Influence of Hot Isostatic Pressing on the Microstructure and Mechanical Properties of a Spray-Formed Al-4.5 wt.% Cu Alloy

Al-4.5 wt.% Cu alloy was spray atomized and deposited at varied spray heights ranging from 300 to 390 mm. The average grain sizes decreased from ~ 29 to ~ 18 μm and a concomitant increase in the hardness and the 0.2% yield strength (YS) with increase in the spray height. The respective hardness values of SF-300, SF-340, and SF-390 are 451 ± 59, 530 ± 39, and 726 ± 39 MPa and the YS are 108 ± 7, 115 ± 8, and 159 ± 10 MPa. The transmission electron micrographs revealed the morphological changes of the Al₂Cu phase from irregular shaped to small plate-shaped and then subsequently to spheroidal shape due to high undercooling encountered during spray atomization with increase in spray height from 300 to 390 mm. The porosity of the spray formed deposits varied between 5 to 12%. Hot isostatic pressing of spray deposits reduced the porosity to less than 0.5% without any appreciable increase in grain size. A dislocation creep mechanism seems to be operative during the secondary processing. A comparison between as-spray formed and hot isostatically pressed deposits exemplifies improvement in mechanical properties as a result of elimination of porosity without affecting the fine grain sizes achieved during the spray-forming process.     

Low Complexity Maximum Likelihood FBMC QAM for Improved Performance in Longer Delay Channels

Wireless Personal Communications - Filter bank multi-carrier (FBMC) is an emerging 5G technology due to its finer spectral characteristics than its counterpart orthogonal frequency-division...     

Two-dimensional (2D) Ti3C2Tx MXene nanosheets with superior adsorption behavior for phosphate and nitrate ions from the aqueous environment

With the advancement of modern industries and metropolitan areas, negative environmental impacts such as eutrophication have become serious issues obstructing the usage of water sources in many countries. In this study, two-dimensional (2D) MXene materials were employed for the adsorptive removal of phosphate and nitrate ions from waters. The adsorption parameters of the sorption system including reaction time, solution pH, background ions, and reusability, were evaluated in batch experiments. Material characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis, Brunauer–Emmett–Teller analysis, and high-resolution transmission electron microscopy were performed. The mechanism of removing phosphate and nitrate was clearly described by various kinds of interactions such as electrostatic interactions, and the complexation was significant to elucidate the adsorption mechanism. The adsorption data for phosphate and nitrate update was determined using different isotherms and kinetic models. Reusability and field studies on the MXenes were also conducted. The above findings demonstrate that 2D MXenes could act as promising adsorbents for the elimination of toxic ions from water/wastewater.     

Applying institutional theories to managing megaprojects

This paper contributes to Rodney Turner's initiative to develop a theory of project management from practice. Organizational scholars studying strategy suggest that more attention needs to be paid to practices involved in organizing, as well as the institutional contexts in which these practices are embedded. Taking a cue from strategy-in-practice approaches, it is proposed that institutional theories can be used to address some questions that have not been answered adequately regarding megaprojects. Institutional theories also seem to be gaining the attention of scholars investigating large, global, infrastructure projects as reported in engineering, management and construction journals. Increasingly, it is evident that the problem areas attached to these projects stretch beyond technical issues: they must be considered as socio-technical endeavours embedded in complex institutional frames. The authors suggest that studying how to deal with institutional differences in the environment of megaprojects has both theoretical and practical implications.     

