A thermodynamic reassessment of the La–Sn system

Thermodynamic modelling of the La–Sn binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. The liquid phase has been described with the association solution model with a ‘ La₁Sn₁’ associated complex. The intermetallic compounds were treated as stoichiometric phases. The calculated phase diagram and the thermodynamic properties of the system are in satisfactory agreement with the majority of the experimental data.     

Assessment of the diffusional mobilities in the face-centred cubic Ag–Zn alloys

Based on the available thermodynamic information and diffusion coefficient data of the Ag-Zn binary system, the atomic mobilities of Ag and Zn in face-centred cubic (fcc) Ag-Zn alloys have been assessed as a function of temperature and composition in terms of the CALPHAD method using the DICTRA software package. Optimized mobility parameters are presented. Comparisons between the calculated and measured diffusion coefficients show that most of the experimental information can be satisfactorily reproduced in the present work. The obtained mobility parameters can also predict reasonable concentration profiles of the diffusion zone in the binary Ag-Zn diffusion couples.     

Observer‐based model reference control of Takagi–Sugeno–Lipschitz systems affected by disturbances using quadratic boundedness

In this paper, a model reference control strategy is proposed in order to perform trajectory tracking in Takagi–Sugeno–Lipschitz (TSL) systems. Since the state vector is assumed not to be completely available for measurement, a proportional observer is added to the control scheme in order to apply an estimate‐feedback control action instead of a state‐feedback one. The overall design of both the controller and the observer gains are performed using a Lyapunov‐based quadratic boundedness specification, in order to improve the robustness against unknown exogenous disturbances. It is shown that the conditions that ensure convergence within ellipsoidal regions of the tracking and estimation errors can be expressed in the form of a linear matrix inequality (LMI) formulation. The effectiveness of the developed control strategy is demonstrated by means of simulation results.     

Thermodynamic evaluation and optimization of Al–Gd, Al–Tb, Al–Dy, Al–Ho and Al–Er systems using a Modified Quasichemical Model for the liquid

The Al–Gd, Al–Tb, Al–Dy, Al–Ho and Al–Er (Al–heavy rare earths) binary systems have been systematically assessed and optimized based on the available experimental data and ab-initio data using the FactSage thermodynamic software. A systematic technique (reduced melting temperature proposed by Gschneidner) was used for estimating the Al–Tb phase diagram due to lack of experimental data. Optimized model parameters of the Gibbs energies for all phases which reproduced all the reliable experimental data to satisfaction have been obtained. The optimization procedure was biased by putting a strong emphasis on the observed trends in the thermodynamic properties of Al–RE phases. The Modified Quasichemical Model, which takes short-range ordering into account, is used for the liquid phase and the Compound Energy Formalism is used for the solid solutions in the binary systems. It is shown that the Modified Quasichemical Model used for the liquid alloys permits one to obtain entropies of mixing that are more reliable than that based on the Bragg–Williams random mixing model which does not take short-range ordering into account.     

Construction of modified embedded atom method potentials for the study of the bulk phase behaviour in binary Pt–Rh, Pt–Pd, Pd–Rh and ternary Pt–Pd–Rh alloys

A first attempt is made to simulate the solid part of the phase diagram of the ternary Pt–Pd–Rh system. To this end, Monte Carlo (MC) simulations are combined with the Modified Embedded Atom Method (MEAM) and optimised parameters entirely based on Density Functional Theory (DFT) data. This MEAM potential is first validated by calculating the heat of mixing or the demixing phase boundary for the binary subsystems Pt–Rh, Pt–Pd and Pd–Rh. For the disordered alloy systems Pt–Rh and Pt–Pd, the MC/MEAM simulation results show a slightly exothermic heat of mixing, thereby contradicting any demixing behaviour, in agreement with other theoretical results. For the Pd–Rh system the experimentally observed demixing region is very well reproduced by the MC/MEAM simulations. The extrapolation of the MEAM potentials to ternary systems is next validated by comparing DFT calculations for the energy of formation of ordered Pt–Pd–Rh compounds with the corresponding MEAM energies. Finally, the validated potential is used for the calculation of the ternary phase diagram at 600 K.     

