Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the a...Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems,wind tunnel experiments were carried out using a 1:50 scale model.Taking a wind barrier with a porosity of 30%as an example,the aerodynamic characteristics of the bridge train system under different wind barrier layouts(single-sided and double-sided),positions(inside and outside)and heights(2.5 m,3.0 m,3.5 m and 4.0 m)were tested.The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system,but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the trains wind pressure distribution,especially on the trains leeward surface.When the wind barriers are arranged on the outside,their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside.As the height of the wind barrier increases,the drag coefficient of the bridge also gradually increases,and the lift coefficient and drag coefficient of the train gradually decrease,but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts.When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge,the drag coefficient of the bridge only increases by 12%,while the drag coefficient of the train decreases by 55%.展开更多
There are learners who cannot solve practical problems in spite of mastering basic scientific knowledge and formula necessary for the solution. One of the reasons might be attributed to the lack in metacognitive abili...There are learners who cannot solve practical problems in spite of mastering basic scientific knowledge and formula necessary for the solution. One of the reasons might be attributed to the lack in metacognitive abilities. The aim of this study was to compare the metacognitive characteristics between non-major and major students in electric engineering and clarify the difference of metacognitive process between these two groups when solving basic problems of electronic circuit. In the experiment, the solving process was compared between non-major and major students in electric engineering using five basic problems. We found that the scores on prediction of result and confidence of own answer differed significantly between non-major and major students, and inferred that the difference of performance was due to the lack in metacognitive ability, especially the plan and the execution abilities. Both prediction of results and confidence of own answer were also found to play a significant role in effective problem solving as important components （subsystems） of metacognition.展开更多
基金Projects(52078504,51822803,51925808) supported by the National Natural Science Foundation of ChinaProject(2021RC3016) supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems,wind tunnel experiments were carried out using a 1:50 scale model.Taking a wind barrier with a porosity of 30%as an example,the aerodynamic characteristics of the bridge train system under different wind barrier layouts(single-sided and double-sided),positions(inside and outside)and heights(2.5 m,3.0 m,3.5 m and 4.0 m)were tested.The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system,but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the trains wind pressure distribution,especially on the trains leeward surface.When the wind barriers are arranged on the outside,their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside.As the height of the wind barrier increases,the drag coefficient of the bridge also gradually increases,and the lift coefficient and drag coefficient of the train gradually decrease,but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts.When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge,the drag coefficient of the bridge only increases by 12%,while the drag coefficient of the train decreases by 55%.
文摘There are learners who cannot solve practical problems in spite of mastering basic scientific knowledge and formula necessary for the solution. One of the reasons might be attributed to the lack in metacognitive abilities. The aim of this study was to compare the metacognitive characteristics between non-major and major students in electric engineering and clarify the difference of metacognitive process between these two groups when solving basic problems of electronic circuit. In the experiment, the solving process was compared between non-major and major students in electric engineering using five basic problems. We found that the scores on prediction of result and confidence of own answer differed significantly between non-major and major students, and inferred that the difference of performance was due to the lack in metacognitive ability, especially the plan and the execution abilities. Both prediction of results and confidence of own answer were also found to play a significant role in effective problem solving as important components （subsystems） of metacognition.
