Effect of post weld heat treatment on microstructure and mechanical properties of gas tungsten arc welded AA6061-T6 alloy

Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure,mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld heat treatment (PWHT) usingXRD, FESEM, EBSD, nanoindentation and tensile tests. The results show that PWHT led to microstructural recovery of the heataffected zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) at the grain boundaries of weld zone. The hardness (Hnano) inall zones increased after PWHT while the elastic modulus (Enano) was improved from 69.93 GPa to 81 GPa in weld area. All resultsindicate that PWHT has created a homogenous microstructure in the weld zone in addition to outstanding improvement inmechanical properties for the weld zone which surpass the base metal.

Corrosion evaluation of friction stir welded lap joints of AA6061-T6 aluminum alloy

Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.

Influence of rotational speed on mechanical properties of friction stir lap welded 6061-T6 Al alloy

The effect of rotational speed on macro and microstructures, hardness, lap shear performance and failure mode of friction stir lap welding on AA6061-T6 Al alloy with 5 mm in thickness was studied by field-emission scanning electron microscopy （FE-SEM）. The results represent much closer hardness distribution in the upper and lower plates at the lowest rotational speed. It indicates the Fe-compounds in the fracture surface of the nugget zone by EDX.

Fabrication of an electrochemical sensor for determination of doxorubicin in human plasma and its interaction with DNA

In this work, an electrochemical sensor was fabricated for determination of an anthracycline, doxorubicin(DOX) as a chemotherapy drug in plasma based on multi-walled carbon nanotubes modified platinum electrode(Pt/MWCNTs). DOX was effectively accumulated on the surface of modified electrode and generated a pair of redox peaks at around 0.522 and 0.647 V(vs. Ag/Ag Cl) in Britton Robinson(B-R) buffer(p H 4.0, 0.1 M). The electrochemical parameters including p H, type of buffer, accumulation time, amount of modifier and scan rate were optimized. Under the optimized conditions, there was a linear correlation between cathodic peak current and concentration of DOX in the range of 0.05–4.0 μg/m L with the detection limit of 0.002 μg/m L. The number of electron transfers(n) and electron transfer-coefficient(α) were estimated as 2.0 and 0.25, respectively. The constructed sensor displayed excellent precision, sensitivity, repeatability and selectivity in the determination of DOX in plasma. Moreover, cyclic voltammetry studies of DOX in the presence of DNA showed an intercalation mechanism with binding constant(K_b) of 1.12×10~5L/mol.

DNA-binding studies of valrubicin as a chemotherapy drug using spectroscopy and electrochemical techniques

In this study, the molecular interactions between valrubicin, an anticancer drug, and fish sperm DNA have been studied in phosphate buffer solution(pH 7.4) using UV–Vis spectrophotometry and cyclic voltammetry techniques. Valrubicin intercalated into double stranded DNA under a weak displacement reaction with methylene blue(MB) molecule in a competitive reaction. The binding constant(kb) of valrubicin-DNA was determined as 1.75×10~3L/mol by spectrophotometric titration. The value of non-electrostatic binding constant(k_t^0) was almost constant at different ionic strengths while the ratio of k_t^0/k_b increased from 4.51% to 23.77%.These results indicate that valrubicin binds to ds-DNA via electrostatic and intercalation modes.Thermodynamic parameters including ΔH^0, ΔS^0and ΔG^0for valrubicin-DNA interaction were determined as-25.21×10~3k J/mol, 1.55×10~2k J/mol K and-22.03 k J/mol, respectively. Cyclic voltammetry study shows a pair of redox peaks for valrubicin at 0.45 V and 0.36 V(vs. Ag/Ag Cl). The peak currents decreased and peak positions shifted to positive direction in the presence of DNA, showing intercalation mechanism due to the variation in formal potential.

Functionalized graphene oxide-reinforced electrospun carbon nanofibers as ultrathin supercapacitor electrode

Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process,non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10 F/g at the current density of 1 A/g, which was approximately three folds more than that of pristine nanofibers.It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure.

Development of Autonomous Travelling Device for Oil Palm FFB （Fresh Fruit Bunches） Harvester

Robot technology is a very promising technology for agricultural sector, but the existing industrial robot could not deliver the above-mentioned criteria. Industrial robot mainly uses high voltage electrical power, which is not available at field and outdoor operation. The only available and reliable power is a hydraulic from the tractor. The harvester robot consumes the hydraulic power from the tractor and at the same time the tractor can be used as a traveling device for the robot. This paper describes the study on the development of autonomous tractor for the oil palm harvester. The development took considerations on the design of the electro-hydraulic system and the control software for the robot structure to be flexible enough to operate in plantation environment.

