The design of a stall-regulated wind turbine to achieve a maximum annual energy output is still a formidable task for engineers. The design could be carried out using an average wind speed together with a standard sta...The design of a stall-regulated wind turbine to achieve a maximum annual energy output is still a formidable task for engineers. The design could be carried out using an average wind speed together with a standard statistical distribution such as a Weibull with k = 2.0. In this study a more elaborated design will be attempted by also considering the statistical bias as a design criterion. The wind data used in this study were collected from three areas of the Lamtakong weather station in Nakhonratchasima Provice, the Khaokoh weather station in Phetchaboon and the Sirindhorn dam weather station in Ubonratchathani, Thailand. The objective is to design a best aerodynamic configurations for the blade (chord, twist and pitch) using the same airfoil as that of NREL Phase VI wind turbine. Such design is carried out at a design wind speed point. Wind turbine blades were optimized for both maximum annual energy production and minimum cost of energy using a method that take into account aerodynamic and structural considerations. The work will be carried out by the program “SuWiTStat” which was developed by the authors and based on BEM Theory (Blade Element Momentum). Another side issue is the credibility of the Weibull statistic in representing the real wind measurement. This study uses a regression analysis to determine this issue.展开更多
本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CP...本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CPUE)以及不同种类渔具(拖网、围网、刺网、张网、钓渔具和其他渔具)的捕捞产量和CPUE的变化。研究表明:我国国内海洋捕捞产量在1979-1998年逐年增加,1998年之后整体呈现下降趋势,国内海洋捕捞总量占海水产品总量的比例逐年下降,从1979年的74.8%下降到2019年的30.5%;虽然渔船总吨位和总功率保持着总体上升的趋势,但是2019年单位功率年渔获量与1999年相比减少了30.6%,单位总吨的年渔获量与1999年相比减少了45.4%。此外,不同种类渔具捕捞产量中,拖网产量一直处于主导地位(产量占比处于64%-42%之间);2000年后,刺网产量处于第二位(16%-22%),张网产量处于第三位(17%-11%),围网等渔具产量均不足10%;2003年后,除张网CPUE较为稳定之外,其它渔具CPUE都呈明显的下降趋势,CPUE的显著减少可能是由于渔船功率和吨位的不断增加及资源量的不断减少造成的。本文研究结果可为我国国内海洋捕捞业结构优化及相关管理政策制定提供参考。展开更多
文摘The design of a stall-regulated wind turbine to achieve a maximum annual energy output is still a formidable task for engineers. The design could be carried out using an average wind speed together with a standard statistical distribution such as a Weibull with k = 2.0. In this study a more elaborated design will be attempted by also considering the statistical bias as a design criterion. The wind data used in this study were collected from three areas of the Lamtakong weather station in Nakhonratchasima Provice, the Khaokoh weather station in Phetchaboon and the Sirindhorn dam weather station in Ubonratchathani, Thailand. The objective is to design a best aerodynamic configurations for the blade (chord, twist and pitch) using the same airfoil as that of NREL Phase VI wind turbine. Such design is carried out at a design wind speed point. Wind turbine blades were optimized for both maximum annual energy production and minimum cost of energy using a method that take into account aerodynamic and structural considerations. The work will be carried out by the program “SuWiTStat” which was developed by the authors and based on BEM Theory (Blade Element Momentum). Another side issue is the credibility of the Weibull statistic in representing the real wind measurement. This study uses a regression analysis to determine this issue.
文摘本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CPUE)以及不同种类渔具(拖网、围网、刺网、张网、钓渔具和其他渔具)的捕捞产量和CPUE的变化。研究表明:我国国内海洋捕捞产量在1979-1998年逐年增加,1998年之后整体呈现下降趋势,国内海洋捕捞总量占海水产品总量的比例逐年下降,从1979年的74.8%下降到2019年的30.5%;虽然渔船总吨位和总功率保持着总体上升的趋势,但是2019年单位功率年渔获量与1999年相比减少了30.6%,单位总吨的年渔获量与1999年相比减少了45.4%。此外,不同种类渔具捕捞产量中,拖网产量一直处于主导地位(产量占比处于64%-42%之间);2000年后,刺网产量处于第二位(16%-22%),张网产量处于第三位(17%-11%),围网等渔具产量均不足10%;2003年后,除张网CPUE较为稳定之外,其它渔具CPUE都呈明显的下降趋势,CPUE的显著减少可能是由于渔船功率和吨位的不断增加及资源量的不断减少造成的。本文研究结果可为我国国内海洋捕捞业结构优化及相关管理政策制定提供参考。
