Generating Predicate Callback Summaries for the Android Framework

One of the challenges of analyzing, testing and debugging Android apps is that the potential execution orders of callbacks are missing from the apps' source code. However, bugs, vulnerabilities and refactoring transformations have been found to be related to callback sequences. Existing work on control flow analysis of Android apps have mainly focused on analyzing GUI events. GUI events, although being a key part of determining control flow of Android apps, do not offer a complete picture. Our observation is that orthogonal to GUI events, the Android API calls also play an important role in determining the order of callbacks. In the past, such control flow information has been modeled manually. This paper presents a complementary solution of constructing program paths for Android apps. We proposed a specification technique, called Predicate Callback Summary (PCS), that represents the callback control flow information (including callback sequences as well as the conditions under which the callbacks are invoked) in Android API methods and developed static analysis techniques to automatically compute and apply such summaries to construct apps' callback sequences. Our experiments show that by applying PCSs, we are able to construct Android apps' control flow graphs, including inter-callback relations, and also to detect infeasible paths involving multiple callbacks. Such control flow information can help program analysis and testing tools to report more precise results. Our detailed experimental data is available at: http://goo.gl/NBPrKsComment: 11 page

Contribution of simulation and gaming to natural resource management issues: An introduction

Nowadays, computer-mediated simulations and games are widely used in the field of natural resource management (NRM). They have proved to be useful for various purposes such as supporting decisionmaking processes and training. First, the specificities of the NRM research field are highlighted. Then, based on the analysis of the articles presented in this special issue of Simulation & Gaming, some key features related to the implementation of gaming in such a context are introduced. Finally, after reviewing the benefits of using simulation games in NRM, the authors stress the ethical issue of changing social relationships among stakeholders by playing a game with some of themGESTION DE L'ENVIRONNEMENT;RESSOURCE NATURELLE;SIMULATION;SOCIOLOGIE;JEU DE ROLE;BENEFITS;CONTEXT;COLLECTIVE POLICY DESIGN;DECISION MAKING;ETHICAL ISSUES;IMPLEMENTATION;NATURAL RESOURCE MANAGEMENT (NRM);SIMULATION GAMES;SOCIAL EMPOWERMENT;SOCIAL RELATIONSHIPS;SOCIOECOLOGICAL SYSTEMS;STAKEHOLDERS

Atollscape: Simulating freshwater management in Pacific Atolls. Spatial processes and time dependence issues

Groundwater has long been ranked as a high priority research area by small island nations in the Pacific. It is the major source of freshwater on the atoll of Tarawa (Rep.of Kiribati) and its availability, quality, management and allocation are central to the atoll¿s sustainable development and poverty alleviation. From a modeling perspective, simulating freshwater lens behavior represents a challenge, as it requires sophisticated numerical models. Such models can hardly fit within an integrated management framework taking into account spatially distributed water use (e.g. wells, trees) and social interactions. Simple analytical solutions exist but they apply for steady-state conditions, verified only on an annual basis. Recent advances in the field of Distributed Artificial Intelligence have permitted the development of a Multi Agent System (MAS) approach, closely related to the problem of complexity. AtollScape uses MAS techniques to simulate water management and freshwater lens behavior on the Tarawa atoll. A distributed and nested structure is used to represent local inputs and uptakes, along with freshwater lens adjustments on a 10 day time steps. (Résumé d'auteur

A mathematical formalization of the parallel replica dynamics

The purpose of this article is to lay the mathematical foundations of a well known numerical approach in computational statistical physics and molecular dynamics, namely the parallel replica dynamics introduced by A.F. Voter. The aim of the approach is to efficiently generate a coarse-grained evolution (in terms of state-to-state dynamics) of a given stochastic process. The approach formally consists in concurrently considering several realizations of the stochastic process, and tracking among the realizations that which, the soonest, undergoes an important transition. Using specific properties of the dynamics generated, a computational speed-up is obtained. In the best cases, this speed-up approaches the number of realizations considered. By drawing connections with the theory of Markov processes and, in particular, exploiting the notion of quasi-stationary distribution, we provide a mathematical setting appropriate for assessing theoretically the performance of the approach, and possibly improving it

Bit error rate measurement of free space optical communication links under laboratory controlled conditions

This paper outlines the experimental investigation of the fog effect on the bit error rate (BER) performance of the free space optical (FSO) communication link under a controlled laboratory environment. The link transmittance and the received signal Q-factor are measured against different levels of fog densities. The link visibility derived from fog attenuation measurement is used to characterize the fog within the chamber. Moreover, the effect of using different average transmitted optical communication power (Popt) on the transmittance and received Q-factor of the link is also studied for light and dense fog densities

The AtollGame Experience: from Knowledge Engineering to a Computer-Assisted Role Playing Game

