Engineering
We consider a preferential growth model where particles are added one by one to the system consisting of clusters of particles. A new particle can either form a new cluster (with probability q) or join an already existing cluster with a... more
We consider a preferential growth model where particles are added one by one to the system consisting of clusters of particles. A new particle can either form a new cluster (with probability q) or join an already existing cluster with a probability proportional to the size thereof. We calculate exactly the probability Pi(k,t) that the size of the ith cluster at time t is k. We analyze the asymptotics, the scaling properties of the size distribution and of the mean size, as well as the relation of our system to recent network models.
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In Ireland, grass is a readily available bioresource. It has previously been established that Green biorefinery (GBR) could become a potential use of Irish grasslands, and a blueprint for a sustainable GBR industry in Ireland has been... more
In Ireland, grass is a readily available bioresource. It has previously been established that Green biorefinery (GBR) could become a potential use of Irish grasslands, and a blueprint for a sustainable GBR industry in Ireland has been developed. The objective of this paper is to use scenario analysis to investigate the sensitivity of the profitability of the GBR blueprint to variations in grass quantity and quality as a function of botanical composition, fertiliser application, and biomass availability. As an outcome of these scenario analyses, the price the GBR can offer to farmers above their production costs (€ t−1 dry matter) was calculated. Results of the scenario analyses determined that GBR systems located in a catchment area of permanent pasture (Lolium perenne > 60%) with annual grass yields in the range of 9–12 t dry matter (DM) ha−1, and supplied with grass biomass with a fibre content of 500–555 g kg−1 DM and a protein content of 110–130 g kg−1 DM, were viable. The most profitable scenarios were generated when nitrogen fertiliser application was greater than 90 kg ha−1 a−1. Biomass availability of less than 30% resulted in reduced profitability and for some scenarios resulted in a loss for both the GBR and farmer due to increased transport costs. Within the scenario assumptions of this study, grass feedstock was valued at €4–€56 t−1 dry matter above production costs. However, this value depended on the yields and biomass availability of the GBR catchment area.
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Several biotic elicitors have been used in Brassicaceae species to enhance their phytochemical quality. However, there is no comparison between elicitors under controlled growth conditions. In order to draw general conclusions about the... more
Several biotic elicitors have been used in Brassicaceae species to enhance their phytochemical quality. However, there is no comparison between elicitors under controlled growth conditions. In order to draw general conclusions about the use of elicitors to enrich ready-to-eat sprouts in health-promoting glucosinolates, the aim of this study was to unveil the effect of the phytohormones methyl jasmonate (25 μM), jasmonic acid (150 μM), and salicylic acid (100 μM), the oligosaccharides glucose (277 mM) and sucrose (146 mM), and the amino acid dl-methionine (5 mM) as elicitors over 8-day sprouting Brassica oleraceae (broccoli), Brassica napus (rutabaga cabbage), Brassica rapa (turnip), and Raphanus sativus (China rose radish and red radish), representative species high in glucosinolates previously studied. Results indicated that the phytohormones methyl jasmonate and jasmonic acid and the sugars acted as effective elicitors, increasing the total glucosinolate contents of the sprouts, p...
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The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the... more
The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the electrostatic interaction energy of ions at closest approach, in determining how the disjoining pressure exerted on the walls depends on the geometrical confinement. Our theory reveals that thermodynamic fluctuations play a vital role in the "squeezing out" of charged layers as the confinement is increased. The model shows good qualitative agreement with previous experimental data, with all parameters independently estimated without fitting.
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The geometrical formulation of continuum mechanics provides us with a powerful approach to understand and solve problems in anelasticity where an elastic deformation is combined with a non-elastic component arising from defects, thermal... more
The geometrical formulation of continuum mechanics provides us with a powerful approach to understand and solve problems in anelasticity where an elastic deformation is combined with a non-elastic component arising from defects, thermal stresses, growth effects or other effects leading to residual stresses. The central idea is to assume that the material manifold, prescribing the reference configuration for a body, has an intrinsic, non-Euclidean, geometrical structure. Residual stresses then naturally arise when this configuration is mapped into Euclidean space. Here, we consider the problem of discombinations (a new term that we introduce in this paper), that is, a combined distribution of fields of dislocations, disclinations and point defects. Given a discombination, we compute the geometrical characteristics of the material manifold (curvature, torsion, non-metricity), its Cartan's moving frames and structural equations. This identification provides a powerful algorithm to ...
