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This paper investigates an adaptive fuzzy controller prescribed performance for uncertain robot systems with actuator saturation. To mitigate the impact of model uncertainty and unknown disturbance, an adaptive fuzzy neural network (AFNN) is designed to approximate model uncertainty, and an adaptive disturbance observer (ADO) based on the AFNN is constructed to approximate the disturbance. For multi-degree-of-freedom robotic systems, an auxiliary system is constructed to alleviate the problem of actuator saturation. Combined with the barrier Lyapunov function, an adaptive prescribed performance controller is designed to realize finite-time tracking control for robotic systems with model uncertainty, external disturbance, and actuator saturation. The superiority and practicability of the designed control method are verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

An ultraviolet (UV)-curing polymer coating is an environmentally friendly coating with no volatile organic compound emissions, which can be used for surface protection of steel. However, pure organic polymer coatings cannot meet the needs of practical applications because of their low hardness, poor thermal stability, and high shrinkage rate. In this paper, different contents of mica particles were mixed into epoxy acrylates to prepare UV-curing organic–inorganic composite coatings. The inorganic material was used to enhance the thermal stability and corrosion resistance performance to solve part of the problems faced by a pure organic polymer coating. This paper discusses the UV-curing process of the composite coating, the distribution of particles in the matrix resin, the mechanical properties of the coating, and its thermal stability and corrosion resistance. The results show that the prepared composite coatings show significant improvements in thermal stability and corrosion resistance. Compared with the epoxy acrylate coating, the T10 of the mica-added composite coating with mica was increased by more than 100°C. At 15 g addition (373,070 Ω cm2), there was a 35 times improvement in the total impedance after immersion in 3.5 wt.% NaCl solution for 24 h compared to that of the epoxy acrylate coating (10,799 Ω cm2). [ABSTRACT FROM AUTHOR]

In this work, we pay attention to investigating fixed-time trajectory tracking with prescribed performance for a multi-degree-of-freedom manipulator system subjected to unknown dynamics and input saturation. The radial basis function neural network (RBFNN) is applied to online compensate for the unknown dynamics of the system. In order to guarantee the transient and steady-state performance of the trajectory tracking control, a prescribed performance function (PPF) is used to transform the tracking error. Based on the transformed error, a fixed-time auxiliary system is proposed to compensate for the input saturation impact. Using the compensation error, a non-singular terminal sliding surface is designed, and the corresponding fixed-time control scheme is also proposed. By Lyapunov theorem, it is proved that the reaching phase of the sliding manifold can be completed in finite time, and the stability of the closed-loop system is analyzed. Experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In order to evaluate the potential of recovering various valuable elements from vanadiferous titanomagnetite tailing (VTMT), the chemical and process mineralogical characterization of VTMT were investigated in this study by various analytical techniques such as XRF, XRD, optical microscopy, SEM, EDS, and AMICS. It was found that VTMT is a coarser powder in general; about 50% of the particle size is greater than 54.30 μm. The total iron content of the VTMT was 22.40 wt.%, and its TiO2 grade is 14.45 wt.%, even higher than those found in natural ilmenite ores. The majority of iron and titanium were located in ilmenite and hematite; 62.84% of hematite and 90.27% of ilmenite were present in monomeric form. However, there is still a portion of ilmenite and hematite embedded in gangue such as anorthite, diopside, and serpentite. For the recovery of valuable fractions such as Fe and TiO2 from VTMT, a treatment process including ball milling–high-intensity magnetic separation–one roughing and three refining flotation was proposed. Finally, a concentrate with TiO2 grade of 47.31% and total Fe (TFe) grade of 35.44% was produced; TiO2 and TFe had recovery rates of 57.71% and 28.23%, respectively. The recovered product is adequate as a raw material for the production of rutile. This study provides a reference and a new research direction for the recycling and comprehensive utilization of VTMT. [ABSTRACT FROM AUTHOR]

