There are four basic operational modes for the hybrid AC/DC microgrid,including AC grid-connected while interconnecting,both off-grid while interconnecting,AC gridconnected without connection,and both off-grid withou...There are four basic operational modes for the hybrid AC/DC microgrid,including AC grid-connected while interconnecting,both off-grid while interconnecting,AC gridconnected without connection,and both off-grid without connection.How to achieve a seamless operational mode transition is an urgent technical need to overcome.First,this paper describes the typical structure of the hybrid microgrid,and places a detailed focus on the power balance and transition strategy.Secondly,it takes the master-slave control structure as an example,and designs the transition logic for different operational modes,and then a method for selecting the slack bus and transition time-sequence is proposed.Based on the different roles that the interlinking converter(IC)plays in the process of modes transition,a voltage-power(U-P)control method for a hybrid AC/DC microgrid is proposed,and the exchanged power is calculated based on the voltage deviation between the rating value and measured value.Finally,a control flowchart for the transition between the four operational modes in transition is designed.Using the PSCAD/EMTDC platform,this paper takes a typical seven-point microgrid structure as an example,the proposed transition strategy is carried out,and the results show that the transition method and time sequence can achieve smooth transition between different operational modes.展开更多
Ocean energy, considered as clean energy, is one kind of marine resources of great importance. Its development and utilization have become an indispensable part of national development strategy in China. Testingfields...Ocean energy, considered as clean energy, is one kind of marine resources of great importance. Its development and utilization have become an indispensable part of national development strategy in China. Testingfields are required when conducting tests of ocean energy generation devices in real sea, which is the key step conducted before engineering prototypes transformed into scale industrialization applications. This paper introduces the construction and operation conditions of large-scale testing fields for wave energy and tidal current energy generation devices and presents a brief comparative analysis. Developing status and related technologies on testingfields for ocean energy power generation in China are also discussed. Furthermore, this paper investigates the necessity of grid-connected test for ocean energy generation and points out that the construction of ocean energy testingfields is helpful to ensure the efficient utilization of ocean energy resources.展开更多
The promising prospect of a terahertz metasurface in sensing and detection applications has attracted increasing attention because of its ability to overcome the classical diffraction limit and the enhancement of fiel...The promising prospect of a terahertz metasurface in sensing and detection applications has attracted increasing attention because of its ability to overcome the classical diffraction limit and the enhancement of field intensity.In this work,a novel scheme based on an all-silicon terahertz plasmon metasurface is proposed and experimentally demonstrated to be a highly sensitive biosensor for the Bacillus thuringiensis Cry1Ac toxin.The regression coefficients between Bacillus thuringiensis protein concentrations and the spectral resonance intensity and frequency were 0.8988 and 0.9238,respectively.The resonance amplitude variation and frequency shift of the metasurface were investigated in terms of both thickness and permittivity change of the analyte,which reflected the protein residue in the actual process.Moreover,the reliability and stability of the metasurface chip were verified by time period,temperature,and humidity control.These results promise the ability of the proposed metasurface chip as a Bacillus thuringiensis protein sensor with high sensitivity and stability.In addition,this novel device strategy provides opportunities for the advancement of terahertz functional applications in the fields of biochemical sensing and detection.展开更多
There are many types of tidal current power generation devices,and it is necessary to make comprehensive evaluation of tidal current power generation devices in order to provide valuable reference for the improvement ...There are many types of tidal current power generation devices,and it is necessary to make comprehensive evaluation of tidal current power generation devices in order to provide valuable reference for the improvement of their performance indexes.On the basis of the analysis of the tidal current power generation device performance indexes,the hierarchical model for comprehensive evaluation of device performance is given in this paper.By normalizing the membership matrix elements based on fuzzy comprehensive evaluation model,all the values of the matrix elements are restrained in the range of0.0 to 1.0,hence the complexity of the calculations is reduced.Vector similarity is used to determine the expert weights which reflect the knowledge and experience of the experts.This paper presents an improved method for rank correlation analysis,and calculates the comprehensive weight value and the final evaluation results of tidal current power generation devices.The presented method improves the credibility of the evaluation.In the end,measured data of two units of tidal current power generation devices are evaluated in the paper,and the effectiveness of the presented method is verified.展开更多
The selection of cadmium-excluding cultivars has been used to minimize the transfer of cadmium into the human food chain. In this experiment, five Chinese soybean plants were grown in three soils with different concen...The selection of cadmium-excluding cultivars has been used to minimize the transfer of cadmium into the human food chain. In this experiment, five Chinese soybean plants were grown in three soils with different concentrations of Cd(0.15, 0.75 and 1.12 mg/kg).Variations in uptake, enrichment, and translocation of Cd among these soybean cultivars were studied. The results indicated that the concentration of Cd in seeds that grew at1.12 mg/kg Cd in soils exceeded the permitted maximum levels in soybeans. Therefore, our results indicated that even some soybean cultivars grown on soils with permitted levels of Cd might accumulate higher concentrations of Cd in seeds that are hazardous to human health. The seeds of these five cultivars were further assessed for interactions between Cd and other mineral nutrient elements such as Ca, Cu, Fe, Mg, Mn and Zn. High Cd concentration in soil was found to inhibit the uptake of Mn. Furthermore, Fe and Zn accumulations were found to be enhanced in the seeds of all of the five soybean cultivars in response to high Cd concentration. Cultivar Tiefeng 31 was found to fit the criteria for a Cd-excluding cultivar under different concentrations of Cd in soils.展开更多
基金This paper is dedicated to the late Professor JS Chiao, who initiated the research in China for rifamycin production employing A. mediterranei more than 30 years ago and who continued the endeavor to resolve the mechanism of the 'nitrate stimulating effect' up to the last breath of his life. This work was supported by the National Natural Science Foundation of China (30830002), the National High Technology Research and Development Program of
China (2007AA021301, 2007AA021503), and the Research Unit Fund of Li Ka Shing Institute of Health Sciences (7103506).
