Acid production with flue gas is a complex nonlinear process with multiple variables and strong coupling.The operation data is an important basis for state monitoring,optimal control,and fault diagnosis.However,the op...Acid production with flue gas is a complex nonlinear process with multiple variables and strong coupling.The operation data is an important basis for state monitoring,optimal control,and fault diagnosis.However,the operating environment of acid production with flue gas is complex and there is much equipment.The data obtained by the detection equipment is seriously polluted and prone to abnormal phenomena such as data loss and outliers.Therefore,to solve the problem of abnormal data in the process of acid production with flue gas,a data cleaning method based on improved random forest is proposed.Firstly,an outlier data recognition model based on isolation forest is designed to identify and eliminate the outliers in the dataset.Secondly,an improved random forest regression model is established.Genetic algorithm is used to optimize the hyperparameters of the random forest regression model.Then the optimal parameter combination is found in the search space and the trend of data is predicted.Finally,the improved random forest data cleaning method is used to compensate for the missing data after eliminating abnormal data and the data cleaning is realized.Results show that the proposed method can accurately eliminate and compensate for the abnormal data in the process of acid production with flue gas.The method improves the accuracy of compensation for missing data.With the data after cleaning,a more accurate model can be established,which is significant to the subsequent temperature control.The conversion rate of SO_(2) can be further improved,thereby improving the yield of sulfuric acid and economic benefits.展开更多
Web information system(WIS)is frequently-used and indispensable in daily social life.WIS provides information services in many scenarios,such as electronic commerce,communities,and edutainment.Data cleaning plays an e...Web information system(WIS)is frequently-used and indispensable in daily social life.WIS provides information services in many scenarios,such as electronic commerce,communities,and edutainment.Data cleaning plays an essential role in various WIS scenarios to improve the quality of data service.In this paper,we present a review of the state-of-the-art methods for data cleaning in WIS.According to the characteristics of data cleaning,we extract the critical elements of WIS,such as interactive objects,application scenarios,and core technology,to classify the existing works.Then,after elaborating and analyzing each category,we summarize the descriptions and challenges of data cleaning methods with sub-elements such as data&user interaction,data quality rule,model,crowdsourcing,and privacy preservation.Finally,we analyze various types of problems and provide suggestions for future research on data cleaning in WIS from the technology and interactive perspective.展开更多
Wireless sensor networks are increasingly used in sensitive event monitoring.However,various abnormal data generated by sensors greatly decrease the accuracy of the event detection.Although many methods have been prop...Wireless sensor networks are increasingly used in sensitive event monitoring.However,various abnormal data generated by sensors greatly decrease the accuracy of the event detection.Although many methods have been proposed to deal with the abnormal data,they generally detect and/or repair all abnormal data without further differentiate.Actually,besides the abnormal data caused by events,it is well known that sensor nodes prone to generate abnormal data due to factors such as sensor hardware drawbacks and random effects of external sources.Dealing with all abnormal data without differentiate will result in false detection or missed detection of the events.In this paper,we propose a data cleaning approach based on Stacked Denoising Autoencoders(SDAE)and multi-sensor collaborations.We detect all abnormal data by SDAE,then differentiate the abnormal data by multi-sensor collaborations.The abnormal data caused by events are unchanged,while the abnormal data caused by other factors are repaired.Real data based simulations show the efficiency of the proposed approach.展开更多
Data quality has exerted important influence over the application of grain big data, so data cleaning is a necessary and important work. In MapReduce frame, parallel technique is often used to execute data cleaning in...Data quality has exerted important influence over the application of grain big data, so data cleaning is a necessary and important work. In MapReduce frame, parallel technique is often used to execute data cleaning in high scalability mode, but due to the lack of effective design, there are amounts of computing redundancy in the process of data cleaning, which results in lower performance. In this research, we found that some tasks often are carried out multiple times on same input files, or require same operation results in the process of data cleaning. For this problem, we proposed a new optimization technique that is based on task merge. By merging simple or redundancy computations on same input files, the number of the loop computation in MapReduce can be reduced greatly. The experiment shows, by this means, the overall system runtime is significantly reduced, which proves that the process of data cleaning is optimized. In this paper, we optimized several modules of data cleaning such as entity identification, inconsistent data restoration, and missing value filling. Experimental results show that the proposed method in this paper can increase efficiency for grain big data cleaning.展开更多
