• 대한교통학회지
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• 제34권1호
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• pp.95-106
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• 2016

우리나라 항공 여객수요는 2014년 기준 국제선 5,700만명, 국내선 2,400만명에 도달하였으며, 지속적인 증가 추세를 보일 것으로 예상되고 있다. 이에 따른 국내 공항시설들의 확충 계획이 활발히 진행되고 있으며, 이를 위해 선행적으로 항공수요 예측을 위한 모형 개발이 필요하다. 우리나라에서는 국내총생산을 설명변수로 한 계량경제모형을 주로 항공수요 모형으로 이용하고 있으며, 시계열 자료의 안정성을 고려하지 않을 때 발생하는 허구적 회귀 현상에 대한 많은 논의가 이루어지지 않은 상태이다. 본 연구에서는 시계열 자료의 안정성을 고려한 항공수요 계량경제모형을 개발하였다. 시계열 자료의 특성을 검정하기 위한 단위근 검정과 변수들 간의 장기균형관계를 분석하기 위한 공적분 검정에 대한 이론적 고찰을 수행하였다. 마지막으로, 시계열 자료의 안정성을 고려한 항공수요 계량경제모형 개발 프로세스를 정립하였다. 정립된 프로세스의 적용 가능성을 검증하기 위해 제주공항 국내선 수요를 대상으로 항공수요 모형을 산정하였다. 수요 모형의 설명변수는 국내총생산과 항공요금지수를 이용하였으며, 기존 항공수요 계량경제모형에서 발생하는 문제점을 해소한 것으로 나타났다.

• 전력전자학회논문지
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• 제21권4호
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• pp.302-311
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• 2016

This paper proposes a hybrid ESS that integrates an energy storage system (ESS) with an uninterruptible power supply (UPS). The hybrid ESS has a demand management and emergency power supply function while increasing the battery utilization of the UPS, which has just been used in a power failure. In addition to the critical load, the proposed system augments the capacity of emergency generation using an additional load, which has voltage and frequency-dependent characteristics to the grid side. The control algorithm of the AC-DC converter and bidirectional DC-DC converter is proposed for demand management and emergency power supply. Furthermore, seamless and autonomous transfer methods to alleviate the transient during mode transfer are proposed. To validate the proposed control scheme, experimental results from a 5 kW prototype are provided.

• 에너지공학
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• 제27권3호
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• pp.68-73
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• 2018

The cement industry is one of the rapidly growing industry in Ethiopia. The average per capita cement consumption of the country has increased from 39kg to 62kg. However, this is still way below than the global average per capita consumption of 500kg. The Ethiopian government is planning to expand its cement industry by upgrading the current cement plants and also opening of new cement plants in order to meet the future demand of the country. Currently, the number of cement plants in Ethiopia has reached to 20. By the year 2025, per capita cement consumption is expected to increase to 179kg. Recently, Ethiopia has become one of Africa's largest market for the cement industry. In addition, Ethiopia has become the major exporter of cement in the Sub-Saharan African region. The Ethiopian cement industry is highly dependent on the use of imported energy sources for its production. This situation has a significant amount of impact on the high production costs of the industry. This paper will try to review the history, production, available resources, the technologies and energy use of the Ethiopian cement industry.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.159-170
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• 2018

This paper aims to develop response modification factors for stiffness degrading structures by incorporating soil-structure interaction effects. A comprehensive parametric study is conducted to investigate the effects of key SSI parameters, natural period of vibration, ductility demand and hysteretic behavior on the response modification factor of soil-structure systems. The nonlinear dynamic response of 6300 soil-structure systems are studied under two ensembles of accelograms including 20 recorded and 7 synthetic ground motions. It is concluded that neglecting the stiffness degradation of structures can results in up to 22% underestimation of inelastic strength demands in soil-structure systems, leading to an unexpected high level of ductility demand in the structures located on soft soil. Nonlinear regression analyses are then performed to derive a simplified expression for estimating ductility-dependent response modification factors for stiffness degrading soil-structure systems. The adequacy of the proposed expression is investigated through sensitivity analyses on nonlinear soil-structure systems under seven synthetic spectrum compatible earthquake ground motions. A good agreement is observed between the results of the predicted and the target ductility demands, demonstrating the adequacy of the expression proposed in this study to estimate the inelastic demands of SSI systems with stiffness degrading structures. It is observed that the maximum differences between the target and average target ductility demands was 15%, which is considered acceptable for practical design purposes.

• 수산경영론집
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• 제16권2호
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• pp.75-87
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• 1985

In 1977, the United States enacted the Magnuson Fishery Conservation and Management Act (MFCMA), which established U.S. Fisheries Conservation Zone (FCZ). The MFCMA grants preference to U.S. harvesters over foreign fleets in the U.S. FCZ. At present, the large stocks of groundfish in the U.S. FCZ off the Alaska coast have been under-utilized in the U.S. domestic market and the fisheries for these groundfish are dominated by foreign fleets. Hence, expected benefits from replacing foreign fisheries by domestic fleets will accrue to the U.S. fishery only by exporting the increased U.S. products to foreign countries. U.S. exports may be dependent on the price levels in the foreign markets raised by the reduced foreign catch from U,S. waters. In this paper, Japanese demand models for Alaska groundfish were estimated. The derived coefficient from the estimated models suggest that a decrease in the Japanese landings from the U.S. FCZ by a thousand metric tons will increase pollock price by 0.017 Yen/kg, cod price by 0.351 Yen/kg, flatfish by 1.074 Yen/kg, and ocean perch by 1.347 Yen/kg in the Japanese market. These results based on percentage would increase 19 percent for pollock price, 11 percent for cod price, 40 percent for flatfish, and 2 percent for ocean perch price.

