28,175 research outputs found
Adaptive neural network-based backstepping fault tolerant control for underwater vehicles with thruster fault
No full textA thruster fault tolerant control (FTC) method is developed for underwater vehicles in the presence of modelling uncertainty, external disturbance and unknown thruster fault. The developed method incorporates the sliding mode algorithm and backstepping scheme to improve its robustness to modelling uncertainty and external disturbance. In order to be independent of the fault detection and diagnosis (FDD) unit, thruster fault is treated as a part of the general uncertainty along with the modelling uncertainty and external disturbance, and radial basis function neural network (RBFNN) is adopted to approximate the general uncertainty. According to the Lyapunov theory, control law and adaptive law of RBFNN are derived to ensure the tracking errors asymptotically converge to zero. Trajectory tracking simulations of underwater vehicle subject to modelling uncertainty, ocean currents, tether force and thruster faults are carried out to demonstrate the effectiveness and feasibility of the proposed method
Inside back cover: enzyme-enabled droplet biobattery for powering synthetic tissues (Angew. Chem. Int. Ed. 44/2024)
No full textA droplet biobattery built from nanolitre droplets, fueled by the enzyme-enabled oxidation of reduced nicotinamide adenine dinucleotide, generates electrical outputs and powers ion fluxes in droplet networks, as reported by Juan Liu, Yujia Zhang, Hagan Bayley et al. in their Communication (e202408665). The enzyme-enabled droplet biobattery opens new avenues in bioelectronics and bioiontronics, exemplified by tasks such as the ability to drive electrochemical signal transmission in integrated synthetic tissues
Liu Kang
No full textLiu Kang: Essays on Art and Culture is a testament to the inexorable passion of an artist who knew no boundaries. This collection of essays, which Liu Kang wrote over 44 years, offers an insight into the artist’s myriad interests as well as his contributions as a first generation Nanyang artist and art educator. Translated into English for this volume, Liu Kang’s essays are accompanied by commentaries and photographs of the artist-author and his subjects
Design and experimental validation of an adaptive sliding mode observer-based fault-tolerant control for underwater vehicles
No full textCost and other practically related reasons can mean that velocity sensors are not available on an underwater vehicle. For such cases, the results in this brief are developed on an observer-based fault-tolerant control for underwater vehicles in the presence of external disturbances and unknown thruster faults. An adaptive sliding mode observer is developed to achieve finite-time convergence where, in comparison to a high-gain-based design for the observer, a nonlinear feedback is constructed based on the position estimation error. Unlike alternatives, a discontinuity term in the developed fault tolerant controller is avoided, and the stability of the controlled dynamics is characterized using the Lyapunov theory. Finally, these new results are supported by both a simulation-based study and experimental verification.</p
Terminal sliding mode‐based tracking control with error transformation for underwater vehicles
No full textOcean currents and waves can cause the initial position of an underwater vehicle to deviate from the initial state of the desired trajectory. For such cases, this paper investigates the finite-time tracking control problem for a vehicle in the presence of large initial tracking errors and external disturbances. A continuous finite-time tracking control scheme is developed for this scenario based on an improved nonsingular terminal sliding mode surface modified by a piecewise function. Compared to the alternative approaches, a method based on error transformation is added to the sliding mode surface, resulting in improved tracking accuracy in the steady state. Then, to reduce the effect of large initial tracking error on the control input signals, an exponential decay function about the initial location of the vehicle is developed to obtain the control law by combining it with a strictly generalized saturation function. In contrast to alternative approaches, a nonlinear structure is used to counteract the approximation error of the neural network used in the modeling of the dynamics. Moreover, it is shown that the tracking error converges to a small neighborhood of zero in a fixed time. Finally, the new control scheme's effectiveness is verified by simulation studies on an underwater vehicle model and the results compared to other existing control designs
Statistical calibration for infinite many future values in linear regression: simultaneous or pointwise tolerance intervals or what else?
No full textStatistical calibration using regression is a useful statistical tool with many applications. For confidence sets for x-values associated with infinitely many future y-values, there is a consensus in the statistical literature that the confidence sets constructed should guarantee a key property. While it is well known that the confidence sets based on the simultaneous tolerance intervals (STI's) guarantee this key property conservatively, it is desirable to construct confidence sets that satisfy this property exactly. Also, there is a misconception that the confidence sets based on the point-wise tolerance intervals (PTI's) also guarantee this property. This paper constructs the weighted simultaneous tolerance intervals (WSTI's) so that the confidence sets based on the WSTI's satisfy this property exactly if the future observations have the x-values distributed according to a known specific distribution F(•).Through the lens of the WSTI's, convincing counter examples are also provided to demonstrate that the confidence sets based on the PTI's do not guarantee the key property in general and so should not be used. The WSTI's have been applied to real data examples to show that the WSTI's can produce more accurate calibration intervals than STI's and PTI's
Phoebus 10: A Journal of Art History
No full texttableOfContents: Homage to the Past: The Art of Yin Xiaofeng by Ralph Gabbard and Liu Liu.. pages 5-1
Cultural exploitation in chinese politics: Reinterpreting liu sanjie
No full textLiu Sanjie is a typical Chinese legendary figure, adapted from folk custom and transformed during many historical and political stages. By comparing the musical film Liu Sanjie with the landscape performing art Impression Liu Sanjie, this paper explores how Liu Sanjie is reconstructed in the Impression to be in accord with contemporary demands (shidaixing). In the film, made during the 1960s, Liu Sanjie was promoted as a heroine fighting against the privileged classes, but in the Impression, her class struggle has been erased and only a harmonious and abstract legend remains. Her ethnicity is promoted by Han elites as not exclusive Zhuang, but shared equally with Han, Miao and Dong ethnicity in an imagined community to propagate a sense of ethnic harmony and unified Chineseness. Her transformation from a realistic character, full of a rebelling spirit, to an abstract and disembodied ‘sense of harmony’, is a complete reinterpretation of a Chinese historical legend. Utilizing a term from Wang Ban (1997), ‘the sublime figure of history’, which refers to an ideology aestheticized by the party state for securing its governance, this paper refers to the bold artistic treatment of Liu Sanjie for cultural exploitation as ‘Liu Sanjie’s sublime’. The paper explores the evolutionary progress of Liu Sanjie from class revolution to art revolution in response to political requirements. The author is a stage-trained performing artist, specialized in both Western opera and Chinese classical and folk singing and dance. He is also a critic and art consultant in the Chinese landscape performing arts industry. These professional roles have allowed privileged access to the top people in this industry
Test Make Sense?
No full textCorresponding author Changyu Liu should be listed as the first corresponding author.No Full Tex
Nonlinearity Mitigation for Multi-channel 64-QAM Signals in a Deployed Fiber Link through Optical Phase Conjugation
No full textWe report nonlinearity mitigation of two 64-QAM signals, tested in a WDM environment, through mid-link optical phase conjugation. Efficient reuse of signal bandwidth and a Q-factor improvement of more than 1.7 dB is demonstrated in a 400 km installed fiber link.</span
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