Relationship between ultrasonic velocity and compressive strength for high-volume mineral-admixtured concrete

Ultrasound is used to evaluate the compressive strength of concrete with mineral admixtures. In addition, the relationship between ultrasound velocity and compressive strength of concrete are evaluated. High-volume fly ash (FA), blast furnace slag (BFS) and FA+BFS are used as the mineral admixtures in replacement of Portland cement (PC).

Compressive strength and ultrasonic pulse velocity (UPV) were determined at the 3-, 7-, 28- and 120-day curing period. Both compressive strength and UPV were very low for all the levels of mineral admixtures at an early age of curing, especially for samples containing FA. However, with the increase of curing period, both compressive strength and UPV of all the samples increased. The relationship between UPV and compressive strength was exponential for FA, BFS and FA+BFS. However, constants were different for each mineral admixture and each level replacement of PC.     

Failure behavior of quasi-isotropic laminates with three-pin loaded holes

This paper presents the effect of hole positions on the failure behavior of glass–epoxy laminated composite plates fabricated from stacking sequence [0/90/±45]_S subjected to a traction force by three-pins. Three different hole distance parameters, namely the ratio of free edge distance to the outer holes/pin diameter (E/D = 1, 2, 3, 4, 5), the ratio of longitudinal distance between the holes/pin diameter (F/D = 2, 4, 6) and the ratio of transverse distance between the parallel holes/pin diameter (G/D = 3, 4, 5) were used to investigate the effects of hole positions on failure load and failure mode. Shear out failure mode which is not the desired mode for a structure occurs around the first and second pin holes very close to the free edge of the specimen (E/D = 1). The other specimens were damaged in bearing mode which is the most desired mode.     

Electrochemical synthesis of poly-2-aminothiazole on mild steel and its corrosion inhibition performance

2-Aminothiazole (AT) was polymerized by electrochemical technique on a mild steel (MS) electrode from 0.01 M monomer containing 0.3 M ammonium oxalate solution. Cyclic voltammetry was used for the synthesis. Poly-2-aminothiazole (pAT) film with a light-brownish color was obtained on the MS surface. The effectiveness of polymer film in preventing corrosion of MS was tested in 0.5 M HCl solution. For corrosion tests, anodic polarization curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques were utilized. The results obtained indicated that, the polymer film adherent to the steel surface. The polymer film gives a good corrosion protection against the attack of corrosive environment.     

Detection of aflatoxin M1 levels by ELISA in white-brined Urfa cheese consumed in Turkey

Aflatoxin M1 (AFM1) is the hydroxylated metabolite of aflatoxin B1 found in a variety of foods. In this study, 127 samples of white-brined Urfa cheese produced mainly in the southeast of Turkey from raw ovine and bovine milks were surveyed for the presence of AFM1 using a competitive Enzyme Linked Immunosorbent Assay (ELISA) technique. The results showed that at detectable levels (≥50 ng/kg), 36 cheese samples (28.3%) were contaminated with AFM1 ranging from 70.61 to 770.97 ng/kg. Of the 36 cheese samples, 13 (10.2%) were found to have levels that exceeded the legal limits of 250 ng/kg established by the Turkish Food Codex. Consequently, the AFM1 contamination levels determined in this study in white-brined Urfa Cheese, which is commonly consumed in the southeast part of Turkey, were not considered to be a serious public health hazard. It was considered to be a potential risk for customers, particularly for infant health.     

Selective CO oxidation over monolithic Au?MgO/Al2O3 catalysts

BACKGROUND: Selective CO oxidation was studied in a hydrogen‐rich environment over monolithic Au/MgO/Al₂O₃ catalysts at 50–150 °C. The wash‐coating of cordierite monoliths with colloidal Al₂O₃ was followed by wet impregnation of MgO; the subsequent deposition of Au was achieved using various methods. All catalysts were characterized using ICP and ESEM. RESULTS: Homogenous deposition‐precipitation was found to be the best Au loading method among those tested for monoliths. The CO conversion over 1%(w/w) Au/1.25%(w/w) MgO/Al₂O₃ was ca 80% at 90 °C. Increasing the Au content of the catalyst from 0.16 to 1.0%(w/w) increased CO conversion and shifted the required temperature to lower values. A similar trend was also observed for maximum CO conversion at increasing W/F_CO ratios. The addition of MgO was beneficial for CO conversion. CONCLUSION: Although CO conversion of ca 80% was lower than that achieved with particulate catalysts, it is high enough as a starting point for further improvement considering the superiority of monolithic supports for practical applications. Copyright © 2011 Society of Chemical Industry     

Microcontroller based digitally controlled ultrasonic motor drive system

Piezoelectric driven ultrasonic motors have been attracted as considerable actuators for the servo speed and position applications in recent years. These motors have important features and advantages to be preferred in the special movement applications. Ultrasonic motors have different operating principles and different drive and control systems than the electromagnetic motors. In this study, microcontroller based digitally controlled drive system has been proposed for a travelling-wave ultrasonic motor. Drive system includes power circuit, interface electronics circuits and microcontroller parts. Power circuit is combined from half-bridge serial-resonance inverter to provide highfrequency two-phase voltages. Interface circuits include gate drive, direction control, opto-coupler and filter circuits. Microcontroller is programmed to generate required digital control signals for overall control of the motor. Related to the reference speed, the microcontroller generates control signal resulting proper driving frequency. Consequently, the actual motor speed tracks the reference speed precisely. The speed feedback is taken from optical encoder and transmitted to the controller as digital speed and position signals. The developed drive system has been tested experimentally. The obtained results show the effectiveness and reliability of the proposed system. The microcontroller based drive system can be applied easily and successfully to the ultrasonic motor.     

A simulated annealing algorithm to find approximate Pareto optimal solutions for the multi-objective facility layout problem

In this article, we consider the facility layout problem which combines the objective of minimization of the total material handling cost and the maximization of total closeness rating scores. Multi-objective optimization is the way to consider the two objectives at the same time. A simulated annealing (SA) algorithm is proposed to find the non-dominated solution (Pareto optimal) set approximately for the multi-objective facility layout problem we tackle. The Pareto optimal sets generated by the proposed algorithm was compared with the solutions of the previous algorithms for multi-objective facility layout problem. The results showed that the approximate Pareto optimal sets we have found include almost all the previously obtained results and many more approximate Pareto optimal solutions.     

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin-Raduskevich (D-R) isotherms. The mean sorption energy (E) of copper sorption onto silica gel was calculated from D-R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.     

Using azomethine-H method determination of boron contents of various foods consumed in Hatay Region in Turkey

In this study, samples of soil and plant (32 species of vegetable and 17 species of fruit) were collected from six different regions of Hatay (Amik Plant, Reyhanl?, K?r?khan, Samanda?, Dörtyol and ?skenderun). The azomethine-H method was used to determine boron content of samples. Furthermore, the correlation among boron content of soil with boron content of plants was investigated. The boron concentrations in the soil samples, were determined between 32.43 (±2.90) and 93.43 (±2.75) ppm. High concentrations of boron were found in thyme (10.44 ± 0.17), mint (6.96 ± 0.15), red cabbage (6.45 ± 0.15), broad-bean (6.28 ± 0.14), quince (5.41 ± 0.11), pomegranate (5.27 ± 0.13) and orange (4.08 ± 0.10). Minimal concentration of boron were found in pumpkin (0.76 ± 0.01), white radish (0.97 ± 0.01), plum (1.16 ± 0.02) and cucumber (1.17 ± 0.01). Most of the foods had boron concentrations in the range of 1.48–3.60 ppm.