Power sector reforms in Brazil and its impacts on energy efficiency and research and development activities

Since the mid-nineties Brazil has implemented significant changes in the country's power sector, including privatization, introduction of competition and the creation of regulatory agency. As reform started in Brazil traditional support to energy efficiency and energy research and development suffered a discontinuation, budget cuts and re-definition of roles of the public agents in charge. At the same time, new regulatory measures and the creation of a national public interest fund have helped to maintain and potentially enhance the country's effort to promote energy efficiency and investments in energy R&D. This paper analyses the impacts of these changes in the areas of energy efficiency and energy research and development and argues for an increased role of developing countries to provide solutions for a meeting energy demand requirements more suitable to their internal markets.     

User acceptance of hedonic digital artifacts: A theory of consumption values perspective

Hedonic digital artifacts have become prevalent in today's society. Their users typically pay for them, and in exchange are generally provided with benefits involving enjoyment. Today's research on technology adoption and use, though, has focused mostly on organizational or personal aids that provide efficiency and effectiveness and are free of charge for users. To bridge this gap, we identified several value drivers of hedonic digital artifacts and measured them in the context of mobile phone ringtones using the theory of consumption values. Hypothesis testing was performed using PLS on data collected from 422 ringtone users. Results confirmed that the overall value of hedonic digital artifacts is a third-order composite assessment, which successfully predicted behavioral usage and positive word-of-mouth intentions. Theoretical and practical implications were discussed.     

Should I e-collaborate with this group? A multilevel model of usage intentions

The use of online collaboration tools for virtual teamwork has been studied extensively, but mainly at the individual-level. We decided to examine the effect of macro-level factors (i.e., team attributes) and applied hierarchical linear modeling analysis to a sample of data collected from 96 individuals nested in 34 virtual teams. Our results suggested that the development of behavioral e-collaboration intentions by individual virtual team members was affected by their perceptions about the system, as described by individual-level IT use theories, and macro-level factors pertaining to the team. The collaboration technology was perceived to be less useful when employed to communicate with social loafers; and collective social loafing negatively influenced the teams’ potency assessments. After controlling for individual-level perceptions of system usefulness, team potency augmented team members’ intentions to use the online collaboration technology with similar teams. It also improved team performance.     

Allowing for missing genotypes in any members of the nuclear families in transmission disequilibrium test

The Transmission Disequilibrium Test (TDT) detects linkage between a marker and a disease-susceptibility locus in the presence of linkage disequilibrium. The TDT requires data on the genotypes of affected offspring and their parents, which might not always be available. For example, for late onset diseases it might be difficult to find parents still alive, or genotypes of offspring might not be available. Genotyping unaffected siblings, combining different genotype data sets, or assuming a model mechanism for missing parents have all been proposed to deal with missing genotypes in parents but not in offspring. In this paper, we propose a Mendel Inheritance-Transmission Disequilibrium Test (MI-TDT) to impute missing genotypes in any members of a family with two affected offspring. Our method does not require any of the remedies mentioned above but simply utilizes the fundamental property of Mendel Inheritance on the transmission of alleles from parents to offspring. Most importantly, the MI-TDT reassures researchers about the declared significant genes when incomplete data is ignored. We illustrate the MI-TDT by identifying significant genes in type 1 diabetes from the Warren families in the United Kingdom.     

An empirical analysis of heuristics for solving the two-machine flow shop problem with job release times

The theoretical analysis of heuristics for solving intractable optimization problems has many well-known drawbacks. Constructed instances demonstrating an exceptionally poor worst-case performance of heuristics are typically too peculiar to occur in practice. Theoretical results on the average-case performance of most heuristics could not be established due to the difficulty with the use of probabilistic analysis. Moreover, the heuristics for which some type of asymptotic optimality has been proven are likely to perform questionably in practice. The purpose of this paper is to confront known theoretical results with our empirical results concerning heuristics for solving the strongly NP-hard problem of minimizing the makespan in a two-machine flow shop with job release times. The heuristics' performance is examined with respect to their average and maximum relative errors, as well as their optimality rate, that is, the probability of being optimal. In particular, this allows us to observe that the asymptotic optimality rate of so called “almost surely asymptotically optimal” heuristic can be zero. We also present a new heuristic with short worst-case running time and statistically prove that it outperforms all heuristics known so far. However, our empirical experiments reveal that the heuristic is on average slower that its competitors with much longer worst-case running times.     