Microstructural and Mechanical Characterization of Two Aluminium Based In Situ Composite Foams

In situ composites are multiphase materials where the reinforcing phase is synthesized within the matrix during composite fabrication. The present paper deals with the processing, microstructural and mechanical characterization of Al?C7Si?C0.3Mg?C10TiB₂ and Al?C4Cu?C10TiB₂ foams. Composite foams with very low relative density (??_r?=?0.17?C0.37) and foams containing uniform cell sizes were successfully processed. Since the TiB₂ particle sizes are less than 2???m and have a good wetting behaviour, TiB₂ can be very good foam stabilizers. Microstructural characterization of the cell walls showed significant grain refinement since TiB₂ is a grain refiner. Elemental mapping clearly showed TiB₂ particles at inter dendritic boundaries. Compression testing of the processed foams showed some interesting features. Stress?Cstrain curve showed a lot of serrations which indicated brittle fracture of the cell walls and edges. Hence, it is observed that a balance should be attained between the grain refinement of ??-Al grains and the amount of TiB₂ particles to obtain desirable mechanical properties. Energy absorbed by the processed foams was calculated and they were observed to be close to that of the commercially available ALPORAS foams.     

Cranberry seed fibre: a promising prebiotic fibre and its fermentation by the probiotic Bacillus coagulans MTCC 5856

Cranberry, a versatile fruit, is known for nutritional as well as medicinal properties due to the presence of bioactive compounds. However, cranberry fruit has not been fully explored for its prebiotic potential. Therefore, this study was conducted to evaluate prebiotic potential of cranberry seed fibre (CSF) and also evaluate its fermentability by the probiotic strain Bacillus coagulans MTCC 5856. The resistance to gastric acid and porcine pancreatic enzymatic (PPE) hydrolysis of CSF was investigated using an in vitro model. It was found that CSF was resistant to gastric acid and also nondigestible to PPE hydrolysis. CSF as sole nutrition source was evaluated for the fermentability by B. coagulans MTCC 5856. A significant amount of short‐chain fatty acids was produced by the B. coagulans MTCC 5856 while fermenting cranberry fibres anaerobically. CSF supported the growth of B. coagulans MTCC 5856 and also inhibited the growth of E. coli ATCC 25922 when cocultured in an anaerobic environment. CSF from the cranberry fruit exhibited prebiotic potential and also found to be fermentable by B. coagulans MTCC 5856. This study provided the scientific evidence of CSF as a prebiotic fibre and also its suitability with the probiotic B. coagulans MTCC 5856 for an ideal synbiotic preparation.     

A numerical approach based on transient thermal analysis toestimate the safe operating frequencies of thyristors

The spatio-temporal distribution of temperatures in high-power SCRs used for switching high di/dt current pulses were simulated using the finite element method (FEM). Two types of SCRs, with amplifying gate (unshorted device), and without amplifying gate (shorted device) structures, were analyzed. The details of the numerical simulation, such as the meshing strategy, the heat source model and the boundary conditions are discussed. Based on the analysis, the failure temperature of the unshorted device was computed to be 1100°C. The peak temperature in the shorted device was, however, found to be 335°C. The instantaneous cooling cycles of the devices and their cooling time constants, as obtained from the simulations, are presented. Based on these parameters, the safe operating frequencies of these devices were estimated     

Microflora of the atmosphere and its control

The development of science has increased the need for control of air contaminants which otherwise may cause serious problems in hospitals, research laboratories, and pharmaceutical and food industries. UV rays, the use of an air filter module and of formaldehyde were evaluated individually as well as in combinations for their efficiency in controling microbial contamination in closed spaces. The module operation was found to be safe and efficient in decontaminating the air. In combination with formaldehyde or UV radiation it was found to completely remove all the micro-organisms of air.     

Comparison of coagulase and thermonuclease activities with enterotoxin production by staphylococci from foods

Coagulase, DNase and enterotoxin production of 200 strains of staphylococci isolated from various foods were compared in order to see to what extent these biochemical tests can replace the enterotoxin assay for predicting food safety. Any degree of coagulase formation was not indicative of DNase activity also. However, all cultures having a 4⁺ score of coagulase showed DNase. DNase activity decreased with heating. No correlation could be seen between coagulase and enterotoxin or DNase and enterotoxin production. In fact, a number of coagulase negative strains were found to produce enterotoxins. Reliability of coagulase or DNase activity for predicting food safety is therefore doubtful.