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Analysing the effect of food supply chain traceability on product waste
No full textThis paper presents initial results from an agent-based simulation study into the impact of supply chain traceability information sharing on food waste reduction in the fresh food supply chain. Based on data collected during a 2019 study of a multi-tier citrus fruit supply chain, a conceptual model of information sharing relationships and their impact on food waste was created. This model formed the basis of an agent-based simulation where the actors in the supply chain share time-and-temperature storage information for the fruit. The model is successfully verified against the case study data, initial findings show that the benefits of traceability are realised further downstream in the supply chain. We further comment on the environmental and social implications of our results
Fan aerodynamics with a short intake at high angle of attack
No full textFans that are designed to maintain thrust at the high angle of attack (AOA) flight condition could exploit the cruise fuel burn benefit of a shorter intake design. This article considers how the fan rotor radial pressure ratio distribution and tip velocity triangle can be designed to improve thrust when coupled to a short intake operating at high AOA. Two AOA values are investigated using unsteady computational fluid dynamics: 20 deg (attached flow) and 35 deg (separated flow). Thrust at high AOA is governed by three key loss and work input mechanisms. (i) Rotor choking loss: Flow is accelerated around the intake bottom lip and enters the rotor with high Mach numbers. Fans designed with a tip-high radial pressure ratio distribution reduced choking loss with a separated intake compared to a mid-high design, particularly when the tip velocity triangle was designed with high diffusion instead of high camber. (ii) Rotor-separation interaction loss: The rotor ingests low mass flow when operating inside the separation and the casing boundary layer separates. High diffusion tip designs strengthened the casing separation, but this penalty did not outweigh improved choking loss. (iii) Work input in radial flows: High AOA generates strong radial flows through the rotor, which alter both the amount and the way work is imparted on the flow. Fans designed with a mid-high radial pressure ratio distribution imparted high work on streamlines migrating toward the hub. Consolidating these findings, we propose two design philosophies for improved thrust at high AOA: High work (mid-high radial pressure ratio distribution) or low loss (tip-high radial pressure ratio distribution with high diffusion tip velocity triangle)
Publisher Correction: Graphene overcoats for ultra-high storage density magnetic media.
No full textPublisher Correction: Graphene overcoats for ultra-high storage density magnetic media
A mechanism-based multi-trap phase field model for hydrogen assisted fracture
No full textWe present a new mechanistic, phase field-based formulation for predicting hydrogen embrittlement. The multi-physics model developed incorporates, for the first time, a Taylor-based dislocation model to resolve the mechanics of crack tip deformation. This enables capturing the role of dislocation hardening mechanisms in elevating the tensile stress, hydrogen concentration and dislocation trap density within tens of microns ahead of the crack tip. The constitutive strain gradient plasticity model employed is coupled to a phase field formulation, to simulate the fracture process, and to a multi-trap hydrogen transport model. The analysis of stationary and propagating cracks reveals that the modelling framework presented is capable of adequately capturing the sensitivity to the hydrogen concentration, the loading rate, the material strength and the plastic length scale. In addition, model predictions are compared to experimental data of notch tensile strength versus hydrogen content on a high-strength steel; a very good agreement is attained. We define and implement both atomistic-based and phenomenological hydrogen degradation laws and discuss similarities, differences and implications for the development of parameter-free hydrogen embrittlement models
Comparing the environmental performance of distributed versus centralized plastic recycling systems: Applying hybrid simulation modeling to life cycle assessment
No full textThe plastic waste dilemma has gained international attention because of increased public awareness and the rise of waste import bans. Sorting and recycling technologies that deal with plastic waste streams exist but face challenges in highly dense urbanized regions such as Singapore because of high space requirements. Multiple small-scale plastic sorting and recycling facilities that are distributed closer to points of waste generation offer the possibility of increasing the recovery of plastic-waste streams in urbanized settings. To holistically quantify the environmental performance of this type of system, a life cycle assessment (LCA) is conducted to compare five different scenarios of distributed and centralized sorting and recycling of plastic bottles and takeaway containers in Singapore. A hybrid simulation model is used to simulate the complex dynamics of waste-processing systems which involves waste generation, collection scheduling, sorting, recycling, and disposal of residual materials. The results of the LCA showed that the life cycle environmental impacts to climate change, water depletion, and terrestrial ecotoxicity of the distributed scenarios were higher than the centralized scenarios by 7–30% depending on the impact category. Although the distributed scenarios had lower total travel distances, their reliance on commercial vans led to their higher environmental impacts than the centralized scenarios. The findings of this study provide motivation for future research in applying hybrid simulation models in LCAs of waste-to-resource exchange networks. The data used to carry out the hybrid simulations and the LCA are provided as Supporting Information. This article met the requirements for a Gold-Silver JIE data openness badge described at http://jie.click/badges
