Numerical Study of Free Convection inside the Differentially Heated Cavity incorporating Variable Property Al2O3-H2O Nanofluid

This paper investigates free convection in a partially heated square cavity filled with alumina-water nanofluid. The investigation is carried out at the three-volume fraction of nanoparticles (0, 0.03, 0.05), two Prandtl numbers (2.66, 6), and constant Grashof number (105) with three shapes of insulating obstacles (Square, Circular, and Rectangular). The results show that the nanofluid volume fraction and Prandtl number significantly enhance the heat transfer. The user-defined function (UDF) is developed and computed to investigate the effect of nanoparticle diameter and its temperature-dependent viscosity on convection. The average Nusselt number (Nu) increased with the temperature-dependent viscosity model and by increasing the percentage concentration of the nanoparticles. For all obstacle shapes, the thermal performance improved with increase in the nano-particle diameter.

Morphology and Mechanical Properties of Fossil Diatom Frustules from Genera of Ellerbeckia and Melosira

Fossil frustules of Ellerbeckia and Melosira were studied using laboratory-based nano X-ray tomography (nano-XCT), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Three-dimensional (3D) morphology characterization using nondestructive nano-XCT reveals the continuous connection of fultoportulae, tube processes and protrusions. The study confirms that Ellerbeckia is different from Melosira. Both genera reveal heavily silicified frustules with valve faces linking together and forming cylindrical chains. For this cylindrical architecture of both genera, valve face thickness, mantle wall thickness and copulae thickness change with the cylindrical diameter. Furthermore, EDS reveals that these fossil frustules contain Si and O only, with no other elements in the percentage concentration range. Nanopores with a diameter of approximately 15 nm were detected inside the biosilica of both genera using TEM. In situ micromechanical experiments with uniaxial loading were carried out within the nano-XCT on these fossil frustules to determine the maximal loading force under compression and to describe the fracture behavior. The fracture force of both genera is correlated to the dimension of the fossil frustules. The results from in situ mechanical tests show that the crack initiation starts either at very thin features or at linking structures of the frustules.

Fetal Hemoglobin Levels as Indicator of Frequency and Duration of Blood Donation

Hemoglobin F is normal hemoglobin seen in minute amount in adults. Increase in its level in adults is an indication of erythropoietic stress, which in most cases is linked to hemoglobinopathy. This study was undertaken to assess if physiological erythropoietic stress as seen in commercial blood donation, can increase it and thus be used as an indicator of frequency and duration of blood donation. The study involved 152 subjects including 88 commercial blood donors and 64 controls. Hemoglobin F was expressed as percentage concentration of the total hemoglobin. Results showed that hemoglobin F significantly increased in commercial blood donors when compared with the controls. There was also strong positive correlation between hemoglobin F level and age of the donors which was not the case with the controls. The results indicate that hemoglobin F level can be used as an indicator of the frequency and duration of blood donation. Though blood donation has some health benefits, the disadvantages of frequent donation outweigh these benefits and should be discouraged.

The first result in the determination of the percentage concentration of sulfuric acid solution based on the gamma transmission technique with an energy of 662 ke

In this study, we propose an approach using the gamma transmission technique based on the combination of the experimental and simulated data for determining the percentage concentration of the acid solution. The experiment consists of a collimated 137Cs radioactive source emitting a narrow gamma beam of 662 keV and a NaI(Tl) detector. Monte Carlo simulation data is used to construct the calibration curve of lnR versus the percentage concentration of acid solution at different temperatures (R is the ratio of the area under a transmission peak for an acid solution relative to that for water). The percentage concentration of the acid solution is determined based on the calibration curve and the experimental ratio R. The obtained results showed that this approach was feasible in which the percent concentration of 7 in total 8 samples of the sulfuric acid solution are less than 5% in comparison with one of the reference samples. There is only one sample with a relative deviation of 7.6%. These preliminary results suggest that it is possible to develop nondestructive testing for the rapid determination of the percentage concentration of acid solutions based on the gamma transmission technique.

Investigation of Kenaf Paper in the Presence of PVA for Transformers Application

This paper presents an investigation on the physio-mechanical properties and AC breakdown voltage of the Kenaf paper in the presence of Polyvinyl Alcohol (PVA) for transformers application. Kenaf bast fibers were used in order to produce the paper through the soda pulping process. The pulps were subjected to beating up to 12,000 revolutions, whereby the PVA was added to the pulps at a different weight percentage concentration up to 12%. Morphological study was carried out on the Kenaf paper based on Scanning Electron Microscopy (SEM). The apparent density, Tensile Index (TI), Burst Index (BI), Tear Index (TeI), and AC breakdown voltage of the Kenaf paper were measured. It is found that the TI and BI of Kenaf paper can be slightly improved through the introduction of PVA. On other hand, the TeI of the Kenaf paper decreases with the increment of the PVA. The AC breakdown voltage of the Kenaf paper slightly increases with the increment of PVA weight percentage concentration.

