• Journal of Information Technology Services
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• v.15 no.4
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• pp.97-109
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• 2016

The rapid deployment of millions of mobile sensors and smart devices has resulted in high demand for opportunistic encounter-based networking. For the cooperative video surveillance of dashboard cameras in nearby vehicles, a fast and energy-efficient asynchronous neighbor discovery protocol is indispensable because a dashboard camera is an energy-hungry device after the vehicle's engine has turned off. In the existing asynchronous neighbor discovery protocols, all nodes always try to discover all neighbors. However, a dashboard camera needs to discover nearby dashboard cameras when an event is detected. In this paper, we propose a fast and energy-efficient asynchronous neighbor discovery protocol, which enables nodes : 1) to have different roles in neighbor discovery, 2) to discover neighbors within a search range, and 3) to report promptly the exact discovery result. The proposed protocol has two modes: periodic wake-up mode and active discovery mode. A node begins with the periodic wake-up mode to be discovered by other nodes, switches to the active discovery mode on receiving a neighbor discovery request, and returns to the periodic wake-up mode when the active discovery mode finishes. In the periodic wake-up mode, a node wakes up at multiples of number ${\alpha}$, where ${\alpha}$ is determined by the node's remaining battery power. In the active discovery mode, a node wakes up for consecutive ${\gamma}$ slots. Then, the node operating in the active discovery mode can discover all neighbors waking up at multiples of ${\beta}$ for ${\beta}{\leq}{\gamma}$ within ${\gamma}$ time slots. Since the proposed protocol assigns one half of the duty cycle to each mode, it consumes equal to or less energy than the existing protocols. A performance comparison shows that the proposed protocol outperforms the existing protocols in terms of discovery latency and energy consumption, where the frequency of neighbor discovery requests by car accidents is not constantly high.

• Journal of Information Technology Services
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• v.13 no.1
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• pp.125-134
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• 2014

Device discovery for D2D (device-to-device) communication enables a device to discover other devices in order to initiate communication with them. Devices should perform the discovery phase using a small quantity of radio resource in a short time and be able to reduce the load of the base station. Legacy device discovery schemes have focused on discovering as many target devices as possible. However, it is not appropriate for peer-to-peer D2D communication scenario. Further, synchronization problems are an important issue for discovery signal transmission. This paper proposes a discovery method that one requesting device discovers a specific target for communication. Multiple antenna beamforming is employed for the synchronization between the base station and a target device. The proposal can reduce the load of the base station using the information that it already maintains and improve the reliability of the device discovery because two times of synchronizations using beamforming among the base station and devices can make the exact discovery of a target device with mobility possible.

• Natural Product Sciences
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• v.19 no.2
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• pp.150-154
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• 2013

A new oleanane-type triterpenoid saponin together with six known saponins were isolated from the roots of Pulsatilla cernua. Their structures were elucidated on the basis of spectroscopic data, including 2D NMR spectra and chemical evidence. Compounds 1 and 6 are reported from this genus for the first time.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.223-226
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• 2003

In this paper, we propose new agent discovery and route discovery schemes to support Mobile IP (MIP) in Ad Hoc networks with wireless backbone. The wireless backbone consisting of stationary wireless routers and Internet gateways (IGs) is a kind of wireless access network of IP-based core network. The proposed scheme utilizes favorable features of wireless backbone such as stable links and no energy constraints. In the agent discovery scheme, backbone-limited periodic Agent Advertisement (AA) and proxy-AA messages are used, which reduce network-wide broadcasting overhead caused by AA and Agent Solicitation messages and decentralize MIP processing overhead in IGs. In order to reduce delay time and control message overhead during route discovery far the destination outside Ad Hoc network, we propose a cache-based scheme which can be easily added to the conventional on-demand routing protocols. The proposed schemes can reduce control overhead during agent discovery and route discovery, and efficiently support MIP in Ad Hoc network with wireless backbone.