• Wind and Structures
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• 제7권3호
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• pp.145-158
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• 2004

The evaluation of the accumulation of permanent set for inelastic structures due to wind action is important in establishing a criterion to select a reduced design wind load and in incorporating the beneficial ductile behaviour in wind engineering. A parametric study of the accumulation of the permanent set as well as the ductility demand for bilinear single-degree-of-freedom (SDOF) systems is presented in the present study. The dynamic analysis of the inelastic SDOF system is carried out using the method of Newmark for artificially generated time history of wind speed. Simulation results indicate that the mean of the normalized damage rate is highly dependent on the natural frequency of vibration. This mean value is relatively insensitive to the damping ratio if the damping ratio is larger than 5%. The scatter associated with the accumulation of the permanent set is very significant. The consideration of the postyield stiffness can significantly reduce the accumulation of the permanent set if the ratio of the yield strength to the expected peak response is small. The results also show that the ductility demand due to the wind action over a period of one hour for flexible structures can be much less than that for rigid structures or structures with larger damping ratio if the SDOF systems are designed with a reduced peak response caused by the fluctuating wind.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.1125-1131
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• 2005

This study is based on the assumption of surface transport linkages between Korea and China. Active economic cooperation between South Korea and North Korea are expected within the near future and Russia and China have interested in the land transport linkages in Korean peninsula. How much freight demands between the two countries that has been mainly dependent on air and sea transportation so far may convert the transport mode to surface transportation are estimated. Particularly, freight demands between South Korea and China's three northeast provinces are focused. The sensitivity analysis depends on transport time and transport cost changes is included. The modal shifts is estimated to be more sensitive to the changes in transport costs than those in transport time, suggesting the importance of transport costs of rail and road. Despite the dearth of data on the surface transport operation in North Korea, the attempts made in this study to estimate the demand conversion are hope to provide reference points for potential effects of the rail and road transport connections between China and the Korea peninsula before our discussions expand to the establishment of freight transport network of the northest Asia and, moreover, the Eurasian continent.

• 농촌계획
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• 제17권1호
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• pp.59-65
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• 2011

Re-visitation have an effect on dependent variables of regional tourism demand model. This study focused on the re-visitation impacts of consideration on sustainable tourism development of tourists as a new factors of tourism. Based on literature reviews, 11 variables were selected, a questionnaire survey was given to 406 tourists divided into 5 tourism sites at Chuncheon city, and logit model and probit model were used for analysis. The fitness levels of two models were very significant(p=0.0000). The study results suggest that the likelihood of the rural tourist to make a return visit is influenced by recognition of sustainable tourism, purchase of souvenir and farm produce, visitation of regional shops, conversation with regional residents, residents' participation on development, age and marriage. The results of such re-visitation demand can provide information for regional development strategies. The approach to re-visitation research impacts of consideration on sustainable tourism development is expected to become a useful foundation in studying on sustainable regional development.

• 자원리싸이클링
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• 제30권5호
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• pp.3-9
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• 2021

우리나라에서 연, 아연, 동, 주석, 니켈, 알루미늄 등의 베이스메탈의 수급구조는 양극화된 특성을 지니고 있다. 연, 아연, 동 등은 국내에 세계적 규모의 생산기업이 있는 반면, 주석, 니켈, 알루미늄 등은 국내 생산기업이 전무하거나, 생산량이 미비하여 내수량의 대부분을 수입에 의존하고 있다. 따라서 베이스메탈의 수입중단 또는 국내생산기업의 생산 중단 등의 공급중단에 따른 리스크에 대한 대비가 필요하다. 본 연구에서는 베이스메탈 6종(구리, 연, 아연, 알루미늄, 니켈, 주석)을 대상으로 수입중단 리스크 발생 시 대응이 필요한 물량과 시장이 대응할 수 있는 물량, 정부가 대응해야 하는 물량(전략비축)을 정량화하였다.

• Advances in Energy Research
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• 제8권1호
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• pp.59-71
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• 2022

Increasing cost of electricity due to rising price of fuel is one of the local community's main issues. In this research, switching of grid dependent system to the grid-tied Photovoltaic (PV) system with net metering for a residential building is proposed. The system is designed by considering the maximum energy demand of the building. The designed system is analyzed using RETScreen on technical, economic and environmental grounds. It is found that the system is able to produce 12,000 kWh/year. The system is capable to fulfill the electricity demand of the building during day time and is also capable to sell the energy to the local grid causing the electric meter to run in reverse direction. During night time, electricity will be purchased from grid, and electric meter will run in the forward direction. The system is economically justified with a payback period of only 3 years with net present value of PKR. 4,758,132. Also, the system is able to reduce 7.2 tons of CO₂ not produced in the entire life of the project.