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Both scientific and industrial communities have a growing interest for marine renewable energies. There is a wide variety of technologies in this domain, with different degrees of maturity. Our work focuses on two models of an H-type vertical axis Darrieus (1931) tidal turbine with the objective of studying the effect of fluid-structure interactions on their performances. Theexperimental studies were carried out on the 15m long and 1m2 square section free surface channel of the Environmental Hydrodynamics Platform at PPRIME Institute (Figure 1). The maximum flow discharge through the channel is Q = 500 l/s.

This paper deals with the study of the flow around a pitching wing at high angle of attack. Different pitching amplitudes and frequencies are studied using DIC and LPT measurements. The Fluid Structure Interactions are shown and exhibit that the vortex shedding could be reduced by actuating the wing at specific frequencies.

When performing Tomo-PIV experiments, the calculation of accurate camera models is a key point for successful measurements. In severe configurations, where optical interfaces are involved and refractive index variations occur along the line of sight, analytical models can fail to accurately represent the projection and back-projection functions. This inability can lead to significant inaccuracies in particle location and volume reconstruction, which has a considerable impact on the calculation of velocity fields. In order to overcome these limitations, an innovative camera model based on the combination of an analytical model, such as a pinhole model or a polynomial model, with discrete corrections is proposed. In this method, the analytical projection and back-projection are adjusted with a discrete correction stored in two adaptive grids that save both memory and computation time. These correction grids require calibration which is performed with triangulation procedures similar to those used in misalignment corrections. The calculation and operation of the model are described in this paper. The performance of the camera model is evaluated on simulated and experimental setups based on a large depth-of-field calibration performed in a glass water tank. The presence of multiple optical interfaces and fluids, resulting in large light deviations, makes it difficult to compute a high accuracy camera model. In this configuration, the proposed technique successfully reduces the triangulation error from 1 pixel to less than 0.01 pixel. The usefulness of the model is demonstrated in a Tomo-PIV experiment where the deflection of light through the water tunnel walls prevents classical analytical functions from accurately modelling the projection and back-projection functions. This corrected model can also solve discontinuity problems in the projection functions and can be used when there are interfaces in the measurement volume. It opens new perspectives in the study of fluid-structure interaction when transparent solids are involved.

The destabilization of an erodible sediment bed by a reproducible impulsive phenomenon is studied experimentally. For this, a specific setup is designed to produce a well-controlled isolated vortex, advected over a uniform sand bed. Particle image velocimetry (PIV) measurements are performed to get fluid flow information; suspended particles images are also recorded. A new measurement technique, based on a stereo-correlation method, provides a precise reconstruction of the bedform morphology over time. Strong turbulent structures (namely sweep events) are evidenced in a near-wall region, where particles are mainly dislodged. The sediment plume follows the vortex: in particular, the upward velocity inside maintains the suspension phenomenon. However, the dispersion process seems to be not dependent on the vortex parameters. Then, the bed morphology is investigated: a scour hole is dug as the vortex hits the granular layer. Its dynamics is described by a typical scour law, even if the initial perturbation is transient. Another area, where the particles settled, can be observed: it behaves like a ripple, with a logarithmic growth of its crest. This deposition region has a specific geometry, studied here by a Fourier contour approach. Finally, a pickup rate is also derived from the morphological data: it appears independent of the vortex and bedform features.

International audience

This paper determines the optimal tenurial contract between a monopoly landlord and a tenant protected by limited liability under both adverse selection (based on the tenant’s ability) and moral hazard (based on the tenant’s choice of effort). We identify different optimal contracts depending on the tenant’s outside option. For intermediate values, there is a threshold of tenant ability depending on the outside option level below which the optimal contract is a separating sharecropping contract, and a pooling one otherwise. We also find that an increase in the outside option does not monotonically increase the tenant’s optimal effort.

