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In this paper, the tracking problem is concerned for a class of nonlinear system. The primary objective is to achieve fixed‐time control performance in the presence of nonvanishing mismatched uncertainties and nonparametric external disturbance. Firstly, in order to estimate disturbance, a fixed‐time extended state observer with fractional power term is developed, the order of which is reduced to alleviate peaking value phenomenon. By reasonably switching among different estimation patterns, both transient and steady‐state performances are balanced. Secondly, by means of fuzzy logic system theory, an ESO‐based adaptive fuzzy control strategy with time‐varying gains is presented, and thus the mismatched nonlinearities are approximated, and the external disturbance is compensated in real time simultaneously. Moreover, by constructing a mixed barrier and quadratic type of Lyapunov function, the fixed‐time stability analysis is put forward for tracking error dynamics based on backstepping methodology. Finally, the advantages and effectiveness are illustrated by a numerical example on wheeled mobile robot. The main characteristic of this paper is to integrate ESO methodology into fuzzy control architecture in fixed‐time sense. As a consequence, not only the output tracking purpose, but also desirable transient performance can be achieved. [ABSTRACT FROM AUTHOR]

The substitution of heteroatoms and the expansion of π‐conjugated units have significant effects on the photoelectric properties of polycyclic aromatic hydrocarbons (PAHs). In this study, based on the experimental molecule PBC, 10 acene derivatives containing the pyrrole group were designed by three strategies: (1) changing the connection position of the pyrrole group, (2) exchanging the position of the N atom, and (3) increasing the length of the π‐linker. Density functional theory (DFT) was used to optimize the molecular geometric structure. Time‐dependent density functional theory (TD‐DFT) was used to calculate the relevant parameters of the excited states. The results show that both of the pyrrole group and the N atom in the para‐position, and the addition of the π‐linker can reduce the energy gap, cause redshift of the linear absorption peak, and increase the two photon absorption (TPA) cross‐section. The analyses of the charge density difference (CDD) and the charge‐transfer matrix (CTM) proved that the electron transfer is mainly concentrated in the π‐linker. Moreover, the participation of the multi‐ring skeleton on both sides decreases gradually with the increase of the length of the π‐linker. The length of the π‐linker changes the dominant transition channel and intramolecular charge‐transfer (ICT) characteristics of TPA, thus affecting the transition dipole moments and nonlinear absorption properties. The second hyperpolarizability of the designed molecule PBI5‐p5 is also significantly superior to that of similar materials reported. It is expected that the above molecular design strategies and comprehensive analysis of nonlinear optical (NLO) properties could provide theoretical support for the research on acene derivatives. [ABSTRACT FROM AUTHOR]

Aim: The aim of the study was to examine the relationships among nurses' shift work disorder, mental health and burnout to inform efforts to alleviate shift work disorder. Design: This cross‐sectional study was conducted in China using a web‐based platform for questionnaire. Methods: The study was comprised of a convenience sample of 1,268 Registered Nurses from 21 public hospitals in mainland China from June 2019–July 2019. Participants completed a web‐based survey designed to collect demographic and other self‐reported data. An independent sample t test and Pearson correlation were performed to analyse the relationship between shift work disorder, mental health and burnout. Results: The vast majority (98.2%) of the participants were women between the ages of 20–59 years. The participants exhibited a higher incidence of mental health problems (58.1%) and burnout (65.5%) and those with shift work disorder exhibited a higher risk of mental health problems and burnout than those who did not have shift work disorder. Our research demonstrated that shift work disorder, combined with other variables, accounted for 40.5% of the variance in mental health (R2 =.405, adjusted R2 =.401, F = 107.214, p <.001) and 36.5% in burnout (R2 =.365, adjusted R2 =.361, F = 90.323, p <.001). Moreover, burnout negatively regulated the relationship between shift work disorder and mental health. Conclusion: High‐risk nurses with shift work disorder were at a much higher risk of mental health problems and burnout. [ABSTRACT FROM AUTHOR]

