Papers by Keyword: Shell

Abstract: This study explored coconut shells in developing Al-Cu-Mg based nanocomposites for fabricating mould parts. The aim is to engineer alternate way through which income can be generated from agricultural wastes and recycling of industrial waste like aluminium cans. Al-Cu-Mg based nanocomposites were produced and characterised. Effects of carbonised and uncarbonised coconut shell nanoparticle (UCSNP) additions on properties of Al-Cu-Mg nanocomposites were compared. Maximum tensile strength was obtained at 10%vol uncarbonised coconut shell nanoparticle additions to Al-Cu-Mg. Increase in tensile strength and elastic modulus were noted with carbonised coconut shell reinforced Al-Cu-Mg nanocomposites against the decrease in the elastic (Young’s) modulus of the UCSNP/Al-Cu-Mg nanocomposites. Despite highest tensile strength of 10%volUCSNP/Al-Cu-Mg, 10%volCCSNP/Al-Cu-Mg nanocomposite is ranked as the best material in this study due to its optimum combination of properties including tensile strength, elastic modulus, tensile strain, impact energy and hardness values. Hence, it has been selected for fabricating open die mould parts to be used in compression sheet forming process for fabricating polymeric standard samples for tensile flexural analyses. Keywords: Al-Cu-Mg, Coconut, Shell, Nanoparticles, Mould fabrication

Abstract: The effect of adding nanomaterial of aluminum oxide (Al2O3), titanium oxide (TiO2) and zirconium oxide (ZrO2) in different concentrations of 0.25, 0.5, 0.75, 1.0, and 1.25 g/L to the cold fluid (water) turbulently flowing with different flow rates of 75, 100, 125, 150, and 175 L/min in tube side countercurrently to hot water flowing with a constant flow rate of 60 L/min in the shell side of shell and tube heat exchanger on the heat transfer rates and overall heat transfer coefficients are experimentally studied. It is found that the addition of nanomaterials gives rise to outlet cold (nano) fluids temperatures causing to enhancement averagely 7.74, 11.25, and 17.38 percent for ZrO2, TiO2, and Al2O3 respectively in heat transfer rate and averagely 12.72, 19.47, and 28.71 percent for ZrO2, TiO2, and Al2O3 respectively in overall heat transfer coefficients. The maximum enhancement values in heat transfer rates and in overall heat transfer coefficients are attained at a flow rate of 150 L/min of cold fluid.

Abstract: Nanofluid is an efficient fluid when used in heat exchanger system because of its larger thermal conductivity compared to conventional fluids such as water, oil, and ethylene glycol (EG). This research used MnFe₂O₄ nanoparticle due to its higher magnetic sensitivity compared to other ferrite nanoparticles and larger thermal conductivity than TiO₂. This research used the MnFe₂O₄ nanoparticle with a combination of EG-Water base fluids in ratios of 40:60, 60:40, and 80:20. MnFe₂O₄ nanofluid mixed with EG-Water base fluids was made using the two-step method with 0.05% MnFe₂O₄ volume fraction in each base fluid ratio. This research used shell and tube type heat exchanger with heat temperature of 60°C and cold temperature of 26°C that were carried out at volumetric flowrate in each base fluid ratio for 0.22 l/m, 0.44 l/m, and 0.66 l/m. This research aimed to find the best combination ratio of EG-Water in thermophysical (thermal conductivity, specific heat, density, and viscosity) and to find the effect of volumetric flowrate variations on the heat exchange characteristics (the Reynold number, the Nusselt number, ∆T LMTD, convection coefficient, heat transfer, and overall heat transfer coefficient). The results of this research were that the sample of EG-Water with 40:60 ratio had the best heat transfer characteristics compared to samples with 60:40 and 80:20 ratios. Meanwhile, for the volumetric flow rate, a higher volumetric flow rate resulted in a larger result.

Abstract: This article discusses the algorithm for calculating the shell structure of arbitrary shape, taking into account the physical nonlinearity of the material used. In determining the parameters of the stress-strain state, a step loading procedure was used. Algorithm for calculating the shell structure of arbitrary shape, taking into account the physical nonlinearity of the used material is discussed in this article. In determining the parameters of the stress-strain state, a step loading procedure was used.

