Integration of hardware and software in a high-performance laboratory reactor

The assembly of a stirred tank reactor capable of precise reaction temperature control is described. The unit allows easy on-line determination of the thermal effect and calculation of heat transfer coefficients and heat capacities. Construction elements are standard, low cost, and high quality. Temperature control is achieved by a heating-cooling loop integrated to the reactor jacket and a cascade control procedure. An important feature of the equipment is the integration of the data acquisition system with the supervisory control system that allows the capability of an advanced strategy for process control and data acquisition. The capability of the reaction system is demonstrated for the microemulsion polymerization of vinyl acetate, by the use of batch and isothermal operational modes. The course of the reaction is followed on-line by the temperature variation of the jacket. Procedures are described for the calibration of the unit. The reactor developed is versatile, is easy to configure and extend, is low cost, and can compete advantageously with commercial reactor units such as the Mettler RC1. © 1996 John Wiley & Sons, Inc.     

Barocalorimetric technique for monitoring pressurized copolymer reactors

The problem of on‐line estimation of the conversion and composition evolutions in a pressurized batch copolymer reactor with temperature and pressure measurements was addressed. The estimation model consisted of mass and energy balances with a pressure equation built from phase‐equilibrium considerations. The application of a nonlinear geometric estimation approach yielded the underlying solvability condition with physical meaning, a straightforward estimator construction, and a conventional‐like tuning procedure. The resulting barocalorimetric estimator was an on‐line dynamic measurement processor with a model‐based predictor and a measurement‐driven corrector, and whose implementation did not require the polymerization rates and heat‐transfer coefficient function dependencies. The technique was tested with a representative laboratory styrene–butadiene system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 475–482, 2005     

Kinetic Study of the Austempering Reactions in Ductile Irons

Kinetics of the reaction that occur during the austempering heat treatment in unalloyed and alloyed ductile irons with 1Cu-0.25Mo, 1Ni-0.25Mo, and 0.7Cu-1Ni-0.25Mo, was studied. The austenitization and austempering cycles were achieved by isothermal dilatometry in cylindrical samples of 2 mm in diameter and 12 mm in length. The specimens were austenitized at 870 °C for 120 min, followed by isothermal holding for 300 min at temperatures between 270 and 420 °C. Kinetic parameters such as the order of reaction “n” and the rate of reaction “k” were calculated using the Johnson-Mehl equation while the empirical activation energy was calculated by means of the Arrhenius equation. It was found that the values of “k” decreased with the addition of Cu, Ni, and Mo as well as with the reduction of the isothermal temperature. The activation energy changes with the austempering temperature, in the range 30,348-58,250 J/mol when the heat treatment was carried out between 370 and 420 °C and 10,336-26,683 J/mol when the temperature varied from 270 to 350 °C. The microstructures in samples austempered at 370 and 315 °C were observed by transmission electron microscopy. No carbides precipitation was observed on samples heat treated at 370 °C for less than 120 min, while at 315 °C carbides of hexagonal structure ε(Fe_2.4C) were found from the beginning of the transformation. The smallest value of activation energy and a slower kinetic transformation seem to be related with the presence of a carbide phase. Additionally, the time results obtained for transformation fractions of 0.05 and 0.95 by the dilatometry analysis were used to build the temperature-time-transformation diagrams for the irons.     

Distillate water quality of a single-basin solar still: laboratory and field studies

Solar water distillation has long been used to provide potable water in locations where the quality of the local water is poor, especially in remote areas where other treatment options are not available. This paper reports on the performance of single-basin, solar stills for the removal of a selected group of inorganic, bacteriological, and organic contaminates. Laboratory and field trials were run on these stills in Southern New Mexico, USA, by New Mexico State University. The still design proved to be very successful in removing non-volatile contaminants from the water. The stills were also successful in removing bacteria if care was taken to avoid cross contamination from the raw water source. Stills had mixed success when it came to the removal of volatile organic compounds, such as pesticides. The ability to remove the organic compounds was directly dependent on the volatility of the compound as measured by the Henry’s law constant. The stills’ ability to remove contaminants from the water did not vary significantly between the units tested in the laboratory and those tested in the field.     

The Sonogel-Carbon electrode as a sol-gel graphite-based electrode

In this work, a novel sol-gel-based procedure to obtain solid carbon composite electrodes is proposed. The procedure is based on the use of sonocatalysis to apply high-energy ultrasound directly to the precursors; this way, ultrasonic cavitation is achieved so that hydrolysis with acidic water is promoted in the absence of any additional solvent and the time needed to get a unique phase is reduced drastically. The mix of sonogel with spectroscopic grade graphite leads to a new type of sol-gel electrode: the Sonogel-Carbon electrode. The amount of water, necessary for hydrolysis to occur, has been studied, as well as the sol pH value and the electrochemical behavior of the Sonogel-Carbon electrode in Britton-Robinson buffer. Mechanical renewal of the electrodes surfaces and background signal stability for at least 42 days have been also tested. We have carried out some tests to check the ability of the synthesized material to give electrochemical response when redox species are present in the background electrolyte. Mechanical and electrochemical studies indicate that the Sonogel-Carbon electrode shows good properties for use as an electrochemical sensor.     

Experimental Assessment of the Sprinkler Application Rate for Steep Sloping Fields

The Programa para el Manejo del Agua y del Suelo (PROMAS) assists the local farming community in introducing new types of locally available irrigation equipment that are both inexpensive and water efficient. Field experiments enabled determining the maximum application rates that cause zero runoff for slopes above 16% for low-cost sprinkler systems.     

Realistic model for the multiple‐input floating‐gate transistor

Multiple‐input floating‐gate transistor (FGMOS) circuit designers face a serious problem along the design process: the lack of a realistic simulation model. For this reason, a solution that properly predicts the initial voltage at the floating gates is presented in this paper. In order to assess the performance of the proposal, a comparison is made against a test circuit fabricated in a 0.5‐µm On‐Semiconductor CMOS process. Based on this comparison, the proposed model is shown to be a fundamental tool in the design of FGMOS circuits. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Age-related differences in collision detection during deceleration.

Observers were presented with displays simulating a 3-D environment with obstacles in the path of motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. On some trials the rate of deceleration resulted in stopping before the collision, whereas on other trials the rate of deceleration resulted in a collision with the obstacles. The observer's task was to detect which trials simulated an impending collision. Proportion of collision judgments was greater for older as compared with younger observers when a collision was not simulated. Older observers showed less sensitivity to detect collisions than younger observers did, particularly at high speeds. The age-dependent results are discussed in terms of analyses based on τ? and constant deceleration. The results suggest that increased accident rates for older drivers may be due to an inability to detect collisions at high speeds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrochemical AFM investigation of horseradish peroxidase enzyme electro-immobilization with polypyrrole conducting polymer

In this paper we investigate the nano-characterization of polypyrrole (Ppy) thin film electro-synthesized on highly oriented pyrolitic graphite (HOPG) with and without horseradish peroxidase enzyme (HRP) using Atomic force microscopy (AFM) performed in contact mode and fluid cell with electrolyte and potential control (ECAFM). In situ electro-synthesis of thin polypyrrole film was made by cyclic volt–amperommetry achieving structured Ppy nanoparticles with two types of particle sizes and the same ellipsoidal shape. Furthermore, the electro-immobilization of HRP, onto this film, was made at a fixed potential, achieving different morphology characterized by highly rough, non-homogeneous structure, and partial maintaining of the ellipsoidal particle in specific sites. The effect of polarization time on morphological parameters was studied and two mechanisms of electro-immobilization of HRP with Ppy conducting polymers were proposed.