Proving Distributed Algorithms by Combining Refinement and Local Computations

Distributed algorithms are considered to be very complex to design and to prove; our paper contributes to the design of correct-by-construction distributed algorithms. The main idea relies upon the development of distributed algorithms following a top/down approach, which is clearly well known in earlier works of Dijkstra, and to use refinement for proving the correctness of the resulting algorithms. However, the link between the problem and the first model remains to be expressed and the refinement is a real help to justify in a very progressive way the choices of design. We propose in this work a framework combining local computations models and refinement to prove the correctness of a large class of distributed algorithms. Local computations models define abstract computing processes for solving problems by distributed algorithms and can be integrated into a the Event-B modelling language to define proof-based patterns for the design of distributed algorithms. We illustrate our approach by examples like the leader election protocol or the distributed coloring algorithm. Our proposal is integrated into an environment called ViSiDiA

The Problem of Experimentation in String Theory

رغم أن نظرية الأوتار نجحت رياضيا في توحيد نظرية النسبية مع نظرية الكوانتم ،إلا أنها أفرزت مفاهيم من الصعب التأكد منها تجريبيا ،كما أن اختبارها تجريبيا يتطلب طاقات خيالية ، لقد دفع هذا ببعض الفيزيائيين إلى معارضة النظرية ووصفها بالخيالية لأنها تبعد الفيزياء عن موضوعها الرئيسي أي عالم المادة ،أما أنصار النظرية فيصفونها بالمشروع الطموح ،و رغم صعوبة توفر أدلة تجريبية فان هذا لا يمنع من التفكير في ابتكار أساليب لاختبار النظريةAlthough string theory has been mathematically successful in uniting the theory of relativity with quantum theory, it has produced concepts that are difficult to ascertain empirically. Experimental testing requires imaginative energies. This has led some physicists to oppose this theory and describe it as imaginary because it distances physics from its central subject, the proponents of the theory describe it as an ambitious project, and although empirical evidence is difficult to provide, this does not preclude reflection on the creation of methods to test the theor

An Introduction to the q-Laguerre-Hahn Orthogonal q-Polynomials

Orthogonal q-polynomials associated with q-Laguerre-Hahn form will be studied as a generalization of the q-semiclassical forms via a suitable q-difference equation. The concept of class and a criterion to determinate it will be given. The q-Riccati equation satisfied by the corresponding formal Stieltjes series is obtained. Also, the structure relation is established. Some illustrative examples are highlighted

Analytical Study of Buckling of Hybrid Multilayer Plates

Thermal buckling behavior of hybrid multilayer plates was investigated in this paper. Different theories of plates taking into account or neglect the transverse shear are presented and the obtained results by these theories are compared. Nonlinear higher-order strain-displacement relations were considered. Using the principle of potential energy, the critical buckling temperatures are determined. Finally, a parametric study of the influence of various parameters such as: aspect ratios: b/a and a/h, thickness of metal, fiber angle and stacking sequence on the critical buckling temperature is shown and discussed. Numerical results indicate that the addition of metal to a composite material and the consideration of the transverse shear deformation have a significant effect on the thermal buckling behavior of simply supported hybrid multilayer plates

INFLUENCE OF UNCERTAINTY IN AERODYNAMIC PERFORMANCE ON THE DYNAMIC RESPONSE OF A TWO STAGE GEAR SYSTEM

In this paper, the nonlinear dynamic response in a wind turbine system is considered and the quantification of uncertainty effects on the variability of this nonlinear response is investigated. Under dynamic conditions, a lumped model with 12 degrees of freedom is proposed taking into account the uncertainty associated to the power coefficient of the input aerodynamic torque. The dynamic response of the two-stage spur gear system is obtained using ODE45 solver of Matlab. The Polynomial Chaos (PC) method is used to introduce the uncertainties on the proposed model. A comparison between the two dynamic responses given by the proposed lumped dynamic model takes into account the uncertainty. It is performed on the existed model without uncertainty. Thus, the efficiency and robustness of the proposed new methodology is evaluated

Chemical composition and biological activities of Salvia officinalis essential oil from Tunisia