基金supported by the National High Technology Research and Development Program(“863”Project)under Grant 2015AA050102.
文摘There are four basic operational modes for the hybrid AC/DC microgrid,including AC grid-connected while interconnecting,both off-grid while interconnecting,AC gridconnected without connection,and both off-grid without connection.How to achieve a seamless operational mode transition is an urgent technical need to overcome.First,this paper describes the typical structure of the hybrid microgrid,and places a detailed focus on the power balance and transition strategy.Secondly,it takes the master-slave control structure as an example,and designs the transition logic for different operational modes,and then a method for selecting the slack bus and transition time-sequence is proposed.Based on the different roles that the interlinking converter(IC)plays in the process of modes transition,a voltage-power(U-P)control method for a hybrid AC/DC microgrid is proposed,and the exchanged power is calculated based on the voltage deviation between the rating value and measured value.Finally,a control flowchart for the transition between the four operational modes in transition is designed.Using the PSCAD/EMTDC platform,this paper takes a typical seven-point microgrid structure as an example,the proposed transition strategy is carried out,and the results show that the transition method and time sequence can achieve smooth transition between different operational modes.
基金supported by Marine RenewablesSpecial Funds(No.GHME2012ZC02)
文摘Ocean energy, considered as clean energy, is one kind of marine resources of great importance. Its development and utilization have become an indispensable part of national development strategy in China. Testingfields are required when conducting tests of ocean energy generation devices in real sea, which is the key step conducted before engineering prototypes transformed into scale industrialization applications. This paper introduces the construction and operation conditions of large-scale testing fields for wave energy and tidal current energy generation devices and presents a brief comparative analysis. Developing status and related technologies on testingfields for ocean energy power generation in China are also discussed. Furthermore, this paper investigates the necessity of grid-connected test for ocean energy generation and points out that the construction of ocean energy testingfields is helpful to ensure the efficient utilization of ocean energy resources.
基金Natural Science Foundation of Shaanxi Province(2020JZ-48)Youth Innovation Team of Shaanxi Universities(21JP084)+1 种基金National Natural Science Foundation of China(31801257,61975163)Open Project of Key Laboratory of Engineering Dielectrics and Its Applications,Ministry of Education(KEY1805).
文摘The promising prospect of a terahertz metasurface in sensing and detection applications has attracted increasing attention because of its ability to overcome the classical diffraction limit and the enhancement of field intensity.In this work,a novel scheme based on an all-silicon terahertz plasmon metasurface is proposed and experimentally demonstrated to be a highly sensitive biosensor for the Bacillus thuringiensis Cry1Ac toxin.The regression coefficients between Bacillus thuringiensis protein concentrations and the spectral resonance intensity and frequency were 0.8988 and 0.9238,respectively.The resonance amplitude variation and frequency shift of the metasurface were investigated in terms of both thickness and permittivity change of the analyte,which reflected the protein residue in the actual process.Moreover,the reliability and stability of the metasurface chip were verified by time period,temperature,and humidity control.These results promise the ability of the proposed metasurface chip as a Bacillus thuringiensis protein sensor with high sensitivity and stability.In addition,this novel device strategy provides opportunities for the advancement of terahertz functional applications in the fields of biochemical sensing and detection.
基金supported by Marine Renewables Special Funds to Implement Programs funded by the government of China(No.GHME2012ZC02)
文摘There are many types of tidal current power generation devices,and it is necessary to make comprehensive evaluation of tidal current power generation devices in order to provide valuable reference for the improvement of their performance indexes.On the basis of the analysis of the tidal current power generation device performance indexes,the hierarchical model for comprehensive evaluation of device performance is given in this paper.By normalizing the membership matrix elements based on fuzzy comprehensive evaluation model,all the values of the matrix elements are restrained in the range of0.0 to 1.0,hence the complexity of the calculations is reduced.Vector similarity is used to determine the expert weights which reflect the knowledge and experience of the experts.This paper presents an improved method for rank correlation analysis,and calculates the comprehensive weight value and the final evaluation results of tidal current power generation devices.The presented method improves the credibility of the evaluation.In the end,measured data of two units of tidal current power generation devices are evaluated in the paper,and the effectiveness of the presented method is verified.
基金financially supported by the National Natural Science Foundation of China as a joint key project (grant No. U1133006)a general project (grant No. 31170473)by the Ministry of Education, People's Republic of China as an innovative team project (grant No. IRT 13024)
文摘The selection of cadmium-excluding cultivars has been used to minimize the transfer of cadmium into the human food chain. In this experiment, five Chinese soybean plants were grown in three soils with different concentrations of Cd(0.15, 0.75 and 1.12 mg/kg).Variations in uptake, enrichment, and translocation of Cd among these soybean cultivars were studied. The results indicated that the concentration of Cd in seeds that grew at1.12 mg/kg Cd in soils exceeded the permitted maximum levels in soybeans. Therefore, our results indicated that even some soybean cultivars grown on soils with permitted levels of Cd might accumulate higher concentrations of Cd in seeds that are hazardous to human health. The seeds of these five cultivars were further assessed for interactions between Cd and other mineral nutrient elements such as Ca, Cu, Fe, Mg, Mn and Zn. High Cd concentration in soil was found to inhibit the uptake of Mn. Furthermore, Fe and Zn accumulations were found to be enhanced in the seeds of all of the five soybean cultivars in response to high Cd concentration. Cultivar Tiefeng 31 was found to fit the criteria for a Cd-excluding cultivar under different concentrations of Cd in soils.