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In this article, a frequency-domain approach is developed to deal with the global consensus problem for a class of general second-order multiagent systems (MASs) subject to actuator saturations. By employing the describing function and the generalized Nyquist criterion, the global consensus problem is thoroughly investigated for both undirected and directed topologies. First, the describing function is introduced to characterize the actuator saturations in the s -plane, and the inherent representation error is quantitatively analyzed from a frequency-domain perspective. Then, by means of the Kronecker product, the addressed consensus problem of the MAS is transformed into a corresponding stability analysis problem for a certain multi-input-multi-output (MIMO) system and, consequently, the generalized Nyquist criterion for MIMO systems is exploited to derive the condition for the global consensus of the MAS where the impact from the actuator saturation is explicitly reflected. Finally, numerical simulations are provided to illustrate the validity of the proposed theoretical result.

Quantitatively studying the biodistribution and transformation of nanomaterials is of great importance for nanotoxicological evaluation. Recently, laser ablation inductively coupled plasma mass spectrometry has been employed to distinguish nanoparticles (NPs) with their dissolved ions in biological samples. The principle of the proposal is based on a hypothesis that the intact NPs sampled by laser ablation will generate discrete sharp pulses of signals in ICP-MS measurement, being totally different from the continuous, relatively lower signals generated by ions. However, it is still a controversy whether NPs could maintain their intactness during the laser ablation. This work found a way to exactly determine the number of NPs sampled for each LA-ICP-MS measurement. It made possible to reveal the signal profile of a single NP in LA-ICP-MS analysis. The results suggest that AuNR, AgNP and TIO2 NP were broken into much smaller secondary NPs during the laser ablation, therefore generating continuous signals in the analyzer. There was a certain probability that the fragmentation of large-sized NP or multiple NPs by laser ablation was not sufficient, leaving some NPs unbroken or some secondary NPs with relatively large sizes to generate discrete pulses of signals in the analyzer. When the intactness of NPs during laser ablation cannot be assured, it is impossible to determine the attribution of mass spectrum signals. These findings compromise the reliability of distinguishing NPs from their dissolved ions by LA-ICP-MS.

Rotating machinery plays an important role in large-scale equipment. The fault diagnosis of rotating machinery is of great significance and can increase industrial safety. Up until now, most existing fault diagnosis techniques have been proposed under the condition that only a single fault will occur at the same time. However, in industrial applications, compound faults are more common to take place due to the tight coupling of different components. To diagnosis compound faults accurately is of great significance to the safe operation of industrial equipment. A fused imbalance learning method is proposed in this article exploiting the nonlinear-mapping ability of neural networks. The dimensionless parameterization combined with time–frequency transformation method is utilized to extract data features and construct different evidence sources. Basic probability assignment with nested structure is generated from a novel weighted extreme learning machine based on sensitivity analysis. Evidence combination is implemented to obtain a final inference about the compound-fault class. Experiments are conducted on a large rotating machinery fault diagnosis experimental platform. Both single faults and compound faults in bearings and wheel gears of the large rotating machinery are considered. Experimental results illustrate the effectiveness of the proposed method.

In this paper, a novel pectin gel-casting method was developed to prepare porous MgAl2O4 ceramics using MgO and Al2O3 powders as raw materials and ficus pumila seeds as the gel source. The effects of pectin content on the properties of MgAl2O4 porous ceramics, such as phase composition, microstructural characteristics, apparent porosity, bulk density, compressive strength, and thermal conductivity, were investigated. The results showed that the linear shrinkage of the samples was about 5%, indicating a near-net shape method. With the increase of pectin content, the porosity of porous MgAl2O4 ceramics increased significantly. The prepared MgAl2O4 porous ceramics with different pectin contents showed high apparent porosity of 58.7–70.1%, low thermal conductivity of 0.328–0.840 W/(mK), and relatively high compressive strength of 0.27–2.45 MPa. The proposed method as a near-net shape forming method provided a novel feasible gel-casting method to fabricate other porous ceramics.

In this work, the CO2 capture performance of polyamidoamine (PAMAM) dendrimer functionalized cellulose nanocrystals (CNCs) of different generations (CNC-G1 ~ G4) was evaluated under dry conditions at 25–45 °C by thermogravimetric analysis. Compared with bare CNCs and CNC-derivatives, including carboxylated CNCs (CNC-COOH) and aminated CNCs (CNC-NH2), the PAMAM dendrimer functionalized CNC-G1 ~ G4 showed higher CO2 capture capacity under different dry conditions, demonstrating the enhanced CO2 capture performance by the PAMAM dendrimer structure on the CNCs. The second generation of PAMAM functionalized CNCs (CNC-G2) exhibited a CO2 capture capacity of 13.31 ± 0.38 mg/g at 25 °C, 9.64 ± 0.60 mg/g at 35 °C, and 9.18 ± 1.27 mg/g at 45 °C, respectively, prevailing among all the samples. Both pseudo-first-order and pseudo-second-order kinetic models were used to fit the adsorption kinetics, while the latter gave better fitting to experimental data. The activation energy obtained from the pseudo-second-order kinetic model was 55.67 kJ/mol for CO2 capture on CNC-G2, indicating an adsorption mechanism of dominant physisorption with slight chemisorption for CO2 capture. The FTIR spectra of CNC-G2 before and after CO2 adsorption–desorption cycle at 45 °C evidenced the formation of ammonium carbamate during CO2 capture, contributing to the high tolerance of CO2 desorption under the subsequent drier conditions (95 °C in N2 gas flow).

