Application of visible and near infrared spectroscopy in non-destructive evaluation of cement materials

In the twenty-first century, there has been rapid urbanization in economically emerging countries. Many scientific research studies have proposed methods to monitor the quality of materials used in engineering works. Quality inspections are most often made of structure-related materials such as concrete. All the concrete used in construction work is subjected to a test that breaks the samples to evaluate its final mechanical strength. In this sense, remote sensing can contribute to mapping and monitoring construction materials, allowing investigation and identification of various properties such as mechanical strength and water content in a non-destructive manner. The materials can be inspected directly on site, in a rapid, non-invasive, and inexpensive manner; this is crucial for the ongoing process of construction. The spectral behaviour of four different mechanical strengths of two cement materials based on Portland cement, cement paste, and mortar was observed using a FieldSpec® 3 spectroradiometer. The spectral curves generated by recording the reflected and absorbed electromagnetic radiation of the samples were interpreted based on the theory of vibrational and electronic spectroscopy. The objective of this work is to show a novel technique for assisting in the analysis of solid samples using visible and near infrared spectroscopy. Through this study, a spectral contrast between different samples of the paste and mortar was found. Besides, it was possible to detect the presence and the corresponding proportion of water in the samples. Wavelet analysis enabled records of statistical evidence of spectral contrast, and showed that the depth of water absorption features is inversely proportional to compressive strength in the cement materials under study. This work is innovative, because there are no studies in the literature on the application of this technique as an aid tool for differentiating compressive strengths of Portland-cement-based materials.     

Factors affecting glaze transparency of ceramic tiles manufactured by the single firing technique

Transparency is an extremely important optical property of several glazes used in the ceramic tile sector. The present work aimed to identify the causes of loss of transparency presented by some ceramic glazes composed of frits with chemical compositions typical of optically transparent glasses. After identifying the causes of low transparency presented by several ceramic glazes based on microstructural analyses, X-ray diffraction and scanning electron microscopy, attempts were made to increase the transparency of these glazes by altering their chemical compositions. The results suggest that the addition of alumina – through distinct mineral sources – may be an interesting alternative to prevent the crystallization of calcium silicates, which reduce the transparency of glazes used in the ceramic tile sector.     

Mycotoxin occurrence in beer produced in several European countries

The occurrence of ochratoxin A, trichothecenes, fumonisins and aflatoxins in a sample of 106 beers produced in several European countries, was investigated. The analyses were conducted using high-performance liquid chromatography with fluorimetric detection for ochratoxin A and aflatoxins, gas-chromatography and high-performance liquid chromatography, both coupled with mass spectrometer, for trichothecenes and fumonisins, respectively. Aflatoxins were not detected in any samples, whereas ochratoxin A, deoxynivalenol and fumonisins were found in a relatively high number of samples. Their presence was at low levels in all samples; however, some differences were observed between the European countries. As regards ochratoxin A, beer samples from southern Europe showed levels always lower than 0.040 μg l^?1, while the samples from other European countries showed significantly higher values, up to 0.189 μg l^?1 (P < 0.001). For fumonisins, the levels of Italian beers were significantly higher compared to the samples from other countries (P = 0.006).     

De-nickelification of 70/30 Cupronickel Tubing in a Cooling Heat Exchanger

A cupronickel heat exchanger failed after 10?years of service. The cooling heat exchanger was in service in a marine environment, with water flowing along shellside and natural gas along tubeside. Many tubes showed leakages during a regular maintenance test. A comprehensive failure analysis of the heat exchanger revealed the de-nickelification process on the external side of the damaged tubes (shellside). The de-nickelification originated from a large deposit of sea water scale, over tube lengths, which completely covered the area just outside the internal portion of the tubesheet, and occurred because of a failure of the regular cleaning operation. Stagnant water and possible hot spot formations on the tubes probably caused the phenomenon.     

