Influence of sample size on strength distribution of advanced ceramics

Strength distribution of advanced ceramics is mostly characterized by Weibull distribution function. The question whether the Weibull distribution always gives the best fit to strength data has been being considered in the last years. The sample size affects the reliable decision of discrimination of different distribution functions (e.g. normal, log-normal, gamma or Weibull). In this paper, 5100 experimental alumina strength data and virtual strength data generated by Monte Carlo simulations are used in order to investigate the effect of sample size on strength distribution of advanced ceramics. It is suggested that, at least 150–200 samples should be used for determination of best fitting distribution function with a statistical fallibility of 10%. Extreme Value Analysis performed with the experimental strength data showed that the Weibull distribution fits the data best and difference between the Weibull and Gumbel distributions appear at the tails.     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Biological treatment of para-chlorophenol containing synthetic wastewater using rotating brush biofilm reactor

A novel rotating brush biofilm reactor (RBBR) was used for para-chlorophenol (4-chlorophenol, 4-CP), COD and toxicity removal from synthetic wastewater containing different concentrations of 4-CP. Effects of major operating variables such as the feed 4-CP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio on the performance of the biofilm reactor were investigated. A Box-Wilson statistical experiment design method was used by considering the feed 4-CP (0-1000 mg l(-1)), COD (2000-6000 mg l(-1)) and A/Q ratio (73-293 m(2) day m(-3)) as the independent variables while the 4-CP, COD and toxicity removals were the objective functions. The results were correlated by a response function and the coefficients were determined by regression analysis. Percent 4-CP, COD and toxicity removals determined from the response functions were in good agreement with the experimental results. 4-CP, COD and toxicity removals increased with decreasing feed 4-CP and increasing A/Q ratio. Optimum conditions resulting in maximum COD, 4-CP and toxicity removals were found to be A/Q ratio of nearly 180 m(2) day m(-3), feed COD of nearly 4000 mg l(-1) and feed 4-CP of less than 205 mg l(-1).     

A new set of design aids for groups of four cylindrical silos due to interstice and internal loadings

The computation of design forces for reinforced concrete groups of four cylindrical silos requires significant computational effort due to continuity in the walls between adjacent silos. This paper presents a simple but accurate procedure for the computation of design forces acting on groups of four cylindrical silos due to stored materials. In this conjunction, finite element analyses were performed by using eight‐node solid elements for various groups of four cylindrical silos under interstice and internal loadings. The design forces at the prescribed sections of interstice and external walls were computed. The silo wall thicknesses, intersection wall thicknesses and intersection wall lengths of these grouped silos were varied with an extensive parametric study to demonstrate their influences on resultant design forces. Design formulas were proposed and dimensionless design coefficients were derived from the comprehensive series of finite element analyses considering the effect of continuity in the walls. The results were expressed in simplified form, so that the prediction of bending moments, axial forces and shear forces became straightforward for design purposes. In addition, the rigidity of the interstice walls was varied by changing the modulus of elasticity and the redistribution of design forces was investigated. Copyright © 2007 John Wiley & Sons, Ltd.     

Electricity generation with simultaneous wastewater treatment by a microbial fuel cell (MFC) with Cu and Cu–Au electrodes

Background: A microbial fuel cell (MFC) consisting of anaerobic and aerobic chambers separated by a salt‐agar slab was used for electricity generation with simultaneous wastewater treatment where copper and gold covered copper wires were used as anode and cathode, respectively. The electrons produced from degradation of carbohydrates in anaerobic chamber traveled through the copper wire generating electricity and the protons were transferred from cathode to anode through the salt‐agar slab. Variation of the current intensity (mA) and the electrical power (mW) were investigated as function of the surface area of anode and also the chemical oxygen demand (COD) content of the synthetic wastewater. Results: The generated power density (mW m^?2) increased with increasing surface area of the electrodes and also with the COD content of the wastewater. Both the current intensity (mA) and the power generated (mW) increased with time and reached maximum levels at the end of batch operation. More than 80% COD removal was achieved in the aerobic chamber with an electricity generation of 2.9 mW m^?2 when the initial COD content was 6000 mg l^?1. Conclusion: The MFC configuration and the use of Cu and Cu‐Au electrodes instead of graphite were proven to be effective for electricity generation with simultaneous wastewater treatment. The electrical current (0.24 mA) and power (2.9 mW m^?2) obtained in our microbial fuel cell are comparable with the literature studies utilizing salt bridge. The microbial fuel cell developed in this study can be improved further to yield higher power generations by modifications. Copyright © 2007 Society of Chemical Industry     

Bioactivity and mineral contents of wild-grown edible Morchella conica in the Mediterranean Region

In this study, antiradical and antimicrobial activity, total phenolic, mineral and heavy metal content of Morchella conica Pers. were determined in the methanolic extracts of dried M. conica collected from wild-grown edible mushroom in the Mediterranean region from Turkey. Free radical scavenging activity was determined to be 43.72 ± 0.13% DPPH decoloration, however, total phenolic activity to be 20.64 ± 0.33 mg GAE/g dry ext. sample. The antimicrobial activity of the extracts was tested against fourteen microorganism including 12 bacteria and 2 yeasts. It was determined that the mushroom extracts had no effect against the bacteria and yeasts. Antimicrobial effect was determined only against Staphylococcus aureus ATCC 29213. M. conica was determined to contain some heavy metals such as arsenic (As), mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and nickel (Ni) in the concentrations of 0.25, 0.06, 0.20, 1.20, 0.70 and 1.10 (mg/kg dw), respectively. Potassium (K), phosphorus (P) and magnesium (Mg) contents were determined to be 20,400, 13,250, and 1,600 (mg/kg dw), respectively, being higher than those of the other minerals in the M. conica extracts.     

