Flow and heat transfer of two immiscible fluids in double-layer optical fiber coating

The coatings of optical fibers are generally characterized by a multi-layer coating structure. In this work, the mathematical modeling of two immiscible non-Newtonian fluids for optical fiber coating inside a straight annular die is developed in the form of a nonlinear differential equation with nonhomogeneous boundary conditions. Two non-Newtonian fluids, namely power law and Phan-Thien–Tanner fluids, are used in the primary and secondary coating dies, respectively. An exact solution is obtained for velocity fields and temperature distributions for the primary and secondary coating resins. The thickness of coated fiber optics is also calculated for both layers. The effect of different emerging parameters on the solution is discussed and sketched.     

Mathematical Modeling of Wear Characteristics of 6061 Al-Alloy-SiCp Composite Using Response Surface Methodology

In the light of attractive wear characteristics as well as high strength to weight ratio, extensive research on Al-based Metal Matrix Composite (MMC) have been carried out globally in the last two decades. However, very limited research has been pursued on tribological behavior of Al-based MMC under combined action of rolling and sliding. This study investigates the wear behavior of 6061 Al-alloy/SiC with 10 vol.% SiCp against hardened and tempered AISI 4340 steel under combined rolling-sliding conditions. 2³ factorial design of experiments have been carried out to see the effect of few parameters, i.e., contact stress, speed and duration with respect to wear. The interaction effect has also been studied by 3D graphical contours. A mathematical model is developed using regression analysis technique for prediction of wear behavior of the MMC and adequacy of the model has been validated using analysis of variance (ANOVA) techniques. Finally, the optimization of parameter has also been done using Design Expert software. The results have shown that Response Surface Methodology (RSM) is an effective tool for prediction of wear behavior under combined sliding and rolling action. It is also found that the wear of MMC is much lower than hardened; tempered AISI 4340 steel and rolling speed has the maximum influence in wear of both materials under investigation.     

Treatment of simulated arsenic contaminated groundwater using GAC‐Cu in batch reactor: Optimization of process parameters

This article deals with the experimental investigation related to the removal of arsenic from a simulated contaminated groundwater by the adsorption onto Cu²⁺ impregnated granular activated carbon (GAC‐Cu) in presence of impurities like Fe and Mn. The effects of adsorbent concentration, pH, and temperature on the percentage removal of total arsenic (As(T)), As(III), and As(V) have been discussed. Under the experimental conditions, the optimum adsorbent concentration for GAC‐Cu has been found to be 6 g/L with an agitation time of 24 h, which reduces the As(T) concentration from 188 to 8.5 µg/L. Maximum removal of As(V) and As(III) has been observed in the pH range of 7–9 and 9–11, respectively. Removal of all the above said arsenic species decreases slightly with increase in temperature. Presence of Fe and Mn increases the adsorption of arsenic species. Under the experimental conditions, at 30°C, maximum % removals of As(T), As(III), As(V), Fe, and Mn are found to be 95.5%, 93%, 98%, 100%, and 40%, respectively. It has also been observed that maximum regeneration (～94%) of spent GAC‐Cu is exhibited by a 5NH₂SO₄ solution.     

Microstructure and water vapor transport properties of functionalized carbon nanotube‐reinforced dense‐segmented polyurethane composite membranes

This work investigates the influence of functionalized multiwall carbon nanotube (MWNT) on microstructure and water vapor transport properties of segmented polyurethane (SPU) membranes. SPUs were reinforced with four different concentration of MWNT viz. 0.25, 0.50, 1.0, and 2.5 wt%. Presence of the microcrystals in all SPU‐MWNT composite membranes was detected by wide angle X‐ray diffraction (WAXD). The percent crystallinity of SPU‐MWNT at 0.25 wt% content of MWNT was increased slightly when compared with the pristine SPU sample. However, further increase of MWNT decreases the order structure. Glass transition temperature was increases with increasing MWNT content in the SPUs, which signifies that MWNT could also affect the amorphous region of SPU. WAXD and transmission electron microscopy (TEM) results evidenced the interaction between SPUs and MWNT. In comparing the water vapor transport properties of MWNT‐SPU composite membranes, it was observed that at 0.25 wt% of MWNT in SPU, water vapor transport property increases slightly at soft segment crystal melting temperature. Further increase of MWNT content has no significant influence on the water vapor transport properties. However, at 2.5 wt% of MWNT in SPU matrix, water vapor transport was decreases due to the increase of stiffness in the polymer chains. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Enhanced Phase Stability and Photoluminescence of Eu3+ Modified t-ZrO2 Nanoparticles

