Mobility and robustness are two important features for practical applications of robots. Soft robots made of polymeric materials have the potential to achieve both attributes simultaneously. Inspired by nature, this research presents soft robots based on a curved unimorph piezoelectric structure whose relative speed of 20 body lengths per second is the fastest measured among published artificial insect-scale robots. The soft robot uses several principles of animal locomotion, can carry loads, climb slopes, and has the sturdiness of cockroaches. After withstanding the weight of an adult footstep, which is about 1 million times heavier than that of the robot, the system survived and continued to move afterward. The relatively fast locomotion and robustness are attributed to the curved unimorph piezoelectric structure with large amplitude vibration, which advances beyond other methods. The design principle, driving mechanism, and operating characteristics can be further optimized and extended for improved performances, as well as used for other flexible devices.

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The aprotic Li-O2 battery has attracted a great deal of interest because, theoretically, it can store far more energy than today's batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O2 cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li2O2, i.e., the desired Li-O2 electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O2 cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O2 cathode in aprotic Li-O2 batteries. The catalyzed Li-O2 cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O2 cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O2 electrochemistry. Instead the presence of noble metal catalysts impaired the cells' reversibility, as evidenced by the decreased O2 recovery efficiency (the ratio of the amount of O2 evolved during recharge/that consumed in the preceding discharge) coupled with increased CO2 evolution during charging. The results reported here provide new insights into the O2 electrochemistry in the aprotic Li-O2 batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O2 reactions in the course of pursuing truly rechargeable Li-O2 batteries.

Since 2012, some scholars, both Chinese and foreign, have argued that China's assertive foreign policy is doomed to fail. Nevertheless, after examining China's foreign relations in the last two years, this paper finds that China has experienced improved relations rather than deteriorating ones. In comparison with the strategy of keeping a low profile (KLP), the strategy of striving for achievement (SFA) shows more efficiency in shaping a favorable environment for China's national rejuvenation. The author applies the theory of moral realism to explaining the role of the SFA strategy and argues that morality can increase both international political strength and the political legitimacy of a rising power. The key difference between the KLP and the SFA is that the former focuses on economic gains and the latter seeks to strengthen political support. That is the reason that the SFA values the role of morality and the KLP does not. Due to these different goals, the SFA strategy differs from the KLP strategy in aspects of tenets, general layouts, working approaches, and methods. So far, the SFA has achieved progress beyond people's expectation from Xi Jinping in 2012. Xi's strong leadership may become a new case suitable for illustrating the theory of moral realism.The year of 2010 was a turning point for both China's international status and its relations with some countries related to East Asia. In 2010, China's GDP surpassed Japan's to rank only behind the United States. The year of 2010 also witnessed rising tensions between China and the United States, Japan, the Philippines, and Vietnam. These tensions intensified China's domestic debate over the necessity of

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Based on the analytical solution of Crouch to the problem of a constant discontinuity in displacement over a finite line segment in an infinite elastic solid, in the present paper, the crack-tip displacement discontinuity elements, which can be classified as the left and the right crack-tip elements, are presented to model the singularity of stress near a crack tip. Furthermore, the crack-tip elements together with the constant displacement discontinuity elements presented by Crouch and Starfied are used to develop a numerical approach for calculating the stress intensity factors (SIFs) of general plane cracks. In the boundary element implementation, the left or the right crack-tip element is placed locally at the corresponding left or right crack tip on top of the constant displacement discontinuity elements that cover the entire crack surface and the other boundaries. The method is called the hybrid displacement discontinuity method (HDDM). Numerical examples are given and compared with the available solutions. It can be found that the numerical approach is simple, yet very accurate for calculating the SIFs of branched cracks. As a new example, cracks emanating from a rhombus hole in an infinite plate under biaxial loads are taken into consideration. The numerical results indicate the efficiency of the present numerical approach and can reveal the effect of the biaxial load on the SIFs. In addition, the hybrid displacement discontinuity method together with the maximum circumferential stress criterion (Erdogan and Sih) becomes a very effective numerical approach for simulating the fatigue crack propagation process in plane elastic bodies under mixed-mode conditions. In the numerical simulation, for each increment of crack extension, remeshing of existing boundaries is not required because of an intrinsic feature of the HDDM. Crack propagation is simulated by adding new boundary elements on the incremental crack extension to the previous crack boundaries. At the same time, the element characters of some related elements are adjusted according to the manner in which the boundary element method is implemented.

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