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41.
42.
Jun Yang Jing Na Guanbin Gao 《International Journal of Adaptive Control and Signal Processing》2019,33(12):1868-1884
This paper provides a modified model reference adaptive control (MRAC) scheme to achieve better transient control performance for systems with unknown unmatched dynamics, where an adaptive law with guaranteed convergence is introduced. We first revisit the standard MRAC system and analyze the tracking error bound by using L2‐norm and Cauchy‐Schwartz inequality. Based on this analysis, we suggest a feasible way to compensate the undesired transient dynamics induced by the gradient descent–based adaptive laws subject to sluggish convergence or even parameter drift. Then, a modified adaptive law with an alternative leakage term containing the parameter estimation error is developed. With this adaptive law, the convergence of both the estimation error and tracking error can be proved simultaneously. This enhanced convergence property can contribute to deriving smoother control signal and improved control response. Moreover, this paper provides a simple and numerically feasible approach to online verify the well‐known persistent excitation condition by testing the positive definiteness of an introduced auxiliary matrix. Comparative simulations based on a benchmark 3‐DOF helicopter model are given to validate the effectiveness of the proposed MRAC approach and show the improved performance over several other MRAC schemes. 相似文献
43.
Ningbo Gao Kailun Chen Cui Quan Shixi Wu 《International Journal of Hydrogen Energy》2021,46(40):20882-20892
A novel catalyst, Nickel supported over MCM-41 coated ceramic membrane (NMC), was developed using coating method and deposition-precipitation method and applied for steam reforming of real tar in fixed bed. The effects of reaction conditions such as Ni loading amount, reaction temperature and mass ratio of steam to tar were also studied. The good dispersion of Ni nanoparticles and the strong interaction between Ni particles and the support were identified by BET, XRD, H2-TPR and SEM/EDS, resulting in the excellent performance of NMC catalysts. Maximum tar conversion of 96.4% and H2 yield of 98.7 mmol g?1 were obtained using 20NMC with a mass ratio of steam to coal tar of 2 at 800 °C. Moreover, 20 NMC exhibited a good stability in 10 h of lifetime test and the resistance of graphitic carbon formation prone to easier regeneration of catalysts illustrated by Raman spectroscopy. It indicates that the utilization of NMC catalysts for tar steam reforming is a promising way. 相似文献
44.
Xiaohong Hao Hang Suo Hui Peng Peixing Xu Xin Gao Su Du 《International Journal of Hydrogen Energy》2021,46(3):2890-2898
Microalgae is promising to be used as feedstock resources for hydrogen production due to its high oil and grease contents. This promotes the development of extraction technology of microalgae oil. In this study, based on the Rayleigh-Plesset equation, the effects of temperature, pressure, ultrasonic power and frequency on the bubble motion of ethanol ultrasound cavitation are investigated. Subsequently, the effects of different process parameters on the extraction rate are studied using Schizochytrium sp. as raw material by stirring or ultrasonic-assisted extraction. And the composition of algae extraction oil is analyzed. The results show that the amplitude of cavitation bubbles increases with the increase of ultrasonic power and decrease of ultrasonic frequency. The extraction rate of algae oil reaches 93.76 ± 0.48% when the ultrasonic power is 150 W, the reaction time is 30 min, the temperature is 50 °C and the liquid-solid ratio is 10:1. 相似文献
45.
共同购买网络的推荐系统应用越加广泛,仅基于网络内生结构变量研究其共同购买链接的经济意义已有局限,故加入网络口碑这一外生变量,进行更全面的分析。采用了社会网络方法中指数随机图模型进行建模,主要围绕产品销售量、产品入度、差评率和评论数4个方面因素,探究其对共同购买网络中共同购买链接形成的影响。结果显示,销售量、产品入度和评论数对共同购买链接形成的影响呈正比关系,而差评率则会显著地降低产品共同购买的几率。该指数随机图构建出的共同购买网络为在线电商平台管理网络口碑和推荐系统优化设计提供有益参考。 相似文献
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48.
