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Naigang Hu,Wanye Xu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.12
Reflector antennas have been widely used in various applications, such as telecommunication and radio astronomy. However, they suffer from electromagnetic (EM) performance degradation caused by structural uncertainties. In this study, a reliability-based design optimization (RBDO) method for reflector antennas that involves EM performance with adaptive kriging modeling is developed for the first time to the authors’ knowledge. An integrated structural-EM analysis procedure for antennas with material property uncertainties is introduced. Then, an adaptive kriging-based reliability analysis method is developed to alleviate the heavy computational costs. To improve kriging modeling efficiency, a priori knowledge of antennas is utilized to reduce the traditional initial sampling region. Finally, the RBDO problem is formulated as a double-loop process with a reliability index constraint. Simulation results show that the proposed method can significantly improve structural reliability with considerably less computational cost.
Naigang Wang,Cuiping Geng,Haiyun Sun,Xia Wang,Fangmin Li,Xunchao Liu 대한약학회 2019 Archives of Pharmacal Research Vol.42 No.12
Hesperetin, a major bioflavonoid in sweetoranges and lemons, exerts an anti-inflammatory effect inpulmonary diseases; however, its effect on lipopolysaccharide(LPS)-induced acute lung injury is unclear. This studyinvestigated the effect of hesperetin on LPS-induced lunginflammatory response. Mice were intratracheally instilledwith 5 mg/kg body weight LPS, and then were given hesperetinorally (10, 20, and 30 mg/kg body weight) 1 h later. Hesperetin dramatically suppressed the levels of interleukin-6 and tumor necrosis factor-α, as well as the number ofinflammatory cells in bronchoalveolar lavage fluid. Besides,it reduced lung injury, wet weight/dry weight ratio, andmyeloperoxidase and lactate dehydrogenase activities, andenhanced superoxide dismutase activity. In addition, hesperetinsignificantly downregulated the Toll-like receptor4 (TLR4) and myeloid differentiation factor 88 (MyD88)protein expression and suppressed nuclear factor-kappa B(NF-κB) activation in lung tissue. Together, these resultsindicated that the anti-inflammatory effect of hesperetin isassociated with the TLR4–MyD88–NF-κB pathway, andthat hesperetin shows therapeutic potential for LPS-inducedacute lung injury.
Naigang Hu,Yiqun Zhang,Guigeng Yang,Dongwu Yang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8
Various uncertainties existing in the manufacturing process, such as imperfect cable lengths and uncertain boundary node locations, will unavoidably deteriorate the shape precision of cable-network antennas. In this paper, an adaptive Kriging-based method is developed to investigate the global sensitivity of uncertain parameters and discover the influential factors. Existing strategies in literature usually use relative error of function values to measure the metamodel accuracy and then to determine when the sequential sampling process should be stopped. However, these indicators are mostly developed based on function values, not the sensitivity indices. Therefore, it is difficult to determine how small the indicators should be for efficiently defining an accurate metamodel for sensitivity analysis. In this paper, a straightforward sensitivity-based indicator is developed to measure the metamodel accuracy, which is defined as the weighted average of absolute errors of sensitivity values between two successive iterations. A use-controlled threshold, combined with the new indicator, can provide an automatic stopping criterion for the adaptive metamodel building process. The proposed method can provide a uniform framework to detect the convergence status effectively for problems with different uncertainties and dimensions. A numerical example and two cable-network antenna examples considering different manufacturing uncertainties are illustrated to validate the new method.
Indirect Estimation Based Active Disturbance Rejection Control for Solar Sail Station-Keeping
Jia Huang,Yuliang Bai,James D. Biggs,Naigang Cui 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.6
This paper presents an indirect estimation based active disturbance rejection control (ADRC) for solar sail station-keeping. In contrast to previous applications of ADRC to spacecraft station-keeping the proposed approach estimates the deviation of the orbit state from the reference orbit, instead of estimating the orbit state directly. Since the deviation of the orbit state varies more slowly than the state itself, the indirect estimation significantly improves the estimation accuracy and hence the station-keeping performance. Moreover, this approach enables a large control time step which is two orders of magnitude larger than those in previous applications. This is beneficial to the implementation of attitude control and power consumption in practice. In addition, errors in the optical properties of the solar sail are taken into account which is a major challenge for solar sail station-keeping that has not been considered in previous station-keeping control design. The simulation results show that the presented ADRC station-keeping is robust to errors in these optical properties.