Estimation of chloride permeability of concretes by empirical modeling: Considering effects of cement type,curing condition and age

In this study, effects of cement type, curing condition, and testing age on the chloride permeability of concrete were investigated experimentally. Chloride permeability of concrete was determined through rapid chloride permeability test (RCPT). The research variables included cement type (i.e. plain and four different blended cements), water–cement ratio (0.65 and 0.45), curing condition (uncontrolled, controlled, and wet curing), and testing age (28, 90, and 180 days). Furthermore, based on the experimental results, a neural network (NN) model-based explicit formulation was proposed to predict the chloride permeability of concrete in terms of the water–cement ratio, aggregate–cement ratio, superplasticizer–cement ratio, cement type, curing condition, and testing age. Finally, proposed NN based explicit formulation was verified by using the data gathered from the literature. The test results indicated that the selected experimental parameters had pronounced effects on the chloride permeability of concretes. Besides, it was found that the empirical model developed by using NN seemed to have a high prediction capability of the chloride permeability of concretes.     

Template‐free microsphere and hollow sphere formation of polymethylanilines

BACKGROUND: Microsphere and/or hollow sphere formation of methyl‐substituted polyaniline derivatives was investigated via chemical polymerization where different sets of conditions were examined. It was found that a variety of parameters (e.g. types and concentrations of monomer and oxidant, polymerization time, solvent with and without acid) have a crucial influence on the morphology of the resulting polyaniline derivatives. RESULTS: Structures with desired morphologies (with or without microspheres and hollow spheres) may be obtained in a controlled manner by changing the parameters. Moreover, the electrochemical and optical properties of the polymers in the presence of acid and/or base were investigated via cyclic voltammetry and UV‐visible and electron spin resonance spectroscopic techniques. It is noteworthy that the morphologies of microspheres and/or hollow spheres remained unchanged after repeated acid and base treatments. CONCLUSION: Micro/hollow spherical structures were successfully prepared via chemical polymerization of various substituted anilines by using ammonium persulfate as oxidant. It was found that the type of oxidant and monomers along with the polymerization time are quite important factors for the formation of micro/hollow spheres. Furthermore, hydrogen bond formation does not play any crucial role for the formation of these spheres. Chemically and electrochemically doped/dedoped states of microspheres and/or hollow spheres are very sensitive, and give rapid response towards vapours of HCl and NH₃, which makes them amenable for use in sensors. Copyright © 2009 Society of Chemical Industry     

Cost Savings in the Ozone Treatment of Paper Mill Effluents Achieved By a Closed-Loop Ozone Control System

Control strategies were created to reduce the operating costs of ozone stages of effluent treatment plants in paper mills as well as to improve the quality of the effluent. Biologically treated effluents from five mills were subjected to laboratory and pilot tests. All COD target values could be reached and maintained with SAC-based control strategies. Disturbing events were compensated with a deviation of only 2% within maximum 3.1 volume exchanges, depending on the kind of event. The SAC (spectral absorption coefficient) was found to be highly suitable for controlling the ozone dosage. In a SME paper mill, 20% of the operating costs of an ozone plant can be saved. The return on investment for such a system is thus about 8 months.     

Single-chip image sensors with a digital processor array

The architectures, implementation and applications of two smart sensors, LAPP and PASIC, are described. The basic idea of these two designs is to integrate an image sensor array with a digital processor array in a single chip. The integrated camera-and-processor eliminates the bottleneck of sequential image read-out that characterizes conventional systems. They provide fast, compact and economic solutions for tasks such as industrial inspection, optical character recognition and robot vision.     

Thermal Stabilities of Peroxidases from Fresh Pinto Beans

Heat stabilities of crude and partially purified soluble (SPOX), ionically bound (IPOX) and total peroxidase (TPOX) from fresh pinto beans were investigated at 55–90°C. Heat inactivation of peroxidase (POX) followed first-order reaction kinetics. Each inactivation curve consisted of two linear parts: initial rapid inactivation (heat-labile) followed by slower inactivation (heat-stable). IPOX showed activation during heat treatment with a highly heat-stable isoenzyme (D₉₀=40 min) which was more heat-stable than SPOX. Activation energies for heat-stable parts of crude IPOX and SPOX were, respectively, 12.1 and 36.4 kcalmol-1 with z values 45.4 and 14.1C°. Heat stable SPOX isoenzymes (D₇₀=22.6) were obtained by 65–95% (NH₄)₂SO₄ precipitation from crude SPOX. Two POX fractions (F1 and F2) were separated from TPOX by ion-exchange chromatography.     

Experimental study on the effect of frost parameters on domestic refrigerator finned tube evaporator coils

In this study, parameters affecting the frost formation on the evaporator of a refrigerator and the structure of frost were examined. Air velocity measurements both at the air inlet and outlet channels of the evaporator were performed, and the effect of air velocity on frost formation was examined. The rate of evaporation of water inside the refrigerator cabin was also recorded.     

Modelling of Stress State,Centre Consolidation and Roll Force in Billet Rolling

Roll pressure models have been derived from theoretical studies, FEM simulations and experimental investigations. A model developed from slip line field theory has been shown to fit well to the experimental results. The Finite Element simulations overestimated the pressure function. This is a common problem in hot rolling experiments, since the problem of measuring the correct rolling temperature makes the estimation of the yield strength very difficult. The difference between the FE calculations and the experimental measurements is a measure for the error in the experimental temperature measurements rather than for the accuracy of the Finite Element Method. Traditional modelling has not been an appropriate tool to evaluate the material flow in the centre of the billet. In spite of the fact that the entire stress state can be modelled by slip line field theory, the slip lines which determine the stress state in the centre coincide for actual geometries only in one single point. Thus the strain increments are known only in that single point. Since a material element passes that point instantaneously, it is not possible to find any finite strains in the centre by integrating any incremental function. By FEM, strain modelling is simple and the possibility to consolidate a porous bloom or ingot core can be determined. FE modelling requires an entirely new approach to the modelling problem. It is not reasonable to use FEM to evaluate only the temperature distribution for the use in roll force models from the previous century. Instead, a fully thermomechanically coupled FE model is suggested. However, the calculation time is still far too long to be used for on‐line control purposes. For this application hybrid modelling can be a solution, where off‐line FE models are combined with empirical modelling, and simplified models can be used for the process control.