Analysis of Microstructures and Mechanical Properties of Particle Reinforced AlSi7Mg2 Matrix Composite Materials

The present study examined the microstructures and mechanical properties (tensile and impact strength, hardness) of selected metal matrix composite materials. SiCp reinforced AlSi7Mg2 matrix composites were produced using gravity and squeeze casting methods and subsequently T6 heat treated. Some of the squeeze casted composites were shaped by extrusion. The extrusion generated an equiaxed matrix structure and SiCp caused a homogeneous distribution. The quasi absence of porosity in the squeeze casted composites led to improved mechanical properties. Whereas an increase in the SiCp ratio resulted in an increase of the tensile strength, it led to a decrease of the impact strength values. The enhancement of the mechanical properties following an applied heat treatment was better for materials shaped by extrusion.     

An Empirical Comparison of Search Approaches for Moving Agents

This study empirically compares existing search approaches used for path planning of moving agents, namely, incremental and real‐time search approaches. The comparisons are performed in both stationary and moving target search problems separately. In each problem domain, well‐known representatives of both approaches are evaluated in partially observable environments where the agent senses a limited area based on its sensor range. In addition to the available algorithms, we propose two algorithms to be used in each problem. The simulations conducted on random grid and maze structures show that the algorithms behave differently and have advantages over each other especially as the sensor range varies. Therefore, the proposed study enables the agent to determine the most appropriate algorithm depending on its priorities and sensor range.     

Microwave assisted transesterification of rapeseed oil

Rapeseed is one of the important vegetable oil sources for biodiesel production due to its high oil content (around 40%). In this study rapeseed oil was converted to biodiesel by transesterification using microwave heating. Experiments were carried out in the presence of two different alkali catalysts which are sodium hydroxide and potassium hydroxide. Effects of various reaction parameters such as catalyst ratio, reaction temperature and time were investigated. Mono-, di- and triglyceride content of biodiesel were determined by gas chromatography analysis. Yield and purity (ester content) percentages of biodiesel were specified in weight, which are 88.3–93.7% and 87.1–99.4%, respectively. The results indicated that microwave heating has effectively increased the biodiesel yield and decreased the reaction time.     

Phenolic inhibitors involved in the natural fermentation of Gemlik cultivar black olives

Olive fruits of the Gemlik variety harvested from different regions of Turkey were placed in aseptic or non-aseptic brines containing 6 % NaCl. Olives of non-aseptic treatment were left to spontaneously ferment under anaerobic conditions. Samples for microbiological and chemical analysis were taken periodically during the course of the fermentation. No lactic acid bacteria growth was observed in three of the six samples, and yeasts were the prevailing microbial group in the other samples. Brines were analyzed for fermentable substrates (glucose, fructose, sucrose and mannitol), fermentation products (organic acids and ethanol) and phenolic–oleosidic compounds. Most of the unprocessed fruits had a low concentration of oleuropein. Hydroxytyrosol and oleoside 11-methyl ester were the main phenolic and oleosidic compounds in all brines. Likewise, the content of antimicrobials such as the dialdehyde form of decarboxymethyl elenolic acid, either free or linked to hydroxytyrosol, in brines was very low, which may permit the growth of lactic acid bacteria in these media. A growth test with two strains of Lactobacillus plantarum was applied to aseptic brines of all samples to determine whether these compounds inhibited lactic acid bacteria growth. The results of this study indicated that Gemlik olive is a “sweet” variety with a low antimicrobial compound content that can be fermented by lactic acid bacteria under favorable conditions.     

Arsenic removal from drinking water by electrocoagulation using iron electrodes

Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm^?2), initial arsenic concentration (50–500 μg L^?1), operating time (0–15 min), electrode surface area (266–665 cm²), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L^?1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm^?2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm² taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L^?1 for electrode surface area of 266 cm². The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.     

