Asynchronous H_∞ Control for Unmanned Aerial Vehicles: Switched Polytopic System Approach

This study is concerned with the H∞control for the full-envelope unmanned aerial vehicles (UAVs) in the presence of missing measurements and external disturbances. With the dramatic parameter variations in large flight envelope and the locally overlapped switching laws in flight, the system dynamics is modeled as a locally overlapped switched polytopic system to reduce designing conservatism and solving complexity. Then, considering updating lags of controller's switching signals and the weighted coefficients of the polytopic subsystems induced by missing measurements, an asynchronous H∞control method is proposed such that the system is stable and a desired disturbance attenuation level is satisfied. Furthermore, the sufficient existing conditions of the desired switched parameter-dependent H∞controller are derived in the form of linear matrix inequality (LMIs) by combining the switched parameter-dependent Lyapunov function method and average dwell time method. Finally, a numerical example based on a highly maneuverable technology (HiMAT) vehicle is given to verify the validity of the proposed method. © 2014 Chinese Association of Automation.

Fault detection and optimization for networked control systems with uncertain time-varying delay

The observer-based robust fault detection filter design and optimization for networked control systems （NOSs） with uncer- tain time-varying delays are addressed. The NCSs with uncertain time-varying delays are modeled as parameter-uncertain systems by the matrix theory. Based on the model, an observer-based residual generator is constructed and the sufficient condition for the existence of the desired fault detection filter is derived in terms of the linear matrix inequality. Furthermore, a time domain opti- mization approach is proposed to improve the performance of the fault detection system. To prevent the false alarms, a new thresh- old function is established, and the solution of the optimization problem is given by using the singular value decomposition （SVD） of the matrix. A numerical example is provided to illustrate the effectiveness of the proposed approach.

A rapid and operator-safe powder approach for latent fingerprint detection using hydrophilic Fe3O4@SiO2-CdTe nanoparticles

A new kind of bifunctional magnetic-fluorescent nanoparticles(NPs)with abundant carboxyls on the surface has been prepared by covalently combining glutathiose(GSH)-modified CdTe quantum dots(QDs)with Fe3O4@SiO2NPs.The silica-coated Fe3O4NPs were functionalized with amino groups by(3-aminopropyl)triethoxysilane to provide Fe3O4@SiO2-NH2NPs,which was then chemically conjugated with GSH-modified CdTe QDs to form bifunctional magnetic-fluorescent NPs,Fe3O4@SiO2-NH-CO-CdTe-QDs NPs.The properties and morphologies of Fe3O4@SiO2-NH-CO-CdTe-QDs NPs were investigated by FTIR,X-ray diffraction,transmission electron microscopy(TEM),absorption and fluorescence spectroscopy and vibrating sample magnetometry.TEM images display that Fe3O4@SiO2-NH-CO-CdTe-QDsNPs possess spherical core-shell structure with a uniform size about 50 nm.The bifunctional NPs were found to exhibit good magnetic and strong fluorescent properties favorable for their application in the detection of latent fingerprints.Furthermore,the carboxyls on the surface of NPs have good absorptions with water in air and the residues of fingerprints so as to not only avoid dust flying to protect the health of operators,but also improve the efficiency of detection.

Common-Ion Effect Triggered Highly Sustained Seawater Electrolysis with Additional NaCl Production

Developing efficient seawater-electrolysis system for mass production of hydrogen is highly desirable due to the abundance of seawater.However,continuous electrolysis with seawater feeding boosts the concentration of sodium chloride in the electrolyzer,leading to severe electrode corrosion and chlorine evolution.Herein,the common-ion effect was utilized into the electrolyzer to depress the solubility of NaCl.Specifically,utilization of 6M NaOH halved the solubility of NaCl in the electrolyte,affording efficient,durable,and sustained seawater electrolysis in NaCl-saturated electrolytes with triple production of H_(2),O_(2),and crystalline NaCl.Ternary NiCoFe phosphide was employed as a bifunctional anode and cathode in simulative and Ca/Mg-free seawater-electrolysis systems,which could stably work under 500 mA/cm^(2) for over 100 h.We attribute the high stability to the increased Na^(+)concentration,which reduces the concentration of dissolved Cl-in the electrolyte according to the common-ion effect,resulting in crystallization of NaCl,eliminated anode corrosion,and chlorine oxidation during continuous supplementation of Ca/Mg-free seawater to the electrolysis system.