Aiming at the problem of poor image illumination correction accuracy, a kernel extreme learning machine optimized based on the differential evolution‐improved marine predators algorithm is proposed to estimate the scene illumination information and restore the image. First, in order to solve the problem of randomization of the initial population of the marine predators algorithm, differential evolutions is used to provide a set of suitable initial populations to the algorithm. Then, an improved algorithm is used to optimize the weight and bias of the kernel extreme learning machine to solve the problem of the randomness of the weight and bias, so that the learning machine converges to the global optimal value and avoids the unstable predictions. Finally, after obtaining the predicted illumination information, the image model is corrected to the image effect under standard illumination through diagonal transformation. It can be seen from the experimental results that the best predictive value of the differential evolution marine predator algorithm learning machine is 0.0135915, and the quasi‐bias is only 0.001687. Compared with traditional illumination estimation algorithms such as random vector functional link and extreme learning machine, the differential evolution marine predator algorithm learning machine algorithm proposed in this article has better stability, higher accuracy of calculated predicted values, and better image restoration effect. [ABSTRACT FROM AUTHOR]

Trans‐ferulic acid‐4‐β‐glucoside (FAG) is a monomer extracted from Radix Aconiti Lateralis Preparata, which is a potential candidate for the prevention and treatment of cold injury. To determine the concentration of FAG in rats, it is essential to develop an ultra‐performance liquid chromatography coupled with MS/MS method. Chromatographic separation was achieved by an Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm). A Xevo triple quadrupole tandem mass spectrometer was used to quantitatively determine FAG in the negative‐ion mode. The standard calibration curve was linear over the concentration range of 0.1–100 μg/mL and 0.0626–31.28 μg/g for rat plasma and liver tissue homogenate samples, respectively. The inter‐ and intra‐batch precision (% relative standard deviation) of the assay was ≤8.29%, and accuracy (% relative error) ranged from −7.41 to 10.99%. The matrix effect was between 92.99 and 102.39%. The oral absolute bioavailability of FAG was obtained as 1.80%. The results of tissue distribution suggested that FAG spread rarely in the liver and brown adipose, which was not propitious to exert its ability to treat cold injury. In general, these studies were significant to provide necessary information for further study. [ABSTRACT FROM AUTHOR]

Highly stretchable and conductive composites have gained tremendous research interests due to the imperative demands in the fields of stretchable electronics and soft robotics. However, it is challenging to maintain the original performance of the composites under complex external deformations. Here, a one‐step dual‐material 3D printing technique is developed to rationally assemble liquid metal (LM) into an elastomer lattice. The 3D interconnected and deformable liquid conductive network is supported by a highly ordered and robust polydimethylsiloxane lattice skeleton, yielding the resultant composites high electrical conductivity (1.98 × 106 S m−1), stretchability (180%), and electromagnetic interference (EMI) shielding effectiveness (72 dB). Unlike those composites with dispersed fillers, the LM/elastomer lattice composites deliver negligible electromechanical coupling, showing a negative resistance change of only −2% at a large tensile strain of 100%. The composites also exhibit strain‐invariant EMI shielding performance in a strain range of 0–100%, and present exceptional stability over 1000 rigorous cycles of stretching and releasing. The applications of the composites in flexible display circuits, microwave shielding layer, and EMI shields in wireless power transmission systems are demonstrated. The current findings suggest an effective strategy for fabricating LM‐based composites with precisely controlled and unprecedented multi‐functionality. [ABSTRACT FROM AUTHOR]

This article focuses on solving the leader‐follower formation tracking problem of multiple mobile robots under a hybrid‐triggered mechanism without leader's velocity measurements. Two kinds of networks are considered: the detection network, which enables the relative detections by agents' onboard sensors, and the communication network, which is used to implement the transmissions of local information. The followers are divided into two groups based on their detection capacity of leader's information. By merely sensing the relative information from the leader, the first group of followers implement high gain observers to estimate leader's angular and linear velocities. In the rest followers, the transmitted information and relative detections from neighboring agents are used to estimate leader's velocities and position in a distributed way; after that, event‐triggered observer‐based controllers are proposed to drive the agents toward desirable formation. Periodic event‐triggered mechanisms (PETMs) are used to avoid continuous‐time checking of event‐triggering conditions; and the maximum allowable sampling periods (checking periods and transmission periods) are determined to guarantee the stability of the sampled‐data system. Since PETM is only applied in communication networks, the mechanism used in this work is a hybrid‐triggered one. Moreover, the inter‐sampling (‐checking, ‐transmission) times are allowed to be time‐varying and asynchronous. Finally, numerical examples are presented to illustrate the effectiveness and conservativeness of the proposed methods. [ABSTRACT FROM AUTHOR]

