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This paper presents new observations of delayed AD (acceleration-derivative) controller in active vibration control and in bifurcation control of a Duffing oscillator. Based on the stability analysis of the linear delayed oscillator, it is found that combination of the two delays in acceleration feedback and velocity feedback has a significant influence on the stable region in the parameter plane of the gains. By calculating the real part of the rightmost characteristic roots of the controlled oscillator with fixed delays, it is shown that a delayed acceleration feedback with positive gain can work much better than the corresponding delayed negative acceleration feedback, which is used in classic control theory. For given feedback gains, by calculating the critical delay values, it is shown that a delayed positive acceleration feedback can result in a much larger stable delay interval than the corresponding delayed negative acceleration feedback does. As an application of these results to a delayed Duffing oscillator with acceleration-derivative feedback, a delayed positive acceleration feedback can be well used to postpone the occurrence of Hopf bifurcation in the delayed nonlinear oscillators. [ABSTRACT FROM AUTHOR]

Abstract: The Cu2O/SnO2/graphene (CSG) and SnO2/graphene (SG) nanocomposite photocatalysts were prepared by simple sol-gel growth method, and characterized by Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) measurements, respectively. The photocatalytic efficiency of catalysts were evaluated by degradation of pendimethalin under visible light irradiation (λ > 420 nm), which conformed that CSG and SG exhibited better photocatalytic activity than SnO2 or graphene alone. An effort has been made to correlate the photoelectro-chemical behavior of these samples to the rate of photocatalytic degradation of pendimethalin. The results demonstrated that the cuprous oxide addition into SG materials could greatly improve the photoelectric activity. The mechanism of photocatalytic reaction is proposed based on the energy band theory and experimental results. The CSG catalyst with higher photocatalytic activity may have great potential in various fields. [Copyright &y& Elsevier]

Abstract: This paper investigates the BIBO stability of a class of fractional-delay systems with rational orders, a stability that holds true if all the characteristic roots have negative real parts only. Based on the Argument Principle for complex functions as well as Hassard’s technique for ordinary time-delay systems, an explicit formula is established for calculating the number of characteristic roots lying in the closed right-half complex plane of the first sheet of the Riemann surface, and in turn a sufficient and necessary condition is obtained for testing the BIBO stability of fractional-delay systems. As shown in the illustrative examples, this stability criterion involves easy computation and works effectively. [Copyright &y& Elsevier]

Provides nonlinear dynamics of controlled mechanical systems. Stability of linear systems; Development of speed and system performance; Scope of hydraulic actuators.

In this work, we analyzed freshly emitted particles from ship exhaust in the Guangzhou port region before and after the implementation of a clean fuel policy. We used a single particle aerosol mass spectrometer (SPAMS) to measure the changes in the chemical compositions of single particles and evaluate the role of V as a tracer for ship emissions. Particles from high sulfur fuel (S F) oil (HS) combustion ships consisted of 54.8% elemental carbon-vanadium-sulfate (EC-V-S) and 25.0% vanadium-sulfate (V-S) particles, while particles from low S F oil (LS) combustion ships were composed of 38.7% organic carbon-sulfate (OC-S) and 28.6% elemental and organic carbon (ECOC) particles. The sulfate-containing particles exhibited a moderate decrease from 95% in HS emissions to 78% in LS emissions, which still suggests the dominant role of sulfate in LS emissions after the implementation of a clean fuel policy. The V-containing particles showed a sharp decrease from 67% in HS emissions to 14% in LS emissions along with the decrease in the relative peak area (RPA) of V, suggesting a remarkable reduction in V in ship exhaust. The count of V-containing particles in urban Guangzhou in June 2017 was generally ten times lower than that in June 2016, which was in accordance with the sharp decrease in V-containing particles in LS emissions rather than in HS emissions. Despite the decrease in V in source-oriented ship emitted particles, the ubiquitous distribution of V in particles from lower S F combustion ships suggests V is still effective as a tracer of ship emissions in port regions after the implementation of the clean fuel policy. Furthermore, the particles from LS emissions were investigated in comparison to those from gasoline vehicles (GV), diesel vehicles (DV) and coal combustion (CC) sources to better resolve ship-related particles in port regions. Unlabelled Image • Freshly emitted single particles from ship exhaust in Guangzhou port before and after clean fuel policy were comparatively studied. • The ubiquitous distribution of V in particles from lower sulfur fuel (LS) combustion ships suggests V is still an effective tracer of ship emissions. • A moderate decrease of sulfate-containing particles in LS particles indicates the persistent dominance of sulfate in ship exhaust. [ABSTRACT FROM AUTHOR]

