汽轮发电机组转子长期连续高速旋转,不可避免地出现转子振动状态变化,而转子振动状态的优劣直接影响整个机组安全运行,对其预警方法的研究势在必行。首先统计转子振动运行规律;其次基于振动运行规律提出转子振动异常阈值计算方法;再次...汽轮发电机组转子长期连续高速旋转,不可避免地出现转子振动状态变化,而转子振动状态的优劣直接影响整个机组安全运行,对其预警方法的研究势在必行。首先统计转子振动运行规律;其次基于振动运行规律提出转子振动异常阈值计算方法;再次依托异常阈值和非线性状态评估(Nonlinear State Estimation Technique,NSET)提出转子振动预警方法;最后利用某电厂机组运行数据进行测试验证,并与基于反向传播(Back Propagation,BP)神经网络的振动预警方法进行对比,结果表明所提方法可以准确有效实现转子振动预警。展开更多
The paper considers a multivariate partially linear model under independent errors,and investigates the asymptotic bias and variance-covariance for parametric component βand nonparametric component F(·)by the ...The paper considers a multivariate partially linear model under independent errors,and investigates the asymptotic bias and variance-covariance for parametric component βand nonparametric component F(·)by the GJS estimator and Kernel estimation.展开更多
风电机组长期工作在恶劣的环境中,导致故障频发,运用合理高效的方法对风电机组部件进行故障预警,具有十分重要的现实意义。提出了一种基于SCADA(Supervisory Control And Data Acquisition)大数据的风电机组故障预警策略,依托现场经数...风电机组长期工作在恶劣的环境中,导致故障频发,运用合理高效的方法对风电机组部件进行故障预警,具有十分重要的现实意义。提出了一种基于SCADA(Supervisory Control And Data Acquisition)大数据的风电机组故障预警策略,依托现场经数据预处理的机组数据,提取出高维数据中的特征向量作为数据样本,建立非线性状态评估(NSET)模型,利用NSET模型以及历史数据确定正常工作状态下的阈值;基于SCADA数据以及预测模型的预测值参数与正常状态下的阈值进行比较,当部件工作出现异常时,预测值与实际值的残差增大,超出预先设定的阈值时发出报警信息。利用故障预警方法能及时发现潜在故障,提前排除重大事故隐患,有助于提高设备的可靠性。展开更多
This study focused on the quantitative evaluation of the impact of the spatio-temporal scale used in data collection and grouping on the standardization of CPUE(catch per unit effort).We used the Chinese squid-jigging...This study focused on the quantitative evaluation of the impact of the spatio-temporal scale used in data collection and grouping on the standardization of CPUE(catch per unit effort).We used the Chinese squid-jigging fishery in the northwestern Pacific Ocean as an example to evaluate 24 scenarios at different spatio-temporal scales,with a combination of four levels of temporal scale(weekly,biweekly,monthly,and bimonthly)and six levels of spatial scale(longitude×latitude:0.5°×0.5°,0.5°×1°,0.5°×2°,1°×0.5°,1°×1°,and 1°×2°).We applied generalized additive models and generalized linear models to analyze the24 scenarios for CPUE standardization,and then the differences in the standardized CPUE among these scenarios were quantified.This study shows that combinations of different spatial and temporal scales could have different impacts on the standardization of CPUE.However,at a fine temporal scale(weekly)different spatial scales yielded similar results for standardized CPUE.The choice of spatio-temporal scale used in data collection and analysis may create added uncertainty in fisheries stock assessment and management.To identify a cost-effective spatio-temporal scale for data collection,we recommend a similar study be undertaken to facilitate the design of effective monitoring programs.展开更多
Traditional econometrics has long employed "points" to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a gi...Traditional econometrics has long employed "points" to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a given period. To address this issue, this paper provides a new methodology for interval time series analysis. The concept of "interval stochastic process" is formally defined as a counterpart of "stochastic process" in point-based econometrics. The authors introduce the concepts of interval stationarity, interval statistics (including interval mean, interval variance, etc.) and propose an interval linear model to investigate the dynamic relationships between interval processes. A new interval-based optimization approach for estimation is proposed, and corresponding evaluation criteria are derived. To demonstrate that the new interval method provides valid results, an empirical example on the sterling-dollar exchange rate is presented.展开更多
In this paper, for the generalized linear models (GLMs) with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators (MQLEs) under some regular conditions are developed. Th...In this paper, for the generalized linear models (GLMs) with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators (MQLEs) under some regular conditions are developed. The existence, weak convergence and the rate of convergence and asymptotic normality of linear combination of MQLEs and asymptotic distribution of single linear hypothesis teststatistics are presented. The results are illustrated by Monte-Carlo simulations.展开更多
For the generalized linear model,the authors propose a sequential sampling procedure based on an adaptive shrinkage estimate of parameter.This method can determine a minimum sample size under which effective variables...For the generalized linear model,the authors propose a sequential sampling procedure based on an adaptive shrinkage estimate of parameter.This method can determine a minimum sample size under which effective variables contributing to the model are identified and estimates of regression parameters achieve the required accuracy.The authors prove that the proposed sequential procedure is asymptotically optimal.Numerical simulation studies show that the proposed method can save a large number of samples compared to the traditional sequential approach.展开更多
文摘汽轮发电机组转子长期连续高速旋转,不可避免地出现转子振动状态变化,而转子振动状态的优劣直接影响整个机组安全运行,对其预警方法的研究势在必行。首先统计转子振动运行规律;其次基于振动运行规律提出转子振动异常阈值计算方法;再次依托异常阈值和非线性状态评估(Nonlinear State Estimation Technique,NSET)提出转子振动预警方法;最后利用某电厂机组运行数据进行测试验证,并与基于反向传播(Back Propagation,BP)神经网络的振动预警方法进行对比,结果表明所提方法可以准确有效实现转子振动预警。
基金Supported by the Anhui Provincial Natural Science Foundation(11040606M04) Supported by the National Natural Science Foundation of China(10871001,10971097)
文摘The paper considers a multivariate partially linear model under independent errors,and investigates the asymptotic bias and variance-covariance for parametric component βand nonparametric component F(·)by the GJS estimator and Kernel estimation.
