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Objective. We introduce a robust image reconstruction algorithm named residual-guided Golub–Kahan iterative reconstruction technique (RGIRT) designed for sparse-view computed tomography (CT), which aims at high-fidelity image reconstruction from a limited number of projection views. Approach. RGIRT utilizes an inner-outer dual iteration framework, with a flexible least square QR (FLSQR) algorithm implemented in the inner iteration and a restarted iterative scheme applied in the outer iteration. The inner FLSQR employs a flexible Golub–Kahan bidiagonalization method to reduce the size of the inverse problem, and a weighted generalized cross-validation method to adaptively estimate the regularization hyper-parameter. The inner iteration efficiently yields the intermediate reconstruction result, while the outer iteration minimizes the residual and refines the solution by using the result obtained from the inner iteration. Main results. The reconstruction performance of RGIRT is evaluated and compared to other reference methods (FBPConvNet, SART-TV, and FLSQR) using projection data from both numerical phantoms and real experimental Micro-CT data. The experimental findings, from testing various numbers of projection views and different noise levels, underscore the robustness of RGIRT. Meanwhile, theoretical analysis confirms the convergence of residual for our approach. Significance. We propose a robust iterative reconstruction algorithm for x-ray CT scans with sparse views, thereby shortening scanning time and mitigating excessive ionizing radiation exposure to small animals. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive sliding mode control strategy based on RBF (Radial Basis Function) neural network for the supercavitating vehicle system with model uncertainties and external disturbance. Aiming at the unknown items in the model, the control strategy compensates the unknown model uncertainty and external disturbance through the RBF neural network, and derives the neural network weight update strategy according to the Lyapunov stability theory which can guarantee the closed loop system asymptotic stability. The simulation results show that this control strategy can enable the supercavitating vehicle to track reference signal when there are model uncertainties and external disturbance, and ensure the convergence of the trajectory tracking error. Compared with the control input of the sliding mode control strategy without RBF neural network, the control input of the adaptive sliding mode control strategy with RBF neural network is also reduced, which further verifies the effectiveness of the RBF adaptive sliding mode control strategy proposed in this paper.

In response to the engineering, miniaturization, and high measurement accuracy requirements of encoders, this paper proposes a new type of absolute photoelectric encoder based on a position-sensitive detector (PSD). It breaks the traditional encoder's code track design and adopts a continuous and transparent code track design, which has the advantages of small volume, high angle measurement accuracy, and easy engineering. The research content of this article mainly includes the design of a new code disk, decoding circuit, linear light source, and calibration method. The experimental results show that the encoder designed in this article has achieved miniaturization, simple installation and adjustment, and easy engineering. The volume of the encoder is Φ50 mm × 30 mm; after calibration, the resolution is better than 18 bits, and the accuracy reaches 5.4″, which further demonstrates the feasibility of the encoder's encoding and decoding scheme. [ABSTRACT FROM AUTHOR]

Two-dimensional topological insulators hosting the quantum spin Hall effect have application potential in dissipationless electronics. To observe the quantum spin Hall effect at elevated temperatures, a wide band gap is indispensable to efficiently suppress bulk conduction. Yet, most candidate materials exhibit narrow or even negative band gaps. Here, via elegant control of van der Waals epitaxy, we have successfully grown monolayer ZrTe5 on a bilayer graphene/SiC substrate. The epitaxial ZrTe5 monolayer crystalizes in two allotrope isomers with different intralayer alignments of ZrTe3 prisms. Our scanning tunneling microscopy/spectroscopy characterization unveils an intrinsic full band gap as large as 254 meV and one-dimensional edge states localized along the periphery of the ZrTe5 monolayer. First-principles calculations further confirm that the large band gap originates from strong spin−orbit coupling, and the edge states are topologically nontrivial. These findings thus provide a highly desirable material platform for the exploration of the high-temperature quantum spin Hall effect.Quantum spin Hall materials hold great potential for future nanoelectronics. Here, authors synthesize a potential host system — monolayer ZrTe5 — and demonstrate it possesses a band gap wide enough for potential room-temperature applications. [ABSTRACT FROM AUTHOR]

Recent studies have shown that a rich variety of exotic physical phenomena can emerge from the presence of electronic flat bands. Using first‐principles calculations, here a monolayered Ca2C possesses a relatively flat band near the Fermi level, and across the whole Brillouin zone is predicted. Next, the weak d0 ferromagnetism in Ca2C is substantially enhanced by a proximity‐coupled electride monolayer of Ca2N is shown. The enhanced magnetism can be attributed to the straightening of the flat band caused by the charge transfer to the electride, while the flattening is tied to the magic ratio of three between the σ and π channels of the effective C─C coupling strength. More surprisingly, even though each of the constituent systems is topologically trivial, the Ca2C/Ca2N heterobilayer is empowered with nontrivial band topology, characterized by a high Chern number tunable by the magnetization orientation or lateral strain. These findings provide a new platform for realizing intriguing magnetic topological metals in 2D materials. [ABSTRACT FROM AUTHOR]