Synthesis and characterization of poppy seed oil methyl esters

Response surface methodology(RSM) was used to determine the optimum conditions of the methanolysis of crude poppy seed oil using Na OCH3 as catalyst. The experiments were run according to five levels, four variable central composite rotatable design(CCRD) using RSM. The reaction variables, i.e., molar ratio of methanol/oil(3:1–9:1), catalyst concentration(0.5 wt%–1.25 wt% Na OCH3), reaction temperature(25–65 °C), and reaction time(20–90 min) were studied. We demonstrated that the molar ratio of methanol/oil, catalyst concentration,and reaction temperature were the significant parameters affecting the yield of poppy seed oil methyl esters(PSOMEs). The optimum transesterification reaction conditions, established using the RSM, which offered a89.35% PSOME yield, were found to be 7.5:1 molar ratio of methanol/oil, 0.75% catalyst concentration, 45 °C reaction temperature, and 90 min reaction time. The proposed process provided an average biodiesel yield of more than 85%. A linear correlation was constructed between the observed and predicted values of the yield.The gas chromatography(GC) analyses have shown that PSOMEs contain linoleic-, oleic-, palmitic-, and stearic-acids as main fatty acids. The FTIR spectrum of the PSOMEs was also analyzed to confirm the completion of the transesterification reaction. The fuel properties of the PSOMEs were discussed in light of biodiesel standards(ASTM D 6751 and EN 14214).

Application Geospatial Technology in Disaster Management

Disasters including natural and manmade make heavy losses in life and property each year. This subject can affect society, economy, and environment and can be a serious threat for development. In 10 years ago over 200 million people are have been effected both life and property. This figure is seven times more than losses in war. After the earthquake in Bam （a city in south Iran）, tsunami in south-eastern of Asia, fire in Australia, and other disasters, the management of disaster has been considered more than before. They have tried to use all facilities and equipment for reduction of disaster damage. Over 80% of necessary data in disaster management are spatial data. Spatial data and advanced technologies have an important role in disaster management because Geographic Information System （GIS） can help in identifying disaster points. GIS combines geospatial data, and hardware, software that can analyze data to produce information. GIS mainly involves saving and analysis of data according to spatial and attribute data. GIS can combine and analyze spatial and non-spatial data .We have made an attempt to consider disasters management according to facilities and role of Geospatial Technology in control of disaster （especially earthquake）.

Production of biodiesel from palm fatty acid distillate using sulfonated-glucose solid acid catalyst:Characterization and optimization

A palm fatty acid distillate （PFAD） has been used for biodiesel production. An efficient sulfonated-glucose acid catalyst （SGAC） was prepared by sulfonation to catalyze the esterification reaction. The effect of three variables i.e. methanol-to-PFAD molar ratio, catalyst amount and reaction time, on the yield of PFAD esters was studied by the response surface methodology （RSM）. The optimum reaction conditions were： 12.2：1 methanol-to- PFAD molar ratio, 2.9% catalyst concentration and 134 rain of time as predicted by the RSM. The reaction under the optimum conditions resulted in 94.5% of the free fatty acid （FFA） conversion with 92.4% of the FAME yield. The properties of the PFAD esters were determined according to biodiesel standards.

Design of Portable Shell and Tube Heat Exchanger for a Solar Powered Water Distiller

This study presents theoretical considerations and results of a portable shell and tube heat exchanger in a solar water distiller system. The device is composed of a glass heat exchanger, which served as a condenser for vapor condensing which were produced in black paint solar absorber. It was also composed of a tank for water source and a tank for produced distilled water. Shell and tube was designed and simulated using an implicit numerical scheme. Simulation results showed that accumulated mass water greatly depended on the inlet vapor temperature and volume, heat exchanger material, coolant water temperature and volume. Thus, changing the material from stainless steel to glass in the same condition （vapor temperature, vapor volume, coolant temperature and coolant volume）. These inexpensive shell and tube heat exchangers permitted to produce 40 litre/day, distilled water from vapor with 378 K inlet temperature in atmosphere pressure. If inlet pressure increases, vapor temperature will decline and thereupon, heat exchanger＇s efficiency tangibility will increase.

Waste Frying Oils-Based Biodiesel: Process and Fuel Properties

The conversion of waste frying oil into a valuable methyl ester (biodiesel) has been successfully conducted and also the acid pre-treatment process was carried out prior to the main biodiesel production process for lowering waste frying oil free fatty acid (FFA) content below 1%. The physicochemical properties of biodiesel were analyzed to ensure the product could meet the standards of fuel properties. The methanolysis was selected as the biodiesel production technique under various mixing speeds namely 350, 400 and 450 rpm, while the other parameters are maintained at the optimum process conditions such as methanol to oil molar ratio is 6:1, percentage of catalyst loading is 1.0% wt, reaction temperature is 60℃, and reaction time is 50 min. Also, the investigation on the kinematic viscosity, density and flash point of biodiesel was performed against a number of rpm. The standards of ASTM D 6751 were applied to measure the entire prescribed properties of biodiesel. The highest yield of biodiesel obtained was 99%. The values of flash point, kinematic viscosity and density were in the range of specified limitations. Other biodiesel properties fulfilled the diesel engine application requirements.