Constructing heterojunction structures is an effective way to produce highly efficient photocatalysts with favorable charge transfer paths. In this study, TiO2 nanotube arrays were synthesized using an electrochemical anodization method, and g-C3N4 nanoparticles were grown in situ on TiO2 nanotubes using three thermal polymerization strategies. Compared with pure TiO2, the g-C3N4/TiO2 heterojunctions exhibited different degrees of enhancement in photoelectrochemical performance under stimulated solar light. The TNT-L heterojunction fabricated by urea solution exhibited excellent photoelectrochemical (PEC) activity and followed a Z-scheme mechanism, which is beneficial for carrier separation and maintaining the original redox capacity of each component. The crystallinity, morphology, chemical composition, and optical properties of the photocatalysts were also analyzed using a series of characterization techniques. [ABSTRACT FROM AUTHOR]

Pancreatic β-cell compensation is a major mechanism in delaying T2DM progression. Here we report the abnormal high expression of circGlis3 in islets of male mice with obesity and serum of people with obesity. Increasing circGlis3 is regulated by Quaking (QKI)-mediated splicing circularization. circGlis3 overexpression enhances insulin secretion and inhibits obesity-induced apoptosis in vitro and in vivo. Mechanistically, circGlis3 promotes insulin secretion by up-regulating NeuroD1 and Creb1 via sponging miR-124-3p and decreases apoptosis via interacting with the pro-apoptotic factor SCOTIN. The RNA binding protein FUS recruits circGlis3 and collectively assemble abnormal stable cytoplasmic stress granules (SG) in response to cellular stress. These findings highlight a physiological role for circRNAs in β-cell compensation and indicate that modulation of circGlis3 expression may represent a potential strategy to prevent β-cell dysfunction and apoptosis after obesity. Pancreatic β-cell compensation is a major mechanism in delaying T2DM progression. Here, the authors show that circGlis3 levels are affected by QKI and FUS expression, and that increasing circGlis3 lengthens β-cell compensation via enhancing insulin secretion and reducing apoptosis. [ABSTRACT FROM AUTHOR]

The decomposition of monazite using calcium oxide is a clean metallurgy technique for the extraction of rare earth elements. The reaction mechanism between CaO and monazite was studied using the diffusion couple technique, while the interfaces under varying annealing temperatures and durations were characterized using X-ray diffraction, electron probe microanalysis, and energy-dispersive X-ray spectroscopy. The interdiffusion coefficients and diffusion activation energies of Ca and Ce in the diffusion layer were calculated, where the corresponding kinetic analysis indicated that the reaction between CePO4 and CaO was controlled by diffusion. The diffusion mechanism was further discussed based on the vacancy mechanism. [ABSTRACT FROM AUTHOR]

Concepts that draw inspiration from soft biological tissues have enabled significant advances in creating artificial materials for a range of applications, such as dry adhesives, tissue engineering, biointegrated electronics, artificial muscles, and soft robots. Many biological tissues, represented by muscles, exhibit directionally dependent mechanical and electrical properties. However, equipping synthetic materials with tissue-like mechanical and electrical anisotropies remains challenging. Here, we present the bioinspired concepts, design principles, numerical modeling, and experimental demonstrations of soft elastomer composites with programmed mechanical and electrical anisotropies, as well as their integrations with active functionalities. Mechanically assembled, 3D structures of polyimide serve as skeletons to offer anisotropic, nonlinear mechanical properties, and crumpled conductive surfaces provide anisotropic electrical properties, which can be used to construct bioelectronic devices. Finite element analyses quantitatively capture the key aspects that govern mechanical anisotropies of elastomer composites, providing a powerful design tool. Incorporation of 3D skeletons of thermally responsive polycaprolactone into elastomer composites allows development of an active artificial material that can mimic adaptive mechanical behaviors of skeleton muscles at relaxation and contraction states. Furthermore, the fabrication process of anisotropic elastomer composites is compatible with dielectric elastomer actuators, indicating potential applications in humanoid artificial muscles and soft robots. Many biological tissues exhibit directionally dependent properties. Here, authors develop tissue-like elastomer composites with programmed mechanical and electrical anisotropy and discuss potential applications in bioelectronics and humanoid artificial muscles. [ABSTRACT FROM AUTHOR]