The color of an object appears different from its true color when illuminated with light sources of different hues. To solve this problem, this article proposes a combination algorithm (SCA‐GWO‐LSSVR) based on the sine‐cosine algorithm (SCA) and the gray wolf optimization (GWO) algorithm to optimize the regression prediction model of the least‐squares support vector regression (LSSVR) algorithm. The performance of the traditional LSSVR is significantly affected by the penalty parameter (gamma) and the sig2 kernel function parameter. The proposed method uses the improved GWO algorithm to search the population to find the best LSSVR parameter solution. The proposed algorithm uses the SCA to create multiple random candidate solutions in population initialization to avoid blind initialization of the GWO algorithm. In the process of iterative optimization, the SCA is infiltrated, and its sine‐cosine wave mathematical model is used to quickly identify the best outward or inward position of the gray wolf. Finally, the LSSVR combines the optimal sig2 kernel function parameters and penalty parameters (gamma) to obtain a highly versatile illumination correction model. The experimental results show that the fitting accuracy of the proposed method reaches 86.8%, which is 5% higher than that of the LSSVR algorithm alone. [ABSTRACT FROM AUTHOR]

Hupehenenine is a novel isosteroid alkaloid that was first isolated from Bulbus Hupehensis Fritillariae. The inhibitory proliferation effect of hupehenenine and its three related alkaloid derivatives, including o‐caproyl‐hupehenenine, o‐(2‐furanoyl)‐hupehenenine, and Δ5(6)‐isopeimine on human lung cancer cell line, human chronic myeloid leukemia cell line, and human thyroid duct cancer cell line in vitro, has been identified. This study first developed a sensitive HPLC‐MS/MS method for the simultaneous quantification of hupehenenine and three alkaloid derivatives in rat plasma and tissues. The developed method was validated, and it was linear over the concentration range of 1–800 ng/mL for all analytes with R2 ≥ 0.9939 and 0.9972, respectively, in rat plasma and rat liver homogenate. The lower limit of quantitation was 1 ng/mL for all analytes. The intra‐day and inter‐day precision and accuracy were satisfactory. This validated method was successfully applied to investigate the pharmacokinetics and tissue distribution of hupehenenine in rats. In pharmacokinetic study, the maximum plasma concentration of rats exists gender difference. Tissue distribution study showed that hupehenenine has good affinity for multiple tissues but is unable to cross the blood–brain barrier. These results may provide a useful reference for further research of hupehenenine and its three related alkaloid derivatives. [ABSTRACT FROM AUTHOR]

Spin‐orbit‐coupled Mott iridates show great similarity with parent compounds of superconducting cuprates, attracting extensive research interest especially for their electron‐doped states. However, previous experiments have been largely limited within a small doping range due to the absence of effective dopants, and therefore the electron‐doped phase diagram remains elusive. Here, an ionic‐liquid‐gating‐induced protonation method is utilized to achieve electron‐doping into a 5d Mott‐insulator built with a SrIrO3/SrTiO3 superlattice (SL), and a systematic mapping of its electron‐doped phase diagram is achieved with the evolution of the iridium valence state from 4+ to 3+, equivalent to doping of one electron per iridium ion. Along increasing doping level, the parent Mott‐insulator is first turned into a localized metallic state with gradually suppressed magnetic ordering, and then further evolves into a nonmagnetic band insulating state. This work forms an important step forward for the study of electron‐doped Mott iridate systems, and the strategy of manipulating the band filling in an artificially designed SL structure can be readily extended into other systems with more exotic states to explore. [ABSTRACT FROM AUTHOR]