Comparative performance of different urea coating materials for slow release

Approximately 70%of the applied urea fertilizer may be lost into the environment.This loss is due to leaching,decomposition and ammonium volatilization in soil,water and air.Through coating,the slow release technology can be used to reduce losses and to increase the fertilizer efficiency.Sulfur has been used as a coating material,but the coating cracks easily because of its friability,sometimes being peeled off from the urea surface.In this study,four types of materials,namely,gypsum,cement,sulfur and zeolite,were mixed and used as coating materials to search for the most effective and cheap coating materials.The primary reasons for selecting these materials were improving fruit quality and preventing plant diseases,providing a plant nutrient,increasing soil fertility and water retention.The materials were also selected based on their availability,processiblity and price.The effects of the coating materials,thickness,drying time,sieving and sealant on the crushing strength and dissolution rate of urea were investigated.Coated urea with the same proportion of gypsum-sulfur exhibited high crushing strength and lower dissolution rate.However,the performance was further enhanced by applying molten paraffin wax on the hot urea surface.SEM images demonstrated that the micro-structure of gypsum-sulfur coated urea after sieving resulted in a smoother coated layer.The efficiency of the coated urea was improved by26%using gypsum-sulfur（20%total coating）,3%paraffin wax and sieving the coating materials before application.

New coating formulation for the slow release of urea using a mixture of gypsum and dolomitic limestone

The use of urea and urea-based fertilizers has increased considerably over the past 15 years. They cur- rently account for approximately 51% of the world＇s agricultural nitrogen consumption. However, about 20-70% of the applied urea fertilizer is lost to the environment, causing serious pollution and increasing costs. These losses come from leaching, decomposition, and ammonium volatilization in the soil during handling and storage. Controlled release by coating can be used to increase urea fertilizer efficiency. We studied the use of gypsum, sulfur, and ground magnesium lime as cost-effective coating materials. All these coating materials contain nutrients required by plants. The effects of the coating composition and proportion of sealant on the rate of urea release and the crushing strength of the coated urea were investigated. We found that coated urea with the same proportion of gypsum-ground magnesium lime （GML） exhibited low urea release and high crushing strength. The performance was enhanced when using polyols as a sealant on the surface of the coated urea. A surface morphology analysis indicated a uniform and smooth surface on the coated film. The efficiency of the coated urea improved by 34.2% when using gypsum-GML （ 1：1 ratio） containing 1.1% oolvols.

Response surface methodology analysis of the photocatalytic removal of Methylene Blue using bismuth vanadate prepared via polyol route

Visible-light driven photocatalyst bismuth vanadate （BiVO4） photocatalyst was synthesized by the polyol route using ethylene glycol. The precipitate was washed, dried and calcined at 450℃ for 3 hr. The sample was characterized by X-ray diffractometry （XRD）, field emission scanning electron microscopy （FE-SEM）, zeta potential, surface area （BET method） and band gap energy via diffuse reflectance spectroscopy （DRS）. The synthesized BiVO4 has a monoclinic phase with a surface area of 4.3 m2/g and a band gap energy of 2.46 eV. A majority of the particles were in the range of 90-130 nm as obtained from the particle size distribution histrogram. The efficiency of the sample as a visible-light driven photocatalyst was examined by photodegrading Methylene Blue （MB）. The effects of some operational photodegradation parameters such as mass loading, initial dye concentration and pH were also examined. Experimental design methodology was applied by response surface modeling and optimization of the removal of MB. The multivariate experimental design was employed to develop a quadratic model as a functional relationship between the percentage removal of MB and three experimental factors （BiVO4 loading, MB initial concentration and pH）. The percentage removal of MB approached 67.21% under optimized conditions. In addition, a satisfactory goodness-of-fit was achieved between the predictive and the experimental results.

Preparation and Properties of Poly(vinyl alcohol)/Chitosan Blend Bio-nanocomposites Reinforced by Cellulose Nanocrystals

The aim of this paper is to report the effect of the addition of cellulose nanocrystals（CNCs） on the mechanical, thermal and barrier properties of poly（vinyl alcohol）/chitosan（PVA/Cs） bio-nanocomposites films prepared through the solvent casting process. The characterizations of PVA/Cs/CNCs films were carried out in terms of X-ray diffraction（XRD）, transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, thermogravimetric analysis（TGA and DTG）, oxygen transmission rate（OTR）, and tensile tests. TEM and SEM results showed that at low loading levels, CNCs were dispersed homogenously in the PVA/Cs matrix. The tensile strength and modulus in films increased from 55.1 MPa to 98.4 MPa and from 395 MPa to 690 MPa respectively, when CNCs content went from 0 wt% to 1.0 wt%. The thermal stability and oxygen barrier properties of PVA/Cs matrix were best enhanced at 1.0 wt% of CNCs loading. The enhanced properties attained by incorporating CNCs can be beneficial in various applications.

