The Experts below are selected from a list of 13023 Experts worldwide ranked by ideXlab platform
Toshio Kuwai - One of the best experts on this subject based on the ideXlab platform.
-
learning curve for endoscopic submucosal dissection of early colorectal neoplasms with a monopolar scissor type knife use of the cumulative sum method
Scandinavian Journal of Gastroenterology, 2020Co-Authors: Akihiro Miyakawa, Toshio Kuwai, Yukie Sakuma, Manabu Kubota, Akira Nakamura, Ei Itobayashi, Haruhisa Shimura, Yoshio Suzuki, Kenji ShimuraAbstract:Although scissor-type knives such as the Stag-Beetle (SB) Knife Jr are expected to result in a safe and easy colorectal endoscopic submucosal dissection (CR-ESD), information regarding the learning...
-
Endoscopic submucosal dissection for early esophageal neoplasms using the Stag beetle knife
World Journal of Gastroenterology, 2018Co-Authors: Toshio Kuwai, Toshiki Yamaguchi, Hiroki Imagawa, Ryoichi Miura, Yuki Sumida, Takeshi Takasago, Yuki Miyasako, Tomoyuki Nishimura, Atsushi YamaguchiAbstract:Endoscopic submucosal dissection for early esophageal neoplasms using the Stag beetle knife
Peter Aerts - One of the best experts on this subject based on the ideXlab platform.
-
Cost of flight and the evolution of Stag beetle weaponry.
Journal of the Royal Society Interface, 2015Co-Authors: Jana Goyens, Sam Van Wassenbergh, Joris J.j. Dirckx, Peter AertsAbstract:Male Stag beetles have evolved extremely large mandibles in a wide range of extraordinary shapes. These mandibles function as weaponry in pugnacious fights for females. The robust mandibles of Cyclommatus metallifer are as long as their own body and their enlarged head houses massive, hypertrophied musculature. Owing to this disproportional weaponry, trade-offs exist with terrestrial locomotion: running is unstable and approximately 40% more costly. Therefore, flying is most probably essential to cover larger distances towards females and nesting sites. We hypothesized that weight, size and shape of the weaponry will affect flight performance. Our computational fluid dynamics simulations of steady-state models (without membrane wings) reveal that male Stag beetles must deliver 26% more mechanical work to fly with their heavy weaponry. This extra work is almost entirely required to carry the additional weight of the massive armature. The size and shape of the mandibles have only negligible influence on flight performance (less than 0.1%). This indicates that the evolution of Stag beetle weaponry is constrained by its excessive weight, not by the size or shape of the mandibles and head as such. This most probably paved the way for the wide diversity of extraordinary mandible morphologies that characterize the Stag beetle family.
-
mechanoreceptor distribution in Stag beetle jaws corresponds to the material stress in fights
Arthropod Structure & Development, 2015Co-Authors: Jana Goyens, Joris J.j. Dirckx, Peter AertsAbstract:Abstract Male Stag beetles (Lucanidae) use their extremely elongated jaws to pinch their rivals forcefully in male–male battles. The morphology of these jaws has to be a compromise between robustness (to withstand the bite forces), length and weight. Cyclommatus metallifer Stag beetles circumvent this trade-off by reducing their bite force when biting with their slender jaw tips. Here we describe the functional mechanism behind the force modulation behaviour. Scanning Electron Microscopy and micro CT imaging show large numbers of small sensors in the jaw cuticle. We find a strong correlation between the distribution of these sensors and that of the material stress in the same jaw region during biting. The jaw sensors are mechanoreceptors with a small protrusion that barely protrudes above the undulating jaw surface. The sensors stimulate dendrites that extend from the neuronal cell body through the entire thickness of the jaw exoskeleton towards the sensors at the external surface. They form a sensory field that functions in a feedback mechanism to control the bite muscle force. This negative feedback mechanism enabled the Stag beetles to evolve massive bite muscles without risking overloading their valuable jaws.
-
biomechanical determinants of bite force dimorphism in cyclommatus metallifer Stag beetles
The Journal of Experimental Biology, 2014Co-Authors: Jana Goyens, Joris J.j. Dirckx, Peter Aerts, Manuel Dierick, Luc Van HoorebekeAbstract:In the Stag beetle family (Lucanidae), males have diverged from females by sexual selection. The males fight each other for mating opportunities with their enlarged mandibles. It is known that owners of larger fighting apparatuses are favoured to win the male-male fights, but it was unclear whether male Stag beetles also need to produce high bite forces while grabbing and lifting opponents in fights. We show that male Cyclommatus metallifer Stag beetles bite three times as forcefully as females. This is not entirely unexpected given the spectacular nature of the fights, but all the more impressive given the difficulty of achieving this with their long mandibles (long levers). Our results suggest no increase in male intrinsic muscle strength to accomplish this. However, morphological analyses show that the long mandibular output levers in males are compensated by elongated input levers (and thus a wider anterior side of the head). The surplus of male bite force capability is realized by enlargement of the closer muscles of the mandibles, while overall muscle force direction remained optimal. To enable the forceful bites required to ensure male reproductive success, male head size and shape are adapted for long input levers and large muscles. Therefore, the entire head should be regarded as an integral part of male armature.