Rare-earth-regulated Ru–O interaction within the pyrochlore ruthenate for electrocatalytic oxygen evolution in acidic media

Ruthenium-based catalyst is one of the most active catalysts for oxygen evolution reaction(OER)in acid media.However,the strong bonding between the Ru sites and oxygen intermediates leads to high overpotential to trigger the OER process.Hence,pyrochlore rare-earth ruthenate(RE_(2)-Ru_(2)O_(7))structures with a series of rare-earth elements(Nd,Sm,Gd,Er,and Yb)were constructed to tune the electronic structure of the Ru sites.Surface structure analysis indicated that the increase of the radius of the rare-earth cations resulted in higher content of defective oxygen(the percentage of the defective oxygen increased from 29.5% to 49.7%) in the RE_(2)Ru_(2)O_(7) structure due to the weakened hybridization of the Ru-O bond.This reduced the valence states of the Ru sites and enlarged the gap between the 4d band center and the Fermi level(E_(F))of Ru,resulting in the weakened adsorption of oxygen intermediates and the improved OER performance in acid media.Among the as-prepared ruthenium pyrochlores,Nd_(2)Ru_(2)O_(7) displayed the lowest OER onset overpotential(210 mV)and Tafel slope(58.48 mV dec^(-1)),as well as 30 times higher intrinsic activity and much higher durability than the state-of-art RuO_(2) catalyst.

单原子钌分散的TiO_(2)促进高效水氧化产过氧化氢

电催化两电子水氧化为分布式合成H_(2)O_(2)提供了一个有效的途径.但是由于缺乏合适的阳极电催化剂,通过两电子水氧化合成H_(2)O_(2)难以兼得高选择性和高产率.本文将钌单原子可控地引入到TiO_(2)中,用于促进高效水氧化产H_(2)O_(2).研究发现,钌单原子的引入优化了材料对含氧中间体的吸附,在获得高电流密度的同时促进了H_(2)O_(2)产生.具体来说,通过对钌掺杂浓度的调控,所合成催化剂在120 mA cm^(-2)的电流密度下实现了62.8%的法拉第效率,并且H_(2)O_(2)产率高达24.2μmol min-1cm^(-2)(10 min内H_(2)O_(2)积累超过400 ppm).本文不仅证明了在高电流密度下高效率产H_(2)O_(2)的可能性,同时也验证了在电催化水氧化过程中调节中间体吸附的重要性.

A comparison of the biological activities of ethyl acetate fractions from the stems and leaves of Penthorum chinense Pursh

Penthorum chinense Pursh(PCP)is a popular traditional medicinal plant in China,widely used for the treatment of a variety of liver diseases.Although it has been long recognized that the main active elements of PCP are contained in ethyl acetate fraction(EAF),little is known so far in terms of the relative effectiveness of EAF derived from the stems versus leaves of this plant.In the current study,we prepared EAF by reflux extraction and sequential extraction from the stems(SEAF)and leaves(LEAF)of PCP and tested their hepatoprotective efficacies.The extract rates and flavonoid contents of LEAF were higher than those of SEAF.EAFs(>50μg·mL^(–1))prevented lipid accumulation in cells and protected against lipotoxicity injury when the concentration exceeded 25μg·mL^(–1).More than 95%free radicals released by 2,2-diphenyl-1-picrylhydrazyl(DPPH)were eliminated by 25μg·mL^(–1)SEAF and 50μg·mL^(–1)LEAF,respectively.Further,EAFs(25μg·mL^(–1))also showed protective antioxidant effects,with the activity of LEAF being significantly higher than that of SEAF.EAFs(10 mg·mL^(–1))also showed similar unspecific bacteriostatic activity.In comparison with SEAF,LEAF contained more flavonoids and had a higher anti-oxidation capability and for these reasons we suggest it should be better for clinical use.