• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1733-1751
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• 2015

The IEEE 802.15.4 standard not only provides a maximum of seven guaranteed time slots (GTSs) for allocation within a superframe to support time-critical traffic, but also achieves ultralow complexity, cost, and power in low-rate and short-distance wireless personal area networks (WPANs). Real-time wireless body area sensor networks (WBASNs), as a special purpose WPAN, can perfectly use the IEEE 802. 15. 4 standard for its wireless connection. In this paper, we propose an adaptive GTS allocation scheme for real-time WBASN data transmissions with different priorities in consideration of low latency, fairness, and bandwidth utilization. The proposed GTS allocation scheme combines a weight-based priority assignment algorithm with an innovative starvation avoidance scheme. Simulation results show that the proposed method significantly outperforms the existing GTS implementation for the traditional IEEE 802.15.4 in terms of average delay, contention free period bandwidth utilization, and fairness.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.200-204
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• 2007

The release of IEEE 802.15.4 PHY-MAC standard represents a milestone in developing of commercial wireless sensor network pursuing low power and low cost. In this paper, IEEE 802.15.4 Medium Access Control (MAC) protocol was analysed at the point of power consumption. This analysis measured the amount of the rest of power after transmitting data with beacon enabled mode and the power consumption of each node in the time period. ns-2 simulation is used to verify the analysis.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.216-222
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• 2003

Train control by radio based communication is one of the interesting new fields in train signal. The radio based control has more benefits, low headway and low construction and maintenance cost, than conventional control. In this paper, a safe and efficient train operation is introduced. Triple radio communications, train to train, train to station, and train to central traffic control, are used to increase the reliability. One of these communications channels has a fault; the others can take the functions of it. Absolute position of a train is transmitted to station via radio communication. In the station, the interlocking mechanism should be activated as the legacy.

• Electronics and Telecommunications Trends
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• v.38 no.5
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• pp.114-124
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• 2023

Recently, there have been the World Economic Forum's space economy guidelines, the International Telecommunication Union's regulations for each satellite orbit, the development of chips using satellite communication by global manufacturers and service providers, and the registration of key telecommunication businesses. Accordingly, trends in low-orbit 5G satellite communication services in Korea were investigated and analyzed, and the current situation in Korea was diagnosed. Korea's satellite communications accounts for 0.31% of all satellites when analyzed centering on countries with 20 or more satellites. Korea's communication satellite holdings are insufficient compared to 187 times that of the United States, 45 times that of Russia, and 18 times that of China. There is no link technology between 5G and LEO, and the cost of launch vehicles is high. In addition, it is judged that the ecosystem of equipment companies in the low-orbit 5G-NTN business model is insufficient.

• Korean Journal of Construction Engineering and Management
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• v.25 no.3
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• pp.27-36
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• 2024

The effective control of cost overrun is a crucial issue for construction companies to secure profitability. Especially in situations where cost pressures are significant due to factors such as rising raw material prices and increased financial costs due to high-interest rate policies, cost overruns resulting from project failures have a highly detrimental impact on the profitability of construction firms. The objective of this study is to analyze the current status of cost overrun control measures adopted by construction companies using the IPA technique and provide key characteristics and implications. The IPA analysis results showed that practitioners in general contractors exhibit a high level of interest and effort regarding cost overrun while the performance level is relatively low. Nevertheless, the measures considered important to control cost overruns generally show a high tendency for execution as well. Cost overrun control measures that show high importance but low execution are primarily related to collaboration and communication sectors. To effectively control cost overruns, enhancing collaboration and communication with construction supervisors/CM, headquarters, and regulatory authorities emerged as the most urgent need. Through this study, the current status and areas for improvement regarding cost overrun control measures in general contractors can be identified. This can be valuable for deriving directions and enhancements for future cost overrun control strategy development.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.6
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• pp.265-278
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• 2013

