• Journal of Power Electronics
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• 제10권1호
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• pp.72-78
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• 2010

In this paper the operation of a double-fed wound-rotor induction machine, coupled to a wind turbine, as a generator at sub-synchronous speeds is investigated. A novel approach is used in the analysis, namely, the rotor power flow approach. The conditions necessary for operating the machine as a double-fed induction generator (DFIG) are deduced. Formulae describing the factors affecting the range of sub-synchronous speeds within which generation occurs are deduced. The variations in the magnitude and phase angle of the voltage injected to the rotor circuit as the speed of the machine changes to achieve generation at the widest possible sub-synchronous speed range is presented. Also, the effect of the rotor parameters on the generation range is presented. The analysis proved that the generation range could increase from sub-synchronous to super-synchronous speeds, which increases the amount of energy captured by the wind energy conversion system (WECS) as result of utilizing the power available in the wind at low wind speeds.

• Earthquakes and Structures
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• 제17권6호
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• pp.577-590
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• 2019

The seismic response of structures to strong ground motions is a complex problem that has been studied for decades. However, most of current seismic regulations do not assess the potential level of damage that a structure may undergo during a strong earthquake. This will happen in spite that the design objectives for any structural system are formulated in terms of acceptable levels of damage. In this article, we analyze the expected damage in single-degree-of-freedom systems subjected to long-duration ground motions generated in soft soil sites, such as those located in the lakebed of Mexico City. An energy-based methodology is formulated, under the consideration of input energy as the basis for the evaluation process, to estimate expected damage. The results of the proposed methodology are validated with damage curves established directly with nonlinear dynamic analyses.

• Journal of Plant Biotechnology
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• 제34권2호
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• pp.95-101
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• 2007

The transport biofuel is emerging a promising option to realize the sustainable growth of our society. Two biofuels, bioethanol and biodiesel, are currently used in the transport sector. As the production of biofuels is getting activated, the stable supply of the feedstocks is becoming a critical issue. Active works have been carried out to secure the stable supply of the raw materials for the production of biofuels. One approach is the breeding of the energy crops to get higher productivity and / or the desirable fuel properties. The other approach is finding new energy crops which may not be used for edible purpose. First current aspects and challenging issues for the implementation of biofuels have been introduced. Finally the recent works and future prospects on the development of the energy crops are summarized.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1237-1255
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• 2014

In wireless sensor networks (WSNs), hierarchical clustering is an efficient approach for lower energy consumption and extended network lifetime. In cluster-based multi-hop communications, a cluster head (CH) closer to the sink is loaded heavier than those CHs farther away from the sink. In order to balance the energy consumption among CHs, we development a novel cluster-based routing protocol for corona-structured wireless sensor networks. Based on the relaying traffic of each CH conveys, adequate radius for each corona can be determined through nearly balanced energy depletion analysis, which leads to balanced energy consumption among CHs. Simulation results demonstrate that our clustering approach effectively improves the network lifetime, residual energy and reduces the number of CH rotations in comparison with the MLCRA protocols.

• 국제초고층학회논문집
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• 제6권2호
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• pp.177-185
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• 2017

This research suggests the most effective way for improving energy efficiency in tall buildings is a "fabric-first" approach. This involves optimizing the performance of the building form and envelope as a first priority, with additional technologies a secondary consideration. The paper explores a specific fabric-first energy standard known as "Passivhaus". Buildings that meet this standard typically use 75% less heating and cooling. The results show tall buildings have an intrinsic advantage in achieving Passivhaus performance, as compared to low-rise buildings, due to their compact form, minimizing heat loss. This means high-rises can meet Passivhaus energy standards with double-glazing and moderate levels of insulation, as compared to other typologies where triple-glazing and super-insulation are commonplace. However, the author also suggests that designers need to develop strategies to minimize overheating in Passivhaus high-rises, and reduce the quantity of glazing typical in high-rise residential buildings, to improve their energy efficiency.

