Thermochemistry, lattice energetics and stability of hexahalogenohafnates

The enthalpies of thermal dissociation (Δ_dH) and formation (Δ_fH) found in the literature as well as the crystal lattice energies (E_c) of inorganic and organic hexahalogenohafnates (M^I₂(or M^{II)HfX2−₆}; M^I and M^II denote monovalent and divalent cations respectively and X denotes a halogen) are reviewed and discussed. The enthalpies of formation of the salts were evaluated using the above-mentioned Δ_dH values and known enthalpies of formation of products of decomposition. Combination of the enthalpies of formation of hexahalogenohafnates thus obtained or those of the literature with the literature values of the enthalpy of formation of cations and theoretically determined enthalpies of formation of HfX²⁻₆ (or electrostatic lattice energies of the salts) afforded lattice energies of the salts (or enthalpies of formation of gaseous HfX²⁻₆). Values of Δ_fH were also assessed taking theoretically obtained electrostatic lattice energies of the salts and enthalpies of formation of HfX²⁻₆ and literature or theoretically determined values of the enthalpy of formation of gaseous cations. The independent sets of crystal lattice energies and thermochemical radii for HfX²⁻₆ were obtained following the Kapustinskii—Yatsimirskii approach. Combination of the latter method with the thermochemical cycle afforded information on the influence of the dimensions of ions on the thermodynamic stability of hexahalogenohafnates with respect to dissociation and oxidation processes. The thermochemical quantities of experimental and theoretical origin correlate with each other reasonably well, thus increasing their reliability.     

Determination of Active Slip/Twinning Modes in AZ31 Mg Alloy Near Room Temperature

In order to determine the deformation modes in AZ31 magnesium alloy at room temperature, computer simulations of deformation texture development and calculation of formability have been carried out. The simulation results were compared with the measured texture results. Based on agreement between the experiments and simulations the active deformation modes were determined. A Visco Plastic Self Consistent model was employed for the simulation of plastic deformation. Simulations and experiments were performed for different initial textures. The goal of the study was to develop the understanding of deformation texture evolution and its effects on mechanical properties of magnesium, with an ultimate goal of improving room temperature formability of magnesium alloys. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

Applications of texture in thin films

Thin films are important in a variety of applications, including optical, magnetic,and electronic devices. The origin of microstructure in films formed by physical vapor deposition depends primarily on the homologous deposition temperature, which determines the grain structure and substructure. Texture is coupled to grain structure development through several kinetic parameters, principally surface diffusivity and interfacial energy. The representation of such fiber textures is facilitated by simplified pole intensity versus tilt angle plots rather than entire pole figures. The reliability of thin film interconnection materials such as aluminum alloys is heavily leveraged on both texture and grain structure. The properties of thin magnetic films depend on both the crystallographic texture and the grain shape anisotropy.     

Case‐based approach for supporting strategy decision making

The practice of strategy decision making proves that when the management board is strongly limited in its capacity to take rational actions, specifically in the context of great decision complexity and uncertainty, it is considered good practice to refer to experience through reasoning by analogy. In this paper, we would like to concentrate on supporting strategic decisions in small and medium enterprises (SMEs). The complexity of analogy‐based reasoning has its roots in an attempt to solve new problems based on past cases from a different domain, while we will focus on case‐based approach for a single domain. Additionally, we have chosen case‐based reasoning as a suitable decision‐making paradigm because it is corresponds to managers’ decision‐making behaviour. We present the STRATEGOS case‐based reasoning system for supporting strategic decision making by SMEs management boards and then the system evaluation by the dozens of chief executive officers (CEOs) from SMEs is presented. The results of the survey are promising and show the remarkable correspondence of the proposed solution with expectations and strategic behaviour of CEOs.     

Controllability of second-order infinite-dimensional systems

In the paper, the approximate controllability of linear abstract second-order infinite-dimensional dynamical systems is considered. It is proved using the frequency-domain method, that approximate controllability of second-order system can be verified by the approximate controllability conditions for the corresponding simplified first-order system. General results are then applied for approximate controllability investigation of a vibratory dynamical system modeling flexible mechanical structure. Some special cases are also considered. Moreover, remarks and comments on the relationships between different concepts of controllability are given. The paper extends earlier results on approximate controllability of second-order abstract dynamical systems.     

Disjunctive databases for representing repairs

This paper addresses the problem of representing the set of repairs of a possibly inconsistent database by means of a disjunctive database. Specifically, the class of denial constraints is considered. We show that, given a database and a set of denial constraints, there exists a (unique) disjunctive database, called canonical, which represents the repairs of the database w.r.t. the constraints and is contained in any other disjunctive database with the same set of minimal models. We propose an algorithm for computing the canonical disjunctive database. Finally, we study the size of the canonical disjunctive database in the presence of functional dependencies for both subset-based repairs and cardinality-based repairs.     

The COCA quality model for user documentation

According to Pedraz-Delhaes, users evaluate both the product and the vendor on the basis of provided documentation. Thus, a question arises as to what quality characteristics should be taken into account when making a decision about accepting a given user manual. There are some proposals (e.g., ISO Std. 26513 and 26514), but they contain too many quality characteristics and lack orthogonality. The goal of this paper is to propose a simple quality model for user documentation, along with acceptance methods based on it. The model is to be orthogonal and complete. As a result, the COCA quality model is presented, which comprises four orthogonal quality characteristics: Completeness, Operability, Correctness, and Appearance. To check completeness, the proposed quality model has been compared with many other quality models that are directly or indirectly concerned with user documentation. Moreover, two acceptance methods are described in the paper: pure review based on ISO Std. 1028:2008, and documentation evaluation test (a type of browser evaluation test), which is aimed at assessing the operability of user documentation. Initial quality profiles have been empirically collected for both methods—they can be used when interpreting evaluation results obtained for a given user manual.     

Theories of initial segments of standard models of arithmetics and their complete extensions

We investigate families of finite initial segments of standard models for various arithmetics. We give an axiomatization of the theory of sentences true in almost all finite models with addition. We also characterize its complete extensions and relate its infinite models to models of Presburger arithmetic.We also estimate the complexity of complete extensions of the arithmetic with addition and multiplication.     

Functional Differentiation of Computer Programs

We present a purely functional implementation of the computational differentiation tools—the well known numeric (i.e., not symbolic) techniques which permit one to compute point-wise derivatives of functions defined by computer programs economically and exactly (with machine precision). We show how the use of lazy evaluation permits a transparent and elegant construction of the entire infinite tower of derivatives of higher order for any expressions present in the program. The formalism may be useful in various problems of scientific computing which often demand a hard and ungracious human preprocessing before writing the final code. Some concrete examples are given.