Selecting mutation operators with a multiobjective approach

The mutation score is an important measure to evaluate the quality of the test cases. It is obtained by executing a lot of mutant programs generated by a set of operators. A common problem, however, is that some operators can generate unnecessary and redundant mutants. Because of this, different strategies were proposed to find a set of operators that generates a reduced number of mutants without decreasing the mutation score. However, the operator selection, in practice, may include real constraints and is dependent on diverse factors besides the number of mutants and score, such as: number of test data, execution time, number of revealed faults, number of equivalent mutants, etc. In fact this is a multi-objective problem, which does not have a single solution. Different set of operators exist for multiple objectives to be satisfied, and some restrictions can be used to choose among the existing sets. To make this choice possible, in this paper, we introduce a multi-objective strategy. We investigate three multi-objective algorithms and introduce a procedure to establish a set of operators to prioritize mutation score. Better results are obtained in comparison with traditional strategies.     

A Benders Decomposition Method for Solving Stochastic Complementarity Problems with an Application in Energy

In this paper we present a new Benders decomposition method for solving stochastic complementarity problems based on the work by Fuller and Chung (Comput Econ 25:303–326, 2005; Eur J Oper Res 185(1):76–91, 2007). A master and subproblem are proposed both of which are in the form of a complementarity problem or an equivalent variational inequality. These problems are solved iteratively until a certain convergence gap is sufficiently close to zero. The details of the method are presented as well as an extension of the theory from Fuller and Chung (2005, 2007). In addition, extensive numerical results are provided based on an electric power market model of Hobbs (IEEE Trans Power Syst 16(2):194–202, 2001) but for which stochastic elements have been added. These results validate the approach and indicate dramatic improvements in solution times as compared to solving the extensive form of the problem directly.     

Dynamics and Structure of the 30 Largest North American Companies

In this paper we describe a method to analyze the structure and dynamics of the 30 largest North American companies. The method combines the tools of symbolic time series analysis (Daw et al. in Rev Sci Instrum 74:916–930, 2003) with the nearest neighbor single linkage clustering algorithm (Mantegna and Stanley in An introduction to econophysics: Correlations and complexity in finance, Cambridge University Press, UK, 2000). Data symbolization allows to obtain a metric distance between two different time series that is used to construct a minimal spanning tree allowing to compute an ultrametric distance. From the analysis of time series data of companies included in Dow Jones Industrial Average, we derive a hierarchical organization of these companies. In particular, we detect different clusters of companies which correspond with their common production activities or their strong interrelationship. The obtained classification of companies can be used to study deep relationships among different branch of economic activities and to construct financial portfolios.     

Finite dose skin penetration: a comparison of concentration-depth profiles from experiment and simulation

In this paper we present a mathematical diffusion model describing the transient transdermal penetration of two non-volatile substances, the lipophilic flufenamic acid and the hydrophilic caffeine, after finite dosing in an aqueous vehicle system. A striking feature of this microscopic diffusion model is its ability to predict concentration-depth profiles. Relevant input parameters are obtained from a previously published infinite dose study (Naegel et?al in Eur J Pharm Biopharm 68:368?C379, 2008; Hansen et?al in Eur J Pharm Biopharm 68:352?C367, 2008). The quality of the model has been evaluated by comparing the concentration-depth profiles in stratum corneum (SC) and deeper skin layers of the experiment with those of the simulation. The results from the experiment and the simulation are in good agreement. The study addresses benefits and shortcomings of the model, and discusses future perspectives such as incorporating different morphological regions of the SC.     

A modified Benders decomposition method for efficient robust optimization under interval uncertainty

The goal of robust optimization problems is to find an optimal solution that is minimally sensitive to uncertain factors. Uncertain factors can include inputs to the problem such as parameters, decision variables, or both. Given any combination of possible uncertain factors, a solution is said to be robust if it is feasible and the variation in its objective function value is acceptable within a given user-specified range. Previous approaches for general nonlinear robust optimization problems under interval uncertainty involve nested optimization and are not computationally tractable. The overall objective in this paper is to develop an efficient robust optimization method that is scalable and does not contain nested optimization. The proposed method is applied to a variety of numerical and engineering examples to test its applicability. Current results show that the approach is able to numerically obtain a locally optimal robust solution to problems with quasi-convex constraints (≤ type) and an approximate locally optimal robust solution to general nonlinear optimization problems.     

