Performance investigation of ozone-friendly R404A and R507 refrigerants as alternatives to R22 in a window air-conditioner

In this study, experimental research was carried out to investigate the performance of R22 and its ozone-friendly alternative refrigerants (R404A and R507) in a window air-conditioner. The performance parameters of the system using R22 were considered as benchmarks and those obtained using alternative refrigerants were compared. Experimental results showed that R22 had the lowest pressure ratio and discharge temperature closely followed by R507. The average discharge temperature obtained using R507 and R404A were 4.2% and 15.3% higher than that of R22, respectively. The lowest compressor power and energy consumption were obtained from R507 retrofitted system. Also, the highest refrigeration capacity and coefficient of performance (COP) were obtained using R507 in the system. The average refrigeration capacities of R507 and R404A were 4.7% higher and 8.4% lower than that of R22, respectively, while the average COP of R507 increased by 10.6% and that of R404A reduced by 16.0% with respect to that of R22. Generally, the investigation has revealed that R507 can be used successfully as a retrofitting refrigerant in existing window air-conditioners originally designed to use R22 in the event of HCFC phased out.     

Concentration profile of selected polycyclic aromatic hydrocarbon (PAH) fractions in some processed meat and meat products

This study investigates the concentration profiles of selected polycyclic aromatic hydrocarbon (PAH) fractions in selected processed meats, in order to evaluate their dietary and health implications. Smoked, grilled and boiled meat products were bought from different locations in Cape Town and Cape Town environs. PAHs were extracted from each meat sample according to standard methods. The concentrations of benzo[k]fluoranthene (BkP), benzo[a]pyrene (BaP), indeno[1, 2, 3-cd]pyrene (IP), and benzo[g, h, i]perylene(BghiP) in the processed meat extracts were determined using a gas chromatograph coupled with flame ionization detector. Total PAH concentrations in smoked, grilled and boiled chicken fillets, pork, and beef stripes were ranged 2.79, 0.99, 2.33 μg/kg; 19.11, 11.17, 15.04 μg/kg; and 14.84, 9.29, 7.20 μg/kg respectively. There were significant differences (p > 0.05) in the concentration levels of PAHs detected in different types, with the highest levels observed in smoked pork meat. The concentration of BkP, BaP, IP and BghiP detected in the various meat samples were below the EU and WHO dietary exposure limit.     

Effect of orientation of crystal face of silver and its alloying with gold on properties of thin anodic Ag(I) oxide films: II. Photopotential

The current efficiency of the formation of anodic oxide on polycrystalline silver is shown to decrease with an increase in the concentration of KOH solutions, while the rate-limiting stage remains the solid-phase mass transfer. Photopotential in nano-size Ag(I) oxide films anodically formed on polycrystalline silver is independent of the OH⁻ ion concentration, which means that a photoresponse is generated in the bulk oxide. The n-type conductivity of oxide films on silver, Ag-Au alloys, and low-index silver crystal faces, which was determined previously when measuring photocurrent, is confirmed. Replacing polycrystalline silver with its monocrystals results in a substantial decrease in the photopotential amplitude due to the decrease in the deviation from a stoichiometric composition. The electron mobility and the partial electronic photoconductivity in the anodic Ag(I) oxide depend on the orientatinon of the crystal face in silver and the gold content. At E = 0.56 V, a series of changes in these characteristics correlates to the changes in other structure-dependent parameters of Ag₂O oxide (the optical absorption coefficient α, the concentration of donor defects N _D, the width of the spatial charge region W, and the Debye screening length L _D).     

Emissions from petroleum products consumption in north-central region of Nigeria

Gasoline and diesel combustion emits particulate matter and oxides of nitrogen that have been a major source of pollution in the north-central region of Nigeria. These have led to adverse effect both on individuals and on the environment at large. The emission rate from the petroleum product combustion was investigated using the emission factor approach. From result of the investigated air emissions, it was observed that Abuja the federal capital of Nigeria being the highest consumer of the product had the highest emission rate.     

