Search

This study is concerned with the joint estimation problem for a class of nonlinear systems with the simultaneous unknown of the system state, the parameter, as well as the input signal. A composite estimation scheme is proposed where the estimator consists of both linear and nonlinear components, under which the estimation performance is improved. The analysis and synthesis issues of the developed estimation algorithm are addressed for both the continuous‐time case and the discrete‐time case. By utilizing the Lyapunov stability theory combined with the singular value decomposition technique, sufficient conditions are established for both continuous‐time and discrete‐time cases to guarantee the convergence of the estimation error, rather than the boundedness in most of the existing literature. To facilitate the algorithm implementation in practical engineering, the Newton–Raphson method is adopted to deal with the feasibility issue for the discrete‐time case. Numerical simulations are provided for both the continuous‐ and discrete‐time cases to demonstrate the effectiveness of the proposed joint estimation strategies. [ABSTRACT FROM AUTHOR]

Cracking of concrete induced by rebar corrosion is a main cause for deterioration of reinforced concrete structures especially for those exposed to chloride environment. In all of the parameters influencing the service life of concrete structures, water‐to‐cement ratio is a very important one for it determines the resistance of concrete against chloride aggression and corrosion‐induced damage. In this paper, the parameters in corrosion process influenced by water‐to‐cement ratio of concrete (w/c) are screened all‐round which include concrete tensile strength ft, elastic modulus Ec, porous zone thickness δ0, corrosion current density icorr, critical chloride content Ccr, and chloride diffusion coefficient Dcl. The influences of w/c on the chloride penetration stage and the corrosion damage stage are studied. The first stage is expressed by Fick's second law, and the second stage is calculated using a commonly used analytical model, i.e. the thick‐walled cylinder model. It is found that with the increase of w/c, the change of some parameters (ft↑, Ccr↑, Dcl↓, icorr↓) will induce increase of the service life, while the change of the others (Ec↑, δ0↓) will induce decrease of the service life. The diffusion stage and damage stage both shorten with the increase of w/c, and thus the total service life decreases with the increase of w/c. These results show that the increase of w/c presents a negative effect on the service life of concrete structures in total. In addition, with the increase of w/c, the service life for various concrete cover thicknesses and rebar diameters decrease in a similar tendency. For probability analyses, it is found that the probability density curves under different w/c are almost symmetric but show a little left‐skewed, and the total service life for various w/c fluctuates about 0.6 to 1.0 year. [ABSTRACT FROM AUTHOR]

This study presents atmospheric‐pressure plasma as a novel catalyst‐free pretreatment method for raw wheat straw (RWS) biomass. The work explores the effects of processing parameters, such as milled particle size, moisture content of RWS, and plasma generations, on pretreatment efficiency. To understand the mechanisms behind the enhanced pretreatment efficiency, various analysis techniques were used to analyze the physical and chemical properties of RWS before and after pretreatment. The analysis reveals that plasma pretreatment significantly damages the surface smoothness of RWS and enhances the decomposition of lignocellulosic structures. These effects are primarily attributed to the reactive species generated by the pulsed discharge, rather than the accompanying UV radiation, acidification, or heating actions during plasma pretreatment. [ABSTRACT FROM AUTHOR]

Packed cartridges have been widely used in solid-phase extraction. However, there are still some drawbacks, such as they are blocked easily and the method is time-consuming. In view of the advantages of monoliths, a monolithic extraction material has been directly synthesized in a glass syringe without any gap between the monolith and syringe inner wall. The monolithic syringe was modified with graphene oxide by loading graphene oxide dispersion onto it. The content of graphene oxide and the surface topography of the monolith have been evaluated by elemental analysis and scanning electron microscopy, respectively, which confirmed the successful modification. This prepared graphene oxide-modified monolithic syringe was directly used as a traditional solid-phase extraction cartridge. As expected, it shows good permeability and excellent capability for the extraction of quaternary ammonium alkaloids. The sample loading velocity (1-6 mL/min) does not affect the recovery. Under the optimal conditions, good linearities ( R = 0.9992-0.9998) were obtained for five quaternary ammonium alkaloids, and the limits of detection and quantification were 0.5-1 and 1-2 μg/L, respectively. The proposed method was successfully applied for the analysis of quaternary ammonium alkaloids in Chinese patent medicine. [ABSTRACT FROM AUTHOR]

