Thermodynamic description of the Mg–Eu binary system

Thermodynamic assessment of the Mg–Eu binary system has been carried out by combining first-principles calculations and Miedema’s theory with CALPHAD method. Firstly, the mixing enthalpy of the liquid alloys was calculated by using Miedema’s theory, and formation enthalpies of the intermetallic compounds were calculated by using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA). Subsequently, the liquid phase was described employing a simple substitutional model, of which the excess Gibbs energy was formulated with a Redlich-Kister expression. And the solubility of Eu in HCP_(Mg) and Mg in BCC_(Eu) were neglected. While the intermetallic compounds Mg₁₇Eu₂, Mg₅Eu, Mg₄Eu, Mg₂Eu and MgEu, were treated as stoichiometric compounds. Consequently, a set of self-consistent thermodynamic parameters for all stable phases in the Mg–Eu binary system were obtained, which can reproduce most of the thermodynamic and phase boundary data.     

Thermodynamic assessment of the Ni–Sc binary system

On the basis of the experimental data of the phase equilibria and the thermochemical properties, a critical evaluation for the Ni–Sc binary system has been carried out using the CALPHAD (Calculation of Phase Diagrams) method. The associated model is used for the liquid phase containing the constituent species Ni, Sc and ScNi. The terminal solid solutions Fcc_A1 (Ni), Hcp_A3 (Sc), and Bcc_A2 (Sc) are described by the solution model with the Redlich–Kister polynomial. The intermetallic compounds, ScNi₅, Sc₂Ni₇, ScNi and Sc₂Ni, are treated as strict stoichiometric compounds. The compound with a homogeneity range, (ScNi₂), is modeled using two sublattices as (Sc,Ni)_0.333(Sc,Ni)_0.667. A set of self-consistent thermodynamic parameters for the Ni–Sc binary system is obtained. The calculated results agree well with the available experimental data from literatures.     

Experimental study and thermodynamic assessment of the erbium–hydrogen binary system

The erbium–hydrogen (Er–H) binary system has been investigated experimentally. New solubility limits and extensions of the homogeneity domains have been measured, using several experimental techniques, and high purity materials. A thermodynamic assessment of the system using the Calphad method has been performed. The calculated phase diagram shows a fair agreement with the experimental data. Both experimental and calculated phase diagrams obtained differ significantly from the one available in the literature.     

The verification and analysis on the results of the video retrieval system

The retrieval of video information is a key multimedia technology, which has been paid wide-range attention recently. This paper introduces the verification and analysis of video information results in the video retrieval system from three aspects： first, the way of the browse and navigation; second, video summary; third, display and interaction interface.     

Phase diagram and thermodynamic properties of the GdBr3–CsBr binary system

Phase diagram of the GdBr₃-CsBr binary system was established by Differential Scanning Calorimetry (DSC) method. This system exhibits three stoichiometric compounds, namely Cs₃GdBr₆, Cs₃Gd₂Br₉ and CsGd₂Br_7; and three eutectics located at GdBr₃ molar fraction x = 0.11 (T = 847 K), x = 0.52 (T = 798 K) and x = 0.72 (T = 859 K), respectively. Cs₃GdBr₆ undergoes a solid–solid phase transition at 701 K and melts congruently at 1077 K. Cs₃Gd₂Br₉ melts incongruently at 841 K and finally CsGd₂Br₇ undergoes a solid–solid phase transition at 788 K and melts congruently at 880 K. Experimentally determined phase diagram was optimized by CALPHAD method and thermodynamic properties of compounds existing in the system were estimated. Phase transition of pure GdBr₃were determined at 533 K and ΔH_tr = 0.41 kJ mol^-1.     

Phase diagram and thermodynamic properties of the LaI3–RbI binary system

Differential Scanning Calorimetry (DSC) method was used to determine phase equilibria in the LaI₃–RbI binary system, and heat capacity of LaI₃ and compounds existing in the system under investigation. Two compounds were identified in the solid phase of this system. First of them, Rb₂LaI₅, melts incongruently at 809 K. The second one, Rb₃LaI₆, forms at 686 K from Rb₂LaI₅ and RbI, undergoes a solid-solid transition at 706 K and melts congruently at 864 K. The compositions of RbI–Rb₃LaI₆ and Rb₂LaI₅–LaI₃ eutectics corresponding to LaI₃ mole fraction of x = 0.177 (T = 789 K) and x = 0.472 (T = 773 K), respectively were found from Tammann's diagrams. The LaI₃–RbI pseudobinary system was also optimized by CAPLHAD method. Thermodynamic properties of the liquid phase were modelled using Associate Solution Model.     

Thermodynamic re-assessment of the Mg–Gd binary system coupling the microstructure evolution during ageing process

According to the available experimental phase equilibrium relations, thermochemical properties and the experimentally observed ageing precipitation sequence from literatures, the thermodynamic re-modeling and re-assessment of the Mg–Gd binary system have been carried out by means of CALPHAD (CALculation of PHAse Diagram) technique. The metastable phases, including GP zones (D0₁₉-type) and Mg₇Gd intermediate, are described by the models (Gd,Mg%)_0.75(Gd%,Mg)_0.25 and (Gd,Mg%)_0.875(Gd%,Mg)_0.125, respectively, in order to deal with the order-disorder transitions between the ordered phases GP zones (D0₁₉-type)/Mg₇Gd intermediate and the disordered solid solution HCP_A3(Gd,Mg). With the considerations of the influences of elastic strain energies and interface energies on the thermodynamic driving forces, the effective driving forces for the precipitates to nucleate are calculated to match the ageing precipitation sequence, α(Mg)_SSSS(supersaturated solid solution)→ GP zones (D0₁₉-type)→ β′(c-bco, Mg₇Gd)→ β₁(D0₃, Mg₃Gd)→ β(fcc, Mg₅Gd). A set of the self-consistent thermodynamic parameters has been obtained. The present calculations of the phase diagram, the thermochemical properties, and the precipitation driving forces of the typical Mg–Gd alloys with x(Gd) = 0.01819 and 0.0318 at 498 K, are not only well consistent with the reported experimental data but also in a satisfactory agreement with the precipitation sequence in the early stage of ageing observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).     

