Mass-Transfer Enhancement by a Reversible Chemical Reaction Across the Interface of a Bubble Rising Under Stokes Flow

Mass transfer around a bubble rising in a liquid under Stokes regime is investigated when a reversible chemical reaction, A !B, is taken into account. Four dimensionless parameters control the interfacial transfer rate: the Peclet and Damkohler numbers, the ratio of the diffusion coefficient of both species, and the reaction equilibrium constant. The € mass-transfer equations are solved numerically with a finite element technique. A boundary layer approach is also proposed and solved with a coupled technique of finite difference and Chebyshev-spectral method. The equilibrium constant and the ratio of diffusion coefficients have a strong influence on the coupling between the chemical reaction and mass transfer leading to an increase of the Sherwood number. The interaction between the chemical reaction and advection is clearly established by the simulations. Conditions corresponding to Peclet number larger than the Damkohler number reduces the effect of the chemical reaction

QoLR: An R Package for the Longitudinal Analysis of Health-Related Quality of Life in Oncology

Health-related quality of life has become increasingly important in clinical trials over the past two decades. The R package QoLR is a recently developed package for the longitudinal analysis of health-related quality of life in oncology. This package contains the scoring of most of the European Organisation for Research and Treatment of Cancer quality of life questionnaires and some programs to analyze the time to a health-related quality of life score deterioration as a modality of longitudinal analysis in oncology

effets incitatifs de la prime pour l'emploi : une évaluation difficile.

L’idée que des problèmes d'offre affectent le marché de travail aboutit, au début des années 2000, à la création de la prime pour l'emploi (PPE), adoptée dans le cadre d'un ensemble de réformes visant à rendre plus rémunérateur le passage du non-emploi à l'emploi. La loi du 30 mai 2001 portant sa création présente ainsi sa finalité : « Afin d'inciter au retour à l'emploi ou au maintien de l'activité, il est institué un droit à récupération fiscale, dénommé prime pour l'emploi, au profit des personnes physiques domiciliées en France ». À partir de l'enquête Revenus fiscaux (ERF) de 2001, deux méthodes sont utilisées pour évaluer un éventuel effet de la PPE sur l’emploi, chaque fois en organisant la comparaison entre un groupe de traitement (constitué par ses bénéficiaires potentiels) et un groupe de contrôle dont les membres ne sont pas affectés par la mesure mais ont des caractéristiques proches de celles du premier groupe. Il n’apparaît pas d’effet significatif de la PPE sur l'emploi, y compris en se focalisant sur l'emploi des femmes mariées. Ces résultats, cohérents avec ceux des études ex ante, qui soulignaient le faible caractère incitatif de la réforme, s'expliquent, d'une part, par la faiblesse des montants de la PPE en 2001 et, d'autre part, sans doute aussi par le décalage important entre la reprise d'activité et le versement effectif de la PPE (qui peut atteindre jusqu'à 18 mois), qui réduit sa visibilité. Ces résultats doivent être cependant relativisés. Tout d'abord, notre étude porte sur la PPE versée au titre des revenus de 2001 et le dispositif était probablement encore peu connu une année seulement après son instauration. Depuis, la PPE a été aménagée (augmentation des montants distribués en cas d’emploi à temps partiel, revalorisation de la prime versée, acompte et mensualisation) ce qui, combiné à son apprentissage par les agents, a pu en modifier l'impact incitatif.

The Incentive Effects of the French Tax Credit for Low Wage Earners: a Difficult Evaluation

In 2001 the French government introduced a tax credit for low wage earners, called prime pour lemploi. This programme was designed to solve supply problems on the labour market and was adopted as part of a series of reforms to make more profitable the transition from unemployment to employment. On the basis of the 2001 Tax Income Survey, this study evaluates the possible effect of the French tax credit on unemployment with a difference in differences method, based on the comparison of a treatment group against a control group, which has similar characteristics but is supposed not to be affected by the scheme. Two different statistical methods are used for the construction of the groups, using either the estimation of potential wages or the probability to benefit from the programme. No significant effect on employment emerges, including when focusing on the employment of married women.Labour Incentives, Difference in Differences, Tax Credit

