Comparison on efficiency factors of F and C types of fly ashes

Fly ashes are obtained from thermal power plants and they are pozzolanic materials, which can act as partial replacement material for both portland cement and fine aggregate. With their economical advantages and potential for improving fresh and hardened concrete performance, they have some benefits for using in concrete industry. In this study, the objective was to find the efficiency factors of Turkish C and F-type fly ashes and to compare their properties. Three different cement dosages were used (260, 320, 400 kg/m³), two different ratios (10% and 17%) of cement reduced from the control concretes and three different ratios (depending on cement reduction ratio) of fly ash were added into the mixtures. At the ages of 28 and 90 days, compressive strength, modulus of elasticity and ultrasound velocity tests were carried out. From the compressive strength results, the k efficiency factors of C and F-type fly ashes were obtained. As a result, it is seen that efficiency factors of the concrete produced by the replacement of F and C type fly ashes with cement increase with the increase in cement dosage and concrete age.     

Investigation of water gas-shift activity of Pt–MOx–CeO2/Al2O3 (M = K,Ni, Co) using modular artificial neural networks

The water gas shift activity of promoted Pt–CeO₂/Al₂O₃ catalysts were investigated in this work. The catalysts were prepared by incipient to wetness impregnation and tested using a microflow reaction system. It was found that K has beneficial effects under product-containing feed compositions while Co and Ni promoters worsen catalyst performance. The reaction temperature and feed H₂O/CO ratio positively affect the catalytic activity, whereas CO₂ and H₂ addition to the feed decreases CO conversion, as expected. The experimental results were also modeled using modular neural networks, at which the catalyst preparation and operational (reaction) variables were used together in the same network because they are interacting but processed differently because they are dissimilar in their form (i.e. categorical versus continuous) and their effects on catalytic activity. It was concluded that the effects of catalyst preparation and operational variables and their relative importance could be comprehended more accurately by using this approach, which may be also employed in other similar systems.     

A comprehensive study on mechanical properties of Bi1.8Pb0.4Sr2MnxCa2.2Cu3.0Oy superconductors

This study manifests the crucial change in the mechanical performances of Bi_1.8Pb_0.4Sr₂Mn_xCa_2.2Cu_3.0O_y superconductor samples (x = 0, 0.03, 0.06, 0.15, 0.3 and 0.6) prepared by conventional solid-state reaction method by use of Vickers microhardness (H_v) measurements carried out at different applied loads, (0.245 N ≤ F ≤ 2.940 N). Load dependent microhardness, load independent microhardness, Young’s (elastic) modulus and yield strength values being account for the potential technological and industrial applications are evaluated from the hardness curves and compared with each other. It is found that the H_v, elastic modulus and yield strength obtained decrease (increase) with the enhancement of the applied load for the undoped (doped) samples. Surprisingly, the results of the H_v values illustrate that the samples doped with x = 0.03, 0.06, 0.15, 0.3 and 0.6 exhibit reverse indentation size effect (RISE) feature whereas the pure sample obeys indentation size effect (ISE) behavior. Furthermore, the experimental results are examined with the aid of the available methods such as Meyer’s law, proportional sample resistance model (PSR), elastic/plastic deformation (EPD), Hays–Kendall (HK) approach and indentation-induced cracking (IIC) model. The results inferred show that the hardness values calculated by PSR and EPD models are far from the values of the plateau region, meaning that these models are not adequate approaches to determine the real microhardness value of the Mn doped Bi-2223 materials. On the other hand, the HK approach is completely successful for the explanation of the ISE nature for the pure sample while the IIC model is obtained to be the best model to describe the hardness values of the doped materials exhibiting the RISE behavior. Additionally, the bulk porosity analysis for the samples reveals that the porosity increases monotonously with the increment in the Mn inclusions inserted in the Bi-2223 system, presenting the degradation of the grain connectivity.     

Effect of Boron and Heat Treatment on Mechanical Properties of White Cast Iron for Mining Application

 Heat treatment methods were applied to white cast iron for improving the impact and wear resistance. Additionally, chemical composition optimization was made. Furthermore, the effect of boron addition on such applications was investigated. Samples were investigated by using optical and electron microscope methods. Hardness, wear and impact tests were conducted. The results showed that the secondary carbides in the standard alloy were iron-enriched, needle-like carbides M3C when the boron-added alloy contained Fe23(C,B)6 type, globular secondary carbides. It was concluded that heat treatment B provided higher wear and hardness properties, compared to the standard heat treatment. Optimum mechanical properties were obtained by lower destabilisation temperatures and increasing temperature reduced the wear resistance and hardness.     

Biodiversity and technological properties of yeasts from Turkish sourdough

Food Science and Biotechnology - In this study, yeasts were isolated and characterized from twelve traditional sourdough samples which belongs to Black Sea and Aegean regions of Turkey. Twenty six...     

Case for Expanding the Claim Dispute Resolution Training of TxDOT Personnel

Texas Department of Transportation (TxDOT) currently uses general alternative dispute resolution and dispute management tactics to resolve construction claims. The successful application by TxDOT of project partnering methods, critical path management, and the Contract Claims Committee has resulted in a relatively low number of claims filed. However, one weakness in TxDOT’s current methodology is the lack of specific protocol for project-level personnel and administrators. The following survey of TxDOT dispute resolution methods emphasizes the importance of developing a personnel training catalog for Area Engineers in order to avoid costly claim dispute escalation. As the individual primarily responsible for resolving project and district-level disputes, the Area Engineer should be equipped with dispute resolution training if TxDOT wishes to improve the efficiency of its alternative dispute resolution protocol.     

Analysis of effects of sizes of orifice and pockets on the rigidity of hydrostatic bearing using neural network predictor system

This paper presents a neural network predictor for analysing rigidity variations of hydrostatic bearing system. The designed neural network has feedforward structure with three layers. The layers are input layer, hidden layer and output layer. Two main parameter could be considered for hydrostatic bearing system. These parameters are the size of bearing pocket and the orifice dimension. Due to importancy of these parameters, it is necessary to analyse with a suitable optimisation method such as neural network. As depicted from the results, the proposed neural predictor exactly follows experimental desired results.     

Investigation of microstructure and wear behaviors of al matrix composites reinforced by carbon nanotube

In this study, the effect of CNT amount in Al-CNT composites produced by adding carbon nanotube (CNT) to 7075 Al alloy in various amounts on microstructure and wear behaviors of aluminum matrix composites was investigated. CNT was added to 7075 Al alloy powder at five different amounts. The powders were mechanically milled for 2 hours. Mechanical milled powders were cold pressed and then pre-shaped by hot pressing. Pre-shaped samples were sintered for 1 hour under 10^?6 millibar in 580°C. Microstructure examinations, hardness measurements, and wear tests were carried out. The results show that CNT's in the microstructure were agglomerated as nanotube amount increases and there was no uniform distribution. The highest hardness value was obtained in AMC reinforced with 1% CNT while it is seen that hardness of the composite decreases and weight loss increases as CNT amount increases.