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RISS 인기검색어
- 검색키워드
- 저자 : G.Riahy (검색결과 4 건)
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Experimental and Simulation Results for Sliding Mode Dynamic Wind Turbine Control using a DC Chopper
G.Riahy,P.Freere,D.G.Holmes 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
Wind speeds can vary rapidly and wind turbines cannot easily follow these variations because of their inertia and aerodynamic characteristics. For maximum energy extraction, the turbine blades should operate at their optimum tip speed ratio, but with rapid changes in wind speed, this is usually not possible. To improve the energy extraction from turbulent wind, it is necessary to establish an effective measure of the high frequency component of the wind, and then to use this measure to optimise the operation of the turbine controller for maximum energy extraction. This paper presents an approach for combining readings from three anemometers into a composite wind speed measurement, and using this signal to control the operation of a permanent magnet generator to achieve maximum energy extraction. The method combines simulation and experimental investigations into a heuristic algorithm, and demonstrates its effectiveness with field trials.<br/>
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Riahi, K.,Kriegler, E.,Johnson, N.,Bertram, C.,den Elzen, M.,Eom, J.,Schaeffer, M.,Edmonds, J.,Isaac, M.,Krey, V.,Longden, T.,Luderer, G.,Mejean, A.,McCollum, D.L.,Mima, S.,Turton, H.,van Vuuren, D.P. American Elsevier 2015 TECHNOLOGICAL FORECASTING AND SOCIAL CHANGE Vol.90 No.1
This paper provides an overview of the AMPERE modeling comparison project with focus on the implications of near-term policies for the costs and attainability of long-term climate objectives. Nine modeling teams participated in the project to explore the consequences of global emissions following the proposed policy stringency of the national pledges from the Copenhagen Accord and Cancun Agreements to 2030. Specific features compared to earlier assessments are the explicit consideration of near-term 2030 emission targets as well as the systematic sensitivity analysis for the availability and potential of mitigation technologies. Our estimates show that a 2030 mitigation effort comparable to the pledges would result in a further ''lock-in'' of the energy system into fossil fuels and thus impede the required energy transformation to reach low greenhouse-gas stabilization levels (450ppm CO<SUB>2</SUB>e). Major implications include significant increases in mitigation costs, increased risk that low stabilization targets become unattainable, and reduced chances of staying below the proposed temperature change target of 2<SUP>o</SUP>C in case of overshoot. With respect to technologies, we find that following the pledge pathways to 2030 would narrow policy choices, and increases the risks that some currently optional technologies, such as carbon capture and storage (CCS) or the large-scale deployment of bioenergy, will become ''a must'' by 2030.
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The impact of near-term climate policy choices on technology and emission transition pathways
Eom, J.,Edmonds, J.,Krey, V.,Johnson, N.,Longden, T.,Luderer, G.,Riahi, K.,Van Vuuren, D.P. American Elsevier 2015 TECHNOLOGICAL FORECASTING AND SOCIAL CHANGE Vol.90 No.1
This paper explores the implications of delays (to 2030) in implementing optimal policies for long-term transition pathways to limit climate forcing to 450ppm CO<SUB>2</SUB>e on the basis of the AMPERE Work Package 2 model comparison study. The paper highlights the critical importance of the period 2030-2050 for ambitious mitigation strategies. In this period, the most rapid shift to low greenhouse gas emitting technology occurs. In the delayed response emission mitigation scenarios, an even faster transition rate in this period is required to compensate for the additional emissions before 2030. Our physical deployment measures indicate that the availability of CCS technology could play a critical role in facilitating the attainment of ambitious mitigation goals. Without CCS, deployment of other mitigation technologies would become extremely high in the 2030-2050 period. Yet the presence of CCS greatly alleviates the challenges to the transition particularly after the delayed climate policies, lowering the risk that the long-term goal becomes unattainable. The results also highlight the important role of bioenergy with CO<SUB>2</SUB> capture and storage (BECCS), which facilitates energy production with negative carbon emissions. If BECCS is available, transition pathways exceed the emission budget in the mid-term, removing the excess with BECCS in the long term. Excluding either BE or CCS from the technology portfolio implies that emission reductions need to take place much earlier.
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Cervical Inclination Angle: Normative Values in an Adult Multiethnic Asymptomatic Population
Jean Charles Le Huec,Zeeshan M. Sardar,Emanuele Quarto,Meghan Cerpa,Michael P. Kelly,Kazuhiro Hasegawa,Hwee Weng Dennis Hey,Hee-Kit Wong,Hend Riahi,Lawrence G. Lenke,Stéphane Bourret,MEANS study group 대한척추신경외과학회 2022 Neurospine Vol.19 No.4
Objective: The role of the craniocervical complex in spinal sagittal alignment has rarely been analyzed but it may play a fundamental role in postoperative mechanical complications. The aim of the study is to analyze the normative value of the cervical inclination angle (CIA) in an adult asymptomatic multiethnic population. Methods: Standing full-spine EOS of adult asymptomatic volunteers from 5 different countries were analyzed. The CIA was analyzed globally and then in each decade of life. Different ethnicities were compared. Comparisons between different groups was performed using a t-test and statistical significance was considered with a p-value < 0.05. Results: EOS of 468 volunteers were analyzed. The global mean CIA was 80.2° with a maximum difference of 9° between T1 and T12 (p < 0.001). The CIA remains constant until 60 years old then decreases significantly passing from a mean value before 20 years old of 82.25° to 73.65° after 70 years old. A statistically significant difference was found between the Arabics and other ethnicities with the formers having an inferior CIA: this was related to a mean older age (p < 0.05) and higher body mass index (p < 0.05) in the Arabics. Conclusion: The CIA remains constant until 60 years old and then reduces slightly but never under 70°. This angle is helpful to evaluate the lever arm at the upper instrumented vertebra after an adult spinal deformity surgery and could predict the occurrence of a proximal junctional kyphosis when its value is lower than normal. Further clinical studies must confirm this theory.
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