A coupled two-ring-network with time delay is developed to avoid the weakness of a simple ring topology. The divide and conquer algorithm is used to analyze the distribution of the eigenvalues of the adjacent matrix. The stability of the equilibrium and inter-layer synchronization of the periodic dynamics are studied, and the dynamical interactions between coupled rings which lead to complicated mirror and reflection waves are further analyzed. Special attention is paid on the generalized synchronization between two rings when the adjacent matrix has repeated eigenvalues. Numerical simulations verify the theoretical results, and show that the appropriate settings of the time delay and transverse coupling can guarantee the "backup and recovery" procedure. • A coupled rings model is developed to avoid the weakness of a ring topology. • A divide and conquer algorithm is used to give distributions of the eigenvalues. • Stability of the periodic solutions is analyzed when system has repeated eigenvalues. • The inter-layer synchronization in the coupled rings is analyzed. • The proposed model can be used to achieve the "back and recovery" procedure. [ABSTRACT FROM AUTHOR]

For the stability analysis of time-delay systems, the available methods usually require the exact evaluation of some quantities. The definite integral stability method, originated from the Argument Principle or the Cauchy Theorem, is effective because it only requires a rough estimation of the testing integral over a finite interval to judge stability. However, no general rule is given in the literature for properly choosing the upper limit of the testing integral. In this paper, two simple algorithms are presented for finding the parameter-dependent critical upper limit and a parameter-independent upper limit without any restriction on the number of time delays. These results improve and complete the definite integral stability method. As illustrated by the numerical examples, the proposed algorithms work effectively and accurately. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reveal the concentration characteristics of three different types of VOCs. • Explore the drivers of photochemically consumed VOCs to generate O 3. • Quantify the effect of photochemical consumed VOCs sources on O 3 formation. Ground-level ozone (O 3) pollution has received widespread attention because its rising trend and adverse ecological impacts. However, the extremely strong photochemical reactions of its precursor volatile organic compounds (VOCs) increase the difficulty of reducing VOCs emissions to alleviate O 3. Here, we carried out a one-year comprehensive observation in two representative cities, Tianjin (TJ, Northern China) and Guangzhou (GZ, Southern China). By revealing the concentration characteristics of three different types of VOCs, i.e., initial VOCs without photochemical reaction (In-VOCs), consumed VOCs (C-VOCs), and measured VOCs after the reaction (M-VOCs), we elucidated the important role of C-VOCs in the formation of O 3. Although the overall trends were similar in both cities, the average concentration level of VOCs in GZ was 8.2 ppbv higher than that in TJ, and the photochemical loss of VOCs was greater by 2.2 ppbv. In addition, various drivers affecting O 3 generation from C-VOCs were specifically explored, and it was found that most alkenes of TJ were key substances for rapid O 3 formation compared to aromatics of GZ. Meanwhile, favorable meteorological conditions such as high temperature (T > 31 °C in TJ, and T > 33 °C in GZ), low relative humidity (56% in TJ and 45% in GZ), and stable atmospheric environment (proper pressure and gentle wind speed) also contribute to the generation of O 3. More importantly, we combined chemical kinetics and receptor model to quantify the three-type VOCs source contributions and assess the potential impact of C-VOCs sources on O 3 production, thus proposing environmental abatement technologies corresponding to the three types of VOCs. The differences in the comparison results of the three-type VOCs highlight the need to reduce O 3 pollution from C-VOCs sources, which provides insights for future clean air policies development. [ABSTRACT FROM AUTHOR]