Detection and classification of large bowel obstruction from X-ray images using machine learning algorithms

Large bowel obstruction (LBO) occurs when there is a blockage or twisting in the large bowel that prevents wastes and gas from passing through. If left untreated, the blockage cuts off blood supply to the colon, causing sections of it to die which results in high rates of morbidity and fatality. The examination of clinical symptoms of LBO involves careful inspection of the cecum and colon. Radiologists use X-rays to inspect the clinical signs. Some research has been done to automate the detection of related abdominal and intestinal diseases. However, all these studies concentrate only on detecting Crohn's, ulcerative colitis, Acute Appendicitis, colorectal cancer, celiac diseases, liver diseases, and chronic kidney diseases. Automatic detection and classification of LBO has not been given due attention so far to the best of the authors knowledge. To address this challenge, we have designed a model for the detection and classification of LBO. The models development comprises of stages such as preprocessing, detection, segmentation, feature extraction, and classification. We used YOLOv3 for detection and used a gray scale level co-occurrence matrix (GLCM), and a convolutional neural network for feature extraction, while support vector machine (SVM) and softmax were used for classification. The proposed model achieved a diagnostic accuracy of 89% when feature extraction methods such as CNN and median filter with softmax classifier were used. CNN and Gaussian filter with soft max classifier achieved 91%, while CNN and anisotropic filter with soft max classifier achieved 92%. GLCM with threshold segmentation and Gaussian filter with SVM classifier achieved 87%, while CNN with watershed segmentation and Gaussian filter with SVM classifier achieved 97% and CNN-GLCM with watershed segmentation and anisotropic diffusion filter with SVM classifier achieved 98% for detection and classification of LBO. Finally, this paper presented a performance analysis of various machine learning approaches for detection and classification of LBO. Hence, our model is designed to assist human experts (Radiologists) in diagnosing LBO.     

Direct error in constitutive equation formulation for inverse heat conduction problem

We present a mixed numerical formulation that handles discontinuities well for scalar hyperbolic partial differential equations. The formulation is based on a least‐square error in the constitutive equation. It is motivated by scalar inverse diffusion problems with interior data and applies to convection of a passive scalar in a discontinuous compressible flow field. We motivate the need for a mixed formulation by discretizing using an irreducible finite element method and discuss some of the limitations of that approach. We then develop and prove that the mixed formulation is well posed and verify that it works for problems with continuous and discontinuous thermal conductivity distributions.     

DETERMINATION OF TRACE AND MAJOR ELEMENTS IN WATER ON OIL PALM PLANTATIONS BY INDUCTIVELY COUPLED PLASMA-OPTICAL EMISSION SPECTROMETRY

The oil palm is an economic crop that has gained worldwide recognition due to its importance. Produce such as the stem, fruits, and leaves contain phytonutrients and antioxidants that are mediators of cellular functions and a cure for various ailments. The oil palm plantations receive inputs of elements from natural and anthropogenic sources. However, while some of the elements are beneficial, they may be toxic at high concentrations. The quality of ground water is important due to the possible uptake of trace and major elements by the oil palm. In this study, the concentrations of fifteen elements in ground water from oil palm plantations in southern Nigeria were measured. The inductively coupled plasma optical emission spectrometer (ICP-OES) was the instrument of choice because of its multielemental capabilities. The study revealed that of the trace elements, the highest concentrations were obtained for lead (Pb) (0.090–10.29 mg/L), while the lowest concentrations were obtained for cadmium (Cd) (0.119–0.391 mg/L). The concentration of the metals were compared with water quality standards established by the World Health Organization in 2011.     

In-vitro multienzyme digestibility of protein of some plant source flours blended with bovine plasma protein concentrate

The in-vitro multienzyme protein digestibilities of the flours of maize, cassava, pigeon pea (Cajanus cajan), African yambean (Sphenostylis stenocarpa) and bambara groundnut (Vigna subterranea), blended with bovine plasma protein concentrate were investigated. The multienzyme system consists of trypsin, chymotrypsin and peptidase. It was found that the addition of bovine plasma protein concentrate improved the protein digestibility of the flours compared with flours without the additive. The digestibilities were increased by between 3% in bambara groundnut blended flour to about 10% in cassava blended flour. When the flours were wet-heat treated, the digestibilities further increased in all samples with increments between 7·5 % in bambara groundnut and 16·6% in cassava flour. Bovine plasma protein concentrate may be a good source of protein for the fortification of protein-deficient foods, particularly maize and cassava flours.     

Isolation,fractionation and characterisation of proteins from Mucuna bean

The chemical composition and fractional distribution of protein isolates prepared from species of Mucuna bean were studied. Using six different extraction media, the yield of protein based on the Kjeldahl procedure varied from 8% to 34%, and the protein content varied from 75% to 95%. When the yields were high, the colour of the isolates generally tended to be dark and unsatisfactory. Hence, the use of chemical treatments and high pressure processing were explored.