• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.904-913
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• 2006

The QoS(Quality of Service) of VoD(Video on Demand) systems can be improved by reducing the faults that the stream service request from clients is rejected by the VoD server or lost during the service. This paper proposes a model of Dynamic Workload Balancer that can adjust the workload dynamically through the periodical monitoring of the VoD system, and so increase the throughput. The proposed model runs independently from the VoD system by adopting the agent concept. The model comprises the agency part interfacing the VoD system and the intelligence part reasoning or teaming the facts required for the adjustment of workload. An experiment of implementing a simulator was conducted to see whether or not application of the proposed model to VoD system is effective. As a result of the experiment, it was found that the throughput was relatively increased when the proposed model was applied compared to existing means.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.53-60
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• 2005

Considerable efforts has been recently devoted to the determination of accurate channel models for the power line environment, both for the indoor and outdoor cases. The common limitation of the known and previously published models is the particular type of approach followed. This paper is concerned with a power line channel characteristic measurement for the more fast and efficiently power line communication experiment. The need arises from the fact that indoor power cables consist of conductors and inductors. A capacitive load simulator is a essential equipment in the power line modem development for indoor power line network. We accomplished a channel data base by the frequency response method about the total 224 capacitor load cases. On the basis of this measurement modeling it is here revealed that the power line communication channel is a more deterministic media.

• The Journal of Korean Association of Computer Education
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• v.11 no.2
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• pp.107-117
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• 2008

The agent system that can adjust the workload dynamically through thc periodical monitoring of the VoD system comprises the agency part interfacing the VoD system and the intelligence part reasoning or learning the facts required for the adjustment of workload. This paper proposes a learning method that can apply to the intelligence part of the agent system. The proposed method can adjust the workload more efficiently by the rule's reasoning process and case-based learning process. An experiment of implementing a simulator was conducted to see whether or not application of the proposed method to VoD systems is efficient. As a result of the experiment, it was found that the throughput and the average waiting time of the VoD server were relatively improved when the proposed method was applied compared to existing means.

• Journal of the HCI Society of Korea
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• v.14 no.2
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• pp.21-29
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• 2019

Take-over requests in semi-autonomous cars must be handled properly in the case of road obstacles or curved roads in order to avoid accidents. In these situations, situation awareness and appropriate decision making are essential for distracted drivers. This study used a driving simulator to investigate the components of auditory-visual information systems that affect safety, workload, and trust. Auditory information consisted of either voice guidance providing situation awareness for the take-over or a beep sound that only alerted the driver. Visual information consisted of either a screen showing how to maneuver the vehicle or only an icon indicating a take-over situation. By providing auditory information that increased situation awareness and visual information that aided decision making, trust and safety increased, while workload decreased. These results suggest that the levels of situation awareness and decision making ability affect trust, safety, and workload for drivers.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.166-171
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• 2019

This paper has designed a current mode class D power amplifier to increase the transmission efficiency of a 6.78 MHz wireless power transfer (WPT) transmitter and to ensure stable characteristics even when the transmitting and receiving coil intervals change. By reducing the loss due to the parasitic capacitor component of the transistor, which limits the theoretical efficiency of the linear amplifier, this research has improved the efficiency of the power amplifier. The circuit design simulator was used to design the high efficiency amplifier, and the power output and efficiency characteristics according to the load impedance change have been simulated and verified. In the simulation, 42.1 dBm output and 95% efficiency was designed at DC bias 30 V. The power amplifier was fabricated and showed 91% efficiency at the output of 42.1 dBm (16 W). The transmitting and receiving coils were fabricated for wireless power transfer of the drone, and the maximum power added efficiency was 88% and the output power was $42.1dBm{\pm}1.7dB$ according to the load change causing from the coil intervals.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.7
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• pp.650-664
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• 2000

NOW(Network of Workstations) is considered as a platform for running parallel programs by many people. One of the fundamental problems that must be addressed to achieve good performance for parallel programs on NOW is the determination of efficient job scheduling policies. Currently most research on NOW assumes that all the workstations in the NOW have the same processing power. In this paper we consider a NOW in which workstations may have different computing power. We introduce 10 classes of space sharing-based scheduling policies that can be applied to the NOW with heterogeneous computing power. We compare the performance of these scheduling policies by using the simulator which accepts synthetically generated sequential and parallel workloads and generates the response time and waiting time of parallel jobs as performance indices of various scheduling strategies. Through the experiments the case when a parallel program is partitioned heterogeneously in proportion to the computing power of workstations is shown to have better performance than when a parallel program is partitioned into parallel processes of the same size. When the owner returns to the workstation which is executing a parallel process, the policy which just lowers the priority of the parallel process shows better performance than the one which migrates the parallel process to a new idle workstation. Among the policies which use heterogeneous partitioning and process priority lowering, the adaptive policy performed best across the wide range of inter-arrival time of parallel programs but when the load imbalance among parallel processes becomes very high, the modified adaptive policy performed better.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.1 no.1
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• pp.58-69
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• 2002

Most of the traffic accidents are a rear-end collision and a clash generated in the signalized intersection on the local roads. So, it is demanded that the high-quality of signal control and dilemma zone control. According to the cases generated by foreign countries, we established the strategies which are composed of Volume-Density Control, strategy of the dilemma zone control using R-detector (microwave detector) In Japan and EC-DC Control. MOEs(Measure of effectiveness) are car numbers in the dilemma zone , max-out probability in the safe side and the average stopping delay in the progress side. We choose a signalized intersection in rural highway to analyze the effect of the strategies and practiced an on-the-spot survey. The result of the survey is applied to the basic data in the simulator. Consequently, strategy of the dilemma zone control using R-detector(microwave detector) in Japan is the best effective in the safe side and EC-DC control is the best in the progress side. Based on the result, we developed the effective strategy of the signal control . This strategy is composed of the strategy of Japan and the detector on the stopping line used in the EC-DC control. On the result of the analysis, new strategy is the best effective in two sides.

• Journal of Welding and Joining
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• v.16 no.5
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• pp.108-118
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• 1998

This study proposes th analysis and evaluation method of time series ultrasonic signal using the chaos feature extraction for ultrasonic pattern recognition. Features extracted from time series data using the chaos time series signal analyze quantitatively weld defects. For this purpose, analysis objective in this study is fractal dimension and Lyapunov exponent. Trajectory changes in the strange attractor indicated that even same type of defects carried substantial difference in chaosity resulting from distance shifts such as 0.5 and 1.0 skip distance. Such differences in chaosity enables the evaluation of unique features of defects in the weld zone. In quantitative chaos feature extraction, feature values of 4.511 and 0.091 in the case of side hole and 4.539 and 0.115 in the case of vertical hole were proposed on the basis of fractal dimension and Lyapunov exponent. Proposed chaos feature extraction in this study can enhances ultrasonic pattern recognition results from defect signals of weld zone such as side hole and vertical hole.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.229-234
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• 2007

In the IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time. which is uniformly selected from the Contention Window (CW) This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. The BEB scheme suffers from a unfairness problem and low throughput under high traffic load. In this paper, I propose a new backoff algorithm for use with the IEEE 802.11 Distributed Coordination Function.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.91-94
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• 2007

In the IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time, which is uniformly selected from the Contention Window (CW). This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. The BEB scheme suffers from a fairness problem and low throughput under high traffic load. In this paper, I propose a new backoff algorithm for use with the IEEE 802.11 Distributed Coordination Function.