China is rich in shale gas resources and has broad prospects for development. However, the quality of shale gas resources in China is different from that in the United States, so independent unique technologies are urgently required in China. In this regard, PetroChina has carried out theoretical and technical researches systematically on shale gas in Longmaxi Formation in southern Sichuan according to its geology-engineering characteristics. Guided by the “three-control” theory for marine shale gas enrichment and high yield (i.e. sedimentary diagenesis controls reservoir, preservation conditions control accumulation, and continuous thickness of Type I reservoir controls production), six key exploration and development technologies in southern China have been innovatively developed for marine shale gas which experienced multi-stage tectonic evolution. The technologies include comprehensive geological evaluation technology, development optimization technology, optimal and fast drilling technology for horizontal well, volume fracturing technology for horizontal well, factory-like operation technology, and efficient clean production technology. These technologies have enabled the large-scale commercial recovery of shale gas. By the end of 2019, PetroChina had obtained proved geological reserves of 1.06 × 1012 m3, had built production capacity of 10 × 109 m3, and had cumulative gas production of 20 × 109 m3 in southern Sichuan. The remarkable results of application are of great significance for vigorously developing shale gas industry to reduce external dependence, ensure national energy security, and realize the strategy of “ecological priority and green development".

Social relationships are critical to the group decision-making (GDM) process, especially for large-scale scenarios. Conventional GDM models have several drawbacks when applied to large-scale GDM problems. In this paper, we propose an evidential three-way theoretic model for large-scale group decision analysis based on the introduction of ego networks. A similarity matrix of all individuals is obtained after ego network generation via social network feature extraction. Rough and smooth detection are then conducted in the framework of three-way decisions. Specifically, the degree of organizational influence is analyzed based on the generated basic probability assignments (BPAs), and the individuals are divided into several organizations. After an opinion collection process, preference evolution is implemented via a social influence network (SIN) technique and a fuzzy preference relation (FPR) model. Then, the global final scores of all the alternatives are obtained using an aggregation process. Finally, we conduct a simulation experiment to illustrate the entire procedure. Based on a comparison of related methods, we believe that the proposed method can reasonably solve real-world large-scale group decision-making (LSGDM) problems and has good practicability and effectiveness.

The classical Darcy’s law cannot effectively describe the microscopic flow rules of shale gas. In addition, conducting gas transport experiments in nanopores is difficult, and the correctness of th...

The microstructure evolution and the pitting corrosion resistance of a supermartensitic stainless steel after deep cryogenic treatment process were clarified through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM) and electrochemical methods. The results showed that the microstructure of supermartensitic stainless steel mainly consisted of reversed austenite, tempered martensite, and M23C6 carbides after tempering. The deep cryogenic treatment promoted the refinement of the martensite laths and the precipitation of the carbides in comparison with the traditional process. TEM analysis indicated that the segregation of Si atoms at the boundary was found at the interface between carbide and martensite. The pitting corrosion potential of the specimens subjected to deep cryogenic treatment decreased with the elevated tempering temperature, and the lowest pitting corrosion potential was found at the tempering temperature of 650 °C. The sensitivity of the pitting corrosion potential was attributed to the precipitation of M23C6 carbides and Si atoms segregation. Si atoms segregation engendered the formation of Cr-depleted zone near M23C6 and impeded the recovery of Cr-depleted zone.

Magneto-electric materials with low loss have prospective applications in microwave systems as they enable miniaturization and broadband impedance matching. Two example applications are antennas and filters in sub-6G communication systems. Therefore, high-accuracy and wideband testing are critical for magneto-electric materials, whose complex permittivity and permeability are usually dependent on frequency. In this paper, the mutual interference between the electric and magnetic field within magneto-electric material samples was seriously considered. It was found that the results calculated with the original perturbation formula were overestimated when the sample size was not so small or higher-order modes are used, especially when the electric or magnetic field is perpendicular to the material under test. Two methods based on perturbation, namely the iteration method and the multi-state method are proposed to reduce the impact of the mutual interference, which have been proven to be direct and effective through theoretical analysis and experiments. Finally, several rod-shaped specimens processed from several standard dielectric materials (PTFE, fused silica, Al2O3) and synthesized magneto-electric materials were measured in a fabricated cavity with a vector network analyzer. Experimental results show that the results obtained by the modified formula are more accurate than those obtained by the original formula, and are in good agreement with the data measured by other methods.

This paper is concerned with the finite-horizon H ∞ filtering and fault isolation problems for a class of discrete time-varying systems subject to possible actuator fault and sensor saturation. A s...