Mathematical modelling of an industrial furnace for high‐temperature heat treatment of wood

There are various high‐temperature treatment methods for wood. In the “Bois Perdure” process, the thermal treatment of wood is carried out in a furnace by contacting it with hot combustion gases over 200°C without the addition of any chemicals in order to improve its dimensional stability and durability. The treatment eliminates free and bound water in the wood and modifies its molecular structure. In this study, a mathematical model describing the industrial furnace has been developed. The overall model consists of a 3‐D unsteady‐state sub‐model which solves for the flow, heat, and mass transfer in the gas coupled with a 1‐D unsteady‐state sub‐model which calculates the heat and mass transfer in the wood. The 3‐D gas sub‐model was developed using the commercial CFD code CFX. The 1‐D wood sub‐model is based on the solution of simultaneous heat and mass transfer equations (Luikov equations) using the implicit finite difference formulation. The model predicts the temperature and moisture distributions in the wood as well as the flow, heat, and moisture profiles in the gas. The model results are compared with the data obtained from the industrial furnace, and a good agreement was found between them.     

Activated Carbon Addition to an Activated Sludge Model Reactor for Color Removal from a Cotton Textile Processing Wastewater

Color removal from cotton textile processing wastewater by addition of powdered activated carbon (PAC) into a lab-scale activated sludge system was examined. The activated sludge system was continuously operated in different sludge ages (SRTs) and hydraulic retention times (HRTs). SRT = 30?d and HRT = 1.6?d operation resulted in up to 36% color removal and 94% COD removal. PAC was added 100, 200, and 400 mg/L into the activated sludge system under these operating conditions. The results indicated that 100 mg/L PAC was sufficient to remove the maximum color measured (up to 50 m?1) from the wastewater. The addition of PAC did not affect chemical oxygen demand (COD) removal significantly. Oxygen uptake rate (OUR) tests were also performed to investigate the microbial activities controlling the system performance. The average OUR was 74.1 mg/L/h without PAC addition while it was 70 mg/L/h with PAC addition. Adsorbable organic halogens of the effluent wastewater decreased from 400 to 50 μg/L with the addition of PAC. Toxicity dilution factor decreased from 2 to 1.5 with the PAC addition into the activated sludge system.     

An overlooked complication of hemodialysis: Hoarseness

In hemodialysis patients, some degree of transient hoarseness may occur at the end of the dialysis, and it may be a wearisome, recurrent, and severe state for some hemodialysis patients. However, to date, it has not been a well‐defined complication of hemodialysis. The aim of this study was to state this complication and to throw light on it. Four hundred fifty‐nine hemodialysis patients were questioned about any change in voice quality during hemodialysis. The patients who had this complaint (n = 70) were included in the study, and the group of patients who suffered hoarseness (subgroup 1: severe, subgroup 2: moderate, subgroup 3: mild) were compared with each other and with the control group, which did not suffer hoarseness (n = 51). Hoarseness was found in 15.2% of the hemodialysis patients. The duration of their hoarseness was minumum 1 to maximum 24 hours. In the control group, coronary artery disease (P = 0.056), congestive heart failure (P = 0.049), autonomic neuropathy (P = 0.001), severe intradialytic hypotensive attacks (P = 0.000), heart valve abnormalities (P = 0.000), and left ventricular diastolic dysfunction (P = 0.000) were significantly lower than in hoarseness group. Older age (P = 0.024), coronary artery disease (P = 0.014), autonomic neuropathy (P = 0.011), and intradialytic hypotensive attacks (P = 0.0001), were associated with severe and moderate hoarseness. In the comparison of % change for systolic and diastolic blood pressure between the hoarseness subgroups, diastolic blood pressure change was not different (P = 0.521), but systolic blood pressure change was statistically lower in mild group than moderate (P = 0.033) and severe subgroup (P = 0.029). Dialysis‐induced hypotension may be the main contributor of transient hoarseness. Especially elderly and cardiovascularly compromised patients, who are vulnerable to rapid changes in volume status may experience it to serious extent and this complication may be mediated by autonomic nervous control related with volume depletion.