In this paper, we propose a rule management system for data cleaning that is based on knowledge. This system combines features of both rule based systems and rule based data cleaning frameworks. The important advantag...In this paper, we propose a rule management system for data cleaning that is based on knowledge. This system combines features of both rule based systems and rule based data cleaning frameworks. The important advantages of our system are threefold. First, it aims at proposing a strong and unified rule form based on first order structure that permits the representation and management of all the types of rules and their quality via some characteristics. Second, it leads to increase the quality of rules which conditions the quality of data cleaning. Third, it uses an appropriate knowledge acquisition process, which is the weakest task in the current rule and knowledge based systems. As several research works have shown that data cleaning is rather driven by domain knowledge than by data, we have identified and analyzed the properties that distinguish knowledge and rules from data for better determining the most components of the proposed system. In order to illustrate our system, we also present a first experiment with a case study at health sector where we demonstrate how the system is useful for the improvement of data quality. The autonomy, extensibility and platform-independency of the proposed rule management system facilitate its incorporation in any system that is interested in data quality management.展开更多
In order to improve the data quality,the big data cleaning method for distribution networks is studied in this paper.First,the Local Outlier Factor(LOF)algorithm based on DBSCAN clustering is used to detect outliers.H...In order to improve the data quality,the big data cleaning method for distribution networks is studied in this paper.First,the Local Outlier Factor(LOF)algorithm based on DBSCAN clustering is used to detect outliers.However,due to the difficulty in determining the LOF threshold,a method of dynamically calculating the threshold based on the transformer districts and time is proposed.In addition,the LOF algorithm combines the statistical distribution method to reduce the misjudgment rate.Aiming at the diversity and complexity of data missing forms in power big data,this paper has improved the Random Forest imputation algorithm,which can be applied to various forms of missing data,especially the blocked missing data and even some completely missing horizontal or vertical data.The data in this paper are from real data of 44 transformer districts of a certain 10 kV line in a distribution network.Experimental results show that outlier detection is accurate and suitable for any shape and multidimensional power big data.The improved Random Forest imputation algorithm is suitable for all missing forms,with higher imputation accuracy and better model stability.By comparing the network loss prediction between the data using this data cleaning method and the data removing outliers and missing values,it can be found that the accuracy of network loss prediction has improved by nearly 4%using the data cleaning method identified in this paper.Additionally,as the proportion of bad data increased,the difference between the prediction accuracy of cleaned data and that of uncleaned data is more significant.展开更多
Data cleaning is considered as an effective approach of improving data quality in order to help practitioners and researchers be devoted to downstream analysis and decision-making without worrying about data trustwort...Data cleaning is considered as an effective approach of improving data quality in order to help practitioners and researchers be devoted to downstream analysis and decision-making without worrying about data trustworthiness.This paper provides a systematic summary of the two main stages of data cleaning for Internet of Things(IoT)data with time series characteristics,including error data detection and data repairing.In respect to error data detection techniques,it categorizes an overview of quantitative data error detection methods for detecting single-point errors,continuous errors,and multidimensional time series data errors and qualitative data error detection methods for detecting rule-violating errors.Besides,it provides a detailed description of error data repairing techniques,involving statistics-based repairing,rule-based repairing,and human-involved repairing.We review the strengths and the limitations of the current data cleaning techniques under IoT data applications and conclude with an outlook on the future of IoT data cleaning.展开更多
