widely used in various areas such as intelligent traffic systems.

• The Journal of Korea Robotics Society
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• v.7 no.3
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• pp.205-215
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• 2012

A GPS sensor is widely used in many areas such as navigation, or air traffic control. Particularly, the car navigation system is equipped with GPS sensor for locational information. However, when a car goes through a tunnel, forest, or built-up area, GPS receiver cannot get the enough number of satellite signals. In these situations, a GPS receiver does not reliably work. A GPS error can be formulated by sum of bias error and sensor noise. The bias error is generated by the geometric arrangement of satellites and sensor noise error is generated by the corrupted signal noise of receiver. To enhance GPS sensor accuracy, these two kinds of errors have to be removed. In this research, we make the road database which includes Road Database File (RDF). RDF includes road information such as road connection, road condition, coordinates of roads, lanes, and stop lines. Among the information, we use the stop line coordinates as a feature point to correct the GPS bias error. If the relative distance and angle of a stop line from a car are detected and the detected stop line can be associated with one of the stop lines in the database, we can measure the bias error and correct the car's location. To remove the other GPS error, sensor noise, the Kalman filter algorithm is used. Additionally, using the RDF, we can get the information of the road where the car belongs. It can be used to help the GPS correction algorithm or to give useful information to users.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.3
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• pp.27-33
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• 2009

Content used in mashups is typically obtained from a third party source through a public interface or API (web services). Other methods of obtaining content for mashups include Web feeds (e.g. RSS or Atom), and screen scraping. A mashup or meshup Web application has two parts: A new service delivered through a Web page, using its own data and data from other sources. The blended data, made available across the Web through an API or other protocols such as HlTP, RSS, REST, etc. There are many types of mashups, such as consumer mashups, data mashups, and Business Mashups. The most common mashup is the consumer mashup, which are aimed at the general public. Examples include Google Maps, iGuide, and RadioClouds. 4D Wall-map display is data mashups combine similar types of media and information from multiple sources into a single representation. This technology focus data into a single presentation and allow for collaborative action among ITS-related information sources.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.82-88
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• 2009

Video proxy server which is located near clients can store the frequently requested video data in storage space in order to minimize initial latency and network traffic significantly. However, due to the limited storage space in video proxy server, an appropriate video selection method is needed to store the videos which are frequently requested by users. Thus, we present a virtual caching technique to efficiently store the video in video proxy server. For this purpose, we employ a virtual memory in video poky server. If the video is requested by user, it is loaded in virtual memory first and then, delivered to the user. A video which is loaded in virtual memory is deleted or moved into the storage space of video poxy sewer depending on the request condition. In addition, virtual memory is divided into each segment area in order to store the segments efficiently and to avoid the fragmentation. The simulation results show that the proposed method performs better than other methods in terms of the block hit rate and the number of block deletion.

• Journal of Korean Foot and Ankle Society
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• v.23 no.4
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• pp.183-188
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• 2019

Purpose: Bone contusion is usually treated with conservative therapy for 3 months. Bone contusion around knee and hip joints has been extensively reported on, but there are scant reports on this condition in foot and ankle joints. This study evaluated the nature, characteristics and location of bone contusion around foot and ankle joints to enlighten clinicians on how to better treat this disease entity. Materials and Methods: We classified bone contusion of the 76 patients into three types (102 sites; 47 ankle sprains, 18 traffic accidents, 11 falls) according to the Costa-Paz system with employing magnetic resonance imaging (MRI), and the study then analyzed the common sites and areas of occurrence according to the mechanism of injury and duration of pain after first conducting conservative therapy. Results: Of the 76 patients (102 sites) on the MRI, 43 case (42.2%) for talus, 19 cases for distal tibia, and 12 cases for calcaneus were involved. The classification, according to the Costa-Paz system, was Type I, 51 cases; Type II, 32 cases; and Type III, 19 cases. The duration of pain after conservative treatment was 12.15±2.17 weeks for Type I, 14.5±2.15 weeks for Type II, and 21.0±3.8 weeks for Type III. Conclusion: The most common location of post-traumatic bone contusion around both the foot and ankle is the talus, distal tibia, and calcaneus. The most common type of injury noted on MRI is a diffuse signal with change of the medullary component (Type I), In cases of bone contusion extending to a subjacent articular surface or disruption or depression of the normal contour of the cortical surface (Types II, III), the patients' pain appears to last longer. Thus, it is necessary to consider a longer period of conservative treatment in cases of Types II and III bone contusion because the patients' pain may last longer than 3 months.