摘要 : In this article, the issue of sliding mode control for nonlinear stochastic Markovian jump systems with uncertain time-varying delay is investigated. Considering the system state measurements and the state-dependent disturbances are not available for feedback purposes, an observer-based adaptive control strategy is proposed. Based on the decomposition of the input matrices, the state-space representation of the system is turned into a regular form with the aid of T–S fuzzy models first. Then, a fuzzy observer system is constructed, which could be transformed into two lower order subsystems. By choosing a common linear switching surface, on which it also obtains linear sliding mode dynamics in a simple form. Further, an adaptive controller is synthesized relying on the bounded system delay information to ensure the estimated states driven on the predefined sliding surface and remain the sliding motion. Also, the stochastic stability analysis of the sliding mode dynamics is undertaken with two types of transition rates, and an interesting result reveals that the stability for the dynamics with type of uncertain transition rates may cover the completely known type. Finally, a single-link robot arm model is provided to verify the validity of the proposed method.

摘要 : Workplace accidents would incur various losses to the injured workers and their families, employers and society. This study aims to investigate the magnitude of workplace accident costs to building contractors and identify factors influencing workplace accident costs of building projects. Data were collected using multiple techniques (structured interviews, archival records and questionnaires) from 47 completed building projects in Singapore. Data were analyzed using bivariate correlation analysis and moderated regression analysis. It is found that the average direct accident costs, indirect accident costs and total accident costs of building projects account for 0.165%, 0.086% and 0.25% of contract sum, respectively. It is concluded that workplace accident costs of building projects are influenced by accident rates, project hazard level, project size, company size and the involvement of sub-contractors. The findings of this study may enhance decision makers’ understanding of financial implications of workplace accidents in their building projects and motivate them to undertake accident prevention initiatives voluntarily.

摘要 : This study was undertaken to evaluate the characteristics of household solid waste (HSW) generation and to identify opportunities and benefits for waste recycling in a typical developed city of Suzhou in East China. A four-stage systematic tracking survey of 240 households was conducted for one week in each season starting from the summer of 2011 to the spring of 2012. And the driving forces behind HSW generation were analyzed using a multiple linear regression model. Results show that Suzhou's HSW generation rate was 280.5 g/cap/day, and the annual generation of HSW reached 568 thousand tons, among which, 89.3% were compostable and recyclable waste. Education level of the household daily manager has a major impact on HSW generation rate. And other factors, such as local customs and culture, consumption patterns and residential lifestyles could also influence HSW generation. It could achieve annual economic benefit of 15.9 million RMB, reduce 32.6 million tons of CO2 equivalent emissions, and supply nearly 3500 job opportunities in Suzhou if source separation practice well. Implications of our results for HSW management in Suzhou and other Chinese cities were also discussed.

摘要 : In recent years, as an energy storage device with a fast charge and discharge speed, long cycle life, and good stability, flexible supercapacitors (SCs) have been extensively used in flexible electronic devices such as smart textiles, flexible display screens, and micro-robots. Combining the advantages of conductive materials and hydrogels, conductive polymer hydrogels have good flexibility, biocompatibility, and adjustable mechanical and electrochemical properties, which enable them to be used as electrolyte or electrode materials for flexible SCs, endowing flexible SCs with various excellent properties and meeting their various working requirements. This paper comprehensively reviews the flexible SCs based on conductive polymer hydrogels, from the design, synthesis and application aspects of conductive polymer hydrogels, the various superior functions (e.g., self-healing, high stretchability and compressibility, high toughness, electrochromic and shape memory) of flexible SCs based on conductive polymer hydrogels to different structures of flexible SCs, including fiber-shaped structures, all-in-one sandwich structures, and in-plane interdigital microstructures. Finally, we summarize the challenges faced by flexible SCs based on conductive polymer hydrogels, which provides new research directions and prospects for future development in this field.