Current methodologies for cleaning wind power anomaly data exhibit limited capabilities in identifying abnormal data within extensive datasets and struggle to accommodate the considerable variability and intricacy of ...Current methodologies for cleaning wind power anomaly data exhibit limited capabilities in identifying abnormal data within extensive datasets and struggle to accommodate the considerable variability and intricacy of wind farm data.Consequently,a method for cleaning wind power anomaly data by combining image processing with community detection algorithms(CWPAD-IPCDA)is proposed.To precisely identify and initially clean anomalous data,wind power curve(WPC)images are converted into graph structures,which employ the Louvain community recognition algorithm and graph-theoretic methods for community detection and segmentation.Furthermore,the mathematical morphology operation(MMO)determines the main part of the initially cleaned wind power curve images and maps them back to the normal wind power points to complete the final cleaning.The CWPAD-IPCDA method was applied to clean datasets from 25 wind turbines(WTs)in two wind farms in northwest China to validate its feasibility.A comparison was conducted using density-based spatial clustering of applications with noise(DBSCAN)algorithm,an improved isolation forest algorithm,and an image-based(IB)algorithm.The experimental results demonstrate that the CWPAD-IPCDA method surpasses the other three algorithms,achieving an approximately 7.23%higher average data cleaning rate.The mean value of the sum of the squared errors(SSE)of the dataset after cleaning is approximately 6.887 lower than that of the other algorithms.Moreover,the mean of overall accuracy,as measured by the F1-score,exceeds that of the other methods by approximately 10.49%;this indicates that the CWPAD-IPCDA method is more conducive to improving the accuracy and reliability of wind power curve modeling and wind farm power forecasting.展开更多
There are errors in multi-source uncertain time series data.Truth discovery methods for time series data are effective in finding more accurate values,but some have limitations in their usability.To tackle this challe...There are errors in multi-source uncertain time series data.Truth discovery methods for time series data are effective in finding more accurate values,but some have limitations in their usability.To tackle this challenge,we propose a new and convenient truth discovery method to handle time series data.A more accurate sample is closer to the truth and,consequently,to other accurate samples.Because the mutual-confirm relationship between sensors is very similar to the mutual-quote relationship between web pages,we evaluate sensor reliability based on PageRank and then estimate the truth by sensor reliability.Therefore,this method does not rely on smoothness assumptions or prior knowledge of the data.Finally,we validate the effectiveness and efficiency of the proposed method on real-world and synthetic data sets,respectively.展开更多
Recently,Massive Open Online Courses(MOOCs)is a major way of online learning for millions of people around the world,which generates a large amount of data in the meantime.However,due to errors produced from collectin...Recently,Massive Open Online Courses(MOOCs)is a major way of online learning for millions of people around the world,which generates a large amount of data in the meantime.However,due to errors produced from collecting,system,and so on,these data have various inconsistencies and missing values.In order to support accurate analysis,this paper studies the data cleaning technology for online open curriculum system,including missing value-time filling for time series,and rulebased input error correction.The data cleaning algorithm designed in this paper is divided into six parts:pre-processing,missing data processing,format and content error processing,logical error processing,irrelevant data processing and correlation analysis.This paper designs and implements missing-value-filling algorithm based on time series in the missing data processing part.According to the large number of descriptive variables existing in the format and content error processing module,it proposed one-based and separability-based criteria Hot+J3+PCA.The online course data cleaning algorithm was analyzed in detail on algorithm design,implementation and testing.After a lot of rigorous testing,the function of each module performs normally,and the cleaning performance of the algorithm is of expectation.展开更多
Purpose： The authors aim at testing the performance of a set of machine learning algorithms that could improve the process of data cleaning when building datasets. Design/methodology/approach： The paper is centered ...Purpose： The authors aim at testing the performance of a set of machine learning algorithms that could improve the process of data cleaning when building datasets. Design/methodology/approach： The paper is centered on cleaning datasets gathered from publishers and online resources by the use of specific keywords. In this case, we analyzed data from the Web of Science. The accuracy of various forms of automatic classification was tested here in comparison with manual coding in order to determine their usefulness for data collection and cleaning. We assessed the performance of seven supervised classification algorithms （Support Vector Machine （SVM）, Scaled Linear Discriminant Analysis, Lasso and elastic-net regularized generalized linear models, Maximum Entropy, Regression Tree, Boosting, and Random Forest） and analyzed two properties： accuracy and recall. We assessed not only each algorithm individually, but also their combinations through a voting scheme. We also tested the performance of these algorithms with different sizes of training data. When assessing the performance of different combinations, we used an indicator of coverage to account for the agreement and disagreement on classification between algorithms. Findings： We found that the