• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.450_451
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• 2009

최근 부하증가에 대한 안정적 전력공급과 환경문제 해결은 전 세계적 이슈로 등장되고 있으며, 그 해결책으로써 분산형전원(Distributed generation, DG)에 대한 관심이 높아지고 있다. DG는 경제적 효율적 이유로 기존 전력계통과 연계해 운전되는데, 태양광이나 풍력과 같은 재생에너지를 이용한 DG의 불확실하며 빈번한 출력변동은 배전계통의 전압조정을 어렵게 만든다. 배전계통의 전압조정을 위해 배전용변전소의 부하시 탭 변환기(Under Load Tap Changer, ULTC)가 이용되고 있다. ULTC는 부하변동에 따른 배전선로상 전압강하를 보상하는 선로 전압강하보상법(Line Drop Compensation, LDC)에 의해 조정된다. LDC 전압조정법에서, 측정된 뱅크전류와 미리 설정된 LDC 정정치(LDC parameters, 부하중심점 전압과 등가 임피던스)를 이용해 ULTC의 송출전압을 결정한다. LDC 정정치 설계시, 기존에는 ULTC 탭 동작횟수를 줄이는 것이 주요 목표였고, 이 목표는 DG 도입을 제한하는 큰 원인이 되고 있다. 그러므로 본 논문에서는 DG 도입을 증가시키는 새로운 ULTC 전압조정법을 제시하고 모델 배전계통 시뮬레이션을 통해 그 유효성을 확인한다.

• Journal of the Korea Society of Computer and Information
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• v.29 no.5
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• pp.177-187
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• 2024

177-Existing music recommendation systems do not sufficiently consider the discrepancy between the intended emotions conveyed by song lyrics and the actual emotions felt by users. In this study, we generate topic vectors for lyrics and user comments using the LDA model, and construct a user preference model by combining user behavior trajectories reflecting time decay effects and playback frequency, along with statistical characteristics. Empirical analysis shows that our proposed model recommends music with higher accuracy compared to existing models that rely solely on lyrics. This research presents a novel methodology for improving personalized music recommendation systems by integrating emotion recognition and user behavior analysis.

• Journal of Broadcast Engineering
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• v.14 no.5
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• pp.573-588
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• 2009

In this paper, we propose a novel video quality degradation monitoring scheme titled VR-VQMS(Visual Rhythm based Video Quality Monitoring Scheme) over an IPTV service prone to packet losses during network transmission. Proposed scheme quantifies the amount of quality degradation due to packet losses, and can be classified into a RR(reduced-reference) based quality measurement scheme exploiting visual rhythm data of H.264-encoded video frames at a media server and reconstructed ones at an Set-top Box as feature information. Two scenarios, On-line and Off-line VR-VQMS, are proposed as the practical solutions. We define the NPSNR(Networked Peak-to-peak Signal-to-Noise Ratio) modified by the well-known PSNR as a new objective quality metric, and several additional objective and subjective metrics based on it to obtain the statistics on timing, duration, occurrence, and amount of quality degradation. Simulation results show that the proposed method closely approximates the results from 2D video frames and gives good estimation of subjective quality(i.e.,MOS(mean opinion score)) performed by 10 test observers. We expect that the proposed scheme can play a role as a practical solution to monitor the video quality experienced by individual customers in a commercial IPTV service, and be implemented as a small and light agent program running on a resource-limited set-top box.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1976-1985
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• 2015

The amount of packets in palyout buffer of video streaming receiver can be changed by network condition, and saturated and exhausted by the delay and jitter. Especially, if the amount of incoming video traffic exceeds the maximum allowed playout buffer, buffer overflow problem can be generated. It makes the deterioration of video image and the discontinuity of playout by skip phenomenon. Also, if the incoming packets are delayed by network confusion, the stop phenomenon of video image is made by buffering due to buffer underflow problem. To solve these problems, this paper proposes the video streaming receiver with token bucket scheme which automatically establishes the important parameters like token generation rate r and bucket maximum capacity c adapting to the pattern of video packets. The simulation results using network simulator-2 (NS-2) and joint scalable video model (JSVM) show that the proposed token bucket scheme with automatic establishment parameter provides better performance than the existing token bucket scheme with manual establishment parameter in terms of the generation number of overflow and underflow, packer loss rate, and peak signal to noise ratio (PSNR) in three test video sequences.

