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In this paper, the oscillatory behavior of the solutions for a Parkinson's disease model with discrete and distributed delays is discussed. The distributed delay terms can be changed to new functions such that the original model is equivalent to a system in which it only has discrete delays. Using Taylor's expansion, the system can be linearized at the equilibrium to obtain both the linearized part and the nonlinearized part. One can see that the nonlinearized part is a disturbed term of the system. Therefore, the instability of the linearized system implies the instability of the whole system. If a system is unstable for a small delay, then the instability of this system will be maintained as the delay increased. By analyzing the linearized system at the smallest delay, some sufficient conditions to guarantee the existence of oscillatory solutions for a delayed Parkinson's disease system can be obtained. It is found that under suitable conditions on the parameters, time delay affects the stability of the system. The present method does not need to consider a bifurcating equation. Some numerical simulations are provided to illustrate the theoretical result. [ABSTRACT FROM AUTHOR]

Sustainability and precision are fundamental requirements for machining processes. In this study, novel energy consumption and surface roughness models are established to support the multi-objective (sustainability and precision) optimisation of machining processes. In this study, the following innovative characteristics are exhibited: (i) a physically interpretable energy consumption model is designed by considering correlations between key machining parameters and machining powers used in different machining zones; (ii) a surface roughness model is designed based on combined machine learning models, and optimised weights for the combination are achieved using the genetic algorithm; (iii) based on the energy consumption and surface roughness models, a Pareto-based multi-objective optimisation algorithm is devised to obtain optimised machining parameters. Orthogonal experiments were conducted to validate the models and algorithm. Results show that the energy consumption model reached an average absolute percentage error of only 1.7% and an R2 determination coefficient of 99.1%. In comparison with other models, the surface roughness model designed in this study achieved the best performance (the mean absolute percentage error (MAPE) reached 2.5%, and the R2 coefficient was above 95%). The Pareto optimal solution set for machining parameters was obtained efficiently. [ABSTRACT FROM AUTHOR]

The application of sustainable manufacturing technologies is the new challenge faced by enterprises, industries, and researchers under the background of supporting carbon peak and carbon neutral. This paper studies how to reduce the energy consumption of hole machining through optimizing tool path and cutting parameters simultaneously. The integrated optimization methodology can further reduce the energy consumption comparing with optimizing the tool path or cutting parameters separately. Firstly, the energy model of hole machining is established based on machine tools' energy composition, tool path planning, and process parameters. Due to the fact that tool path planning as air cutting process has big relationship with reducing energy, especially for hole group with a big proportion, the tool path of hole processing is optimized by the improved ant colony algorithm to solve the issue considering the distance from one hole to the next hole. Based on this optimized path, a multi-objective optimization model for one hole cutting parameters is established, considering the spindle speed and feed rate as the optimization variables and machining time, energy consumption, and surface roughness as the objective function. The non-dominated sorting genetic algorithm (NSGA-II) is employed to solve the multi-objective optimization problem of hole machining. Finally, the case study with 50 holes is used to testify the application of the proposed method to provide the practical energy efficiency strategy for hole group or multi-hole parts on CNC machines assisting in achieving sustainable production in manufacturing sectors. [ABSTRACT FROM AUTHOR]

There is a variety of schemes when a part with multiple features is processed in CNC machines, and hence, different feature sequencing and cutting parameter selections affect not only productivity but also energy consumption. This paper concentrates on the energy-saving strategy by optimizing the feature processing sequence and machining parameters in the part processing stage through reducing the energy consumption of the non-cutting and cutting process respectively. Firstly, the energy consumption of the cutting of parts is established using unit volume cutting energy (SEC) on cutting volume, while the normal feed and the rapid feed are established in different moving axes, respectively. Meanwhile, the detailed energy model is established considering rapid feed and general feed path in the X, Y, Z + , Z − directions for analyzing the impact of feature sorting on reducing the energy consumption of non-cutting. The non-cutting energy consumption model is established involving automatic tool change, ordinary feed, and fast feed factors. Based on the developed model, the multi-objective optimization of cutting energy consumption, machining quality, and machining time is carried out by NSGA-II algorithm, and the path optimization of empty cutting energy consumption is carried out by genetic algorithm. Finally, a cutting orthogonal experiment is executed to collect energy consumption data, analyze the data, and fit the data to establish a specific energy consumption model for each processing stage. A case study of a part with eight features is used to optimize sequencing and parameters, which shows the effectiveness and validity of the proposed method. [ABSTRACT FROM AUTHOR]

For improving energy efficiency of machining process, extensive studies focused on how to establish energy consumption model and optimize cutting parameters. However, the existing methods lack a systematic method to promote the widespread use of energy efficiency methods in industry. This paper proposes a systematic method integrating energy model, experiment design, and multi-objective optimization model. Firstly, the energy model is established considering cutting energy and non-cutting energy. Then, the orthogonal experiment is designed with the three levels of four factors of spindle speed, feed speed, cutting depth, and cutting width in the X and Y cutting directions. The data of energy consumption, surface quality, and machining time are obtained to study the effects of different cutting elements and cutting directions. Meanwhile, the standby, spindle idling, feed, SEC (specific energy consumption), material cutting, and idling feed models of the CNC machine tools are established based on the experimental data. Additionally, five sets of experimental data are tested for verifying the accuracy of the established energy consumption model, which can reach 99.4%. Finally, a multi-objective optimization model for high efficiency and energy saving of processing process is established to optimize the cutting parameters considering energy consumption, processing time, and surface quality simultaneously. Combining the case of milling with constraints including machine tool performance, tool life, processing procedures, and processing requirements, the Pareto solution set is used to solve the Pareto of the target model. Through drawing a three-dimensional needle graph and two-dimensional histogram, the optimal cutting parameter combination for rough machining and semi-finish machining is provided assisting in promoting the application of the sustainable techniques in the industry. [ABSTRACT FROM AUTHOR]