Experimental Study of an Adding Interferometer at Millimeter Waves

In order to study an original detection architecture for future cosmology experiments based on wide band adding interferometry, we have tested a single baseline bench instrument based on commercial components. The instrument has been characterized in the laboratory with a wide band power detection setup. A method which allows us to reconstruct the complete transfer function of the interferometer has been developed and validated with measurements. This scheme is useful to propagate the spurious effects of each component till the output of the detector.     

Chlorinated Polycyclic Aromatic Hydrocarbons Associated with Drinking Water Disinfection: Synthesis,Formation under Aqueous Chlorination Conditions and Genotoxic Effects

Polycyclic aromatic hydrocarbons (PAHs) are among the most persistent and toxic organic micropollutants present in water and several of them are mutagenic and carcinogenic. Although it has been shown that chlorinated derivatives of PAHs (Cl-PAHs) may be formed during the water chlorination procedure, little is known about their potential genotoxic and carcinogenic effects. The objectives of the present work were to prepare and characterize the major chlorinated derivatives of benzo[a]pyrene (BaP) and fluoranthene (Fluo), to develop an analytical methodology for their quantification in water samples and to analyse their potential genotoxicity. Chlorinated standards were prepared by a newly developed two phase method (water/n-hexane) using sodium hypochlorite. 6-Chloro-benzo[a]pyrene was selectively obtained from BaP, while 1,3-dichloro-fluoranthene and 3-chloro-fluoranthene were obtained from Fluo. All products were isolated and characterized by nuclear magnetic resonance and mass spectrometry. The formation of BaP- and Fluo-chlorinated derivatives under aqueous chlorination conditions was observed using a SPE-HPLC-FLD methodology. In addition, the cytotoxic and genotoxic activities of the three chlorinated derivatives were analyzed in comparison to their parent compounds, in a human-derived hepatoma cell line using the neutral red uptake and comet assays, respectively. The results showed that, at the equimolar doses of 100 and 125 μM, 6-Cl-BaP was able to induce a significantly higher level of DNA damage than BaP, suggesting a more potent genotoxic effect. In contrast, neither Fluo nor its chlorinated derivatives were genotoxic in the same cell line. The identification of new and possibly hazardous water chlorination by-product from PAHs emphasizes the need to minimize total organic carbon content of raw water and the implementation of safer water disinfection methods.     

Processing of short fiber reinforced polypropylene. II: Statistical study of the effects of processing conditions on the impact strength

Within the general objective of analyzing and modeling the processability of polypropylene and of its short fiber composites, a statistical analysis of the relationship between processing conditions and final properties has been performed applying modern experimental design concepts. In order to gather the largest amount of information with a manageable quantity of experiments, Taguchi methods were used for the design of injection molding tests and for the analysis of experimental fiber orientation and impact strength results. Two levels of each variable of interest were selected, and the results of the analysis not only show which of the processing variables are predominant but also show that interactions between variables must be taken into account. The approach presented here offers a viable route to the scaling-up of the injection molding process through the reduction of the number of variables in the prediction of the processing behavior of semicrystalline polymers and of their composites.     

A constrained optimization approach to preserving prior knowledge during incremental training

In this paper, a supervised neural network training technique based on constrained optimization is developed for preserving prior knowledge of an input-output mapping during repeated incremental training sessions. The prior knowledge, referred to as long-term memory (LTM), is expressed in the form of equality constraints obtained by means of an algebraic training technique. Incremental training, which may be used to learn new short-term memories (STMs) online, is then formulated as an error minimization problem subject to equality constraints. The solution of this problem is simplified by implementing an adjoined error gradient that circumvents direct substitution and exploits classical backpropagation. A target application is neural network function approximation in adaptive critic designs. For illustrative purposes, constrained training is implemented to update an adaptive critic flight controller, while preserving prior knowledge of an established performance baseline that consists of classical gain-scheduled controllers. It is shown both analytically and numerically that the LTM is accurately preserved while the controller is repeatedly trained over time to assimilate new STMs.