Investigation of the magnetic field response from eddy current inspection of defects

Eddy current testing is one of the most widely used methods in non-destructive testing for the inspection of conductive materials. Numerical modelling of eddy current testing has emerged as an important approach alongside experimental studies. This paper investigates an application of numerical modelling and experimental study as a means of the quantitative non-destructive evaluation (QNDE) of defects in conductive samples. There are two methods of measuring eddy current response, more commonly by measuring the change in impedance of the eddy current probe coil, or as used in this work, by measuring the change in magnetic field directly using magnetic field sensors such as superconducting quantum interference devices, giant magneto resistance, or as in this case Hall sensors. Specifically, measurements made using an eddy current probe containing an excitation coil and a Hall sensor, experimentally obtained using an X?CY scanner table, are compared with a numerical (finite element method) model. The discrepancies between the experimental tests and the numerical models have been analysed and explained, which is an important factor in engineering applications of QNDE.     

Treatment of textile dyehouse wastewater by TiO2 photocatalysis

The oxidative degradation of an actual textile dyehouse wastewater was investigated by means of photocatalysis in the presence of TiO2. The UV-A-induced photocatalytic oxidation over TiO2 suspensions was capable of decolorizing the effluent completely, as well as reducing chemical oxygen demand (COD) sufficiently (COD reduction generally varied between about 40% and 90% depending on the operating conditions) after 4 h of treatment. Two crystalline forms of TiO2, viz. anatase and rutile, were tested for their photocatalytic activity and anatase was found to be more active than rutile. The extent of photocatalytic degradation was found to increase with increasing TiO2 concentration up to 0.5 g/L TiO2, above which degradation remained practically constant, reaching a plateau. Furthermore, textile effluent degradation was enhanced at acidic conditions (i.e. pH = 3) and in the presence of hydrogen peroxide. To assess catalyst activity on repeated use, experiments were performed where the catalyst was recovered and reused; after three successive uses, TiO2 had sufficiently retained its photocatalytic activity. Finally, the luminescent marine bacteria Vibrio fischeri was used to assess the acute ecotoxicity of samples prior to and after the photocatalytic treatment and it was found that ecotoxicity was fully eliminated following photocatalytic oxidation.     

Synthesis of A356 Al–high-Ca fly ash composites by pressure infiltration technique and their characterization

Eight types of A356 Al–fly ash composites were produced by pressure infiltration of high-Ca lignite fly ash. This type of ash was used for the first time in Al-composites synthesis, and particularly by liquid metal infiltration techniques. After examining mineralogy and chemistry, specific, narrow ash size fractions were used for the synthesis of composites, and properties linked to microstructure and wear strength of the materials. The effect of using ground ash particles on the microstructure and tribological performance of the composites was also investigated. It was concluded that using fine, high-Ca ash particles can improve the properties of composites, and that using ash particles in a ground form can better facilitate the production process of MMCs.     

Observations on the estimation of scavenging activity of phenolic compounds using rapid 1,1-diphenyl-2-picrylhydrazyl (DPPH<Superscript>•</Superscript>) tests

Rapid 1,1-diphenyl-2-picrylhydrazyl (DPPH^•) tests are often applied to classify the scavenging activity of phenolic compounds (AH). Published analytical protocols differ in more than one experimental condition, and results for the relative order or magnitude of activity are often contradictory. In this work, parameters such as duration of test, [AH]/[DPPH^•] molar ratio, and solvent effects were examined and discussed. The test duration and the value of the [AH]/[DPPH^•] ratio did not influence the order of activity among tested antioxidants. Ethanol, commonly used as solvent in such tests, was compared with acetonitrile and tert-butyl alcohol. Solvent properties such as the ability to form hydrogen bonds with the AH seem to influence the level of the relative activity (%RSA). Higher %RSA values were observed in ethanol. The activity of the most polar compounds was affected the most, and in some cases (caffeic, dihydrocaffeic, and rosmarinic acids) the order of activity was changed owing to different kinetics. Standardization of the analytical protocol should include a 20-min reaction period and a molar ratio that permits attainment of a 60–80% RSA value for the most potent antioxidant. Solvent choice is critical for classifying activity. Safe classification can be based only on results from kinetic studies.     

Mapping commuter cycling risk in urban areas

Cycling is becoming an increasingly important transportation option for commuters. Cycling offers exercise opportunities and reduces the burden of motor vehicle travel on society. Mapping the risk of collision between cyclists and motor vehicles in urban areas is important to understanding safe cyclist route opportunities, making informed transportation planning decisions, and exploring patterns of injury epidemiology. To date, many geographic analyses and representations of cyclist risk have not taken the concept of exposure into account. Instead, risk is either expressed as a rate per capita, or as a count of events. Using data associated with the City of Hamilton, Canada, we illustrate a method for mapping commuter cyclist collision risk per distance travelled. This measure can be used to more realistically represent the underlying geography of cycling risk, and provide more geographically and empirically meaningful information to those interested in understanding how cycling safety varies over space.     

Sorption of reactive dyes from aqueous solutions by ordered hexagonal and disordered mesoporous carbons

In the present study two synthetic mesoporous carbons, a highly ordered CMK-3 sample with hexagonal structure and a disordered mesoporous carbon (denoted DMC) were investigated for the sorption of Remazol Red 3BS (C.I. 239) dye in comparison to three commercial activated carbons and a HMS mesoporous silica with a wormhole pore structure. The structural, porosity and surface characteristics of the materials were evaluated using XRD, TEM, N₂ porosimetry, FT-IR spectroscopy and zeta-potential measurements. Optimal dye sorption occurred at pH ～2. Equilibrium sorption data followed the Langmuir model and showed that the two synthetic mesoporous carbons exhibit higher sorption capacities (q_max ～ 500–580 mg/g at 25 °C) in comparison to the commercial activated carbons which possessed either microporous (Takeda 5A and Calgon carbon) or combined micro-/mesoporous (Norit SAE-2) structures and to the HMS mesoporous silica. Thermodynamic parameters as the change in free energy, enthalpy, and entropy of sorption were also estimated. Kinetic studies were carried out and showed a rapid sorption of dye in the first ca. 30 min while equilibrium was reached after ca. 3 h. The sorption kinetics of dye was best described by a second-order kinetic model. A surfactant enhanced carbon regeneration (SECR) technique was used to regenerate the dye-loaded carbon sorbents.     

COSMO‐based computer‐aided molecular/mixture design: A focus on reaction solvents

In this article, we investigate reaction solvent design using COSMO‐RS thermodynamics in conjunction with computer‐aided molecular design (CAMD) techniques. CAMD using COSMO‐RS has the distinct advantage of being a method based in quantum chemistry, which allows for the incorporation of quantum‐level information about transition states, reactive intermediates, and other important species directly into CAMD problems. This work encompasses three main additions to our previous framework for solvent design (Austin et al., Chem Eng Sci. 2017;159:93–105): (1) altering the group contribution method to estimate hydrogen‐bonding and non‐hydrogen‐bonding σ‐profiles; (2) ab initio modeling of strong solute/solvent interactions such as H‐bonding or coordinate bonding; and (3) solving mixture design problems limited to common laboratory and industrial solvents. We apply this methodology to three diverse case studies: accelerating the reaction rate of a Menschutkin reaction, controlling the chemoselectivity of a lithiation reaction, and controlling the chemoselectivity of a nucleophilic aromatic substitution reaction. We report improved solvents/mixtures in all cases. © 2017 American Institute of Chemical Engineers AIChE J, 63: 104–122, 2018