Enhancing the performance of hybrid genetic algorithms by differential improvement

A differential improvement modification to Hybrid Genetic Algorithms is proposed. The general idea is to perform more extensive improvement algorithms on higher quality solutions. Our proposed Differential Improvement (DI) approach is of rather general character. It can be implemented in many different ways. The paradigm remains invariant and can be easily applied to a wider class of optimization problems. Moreover, the DI framework can also be used within other Hybrid metaheuristics like Hybrid Scatter Search algorithms, Particle Swarm Optimization, or Bee Colony Optimization techniques.     

Cooperative Cover of Uniform Demand

Networks and Spatial Economics - We investigate the total covered area by multiple facilities applying the cooperative cover model. We found that the cooperative cover area is much larger than the...     

Testing equality of covariance matrices when data are incomplete

In the statistics literature, a number of procedures have been proposed for testing equality of several groups’ covariance matrices when data are complete, but this problem has not been considered for incomplete data in a general setting. This paper proposes statistical tests for equality of covariance matrices when data are missing. A Wald test (denoted by T₁), a likelihood ratio test (LRT) (denoted by R), based on the assumption of normal populations are developed. It is well-known that for the complete data case the classic LRT and the Wald test constructed under the normality assumption perform poorly in instances when data are not from multivariate normal distributions. As expected, this is also the case for the incomplete data case and therefore has led us to construct a robust Wald test (denoted by T₂) that performs well for both normal and non-normal data. A re-scaled LRT (denoted by R^*) is also proposed. A simulation study is carried out to assess the performance of T₁, T₂, R, and R^* in terms of closeness of their observed significance level to the nominal significance level as well as the power of these tests. It is found that T₂ performs very well for both normal and non-normal data in both small and large samples. In addition to its usual applications, we have discussed the application of the proposed tests in testing whether a set of data are missing completely at random (MCAR).     

A study of partial F tests for multiple linear regression models

Partial F tests play a central role in model selections in multiple linear regression models. This paper studies the partial F tests from the view point of simultaneous confidence bands. It first shows that there is a simultaneous confidence band associated naturally with a partial F test. This confidence band provides more information than the partial F test and the partial F test can be regarded as a side product of the confidence band. This view point of confidence bands also leads to insights of the major weakness of the partial F tests, that is, a partial F test requires implicitly that the linear regression model holds over the entire range of the covariates in concern. Improved tests are proposed and they are induced by simultaneous confidence bands over restricted regions of the covariates. Power comparisons between the partial F tests and the new tests have been carried out to assess when the new tests are more or less powerful than the partial F tests. Computer programmes have been developed for easy implements of these new confidence band based inferential methods. An illustrative example is provided.     

Etude des caractéristiques résiduelles des sols du site instable de Bouchegouf (Algerie)

Cet article présente une étude comparative des caractéristiques résiduelles obtenues à l'aide de l'appareil de cisaillement annulaire et de la boite de cisaillement alterné. Les échantillons de sols étudiés proviennent du site instable de Bouchegouf (Algérie). Des corrélations entre les différents paramètres pouvant influer sur ces caractéristiques résiduelles ont été faites. Il a été, notamment, montré que les résultats obtenus à l'aide de l'appareil de Bromhead sur des échantillons remaniés sont très voisins de ceux obtenus à l'aide du cisaillement alterné sur des échantillons intacts quand la fraction argileuse est importante.