When a wind turbine is struck by lightning,its blades are usually rotating.The effect of blade rotation on a turbine＇s ability to trigger a lightning strike is unclear.Therefore,an arching electrode was used in a win...When a wind turbine is struck by lightning,its blades are usually rotating.The effect of blade rotation on a turbine＇s ability to trigger a lightning strike is unclear.Therefore,an arching electrode was used in a wind turbine lightning discharge test to investigate the difference in lightning triggering ability when blades are rotating and stationary.A negative polarity switching waveform of 250/2500 μs was applied to the arching electrode and the up-and-down method was used to calculate the 50%discharge voltage.Lightning discharge tests of a 1：30 scale wind turbine model with 2,4,and 6 m air gaps were performed and the discharge process was observed.The experimental results demonstrated that when a 2 m air gap was used,the breakdown voltage increased as the blade speed was increased,but when the gap length was 4 m or longer,the trend was reversed and the breakdown voltage decreased.The analysis revealed that the rotation of the blades changes the charge distribution in the blade-tip region,promotes upward leader development on the blade tip,and decreases the breakdown voltage.Thus,the blade rotation of a wind turbine increases its ability to trigger lightning strikes.展开更多
AIM:To describe confidence interval calculation for antidotal potency ratios using bootstrap method.METHODS:We can easily adapt the nonparametric bootstrap method which was invented by Efron to construct confidence in...AIM:To describe confidence interval calculation for antidotal potency ratios using bootstrap method.METHODS:We can easily adapt the nonparametric bootstrap method which was invented by Efron to construct confidence intervals in such situations like this.The bootstrap method is a resampling method in which the bootstrap samples are obtained by resampling from the original sample.RESULTS:The described confidence interval calculation using bootstrap method does not require the sampling distribution antidotal potency ratio.This can serve as a substantial help for toxicologists,who are directed to employ the Dixon up-and-down method with the application of lower number of animals to determine lethal dose 50 values for characterizing the investigated toxic molecules and eventually for characterizing the antidotal protections by the test antidotal systems.CONCLUSION:The described method can serve as a useful tool in various other applications.Simplicity ofthe method makes it easier to do the calculation using most of the programming software packages.展开更多
Dose–response experiments and data analyses are often carried out according to an optimal design under a model assumption.A two-parameter logistic model is often used because of its nice mathematical properties and p...Dose–response experiments and data analyses are often carried out according to an optimal design under a model assumption.A two-parameter logistic model is often used because of its nice mathematical properties and plausible stochastic response mechanisms.There is an extensive literature on its optimal designs and data analysis strategies.However,a model is at best a good approximation in a real-world application,and researchers must be aware of the risk of model mis-specification.In this paper,we investigate the effectiveness of the sequential EDdesign,the D-optimal design,and the up-and-down design under the three-parameter logistic regression model,and we develop a numerical method for the parameter estimation.Simulations show that the combination of the proposed model and the data analysis strategy performs well.When the logistic model is correct,this more complex model has hardly any efficiency loss.The three-parameter logistic model works better than the two-parameter logistic model in the presence of model mis-specification.展开更多
基金supported by the China State Grid Corp headquarters project in 2015(SGTYHT/14JS-188)
文摘When a wind turbine is struck by lightning,its blades are usually rotating.The effect of blade rotation on a turbine＇s ability to trigger a lightning strike is unclear.Therefore,an arching electrode was used in a wind turbine lightning discharge test to investigate the difference in lightning triggering ability when blades are rotating and stationary.A negative polarity switching waveform of 250/2500 μs was applied to the arching electrode and the up-and-down method was used to calculate the 50%discharge voltage.Lightning discharge tests of a 1：30 scale wind turbine model with 2,4,and 6 m air gaps were performed and the discharge process was observed.The experimental results demonstrated that when a 2 m air gap was used,the breakdown voltage increased as the blade speed was increased,but when the gap length was 4 m or longer,the trend was reversed and the breakdown voltage decreased.The analysis revealed that the rotation of the blades changes the charge distribution in the blade-tip region,promotes upward leader development on the blade tip,and decreases the breakdown voltage.Thus,the blade rotation of a wind turbine increases its ability to trigger lightning strikes.
文摘AIM:To describe confidence interval calculation for antidotal potency ratios using bootstrap method.METHODS:We can easily adapt the nonparametric bootstrap method which was invented by Efron to construct confidence intervals in such situations like this.The bootstrap method is a resampling method in which the bootstrap samples are obtained by resampling from the original sample.RESULTS:The described confidence interval calculation using bootstrap method does not require the sampling distribution antidotal potency ratio.This can serve as a substantial help for toxicologists,who are directed to employ the Dixon up-and-down method with the application of lower number of animals to determine lethal dose 50 values for characterizing the investigated toxic molecules and eventually for characterizing the antidotal protections by the test antidotal systems.CONCLUSION:The described method can serve as a useful tool in various other applications.Simplicity ofthe method makes it easier to do the calculation using most of the programming software packages.
基金fundings from the National Natural Science foundation of China[Grant Number 11871419]the Natural Science and Engineering Research Council of Canada.
文摘Dose–response experiments and data analyses are often carried out according to an optimal design under a model assumption.A two-parameter logistic model is often used because of its nice mathematical properties and plausible stochastic response mechanisms.There is an extensive literature on its optimal designs and data analysis strategies.However,a model is at best a good approximation in a real-world application,and researchers must be aware of the risk of model mis-specification.In this paper,we investigate the effectiveness of the sequential EDdesign,the D-optimal design,and the up-and-down design under the three-parameter logistic regression model,and we develop a numerical method for the parameter estimation.Simulations show that the combination of the proposed model and the data analysis strategy performs well.When the logistic model is correct,this more complex model has hardly any efficiency loss.The three-parameter logistic model works better than the two-parameter logistic model in the presence of model mis-specification.
