In this paper the heat withstanding mechanism of heat-resisting aluminum alloy conductor is discussed, the types and performance of the conductor and its application on transmission lines are analyzed and introduced, ...In this paper the heat withstanding mechanism of heat-resisting aluminum alloy conductor is discussed, the types and performance of the conductor and its application on transmission lines are analyzed and introduced, and suggestions on accelerating exploitation and application of the conductor are put forward.展开更多
This paper presents a new technique in the high dielectric constant composite oxide film preparation. On the basis of nano-compsite high dielectric constant aluminum oxide fdm growth technology, a new idea of adultera...This paper presents a new technique in the high dielectric constant composite oxide film preparation. On the basis of nano-compsite high dielectric constant aluminum oxide fdm growth technology, a new idea of adulterating Si oxide species into the aluminum composite film was proposed. As a result, the specific capacitance and withstanding voltage of the composite oxide film formed at the anodizing voltage of 20V are enhanced, and the leakage current of the aluminum composite oxide fdm is reduced through incorporation of Si oxide species.展开更多
Excitation transformer is an important component of the power plant transformer group equipment. Its reliable operation is an important factor to ensure the stable safety of the unit. In recent years, due to the failu...Excitation transformer is an important component of the power plant transformer group equipment. Its reliable operation is an important factor to ensure the stable safety of the unit. In recent years, due to the failure of excitation transformer, some power plants have not stop, which has a great impact on the safety of equipment and power supply stability. Combined with the several failures of excitation transformer in a power generation enterprise in recent years, this paper sorts out the problems of excitation transformer in power plant caused by failure one by one, analyzes the causes in depth, and puts forward countermeasures.展开更多
During on-site withstand voltage tests of gas-insulated switchgears(GIS),once a breakdown occurs,it is hard to locate the breakdown position due to the intricate branch structures and minimal breakdown energy.The exis...During on-site withstand voltage tests of gas-insulated switchgears(GIS),once a breakdown occurs,it is hard to locate the breakdown position due to the intricate branch structures and minimal breakdown energy.The existing methods may require the placement of a large number of sensors with unsatisfactory accuracy,which adversely affects the process of inspecting and repairing,as well as the subsequent tests.To address this issue,this paper introduces a novel GIS breakdown location method.This method is predicated on the natural frequency of the transient voltage caused by the breakdown.The relationship between the breakdown position and the natural frequency is first derived,which is referred to as the location equation.Then,the natural frequency characteristics are discussed from both mathematical and energy perspectives.Based on these characteristics,the location method is proposed that utilises the location equation and the frequencies at two measurement points.The results of the laboratory experiments demonstrate the accuracy of the method and certain advantages over the ultrasonic method.Further,the effectiveness of the method in GIS and gas-insulated transmission lines(GIL)with complex structures and high voltage levels is also confirmed by simu-lation cases and field experimental data.展开更多
In the face of accelerating global climate change,developing crops that can withstand extreme environmental conditions,such as cold temperatures at high latitudes,has become a critical challenge for ensuring global fo...In the face of accelerating global climate change,developing crops that can withstand extreme environmental conditions,such as cold temperatures at high latitudes,has become a critical challenge for ensuring global food security.In addition,as the population increases,it is essential to expand planting areas to northern regions with lower accumulated yearly temperatures.Natural variations of crops are artificially selected to adapt to extreme temperature environments during their domestication.For the temperate crops like maize and rice,striking a tradeoff between growth development and cold tolerance is essential for breeding.展开更多
Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the ac...Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV·mm–1 were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations(< 2 kV·mm–1) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization.展开更多
Scientists said on Monday they had genetically engineered rice to withstand drought, salt water and cold temperatures by borrowing a gene from the E. coli bacteria. [译文]星期一,科学家们称他们已经利用遗传工程学,借用...Scientists said on Monday they had genetically engineered rice to withstand drought, salt water and cold temperatures by borrowing a gene from the E. coli bacteria. [译文]星期一,科学家们称他们已经利用遗传工程学,借用大肠埃舍利希氏 杆菌的基因培育出了耐干旱、耐咸水、耐严寒的稻米。展开更多
IF there is one name that is familiar to Chinese aged 10 to 80 it is Guo Lanying. Recently a recital was held by CCTV in honor of her 60-year career. When Guo Lanying took the stage, she was met with a lengthy standin...IF there is one name that is familiar to Chinese aged 10 to 80 it is Guo Lanying. Recently a recital was held by CCTV in honor of her 60-year career. When Guo Lanying took the stage, she was met with a lengthy standing ovation. Her voice was choked with emotion. Behind her was a smiling photograph of her that was taken at the start of her opera career. Guo Lanying was born in 1930展开更多
文摘In this paper the heat withstanding mechanism of heat-resisting aluminum alloy conductor is discussed, the types and performance of the conductor and its application on transmission lines are analyzed and introduced, and suggestions on accelerating exploitation and application of the conductor are put forward.
