Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g...Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g., the strong pressure fluctuation, the shaft swing, and the impeller damage. The instability is related to the vortices generated in the channels of the reversible pump turbines in the generating mode. In the present paper, a new omega vortex identification method is applied to the vortex analysis of the reversible pump turbines. The main advantage of the adopted algorithm is that it is physically independent of the selected values for the vortex identification in different working modes. Both weak and strong vortices can be identified by setting the same omega value in the whole passage of the reversible pump turbine. Five typical modes（turbine mode, runaway mode, turbine brake mode, zero-flow-rate mode and reverse pump mode） at several typical guide vane openings are selected for the analysis and comparisons. The differences between various modes and different guide vane openings are compared both qualitatively in terms of the vortex distributions and quantitatively in terms of the areas of the vortices in the reversible pump turbines. Our findings indicate that the new omega method could be successfully applied to the vortex identification in the reversible pump turbines.展开更多
采用诱集法和单孢接种培养技术,自湖北省不同棉区的棉花根际土壤中分离到能在棉花上形成VA菌根的真菌孢子和孢子果,依其显微形态特征对大部分菌株进行了种的鉴定。在已鉴定到种的6个菌株中,除Glomus mosseae(Nicol.and Gerd.)Gerd.and T...采用诱集法和单孢接种培养技术,自湖北省不同棉区的棉花根际土壤中分离到能在棉花上形成VA菌根的真菌孢子和孢子果,依其显微形态特征对大部分菌株进行了种的鉴定。在已鉴定到种的6个菌株中,除Glomus mosseae(Nicol.and Gerd.)Gerd.and Trappe和G.intraradices Schenck and Smith外,G.hoi Berch and Trappe.G.albidum Walker and Rhodes,G.ambisporum ⅡSmith and Schenck和G.geosporum(Nicol.and Gerd.)Walker4个种均为我国的新记录,其中G.albidam由于与Walker的描述不尽一致故命名为潜江变种(var.Qianjiang)。展开更多
With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding...With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding,handling,etc.,and have a great role in these sectors.Recently,the robotic technology is developing towards high precision,high intelligence.Robot calibration technology has a great significance to improve the accuracy of robot.However,it has much work to be done in the identification of robot parameters.The parameter identification work of existing serial and parallel robots is introduced.On the one hand,it summarizes the methods for parameter calibration and discusses their advantages and disadvantages.On the other hand,the application of parameter identification is introduced.This overview has a great reference value for robot manufacturers to choose proper identification method,points further research areas for researchers.Finally,this paper analyzes the existing problems in robot calibration,which may be worth researching in the future.展开更多
In the present review, recent progress on the vortex identification methods are introduced with a focus on the newly proposed omega method（ Ω method）. The advantages of Ω method are summarized with many illustrati...In the present review, recent progress on the vortex identification methods are introduced with a focus on the newly proposed omega method（ Ω method）. The advantages of Ω method are summarized with many illustrating examples. Furthermore, comparing with other existing methods（e.g., Q criterion and λ2 criterion）, one of the characteristics of Ω method is its independence on the chosen threshold values for vortex identifications. The important parameters involved for the practical applications of Ω method are further discussed in detail together with the physical interpretation of the Ω and some suggestions of the future work. Other emerging topics（e.g., Lagrangian coherent structure and Rortex） are also introduced with comments.展开更多
基金Project supported by the National Key R&D Program of China(Project No.2018YFB0604304-04)the National Natural Science Foundation of China(Grant No.51506051)
文摘Reversible pump turbines are widely employed in the pumped hydro energy storage power plants. The frequent shifts among various operational modes for the reversible pump turbines pose various instability problems, e.g., the strong pressure fluctuation, the shaft swing, and the impeller damage. The instability is related to the vortices generated in the channels of the reversible pump turbines in the generating mode. In the present paper, a new omega vortex identification method is applied to the vortex analysis of the reversible pump turbines. The main advantage of the adopted algorithm is that it is physically independent of the selected values for the vortex identification in different working modes. Both weak and strong vortices can be identified by setting the same omega value in the whole passage of the reversible pump turbine. Five typical modes（turbine mode, runaway mode, turbine brake mode, zero-flow-rate mode and reverse pump mode） at several typical guide vane openings are selected for the analysis and comparisons. The differences between various modes and different guide vane openings are compared both qualitatively in terms of the vortex distributions and quantitatively in terms of the areas of the vortices in the reversible pump turbines. Our findings indicate that the new omega method could be successfully applied to the vortex identification in the reversible pump turbines.
文摘采用诱集法和单孢接种培养技术,自湖北省不同棉区的棉花根际土壤中分离到能在棉花上形成VA菌根的真菌孢子和孢子果,依其显微形态特征对大部分菌株进行了种的鉴定。在已鉴定到种的6个菌株中,除Glomus mosseae(Nicol.and Gerd.)Gerd.and Trappe和G.intraradices Schenck and Smith外,G.hoi Berch and Trappe.G.albidum Walker and Rhodes,G.ambisporum ⅡSmith and Schenck和G.geosporum(Nicol.and Gerd.)Walker4个种均为我国的新记录,其中G.albidam由于与Walker的描述不尽一致故命名为潜江变种(var.Qianjiang)。
基金supported in part by the National Natural Science Foundation of China(61772493)in part by the Guangdong Province Universities and College Pearl River Scholar Funded Scheme(2019)in part by the Natural Science Foundation of Chongqing(cstc2019jcyjjq X0013)。
文摘With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding,handling,etc.,and have a great role in these sectors.Recently,the robotic technology is developing towards high precision,high intelligence.Robot calibration technology has a great significance to improve the accuracy of robot.However,it has much work to be done in the identification of robot parameters.The parameter identification work of existing serial and parallel robots is introduced.On the one hand,it summarizes the methods for parameter calibration and discusses their advantages and disadvantages.On the other hand,the application of parameter identification is introduced.This overview has a great reference value for robot manufacturers to choose proper identification method,points further research areas for researchers.Finally,this paper analyzes the existing problems in robot calibration,which may be worth researching in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51506051,51606221)
文摘In the present review, recent progress on the vortex identification methods are introduced with a focus on the newly proposed omega method（ Ω method）. The advantages of Ω method are summarized with many illustrating examples. Furthermore, comparing with other existing methods（e.g., Q criterion and λ2 criterion）, one of the characteristics of Ω method is its independence on the chosen threshold values for vortex identifications. The important parameters involved for the practical applications of Ω method are further discussed in detail together with the physical interpretation of the Ω and some suggestions of the future work. Other emerging topics（e.g., Lagrangian coherent structure and Rortex） are also introduced with comments.