Controlling phosphonic acid substitution degree on proton conducting polyphosphazenes

This paper is to describe the development of a synthetic strategy for the preparation of phosphonic acid functionalized poly(aryloxyphosphazene) membranes with different substitution degree of phosphonic acid. Synthesized polymers have been characterized by standard spectroscopic techniques; FT-IR, ¹H, ³¹P and ¹⁹F NMR and element analysis. Proton conductivities of phosphonic acid substituted polymers have been investigated with impedance spectroscopy at different temperatures. Furthermore, the correlations of the proton conductivity and ion exchange capacity with the substitution degree of phosphonic acid have also been investigated. Thermal properties and water uptake properties of the polymers are also investigated. It is found that the proton conductivity and initial decomposition temperature of the polymers increases up to an appropriate amount of phosphonic acid substitution degree, which can be a useful PEM candidate for fuel cells.     

The search for optimal feature set in power quality event classification

The significance of detection and classification of power quality (PQ) events that disturbs the voltage and/or current waveforms in the electrical power distribution networks is well known. Consequently, in spite of a large number of research reports in this area, the problem of PQ event classification remains to be an important engineering problem. Several feature construction, pattern recognition, analysis, and classification methods were proposed for this purpose. In spite of the extensive number of such alternatives, a research on the comparison of “how useful these features with respect to each other using specific classifiers” was omitted. In this work, a thorough analysis is carried out regarding the classification strengths of an ensemble of celebrated features. The feature items were selected from well-known tools such as spectral information, wavelet extrema across several decomposition levels, and local statistical variations of the waveform. The tests are repeated for classification of several types of real-life data acquired during line-to-ground arcing faults and voltage sags due to the induction motor starting under different load conditions. In order to avoid specificity in classifier strength determination, eight different approaches are applied, including the computationally costly “exhaustive search” together with the leave-one-out technique. To further avoid specificity of the feature for a given classifier, two classifiers (Bayes and SVM) are tested. As a result of these analyses, the more useful set among a wider set of features for each classifier is obtained. It is observed that classification accuracy improves by eliminating relatively useless feature items for both classifiers. Furthermore, the feature selection results somewhat change according to the classifier used. This observation shows that when a new analysis tool or a feature is developed and claimed to perform “better” than another, one should always indicate the matching classifier for the feature because that feature may prove comparably inefficient with other classifiers.     

Modelling of a new solar air heater through least-squares support vector machines

This paper reports on a modelling study of new solar air heater (SAH) system efficiency by using least-squares support vector machine (LS-SVM) method. In this study, a device for inserting an absorbing plate made of aluminium cans into the double-pass channel in a flat-plate SAH. A SAH system is a multi-variable system that is hard to model by conventional methods. As regards the LS-SVM, it has a superior capability for generalization, and this capability is independent on the dimensionality of the input data. In this study, a LS-SVM based method was intended to adopt SAH system for efficient modelling. For modelling, different mass flow rates in flow duct and collector types are used and then for obtaining the optimum LS-SVM parameters, such as regularization parameter, and optimum kernel function and parameters, several tests have been carried out. The performance of the proposed methodology was evaluated by using several statistical validation parameters. It is found that root mean squared error (RMSE) value is 0.0024, the coefficient of multiple determinations (R²) value is 0.9997 and coefficient of variation (cov) value is 2.1194 for the proposed radial basis function (RBF)-kernel LS-SVM method at 0.03 kg/s air mass flow rate. It is found that RMSE value is 0.0135, R² value is 0.9991 and cov value is 2.9868 for the proposed RBF-kernel LS-SVM method at 0.05 kg/s air mass flow rate. Comparison between predicted and experimental results indicates that the proposed LS-SVM model can be used for estimating the efficiency of SAHs with reasonable accuracy.     

Exploring the types and reasons of Internet-triggered academic dishonesty among Turkish undergraduate students: Development of Internet-Triggered Academic Dishonesty Scale (ITADS)

Internet contributes to the development of science and facilitates scientific demeanors while it also serves as a ground for academic misdemeanors. Recent studies indicate that Internet facilitates and spreads academic dishonesty. The purpose of the current study is to investigate the extent of involvement of Turkish university students in academic dishonesty practices facilitated through Internet (i.e. e-dishonesty) and to question the conditions which lead to e-dishonesty. Three hundred and forty nine education faculty students from the most populated state university in Turkey were administered two Likert-Scale questionnaires developed by the researchers. After the reliability and validity conditions were met, two exploratory factor analyses were conducted. The first one revealed the factors constituting common types of e-dishonesty among undergraduate students which were fraudulence, plagiarism, falsification, delinquency, and unauthorized help. The second factor analysis exhibited individual and contextual factors triggering e-dishonesty which were named as individual factors, institutional policies and peer pressure. Results of both analyses are discussed and suggestions for further research are provided.