The dynamic performances of a polyurethane-reinforced ballast bed and an unreinforced ballast bed at an operation site were tested by using the impact excitation technique. The influences of the ballast beds with and without polyurethane reinforcement on the natural frequency were investigated, along with the vertical and longitudinal vibration transmission characteristics of the track structure. The results show the following. Compared to the ballast bed, the polyurethane ballast bed has an inhibitory effect on the rail vibration in the range of 200–400 Hz, but there is an increased rail vibration amplitude in the higher frequency range. The polyurethane-reinforced ballast bed significantly increases the amount and amplitude of the dominant vibration frequencies of the sleeper. As the frequency increases (> 90 Hz), the superstructure of the polyurethane track rapidly transfers from being flexible to rigid, and the track thus absorbs and dissipates the impact load, quickly damping the vibration in the range of 90–470 Hz. The calculation results of the displacement transmission ratio (DTR) proposed in this study also support this finding, suggesting the use of DTR to more intuitively evaluate the vibration damping effect of each component of the track. The polyurethane material reinforces the ballast bed rather than the damping vibration, thereby improving the stability of the track structure. [ABSTRACT FROM AUTHOR]

With networking, big data and rapid development and wide application of 5G networks, traditional network architecture cannot handle massive amounts of media data generated by a large number of mobile or PC devices. In recent years, events on multimedia and data copyright violations of a substantial increase, data security and privacy protection of many original multimedia users is suffering an unprecedented challenge. On the other hand, due to the center and the invariance of the block chain, block chain has become a promising multimedia security technology. Blockchain technology provides a common, digitized and distributed books, P2P network composed of all peer nodes interconnected to each other, all participating nodes are equal, collaborative service, compared to traditional architecture under a single central point, can greatly reduce the risk of single point of failure. In this paper, based access scheme in combination with the secure multi-computing protocol blockchain system, the user needs to conduct the authentication system under the multi-computing in order to receive the data, greatly enhance the data safety of multimedia in complicated communication sceneries. In addition, the program mentioned in the text and related simulations and proof of security, usability and reliability can be guaranteed. [ABSTRACT FROM AUTHOR]

Developments of soft network materials with rationally distributed wavy microstructures have enabled many promising applications in bio-integrated electronic devices, due to their abilities to reproduce precisely nonlinear mechanical properties of human tissues/organs. In practical applications, the soft network materials usually serve as the encapsulation layer and/or substrate of bio-integrated electronic devices, where deterministic holes can be utilized to accommodate hard chips, thereby increasing the filling ratio of the device system. Therefore, it is essential to understand how the hole-type imperfection affects the stretchability of soft network materials with various geometric constructions. This work presents a systematic investigation of the imperfection sensitivity of mechanical properties in soft network materials consisting of horseshoe microstructures, through combined computational and experimental studies. A factor of imperfection insensitivity of stretchability is introduced to quantify the influence of hole imperfections, as compared to the case of perfect soft network materials. Such factor is shown to have different dependences on the arc angle and normalized width of horseshoe microstructures for triangular network materials. The soft triangular and Kagome network materials, especially with the arc angle in the range of (30 ∘ , 60 ∘ ), are found to be much more imperfection insensitive than corresponding traditional lattice materials with straight microstructures. Differently, the soft honeycomb network materials are not as imperfection insensitive as traditional honeycomb lattice materials. [ABSTRACT FROM AUTHOR]

In this paper, a bijection, which projects the shape manifold as a linear manifold, is proposed to simplify the nonlinear problems of shape analysis. Shapes are represented by the direction function of discrete curves. These shapes are elements of a finite-dimensional shape manifold. We discuss the shape manifold from three perspectives: extrinsic, intrinsic and global using the reference coordinate system. Then, we construct another manifold, in which the reference frame is the Fourier basis and the associated related coordinate is the Fourier coefficients obtained by Fourier transformation. This transformation ensures a bijection between the local spaces of two manifolds. In the constructed manifold, the nonlinear structure is described by the reference frames. Consequently, we obtain a linear manifold only using the related coordinate. The performance of our method is illustrated by the applications of shape interpolation, transportation of shape deformation and shape retrieval. [ABSTRACT FROM AUTHOR]

