Enhancing Sensitivity of Fiber Bragg Grating-Based Temperature Sensors through Teflon Coating

Wireless Personal Communications - As global warming and climate change persistently threaten our planet, especially in developing countries, environmental monitoring becomes more and more...     

Hybrid sine cosine artificial bee colony algorithm for global optimization and image segmentation

Artificial bee colony (ABC) algorithm is an efficient biological-inspired optimization method, which mimics the foraging behavior of honey bees to solve the complex and nonlinear optimization problems. However, in some cases, it suffers from inefficient exploration, low exploitation and slow convergence rate. These shortcomings cause the problem of stagnation at local optimum which is dangerous in determining the true solution (optima) of the problem. Therefore, in the present paper, an attempt has been made toward the removal of the drawbacks from the classical ABC by proposing a novel hybrid method called SCABC algorithm. The SCABC algorithm hybridizes the ABC with sine cosine algorithm (SCA) to upgrade the level of exploitation and exploration in the classical ABC algorithm. The SCA is a recently introduced algorithm, which uses the trigonometric functions sine and cosine to perform the search. The validation of the SCABC algorithm is performed on a well-known benchmark set of 23 optimization problems. The various analysis metrics such as statistical, convergence and performance index analysis verify the better search ability of the SCABC as compared to classical ABC, SCA. The comparison with some other optimization algorithms demonstrates a comparatively better state of exploitation and exploration in the SCABC algorithm. Moreover, the SCABC is also employed on multilevel thresholding problems. The various performance measures demonstrate the efficacy of the SCABC algorithm in determining the optimal thresholds of gray images.

     

Excellent boron emitter passivation for high‐efficiency Si wafer solar cells using AlOx/SiNx dielectric stacks deposited in an industrial inline plasma reactor

Excellent passivation of boron emitters is realised using AlO_x/SiN_x dielectric stacks deposited in an industrial inline plasma‐enhanced chemical vapour deposition reactor. Very low emitter saturation current density (J_0e) values of 10 and 45 fA/cm² are obtained for 180 and 30 Ω/sq planar p⁺ emitters, respectively. For textured p⁺ emitters, the J_0e was found to be 1.5–2 times higher compared with planar emitters. The required thermal activation of the AlO_x films is performed in a standard industrial fast‐firing furnace, making the developed passivation stack industrially viable. We also show that an AlO_x thickness of 5 nm in the AlO_x/SiN_x stack is sufficient for obtaining a J_0e of 18 fA/cm² for planar 80 Ω/sq p⁺ emitters, which corresponds to a 1‐sun open‐circuit voltage limit of the solar cell of 736 mV at 25 °C. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrospun mat of thermal-treatment-induced nanocomposite hydrogel of polyvinyl alcohol and cerium oxide for biomedical applications

Hydrogels are one of the most thought-provoking formulations used widely for biomedical applications. In the present investigation, poly(vinyl) alcohol (PVA) and its cerium oxide (CO) composite-based hydrogels were prepared by the combination of electrospinning and thermal processing technique. The partial crosslinking, along with time-controlled heating (10 min), delivered PVA hydrogel. The mechanism was explained with Fourier-transform infrared spectroscopy analysis, where the hydroxyl group disappeared in long-duration (30 min) of heat treatment and they retain in lesser duration. The heat-treated PVA transformed from amorphous to crystalline, since the T_g of PVA disappeared in 30 min heat treatment, while the T_g increased to 85°C (10 min heat treatment) from 70°C in PVA, suggested the full and partial crystallinity. The swelling and porosity studies reveal the hydrogel formation of heat-treated PVA. Interestingly, CO reinforced PVA composites show better swelling with respect to heat-treated PVA. Furthermore, CO reinforced PVA hydrogel demonstrated better biocompatibility platelet adhesion and accelerated wound healing competence.     

Surface alloying of miniature components by micro-electrical discharge process

Surface alloying is necessary to enhance the surface features of machine elements. In the present study, feasibility of micro-electric discharge machining (micro-EDM) process for surface alloying has been investigated. Experiments are conducted on Nickel sheets using tool of Ti6Al4V with EDM oil and kerosene as dielectric. The surface modification takes place by spark discharges on localized regions of the work piece and the tool surface causing melting of tool and work piece, disassociation of dielectric, alloying, and quenching in the electrolyte. The samples were analyzed by field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, microhardness testing machine, and X-ray diffraction. Recast layers obtained have distinct structure and composition as compared to the work piece. Average recast layer thickness varied from 10.72 to 69.8?µm in case of EDM oil and from 13.5 to 31.6?µm in case of kerosene by varying voltage, pulse duration (on time) and frequency during the experiment. The microhardness of the machined surfaces was obtained in a wide range of 161.61–338.25 HV whereas the microhardness of unaffected base metal was 132.25 HV. Titanium carbide (TiC) was deposited and consequently there was improvement in the hardness of the work piece.     

