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In this research, the aluminum (Al2024) matrix composites are reinforced with nano magnesium oxide (MgO) and multi-walled carbon nanotubes (MWCNTs). The aim of Al2024 alloy reinforced with MgO and MWCNTs is to reveal the effects of the reinforcement particle ratio on the microstructure and mechanical properties of the hybrid composites, to find the optimum hybrid ratio, and to form a stronger hybrid composite. The composites with the different hybrid ratios are produced via stir casting method. The theoretical and measured densities and porosity content of the composites are studied. The microstructure and fracture surface of the composites are examined by optical microscopy, scanning electron microscopy (SEM), and electron dispersive spectrum (EDS). The hardness, compression, and tensile properties of the composites are studied in this work. Results indicated that the hardness of the aluminum (Al) matrix composites (AMCs) is significantly improved after the reinforcement with MgO and carbon nanotube (CNT), and also heat treatment of T6. The stress–strain curve of the composites is tested by a material testing machine. The maximum tensile and compression strengths are obtained at Al2024-0.2 wt.% (MgO 50% + CNT 50%) the composite as 226 MPa and 684 MPa, respectively.The hardness, compression, and tensile strengths of the hybrid composites are higher than 1.51, 1.39, and 1.31 than that of the base metal. After heat treatment of T6, the maximum harness, compression, and tensile strengths are obtained by 102 HB, 730 MPa, and 277 MPa, respectively, which are 1.82, 1.49, and 1.61 times higher hardness than that that of the base Al2024 alloy. The main strengthening mechanism of nano-MgO particles and MWCNTs-reinforced Al2024/MgO/CNTs composites is observed by the precipitation strengthening mechanism. [ABSTRACT FROM AUTHOR]

Energy storage systems have received increasing attention in recent years because of the requirements of energy supply with respect to the growing population and technology. Among the technologies of energy storage devices, supercapacitors become popular due to their superior characteristics such as high power density, extremely fast charge-discharge capability and long life cycle. A wide variety of materials are already in use to fabricate supercapacitors. Carbon and its derivatives are common materials among the electrode materials of supercapacitors. In this study, electrochemical behaviour of flexible graphite filaments are investigated in different media in order to elucidate the performance of graphite as a supercapacitor material. Electrochemical experiments of graphite electrode are carried out in sodium sulphate (Na2SO4), hydrochloric acid (HCl), potassium hydroxide (KOH) and Ethaline deep eutectic solvent as electrolyte media. Graphite filament is cycled at wide potential window (from -1 V to 1 V) at various scan rates in the range of 5 to 100 mV s-1 in order to observe the associated electrochemical behaviour and performance. Graphite filament electrodes without any treatment can be used in Ethaline and aqueous Na2SO4 electrolytes. However, these electrodes cannot be used in acidic or alkaline media with high potential window of 2 V. [ABSTRACT FROM AUTHOR]

The aim of the study is to research and compare the influences of the confirmed cases, test number and time range on the death and recovery rates in the United State of America, China, and Turkey, and to find out the effect of the epidemic in the near future of Turkey. The modelling and prediction of effects of the day, case and test numbers of COVID-19 infection in the USA, China and Turkey are carried out using the artificial neural network approach (ANN). The system are trained and tested with the different numbers of neurons, hidden layers and activation functions to increase the reliability and accuracy of model. The proposed models have a high R2 value for China and Turkey. We can say according to the results that the measures taken by the USA are inadequate. The formulation is applied to predict the effect of Covid-19 infection in Turkey. The test number that is an important factor in detecting the cases should be increased. The results show a good fit between the observed data and those obtained by the ANN model. If the precautions are strictly followed, the case number will be decreased significantly after 160 days for Turkey according to result of the proposed model but due to the uncontrolled variables, this time may result in between 200 and 250 days. [ABSTRACT FROM AUTHOR]

A bulk brass containing Cu-Zn was oxidized at high temperatures (from 200 °C to 700 °C). The samples were cold rolled to reduce their thickness and the annealing process was applied. The specimens were heated at different temperatures in a furnace for the same duration (45 minutes). This paper examines the corrosion behavior of brass having an oxide surface obtained by heat treatment. The corrosion rate experiments were conducted by linear sweep voltammetry using a potentiostat. The corrosion properties of the specimens were analyzed by scanning the electrodes in saline water including 3.5% NaCl at the scan rate of 2 mV s-1. The corrosion behavior of the electrodes was investigated by two subsequent cycles. The change of the heated brass surface occurring after the corrosions test was also investigated. While the corrosion rate of the nonannealed brass electrode was similar to that of annealed specimens for the first scan, the corrosion rate of heat-treated specimens was dramatically decreased for the second scan. Pitting corrosion of non-heated brass and passivation behavior of heated brass electrodes were observed. Therefore, heat-treatment of brass can cause higher corrosion resistivity of the brass surface. [ABSTRACT FROM AUTHOR]

Penetration is the most critical concept in ballistic studies. Penetration is defined as the ability to penetrate the target. Bullet tip geometry and velocity are the most important factors in terms of the penetration. There are many limitations in increasing the velocity of the bullet. Therefore, projectile geometry can be studied in this field. So, in this study, six different tip geometry of bullet are investigated in terms of the ballistic impact performance. Numerical simulations are performed in ANSYS program, which is the finite element program. Explicit dynamics toolbox is used to perform the numerical study. Six different tip geometry of bullet was modeled in 3D modeling program. The geometries are transferred to the ANSYS workbench program. Initial velocity is accepted as 300 m/s for all conditions. Within this study, the impact energy performance of six different bullet tip geometry was obtained. In addition, stress and deformation results on the target were also compared. [ABSTRACT FROM AUTHOR]

The influence of Borax/SiC content on the tensile modulus of Carbon/epoxy and Kevlar/epoxy composites was analyzed using artificial neural network approach with six neuron in one hidden layer in this study. The correlation coefficient, R2, mean square error and mean absolute error was used to state the performance and error evaluation criteria of the proposed model/system. Borax and SiC ratios was changed between 0 and 10%. Addition of SiC caused to an increase on the tensile modulus of Carbon/epoxy and Kevlar/epoxy composites but Borax addition induced the decrease of it of these composites. [ABSTRACT FROM AUTHOR]

The shear modulus of the composite materials and the elastic properties of the fiber are similar to each other. In this study, the effect of reinforcing type and weight ratio on the shear modulus of carbon/epoxy and kevlar/epoxy composites was theoretically investigated and the average error rates and correlation values were analyzed. Artificial neural networks approach was used in the study. The ratio of Ssa/SiC was determined as minimum and maximum of 0 and 20, respectively. In artificial neural network method, 6 neurons one hidden layer were used. It was observed that SiC was an important reinforcing phase for kevlar/epoxy composites but it was not for carbon/epoxy composites. [ABSTRACT FROM AUTHOR]

In the present study, V-shaped arc welding of the AISI 1045 steel is modeled by using 2D Finite Element Model (FEM). The temperature distribution, microstructure, grain growth, and the hardness of the heat-affected zone (HAZ) of the welding are simulated. The experimental work is carried out to validate the FE model. The very close agreement between the simulation and experimental results show that the FE model is very effective for predicting the microstructure, the phase transformation, the grain growth and the hardness. The effect of preheat temperature on the martensite formation is analysed, and it is shown that 225 °C preheating completely eliminates the martensite formations for the 12 mm thick plate. [ABSTRACT FROM AUTHOR]