Search

A comprehensive RFD-FTC-DCA system is proposed for the hypersonic vehicle with saturation constraints to resist the control surface damage, actuator faults, disturbances and parameter perturbation. Firstly, the hypersonic vehicle fault model is established. Secondly, the robust fault detection (RFD) observer is designed to detect the control surface damage and actuator faults accurately under the influences of disturbances and parameter perturbation. Thirdly, the fault-tolerant control (FTC) law is designed to resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously. Finally, a dynamic control allocation (DCA) algorithm is designed to reallocate the FTC law and limit the deflection angle and velocity within saturation constraint. The comparison simulation results are presented to demonstrate that the RFD observer can detect the faults accurately and reduce false alarm rates effectively, the FTC law can resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously, and the tracing errors of attack angle, side-slip angle and roll angle are only $ \pm 0.7^\circ $ ± 0.7 ∘ , $ \pm 0.2^\circ $ ± 0.2 ∘ and $ \pm 1.5^\circ $ ± 1.5 ∘ , respectively, and the DCA algorithm can reallocate the FTC law and limit the deflection angle and velocity within saturation values. [ABSTRACT FROM AUTHOR]

This paper focuses on the distributed resource allocation problem of a second-order multi-agent system with external disturbances. The global network resource equality constraint is considered. A distributed algorithm with an exponential convergence rate is proposed based on an internal model for a known bounded disturbance. By using the active disturbance approach to design a reduced-order extended state observer, the proposed algorithm is modified to reject an unknown external disturbance. Moreover, exponential convergence is achieved through the Lyapunov theory when the disturbance is constant. When the differential of the disturbance is bounded, by adjusting the control parameter of the observer, the proposed algorithm converges to an arbitrarily small neighbourhood of the optimal solution. Finally, our simulation results demonstrate the effectiveness of our proposed algorithm. [ABSTRACT FROM AUTHOR]

Widely linear beamforming is known to outperform the conventional adaptive beamforming by fully employing the non-circularity of non-circular signals. In this paper, a robust widely linear beamformer (WLB) is proposed to achieve satisfactory output and robustness in low computational complexity. The augmented signal-of-interest (SOI) covariance matrix is built by performing integration over SOI angular sector. The principal eigenvector of the augmented SOI covariance matrix is taken as the SOI extended steering vector. The received signal vector is projected into the interference-plus-noise subspace to remove the SOI component and derive the augmented interference covariance matrix. The augmented noise covariance matrix is added to the derived augmented interference covariance matrix so that the augmented interference-plus-noise covariance matrix can be reconstructed. The proposed WLB possesses lower computational complexity than the state-of-the-art WLBs due to the avoidance of convex optimization programming. Numerical simulations illustrate the effectiveness of the proposed WLB. [ABSTRACT FROM AUTHOR]

The performance of traditional reconstruction-based robust adaptive beamformers may degrade when the array is not well calibrated. This performance degradation is mainly caused by the Capon spectrum estimator which can not estimate the spatial power spectrum accurately. In contrast to existing approaches, we propose two new reconstruction-based robust adaptive beamformers by using the accurate iterative adaptive approach (IAA) spectrum to combat the covariance matrix uncertainties and the steering vector mismatches. The first one employs the low-complexity IAA (IAA-LC) algorithm to obtain the interference power estimates and reconstruct the interference-plus-noise covariance matrix (INCM) with the computational complexity further reduced. The second one reconstructs the INCM by updating the power estimates corresponding to each interference steering vector with the use of knowledge-aided IAA (IAA-KA) algorithm. The desired signal steering vector is corrected by searching for the direction corresponding to the maximum power, which circumvents the use of optimization program. Simulation results show that our proposed beamformers outperform the others and can achieve the robust performance in the cases of array model mismatches. [ABSTRACT FROM AUTHOR]

The performance of adaptive beamformers is susceptible to the steering vector mismatches and covariance matrix uncertainties. In contrast to traditional subspace methods, the proposed subspace method is robust against model mismatches. The signal-plus-interference covariance matrix (SICM) is reconstructed by projecting the enhanced covariance matrix onto the signal-plus-interference subspace which is formed using the property of covariance matrix. The array steering vector is adjusted by projecting the presumed steering vector onto the signal subspace which is structured using the major eigenvectors of the enhanced covariance matrix. The major eigenvectors are selected when the correlation coefficient between the presumed steering vector and the eigenvector exceeds a certain threshold. By combining the reconstructed SICM with the adjusted array steering vector, the proposed beamformer can provide robust performance. In comparison with many existing robust techniques, the proposed method performs well in both high and low signal-to-noise ratio scenarios. Several examples are carried out to illustrate the superiority of our method. [ABSTRACT FROM AUTHOR]

