Sequence Of Transformation Steps Research Articles

Formal modeling and verification of an enhanced variant of the IEEE 802.11 CSMA/CA protocol

In this paper, we present a formal method for modeling and checking an enhanced version of the carrier sense multiple access with collision avoidance protocol related to the IEEE 802.11 MAC layer, which has been proposed as the standard protocol for wireless local area networks. We deal mainly with the distributed coordination function (DCF) procedure of this protocol throughout a sequence of transformation steps. First, we use the unified modeling language state machines to thoroughly capture the behavior of wireless stations implementing a DCF, and then translate them into the input language of the UPPAAL model checking tool, which is a network of communicating timed automata. Finally, we proceed by checking of some of the safety and liveness properties, such as deadlock-freedom, using this tool.

Physical and Structural Characterization of a Monocrystalline Cu-13.7Al-4.2Ni Alloy Subjected to Thermal Cycling Treatments

A monocrystalline alloy with nominal 82wt pctCu-13.7wt pctAl-4.2wt pctNi composition and exhibiting reversible martensitic transformation (RMT) was subjected to multiple heating and cooling cycles within the RMT range of critical temperatures. Both untreated and cyclic treated alloy samples were characterized by X-ray diffraction, optical microscopy, differential scanning calorimetry, and Vickers microhardness. The results indicated that the alloy presents a complex RMT behavior disclosing a sequence of transformation steps: β 1 ↔ R and R ↔ β′1 + γ′1 as well as possible β 1 ↔ β′1 and β′1 ↔ γ′1 direct reactions. The thermal cycling treatment inhibits the development of γ′1 martensite without much change in both the physical and microstructure characteristics. This suggests a good resistance of the alloy to irreversible structural changes.

Divergent Synthesis of 48 Heparan Sulfate-Based Disaccharides and Probing the Specific Sugar–Fibroblast Growth Factor-1 Interaction

Several biological processes involve glycans, yet understanding their ligand specificities is impeded by their inherent diversity and difficult acquisition. Generating broad synthetic sugar libraries for bioevaluations is a powerful tool in unraveling glycan structural information. In the case of the widely distributed heparan sulfate (HS), however, the 48 theoretical possibilities for its repeating disaccharide call for synthetic approaches that should minimize the effort in an undoubtedly huge undertaking. Here we employed a divergent strategy to afford all 48 HS-based disaccharides from just two orthogonally protected disaccharide precursors. Different combinations and sequence of transformation steps were applied with many downstream intermediates leading up to multiple target products. With the full disaccharide library in hand, affinity screening with fibroblast growth factor-1 (FGF-1) revealed that four of the synthetic sugars bind to FGF-1. The molecular details of the interaction were further clarified through X-ray analysis of the sugar-protein cocrystals. The capability of comprehensive sugar libraries in providing key insights in glycan-ligand interaction is, thus, highlighted.

Double-Pullback Transitions and Coalgebraic Loose Semantics for Graph Transformation Systems

The classical algebraic approach to graph transformation is a mathematical theory based on categorical techniques with several interesting applications in computer science. In this paper, a new semantics of graph transformation systems (in the algebraic, double-pushout (DPO) approach) is proposed in order to make them suitable for the specification of concurrent and reactive systems. Classically, a graph transformation system comes with a fixed behavioral interpretation. Firstly, all transformation steps are intended to be completely specified by the rules of the system, that is, there is an implicit frame condition: it is assumed that there is a complete control about the evolution of the system. Hence, the interaction between the system and its (possibly unknown) environment, which is essential in a reactive system, cannot be modeled explicitly. Secondly, each sequence of transformation steps represents a legal computation of the system, and this makes it difficult to model systems with control. The first issue is addressed by providing graph transformation rules with a loose semantics, allowing for unspecified effects which are interpreted as activities of the environment. This is formalized by the notion of double-pullback transitions, which replace (and generalize) the well-known double-pushout diagrams by allowing for spontaneous changes in the context of a rule application. Two characterizations of double-pullback transitions are provided: the first one describes them in terms of extended direct DPO derivations, and the second one as incomplete views of parallel or amalgamated derivations. The issue of constraining the behavior of a system to transformation sequences satisfying certain properties is addressed instead by introducing a general notion of logic of behavioral constraints, which includes instances like start graphs, application and consistency conditions, and temporal logic constraints. The loose semantics of a system with restricted behavior is defined as a category of coalgebras over a suitable functor. Such category has a final object which includes all finite and infinite transition sequences satisfying the constraints.

Creating the architecture of a manufacturing framework by design patterns

The class and interaction structure of object-oriented designs may become fairly complex, and consequently difficult to develop and understand. Design patterns allow to govern this complexity. This paper presents the design process of a domain-specific black-box framework for the control of automated manufacturing systems. The design is performed as a sequence of transformation steps, guided by the use of generative design patterns. Starting out from a domain-specific model, which does not provide a degree of reusability sufficiently high for a framework, the transformation steps increase the reusability until a satisfactory degree is reached. The resulting class and interaction structure allows to create each application of the considered manufacturing subdomain by selecting, configuring and parameterizing of the framework classes.

Modelling the software process in terms of the system representations and transformation steps used

The software development process is viewed as the evolution of an initial representation of the required system through a sequence of transformation steps and intermediate representations, culminating in the delivered software. In the general case, the intermediate representations are based on different linguistic systems. It is argued that any representation and any transformation step can usefully be characterized in terms of its degree of possession of each of a small number of properties. It is then shown that the degree of possession of these properties can influence important software process outcomes. The paper concludes by claiming that the proposed paradigm brings one closer to the ‘core’ of the software development process than do most other approaches to software process modelling.