This study introduces a reduced-order leg dynamic model to simplify the controller design and enhance robustness. The proposed multi-loop control scheme tackles tracking control issues in legged robots, including joint angle and contact-force regulation, disturbance suppression, measurement delay, and motor saturation avoidance. Firstly, model predictive control (MPC) and sliding mode control (SMC) schemes are developed using a simplified model, and their stability is analyzed using the Lyapunov method. Numerical simulations under two disturbances validate the superior tracking performance of the SMC scheme. Secondly, an Nth-order linear active disturbance rejection control (LADRC) is designed based on a simplified model and optimization problems. The second-order LADRC-SMC scheme reduces the contact-force control error in the SMC scheme by ten times. Finally, a fourth-order LADRC-SMC with a Smith Predictor (LADRC-SMC-SP) scheme is formulated, employing each loop controller independently. This scheme simplifies the design and enhances performance. Compared to numerical simulations of the above and existing schemes, the LADRC-SMC-SP scheme eliminates delay oscillations, shortens convergence time, and demonstrates fast force-position tracking responses, minimal overshoot, and strong disturbance rejection. The peak contact-force error in the LADRC-SMC-SP scheme was ten times smaller than that in the LADRC-SMC scheme. The integral square error (ISE) values for the tracking errors of joint angles θ 1   and θ 2 , and contact force f , are 1.6636 × 1 0 − 28   r a d 2 ⋅ s , 1.7983 × 1 0 − 28   r a d 2 ⋅ s , and 1.8062 × 1 0 − 30   N 2 ⋅ s , respectively. These significant improvements in control performance address the challenges in single-leg dynamic systems, effectively handling disturbances, delays, and motor saturation. [ABSTRACT FROM AUTHOR]

With the application of encoders in artificial intelligence and aerospace, the demand for the miniaturization and high measurement accuracy of encoders is increasing. To solve this problem, a new absolute matrix encoder is proposed in this paper, which can realize 19-bit matrix coding by engraving two circles of matrix code, and has the advantages of fewer circles of code disk engraving and higher measurement accuracy. This article mainly focuses on the design of a new matrix code disk, encoding and decoding methods, decoding circuit design, Matlab simulation analysis, and experimental error analysis. The experimental results show that the encoder designed in this paper achieves ultra-small volume Φ30 mm × 20 mm, and the angle measurement accuracy is 2.57". [ABSTRACT FROM AUTHOR]

This paper modeled forced and free vibrations of an axially functionally graded (AFG) porous Rayleigh nanotube containing fluid surrounded by a viscoelastic foundation and acted by a traveling load. The material characteristics of the nanotube are graded longitudinally according to a power-law rule. Also, different porosity models in the longitudinal direction of the system are taken into account. The nonlocal strain gradient theory (NSGT) is applied to reflect the size-dependency of the model. The governing dynamic equation of the system incorporating the scale effects is derived by considering the effects of slip boundary conditions for the internal fluid. The vibration response of the system is obtained analytically. Several comparison studies verify this study's results. Various dynamic phenomena, such as cancellation and maximum free response, are discussed in different operating conditions of the system. Besides, a detailed parametric investigation is conducted to identify the effects of influential parameters, including material gradient, porosity coefficient, fluid velocity, scale parameter ratio, and substrate characteristics, on the dynamic behavior of the system. These research results could be valuable in designing and optimizing advanced nanosensors and targeted drug delivery systems. [ABSTRACT FROM AUTHOR]

This study investigates the linkage from income class to pro-environmental behaviour among people with different income levels. By setting a hierarchical regression model and using data from the World Value Survey (WVS), this study finds that higher income reinforces pro-environmental behaviour. In addition, income satisfaction significantly strengthen the relationship between income class and pro-environmental behaviour, such that the link between them gets stronger when the individuals are satisfied with their income. The findings show that income level and income satisfaction go hand-in-hand in bringing about pro-environmental engagement. [ABSTRACT FROM AUTHOR]

Torsion deformable spatial beam and Costello theory are used to establish longitudinal-torsional-lateral coupled model of round balance rope. Based on Coulomb's friction law and longitudinal-torsional-lateral coupled model, the nonlinear coupled dynamic model with friction constraint of round balance rope is established. Meanwhile, time-varying multi-segments non–equal-length element transformation method (TMN-ETM) is proposed to save computation time. Then, natural frequencies, lateral responses are calculated when the coupled stiffness coefficient is zero. And the calculations are compared with traditional solution method. The results show that only about few areas in the round balance rope loop have large stress norm value, while the rest parts have small stress values. Besides, dynamic responses of the balance rope with balance rope suspension rotor releasing are conducted. When the static friction is converted to dynamic friction, the friction torque and angle acceleration will be mutated at the switching instants, and slip-stick transition in angle acceleration occurs. [ABSTRACT FROM AUTHOR]