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We analyze the design of a mechanism to extract a ranking of individuals according to a unidimensional characteristic, such as ability or need. Individuals, connected on a social network, only have local information about the ranking. We show that a planner can construct an ex post incentive compatible and efficient mechanism if and only if every pair of friends has a friend in common. We characterize the windmill network as the sparsest social network for which the planner can always construct a complete ranking. (JEL D11, D82, D83, D85, O12, Z13)

The overall usefulness of the bursting energy absorption (BEA) was studied for a better analysis of paper strength properties. Additionally, the changes of the BEA during more complex deformations of paper products, e.g., preliminary or simultaneous tensile and burst, were determined. For the purpose of the research, an experimental setup was designed. The results showed that the correlation between BEA and bursting strength was linear, but the proportionality strongly depended on paper grade. Thus, a more accurate method to characterize the bursting resistance (BR) of paper was proposed. The BR parameter is described by the three following parameters: average bursting strength, average bursting energy absorption, and the slope of the fitted linear regression curve (relationship between the bursting energy absorption and the bursting strength). This method revealed new mechanical behaviors of papers related to their preloading.

The problem of damage in heterogeneous materials has received particular attention in recent years. The numerical models currently used in the simulation of damage require an internal length that is not currently related to a characteristic length of the material components. However, understanding damage regarding the size of the heterogeneities of the material is of crucial importance, particularly in civil engineering. The Fiber Bundle Model has been widely used to qualitatively address the issue of damage in heterogeneous media by studying the statistics of failure events during damage. The so-called ZIP model derives from Fiber Bundle Model to mimic crack propagation. In this work, a spatial correlation of tensile strength of fibers is added to the ZIP model to highlight the role of heterogeneity size in statistics of failure events during crack propagation. The addition of spatial correlation into the ZIP model modifies the distribution of failure events. Indeed, for a simulated material without spatial correlation, failure events follow two regimes. By adding a spatial correlation to the material, a transitional regime appears. The influence of spatial correlation on fiber rupture avalanche strongly depends on the ratio between the sizes of the shapes of the stress field and of the heterogeneities.

Firstly, a low operating temperature and high performance sensor for H2S detection based on α-Fe2O3/TiO2 heterojunction nanoparticles (NPs) was developed by a liquid phase reaction with low synthesis temperature. Secondly, the microstructures and chemical compositions of the gas sensing material were analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscope, energy dispersive spectrometer and X-ray photoelectron spectra methods. Thirdly, with the 50 mol% α-Fe2O3 doping amount and operating temperature of 120 °C, the gas sensing performances of the developed α-Fe2O3/TiO2 NPs composite sensor to H2S were obtained: the responses of 3.4–15.6 to 1–50 ppm H2S, a linear relationship between the sensor response and the H2S concentration, the acceptable response/recovery time of 25 s and 48 s to 50 ppm H2S, excellent selectivity (10 times higher than those of the other tested gases) to H2S, and good repeatability and stability in 1-month duration. These excellent H2S gas sensing performances were attributed to the effects of n–n heterojunctions of two metal oxides, which were discussed in detail. Finally, the superior performances of the developed α-Fe2O3/TiO2 NPs composite sensor were compared with the other reported H2S sensors, which the low operating temperature of 120 °C was highlighted.

A planner aims to target individuals who exceed a threshold in a characteristic, such as wealth or ability. The individuals can rank their friends according to the characteristic. We study a strategy-proof mechanism for the planner to use the rankings for targeting. We discuss how the mechanism works in practice, when the rankings may contain errors., Forthcoming in AEA Papers & Proceedings

International audience; This paper analyzes the strategy of a monopolistic digital platform serving users from two jurisdictions with different corporate tax rates. We consider two profit-splitting rules, Separate Accounting and Formula Apportionment based on the number of users in the two jurisdictions. We show that, even in the absence of transfer pricing, the platform shifts profit from the high-tax to the low-tax jurisdiction exploiting network externalities under Separate Accounting and manipulating the apportionment key under Formula Apportionment. In order to shift profit, the platform distorts prices and quantities. Under Separate Accounting, the direction of the distortions depends on the sign of the externalities. We use a numerical simulation to show that the ranking of fiscal revenues under the two regimes differs in the two jurisdictions: The high-tax jurisdiction prefers Separate Accounting to Formula Apportionment, whereas the low-tax jurisdiction prefers Formula Apportionment to Separate Accounting.

We propose and study a strategic model of hiding in a network, where the network designer chooses the links and his position in the network facing the seeker who inspects and disrupts the network. We characterize optimal networks for the hider, as well as equilibrium hiding and seeking strategies on these networks. We show that optimal networks are either equivalent to cycles or variants of a core-periphery networks where every node in the periphery is connected to a single node in the core., 27 pages

Conventional fabrication of microfluidic channels/devices faces challenges such as single use channels, material incompartibility, and/or significant time consumption. We propose a flexible platfor...

Mercury intrusion porosimetry (MIP) is an inexpensive and common technique to characterize porous structures like paper. One major limitation of MIP is the lack of information about the arrangement of pores in the structure, information that is particularly relevant for multilayer structures such as thickness-structured paper. In this article, results from Synchrotron X-ray 3D microtomography are combined with MIP data to provide in-depth and improved information about the structures.