Tetragonal ( t ) ZrO₂ nanoparticles have been obtained by a partial Eu³⁺→Zr⁴⁺ substitution, synthesized using a simple oxalate method at a moderate temperature of 650°C in air. The Eu³⁺ additive, 2 mol% used according to the optimal photoluminescence (PL), gives small crystallites of the sample. On raising the temperature further, the average crystallite size D grows slowly from 16 nm to a value as big as 49 nm at 1200°C. The Eu³⁺: t -ZrO₂ nanoparticles have a wide PL spectrum at room temperature in the visible to near-IR regions (550–730 nm) in the ⁵D₀→⁷F_J (Eu³⁺), J =1–4, electronic transitions. The intensity of the ⁵D₀→⁷F₄ group is as large as that of the characteristic ⁵D₀→⁷F₂ group of the spectrum in the forced electric-dipole allowed transitions. The enhanced t -ZrO₂ phase stability and wide PL can be attributed to the combined effects of an amorphous Eu³⁺-rich surface and part of the Eu³⁺ doping of ZrO₂ of small crystallites.     

高非线性光子晶体光纤中布拉格光栅的制作

采用相位掩模版法实验研究了高非线性掺锗光子晶体光纤中布拉格光栅的制作。实验中采用的光子晶体光纤的非线性系数约为12 W^－1km^－1,模场直径约为2.4 mm。 分析了布拉格光栅的反射率随着曝光脉冲数的变化,随着曝光脉冲数的增加其反射率逐渐达到饱和,继续增加曝光量发射率开始下降。实验验证了可以在高非线性光子晶体中写入布拉格光栅,得到光栅的反射率为44.4%,这对于研究光纤布拉格光栅的非线性效应和应用具有重要意义。讨论了影响布拉格光栅写入效率的因素。     

Investigation of waste heat recovery system at supercritical conditions with vehicle drive cycles

Waste heat recovery (WHR) for internal combustion engines in vehicles using Organic Rankine cycle (ORC) has been a promising technology. The operation of the ORC WHR system in supercritical conditions has a potential to generate more power output and thermal efficiency compared with the conventional subcritical conditions. However, in supercritical conditions, the heat transfer process in the evaporator, the key component of the ORC WHR system, becomes unpredictable as the thermo-physical properties of the working fluid change with the temperature. Furthermore, the transient heat source from the vehicle’s exhaust makes the operation of the WHR system difficult. We investigated the performance of the ORC WHR system at supercritical conditions with engine’s exhaust data from real city and highway drive cycles. The effects of operating variables, such as refrigerant flow rates, evaporator and condenser pressure, and evaporator outlet temperature, on the performance indicators of the WHR system in supercritical conditions were examined. Simulation of operating parameters and the boundary of the WHR system are also included in this paper.

     

Titanium machining with new plasma boronized cutting tools

Titanium is a commonly used material in various critical applications such as aerospace and biomedical applications. In this article, for the first time in the literature, development and implementation of a novel plasma boronizing process on Tungsten Carbide (WC) cutting tools is introduced. Plasma boronizing on WC tools is performed with gas combination of 10% BF₃, 40% Argon and 50% H₂ at different temperatures and durations. Performance enhancements of plasma boronized WC tools on Titanium (Ti-6Al-4V) machining are investigated under various cutting conditions. It is found that new plasma boronizing of WC is a very cost effective solution for significantly increasing tool life in Titanium machining.     

Effect of microstructure and chemical composition of hardfacing alloy on abrasive wear behavior

Hardfacing, a surface modification technique, is used to rebuild the surface of a workpiece. The economic success of the process depends on selective application of hardfacing material and its chemical composition for a particular application. In this context, three hardfacing electrodes having different chemical compositions have been selected and their abrasive wear responses was compared with that of mild steel. The emphasis has been made to realize the effect of microstructure and chemical composition on the wear response of the hardfacing material with respect to mild steel. It has been observed that the wear rate of hardfacing alloys is lower than that of mild steel. The hardfacing alloy having the highest chromium content exhibits the lowest wear rate.     

Effect of Varying Amount of Polyethylene Glycol (PEG-600) and 3-Aminopropyltriethoxysilane on the Properties of Chitosan based Reverse Osmosis Membranes

Chitosan and polyethylene glycol (PEG-600) membranes were synthesized and crosslinked with 3-aminopropyltriethoxysilane (APTES). The main purpose of this research work is to synthesize RO membranes which can be used to provide desalinated water for drinking, industrial and agricultural purposes. Hydrogen bonding between chitosan and PEG was confirmed by displacement of the hydroxyl absorption peak at 3237 cm⁻¹ in pure chitosan to lower values in crosslinked membranes by using FTIR. Dynamic mechanical analysis revealed that PEG lowers Tg of the modified membranes vs. pure chitosan from 128.5 °C in control to 120 °C in CS-PEG5. SEM results highlighted porous and anisotropic structure of crosslinked membranes. As the amount of PEG was increased, hydrophilicity of membranes was increased and water absorption increased up to a maximum of 67.34%. Permeation data showed that flux and salt rejection value of the modified membranes was increased up to a maximum of 80% and 40.4%, respectively. Modified films have antibacterial properties against Escherichia coli as compared to control membranes.