Platelets play a major role in thrombo-embolic diseases, notably by forming a thrombus that can ultimately occlude a vessel. This may provoke ischemic pathologies such as myocardial infarction, stroke or peripheral artery diseases, which represent the major causes of death worldwide. The aim of this study was to evaluate the specificity of radiolabeled Rat-Anti-Mouse antibody (RAM.1). Methods We describe a method to detect platelets by using a RAM.1 coupled with the chelating agent hydrazinonicotinic acid (HYNIC) conjugated to 99mTc, for Single Photon Emission Computed Tomography (SPECT). To induce platelet accumulation at a site of interest, we used a mouse model of FeCl3 induced injury of the carotid artery. 90 min after i.v. injection of [99mTc][Tc(HYNIC)-RAM.1], biodistribution of the radiolabeled RAM.1 was assessed, SPECT imaging and histological analysis were performed on the mice that underwent FeCl3-induced vessel damage. Results We demonstrated a quick and strong affinity of the radiolabeled RAM.1 for the platelet thrombus. Results clearly demonstrated the ability of this radioimmunoconjugate for detecting thrombi from 10 min post injection with an exceptional thrombi uptake. Using FeCl3, the median ratio between the thrombus and the background was 12.4 (range 9.3–42.3) as compared to 1.0 (range: 0.86–2.7) p

2D numerical simulations of tidal bores were obtained using the OpenFOAM CFD software to solve the Navier–Stokes equations by means of the Finite Volume Method by applying a LES turbulence model. The trajectories of non-cohesive sediment particles beneath tidal bores were estimated using a tracker method. Using the fourth order Runge–Kutta scheme, the tracker method solves the Maxey and Riley equations, which requires the knowledge of the velocity field at time t. From 2D numerical simulations of tidal bores, we proposed a classification of tidal bores with respect to the Froude number Fr (or r the ratio of water depths). For a Froude number 1 F r 1.43 ( 1 r 1.57 ), the tidal bore is undular. For a Froude number 1.43 F r 1.57 ( 1.57 r 1.75 ), the tidal bore is partially breaking, which is similar to the transitional tidal bore defined by Furgerot (2014). And for a Froude number F r > 1.57 ( r > 1.75 ), the tidal bore is totally breaking. The numerical results of trajectories of non-cohesive sediment particles are similar to the type of trajectories given by the analytical model proposed by Chen et al. (2012) with some modifications to take into account the effects of gravity, elevation, and attenuation. The parameters of modified Chen's model, β 1 , β 2 and β 3 , are linearly proportional to the Froude number Fr. This is because the level of turbulence for undular tidal bores is low. The flow induced by an undular tidal bore is not complex. This physical phenomenon is quasi linear. The parameter β 1 , related to the front celerity of the undular tidal bore, decreases when the Froude number Fr increases. The parameter β 2 , related to the elevation, increases when the Froude number Fr increases. And the parameter β 3 , related to the attenuation of the secondary waves, increases when the Froude number Fr increases.

This paper deals with financial contracting between a lender and a borrower with a project to finance. The borrower is protected by limited liability. We consider that the revenue from the project is observable and verifiable but its distribution is influenced by both the borrower’s choice of action and the project’s quality, which are private information. We find that debt contracts are endogenously optimal, as under moral hazard alone. Moreover, while moral hazard leads to credit rationing for the lowest-quality projects only, adding adverse selection creates a bang-bang result: either all projects or none are credit rationed.

International audience; Le calcul des modèles de caméra est une opération cruciale pour le succès de mesures de tomo-PIV. Dans des configurations extrêmes, lorsque des interfaces optiques entrent en jeu ou que des variations d’indice de réfraction apparaissent dans la zone de mesure, les modèles de caméra analytiques ne peuvent pas toujours assurer les opérations de projection avec une précision satisfaisante. Cette incapacité à représenter la projection réelle peut conduire à des erreurs importantes sur les champs de vitesse calculés. Afin de surmonter ces difficultés, un nouveau modèle de caméra basé sur l’association d’un modèle sténopé et d’une correction locale discrète est présenté dans cet article. Avec ce modèle, la projection et la rétroprojection sténopé sont ajustées avec une correction discrète stockée dans deux grilles adaptatives dédiées. Ces grille de correction, dont la structure est optimisée en terme de performance de calcul et d’espace de stockage, sont calibrées à l’aide d’une procédure basée sur la triangulation de particules image. La calibration et le fonctionnement de ce modèle font l’objet de cet article. Les performances du modèles sont évaluées par l’étude d’un cas simulé et numérique, basés sur la calibration d’une expérience de tomo-PIV à profondeur de champ élevée dans un aquarium à parois de verre. La profondeur de champ élevée associée aux interfaces optiques et aux changements de milieux rend la calibration difficile. Dans cette configuration, la correction discrète proposée a pu réduire avec succès l’erreur de triangulation de 1 pixel à une valeur inférieure à 0.01 pixel. Ce modèle permet également la prise en compte de discontinuités dans les fonctions de projection et peut être utilisé lorsqu’il y a des interfaces optiques présentes dans le volume de mesure. Il ouvre, de ce fait, de nouvelles perspectives pour l’étude des interactions fluide-structure avec l’utilisation de solides transparents.