The aim of this study is to evaluate the chemical composition, antioxidant, antimicrobial, insecticidal and allelopa- thic activities of Tunisia Salvia officinalis essential oil (SoEO). The SoEO was characterized by the presence of 49 components with camphor (25.14 %), α-thujone (18.83 %), 1,8-cineole (14.14 %), viridiflorol (7.98 %), β-thu- jone (4.46 %) and β-caryophyllene (3.30 %) as the major components, determined by gas chromatography-mass spectrometry. The level of antioxidant activity, determined by complementary tests, namely 2,2-diphenyl-1-pic- rylhydrazyl radical-scavenging (IC50= 6.7 mg/mL), linoleic acid peroxidation (IC50= 9.6 mg/mL) and ferric reduc- ing assays (IC50= 28.4 mg/mL), was relatively moderate. The SoEO was also screened for its antimicrobial activity. Good to moderate inhibitions were recorded for most of tested microorganisms. It also exhibited important insec- ticidal activity against Spodoptera littoralis larvae and Tribolium castaneum adults with LC50 values of 55.99 and 97.43 µl/L air, respectively. The effect of the SoEO on seeds germination and growth showed different activities against radical and hypocotyl elongation of the tested species. These results suggest the potential use of the SoEO as natural antimicrobial preservative in cosmetic, pharmaceutical industry and in pest management

High-displacement electret-based energy harvesting system for powering leadless pacemakers from heartbeats

In vivo biomedical devices are one of the most studied applications for vibrational energy harvesting. In this paper, we investigated a novel high-displacement device for harvesting heartbeats to power leadless implantable pacemakers. Due to the location peculiarities, certain constraints must be respected for the design of such devices. Indeed, the total dimension of the system must not exceed 5.9 mm to be usable within the leadless pacemakers and it must be able to generate accelerations lower than 0.25 m/s2 at frequencies of less than 50 Hz. The proposed design is an electrostatic system based on a square electret of dimension 4.5 mm. It is based on the Quasi-Concertina structure, which has a very low resonant frequency of 26.02 Hz and a low stiffness of 0.492 N/m, allowing it to be very useful in such an application. Using a Teflon electret charged at 1000 V, the device was able to generate an average power of 10.06 μW at a vibration rate of 0.25 m/s2 at the resonant frequency

Analyse dynamique et statique des poutres non-homogènes épaisses avec l’utilisation du concept de l’axe neutre.

Dans ce travail, une nouvelle théorie de déformation de cisaillement des poutres et une nouvelle fonction de gauchissementsont présentées pour analyser la flexion statique et la vibration des poutres fonctionnellement graduées, La théorie développée considère une vibration d’ordre élevé de la déformation de cisaillement transversal à travers la hauteur de la poutre et satisfait la nullité de la contrainte de cisaillement aux surfaces supérieures et inferieures de la poutre, La position de l’axe neutre est déterminée afin d’éliminer le couplage membrane-flexion. Les propriétés matérielles de la poutre fonctionnellement graduée FGM sont supposées être variées selon une loi de distribution polynomiale de la fraction volumique des constituants, les résultats trouvés sont illustrés et comparés avec d’autres connus dans la litératture

A Comprehensive Review of Video Steganalysis

Steganography is the art of secret communication and steganalysis is the art of detecting the hidden messages embedded in digital media covers. One of the covers that is gaining interest in the field is video. Presently, the global IP video traffic forms the major part of all consumer Internet traffic. It is also gaining attention in the field of digital forensics and homeland security in which threats of covert communications hold serious consequences. Thus, steganography technicians will prefer video to other types of covers like audio files, still images or texts. Moreover, video steganography will be of more interest because it provides more concealing capacity. Contrariwise, investigation in video steganalysis methods does not seem to follow the momentum even if law enforcement agencies and governments around the world support and encourage investigation in this field. In this paper, we review the most important methods used so far in video steganalysis and sketch the future trends. To the best of our knowledge this is the most comprehensive review of video steganalysis produced so far

Une nouvelle théorie quasi-3D pour l'étude de la flexion thermomécanique des plaques fonctionnellement graduées épaisses

Ce travail de recherche a pour but d'étudier l'analyse de flexion thermomécanique des plaques fonctionnellement graduées épaisses en proposant une nouvelle théorie quasi-3D de déformation de cisaillement. Le modèle mathématique utilisé propose seulement 5 variables comme dans le cas de la théorie de la déformation au cisaillement du premier ordre (FSDT). Contrairement aux théories d'ordres élevés (HSDT) cette théorie présente un nouveau champ de déplacement qui comprend des variables intégrales indéterminées. Les propriétés mécaniques de la plaque fonctionnellement graduée sont supposées changer dans le sens de l'épaisseur selon une loi de puissance (P-FGM). Les équations gouvernantes pour l'étude de flexion thermomécanique sont obtenues par le principe du travail virtuel et résolues par une méthode de type Navier. Des résultats intéressants sont déterminés et comparés aux résultats trouvés par les théories HSDT et 2D. Les influences de l'épaisseur de la plaque et de l'index de loi de puissance sur la flèche et les contraintes des plaques FGM épaisses seront représentées