In this article, a new event-triggered $H_{i}/H_{\infty }$ optimization fault detection (FD) scheme is proposed for linear discrete time systems. A linear discrete time system with varying sampling periods is first presented to describe the dynamics of an event-triggered system. Based on this, an observer-based fault detection filter (FDF) is constructed as an event-triggered residual generator so that the generated residual signal is completely decoupled from the event-triggered transmission error. The design of event-triggered FDF is formulated as a multiobjective optimization problem denoted by $H_{i}/H_{\infty }$ and an optimal solution can be obtained by recursive calculation of Riccati equations. In addition, an event-triggered residual evaluation strategy is also presented. Comparing with the existing event-triggered FD schemes, the major contribution of this article is to decouple the residual signals from the event-triggered transmission errors completely and, consequently, the FD performance can be improved significantly. Moreover, an optimal tradeoff between the robustness of residual to unknown input and the sensitivity of residual to fault is achieved in the sense of $H_{i}/H_{\infty }$ optimization, while the design of FDF and event generator can be carried out independently. To demonstrate the effectiveness of the proposed method, a vehicle lateral dynamic system is used as a simulation example.

Exploring new structures of synthetic two-dimensional (2D) nanomaterials plays a crucial role in the development of such burgeoning materials toward more appealing functions and innovative potentia...

So far, problems of intermittent fault (IF) detection and detectability have not been fully investigated in the multivariate statistics framework. The characteristics of IFs are small magnitudes and short durations, and consequently traditional multivariate statistical methods using only a single observation are no longer effective. Thus in this paper, moving average T 2 control charts (MA-TCCs) with multiple window lengths, which simultaneously employ a bank of MA-TCCs with different window lengths, are proposed to address the IF detection problem. Methods to reduce false/missing alarms and infer the IFs’ appearing and disappearing time instances are presented. In order to analyze the detection capability for IFs, definitions of guaranteed detectability are introduced, which is an extension and generalization of the original fault detectability concept focused on permanent faults (PFs). Then, necessary and sufficient conditions are derived for the detectability of IFs, which may appear and disappear several times with different magnitudes and durations. Based on these conditions, some optimal properties of two important window lengths are further discussed. In this way, a theoretical framework for the analysis of IFs’ detectability is established as well as extended discussions on how the theoretical results can be adapted to real-world applications. Finally, simulation studies on a numerical example and the continuous stirred tank reactor (CSTR) process are carried out to show the effectiveness of the developed methods.

Water shortages and pollution in China are severe situations caused by rapid economic development and urbanization. The current water-conservation policies focus on implementing new technologies and management strategies at important spatial nodes while neglecting the significance of the response from the community and the public. In this paper, the elements that influence the public participation of water conservation within the community are analyzed and divided into three levels: the internal world elements of the residents, the different individual characters of the residents, and external world elements. Among these three levels, the internal world element level, including the desire to realize oneself, is crucial, as it will significantly strengthen an individual's participation activity once motivated. Based on Maslow's five-level theory of human needs, to establish a model of public participation in water-conservation communities, economic benefits, environmental improvement benefits, and the self-fulfilling satisfaction of participation will become the motivation for the model to function. In a new project, reclaimed water landscapes are established in the community, and eco-recreational activities with water-conservation themes are organized to guide and encourage public participation to foster water-conservation consciousness and to establish aging water-conservation guiding policies and implementation methods in the community.

Recently, increasing attention has been paid on extending the π-conjugation structures of viologens (1,1′-disubstituted-4,4′-bipyridylium salts) by incorporating planar aromatic units into the bipyridinium backbones. Various viologen derivatives with extended π-conjugation structures have been synthesized, including the N-termini aromatic substituted viologens, the extended π-conjugated viologens (denoted as ECVs) as well as the π-conjugated oligomeric viologens (denoted as COVs). These compounds typically exhibit interesting properties distinguished from those of an isolated viologen unit, which make them as new class of electron deficient supra-/molecular building blocks in supramolecular chemistry and materials science. In this review, we would like to highlight the recent advances of viologen derivatives with extended π-conjugation structures in versatile applications ranging from electrochromic and energy storage materials, the ECV/COV-based supramolecular self-assembly systems including the linear supramolecular polymers and 2D/3D supramolecular organic frameworks (SOFs), to the viologen-based covalent organic frameworks (COFs)/networks. We hope this review will serve as an in-time summary worthy of referring, more importantly, to provide inspiration in the rational design of novel molecules with unexplored properties and functions.

Objectives To develop a new Chinese medicine (CM)-based drug and to evaluate its safety and effect for suppressing acute respiratory distress syndrome (ARDS) in COVID-19 patients. Methods A putative ARDS-suppressing drug Keguan-1 was first developed and then evaluated by a randomized, controlled two-arm trial. The two arms of the trial consist of a control therapy (alpha interferon inhalation, 50 µg twice daily; and lopinavir/ritonavir, 400 and 100 mg twice daily, respectively) and a testing therapy (control therapy plus Keguan-1 19.4 g twice daily) by random number table at 1:1 ratio with 24 cases each group. After 2-week treatment, adverse events, time to fever resolution, ARDS development, and lung injury on newly diagnosed COVID-19 patients were assessed. Results An analysis of the data from the first 30 participants showed that the control arm and the testing arm did not exhibit any significant differences in terms of adverse events. Based on this result, the study was expanded to include a total of 48 participants (24 cases each arm). The results show that compared with the control arm, the testing arm exhibited a significant improvement in time to fever resolution (P=0.035), and a significant reduction in the development of ARDS (P=0.048). Conclusions Keguan-1-based integrative therapy was safe and superior to the standard therapy in suppressing the development of ARDS in COVID-19 patients. (Trial registration No. NCT 04251871 at www.clinicaltrials.gov) Electronic Supplementary Material Supplementary material is available in the online version of this article at 10.1007/s11655-020-3426-7.

