When studying the dam-break flow phenomenon,the basic hydrodynamic features of the dam-break flow at the gate location should be verified primarily.In this study,laboratory experiments were performed in a rectangular ...When studying the dam-break flow phenomenon,the basic hydrodynamic features of the dam-break flow at the gate location should be verified primarily.In this study,laboratory experiments were performed in a rectangular and horizontal flume with the same initial water head setting on the dry and wet downstream bed conditions.Water surface elevation was extracted through image analysis and validated by comparing with the data measured using a wave gauge.Temporal variation of the water surface elevation at the gate location,quantified in terms of high-speed video recorded images,can be divided into three stages,the sharp decreasing stage,the relatively steady stage,and the gradually decreasing stage.Applicability of several classic analytical solutions of the dam-break problem at the gate location was validated using present experimental data.Ritter's solution is effective for the dry bed condition while Stoker's solution could be applied to the wet bed case,and both are only applicable during the steady stage.Lin' solution reproduces the gate-site hydrographs well during both the relatively steady and the gradually decreasing stages,especially for the condition under which the down-upstream water depth ratio is smaller than 0.138.展开更多
[Objective] This study aimed to explore the effects of soil erosion on the productivity of sloping field. [Method] Through removing of and covering with topsoil in a micro-plot experiment, the effect of soil erosion o...[Objective] This study aimed to explore the effects of soil erosion on the productivity of sloping field. [Method] Through removing of and covering with topsoil in a micro-plot experiment, the effect of soil erosion on productivity of sloping field was studied. [Result] The results showed that there was extremely significantly posi- tive correlation between the thicknesses of covered topsoil with either the yield of maize seeds or the yield of maize stalks, which indicated that the yields of maize seeds and maize stalks decreased extremely significantly with the increase of the amount of surface soil loss caused by erosion on the sloping field. The yields of maize seeds and maize stalks decreased by 29.62% and 24.46% respectively in the treatment with removal of a 15 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks decreased by 17.31% and 20.14% re- spectively in the treatment with removal of a 10 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks decreased by 12.69% and 11.51% respectively in the treatment with removal of a 5 cm thick layer of ma- ture topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 10.00% and 9.35% respectively in the treatment with covering with a 5 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 15.77% and 16.19% respectively in the treatment with covering with a 10 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 17.69% and 25.18% respectively in the treat- ment with covering with a 15 cm thick layer of mature topsoil in the plow layer. [Conclusion] This study provides a basis for assessing the effect of soil erosion on sloping field.展开更多
This paper stems from an artistic experiment,in which a distinguished violinist received completely different prices for performing in varying locations.This may be due to the difference in the performance locations,a...This paper stems from an artistic experiment,in which a distinguished violinist received completely different prices for performing in varying locations.This may be due to the difference in the performance locations,and the value of art in the heart of the audience.展开更多
Several factors can influence learning process and the overall students’performance but it seems that few studies had made attempt to investigate the influence of teachers and school factors on students’achievement ...Several factors can influence learning process and the overall students’performance but it seems that few studies had made attempt to investigate the influence of teachers and school factors on students’achievement especially in a technological-driven world where Basic Science performance is low.The study investigated teachers’characteristics and school factors as correlates of students’achievement in Basic Science in Oyo State.The survey research was anchored on constructivism and theory of learning.Multi-stage sampling procedures were employed to select all the 33 Local Government Areas of Oyo State.Two schools each,66 teachers and 1,980 students participated in the study.Three validated instruments used to gather information are:Teachers’Characteristics and School Factors Questionnaire with r=0.84,Teachers’Observational Sheet with r=0.87,and Basic Science Achievement Test with r=0.87.Data were analyzed using descriptive and inferential statistics at 0.05 level of significance.Significant relationship was found between teachers’experience(r=0.77,0.003,P<.05),teachers’subject mastery(r=0.66,0.019,P<.05),school location(r=0.62,0.031,P<.05),and students’achievement.School facilities(β=1.244;t=2.487;p<0.05)contributed significantly to the prediction.The variables jointly explained 82%of the variance observed in students’achievement in Basic Science.There is a strong correlation of variables on students’achievement.Teachers should improve on their subject mastery skill while enabling environment should be provided by the government.展开更多
