Table of Contents - Volume 19 Number 2

This study investigates the effect of various fiber laser process parameters on texture diameter, depth and surface roughness of circular shaped textures fabricated on the commercially cast iron piston ring segments. Piston ring segments with hardness 410 HV, Young’s Modulus of 250 Gpa and surface roughness of 0.482 µm were used for the experimentation. The fiber laser system (Marko Laser, Germany), was used for the fabrication of textures on the cast iron segments having specifications like power of 20W, wavelength of 1062nm, maximum frequency 200KHz, maximum speed range of 15000 mm/s. The laser frequency, power, speed and number of loops are the input parameters which were varied to find its effect on the texture dimensions. The approximate target values to be achieved for circular texture dimensions are texture diameter of 100µm (bilateral tolerance of 10µm), texture depth of 20µm (bilateral tolerance of 3µm) and texture surface roughness of 3µm (bilateral tolerance of 0.5µm) respectively. A confocal microscope with three dimensional surface profiler was used to measure the surface topography of the textured surfaces. It has been observed that with increase in laser power initially texture diameter has been reduced but found to be increased for the maximum power condition, while dimple depth and surface roughness of the textures found to be increased gradually. Also with increase in frequency has not a significant effect on the texture diameter but the texture depth and surface roughness has been enhanced drastically. In the similar way with increase in the laser speed and number of loops, initially there was decrease in the texture dimensions but as the speed and number of loops increased the texture dimensions also has a slight enhancement on it. It may be concluded that laser power and laser frequency has a significant impact on the texture dimensions as compared to laser speed and number of loops. Also it can be summarized that for achieving the targeted values of the texture dimensions like texture diameter, texture depth and texture surface roughness on the piston ring surface the laser power of 12W, 8W and 8W, laser frequency of 25 KHz, 25 KHz and 20 KHz, laser scan speed of 170 mm/sec, 140 mm/sec and 110 mm/sec and number of laser loops of 5, 4 and 2 may be used respectively.

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This work aims to assess the enhancement of optical properties for porous GaN nanostructures, which fabricated by Photoelectrochemical etching under different current densities. The changing of optical properties for different samples were investigated by Photoluminescence (PL) spectroscopy. A strong near band-gap-edge emission (NBE) was detected with peak energy 3.40 eV for as-grown and sample etched at 5mA/cm2, while its 3.41 and 3.42 eV for samples etched with 10 and 20mA/cm2 respectively. Also, another peak emission from the sapphire substrate at peak 1.7 eV was observed. The PL peak intensity of the porous samples have increased with increasing the porosity, while the FWHM of the near-band-edge peak was decreased in 5 and 10mA/cm2 samples compared to as-grown non-etched sample, indicated that the pore size decreased with etching current density and porosity. Finally, the change of refractive with porosity was investigated in the porous GaN nanostructure.

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Present-day construction is greatly influenced by steel-concrete column composites. Steel-concrete composite gained extensive attention around the globe, which made steel-concrete composite utilization in construction more attractive than conventional reinforced cement concrete design. Different architectural culture has introduced inexhaustible diversification of different columns. One of the most widely used is concrete-encased columns. These columns are those in which steel is encased in reinforced concrete. Combining these two materials leads to less cross-sectional area, high rigidity, and improved lateral resistance. However, some construction difficulties are evident. A comprehensive overview of the state of the art of evolution of composite columns in building structures based on experimental numerical and analytical studies is emphasized in the paper. Moreover, replacing concrete with various materials such as cement aggregates, limestones, fly ash, and industrial waste is suggested to deal with the high cost of the construction.

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The binary and ternary adsorptions of Pb (II), methyl orange (MO) and brilliant blue (BB) on engineered biochar (Fe₂O₃-BC) nano-composite using pyrolysis and microwave activation were investigated in this work. Batch experiments were conducted to investigate the capacity of Fe₂O₃-BC to remove MO, Pb and BB in binary and ternary aqueous solutions. MO removal was higher in MO-Pb binary solution than in ternary MO solution. A large amount of adsorbent dosage, high concentration and longer time were witnessed to achieve maximum removals in ternary solutions as compared to binary solutions. The Langmuir plots indicated that the isotherm can be used to describe sorption studies of both MO dye and Pb²⁺, while Temkin isotherm was not in agreement with the results. The closeness of R² value to 1 indicated that the data obtained fits Langmuir Isotherm model of monolayer adsorption kinetics. It was concluded that the Fe₂O₃-BC nano-composite has a series of distinct homogeneous sites available for binding the MO anions in solution. Therefore, the use of Fe₂O₃-BC nano-composite for small scale community water purification is a novel cause.

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