performance of the algorithms used vary with the size of the sample for training. However, for the classification exercise in this paper the best performing algorithms were SVM and Boosting. The combination of these two algorithms achieved a high agreement on coverage and was highly accurate. This combination performs well with a small training dataset （10%）, which may reduce the manual work needed for classification tasks. Research limitations： The dataset gathered has significantly more records related to the topic of interest compared to unrelated topics. This may affect the performance of some algorithms, especially in their identification of unrelated papers. Practical implications： Although the classification achieved by this means is not completely accurate, the amount of manual coding needed can be greatly reduced by using classification algorithms. This can be of great help when the dataset is big. With the help of accuracy, recall,and coverage measures, it is possible to have an estimation of the error involved in this classification, which could open the possibility of incorporating the use of these algorithms in software specifically designed for data cleaning and classification.展开更多
There are a number of dirty data in observation data set derived from integrated ocean observing network system. Thus, the data must be carefully and reasonably processed before they are used for forecasting or analys...There are a number of dirty data in observation data set derived from integrated ocean observing network system. Thus, the data must be carefully and reasonably processed before they are used for forecasting or analysis. This paper proposes a data pre-processing model based on intelligent algorithms. Firstly, we introduce the integrated network platform of ocean observation. Next, the preprocessing model of data is presemed, and an imelligent cleaning model of data is proposed. Based on fuzzy clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means clustering. The proposed dynamic algorithm can automatically f＇md the new clustering center with the updated sample data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results through observation data analysis.展开更多
针对风电机组齿轮箱油池温度异常难以早期预警的问题,提出一种基于数据采集与监视控制(supervisory control and data acquisition,SCADA)数据的故障预警方法,以提升机组运行可靠性。首先,结合风速-功率分布特征,采用四分位法与基于数...针对风电机组齿轮箱油池温度异常难以早期预警的问题,提出一种基于数据采集与监视控制(supervisory control and data acquisition,SCADA)数据的故障预警方法,以提升机组运行可靠性。首先,结合风速-功率分布特征,采用四分位法与基于数据离散度的纵向滤波剔除异常功率点;接着,利用随机森林算法筛选影响油池温度的关键输入特征,构建基于类别提升(categorical boosting,CatBoost)算法的温度预测模型,并采用树结构parzen估计器(tree-structured parzen estimator,TPE)优化其超参数;最后,基于残差分布,通过统计过程控制确定动态预警阈值。在某风电场实际故障案例中,该模型在齿轮箱故障发生前约5 h发出有效预警,残差超出控制限的时间点与故障发展过程高度吻合。所提方法能有效识别油池温度异常工况,具备良好的早期预警能力与工程应用价值。展开更多
基金supported by the National Natural Science Foundation of China(61873006)Beijing Natural Science Foundation(4204087,4212040).
文摘Acid production with flue gas is a complex nonlinear process with multiple variables and strong coupling.The operation data is an important basis for state monitoring,optimal control,and fault diagnosis.However,the operating environment of acid production with flue gas is complex and there is much equipment.The data obtained by the detection equipment is seriously polluted and prone to abnormal phenomena such as data loss and outliers.Therefore,to solve the problem of abnormal data in the process of acid production with flue gas,a data cleaning method based on improved random forest is proposed.Firstly,an outlier data recognition model based on isolation forest is designed to identify and eliminate the outliers in the dataset.Secondly,an improved random forest regression model is established.Genetic algorithm is used to optimize the hyperparameters of the random forest regression model.Then the optimal parameter combination is found in the search space and the trend of data is predicted.Finally,the improved random forest data cleaning method is used to compensate for the missing data after eliminating abnormal data and the data cleaning is realized.Results show that the proposed method can accurately eliminate and compensate for the abnormal data in the process of acid production with flue gas.The method improves the accuracy of compensation for missing data.With the data after cleaning,a more accurate model can be established,which is significant to the subsequent temperature control.The conversion rate of SO_(2) can be further improved,thereby improving the yield of sulfuric acid and economic benefits.
文摘Web information system(WIS)is frequently-used and indispensable in daily social life.WIS provides information services in many scenarios,such as electronic commerce,communities,and edutainment.Data cleaning plays an essential role in various WIS scenarios to improve the quality of data service.In this paper,we present a review of the state-of-the-art methods for data cleaning in WIS.According to the characteristics of data cleaning,we extract the critical elements of WIS,such as interactive objects,application scenarios,and core technology,to classify the existing works.Then,after elaborating and analyzing each category,we summarize the descriptions and challenges of data cleaning methods with sub-elements such as data&user interaction,data quality rule,model,crowdsourcing,and privacy preservation.Finally,we analyze various types of problems and provide suggestions for future research on data cleaning in WIS from the technology and interactive perspective.