Ibuprofen (IBU) has been shown to improve periodontal treatment outcomes. The aim of this study was to develop a new anti-inflammatory scaffold by functionalizing an electrospun nanofibrous poly-ε-caprolactone membrane with IBU (IBU-PCL) and to evaluate its impact on periodontal inflammation, wound healing and regeneration in vitro and in vivo. IBU-PCL was synthesized through electrospinning. The effects of IBU-PCL on the proliferation and migration of epithelial cells (EC) and fibroblasts (FB) exposed to Porphyromonas gingivlais lipopolysaccharide (Pg-LPS) were evaluated through the AlamarBlue test and scratch assay, respectively. Anti-inflammatory and remodeling properties were investigated through Real time qPCR. Finally, the in vivo efficacy of the IBU-PCL membrane was assessed in an experimental periodontitis mouse model through histomorphometric analysis. The results showed that the anti-inflammatory effects of IBU on gingival cells were effectively amplified using the functionalized membrane. IBU-PCL reduced the proliferation and migration of cells challenged by Pg-LPS, as well as the expression of fibronectin-1, collagen-IV, integrin α3β1 and laminin-5. In vivo, the membranes significantly improved the clinical attachment and IBU-PCL also reduced inflammation-induced bone destruction. These data showed that the IBU-PCL membrane could efficiently and differentially control inflammatory and migratory gingival cell responses and potentially promote periodontal regeneration.

Platelets play a major role in thrombo-embolic diseases, notably by forming a thrombus that can ultimately occlude a vessel. This may provoke ischemic pathologies such as myocardial infarction, stroke or peripheral artery diseases, which represent the major causes of death worldwide. The aim of this study was to evaluate the specificity of radiolabeled Rat-Anti-Mouse antibody (RAM.1).We describe a method to detect platelets by using a RAM.1 coupled with the chelating agent hydrazinonicotinic acid (HYNIC) conjugated toWe demonstrated a quick and strong affinity of the radiolabeled RAM.1 for the platelet thrombus. Results clearly demonstrated the ability of this radioimmunoconjugate for detecting thrombi from 10 min post injection with an exceptional thrombi uptake. Using FeClThanks to the high sensitivity of SPECT, we provided evidence that [

International audience; Optical metrology includes a set of non-contact measurement methods to quantify shapes, surfaces, distances, deformations, displacements or colorimetry. Optical measurement methods have the advantage of being non-intrusive while allowing instantaneous measurements over extended areas. The applications of optical metrology concern all fields of engineering. The paper presents developments related to surface and to 4D measurements (3D displacements + time). Different methods in the fields of solid and fluid mechanics are described and are illustrated by applications. Their applications in different fields for static or dynamic measurements and the limits is discussed in the paper.

The aim of the paper is to determine the impact of severance payment on the motivation of the worker to make an effort, when there is a risk for him to be dismissed once his effort was made. We highlight through a two-stage model the various factors which influence the dismissal decision by the firm and the worker's effort, such as the initial wage, the litigation costs and the relative bargaining powers of the parties when the relationship ends or goes on. In this context, we show that the impact of the severance payment paid ex post in case of dismissal on the level of effort chosen by the worker ex ante may depend on such characteristics.

