• Journal of Korea Multimedia Society
• /
• v.20 no.1
• /
• pp.1-9
• /
• 2017

Explosive deployment of smart mobile devices such as smart phones, and tablets along with expansion of wireless internet bandwidth have enabled the deployment of mobile video streaming such that video traffic becomes the most important service in wireless networks. Recently, for more efficient video streaming services, the ISO MPEG group standardized a protocol called DASH (Dynamic Adaptive Streaming over HTTP) and the standard has been quickly adopted by many service providers such as YouTube and Netflix. Despite of the convenience of mobile streaming services, users also suffer from low QoE(Quality of Experience) due to dynamic channel fluctuations and unnecessary downloading due to high churning rates. This paper proposes a noble efficient video rate selection algorithm considering user buffer level, channel condition and churning rate. Computer simulation based performance study showed that the proposed algorithm improved the QoE significantly compared to a method that determines the video rate based on current channel conditions. Especially, the proposed method reduced the rebuffering rate, one of the most important performance factors of the QoE, to a nonnegligible level.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2014.06a
• /
• pp.22-25
• /
• 2014

UHDTV방송을 준비하면서 대용량 영상데이터의 전송이 중요시 되고 있다. 그러나 이용자의 미디어 이용행태는 언제 어디서나 쉽게 이용할 수 있는 매체를 더 선호하고 있다. 본 연구에서는 수신능률을 높이고, 향후 8K UHDTV 등 초고화질 서비스도 가능하도록 TV채널 폭의 확장에 의한 UHDTV방송의 효과를 제시하고자 한다.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.36
• /
• pp.143-170
• /
• 2007

In order to analyze the distribution channel of marine products in Korea, this study shows SCM approach to redesign of the marine distribution channel with case study related to previous literatures. In view of the supply chain and the future impact of RFID on the marine SCM on the recognition of the importance of the seafood traceability system, this study also provides the possibility to accomplish effective SCM for integration of production, storage, transportation, delivery, and sale when RFID is used in the seafood distribution channel based on the expansion of awareness on the marine product traceability. The traceability system for seafood is considered as the distribution infrastructure established in RFID deployment. By introducing Lotte mart case, this case study also discusses the marine distribution structure in view of the supply chain, to present an effective foundation for supplying seafood throughout production, distribution, and consumption. This is achieved by introducing RFID in an ubiquitous environment, and suggesting far more efficient control planning throughout the seafood distribution channel in view of the expected effects resulting from the introduction. In addition, as the alternative of solving this situation, this study propose the supply chain in seafoods by comprehensive management in whole distribution channels. In the SCM in seafood perspectives, HACCP can take into account the whole seafood chain from the point of supply to the point of consumption when assessing hazards. As the contributions of this study, this study emphasizes the seafood industry first should require the establishment of the relevant infrastructure, for which the efforts of the government and demonstrative project participants are essential.

• International Area Studies Review
• /
• v.12 no.3
• /
• pp.25-47
• /
• 2008

This paper tries to explore the impact of economic globalization on social capital accumulation. To investigate direct effect, we build a model and derive a proposition which can explain the relative decline in social capital brought about by market expansion. Besides direct effect, we also explore channel effect through democracy, government size, education attainment, and inequality. We estimate direct and channel effect of globalization using cross section of 65 countries data time period 1980-1999 using three-stage least squares(3SLS). Results are in line with predictions and clearly support that globalization significantly and negatively affects social capital accumulation. Channel effect also shows that globalization has a negative effect through aggravating income inequality while it has a positive effect through higher education attainment, higher level of democracy and larger government spending. Such a net negative channel effect reinforces our prediction. As a robustness check we estimate other sets of data and the result strongly supports our theory.

• Korean Journal of Environment and Ecology
• /
• v.22 no.6
• /
• pp.658-665
• /
• 2008

One of the characteristics of fluvial river channel with sand bed-material is the existence of movable sand bars not occupied with vegetation. However, sand bars at the Hahoe's reach of the Nakdong River showing a double-meandering channel has been changed into expanding vegetation area. Moreover, sand material, in recent years, has stopped moving to downstream in channel and the number and area of bare bars which did not occupied by vegetation have been decreased. In order to find out the mechanism, we carried out the channel characteristics surveys such as hydro-geomorphologic, soil physio-chemical and vegetation surveys were conducted twice on autumn season in 2005,2006. The results so far achieved showed that the reduced discharge of transported sediment and duration of dry season might be critical factors for the spread of luxuriant vegetation. The vegetation area was significantly expanded by floods exceeding the subsequent dominant flow discharge. Furthermore, the expansion of vegetation area was highly correlated with the supply of organic matter, nutrients and alteration of soil texture by sediment deposition during the flooding event.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.8
• /
• pp.1502-1509
• /
• 2006