This study compares the effects of three techniques for reinforcing recycled concrete aggregate (RCA): chemical reinforcement, biological modification, and chemical-biological synergistic reinforcement. It evaluates their impact on both RCA and recycled aggregate concrete (RAC), analyzing their economic costs and environmental impacts through a life cycle assessment. The results indicate that composite reinforcement is more effective than individual methods, demonstrating the highest compressive strength and the best resistance to chloride ion penetration when RCA is replaced at a rate of 50%. Chemical reinforcement proves to be more economical, while biological modification shows less environmental impact. However, chemical-biological synergistic reinforcement requires further optimization to reduce both cost and environmental impact. This study offers valuable insights for the development of chemical-biological composite strengthening techniques and suggests avenues for cost reduction in practical applications. [Display omitted] • The chemical-biological synergistic strengthening method is studied. • The strengthening mechanism of the three strengthening techniques is revealed. • The improvement of the mechanical properties of RAC depend more on the mechanical properties and surface structure of RCA. • The cost analysis and environmental impact assessment of the three strengthening methods are carried out. [ABSTRACT FROM AUTHOR]

• An energy model is set up based on energy consumption analyses of machining processes; • NC codes are structurally evaluated and then popularised into the energy model; • A hybrid GA-ACA algorithm is designed to minimise air-cutting toolpaths to optimise the energy model. Machining processes comprise numerous energy consumption activities. Given the significance of the circular economy and manufacturing sustainability to modern societies, it is paramount to design effective methodologies to accomplish energy-efficient machining processes. With this aim, this research presents a new approach of energy consumption optimisation for machining processes based on numerical control (NC) programs. In the approach, the following innovative characteristics are exhibited: (i) An energy model is systematically established based on a detailed analysis of energy consumption activities in machining processes; (ii) NC programs for specific machining processes are assessed in detail and popularised into the energy model for instantiation; (iii) An optimisation algorithm hybridising the genetic algorithm and the ant colony algorithm is designed to minimise air-cutting toolpaths to optimise the energy model. Two case studies were conducted to validate the presented approach. The case studies revealed that the accuracy of the energy model was 95.3% of the actual energy consumption. The studies also showed that, based on the optimised energy model, the total length of air-cutting toolpaths was reduced by 43.8%, and the total machining time was diminished by 25.8%. It can be concluded that the developed approach can achieve substantial energy savings, and therefore it is highly promising to support machining industries to meet their sustainable targets. [ABSTRACT FROM AUTHOR]

Coexistence of crystals with multiple facets on an individual particle or different crystals is prevalent in real environments. However, the reduction efficiency of individual crystal facets in facet-combined system is still enigmatic. This study aimed to determine the reduction efficiencies of different facets of hematite by Shewanella oneidensis MR-1. An iron isotope tracer was used to distinguish Fe(II) produced from reduction of the combined and separate hematite {001} and {100} facets, i.e., Hem {001} nanoplates and Hem {100} nanorods. Hem {001} nanoplates was reduced 1.8 times more significantly than Hem {100} nanorods when the two facets combined, whereas Hem {001} nanoplates was reduced only 1.2 times more significantly than Hem {100} nanorods in separate reactors. Initial ~ 72% and final ~ 63% of reduced atoms from Hem {001} nanoplate demonstrated the facet-preferential reduction of hematite crystal when the facets combined. The pseudo-first-order rate constants (k) of reduced Fe(II) for Hem {001} nanoplates and {100} nanorods were 3.2 and 2.0 × 10−2 d−1, respectively. We attributed the more efficient reduction of Hem {001} nanoplates than Hem {100} nanorods to their differences in surface hydroxyl groups, surface charges, ligand-bound conformation and steric effects. These findings provide new insights into microbe-mineral interaction based on the crystal facet and the overall role of Fe oxides nanocrystals in the environments. [Display omitted] • 56Fe- and NAFe-enriched hematite facets were synthesized for tracking Fe provenance during microbially mediated reduction. • Initial and final fractions of Fe(II) produced by the preferential reduction of Hem {001} nanoplates were ~ 72% and ~ 63%. • The k values of Fe(II) generation were 3.2 × 10−2 d−1 for Hem {001} nanoplates and 2.0 × 10−2 d−1 for Hem {100} nanorods. • Preferential reduction of Hem {001} nanoplate in facet-combined system was greater than that in facet-separate system. [ABSTRACT FROM AUTHOR]

Sustainable product design is one of the key challenges for manufacturers to achieve sustainability, whereas it is not clear what products mean sustainability due to subjectivity of concept. This paper proposes a novel assessment methodology for evaluating product sustainability performance based on quantitative and qualitative information. Product sustainability performance index (PSPI) is defined to assist designers and engineers to evaluate and compare the relative sustainability performance of different product. An evaluation model is established based on six dimension sustainability elements (Environment, Economy, Society, Functionality, Manufacturability, and Reusability) in order to provide a new comprehensive sustainability assessment framework in a closed-loop life cycle system. Furthermore, the multi-level hierarchical structure based on criteria and corresponding sub-criteria is utilized in order to conduct more effective analysis. The improved fuzzy multi-criteria decision method is employed incorporating subjective judgment and objective information to determine weights of criteria and related sub-criteria in real decision-making situation. The positive-ideal and negative-ideal solutions are employed to satisfy the designers' desire to be as close as possible from the positive-ideal solutions. Sustainability performances of different manufactured products are assessed by integrating different levels sub-criteria into criteria. Illustrative example involving Bridgeport manual mill and Mori Seiki DuraVertical 5060 in three use environments is discussed to demonstrate the feasibility of the proposed methodology. [ABSTRACT FROM AUTHOR]