As a novel solid-phase extraction material, zinc sulfide nanosheets were prepared by a simple method and were used to extract flavonoids. We used scanning electron microscopy to show its nanosheet morphology and energy dispersive X-ray spectroscopy and powder X-ray diffraction to confirm its chemical and phase compositions. Coupled to a high-performance liquid chromatography, the zinc sulfide nanosheets were packed into a microcolumn and were used to extract four model flavonoids to examine their extraction ability. The parameters of sample loading and elution were investigated. Under optimized conditions, the analytical method for flavonoids was established. For the method, wide linearities from 1 to 250 μg/L and low limits of detection from 0.25 to 0.5 μg/L were obtained. The relative standard deviations for single column repeatability and column to column reproducibility were less than 7.7 and 10.4%, respectively. The established method was also used to analyze two real samples and the recoveries from 88.7 to 98.2% further proved the reliability of the method. Moreover, the zinc sulfide nanosheets have good stability and that in one column can be reused for more than 50 times. This work proves that the prepared zinc sulfide nanosheets are a good candidate as the flavonoids sorbent. [ABSTRACT FROM AUTHOR]

In this study, the stochastic sampled‐data approach is developed to deal with the H∞ control problem for a class of linear multi‐agent systems. For each agent, signals should be transmitted to the control input, including not only its own measurements, but also the output information received from the neighbour agents. The relationships of information communications between the whole multi‐agents are totally reflected by a weighted directed graph with a fixed topology structure. To the addressed problem, the author's focus is to design an output feedback controller for each agent such that, for the external energy bounded disturbances, the exponential stability in the mean square sense and interference rejection ability under consideration can be guaranteed. By assuming that the sampling period of each agent switches between two values in a probabilistic way, the stochastic sampling phenomenon is well characterised in every sampling tasks. In virtue of Lyapunov theory and semi‐definite programming method, sufficient conditions are derived to ensure the exponential stability as well as H∞ performance, and the feedback controllers are also designed by solving some certain matrix inequalities. Finally, a numerical simulation is given to demonstrate the validness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Summary: This paper is concerned with the distributed secure balancing control problem for battery energy storage systems (BESSs) in a Direct Current (DC) microgrid. The Denial‐of‐service (DoS) attacks, which appear in a random way, are taken into account during the data exchange of individual BESS units. By introducing a well‐designed compensation term, an improved distributed consensus algorithm is developed to deal with the state‐of‐charge (SOC) balance issue in the presence of randomly occurring cyber attacks. With the aid of the Lyapunov stability theory, sufficient conditions are established for the networked control system such that the balance of the SOC for each BESS unit is achieved under certain constraints. The effectiveness of the proposed balance scheme is verified by a series of illustrative simulation experiments. [ABSTRACT FROM AUTHOR]

A novel graphene oxide decorated with silver nanoparticles coating on a stainless-steel fiber for solid-phase microextraction was prepared. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid-phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4-116.3% with relative standard deviations less than 16.2%. [ABSTRACT FROM AUTHOR]

CdS nanoparticles coated on a stainless-steel wire for solid-phase microextraction was prepared. Scanning electron microscopy showed that the CdS nanoparticles clustered together to form a porous structure and X-ray diffraction confirmed that the CdS nanoparticles were the wurtzite phase. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined by the headspace method. The parameters of adsorption time, adsorption temperature, salt concentration, desorption time, and desorption temperature were investigated and optimized. For the method, wide linearity and low limits of detection from 5 to 15 ng/L were obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.2 and 12.6%, respectively. The enrichment factors were from 1155.6 to 3905.4, showing the fiber has good extraction capacity for polycyclic aromatic hydrocarbons. Moreover, the fiber can be used more than 50 times, exhibiting good stability. The established method was also used to analyze the polycyclic aromatic hydrocarbons in two real samples, and the recoveries from 82.7 to 114.2% further proved the reliability of the method. [ABSTRACT FROM AUTHOR]

The article looks at a study which is conducted for high-precision lithium isotope geochemical measurements on the newly discovered brines from drilled holes to reveal the relationship between high concentration of lithium in the potassium-rich brines and basalts. It mentions lithium was separated from water samples by drying water samples and lithium isotope analysis was performed using inductively coupled plasma mass spectrometry (ICP-MS).