基金This work is supported by the National Natural Science Foundation of China(Grant No.61672282)the Basic Research Program of Jiangsu Province(Grant No.BK20161491).
文摘Wireless sensor networks are increasingly used in sensitive event monitoring.However,various abnormal data generated by sensors greatly decrease the accuracy of the event detection.Although many methods have been proposed to deal with the abnormal data,they generally detect and/or repair all abnormal data without further differentiate.Actually,besides the abnormal data caused by events,it is well known that sensor nodes prone to generate abnormal data due to factors such as sensor hardware drawbacks and random effects of external sources.Dealing with all abnormal data without differentiate will result in false detection or missed detection of the events.In this paper,we propose a data cleaning approach based on Stacked Denoising Autoencoders(SDAE)and multi-sensor collaborations.We detect all abnormal data by SDAE,then differentiate the abnormal data by multi-sensor collaborations.The abnormal data caused by events are unchanged,while the abnormal data caused by other factors are repaired.Real data based simulations show the efficiency of the proposed approach.
文摘Data quality has exerted important influence over the application of grain big data, so data cleaning is a necessary and important work. In MapReduce frame, parallel technique is often used to execute data cleaning in high scalability mode, but due to the lack of effective design, there are amounts of computing redundancy in the process of data cleaning, which results in lower performance. In this research, we found that some tasks often are carried out multiple times on same input files, or require same operation results in the process of data cleaning. For this problem, we proposed a new optimization technique that is based on task merge. By merging simple or redundancy computations on same input files, the number of the loop computation in MapReduce can be reduced greatly. The experiment shows, by this means, the overall system runtime is significantly reduced, which proves that the process of data cleaning is optimized. In this paper, we optimized several modules of data cleaning such as entity identification, inconsistent data restoration, and missing value filling. Experimental results show that the proposed method in this paper can increase efficiency for grain big data cleaning.
文摘In this paper, we propose a rule management system for data cleaning that is based on knowledge. This system combines features of both rule based systems and rule based data cleaning frameworks. The important advantages of our system are threefold. First, it aims at proposing a strong and unified rule form based on first order structure that permits the representation and management of all the types of rules and their quality via some characteristics. Second, it leads to increase the quality of rules which conditions the quality of data cleaning. Third, it uses an appropriate knowledge acquisition process, which is the weakest task in the current rule and knowledge based systems. As several research works have shown that data cleaning is rather driven by domain knowledge than by data, we have identified and analyzed the properties that distinguish knowledge and rules from data for better determining the most components of the proposed system. In order to illustrate our system, we also present a first experiment with a case study at health sector where we demonstrate how the system is useful for the improvement of data quality. The autonomy, extensibility and platform-independency of the proposed rule management system facilitate its incorporation in any system that is interested in data quality management.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grant U1966207 and 51822702in part by the Key Research and Development Program of Hunan Province of China under Grant 2018GK2031+1 种基金in part by the 111 Project of China under Grant B17016,in part by the Innovative Construction Program of Hunan Province of China under Grant 2019RS1016in part by the Excellent Innovation Youth Program of Changsha of China under Grant KQ1802029.
文摘In order to improve the data quality,the big data cleaning method for distribution networks is studied in this paper.First,the Local Outlier Factor(LOF)algorithm based on DBSCAN clustering is used to detect outliers.However,due to the difficulty in determining the LOF threshold,a method of dynamically calculating the threshold based on the transformer districts and time is proposed.In addition,the LOF algorithm combines the statistical distribution method to reduce the misjudgment rate.Aiming at the diversity and complexity of data missing forms in power big data,this paper has improved the Random Forest imputation algorithm,which can be applied to various forms of missing data,especially the blocked missing data and even some completely missing horizontal or vertical data.The data in this paper are from real data of 44 transformer districts of a certain 10 kV line in a distribution network.Experimental results show that outlier detection is accurate and suitable for any shape and multidimensional power big data.The improved Random Forest imputation algorithm is suitable for all missing forms,with higher imputation accuracy and better model stability.By comparing the network loss prediction between the data using this data cleaning method and the data removing outliers and missing values,it can be found that the accuracy of network loss prediction has improved by nearly 4%using the data cleaning method identified in this paper.Additionally,as the proportion of bad data increased,the difference between the prediction accuracy of cleaned data and that of uncleaned data is more significant.