The demand for efficient and cost-effective anode materials in microbial fuel cells (MFCs) provides the impetus to use carbon derived from solid waste to support bacterial growth and proliferation. Here we show that the municipal sludge-derived carbon (SC) with a porous structure and abundant surface functional groups is effective in improving performance of MFCs. The SC is coated on the 3-D graphite felt (GF) surface by pyrrole electropolymerization in order to increase the surface cites that are interacted with bacteria, resulting in the formation of PPy/SC-modified GF anode. The scanning electron microscopy analysis indicates that the PPy/SC-modified GF can substantially increase anode surface area. The X-ray photoelectron spectroscopy (XPS) results suggest that the PPy/SC-modified GF anode possesses higher surface N/C ratio and higher relative contents of O C–NH 2 and O C–O functional groups than other counterpart anodes. These characteristics are essential for increasing bacterial attachment to the anode surface, electron-transfer rate and thus anode performance and power performance. The maximum power density resulting from the PPy/SC-modified GF anode was 568.5 mW m −2 (13.6 W m −3 ) increased by 1.9, 2.7 and 3.5 times as compared to the PPy/AC-modified GF anode, the PPy alone-modified GF anode and the unmodified GF anode, respectively. [ABSTRACT FROM AUTHOR]

The influences of colloidal nanoBoehmite (CNB) and colloidal nanoSiO 2 (CNS) on fly ash cement mortar hydration and microstructure development of fly ash cement pastes were investigated. The results revealed that fly ash cement hydration was accelerated by CNB and CNS at early age thus enhancing the early age strength of the materials. Although higher content of nanoparticles significantly hindered cement hydration, adding appropriate amount of CNB and CNS benefited the development of compressive strength both at early and later age. [ABSTRACT FROM AUTHOR]

Here we show that concomitant removal of phenol and nitrogen can be accomplished in a single dual-chamber microbial fuel cell (MFC) reactor, in which the two chambers are separated with an anion-exchange membrane. A series of experiments were performed with ammonium (230 NH 4 + –N mg L −1 ) and phenol (with concentrations varying from 0 to 1400 mg L −1 ) fed to the aerobic cathode chamber of the MFC. Experimental results demonstrated that no apparent inhibitory effect of phenol on the nitrifying reaction was noted even at the phenol concentration up to 600 mg L −1 . For all the experiments, simultaneous nitrification and denitrification was achieved in the MFC. In comparison to the traditional aerobic bioreactor (ABR) and the same MFC run under the open-circuit condition, the MFC reactor allowed less inhibition of nitrification to phenol exposure and higher rate of nitrogen removal. The data of bacterial analysis revealed that electrochemically active bacteria and denitrifiers in the anaerobic chamber play a significant role in electricity generation and anaerobic denitrification, respectively, while phenol-degrading bacteria, nitrifiers, and denitrifiers in the aerobic cathode chamber are responsible for phenol oxidation, aerobic nitrification and aerobic denitrification, respectively. These results imply that the MFC holds potential for simultaneous removal of phenolic compounds and nitrogen contained in some particular industrial wastewaters. [ABSTRACT FROM AUTHOR]

In this paper, a class of nonautonomous Lotka-Volterra type multispecies competitive systems with delays is studied. By employing Lyapunov functional, some sufficient conditions to guarantee the existence of almost periodic solutions for the Lotka-Volterra system are obtained. [ABSTRACT FROM AUTHOR]

Highlights: [•] Anode-biofilm ET rate differs greatly in different BES operational modes. [•] Bioelectroactive species with different formal potentials function as ET mediators. [•] The amount of available bioelectroactive species determines anode-biofilm ET rate. [•] MEC is the only feasible BES operational mode for advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

The development of sustainability assessment for machining process is considered as one of the crucial strategies to realize sustainable design and manufacturing, while existing methods focusing on environmental assessment have limits due to neglect economic and social impacts. This paper proposes an assessment approach for evaluating sustainability performance of machining process with respect to a consistent set of environmental, economic, and social criteria in order to select a machining strategy from sustainable manufacturing viewpoint. Sustainability assessment criteria are identified to compare different machining parameter alternatives; cutting noise, especially, is defined as an important criterion of social impact, and energy, lubricant oil, and cutting fluids consumption are identified as criteria of environmental impact. Additionally, the weights of criteria are determined using entropy weight approach with the advantage of objective evaluation by exploiting the useful information of data to a maximum extent. Furthermore, sustainability performance of machining process is calculated based on extension theory through utilizing correlation function between evaluated matter-element and classical field matter-element. Face milling test conducted on CNC vertical machining center not only illustrates validity of the proposed method for assisting the engineers or designers to define sustainability performance of machining process, but also proves the relationship between cutting parameters and cutting noise. [ABSTRACT FROM AUTHOR]

[Display omitted] • The existing enhancement technologies of recycled aggregate are reviewed. • The technical difficulties and research prospect of strengthening RA are analyzed. • The environmental impact and economic cost of each technology are evaluated comprehensively. With the prosperity and further development of the construction industry, the consumption of construction resources is increasing each year. Additionally, a large amount of construction waste applies great pressure on the environment. The use of construction solid waste to prepare recycled aggregate (RA) has become a hot issue worldwide. RA obtained by simple crushing of building solid waste has a series of problems, such as irregular shape, large water absorption, high crushing value and low apparent density, which limit its reapplication in concrete. In this paper, the research results of RA enhancement technologies are summarized from the aspects of the strengthening mechanism, influencing factors and improvement effect of modified recycled aggregate (mRA). At the same time, the problems existing in the current research are summarized, and some solutions are put forward for the reference of researchers. At present, the modification methods of RA mainly include physical enhancement technology, chemical strengthening technology and microbial-induced carbonate precipitation (MICP) technology. All the results show that these three kinds of aggregate strengthening technologies can improve the properties of RA, but a series of problems hinder the engineering application of mRA. The inhomogeneity of the aggregate source greatly affects the overall modification effect of RA. The utilization of aggregate separation technology should be the first step to strengthen RA. It is difficult to obtain satisfactory results using a single method. Compound enhancement is the developing direction of RA strengthening technology. [ABSTRACT FROM AUTHOR]