In this paper, we proposed reliability and capacity enhancement methods for IEEE 802.15.3 HDR-WPAN (High Data Rate-Wireless Personal Area Network) system which is currently getting an interest in home network technology adopting a MIMO technique. We also analyzed performance or the proposed system through a computer simulation. The HDR-WPAN system using V-BLAST algorithm, transmitting the different signal vector to each other's sub-channel, can get the transmission speed of more than 110Mbps using two Tx/Px antenna without bandwidth expansion in TCM-64QAM mode. Also the proposed system has reliability of 104 at $E_b/N_0=35dB$ under the Rayleigh fading channel in case of two Tx/Rx antenna with MMSE algorithm. The HDR-WPAN system adopting V-BLAST method has its drawback which is very complicated to determine the decision-ordering at the receiver. But, the proposed system enhances the transmission capacity and reliability without extra bandwidth expansion by sending data streams to multiple antennas.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.6
• /
• pp.591-597
• /
• 2013

Because most existing non-Newtonian models are not suitable for application to the lattice Boltzmann method, theoretical and numerical studies in this regard remain challenging. In this study, the hydrokinetic (HK) model was modified and applied to a 3D sudden contraction-expansion channel flow, and the characteristics of the HK model flow were evaluated to generate non-trivial predictions in three-dimensional strong shear flows. The HK model is very efficient for application to the lattice Boltzmann method because it utilizes the shear rate and relaxation time. However, the simulation would be unstable in a high shear flow field because the local relaxation time sharply decreases with an increase in the shear rate in a strong shear flow field. In the HK model, it may become necessary to truncate the relaxation time and non-dimensional parameter to obtain stable numerical results.

• Journal of Information Technology Applications and Management
• /
• v.14 no.2
• /
• pp.27-47
• /
• 2007

In an effort to apply IT to practices of learning, universities are trying to implement e-Learning systems and expanding the extent of their usage. Nowadays, e-Learning systems are not only used for conducting web-based distance learning, but also used for supporting traditional classes education by encouraging communication and information sharing between instructors and learners or among the learners. There is relatively lack of studies on the exploitation of e-Learning systems in the traditional classes, in comparison with a distance education. Specifically, howe-Learning systems could support the traditional class and/or which benefits e-Learning systems could offer in the classes are among the important issues. In this study, we suggest that e-Learning systems would be the rich media to communicate and exchange information among people who participate in a class. We derive key variables like media richness and media experience from Media Richness Theory and from Channel Expansion Theory. Moreover, Media usefulness and Satisfaction of a learner with e-Learning system is drawn from the literature on IS success. We examine the effects of perceived media richness, media usefulness, and media experience on leaner's satisfaction with e-Learning systems. In addition, we also investigate learner's media usefulness perception which is positively related to media richness and media experience. Finally, learner's experience with e-Learning systems affects perceived media richness. Based on the results of an empirical test. we first suggest that perceived media richness with e-Learning systems contributes to increase media usefulness and satisfaction of a learner. Second, media experience is an important predictor of media richness and media usefulness perception. Consequently, the result can support Channel Expansion Theory. Finally, media usefulness perception affects learner's satisfaction with e-Learning systems.

• Journal of Korean Port Research
• /
• v.7 no.2
• /
• pp.37-60
• /
• 1993

Because of the rapid growing traffic volumes of cargo, especially between Seoul and Inchon, and lack of investment into transport infrastructure in the past, in Kyong-in area have suffered from the serious traffic congestion in the public-road and the express-way network, But the further expansion of the traffic volume in near future is difficult due to burden of the higher expansion of the traffic volume in near future is difficult due to burden of the higher construction cost. Although the traffic congestion on the Kyung-in railway, is not very serious comparing with the road sector, the shortage of capacity on some main lines becomes emerged as a problem as railway traffic has increased. Unlike these two modes, the water transport, which has been paid relatively less attention for commodity transport in Kyong-in area, has not any constaint in this respect. Han river has been used as a water transport route in Chosun Dynasty which is called Cho-wun. This paper therefore aims to propose the availability of Han river as the alternative water transportation mode, in order to decrease the congestion between Seoul-Inchon by considering the construction of Kyong-in artificial water channel in near future. In this paper, we investigate the availability of Nanji-do as the physical distribution depot connecting with the circulation express way in the national capital distribution depot connecting with the circulation express way in the national capital. We also estimate the traffic volume by using the push-barge carrier (300DWT) in the same channel through the simulation under some assumptions such as ship's turnaround time, speed, etc.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.5
• /
• pp.111-115
• /
• 2014

Power line communications can be utilized to build up the data transmission network wherever the electricity is available. This type of communication system could provide a basis for the network construction in many application areas which include the smart grid and home networks. On the other hand the power line communication is vulnerable to various types of interferences and noises. Also, its channel characteristics are constantly changing depending on the type and the amount of electrical loads connected to the network. Especially, the usage of DC power supply has been increased due to the explosive expansion of smart devices in our daily lives which result in the increased level of interferences on the power line channel. In this paper, the effect of the operation of the DC power supplies on the channel characteristics and the data transmission performance is analyzed through the experiments.