Lower bounds and a tabu search algorithm for the minimum deficiency problem

An edge coloring of a graph G=(V,E) is a function c:E→ℕ that assigns a color c(e) to each edge e∈E such that c(e)≠c(e′) whenever e and e′ have a common endpoint. Denoting S _v (G,c) the set of colors assigned to the edges incident to a vertex v∈V, and D _v (G,c) the minimum number of integers which must be added to S _v (G,c) to form an interval, the deficiency D(G,c) of an edge coloring c is defined as the sum ∑ _v∈V D _v (G,c), and the span of c is the number of colors used in c. The problem of finding, for a given graph, an edge coloring with a minimum deficiency is NP-hard. We give new lower bounds on the minimum deficiency of an edge coloring and on the span of edge colorings with minimum deficiency. We also propose a tabu search algorithm to solve the minimum deficiency problem and report experiments on various graph instances, some of them having a known optimal deficiency.     

Gender homophily from spatial behavior in a primary school: A sociometric study

We investigate gender homophily in the spatial proximity of children (6–12 years old) in a French primary school, using time-resolved data on face-to-face proximity recorded by means of wearable sensors. For strong ties, i.e., for pairs of children who interact more than a defined threshold, we find statistical evidence of gender preference that increases with grade. For weak ties, conversely, gender homophily is negatively correlated with grade for girls, and positively correlated with grade for boys. This different evolution with grade of weak and strong ties exposes a contrasted picture of gender homophily.     

Extending health care coverage: Potential linkages between statutory social security and community-based social protection

Abstract   The extension of social health protection in developing countries is widely recognized as a priority. Various financing and institutional methods can be used in pursuing this objective, but none of them can achieve universal coverage in the short term. Based on an analysis of the respective strengths and weaknesses of social health insurance and community-based health care schemes, this article demonstrates the high potential of coverage extension strategies that use a pluralistic institutional approach to establish linkages and exploit complementarities optimally. A typology of potential linkages among different methods is presented and their value added illustrated using country examples.     

International accounting: a French perspective

The objective of this article is to show how slow and imperfect the international accounting harmonization and standardization process is, based on the example of France but also some other European countries. One of the explanations is that accounting is a mirror of a society. Therefore, international harmonization and standardization is a response to social needs, a compromise among different interests, not only a technical process.     

Estimation in the multipath change point problem for correlated data

In many experiments, several measurements on the same variable are taken over time, a geographic region, or some other index set. It is often of interest to know if there has been a change over the index set in the parameters of the distribution of the variable. Frequently, the data consist of a sequence of correlated random variables, and there may also be several experimental units under observation, each providing a sequence of data. A problem in ascertaining the boundaries between the layers in geological sedimentary beds is used to introduce the model and then to illustrate the proposed methodology. It is assumed that, conditional on the change point, the data from each sequence arise from an autoregressive process that undergoes a change in one or more of its parameters. Unconditionally, the model then becomes a mixture of nonstationary autoregressive processes. Maximum-likelihood methods are used, and results of simulations to evaluate the performance of these estimators under practical conditions are given.     

Uniform asymptotic linearity in a regression parameter of a process based on a rank statistic

For X₁, …, X_N a random sample from a distribution F, let the process S^δ_N(t) be defined as where K²_N = σ^N_i=1(c_i ? c?)² and R x_i, + Δd, is the rank of X_i + Δd_i, among X₁ + Δd₁, …, X_N + Δd_N. The purpose of this note is to prove that, under certain regularity conditions on F and on the constants c_i and d_i, S^Δ_N (t) is asymptotically approximately a linear function of Δ, uniformly in t and in Δ, |Δ| ≤ C. The special case of two samples is considered.     

A structural analysis of greening the supplier,environmental performance and competitive advantage

A clear research need has been identified to confirm the structural relationships between greening the supplier, enhanced environmental performance and improved competitive advantage, to provide an impetus for firms to green their suppliers. A mail survey was conducted and empirical data of 119 ISO 14001 manufacturing firms in Malaysia was gathered for this study. Structural equation modelling technique was applied in this research article. Results from the analysis, reveal the existence of a positive and significant linkage between green suppliers with both environmental performance and competitive advantage. At the same time, environmental performance has also been shown to positively and significantly affect competitive advantage; while environmental performance plays a partial mediating role between greening the supplier and competitiveness. Such significant finding is especially essential for the manufacturing sector registered with ISO 14001 who intend to enhance their environmental performance and carve a niche competitive edge in the business arena.     

An Axiomatization of Cumulative Prospect Theory for Decision Under Risk

Cumulative prospect theory was introduced by Tversky and Kahneman so as to combine the empirical realism of their original prospect theory with the theoretical advantages of Quiggin's rank-dependent utility. Preference axiomatizations were provided in several papers. All those axiomatizations, however, only consider decision under uncertainty. No axiomatization has been provided as yet for decision under risk, i.e., the case in which given probabilities are transformed. Providing the latter is the purpose of this note. The resulting axiomatization is considerably simpler than that for uncertainty.