Abstract: Microbial reduction of insoluble iron minerals by dissimilatory iron reducing bacteria (DIRB) is an important environment process in the iron biogeochemical cycle. We reported that the bio-current generated from oxidation of organic matter by these bacteria in the presence of iron oxides can be used as an indicator for microbial dissolution of insoluble iron oxides. Bioelectrochemical experiments were conducted to investigate the effects of the specific bacteria and the phase identity of iron oxides on bio-current generation by recording the current response as a result of a poised constant potential. Experimental results indicated that the bio-current generation can be greatly enhanced by iron oxide addition under all the conditions varying in the type of pure culture or iron oxide. The increase in the bio-current was linearly correlated with the increased concentration of biogenic Fe(II) detected either by chemical analysis or cyclic voltammetry (CV) tests. This can be understood based on the proposed mechanism that the Fe(II)/Fe(III) couple functions as the electron mediator shuttling electrons from the microbes to the electrodes. [Copyright &y& Elsevier]

GC- MS analysis was performed on the coking sludge from a coking wastewater treatment plant (WWTP) to allow detailed chemical characterization of polycyclic aromatic hydrocarbons ( PAHs). The identification and characterization of the isomers of PAHs was based on a positive match of mass spectral data of their isomers with mass spectra databases or based on a comparison of electron impact ionization mass spectra and retention times of target compounds with those reference compounds. In total, 160 PAH compounds including numerous N-, O-, S-, OH-, and Cl-containing derivatives were positively identified for the first time. Quantitative analysis of target compounds was performed in the selected ion-monitoring mode using the internal standard method. The total concentrations of selected compounds in the coking sludge samples from the anaerobic tank, aerobic tank, hydrolytic tank, and secondary clarifier of the WWTP ranged from 1690 ± 585 to 6690 ± 522 mg/kg, which were much higher than those in other industrial and municipal sludges. PAHs with four and five rings were found to be the dominant compounds, and diagnostic ratios of these compounds suggested that they had the characteristics of coal combustion and pyrolysis. [ABSTRACT FROM AUTHOR]

Abstract: The effects of delays on dynamical networks and the stability analysis of time delayed systems have received a notable attention over the past decades. In this paper, the effects of delays on the oscillatory properties of a neural ring networks model are considered. The existence of oscillations for a specific type of recurrent neural network with time delays between neural interconnections is investigated. By using Chafee’s closed orbit theory, some sufficient conditions for permanent oscillations are obtained. Simple and practical criteria for selecting the range of parameters in this network model are also derived. Among other things, the solutions that we provide can be applied to various activation functions. A few computer simulations are presented to support our analysis. The present study can be applied to analyze under which conditions a ring network could be exploited as an oscillatory pattern generator. [Copyright &y& Elsevier]

Abstract: A unique one-step method for fabrication of a membraneless microbial fuel cell (MFC) cathode was developed by coating a conductive polymer onto stainless steel mesh. The resulting polypyrrole/anthraquinone-2-sulfonate (PPy/AQS) film was synthesized via electropolymerization using AQS as the dopants. The scanning electron microscopy results indicated that the PPy/AQS film was uniformly formed on the metal mesh electrode without cracks on its surface and featuring a globular structure. Being equipped with such a cathode that was able to catalyze oxygen reduction and prevent water leakage, the membraneless MFC allowed power generation over 250h and exhibited a maximum power density of 575mWm−2. Increasing film thickness seemed to result in a reduction in power performance due to the increased ohmic resistance of the cathode material and the enhanced difficulty for oxygen diffusion inside the cathode. [Copyright &y& Elsevier]

In this paper, we present new results on multistability and attractivity of second-order networks with unsupervised Hebbian-type learning component and time-varying delays. By using the properties of activation functions, we divide state space into invariant sets and establish new criteria of coexistence of equilibrium points which are exponentially stable. The attained results show that second-order synaptic interactions and learning behaviour have an important effect on the multistable convergence of the networks. Finally, numerical simulations will illustrate multistable learning dynamics of second-order networks. [ABSTRACT FROM AUTHOR]

Abstract: The Fe(III)/Fe(II) couple can play a significant role in the abiotic reduction of 2-nitrophenol (2-NP) at the cathode chamber of a microbial fuel cell (MFC). Experimental results demonstrate that Fe(II) addition to the cathode chamber contributes to a significant increase in the reaction rate of 2-NP removal and the power performance of MFC. Observed pseudo first-order rate constants and power densities are heavily dependent on the identity of the Fe(II)-complexing ligands. The Fe(II) complex coordinated with citrate results in the highest rate constant up to 0.12h−1 as compared to other organically complexed iron species including Fe(II)–EDTA, Fe(II)–acetate and Fe(II)–oxalate, and iron species uncomplexed with any organic ligands. In addition, the presence of Fe(II)–citrate species leads to a maximum volumetric power density of 1.0Wm−3, which is the highest value among those obtained with other iron species for the similar MFC system. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we discuss the existence of oscillations in a specific recurrent neural network: the 3-node network with two weight parameters and one time delay. Simple and practical criteria for fixing the range of the parameters in this network model are derived. Computer simulations are used to show typical patterns and to point out that these criteria are only sufficient conditions for such oscillations to happen. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study is to compare the performance of different membrane cathode assembly (MCA) and cloth-cathode assembly (CCA) in air-chamber microbial fuel cells (MFCs) and provide an optimum cathode configuration for MFC scaling up. Two MCAs were prepared by hot-pressing carbon cloth containing cathodic catalyst to anion exchange membrane (AEM) and cation exchange membrane (CEM), respectively. A CCA was built by coating GORE-TEX® cloth with a mixture of nickel-based conductive paint and cathodic catalyst. Under the fed-batch mode using brewery wastewater, the MFCs were compared with respect to power production, coulombic efficiency, COD removal, internal resistance and material cost. The experimental results show that CCA is a more favorable alternative than MCAs due to its easier preparation, higher maximum power density and COD removal, and lower internal resistance and cost. The optimum cathode assembly of CCA is cost-effective and mechanically robust enough to meet the important requirements for MFC scalability. [Copyright &y& Elsevier]