基金supported by the National Key Research and Development Program of China(No.2021YFB3300502)National Natural Science Foundation of China(NSFC)(Nos.62202126 and 62232005)Heilongjiang Postdoctoral Financial Assistance(No.LBH-Z21137).
文摘Data cleaning is considered as an effective approach of improving data quality in order to help practitioners and researchers be devoted to downstream analysis and decision-making without worrying about data trustworthiness.This paper provides a systematic summary of the two main stages of data cleaning for Internet of Things(IoT)data with time series characteristics,including error data detection and data repairing.In respect to error data detection techniques,it categorizes an overview of quantitative data error detection methods for detecting single-point errors,continuous errors,and multidimensional time series data errors and qualitative data error detection methods for detecting rule-violating errors.Besides,it provides a detailed description of error data repairing techniques,involving statistics-based repairing,rule-based repairing,and human-involved repairing.We review the strengths and the limitations of the current data cleaning techniques under IoT data applications and conclude with an outlook on the future of IoT data cleaning.
基金supported by the National Natural Science Foundation of China(Project No.51767018)Natural Science Foundation of Gansu Province(Project No.23JRRA836).
文摘Current methodologies for cleaning wind power anomaly data exhibit limited capabilities in identifying abnormal data within extensive datasets and struggle to accommodate the considerable variability and intricacy of wind farm data.Consequently,a method for cleaning wind power anomaly data by combining image processing with community detection algorithms(CWPAD-IPCDA)is proposed.To precisely identify and initially clean anomalous data,wind power curve(WPC)images are converted into graph structures,which employ the Louvain community recognition algorithm and graph-theoretic methods for community detection and segmentation.Furthermore,the mathematical morphology operation(MMO)determines the main part of the initially cleaned wind power curve images and maps them back to the normal wind power points to complete the final cleaning.The CWPAD-IPCDA method was applied to clean datasets from 25 wind turbines(WTs)in two wind farms in northwest China to validate its feasibility.A comparison was conducted using density-based spatial clustering of applications with noise(DBSCAN)algorithm,an improved isolation forest algorithm,and an image-based(IB)algorithm.The experimental results demonstrate that the CWPAD-IPCDA method surpasses the other three algorithms,achieving an approximately 7.23%higher average data cleaning rate.The mean value of the sum of the squared errors(SSE)of the dataset after cleaning is approximately 6.887 lower than that of the other algorithms.Moreover,the mean of overall accuracy,as measured by the F1-score,exceeds that of the other methods by approximately 10.49%;this indicates that the CWPAD-IPCDA method is more conducive to improving the accuracy and reliability of wind power curve modeling and wind farm power forecasting.
基金National Natural Science Foundation of China(No.62002131)Shuangchuang Ph.D Award(from World Prestigious Universities)of Jiangsu Province,China(No.JSSCBS20211179)。
文摘There are errors in multi-source uncertain time series data.Truth discovery methods for time series data are effective in finding more accurate values,but some have limitations in their usability.To tackle this challenge,we propose a new and convenient truth discovery method to handle time series data.A more accurate sample is closer to the truth and,consequently,to other accurate samples.Because the mutual-confirm relationship between sensors is very similar to the mutual-quote relationship between web pages,we evaluate sensor reliability based on PageRank and then estimate the truth by sensor reliability.Therefore,this method does not rely on smoothness assumptions or prior knowledge of the data.Finally,we validate the effectiveness and efficiency of the proposed method on real-world and synthetic data sets,respectively.