The article discusses the proposed model for marine potash deposits formed in the small continental blocks of China. Topics include the importance of extremely arid events for the brine to evaporate quickly and to precipitate potash minerals in a short time, the separation and formation of sub-basins due to tectonic movements, and the development of marine-related potash deposits in marine basins of small continental blocks through the coupling of climate events and tectonic separation.

An abstract of the article "Provenance and Paleogeography of the Late Cretaceous Mengyejing Formation, Simao Basin, southeastern Tibetan Plateau," by Wang Licheng and colleagues is presented.

A zirconium(IV)‐based metal organic framework, composed of 4,4′‐biphenyldicarboxylic acid ligands and Zr6O4(OH)4 clusters, was successfully fabricated. Characterizations were performed on fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller, and thermogravimetric analysis, which confirmed that it possessed large specific surface area, high pore volume, and strong acid resistant stability. Furthermore, the prepared material containing biphenyl skeleton and a large number of Zr‐O bonds, can grasp acid herbicides especially phenoxyacetic acid herbicides with aromatic structures through π‐π interaction, hydrophobic interaction and Zr‐O‐H+ bonds. Based on these advantages, a method was developed for the determination of four phenoxyacetic acid herbicides from vegetable samples. Under the optimal conditions, wide linearities from 0.3 to 250 μg/L and low limits of detection from 0.1 to 0.5 μg/L were obtained. The intra‐ and interday relative standard deviations were 1.56‐3.92 and 5.01‐7.65%, respectively. The proposed method was applied to analyze phenoxyacetic acid herbicides residues in the tomato, cucumber, and white gourd samples. The satisfactory recoveries (86.12–103.44%) for the spiked samples in vegetable samples were achieved which demonstrated the method was an efficient pretreatment procedure and has a potential application for the trace determination of phenoxyacetic acids from a complex matrix. [ABSTRACT FROM AUTHOR]

The Mengyejing potash deposit is located in the southern port of the Simao Basin, Yunnan Province, and is hosted in mid-Cretaceous strata. The chemical compositions of fluid inclusions in halite crystals, collected from the level-610 adit in the deposit, were analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results show that the brine is of the Na-K-Mg-Ca-Cl type and has K concentrations that are distinctly higher than those of Mg and Ca, unlike normal brines associated with Cretaceous halite. The high K concentrations indicate that the degree of evaporation of the ancient Mengyejing saline lake was very high, reaching the sylvite deposition stage but rarely reaching the carnallite deposition stage. The trajectory of the H and O isotopic compositions of the brines in the halite-hosted fluid inclusions corresponds to intense evaporation, indicating that the net evaporation exceeded the net inflow of brines. These brine compositions in halite-hosted fluid inclusions were likely formed by the dissolution of previously deposited K-bearing minerals by fresh continental and/or seawater, forming a type of modified seawater, with deep hydrothermal fluids potentially supplying additional potassium. The basin likely experienced multiple seawater incursion, dissolution and redeposition events in a high-temperature environment with high evaporation rates. [ABSTRACT FROM AUTHOR]