• Korean Journal of Environmental Agriculture
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• v.27 no.3
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• pp.231-238
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• 2008

This study proposed the method of phosphate recovery from municipal wastewater by using ferrous iron waste, generated from the mechanical process in the steel industry. In the analysis of XRD, ferrous iron waste was composed of $Fe_3O_4$ (magnetite), practically with $Fe^{2+}$ and $Fe^{3+}$. It had inverse spinel structure. In order to identify the adsorption characteristic of phosphate on ferrous iron waste, isotherm adsorption test was designed. Experimental results were well analyzed by Freundlich and Langmuir isotherm theories. Empirical constants of all isotherms applied increased with alkalinity in the samples, ranging from 1.2 to 235 $CaCO_3/L$. In the regeneration test, empirical constants of Langmuir isotherm, i.e., $q_{max}$ (maximum adsorption capacity) and b (energy of adsorption) decreased as the frequency of regeneration was increased. Experiment was further performed to evaluate the performance of the treatment scheme of chemical precipitation by ferrous iron waste followed by biological aerated filter (BAF). The overall removal efficiency in the system increased up to 80% and 90% for total phosphate (TP) and soluble phosphate (SP), respectively, and the corresponding effluent concentrations were detected below 2 mg/L and 1 mg/L for TP and SP, respectively. However, short-circuit problem was still unsolved operational consideration in this system. The practical concept applied in this study will give potential benefits in achieving environmentally sound wastewater treatment as well as environmentally compatible waste disposal in terms of closed substance cycle waste management.

• Journal of Digital Contents Society
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• v.15 no.2
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• pp.251-261
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• 2014

In the typical P2P VOD system, it is very important to develop the fast and efficient peer searching scheme since the peers frequently join and leave to/from P2P system. This paper proposes a new peer searching scheme for P2P VOD system based on DHT network environment. The proposed scheme constructs DHT network by managing the peers having close playback starting times and close network locations into a peer all together. The peer information is mapped onto DHT nodes by hashing the key values each of which consists of the starting time and network location of the peer. From the simulation results, the number of messages required to search the partner peers are decreased, and the number of buffer maps exchanging among the peers are also decreased. The proposed scheme can reduce the average network distances among the partner peers. As a result, the proposed scheme makes routing more efficient and it saves the network resources by decreasing communication traffic overhead.

• Smart Media Journal
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• v.6 no.4
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• pp.94-100
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• 2017

Procurement of development funds is a very difficult process in the Korean game industry where competition is fierce. Recently, crowdfunding has been used as a convenient platform to attract potential investors to secure the development cost of the game. This study explored the factors influencing the success of crowdfunding for game development projects. We collected data on 229 game development projects in Tumblebuck, a reward-based crowdfunding site in Korea. According to the results of the logistic regression model, the factors that have a positive effect on the success of funding are the average compensation amount relative to the target amount, the number of SNS shares, the number of updates, and the originality of the proposed game. Video playback time has been found to have a negative impact. Based on the results of this study, it is expected that planning a game development project considering the variables affecting the success of crowdfunding will help financing.

• Journal of Digital Convergence
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• v.13 no.4
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• pp.341-348
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• 2015

As a result of growth of digital music market in Korea, Creator's rights and interests have been at the heart of the debate in terms of legal system. In the music industry, digital music revenue has now overtaken records sales and compared to download service it is now clear that music streaming and subscription is mainstream model in the rise of the worldwide market of digital music. This trend is also indentical to the domestic and withholding regulations for music service and creator's rights and interests have become an ever growing issue. Ministry of Culture, Sports ad Tourism decided the revision of withholding regulations for the digital music service in 2013. The amendment is to change its policy of charging music service from the flat rate pricing to a usage-based system. This paper brought forward some disputable points such as fair division of profit, reasonable pricing for consumers etc. about the revision. Therefore, improvement of system and change in the perception of such copyrights are still required for both the encouragement of creator's activities and the high consumer satisfaction.

• Journal of the Korean Chemical Society
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• v.42 no.1
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• pp.28-35
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• 1998

Microorganisms such as alga are able to uptake toxic and heavy metal ions. After Cd(Ⅱ) was preconcentrated on the carbon paste electrode constructed by incorporating alga (Anabaena), it was determined with differential pulse anodic stripping voltammetry. A well-defined oxidation peak of Cd(Ⅱ) was obtained at - 0.75 V vs. SCE. We investigated the optimum conditions using the peak, which are the effect of the amount of alga, pH, ionic strength, temperature, and preconcentration time on the preconcentration of Cd(Ⅱ) and that of the reduction time and potential on the reduction of Cd(Ⅱ) preconcentrated. Calibration curve for the determination of Cd(Ⅱ) was linear over the range of $1.0{\times}10^6\;M\;to\;8.0{\times}10^6$\;M (R=0.9978) and the detection limit was $5.0{\times}10^{-7}$\;M. The relative standard deviation was 3.1% (n=6) for $7.0{\times}10^{-6}\;M Cd(Ⅱ). In regeneration of the electrode surface with 0.1 M HCl, the response was reproducible continuously by 10 times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.435-441
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• 2009

The one-time password system solves the problem concerning password reuse caused by the repeated utilization of an identical password. The password reuse problem occurs due to the cyclic repetition at the time of password creation, and authentication failure can occur due to time deviation or non-synchronization of the number of authentication. In this study, the password is created asynchronously and exchanged with the user, who then signs using a digital signature in exchange for the password and a valid verification is requested along with the certificate to ensure non-repudiation. Besides this, a verification system for one-time password is proposed and designed to improve security by utilizing the validity verification that is divided into certificate verification and password verification. Comparative analysis shows that the mechanism proposed in this study is better than the existing methods in terms of replay attack, non-repudiation and synchronization failure.