Abstract: This study reports a new approach of improving performance of microbial fuel cells (MFCs) by using a polypyrrole/anthraquinone-2,6-disulphonic disodium salt (PPy/AQDS)-modified anode. The immobilization of AQDS on a carbon felt anode was accomplished by electropolymerization of pyrrole while using AQDS as the dopant. The dual-chamber MFC operated with this modified anode in the presence of Shewanella decolorationis S12 showed the maximum power density of 1303mWm−2, which was 13 times larger than that obtained from the MFC equipped with an unmodified anode. Evidence from cyclic voltammerty (CV) and scanning electron microscopy (SEM) results indicated that the increase in power generation was assigned to the increased surface area of anode, the enhanced electron-transfer efficiency from the bacteria to the anode via immobilized AQDS, and an increase in the number of bacteria attached to anode. [Copyright &y& Elsevier]

Abstract: This study reports on the modification of the anode and the cathode in a dual-chamber microbial fuel cell (MFC) with a polypyrrole (PPy)/anthraquinone-2,6-disulfonate (AQDS) conductive film to boost its performance and the application of the MFC to drive neutral electron-Fenton reactions occurring in the cathode chamber. The MFC equipped with the conductive film-coated anode and cathode delivered the maximum power density of 823mWcm−2 that was one order of magnitude larger than that obtained in the MFC with the unmodified electrodes. This was resulted from the enhanced activities of microbial metabolism in the anode and oxygen reduction in the cathode owing to the decoration of both electrodes with the PPy/AQDS composite. The MFC with the modified electrodes resulted in the largest rate of H2O2 generation in the cathode chamber by the two-electron reduction of O2. The increase in the concentration of H2O2 was beneficial for the enhancement in the amount of hydroxyl radicals produced by the reaction of H2O2 with Fe2+, thus allowing an increased oxidative ability of the electro-Fenton process towards the decolorization and mineralization of an azo dye (i.e., Orange II) at pH 7.0. [Copyright &y& Elsevier]

Abstract: On-chip integration of fuel cells enables extremely compact reactor and maximizes the fuel storage volume, which is especially intriguing to applications where form factor is limited, such as wireless sensor nodes. This paper presents a serially connected monolithic fuel cell array based on planar configuration. High surface area catalysts were integrated on the chip by selective electrodeposition. An analytical model was proposed to model the electrode efficiency and to optimize the electrode dimensions. An equivalent circuit model was proposed to model the crosstalk effect between the serially connected fuel cells. Experiments were designed to verify these models. On-chip serial connection of twin-cell was successfully demonstrated for both gaseous and liquid fuels. [Copyright &y& Elsevier]

A novel Si-based micromachined electrode composed of polypyrrole (PPy)/Nafion® film and electrochemically deposited Pt nanocatalysts was prepared for microfabricated fuel cell applications. In addition to its high surface area to host nanocatalyst particles, the PPy/Nafion composite film offers good electron and proton conductivity, and the fabrication of such films is largely compatible with the micromachining process. The resulting catalyzed microelectrodes exhibit high electrochemically active surface area and high catalyst utilization. The corresponding Si-based micro membrane-electrode assembly demonstrates good cell polarization characteristics using the H2/O2 feed. [Copyright &y& Elsevier]

Abstract: A novel Si-based micromachined electrode composed of polypyrrole (PPy)/Nafion® film and electrochemically deposited Pt nanocatalysts was prepared for the microfabricated fuel cell applications. In addition to its high surface area to host nanocatalyst particles, the PPy/Nafion® composite film offers good electron and proton conductivity and the fabrication of such films is largely compatible with the micromachining process. The resulted catalyzed microelectrodes exhibit high electrochemical active surface area and high catalyst utilization. The corresponding Si-based micro membrane–electrode-assembly demonstrates good cell polarization characteristics using the H2/O2 feed. [Copyright &y& Elsevier]

Abstract: Submicron-scale silicon pillars produced by a novel lithography-free process were demonstrated to be excellent catalyst support structures for the depositions of Pt and Pt–Ru in liquid-fed microfabricated fuel cell applications. Operating conditions of the polysilicon CVD process and the etching duration were controlled in order to form the pillars with the desired dimension. The pillar-supported catalysts obtained from the electrochemical deposition exhibit good mass activity (0.220A/mg at 0.5V (vs. Ag/AgCl) for Pt–Ru) towards methanol oxidation compared to the carbon-supported counterparts. Moreover, the development of this pillar-based support structure is a step closer to the realization of the monolithic integration of a Si-based microfabricated fuel cell. [Copyright &y& Elsevier]

Abstract: By using a Liapunov functional, the conditions of existence and uniqueness of almost periodic solutions for some integrodifferential equations are obtained. [Copyright &y& Elsevier]

A set of sufficient conditions is derived for the existence of almost periodic solutions of some delay differential equations by using exponential dichotomy and fixed-point theorem. This criterion provides a method for the existence analysis of almost periodic solution of time delay systems. [Copyright &y& Elsevier]

By using the exponential dichotomy theory, this paper investigated the existence of almost periodic solutions of forced Lie´nard-type equations with time delays. A sufficient condition on the existence of almost periodic solutions for this class equation is obtained. [Copyright &y& Elsevier]

By using Lyapunov functional, the conditions of existence and uniqueness of almost periodic solutions for delay Logistic equations are obtained. [Copyright &y& Elsevier]

• Magnetic Pd/CoFe 2 O 4 nanoparticles were prepared by chemical deposition. • Metallic Pd was actively interacted with CoFe 2 O 4. • Pd/CoFe 2 O 4 particle electrodes in the 3D reactor were effective in removing 2,4-DCP. • Alkaline condition was favorable for achieving increased dechlorination performance. • These catalysts exhibit attractive stability and recyclability in long-term use. Moveable catalysts in a three-dimensional (3D) electrochemical reactor offer benefits for pollutant dechlorination because of increased active sites and mass transfer, but they suffer from difficulties in catalyst recovery. Herein, we demonstrate that magnetic Pd/CoFe 2 O 4 catalysts are highly active, durable, and recyclable when used in the electrochemical dechlorination of 2,4-dichlorophenol (2,4-DCP). Highly dispersed nano-sized Pd/CoFe 2 O 4 catalysts were successfully synthesized using an easy chemical deposition method. Tests on the effects of the initial solution pH showed that the alkaline condition was favorable for achieving increased dechlorination performance in terms of increased reaction rate and higher current efficiency. Greater amounts of surface-adsorbed atomic H (H ads *) formed and Pd with an electron-rich state as a consequence of metal-support interaction under the alkaline condition may play important roles in the effectiveness. The Pd/CoFe 2 O 4 particle electrodes in the 3D reactor were effective in removing 2,4-DCP with different concentrations. Notably, at a current density of 2.50 mA cm−2, 200 mg L−1 2,4-DCP can be dechlorinated to phenol within 30 min with current efficiency of 64.4%. The findings demonstrate that magnetic Pd/CoFe 2 O 4 catalysts hold distinct promise for application in the 3D electrochemical dechlorination process. [ABSTRACT FROM AUTHOR]

