Back-Stepping and Neural Network Control of a Mobile Robot for Curved Weld Seam Tracking

AbstractThis paper proposes a back-stepping and neural network hybrid control method for mobile platform and slider of mobile robot used in shipbuilding welding. The kinematics model of the robot is built firstly, and then a motion controller is designed based on the model and back-stepping method. Stability of the controller is proved through use of Liapunov theory. For improving the tracking precision and anti-interference performance of the controller, a neural network is designed to identify the kinematical model of the robot and to adjust the control coefficients in real time based on the tracking errors. The simulation and experiments have been done to verify the effectiveness of the proposed controllers

Free Vibration of Axially Functionally Graded Beam

Axially functionally graded (AFG) beam is a special kind of nonhomogeneous functionally gradient material structure, whose material properties vary continuously along the axial direction of the beam by a given distribution form. There are several numerical methods that have been used to analyze the vibration characteristics of AFG beams, but it is difficult to obtain precise solutions for AFG beams because of the variable coefficients of the governing equation. In this topic, the free vibration of AFG beam using analytical method based on the perturbation theory and Meijer G-Function are studied, respectively. First, a detailed review of the existing literatures is summarized. Then, based on the governing equation of the AFG Euler-Bernoulli beam, the detailed analytic equations are derived on basis of the perturbation theory and Meijer G-function, where the nature frequencies are demonstrated. Subsequently, the numerical results are calculated and compared, meanwhile, the analytical results are also confirmed by finite element method and the published references. The results show that the proposed two analytical methods are simple and efficient and can be used to conveniently analyze free vibration of AFG beam

High-Frequency Fractional Predictions and Spatial Distribution of the Magnetic Loss in a Grain-Oriented Magnetic Steel Lamination

Grain-oriented silicon steel (GO FeSi) laminations are vital components for efficient energy conversion in electromagnetic devices. While traditionally optimized for power frequencies of 50/60 Hz, the pursuit of higher frequency operation (f ≥ 200 Hz) promises enhanced power density. This paper introduces a model for estimating GO FeSi laminations’ magnetic behavior under these elevated operational frequencies. The proposed model combines the Maxwell diffusion equation and a material law derived from a fractional differential equation, capturing the viscoelastic characteristics of the magnetization process. Remarkably, the model’s dynamical contribution, characterized by only two parameters, achieves a notable 4.8% Euclidean relative distance error across the frequency spectrum from 50 Hz to 1 kHz. The paper’s initial section offers an exhaustive description of the model, featuring comprehensive comparisons between simulated and measured data. Subsequently, a methodology is presented for the localized segregation of magnetic losses into three conventional categories: hysteresis, classical, and excess, delineated across various tested frequencies. Further leveraging the model’s predictive capabilities, the study extends to investigating the very high-frequency regime, elucidating the spatial distribution of loss contributions. The application of proportional–iterative learning control facilitates the model’s adaptation to standard characterization conditions, employing sinusoidal imposed flux density. The paper deliberates on the implications of GO FeSi behavior under extreme operational conditions, offering insights and reflections essential for understanding and optimizing magnetic core performance in high-frequency applications

Experience in prenatal ultrasound diagnosis of fetal microtia and associated abnormalities

