• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2005년도 전력전자학술대회 논문집
• /
• pp.690-692
• /
• 2005

Among many other alternative energy resources, small scale hydropower has been brought into attention as a reliable source of energy today, which had been relatively neglected since 1960s. Present low head of Francis turbines and small scale hydro turbines, however, have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develope the Francis turbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the changable design conditions could be attained. The Francis turbine of a new concept was designed based on changable design conditions, hydrodynamics and theory of power transmission.

• Journal of Electrical Engineering and Technology
• /
• 제2권2호
• /
• pp.201-207
• /
• 2007

As the power industry moves towards open competition, there has been a need for methodology to evaluate distribution power system reliability by using customer interruption costs, particularly in power supply zones under the competitive electricity market. This paper presents an algorithm to evaluate system average interruption duration index, expected energy not supplied, and system outage cost taking into consideration failure rate of the distribution facility and industrial customer interruption cost. Also, to apply this algorithm to evaluate system outage cost presented in this paper, the distribution arrangement of a dual supply system consisting of mostly high voltage customers in an industrial complex in Korea is used as a sample case study. Finally, evaluation results of system interruption cost, system average interruption duration index, and expected energy not supplied in the sample industrial complex area are shown in detail.

• 동력기계공학회지
• /
• 제9권3호
• /
• pp.39-43
• /
• 2005

Among many other alternative energy resources, small scale hydropower has been brought into attention as a reliable source of energy today, which had been relatively neglected since 1960s. Present low head of Francis turbines and small scale hydroturbines, however, have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develope the Francis turbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could alleviated and competition with other alternative energy sources in the changable design conditions could attained. The Francis turbine of a new concept was designed based on changable design conditions, hydrodynamics and theory of power transmission. The result of the study shows that two stages runner is more efficient, cheaper in construction, faster responding, and easier maintaining than single stage runner of Francis turbine

• Bulletin of the Korean Chemical Society
• /
• 제6권5호
• /
• pp.291-295
• /
• 1985

The efficiency of photosensitization of methyl linoleate (ML) oxidation by N-acetyl-L-trypophan(NAT) and 3-methyl indole(scatole) was markedly enhanced by increased concentration of ML in ethanol solution. The fluorescence intensities of sensitizers were observed to be quenched by ML, indicating that ML interacts with the indole excited singlet state. The inhibition of photosensitization by azide demonstrated a possible role of singlet oxygen in the photosensitization. The steady state kinetic treatment of azide inhibition of photosensitization was expected to show linear increase of reciprocal yield of ML oxidation product vs. reciprocal ML concentration at constant azide concentration, but the actual slope was nonlinear. This indicates another competing reaction involved in the photosensitization, As a possible competing reaction, electron transfer from ML to the excited sensitizer was proposed, since the measured fluorescence quenching rate constant closely resembled electron transfer rate constant determined from ML concentration dependence of oxidation product formation.

• 대한금속재료학회지
• /
• 제48권4호
• /
• pp.305-314
• /
• 2010

The development of textures and microstructures during plastic deformation in a hot-extruded AZ 31 Mg alloy was investigated using a compression test with such parameters as deformation temperature, strain rate. It was observed from true stress-strain curves that twinning involves changes of the flow stresses. In the early stages of deformation at temperatures lower than $200^{\circ}C$, the occurrence of twins resulted in a decrease of the work-hardening rate, which increased drastically at a true strain of -0.05. The evolution of the deformation textures were assessed with the aid of EBSD analyses in terms of the competition between twinning and slip activity.

• KDI Journal of Economic Policy
• /
• 제31권2호
• /
• pp.235-266
• /
• 2009

본 연구는 장기간의 시계열 자료를 이용하여 우리 경제의 수출가격에 대한 환율전가율 변화를 실증적으로 분석한 것이다. 분석 결과, 외환위기를 전후로 수출가격에 대한 환율전가율이 하락하였음을 발견하였는데, 이는 우리나라의 수출기업이 환율 변동의 영향을 수출가격에 전가하기 보다 내부적으로 마크업 조정을 통해 흡수하는 경향이 외환위기 이후에 더욱 높아졌음을 의미한다. 또한 환율전가율의 비대칭성 분석을 통해 외환위기 이후의 환율전가율 하락은 거의 대부분 환율이 하락했을 때 발생하였음을 발견하였는데, 이는 외환위기 이후 환율이 하락하는 시기에 수출기업들이 달러표시 수출가격을 인상하는 대신에 해외시장에서의 시장점유율을 유지하는 전략을 채택해 왔음을 시사한다. 한편, 이러한 환율전가율의 하락은 환율 변동성의 확대와 세계시장에서 중국과의 경쟁이 심화되면서 나타난 것으로 분석되었다.