Highly efficient and effective porous ZnO nanorod arrays were fabricated by annealing ZnO nanorod arrays grown on a substrate using a simple hydrothermal method. The annealing had a positive effect on the nanorod morphology, structure and optical properties. The porosity was closely related to the annealing temperature. After heating at 450 °C, pores appeared on the nanorods. It was demonstrated that the porosity could be exploited to improve the visible light absorption of ZnO and reduce the bandgap from 3.11 eV to 2.99 eV. A combination of improved charge separation and transport of the heat-treated ZnO thus led to an increase in the photoelectrochemical properties. At an irradiation intensity of 100 mW/cm−2, the photocurrent density of the porous nanorod array was approximately 1.3 mA cm−2 at 1.2 V versus Ag/AgCl, which was five times higher than that of the ZnO nanorods. These results revealed the synthesis of promising porous ZnO nanorods for photoelectrochemical applications.

This paper addresses the detection problem of intermittent sensor faults for linear time-varying (LTV) systems with stochastic uncertainties. A robust filter is proposed which has advantages of zero mean and minimum state estimation error covariance. Then a corresponding residual generator is constructed and the quantitative influence of sensor faults on it is analyzed. Next, we design the evaluation function and detection threshold to achieve intermittent fault detection (IFD). Besides, the detectability of sensor faults is also provided. Finally, a simulation study is carried out to illustrate the effectiveness and applicability of our proposed method.

The recently proposed digital reconfigurable metasurfaces make it possible to manipulate electromagnetic (EM) waves flexibly. However, most existing reconfigurable metasurfaces can only exhibit a relatively single performance in the spatial domain. Here, we propose a general frequency- and spatial-domain reconfigurable metasurface (FSRM) that can manipulate the EM waves and realize reconfigurable functions in multifrequency bands. In the frequency domain, FSRM can convert different linearly polarized (LP) incident waves into left- and right-hand circularly polarized reflected waves, in which PIN diodes are used to switch the polarization conversions in different frequency bands. When the polarization direction of the incident LP wave is 45° from the +x-axis, the FSRM modulates the incident waves as a 1-bit programmable metasurface in the spatial domain. Two-dimensional beam scanning, vortex beams with orbital angular momentums, and specific beams with desired transmission directions are demonstrated via real-time adjustment of the digital coding state. To validate the modulation methodology, an FSRM prototype is fabricated and measured, which could respond to different functions for different polarization incidences. The measured results agree well with the theoretical analyses. The proposed FSRM will provide new opportunities for smart material designs.

Tissue engineering is promising in realizing successful treatments of human body tissue loss that current methods cannot treat well or achieve satisfactory clinical outcomes. In scaffold-based bone tissue engineering, a high performance scaffold underpins the success of a bone tissue engineering strategy and a major direction in the field is to produce bone tissue engineering scaffolds with desirable shape, structural, physical, chemical and biological features for enhanced biological performance and for regenerating complex bone tissues. Three-dimensional (3D) printing can produce customized scaffolds that are highly desirable for bone tissue engineering. The enormous interest in 3D printing and 3D printed objects by the science, engineering and medical communities has led to various developments of the 3D printing technology and wide investigations of 3D printed products in many industries, including biomedical engineering, over the past decade. It is now possible to create novel bone tissue engineering scaffolds with customized shape, architecture, favorable macro-micro structure, wettability, mechanical strength and cellular responses. This article provides a concise review of recent advances in the R & D of 3D printing of bone tissue engineering scaffolds. It also presents our philosophy and research in the designing and fabrication of bone tissue engineering scaffolds through 3D printing., Highlights • 3D printing of bioceramic pastes followed by sintering improves bone formation. • Cryogenic 3D printing of drug loaded polymer solution supports cell differentiation. • Surface modification of 3D printed scaffolds improves the cellular responses.

In the past decades, with the rapid development of modern technologies, a special kind of fault, the intermittent fault (IF) has become a serious threat to system securities. Although fruitful research results have been obtained for fault diagnosis, most of them are concerned with permanent faults. Furthermore, up to now, there has been no overview on the diagnosis techniques for IFs in dynamic systems. In fact, IFs are common in a variety of fields, whereas their research is far from mature and many open issues still remain to be solved. Therefore, in this overview, our main objective is to attract direct attentions from more researchers and engineers into the fascinating area of IF diagnosis. In this paper, the concept, research background, challenges and research motivations of IFs are introduced. Then, current research into diagnostics of IFs is reviewed, along with discussions on their strengths, limitations, and future directions.

