The study of MIG weldability of heat-treated aluminum alloys

In this article, Metal Inert Gas (MIG) weldability of commercially received and aged samples of 6061-T₆ and 7075-T₆₅₁ aluminum alloys was investigated. The welding joints were prepared in ten different combinations. Microstructure, microhardness, EDX, energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were used in order to evaluate the effect of aged heat treatment on the performance of welded joints. In addition, the mechanical properties of welding joints were characterized using the tensile and microhardness tests. In conclusion, it was shown that prewelding aging heat treatment improves the mechanical properties of welding joints.     

Metallurgical and Corrosion Properties of Explosively Welded Ti6Al4V/Low Carbon Steel Clad

Titanium alloy (Ti6Al4V) and Iow carbon steel (LCS) were joined by explosive welding method using different ratios of explosive. Some metallurgical properties of joined samples were investigated. Joined samples were examined by means of optical microscope, scanning electron microscope (SEM) and tensile-shearing tests. Bending, tensile, hardness and corrosion behaviour of the samples were investigated. Separation was not occurred on the joining interface after tensile-shearing and bending tests. It is seen that hardness of both plates were increased with increasing explosive.It is found that increasing explosive ratio leads to an increase in corrosion. It is also found that corrosion rate was high at the beginning of the experiment but the rate of the corrosion decreased subsequently during the experiment.     

Dissolution kinetics of ulexite in acetic acid solutions

Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kJ/mol.     

Smartphone based sperm counting - an alternative way to the visual assessment technique in sperm concentration analysis

Sperm Counting is the first phase of the infertility diagnosis. Computer Aided Sperm Analysis (CASA) and Visual Assessment (VA) are two evaluation techniques employed in analyses. VA is carried out by observing sperm on counting chambers. Therefore, diagnosis strongly depends on the skills and experiences. CASA isolates the human factor by utilizing the computer based techniques. However, it is more costly than VA and requires exhausted parameter settings. In this study, we present a novel approach that uses smartphone and computer for sperm counting analysis. Smartphone is used to obtain images similar to VA technique. Then, sample videos are transferred to the computer side where we developed the Computerized Sperm Counting Software (CSCS) to count the sperm using counting chambers and eliminate human effects. CSCS consists of four modules: (1) Data Acquisition and Organization, (2) Regions of Interest (ROI) detection, (3) Motile/Immotile Sperm Detection, (4) Counting. Smartphone based data acquisition provided less costly design contrary to CASA systems. ROI extraction was realized by a combinational approach of line detection and segmentation methods. Background and Foreground extractions were employed in immotile and motile sperm detection process, respectively. Additionally, active contour was implemented to enhance the segmentation of immotile sperm. As the final step, detected sperms were counted by pixel based blob analysis. According to experimental results, the proposed smartphone based sperm concentration analysis can be adapted in laboratories due to its modularity, functionality, accuracy and cost when compare to CASA and VA based sperm counting analysis.

     

The Implementation of Optimization Methods for Contrast Enhancement

The performances of the multivariate techniques are directly related to the variable selection process, which is time consuming and requires resources for testing each possible parameter to achieve the best results. Therefore, optimization methods for variable selection process have been proposed in the literature to find the optimal solution in short time by using less system resources. Contrast enhancement is the one of the most important and the parameter dependent image enhancement technique. In this study, two optimization methods are employed for the variable selection for the contrast enhancement technique. Particle swarm optimization (PSO) and artificial bee colony (ABC) optimization methods are implemented to the histogram stretching technique in parameter selection process. The results of the optimized histogram stretching technique are compared with one of the parameter independent contrast enhancement technique; histogram equalization. The results show that the performance of the optimized histogram stretching is better not only in distorted images but also in original images. Histogram equalization degraded the original images while the optimized histogram stretching has no effect due to being an adaptive solution.     

Investigation of the Microstructural,Mechanical and Corrosion Properties of Grade A Ship Steel-Duplex Stainless Steel Composites Produced <Emphasis Type="Italic">via</Emphasis> Explosive Welding

Grade A ship-building steel-AISI 2304 duplex stainless steel composite plates were manufactured via explosive welding. The AISI 2304 plates were used to clad the Grade A plates. Optical microscopy studies were conducted on the joining interface for characterization of the manufactured composite plates. Notch impact, tensile-shear, microhardness, bending and twisting tests were carried out to determine the mechanical properties of the composites. In addition, the surfaces of fractured samples were examined by scanning electron microscopy (SEM), and neutral salt spray (NSS) and potentiodynamic polarization tests were performed to examine corrosion behavior. Near the explosion zone, the interface was completely flat, but became wavy as the distance from the explosion zone increased. The notch impact tests indicated that the impact strength of the composites decreased with increasing distance from the explosion zone. The SEM studies detected brittle behavior below the impact transition temperature and ductile behavior above this temperature. Microhardness tests revealed that the hardness values increased with increasing distance from the explosion zone and mechanical tests showed that no visible cracking or separation had occurred on the joining interface. The NSS and potentiodynamic polarization tests determined that the AISI 2304 exhibited higher corrosion resistance than the Grade A steel.     

A Kinetic Model for Dissolution of Zinc Oxide Powder Obtained from Waste Alkaline Batteries in Sodium Hydroxide Solutions

Metallurgical and Materials Transactions B - The determination of individual dissolution behaviors of zinc and manganese in waste alkaline battery powders is an important subject from the points of...     

A direct-sequence spread-spectrum communication system for integrated sensor microsystems.

Some of the most important challenges in health-care technologies have been identified to be development of noninvasive systems and miniaturization. In developing the core technologies, progress is required in pushing the limits of miniaturization, minimizing the costs and power consumption of microsystems components, developing mobile/wireless communication infrastructures and computing technologies that are reliable. The implementation of such miniaturized systems has become feasible by the advent of system-on-chip technology, which enables us to integrate most of the components of a system on to a single chip. One of the most important tasks in such a system is to convey information reliably on a multiple-access-based environment. When considering the design of telecommunication system for such a network, the receiver is the key performance critical block. The paper describes the application environment, the choice of the communication protocol, the implementation of the transmitter and receiver circuitry, and research work carried out on studying the impact of input data characteristics and internal data path complexity on area and power performance of the receiver. We provide results using a test data recorded from a pH sensor. The results demonstrate satisfying functionality, area, and power constraints even when a degree of programmability is incorporated in the system.     

Investigation of Leaching Kinetics of Copper from Malachite Ore in Ammonium Nitrate Solutions

The production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303?K to 323?K [30?°C to 50?°C]) and diffusion through a porous product layer (323?K to 343?K [50?°C to 70?°C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50?kJ/mol, respectively.