Entropy generation in an unsteady Eyring‐Powell hybrid nanofluid flow over a permeable surface: A Lie group analysis

In thermal processes, the choice of the thermofluid plays an essential role in minimizing entropy generation and thereby improving thermal efficiency. In this study, entropy generation in a viscous hybrid nanofluid described by the Eyring‐Powell model is investigated. The model accounts for the effect of the nanoparticle volume fraction and viscous dissipation on an Eyring‐Powell Cu‐Al₂O₃/ethylene glycol nanofluid. A similarity solution to the time‐dependent model is found using the Lie group symmetry technique. The bivariate spectral quasi‐linearization method is used for the solution of the self‐similar transport equations. We analyze the effects of the nanoparticle volume fraction, suction/injection, and viscous dissipation on the fluid properties. The skin friction and Nusselt number are determined. A comparison between the Nusselt number of a regular nanofluid and a hybrid nanofluid shows that the hybrid nanofluid has better thermal characteristics compared with the regular nanofluid. The findings show that a decrease in the nanoparticle volume fraction and Eckert number minimizes entropy generation in the system.     

The distribution and significance of dimethyldibenzothiophenes,trimethyldibenzothiophenes and benzo[b]naphthothiophenes in source rock extracts from offshore Niger Delta basin,Nigeria

The distribution of dimethyldibenzothiophenes, trimethyldibenzothiophenes and benzo[b]naphthothiophenes were investigated in rock extracts from Niger Delta, Nigeria, by gas chromatography-mass spectrometry. The dimethyldibenzothiophenes were characterized by the predominance of 4,6-dimethyldibenzothiophene and 3,6-dimethyldibenzothiophene while 2,4,6-trimethyldibenzothiophene was the dominant compound among the trimethyldibenzothiophenes. Among the benzo[b]naphthothiophenes, the abundance of benzo[b]naphtho[2,1-d]thiophene was higher than other isomers. The rock samples were found to have immature to early mature status. The dimethyl- and trimethyldibenzothiophene ratios showed good correlation with 4-/1-methyldibenzothiophen ratio, T_max (°C) and % Ro, indicating their dependency on maturity increase. The distribution and abundance of dimethyldibenzothiophenes and trimethyldibenzothiophenes were found to be effective in determining the thermal maturity of source rock extracts in Niger Delta basin.     

Effect of Variety and Initial Moisture Content on Physical Properties of Improved Millet Grains

Physical properties of agricultural materials are important for the design of appropriate equipment and systems for harvesting and post-harvest operations such as cleaning, conveying and storage. The study was conducted to determine the effect of variety and initial moisture content on some physical properties of improved Nigerian millet grains. Improved varieties of millet obtained were conditioned to different moisture contents (10, 20 and 30%) and their physical properties were determined. The grain length, width, thickness and effective geometric mean diameter increased with increasing moisture content irrespective of millet varieties, while aspect ratio (which relates kernel width and length and determines whether grains will slide or roll on their flat surfaces during handling and processing) decreased with increase in moisture content. Static coefficient of friction ranged from 0.44 – 0.99, 0.45 – 0.82, 0.40 – 0.70 and 0.37 – 0.67 for wood, mild steel, galvanized steel and glass respectively. The static coefficients of friction (an important parameter in predicting the lateral pressure on a retaining wall in storage bins or design of bins and hoppers for gravity flow) were found to increase as the moisture content increased. The study showed that variety and initial moisture content had significant effect (P < 0.05) on the physical properties determined. Hence, variety and initial moisture content are critical in the design of equipment for processing, handling and storage of millet grains.     

Laser Additive Manufactured Ti–6Al–4V Alloy: Heat Treatment Studies

The effect of heat treatment on microstructure and mechanical behaviours of direct metal laser sintered Ti–6Al–4V samples have been studied. Rectangular parts were built in two different directions; vertical and horizontal and subjected to two different heat treatment cycles: above β transus and below β transus with air cooling. Surface characteristics, microstructural examination and mechanical properties have been investigated. Below β transus treatment creates a modification in the surface morphology with a fine dimple network. Above β transus treatment leads to extensive grain growth at the middle section of the vertically build component thereby increasing its microhardness. Both the selected heat treatment cycles significantly reduces the tensile strength and improves the elongation when compared to as-sintered material. However, below transus temperature treated vertical built specimen results in optimum combination of tensile strength (1124 MPa) and elongation (20%). Higher coefficient of friction has been recorded for specimens after heat treatment.     