基金This work was supported by the National Nature Science Foundation of China under Grant No.60601006.
文摘This paper presents a new technique in the high dielectric constant composite oxide film preparation. On the basis of nano-compsite high dielectric constant aluminum oxide fdm growth technology, a new idea of adulterating Si oxide species into the aluminum composite film was proposed. As a result, the specific capacitance and withstanding voltage of the composite oxide film formed at the anodizing voltage of 20V are enhanced, and the leakage current of the aluminum composite oxide fdm is reduced through incorporation of Si oxide species.
文摘Excitation transformer is an important component of the power plant transformer group equipment. Its reliable operation is an important factor to ensure the stable safety of the unit. In recent years, due to the failure of excitation transformer, some power plants have not stop, which has a great impact on the safety of equipment and power supply stability. Combined with the several failures of excitation transformer in a power generation enterprise in recent years, this paper sorts out the problems of excitation transformer in power plant caused by failure one by one, analyzes the causes in depth, and puts forward countermeasures.
基金National Key R&D Program of China,Grant/Award Numbers:2022YFB2403700,2022YFB2403705。
文摘During on-site withstand voltage tests of gas-insulated switchgears(GIS),once a breakdown occurs,it is hard to locate the breakdown position due to the intricate branch structures and minimal breakdown energy.The existing methods may require the placement of a large number of sensors with unsatisfactory accuracy,which adversely affects the process of inspecting and repairing,as well as the subsequent tests.To address this issue,this paper introduces a novel GIS breakdown location method.This method is predicated on the natural frequency of the transient voltage caused by the breakdown.The relationship between the breakdown position and the natural frequency is first derived,which is referred to as the location equation.Then,the natural frequency characteristics are discussed from both mathematical and energy perspectives.Based on these characteristics,the location method is proposed that utilises the location equation and the frequencies at two measurement points.The results of the laboratory experiments demonstrate the accuracy of the method and certain advantages over the ultrasonic method.Further,the effectiveness of the method in GIS and gas-insulated transmission lines(GIL)with complex structures and high voltage levels is also confirmed by simu-lation cases and field experimental data.
基金the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.32200244)the National Key Research and Development Program of China(Grant No.2020YFA0509901-1)for financial support。
文摘In the face of accelerating global climate change,developing crops that can withstand extreme environmental conditions,such as cold temperatures at high latitudes,has become a critical challenge for ensuring global food security.In addition,as the population increases,it is essential to expand planting areas to northern regions with lower accumulated yearly temperatures.Natural variations of crops are artificially selected to adapt to extreme temperature environments during their domestication.For the temperate crops like maize and rice,striking a tradeoff between growth development and cold tolerance is essential for breeding.
文摘Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV·mm–1 were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations(< 2 kV·mm–1) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization.
文摘Scientists said on Monday they had genetically engineered rice to withstand drought, salt water and cold temperatures by borrowing a gene from the E. coli bacteria. [译文]星期一,科学家们称他们已经利用遗传工程学,借用大肠埃舍利希氏 杆菌的基因培育出了耐干旱、耐咸水、耐严寒的稻米。
文摘IF there is one name that is familiar to Chinese aged 10 to 80 it is Guo Lanying. Recently a recital was held by CCTV in honor of her 60-year career. When Guo Lanying took the stage, she was met with a lengthy standing ovation. Her voice was choked with emotion. Behind her was a smiling photograph of her that was taken at the start of her opera career. Guo Lanying was born in 1930