The identification accuracy of inertia tensor of combined spacecraft, which is composed by a servicing spacecraft and a captured target, could be easily affected by the measurement noise of angular rate. Due to frequently changing operating environments of combined spacecraft in space, the measurement noise of angular rate can be very complex. In this paper, an inertia tensor identification approach based on deep learning method is proposed to improve the ability of identifying inertia tensor of combined spacecraft in the presence of complex measurement noise. A deep neural network model for identification is constructed and trained by enough training data and a designed learning strategy. To verify the identification performance of the proposed deep neural network model, two testing set with different ranks of measure noises are used for simulation tests. Comparison tests are also delivered among the proposed deep neural network model, recursive least squares identification method, and tradition deep neural network model. The comparison results show that the proposed deep neural network model yields a more accurate and stable identification performance for inertia tensor of combined spacecraft in changeable and complex operating environments.

The ionic liquids (ILs) are reported to perform well in enhancing the oil–solid separation (in pure state or in solution) and oil–water separation (in solution) processes through interfacial altera...

Technical advancement has propelled the proliferation of unmanned vehicles. Out of the multiple paths between origin (O) and destination (D), the optimal O-D path should be selected in the light of travel distance, travel time, fuel cost and pollutant emissions. This paper proposes a dynamic path planning strategy based on fuzzy logic (FL) and improved ant colony optimization (ACO). Firstly, the classic ACO was improved into the rank-based ant system. The rank-based ant system works well in static environments, but cannot adapt well to dynamic environments. Considering the difficulty in accurate digitization of dynamic factors, the improved ACO was integrated with the FL into the fuzzy logic ant colony optimization (FLACO) to find the optimal path for unmanned vehicles. Finally, the FLACO, the classic ACO and the improved ACO were separately applied to find the optimal path in a road network, with a novel concept called virtual path length. The results show that the FLACO output the shortest virtual path among the three algorithms, i.e. identified the most cost-effective path. This mean the FLACO can find the most efficient and safe path for unmanned vehicles in a dynamic manner.

The effect of heat treatment and deep cryogenic treatment on microstructural evolution of low carbon martensitic bearing steel was investigated. The experimental results showed that the lath martensite was obtained by quenching and a few twins as substructures formed in some martensitic laths. The rudiment of sub-interfaces of martensitic lath was formed in the high-density dislocation regions after deep cryogenic treatment; meanwhile, the number of twins increased, especially in the high-density dislocation regions. This phenomenon is due to the increase in internal stress caused by cryogenic treatment. After tempering, the rudiment of sub-interface further evolved into the martensitic lath boundary, and thus the original martensitic laths were refined. The twins formed by cryogenic treatment did not disappear after tempering. In addition, small quantities of annealing twins formed in tempering process. Martensitic laths morphology and substructures in different stages of the heat and deep cryogenic treatment were observed by transmission electron microscopy.

By using La(NO3)3•6H2O, Ca(NO3)2•4H2O, and Mn(CH3COO)2•4H2O as starting raw materials together with methanol, three kinds of La0.67Ca0.33MnO3 (LCMO) solutions, denoted as LCMO–BzAc, LCMO–AcAc, and LCMO–BPY, respectively, were obtained. The samples were fabricated via the photosensitive solution method with benzoylacetone (BzAc), acetylacetone (AcAc), and 2, 2′-bipyridine (BPY) as chelating reagents. The chelation mechanism of the metal ions was investigated via ultraviolet spectroscopy. The photosensitive compounds were decomposed after UV exposure and their products reduced the solubility of the LCMO gel films in organic solvents. The patterned LCMO thin films were then fabricated by using the self-photosensitive properties of their gel films. Through the mask micromachining process, the LCMO micropatterns prepared by using the LCMO–BzAc solution exhibited the highest quality. Moreover, they also presented good performance when the mask-free method was employed. The magnetic properties of the micropatterned LCMO films were investigated in detail and the results revealed that the micropatterning did not influence their saturation magnetization.

Various types of healthcare waste (or medical waste) generated by urban healthcare activities have increased due to the expansion of urban population and medical needs. As healthcare wastes are harmful to both the environment and human health, managing medical waste is becoming progressively more important. Constructing an optimized medical waste recycling network is one of the key problems in the management of urban healthcare waste. This paper conducts a two-stage reverse logistics network design for urban healthcare waste. The first stage involves the prediction of the amount of medical waste. Based on the Grey GM(1,1) prediction model, the amount of medical waste in multi-period of the target hospitals is predicted. In the second stage, a multi-objective model aimed at minimizing operating costs and minimizing environmental impact is developed for facilities allocation decisions, which include the configuration of key facilities such as hospitals, collection centers, transshipment centers, processing centers, and disposal sites, as well as medical waste flow control among facilities. A dynamic approach for the healthcare waste reverse logistics network is constructed by combining the Grey GM(1,1) prediction method with multi-objective optimization model. Sensitivity analysis of key parameters has been performed to analyze their impact on network performance. Some insightful management practices have been revealed.

