In this brief, the problem of composite anti-disturbance tracking control for a class of strict-feedback systems with unmatched unknown nonlinear functions and external disturbances is investigated. ...A disturbance-observer-based control (DOBC) in combination with a neural network scheme and back-stepping method is developed to achieve a composite anti-disturbance controller design that provides guaranteed performance. In the proposed method, a conventional disturbance observer and a radial basis function neural network (RBFNN) are combined into a new disturbance observer to estimate the unmatched disturbances. As compared with conventional DOBC methods, the primary merit of the proposed method is that the unknown nonlinear functions are approximated using the RBFNN technique, and not regarded as part of the disturbances or estimated by a conventional disturbance observer. Hence, the proposed method can obtain higher control accuracy than the conventional DOBC methods. This advantage is validated by simulation studies.
In this technical note, the problem of finite-time output regulation control for a class of disturbed system under mismatching condition is investigated via a composite control design manner. The ...composite controller is developed by using a finite time control technique and a finite time disturbance observer (FTDO). A key idea is to design virtual control laws based on estimation values of the disturbances and the ith (1 ≤ i ≤ n - 1 where n is the order of the system) order derivative of disturbances. Finite time stability analysis for the augmented system is presented by means of Lyapunov stability theorems, which shows that the system output is regulated to zero in finite time even in the presence of mismatched disturbances. A motion control application demonstrates the effectiveness and attractive properties of the proposed method.
•Phosphoryl functionalized mesoporous silica (TBP-SBA-15) is synthesized.•The amino and phosphoryl groups are successfully grafted on SBA-15.•TBP-SBA-15 has high and rapid uranium adsorption capacity ...in broad pH range.•The U(VI) adsorption of TBP-SBA-15 is spontaneous and belongs to chemical adsorption.
Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N2 adsorption–desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10min with the sorbent dose of 1g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG0, ΔH0 and ΔS0) confirmed that the adsorption process was endothermic and spontaneous.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Condition monitoring and fault diagnosis of the bearing are essential for the smooth operation of rotating machinery. In this paper, an end-to-end intelligent fault diagnosis method for bearing ...combining one-dimensional convolutional neural network with long short-term memory network (1DCNN-LSTM) is proposed for the deficiencies of existing fault diagnosis methods. First, the proposed method takes one-dimensional fault data directly as input. Second, one-dimensional convolutional neural network (1DCNN) is used for self-adaptively extracting robust features from the original bearing signal, and more features are extracted while ensuring the validity and saliency of the extracted features by combining maximum pooling and average pooling layers to downsample features. Then, long short-term memory network (LSTM) is used to learn the temporal dependencies among features. At last, fault identification is achieved. 1DCNN-LSTM does not require any manual feature extraction, and the errors caused by reliance on expert experience and incomplete information in traditional feature extraction methods are avoided. The results show that the proposed classifier with good generalization performance not only diagnoses the category of fault quickly and accurately under different load conditions but also achieves an average fault identification accuracy of 99.95%. For its powerful learning abilities, this method can also be applied to the bearing fault diagnosis of rotating machinery in many fields.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Mixed transition metal oxides with hierarchical, porous structures, constructed from interconnected nano-building blocks, are considered promising positive electrodes for high-performance hybrid ...supercapacitors. Here we report our findings in design, fabrication, and characterization of 3D hierarchical, porous quaternary zinc-nickel-aluminum-cobalt oxide (ZNACO) architectures assembled from well-aligned nanosheets grown directly on nickel foam using a facile and scalable chemical bath deposition process followed by calcination. When tested as a binder-free electrode in a 3-electrode configuration, the ZNACO display high specific capacity (839.2Cg−1 at 1Ag−1) and outstanding rate capability (~82% capacity retention from 1Ag−1 to 20Ag−1), superior to those of binary-component NiCo2O4 and ZnCo2O4 as well as single-component Co3O4 electrode. More remarkably, a hybrid supercapacitor consisting of an as-fabricated ZNACO positive electrode and an activated carbon negative electrode exhibits a high energy density of 72.4Whkg−1 at a power density of 533Wkg−1 while maintaining excellent cycling stability (~90% capacitance retention after 10,000 cycles at 10Ag−1), demonstrating a promising potential for development of high-performance hybrid supercapacitors. Further, the unique electrode architecture is also applicable to other electrochemical systems such as batteries, fuel cells, and membrane reactors.
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•3D hierarchical porous Zn-Ni-Al-Co oxide (ZNACO) nanosheets grown directly on Ni foam is constructed for the first time.•The resultant binder-free electrodes manifest outstanding electrochemical performances with high capacity, excellent rate capability and cycling stability.•The synergetic contribution and advantageously structural features contribute to outstanding capacitive performance.•The assembled ZNACO//AC hybrid supercapacitor achieved a remarkable energy density of 72.4Whkg−1 at a power density of 533Wkg−1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Dielectric elastomer (DE) composites have attracted much attention owing to their potential applications such as flexible electronics, energy storage, artificial muscles and sensors. The underlying ...mechanism to improve the electromechanical performance of DE is believed to be the interfacial polarization between fillers and matrix. Thus, understanding the interfacial polarization mechanism is a key to design and produce high performance DE composites. Despite of extensive works on studying the effect of fillers on interfacial polarization, the role of molecular polarity of matrix is still lacking. Thus, in this study, we prepared three kinds of carbon nanotubes (CNTs)/hydrogenated nitrile butadiene rubber (HNBR) DE composites with different molecular polarity of HNBR as the matrices and a special kind of aligned CNTs as the high dielectric constant (ε′) fillers to study the role of molecular polarity of HNBR on interfacial polarization and dielectric properties of the composites. These composites exhibit the similar dispersion and filler network of CNTs in matrices, which is a precondition of this study. Interestingly, at the same content of CNTs (higher than the percolation threshold), the ε′ of these composites largely increases with the enhancement of the molecular polarity of HNBR, whereas the ε′ of these pure HNBR matrices is very close. An equivalent circuit was then established to quantitatively analyze the interfacial polarization mechanism, and it fits well with the experiment data. This study demonstrates for the first time that the higher molecular polarity of matrix leads to the stronger interfacial polarization and thus results in higher ε′ of the composites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•The interfacial cross-linking bonding between E-TiO2 and PMVS-COOH was formed.•Both dipole and interfacial polarization lead to the large increase in ε′.•The mechanical strength was ...largely improved due to good interfacial interaction.•The actuated strain at low electrical field was largely improved.