文摘Recently,Massive Open Online Courses(MOOCs)is a major way of online learning for millions of people around the world,which generates a large amount of data in the meantime.However,due to errors produced from collecting,system,and so on,these data have various inconsistencies and missing values.In order to support accurate analysis,this paper studies the data cleaning technology for online open curriculum system,including missing value-time filling for time series,and rulebased input error correction.The data cleaning algorithm designed in this paper is divided into six parts:pre-processing,missing data processing,format and content error processing,logical error processing,irrelevant data processing and correlation analysis.This paper designs and implements missing-value-filling algorithm based on time series in the missing data processing part.According to the large number of descriptive variables existing in the format and content error processing module,it proposed one-based and separability-based criteria Hot+J3+PCA.The online course data cleaning algorithm was analyzed in detail on algorithm design,implementation and testing.After a lot of rigorous testing,the function of each module performs normally,and the cleaning performance of the algorithm is of expectation.
基金supported by National Natural Science Foundation of China(NSFC)(Grant No.:71173154)The National Social Science Fund of China(NSSFC)(Grant No.:08BZX076)the Fundamental Research Funds for the Central Universities
文摘Purpose： The authors aim at testing the performance of a set of machine learning algorithms that could improve the process of data cleaning when building datasets. Design/methodology/approach： The paper is centered on cleaning datasets gathered from publishers and online resources by the use of specific keywords. In this case, we analyzed data from the Web of Science. The accuracy of various forms of automatic classification was tested here in comparison with manual coding in order to determine their usefulness for data collection and cleaning. We assessed the performance of seven supervised classification algorithms （Support Vector Machine （SVM）, Scaled Linear Discriminant Analysis, Lasso and elastic-net regularized generalized linear models, Maximum Entropy, Regression Tree, Boosting, and Random Forest） and analyzed two properties： accuracy and recall. We assessed not only each algorithm individually, but also their combinations through a voting scheme. We also tested the performance of these algorithms with different sizes of training data. When assessing the performance of different combinations, we used an indicator of coverage to account for the agreement and disagreement on classification between algorithms. Findings： We found that the performance of the algorithms used vary with the size of the sample for training. However, for the classification exercise in this paper the best performing algorithms were SVM and Boosting. The combination of these two algorithms achieved a high agreement on coverage and was highly accurate. This combination performs well with a small training dataset （10%）, which may reduce the manual work needed for classification tasks. Research limitations： The dataset gathered has significantly more records related to the topic of interest compared to unrelated topics. This may affect the performance of some algorithms, especially in their identification of unrelated papers. Practical implications： Although the classification achieved by this means is not completely accurate, the amount of manual coding needed can be greatly reduced by using classification algorithms. This can be of great help when the dataset is big. With the help of accuracy, recall,and coverage measures, it is possible to have an estimation of the error involved in this classification, which could open the possibility of incorporating the use of these algorithms in software specifically designed for data cleaning and classification.
基金Key Science and Technology Project of the Shanghai Committee of Science and Technology, China (No.06dz1200921)Major Basic Research Project of the Shanghai Committee of Science and Technology(No.08JC1400100)+1 种基金Shanghai Talent Developing Foundation, China(No.001)Specialized Foundation for Excellent Talent of Shanghai,China
文摘There are a number of dirty data in observation data set derived from integrated ocean observing network system. Thus, the data must be carefully and reasonably processed before they are used for forecasting or analysis. This paper proposes a data pre-processing model based on intelligent algorithms. Firstly, we introduce the integrated network platform of ocean observation. Next, the preprocessing model of data is presemed, and an imelligent cleaning model of data is proposed. Based on fuzzy clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means clustering. The proposed dynamic algorithm can automatically f＇md the new clustering center with the updated sample data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results through observation data analysis.
文摘针对风电机组齿轮箱油池温度异常难以早期预警的问题,提出一种基于数据采集与监视控制(supervisory control and data acquisition,SCADA)数据的故障预警方法,以提升机组运行可靠性。首先,结合风速-功率分布特征,采用四分位法与基于数据离散度的纵向滤波剔除异常功率点;接着,利用随机森林算法筛选影响油池温度的关键输入特征,构建基于类别提升(categorical boosting,CatBoost)算法的温度预测模型,并采用树结构parzen估计器(tree-structured parzen estimator,TPE)优化其超参数;最后,基于残差分布,通过统计过程控制确定动态预警阈值。在某风电场实际故障案例中,该模型在齿轮箱故障发生前约5 h发出有效预警,残差超出控制限的时间点与故障发展过程高度吻合。所提方法能有效识别油池温度异常工况,具备良好的早期预警能力与工程应用价值。