Atomic mobilities and diffusional growth in solid phases of the V–Nb and V–Zr systems

In conjunction with the thermodynamic parameters in the literature, the atomic mobilities of the V–Nb and V–Zr bcc alloys were assessed from experimental diffusion coefficients. The assessed atomic mobilities are given as functions of temperatures and composition in the CALPHAD format. Comparisons between the calculated and experimental quantities show that the obtained mobility parameters enable most of the experimental diffusion data to be well reproduced. Based on the velocity constructions for lattice planes in V/Nb diffusion couples, the displacements of Kirkendall makers were investigated under various annealing conditions, and the results are in general agreement with experimental values. In addition, computational studies of V/Zr diffusion couples were carried out for the kinetic behaviors of V ₂Zr at various annealing temperatures, from which the temperature dependence of the interdiffusion coefficients for V ₂Zr was evaluated.     

Experimental study and thermodynamic assessment of the Ag–Ti system

A thermodynamic assessment of the binary Ag–Ti system was performed based on the evaluation of the literature and the results of the present experiments. For the experimental study, special deep embedding diffusion couples were prepared and analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The phase equilibrium relationship and the conjugate phase compositions were determined at 1023 K, 1253 K, 1373 K and 1474 K respectively. For the thermodynamic assessment, the Redlich–Kister polynomial was used to describe the solution phases, liquid (L), bcc, hcp, and fcc. The sublattice-compound energy model was employed to describe the intermediate phase, (AgTi), with a homogeneity range. The other intermediate phase, AgTi₂, without a homogeneity range was treated as the stoichiometric phase. A set of self-consistent thermodynamic parameters of the Ag–Ti system has been obtained. The calculated phase diagram was presented and compared with the experimental data.     

Analysis and control of switched linear systems via modified Lyapunov–Metzler inequalities

This paper addresses analysis and switching control problems of continuous/discrete‐time switched linear systems. A particular class of matrix inequalities, the so‐called Lyapunov–Metzler inequalities, will be modified to provide conditions for stability analysis and output feedback control synthesis under a relaxed min‐switching logic. The switching rule combined with switching output feedback controllers will be designed to stabilize the switched system and satisfy a prespecified gain performance. The proposed analysis and switching control approach could refrain frequent switches commonly observed in min‐switching based designs. The effectiveness of the proposed approach will be illustrated through numerical examples. Copyright © 2012 John Wiley & Sons, Ltd.     

Interactivity in human–computer interaction: a study of credibility, understanding, and influence

Advancements in computer technology have allowed the development of human-appearing and -behaving virtual agents. This study examined if increased richness and anthropomorphism in interface design lead to computers being more influential during a decision-making task with a human partner. In addition, user experiences of the communication format, communication process, and the task partner were evaluated for their association with various features of virtual agents. Study participants completed the Desert Survival Problem (DSP) and were then randomly assigned to one of five different computer partners or to a human partner (who was a study confederate). Participants discussed each of the items in the DSP with their partners and were then asked to complete the DSP again. Results showed that computers were more influential than human partners but that the latter were rated more positively on social dimensions of communication than the former. Exploratory analysis of user assessments revealed that some features of human–computer interaction (e.g. utility and feeling understood) were associated with increases in anthropomorphic features of the interface. Discussion focuses on the relation between user perceptions, design features, and task outcomes.     

A critical thermodynamic assessment of the Mg–Ni, Ni–Y binary and Mg–Ni–Y ternary systems

A thorough review and critical evaluation of phase equilibria and thermodynamic data for the phases in the Mg–Ni–Y ternary system have been carried out over the entire composition range from room temperature to above the liquidus. This system is being modeled for the first time using the modified quasichemical model which considers the presence of short range ordering in the liquid. The Gibbs energies of the different phases have been modeled, and optimized model parameters that reproduce all the experimental data simultaneously within experimental error limits have been obtained. For the liquid phases, the modified quasichemical model is applied. A sublattice model within the compound-energy formalism is used to take proper account of the structures of the binary intermediate solid solutions. The Mg–Ni and Ni–Y binary systems have been re-optimized based on the experimental phase equilibrium and thermodynamic data available in the literature. The optimized thermodynamic parameters for the Mg–Y system are taken from the previous thermodynamic assessment of the Mg–Cu–Y system by the same authors. The constructed database has been used to calculate liquidus projection, isothermal and vertical sections which are compared with the available experimental information on this system. The current calculations are in a good agreement with the experimental data reported in the literature.     

