Effect of electric current on porosity of concrete

The paper describes the influence of electric current on the porosity of concrete samples after electrically accelerated tests and other electrokinetic treatments. Three different concrete mixtures consisting of CEM I 42.5R, CEM II / A-M(S-LL) 42.5R, and CEM I 42.5R with 10 % replacement of cement by microsilica were examined. Direct current (DC) test was performed on fully saturated samples. The samples were loaded with a constant voltage of 20 V for 24 hours in chambers filled with NaOH solution. The changes in porosity were examined using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and open porosity (OP). The results of open porosity indicate an increase in porosity for all mixtures measurements of ∼0.6 %–2 % for treated samples. The MIP showed increase of volume of pores with radius smaller than 0.01 μm after DC test. According to X-ray diffraction (XRD) and Thermogravimetric analysis (TGA) there was ∼2 % less calcite after DC test

Predicted Corrosion Performance of Organofunctional Silane Coated Steel Reinforcement for Concrete Structures: An Overview

This article provides a comprehensive overview of the potential use of organofunctional silane coatings in the corrosion protection of concrete reinforcement in close relation to other commercially used coating technologies—i.e., epoxy coatings and bath hot-dip galvanizing coatings. The application technology of the steel surface is described in detail, and the corrosion performance and bond strength in concrete are compared. The paper also points out the possibility of improving the durability of epoxy coatings by the addition of silanes and, in the case of application to the surface of hot-dip galvanized steel, they can prevent corrosion of the coating by hydrogen evolution. The application potential of organofunctional silanes is also presented in the form of hydrophobic coatings on concrete surfaces or as corrosion inhibitors in simulated concrete pore solutions. The use of a suitable type of modified silane coating on the surface of carbon steel reinforcement can increase the corrosion performance and can also increase the bond strength in concrete. However, these facts need to be experimentally verified

Contactless ECG scanning device hardware design proposal

In this paper proposals on construction of the contactless ECG scanning system hardware are described. The philosophy of the system is based on the idea of creating a simple-to-be-worn dress that includes capacitive ECG sensors the outputs of which are transferred to the A/D converter of a processing device. Contemporary technologies enable sewing of the sensors as well as the connecting wires into the dress. The processing device receives three analogous signals corresponding to the potential differences sensed on the body of the measured person. The paper is focused on the problem of getting and transmitting this signal to the processing device. Copyright © (2012) by the International Measurement Federation (IMEKO)

Employing self organizing migrating algorithm at electrical circuitry designing

Electrical circuit designers use a wide variety of software intended to make their work easier. In some cases, several steps of processing the design can be automated or, at least, processed with computers. The logical trend then tends to employ the artificial intelligence as a powerful instrument. In this article we display the usage of artificial intelligence algorithms at searching for the optimal load line of some basic active devices that are utilized in low frequency amplifiers - transistors and vacuum valves

Kinetics of Zinc Corrosion in Concrete as a Function of Water and Oxygen Availability

This paper studies the effect of water as an oxidation agent and also of oxygen on zinc corrosion kinetics in active state in concrete, using high-sensitivity electrical resistance sensors. It was proven that zinc corrosion in active state is strongly affected by the presence of water at its surface. Zinc corrosion in real concrete in the absence of water can be misinterpreted as salt passivity. The presence of oxygen results in an increase of zinc corrosion rate, however at pH 12.6, passivity can occur. It was verified that corrosion products consisting primarily of Ca[Zn(OH)3]2·2H2O cannot effectively passivate zinc surface in concrete, even after 1800 h of exposure and zinc, or hot-dip galvanized steel can corrode at an unacceptable corrosion rate (more than 4 µm·a−1)

Planar inductor optimised by evolutionary algorithm

Planar inductors made on a printed circuit boards are rather commonly employed today and there are various software applications to help the designer with their proposals. These applications are usually based on numerical methods created according to commonly utilized approximations. In this paper, there is described the design of a single layer spiral inductor with parameters optimized by Self-Organizing Migrating Algorithm in order to achieve required inductance while the resistance of the inductor is as low as possible

Single and double layer spiral planar inductors optimisation with the aid of Self-Organising Migrating Algorithm

Planar inductors made on a printed circuit boards are rather commonly employed today and there are various software applications to help the designer with their proposal. In this paper we describe the optimisation of a single and double layer spiral inductors made by the help of evolutionary Self-Organizing Migrating Algorithm in order to achieve the required inductance while the resistance of the inductor's conductor was as low as possible. Primarily, these inductors are of large extent, supposed to be utilized at low-frequency applications such as proximity sensors or metal detectors, but the results stated in this paper can be generalized for various applications. A simple Maple algorithm was also created in order the results gained from the evolutionary algorithm could be verified

Application of differential evolution for audio transformers optimization

In audio applications transformers are still employed due to several of their features. They are helpful at noise optimisation in circuits where two blocks are connected, having different output and input impedance. For example, when connecting a low-impedance microphone to an amplifier the input of which is of high impedance, not only the impedances are matched by the transformer, but the voltage gain obtained due to the high turns ratio lets the constructer decrease the gain of the amplifier stage as well, which contributes also to decreasing of the noise. Unfortunately, the design of such transformer is very complex, combining electrical, mechanical and geometrical issues. Therefore the authors of this paper decided to create an algorithm that helps the designer to design the transformer according to the requirements by means of Differential Evolution. The description of this method as well as its results is described in this paper

Flat coil optimizer in the meaning to coil optimization

Planar inductors made on a printed circuit board are rather commonly employed today and there are various software applications to help the designers with their proposal. In this paper the authors describe the application called Flat Coil Optimizer developed by them. This application serves for designing proper geometrical dimensions of a single layer spiral coil made on the printed circuit board in order it achieved the desired inductance while its serial resistance is as low as possible. In order to process such optimization, two different approaches have been utilized. Firstly, the optimization can be processed analytically and secondly, Differential evolution can be applied as well. This feature allows the user to decide which method he/she wants to apply and in case of doubts the user can verify the results by employing the other method

Chemical Removal of Lead Corrosion Products

Restoration treatment, specimen preparation or mass loss measurements on coupons made of lead require a reliable process of dissolution of corrosion products. In this study, several types of model corrosion products with compositions representative of those found on real objects were prepared and characterized. Ten solutions were then thoroughly tested in interval cleaning experiments, regarding the efficiency of removal of the corrosion products, corrosivity towards bare lead, and remnants left on the surface. The solution recommended in the current version of the ISO 8470 standard was found to be improper for the cleaning of both historical artefacts and corrosion coupons due to its inability to remove sulfide corrosion products and the risk of surface contamination and staining. A solution of 20% hydrochloric acid is the best choice for the preparation of lead coupons before exposure or for evaluation of mass loss of exposed samples because its somewhat higher corrosivity towards metallic lead is tolerable for these applications. Rochelle salt solution was found to be optimal for the cleaning of historical artefacts free of sulfide corrosion products due to the lowest corrosivity. None of these alternative solutions leave remnants on the surface and they are efficient at laboratory temperature