Bonding calculus

We present the bonding calculus, a calculus in which it is easy to handle covalent bonds between molecules. Our purpose is to use bonding calculus to model the dynamics of the interactions in biochemical systems. We provide an operational semantics by means of a transition system, and use a known software platform to both simulate the chemical reactions described naturally in bonding calculus and verify their specific properties.     

RISE: A general simulation interoperability middleware container

In recent years, new services on the Internet have enabled global cooperation; in particular, the Web has enabled new distributed simulation technology. Much research has been devoted to develop middleware interoperability methods on the Web. However, most existing methods have constraints in the structural rules that are placed on the design of middleware interoperability methods. For example, such constraints make it difficult to enhance interoperability via decoupling systems implementations and design, which is essential in open computing networks, as in the case of the Web. In order to achieve such objectives we present the RISE (RESTful Interoperability Simulation Environment) middleware. This all-purpose WS-based distributed simulation middleware decouples design and implementation while allowing composition scalability and dynamicity. Furthermore, it supports experiment-oriented frameworks and has the ability to put Web 2.0 services in the simulation loop. RISE is the first existing middleware to achieve such objectives, and the first to employ RESTful Web-services. We present the foundations for meeting the above objectives, and the distinct characteristics of RISE from existing Web-based approaches.     

Why do you play World of Warcraft? An in-depth exploration of self-reported motivations to play online and in-game behaviours in the virtual world of Azeroth

Massively multiplayer online role-playing games (MMORPGs) are video games in which players create an avatar that evolves and interacts with other avatars in a persistent virtual world. Motivations to play MMORPGs are heterogeneous (e.g. achievement, socialisation, immersion in virtual worlds). This study investigates in detail the relationships between self-reported motives and actual in-game behaviours. We recruited a sample of 690 World of Warcraft players (the most popular MMORPG) who agreed to have their avatar monitored for 8 months. Participants completed an initial online survey about their motives to play. Their actual in-game behaviours were measured through the game’s official database (the Armory website). Results showed specific associations between motives and in-game behaviours. Moreover, longitudinal analyses revealed that teamwork- and competition-oriented motives are the most accurate predictors of fast progression in the game. In addition, although specific associations exist between problematic use and certain motives (e.g. advancement, escapism), longitudinal analyses showed that high involvement in the game is not necessarily associated with a negative impact upon daily living.     

Developing an operational rangeland water requirement satisfaction index

Developing an operational water requirement satisfaction index (WRSI) for rangeland monitoring is an important goal of the famine early warning systems network. An operational WRSI has been developed for crop monitoring, but until recently a comparable WRSI for rangeland was not successful because of the extremely poor performance of the index when based on published crop coefficients (K _c) for rangelands. To improve the rangeland WRSI, we developed a simple calibration technique that adjusts the K _c values for rangeland monitoring using long-term rainfall distribution and reference evapotranspiration data. The premise for adjusting the K _c values is based on the assumption that a viable rangeland should exhibit above-average WRSI (values >80%) during a normal year. The normal year was represented by a median dekadal rainfall distribution (satellite rainfall estimate from 1996 to 2006). Similarly, a long-term average for potential evapotranspiration was used as input to the famine early warning systems network WRSI model in combination with soil-water-holding capacity data. A dekadal rangeland WRSI has been operational for east and west Africa since 2005. User feedback has been encouraging, especially with regard to the end-of-season WRSI anomaly products that compare the index's performance to ‘normal’ years. Currently, rangeland WRSI products are generated on a dekadal basis and posted for free distribution on the US Geological Survey early warning website at http://earlywarning.usgs.gov/adds/     

Evaluation of Tone Mapping Operators for HDR‐Video

Eleven tone‐mapping operators intended for video processing are analyzed and evaluated with camera‐captured and computer‐generated high‐dynamic‐range content. After optimizing the parameters of the operators in a formal experiment, we inspect and rate the artifacts (flickering, ghosting, temporal color consistency) and color rendition problems (brightness, contrast and color saturation) they produce. This allows us to identify major problems and challenges that video tone‐mapping needs to address. Then, we compare the tone‐mapping results in a pair‐wise comparison experiment to identify the operators that, on average, can be expected to perform better than the others and to assess the magnitude of differences between the best performing operators.