International audience; We analyze a three-sided matching market where institutions own objects and individuals belong to institutions. Institutions pool their objects to enlarge the choice set of individuals. For any institution, the number of individuals who receive an object must be equal to the number of objects initially owned. Under this distributional constraint, individually rational and fair assignments may fail to exist. However, when the number of individuals is sufficiently large, fair assignments exist and can be found using a new algorithm, called the Nested Deferred Acceptance algorithm with interrupters (NDAI). This procedure nests a one-to-one matching between agents and objects and a one-to-many matching between objects and institutions. We show that it outputs a matching which is Pareto optimal among fair matchings and strategy-proof for individuals. When agents belong to several institutions, the NDAI results in assignments which are fair for agents of the same institution.

Several low-density crumpled paper-based materials were fabricated by varying both the volume fraction and the geometry and mechanical properties of paper sheets. Their 3D architecture was investigated using X-ray microtomography. Microstructure descriptors such as the pore size distribution, the mean curvature distribution and the volume fraction of ordered domains were finely analyzed. Their mechanical properties were also assessed using uniaxial compression tests. Our results showed that crumpled materials exhibited a particular porous microstructure with a reproducible mechanical behavior between foams and entangled fibrous materials. Their compressive behavior was characterized by successive elastic, strain-hardening and densification regimes. The effects of the geometry, microstructure and mechanical properties of the sheets on the process-induced microstructures and mechanical performances were discussed. In particular, a simple micromechanical approach was used to estimate analytically and from the 3D images the role of ridges and ordered domains on the mechanical properties of crumpled papers. The evolution of their Young's moduli and yield stresses were studied as a function of their relative densities and compared with experimental data available in the literature for other cellular materials, showing that crumpled papers are promising renewable alternatives to standard polymer foams for several engineering applications, due to the proper combination of mechanical properties, porosity, cost, and easy fabrication. Keywords: Crumpled sheets, Paper, Self-locked architecture, Core materials, Microstructure, Compression behavior, Structural applications, Sandwich panel

In liberalized network industries, entrants can either compete for service using the existing infrastructure (access) or deploy their own infrastructure capacity (bypass). In this paper, we demonstrate that, under the threat of bypass, the access price set by an unregulated and vertically integrated incumbent is compatible with productive efficiency. This means that the entrant bypasses the existing infrastructure only if it can produce the network input more efficiently. We show that the incumbent lowers the access price compared to the ex-post efficient level to strategically deter inefficient bypass by the entrant. Accordingly, from a productive efficiency point of view, there is no need to regulate access prices when the entrant has the option to bypass. Despite that, we show that restricting the possibilities of access might be profitable for consumers and welfare because competition is fiercer under bypass.

This paper revisits the analysis of stable sets in two-player strategic-form games. Our two main contributions are (i) to establish a connection between myopic stable sets and the stable matchings of an auxiliary two-sided matching problem and (ii) to identify a structural property of 2-player games, called “the block partition property,” which helps characterize the strategy profiles that are indirectly dominated by a fixed profile. Our analysis also generalizes and unifies existing results on myopic and farsighted stable sets in 2-player games.

Paper-based platforms for biological studies have received significant attention given that cellulose is ubiquitous, biocompatible, and can be readily organized into tunable fibrous structures. In the latter form, effect of complexity in surface morphologies (roughness, porosity and fiber organization) on cell-substrate interaction has not been thoroughly explored. We infer that altering the properties of a fibrous material should lead to significant changes in cellular microenvironment and direct the deposition of structurally analogous extracellular matrix (fiber-fiber templating) like collagen. Here, we elucidate the effect of varying paper roughness and surface chemistry on NIH/3T3 fibroblasts via organization of excreted collagen. Collagen intensity was found to increase linearly with paper porosity, indicating a 3D culture platform. The intensity, however, decays over time due to biodegradation of the substrate. Stability can be improved by introducing fluorinated alkyl silanes to yield hydrophobic paper. This process concomitantly transforms the substrate to a 2D-like scaffold where collagen is predominantly assembled on the surface, thus changing the cellular microenvironment. Altering surface energy also led to fluctuations in collagen intensity and organization over time for smooth (calendered) paper substrates. We infer that the increased roughness improves collagen adsorption through capillary driven petal effect. In general, the influence of the substrate simultaneously affects its ability to host collagen and guide orientation. These findings offer insights into the effects of secondary structures and chemistry of fibrous polymeric materials on cell culture, which we propose as vital parameters when using paper-based platforms.

We analyze the formation of partnerships in social networks. Players need favors at random times and ask their neighbors in the network to form exclusive long-term partnerships that guarantee reciprocal favor exchange. Refusing to provide a favor results in the automatic removal of the underlying link. When favors are costly, players agree to provide the first favor in a partnership only if they otherwise face the risk of eventual solitude. In equilibrium, the players essential for realizing every maximum matching can avoid this risk and enjoy higher payoffs than inessential players. Although the search for partners is decentralized and reflects local incentives, the strength of essential players drives efficient partnership formation in every network. When favors are costless, players enter partnerships at any opportunity and every maximal matching can emerge in equilibrium. In this case, efficiency is limited to special linking patterns: complete and complete bipartite networks, locally balanced bipartite networks with positive surplus, and factor-critical networks.

We analyze the dynamic assignment of objects to agents organized in a constant size waiting list. Applications include the assignment of social housing and organs for transplants. We analyze the optimal design of probabilistic queuing disciplines, punishment schemes, and information release. With private values, all agents prefer first-come first-served to the lottery, but waste is lower at the lottery. With common values, all agents prefer first-come first-served to any other mechanism, and waste is minimized at the lottery. Punishment schemes accelerate turnover in the queue and information release increases the value of agents at the top of the waiting list. (JEL C78, D44, D82)