• O 2 •− was generated through the single electron transfer from structural Fe(II) in magnetite to adsorbed O 2. • Surface oxygen vacancies on magnetite accelerated electron transfer from Fe(II) to O 2. • H 2 O 2 and O 2 •−primarily contributed to As(III) oxidation. • The oxidation of As(III) occurred mainly on the magnetite surface. Magnetite is a reductive Fe(II)-bearing mineral, and its reduction property is considered important for degradation of contaminants in groundwater and anaerobic subsurface environments. However, the redox condition of subsurface environments frequently changes from anaerobic to aerobic owing to natural and anthropogenic disturbances, generating reactive oxygen species (ROS) from the interaction between Fe(II)-bearing minerals and O 2. Despite this, the mechanism of ROS generation induced by magnetite under aerobic conditions is poorly understood, which may play a crucial role in As(III) oxidation. Herein, we found that magnetite could activate O 2 and induce the oxidative transformation of As(III) under aerobic conditions. As(III) oxidation was attributed to the ROS generated via structural Fe(II) within the magnetite octahedra oxygenation. The electron paramagnetic resonance and quenching tests confirmed that O 2 •−, H 2 O 2 , and •OH were produced by magnetite. Moreover, density function theory calculations combined with experiments demonstrated that O 2 •− was initially formed via single electron transfer from the structural Fe(II) to the adsorbed O 2 ; O 2 •− was then converted to •OH and H 2 O 2 via a series of free radical reactions. Among them, O 2 •−and H 2 O 2 were the primary ROS responsible for As(III) oxidation, accounting for approximately 52 % and 19 % of As(III) oxidation. Notably, As(III) oxidation mainly occurred on the magnetite surface, and As was immobilized further within the magnetite structure. This study provides solid evidence regarding the role of magnetite in determining the fate and transformation of As in redox-fluctuating subsurface environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Delaminated MXene was incorporated into cement to improve the properties of cement composites, and its effects on the hydration process, microstructures, and mechanical properties were investigated, respectively. The investigation results showed that delaminated MXene was well-dispersed in the cement matrix and significantly reinforced the compressive strength of cement, especially when the addition is 0.01 wt%. Meanwhile, the total hydration heat of cement hydration and the quantity of hydration products were increased with the addition of delaminated MXene. In addition, the formation of HD C-S-H gel was promoted, and the microstructure of hydrated cement became more compact. [ABSTRACT FROM AUTHOR]

In situ and simultaneous remediation of a variety of pollutants in sediments remains a challenge. In this study, we report that the combination of electrocoagulation (EC) and electrooxidation (EO) is efficient in the immobilization of phosphorus and heavy metals and in the oxidation of ammonium and toxic organic matter. The integrated mixed metal oxide (MMO)/Fe anode system allowed the facile removal of ammonium and phosphorus in the overlying water (99% of 10 mg/L NH 4 +-N and 95% of 10 mg/L P disappeared in 15 and 30 min, respectively). Compared with the controls of the single Fe anode and single MMO anode systems, the dual MMO/Fe anode system significantly improved the removal of phenanthrene and promoted the transition of Pb and Cu from the mobile species to the immobile species. The concentrations of Pb and Cu in the toxicity characteristic leaching procedure extracts were reduced by 99% and 97% after an 8 hr operation. Further tests with four real polluted samples indicated that substantial proportions of acid-soluble fraction Pb and Cu were reduced (30%–31% for Pb and 16%–23% for Cu), and the amounts of total organic carbon and NH 4 +-N decreased by 56%–71% and 32%–63%, respectively. It was proposed that the in situ electrogenerated Fe(II) at the Fe anode and the active oxygen/chlorine species at the MMO anode are conducive to outstanding performance in the co-treatment of multiple pollutants. The results suggest that the EC/EO method is a powerful technology for the in situ remediation of sediments contaminated with different pollutants. • Electrocoagulation coupled with electrooxidation is effective in sediment remediation • The dual MMO/Fe anode system allows oxidation of ammonium and organic pollutants • Immobilization of phosphorus, Pb, and Cd is also achieved in the system • Electrogenerated Fe(II) and active oxygen/chlorine are the key species [Display omitted]. [ABSTRACT FROM AUTHOR]

