Showing papers by "Tunis University published in 1992"

On the lattice of specifications: Applications to a specification methodology

Abstract: In this paper we investigate the lattice properties of the natural ordering between specifications, which expresses that a specification expresses a stronger requirement than another specification. The lattice-like structure that we uncover is used as a basis for a specification methodology.

Construction of a real-world bilevel linear programming model of the highway network design problem

Abstract: The formulation of the highway network design problem (NDP) as a bilevel linear program (BLP) allows more realistic solutions taking into account the reaction of users to improvements made by the system. In this paper, a conceptual framework for the optimization of investments in inter-regional highway networks in developing countries is proposed. The model is applied to the Tunisian network using actual data. Considerable effort was expended to make the implementation as realistic as possible, taking into consideration travel times, operating costs, accident costs, improvement costs, conservation laws, and effects of intra-regional flows. A new formulation allowing the incorporation of any improvement cost functions, including non-convex and non-concave functions, is introduced.

Molecular Analysis of the Androgen Receptor Gene in 52 Patients with Complete or Partial Androgen Insensitivity Syndrome: A Collaborative Study

Abstract: In patients with androgen insensitivity syndrome (AIS), RFLP study of the androgen receptor gene made it possible to analyze whether deletions or mutations could be responsible for abnormalitities in

Recombination Processes in Short‐Period GaAsAlAs Superlattices of Type II

Abstract: An extensive study of time-resolved photoluminescence is made in the temperature range 1.8 to 50 K on nine samples of type-II GaAsAlAs (001) superlattices. In previous publications, the region is identified where the states derived from Xz valleys are lower than those derived from Xxy valleys, in agreement with a simple model involving the competition between X-type valley anisotropy and X valleys splitting caused by the small lattice mismatch between AlAs and GaAs. An analysis is given of the luminescence processes and of their evolution with temperature, as a function of AlAs and GaAs layer thicknesses. Excitons localized by interface roughness are found to decay through radiative processes at low temperature. A model of thermal excitation from the tail of localized exciton states is introduced, which helps to identify the pertinent parameters of temperature behaviour in these samples. On presente une etude de la photoluminescence resolue en temps de neuf echantillons de superreseaux GaAs/AlAs (001) de type II dans l'intervalle de temperature 1,8 a 50 K. Dans une publication precedente, nous avions identifie la region ou les etats derives de la vallee Xz sont plus bas que ceux issus de vallees Xxy, d'apres un modele invoquant la competition entre l'effet de l'anisotropie de masse des vallees X et l'eclatement de ces měmes vallees dǔ au petit desaccord de maille entre GaAs et AlAs. On presente une analyse des processus de luminescence et de leur evolution avec la temperature, en fonction des epaisseurs des couches de GaAs et d'AlAs. On trouve que le declin des excitons localises par la rugosite d'interface est domine par les processus radiatifs a basse temperature. On propose un modele d'excitation thermique a partir d'une queue d'etats localises, qui met en evidence les parametres pertinents du comportement en temperature de ces echantillons.

Teaching Programming Via Specification, Execution and Modification of Reusable Components: An Integrated Approach

Abstract: In computer science curriculum, it is a challenge to define and teach a first programming course including software engineering concepts and integrating programming paradigms. The aim of this paper is to present a teaching approach to address this problem. Experimented in the university of Tunis III, the approach is caracterised by the use of software library units representing actually Prolog and Ada programs respectively as specifications and implementations. Specifically, at the level of its goal, the approach is oriented by external and internal software qualities; at the level of its strategy, the approach is based on program execution and program modification; and at the level of its conceptual formalisation, the approach uses a relational view.

A Novel Approach to the Synthesis of 4H-3,1-Benzoxazines.

Abstract: Imidates of type 1 react with organometallic reagents to give 4H-3,1-benzoxazines 2 in good yield. Synthetic Considerations and Spectroscopic details are discussed.