On the infiltration behavior of Al, Al-Li, and Mg meltas through SiC p bed

Aluminum, Al-Li(8090), and Mg matrix composites with uniform distributions of SiC _p reinforcement have been prepared by the vacuum infiltration technique. The infiltration kinetics have been found to increase in the order of Al, Al-Li, and Mg. The Al-Li alloy and Mg as matrix materials have shown improved wettability with SiC _p in comparison to Al, leading to enhanced infiltration kinetics and reduced reinforcement degradation in the former cases. The infiltration kinetics are insensitive to preheat temperature beyond a critical temperature, which is close to the melting point of the matrix. A marginal improvement in infiltration kinetics could be obtained with Cu and Ni coating on SiC and on its dynamic oxidation. The improvement is significant at a higher preheat temperature of SiC. The Vickers hardness, measured on the SiC particles, has been shown to be an index of the strength of the interface between the matrix and reinforcement in the composite.     

An experimental analysis of effective high speed turning of superalloy Inconel 718

Superalloy, Inconel 718 is widely used in the sophisticated applications due to its unique properties. However, machining of such superior material is difficult and costly due its peculiar characteristics. The present article is an attempt to suggest Taguchi optimization technique to study the machinability of Inconel 718 with respect to cutting force, cutting temperature, and tool life in high speed turning of Inconel 718 using cemented tungsten carbide (K20) cutting tool. Therefore, the objective of this work is divided into two phases: (i) to demonstrate a correlation between cutting speed, feed, and depth of cut with respect to cutting force, cutting temperature, and tool life in a process control of high speed turning of Inconel 718 in order to identify the optimum combination of cutting parameters; (ii) to show the effect of high speed cutting parameters on the tool wear mechanism and chip analysis. These correlations were obtained by multiple linear regressions. The confirmation tests were carried out to make a comparison between the experimental results and mathematical models proposed. The proposed models agree well with the experimental results.     

Enzyme-Assisted Process for Production of Superior Quality Vanilla Extracts from Green Vanilla Pods Using Tea Leaf Enzymes

Vanilla planifolia Andrews is a perennial tropical vine and is an orchid grown for its pleasant flavor. There is an increasing trend world over for using natural flavors. Vanilla being an important food flavoring ingredient, the demand for natural vanilla extract is increasing. Hence, the aim of the present study was to prepare vanilla extract from green beans without going through the elaborate and time-consuming conventional curing process. Vanilla beans after size reduction were mixed in a suitable proportion with tea leaf enzyme extract (TLEE) and incubated to facilitate action of enzymes on vanilla flavor precursors. The beans mix was squeezed, and the filtrate was treated with ethanol to extract the vanilla flavor. TLEE-treated extracts had higher vanillin content (4.2%) compared to Viscozyme extract (2.4%). Also, it had higher intensity of vanilla flavor, sweet, and floral notes. Further, electronic nose analysis confirmed the discrimination between extracts. It was concluded that the use of TLEE is very much useful to obtain higher yield of vanilla extract and superior quality vanilla flavor, which avoids the traditional laborious and time-consuming curing process.     

Tribological Investigation of AZ91/SiC Magnesium Hybrid Composite under Dry,Oil and Nanofluids Lubricating Conditions

Silicon - In present research AZ91D/SiC composites were developed using advanced vacuum assisted stir casting process. The tribological properties of AZ91D/SiC composites under dry, oil and...     

Effect of sodium sulfite,tartaric acid,tannin, and glucose on rheological properties,release of aroma compounds,and color characteristics of red wine

Food Science and Biotechnology - In this study, we evaluated the effect of addition of non-volatile compounds (sodium sulfite, tartaric acid, tannin, and glucose) on the rheological properties,...     

Parameter Optimization of Rotary Ultrasonic Machining on Quartz Glass Using Response Surface Methodology (RSM)

In the current research, rotary ultrasonic machining was used to drill holes in quartz material. The effect of different RUM parameters namely tool feed rate, tool rotational speed and ultrasonic power on material removal rate and surface roughness has been studied experimentally. The response surface methodology with central composite design has been used to design the experiments. From the desirability approach, the optimum setting of the rotary ultrasonic machining parameters was found to be the tool rotational speed of 4968 rpm, feed rate of 0.55 mm/min, and ultrasonic power of 80% for achieving the maximum MRR of 0.2135 mm3/s and minimum SR of 0.3685 μm. Microstructure analysis of the machined surface was performed by using scanning electron microscopy in order to study the mechanisms of material removal under the different settings of RUM parameters. It was observed that at very low feed (0.08 mm/min) and high rpm (5681) the material is predominantly removed by plastic deformation whereas at high feed (0.92 mm/min) and low rpm (2318) the material is removed by brittle fracture.     

Cryptanalysis and improvement of authentication scheme for roaming service in ubiquitous network

Abstract

The paper analyzes a recently proposed secure authentication and key agreement scheme for roaming service in a ubiquitous network. In 2018, Lee et al. proposed a biometric-based anonymous authentication scheme for roaming in ubiquitous networks. But, we found that Lee et al. scheme is prone to the off-line dictionary attack when a user’s smart device is stolen, replay attack due to static variables and de-synchronization attack when an adversary blocks a message causing failure of authentication mechanism. Further, the scheme lacks no key control property and has incorrect XOR calculation. In the sequel, we presented an improved biometric based scheme to remove the weaknesses in Lee et al.’s scheme, which also does not require an update of identity in every session, hence preventing de-synchronization attack. Also, the security of the proposed schemes were analyzed in a widely accepted random oracle model. Further, computational and communication cost comparisons indicate that our improved scheme is more suitable for ubiquitous networks.     

Correlation Processor Based Sidelobe Suppression for Polyphase Codes in Radar Systems

Wireless Personal Communications - Peak sidelobe level (PSL), integrated sidelobe level (ISL) and signal to noise ratio (SNR) are the main performance indices in pulse compression radar. Pulse...     

Thermal gain of multilayer stacks

A theory for the spectral emittance and thermal gain of multilayer stacks is presented. The theory only requires knowledge of the optical constants and thicknesses of different layers for computation of the spectral emittance and thermal gain. Numerical results show that the optical properties and thicknesses of various layers and the substrate of the stack play a vital role in determining the spectral emittance and thus the total thermal gain of the stack.