The necessity for developing an efficient and cost-effective in situ bioremediation technology for sediments contaminated with polychlorinated biphenyls (PCBs) has prompted the application of low-voltage electrical fields to anaerobic digestion systems. Here we show that the use of a sediment-based bio-electrochemical reactor (BER) poised at a potential of − 0.50 V (vs. a standard calomel electrode, SCE) substantially enhanced the reduction of 2,3,4,5-tetrachlorobiphenyl (PCB 61) when acetate was added as a carbon source. The addition of surfactant Tween 80 to the BER further accelerated the PCB 61 transformation. The comparative study of closed- and open-circuit reactors demonstrated the enrichment conditions affecting the bacterial community structure, the dominant dechlorination metabolisms, and thus the extent, the rate and the products of the reduction of PCBs. The dominant bacterial dechlorinators detected in the BERs in the presence of acetate and Tween 80 are Dehalogenimonas , Dehalobacter , Sulfuricurvum , Dechloromonas and Geobacter , which should be responsible for PCB dechlorination. This study improves understanding of the key factors influencing dechlorination activity in sediment-based BERs polarized at a low potential, as well as the metabolic mechanisms dominating in the PCB dechlorination process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe, Cu co-doped promotes electron transfer of ORR. • Fe, Cu co-doped adjust d-band of elements. • Fe, Cu act synergistically through redox coupling. • FeCu@CN shows the remarkable stability in application of MFC. Air cathode microbial fuel cell (AC-MFC) cannot be used on a large scale because of its low oxygen reduction reaction (ORR) efficiency. Despite the fact that bimetallic catalysts can greatly enhance the oxygen reduction rate by regulating the electronic structure of the active site, the flaws of insufficient exposure of the active site and easy metal agglomeration limit its catalytic activity. Herein, we report on the preparation of a stable heteroatomic substrate using a copper material organic framework as a precursor, covered by Fe-based active sites. As a result of dipole-dipole interactions, the reduced product Fe2+ forms a weak Fe-O surface that is conducive to the adsorption of active substances. The presence of Fe0 enhances the electrical conductivity of the catalytic, thus promoting ORR efficiency. Through redox coupling, the D-band center of Fe at FeCu@CN is optimized and brought close to the Fermi level to facilitate electron transfer. Notably, FeCu@CN demonstrates a superior power density of 2796.23 ± 278.58 mW m−3, far exceeding that of Pt/C (1363.93 ± 102.56 mW m−3), in the application of microbial fuel cells (MFCs). Meanwhile, the MFC-loaded FeCu@CN maintains excellent stability and outstanding output voltage after 1000 h, which provides feasibility for large-scale application. [ABSTRACT FROM AUTHOR]

• The effect of EPS on PFS reduction and secondary mineral formation was studied. • EPS impeded PFS aggregation and contained electron shuttle, and thus can promote Fe(III) reduction by Shewanella oneidensis MR-1. • EPS can chemically reduce the Fe(III) in PFS in abiotic conditions. • The DNA and protein in EPS can be enzymatically degraded and then precipitated with Fe(II), forming vivianite. Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances (EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs (PFS) by Shewanella oneidensis MR-1 (S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite. EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(III). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(II) was 107.9, 111.0, and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail. [Display omitted] [ABSTRACT FROM AUTHOR]

The γ-Ca 2 SiO 4 (γ-C 2 S) binder is synthesized at lower temperatures, consumes less limestone, and does not require quick cooling. However, γ-C 2 S is a non-hydraulic phase. Test results of the present work showed that mortars made with γ-C 2 S binder did not setting and hardening until they were exposed to water and gaseous CO 2 , simultaneously, and could fully harden within 24 h. During hardening process, calcite (CaCO 3 ) and highly polymerized silica gels (SiO 2 ) were formed, which were responsible for the strength development. The results here provide new insight into potential means to yield prefabricated building products with γ-C 2 S binder, efficiently. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic pollutants in landfill leachate concentrate can be fastly removed using dual-anode electrochemical Fe2+/HClO system. • The generated oxidative Fe(IV) species enabled efficient coupling and polymerization of small organics. • The generation of toxic byproduct can be minimized. The strategy to mineralize dissolved organics for the decontamination of landfill leachate concentrate (LLC) is expensive. Because mineralization requires high stoichiometric ratio of oxidants (e.g., •OH) or electron transfer (i.e., energy) to the pollutant molecules. Whereas, transferring the dissolved organic pollutants into separable insoluble matters is an energy-saving strategy. Herein, we developed a dual-anode Fe2+/HClO system for removing dissolved organic pollutants in LLC through insolubilization based on oxidative coupling. In this system, the majority of dissolved organic pollutants were transferred into insoluble substances, which could be removed easily. As a result, 89.8 % of the dissolved organic carbon (DOC) in LLC was fast removed in 3 h with a low specific energy consumption (SEC, 4.0 kWh kg−1 COD and 17.6 kWh kg−1 DOC), and the formation of toxic by-products can be well controlled to total organic chlorine (TOCl) < 0.1 mg/L. The formation of insoluble substances was attributed to the oxidative coupling of organic small molecules into the macromolecular ones. This was evidenced by the generation of insoluble compounds with the larger molecular mass, and the formation of coupling or polymerization products of the model pollutant (guaiacol). The predominant mechanism was proposed that Fe(IV) was generated in the dual-anode Fe2+/HClO system, and Fe(IV) oxidized pollutants to produce organic radicals, then the organic radicals coupled and polymerized to form larger molecules and insoluble compounds. This work offers a novel electrochemical method for efficient removal of organic pollutants in LLC with minimal toxic by-products generated, and revealed the significance of oxidative coupling process in the electrochemical Fe2+/HClO system. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation (EO) can effectively reduce the degree of humification and toxicity of landfill leachate by generating highly active oxidative species in situ. However, the selective and competitive oxidation of humic acid (HA) and ammonia (NH 4 +) and the role of different oxidative species during the EO process in complex aqueous conditions remain unclear. In this study, a nanostructured tin-antimony electrode (Ti/Sb-SnO 2 NFs) was prepared and compared with three types of commercial electrodes (Ti/Ir-RuO 2 , Ti 4 O 7 , Ti/Sb-SnO 2) in terms of electrochemical properties and electrocatalytic oxidation of HA and NH 4 +. The de-humification capacity, interactive effects of HA and NH 4 + on each other's oxidation by different oxidative species, as well as the related oxidation byproducts were investigated. The differences in pollutant electrooxidation among the different electrodes were found to be insignificant. The presence of HA was found to be detrimental to NH 4 + degradation while reducing the N 2 conversion rate. Interestingly, NH 4 + initially inhibited the degradation rates of HA while promoted the degradation and reduced the accumulation of organic chlorine during the later EO process. A proposed mechanism accounts for both competitive and promotional effects for simultaneous HA and NH 4 + oxidation during the EO process. [Display omitted] • The mechanism for the competitive and promotional effects for simultaneous oxidation has been proposed. • Ammonia promoted the degradation of humic acid at the late stage via consuming reactive chlorine species. • Pre-oxidation of humic acid by reactive chlorine species is crucial for subsequent hydroxyl radical oxidation. • The reasons resulting in insufficient degradation of organic matters have been figured out. [ABSTRACT FROM AUTHOR]