基金financially supported by the Natural Science Foundation of Zhejiang Province,China(No.LR14E090002)the National Natural Science Foundation of China(No.11632012)the Open Research Fund Program of State key Laboratory of Hydroscience and Engineering(No.sklhse-2016-B-02)
文摘When studying the dam-break flow phenomenon,the basic hydrodynamic features of the dam-break flow at the gate location should be verified primarily.In this study,laboratory experiments were performed in a rectangular and horizontal flume with the same initial water head setting on the dry and wet downstream bed conditions.Water surface elevation was extracted through image analysis and validated by comparing with the data measured using a wave gauge.Temporal variation of the water surface elevation at the gate location,quantified in terms of high-speed video recorded images,can be divided into three stages,the sharp decreasing stage,the relatively steady stage,and the gradually decreasing stage.Applicability of several classic analytical solutions of the dam-break problem at the gate location was validated using present experimental data.Ritter's solution is effective for the dry bed condition while Stoker's solution could be applied to the wet bed case,and both are only applicable during the steady stage.Lin' solution reproduces the gate-site hydrographs well during both the relatively steady and the gradually decreasing stages,especially for the condition under which the down-upstream water depth ratio is smaller than 0.138.
基金Supported by the Special Fund of International Plant Nutrition Institute Fund (NMS-Yunnan200801)~~
文摘[Objective] This study aimed to explore the effects of soil erosion on the productivity of sloping field. [Method] Through removing of and covering with topsoil in a micro-plot experiment, the effect of soil erosion on productivity of sloping field was studied. [Result] The results showed that there was extremely significantly posi- tive correlation between the thicknesses of covered topsoil with either the yield of maize seeds or the yield of maize stalks, which indicated that the yields of maize seeds and maize stalks decreased extremely significantly with the increase of the amount of surface soil loss caused by erosion on the sloping field. The yields of maize seeds and maize stalks decreased by 29.62% and 24.46% respectively in the treatment with removal of a 15 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks decreased by 17.31% and 20.14% re- spectively in the treatment with removal of a 10 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks decreased by 12.69% and 11.51% respectively in the treatment with removal of a 5 cm thick layer of ma- ture topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 10.00% and 9.35% respectively in the treatment with covering with a 5 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 15.77% and 16.19% respectively in the treatment with covering with a 10 cm thick layer of mature topsoil in the plow layer; the yields of maize seeds and maize stalks increased by 17.69% and 25.18% respectively in the treat- ment with covering with a 15 cm thick layer of mature topsoil in the plow layer. [Conclusion] This study provides a basis for assessing the effect of soil erosion on sloping field.
文摘This paper stems from an artistic experiment,in which a distinguished violinist received completely different prices for performing in varying locations.This may be due to the difference in the performance locations,and the value of art in the heart of the audience.
文摘Several factors can influence learning process and the overall students’performance but it seems that few studies had made attempt to investigate the influence of teachers and school factors on students’achievement especially in a technological-driven world where Basic Science performance is low.The study investigated teachers’characteristics and school factors as correlates of students’achievement in Basic Science in Oyo State.The survey research was anchored on constructivism and theory of learning.Multi-stage sampling procedures were employed to select all the 33 Local Government Areas of Oyo State.Two schools each,66 teachers and 1,980 students participated in the study.Three validated instruments used to gather information are:Teachers’Characteristics and School Factors Questionnaire with r=0.84,Teachers’Observational Sheet with r=0.87,and Basic Science Achievement Test with r=0.87.Data were analyzed using descriptive and inferential statistics at 0.05 level of significance.Significant relationship was found between teachers’experience(r=0.77,0.003,P<.05),teachers’subject mastery(r=0.66,0.019,P<.05),school location(r=0.62,0.031,P<.05),and students’achievement.School facilities(β=1.244;t=2.487;p<0.05)contributed significantly to the prediction.The variables jointly explained 82%of the variance observed in students’achievement in Basic Science.There is a strong correlation of variables on students’achievement.Teachers should improve on their subject mastery skill while enabling environment should be provided by the government.
