Sorption of Scandium from Sulfuric–Chloride Solutions by Activated Carbons

Sorption of scandium by activated carbons of VSK, DAS, and PFT brands of different origin (coconut shell, anthracite, and thermosetting-plastic waste, respectively) from sulfuric–chloride solutions (pH 2) simulating the composition of solutions for the underground leaching of complex ores is studied in batch conditions. It is established that the sorption of scandium by carbons of DAS and VSK brands proceeds with the highest distribution coefficients (133 and 45.8 cm3/g, respectively). Herewith, the sorption of scandium by DAS carbon is also characterized by a large volume coefficient (116 $${{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} \mathord{\left/ {\vphantom {{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}} \right. \kern-0em} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}$$). Sorption isotherms of scandium by these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm3/g, respectively. The integral kinetic curves of sorption of scandium are found by the method of the limited volume of the solution, and their linearization according to the kinetic models of the pseudo-first and pseudo-second order, the Elovich model, and the Weber–Morris intraparticle diffusion model evidences that the sorption kinetics of scandium by VSK carbon with a higher correlation coefficient (0.999) is described using the pseudo-second-order model. Processing the kinetic data on the sorption of scandium by DAS carbon showed that, when using all models, the correlation coefficient is low (<0.939) and the highest value is observed when applying the intraparticle diffusion model. It is assumed that the sorption of scandium occurs in the mixed diffusion region. The possibility of eluting scandium from VSK and DAS carbons by the sodium carbonate solution (10%) is studied under the batch conditions and the degree of desorption of scandium for two elution steps is 84.0 and 90.4%, respectively.     

Spatiotemporal Visualizations for the Measurement of Oropharyngeal Transit Time From Videofluoroscopy

Videofluoroscopy remains one of the mainstay methods for clinical swallowing assessment, yet its interpretation is both complex and subjective. This, in part, reflects the difficulties associated with estimation of bolus transit time through the oral and pharyngeal regions by visual inspection, and problems with consistent repeatability. This paper introduces a software-only framework that automatically determines the time taken for the bolus to cross 1-D anatomical landmarks representing the oral and pharyngeal region boundaries ( Fig. 1). The user-steered delineation algorithm live-wire and straight-line annotators are used to demarcate the landmark on a frame prior to the swallow action. The rate of change of intensity of the pixels in each landmark is used as the detection feature for bolus presence that can be visualized on a spatiotemporal plot. Artifacts introduced by head and neck movement are removed by updating the landmark coordinates using affine parameters optimized by a genetic-algorithm-based registration method. Heuristics are applied to the spatiotemporal plot to identify the frames during which the bolus passes the landmark. Correlation coefficients between three observers visually inspecting twenty-four 5-mL single swallow clips did not exceed 0.42. Yet the same measurements taken using this framework on the same clips had correlation coefficients exceeding 0.87.      

Finite-Difference Solution of Forced Convection from a Hot-Film Probe in a Reversing Flow

Abstract

A finite-difference solution of the unsteady boundary-layer equations is described for a periodically reversing flow parallel to the axis of a thin cylinder with a heated spanwise strip. The application is to the calibration of hot-film probes used for in vivo blood flow velocity measurements. The numerical results are compared with experimental and analytic results of previous investigations. The present results do not fully explain the large phase shift in heat transfer rate between theory and experiment found in a previous study. However, this phase shift is reduced in cases involving backflow. The results further indicate that inclusion of lateral diffusion and transverse curvature does not significantly affect phase as previously suggested, but that they are important factors in determining the magnitude of the heat transfer rate and hence, the magnitude of the measured velocity.     

Optical Coupling Methods for Cost-Effective Polymer Optical Fiber Communication

In this paper, we report cost-effective light coupling methods for polymer optical fiber (POF) communication. Here, we compare the various optical coupling schemes in detail. By optical simulations, we analyze the conventional light coupling schemes, namely the direct coupling, lens coupling, and lensed fiber coupling. The simulation studies reveal that a lensed fiber tip particularly at the receiver side improves the light coupling efficiency to a great extent. The optimized lensed POF design confers an 85% coupling efficiency. Lensed POFs are realized with two low-cost fabrication methods. The characterization of the lensed POF are carried out to evaluate the lensing properties and hence to optimize the fabrication process.     

Buckling of a Weakened Column

The buckling problem of a column weakened at an interior location is studied for the first time. The weakness is modeled by a rotationally restrained junction. Exact buckling load values are obtained for the weakened column with various end conditions. Depending on the end conditions of the column, the buckling loads show sensitivity (and insensitivity) to junction location and rotational stiffness. The optimum location of the junction could be at the midpoint, at the ends, or somewhere in between.     

Buckling of Circular Mindlin Plates with an Internal Ring Support and Elastically Restrained Edge

This paper is concerned with the elastic buckling problem of circular Mindlin plates with a concentric internal ring support and elastically restrained edge. In solving this problem analytically, the circular plate is first divided into an annular segment and a core circular segment at the location of the internal ring support. Based on the Mindlin plate theory, the governing differential equations for the annular and circular segments are then solved exactly and the solutions brought together by using the interfacial conditions. New exact critical buckling loads of circular Mindlin plate with an internal ring support and elastically restrained edge are presented for the first time. The optimal radius of the internal ring support for maximum buckling load is also found. An approximate relationship between the buckling loads of such circular plates based on the classical thin plate theory and the Mindlin plate theory is also explored.     

Response characteristics of all-solid-state pH sensor using Li5YSi4O12 glass

A new type of all-solid-state pH sensor was investigated for the monitoring of pH in high temperature. The all-solid-state pH sensor consists of two half-cells: indicator electrode using the Li₅YSi₄O₁₂ glass and an Ag/AgCl reference electrode coated with Nafion film. A stable Nafion film was achieved by heat treating at 100 °C for 1 h. The electromotive force (EMF) of the all-solid-state pH sensor decreased linearly with pH increase in water in accordance with the Nernst's equation. The all-solid-state pH sensor operated stably up to 80 °C. The sensitivity of the all-solid-state pH sensor against pH was high, and the EMF was also scarcely influenced by the presence of inorganic ions such as Li⁺, Na⁺ and Cl⁻. It was practically confirmed by the pH titration test that the all-solid-state pH sensor behaved similar to the commercial pH meter with the conventional glass electrode. In addition, the all-solid-state pH sensor showed same equivalence point both at high temperature and low temperature operations.     

Influence of distributed wind generation and load composition on voltage sags

The envisaged increased penetration of distributed generation (DG) in electrical power networks poses challenging technical and contractual issues to both utilities and industry. Technical issues related to power quality, in particular to voltage-sag propagation and characteristics in networks with a large penetration of fixed speed wind DG are addressed. A comprehensive analysis of voltage-sag propagation in a realistic distribution network is performed. The influence of network topology, location and percentage of connected wind generation, network loading and load composition is investigated in detail. It is shown that the influence of DG on voltage-sag characteristics and propagation is strongly dependent on its location and on load composition.