Based on Bingham rheological model,a three-dimensional numerical simulation model for long-distance pipeline transportation is established by computational fluid dynamics(CFD)to study the pipeline transportationproper...Based on Bingham rheological model,a three-dimensional numerical simulation model for long-distance pipeline transportation is established by computational fluid dynamics(CFD)to study the pipeline transportationproperties of high sliming paste from a copper mine in China.Based on the rheological properties test,the pressure and velocity of pipeline and elbow are simulated by CFD under different mass concentrations and different stowing capacities.The results show that the pipeline resistance of whole-tailings paste with high sliming while without pumping agent is much higher than that with high sliming and pumping agent at the same mass concentration,and the pipeline resistance of whole-tailings paste with high sliming while without pumping agent is much higher than that with low sliming while without pumping agent.It is very important to add pumping agent to whole-tailings paste with high sliming,and the resistance changes with mass concentration and stowing capacity at the same cement-to-sand ratio of1:5and tailings-to-waste ratio of6:1.However,the change is just limited,that is to say,the paste transportation system is of good stability.Furthermore,at the elbow,the maximum pressure and velocity transfer to the outside of the pipe from the inside.However,lubricating layer is formed at the pipe wall because of high content of fine particles in whole-tailings paste,which will protect the elbow from abrasion.CFD provides an intuitive and accurate basis for pipeline transportation study,and would have a wider application space in the study of paste rheological properties and resistance reduction methods.展开更多
This research studied accessibility to secondary schools in some parts of Benue State. The objective of the study was to determine the level of accessibility to secondary school. The study adopted survey, field observ...This research studied accessibility to secondary schools in some parts of Benue State. The objective of the study was to determine the level of accessibility to secondary school. The study adopted survey, field observation and measurement to obtain the needed data. The study adopted gravity model as the related theoretical framework. GIS and descriptive statistical techniques were employed to map, visualize and analyze the data. The result shows that accessibility to secondary school in the three Local Government Areas is generally low, though it varies between schools, within and between Local Government Areas. This depicts a very stressful schooling condition for the majority of students, and has far-reaching implications in terms of lack of skilled manpower, inadequate facilities and consequently low standards in the educational system. To ensure effective and valid decision-making, and maintain high standards in the system, it was recommended that equitable and systematic distribution of school facilities should be embraced. Furthermore, more schools should be established in the areas which currently have low accessibility to bridge the accessibility gap and encourage active participation and consistent attendance at schools among the students.展开更多
基金Project(2016YFC0600709)supported by the National Key R&D Program of ChinaProject(51574013)supported by the National Natural Science Foundation of ChinaProject(FRF-TP-17-024A1)supported by the Fundamental Research Funds for the Central Universities,China
文摘Based on Bingham rheological model,a three-dimensional numerical simulation model for long-distance pipeline transportation is established by computational fluid dynamics(CFD)to study the pipeline transportationproperties of high sliming paste from a copper mine in China.Based on the rheological properties test,the pressure and velocity of pipeline and elbow are simulated by CFD under different mass concentrations and different stowing capacities.The results show that the pipeline resistance of whole-tailings paste with high sliming while without pumping agent is much higher than that with high sliming and pumping agent at the same mass concentration,and the pipeline resistance of whole-tailings paste with high sliming while without pumping agent is much higher than that with low sliming while without pumping agent.It is very important to add pumping agent to whole-tailings paste with high sliming,and the resistance changes with mass concentration and stowing capacity at the same cement-to-sand ratio of1:5and tailings-to-waste ratio of6:1.However,the change is just limited,that is to say,the paste transportation system is of good stability.Furthermore,at the elbow,the maximum pressure and velocity transfer to the outside of the pipe from the inside.However,lubricating layer is formed at the pipe wall because of high content of fine particles in whole-tailings paste,which will protect the elbow from abrasion.CFD provides an intuitive and accurate basis for pipeline transportation study,and would have a wider application space in the study of paste rheological properties and resistance reduction methods.
文摘This research studied accessibility to secondary schools in some parts of Benue State. The objective of the study was to determine the level of accessibility to secondary school. The study adopted survey, field observation and measurement to obtain the needed data. The study adopted gravity model as the related theoretical framework. GIS and descriptive statistical techniques were employed to map, visualize and analyze the data. The result shows that accessibility to secondary school in the three Local Government Areas is generally low, though it varies between schools, within and between Local Government Areas. This depicts a very stressful schooling condition for the majority of students, and has far-reaching implications in terms of lack of skilled manpower, inadequate facilities and consequently low standards in the educational system. To ensure effective and valid decision-making, and maintain high standards in the system, it was recommended that equitable and systematic distribution of school facilities should be embraced. Furthermore, more schools should be established in the areas which currently have low accessibility to bridge the accessibility gap and encourage active participation and consistent attendance at schools among the students.