More on the phase-plane analysis of a relay control system†

The transcendental equation relating the parameters of a closed trajectory of a relay system containing a symmetrical two-position element, a dead element and a rational part of the second order has two solutions. It will be shown that only one of these solutions supplies the self-oscillation of the system.

The phase-plane method is developed for systems containing a relay element with hysteresis. The effect of varying any parameter of the system on the period and amplitude of the self-oscillation can be predicted from the transcendental equation.     

Re-optimization of the binary Sb − Se system aided by ab-initio calculations

Based on the ab-initio calculations the thermodynamics of the Sb₂Se₃ intermediate phase was modeled and used in the calculations of the Sb–Se phase diagram together with the thermodynamic properties of liquid phase elaborated by the association model. The modeled heat capacity of Sb₂Se₃ phase shows excellent agreement with the experiment data available in the literature in the wide temperature range. The calculated equilibrium lines of the Sb–Se phase diagram good correlate with the experimental ones. The determined thermodynamic parameters can be applied in future calculations of the high-ordered systems and for determination of the Sb₂Se₃ thermoelectric properties.     

Design and performance analysis of tracking controller for uncertain nonlinear composite system using neural networks

Based on high order dynamic neural network, this paper presents the tracking problem for uncertain nonlinear composite system, which contains external disturbance, whose nonlinearities are assumed to be unknown. A smooth controller is designed to guarantee a uniform ultimate boundedness property for the tracking error and all other signals in the dosed loop. Certain measures are utilized to test its performance. No a priori knowledge of an upper bound on the “optimal” weight and modeling error is required; the weights of neural networks are updated on-line. Numerical simulations performed on a simple example illustrate and clarify the approach.     

The effects of deprivation of cigarette smoking on psychomotor performance∗

Increased restrictive action has been taken to limit tobacco smoking in a variety of public and occupational settings without regard to the behavioural effects of these actions on smokers. Two studies were undertaken; one examining the performance of 16 college female cigarette smokers under conditions of smoking or deprivation, and the second study investigating 16 males from the same population. Performance scores, taken from an instrumented complex psychomotor device, were adjusted for ability as determined from a training period on the device and then compared between smoking conditions. In both studies, deprived smokers performed significantly less well on the pursuit tracking task while reaction time, vigilance and mental arithmetic tasks were not affected. Results are discussed in terms of the negative effects on performance and the possible implications for work situations.     

Thermodynamic re-assessment of the Mg–Y binary system coupling with the precipitation sequence during aging process

The experimentally observed aging precipitation sequence of the Mg–Y alloys from literatures is α(Mg)_SS(supersaturated)→ β''(c-bco like GP zones)→ β′(c-bco, metastable coherent Mg₇Y)→ β(bcc, stable incoherent Mg₂₄Y₅). Compared with the equilibrium phase diagram, Mg₇Y is not a stable precipitate, but from the view point of the crystal structure, Mg₇Y is an ordering product of HCP_A3(Mg). The Mg–Y binary system has been thermodynamically re-assessed by means of CALPHAD technique in order to study its aging precipitation sequence in the present work. Three solution phases, HCP_A3, BCC_A2 and Liquid, are modeled with the Redlich-Kister polynomial. The intermetallic compounds Mg₂Y and Mg₂₄Y₅ have been described by the following formulas, (Mg, Y)_0.6667(Mg, Y)_0.3333 and Mg_0.8276(Mg, Y)_0.1379 Y_0.0345, respectively. Especially for order-disorder transitions, the following two-sublattice models (Mg, Y)_0.5(Mg, Y)_0.5 and (Mg, Y)_0.875(Mg, Y)_0.125 have been used to describe the stable MgY/BCC_A2 and the metastable Mg₇Y/HCP_A3, respectively. Based on the satisfied optimization of equilibrium phase diagram, the order-disorder transition between the metastable intermediate Mg₇Y and the stable phase HCP_A3 is assessed to ensure that Mg₇Y has a big enough driving force but not a lowest Gibbs free energy change to precipitate preferentially from the supersaturated α(Mg). Meanwhile, in order to match the aging precipitation sequence of the Mg–Y alloys, the effective nucleation driving forces for the precipitated phases are calculated by subtracting the interfacial energy and the elastic strain energy from the thermodynamic driving force. A set of self-consistent thermodynamic parameters has been obtained to agree satisfactorily with the reported experimental data from literatures, including the phase diagram, the thermochemical properties, and the aging precipitation sequence of the typical Mg–Y alloys with x(Y) = 0.0232 at 473 K.     

On the phase-plane analysis of relay control system with dead time†

An exact method of analysis of non-linear systems containing a two-position relay element and a dead-time element is given using the phase-plane concept. Equations of the switching lines for both unsymmetrical and symmetrical relay characteristics are obtained under consideration of the dead time. Expressions to evaluate the period and amplitude of the self-oscillation of the system are derived from the stable limit cycle in the phase plane.

This method is developed for a second-order system with a zero in its transfer function. For such a system it is indicated with a help of an example that approximation methods as the describing function yield large errors because the low-pass condition is not satisfied. The phase-plane method will be developed for other relay characteristics.