• Journal of The Korean Association of Information Education
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• v.12 no.1
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• pp.89-97
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• 2008

The purpose of this study was to design a system of web-based discovery learning and testify its effectiveness, in order to complement the difficulties of discovery learning considered to be hard to be applied to the school education because of shortage of time and materials, though discovery learning is one of inquiry learning emphasized in the 7th national curriculum of elementary science. As for the process of testifying, it compared the differences between comparative group with normal discovery learning model and experimental group with web-based system of discovery learning model, targeting the subject of extending spring among the 4th grade science. As a result, the experimental group achieved higher academic performance compared to the comparative group applied to the normal discovery learning model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.2052-2067
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• 2011

Complementary trees are two spanning trees rooted at the sink node satisfying that any source node's two paths to the sink node on the two trees are node-disjoint. Complementary trees routing strategy is a special node-disjoint multi-path routing approach. Several complementary trees routing algorithms have been proposed, in which path discovery methods based on depth first search (DFS) or Dijkstra's algorithm are used to find a path for augmentation in each round of path augmentation step. In this paper, a novel path discovery method based on multi-tree-growing (MTG) is presented for the first time to our knowledge. Based on this path discovery method, a complementary trees routing algorithm is developed with objectives of low average path length on both spanning trees and low complexity. Measures are employed in our complementary trees routing algorithm to add a path with nodes near to the sink node in each round of path augmentation step. The simulation results demonstrate that our complementary trees routing algorithm can achieve low average path length on both spanning trees with low running time, suitable for wireless sensor networks in industrial scenarios.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.8
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• pp.3-12
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• 2016

Bluetooth Low Energy (BLE) protocol has attracted attention as a promising technology for low data throughput and low energy wireless sensor networks. Fast device discovery is very important in a BLE based wireless network. It is necessary to configure the network to work with minimized energy consumption because the BLE network nodes are expected to operate a long time typically on a coin cell battery. However, since it is difficult to obtain low energy and low latency at the same time, the BLE standard introduces wide range setting of parameters related to device discovery process and let the network operators to set up parameter values for the application. Therefore, it is necessary to analyze the performance of device discovery according to the related parameter values prior to BLE network operation. In this paper we analyze the expected value and the cumulative distribution function of the number of advertisements for device discovery in the BLE network. In addition, we propose a scheme for controlling the interval between advertising events that can improve the performance of device discovery without increasing energy consumption.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.154-156
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• 2006

These days wireless sensor networks receive much attention from industry and researchers on various fields. The challenge is that wireless sensor networks have limited resources. Nevertheless, the route discovery in ZigBee sensor networks is performed by simple flooding when the original racket is rebroadcasted at least once by every node in a network. Such uncontrolled flooding generates an excessive number of packets competing for the media and causes a high collision rate. In this article, we propose a suitable packet Time-To-Live value to solve problems of uncontrolled flooding in ZigBee networks. It is shown that more sufficient route discovery in a ZigBee network can save network resources and lengthen the life of a sensor network.

• Journal of The Korean Association For Science Education
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• v.25 no.7
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• pp.711-720
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• 2005

The purpose of this study was to understand mechanisms of scientific discovery and how this can help students, as young scientists, to understand scientific ideas in the science classroom. To unravel this mechanism, this study employed the notion of chaos. This phenomena was rediscovered by Edward Lorenz. In this paper, the general concept of chaos was briefly discussed in relation with previous scientific theories such as Newtonian physics and quantum mechanics. Following this, discovery constraints in terms of available technology at the time was described. In addition, Lorenz's psychological processes during the discovery was also discussed. Based on analysis, major implications for the field of science education were the provision of relevant schemata, the use of cognitive tools, the presentation of problems with various representational forms, and the sharing of ideas with others.

• Journal of the Korean Society for information Management
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• v.33 no.4
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• pp.125-157
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• 2016

As the domestic companies which have made inroads into foreign markets have more lawsuits, these companies' demands for responding to E-Discovery are also increasing. E-Discovery, derived from Anglo-American law, is the system to find electronic evidences related to lawsuits among scattered electronic data within limited time, to review them as evidences, and to submit them. It is not difficult to find, select, review, and submit evidences within limited time given the reality that the domestic companies do not manage their records even though lots of electronic records are produced everyday. To reduce items to be reviewed and proceed the process efficiently is one of the most important tasks to win a lawsuit. The Predictive Coding is a computer assisted review instrument used in reviewing process of E-Discovery, which is to help companies review their own electronic data using mechanical learning. Predictive Coding is more efficient than the previous computer assister review tools and has a merit to select electronic data related to lawsuit. Through companies' selection of efficient computer assisted review instrument and continuous records management, it is expected that time and cost for reviewing will be saved. Therefore, in for companies to respond to E-Discovery, it is required to seek the most effective method through introduction of the professional Predictive Coding solution and Business records management with consideration of time and cost.