Numerical modelling for lubrication of the rolling process line contact by hard EHL theory using boundary elebent method

The contact characteristics of rigid cylinders lubricated by Newtonian liquids are inves-tigated in this paper using hard elastohydrodynamic lubrication (EHL) theory. Numerical modelingis formulated for the coupled set of generalized pressure and plane strain elasticity equations for afinite plane model and a circular representation of the junction under a pure hard rolling line con-tact using boundary element method (BEM). Also a numerical routine is developed to compute filmthickness and pressure profiles and the results are evaluated for a range of possible dimen-sionless parameters such as speed and load. The hydrodynamic equation is also transformed intoa form of boundary integral equation, which is solved by Simpson’s rule. The elasticity equationwith boundary conditions was solved by constant and quadratic elements based on an iterativeprocedure by assuming an initial film thickness. From the comparative study between the presentNewtonian model and the previously published results proved to be very effective and efficient andhigh precision is easily achieved for such rolling elements as well. The computed results areshown to be amenable to standard boundary element formulation of EHL problem in the contactregion and show that speed and load have influential effects on the lubricating film shape.

Complex dielectric modulus and relaxation response at low microwave frequency region of dielectric ceramic Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54)

The desirable characteristics of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54)include high dielectric constant,low loss tangent,and high quality factor developed a new field for electronic applications.The microwave dielectric properties of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54),with x?0:15 ceramics at different sintering temperatures(600–1300C)were investigated.The phenomenon of polarization produced by the applied electric field was studied.The dielectric properties with respect to frequency from 1MHz to 1.5 GHz were measured using Impedance Analyzer,and the results were compared and analyzed.The highest dielectric permittivity and lowest loss factor were defined among the samples.The complex dielectric modulus was evaluated from the measured parameters of dielectric measurement in the same frequency range,and used to differentiate the contribution of grain and grain boundary.

Morphology and dielectric properties of single sample Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)nanoparticles prepared via mechanical alloying

Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials.Nickel-zinc ferrite nanoparticles with composition Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties.The single sample with nanosized pellet was sintered from 600℃to 1200℃and analyzed by X-ray diffraction(XRD)to investigate the phases of the powders and by field emission scanning electron microscopy(FESEM)for the morphology and microstructure analyses.Dielectric properties such as dielectric constant(e″)and dielectric loss(e′)were studied as functions of frequency and temperature for Ni_(0.5)Zn_(0.5)Fe_(2)O_(4).The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30℃to 250℃.The results showed that single phase Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)cannot be formed by milling alone and therefore requires sintering.The crystallization of the ferrite sample increased with increasing sintering temperature,while the porosity decreased and the density and average grain size increased.Evolution of the microstructure resulted in three activation energies of grain growth,where above 850℃there was a rapid grain growth in the microstructure.Dielectric constant and loss factor decreased with the increase in frequency.The optimum sintering temperature of Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)was found to be 900℃which had high dielectric constant and low dielectric loss.

Application of GIS for the identification and demarcation of selective heavy metal concentrations in the urban groundwater

Groundwater is the most appropriate and widely used source of drinking water, which is increasingly threatened by pollution from industrial and agricultural activities. To check the severity of the problem, 156 groundwater samples were collected from various depths （60-110 ft） of 52 different localities in Faisalabad city, the third largest metropolis in Pakistan, and analyzed for the metals （Zn, Cu, Cd, Ni, Pb, Mn and Fe） concentration in 2009. Quantification was done by using Flame Atomic Absorption Spectrophotometer technique and the results were compared with WHO standards for drinking water quality. Results showed that the levels of Cu, Mn and Fe were below the WHO standards while the concentrations of Zn, Cd, Ni and Pb were above the recommended levels of safe drinking water. Correlation analysis among the occurrence of these heavy metals revealed a highly significant and positive correlation of Mn with Zn and Fe. A significant and positive correlation of Cd was also found with Cu and groundwater depth showing that there is strong association between Cu-Cd pair and that the Cd concentration varies with depth of groundwater in the study area. Regional patterns of heavy metals occurrence were mapped using Geographical Information System （GIS） for the identification and demarcation of risk areas. The concentration maps may be used by policymakers of the city to mitigate groundwater pollution.