Since some metal-organic cages (MOCs) have been synthesized in past several years, the applications of MOCs such as drug delivery, molecular recognition, separation, catalysis, and gas storage, etc. have been witnessed with a significant increase. However, to the best of our knowledge, so far no one has used MOCs as chiral stationary phase to separate chiral compounds in CEC. In this study, three MOCs were developed as the stationary phase for CEC separation of enantiomers. The MOCs coated capillary column showed good chiral recognition ability for some chiral compounds, including amine, alcohols, ketone, etc. The influence of buffer concentration, applied voltage, pH of buffer solution on the chiral separations was also investigated. The RSDs of run-to-run, day-to-day, and column-to-column for retention time were 2.1-4.67%, 1.2-4.36%, and 3.62-6.43%, respectively. This work reveals that the chiral MOCs material is feasible for the enantioseparation in CEC.

Exploiting photocatalysts with environmental friendliness, noble-metal-free and high efficiency is a great challenge for photocatalytic hydrogen evolution under visible light. In this work, we had successfully loaded anatase titanium dioxide with a special graphene structure [the reduced graphene oxide loaded on amine-functionalized poly (styrene/glycidyl methacrylate) (rGO/PSGM) microspheres. This special structure could greatly improve the catalytic performance of TiO2 in the visible light. The nonmetallic elements (C, N, F, P and S) were doped with TiO2 to further improve the performance of the composite photocatalysts in the visible-light region. After the first-principles density functional theory calculation, the calculated results of the density of states and dielectric function showed that the doped N element has the highest optical absorption capacity. We had proved this through experimental synthesis. Under the full-wavelength illumination, the degradation rate was 20 times higher than that of physically mixed sample; under the visible light, the k value of the degradation rate was 0.0046 min−1 while physically mixed sample had almost no reaction within 5 h. Our study provides a promising approach to achieving efficient photocatalytic reaction under visible light based on TiO2 and graphene without precious metals.

The reactor is an extreme environment of high temperature, high pressure, and high radiation dose. Damage accumulates in structural materials over service time. It will eventually lead to material failure, such as hardening, embrittlement, and swelling. The radiation damage accumulation is an inherent, complex, and multiscale process, which has been studied extensively with multiscale modeling and simulation methods. The rapid development of high-performance computing makes it possible to accurately operate multiscale simulation for the microstructure evolution of irradiated reactor materials. The European Union, the USA, and China have put great effort into this, and many related works have been carried out. This paper first outlines the basic application of multiscale modeling and simulation technology in understanding the effects of radiation on reactor structural materials. Then, some relevant projects carried out by the USA, the European Union, and China in recent years are summarized. Next, the paper focuses on three widely used simulation techniques at different scales: molecular dynamics, kinetic Monte Carlo, and cluster dynamics. For each method, some key developments in algorithms and computer implementations are reviewed. Finally, the comparison between them is discussed.

In this paper, the design problem of data-injection attacks is investigated for a class of cyber-physical systems (CPSs) whose inputs can be changed by the malicious adversary. A novel attack design method is proposed by solving an optimization problem based on Kullback–Leibler divergence (KLD). It can make maximum influence on the residual sequences in the sense of probability distribution but cannot be detected by the detector with preset significance level. A simulation study is carried out to demonstrate the effectiveness and applicability of the proposed method.

This article investigates the distributed active fault-tolerant cooperative control problem for leader-follower multiagent systems (MASs) in the presence of multiple faults, communication delays, and external disturbances. A new distributed consensus protocol is put forward to ensure the state consensus of MASs, which can be served as a nominal controller in fault-free cases with communication delays and external disturbances. A novel distributed time-delay intermediate observer, which can estimate system states and multiple faults simultaneously, is derived based on the time-delay closed-loop system equation. By integrating a fault compensation mechanism into the nominal controller, a distributed active fault-tolerant consensus controller is constructed for the follower agents to eliminate the adverse effects of multiple faults. Simulation examples are provided to demonstrate the effectiveness of the proposed method.

The ultrastretchable (over 12 400%) hydrogel with long-lasting adhesion, strong antibacterial activity, and robust spinnability is developed based on the oxidative decarboxylation and quinone-catechol reversible redox reaction induced by Ag-lignin nanoparticles in a precursor solution containing citric acid (CA), acrylic acid (AA), and poly (acrylamide-co-acrylic acid) (P(AAm-co-AA)). With massive reversible interactions including hydrogen bonds and electrostatic forces, such hydrogel exhibits promising injectability and is facilely spun via manual drawing, draw-spinning, and electrospinning for manufacturing strong hydrogel micro/nanofibers. The resulting fibers exhibit excellent mechanical properties, including tensile stress of 422.0 MPa, strain of 86.5%, Young's modulus of 8.7 GPa, and toughness of 281.6 MJ m-3 . The hydrogel microfibers obtained from a house-built spinner are scaled-up fabricated while retaining promising mechanical properties, as evidenced by lifting a load (317.2 g) using the spun fibers of ≈33 000 times lighter weight (9.5 mg), indicating their great potentials in the applications such as net and safety cord which require robust mechanical properties. Moreover, assisted by a commercial electrospinning machine, nanosized hydrogel fibers are facilely spun on personal protective equipment such as a mask to offer an antiseptic coating with near 100% killing efficiency against airborne bacteria aerosols, demonstrating the capability of spun hydrogel fibers on disinfection-related applications.