With the recent advancements in various wireless communication technologies, the importance of mobile multicasting is coming to the fore, in an effort to use network resources more efficiently. In the past, when various mobile IP-based multicast techniques were proposed, the focus was put on the costs needed for network delivery for providing multicast services, as well as on minimizing the multicast handover delay. For techniques using MIPv6 (Mobile IPv6), a host-based mobility management protocol, however, it is fundamentally difficult to resolve the problems of handover delay and tunnel convergence. To resolve these problems, a network-based mobility management protocol called PMIPv6 (Proxy Mobile IPv6) was standardized. Although performance is improved in PMIPv6 over MIPv6, it still suffers from the problems of handover delay and tunnel convergence. In this paper, to overcome these limitations, a technique called LFH (Low-cost and Fast Handoff) is proposed for fast and low-cost mobility management with multicasting support in PMIPv6 networks. To reduce the interactions between the complex multicast routing protocol and the multicast messages, a simplified proxy method called MLD (Multicast Listener Discovery) is implemented and modified. Furthermore, a TCR (Tunnel Combination and Reconstruction) algorithm was used in the multicast handover procedure within the LMA (Local Mobility Anchor) domain, as well as in the multicast handover procedure between domains, in order to overcome the problem of tunnel convergence. As a result, it was found that LFH has reduced multicast delay compared to other types of multicast techniques, and that it requires lower costs as well.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.236.1-236.1
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• 2015

The surface morphology of front transparent conductive oxide (TCO) films is very important to achieve high current density in amorphous silicon (a-Si) thin film solar cells since it can scatter the light in a better way. In this study, we present the low cost hydrothermal deposited uniform zinc oxide (ZnO) nano-flower structure with various aspect ratios for a-Si thin film solar cells. The ZnO nano-flower structures with various aspect ratios were grown on the RF magnetron sputtered AZO films. The diameters and length of the ZnO nano-flowers was controlled by varying the annealing time. The length of ZnO nano-flowers were varied from 400 nm to $2{\mu}m$ while diameter was kept higher than 200 nm to obtain different aspect ratios. The ZnO nano-flowers with higher surface area as compared to conventional ZnO nano structure are preferred for the better light scattering. The conductivity and crystallinity of ZnO nano-flowers can be enhanced by annealing in hydrogen atmosphere at 350 oC. The vertical aligned ZnO nano-flowers showed higher haze ratio as compared to the commercially available FTO films. We also observed that the scattering in the longer wavelength region was favored for the high aspect ratio of ZnO nano-flowers. Therefore, we proposed low cost and vertically aligned ZnO nano-flowers for the high performance of thin film solar cells.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.711-716
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• 2003

This study considers the implementation issues of the inter-vehicle communication system for the vehicle platoon experiments via a testbed. The testbed, which consists of three scale vehicles and one RCS(remote control station), is developed as a tool for functions evaluation between simulation studies and full-sized vehicle researches in the previous study. The cooperative communication of the vehicle-to-vehicle or the vehicle-to-roadside plays a key role for keeping the relative spacing of vehicles small in a vehicle platoon. The static platoon control, where the number of vehicles remains constant, is sufficient for the information to be transmitted in the suitably fixed interval, while the dynamic platoon control such as merge or split requires more flexible network architecture for the dynamical coordination of the communication sequence. In this study, the wireless communication device and the reliable protocol of the flexible network architecture are implemented for our testbed, using the low-cost, ISM band transceiver and the 8-bit microcontroller.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.109-112
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• 2010

Recently, communication components prefer Bluetooth or Zigbee for PAN. However, using these makes expensive and complicated products such as audio equipments, mobile phones, PC, etc. for transmitting simple messages with low rate. In this paper, we propose wireless communication method using ultrasonic in the audio frequency limit band with speakers and microphones which are in products. We suggest transmitting and receiving methods in the audio frequency limit band for transmitting data without affecting audio signal, and implement an ultrasonic communication modem. Finally, we verify the performance of the ultrasonic communication modem by experiments in an environment with background noise.

• Journal of the Korean Graphic Arts Communication Society
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• v.10 no.1
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• pp.35-54
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• 1992

Direct electrostatic coating method is simple, low cost and environmentally useful method. We are investigated on the coating of carrier transfer polymer layer on the carrier generate inorganic pigment layer using direct electrostatic coating method. The sample was obtained electrostatic deposite layer by fusing and calendering on the copper phthalocyanine. we could be found several polymer thin film shows good bond properties between film and pigment layer.