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Life cycle assessment of kerbside waste material for an open-looped and closed-loop production– towards circular economy designs
No full textUrbanization growth has increased the generation of municipal solid waste (MSW) and has the potential for recycling and reuse. However, it is frequently limited to a linear lifecycle mode which end up in landfills. A novel attributional lifecycle inventory model for lifecycle assessment based on value retention process (VRP) model of circular economy was developed to quantify the lifecycle inventory and measure the environmental impacts of multiple lifecycle stages, from in-community separation to the end-of-use/life stage and subsequent lifecycles. This investigation focused on assessing the environmental impacts of two distinct in-community waste glass separation methods - separate kerbside glass recycling bin (SKGRB) and mixed kerbside recycling bin (MKRB) - in combination with two recycling approaches - open-loop (asphalt) and closed-loop (glass container). The goal of the study was to make a comparative evaluation of the environmental impacts of these methods. Results showed that the SKGRB method had better environmental performance (40–60% reduction compared to the MKRB method) for both materials. Closed-loop recycling of glass container production had higher environmental impacts due to higher energy consumption in production in one lifecycle, while the open-loop recycling method of asphalt had higher environmental impacts despite fewer circulations, due to higher production volume in 21 years. The results of the sensitivity/uncertainty analysis showed that environmental impacts decreased as the allocation coefficient decreased, reaching stability when the coefficient reached the waste materials percentage in the new product's mixed design
Assessment of the Efficiency of Eco-Friendly Lightweight Concrete as Simulated Repair Material in Concrete Joints
No full textThe high production of carbon dioxide from concrete cement manufacturing and the high utilization of natural resources in concrete has been a concern for research in recent decades. Eco-friendly concrete (Eco-Con) is a type of concrete that uses less energy in its production, utilizes waste materials, produces less carbon dioxide, and is durable. This study assesses the efficiency of the proposed lightweight Eco-Con mixes with 32 MPa compressive strength in repairing different types of concrete structures. Rubber and lightweight expanded clay aggregate (LECA) were used as lightweight materials in the Eco-Con mixes. One Portland cement concrete mix (CC) and three different Eco-Con mixes, namely geopolymer rubber concrete (GR), geopolymer LECA concrete (GL), and rubber-engineered cementitious composite (RECC), were produced and compared. The concrete mixes were utilized as simulated 'repair' materials in several types of concrete joints, namely reinforced slab-beam joints (400 x 300 mm L-shape, 500 mm width, and 100 mm thickness) subjected to bending, concrete joints in beams (100 x 100 x 350 mm) subjected to bending, and concrete joints in unconfined and fiber-reinforced polymer (FRP) confined columns (100 mm diameter and 200 mm height) subjected to axial compression. The reinforced slab-beam joint and FRP-confined column joint were tested with two joint angles of 0 degrees and 45 degrees. The results indicated that RECC is an efficient lightweight Eco-Con alternative to Portland cement concrete in repairing concrete structural elements, especially beams and FRP-confined columns, as it increased their strength capacities by 43% and 190%, respectively. At the tested joint angles (0 degrees or 45 degrees), the use of Eco-Con mixes showed relatively lower slab-beam joint strength capacity than that of the CC mix by up to 14%. A joint angle of 45 degrees was better than 0 degrees, as it showed up to 7% better slab-beam joint strength capacity. Using shear connectors in slab-beam joints had adverse effects on concrete cracking and deformability
Material extrusion of metals: Enabling multi-material alloys in additive manufacturing
No full textThis article discusses the use of Material Extrusion of Metals (MEX/M - defined in ISO/ASTM 52900) technology for producing multi-material components, which offers a cost-effective and efficient method without requiring major adaptations to existing equipment. The article presents the successful manufacture of 316L/17–4PH multi-alloy steel cubes for four different sintering temperatures using commercially available equipment and feedstock. The feasibility study of the multi-material samples was supported by analyzing the shrinkage, optical density, and microstructure as output parameters. Unlike other works, the multi-material produced parts showed regular shrinkage behaviour and no major deformation, indicating the possibility of creating functional parts without the need for post-processing. Interestingly, relevant findings were made on the different shrinkage values obtained for the constellations considered. Further in-depth investigation of each parameter involved in all the stages of the chain value (extrusion, debinding, and sintering) will be key to support the present results. Additional research into the mechanical and magnetic properties of the samples produced could lead this combination of materials to applications in various industries including automotive and aerospace
