Periodic and Chaotic Flapping of Insectile Wings

Insects use flight muscles attached at the base of the wings to produce impressive wing flapping frequencies. The maximum power output of these flight muscles is insufficient to maintain such wing oscillations unless there is good elastic storage of energy in the insect flight system. Here, we explore the intrinsic self-oscillatory behavior of an insectile wing model, consisting of two rigid wings connected at their base by an elastic torsional spring. We study the wings behavior as a function of the total energy and spring stiffness. Three types of behavior are identified: end-over-end rotation, chaotic motion, and periodic flapping. Interestingly, the region of periodic flapping decreases as energy increases but is favored as stiffness increases. These findings are consistent with the fact that insect wings and flight muscles are stiff. They further imply that, by adjusting their muscle stiffness to the desired energy level, insects can maintain periodic flapping mechanically for a range of operating conditions

Automatic Curriculum Learning With Over-repetition Penalty for Dialogue Policy Learning

Dialogue policy learning based on reinforcement learning is difficult to be applied to real users to train dialogue agents from scratch because of the high cost. User simulators, which choose random user goals for the dialogue agent to train on, have been considered as an affordable substitute for real users. However, this random sampling method ignores the law of human learning, making the learned dialogue policy inefficient and unstable. We propose a novel framework, Automatic Curriculum Learning-based Deep Q-Network (ACL-DQN), which replaces the traditional random sampling method with a teacher policy model to realize the dialogue policy for automatic curriculum learning. The teacher model arranges a meaningful ordered curriculum and automatically adjusts it by monitoring the learning progress of the dialogue agent and the over-repetition penalty without any requirement of prior knowledge. The learning progress of the dialogue agent reflects the relationship between the dialogue agent's ability and the sampled goals' difficulty for sample efficiency. The over-repetition penalty guarantees the sampled diversity. Experiments show that the ACL-DQN significantly improves the effectiveness and stability of dialogue tasks with a statistically significant margin. Furthermore, the framework can be further improved by equipping with different curriculum schedules, which demonstrates that the framework has strong generalizability

Equilibrium Analysis of Channel Structure Strategies in Uncertain Environment

Abstract In this paper, we consider a pricing decision problem with two competing supply chains which distribute differentiated but competing products in the same market. Each chain can be vertically integrated or decentralized based on the choice of the manufacturer. The manufacturing costs, sales costs and consumer demands are characterized as uncertain variables, whose distributions are estimated by experienced experts. Meanwhile, uncertainty theory and game theory are employed to formulate the pricing decision problems. The equilibrium behaviors (how the supply chain members make their own pricing decisions on wholesale prices and retailer markups) at operational level under three possible scenarios are derived. Numerical experiments are also given to explore the impacts of the parameters’ uncertain degrees on supply chain members’ pricing decisions. The results demonstrate that the supply chain uncertain factors have great influences on equilibrium prices. In addition, we also evaluate the effects of competing intensity (substitutability) of the two products on the strategy behaviors, vertically integrated channel strategy versus decentralized strategy, of the manufacturers. It is found that the manufacturers are better off to distribute their products through a decentralized channel rather than an integrated one when the substitutability is greater than some value. Besides, the uncertain factors in the supply chain might reduce the value contrast to the one in deterministic case. Some other interesting managerial highlights are also provided in this paper

Trade remedy measures in the WTO and regional trade agreements

Trade remedy measures (TRMs) in international economic law refer to antidumping measures, countervailing duties and safeguard measures. They are designed to respond to unfair trade practices or to compensate the negative impact on domestic industries resulting from tariff concessions made under the trade liberalization arrangements. Due to the importance of these instruments, the rules on TRMs are strengthened in the WTO legal framework and established on non-discriminatory basis towards all WTO Members. However, with the proliferation of regional trade agreements (RTA) in recent decades, it was noticed that, most RTAs adopted innovative approaches on TRMs among their regional partners. Such incoherence has brought a series of trade disputes and arguments concerning the conflicts between the WTO and RTA. Current central issues in this area are whether those innovative TRMs are consistent with WTO law and what is the appropriate approach to examine the legality of those measures. Against the canvas of WTO trade remedy rules, this research first investigates the diversified trade remedy approaches in RTAs and their impact on international trade. It then clarifies the ambiguous legal criteria against which TRMs in RTAs should be judged in order to be WTO-consistent. Thereafter, a methodology through which a RTA-specific TRM could be tested against the WTO’s criteria is also developed. It is argued that facilitating TRMs in RTAs must always adhere to the criteria laid down by the WTO, e.g. GATT Article XXIV. In particular, a “necessity test” should be applied when examining the legality of a special TRM in RTAs, in the case where a dispute arises between the RTA members and third countries on the issue. In order to bring the RTA-specific TRMs into compliance with WTO law, this research also looks at the WTO surveillance mechanism on RTAs. Considering a number of difficulties that have arisen in the GATT/WTO’s surveillance of RTAs in the past, the thesis addresses what positive measures can be taken in the future and whether TRMs in RTAs should be scrutinized by WTO political organs or through the dispute settlement mechanism

Realization of active metamaterials with odd micropolar elasticity

Materials made from active, living, or robotic components can display emergent properties arising from local sensing and computation. Here, we realize a freestanding active metabeam with piezoelectric elements and electronic feed-forward control that gives rise to an odd micropolar elasticity absent in energy-conserving media. The non-reciprocal odd modulus enables bending and shearing cycles that convert electrical energy into mechanical work, and vice versa. The sign of this elastic modulus is linked to a non-Hermitian topological index that determines the localization of vibrational modes to sample boundaries. At finite frequency, we can also tune the phase angle of the active modulus to produce a direction-dependent bending modulus and control non-Hermitian vibrational properties. Our continuum approach, built on symmetries and conservation laws, could be exploited to design others systems such as synthetic biofilaments and membranes with feed-forward control loops.Comment: Main text, 6 figures, methods, and supplementary informatio