• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.29-38
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• 2018

This study aims to propose a method for the estimation of operational delay cost using transportation card data in bus accidents. Average operational delay time from bus accidents was surveyed among 12 bus companies through an interview method. Then, the operational delay cost was estimated using actual traffic accident data and transportation card data. Results showed that average loss time per bus accident was found to be 45 minutes. In addition, total occupancy of 659 was estimated for the accidents investigated using transportation card data, resulting a total loss time of 494.25 hours. An estimated operational delay cost was 186.9 thousand won per accident, which was 6.37% of social agency cost. The magnitude of this number implied that operational delay cost may have a significant impact on traffic accident cost if included.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.548-558
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• 2014

Load distribution is vital to the performance of multipath transport. The task becomes more challenging in real-time multimedia applications (RTMA), which impose stringent delay requirements. Two key issues to be addressed are: 1) How to minimize end-to-end delay and 2) how to alleviate packet reordering that incurs additional recovery time at the receiver. In this paper, we propose sub-packet based multipath load distribution (SPMLD), a new model that splits traffic at the granularity of sub-packet. Our SPMLD model aims to minimize total packet delay by effectively aggregating multiple parallel paths as a single virtual path. First, we formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on progressive approximation method. Second, in the solution, we analyze queuing delay by introducing D/M/1 model and obtain the expression of dynamic packet splitting ratio for each path. Third, in order to describe SPMLD's scheduling policy, we propose two distributed algorithms respectively implemented in the source and destination nodes. We evaluate the performance of SPMLD through extensive simulations in QualNet using real-time H.264 video streaming. Experimental results demonstrate that: SPMLD outperforms previous flow and packet based load distribution models in terms of video peak signal-to-noise ratio, total packet delay, end-to-end delay, and risk of packet reordering. Besides, SPMLD's extra overhead is tiny compared to the input video streaming.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.241-269
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• 2012

Wireless networks composed of multimedia-enabled resource-constrained sensor nodes have enriched a large set of monitoring sensing applications. In such communication scenario, however, new challenges in data transmission and energy-efficiency have arisen due to the stringent requirements of those sensor networks. Generally, congested nodes may deplete the energy of the active congested paths toward the sink and incur in undesired communication delay and packet dropping, while bit errors during transmission may negatively impact the end-to-end quality of the received data. Many approaches have been proposed to face congestion and provide reliable communications in wireless sensor networks, usually employing some transport protocol that address one or both of these issues. Nevertheless, due to the unique characteristics of multimedia-based wireless sensor networks, notably minimum bandwidth demand, bounded delay and reduced energy consumption requirement, communication protocols from traditional scalar wireless sensor networks are not suitable for multimedia sensor networks. In the last decade, such requirements have fostered research in adapting existing protocols or proposing new protocols from scratch. We survey the state of the art of transport protocols for wireless multimedia sensor networks, addressing the recent developments and proposed strategies for congestion control and loss recovery. Future research directions are also discussed, outlining the remaining challenges and promising investigation areas.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.45-51
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• 2009

In this paper, a transparency analysis and network-adaptive transport scheme are proposed in order to improve transparency of EBA-based force-reflecting teleoperation. EBA guarantees stability of force-reflecting teleoperation over network delay and loss but has limitation that it cannot overcome transparency deterioration of haptic interactions. The proposed transparency analysis quantifies the force feedback distortion caused by network delay and loss. Based on the analysis, the proposed haptic data synchronization and transmission rate control schemes adapt synchronization delay and transmission rate to current network state for more transparent haptic interaction. Through Matlab/Simulink simulations, it is confirmed that the proposed analysis provides an acceptable quantification method about haptic interaction quality and that the proposed haptic data transport scheme effectively improves haptic interaction quality with respect to network delays and losses.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.543-547
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• 2008

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.26-30
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• 2002

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.4
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• pp.60-67
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• 2010

Delay reduction of vehicles at the intersection is highly dependent on the signal operation method. Most previous traffic operations have focused on minimizing delay by adjust traffic offset. However, these methods have limitation in solving traffic problem if the volume reaches or exceeds the capacity. In this paper, it was analyzed that the effectiveness of various signal operation methods such as left-turn prohibition, and using protected mixed with permitted left turn using the traffic data from Daejeon city. In case of the left-turn prohibition of a intersection, the control delay reduced from 54.2 seconds to 22.7 seconds and especially, the delay of the southbound was drastically reduced. In addition, the delay was highly reduced from 27.0 seconds to 12.1 seconds when the operation system was changed to use protected mixed with permitted left turn.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.104-113
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• 2009

Recently, high-speed Internet users and broadband network infrastructure are increasing. However, the TCP protocol widely used in the Internet is an appropriate transport only for the legacy Internet, it is inefficient for traffic transport for network environments with large bandwidth-delay product. In order to remedy this problem, there have been many researches about improved congestion control algorithms for broadband networks. In these studies, most of performance evaluation has been done by simulations. In this paper, after we reviewed the proposed high bandwidth transport layer protocols, we implemented a real testbed, measured the performance and analyzed the problems of high-speed transport protocols through the international research network TEIN2 between three nations, Korea, China, and Germany.

• The Korean Journal of Emergency Medical Services
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• v.25 no.1
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• pp.125-134
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• 2021

Purpose: The purposes of this study were to determine the changes in the pattern of patients who were transferred to the emergency room through inter-hospital private institutions and to determine how long transport takes following the COVID-19 outbreak. Methods: This retrospective observational study analyzed the emergency medical services reports of private institutions following the COVID-19 outbreak in South Korea. The study was conducted in Busan between January 19, 2019 and January 18, 2020, and between January 19, 2020 and January 18, 2021. Results: Upon comparing the patient transport times during the "Pre-COVID-19 period" and "COVID-19 period," a significant delay was noticed in the preparation for transfer of patients during the "COVID-19 period" (p<.05). There were significantly more patients with respiratory infections and patients who complained of general symptoms during the "COVID-19 period." Moreover, there was a higher frequency of patients who were transferred to a 'Level I' emergency room during the "COVID-19 period" compared to during the "Pre-COVID-19 period" (p<.05). Conclusion: Following the COVID-19 outbreak, there is a delay in patient transport to the emergency room through private institution inter-hospital transport and an increase in the number of patients complaining of respiratory infection symptoms. Thus, emergency medical services need additional administrative and economic support to transport infected patients.

• Journal of Power Electronics
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• v.12 no.1
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• pp.98-103
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• 2012

This paper presents a digital pulse width modulator (DPWM) with a reduced digital modulation delay (a transport delay of the modulator) during the transient response of power converters. During the transient response operation of a power converter, as a result of dynamic variations such as load step-up or step-down, the closed loop controller will continuously adjust the duty cycle in order to regulate the output voltage. The larger the modulation delays, the larger the undesired output voltage deviation from the reference point. The three conventional DPWM techniques exhibit significant leading-edge and/or trailing-edge modulation delays. The DPWM technique proposed in this paper, which results in modulation delay reductions, is discussed, experimentally tested and compared with conventional modulation techniques.