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ABSTRACT The Kirchhoff equations for elastic tubes are modified to include the effect of fluid flow. Using the techniques of linear and nonlinear analysis specially developed for the Kirchhoff equations, the effect of the fluid flow on... more
ABSTRACT The Kirchhoff equations for elastic tubes are modified to include the effect of fluid flow. Using the techniques of linear and nonlinear analysis specially developed for the Kirchhoff equations, the effect of the fluid flow on the basic twist-to-writhe instability is investigated. The results suggest an intriguing modification of the bifurcation threshold due to the flow. Beyond threshold the buckled tube acquires a slight curvature which modifies the flow rate and results in a correction to nonlinearity of the amplitude equation governing the deformation dynamics.
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We introduce a geometric framework to calculate the residual stress fields and deformations of nonlinear solids with inclusions and eigenstrains. Inclusions are regions in a body with different reference configurations from the body... more
We introduce a geometric framework to calculate the residual stress fields and deformations of nonlinear solids with inclusions and eigenstrains. Inclusions are regions in a body with different reference configurations from the body itself and can be described by distributed eigenstrains. Geometrically, the eigenstrains define a Riemannian 3-manifold in which the body is stress-free by construction. The problem of residual stress calculation is then reduced to finding a mapping from the Riemannian material manifold to the ambient Euclidean space. Using this construction, we find the residual stress fields of three model systems with spherical and cylindrical symmetries in both incompressible and compressible isotropic elastic solids. In particular, we consider a finite spherical ball with a spherical inclusion with uniform pure dilatational eigenstrain and we show that the stress in the inclusion is uniform and hydrostatic. We also show how singularities in the stress distribution emerge as a consequence of a mismatch between radial and circumferential eigenstrains at the centre of a sphere or the axis of a cylinder.
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Spherical neodymium-iron-boron magnets are permanent magnets that can be assembled into a variety of structures owing to their high magnetic strength. A one-dimensional chain of these magnets responds to mechanical loadings in a manner... more
Spherical neodymium-iron-boron magnets are permanent magnets that can be assembled into a variety of structures owing to their high magnetic strength. A one-dimensional chain of these magnets responds to mechanical loadings in a manner reminiscent of an elastic rod. We investigate the macroscopic mechanical properties of assemblies of ferromagnetic spheres by considering chains, rings and chiral cylinders of magnets. Based on energy estimates and simple experiments, we introduce an effective magnetic bending stiffness for a chain of magnets and show that, used in conjunction with classic results for elastic rods, it provides excellent estimates for the buckling and vibration dynamics of magnetic chains. We then use this estimate to understand the dynamic self-assembly of a cylinder from an initially straight chain of magnets.
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... The usual approach to modelling these structures is to assume that they can be represented as an elastic filament subject to the classical laws of mechanics and elasticity theory. ... We first givea brief summary of the kinematics (ie... more
... The usual approach to modelling these structures is to assume that they can be represented as an elastic filament subject to the classical laws of mechanics and elasticity theory. ... We first givea brief summary of the kinematics (ie the relationship between positions and ...
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... processes such as epitaxial growth where material is fed in the system and reorganize on the substrate but mostly refers to phenomena associated with phase transition: the interface between the phases evolves in time to produce a... more
... processes such as epitaxial growth where material is fed in the system and reorganize on the substrate but mostly refers to phenomena associated with phase transition: the interface between the phases evolves in time to produce a crystal (Langer, 1980, Ben Amar and Pomeau ...
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The continuum mechanical treatment of biological growth and remodeling has attracted considerable attention over the past fifteen years. Many aspects of these problems are now well-understood, yet there remain areas in need of significant... more
The continuum mechanical treatment of biological growth and remodeling has attracted considerable attention over the past fifteen years. Many aspects of these problems are now well-understood, yet there remain areas in need of significant development from the standpoint of experiments, theory, and computation. In this perspective paper we review the state of the field and highlight open questions, challenges, and avenues for further development.
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Radiofrequency (13.56MHz) plasma enhanced chemical vapor deposition process is used for deposition of SiOx films on bell metal substrates using Ar/hexamethyldisiloxane/O2 glow discharge. The DC self-bias voltage developed on the... more
Radiofrequency (13.56MHz) plasma enhanced chemical vapor deposition process is used for deposition of SiOx films on bell metal substrates using Ar/hexamethyldisiloxane/O2 glow discharge. The DC self-bias voltage developed on the substrates is observed to be varied from −35V to −115V depending on the RF power applied to the plasma. Plasma potential measurements during film deposition process are carried out by