A Systematic Approach to the Petri Net Based Specification of Concurrent Systems

We describe an approach to the specification of concurrent systems which enables a Petri net model of a system to be built up in a systematic way starting from a trace-based CSP specification. This method enables the separate specification of the behavior of each component (process) and their interactions in terms of the feasible sequences of events in which they can be involved. A set of rules is then applied to transform the trace-based specifications into a complete Petri net that is analyzed and/or executed to validate system behavior. The domain transformation procedure is fully automatable. The specification of a safety-critical railway control system is used as a case study.     

Evaluation of flooded areas with satellite imagery using an objective hydrologic criterion

A method for computing flooded areas in relation to precedent climatic conditions in a plain area is evaluated. The studied area includes the most important production area for cattle breeding in Argentina; therefore, waterlogging periods create significant economic losses. In order to conduct this study, Landsat images that represent different hydrological conditions were used. The method is based on the frequency analysis of rainfall records of the 30, 60 and 120 days prior each image, thus obtaining a seasonally weighted mean frequency. In order to minimize biases of individual images, the images were combined linearly so as to obtain composed images with the desired antecedent precipitation frequency. Then, the flooded areas were associated with the frequency of the antecedent rainfall. Therefore, frequencies equal to or higher than 50% are associated with semi‐permanent or permanent lentic waterbodies. Consequently, lower frequencies are associated with waterlogged areas reaching 35% of flooded area for a 20% precipitation frequency.     

Reliable Systems on Unreliable Fabrics

The continued scaling of silicon fabrication technology has led to significant reliability concerns, which are quickly becoming a dominant design challenge. Design integrity is threatened by complexity challenges in the form of immense designs defying complete verification, and physical challenges such as silicon aging and soft errors, which impair correct system operation. The Gigascale Systems Research Center Resilient-System Design Team is addressing these key challenges through synergistic research thrusts, ranging from near-term reliability stress reduction techniques to methods for improving the quality of today's silicon, to longer-term technologies that can detect, recover, and repair faulty systems. These efforts are supported and complemented by an active fault-modeling research effort and a strong focus on functional-verification methodologies. The team's goal is to provide highly effective, low-cost solutions to ensure both correctness and reliability in future designs and technology nodes, thereby extending the lifetime of silicon fabrication technologies beyond what can be currently foreseen as profitable.     

A Double Adaptive Algorithm for Multidimensional Integration on Multicore Based HPC Systems

In this work, a parallel double adaptive algorithm for the computation of a multidimensional integral on multicore based multicomputer systems is described. This new algorithm is the revision of a procedure developed by one of the present authors for multicomputer systems, with the aim to introduce features for an efficient implementation in multicore based hierarchical environments. Two different adaptive strategies have been combined together in the algorithm: a first procedure is responsible for load balancing among the system nodes and a second one is responsible for coordinating the cores within a single node. The performance is analyzed and experimental results on a Blade Server with 8 nodes and 2 quad-core CPUs per node have been achieved.     

Computational Simulations for the Assessment of the Mechanical Properties of Glass with Controlled Porosity

Porous glass with closed controlled porosity is used as a model system in order to numerically assess the effect of pores on the macroscopic mechanical and fracture behavior of brittle solids. A computational code called OOF, which converts digitalized two-dimensional (2-D) images of materials microstructures into finite element meshes, is adopted, so that the effect of 2-D microstructural features (e.g. pore size and shape) on the global mechanical response of the material can be determined. Firstly, microstructures of porous glass bodies containing isolated pores were considered. These specimens were numerically investigated in terms of fracture initiation and propagation: the numerical model predicted that larger pores initiate fracture, in agreement with experimental results. Then, the effect of porosity on the elastic and fracture properties was thoroughly investigated by means of model two-dimensional microstructures consisting of selected area fractions of pores (equivalent to pore volume fractions in three dimensions) and with prescribed pore shape, orientation and dimensions. In particular, the effect of pore dimension and shape was studied, finding that the critical stress for crack initiation scales with pore dimension and aspect ratio, i.e. oblate and larger pores oriented perpendicularly to the stress direction cause a higher reduction of strength of the specimen. Finally, several 2-D microstructures characterized by different values of area fraction of pores of the same shape were investigated, in order to determine the variation of elastic properties and the fracture response of porous glasses with pore content. The study confirms the suitability of the 2-D OOF code to investigate the mechanical and fracture behavior of porous materials. Issues regarding the limitation of the model due to its 2-D character are also discussed where appropriate.     