With structural diversity of water-soluble polysaccharides, their precise quantitative analysis by phenol‑sulfuric acid method becomes more difficult and challenging. In this study, the quantification analysis of dextran and glucose in phenol sulfuric acid method was compared in this paper. When the concentration is below 90 μg/mL, the quantification of glucose is close to theoretical value, however, glucose derivatives have significantly different absorption. Later, quantitative factors of water-soluble polysaccharide in RID measurement were investigated. The optimum temperature was 40 °C and linear range was 0.3125–10.0 mg/mL in RID for dextrans (1.0–500 kDa) and glucose derivatives. Method validation studies of the RID method were further performed and compared to conventional phenol sulfuric acid method, which demonstrated that RID measurement is more reliable and satisfactory method. The intervention of water-soluble impurity in RID response should be well control below 6% (w/w). By comparison, the RID measurement could well alleviate drawbacks in phenol‑sulfuric acid method. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this work, the multi-walled carbon nanotubes-COOH (MWCNTs-COOH)/graphene (GNs)/gold nanoparticles (AuNPs) composite materials were synthesized by in situ growth of AuNPs on the surface of the MWCNTs-COOH/GNs. And then, the Bilirubin oxidase (BUD) was immobilized on the surface of the film to construct a biosensor for determination of Bilirubin. Morphology of the nanomaterials was analyzed by field-emission scanning electron microscopy, high resolution transmission electron microscopy, Brunauer–Emmett–Teller, and X-ray photoelectron spectroscopy. The performance of the biosensor was studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometric response (i–t). It was demonstrated that the nanocomposite materials exhibited enhanced fast electron transfer and excellent biocompatibility. In this assay, the MWCNTs-COOH/GNs/AuNPs composite film based biosensor showed prominently electrocatalytic activity for the detection of Bilirubin with a linear range from 1.33μM to 71.56μM and the low limit of detection (LOD) is 0.34μM based on a signal to noise ratio (S/N=3). Meanwhile, the apparent Michaelis–Menten constant (K m ) was 64.86μM. In addition, this biosensor exhibited satisfying reproducibility, stability, feasibility and fast responses. These results provide a novel way for exact detection of Bilirubin in biotechnology and clinical diagnosis, and broaden the application of graphene and carbon nanotubes in biomaterials. [Copyright &y& Elsevier]

Abstract: Well-dispersed PtPdAu ternary alloy nanoparticles were synthesized on graphene sheets via a simple one-step chemical reduction method in ethylene glycol (EG) and water system, in which EG served as both reductive and dispersing agent. The electrocatalytic activity of PtPdAu/G was tested by methanol oxidation reaction (MOR). The catalyst was further characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which indicated that the as-synthesized PtPdAu nanoparticles with alloy structures were successfully dispersed on the graphene sheets. Electrocatalytic properties of the catalyst for MOR in alkaline have been investigated by cyclic voltammetry (CV), chronoamperometry and Tafel curves. The electrocatalytic activity and stability of PtPdAu/G were superior to PtPd/G, PtAu/G and Pt/G. In addition, the anodic peak current on PtPdAu/G catalyst was proportional to the concentration of methanol in the range of 0.05–1.00M. This study implies that the prepared catalyst have great potential applications in fuel cells. [Copyright &y& Elsevier]

Through hot water extraction, protein removal and chromatographic purification, DWPP-Is was found to be the major polysaccharide present in the stem of D. wardianum. The Mn and Mw of DWPP-Is were 29.0 kDa and 98.6 kDa, respectively. Furthermore, mannose and glucose were found to be the most abundant monosaccharides in DWPP-Is. Their backbones consist of (1 → 4)- β - d -Glc p and O -acetylated (1 → 4)- β - d -Man p , which are similar to the structures of other anti-tumour Dendrobium polysaccharides. The inhibition rate of DWPP-Is treatment on SPC-A-1 cells (2 mg/mL, 72 h) reached 56.0%. Intragastric administration of DWPP-Is on A549 tumour-bearing KM mice (10 mg/mL, 0.2 mL) exhibited similar inhibition ratios to that of erlotinib hydrochloride (2 mg/mL). Moreover, the highest inhibition was observed in P-CK treatment combined with DWPP-Is, reaching an inhibition rate of 23.4%. These results suggest that DWPP-Is has the potential to be a functional agent for lung cancer prevention. • Three polysaccharide fractions were extracted from the stem of Dendrobium wardianum. • The Mn and Mw of DWPP-Is were 29.0 kDa and 98.6 kDa, respectively. • DWPP-Is was major composed of mannose and glucose. • The backbones of DWPP-Is was consist of (1 → 4)- β - d -Glc p and O -acetylated (1 → 4)- β - d -Man p. • DWPP-Is exhibited good inhibition on SPC-A-1 cells in vitro and A549 cells in vivo. [ABSTRACT FROM AUTHOR]