Projection-Based Adaptive Backstepping Control of a Transport Aircraft for Heavyweight Airdrop

An autopilot inner loop that combines backstepping control with adaptive function approximation is developed for airdrop operations. The complex nonlinear uncertainty of the aircraft-cargo model is factorized into a known matrix and an uncertainty function, and a projection-based adaptive approach is proposed to estimate this function. Using projection in the adaptation law bounds the estimated function and guarantees the robustness of the controller against time-varying external disturbances and uncertainties. The convergence properties and robustness of the control method are proved via Lyapunov theory. Simulations are conducted under the condition that one transport aircraft performs a maximum load airdrop task at a height of 82 ft, using single row single platform mode. The results show good performance and robust operation of the controller, and the airdrop mission performance indexes are satisfied, even in the presence of ±15% uncertainty in the aerodynamic coefficients, ±0.01 rad/s pitch rate disturbance, and 20% actuators faults

Variations in growth traits and wood physicochemical properties among Pinus koraiensis families in Northeast China

This study aimed to explore and improve the different economic values of Pinus koraiensis (Siebold and Zucc.) by examining the variations in 6 growth traits and 9 physicochemical wood properties among 53 P. koraiensis half-sib families. Growth traits assessed included height, diameter at breast height, volume, degree of stem straightness, stem form, and branch number per node, while wood properties assessed included density, fiber length and width, fiber length to width ratio, and cellulose, hemicellulose, holocellulose, lignin, and ash contents. Except for degree of stem straightness and branch number per node, all other traits exhibited highly significant variations (P < 0.01) among families. The coefficients of variation ranged from 5.3 (stem form) to 66.7% (ash content), whereas, the heritability ranged from 0.136 (degree of stem straightness) to 0.962 (ash content). Significant correlations were observed among growth traits and wood physicochemical properties. Principal component analysis identified four distinct groups representing growth traits, wood chemical and physical properties, and stem form traits. Multi-trait comprehensive evaluation identified three groups of elite families based on breeding objectives, including rapid growth, improved timber production for building and furniture materials, and pulpwood production. These specific families should be used to establish new plantations

Rugged, Tunable Extended-Cavity Diode Laser

A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research

High-altitude cerebral hypoxia promotes mitochondrial dysfunction and apoptosis of mouse neurons

IntroductionNeuronal cell death is an important factor in the pathogenesis of acute high-altitude cerebral hypoxia; however, the underlying molecular mechanism remains unclear. In this study, we tested if high-altitude hypoxia (HAH) causes neuronal death and mitochondrial dysfunction using various in vivo and in vitro approaches.MethodsAcute high-altitude cerebral hypoxia was induced by hypobaric hypoxia chamber in male mice. we explored the mechanisms of neuronal cell death using immunofluorescence, western blotting, transmission electron microscopy, and flow cytometry. Next, mitochondrial function and morphology were observed using Jc-1 staining, seahorse assay, western blotting, MitoTracker staining, and transmission electron microscopy. Moreover, open field test, elevated plus test, and Morris water maze were applied for animal behavior.ResultsResults revealed that HAH disrupted mitochondrial function and promoted neuronal apoptosis and necroptosis both in HT-22 cells and in mouse hippocampal neurons. Moreover, the mitochondrial membrane potential and adenosine triphosphate production decreased in neurons after HAH, while oxidative stress and mitochondrial fission increased. Behavioral studies suggested that HAH induced anxiety-like behavior and impaired spatial memory, while it had no effect on athletic ability.DiscussionThese findings demonstrated that HAH promotes mitochondrial dysfunction and apoptosis of mouse neurons, thus providing new insights into the role of mitochondrial function and neuronal cell death in acute high-altitude cerebral hypoxia

Effect of the element ratio in the doping component on the properties of 0.975(0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3)–0.025Bix/3Mgy/3Nbz/3O3 ceramics

A new series of ternary perovskite 0.975(0.8Bi Na TiO –0.2Bi K TiO )–0.025Bi Mg Nb O (BNT–BKT–BMN, BMN‐xyz) ceramics were designed and synthesized. The effect of the element ratio in the doping component BMN on the strain, ferroelectric, piezoelectric, and dielectric properties of the BNT–BKT matrix were studied. The BMN‐430 composition without Nb element exhibits the typical features of non‐ergodic relaxor, which is characterized by a higher piezoelectric coefficient d and a butterfly‐shaped strain curve with negative strain. The introduction of trace Nb can significantly enhance the ergodicity of the system, reflecting in the high positive strain response and strain coefficient (d33∗\u3e750pm/V) of BMN‐321 composition. In contrast, there is no significant difference in the properties between the presence and absence of Mg element. The temperature‐dependent electrical behaviors of BMN‐xyz ceramics were analyzed based on impedance spectroscopy. This study may be helpful to the design of the chemical modification strategy for the BNT‐based relaxor ferroelectrics. [Figure not available: see fulltext.] 1/2 1/2 3 1/2 1/2 3 x /3 y /3 z /3 3 3

Enhanced magnetic performance of BiFeO3 by cerium substitution

© 2020 Elsevier Ltd and Techna Group S.r.l. Micrometre-sized pure BiFeO3 (BF) and Ce-doped Bi0.9Ce0.1FeO3 (BCF) powders were synthesized by using conventional hydrothermal (H) and microwave assisted hydrothermal (MH) methods. The BF-H and BCF-H show obviously enhanced weak ferromagnetic characteristic, in which the BCF-H exhibits excellent magnetic performance, with significantly increased maximum magnetization of ∼3.6 emu/g (under 50 kOe magnetic field) and remanent magnetization of ∼0.268 emu/g at room temperature. The superior magnetic property of BCF-H could be attributed to the suppression of spiral structure and the modulation of canting angle of spins in antiferromagnetic sublattices

Enhanced temperature stable dielectric property and energy-storage performance of (1-x)(0.66Bi0.5Na0.5TiO3–0.34Sr0.7Bi0.2TiO3)– xK0.5Nd0.5TiO3 lead-free relaxor electroceramics

© 2020 Elsevier Ltd and Techna Group S.r.l. In this study, (1-x)(0.66Bi0.5Na0.5TiO3–0.34Bi0.2Sr0.7TiO3)–xK0.5Nd0.5TiO3 (BNBST–xKNT) ceramics were designed and synthesized, and they present significantly enhanced dielectric temperature stability and energy storage properties. The BNBST–0.06KNT composition exhibits a remarkable dielectric stability, as reflected in its stable dielectric constant (△ԑ/ԑ150 °C \u3c ±15%) over a broad temperature range (25–401 °C). BNBST–0.02KNT achieves a high energy storage density Wrec = 1.2 J/cm3 under 110 kV/cm with an energy storage efficiency η of 76.9%, and the improved energy storage property originates from the improved breakdown field strength and decreased hysteresis behavior. The electrical conductivity and relaxation behaviors of BNBST–xKNT were also analyzed via impedance spectroscopy