SUMMARY: 'Candidatus Phytoplasma tritici' ('Ca. P. tritici') is an insect‐borne obligate pathogen that infects wheat (Triticum aestivum) causing wheat blue dwarf disease, and leads to yield losses. SWP12 is a potential effector secreted by 'Ca. P. tritici' that manipulates host processes to create an environment conducive to phytoplasma colonization, but the detailed mechanism of action remains to be investigated. In this study, the expression of SWP12 weakened the basal immunity of Nicotiana benthamiana and promoted leaf colonization by Phytophthora parasitica, Sclerotinia sclerotiorum, and tobacco mild green mosaic virus. Moreover, the expression of SWP12 in wheat plants promoted phytoplasma colonization. Triticum aestivum WRKY74 and N. benthamiana WRKY17 were identified as host targets of SWP12. The expression of TaWRKY74 triggered reactive oxygen species bursts, upregulated defense‐related genes, and decreased TaCRR6 transcription, leading to reductions in NADH dehydrogenase complex (NDH) activity. Expression of TaWRKY74 in wheat increased plant resistance to 'Ca. P. tritici', and silencing of TaWRKY74 enhanced plant susceptibility, which indicates that TaWRKY74 is a positive regulator of wheat resistance to 'Ca. P. tritici'. We showed that SWP12 weakens plant resistance and promotes 'Ca. P. tritici' colonization by destabilizing TaWRKY74. Significance Statement: Phytoplasma is an important group of plant pathogens, and infection of wheat (Triticum aestivum) can lead to yield reduction. Understanding the pathogenic mechanism of wheat blue dwarf phytoplasma effectors will help to improve the prevention and control strategies of wheat phytoplasma diseases. [ABSTRACT FROM AUTHOR]

The physical and geochemical character of the post‐depositional changes present in the Early‐Middle Jurassic carbonate‐dominated units (Samana Suk, Shinawari, Chiltan and Loralai formations) of the Indus Basin, Pakistan have been addressed. The study is based on 11 sections along a N‐S transect on the western margin of the Indian Plate to provide an insight into the nature of cementation and dolomitization behavior by using an integrated petrographic and geochemical analysis. The carbonates located in the northern proximity are dominated by the eogenetic signatures of hardgrounds, biogenic micritization, and iron‐containing burrows. The pattern and yellowish‐brown coloration of the burrows is distinct, and shows a positive relationship with the Fe, Si, Al, K, Mn concentrations, and meteoric phase. The transition from the Early to Middle Jurassic is marked by a correspondent increase in the dolomitization and bioturbation but its intensity decreases from north to the south. The packing index and marine phreatic environments generally increase towards the south. The planar‐s to planar‐e protodolomite and dolomite proper have particularly targeted the micritic facies and allochems, courtesy of retaining high‐magnesian calcite waters, and the geochemical analysis also reveals some dedolomitization, associated with sequence boundaries. The pore occluding cements of the Samana Suk and Chiltan formations are Fe deficient and have low Sr and Mn levels, as compared to the Shinawari Formation. The latter has an elevated concentration of Fe, Mg, Si, Al, Sr, Mn, and the Fe + Mn versus Sr relationship and Mn* values suggest that cementation dominantly occurred in the oxic‐dysoxic zones of sub‐tropical climate. [ABSTRACT FROM AUTHOR]

SUMMARY Most robust and noninteractive threshold public key encryption (PKE) schemes have only been proven secure against chosen-ciphertext attacks under the static corruption model; yet, the dynamic corruption model is more reasonable. In this paper, on the basis of bilinear groups of prime order and dual pairing vector spaces, we propose a threshold PKE scheme that is noninteractive, robust and, secure against adaptive chosen-ciphertext attacks under the dynamic corruption model without random oracles. Moreover, our scheme is shown to be more efficient than currently existing fully secure threshold PKE schemes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A zirconium(IV)‐based metal–organic framework material (MOF‐808) has been synthesized in a simple way and used for the extraction of phenoxyacetic acids in complex samples. The material has good thermal and chemical stability, large specific surface area (905.36 m²/g), and high pore size (22.18 Å). Besides, it contains a large amount of Zr‐O groups, easy‐to‐form Zr‐O‐H bond with carboxyl groups of phenoxyacetic acids, and possesses biphenyl skeleton structure, easy to interact with compounds through π‐π and hydrophobic interactions. These characteristics make the material very suitable for the extraction of certain compounds with a high extraction efficiency and excellent selectivity. The extraction conditions were optimized, and then an analytical method was successfully established and applied for analysis of actual samples. The solid‐phase extraction method based on prepared material had a wide linear range of 0.2–250 μg/L and a low detection limit of 0.1–0.5 μg/L for four phenoxyacetic acid compounds including 2,4‐dichlorophenoxyacetic acid, 2‐(2,4‐dichlorophenoxy) propionic acid, 4‐chlorophenoxyacetic acid, and dicamba. The relative standard deviations of intra‐ and interday precision were 1.8–3.8 and 4.3–6.9%, and the recoveries after spiking were between 77.1 and 109.3%. The results showed that the material is a desired substituent for the extraction of compounds with benzene ring structure containing carboxyl groups. [ABSTRACT FROM AUTHOR]