摘要 : Long-term wastewater irrigation or solid waste disposal has resulted in the heavy metal contamination in both soil and groundwater. It is often separately implemented for remediation of contaminated soil or groundwater at a specific site. The main objective of this study was to demonstrate the hypothesis of simultaneous remediation of both heavy metal contaminated soil and groundwater by integrating the chemical immobilization and pump-and-treat methods. To accomplish the objective, three experiments were conducted, i.e., an incubation experiment was first conducted to determine how dairy-manure-derived biochar and phosphate rock tailing induced immobilization of Cd in the Cd-contaminated soils; second, a batch sorption experiment was carried out to determine whether the pre-amended contaminated soil still had the ability to retain Pb, Zn and Cd from aqueous solution. BCR sequential extraction as well as XRD and SEM analysis were conducted to explore the possible retention mechanism; and last, a laboratory-scale model test was undertaken by leaching the Pb, Zn, and Cd contaminated groundwater through the pre-amended contaminated soils to demonstrate how the heavy metals in both contaminated soil and groundwater were simultaneously retained and immobilized. The incubation experiment showed that the phosphate biochar were effective in immobilizing soil Cd with Cd concentration in TCLP (toxicity characteristics leaching procedure) extract reduced by 19.6 % and 13.7 %, respectively. The batch sorption experiment revealed that the pre-amended soil still had ability to retain Pb, Zn, and Cd from aqueous solution. The phosphate-induced metal retention was mainly due to the metal–phosphate precipitation, while both sorption and precipitation were responsible for the metal stabilization in the biochar amendment. The laboratory-scale test demonstrated that the soil amended with phosphate removed groundwater Pb, Zn, and Cd by 96.4 %, 44.6 %, and 49.2 %, respectively, and the soil amended with biochar removed groundwater Pb, Zn, and Cd by 97.4 %, 53.4 %, and 54.5 %, respectively. Meanwhile, the metals from both groundwater and soil itself were immobilized with the amendments, with the leachability of the three metals in the CaCl2 and TCLP extracts being reduced by up to 98.1 % and 62.7 %, respectively. Our results indicate that the integrated chemical immobilization and pump-and-treat method developed in this study provides a novel way for simultaneous remediation of both metal-contaminated soil and groundwater.

摘要 : To enhance the adsorption capacity and affinity of graphene oxide (GO) for heavy metals and dyes, a magnetic graphene oxide composite (MGO) was synthesized with magnetic Fe3O4 and graphene oxide and used to study the adsorption performance for the heavy metal Hg(II) and the dye methylene blue (MB). The adsorbents were characterized by XRD, FTIR, zeta potential, BET, SEM-EDS, magnetic properties, Raman and XPS analyses. Batch adsorption experiments were performed to evaluate the adsorption conditions and reusability. The results show that the as-prepared MGO had a much higher Langmuir surface area of 1259.9 m2 g−1. The kinetic data well fitted the pseudo-second order and intra-particle diffusion equations. The adsorption isotherm of MGO for Hg(II) and MB were best described by the Langmuir model with a maximum adsorption capacity of 71.3 and 306.5 mg g−1, respectively, which surpassed the adsorption capacities of many other materials. And this result was also much higher than the adsorption capacity of GO for Hg(II) and MB of only 32.7 and 216.7 mg g−1. Overall the adsorption processes of Hg(II) and MB onto MGO were controlled by intra-particle diffusion and involved some chemisorption. The thermodynamics indicated that the adsorption process of MGO for Hg(II) and MB was endothermic and spontaneous in nature. Moreover, the adsorption capacity of MGO was still over 80% of the initial saturation adsorption capacity after being used five times. Lastly, we found out that the as-synthesized MGO was efficient for Hg(II) removal from real chloralkali wastewater. Results of this work suggest that the magnetic GO nanoparticles may be a promising adsorbent for the adsorption of heavy metals and dyes from wastewater.

摘要 : In this study, an event-triggered control strategy is proposed to achieve consensus in a multi-agent system under a directed topology. The proposed control strategy utilises a piecewise continuous control law and an event-triggering function for each agent. The control law only updates at discrete event instants computed using an event-triggering function, which depends on the states of the agents at the current and outdated event instant. This control approach is first applied to a first-order system and is further extended to a second-order system. Simulation examples are presented to illustrate the efficiency of the proposed control strategy.