The effects of grain size and fractal porosity on thermal conductivity of nano-grained graphite: A molecular dynamics study
No full textThe thermal conductivity of isotropic graphite is a crucial parameter in mechanical and nuclear engineering. However, obtaining its value accurately is still difficult, especially under irradiation and high ambient temperature conditions. In this study, the nano-grained graphite models with different grain sizes and arrangements are designed, and corresponding thermal conductivity is calculated with equilibrium and non-equilibrium molecular dynamics methods. The results show that the thermal conductivity of nano-grained graphite varies between 3 to 5 W/(m·K) and decreases exponentially with the increase of the number of nanograins, while the arrangement of nanograins has almost no effect on the thermal conductivity. In addition, the effect of porosity of nano-polycrystalline graphite is analyzed by constructing fractal porous structures with different fractal dimensions and stages, of which the pore characteristics are determined with the initial zero-stage structure. The thermal conductivity of porous graphite increases with increasing fractal dimension and decreasing fractal porosity and the outcomes of molecular dynamics simulations are verified with the theoretical model results
Bo-derived waste neem to enriching reinforced hybrid composite for environmental remediation
No full textThe utilization of natural fibres often entails a lesser environmental impact when compared to synthetic fibres. Biodegradable natural fibres minimize waste and pollution, and promote sustainability, but their weaker bonds limit their resilience. These issues can be addressed by customizing the composite's mechanical properties with natural and synthetic fibres. In this study, hybrid composites were created using the hand layup method with a novel dissimilar layer arrangement of neem (N), sisal (S), and glass (G) fibre and analyze its mechanical and thermal properties. Experimental observation shows that the GN composite had a higher maximum ultimate tensile strength of 26 N/mm2 than the GS, GNS, and GSN composites. The GN composite had a percentage elongation of 6.33%, similar to the percentage elongation of the GS composite (6.833%), and it also had a higher ultimate shear strength of 50 MPa. The composite GS absorbed 6.6 J energy, higher than the composites GN, GNS, and GNS, which absorbed 6.1 J, 4.5 J, and 4.5 J, respectively. The fractured surface's SEM images were obtained and analyzed for failure. The results demonstrated that the hybridization was effective, and better properties can be obtained by combining neem, sisal, and glass fiber, and it can be used for other requirements, including strength, weight, cost, and ecological impact
Identification of specific markers for human pluripotent stem cell-derived small extracellular vesicles
No full textPluripotent stem cell-derived small extracellular vesicles (PSC-sEVs) have demonstrated great clinical translational potential in multiple aging-related degenerative diseases. Characterizing the PSC-sEVs is crucial for their clinical applications. However, the specific marker pattern of PSC-sEVs remains unknown. Here, the sEVs derived from two typical types of PSCs including induced pluripotent stem cells (iPSC-sEVs) and embryonic stem cells (ESC-sEVs) were analysed using proteomic analysis by liquid chromatography with tandem mass spectrometry (LC-MS/MS), and surface marker phenotyping analysis by nanoparticle flow cytometry (NanoFCM). A group of pluripotency-related proteins were found to be enriched in PSC-sEVs by LC-MS/MS and then validated by Western Blot analysis. To investigate whether these proteins were specifically expressed in PSC-sEVs, sEVs derived from seven types of non-PSCs (non-PSC-sEVs) were adopted for analysis. The results showed that PODXL, OCT4, Dnmt3a, and LIN28A were specifically enriched in PSC-sEVs but not in non-PSC-sEVs. Then, commonly used surface antigens for PSC identification (SSEA4, Tra-1-60 and Tra-1-81) and PODXL were gauged at single-particle resolution by NanoFCM for surface marker identification. The results showed that the positive rates of PODXL (>50%) and SSEA4 (>70%) in PSC-sEVs were much higher than those in non-PSC-sEVs (<10%). These results were further verified with samples purified by density gradient ultracentrifugation. Taken together, this study for the first time identified a cohort of specific markers for PSC-sEVs, among which PODXL, OCT4, Dnmt3a and LIN28A can be detected with Western Blot analysis, and PODXL and SSEA4 can be detected with NanoFCM analysis. The application of these specific markers for PSC-sEVs identification may advance the clinical translation of PSCs-sEVs
Process modelling and techno-economic analysis of anaerobic digestion of sewage sludge integrated with wet oxidation using a gravity pressure vessel and thermal hydrolysis
