Online Prototype Alignment for Few-shot Policy Transfer

Domain adaptation in reinforcement learning (RL) mainly deals with the changes of observation when transferring the policy to a new environment. Many traditional approaches of domain adaptation in RL manage to learn a mapping function between the source and target domain in explicit or implicit ways. However, they typically require access to abundant data from the target domain. Besides, they often rely on visual clues to learn the mapping function and may fail when the source domain looks quite different from the target domain. To address these problems, we propose a novel framework Online Prototype Alignment (OPA) to learn the mapping function based on the functional similarity of elements and is able to achieve the few-shot policy transfer within only several episodes. The key insight of OPA is to introduce an exploration mechanism that can interact with the unseen elements of the target domain in an efficient and purposeful manner, and then connect them with the seen elements in the source domain according to their functionalities (instead of visual clues). Experimental results show that when the target domain looks visually different from the source domain, OPA can achieve better transfer performance even with much fewer samples from the target domain, outperforming prior methods.Comment: This paper has been accepted at ICML202

Corrosion behavior investigation of gallium coating on magnesium alloy in simulated body fluid

Magnesium alloys are widely used as biodegradable medical biomaterials due to their density and modulus of elasticity close to that of human bone. However, too rapid degradation in the physiological environment limits their application. In this paper, the non-toxic and easy alloying properties of liquid metal gallium are utilized to make it a coating material for biomedical Mg–Nd alloys, which is used to solve the problem of the rapid degradation rate of Mg alloys. The corrosion resistance of the Ga–Mg alloy layer was investigated by in vitro immersion in simulated body fluid (SBF) and electrochemical experiments, and a microhardness tester characterized the surface hardness. In addition, the phase transformation of the Ga–Mg alloy layer was systematically investigated in combination with XRD diffraction results. The results showed that by adjusting the alloying time of Ga with Mg–Nd in liquid metal, a “retarded layer” with high hardness, stability, and good corrosion resistance was obtained. This study is expected to expand the application of Mg alloy materials in medicine