Drilled displacement (DD) piles with a screw-shaped shaft (referred to as DD piles) are installed using a continuous full thread hollow rod (without a displacement body) inserted and advanced in the soil by both a vertical force and a torque. As a type of newly developed pile, current understanding of the bearing mechanism of DD piles is unsatisfactory, which restricts their further applications in engineering. The primary aim of this paper is to study the bearing mechanism of this type of pile using a numerical method. First, a numerical model for calculating the bearing capacity of the DD piles was created and validated by a laboratory test. Then, the effects of the parameters of pile–soil interface, soil strength, and pile geometrical parameters on the bearing mechanism of the DD piles were investigated in parametric studies. The results of parametric studies show that the limit shear stress on the pile–soil interface, the friction angle of surrounding sand, screw pitch, and thread width significantly influence the bearing capacity of the DD piles, whereas the friction coefficient at the pile–soil interface and the thread thickness have little effect. Based on the results of the parametric studies, the failure mechanism of the DD piles under vertical load is analyzed. Finally, an equation for predicting the ultimate bearing capacities of helical piles based on cylindrical shear failure was used for estimating the bearing capacity of the DD piles, and the calculated results were verified with the numerical results. [ABSTRACT FROM PUBLISHER]

Secondary metabolites generated by marine fungi have relatively small molecular weights and excellent activities and have become an important source for developing drug lead compounds. The review summarizes the structures of novel small-molecule compounds derived from marine fungi in recent years; introduces representative monomers in antimicrobial, antitumor, anti-viral, and anti-neuritis aspects; and discusses their biological activities and molecular mechanisms. This review will act as a guide for further discovering marine-derived drugs with novel chemical structures and specific targeting mechanisms. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI) is a common lung disease with increasing morbidity and mortality rates due to the lack of specific drugs. Impaired alveolar fluid clearance (AFC) is a primary pathological feature of ALI. Epithelial sodium channel (ENaC) is a primary determinant in regulating the transport of Na+ and the clearance of alveolar edema fluid. Therefore, ENaC is an important target for the development of drugs for ALI therapy. However, the role of ENaC in the progression of ALI remains unclear. Inhibition of early growth response factor (EGR-1) expression has been reported to induce a protective effect on ALI; therefore, we evaluated whether EGR-1 participates in the progression of ALI by regulating ENaC-α in alveolar epithelium. We investigated the potential mechanism of EGR-1-mediated regulation of ENaC in ALI. We investigated whether EGR-1 aggravates the pulmonary edema response in ALI by regulating ENaC. ALI mouse models were established by intrabronchial injection of lipopolysaccharides (LPS). Lentiviruses with EGR-1 knockdown were transfected into LPS-stimulated A549 cells. We found that EGR-1 expression was upregulated in the lung tissues of ALI mice and in LPS-induced A549 cells, and was negatively correlated with ENaC-α expression. Knockdown of EGR-1 increased ENaC-α expression and relieved cellular edema in ALI. Moreover, EGR-1 regulated ENaC-α expression at the transcriptional level, and correspondingly promoted pulmonary edema and aggravated ALI symptoms. In conclusion, our study demonstrated that EGR-1 could promote pulmonary edema by downregulating ENaC-α at the transcriptional level in ALI. Our study provides a new potential therapeutic strategy for treatment of ALI. EGR-1 expression was increased in LPS-induced ALI mice and associated with aggravated pulmonary edema EGR-1 induced pulmonary edema relying on regulating the expression of ENaC-α at the transcriptional level by manipulating the promoter [ABSTRACT FROM AUTHOR]

With the in situ-formed [MDMAP]+ (MDMAP+ = 1-methyl-4-dimethylaminopyridine) cations as structure-directing agents, a new chain-typed iodoplumbate hybrid, i.e., [MDMAP]PbI3 (1) has been solvothermally obtained and structurally characterized. Compound 1 belongs to the Pbca (No. 61) space group and has an infinite one-dimensional (1 D) [Pb2I6]n2n− anionic chain. Interestingly, it exhibits the semiconductor behavior with the band gap of 2.82 eV, which endows it with rapid and conspicuous photocurrent response property. Presented in this work also includes its thermal stability, X-ray photoelectron spectroscopy characterization and theoretical studies. [ABSTRACT FROM AUTHOR]