This paper proposes and implements a lightweight, “real-time” localization system (SORLA) with artificial landmarks (reflectors), which only uses LiDAR data for the laser odometer compensation in the case of high-speed or sharp-turning. Theoretically, due to the feature-matching mechanism of the LiDAR, locations of multiple reflectors and the reflector layout are not limited by geometrical relation. A series of algorithms is implemented to find and track the features of the environment, such as the reflector localization method, the motion compensation technique, and the reflector matching optimization algorithm. The reflector extraction algorithm is used to identify the reflector candidates and estimates the precise center locations of the reflectors from 2D LiDAR data. The motion compensation algorithm predicts the potential velocity, location, and angle of the robot without odometer errors. Finally, the matching optimization algorithm searches the reflector combinations for the best matching score, which ensures that the correct reflector combination could be found during the high-speed movement and fast turning. All those mechanisms guarantee the algorithm’s precision and robustness in the high speed and noisy background. Our experimental results show that the SORLA algorithm has an average localization error of 6.45 mm at a speed of 0.4 m/s, and 9.87 mm at 4.2 m/s, and still works well with the angular velocity of 1.4 rad/s at a sharp turn. The recovery mechanism in the algorithm could handle the failure cases of reflector occlusion, and the long-term stability test of 72 h firmly proves the algorithm’s robustness. This work shows that the strategy used in the SORLA algorithm is feasible for industry-level navigation with high precision and a promising alternative solution for SLAM.

Museum cultural relics represent a special material cultural heritage, and modern interpretations of them are needed in current society. Based on the catalogue data of cultural relics published by the State Administration of Cultural Heritage, this paper analyzes the continuity and intermittentness of cultural relics in time series by using the method of continuity judgment of cultural relics, analyzes the aggregation and migration of cultural relics in space by using the method of spatial analysis, and then uses cosine similarity to explain the similarity distribution in space and time. The results show that the overall distribution of cultural relics exhibits the characteristics of class aggregation, dynasty aggregation and regional aggregation. From the perspective of a time scale, cultural relics have different “life cycles”, displaying continuity, intermittentness, and similarity. From the perspective of a spatial scale, the cultural relic distribution forms a small “cultural communication circle”, showing aggregation, migration, and similarity. The temporal and spatial distribution of cultural relics exhibited more similar characteristics among dynasties that were closer together than those that were far away.

Phytic acid derived carbons provide an excellent dual functionality for lithium- and sodium-ion batteries under tuned pyrolysis temperature. The acquired carbon at 800 °C is suitable to lithium-ion batteries due to its high surface area (1426.75 m2 g−1) and hierarchical porous structure. Tested against Li, it delivers a high capacity of 1787 mA h g−1 and coulombic efficiency of 82%. Another obtained carbon at 950 °C is suitable to sodium-ion batteries due to its large lattice spacing (0.4115 nm), defect density and phosphorus content (1.12%). Tested against Na, it delivers the initial specific capacity of 387 mA h g−1 with coulombic efficiency of 50.6%, and maintains a high reversible capacity of 300 mA h g−1 after 300 cycles at a current rate of 100 mA g−1. High energy density and power density are also acquired in lithium- and sodium-ion batteries. The effects of pyrolysis temperature on microstructure and electrochemical behaviours of carbons are discussed detailedly. It is proved that the carbons with tuned pyrolysis temperature behave differently due to a synergistic effect among the lattice spacing, graphitization degree, defect density, phosphorus concentration and porous structure.

A metalens is the artificial surface made of billions of sub-wavelength elements and can bend light like traditional optical lens with significant efficiency and already attracted enormous research interests. However, the focus steering mechanism as an important part of optical system, is still under investigation for metalens. In this work, we describe an optical phased array model with the focalization and beam-steering features with specific phase relationship. To realize the focus-steering function on silicon metalens, the cascaded PIN junction enhanced by Fabry–Perrot cavity as the phase shifter is designed with metalens to provide up to 2 π phase variation. Silicon metalens with a diameter of 43 μ m and a focus of 40 μ m , at 1.55 um wavelength is verified in FDTD simulation. The results show that 10 μ m axial displacement is achieved with a carrier injection of 1019 cm−3 with the efficiency of 44%. At the end, the beam focalization and beam steering mechanism are investigated and analyzed. This focus steering mechanism could be deployed to many attractive near-infrared applications, such as fluorescence microscopy and LIDAR.