Design and Fabrication of a Plastic Biogas Digester for the Production of Biogas from Cow Dung

Biogas digester dimensions and materials of construction are important factors of consideration during the design and fabrication phase. The aim of this study is to provide a detailed analysis of the design and fabrication of a 2.15 m3 pilot plastic biogas digester for biogas generation. To establish this, a design equation covering the volume of the digester, inlet and outlet chambers, and digester cover plate were developed considering the shape of the digester. The digestion chamber of the biogas digester under study was fabricated using high-density polyethylene (HDPE) plastic, while the inlet and outlet chambers were constructed with bricks/cement. The study was motivated due to some limitations such as leakage associated with previous designs. In the present study, a ventilation test was conducted after the fabrication to ensure the digester is leak free. Results obtained showed a total volumetric methane gas yield of 2.18 m3 (54.50%) and carbon dioxide yield of 1.77 m3 (44.25%) making up a total biogas yield of 4.00 m3. In addition, the percentage concentration of methane and carbon dioxide were found to be 60% and 30%, respectively. The developed plastic biogas digester has been found to be appropriate for biogas production using cow dung as substrate.

Synthesis of bio-oil from waste Trichosanthes cucumerina seeds: a substitute for conventional fuel

The present study explores the methodology for the synthesis of bio-oil from waste trichosanthes cucumerina seeds by the solvent extraction method. It investigates the yield percentage, concentration of free fatty acids and acid contents in the extracted bio-oil. Effects of size of the crushed seeds, moisture content, extraction time, solvent to seed ratio and extraction temperatures were examined. The non-polar hexane solvent resulted in a higher percentage of oil yield (28.4 ± 0.4%) for the crushed seed size of 0.21 mm, 6% moisture content, 270 min extraction time, 68 °C temperature and 6:1(ml/g) of solvent to seed ratio. The synthesized bio-oil was characterized using Fourier Transform Infra-Red spectrum and Gas Chromatography–Mass Spectroscopy analysis. The properties of the bio-oil and biodiesel were assessed according to the American Society for Testing and Materials and the Association of Official Analytical Chemists standards. The obtained methyl-ester by trans-esterification process results in the fuel properties closer to the conventional fuel. Thus, Trichosanthes cucumerina bio-diesel can be used as a potential substitute.

XRF analysis of heavy metals contents in oak wood (Quercur robur L.)

XRF analysis of heavy metals contents in oak wood (Quercur robur L.). The aim of this study was to determine an amount of adsorbed metals ions from water solutions by oak ( Quercus robur L.) shavings. This paper focuses on XRF analysis of metal contents in examined samples. Necessary material was obtained from damaged flooring strips. Samples were soaked with standard water solutions of lead (II) nitrate, cadmium nitrate and mercury (II) chloride. After 7 days wood shavings were dried and reduced to ashes in muffle furnace. Content of adsorbed metal was marked (XRF) and classified depending on percentage concentration of metal ions in solutions.

Hybrid siliconized–epoxidized EPDM/polyurethane (eEPDM-g-APTES/HTPDMS/PU) matrices for potential application in cable insulation

Hybrid matrices (epoxidized of ethylene–propylene–diene monomer (eEPDM) -g-aminopropyltriethoxysilane (APTES)/hydroxyl terminated polydimethylsiloxane (HTPDMS)/polyurethane (PU)) were developed based on eEPDM with 3-APTES coupling agent and varying weight percentages (0.75, 1.50, 2.25, and 3.00 wt%) of PU prepolymer as coreactant using 7.5 wt% of HTPDMS as chain extender using suitable experimental conditions. The formation of hybrid matrices and their structure were characterized by Fourier transform infrared (FTIR). The thermal and morphological properties of the hybrid matrices were analyzed using differential scanning calorimetry and scanning electron microscope, respectively. Mechanical properties (tensile strength, elongation at break (%), Young’s modulus, and hardness) were characterized as per ASTM standards. Data resulted from mechanical studies, it was noticed that the incorporation of 3-APTES, HTPDMS, and PU into eEPDM has improved the elongation at break (%) and lowered the values of tensile strength, Young’s modulus, and hardness according to the percentage concentration. Morphological studies indicate the presence of heterogeneous morphology. Data obtained from different studies, it suggested that the hybrid matrices developed in the present work can be used as cable insulates for high-performance industrial and engineering applications.

Kajian Model Interaksi pada Adsorpsi Logam Berat Kadmium (Cd2+) dengan Menggunakan Adsorben dari Pasir Hitam

This study aimed to analyze the adsorption ability of black sand in the metal ions adsorb cadmium (Cd2+) with a concentration of 70 ppm to a solution with a pH of 4,5. The black sand is used is 40 mesh. This research was conducted by batch adsorption system naturally and adsorption kinetics modeling. Kinetics of adsorption reached equilibrium at time t = 120 minutes with the percentage concentration of adsorbed Cd2+ 18,5%. In the adsorption kinetics modeling correlation coefficient is almost the same between the equations of first order and second order in the amount of 0.98 and 0.99. The result indicated that the type of interaction Cd2+ ions on the surface of black sands occur in chemistry and physics. The adsorption kinetics of diffusion modeling of internal and external diffusion of the correlation coefficient of 0,85 and 0,71. From this data it can be seen that in this study is modeling kinetic internal diffusion trend that shows adsorbent particles are inter sand surface area that experienced internal inter-particle pore diffusion.