Abstract: A new three‐dimensional graphene oxide‐wrapped melamine foam was prepared and used as a solid‐phase extraction substrate. β‐Cyclodextrin was fabricated onto the surface of three‐dimensional graphene oxide‐wrapped melamine foam by a chemical covalent interaction. In view of a specific surface area and a large delocalized π electron system of graphene oxide, in combination with a hydrophobic interior cavity and a hydrophilic peripheral face of β‐cyclodextrin, the prepared extraction material was proposed for the determination of flavonoids. In order to demonstrate the extraction properties of the as‐prepared material, the adsorption energies were theoretically calculated based on periodic density functional theory. Static‐state and dynamic‐state binding experiments were also investigated, which revealed the monolayer coverage of flavonoids onto the β‐cyclodextrin/graphene oxide‐wrapped melamine foams through the chemical adsorption. 1H NMR spectroscopy indicated the formation of flavonoids–β‐cyclodextrin inclusion complexes. Under the optimum conditions, the proposed method exhibited acceptable linear ranges (2–200 μg/L for rutin and quercetin‐3‐O‐rhamnoside; 5–200 μg/L for quercetin) with correlation coefficients ranging from 0.9979 to 0.9994. The batch‐to‐batch reproducibility (n = 5) was 3.5–6.8%. Finally, the as‐established method was satisfactorily applied for the determination of flavonoids in Lycium barbarum (Goji) samples with relative recoveries in the range of 77.9–102.6%. [ABSTRACT FROM AUTHOR]

A new polyethylene glycol/graphene oxide composite material bonded on the surface of a stainless-steel wire was used for solid-phase microextraction. The layer-by-layer structure increased the adsorption sites of the novel fiber, which could facilitate the extraction of trace compounds. The polyethylene glycol/graphene oxide was characterized by Fourier transform infrared spectroscopy and elemental analysis, which verified that polyethylene glycol was successfully grafted onto the surface of graphene oxide. The performance of the polyethylene glycol/graphene oxide coated fiber was investigated for phenols and phthalate esters coupled with gas chromatography with flame ionization detection under the optimal extraction and desorption conditions, and the proposed method exhibited an excellent extraction capacity and high thermal stability. Wide linear ranges were obtained for the analytes with good correlation coefficients in the range of 0.9966-0.9994, and the detection limits of model compounds ranged from 0.003 to 0.025 μg/L. Furthermore, the as-prepared fiber was used to determine the model compounds in the water and soil samples and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

In the initial phase of this study, graphene oxide (GO)/silica was fabricated by assembling GO onto the silica particles, and then gold nanoparticles (GNPs) were used to modify the GO/silica to prepare a novel stationary phase for high-performance liquid chromatography. The new stationary phase could be used in both reversed-phase chromatography and hydrophilic interaction liquid chromatography modes. Good separations of alkylbenzenes, isomerides, amino acids, nucleosides, and nucleobases were achieved in both modes. Compared with the GO/silica phase and GNPs/silica phase, it is found that except for hydrophilicity, large π-electron systems, hydrophobicity, and coordination functions, this new stationary phase also exhibited special separation performance due to the combination of 2D GO with zero-dimensional GNPs. [ABSTRACT FROM AUTHOR]