Nikfarjam Farhad - One of the best experts on this subject based on the ideXlab platform.
-
The LS-Stag immersed boundary/cut-cell method for non-Newtonian flows in 3D extruded geometries
'Elsevier BV', 2018Co-Authors: Nikfarjam Farhad, Cheny Yoann, Botella OlivierAbstract:International audienceThe LS-Stag method is an immersed boundary/cut-cell method for viscous incompressible flows based on the Staggered MAC arrangement for Cartesian grids, where the irregular boundary is sharply represented by its level-set function, results in a significant gain in computer resources (wall time, memory usage) compared to commercial body-fitted CFD codes. The 2D version of LS-Stag method is now well-established (Y. this paper presents its extension to 3D geometries with translational symmetry in the z direction (hereinafter called 3D extruded configurations). This intermediate step towards the fully 3D implementation can be applied to a wide variety of canonical flows and will be regarded as the keystone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this Stage of development. The LS-Stag method is then applied to various Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion) for which benchmark results and experimental data are available. The purpose of these investigations are (a) to investigate the formal order of accuracy of the LS-Stag method, (b) to asses the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows) (c) to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods)
-
Extension of the LS-Stag immersed boundary/cut-cell method to 3D extruded geometries : Application to Newtonian and non-Newtonian flows
2018Co-Authors: Nikfarjam FarhadAbstract:La méthode LS-Stag est une méthode de type frontière immergée/cut-cell pour le calcul d’écoulements visqueux incompressibles qui est basée sur la méthode MAC pour grilles cartésiennes décalées, où la frontière irrégulière est nettement représentée par sa fonction level-set, résultant en un gain significatif en ressources informatiques par rapport aux codes MFN commerciaux utilisant des maillages qui épousent la géométrie. La version 2D est maintenant bien établie et ce manuscrit présente son extension aux géométries 3D avec une symétrie translationnelle dans la direction z (configurations extrudées 3D). Cette étape intermédiaire sera considérée comme la clé de voûte du solveur 3D complet, puisque les problèmes de discrétisation et d’implémentation sur les machines à mémoire distribuée sont abordés à ce stade de développement. La méthode LS-Stag est ensuite appliquée à divers écoulements newtoniens et non-newtoniens dans des géométries extrudées 3D (conduite axisymétrique, cylindre circulaire, conduite cylindrique avec élargissement brusque, etc.) pour lesquels des résultats de références et des données expérimentales sont disponibles. Le but de ces investigations est d’évaluer la précision de la méthode LS-Stag, d’évaluer la polyvalence de la méthode pour les applications d’écoulement dans différents régimes (fluides newtoniens et rhéofluidifiants, écoulement laminaires stationnaires et instationnaires, écoulements granulaires) et de comparer ses performances avec de méthodes numériques bien établies (méthodes non structurées et de frontières immergées)The LS-Stag method is an immersed boundary/cut-cell method for viscous incompressible flows based on the Staggered MAC arrangement for Cartesian grids where the irregular boundary is sharply represented by its level-set function. This approach results in a significant gain in computer resources compared to commercial body-fitted CFD codes. The 2D version of LS-Stag method is now well-established and this manuscript presents its extension to 3D geometries with translational symmetry in the z direction (3D extruded configurations). This intermediate step will be regarded as the milestone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this Stage of development. The LS-Stag method is then applied to Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion, etc.) for which benchmark results and experimental data are available. The purpose of these investigations is to evaluate the accuracy of LS-Stag method, to assess the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows, granular flows) and to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods
-
Extension de la méthode LS-Stag de type frontière immergée/cut-cell aux géométries 3D extrudées : applications aux écoulements newtoniens et non newtoniens