• Structural Engineering and Mechanics
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• 제23권2호
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• pp.177-193
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• 2006

Determining the hysteretic energy demand and dissipation capacity and level of damage of the structure to a predefined earthquake ground motion is a highly non-linear problem and is one of the questions involved in predicting the structure's response for low-performance levels (life safe, near collapse, collapse) in performance-based earthquake resistant design. Neural Network (NN) analysis offers an alternative approach for investigation of non-linear relationships in engineering problems. The results of NN yield a more realistic and accurate prediction. A NN model can help the engineer to predict the seismic performance of the structure and to design the structural elements, even when there is not adequate information at the early stages of the design process. The principal aim of this study is to develop and test multi-layered feedforward NNs trained with the back-propagation algorithm to model the non-linear relationship between the structural and ground motion parameters and the hysteretic energy demand in steel moment resisting frames. The approach adapted in this study was shown to be capable of providing accurate estimates of hysteretic energy demand by using the six design parameters.

• 방사성폐기물학회지
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• 제19권2호
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• pp.255-266
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• 2021

Solid-state mechanochemical reduction combined with subsequent melting consolidation was suggested as a technical option for the oxide reduction in pyroprocessing. Ni ingot was produced from NiO as a starting material through this technique while Li metal was used as a reducing agent. To determine the technical feasibility of this approach for pyroprocessing, which handles spent nuclear fuels, thermodynamic calculations of the phase stabilities of various metal oxides of U and other fission elements were made when several alkaline and alkali-earth metals were used as reducing agents. This technique is expected to be beneficial, not only for oxide reduction but also for other unit processes involved in pyroprocessing.

• 한국경영과학회지
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• 제4권2호
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• pp.35-39
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• 1979

In order to recommend future national policy directions on energy supply and consumption and to suggest energy technological priorities to be developed, comprehensive energy models have been developed through this study in a sense of strategic and systematic approach. The “energy input-output model” has been formulated to analyze the mutual impacts between energy consumption patterns and industrial structures and to calculate energy intensities of industrial sectors. The long-term energy demands to the year 2000 were forecasted by using multi-regressional method and the optimal energy flow balances for five-year interval have been studied by using the “energy linear programming model” being took full account of interfuel substitutability and technology.

• The Journal of Asian Finance, Economics and Business
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• 제7권1호
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• pp.101-110
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• 2020

Energy and energy consumption play an important role in strategies for socio-economic development of the country. In 1995, Vietnam officially entered the 500 kV North-South transmission power line exploits, with a full length of 1,487 km. The purpose of this study is to investigate the breakpoint and the transition effect of energy consumption to economic growth in Vietnam during the period of 1980-1994, and 1995-2016. The Autoregressive Distributed Lag (ARDL) approach and the Bounds test are used to test for the presence of cointegration, whereas the Toda and Yamamoto procedure Granger causality test is used for the direction of causality. The result of the Bounds test validates the existence of cointegration among the included variables. The empirical results provide evidence that energy consumption has a positive impact on the economic growth of Vietnam in the long run. The causality test shows that there is bi-directional causality between energy consumption and economic growth, supported feedback hypothesis. There is a breakpoint in 1995 and the contribution of energy consumption in economic growth in the period of 1995-2016 is lower than the stage 1980-1994. This study suggests Government authorities explore new sources of energy to achieve sustainable economic development in the long run.

• 한국지역지리학회지
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• 제10권1호
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• pp.110-131
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• 2004

본 연구에서는 동북아시아 에너지 공급에 중요한 영향을 미치게 될 시베리아송유관 건설과 관련하여 중국과 일본 양국이 시베리아 송유관을 자국에 유리한 방향으로 유치하려는 시도에 대한 정치경제학적 분석이다. 먼저 시베리아 송유관 건설과 관련한 지금까지의 경과를 조명한다. 다음으로 시베리아 송유관 건설문제와 관련된 러시아 국내적 및 국제적 요인을 분석하고, 이를 배경으로 러시아 에너지 공급과 관련하여 논의되는 중상주의적 및 자유주의적 접근의 적실성을 검토하였다. 분석의 결과 중상주의적 접근과 자유주의적 접근의 이분법은 행위주체로서 러시아에만 초점을 맞추고 있다는 점에서 한계를 가지고 있었다. 그 대신 러시아가 동북아지역에서 경제적 안보를 중시하면서 중상주의적 접근과 자유주의적 접근을 아우르는 에너지 공급정책을 추진하고 있다는 점에서 중상주의적-자유주의적 접근의 이분법적 분석방법의 대안으로 정치경제학적 접근이 유효한 것으로 나타났다. 마지막으로 한국의 상황에서 시베리아 송유관 건설이 가지는 함의를 제시하였다.