A cascade intelligent fault diagnostic technique for nuclear power plants

Safe operation of nuclear power plant is one of the most important tasks in nuclear power development. This justifies the variety of methods that have been proposed to support the operators in the task of plant condition monitoring, fault detection, and diagnosis. A number of hybrid fault detection and diagnosis methods have also been proposed, with their attendant weaknesses. This work proposes the hybrid of principal component analysis (PCA), signed directed graph (SDG), and Elman Neural Network (ENN) for fault detection, fault isolation, and severity estimation, respectively. The proposed hybrid method is verified with the data derived from Personal Computer Transient Analyzer (PCTRAN) simulation. The verification result shows that the PCA-based fault detection methodology realized timely detection of anomaly in the simulated nuclear power plants system, the SDG-based fault recognition method was able to isolate the system abnormality and identify the root causes, and the ENN-based fault severity estimation method presents the failure fraction of fault, representing the severity. With this integrated hybrid method, more fault information is provided for the operators, which serves as a good foundation for further decision-making and interventions.     

Proximate and Cholesterol Composition of Selected Fast Foods Sold in Nigeria

Fast foods consumption has been on the increase in Nigeria raising concerns about the nutritional and health implications. This study was carried out to determine the proximate composition and cholesterol contents of four commonly consumed fast foods (doughnut, chicken pie, roasted chicken, and Jollof rice) sold in Nigeria. Commonly consumed fast foods and most widely patronized fast food outlets were determined by a preliminary survey. There was a wide variation in the proximate composition and cholesterol contents of the food samples. Average dry matter ranged between 68.8 – 84.0 g while the range of values for ash, crude fibre, crude fat, crude protein and nitrogen free extract were 0.89 – 2.45%, 0.56 – 7.53%, 10.99 – 18.52%, 1.81 – 9.71% and 43.32 – 66.98% respectively. Energy content of the fast foods ranged between 304.9 and 400.8 Kcal/100 g. Cholesterol levels ranged between 10.40 – 117.80 (mg/100 g) in the food samples. This study has established the fact that fast foods are concentrated sources of energy, low fibre and high dietary cholesterol and could significantly contribute to dietary cholesterol intake with implications for cardiovascular health.     

Microbial quality of “doubles” sold in Trinidad

A cross-sectional study was conducted to determine the prevalence and characteristics of Escherichia coli, Staphylococcus aureus, Bacillus spp. and Salmonella spp. in “bara”, “channa”, condiments/spices and ready-to-eat “doubles” sold by vendors in the St. George and Caroni counties of Trinidad. Of 196 samples of each of “bara”, “channa”, condiments/spices and ready-to-eat “doubles” examined, E. coli was detected in 0 (0.0%), 14 (7.1%), 96 (49.0%) and 67 (34.2%), respectively; Staphylococci were isolated from 104 (53.1%), 71 (36.2%), 129 (65.8%) and 123 (62.8%) samples, respectively; and Bacillus spp. were recovered from 22 (11.2%), 85 (43.4%), 100 (51.0%) and 88 (44.9%) samples, respectively. Salmonella spp. were not isolated from any sample. Of the 177 isolates of E. coli recovered from all sources, 9 (5.1%), 7 (4.0%) and 47 (26.6%) were mucoid, haemolytic and non-sorbitol fermenters (NSF), respectively, but none agglutinated with O157 antiserum. Of 427 staphylococcal isolates, 130 (30.4%) were confirmed as S. aureus of which 20 (15.4%) were haemolytic and 84 (64.6%) pigmented, while 17 (20.7%) of 82 strains of S. aureus tested produced enterotoxins. Ready-to-eat “doubles”, a popular food in Trinidad, therefore pose a potential health risk to consumers due to the high level of contamination with bacteria.