A METHODOLOGY FOR DETECTING BREAKS IN THE MEAN AND COVARIANCE STRUCTURE OF TIME SERIES

Some structural break techniques defined in the time and frequency domains are presented to explore, at the same time, the empirical evidence of the mean and covariance instability by uncovering regime-shifts in some inflation series. To that effect, we pursue a methodology that combines two approaches; the first is defined in the time domain and is designed to detect mean-shifts, and the second is defined in the frequency domain and is adopted to study the instability problem of the covariance function of the series. The proposed methodology has a double interest since, besides the detection of regime-shifts occasioned in the covariance structure of the series, it allows taking into account the presence of mean-shifts in this series. Note that unlike the works existing in the literature which often adopt a single technique to study the break identification problem, our methodology combines two approaches, parametric and nonparametric, to examine this problem.Structural change, mean and variance shifts, parametric and nonparametric approaches.

wrong estimation of the true number of shifts in structural break models: Theoretical and numerical evidence

The aim of the paper is to consider the problem of selecting the number of breaks in the mean of a time series. Indeed, we prove analytically and show by a Monte Carlo study that some model selection criteria will tend to choose a spuriously high number of structural breaks when the process is trend-stationary without changes. The important question suggested by our results is that of distinction between trend-stationary process and random walk when modelling real data series.Model selection

Structural Breaks in the Mexico's Integration into the World Stock Market

This article investigates the evolution of the Mexican stock market integration into the world market. First, we estimate the time-varying Mexican degree of market integration using an international conditional version of the CAPM with segmentation effects. Second, we study the structural breaks in this series. Finally, we relate the obtained results to important facts and economic events

Structural Breaks in the Mexico's Integration into the World Stock Market

This article investigates the evolution of the Mexican stock market integration into the world market. First, we estimate the time-varying Mexican degree of market integration using an international conditional version of the CAPM with segmentation effects. Second, we study the structural breaks in this series. Finally, we relate the obtained results to important facts and economic event

Phase boundary between Na-Si clathrates of structures I and II at high pressures and high temperatures

Understanding the covalent clathrate formation is a crucial point for the design of new superhard materials with intrinsic coupling of superhardness and metallic conductivity. Silicon clathrates have the archetype structures that can serve an existant model compounds for superhard clathrate frameworks "Si-B", "Si-C", "B-C" and "C" with intercalated atoms (e.g. alkali metals or even halogenes) that can assure the metalic properties. Here we report the in situ and ex situ studies of high-pressure formation and stability of clathrates Na8Si46 (structure I) and Na24+xSi136 (structure II). Experiments have been performed using standard Paris-Edinburgh cells (opposite anvils) up to 6 GPa and 1500 K. We have established that chemical interactions in Na-Si system and transition between two structures of clathrates occur at temperatures below silicon melting. The strong sensitivity of crystallization products to the sodium concentration have been observed. A tentative diagram of clathrate transformations has been proposed. At least up to ~6 GPa, Na24+xSi136 (structure II) is stable at lower temperatures as compared to Na8Si46 (structure I)

Analysis of the evolution of a Roman urban space by GPR survey

We identify the previous phases of a building by means of GPR of a Roman quarter. We analyze the data from excavations and geophysics in a complementary way to understand the evolution of an urban space

Acute pancreatitis due to pancreatic hydatid cyst: a case report and review of the literature

Hydatid disease is a major health problem worldwide. Primary hydatid disease of the pancreas is very rare and acute pancreatitis secondary to hydatid cyst has rarely been reported. We report the case of a 38-year-old man who presented acute pancreatitis. A diagnosis of hydatid cyst of the pancreas, measuring 10 cm, was established by abdominal computed tomography before surgery. The treatment consisted of a distal pancreatectomy. The postoperative period was uneventful. Additionally, a review of the literature regarding case reports of acute pancreatitis due to pancreatic hydatid cyst is presented

Relation entre la Responsabilité Sociale des Entreprises et la Performance Financière : Cas des entreprises tunisiennes

Cet article analyse la relation entre la responsabilité sociale des entreprises (RSE) et la performance financière (PF). Cette dernière est devenue omniprésente dans les discours économiques et académiques ainsi que dans les débats. Cette analyse est basée sur une revue de littérature de la responsabilité sociale des entreprises. En premier lieu, nous allons présenter les principales définitions théoriques ainsi que les définitions des différentes notions de performance. En deuxième lieu, une recherche empirique est établie sur la relation entre RSE et PF, ainsi que sur l’interaction entre la performance sociale (PS) et celle financière des petites et moyennes entreprises (PME). En dernier lieu, nous allons étudier la relation entre des Parties Prenantes (PP)et la PF. Nous avons utilisé une approche d'enquête par questionnaire auprès de 60 PME, les données ont été recueillies auprès des entreprises de différents secteurs d’activités en Tunisie. Dans ce questionnaire, il y a 46 items qui ont été utilisés avec une échelle de Likert à 5 points (1 signifient « fortement en désaccord » et 5 signifient « fortement d'accord ») pour estimer les relations proposées dans le modèle conceptuel. En étudiant les liens de causalité et en confirmant les hypothèses de recherche, les résultats ont montré un impact positif entre Performance Financière, Performance Sociale, Responsabilité Sociale et Parties Prenantes

En quoi l'entrepreneuriat social et l'innovation sociale constituent-ils un avantage concurrentiel pour les entreprises ?

Ces dernières années, la recherche scientifique a suscité un débat sur un certain nombre de concepts interconnectés englobant deux dimensions apparemment contradictoires : la dimension sociale et la dimension économique. L'objectif principal de cette étude est de démontrer la relation entre l'entrepreneuriat social, le concept d'innovation sociale et leur impact sur la concurrence. L'entrepreneuriat social et l'innovation sociale sont devenus des métaphores puissantes pour de nouvelles formes et de nouveaux modèles de solutions de création de valeur commerciale. En fait, notre défi consiste à déterminer les principaux moteurs de la capacité d'innovation des entreprises et quel serait le niveau approprié de capacité d'innovation pour être compétitif ? La méthode de recherche a été conduite par un questionnaire qui a été administré sur un échantillon de 100 entreprises sociales tunisiennes financées par des banques de financement de petites et moyennes entreprises, afin de porter un jugement sur la capacité d’innovation à créer un avantage concurrentiel et accroitre sa part de marché. Les résultats montrent l'importance de la capacité d'innovation et son impact positif sur la réalisation d'un avantage concurrentiel