Thin-Layer Drying of Mate Leaves (Ilex paraguariensis) in a Conveyor-Belt Dryer: A Semi-Automatic Control Strategy Based on a Dynamic Model

A feedback strategy of drying control of mate leaves in a thin-layer conveyor-belt dryer was experimentally evaluated. Moisture content in the discharge of the continuous dryer was controlled by manually adjusting the speed of the moving belt between 3.7 × 10^?4 and 15.2 × 10^?4 m s^?1 for approximately 7200 s in 120 s time steps. The sets of PID controller parameters and manipulated conveyor velocities were computed with a dynamic drying model at conditions identical to those found in the closed-loop experiments. The model is represented by a system of two partial differential equations built by energy and solute mass balances in the solid phase of the dryer. A large set of experimental drying curves and temperature of mate leaves as a function of drying time, in the temperature range from 55 to 130°C, confirmed the reliability of the considered model. Experimental closed-loop responses of discharge moisture content in the presence of disturbances in the feed moisture content (≈ 0.5 ? 1.7 dry basis) and variations in set-point (≈ 0.1 ? 1.0 dry basis) validated the suggested control scheme.     

Optical technique DPIV in measurements of granular material flows, Part 1 of 3—plane hoppers

The aim of this paper is to present the evolution of plug flow developing in three densely packed granular materials in the model of a hopper made of Plexiglas. For this purpose, the digital particle image velocimetry (DPIV) technique is applied to analyse the flow field of the granular material. When discharge starts, a plug flow zone in the flowing material expands upward. This zone changes its width reaching the upper surface of the material. The plug flow evolution as a function of time is described using DPIV. This technique yields the velocity profiles of flowing granular materials, velocity magnitude contours, vector fields, velocity distributions on certain levels in the model and traces of the selected particles. The results obtained for the evolution of the vertical velocity, height and width of the plug flow zone as a function of time, measured at the symmetry axis of the model for the amarantus seed are compared to the results obtained by Waters and Drescher. Measurements of the stagnant boundary as a function of time are compared to the results available in the literature.     

Analysis of Design Parameters in Anode‐Supported Solid Oxide Fuel Cells Using Response Surface Methodology

Achieving high performance from a solid oxide fuel cell (SOFC) requires optimal design based on parametric analysis. In this paper, design parameters, including anode support porosity, thicknesses of electrolyte, anode support, and cathode functional layers of a single, intermediate temperature, anode‐supported planar SOFC, are analyzed. The response surface methodology (RSM) technique based on an artificial neural network (ANN) model is used. The effects of the cell parameters on its performance are calculated to determine the significant design factors and interaction effects. The obtained optimum parameters are adopted to manufacture the single units of an SOFC through tape casting and screen‐printing processes. The cell is tested and its electrochemical characteristics, which show a satisfactory performance, are discussed. The measured maximum power density (MPD) of the fabricated SOFC displays a promising performance of 1.39 W cm^–2. The manufacturing process planned to fabricate the SOFC can be used for industrial production purposes.     

关于电子实验教学虚拟化改革的思考

以虚拟电子工作台为例，简要介绍计算机仿真实验技术及由此带来的现代电子电路实验方法的变革，着重讨论该实验方法在实验教学中的本质与实物实验的关系及实施策略。     

Experimental validation of a model of an uncontrolled bicycle

In this paper, an experimental validation of some modelling aspects of an uncontrolled bicycle is presented. In numerical models, many physical aspects of the real bicycle are considered negligible, such as the flexibility of the frame and wheels, play in the bearings, and precise tire characteristics. The admissibility of these assumptions has been checked by comparing experimental results with numerical simulation results. The numerical simulations were performed on a three-degree-of-freedom benchmarked bicycle model. For the validation we considered the linearized equations of motion for small perturbations of the upright steady forward motion. The most dubious assumption that was validated in this model was the replacement of the tires by knife-edge wheels rolling without slipping (non-holonomic constraints). The experimental system consisted of an instrumented bicycle without rider. Sensors were present for measuring the roll rate, yaw rate, steering angle, and rear wheel rotation. Measurements were recorded for the case in which the bicycle coasted freely on a level surface. From these measured data, eigenvalues were extracted by means of curve fitting. These eigenvalues were then compared with the results from the linearized equations of motion of the model. As a result, the model appeared to be fairly accurate for the low-speed low-frequency behaviour.     

化工实验异常数据的取舍

本文慨略介绍了重复测量中异常数据取舍的主要方法,分析、探讨了其取舍原理和取舍标准,并将其中格拉布斯法扩展应用于一般化工实验数据处理,弥补了目前化工实验中异常数据取舍方法的不足。     

Pedestrian conspicuity research: a review

This review sets out to evaluate the ways in which pedestrian conspicuity has been defined and measured and to consider the various scenarios in which studies of pedestrian conspicuity have been conducted. Research from the psychological and human factors literature is reviewed, in addition to relevant studies on conspicuity that fall outside the scope of applied psychology. Methodological differences between these studies are compared and their ecological validity in terms of the real-world context of pedestrians at risk from vehicles is discussed. The authors argue that there have been many methodological differences in pedestrian conspicuity studies, but that this may not necessarily be problematic when investigating a phenomenon with multiple causal factors. However, suggestions are made for improving ecological validity and establishing a more unified framework for future research in this area.     

Experiments on conical shell reducers under uniform external pressure

In previous studies, a proliferation of research work has been undertaken on the buckling behavior of shell structures particularly conical shells. Nonetheless, no experimental studies are found in the literature on the buckling of a full and real configured model of a slender shell reducer with two cylindrical end boundaries. To this end, buckling behavior of three conical shell reducers under uniform peripheral pressure was investigated and evaluated experimentally in this paper. In addition, relevant FE simulations as well as theoretical predictions were taken into account to compare buckling load and modes of deformation. Derived results were aimed at generalizing the data for conical reducers in full scale within the range of this study.     

3D CFD modeling and experimental characterization of HT PEM fuel cells at different anode gas compositions

A numerical and experimental characterization of the performance of a High Temperature Polymer Electrolyte Membrane Fuel Cell (HT PEM FC) is presented.Starting from the fluid dynamic optimization performed in a previous work, a detailed 3D CFD-electrochemical model of a single HT PEM FC is developed, in order to describe the internal fluid dynamic fields coupled to the electrochemical reactions.To validate the numerical activity, an experimental campaign has been conducted on a single-cell prototype built ad-hoc, with both pure H₂ and Syngas anodic feeding.The results of both the numerical and experimental investigations are compared to the performance of commercial HT PEM Fuel Cells, proving the good accuracy of our numerical method as well as the consistency of the experimental setup.     

大孔树脂富集分离葡萄叶总黄酮的研究

目的优化大孔吸附树脂分离纯化葡萄叶黄酮类化合物的工艺条件。方法采用分光光度法,以芦丁为标准品,采用硝酸铝显色法测定总黄酮含量;以葡萄叶总黄酮的含量、吸附量和解吸率为考察指标,通过静态及动态实验,筛选出理想的吸附树脂,并通过单因素试验确定了葡萄叶总黄酮富集分离的优选操作条件。结果 D-101树脂是吸附葡萄叶提取液中总黄酮较理想的树脂,对其优化的工艺参数为:最佳吸附p H值:p H=3,洗脱剂浓度:70%的乙醇,最佳上样流速:0.8 m L/min,最佳上样液浓度:65.65 mg/L,最佳解吸流速:0.8m L/min。结论 D-101树脂对葡萄叶总黄酮的吸附量大,解吸容易,环境友好,确定的吸附与洗脱条件简单可行,此工艺具有良好的产业化前景。