Ting Yu Wen Nie Zehua Hong Yihong He Jing Chen Xue Mi Shuping Yang Xiaoling Li Bilan Wang Yunzhu Lin Xiang Gao 《Advanced functional materials》2021,31(22):2100715
Normalizing the tumor-induced immune deficiency in the immunosuppressive tumor microenvironment (TME) through increasing the efficient infiltration and activation of antitumoral immunity in TME is the core of promising immunotherapy. Herein, a Cyclo(Arg-Gly-Asp-d -Phe-Lys) (RGD) peptides-modified combinatorial immunotherapy system based on the self-assembly of the nanoparticles named RGD-DMA composed of RGD-PEG-PLA, methoxy poly(ethylene glycol)-poly(lactide) (MPEG-PLA) and 1,2-Dioleoyl-3-trimethylammonium-propane (DOTAP) is used to codeliver the immunostimulatory chemokine CCL19-encoding plasmid DNA (CCL19 pDNA) and immune checkpoint ligand PD-L1 inhibitor (BMS-1). The RGD-DMA/pCCL19-BMS-1 system not only exhibited significant inhibition of tumor progression but also induced locally high concentrations of immunostimulatory cytokines at tumor sites without causing an obviously systemic inflammatory response. The immunosuppressive TME is efficaciously reshaped by the coadministration of RGD-DMA/pCCL19 and BMS-1, as indicated by the activated T lymphocytes, increased intratumoral-infiltration of mature dendritic cells (DCs), and the repolarization of macrophages from pro-tumoral M2-phenotype toward tumoricidal M1-phenotype. The upregulated PD-L1 expression at tumor sites caused by the increased IFN-γ levels after immunostimulatory gene therapy further demonstrated the synergistic effects of BMS-1 in counteracting the inhibitory role of PD-L1 expression in antitumor immunity. Therefore, the combination of immunostimulating therapy and immune checkpoint inhibitor that synergistically target multiple immune regulatory pathways demonstrates significant potential as a novel immunotherapy approach. 相似文献
49.
Yanhuizhi Feng Huai-Ling Gao Di Wu Yu-Teng Weng Ze-Yu Wang Shu-Hong Yu Zuolin Wang 《Advanced functional materials》2021,31(43):2105348
Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications. 相似文献
50.
Yunxia Liu Hui Wang Daiyan Chen Lin Gao Xin Wang Xian Jian Chunhong Mu Xin Xu Yujie Zhao Liangjun Yin 《Ceramics International》2021,47(3):3244-3251
Chemical stability of phosphors is critical to the efficiency and lifetime of the white light-emitting diodes. Therefore, many strategies have been adopted to improve the stability of phosphors. However, it is still lack of report on the improvement of thermal stability and hydrolysis resistance of phosphors by a single layer coating. Due to the high transmittance and high chemical inertness of graphene, it was coated on the surface of Sr2Si5N8:Eu2+ phosphor by chemical vapor deposition, aiming to improve its thermal stability and hydrolysis resistance. The chemical composition and microstructure of the coating were characterized and analyzed. A nanoscale carbon layer was attached on the surface of Sr2Si5N8:Eu2+ phosphor particles in an amorphous state. In coated Sr2Si5N8:Eu2+ phosphor, the oxidation degree of Eu2+ to Eu3+ was significantly suppressed. At the same time, the surface of Sr2Si5N8:Eu2+ particle turned from hydrophilic to hydrophobic after carbon coating, and consequently the hydrolysis resistance of Sr2Si5N8:Eu2+ phosphor was greatly improved. After tests at 85 °C and 85% humidity for 200 h, the carbon coated Sr2Si5N8:Eu2+ phosphor still maintained about 95% of its initial luminous intensity as compared with 35% of the uncoated. By observing the in-situ microstructure evolution of coated phosphor in air-water vapor environment, remained presence of the carbon layer even at 500 °C explained the excellent chemical stability of carbon coated Sr2Si5N8:Eu2+ phosphor in complex environment. These results indicate that a nanoscale carbon layer can be used to provide superior thermal stability and hydrolysis resistance of (oxy) nitrides phosphors. 相似文献