Characterization of structural alumina ceramics used in ballistic armour and wear applications

Structural alumina ceramics used in ballistic armour and wear applications with varying alumina contents and manufactured using both slip casting and dry pressing techniques, have been investigated and characterized in terms of their hardness, elastic modulus, fracture toughness, and microstructural characteristics. For a given alumina content, fracture toughness decreases with increasing hardness. Dry pressed samples show slightly higher hardness, and lower fracture toughness for the same alumina content. The hardness, elastic modulus and fracture toughness are higher for the 98% alumina samples while the differences between the lower alumina samples (95 and 91%) are negligible. The grain sizes are bimodal with the majority 3 m and the size range narrows with decreasing alumina content. The microstructures are composed of a matrix phase, corundum (-Al₂O₃), grain boundary phases consisting of a glassy phase with varying Al₂O₃, SiO₂, and CaO contents, a crystalline phase, triclinic anorthite (CaAl₂Si₂O₈), and an additional phase, spinel (MgAl₂O₄), in the lower alumina samples. The proportion of the boundary phase increases with decreasing alumina content and no effect of fabrication method is observed.     

Chemical ionization mass spectrometer instrument for the measurement of tropospheric HO2 and RO2

Laboratory characterizations of the peroxy radical chemical ionization mass spectrometer (PerCIMS) instrument have been performed. The instrument functions by drawing ambient air through a 50-microm-diameter orifice into an inlet held at low pressure. Peroxy radicals (HO2 and RO2) within this air are detected by amplified chemical conversion into a unique ion (HSO4-) via the chemistry initiated by the addition of NO and SO2 to the inlet. HSO4- ions are then quantified by a quadrupole filter mass spectrometer. PerCIMS provides measurements of the sum of peroxy radicals, HO2 + RO2 (HOxROx mode), or the HO2 component only (HO2 mode), achieved through the control of concentration of NO and SO2 added to the instrument. The characterization and response of this instrument have been evaluated through modeling of inlet chemistry and laboratory experiments and have also been demonstrated through successful deployment during field campaigns. The performance of PerCIMS with respect to calibration pressure and relative humidity is reported, as are the sensitivities of the instrument to organic peroxy radicals with different hydrocarbon groups. These data show PerCIMS to be a practical field instrument for the fast and accurate evaluation of the concentration of peroxy radicals over a variety of atmospheric conditions. The estimated accuracy of the derived [HOxROx] concentrations is +/- 35% (at the 95% confidence interval), while [HO2] measurements have accuracies of +/- 41% (at the 95% confidence interval). Typical precision of measurements well above the detection limit is 10%, and typical detection limits are 1 x 10(7) radicals cm(-3) for 15-s averaging times.     

Surface characterisation and reaction kinetics of silver nanoparticles mediated by the leaf and flower extracts of French marigold (Tagetes patula)

In this study, French marigold''s leaf and flower were used for the synthesis of silver nanoparticles (SNPs) in order to explore their potentials towards bioreduction of Ag⁺ to Agᵒ. The as‐synthesised SNPs were characterised using UV–Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X‐ray diffraction, transmission electron microscopy, and zeta‐potential analysis. The results obtained showed that the particles are polydispersed with sizes in the range 15.8–42.8 nm. The bioreduction was believed to be due to the amides, aldehyde functional groups, and essential oils present in the extracts as confirmed by the FTIR analysis. The growth mechanism involved in the reaction was studied which revealed oriented attachment (OA) onwards Ostwald ripening in the case of the flower‐mediated synthesis and typical OA in the leaf‐mediated synthesis. The studied kinetics of the particle formation showed that the reaction is possibly a pseudo‐first‐order reaction with some diffusion‐controlled mechanism which is driven by high surface area to volume ratio in both the leaf‐ and flower‐mediated synthesis.Inspec keywords: ultraviolet spectra, nanoparticles, visible spectra, particle size, reaction kinetics, transmission electron microscopy, electrokinetic effects, X‐ray diffraction, scanning electron microscopy, nanomedicine, silver, nanofabrication, biomedical materials, Fourier transform infrared spectraOther keywords: powder X‐ray diffraction, transmission electron microscopy, zeta‐potential analysis, bioreduction, aldehyde functional groups, FTIR analysis, flower‐mediated synthesis, leaf‐mediated synthesis, pseudofirst‐order reaction, surface characterisation, silver nanoparticles, flower extracts, French marigold, UV‐visible spectroscopy, Fourier transform infrared spectroscopy, Tagetes patula, attachment onwards Ostwald ripening, Ag     