The optimal scattering structures for light-trapping in ultra-thin photovoltaic devices
No full textThe introduction of light scattering structures for efficient absorption of incident illumination is essential in ultra-thin solar cells given their reduced optical path length. The growing interest in these devices demands attaining high efficiencies through the identification of optimal designs to maximise the absorption of incident photons. A pathway towards such high efficiencies is the implementation of transparent scattering structures to minimise parasitic losses. We study the performance of these structures by focusing on dielectric/high-band-gap semiconductor scattering layers in an ultra-thin (80 nm) GaAs solar cell. Comparisons with absorptive scattering layers are enabled by presenting data for an equivalent device with metal/dielectric structures. Following a previously reported light management optimisation method which is guided by the dispersion of the avail- able waveguide modes, we find an improved performance for the transparent scattering layers. Our study also compares the light absorption enhancement offered by transparent photonic crystal diffractive arrays to that of transparent quasi-random geometries which target the diffracted power to the most favourable waveguide modes in the device. We find the former designs to have a superior performance in our device of interest, and the latter to suffer from greater reflection losses. Finally, our results also demonstrate the effectiveness of the optimisation method used and its applicability to multiple device architectures for the design of high-efficiency photovoltaics
Characterising the variability in wrinkling during the preforming of non-crimp fabrics
No full textThe preforming of textile reinforcements during composite manufacturing is subject to significant variability, which affects the predictability of critical defects such as wrinkles in the component. Therefore, wrinkling variability needs to be quantified so that it can be accounted for during production and in process simulations. This study characterises the variability in the wrinkling behaviour of a biaxial non-crimp fabric during hemispherical preforming under various conditions. A variability characterisation method is developed that decouples and quantifies the variability in wrinkle amplitude and wrinkle location. The results show that the fabric architecture and the specific forming layup have a significant influence on both the wrinkle amplitude and location variability, with the location variability being more sensitive to changes in the forming process than the amplitude variability. The method can be applied to characterise the variability for various surface defects or variables and thus used as a benchmarking tool for preforming processes
Can titanium oxide nanotubes facilitate intracellular delivery by laser-assisted photoporation?
No full textIn the present study, a newly developed nanosecond pulse laser-assisted photoporation using titanium-oxide nanotubes (TNT) for highly efficient intracellular delivery has been established. The proof of concept for the possibilities of intracellular delivery after irradiation of nanosecond pulse laser on TNT has been validated. TNT on titanium sheets using the electrochemical anodization technique at different voltage and time has been developed. The extensive X-ray photoelectron spectroscopy (XPS) study confirms the presence of different titanium oxide species such as TiO2, TixOy (TiO/Ti2O3/Ti3O5) having different concentrations in TNT formed by different anodization voltage and time along with a minor quantity of Ti metal (Ti0). Formation of sub-oxides results in oxygen defects in TNT. It has also been evidenced from XPS that the anodization voltage and time can change the concentration of oxygen defects on the nanotubes. Due to the formation of oxygen defects, nanotubes have the quasi-metallic and metallic properties. These properties of the nanotubes may facilitate the intracellular delivery by various mechanisms after irradiation of nanosecond pulse laser. Using this technique, we successfully have delivered Propidium iodide (PI) and dextran into HeLa cells (HeLa- human cervical cancer cells) with high transfection efficiency and cell viability on nanotubes formed at 15 V/2 h
The convective Stefan problem: shaping under natural convection
No full textWhat is the shape formed by a body that is melting or dissolving into an ambient fluid? We present a theoretical analysis of the dynamics of melting or dissolving bodies in the common situation where the transfer of heat or solute at the surface creates a thin thermal or solutal convective boundary layer along its surface. By conducting a general analysis of a mathematical model describing the shape evolution of such bodies (Pegler & Davies Wykes, J. Fluid Mech., vol. 900, 2020, A35), we reveal new phenomena relating to the emergence of fundamental similarity solutions, asymptotic transitions, tip structure and the conditions for the development of sharp versus blunted tips. A universal regime diagram is developed showing asymptotic transitions between two different classes of similarity solutions. With time, the tip of initially rectangular bodies is found to descend as at early times, but transitions to the considerable faster power of at long times, for example. Surprisingly, the tips of certain shapes, including initially rectangular bodies, sharpen continuously, whilst those of others, including initially conic bodies, blunt for all times. For the former case, the tip curvature grows rapidly as, forming a needle-like shape. More general initial shapes can produce multiple transitions between sharpening and blunting. These results provide foundational understanding of buoyancy-driven fluid sculpting that underlies numerous natural and industrial applications