Thermodynamic assessment of Sn–Cu–Ce system

Phase relations of Sn–Cu–Ce system are important in understanding metallurgical role of Ce in Sn–Cu based lead-free solder alloys. Thermodynamic assessment of Sn–Cu–Ce ternary system has been done based on experimental data about phase equilibria and thermodynamic properties by using the CALPHAD approach combined with first-principle calculations of formation enthalpy of key compounds. The solution phases (liquid, Fcc_A1, Bcc_A2 and Bct_A5) were treated as substitutional, of which the excess Gibbs energies were modeled by the Redlich–Kister polynomial. Considering its crystal structure and solid solubility range, intermetallic compound Ce₁₁Sn₁₀ was described with a three-sublattice model (Ce)_0.429(Sn)_0.429(Ce,Cu,Sn)_0.142. Other binary and ternary intermetallic compounds were described as stoichiometric phases because of their limited homogeneity ranges. During optimization, Ce–Sn binary system was first assessed; then phase relations in Sn–Cu–Ce ternary system were modeled by combining with the optimized Ce–Cu and Cu–Sn binary systems in literatures. A set of thermodynamic parameters for all known phases were obtained, which can reproduce most experimental data. The Scheil model was used to simulate the process of non-equilibrium solidification for a series of alloys.     

Mixed hierarchical-functional fault models for targeting sequential cores

Current work presents a set of fault models allowing high coverage for sequential cores in systems-on-a-chip. We propose a novel approach combining a hierarchical fault model for functional blocks, a functional fault model for multiplexers and a mixed hierarchical-functional fault model for comparison operators, respectively. The fault models are integrated into a fast high-level decision diagram based test path activation tool. According to the experiments, the proposed method significantly outperforms state-of-the-art test pattern generation tools. The main new contribution of this paper is a formal definition of high-level decision diagram representations and the combination of the three fault models in order to target high gate-level stuck-at fault coverage for sequential cores.     

Pushing requirements changes through to changes in specifications

Requirements changes can occur both during and after a phase of development for a variety of reasons, including error correction and feature changes. It is difficult and intensive work to integrate requirements changes made after specification is completed. Sequence-based specification was developed to convert ordinary functional software requirements into complete, consistent, and traceably correct specifications through a constructive process. Algorithms for managing requirements changes meet a very great need in field application of the sequence-based specification method. In this paper we propose to capture requirements changes as a series of atomic changes in specifications, and present polynomial-time algorithms for managing these changes. The algorithms are built into the tool support with which users are able to push requirements changes through to changes in specifications, maintain old specifications over time and evolve them into new specifications with the least amount of human interaction and rework. All our change algorithms are supported by rigorous mathematical formulation and proof of correctness. The application example is a safe controller. Software Quality Research Lab, Department of Electrical Engineering and Computer Science, University of Tennessee at Knoxville, http://www.cs.utk.edu/sqrl/     

Distributed nonlinear control algorithms for network consensus

In this paper, we develop a thermodynamic framework for addressing consensus problems for nonlinear multiagent dynamical systems with fixed and switching topologies. Specifically, we present distributed nonlinear static and dynamic controller architectures for multiagent coordination. The proposed controller architectures are predicated on system thermodynamic notions resulting in controller architectures involving the exchange of information between agents that guarantee that the closed-loop dynamical network is consistent with basic thermodynamic principles.     

3D conforming power diagrams for radial LGR in CPG reservoir grids

Mesh generation becomes a crucial step in reservoir flow simulation of new generation. The mesh must faithfully represent the architecture of the reservoir and its heterogeneity. In (Flandrin et al. in IJNME 65(10):1639–1672, 2006) a three-dimensional hybrid mesh model was proposed to capture the radial characteristics of the flow around the wells. In this hybrid mesh, the reservoir is described by a non-uniform Cartesian structured mesh and the drainage areas around the wells are represented by structured radial circular meshes. Unstructured polyhedral meshes are used to connect these two kinds of structured grids. The construction of these transition meshes is based on 3D power diagrams (Aurenhammer in SIAM J Comput 16(1):78–96, 1987) to ensure finite volume properties such as mesh conformity, dual orthogonality and cell convexity. In this paper, we propose an extension of this hybrid model to the case where the reservoir is described by a corner point geometry (CPG) grid. At first, the CPG grid is mapped, in a reference space, into a non-uniform Cartesian grid by minimizing the mapping deformation. Then, a hybrid mesh is generated in this reference space using the previous method. Finally, this mesh is mapped back into the real space. Some quality criterions are introduced to measure and improve the quality of the polyhedral transition mesh.     

Splitting a Delaunay Triangulation in Linear Time

Abstract. Computing the Delaunay triangulation of n points requires usually a minimum of Ω(n log n) operations, but in some special cases where some additional knowledge is provided, faster algorithms can be designed. Given two sets of points, we prove that, if the Delaunay triangulation of all the points is known, the Delaunay triangulation of each set can be computed in randomized expected linear time.     

A thermodynamic assessment of Ni–Sb system

The Ni–Sb system was critically assessed by means of the CALculation of PHAse Diagram (CALPHAD) technique. The solution phases, Liq and (αNi), were modelled as the substitutional solutions with the Redlich–Kister equation. The intermediate phases, (γNiSb) and (βNi₃Sb), with homogeneity ranges were described respectively using three-sublattices (Sb)_1/3(Ni%,V a)_1/3(V a%,Ni)_1/3 and (Sb)_1/4(Ni%,V a)_1/2(Ni%,V a)_1/4 based on their structure features. Corresponding to the phase (βNi₃Sb), the two low-temperature phases of (δNi₃Sb) and (θNi₅Sb₂) with narrow homogeneity ranges were modelled as two-sublattice, (Ni)_3/4(Sb,Ni)_1/4 and (Ni)_5/7(Sb,Ni)_2/7. The intermetallic compound ζNiSb₂ with no homogeneity ranges was treated as stoichiometric compound. The phase ε$\epsilon$Sb was considered as pure Sb for the solubility of Ni in ε$\epsilon$Sb is very low. A set of self-consistent thermodynamic parameters of the Ni–Sb system was obtained. The optimized phase diagram and thermodynamic properties were presented and compared with experimental data.     

Experimental study and thermodynamic modelling of the ZrO2–LaO1.5 system

Phase relations in the ZrO₂–LaO_1.5 system were studied experimentally in the temperature range from 1673 to 1973 K. X-ray diffraction and scanning electron microscopy were employed to obtain the structural information and the compositions of the tetragonal and pyrochlore (La₂Zr₂O₇) phases. The solubility of LaO_1.5 in the tetragonal phase was determined to be very small. The homogeneity range of the pyrochlore phase is estimated to be less than 2 mol% at 1973 K, and less than 1 mol% at 1673 K according to the present work. Based on the experimental results obtained in this work, as well as the available phase diagram and thermodynamic data in literature, a self-consistent thermodynamic assessment was carried out by using the ionic sublattice solution model.     

Critical thermodynamic evaluation of oxide systems relevant to fuel ashes and slags,Part 4: Sodium oxide–potassium oxide–silica

A thermochemical assessment was performed for the system K₂O–Na₂O–SiO₂. The modified associate species model was applied to the ternary liquid in the system. All binary subsystems remained unchanged. The new databank was used for the representation of the phase equilibria in the ternary system including the quasi-binary sections of the ternary diagram. The calculated phase relations are in good agreement with the experimental data. The phase equilibria in the experimentally uninvestigated region near the alkali oxide edge are proposed as extrapolations using the new databank.