No full textAnaerobic digestion (AD) of sewage sludge is used to biodegrade sewage sludge into biomethane and digestate. With the addition of thermal processes such as thermal hydrolysis (TH) and wet oxidation (WO), AD biodegradability generally improves. Implementation of additional treatment is challenging due to the limitation in the mass and energy balances. Hence, tools such as process simulation can be utilized to predict the input and output around the process. In addition, an economic analysis needs to be conducted to check the economic feasibility. The techno-economic analysis (TEA), an integrated method to evaluate a process scheme through simulation and subsequent economic analysis, is effective in providing a systematic understanding of economic implications and the feasibility of a process by identifying the bottlenecks and uncertainties that have a significant impact on the technology. TEA of AD, especially incorporating the TH or WO using gravity pressure vessel (GPV) technology, is limited in the literature. A comprehensive TEA of the AD and the pre- and post-treatment schemes can be utilized to determine the most feasible pathway for sludge treatment for implementation in the wastewater industry. In this study, TEA for four different scenarios of AD was conducted using Aspen Plus and economic analysis tools: (1) without any pre- or post-treatment, (2) with TH pre-treatment, (3) with 100 % WO post-treatment, and (4) with 20 % partial wet oxidation (PWO) and acid hydrolysis pre- or post-treatment. A simulation model (GPVM) was developed using Aspen Plus to mimic the GPV reactor. The study outcomes showed that Scenario 3 with 100 % WO post-treatment was the most suitable for processing parameters and sludge treatment cost. The sensitivity analysis concluded that operating cost and plant capacity are the dominant factors that impact the plant feasibility significantly
Hydrogen energy storage requirements for solar and wind energy production to account for long-term variability
No full textWind and solar energy production are plagued, in addition to short-term variability, by significant seasonal variability. The aim of this work is to show the variability of wind and solar energy production, and to compute the hydrogen energy storage needed to address this variability while supplying a stable grid. This is the very first work where the extent of the hydrogen energy storage needed to make stable a grid only supplied by wind and solar energy in Australia is computed. An annual grid demand of 570 TWh in Australia may require 327 GW of installed capacity of wind and solar, 809 TWh of non-dispatchable electricity, and 48 TWh of hydrogen energy storage. While the theoretical maximum power of the electrolysers is 267 GW, the average power is only 46 GW, permitting huge savings in electrolysers capacity adopting a high efficiency energy storage such as flow batteries in between wind and solar producers and electrolysers. The power of the hydrogen generators is 167 GW. The outcome aligns seamlessly with the recent evaluation conducted by the Royal Society regarding the energy storage requirements in the United Kingdom by 2050 to fulfil the net zero commitment in a 570 TWh annually stable grid, with hydrogen similarly serving as the primary source
Weak electron-phonon coupling contributing to enhanced thermoelectric performance in n-type TiCoSb half-Heusler alloys
No full textn-type TiCoSb half-Heusler (HH) alloys show lower thermoelectric performance may be notably owing to the low valley degeneracy of the conduction band. Here, we show that this drawback can be counterbalanced by a decrease in the deformation potential coefficient and hence, weak electron-phonon coupling strength driven by the substitution of Nb for Ti in the n-type alloys Ti1-xNbxCoSb0.96Bi0.04. The combined substitutions of Nb and Bi yield a reduction of ∼86% in the deformation potential of the conduction band minimum, with the lowest value of ∼5 eV at 300 K achieved in Ti0.85Nb0.15CoSb0.96Bi0.04. This effect leads to enhanced power factor from ∼0.018 mW m−1 K−2 for x = 0 to ∼1.69 mW m−1 K−2 for x = 0.15 at RT due to the resulting strong increase in electron mobility by one order of magnitude. Both the isovalent Bi and aliovalent Nb substitutions further contribute to decrease the lattice thermal conductivity owing to enhanced mass and strain field fluctuations. The beneficial combined effects of weaker electron-phonon coupling and enhanced point-defect phonon scattering results in a higher dimensionless thermoelectric figure of merit ZT, with a peak value ∼ 0.37 at 870 K in Ti0.85Nb0.15CoSb0.96Bi0.04, representing a ∼ 375% improvement with respect to pristine TiCoSb
A New Method to Estimate the Point Spread Function of Satellite Imagers From Edge Measurements
No full textThe 2-D Point Spread Function (PSF) of satellite imaging sensors is usually estimated from two perpendicular edge measurements. It has been shown that this method is only valid for a sensor with a low optical factor 'Q' (defined as the wavelength times the F number divided by the pixel pitch), so a new method is required to estimate the PSF for sensors with moderate and high Q. In this work, a new three-edge method that estimates the PSF by quadratic interpolation in the spatial frequency domain is assessed and shown to complement the current two-edge method. The use of both methods allows the estimation of the PSF down to one order of magnitude below its peak response. The new method is assessed using a generic sensor system methodology that considers the optical design parameters of the sensor as independent variables. Results are graphically represented as constant Mean Absolute Percentage Errors (MAPEs) contours drawn on a plane of optical designs in which each point represents an imaging channel with a specific Q and optical aperture's obstruction ratio