Set-theoretic solutions of the Yang–Baxter equation, graphs and computations

We extend our recent work on set-theoretic solutions of the Yang–Baxter or braid relations with new results about their automorphism groups, strong twisted unions of solutions and multipermutation solutions. We introduce and study graphs of solutions and use our graphical methods for the computation of solutions of finite order and their automorphisms. Results include a detailed study of solutions of multipermutation level 2.     

Simultaneous measurement of Pb, Cd and Zn using differential pulse anodic stripping voltammetry at a bismuth/poly(p-aminobenzene sulfonic acid) film electrode

A novel sensor was developed for simultaneous detection of Pb, Cd and Zn, based on the differential pulse anodic stripping response at a bismuth/poly(p-aminobenzene sulfonic acid) (Bi/poly(p-ABSA)) film electrode. This electrode was generated in situ by depositing simultaneously bismuth and the metals by reduction at −1.40 V on the poly(p-ABSA) modified electrode. Compared with the bismuth film electrode, the Bi/poly(p-ABSA) film electrode can yield a larger stripping signal for Pb, Cd and Zn. Under the optimum conditions, a linear response was observed for Cd and Zn in the range from 1.00 to 110.00 μg L⁻¹ and for Pb in the range from 1.00 to 130.00 μg L⁻¹. The detection limits of Pb(II), Cd(II) and Zn(II) were 0.80, 0.63 and 0.62 μg L⁻¹, respectively. Finally this sensor had been applied to the simultaneous determination of Pb(II), Cd(II) and Zn(II) in river water samples and the results were quite corresponding to the value obtained by atomic absorption spectrometry.     

The factors that affect the performance of open source software development – the perspective of social capital and expertise integration

Drawing on social capital theory, we develop a theoretical model aiming to explore how open source software (OSS) project effectiveness (in terms of team size, team effort and team's level of completion) is affected by expertise integration. This in turn is influenced by three types of social capital – relational capital, cognitive capital and structural capital. In addition, this study also examines two moderating effects – the impact of technical complexity on the relationship between cognitive capital and expertise integration, and of task interdependence on the relationship between expertise integration and task completion. Through a field survey of 160 OSS members from five Taiwanese communities, there is support for some of the proposed hypotheses. Both reciprocity and centrality affect expertise integration as expected, but the influence of commitment and cognitive capital (including expertise and tenure) on expertise integration is not significant. Finally, expertise integration affects both team size and team effort, which in turn jointly influence task completion. This research contributes to advancing theoretical understanding of the effectiveness of free OSS development as well as providing OSS practitioners with insight into how to leverage social capital for improving the performance of OSS development.     

Pareto–Koopmans efficiency in two‐stage network data envelopment analysis in the presence of undesirable intermediate products and nondiscretionary factors

Many studies have recently been conducted on the evaluation of system performance with a two‐stage network structure in data envelopment analysis (DEA) literature. One of the topics of interest to researchers has been the mitigation of undesirable products or nondiscretionary factors into their corresponding possible production set (PPS) and their impact on overall efficiency calculations. Determination of decision‐making units (DMUs) with Pareto–Koopmans efficiency status is decisive in identifying benchmark units. The calculated overall efficiency status is compromised when both undesirable products and nondiscretionary factors are present. This work utilizes an axiomatic approach. A novel PPS for a two‐stage network in presence of undesirable intermediate products and nondiscretionary exogenous inputs is introduced. Based on this PPS and by focusing on the principle of mathematical dominance, new models for evaluating overall and divisional efficiencies are presented. In addition, by proposing a two‐step network DEA approach, a necessary and sufficient condition for detection of DMUs with Pareto–Koopmans efficiency status is provided. And by introducing a two‐step algorithm, a novel technique for determining overall efficiency conditions is produced. Finally, the proposed technology is applied to a practical example, and outcomes are discussed.