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Effect of biaxial cyclic tension on the fatigue life and damagemechanisms of Cr–Mo steel
No full textInternational audienceCombined cyclic tension and internal pressure tests with various proportions of each loading were run ona 2.5%Cr–1%Mo steel to investigate the effect of positive stress biaxiality on fatigue lives and damagemechanisms. While moderate stress biaxiality had a beneficial effect on fatigue lives, attributed mainlyto a retardation of crack initiation, equibiaxial tension had a slightly detrimental effect, attributed to a‘‘pseudo size effect”. Intergranular facets associated with temper and hydrogen embrittlement wereobserved on the fracture surfaces. The evolutions of their surface fraction with DK and load biaxialitysuggested a possible reduction in crack growth rate at moderate biaxialities. Several popular multiaxialfatigue criteria failed to describe all fatigue data. Thus, a new fatigue criterion based on Gerber’s parabolahas been proposed. It captures the evolution of the endurance limit under the combined effects of apositive mean stress and positive biaxiality
On the convergence of the Sakawa-Shindo algorithm in stochastic control
No full textInternational audienceWe analyze an algorithm for solving stochastic control problems,based on Pontryagin's maximum principle, due to Sakawa andShindo in the deterministic case and extended to the stochasticsetting by Mazliak. We assume that either the volatility is anaffine function of the state, or the dynamics are linear. We obtain a monotone decrease of the cost functions as well as,in the convex case, the fact that the sequence of controls is minimizing, and converges to an optimal solution if it is bounded. In a specific case we interpret the algorithm as the gradient plus projection method and obtain a linear convergence rate to the solution
Second order analysis of state-constrained control-affine problems
No full textInternational audienceIn this article we establish new second order necessary and suffi-cient optimality conditions for a class of control-affine problems with a scalar control and a scalar state constraint. These optimality conditions extend to the constrained state framework the Goh transform, which is the classical tool for obtaining an extension of the Legendre condition
Sensitivity of the sea circulation to the atmospheric forcing in the Sicily Channel
No full textInternational audienceWe investigate the sensitivity of the sea surface circulation in the Sicily Channel to surface winds, using a15-year long (1994–2008) air-sea coupled numerical simulation. Analysis is based on the clustering of sixmain wind regimes over the Sicily Channel domain. The analysis of the corresponding sea current clustersshows that sea circulation in this area is sensitive to surface wind patterns. This wind modulates thestrength of the two main branches of the sea circulation in the Sicily Channel (i.e. the AtlanticTunisian Current and the Atlantic Ionian Stream). The modulation of these two currents depends onthe wind regime, and displays a strong seasonal variability. It is also shown that the sea circulation inthe Sicily Channel is strongly controlled by the thermohaline circulation and the bathymetry (geostrophiccurrent). However, the contribution to the total current of its ageostrophic component forced by thesurface winds is significant, with a correlation coefficient varying from 0.3 to 0.7
Searches for a heavy scalar boson H decaying to a pair of 125 GeV Higgs bosons hh or for a heavy pseudoscalar boson A decaying to Zh, in the final states with h to tautau
No full textSubmitted to Phys. Lett. B ; see paper for full list of authorsInternational audienceA search for a heavy scalar boson H decaying into a pair of lighter standard-model-like 125 GeV Higgs bosons h and a search for a heavy pseudoscalar boson A decaying into a Z and an h boson are presented. The searches are performed on a dataset corresponding to an integrated luminosity of 19.7 inverse femtobarns of pp collision data at a centre-of-mass energy of 8 TeV, collected by CMS in 2012. A final state consisting of two tau leptons and two b jets is used to search for the H to hh decay. A final state consisting of two tau leptons from the h boson decay, and two additional leptons from the Z boson decay, is used to search for the decay A to Zh. The results are interpreted in the context of both the minimal supersymmetric extension of the standard model and two-Higgs-doublet models. No excess is found above the standard model expectation and upper limits are set on the heavy boson production cross sections in the mass ranges 260<m[H]<350 GeV and 220<m[A]<350 GeV
Stratified regression Monte-Carlo scheme for semilinear PDEs and BSDEs with large scale parallelization on GPUs
No full textInternational audienceIn this paper, we design a novel algorithm based on Least-Squares Monte Carlo (LSMC) in order to approximate the solution of discrete time Backward Stochastic Differential Equations (BSDEs). Our algorithm allows massive parallelization of the computations on multicore devices such as graphics processing units (GPUs). Our approach consists of a novel method of stratification which appears to be crucial for large scale parallelization