HAL CCSD, 2018Co-Authors: Nikfarjam FarhadAbstract:The LS-Stag method is an immersed boundary/cut-cell method for viscous incompressible flows based on the Staggered MAC arrangement for Cartesian grids where the irregular boundary is sharply represented by its level-set function. This approach results in a significant gain in computer resources compared to commercial body-fitted CFD codes. The 2D version of LS-Stag method is now well-established and this manuscript presents its extension to 3D geometries with translational symmetry in the z direction (3D extruded configurations). This intermediate step will be regarded as the milestone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this Stage of development. The LS-Stag method is then applied to Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion, etc.) for which benchmark results and experimental data are available. The purpose of these investigations is to evaluate the accuracy of LS-Stag method, to assess the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows, granular flows) and to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods)La méthode LS-Stag est une méthode de type frontière immergée/cut-cell pour le calcul d’écoulements visqueux incompressibles qui est basée sur la méthode MAC pour grilles cartésiennes décalées, où la frontière irrégulière est nettement représentée par sa fonction level-set, résultant en un gain significatif en ressources informatiques par rapport aux codes MFN commerciaux utilisant des maillages qui épousent la géométrie. La version 2D est maintenant bien établie et ce manuscrit présente son extension aux géométries 3D avec une symétrie translationnelle dans la direction z (configurations extrudées 3D). Cette étape intermédiaire sera considérée comme la clé de voûte du solveur 3D complet, puisque les problèmes de discrétisation et d’implémentation sur les machines à mémoire distribuée sont abordés à ce stade de développement. La méthode LS-Stag est ensuite appliquée à divers écoulements newtoniens et non-newtoniens dans des géométries extrudées 3D (conduite axisymétrique, cylindre circulaire, conduite cylindrique avec élargissement brusque, etc.) pour lesquels des résultats de références et des données expérimentales sont disponibles. Le but de ces investigations est d’évaluer la précision de la méthode LS-Stag, d’évaluer la polyvalence de la méthode pour les applications d’écoulement dans différents régimes (fluides newtoniens et rhéofluidifiants, écoulement laminaires stationnaires et instationnaires, écoulements granulaires) et de comparer ses performances avec de méthodes numériques bien établies (méthodes non structurées et de frontières immergées
Adam Lerer - One of the best experts on this subject based on the ideXlab platform.
-
prosocial learning agents solve generalized Stag hunts better than selfish ones
Adaptive Agents and Multi-Agents Systems, 2018Co-Authors: Alexander Peysakhovich, Adam LererAbstract:Real world interactions are full of coordination problems [2, 3, 8, 14, 15] and thus constructing agents that can solve them is an important problem for artificial intelligence research. One of the simplest, most heavily studied coordination problems is the matrixform, two-player Stag Hunt. In the Stag Hunt, each player makes a choice between a risky action (hunt the Stag) and a safe action (forage for mushrooms). Foraging for mushrooms always yields a safe payoff while hunting yields a high payoff if the other player also hunts but a very low payoff if one shows up to hunt alone. This game has two important Nash equilibria: either both players show up to hunt (this is called the payoff dominant equilibrium) or both players stay home and forage (this is called the risk-dominant equilibrium [7]).
-
prosocial learning agents solve generalized Stag hunts better than selfish ones
arXiv: Artificial Intelligence, 2017Co-Authors: Alexander Peysakhovich, Adam LererAbstract:Deep reinforcement learning has become an important paradigm for constructing agents that can enter complex multi-agent situations and improve their policies through experience. One commonly used technique is reactive training - applying standard RL methods while treating other agents as a part of the learner's environment. It is known that in general-sum games reactive training can lead groups of agents to converge to inefficient outcomes. We focus on one such class of environments: Stag Hunt games. Here agents either choose a risky cooperative policy (which leads to high payoffs if both choose it but low payoffs to an agent who attempts it alone) or a safe one (which leads to a safe payoff no matter what). We ask how we can change the learning rule of a single agent to improve its outcomes in Stag Hunts that include other reactive learners. We extend existing work on reward-shaping in multi-agent reinforcement learning and show that that making a single agent prosocial, that is, making them care about the rewards of their partners can increase the probability that groups converge to good outcomes. Thus, even if we control a single agent in a group making that agent prosocial can increase our agent's long-run payoff. We show experimentally that this result carries over to a variety of more complex environments with Stag Hunt-like dynamics including ones where agents must learn from raw input pixels.
Kenji Shimura - One of the best experts on this subject based on the ideXlab platform.
-
learning curve for endoscopic submucosal dissection of early colorectal neoplasms with a monopolar scissor type knife use of the cumulative sum method
Scandinavian Journal of Gastroenterology, 2020Co-Authors: Akihiro Miyakawa, Toshio Kuwai, Yukie Sakuma, Manabu Kubota, Akira Nakamura, Ei Itobayashi, Haruhisa Shimura, Yoshio Suzuki, Kenji ShimuraAbstract:Although scissor-type knives such as the Stag-Beetle (SB) Knife Jr are expected to result in a safe and easy colorectal endoscopic submucosal dissection (CR-ESD), information regarding the learning...