International audience; En Tomo-PIV, on peut distinguer deux familles de méthodes pour reconstruire des volumes de particules : les méthodes « orientées voxel », où l'on s'intéresse au calcul de l'intensité pour chaque voxel du volume et les méthodes « orientées objets » où l'on considère que le volume à reconstruire est un espace parcimonieux composé d'objets 3d à reconstruire. Dans [1], nous avons proposé la méthode de reconstruction stochastique orientée objet IOD-PVRMPP. Elle comprend deux parties fondées sur les processus ponctuels marqués (PPM) : PVRMPP qui permet de résoudre le problème de manière parcimonieuse et facilite l'introduction d'information a priori sur les objets à reconstruire ; IOD qui fournit une distribution initiale de particules 3d à l'algorithme PVRMPP afin d'accélérer la convergence de l'algorithme. Nous avons montré que, sur des données synthétiques, la méthode IOD-PVRMPP donne de meilleurs résultats que l'algorithme de référence MinLOS-MART [2] jusqu'à des densités de particules de 0,05 ppp. Nous proposons ici une adaptation de la méthode IOD-PVRMPP afin de pouvoir traiter les données expérimentales provenant de l'étude d'un écoulement dans un canal turbulent derrière une grille [3]. Nous montrons là encore que les résultats obtenus sont sensiblement meilleurs que ceux obtenus par MinLOS-MART.

International audience

This study examines the relationship between identification and attendance at team sporting events. Based on Daniel Wann's Spectator Sport Team Identification Index attributes were selected to measure the relationship between identification and decision to attend road games of the Carolina Hurricanes. The study was conducted at the RBC Center in Raleigh, North Carolina during a weekday home game and a weekend home game. Fans of differing levels of ticket purchasing behavior were surveyed. The different levels ranged from season ticket holders to mini plan purchasers to game day purchasers. The results of the study indicated that team identification is a predictor of attendance at road games. Index items, in particular, that were stronger relationships include: "how closely the fan followed the team," "how strongly the fan's friend deemed them as a fan of the team," and "how important is being a fan of the team to them." The results show that the relationship between team identification and attendance at road games is unaffected by the type of ticket the fan purchased or whether they attend a weekend or weekday game. Professionals in the area of sport management can utilize the results in order to increase as well as cultivate their fan base. Currently, attendance figures for the National Hockey League are relatively low in comparison to other professional sports leagues in America. Therefore, offering trips to road games provides teams the opportunity to strengthen current relationships with fans and develop new relationships.

This research examines the influence of distance on the travel behaviour of fans of professional hockey teams; specifically, with reference to theories of distance decay, the research examines the strength of influence that travel distance has on professional hockey fans' road game attendance. Data collection occurred at the RBC Centre located in Raleigh, North Carolina. A questionnaire was developed and distributed to fans of the Carolina Hurricanes of the National Hockey League at the RBC Centre. The results of the analysis indicated that distance influences the travel behaviour of fans of professional hockey teams, and that for respondents there is a relationship between distance and travel behaviour and the type of ticket they purchased and when they attended a game. When factoring in the mode of transportation, the relationship between the variables changes. By understanding the nuances and complexities of the relationships between distance and travel behaviour, sport, recreation and leisure planners...

A simultaneous SPIV-PLIF measurement in water is used to study a pulsed jet in a crossflow. In the longitudinal plane of symmetry of the flow, the velocity fields are measured using Stereoscopic Particle Image Velocimetry (SPIV) and the concentration fields with Planar Laser Induced Fluorescence (PLIF). At the same time, a PLIF measurement is carried out in an orthogonal plane. To take into account the PLIF error sources (spatio-temporal laser intensity variations and out-of-plane fluorescence due to SPIV particles seeding), a special data processing technique has been developed. It allows the study of mixing at an early stage of the development of a pulsed jet in a crossflow. The studied jet is characterized by the Reynolds number Rej = 500 based on the mean jet velocity Uj = 1.67 cm/s, velocity ratio R = 1, sinusoidal forcing amplitude ratio Aj = 2, and the stroke ratio Sr = 2.23.

