• Journal of The Korean Astronomical Society
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• v.48 no.4
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• pp.207-212
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• 2015

We introduce the Lee Sang Gak Telescope (LSGT), a remotely operated, robotic 0.43-meter telescope. The telescope was installed at the Siding Spring Observatory, Australia, in 2014 October, to secure regular and exclusive access to the dark sky and excellent atmospheric conditions in the southern hemisphere from the Seoul National University (SNU) campus. Here, we describe the LSGT system and its performance, present example images from early observations, and discuss a future plan to upgrade the system. The use of the telescope includes (i) long-term monitoring observations of nearby galaxies, active galactic nuclei, and supernovae; (ii) rapid follow-up observations of transients such as gamma-ray bursts and gravitational wave sources; and (iii) observations for educational activities at SNU. Based on observations performed so far, we find that the telescope is capable of providing images to a depth of R = 21:5 mag (point source detection) at 5-σ with 15 min total integration time under good observing conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4259-4271
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• 2016

With the increased popularity of IEEE 802.11 WLAN, the density of the WLAN devices per access point has also increased, resulting in throughput performance degradation. One of the solutions to the problem is improving the protocol efficiency by a using multi-round contention scheme. This paper first discusses how to estimate the number of contending stations in a WLAN network by using minimum elapsed backoff counter values that can be easily monitored by each station. An approximate closed form expression is derived for the number of active contending stations using the smallest backoff counter value in the network. We then apply this result to adapt the number of contending rounds according to the network loading level to enhance the throughput performance of a multi-round contention scheme. Through simulation, we show that the accuracy of the estimation algorithm depends on the contention parameters of W and the number of backoff counter observing samples, and found a reasonable value for each parameter. We clearly show that our adaptive multi-round contention scheme outperforms the standard contention scheme that uses a fixed number of rounds.

• Journal of Biosystems Engineering
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• v.32 no.3
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• pp.173-178
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• 2007

This research was conducted to develop and analyze a wireless monitoring system for judging if sick or dead layers (SDL) exist in multi-tier layers battery (MLB) by machine vision, and to evaluate the performance between a wired monitoring system and it. This study used the AP (Access Point), the RS-285 to RS-232 converter, RS-232 to Ethernet converter, PICBASIC board and upgraded lump image processing method to change wired monitoring system into wireless monitoring system. The system was tested at a pilot farm and farm layer house. Results showed that monitoring judgement success rate at a pilot farm on normal cage (without SDL) was 82.3% and that on abnormal cage (with SDL) was 87.5%, respectively. And communication performance test results showed at farm layer house was $700{\sim}900$ kbps while equipments operated. There were dropped slightly than performance of wired monitoring system, however, the quantity was too small to make a significant difference of performance of the controling system developed for wireless communication.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1678-1681
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• 2005

The disk cam mechanism cam produce a positive motion with a relatively few components. In the present paper a shape design of cam using the relative velocity method and the machining information analysis using the circular interpolation are introduced. In the first part of the paper a machining information at each point using the circular interpolation is taken. This study purposes the analysis method of the cutting error due to the moving path of the cutter, so that we can lead to the optimum design in a disk cam mechanism..

• Journal of the Ergonomics Society of Korea
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• v.29 no.5
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• pp.763-770
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• 2010

The use of web widgets on desktop and mobile devices has been increasing rapidly. Web widgets provide access to activities and information from various sources across the web. As the number of supported widgets increases, managing widgets and finding relevant or interesting widgets becomes more complex. In addition, interacting with widgets in web service systems can be difficult, especially for novice users. Up to this point, there has been little research on web widget usability. This paper performs an experimental study regarding user interfaces of web widgets based on the mouse tracking and work-flow analysis. In the experiment, four sites providing widget services are chosen - iGoogle, Netvibes, My yahoo, and Wizard. The experiment participants perform three assigned tasks in the chosen sites, and their mouse operations are recorded using Camtasia, a screen casting software. Mouse tracking analysis is performed based on the recorded data in order to analyze common user behaviors. In addition, work-flow diagrams representing the operational flows to carry out the given tasks in each web site are constructed so as to visually and systematically analyze detailed usage patterns. The experimental study results presented in this paper can contribute to developing guidelines for highly usable and accessible interface design of web widgets.

• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.509-515
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• 2005

This paper explores the throughput of DCF protocol with both the traffic intensity and MSDU size at the MAC layer in the 802.11a wireless LAN. By exploring the throughput of DCF protocol with the data rate of 6Mbps, 12 Mbps, 24 Mbps and 54 Mbps, we find the fact that the less the data rate be, the higher the throughput be. We also find, from the throughput calculation by means of traffic intensity and MSDU size, that the longer the MSDU size is, the higher the throughput is. We also found the traffic intensity that the throughput is at the maximum point with the fixed MSDU size.

• The Journal of Korean Physical Therapy
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• v.17 no.1
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• pp.108-122
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• 2005

The gait training strategy in very important things for central nervous system(CNS) injury patients. There are many method and strategy for regaining of the gait who had CNS injury. A human being has central pattern generator(CPG) is spinal CPG for locomotion. It is a neural network which make the cyclical patterns and rhythmical activities for walking. Sensory input from loading and hip position is essential for CPG stimulation that makes the central neural rhythm and pattern generating structure. From sensory input, the proprioceptive information facilitate proximal muscles that controlled in voluntarily from cortical level and visual and / or acoustical information facilitate distal muscles that controlled voluntarily from subcortical level. Gait training method can classify that is functional level and structural level. Functional level includ level surface gait, going up and down the stair. It is important to facilitate a guide tempo in order to activate the central pattern generators. During the functional test or functional activities, can point out the poor period in gait that have to be facilitate in structural level. There are many access methods with patient position and potentiality. The methods are using of rhythmic initiation, replication and combination of isotonic with standing position. Clinically using it on weight transfer onto the stance leg, loading response, loading response and pre-swing, terminal stance, up and downwards stairs.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.734-737
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• 2004

The synthetic fibers such as polypropylene(PP) and polyvilyl-alcohol(PVA) fiber are poised as a low cost alternative for reinforcement in structural applications. It has been reported that synthetic fiber in cement composites can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. High performance fiber reinforced cementitious composite(HPFRCCs) shows ultra high ductile behavior in the hardened state, because of the fiber bridging properties. Therefore, a variety of experiments have being performed to access the performance of HPFRCCs recently. The research emphasis is on the flexural behavior of HPFRCCs made in synthetic fibers, and how this affects the composite property, and ultimately its strain-hardening performance. Three-point bending tests on HPFECCs are carried out. As the result of the bending tests, HPFRCCs showed high flexural strength and ductility. HPFRCCs made in PVA or Hybrid fiber were, also, superior to PP of singleness. On the other hand, effect of sand volume fraction on HPFRCCs made in PP was insignificant.

• Journal of the Korea Computer Industry Society
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• v.3 no.5
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• pp.547-556
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• 2002

This paper was proposed a wave path loss prediction algorithm using multilayer perceptron (MLP) model and wave propagation characteristic parameters for Wireless LAN in indoor radio environments. Receiving power was predicted by calculating indoor path loss in a Wireless LAN that has transmission power of 100mW and frequency of 2.4GHz, and was compared with measured. In the result of measurement shows that there is a difference between predicted and measured receiving power which can be reduced by an accurate analysis of the various path loss factors. In order to fix the access point(AP) positions was used the proposed a wave path loss prediction algorithm, and designed the optimum cell for Wireless LAN.

• Journal of Korean Library and Information Science Society
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• v.33 no.3
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• pp.235-256
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• 2002

The purpose of this study is to suggest a reform after detecting out issues and problems associated with the KCR 4th ed.(draft). KCR(Korean Cataloguing Rules) is representative cataloguing rules in Korea, the 4th ed.(draft) of which was prepared by Cataloguing Committee(department of KLA) in 2001. As a result of this study, a lot of problem which are glossary, context, inconsistency of the contents, rules applied to card catalog, and others, were found out. Thus, substantial improvements were able to be suggested.