Abstract: The application of the numerical-analytical boundary elements method (NA BEM) to the calculation of shells is considered. The main problem here is due to the fact that most of the problems of statics, dynamics and stability of shells are reduced to solving an eighth-order differential equation. As a result, all analytical expressions of the NA BEM (fundamental functions, Green functions, external load vectors) turn out to be very cumbersome, and intermediate transformations are associated with eighth-order determinants. It is proposed along with the original differential equation to consider an equivalent system of equations for the unknown state vector of the shell. In this case, calculations of some analytical expressions related to high-order determinants can be avoided by using the Jacobi formula. As a result, the calculation of the determinant at an arbitrary point reduces to its calculation at the point , which leads to a significant simplification of all analytical expressions of the numerical-analytical boundary elements method. On the basis of the proposed approach, a solution is obtained of the problem of bending a long cylindrical shell under the action of an arbitrary load, the stress-strain state of which is described by an eighth-order differential equation. The results can be applied to other types of shells.

Abstract: The use of prefabricated mini silo structures enables us to build containers for grain or animal feed and to transport the structural elements to the installation site. Traditional types of strengthening of concrete structures are steel and concrete cages. Polymer materials are widely used in construction. The methods of strengthening modern materials, such as lamellae, are being increasingly used. The issue of strengthening the structures with composite polymer materials is relevant.

Abstract: Nanoweb fabricated by electrospinning has a large specific area and a small pore size which can be controlled through a spinning process to enable a strong adsorption and selective permeability. It is required to produce nanofiber of different polymer mixture with a limited miscibility for improvement of physical, chemical, or biological properties. In this study, poly (vinyl alcohol) (PVA)/polyurethane (PU) nanofibers were produced by coaxial electrospinning. PVA (core)/PU (shell) nanofibers were defect-free and had a uniform thickness. The pseudo core/shell structure of PVA/PU nanofibers was confirmed by transmission electron microscopy. The presence of PVA and PU in the nanofibers was identified by ¹³C solid state nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, and X-ray diffraction analysis. Water contact angle was reduced by incorporation of PVA in a core of PU nanofiber. For variety of biomedical applications, bioactive substances such as antibiotics and proteins can be incorporated in a core of hydrophobic PU nanofiber by coaxial electrospinning of water-soluble polymer/bioactive substance mixture.

Abstract: To infer the early evolution of mollusc shell microstructures we must know the most ancient fossil record of molluscs. Fortunately the shells of many early molluscs are preserved via internal coatings and replacements by apatite that record sub-micrometer structural details that otherwise would be lost during diagenetic recrystallization. We herein discuss the methodology by which one can infer original shell microstructure from phosphatized fossils, pointing out the main problems and solutions in interpreting these traces of original shell crystal morphology. We also review the information these fossils have provided about the earliest evolution of the mollusc shell. Our long-term goal is to create a dataset of microstructures in early molluscs, which will be useful in understanding the incipient evolutionary arms race between molluscs and their predators, and will help elucidate how the mollusc biomineralization toolkit was built through time.

Abstract: It is known for a long time that calcified tissues secreted by aquatic or terrestrial invertebrates – such as mollusc shells – have the ability to concentrate large amounts of pollutants, in particular heavy metals. In the present paper, we have found an extremely rapid and easy procedure to qualitatively detect the putative presence of heavy metals in shells, without having to use sophisticated techniques such as Wavelength Dispersive Spectroscopy, atomic adsorption spectroscopy or ICP-MS. Our method rests on the capacity of the silver enhancement chemicals that are traditionally used in immunogold localization experiments to increase the size of heavy metal nanoparticles, whatever the chemical element. It goes as follows: freshly broken pieces of shells that are suspected to contain traces of heavy metals are simply incubated 15 minutes in few drops of a silver enhancement solution (British Biocell International), and, after short rinsing and drying, the shell fragments are directly observed with a tabletop Scanning Electron Microscope, under back scattered electron (BSE) mode without any further preparation. Heavy metals nanoparticles are detected as bright spots. Our method is extremely fast (about half an hour in total), and may be used as a quick check for pre-selecting series of calcified samples prior to the quantitative analysis of their heavy metal content.

Abstract: Proteomics is an efficient high throughput technique developed to identify proteins from a crude extract using sequence homology. Advances in Next Generation Sequencing (NGS) have led to increase knowledge of several non-model species. In the field of calcium carbonate biomineralization, the paucity of available sequences (such as the ones of mollusc shells) is still a bottleneck in most proteomic studies. Indeed, this technique needs proteins databases to find homology. The aim of this study was to perform different data mining approaches in order to identify novel shell proteins. To this end, we disposed of several publicly non-model molluscs databases. Previously identified molluscan shell matrix sequences were used as keyword to query annotated databases. BLAST tools and KASS program (KEGG Automatic Annotation Server) were developed to analyse other non-annotated databases. Our results suggest that the efficiency of these methods depends on the quality of the shared data. Finally, an in-house shell matrix protein database has been generated.