Asymptotically efficient GNSS trilateration

Localization based on the reception of radio-frequency waveforms is a crucial problem in many civilian or military applications. It is also the main objective of all Global Navigation Satellite System (GNSS). Given delayed and Doppler shifted replicas of the satellites transmitted signals, the most widespread approach consists in a suboptimal two-step procedure. First, estimate the delays and Dopplers from each satellite independently, then estimate the user position and speed thanks to a Least Square (LS) minimization. More accurate and robust techniques, such as a direct Maximum Likelihood (ML) maximization, that exploit the links in between the different channels exist but suffer from an heavy computational burden that prevent their use in real time applications. Two-steps procedures with an appropriate Weighted LS (WLS) minimization are shown to be asymptotically equivalent to the ML procedure. In this paper, we develop a closed-form expression of this WLS asymptotically efficient solution. We show that this simple expression is the sum of two terms. The first one, depending on the pseudo-ranges is the widespread used WLS solution. The second one is a Doppler-aided corrective term that should be taken into account to improve the position estimation when the observation time increases

Water weathering in rocks discontinuities

The behavior of rock discontinuities at different spatial scales remains a major challenge for scientists who want to understand the rock alteration, both in the triggering of rock-fall and in the evolution of the cliffs. Our research aim to take into account the geomorphological features related to the slopes and rock discontinuities subject to weathering conditions. Several studies show the physical effect of water in the alteration of rock through cracks and micro cracks. In Cultural Heritage point of view, a rock discontinuity could be described or analyzed as the interface between stone and joint in buildings. The mechanical and physical discontinuity behavior and its time evolution have a strong influence on the onset of instability of the blocks and on their strength. The effects of climate change (increase of rainfall, temperature fluctuation...), may significantly increase the inception of phenomena such rock falls, stone degradation and damages on monuments. The aim of this study is to characterize the chemical influence of water flowing inside the discontinuity and also through the porous stone matrix. This paper focus on experiments performed in order to analyze the effects of physical and chemical alteration on the mechanical behavior of porous limestone. Limestone is a both commonly stone used in construction of cultural heritage buildings and found on French territory. These experiments could have some interesting results in restoration or conservation of building. We'll present the results of the first two experiments performed in quasi-static and dynamic of the flowing process. The observation and the monitoring of the alteration process are performed in order to determine the physical and chemical reactions involved in this phenomenon. This one we'll be linked to the mechanical aspect of the massif and or the building

What Are the Stages of the Creative Process? What Visual Art Students Are Saying.

Within the literature on creativity in the arts, some authors have focused on the description of the artistic process (Patrick, 1937; Getzels and Csikszentmihalyi, 1976; Mace and Ward, 2002; Yokochi and Okada, 2005) whereas others have focused on the creative process (Wallas, 1926; Osborn, 1953/1963; Runco and Dow, 1999; Howard et al., 2008). These two types of processes may be, however, somewhat distinct from each other because the creative process is not always dedicated to artistic creation, and productive work in the arts may not always involve creativity, in terms of specifically original thinking. Our goal is to identify the specific nature of the artistic creative process, to determine what are the basic stages of this kind of process. This description can then be integrated in a Creative process Report Diary (CRD; Botella et al., 2017) which allows self-observations in situ when participants are creating

Le théâtre et les robots

Le robot est né au théâtre en 1920, sous la plume du dramaturge tchèque Karel Capek. Sa pièce R.U.R (Rossum Universal Robot) met en scène la révolte d’hommes robots. Les robots sont ensuite devenus très populaires avec le cinéma, de Metropolis (1926) à Blade runner, Matrix ou Wall-E en passant par Terminator et Star Wars, ainsi que dans la littérature S.F. depuis I Robot d’Isaac Asimov (1950) et dans les comics depuis Astro Boy (1951). Le point de départ de cette rencontre entre Oriza Hirata ..

Construire l'insertion des travailleurs handicapés : le rôle de la négociation collective

L'insertion par et dans l'emploi des personnes handicapées constitue l'un des volets des politiques publiques. Si la loi du 10 juillet 1987 oblige les entreprises privées de vingt salariés ou plus, à employer 6 % au moins de travailleurs handicapés, elle leur permet de se libérer de cette obligation en faisant application d'un accord de branche, de groupe, d'entreprise ou d'établissement, prévoyant « la mise en œuvre d'un programme (...) en faveur des travailleurs handicapés » (art. L. 5212-8 du Code du travail). Or seules quatre branches ont utilisé cette possibilité (1987-2008). Le présent rapport vise à apporter des éléments d'explication à cette situation, en confrontant les textes avec la pratique, le cadre juridique avec les stratégies d'acteurs, afin, notamment, de mieux saisir les usages des dispositifs mis en place par le droit