The present study aimed to understand the molecular mechanism underlying the light-induced depression of photosynthetic capacity in a typically shade-tolerant species Panax notoginseng grown under different light intensities. Photosynthetic performance was declined in the low-light- and high-light-grown plants. The physiological plasticity was low, while the plasticity of morpho-anatomy traits, biomass allocation and biochemical traits was great in response to the light environment. High light enhanced the expression of genes related to reactive oxygen scavenging, pentose phosphate pathway and glycolysis. The expression of genes involved in the light reaction was suppressed in low light, along with a reduction in Rubisco activity. The expression of genes encoding Rubisco was repressed in high light. Photosynthetic capacity in low light might be inhibited by the deceleration on light reaction and by the increase of inactivated Rubisco, high-light-induced decrease of photosynthetic performance might result from the deceleration on Calvin cycle. Abbreviations:Anet, net assimilation rate; LCP, light compensation point; PQ, plastoquinone pool; LSP, light saturation point; PPFD, photosynthetic photon flux density; Ci, internal leaf CO2 concentration; Amax, maximum net photosynthesis rate; CE, carboxylation efficiency; Jmax, maximum electron transfer rate; Vcmax, maximum carboxylation efficiency; Rd, dark respiration rate; Fv/Fm, maximum quantum yield of photosystem II; ΦPSII, PSII photochemical quantum yield; qP, photochemical quenching; Fv′/Fm′, photochemical efficiency of PSII in the light; NPQ, non-photochemical quenching; Φf.d, fluorescence quenching dissipation; ΦNPQ, non-photochemical quenching dissipation; (V + A+Z), the xanthophyll cycle pigment pool; L, lutein; N, neoxanthin; β-Car, β-Carotene; SOD, superoxide dismutase; CAT, catalase; POD, peroxidase; APX, ascorbate peroxidase; MDHAR, monodehydroascorbate reductase; DHAR, dehydroascorbate reductase [ABSTRACT FROM AUTHOR]

The fine particles are considered a significant pollution problem. The wet electrostatic precipitators (ESPs) have advantages of efficient collection of the fine particles with lower pressure drop and eliminating reentrainment. The wetting properties of the collector surfaces have significantly important effect on wet ESPs’ stable and secure operation. The modified rigid collector (MRC) was modified by coating specific vinyl ester resin composites and loose glass fiber cloth over the conventional carbon steel in a certain way. The rigid collector surfaces before and after modification had been characterized by scanning electron microscopy (SEM) and interface tensiometer. The effect of operating temperatures on the wetting properties of the rigid collector surfaces before and after modification was investigated. The temperature range was 40~90 °C, and the wetting properties contained liquid holdup, surface flow rate, film rate, average film thickness, and critical saturation time. The modified rigid collector surface exhibited excellent wetting properties at the operating temperatures. The fine particles collection performance compared among the MRC, the conventional rigid collector (CRC), and the flexible collector (FC) in the wet ESPs was investigated. The effects of the applied voltage, the water film, corona power, and the specific collecting area on the fine particles collection were evaluated. The modified rigid collector provided high fine particles collection effect with lower energy and water consumption. Implications: To improve the submicron particles collection efficiency and decrease energy and water consumption, the formation of uniform water film over the collector surfaces has been widely studied. The modified rigid collector was modified by coating specific vinyl ester resin composites and loose glass fiber cloth (ERGF) over the conventional carbon steel (CCS) in a certain way. The modified rigid collector surface exhibited excellent wetting properties. The wet ESPs by the modified rigid collector exhibited significantly higher particles collection efficiency than by the conventional rigid collector. [ABSTRACT FROM AUTHOR]

Context: Cathepsin S (CTSS) activity is elevated in Sjögren's Syndrome (SS) patient tears. Objective: To evaluate longitudinal expression of tear and tissue CTSS activity relative to other disease indicators in Non-Obese Diabetic (NOD) mice. Methods: CTSS activity was measured in tears and lacrimal glands (LG) from male 1–6 month (M) NOD and 1 and 6 M BALB/c mice. Lymphocytic infiltration was quantified by histopathology, while disease-related proteins (Rab3D, CTSS, collagen 1) were quantified using q-PCR and immunofluorescence. Results: In NOD LG, lymphocytic infiltration was noted by 2 M and established by 3 M (p < 0.01). IFN-ɣ, TNF-α, and MHC II expression were increased by 2 M (p < 0.01). Tear CTSS activity was significantly elevated at 2 M (p < 0.001) to a maximum of 10.1-fold by 6 M (p < 0.001). CTSS activity in LG lysates was significantly elevated by 2 M (p < 0.001) to a maximum of 14-fold by 3 M (p < 0.001). CTSS and Rab3D immunofluorescence were significantly increased and decreased maximally in LG acini by 3 M and 2 M, respectively. Comparable changes were not detected between 1 and 6 M BALB/c mouse LG, although Collagen 1 was decreased by 6 M in LG of both strains. Conclusion: Tear CTSS activity is elevated with other early disease indicators, suggesting potential as an early stage biomarker for SS. [ABSTRACT FROM AUTHOR]