• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1346-1355
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• 2005

Recently, the development of passive optical networks (PON) for FTTH (Fiber-To-The-Home) have been actively conducted. In PON, a burst-mode transceiver is one of key modules. In this paper, we have made the protype module of a 155.52 Mpbs optical burst-mode transceiver with commercially available chips and then have measured the performance. Also, a new method of burst-mode clock recovery have been proposed. The burst-mode clock recovery implemented by using CPLD(Complex Programmable Logic Device) has coupled with the above burst-mode transceiver and has been tasted.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.484-489
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• 2002

Whenever the accidents occur in the railway areas, their prompt recovery is very important. The individual way has been used to resolve these accidents by direct visiting the site and reporting to others who cares for these cases. As a result, we are planning to operate the MTS (Moving picture Transmission System) for a timely information's transmission to the related peoples in the central control center by transforming the picture information on the accident-site to the digital information. The proposed system is not a transmission system using exclusive lines, but utilizing the existing railway computer network. We construct a network server device so that a dispatcher can easily connect with the server through the railway intranet. In some railway environments such as disturbed field situations and geographical condition(in tunnels and bridges, etc) building up the wired network is difficult. Solving this problem, we reviewed the wireless network. Finally we proposed the mixed wireless network that is able to cover the wired network. We then installed and tested the wired network and wireless network respectively in wayside of a railway field. Through the testing, we identified many detailed matters for some network construction approaches to the control room and many field device-connecting schemes. This research will contribute to minimize the number of staff dispatched to a disturbed field, decrease the accident recovery time and improve the quality of service to the passenger.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.16-17
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• 2005

Local lifetime control by ion implantation has become an useful tool for production of modern power devices. In this work, punch-through diodes were irradiated with protons for the high speed power diode fabrication. Proton irradiation was executed at the various energy and dose conditions. Characterization of the device was performed by I-V, C-V and Trr measurement. We obtained enhanced reverse recovery time characteristics which was about 45% of original device and about 73% of electron irradiated device. The measurement results showed that proton irradiation was able to effectively reduce minority carrier lifetime.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.1
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• pp.1-10
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• 2018

Recently, interest in the development of alternative water resources has been increasing rapidly due to environmental pollution and depletion of water resources. In particular, seawater desalination has been attracting the most attention as alternative water resources. As seawater desalination consumes a large amount of energy due to high operating pressure, many researches have been conducted to improve energy efficiency such as energy recovery device (ERD). Consequently, this study aims to compare the energy efficiency of RO process according to ERD of isobaric type which is applied in scientific control pilot plant process of each $100m^3/day$ scale based on actual RO product water. As a result, it was confirmed that efficiency, mixing rate, and permeate conductivity were different depending on the size of the apparatus even though the same principle of the ERD was applied. It is believed that this is caused by the difference in cross-sectional area of the contacted portion for pressure transfer inside the ERD. Therefore, further study is needed to confirm the optimum conditions what is applicable to the actual process considering the correlation with other factors as well as the factors obtained from the previous experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.1
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• pp.35-44
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• 2020

The growing use of public blockchain-based virtual cryptocurrency calls for secure management of blockchain account information managed through cryptocurrency wallet programs. The previously proposed wallet program has high security in terms of managing an account's private key, but low security in managing an account's recovery phrase. Therefore, in this paper, we propose a safe management system of blockchain account recovery string based on the new user authentication method using the user's mobile device information and OTP technique to overcome the problem of the existing account recovery string management method. It also conducts an analysis of the proposed blockchain account recovery string management system based on the expected behavior scenario.

• Journal of Bio-Environment Control
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• v.12 no.3
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• pp.107-113
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• 2003

This study was carried out to improve the performance of pre-developed heat recovery devices attached to exhaust-gas flue connected to combustion chamber of greenhouse heating system. Four different units were compared in the aspect of heat recovery performance; A-, B-, and C-types are exactly the same with the old ones reported in previous studies. D-type newly developed in this experiment is mainly different with the old ones in its heat exchange area and tube thickness. But airflow direction(U-turn) and pipe arrangement are similar with previous three types. The results are summarized as follows; 1. System performances in the aspect of heat recovery efficiency were estimated as 42.2% for A-type, 40.6% for B-type, 54.4% for C-type, and 69.2% for D-type. 2. There was not significant improvement of heat recovering efficiency between two different airflow directions inside the heat exchange system. But considering current technical conditions, straight air flow pattern has more advantage than hair-pin How pattern (U-turn f1ow). 3. The main factors influencing on heat recovery efficiency were presumably verified to be the total area of heat exchange surface, the thickness of ail-flow pipes, and the convective heat transfer coefficient influenced by airflow velocity under the conditions of allowable pipe durability and safety. 4. Desirable blower capacity for each type of heat recovery units were significantly different to each other. Therefore, the optimum airflow capacity should be determined by considering in economic aspect of electricity required together with the optimum heat recovery performance of given heat recovery systems.