Variations in illumination lead to serious errors in the evaluation of chromatic aberration. We propose an illumination correction model based on the opposition‐based learning improved whale optimization algorithm for support vector regression optimization, named "OBL‐IWOA‐SVR." Because the initial population quality of the whale optimization algorithm has a significant impact on the solution speed and accuracy, the Opposition‐based learning strategy is adopted in this article to mix the original population and its opposite individuals and select the best as the new population, replacing the random initialization to generate a more suitable initial population. This increases the diversity of the population and thus overcomes the impact of the quality of the initial population on the algorithm performance. Secondly, the proposed algorithm adopts the adaptive weight and the convergence factor based on the variation of the cosine law to balance the algorithm's global exploration ability and local development ability and enhance the convergence accuracy. Finally, the algorithm utilizes good global searching ability to optimize the penalty factor and nuclear parameters and obtains the optimal support vector machine parameter combination to construct the illumination correction model OBL‐IWOA‐SVR accurately and robustly. Experimental results show that the illumination correction model proposed in this article is found superior to other models in significance analysis: the root mean square error of the proposed model is 0.0173, the smallest of all illumination correction models. Furthermore, the model exhibits good stability and high illumination estimation accuracy. [ABSTRACT FROM AUTHOR]

Summary: Deep‐sea ecosystems, such as cold seeps and hydrothermal vents, have high biomass, even though they are located in the benthic zone, where no sunlight is present to provide energy for organism proliferation. Based on the coexistence of the reduced gases and chemoautotrophic microbes, it is inferred that the energy from the reduced gases supports the biocoenosis of deep‐sea ecosystems. However, there is no direct evidence to support this deduction. Here, we developed and placed a biocoenosis generator, a device that continuously seeped methane, on the 1000‐m deep‐sea floor of the South China Sea to artificially construct a deep‐sea ecosystem biocoenosis. The results showed that microorganisms, including bacteria and archaea, appeared in the biocoenosis generator first, followed by jellyfish and Gammaridea arthropods, indicating that a biocoenosis had been successfully constructed in the deep sea. Anaerobic methane‐oxidizing archaea, which shared characteristics with the archaea of natural deep‐sea cold seeps, acted as the first electron acceptors of the emitted methane; then, the energy in the electrons was transferred to downstream symbiotic archaea and bacteria and finally to animals. Nitrate‐reducing bacteria served as partners to complete anaerobic oxidation of methane process. Further analysis revealed that viruses coexisted with these organisms during the origin of the deep‐sea biocoenosis. Therefore, our study mimics a natural deep‐sea ecosystem and provides the direct evidence to show that the chemical energy of reduced organic molecules, such as methane, supports the biocoenosis of deep‐sea ecosystems. [ABSTRACT FROM AUTHOR]

Summary: In the performance evaluation of structures under disastrous actions, for example, earthquakes, it is important to take into account the randomness of structural parameters. Generally, these random parameters are treated either as independent or perfectly dependent, but practically they are partly dependent. This article aims at developing a point selection strategy for uncertainty quantification of nonlinear structures involving probabilistically dependent random parameters characterized by copula function. For this purpose, the point selection strategy for structures involving independent basic variables is first revisited. As an improvement, a generalized F‐discrepancy diminishing oriented iterative screening algorithm is proposed. Then, combining with the conditional sampling method, a conditional point set rearrangement method and a conditional iterative screening‐rearrangement method are proposed for probabilistically dependent variables. These new point selection strategies are readily incorporated into the probability density evolution method for uncertainty quantification of nonlinear structures involving dependent random parameters, which is characterized by copula function. The proposed methods are illustrated by two examples including a shear frame with hysteretic restoring forces and a reinforced concrete frame structure with the damage constitutive model of concrete, where the material parameters are probabilistically dependent. The results demonstrate the effectiveness of the proposed method. Problems to be studied are discussed. [ABSTRACT FROM AUTHOR]

We systematically studied the chemical reactivities of 13 metal-organic frameworks (MOFs) under vapor-assisted aging (VAG) at room temperature. The MOFs aged in solvent vapor at room temperature showed unexpectedly high reactivities for transformations into structures with other coordination networks. In addition, three MOFs reacted with 4,4′-bipyridine to form three-dimensional microporous MOFs under VAG conditions at room temperature. [ABSTRACT FROM AUTHOR]