Purpose:To evaluate the sensitivity and specificity of the screening modes of frequency-doubling technology(FDT),tendency-oriented perimetry(TOP),SITA Standard(SS)and SITA Fast(SF)in perimetrically inexperienced indiv...Purpose:To evaluate the sensitivity and specificity of the screening modes of frequency-doubling technology(FDT),tendency-oriented perimetry(TOP),SITA Standard(SS)and SITA Fast(SF)in perimetrically inexperienced individuals.Methods:One eye of 64 glaucoma patients and 53 normal subjects who had never undergone automated perimetry were tested with programs C-20-5(FDT),G1(TOP)and 24-2(SS and SF).The gold standard for glaucoma was the presence of a typical glaucomatous optic disc appearance on stereoscopic examination(judged by a glaucoma expert),and intraocular pressure(IOP)> 21 mmHg.The test order among strategies was randomized for each subject.To define an abnormal visual field,we applied three criteria for SS and SF and two criteria for TOP and FDT,all of which have been previously described in the literature.Sensitivities and specificities among the different criteria were compared using the Cochran test.Results:Frequency-doubling technology showed the shortest mean test duration,followed by TOP,SF and SS(p < 0.05).Sensitivity ranges were 87.5-89.1% for SS,92.2-93.8% for SF,87.5-89.1% for TOP,and 82.8-85.9% for FDT(p=0.34).Specificity ranges were 73.6-83% for FDT,56.6-62.3% for TOP,60.4-69.8% for SF and 66.0-71.7% for SS.The specificity obtained with criterion 2 for FDT(based on the presence of two or more abnormal locations regardless of the severity of abnormal points)was higher than those measured with the other strategies(p < 0.01).Conclusion:When testing individuals with no perimetric experience,moderate sensitivities and specificities should be expected,regardless of the strategy chosen.展开更多
Purpose: To clarify the discrepancy found in literature about a possible learning effect in frequency doubling perimetry (FDT) by measuring the learning effect in a large group of subjects of various ages, with and wi...Purpose: To clarify the discrepancy found in literature about a possible learning effect in frequency doubling perimetry (FDT) by measuring the learning effect in a large group of subjects of various ages, with and without perimetric experience, and with and without glaucoma Methods: Two FDT measurements were performed in three groups: young normals without perimeric experience (group I, n =26), aged normals without perimetric ex-展开更多
LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical su...LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.展开更多
Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing...Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing the anti-accident technical measures, improving the installation and debugging level, and strengthening operation inspection, are proposed.展开更多
Linear mixed models are popularly used to fit continuous longitudinal data, and the random effects are commonly assumed to have normal distribution. However, this assumption needs to be tested so that further analysis...Linear mixed models are popularly used to fit continuous longitudinal data, and the random effects are commonly assumed to have normal distribution. However, this assumption needs to be tested so that further analysis can be proceeded well. In this paper, we consider the Baringhaus-Henze-Epps-Pulley （BHEP） tests, which are based on an empirical characteristic function. Differing from their case, we consider the normality checking for the random effects which are unobservable and the test should be based on their predictors. The test is consistent against global alternatives, and is sensitive to the local alternatives converging to the null at a certain rate arbitrarily close to 1/V~ where n is sample size. ^-hlrthermore, to overcome the problem that the limiting null distribution of the test is not tractable, we suggest a new method： use a conditional Monte Carlo test （CMCT） to approximate the null distribution, and then to simulate p-values. The test is compared with existing methods, the power is examined, and several examples are applied to illustrate the usefulness of our test in the analysis of longitudinal data.展开更多
Monitoring transmission towers is of great importance to prevent severe thefts on them and ensure the reliability and safety of the power grid operation.Independent component analysis(ICA) is a method for finding unde...Monitoring transmission towers is of great importance to prevent severe thefts on them and ensure the reliability and safety of the power grid operation.Independent component analysis(ICA) is a method for finding underlying factors or components from multivariate statistical data based on dimension reduction methods,and it is applicable to extract the non-stationary signals.FastICA based on negentropy is presented to effectively extract and separate the vibration signals caused by human activity in this paper.A new method combined empirical mode decomposition(EMD) technique with the adaptive threshold method is applied to extract the vibration pulses,and suppress the interference signals.The practical tests demonstrate that the method proposed in the paper is effective in separating and extracting the vibration signals.展开更多