• Journal of the Korea Convergence Society
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• v.11 no.2
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• pp.147-154
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• 2020

This study is about the development of ICT-based wearable devices for vision recovery that can cause functional myopia improvement through accommodation training. Vision Training Device(OTUS) is a head mount type wearable device, which naturally stimulates the contraction and relaxation of the ciliary muscles of eye. Users can conduct customized vision training based on personal vision information stored through the device. In the experiment, the effects of improvement of the symptoms by the accommodation training were compared and analysed for the two groups (16 comparative group and 16 accommodation training group) after causing functional myopia. The result showed the functional myopia improved average 0.44D±0.35 (p<0.05) at the accommodation training group compared to the comparative group. This study proved the effectiveness of vision training device(OTUS) on functional myopia, but further clinical trials are judged necessary to prove the possibility of long-term control of the functional myopia.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.6 no.1
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• pp.1-15
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• 2008

This study was designed to investigate the effect of treadmill exercise of low-intensity and high-intensity on the functional recovery and histological change in spinal cord injury rats. Sprague-Dawley rats were experimented(n=15) for this research. Spinal cord injury was induced by the NYU drop impacter device after laminectomy. After operation, rats were test at modified Tarlov scale at 3 days, and divided into the control group(n=5), experimental group I(n=5, low-intensity treadmill) and experimental group II(n=5, high-intensity treadmill). The rats were disciplined from 7 day through 21 day. Functional recovery was evaluated by the BBB scales and the Grid Walk test for the progressive locomotor recovery at 3, 7, 14, 21 days. Histopathological studies for the muscle in order to observation the change of damage and size of the organized surface which is visible visually it executed hematoxylin & eosin stain. According to the result of 4 weeks of treadmill exercise, group II showed improvement than group I of motor behavior after spinal cord injury.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.738-744
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• 2006

In order to utilize the condensation heat of refrigerants in condenser on the absorption chiller system, the solution cooled condenser (SCC) was proposed using the weak solution of absorber as a cooling medium. The increase of COP with the increase of UA of the solution cooled condenser was approximately 0.009 in maximum with single effect one, and is about maximum 0.008 in occasion of double effect one with series flow compared to that without. In the case of heat exchanger, effectiveness is about 0.85, it's increments are 0.008 and 0.0072, respectively. And solution cooled condenser is more effective device in the single effect absorption system than double effect system for the principle of operation. On the other hand, as the solution split ratio increases when the value of UA is fixed, COP is increased and as the solution split ratio increases when the value of UA is fixed, COP is increased. If the flow rate of cooling water or the value of UA is reduced in order to increases the heat recovery of solution cooled condenser, heat recovery of solution cooled condenser is increased a little but COP is decreased as the system pressure is increased.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.103-106
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• 2003

In this paper, we present a hybrid inertial and vision-based tracking system for VR applications. One of the most important aspects of VR (Virtual Reality) is providing a correspondence between the physical and virtual world. As a result, accurate and real-time tracking of an object's position and orientation is a prerequisite for many applications in the Virtual Environments. Pure vision-based tracking has low jitter and high accuracy but cannot guarantee real-time pose recovery under all circumstances. Pure inertial tracking has high update rates and full 6DOF recovery but lacks long-term stability due to sensor noise. In order to overcome the individual drawbacks and to build better tracking system, we introduce the fusion of vision-based and inertial tracking. Sensor fusion makes the proposal tracking system robust, fast, accurate, and low jitter and noise. Hybrid tracking is implemented with Kalman Filter that operates in a predictor-corrector manner. Combining bluetooth serial communication module gives the system a full mobility and makes the system affordable, lightweight energy-efficient. and practical. Full 6DOF recovery and the full mobility of proposal system enable the user to interact with mobile device like PDA and provide the user with natural interface.