Under anoxic conditions, aqueous Fe(II) (Fe(II) aq)-induced recrystallization of iron (oxyhydr)oxides changes the speciation and geochemical cycle of trace elements in environments. Oxidation of trace element, i.e., As(III), driven by Fe(II) aq -iron (oxyhydr)oxides interactions under anoxic condition was observed previously, but the oxidative species and involved mechanisms are remained unknown. In the present study, we explored the formed oxidative intermediates during Fe(II) aq -induced recrystallization of goethite under anoxic conditions. The methyl phenyl sulfoxide-based probe experiment suggested the featured oxidation by Fe(IV) species in Fe(II) aq -goethite system. Both the Mössbauer spectra and X-ray absorption near edge structure spectroscopic evidenced the generation and quenching of Fe(IV) intermediate. It was proved that the interfacial electron exchange between Fe(II) aq and Fe(III) of goethite initiated the generation of Fe(IV). After transferring electrons to goethite, Fe(II) aq was transformed to labile Fe(III), which was then transformed to Fe(IV) via a proton-coupled electron transfer process. This highly reactive transient Fe(IV) could quickly react with reductive species, i.e. Fe(II) or As(III). Considering the ubiquitous occurrence of Fe(II)-iron (oxyhydr)oxides reactions under anoxic conditions, our findings are expected to provide new insight into the anoxic oxidative transformation processes of matters in non-surface environments on earth. [Display omitted] • Anoxic oxidation of As(III) occurs during Fe(II)-induced goethite recrystallization. • The generation of Fe(IV) intermediate was firstly observed for the anoxic oxidation. • PMSO probe experiments and Mössbauer study clearly evidenced the Fe(IV) generation. • Fe isotopic tracing indicated the Fe atoms of Fe(IV) are of Fe(II) aq origin. • Transformation of Fe(II) to Fe(IV) is via a proton-coupled electron transfer ste. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP), an emerging technique recently, has been investigated in extensive studies for its ability to improve or enhance the properties of materials. This paper mainly explored the effect of MICP on the early strength and hydration products in fly ash blended cement paste (FABC) under different MICP treatment measures. Firstly, the influence of different environment on the growth of microorganism and three calcium source (CaCl 2 , Ca(CH 3 COO) 2 and Ca(NO 3) 2) on the production of calcium carbonate precipitation were investigated. The experimental results presented that the efficiency of CaCO 3 precipitation in the Ca(NO 3) 2 sample by adding bacterial solution is higher than other groups. Compared to untreated specimens, the mechanical properties of FABC paste are adversely affected by direct mixing with bacterial solution (MICP1) due to the fact that the hydration reactions of C 3 S and Ca(OH) 2 (CH) in FABC system were negatively affected as indicated by the hydration heat measurement. In contrast, the early performance of drying-immersing sample in bacterial solution (MICP2) was improved, with a maximum efficacy of 52.03%. The hydration process was facilitated in FABC paste treated with MICP2 treatment, further leading to increased formation of CH, C-S-H and AFt. Furthermore, Nanoindentation showed the HD C-S-H gel and CH were the dominant phases in MICP2 samples, and the matrix became denser with more hydration products, which also confirmed the increase in macroscopic compressive strength. The findings of this work can provide a guidance for the application of FA based on MICP method for enhancing the early strength in cementitious materials. • Compared with Ca(CH 3 COO) 2 and CaCl 2 , the efficiency of CaCO 3 precipitation in the Ca(NO 3) 2 sample is highest. • The hydration process of FABC is negatively affected by MICP1 treatment. • The MICP2 treatment can improve the early compressive strength of FA blended cement. • Nanoindentation detects more HD C-S-H gel and fewer porosity percentage. • More hydration products enhance the macroscopic and microscopic mechanical properties. [ABSTRACT FROM AUTHOR]

Electrochemical technology is a promising technique for separating ammonia from mature landfill leachate. However, the accompanying migration and transformation of coexisting pollutants and strategies for further high-value resourceful utilization of ammonia have rarely received attention. In this study, an electrochemical separation- Rhodopseudomonas palustris electrolysis cell coupled system was initially constructed for efficient separation and conversion of nitrogen in mature landfill leachate to microbial protein with synchronously tracking the transport and conversion of coexisting heavy metals accompanying the process. The results revealed that ammonia concentration in the cathode increased from 40.3 to 49.8% with increasing the current density from 20 to 40 mA/cm2, with less than 3% of ammonia transformation to NO 2 −-N and NO 3 −-N. During ammonia separation, approximately 95% of HM-DOMs (Cr, Cu, Ni, Pb, and Zn) were released into the anolyte due to humus degradation and further diffused to the cathode. A significant correlation was observed between the releases of HM-DOMs. Cu-DOMs accounted for 70.2% of the total Cu content, which was the highest proportion among the heavy metals (HMs). Among the HMs in anolyte, 57.4% of Pb, 52.5% of Ni, and 50.6% of Zn diffused to the cathode, and most of the HMs were removed in the form of hydroxide precipitations due to heavy alkaline catholyte. Compared with the open-circuit condition, the utilization efficiency of NH 4 +-N in the R. palustris electrolysis cell increased by 445.1% with 47% and 50% increases in final NH 4 +-N conversion rate and R. palustris biomass, respectively, due to bio-electrochemical enhanced phototrophic metabolism and acid generation for buffering the strong alkalinity of the electrolyte to maintain suitable growth conditions for R. palustris. [Display omitted] • Electrochemical separation-R. palustris electrolysis cell-coupled system is designed. • Both NH 4 +-N recovery and HMs transformation in landfill leachate was concerned. • HM releases from HM-DOMs show greater correlation for degradation of HA than FA. • Most HMs removed as precipitates and met the China's discharge standard other than Pb. • Microcurrent enhanced ammonia assimilation by R. palustris and buffered catholyte. [ABSTRACT FROM AUTHOR]