文摘风电机组长期工作在恶劣的环境中,导致故障频发,运用合理高效的方法对风电机组部件进行故障预警,具有十分重要的现实意义。提出了一种基于SCADA(Supervisory Control And Data Acquisition)大数据的风电机组故障预警策略,依托现场经数据预处理的机组数据,提取出高维数据中的特征向量作为数据样本,建立非线性状态评估(NSET)模型,利用NSET模型以及历史数据确定正常工作状态下的阈值;基于SCADA数据以及预测模型的预测值参数与正常状态下的阈值进行比较,当部件工作出现异常时,预测值与实际值的残差增大,超出预先设定的阈值时发出报警信息。利用故障预警方法能及时发现潜在故障,提前排除重大事故隐患,有助于提高设备的可靠性。
基金Supported by Shanghai Universities First-class Disciplines Project,Discipline name:Fisheries(A),the National Natural Science Foundation of China(No.NSFC41276156)the National High Technology Research and Development Program of China(863 Program)(No.2012AA092303)+1 种基金the Shanghai Science and Technology Innovation Program(No.12231203900)CHEN Yong’s involvement was supported by the Shanghai Ocean University
文摘This study focused on the quantitative evaluation of the impact of the spatio-temporal scale used in data collection and grouping on the standardization of CPUE(catch per unit effort).We used the Chinese squid-jigging fishery in the northwestern Pacific Ocean as an example to evaluate 24 scenarios at different spatio-temporal scales,with a combination of four levels of temporal scale(weekly,biweekly,monthly,and bimonthly)and six levels of spatial scale(longitude×latitude:0.5°×0.5°,0.5°×1°,0.5°×2°,1°×0.5°,1°×1°,and 1°×2°).We applied generalized additive models and generalized linear models to analyze the24 scenarios for CPUE standardization,and then the differences in the standardized CPUE among these scenarios were quantified.This study shows that combinations of different spatial and temporal scales could have different impacts on the standardization of CPUE.However,at a fine temporal scale(weekly)different spatial scales yielded similar results for standardized CPUE.The choice of spatio-temporal scale used in data collection and analysis may create added uncertainty in fisheries stock assessment and management.To identify a cost-effective spatio-temporal scale for data collection,we recommend a similar study be undertaken to facilitate the design of effective monitoring programs.
基金This work was partially supported by the National Natural Science Foundation of China and Research Granting Committee of Hong Kong
文摘Traditional econometrics has long employed "points" to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a given period. To address this issue, this paper provides a new methodology for interval time series analysis. The concept of "interval stochastic process" is formally defined as a counterpart of "stochastic process" in point-based econometrics. The authors introduce the concepts of interval stationarity, interval statistics (including interval mean, interval variance, etc.) and propose an interval linear model to investigate the dynamic relationships between interval processes. A new interval-based optimization approach for estimation is proposed, and corresponding evaluation criteria are derived. To demonstrate that the new interval method provides valid results, an empirical example on the sterling-dollar exchange rate is presented.
基金supported by Major Programm of Natural Science Foundation of China under Grant No.71690242the Natural Science Foundation of China under Grant No.11471252the National Social Science Fund of China under Grant No.18BTJ040
文摘In this paper, for the generalized linear models (GLMs) with diverging number of covariates, the asymptotic properties of maximum quasi-likelihood estimators (MQLEs) under some regular conditions are developed. The existence, weak convergence and the rate of convergence and asymptotic normality of linear combination of MQLEs and asymptotic distribution of single linear hypothesis teststatistics are presented. The results are illustrated by Monte-Carlo simulations.
基金supported by the National Natural Science Foundation of China under Grant No.11101396the State Key Program of National Natural Science of China under Grant No.11231010the Fundamental Research Funds for the Central Universities under Grant No.WK2040000010
文摘For the generalized linear model,the authors propose a sequential sampling procedure based on an adaptive shrinkage estimate of parameter.This method can determine a minimum sample size under which effective variables contributing to the model are identified and estimates of regression parameters achieve the required accuracy.The authors prove that the proposed sequential procedure is asymptotically optimal.Numerical simulation studies show that the proposed method can save a large number of samples compared to the traditional sequential approach.