An algebraic approach to the design of compilers for object-oriented languages

In this paper we describe an algebraic approach to construct provably correct compilers for object-oriented languages; this is illustrated for programs written in a language similar to a sequential subset of Java. It includes recursive classes, inheritance, dynamic binding, recursion, type casts and test, assignment, and class-based visibility, but a copy semantics. In our approach, we tackle the problem of compiler correctness by reducing the task of compilation to that of program refinement. Compilation is identified with the reduction of a source program to a normal form that models the execution of object code. The normal form is generated by a series of correctness-preserving transformations that are proved sound from the basic laws of the language; therefore it is correct by construction. The main advantages of our approach are the characterisation of compilation within a uniform framework, where comparisons and translations between semantics are avoided, and the modularity and extensibility of the resulting compiler.     

Correct hardware synthesis

This paper presents an algebraic compilation approach to the correct synthesis (compilation into hardware) of a synchronous language with shared variables and parallelism. The synthesis process generates a hardware component that implements the source program by means of gradually reducing it into a highly parallel state-machine. The correctness of the compiler follows by construction from the correctness of the transformations involved in the synthesis process. Each transformation is proved sound from more basic algebraic laws of the source language; the laws are themselves formally derived from a denotational semantics expressed in the Unified Theories of Programming. The proposed approach is based on previous efforts that handle both software and hardware compilation, in a pure algebraic style, but the complexity of our source language demanded significant adaptations and extensions to the existing approaches.     

Structure–properties relationship in single polymer composites based on polyamide 6 prepared by in-mold anionic polymerization

Single polymer composites (SPCs) based on polyamide 6 (PA6) were prepared by in-mold activated anionic ring-opening polymerization (AAROP) of caprolactam in the presence of PA6 textile fibers. The influence of the reinforcing fibers content, their surface treatment, as well as of the temperature of AAROP upon the morphology, crystalline structure, and mechanical properties of the resulting SPCs was followed. The presence of oriented transcrystalline layer (TCL) on the surface of the reinforcing fibers was demonstrated by means of microscopy methods. Its orientation and polymorph structure were determined by synchrotron wide-angle X-ray scattering. Studies on the mechanical behavior in tension of the SPCs showed a well-expressed growth of the stress at break (70–80 %) and deformation at break (up to 150–190 %) in composites with 15–20 wt% of reinforcements. The best mechanical properties were found in SPCs whose reinforcing fibers were solvent-pretreated prior to AAROP in order to remove the original finish. In these samples a stronger adhesion at the fiber/matrix interface was proved by scanning electron microscopy of cryofractured samples. This effect was related to a thinner TCL in which the α-to-γ polymorph transition is impeded.     

Robust optimization of the rate of penetration of a drill-string using a stochastic nonlinear dynamical model

This work proposes a strategy for the robust optimization of the nonlinear dynamics of a drill-string, which is a structure that rotates and digs into the rock to search for oil. The nonparametric probabilistic approach is employed to model the uncertainties of the structure as well as the uncertainties of the bit-rock interaction model. This paper is particularly concerned with the robust optimization of the rate of penetration of the column, i.e., we aim to maximize the mathematical expectation of the mean rate of penetration, respecting the integrity of the system. The variables of the optimization problem are the rotational speed at the top and the initial reaction force at the bit; they are considered deterministic. The goal is to find the set of variables that maximizes the expected mean rate of penetration, respecting, vibration limits, stress limit and fatigue limit of the dynamical system.