Impacts of the Mississippi River spillway opening on faecal coliform concentration in Lake Pontchartrain

This study focuses on explaining the role of the periodic opening of the Bonnet Carré Spillway on the faecal coliform levels in Lake Pontchartrain. Water quality data were collected by the Lake Pontchartrain Basin Foundation to analyse the faecal coliform bacteria levels, turbidity, salinity, temperature, and dissolved oxygen in the lake water. The results show that the faecal coliform concentrations were lower during the spillway opening than the preceding and subsequent months. Statistical analysis shows the dilution effect, characterized by an effective reduction in faecal coliform concentrations due to increase in water turbidity, coupled with decrease in water salinity and dissolved oxygen because of spillway opening. It is also indicated that the combine effect of more than one factor produces a significantly greater reduction in the faecal coliform than each factor acting independently. Periodic spikes in faecal coliform concentrations were observed at sampling points located near the outlets of streams and drainage canals with high settlement densities. A positive correlation (r = 0.78467) was found between the average faecal coliform counts and average monthly precipitations, highlighting the role of precipitation run‐offs. The results of this study indicate that the spillway opening contributed to a reduction in the faecal coliform concentration in the lake's surface water during the studied periods.     

The effects of Aloe vera extract on corrosion and kinetics of corrosion process of zinc in HCl solution

The effect of the extract of Aloe vera leaves on the corrosion of zinc in 2 M HCl solution was studied using weight loss technique. A. vera extract inhibited the corrosion of zinc in 2 M HCl solution and the inhibition efficiency increased with increasing concentration of the extract but decreased with increasing temperature. The adsorption of the inhibitor molecules on zinc surface was in accordance with Langmuir adsorption isotherm. A first-order kinetics relationship with respect to zinc was obtained with and without the extract from the kinetics treatment of the data.     

Applications of artificial intelligence in engineering and manufacturing: a systematic review

Journal of Intelligent Manufacturing - Engineering and manufacturing processes and systems designs involve many challenges, such as dynamism, chaotic behaviours, and complexity. Of late, the...     

Comparative study of antioxidant and antibacterial properties of the edible mushrooms Pleurotus levis,P. ostreatus,P. pulmonarius and P. tuber‐regium

Comparative studies of functional properties among closely related mushroom species, supported by molecular identification, standard cultivation and extraction protocols, are not well documented. We compared antioxidant and antibacterial properties of standardised hydroalcoholic extracts of four Pleurotus species (P. levis, P. ostreatus, P. pulmonarius and P. tuber‐regium). Antioxidant properties were investigated using DPPH and ABTS radical scavenging capacity, total phenolic content, β‐carotene‐linoleic and ORAC assays. Antibacterial effect was assessed using the microplate method. The functional properties of standardised mushroom extracts were different in species studied. β‐carotene–linoleic acid and ORAC assays showed high antioxidant activity, particularly in P. ostreatus. Pleurotus tuber‐regium exhibited the lowest antioxidant activity in the ORAC assay (3316.0 μmol of trolox equivalent mL^?1), but exerted the most potent bacteriostatic and bactericidal activity. Bacillus subtilis showed a high degree of susceptibility to a very low concentration (3.33 μg mL^?1) of P. levis extract. Remarkable antioxidant and antibacterial properties were found in P. levis and P. tuber‐regium compared to the other species studied that are cultivated commercially.