摘要 : Coding techniques are not only a popular strategy for information recording and communication, but also an efficient strategy for information protection. Many species in nature, such as chameleons and peacocks, demonstrate brilliant colourful appearances for camouflage, courtship or communication. The unique optical property that originates from the interaction of light with the periodic nanostructures on their surfaces, known as photonic crystals (PCs), provides an attractive candidate for coding and anti-counterfeiting. Here we present a prototype design for hiding information in photonic crystals by building a coding and encryption relationship between optical stopbands and information units. The hidden messages are protected by three different defense strategies: characteristic optical stopbands, algorithm encryption and angle-dependent encryption, which could dramatically improve the security level of the hidden information. In combination with the large coding capacity, inherent optical stability and robust fabrication process, this PC coding system has great potential for secure information storage and communication, anti-counterfeiting and massively parallelized sensors.

摘要 : Abstract Ni-rich LiNi0.8Co0.1Mn0.1O2 oxide has been modified by ultrathin Al2O3 coatings via atomic layer deposition (ALD) at a growth rate of 1.12 Å/cycle. All characterizations results including TEM, SEM, XRD and XPS together confirm high conformality and uniformity of the resultant Al2O3 layer on the surface of LiNi0.8Co0.1Mn0.1O2 particles. Coating thickness of the Al2O3 layer is optimized at ~2 nm, corresponding to 20 ALD cycles to enhance the electrochemical performance of Ni-rich cathode materials at extended voltage ranges. As a result, 20 Al2O3 ALD-coated LiNi0.8Co0.1Mn0.1O2 cathode material can deliver an initial discharge capacity of 212.8 mAh/g, and an associated coulombic efficiency of 84.0% at 0.1 C in a broad voltage range of 2.7–4.6 V vs. Li+/Li in the first cycle, which were both higher than 198.2 mAh/g and 76.1% of the pristine LiNi0.8Co0.1Mn0.1O2 without the Al2O3 protection. Comparative differential capacity (dQ/dV) profiles and electrochemical impedance spectra (EIS) recorded in the first and 100th cycles indicated significant Al2O3 ALD coating effects on suppressing phase transitions and electrochemical polarity of the Ni-rich LiNi0.8Co0.1Mn0.1O2 core during reversible lithiation/delithiation. This work offers oxide-based surface modifications with precise thickness control at an atomic level for enhanced electrochemical performance of Ni-rich cathode materials at extended voltage ranges.

摘要 : This contribution reports the biosynthesis of CuO NPs via ultrasound method using the Cystoseira trinodis extracts as an eco friendly and time saving process. The characterization of cupric oxide NPs was performed using XRD, FE-SEM, EDX, TEM, AFM, photoluminescence, UV-Vis, Raman and FT-IR spectroscopy investigations. SEM images show the spherical structure with the average crystallite size 6 nm to 7.8 nm of CuO. XRD analysis approved the formation of pure monoclinic crystallite structures of CuO NPs. These observations were confirmed by TEM analysis. The photocatalytic studies reveal the activity of the prepared CuO NPs as an efficient catalyst for the degradation of methylene blue (MB) in the presence of UV and Sunlight. CuO NPs under varying experimental parameters such as dye concentration, catalytic load, pH. The results of the in vitro biological screening effect of CuO NPs (zone of growth inhibition and minimal inhibitory concentrations) in comparison with cephalexin (as a standard compound) using the disc diffusion method was demonstrated the significant bactericidal activity against some bacteria strain including Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis ), Salmonella typhimurium (S. typhimurium), Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), and Streptococcus faecalis (S. faecalis). Furthermore, the Nps found to inhibit the activity of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals effectively. This study introduces a facile, green and low coast method for the synthesis of monoclinic CuO NPs with catalytic, antioxidant and antibacterial properties.