Rare earth elements (REE) were used to study the temporal and spatial processes of soil erosion from different depths and sections of a slope. Two simulated rainfall events were applied to a prepared plot with a slope...Rare earth elements (REE) were used to study the temporal and spatial processes of soil erosion from different depths and sections of a slope. Two simulated rainfall events were applied to a prepared plot with a slope of 22°. The total runoff and sediment yield were collected every minute during the rainfall events. During the first twenty minutes of the first rainfall event, the average rate of rill erosion and the accumulated sediment yield due to rill erosion was 0.5 and 0.3 times higher than for sheet erosion. During this time, most of the erosion occurred on the lower one third of the plot. After 20 min, rill erosion became the dominant process on the slope. The average acceleration in the rate of rill erosion, the rate of rill erosion and the accumulated sediment yield due to rill erosion were 42, 6 and 4 times higher than that of sheet erosion, respectively. During the first 35 minutes of the second rainfall event, the average acceleration in the rate of rill erosion was 6～9 times higher than that of sheet erosion. Afterwards, the slope became nearly stable with little change in either rill or sheet erosion rates. Initially, most of the rill erosion occurred in the lower third of the slope but later the preexisting rillhead in the middle section of the slope became reactivated and erosion in this section of the slope increased rapidly. These results indicate that REE tracer technology is a valuable tool for quantifying spatial and temporal changes in erosion from a soil slope.展开更多
Design and implementation of Internet of Things (IoT) systems require platforms with smart things and components. Two dominant architectural approaches for developing IoT systems are mashup-based and model-based appro...Design and implementation of Internet of Things (IoT) systems require platforms with smart things and components. Two dominant architectural approaches for developing IoT systems are mashup-based and model-based approaches. Mashup approaches use existing services and are mainly suitable for less critical, personalized applications. Web development tools are widely used in mashup approaches. Model-based techniques describe a system on a higher level of abstraction, resulting in very expressive modelling of systems. The article uses Cisco packet tracer 7.2 version, which consists of four subcategories of smart things—home, smart city, industrial and power grid, to design an IoT based control system for a fertilizer manufacturing plant. The packet tracer also consists of boards—microcontrollers (MCU-PT), and single boarded computers (SBC-PT), as well as actuators and sensors. The model facilitates flexible communication opportunities among things—machines, databases, and Human Machine Interfaces (HMIs). Implementation of the IoT system brings finer process control as the operating conditions are monitored online and are broadcasted to all stakeholders in real-time for quicker action on deviations. The model developed focuses on three process plants;steam raising, nitric acid, and ammonium nitrate plants. Key process parameters are saturated steam temperature, fuel flowrates, CO and SO<sub>x</sub> emissions, converter head temperature, NO<sub>x</sub> emissions, neutralisation temperature, solution temperature, and evaporator steam pressure. The parameters need to be monitored in order to ensure quality, safety, and efficiency. Through the Cisco packet tracer platform, a use case, physical layout, network layout, IoT layout, configuration, and simulation interface were developed.展开更多
人工湿地污染物去除的物理、化学和生物学机制是随水流在多孔介质中的迁移过程中发生的,水动力过程决定了废水(包括其中的污染物)和介质表面的接触程度及反应时间,并由此影响到水质净化效果。人工湿地水动力学的研究对于其优化设计、运...人工湿地污染物去除的物理、化学和生物学机制是随水流在多孔介质中的迁移过程中发生的,水动力过程决定了废水(包括其中的污染物)和介质表面的接触程度及反应时间,并由此影响到水质净化效果。人工湿地水动力学的研究对于其优化设计、运行管理具有重要意义。综述了目前人工湿地水动力学研究的相关方法,包括:盐分示踪获得停留时间分布(residence time distribution,RTD)曲线的方法、染料示踪获得水流运移图像的方法,由RTD曲线进行水力效率评价的方法,以及水动力过程模拟的数学方法等。并对人工湿地水动力学的研究及其应用前景进行了展望。展开更多
文摘Rare earth elements (REE) were used to study the temporal and spatial processes of soil erosion from different depths and sections of a slope. Two simulated rainfall events were applied to a prepared plot with a slope of 22°. The total runoff and sediment yield were collected every minute during the rainfall events. During the first twenty minutes of the first rainfall event, the average rate of rill erosion and the accumulated sediment yield due to rill erosion was 0.5 and 0.3 times higher than for sheet erosion. During this time, most of the erosion occurred on the lower one third of the plot. After 20 min, rill erosion became the dominant process on the slope. The average acceleration in the rate of rill erosion, the rate of rill erosion and the accumulated sediment yield due to rill erosion were 42, 6 and 4 times higher than that of sheet erosion, respectively. During the first 35 minutes of the second rainfall event, the average acceleration in the rate of rill erosion was 6～9 times higher than that of sheet erosion. Afterwards, the slope became nearly stable with little change in either rill or sheet erosion rates. Initially, most of the rill erosion occurred in the lower third of the slope but later the preexisting rillhead in the middle section of the slope became reactivated and erosion in this section of the slope increased rapidly. These results indicate that REE tracer technology is a valuable tool for quantifying spatial and temporal changes in erosion from a soil slope.
文摘Design and implementation of Internet of Things (IoT) systems require platforms with smart things and components. Two dominant architectural approaches for developing IoT systems are mashup-based and model-based approaches. Mashup approaches use existing services and are mainly suitable for less critical, personalized applications. Web development tools are widely used in mashup approaches. Model-based techniques describe a system on a higher level of abstraction, resulting in very expressive modelling of systems. The article uses Cisco packet tracer 7.2 version, which consists of four subcategories of smart things—home, smart city, industrial and power grid, to design an IoT based control system for a fertilizer manufacturing plant. The packet tracer also consists of boards—microcontrollers (MCU-PT), and single boarded computers (SBC-PT), as well as actuators and sensors. The model facilitates flexible communication opportunities among things—machines, databases, and Human Machine Interfaces (HMIs). Implementation of the IoT system brings finer process control as the operating conditions are monitored online and are broadcasted to all stakeholders in real-time for quicker action on deviations. The model developed focuses on three process plants;steam raising, nitric acid, and ammonium nitrate plants. Key process parameters are saturated steam temperature, fuel flowrates, CO and SO<sub>x</sub> emissions, converter head temperature, NO<sub>x</sub> emissions, neutralisation temperature, solution temperature, and evaporator steam pressure. The parameters need to be monitored in order to ensure quality, safety, and efficiency. Through the Cisco packet tracer platform, a use case, physical layout, network layout, IoT layout, configuration, and simulation interface were developed.
文摘人工湿地污染物去除的物理、化学和生物学机制是随水流在多孔介质中的迁移过程中发生的,水动力过程决定了废水(包括其中的污染物)和介质表面的接触程度及反应时间,并由此影响到水质净化效果。人工湿地水动力学的研究对于其优化设计、运行管理具有重要意义。综述了目前人工湿地水动力学研究的相关方法,包括:盐分示踪获得停留时间分布(residence time distribution,RTD)曲线的方法、染料示踪获得水流运移图像的方法,由RTD曲线进行水力效率评价的方法,以及水动力过程模拟的数学方法等。并对人工湿地水动力学的研究及其应用前景进行了展望。