Many individuals attending congregate meal sites have chronic conditions that can be impacted by their diet. This study found that congregate meal site participants visit meal sites primarily for social purposes but consume meals while they satisfy their social agenda. Also, individuals that suffer from diabetes, cancer, and heart disease were not aware of what foods were beneficial in prevention and/or maintenance. Specifically, individuals with diabetes, cancer, and heart disease were not able to determine any better than those without those conditions which food types were recommended by nutrition experts, nor which food types were more beneficial in the maintenance or prevention of their conditions.

The aim of this paper is to make use of PIV and high-speed PIV in a research engine of moderate tumbling ratio in order to analyze both the spatial structure of the flow and its temporal evolution during series of consecutive cycles. Appropriate analyzing tools are introduced, and four different points are addressed: (1) the chain of events driving the generation of the three-dimensional mean tumbling motion is investigated; (2) a Lagrangian analysis of the roll-up of the tumbling jet in individual cycles demonstrates a strong cycle to cycle variation during the compression phase (the rms of the position of the jet front being approximately 10% of the piston stroke); (3) focussing on the “breakdown” phase, phase invariant proper orthogonal decomposition enables us to distinguish cycles according to their structure near top dead center (TDC). We show that when the coherent energy of the flow is conserved, there is no increase in the fluctuating kinetic energy; (4) finally, the phase-averaged Reynolds stresses is decomposed into a contribution of the in-cycle coherence and the turbulence carried by the flow states. Approximately 30% of the fluctuating kinetic energy is due to cycle to cycle fluctuations in this chamber near TDC.

In this work, snapshot proper orthogonal decomposition (POD) is used to study a pulsed jet in crossflow where the velocity fields are extracted from stereoscopic particle image velocimetry (SPIV) results. The studied pulsed jet is characterized by a frequency f = 1 Hz, a Reynolds number Re j = 500 (based on the mean jet velocity $${\overline{U}_{j}}$$ = 1.67 cm/s and a mean velocity ratio of R = 1). Pulsed jet and continuous jet are compared via mean velocity field trajectory and Q criterion. POD results of instantaneous, phase-averaged and fluctuating velocity fields are presented and compared in this paper. Snapshot POD applied on one plane allows us to distinguish an organization of the first spatial eigenmodes. A distinction between “natural modes” and “pulsed modes” is achieved with the results obtained by the pulsed and unforced jet. Secondly, the correlation tensor is established with four parallel planes (multi-plane snapshot POD) for the evaluation of volume spatial modes. These resulting modes are interpolated and the volume velocity field is reconstructed with a minimal number of modes for all the times of the pulsation period. These reconstructions are compared to orthogonal measurements to the transverse jet in order to validate the obtained three-dimensional velocity fields. Finally, this POD approach for the 3D flow field reconstruction from experimental data issued from planes parallel to the flow seems capable to extract relevant information from a complex three-dimensional flow and can be an alternative to tomo-PIV for large volume of measurement.

This paper deals with the optimal regulation for cost-reducing R&D and pricing in natural monopoly that is privately informed on its efficiency. We extend the work of Cantner and Kuhn (Rev Econ Des 4:191–204, 1999) and then we are able to analyse the entire effects of the interplay between agent’s efficiency and investment in R&D particularly considering the substitutability case.

We have shown that parathyroid hormone-related protein (PTHrP) is a survival factor for human renal cell carcinoma (RCC) and that its expression is negatively regulated by the von Hippel-Lindau (VHL) tumor suppressor gene at the level of messenger RNA (mRNA) stability, as observed for tumor growth factors (TGFs). Our goals were to analyze the alternative splicing of PTHrP mRNA in human RCC and from these results to identify VHL/hypoxia-induced factor (HIF) system-regulated mRNA-binding proteins involved in PTHrP mRNA stability. We used: (i) a panel of human RCC cells expressing or not VHL; (ii) VHL-deficient 786-0 cells transfected with active or inactive VHL and (iii) human RCC samples and corresponding normal tissues. By quantitative real-time reverse transcription-polymerase chain reaction analysis, the 141 PTHrP mRNA isoform was found to be predominant in all cells and tumors (80%). In cells transfected with VHL, the expressions of all isoforms were decreased by 50%. Eight proteins with molecular weights ranging from 20 to 75 kDa were found to bind to biotinylated transcripts spanning the 141 PTHrP mRNA AU-rich 3'-untranslated region whose abundancy was dependent on VHL expression. The protein having an apparent molecular weight of 30 kDa was identified by western blot as HuR, a RNA-binding protein with stabilizing functions on various mRNA coding for proteins important in malignant transformation including vascular endothelial growth factor and TGF-beta. PTHrP expression studies confirmed the involvement of HuR in PTHrP upregulation in this disease. Common mRNA-binding proteins regulated by the VHL/HIF system may constitute new therapeutic opportunities against human RCC that remains refractory to therapies.

