A partition checkpoint strategy based on data segment priority is presented to meet the timing constraints of the data and the transaction in embedded real-time main memory database systems（ERTMMDBS） as well as to r...A partition checkpoint strategy based on data segment priority is presented to meet the timing constraints of the data and the transaction in embedded real-time main memory database systems（ERTMMDBS） as well as to reduce the number of the transactions missing their deadlines and the recovery time.The partition checkpoint strategy takes into account the characteristics of the data and the transactions associated with it;moreover,it partitions the database according to the data segment priority and sets the corresponding checkpoint frequency to each partition for independent checkpoint operation.The simulation results show that the partition checkpoint strategy decreases the ratio of trans-actions missing their deadlines.展开更多
In this paper, our previous work on Principal Component Analysis (PCA) based fault detection method is extended to the dynamic monitoring and detection of loss-of-main in power systems using wide-area synchrophasor me...In this paper, our previous work on Principal Component Analysis (PCA) based fault detection method is extended to the dynamic monitoring and detection of loss-of-main in power systems using wide-area synchrophasor measurements. In the previous work, a static PCA model was built and verified to be capable of detecting and extracting system faulty events;however the false alarm rate is high. To address this problem, this paper uses a well-known ‘time lag shift’ method to include dynamic behavior of the PCA model based on the synchronized measurements from Phasor Measurement Units (PMU), which is named as the Dynamic Principal Component Analysis (DPCA). Compared with the static PCA approach as well as the traditional passive mechanisms of loss-of-main detection, the proposed DPCA procedure describes how the synchrophasors are linearly auto- and cross-correlated, based on conducting the singular value decomposition on the augmented time lagged synchrophasor matrix. Similar to the static PCA method, two statistics, namely T2 and Q with confidence limits are calculated to form intuitive charts for engineers or operators to monitor the loss-of-main situation in real time. The effectiveness of the proposed methodology is evaluated on the loss-of-main monitoring of a real system, where the historic data are recorded from PMUs installed in several locations in the UK/Ireland power system.展开更多
Antarctic data management is the research focus, which the international Antarctic organizations, e.g. Antarctic Treaty Consultative Meeting(ATCM) , Scientific Committee on Antarctic Research(SCAR), and Council of Man...Antarctic data management is the research focus, which the international Antarctic organizations, e.g. Antarctic Treaty Consultative Meeting(ATCM) , Scientific Committee on Antarctic Research(SCAR), and Council of Managers of National Antarctic Programmes(COMNAP) have been paying close attention to and promoting actively. Through the co effort of international Antarctic organizations and member countries concerned in recent years, Antarctic Data Directory Syatem(ADDS) is established as the most important basic programme for development of the international Antarctic data management system. At present, Joint Committee on Antarctic Data Management(JCADM) is responsible for organizing and coordinating the international Antarctic data management, and implementing the project ADDS.In this paper the background on Antarctic data management in time sequence and the structure of international framework are introduced, meanwhile, it is necessary to develop ADDS first of all. The ADDS mainly consists of the two principal parts: National Antarctic Data Center(NADCs) of all the party members and Antarctic Main Directory(AMD), the best available technology for creating ADDS is to make full use of International Directory Network(IDN) and adopt its Directory Interchange Formats(DIF). In the light of the above requirements, combined with Chinese specific situation, the contents, technical and administrative methods on Chinese Antarctic data management are discussed to promote our related work.展开更多
1553B avionics data bus network may fail due to vibration,temperature,humidity or human error.Therefore,the research on detection technology of 1553B avionics data bus network is an important subject.The key technolog...1553B avionics data bus network may fail due to vibration,temperature,humidity or human error.Therefore,the research on detection technology of 1553B avionics data bus network is an important subject.The key technologies are studied by analyzing the possible faults of the network,including four-wire DC resistance measurement method for conductors-to-shield short test and stub continuity test,equivalent impedance measurement of coupling transformer for main bus continuity test,polarity reversal test base on duty ratio measurement,attenuation measurement base on coupler model,and data path integrity test base on bit error rate calculation.Finally,the implementation methods of key technologies are researched,a portable integrated automatic test system of 1553B data bus network is constructed based on PC 104 computer,and the hardware configuration and test process are especially designed.展开更多
基金Supported by the National Natural Science Foundation of China (60673128)
文摘A partition checkpoint strategy based on data segment priority is presented to meet the timing constraints of the data and the transaction in embedded real-time main memory database systems（ERTMMDBS） as well as to reduce the number of the transactions missing their deadlines and the recovery time.The partition checkpoint strategy takes into account the characteristics of the data and the transactions associated with it;moreover,it partitions the database according to the data segment priority and sets the corresponding checkpoint frequency to each partition for independent checkpoint operation.The simulation results show that the partition checkpoint strategy decreases the ratio of trans-actions missing their deadlines.