Compositional methods for information-hiding
No full textInternational audienceSystems concerned with information hiding often use randomization to obfuscate the link between the observables and the information to be protected. The degree of protection provided by a system can be expressed in terms of the probability of error associated with the inference of the secret information. We consider a probabilistic process calculus to specify such systems, and we study how the operators affect the probability of error. In particular, we characterize constructs that have the property of not decreasing the degree of protection, and that can therefore be considered safe in the modular construction of these systems. As a case study, we apply these techniques to the Dining Cryptographers, and we derive a generalization of Chaum's strong anonymity result
A new Evaluation and Decision Making Framework Investigating the Elimination-by-Aspects Model in the Context of Transportation Projects' Investment Choices
No full textThe Transportation Elimination-by-Aspects (TEBA) framework, a new evaluation and decision makingframework (and methodology) for large transportation projects, is proposed to elicit, structure andquantify the preferences of stakeholder groups across project alternatives. The decision rule used forgroup decision making within TEBA is the individual non-compensatory model of choice elimination byaspects (EBA). TEBA is designed to bring out the decision rule employed by decision makers whenranking the options presented, incorporate various criteria types and ease communication of relevantinformation related to options and criteria for multiple stakeholder groups. It is a platform fordemocratizing the decision making process. The TEBA framework was tested using a case studyinvestigating alternative land connections between Beirut and Damascus. Key results showed that (1)stakeholders have employed EBA in making decisions, (2) a defined group of decision makers will rankoptions differently when provided with modified sets of criteria, (3) the public sector and general publicgroups ranked Impact on Employment among the top criteria, (4) the most important criterion per groupfrom EBA was as expected; (5) the EBA analysis suggested that only 3 to 4 criteria are significant inreaching a decision; (6) aggregation of user assigned weights masked relative importance of criteria insome cases; and (7) analysis of user assigned weights and Minimum Threshold (MT) values suggesthigher risk perception with increased criterion importance. Policy implications include recommendationto reach out to stakeholders for input on decisions, including the “people” but refrain from relying oncriteria weights assigned by “experts” and reduce the “experts”’ role in decision making. Also, it isrecommended to model the decision making in a probabilistic framework rather than a deterministic “onescore” approach, seek to identify a consensus ranking, place particular attention on determining the valuesof the criteria that emerged as “top” at the evaluation stage and continue to emphasize risk measures.Keywords: Transportation Investment, Collective Decision Making, Cost Benefit Analysis, Elimination by Aspects,Consensus Model / Joint Decision Making, Index of Dispersion, Behavioral Choic
Combining structure probing data on RNA mutants with evolutionary information reveals RNA-binding interfaces
No full textInternational audienceSystematic structure probing experiments (e.g. SHAPE) of RNA mutants such as the mutate-and-map protocol give us a direct access into the genetic robustness of ncRNA structures. Comparative studies of homologous sequences provide a distinct, yet complementary, approach to analyze structural and functional properties of non-coding RNAs. In this paper, we introduce a formal framework to combine the biochemical signal collected from mutate-and-map experiments, with the evolutionary information available in multiple sequence alignments. We apply neutral theory principles to detect complex long-range dependencies between nucleotides of a single stranded RNA, and implement these ideas into a software called aRNhAck. We illustrate the biological significance of this signal and show that the nucleotides networks calculated with aRNhAck are correlated with nucleotides located in RNA-RNA, RNA-protein, RNA-DNA and RNA-ligand interfaces. aRNhAck is freely available at http://csb.cs.mcgill.ca/arnhack
Measurement of the differential cross section and charge asymmetry for inclusive pp to W + X production at sqrt(s) = 8 TeV
No full textSubmitted to Eur. Phys. J. C ; see paper for full list of authorsInternational audienceThe differential cross section and charge asymmetry for inclusive pp to W + X to mu-nu + X production at sqrt(s) = 8 TeV are measured as a function of muon pseudorapidity. The data sample corresponds to an integrated luminosity of 18.8 inverse-femtobarns recorded with the CMS detector at the LHC. These results provide important constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10 to the minus 3 to 10 to the minus 1