The ballasted track structure of a high-speed railway repeatedly bears the action of vehicle loads, and the vibration energy is gradually diluted and dissipated due to the ballasted bed. It is difficult to monitor the structural health of ballasted track. By embedding sensors into the ballast, a ballast sensor was obtained. It was positioned on the ballasted track to study the structural health monitoring (SHM) under an impact excitation and to verify the Discrete Element Method (DEM)–Multi-body Dynamics (MBD) co-simulation model. Therefore, the SHM of the ballasted track is realized. The results showed that distributed ballast sensors can realize the SHM status of the ballasted track. Under an impact excitation, the peak of the main vibration frequency of the ballast at the sleeper box, sleeper end and ballast shoulder occurred at a frequency of 153 Hz. At twice the frequency, a secondary peak appeared in the ballast vibration amplitude at the sleeper box, while the vibration amplitudes at the sleeper end and ballast shoulder were suppressed. In low-frequency regime, the vibration damping performance of the ballasted bed structure was better than that in high-frequency regime. When the ballasted track structure was excited by high-frequency vibrations, the surface layer of the ballast at the sleeper box tended to splash, which affected the structural health state. Under the moving wheel load, both sides of the ballasted bed form a "cyclone" shape. [ABSTRACT FROM AUTHOR]

Many biological tissues offer J-shaped stress–strain responses, since their microstructures exhibit a three-dimensional (3D) network construction of curvy filamentary structures that lead to a bending-to-stretching transition of the deformation mode under an external tension. The development of artificial 3D soft materials and device systems that can reproduce the nonlinear, anisotropic mechanical properties of biological tissues remains challenging. Here we report a class of soft 3D network materials that can offer defect-insensitive, nonlinear mechanical responses closely matched with those of biological tissues. This material system exploits a lattice configuration with different 3D topologies, where 3D helical microstructures that connect the lattice nodes serve as building blocks of the network. By tailoring geometries of helical microstructures or lattice topologies, a wide range of desired anisotropic J-shaped stress–strain curves can be achieved. Demonstrative applications of the developed conducting 3D network materials with bio-mimetic mechanical properties suggest potential uses in flexible bio-integrated devices. The development of artificial 3D soft materials and device systems that can reproduce the nonlinear, anisotropic mechanical properties of biological tissues remains challenging. Here, the authors design a class of soft 3D network materials that can offer defect-insensitive, nonlinear mechanical responses closely matched with those of biological tissues. [ABSTRACT FROM AUTHOR]

Magnetic minerals in sediments of the continental shelf are sensitive to environmental changes. Therefore, to determine the exact phases of magnetic minerals is the prerequisite to investigate the paleoenvironmental significances. In this study, a comprehensive rock magnetic investigation, coupled with mineralogical studies, was carried out on the long core NHH01 (with a length of 125.64 m) from the central continental shelf of the South Yellow Sea. Single-domain greigite was identified as the dominant magnetic carrier in sediments between 44.90 and 51.80 m, and terrigenous magnetite is the major magnetic phase in the adjacent layers. The existence of greigite unambiguously indicates an anoxic environment. We tentatively interpreted that such an environment could be formed by the fast sea level changes, long-existing of the cold eddies during warm stages, or in a lake which might be related to locally tectonic uplifting. Therefore, the occurrence of the thick-layer greigite could supply a new perspective to paleoenvironmental or even tectonic studies. [ABSTRACT FROM AUTHOR]

In previous study, we have found the catechol- O-methyltransferase (COMT) Val158Met polymorphism may be associated with the risk of Parkinson's disease (PD) in Asians, especially Japanese population. In this study, we further evaluated the associations of PD wearing-off susceptibility with COMT polymorphisms. We carried out a retrieval of studies and included the relevant studies which met the criteria. After the data were extracted, the Stata software 11.0 was used to analyse the genotype frequencies. A total of five studies were included. The pooled result indicated that genotype AA was significantly associated with the wearing-off risk of PD (AA vs. others: OR = 2.52, 95 % CI 1.21-5.26, P = 0.013; AA vs. GA: OR = 2.51, 95 % CI 1.18-5.34, P = 0.017; AA vs. GG: OR = 2.17, 95 % CI 1.09-4.33, P = 0.027). The results also showed allele A was correlated with PD wearing-off risk (A vs. G: OR = 1.95, 95 % CI 1.18-3.22, P = 0.009). In conclusion, this study suggested that Val158Met polymorphisms in COMT may increase the risk of wearing-off. Further studies with larger sample sizes are needed to confirm our results. [ABSTRACT FROM AUTHOR]