文摘Purpose:To evaluate the sensitivity and specificity of the screening modes of frequency-doubling technology(FDT),tendency-oriented perimetry(TOP),SITA Standard(SS)and SITA Fast(SF)in perimetrically inexperienced individuals.Methods:One eye of 64 glaucoma patients and 53 normal subjects who had never undergone automated perimetry were tested with programs C-20-5(FDT),G1(TOP)and 24-2(SS and SF).The gold standard for glaucoma was the presence of a typical glaucomatous optic disc appearance on stereoscopic examination(judged by a glaucoma expert),and intraocular pressure(IOP)> 21 mmHg.The test order among strategies was randomized for each subject.To define an abnormal visual field,we applied three criteria for SS and SF and two criteria for TOP and FDT,all of which have been previously described in the literature.Sensitivities and specificities among the different criteria were compared using the Cochran test.Results:Frequency-doubling technology showed the shortest mean test duration,followed by TOP,SF and SS(p < 0.05).Sensitivity ranges were 87.5-89.1% for SS,92.2-93.8% for SF,87.5-89.1% for TOP,and 82.8-85.9% for FDT(p=0.34).Specificity ranges were 73.6-83% for FDT,56.6-62.3% for TOP,60.4-69.8% for SF and 66.0-71.7% for SS.The specificity obtained with criterion 2 for FDT(based on the presence of two or more abnormal locations regardless of the severity of abnormal points)was higher than those measured with the other strategies(p < 0.01).Conclusion:When testing individuals with no perimetric experience,moderate sensitivities and specificities should be expected,regardless of the strategy chosen.
文摘Purpose: To clarify the discrepancy found in literature about a possible learning effect in frequency doubling perimetry (FDT) by measuring the learning effect in a large group of subjects of various ages, with and without perimetric experience, and with and without glaucoma Methods: Two FDT measurements were performed in three groups: young normals without perimeric experience (group I, n =26), aged normals without perimetric ex-
文摘LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.
文摘Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing the anti-accident technical measures, improving the installation and debugging level, and strengthening operation inspection, are proposed.
基金supported in part by a grant of Research Grants Council of Hong Kong,and National Natural Science Foundation of China (Grant No. 11101157)
文摘Linear mixed models are popularly used to fit continuous longitudinal data, and the random effects are commonly assumed to have normal distribution. However, this assumption needs to be tested so that further analysis can be proceeded well. In this paper, we consider the Baringhaus-Henze-Epps-Pulley （BHEP） tests, which are based on an empirical characteristic function. Differing from their case, we consider the normality checking for the random effects which are unobservable and the test should be based on their predictors. The test is consistent against global alternatives, and is sensitive to the local alternatives converging to the null at a certain rate arbitrarily close to 1/V~ where n is sample size. ^-hlrthermore, to overcome the problem that the limiting null distribution of the test is not tractable, we suggest a new method： use a conditional Monte Carlo test （CMCT） to approximate the null distribution, and then to simulate p-values. The test is compared with existing methods, the power is examined, and several examples are applied to illustrate the usefulness of our test in the analysis of longitudinal data.
文摘Monitoring transmission towers is of great importance to prevent severe thefts on them and ensure the reliability and safety of the power grid operation.Independent component analysis(ICA) is a method for finding underlying factors or components from multivariate statistical data based on dimension reduction methods,and it is applicable to extract the non-stationary signals.FastICA based on negentropy is presented to effectively extract and separate the vibration signals caused by human activity in this paper.A new method combined empirical mode decomposition(EMD) technique with the adaptive threshold method is applied to extract the vibration pulses,and suppress the interference signals.The practical tests demonstrate that the method proposed in the paper is effective in separating and extracting the vibration signals.