Harmonized salp chain-built optimization

As an optimization paradigm, Salp Swarm Algorithm (SSA) outperforms various population-based optimizers in the perspective of the accuracy of obtained solutions and convergence rate. However, SSA gets stuck into sub-optimal solutions and degrades accuracy while solving the complex optimization problems. To relieve these shortcomings, a modified version of the SSA is proposed in the present work, which tries to establish a more stable equilibrium between the exploration and exploitation cores. This method utilizes two different strategies called opposition-based learning and levy-flight (LVF) search. The algorithm is named m-SSA, and its validation is performed on a well-known set of 23 classical benchmark problems. To observe the strength of the proposed method on the scalability of the test problems, the dimension of these problems is varied from 50 to 1000. Furthermore, the proposed m-SSA is also used to solve some real engineering optimization problems. The analysis of results through various statistical measures, convergence rate, and statistical analysis ensures the effectiveness of the proposed strategies integrated with the m-SSA. The comparison of the m-SSA with the conventional SSA, variants of SSA and some other state-of-the-art algorithms illustrate its enhanced search efficiency.

     

Engineered Smart Textiles and Janus Microparticles for Diverse Functional Industrial Applications

Janus materials are biomimetically inspired systems with two or more functional properties arising as paramount materials for utilization in different fields like Medical, Protective clothing etc. Janus particles can be in different forms like capsule, fiber, nano cage, disc, nano film etc. which are amalgamated with fabric by different processes. Based on the fabrication and constituent elements, Janus materials can be fabricated by incorporating multiple properties like fire-retardancy, catalytic property, thermal regulation etc. This review article enumerates the numerous industrial applications of the Janus fabrics and simultaneously outlines the extensive methodologies utilized for engineering of the Janus fabrics.     

Propylene glycol and ethylene glycol recovery from aqueous solution via reactive distillation

Propylene glycol (PG) and ethylene glycol (EG) are recovered from aqueous solution via reaction with acetaldehyde to form acetals in a reactive distillation column. The reaction takes place over Amberlyst 15 cationic exchange resin catalyst, held in structured packing in the column reactive zone. Gycol solution is fed to the column at the top of the reactive zone and acetaldehyde is fed at the bottom of the reactive zone. The acetals produced, 2,4-dimethyl-1,3-dioxolane from PG and 2-methyl-1,3-dioxolane from EG, form minimum-boiling azeotropes with water and exit the top of the column along with excess acetaldehyde; residual water exits the column as the bottoms stream. In a pilot-scale column, steady-state PG conversions of over 90% are obtained. Hydrolysis of both acetals is rapid and allows complete recovery of high purity PG and EG and recycle of acetaldehyde. Simulation of PG acetalization using a kinetic rate-based model in AspenPlus process simulation software gives good agreement with experimental data using an HETP of . The proposed recovery scheme has application for PG and EG recovery from pure polyol solutions and from mixed polyol streams such as those generated in carbohydrate hydrogenolysis.     

Fiber-reinforced composites in milling and grinding: machining bottlenecks and advanced strategies

Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight. The composite components are manufactured by near net-shape and only require finishing operations to achieve final dimensional and assembly tolerances. Milling and grinding arise as the preferred choices because of their precision processing. Nevertheless, given their laminated, anisotropic, and heterogeneous nature, these materials are considered difficult-to-machine. As undesirable results and challenging breakthroughs, the surface damage and integrity of these materials is a research hotspot with important engineering significance. This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature. First, the formation mechanisms of milling damage, including delamination, burr, and tear, are analyzed. Second, the grinding mechanisms, covering material removal mechanism, thermal mechanical behavior, surface integrity, and damage, are discussed. Third, suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies, including ultrasonic vibration-assisted machining, cryogenic cooling, minimum quantity lubrication (MQL), and tool optimization design. Ultrasonic vibration shows the greatest advantage of restraining machining force, which can be reduced by approximately 60% compared with conventional machining. Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%. MQL shows its advantages in terms of reducing friction coefficient, force, temperature, and tool wear. Finally, research gaps and future exploration directions are prospected, giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites.     

Temperature‐dependent modeling and performance analysis of coupled MLGNR interconnects

The temperature‐dependent circuit modeling and performance in terms of propagation delay, power dissipation, and crosstalk‐induced voltage waveform at the far end of victim line of multilayer graphene nanoribbon (MLGNR) interconnects have been analyzed at 22 nm technology node. A comparative performance analysis between MLGNR interconnects with resistance estimated using temperature‐dependent model and temperature‐independent model is examined. The results obtained are also compared with capacitively coupled interconnects of copper (Cu). The results show that as the temperature is varied from 300 K to 500 K, MLGNR has lower propagation delay and power dissipation as compared to Cu for 1 mm long interconnects. It is also observed that because of the dominance of both low resistance and ground capacitance compared to Cu, MLGNR has better crosstalk‐induced delay and voltage waveforms with rise in temperature at the far end of aggressor and victim line, respectively. Further, simulated results show an average relative improvement in propagation delay of 37.24% and corresponding improvement in power dissipation of approximately 19.59% by using a temperature‐dependent model in comparison to a temperature‐independent model of MLGNR resistance with interconnect lengths varying from 200 to 1000 μm. The reduction in the time duration of victim output pulse over these interconnect lengths also shows a significant improvement of approximately 35% by using temperature‐dependent model as against temperature‐independent model of MLGNR resistance.