• 대한토목학회논문집
• /
• 제30권6D호
• /
• pp.641-654
• /
• 2010

최근 건설산업이 자율과 경쟁을 중시하는 시장주의로 전환됨에 따라 건설기업은 변화된 환경에 대응하고자 노력하고 있다. 본 연구는 급변하는 환경 속에서 살아남기 위하여 건설기업이 취하는 전략 및 핵심역량과 기업의 성과인 성장률 및 수익률과의 상호 연관성을 분석하기 위해 수행되었다. 이론적 고찰을 통하여 건설기업의 전략유형 및 핵심역량을 도출하여 설문조사를 실시하였다. 이를 통해 경쟁우위 전략을 취하는 건설기업의 핵심역량이 가장 우수함을 확인할 수 있었다. 그러나 건설기업이 취하는 전략유형과 성장률 및 수익률은 연관성이 없는 것으로 파악되었다. 또한 건설기업의 핵심역량은 수익률과 관련성이 없는 반면, 성장률과는 상관성이 있는 것으로 분석되었다. 따라서 건설기업이 성장하기 위해서는 경쟁우위 전략의 이행 시 요구되는 핵심역량 확보가 필수적임을 알 수 있었다.

• 한국농촌건축학회논문집
• /
• 제16권3호
• /
• pp.9-18
• /
• 2014

Small and medium-sized local airports have suffered from chronic operating deficits due to many factors except for large airports in Incheon, Gimpo, Jeju and Gimhae. These small and medium-sized local airports have currently been degraded to inefficient airports handling the significantly lower airline demand than their carrying capacities. In this context, this study conducted a survey on the actual conditions of the airline demand in small and medium-sized local airports for the last 10 years after the opening of the Korea Train eXpress and investigated the causes and actual conditions of an increase and a decrease in the airline demand. In addition, it analyzed the functionality, convenience and economic feasibility, competition elements in comparison with other means of transportation, and the actual competitive conditions of local airports. It investigated facility improvements through a field visit for local airports and analyzed the performance rate of passenger demands and the use rate of terminal facilities according to a change in the airline demand. This study aimed to provide basic data in the architectural planning field, needed to establish a plan for the airport revitalization of local airports with the results of an analysis on the actual conditions of small and medium-sized local airports.

• 전자공학회논문지B
• /
• 제31B권11호
• /
• pp.142-150
• /
• 1994

본 논문은 분류된 학습률을 이용한 고속 경쟁 학습에 대한 연구이다. 이연구의 기본 개념은 각 출력 노우드의 연결강도 벡터에 분류된 학습률을 할당하는 것이다. 출력 노우드의 각 연결강도 벡터는 자기 자신의 학습률에 의하여 갱신된다. 각 학습률은 관련되는 출력 노우드가 경쟁에서 승리할 때에만 변화되며, 승리하지 못한 노우드들의 학습률은 변화되지 않는다. 영상 벡터 양자화에 대하여 실험한 결과는 제안한 방법이 기존 경쟁 학습 방법에 비하여 더 빠르게 학습되고 더 좋은 화질을 갖게 됨을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권11호
• /
• pp.4519-4533
• /
• 2015

Hypertext Transfer Protocol (HTTP) adaptive streaming has become a new trend in video delivery. An HTTP adaptive streaming client needs to effectively estimate resource availability and demand. However, due to the bitrate of the video encoded in variable bitrate (VBR) mode, a bitrate mismatch problem occurs. With the rising demand for mobile devices, the likelihood of cases where two or more HTTP adaptive streaming clients share the same network bottleneck and competing for available bandwidth will increase. These mismatch and competition issues lead to network congestion, which adversely affects the Quality of Experience (QoE). To solve these problem, we propose a video rate adaptation scheme for the HTTP video streaming to guarantee and optimize the QoE. The proposed scheme estimates the available bandwidth according to the bitrate of each segment and also schedules the segment request time to expedite the response to the bandwidth variation. We used a multi-client simulation to prove that our scheme can effectively cope with drastic changes in the connection throughput and video bitrate.