• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5C
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• pp.493-505
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• 2003

A new inter-client synchronization framework for multicast media streaming is proposed employing a server-client coordinated adaptive playout control. The proposed adaptive player controls the playback speed of audio and video by adopting the time-scale modification of audio. Based on the overall synchronization status as well as the buffer occupancy level, the playout speed of each client is manipulated within a perceptually tolerable range. Additionally, the server implicitly helps increasing the time available for retransmission while the clients perform an interactive error recovery mechanism with the assistance of playout control. The network-simulator based simulations show that the proposed framework can reduce the playout discontinuity without degrading the media quality, and thus mitigate the client heterogeneity.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.484-488
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• 2009

분산전원의 양적,질적 성장이 가속화되고 전력계통과의 활발한 연계가 예상되는 시기에 기존계통과는 달리 수용가에 전력품질측면으로 미치는 영향에 대한 심층적인 분석과 대안책을 마련하지 않는다면 수용가의 전기안전을 장담할 수 없게 되었다. 따라서 이에 본 논문은 분산전원중에서 풍력발전단지가 전력계통에 연계시 수용가에 미치는 영향을 실측 데이터를 이용해서 전력품질 영향을 분석하였으며, 풍력발전단지가 충분히 발전을 할 때, 인근 수용가의 고조파 패턴은 주로 영향을 받는다는 사실을 확인 할 수 있었다.

• The monthly packaging world
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• s.61
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• pp.164-167
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• 1998

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.34-40
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• 2018

In this study, the optimal buffer size is calculated for seamless video playback on a mobile device. Buffer means the memory space for multimedia packet which arrives in mobile device for video play such as VOD service. If the buffer size is too large, latency time before video playback can be longer. However, if it is too short, playback service can be paused because of shortage of packets arrived. Hence, the optimal buffer size insures QoS of video playback on mobile devices. We model the process of buffering into a discret-time queueing model. Mean busy period length and mean waiting time of Geo/G/1 queue with N-policy is analyzed. After then, we uses the main performance measures to present numerical examples to decide the optimal buffer size on mobile devices. Our results enhance the user satisfaction by insuring the seamless playback and minimizing the initial delay time in VOD streaming process.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.54-63
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• 2004

This paper describes a hybrid QoS guarantee scheme for high quality audio streaming services on the Internet. The continuous playback of the audio data requires the isochronous transmission of the audio data packet through the Internet. In order to retain the QoS at the ultimate destination (client) as the same as servers provide, the transmission protocols should consider the error conditions such as packet loss, and out of order delivery. Generally, the protocols supporting the transmission of continuous media data do not try to recover the errors. The protocols are working somehow for the toll quality multimedia streaming services, but rot for the high quality streaming services, such as the DVD sound/music payback. The hybrid QoS guarantee scheme includes the three mechanisms to overcome the problem. The selective retransmission for the lost packet, the adaptive buffering at client-side, and the adaptive transmission rate at server-side are totally adopted to recover the packet loss with the minimal overhead, to prevent from the buffer starvation during the retransmission, and to maintain the isochronous transmission even after the retransmission. The experiments have shown good results for the high Quality audio streaming services on the Internet.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1371-1380
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• 2007

Study on the instability of waste plastic's thermal pyrolysis oil was carried out for the purpose of improving its quality. The reaction of pyrolysis oil with ozone changed double bonds into aldehydes and ketone, estimated that HDPE pyrolysis oil contained $\sim45$ wt% 1-alkene type olefins, and PP pyrolysis oil did $\sim73$ wt% olefins, which consisted of $\sim47$ wt% secondary and $\sim20$ wt% primary alkenes. The dark brown color and odor of pyrolysis oil were improved by eliminating double bonds, indicated that they were directly related to unsaturated hydrocarbons. Container test showed that metal can affected oil quality worse than the brown glass bottle. Antioxidant added into pyrolysis oil was consumed up to 90% within $2\sim3$ days and the wt. composition of unsaturated hydrocarbons in pyrolysis oil was not changed within 50 days, inferring that instability of pyrolysis oil due to unsaturated bonds can be stabilized by antioxidants. Adsorption test on silica gel, activated carbon and alumina to remove precipitates in oil produced a good result, but not enough to remove moisture. However, cheap anhydrous sodium carbonate showed the best removal efficiency of moisture as well as precipitates in oil. Therefore the pyrolysis oil quality improvement was accomplished by applying anhydrous $Na_2CO_3$ into the production plant.

• 월간 기계설비
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• s.239
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• pp.44-49
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• 2010

국토해양부는 최근 신재생 에너지원으로 주목받고 있는 해양에너지 개발의 일환으로 "해양심층수를 활용한 냉난방 및 온도차 발전기술 개발"에 착수한다고 밝혔다. 이에 따라 그동안 고품질 생수, 식품, 농 수산업 등 주로 산업적 용도로 활용되었던 해양심층수가 앞으로는 신재생 에너지원으로 그 활용폭이 넓어질 전망이다.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.997-1004
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• 2012

In this paper, we propose and implement a signal quality measurement algorithm for CDMA2000 1x terminal. The proposed algorithm is suitable to be implemented in software on a PC-based platform and extract the received signal after carrying out equalization, PN code acquisition and tracking, frequency and phase offset compensation with 4-oversampled input signal. Then, through despreading and demodulation with the extracted signal, the proposed algorithm regenerate the reference signal to be used in measurement. The signal quality is measured using this regenerated signal and the extracted signal.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.361-364
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• 2008

In this paper, several fields for improving shift quality and mode conversion quality are presented and considered. For a series type hybrid vehicle, improving mode conversion quality is important because it changes its speed with its own motors. A parallel type hybrid vehicle usually has AT or AMT, and its motor and engine can work independently. Therefore, improving both of two qualities is equally important in this case. For a power split type hybrid vehicle, improving mode conversion quality is more important due to the existence of planetary gears which change vehicle's speed.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.159-166
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• 2005

In Korea, although the generation of waste plastic has been increasing, the rate of recycling is considerably low and moreover, there is no suitable method for the treatment of waste plastics. However, pyrolysis, which is appropriate for the treatment of highly polymerized compounds, such as plastics, has recently gained much interest. In this study, a property of the products from the pyrolysis of mixed waste plastics, with a possible practical use for the recycling oil produced, were assessed. First of all, in order to investigate the pyrolysis characteristic of waste plastics, TGA (Thermogravimetric analysis) and DCS (Differential Scanning Calorimetry) were performed on a number of different plastics, including PP, LDPE, HDPE, PET and PS, as well as others. According to the result, it appeared that PP was the most efficiently pyrolyzed by changing the temperature, followed by LDPE, HDPE, PET, PS and the other plastics, in that order. From the results, the optimum conditions f3r pyrolysis were set up, and the different waste plastics pyrolyzed. The recycling oil produced from the flammable gases generated during the pyrolysis was com-pared with fuel oil by an analysis using the petroleum quality inspection method on KS(Korea industrial Standard). The results of the analysis showed the recycling oil was of a similar standard to fuel oil, with the exception of the ignition point, with a quality somewhere between that of paraffin oil and diesel fuel. With respect to these results, the quality of the recycling oil produced by the pyrolysis of waste plastics was suf-ficient for use as fuel oil.