Improper presentation of information on restaurant menus can lead to customer dissatisfaction, a loss of profitability, and could influence the ultimate failure of a restaurant operation. Although restaurateurs and customers do agree that information on restaurant menus is important, debate exists on what specific information should be provided. Currently, supporters argue for the provision of nutritional information, while critics question the ability of customers to interpret nutritional information on restaurant menus correctly. This present study, therefore, analyzes responses from 276 restaurant customers to examine information expectations of restaurant menus. A model called Customer Information Expectation of Restaurant Menus (CIERM) was developed using the guidelines set forth in the Truth-in-Menu Law and tested using a confirmatory factor analysis approach. The study found that CIERM is influenced by the factors nutrition information, product information, and food preparation. The study concludes with results, discussion, and recommendations based on the findings.

All business firms are now competing in the global marketplace for the best employee talent available. One stratagem in this effort for suitable employees is utilization of the World Wide Web. Restaurant firms have followed suit and are attempting to attract the best possible employment candidates worldwide. In as much as web site interactions are multidimensional, these companies attempt to demonstrate their inclusive character and varied cultural perspectives as the employer of choice. Restaurant firms identify themselves as equal opportunity employers; however, the lack of multicultural development, as depicted on their web sites, does not reflect this commitment. To study this issue, a content analysis was conducted on the 100 most prominent restaurant firms in the nation. The bounds of this group are based on corporate sales; hence, they are the largest restaurant firms in the nation. Although diversity is broadly constructed to include all minorities, this study will be investigating Hispan...

We study the potential conflict between cost minimization and investment in prevention for a risky venture. A natural monopoly is regulated i) for economic purposes; ii) because it can cause losses of substantial size to third parties (the environment or people). The regulator observes the production cost without being able to distinguish the initial type (an adverse selection parameter) from the effort (a moral hazard variable). In addition, the investment in prevention is non observable (another moral hazard variable) and the monopoly is protected by limited liability. We fully characterize the optimal regulation in this context of asymmetric information plus limited liability. We show that incentives to reduce cost and to invest in safety are always compatible. But, in some cases, higher rents have to be given up by the regulator.

We investigate the effect of ambiguity and ambiguity attitude on the shape and properties of the optimal contract in an adverse selection model with a continuum of types, using the parametric model of ambiguity and ambiguity aversion called the NEO-additive model (Chateauneuf, Eichberger, and Grant, 2007). We show that it necessarily features efficiency and a jump at the top and pooling at the bottom of the distribution. Conditional on the degree of ambiguity, the pooling section may or may not be supplemented by a separating section. As a result, ambiguity adversely affects the principal’s ability to solve the adverse selection problem and therefore the least efficient types benefit from ambiguity with respect to risk. Conversely, ambiguity is detrimental to the most efficient types. This is confirmed in the comparative statics section.

International audience; Optimization of multiplicative algebraic reconstruction technique (MART), simultaneous MART and block iterative MART reconstruction techniques was carried out on synthetic and experimental data. Different criteria were defined to improve the preprocessing of the initial images. Knowledge of how each reconstruction parameter influences the quality of particle volume reconstruction and computing time is the key in Tomo-PIV. These criteria were applied to a real case, a jet in cross flow, and were validated.

