Directed Explicit Model Checking with HSF-SPIN

We present the explicit state model checker HSF-SPIN which is based on the model checker SPIN and its Promela modeling language. HSF-SPIN incorporates directed search algorithms for checking safety and a large class of LTL-specified liveness properties. We start off from the A* algorithm and define heuristics to accelerate the search into the direction of a specified failure situation. Next we propose an improved nested depth-first search algorithm that exploits the structure of Promela Never-Claims. As a result of both improvements, counterexamples will be shorter and the explored part of the state space will be smaller than with classical approaches, allowing to analyze larger state spaces. We evaluate the impact of the new heuristics and algorithms on a set of protocol models, some of which are real-world industrial protocols

Numerical Modeling of Anti-icing Systems and Comparison to Test Results on a NACA 0012 Airfoil

A series of experimental tests were conducted in the NASA Lewis IRT on an electro-thermally heated NACA 0012 airfoil. Quantitative comparisons between the experimental results and those predicted by a computer simulation code were made to assess the validity of a recently developed anti-icing model. An infrared camera was utilized to scan the instantaneous temperature contours of the skin surface. Despite some experimental difficulties, good agreement between the numerical predictions and the experiment results were generally obtained for the surface temperature and the possibility for each runback to freeze. Some recommendations were given for an efficient operation of a thermal anti-icing system

Ice Accretion and Performance Degradation Calculations with LEWICE/NS

The LEWICE ice accretion computer code has been extended to include the solution of the two-dimensional Navier-Stokes equations. The code is modular and contains separate stand-alone program elements that create a grid, calculate the flow field parameters, calculate the droplet trajectory paths, determine the amount of ice growth, calculate aeroperformance changes, and plot results. The new elements of the code are described. Calculated results are compared to experiment for several cases, including both ice shape and drag rise

Numerical modeling of runback water on ice protected aircraft surfaces

A numerical simulation for 'running wet' aircraft anti-icing systems is developed. The model includes breakup of the water film, which exists in regions of direct impingement, into individual rivulets. The wetness factor distribution resulting from the film breakup and the rivulet configuration on the surface are predicted in the numerical solution procedure. The solid wall is modeled as a multilayer structure and the anti-icing system used is of the thermal type utilizing hot air and/or electrical heating elements embedded with the layers. Details of the calculation procedure and the methods used are presented

Resistance to fungicides and streptomycin in Phytophthora parasitica : genetic determinism and use in hybrid determination

Progeny of #Phytophthora parasitica$ derived from the pairings between metalaxyl-resistant MET.1 (A2) carrying homozygous dominant resistance and S1 (A1) wild-type consisted of selfs from each parent and hybrids carrying heterozygous dominant resistance. Similar results were obtained when dimetomorph-resistant DT.1 (A1) carrying homozygous dominant resistance was paired with wild-type S2 (A2). Progeny from the pairing between homozygous Str resistant (A1) to streptomycin and A2 resistant to metalaxyl consisted of selfs and hybrids resistant to either streptomycin or metalaxyl but not both. These results suggest that streptomycin-resistance is cytoplasmic. Progeny from the pairing between homozygous metalaxyl-resistant MET.1 (A1) and homozygous Str (A2) resistant to streptomycin consisted of 28 selfs from A1, 32 selfs form A2, 2 hybrids resulting from the union of A1 oogonium with an A2 antheridium. Progeny from the pairing between homozygous dimetomorph and streptomycin-resistant DT.1 (A1) with wild-type S2 (A2) consisted of 22 selfs A1, 14 selfs A2 and 12 hybrids, two of them resulted from the union A2 oogonium with an A1 antheridium. (Résumé d'auteur

Social Media and Social Transformation Movements: The Role of Affordances and Platforms

Social media (SM) have played a critical role in recent social transformation movements and yet information systems (IS) literature has only sparsely examined the role of particular SM platforms and their affordances that facilitate such collective action, and how such affordances are appropriated for decentralised forms of collaboration and cooperation. We draw on theories of affordances and collective action to identify a range of functional SM affordances, and related SM platforms, impacting online activism in the recent social transformation movements in Egypt, based on field interviews with a variety of movement participants. We identify nine perceived affordances of SM that were instrumental during the social transformation movements. When these affordances are appropriated by movement participants, they interact with and complement each other, thereby significantly impacting mobilization for social change. Our findings provide a more nuanced perspective on the role of SM in social transformation movements and have implications for both IS and collective action theories

From connective actions in social movements to offline collective actions: an individual level perspective

The purpose of this study is to investigate the role of connective action characterised by interconnection and personal communication on social media (SM) for participating in collective action in the physical world of social movements

Dimethomorph and metalaxyl sensitivity in somatic hybrids of Phytophthora parasitica obtained by protoplast fusion

Protoplasts were successfully isolated from wild-type and mutant strains of #Phytophthora nicotianae var. #parasitica using Novozym 234. Putative somatic hybrids were recovered following protoplast fusions from the first time to dimethomorph resistant strain P 310 (Dim r) or metalaxyl P 26 (Met r) by selection on agar amended with dimethomorph and metalaxyl. Fusion products from this cross were resistant to dimethomorph and metalaxyl. Zoospore progeny from the fusion products retained this phenotype, suggesting that nuclear fusion had taken place. (Résumé d'auteur

Prediction of the elastic modulus of the trabecular bone based on X-ray computed tomography

International audienceThis work aims to estimate the apparent Young's modulus of real human trabecular bones using a numerical micro-macro approach. Cylindrical specimens of trabecular bone were extracted from human femur heads, cleaned and scanned using a SkyScan-1072 micro-computed tomography system. 3D volumetric tetrahedral grids were generated from the exploitation of the reconstructed images using original meshing techniques. Numerical compressive tests were simulated, assuming isotropic tissue Young's modulus for all elements. The large size of the volumes implies grids with a high number of nodes, which required the use of a large number of parallel processors in order to perform the finite element calculations. Numerical Young's moduli varied between 1300 MPa and 1600 MPa, with a good agreement with experiments