This paper presents the methodology developed to collect, understand and merge viewpoints coming from different stakeholders in order to build a shared and formal representation of the studied system dealing with groundwater management in the low-lying atoll of Tarawa (Republic of Kiribati). The methodology relies on three successive stages. First, a Global Targeted Appraisal focuses on social group leaders in order to collect different standpoints and their articulated mental models. These collective models are partly validated through Individual Activities Surveys focusing on behavioural patterns of individual islanders. Then, these models are merged into a single conceptual one using qualitative analysis software. This conceptual model is further simplified in order to create a computer-assisted role-playing game.Knowledge Elicitation, Associative Network, Ontology, Water Management, Pacific, Tarawa

ARTrees et artefacts : une exposition artistique pour un sujet de recherche sur l'agroforesterie

Allier art et science permet de dépasser les frontières des connaissances de chacun. Art et science ont en commun d'appréhender et de donner à voir le monde même si chaque démarche le fait selon des modes très différents. C'est cette considération qui a engagé l'équipe du projet ARTree à proposer à de jeunes chercheurs de s'impliquer dans une démarche artistique pour aboutir à une exposition sur le thème de l'agroforesterie. Les jeunes chercheurs ont été invités à produire eux-mêmes des artefacts (peinture, verbatims, exposition) avec l'accompagnement d'une artiste peintre-plasticienne et de chercheurs confirmés. Treize peintures ont été produites et ont été rassemblées en une exposition au Corum de Montpellier, lors de la journée internationale d'agroforesterie "Des Arbres dans nos Assiettes", journée qui a accueilli 2000 visiteurs. Les jeunes chercheurs ont assuré pendant l'exposition un dialogue avec le public autour de leurs oeuvres amenant à des échanges sur leurs travaux scientifiques. Ainsi, le processus artistique engage le chercheur dans des activités de réflexivité et de communication, il produit des artefacts qui facilitent le dialogue et le partage d'expériences. L'exposition a déjà un programme d'itinérance pour susciter de nouveaux regards et dialogues

On the study of the FSO link performance under controlled turbulence and fog atmospheric conditions

In this paper, the effect of turbulence and fog on the free space optical (FSO) communication systems for on off keying (OOK), pulse amplitude modulation (PAM) and subcarrier intensity modulation (SIM) based on binary phase shift keying (BPSK) is experimentally investigated. The experiment is carried out in a controlled laboratory environment where turbulence and fog could be generated in a dedicated FSO chamber. In comparison to 4 PAM signal, the BPSK and OOK NRZ modulation signalling format are more robust against the fog and turbulence effects. In addition BPSK system is much less susceptible to the signal amplitude fluctuation due to turbulence compared to the other two modulation formats

Integral field spectroscopy with SINFONI of VVDS galaxies. II. The mass-metallicity relation at 1.2 < z < 1.6

This work aims to provide a first insight into the mass-metallicity (MZ) relation of star-forming galaxies at redshift z~1.4. To reach this goal, we present a first set of nine VVDS galaxies observed with the NIR integral-field spectrograph SINFONI on the VLT. Oxygen abundances are derived from empirical indicators based on the ratio between strong nebular emission-lines (Halpha, [NII]6584 and [SII]6717,6731). Stellar masses are deduced from SED fitting with Charlot & Bruzual (2007) population synthesis models, and star formation rates are derived from [OII]3727 and Halpha emission-line luminosities. We find a typical shift of 0.2-0.4 dex towards lower metallicities for the z~1.4 galaxies, compared to the MZ-relation in the local universe as derived from SDSS data. However, this small sample of eight galaxies does not show any clear correlation between stellar mass and metallicity, unlike other larger samples at different redshift (z~0, z~0.7, and z~2). Indeed, our galaxies lie just under the relation at z~2 and show a small trend for more massive galaxies to be more metallic (~0.1 logarithmic slope). There are two possible explanations to account for these observations. First, the most massive galaxies present higher specific star formation rates when compared to the global VVDS sample which could explain the particularly low metallicity of these galaxies as already shown in the SDSS sample. Second, inflow of metal-poor gas due to tidal interactions could also explain the low metallicity of these galaxies as two of these three galaxies show clear signatures of merging in their velocity fields. Finally, we find that the metallicity of 4 galaxies is lower by ~0.2 to 0.4 dex if we take into account the N/O abundance ratio in their metallicity estimate.Comment: 7 pages, 4 figures, accepted in A&A Comments: Comments: more accurate results with better stellar mass estimate

Time-randomized stopping problems for a family of utility functions

This paper studies stopping problems of the form $V=\inf_{0 \leq \tau \leq T} \mathbb{E}[U(\frac{\max_{0\le s \le T} Z_s }{Z_\tau})]$ for strictly concave or convex utility functions U in a family of increasing functions satisfying certain conditions, where Z is a geometric Brownian motion and T is the time of the nth jump of a Poisson process independent of Z. We obtain some properties of $V$ and offer solutions for the optimal strategies to follow. This provides us with a technique to build numerical approximations of stopping boundaries for the fixed terminal time optimal stopping problem presented in [J. Du Toit and G. Peskir, Ann. Appl. Probab., 19 (2009), pp. 983--1014]