International audience; Ce mod`ele s’ins`ere dans la controverse sur la n ́ecessit ́e des b ́en ́efices priv ́es dans la r ́emun ́eration des dirigeants. Nous supposons que la divergence d’int ́erˆet entre les actionnaires et les dirigeants provient `a la fois d’un probl`eme d’antis ́election et d’al ́ea moral. Dans le cadre de ce mod`ele mixte, nous montrons que les actionnaires ont int ́erˆet `a ”autoriser” un montant positif de d ́etournement du revenu de l’entreprise y compris si cela engendre une perte s`eche.

Many consumers feel that it is the social responsibility of restaurants to inform them of the nutritional content of food items that may be detrimental to their health or contrary to their beliefs. Current legislation, through the Truth-in-Menu Law, protects consumers from misleading advertisements, but does not mandate that restaurant establishments provide nutritional information. This qualitative study aims to assess how much consumers really know about menu labeling legislation and what information they consider to be most important on restaurant menus. This study found that consumers feel consistency between item description and actual presentation, accuracy of claims, disclosure of ingredients, nutritional information, value and the availability of competent servers to explain any ambiguities were most important. The article concludes with recommendations on where legislation should go and what restaurants can do to provide menus that meet customer expectations.

Cet article caracterise les mecanismes d’approvisionnement optimaux, lorsque les o.reurs detiennent une information privee sur leur parametre d’efficacite productive ainsi que sur le niveau de qualite, observable mais ni verifiable ni contractualisable, qu’ils sont en mesure d’offrir. Nous montrons que la plupart des mecanismes optimaux correspondent a des procedures « mixtes » impliquant simultanement separation et melange de certains types d’offreurs, alors que les procedures traditionnelles de la forme « a prendre ou a laisser » ou d’enchere ne s’averent optimales que dans des situations extremes. De plus, nous etablissons que les proprietes melangeantes 205 ou separatrices affectent l’efficacite allocative de la procedure, de maniere potentiellement contre-intuitive, une procedure moins melangeante pouvant egalement etre moins efficace.

In this paper, a comparative study between experiments and numerical simulations in the developing zone of a non-isothermal plane vertical jet is presented. The low velocity airflow, in aiding the mixed convection regime, discharges from a large rectangular nozzle into a quiescent medium at a higher temperature.The “Reynolds-Averaged” Navier-Stokes equations (RANS) are solved using both the CFD code Fluent® and the Aquilon® code, in each case applying different turbulence models. While the two numerical codes give quite similar results, large differences are observed between measurement and calculation on the entrainment flow rate and other characteristic quantities. This shows that developing regions of jets, in the mixed convection regime, are not yet correctly described by the common turbulence models.

Cet article etudie les tarifs optimaux d’un bien congestible lorsque les consommateurs possedent une information privee tant sur l’evaluation du bien que sur leur cout unitaire d’attente. Il s’ensuit que des conflits apparaissent entre les contraintes de participation et d’incitation. Nous montrons ainsi que le prix usuel, pour lequel le cout unitaire d’attente est commun, est plus eleve que celui prevalant dans le cas ou les usagers ont un cout unitaire d’attente parfaitement correle avec leur evaluation et plus faible que celui pratique quand les usagers ont un cout unitaire d’attente prive.

This paper analyzes optimal nonlinear pricing of a congestible network good. In contrast to the traditional efficiency-on-the-top result in the standard screening model, we show that the presence of a delay cost borne by users leads to upward distortions in consumption for the high-demand users.

Cet article etudie les marches publics avec reconduction. Ces procedures permettent, a l’issue d’une mise en concurrence, de fixer les modalites d’acquisition d’un meme bien pour plusieurs periodes. Les regles optimales d’approvisionnement sur deux periodes sont determinees en presence de dependance temporelle des couts. On montre que la firme annoncant le cout le plus bas dans la mise en competition fournit le bien et recoit une rente a chaque periode. Mais elle doit ceder un droit en premiere periode afin de conserver le marche dans la seconde. De plus, nous proposons deux procedures de concretisation qui etendent le theoreme d’equivalence du prix etabli pour les appels d’offres au premier et au deuxieme prix portant sur une periode

We analyze optimal pricing when a monopolistic firm sells a good on a congestible network with countervailing incentives. We show that the network capacity level is crucial to determine the optimal tariff.