ObjectivePrenatal ultrasound features, associated anomalies and genetic abnormalities of microtia cases were analyzed to explore the feasibility and value of prenatal ultrasound for the diagnosis of microtia.MethodsThe ultrasonographic features, associated anomalies, chromosome examination results and follow-up results of 81 fetuses with congenital microtia were analyzed retrospectively.ResultsAmong the 81 fetuses with microtia diagnosed after birth, 2 cases were missed diagnosis on prenatal ultrasound, and 1 case was diagnosed as unilateral microtia by prenatal ultrasound but was found to be bilateral microtia after birth. Microtia was accompanied by an accessory auricle in 4 cases (4.94%) and low-set ears in 7 cases (8.64%). 22 cases (27.16%) were complicated with other structural anomalies, including 11 cases (13.58%) of cardiac anomalies, 7 cases (8.64%) of ultrasonographic soft marker anomalies, 6 cases (7.41%) of facial anomalies, 6 cases (7.41%) of nervous system anomalies, 3 cases (3.70%) of urogenital system anomalies, 3 cases (3.70%) of digestive tract anomalies and 2 cases (2.47%) of limb anomalies. Chromosome karyotype analysis and gene detection were performed in 44 cases. Trisomy 18, trisomy 13, trisomy 21, pericentric inversion of chromosome 9, partial loss of heterozygosity on chromosome 14, 22q11 microdeletion and a normal karyotype were found in 2 cases, 2 cases, 3 cases, 1 case, 1 case, 1 case, and 34 cases, respectively.ConclusionIn summary, microtia is often accompanied by congenital defects of other organs and structures, especially the heart and face, and prenatal ultrasound diagnosis of microtia and associated anomalies is of important clinical significance

A general strategy for selective detection of hypochlorous acid based on triazolopyridine formation

Triazolopyridines are an important kind of fused-ring compounds. A HOCl-promoted triazolopyridine formation strategy is reported here for the first time in which hypochlorous acid (HOCl) mildly and efficiently promotes the formation of 1,2,4-triazolo[4,3-a]pyridines NT1-NT6 from various 2-pyridylhydrazones N1-N6. N6, a rhodol-pyridylhydrazone hybrid, was developed into a fluorescent probe for the selective detection of HOCl, and successfully applied to probe endogenous HOCl in living cells and zebrafish in situ and in real time. The present intramolecular cyclization reaction is selective and atom-economical, thereby not only providing an important approach for the convenient synthesis of triazolopyridines, but also offering a general strategy for sensitive, selective and biocompatible detection of endogenous HOCl in complex biosystems.</p

Association between parental unhealthy behaviors and offspring’s cardiovascular health status: Results from a cross-sectional analysis of parent–offspring pairs in China

BackgroundCardiovascular health (CVH) in children and adolescents, which might be largely influenced by parental behaviors, may affect the incidence of cardiovascular diseases in adulthood. However, few studies have been conducted to explore the associations between parental behaviors and CVH status of offspring in China.MethodsData were obtained from a cross-sectional survey conducted in Chinese children and adolescents aged 7–18 years old, with a total of 10,043 parent–offspring pairs included. Parental behaviors included moderate to vigorous physical activity (MVPA), dietary behaviors, and weight status. The CVH status of offspring was consulted by The American Heart Association, including seven factors. The associations between parental behaviors and CVH status of offspring were evaluated by multilevel logistic regression. Stratified analyses were conducted to explore the potential modifying influence of sociodemographic factors.ResultsMost of the offspring had five ideal CVH factors; only 21.04% had six to seven ideal CVH factors. Parental unhealthy behaviors were associated with high odds of nonideal CVH status of offspring. Parental overweight/obesity, insufficient MVPA, and unhealthy dietary behaviors could increase the odds of owning one to three ideal CVH factors in offspring, with corresponding odds ratios (ORs) (95% confidence interval) of 1.61 (1.32–1.96), 1.31 (1.10–1.56), and 2.05 (1.43–2.94), respectively. There was a dose–response relationship between parental single unhealthy behavior and the odds of nonideal CVH status in offspring (P-trend &lt; 0.001). Offspring with overweight parents had ORs of 1.25 for nonideal CVH status, compared to offspring with normal-weight parents. Among offspring who had the same number of ideal CVH factors, the cumulative association between unhealthy behaviors of parents and offspring’s nonideal CVH status increased if parents had more unhealthy behaviors (P-trend &lt; 0.001).ConclusionsParental overweight/obesity, insufficient MVPA, and unhealthy dietary behaviors were strongly associated with CVH status in offspring. With a cumulative association, more unhealthy parental behaviors were associated with higher odds of offspring’s nonideal CVH status, suggesting that targeting parental behaviors might facilitate attainment of improving CVH status of children and adolescents