Abstract: The piezoelectric material plays an important role in some special fields. Based on two-scale asymptotic method, the two-scale finite element computational algorithm of simulating the piezoelectric problem in periodic composite is given, the finite element approximate errors are analyzed, and some numerical examples are presented so as to show the effectiveness of the numerical algorithm.
Abstract: Gelatin in fibers form can be used for tissue engineering, wound dressing, or drug carrier. However, it is easily damaged if exposed to water. Thus, it was blended with cellulose acetate. Acetic acid was used as a solvent because it is less toxic. The mass ratios of gelatin to cellulose acetate of 10:0, 8:2, and 6:4 were as precursor solutions. Simple electrospinning was employed to produce gelatin/cellulose acetate fibers. From SEM images, it was shown that the average diameters of gelatin/cellulose acetate fibers from the precursor solutions of 10:0, 8:2, and 6:4 were 534, 649, and 765 nm, respectively. The addition of cellulose acetate increased the viscosity of gelatin/cellulose acetate solution. Moreover, gelatin mass reduction caused a decrease in conductivity of gelatin/cellulose acetate solution. Therefore, increasing in the viscosity or reducing in the conductivity of the precursor solution increased the average diameter of the gelatin/cellulose acetate fibers. The analysis of FTIR spectra showed that the structural changes of gelatin and cellulose acetate occurred after being transformed into gelatin/cellulose acetate nanofibers.
Abstract: One of the key factors that play an important role in the performance of a solid propellant rocket is dependent on its burning rate. A strand burner is a type of apparatus used to measure the propellant burning rate at elevated pressure. This study investigates the relation between burning rates of aluminized ammonium perchlorate at low pressure. Chamber pressure was varied from 1 atm, 3 atm, 5 atm and 7 atm. This study shows that propellant burning rate is about 50%-62% higher when the burn rate test is conducted at atmospheric condition compared to when it is done in inert gas. The investigation’s results also revealed an increasing propellant burning rate when the chamber pressure is increased. In conclusion, the burning condition and chamber pressure influences the propellant burning rate.
Abstract: This study examines the effect of Er2O3 addition (0 to 2.0 mol.%) on microstructure and electrical characteristics of ZnO-based varistor ceramics prepared by high energy ball milling and sintering at 1200 °C for 1 h. With increasing Er2O3 content, the densification process diminishes marginally, but the grain size reduces dramatically due to the formation of Er-rich phases that inhibit grain coarsening specifically when the amount of Er2O3 addition is above 0.1 mol.%. The ZnO-based varistor modified with incorporation of 0.5 mol.% Er2O3 exhibits excellent varistor properties, since the breakdown field is increased from 1324 to 2320 V cm-1 and the nonlinear coefficient is enhanced from 23.1 to 27.4 when compared with the un-added ones.
Abstract: This work is focused on studying the effect of liquid layer level (height above a target material) on zinc oxide nanoparticles (ZnO and ZnO2) production using liquid-phase pulsed laser ablation (LP-PLA) technique. A plate of Zn metal inside different heights of an aqueous environment of cetyl trimethyl ammonium bromide (CTAB) with molarity (10-3 M) was irradiated with femtosecond pulses. The effect of liquid layer height on the optical properties and structure of ZnO was studied and characterized through UV-visible absorption test at three peaks at 213 nm, 216 nm and 218 nm for three liquid heights 4, 6 and 8 mm respectively. The obtained results of UV–visible spectra test show a blue shift accompanied with decreasing the liquid level above the target due to the increase in ablation rate and particles production. This blue shift indicates getting a smaller size of nanoparticles and the quantum confinement property of nanoparticles. Also the FTIR transmittance spectra of ZnO2 nanoparticles prepared in these states show a characteristic ZnO absorption at 435 cm−1 – 445 cm−1.
Abstract: Spectroscopy Fourier Transform Infrared (FTIR) – Attenuated Total Reflectance (ATR) used to study the surface of polymeric materials on polymeric substrates using a sensitive technique for chemical profiling, study of reflection spectroscopy, and a non-invasive. In this study we will investigate of Polytetrafluoroethylene (PTFE) deposition in carbon composite paper without damaging its structure by FTIR-ATR. Carbon composite paper was prepared by mixing the carbon material from coconut fiber and polymer binder in xylen as solvent, casted on glass substrate, and then rolled to make a sheet. Coating process was done by dipped the carbon composite paper in the PTFE suspension with different content of 10 wt%, 20 wt% and 30 wt% for 30 minutes and dried at room temperature for one night and heated at 150°C for 30 minutes, and finally heated at 350°C for 30 minutes to melt the PTFE. All samples were analyzed by using FTIR-ATR and SEM-EDS. Deposition of PTFE with different content in carbon composite papers could be observed by FTIR-ATR. The peaks located at near 1205 cm-1 and 1154cm-1 with different intensity for each PTFE contents. FTIR-ATR could be used as a pre-detection method of PTFE deposition in carbon composite paper before using SEM-EDS, because FTIR-ATR would be reflected at the highly reflective surface.
Abstract: The corrosion inhibition of Garcinia indica extract (GIE) on 6063 aluminum alloy was investigated in 0.5 M sodium hydroxide (NaOH) solution by weight loss method and Tafel polarization techniques. The effects of inhibitor concentrations, temperature on the inhibitor action were investigated. Inhibition efficiency was found to increase with increase in concentration of inhibitor and it increased with increase in the temperature. The kinetic parameters and thermodynamic parameters were calculated. The adsorption of GIE was found to be through chemisorption and obeyed Langmuir adsorption isotherm.
Abstract: The bimetallic weld joints are widely utilized in the pressurized water reactors, boiling water reactors, heat exchangers in process industries, heat transport piping system utilized in nuclear plants, etc. The present study is aimed at analyzing the bimetallic weld strength degradation due to thermal fatigue. For generating thermal fatigue like conditions, an experimental test rig has been developed. The bimetallic weld between low alloy steel SA 516 grade 70 and stainless steel 304 L was prepared. The experimental results show that, heating time, notch radius and number of cycles have the effect on tensile properties of bimetallic welds.
Abstract: In this paper, an attempt has been made to apply the neural network (NN) techniques to predict the mechanical properties of friction stir welded composite materials. Nowadays, friction stri welding of composites are predominatally used in aerospace, automobile and shipbuilding applications. The welding process parameters like rotational speed, welding speed, tool pin profile and type of material play a foremost role in determining the weld strength of the base material. An error back propagation algorithm based model is developed to map the input and output relation of friction stir welded composite material. The proposed model is able to predict the joint strength with minimum error.
Abstract: High performance fabrics are preferable for armor systems due to their lightweight structure and flexibility. High performance fabrics are generally used in body armor design for personal protection. However, these fabrics are utilized to cover the living space in military vehicles such as helicopters and armored vehicles. Besides, pilot seats in combat helicopters are included in utilization area of high performance fabrics. On the other hand armor is defined as a defensive covering to protect body or something against attacking threats. Protection is provided by absorbing the kinetic energy of the attacking threats and stopping them before any damage occurs in the target. This paper offers an overview of high performance fabrics in armor systems.