Silicone rubber (SiR) is one of the most promising dielectric elastomer (DE) materials for DE actuator, but it is still limited by low properties such as mechanical strength, dielectric constant and actuated strain at low electric fields. In this study, we report the design and preparation of SiR DE composite with simultaneously improved tensile strength, dielectric constant and actuated strain at low electric fields by introducing both polar functional group and multifunctional filler. Firstly, carboxyl groups were grafted onto polymethylvinylsiloxane (PMVS) by using a radical-mediated thiol-ene click reaction to improve the dipole polarizability. Meanwhile, epoxy group-functionalized TiO2 (E-TiO2) particles as multifunctional fillers were prepared and filled into carboxyl groups modified PMVS (PMVS-COOH). The esterification reactions between carboxyl groups of PMVS-COOH and epoxy groups of E-TiO2 results in interfacial covalent cross-linking, good interfacial interaction, and strong interfacial polarizability of E-TiO2/PMVS-COOH dielectric composites. As a result, the tensile strength largely increases from 0.33 MPa to 0.89 MPa as the content of E-TiO2 increases from 10 phr to 30 phr. The dielectric constant at 103 Hz of the composite with 30 phr E-TiO2 reaches 8.98, which is 3.3 times as reference SiR due to the simultaneously improved dipole and interfacial polarizability. The actuated strain at low electrical field (15 kV·mm−1) of the composite with 30 phr E-TiO2 reaches 3.7% without any pre-strains, which is 5.2 times than that of reference SiR. Our study provides a simple and effective strategy to simultaneously improve the mechanical, dielectric and actuated properties of SiR DE.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A derivatization method combined with high-performance liquid chromatography-fluorescence detection (HPLC-FLD) was used to evaluate the dissipation, residue distribution and risk assessment of ...emamectin benzoate in whole longan and pulp. The average recoveries were 82-111% with relative standard deviation (RSD) less than 11%. The limit of quantification (LOQ) was 0.001 mg/kg in longan and pulp. The half-lives were 3.3-4.2 days. The terminal residues in whole longan were <0.001-0.025 mg/kg applied two and three times at two levels of dosage with PHIs of 10, 14, and 21 days. The residues in whole longan had a higher quantity than those in the pulp, and the terminal residues of pulp were all lower than LOQ (0.001 mg/kg). The chronic risk of emamectin benzoate was not negligible to humans depending on ADI% value, which was higher than 1; and the acute risk was acceptable to the consumer. This study could provide guidance for the safe use of emamectin benzoate in longan and serve as a reference for the establishment of maximum residue limits (MRLs) in China.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The issue of fixed-time trajectory tracking control for the autonomous surface vehicles (ASVs) system with model uncertainties and external disturbances is investigated in this paper. Particularly, ...convergence time does not depend on initial conditions. The major contributions include the following: (1) An integral sliding mode controller (ISMC) via integral sliding mode surface is first proposed, which can ensure that the system states can follow the desired trajectory within a fixed time. (2) Unknown external disturbances are absolutely estimated by means of designing a fixed-time disturbance observer (FTDO). By combining the FTDO and ISMC techniques, a new control scheme (FTDO-ISMC) is developed, which can achieve both disturbance compensation and chattering-free condition. (3) Aiming at reconstructing the unknown nonlinear dynamics and external disturbances, a fixed-time unknown observer (FTUO) is proposed, thus providing the FTUO-ISMC scheme that finally achieves trajectory tracking of ASVs with unknown parameters. Finally, simulation tests and detailed comparisons indicate the effectiveness of the proposed control scheme.
This study established a QuEChERS high-performance liquid chromatography/tandem triple-quadrupole mass spectrometry method for determining azoxystrobin, pyraclostrobin, picoxystrobin, difenoconazole, ...chlorantraniliprole, imidacloprid, and cyantraniliprole and its metabolite (IN-J9Z38) in litchi and longan, and applied this method to the real samples. The residues in samples were extracted with acetonitrile and purified with nano-ZrO2, C18, and PSA. The samples were then detected with multireactive ion monitoring and electrospray ionization in the positive ion mode and quantified using the external matrix-matched standard method. The results showed good linearities for the eight analytes in the range of 1−100 μg/L, with correlation coefficients (r2) of >0.99. The limit of quantification was 1−10 μg/kg, and the limit of detection was 0.3−3 μg/kg. Average recovery from litchi and longan was 81−99%, with the relative standard deviation of 3.5−8.4% at fortified concentrations of 1, 10, and 100 μg/kg. The developed method is simple, rapid, efficient, and sensitive. It allowed the rapid screening, monitoring, and confirming of the aforementioned seven pesticides and a metabolite in litchi and longan.
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