文摘In this paper, our previous work on Principal Component Analysis (PCA) based fault detection method is extended to the dynamic monitoring and detection of loss-of-main in power systems using wide-area synchrophasor measurements. In the previous work, a static PCA model was built and verified to be capable of detecting and extracting system faulty events;however the false alarm rate is high. To address this problem, this paper uses a well-known ‘time lag shift’ method to include dynamic behavior of the PCA model based on the synchronized measurements from Phasor Measurement Units (PMU), which is named as the Dynamic Principal Component Analysis (DPCA). Compared with the static PCA approach as well as the traditional passive mechanisms of loss-of-main detection, the proposed DPCA procedure describes how the synchrophasors are linearly auto- and cross-correlated, based on conducting the singular value decomposition on the augmented time lagged synchrophasor matrix. Similar to the static PCA method, two statistics, namely T2 and Q with confidence limits are calculated to form intuitive charts for engineers or operators to monitor the loss-of-main situation in real time. The effectiveness of the proposed methodology is evaluated on the loss-of-main monitoring of a real system, where the historic data are recorded from PMUs installed in several locations in the UK/Ireland power system.
文摘Antarctic data management is the research focus, which the international Antarctic organizations, e.g. Antarctic Treaty Consultative Meeting(ATCM) , Scientific Committee on Antarctic Research(SCAR), and Council of Managers of National Antarctic Programmes(COMNAP) have been paying close attention to and promoting actively. Through the co effort of international Antarctic organizations and member countries concerned in recent years, Antarctic Data Directory Syatem(ADDS) is established as the most important basic programme for development of the international Antarctic data management system. At present, Joint Committee on Antarctic Data Management(JCADM) is responsible for organizing and coordinating the international Antarctic data management, and implementing the project ADDS.In this paper the background on Antarctic data management in time sequence and the structure of international framework are introduced, meanwhile, it is necessary to develop ADDS first of all. The ADDS mainly consists of the two principal parts: National Antarctic Data Center(NADCs) of all the party members and Antarctic Main Directory(AMD), the best available technology for creating ADDS is to make full use of International Directory Network(IDN) and adopt its Directory Interchange Formats(DIF). In the light of the above requirements, combined with Chinese specific situation, the contents, technical and administrative methods on Chinese Antarctic data management are discussed to promote our related work.
基金supported by the Key Equipment Research Project of Air Force of China(KJ2011215)
文摘1553B avionics data bus network may fail due to vibration,temperature,humidity or human error.Therefore,the research on detection technology of 1553B avionics data bus network is an important subject.The key technologies are studied by analyzing the possible faults of the network,including four-wire DC resistance measurement method for conductors-to-shield short test and stub continuity test,equivalent impedance measurement of coupling transformer for main bus continuity test,polarity reversal test base on duty ratio measurement,attenuation measurement base on coupler model,and data path integrity test base on bit error rate calculation.Finally,the implementation methods of key technologies are researched,a portable integrated automatic test system of 1553B data bus network is constructed based on PC 104 computer,and the hardware configuration and test process are especially designed.
