Accurate simulation estimates of phase behaviour in ternary mixtures with prescribed composition

This paper describes an isobaric semi-grand canonical ensemble Monte Carlo scheme for the accurate study of phase behaviour in ternary fluid mixtures under the experimentally relevant conditions of prescribed pressure, temperature and overall composition. It is shown how to tune the relative chemical potentials of the individual components to target some requisite overall composition and how, in regions of phase coexistence, to extract accurate estimates for the compositions and phase fractions of individual coexisting phases. The method is illustrated by tracking a path through the composition space of a model ternary Lennard-Jones mixture.Comment: 6 pages, 3 figure

Supply chain temple of resilience

In March 2011, an earthquake and tsunami hit the north-eastern coastline of Japan. Honda, Toyota, Nissan and Subaru all had plants in or close to the affected region, and were forced to close them

Simulation studies of fluid critical behaviour

We review and discuss recent advances in the simulation of bulk critical phenomena in model fluids. In particular we emphasise the extensions to finite-size scaling theory needed to cope with the lack of symmetry between coexisting fluid phases. The consequences of this asymmetry for simulation measurements of quantities such as the particle density and the heat capacity are pointed out and the relationship to experiment is discussed. A general simulation strategy based on the finite-size scaling theory is described and its utility illustrated via Monte-Carlo studies of the Lennard-Jones fluid and a two-dimensional spin fluid model. Recent applications to critical polymer blends and solutions are also briefly reviewed. Finally we consider the outlook for future simulation work in the field.Comment: 35 pages Revtex, 11 eps figures. Review article to appear in J. Phys.: Condens. Matte

A non-equilibrium Monte Carlo approach to potential refinement in inverse problems

The inverse problem for a disordered system involves determining the interparticle interaction parameters consistent with a given set of experimental data. Recently, Rutledge has shown (Phys. Rev. E63, 021111 (2001)) that such problems can be generally expressed in terms of a grand canonical ensemble of polydisperse particles. Within this framework, one identifies a polydisperse attribute (`pseudo-species') $\sigma$ corresponding to some appropriate generalized coordinate of the system to hand. Associated with this attribute is a composition distribution $\bar\rho(\sigma)$ measuring the number of particles of each species. Its form is controlled by a conjugate chemical potential distribution $\mu(\sigma)$ which plays the role of the requisite interparticle interaction potential. Simulation approaches to the inverse problem involve determining the form of $\mu(\sigma)$ for which $\bar\rho(\sigma)$ matches the available experimental data. The difficulty in doing so is that $\mu(\sigma)$ is (in general) an unknown {\em functional} of $\bar\rho(\sigma)$ and must therefore be found by iteration. At high particle densities and for high degrees of polydispersity, strong cross coupling between $\mu(\sigma)$ and $\bar\rho(\sigma)$ renders this process computationally problematic and laborious. Here we describe an efficient and robust {\em non-equilibrium} simulation scheme for finding the equilibrium form of $\mu[\bar\rho(\sigma)]$. The utility of the method is demonstrated by calculating the chemical potential distribution conjugate to a specific log-normal distribution of particle sizes in a polydisperse fluid.Comment: 6 pages, 3 figure

Quantifying density fluctuations in water at a hydrophobic surface: evidence for critical drying

Employing smart Monte Carlo sampling techniques within the grand canonical ensemble, we investigate the properties of water at a model hydrophobic substrate. By reducing the strength of substrate-water attraction we find that fluctuations in the local number density, quantified by a rigorous definition of the local compressibility $\chi(z)$, increase rapidly for distances $z$ within $1$ or $2$ molecular diameters from the substrate as the degree of hydrophobicity, measured by the macroscopic contact angle $\theta$, increases. Our simulations provide evidence for a continuous (critical) drying transition as the substrate-water interaction becomes very weak: $\cos(\theta)\to -1$. We speculate that the existence of such a transition might account for earlier simulation observations of strongly enhanced density fluctuations

RFID Demystified: Part 3. Company Case Studies.

In the previous two parts of RFID Demystified we have discussed the technology, possible benefits and areas of application for with Radio Frequency Identification (RFID) systems. In this final part we review Company Case-Studies of those who have decided to apply the technology within their organisation. It will be seen that considerable benefits are being experienced within some organisations, pilot applications are increasing our learning and providing a foundation for the future success of projects in this area

Understanding collaborative supply chain relationships through the application of the Williamson organisational failure framework

Many researchers have studied supply chain relationships however, the preponderance of open markets situations and ‘industry-style’ surveys have reduced the empirical focus on the dynamics of long-term, collaborative dyadic relationships. Within the supply chain the need for much closer, long-term relationships is increasing due to supplier rationalisation and globalisation (Spekman et al, 1998) and more information about these interactions is required. The research specifically tested the well-accepted Williamson’s (1975) Economic Organisations Failure Framework as a theoretical model through which long term collaborative relationships can be

Polydispersity induced solid-solid transitions in model colloids

Specialized Monte Carlo simulation techniques and moment free energy method calculations, capable of treating fractionation exactly, are deployed to study the crystalline phase behaviour of an assembly of spherical particles described by a top-hat "parent" distribution of particle sizes. An increase in either the overall density or the degree of polydispersity is shown to generate a succession of phase transitions in which the system demixes into an ever greater number of face-centred cubic "daughter" phases. Each of these phases is strongly fractionated: it contains a much narrower distribution of particle sizes than is present in the system overall. Certain of the demixing transitions are found to be nearly continuous, accompanied by fluctuations in local particle size correlated over many lattice spacings. We explore possible factors controlling the stability of the phases and the character of the demixing transitions.Comment: 14 pages, 13 figure