Towards Model-Driven V&V assessment of railway control systems

Verification and Validation (V&V) activities aiming at certifying railway controllers are among the most critical and time-consuming in system development life cycle. As such, they would greatly benefit from novel approaches enabling both automation and traceability for assessment purposes. While several formal and Model-Based approaches have been proposed in the scientific literature, some of which are successfully employed in industrial settings, we are still far from an integrated and unified methodology which allows guiding design choices, minimizing the chances of failures/non-compliances, and considerably reducing the overall assessment effort. To address these issues, this paper describes a Model-Driven Engineering approach which is very promising to tackle the aforementioned challenges. In fact, the usage of appropriate Unified Modeling Language profiles featuring system analysis and test case specification capabilities, together with tool chains for model transformations and analysis, seems a viable way to allow end-users to concentrate on high-level holistic models and specification of non-functional requirements (i.e., dependability) and support the automation of the V&V process. We show, through a case study belonging to the railway signalling domain, how the approach is effective in supporting activities like system testing and availability evaluation.     

Structure and transformation of low‐temperature phases of 1,3‐distearoyl‐2‐oleoyl glycerol

Polymorphic transformations of 1,3‐distearoyl‐2‐oleoyl glycerol (SOS) at low temperatures (10 °C–30 °C) have been studied by time‐resolved synchrotron X‐ray diffraction (XRD) measurements at small and wide angles. Three structures have been identified: α‐phase structure forms by quenching to 10 °C from the liquid state, a metastable structure formed simultaneously with α‐phase and γ‐phase formed at 30 °C during α‐melt‐mediated crystallisation as well as at the pre‐melting temperature (22.5 °C) of the α‐phase when the coexistence of two phases (α and γ) is observed. The metastable structure produces three broad peaks in XRD patterns at small angles (one strong and two weak peaks corresponding to d‐spacings of ～4 nm, ～12 nm and ～1.5 nm respectively) and a peak in X‐ray diffraction patterns at wide angles (0.42 nm). A model is proposed for the metastable structure based on a combination of double‐ and triple‐chain packing of SOS molecules due to the similar length of alkyl chains (stearoyl and oleoyl) in the molecules.     

Mobile computing in urban emergency situations: Improving the support to firefighters in the field

Communication support is a serious limitation for Latin American firefighters when they deal with emergency situations. The insufficient number of radio channels and the impossibility to deliver digital information force firemen to improvise during response processes, e.g., to make decisions using their experience and poor or null supporting information. These improvised actions affect the time required to take control of an emergency, and also affect the evolution of the crisis situation. Provided most of Latin American fire companies are volunteer organizations, communication solutions that could help to overcome these problems are usually expensive for them. This article presents a low-cost mobile collaborative application, which may be used in emergency situations to overcome most of the firefighters’ communication problems. The application, named MobileMap, is the result of the research and development work conducted by the authors, supported by a Chilean fire company, during the last three years. MobileMap allows ad hoc communication, decisions support and collaboration among firefighters in the field using mobile devices. This solution complements the radio communication systems. Since the interactions supported by MobileMap are recorded, it is possible to analyze such information after the crisis and learn for future emergencies. The tool was evaluated in simulated and real scenarios, and the obtained results are highly encouraging.     

Emergent Semantics and Cooperation in Multi-knowledge Communities: the ESTEEM Approach

In the present global society, information has to be exchangeable in open and dynamic environments, where interacting users do not necessarily share a common understanding of the world at hand. This is particularly true in P2P scenarios, where millions of autonomous users (peers) need to cooperate by sharing their resources (such as data and services). We propose the Esteem approach (Emergent Semantics and cooperaTion in multi-knowledgE EnvironMents), where a comprehensive framework and a platform for data and service discovery in P2P systems are proposed, with advanced solutions for trust and quality-based data management, P2P infrastructure definition, query processing and dynamic service discovery in a context-aware scenario. In Esteem, semantic communities are built around declared interests in the form of manifesto ontologies and their autonomous nature is preserved by allowing a shared semantics to naturally emerge from the peer interactions. Inside the borders of semantic communities data and services are discovered, queried and invoked in a resource sharing scenario, where the context in which users interoperate and the trust of exchanged information are also relevant aspects to take into account.