A kind of thin film composite polyamide nanofiltration (NF) membrane was synthesized via the interfacial polymerization between a new diamine monomer of 4,4′-diaminodiphenylmethane and trimesoyl chloride on the surface of cross-linked polyetherimide, and evaluated in some organic solvents including ACN, MeOH, EtOH, THF, etc. The optimal organic solvent NF membrane was selected to prepare respectively the hydrophilic membrane (Phi-NF) via grafting of Tris and the hydrophobic membrane (Pho-NF) via grafting of 2,2,2-trifluoroethylamine, combining with the characterization of ATR-FTIR, XPS, SEM, 13C NMR, AFM, etc. The permeance values of Phi-NF and Pho-NF membranes change greatly with organic solvents. Pho-NF-2 possesses the highest permeance of 66.4 L m−2 h−1 MPa−1 in THF with the erythrosin B (EB) rejection of 99.5%. Through analyzing the physiochemical properties of the organic solvents and calculating the surface energy, the correlations are deduced for the synthesized membranes, illustrating that the permeances of organic solvents are roughly proportional to the specific solvent properties for Phi-NF-2 and Pho-NF-2. The results suggest one promising method to enhance the separation performance of organic solvent NF membranes.

Aiming at disclosing the quantitative effects of Coulomb forces on the filtration efficiency of aerosol particles, a three-dimensional random fiber model was established to describe the microstructure of fibrous filters. Then, computational models including the flow model, particle model, and electric field model were constructed to estimate the filtration efficiency using the Fluent custom user-defined function program, neglecting the non-uniformity of the fiber potential and the particle charge distribution. The simulation results using the established models agreed with the data in the literature. In particular, the electric field force was found to be one of the important factors required to improve the filtration efficiency estimation accuracy for the ultrafine particles. Moreover, the variation tendencies of the filtration efficiency and the pressure drop of fibrous filters were studied based on the influence factors of the fiber potential, particle charge-to-mass ratio, solid volume fraction, fiber diameter, and face velocity. The established models and estimated results will provide important guidance on the design of high-efficiency particulate air filters for aerosol particles.

International audience; Molten salt pyrolysis driven by concentrated solar radiation is well positioned to utilize solar energy and lignite effectively. This study focused on the effects of temperature (500, 600, 700 and 800 °C) and molten carbonate salt (Li2CO3-Na2CO3-K2CO3) on properties of char obtained from lignite pyrolysis, as well as gas and tar products for revealing their formation mechanism and transformation process. Molten salt pyrolysis of HulunBuir lignite produced more gas products and less char compared to conventional pyrolysis owing to the enhanced heat transfer and catalytic effect of molten salt. The char yield decreased from 58.4% to 43.4%, and the gas yield (especially CO2, H2 and CO) increased from 28.3% to 46.1% at 800 °C. CO2, CO and H2 production increased about 60.43%, 103.42% and 65.2% at 800 °C, respectively. Additionally, the presence of molten salt improved the tar quality with more hydrocarbon content (maximum increase of 5.8%) and less oxygenated compounds. The structure and reactivity relationship of char was characterized by XRD, BET, SEM, FTIR, Raman spectroscopy and TGA. Molten salt generated char had a higher reactivity due to the increase of disorder, surface area, microporosity (maximum of 71.74%) and active sites.

Establishing interfacial science to understand molecular mechanisms of stabilizing water in heavy crude oil (W/O) emulsions is challenging due to non-transparent nature of crude oil even in diluted systems, as most of the interfacial property measurements are based on visualization of the experimental systems. This study investigates whether interfacial properties measured using transparent O/W emulsion systems could be used to understand the stability of W/O emulsion systems. With the same chemistry of interfacially active polyaromatic compounds (C5Pe and C5PeC11) in xylene as the model oil, the interfacial tension, crumpling ratio, dilatational rheology and coalescence time of W/O and O/W systems were measured. For less surface active C5PeC11, the interfacial tensions for W/O and O/W systems were similar. For more surface active C5Pe, the interfacial tension of the W/O system was lower than that of the O/W system, while the film rigidity and viscoelasticity of the W/O system were higher than that of the O/W system. At low C5Pe concentration, the coalescence time for the W/O system was lower than that for the O/W system with the coalescence time for the W/O system being higher at higher C5Pe concentrations. The results reveal that even though the interfacial properties measured using reverse O/W system exhibit similar qualitative trends, care should be taken when quantitatively studying W/O emulsions using interfacial property measurements of the O/W system due to the difference in most of the interfacial properties measured using the W/O and O/W systems.

The results of clustering are often affected by covariates that are independent of the clusters one would like to discover. Traditionally, alternative clustering algorithms can be used to solve such clustering problems. However, these suffer from at least one of the following problems: (1) Continuous covariates or nonlinearly separable clusters cannot be handled; (2) assumptions are made about the distribution of the data; (3) one or more hyper-parameters need to be set. The presence of covariates also has an effect in a different type of problem such as semi-supervised learning. To the best of our knowledge, there is no existing method addressing the semi-supervised learning setting in the presence of covariates. Here we propose two novel algorithms, named kernel conditional clustering (KCC) and kernel conditional semi-supervised learning (KCSSL), whose objectives are derived from a kernel-based conditional dependence measure. KCC is parameter-light and makes no assumptions about the cluster structure, the covariates, or the distribution of the data, while KCSSL is fully parameter-free. On both simulated and real-world datasets, the proposed KCC and KCSSL algorithms perform better than state-of-the-art methods. The former detects the ground truth cluster structures more accurately, and the latter makes more accurate predictions., Knowledge and information systems, 62 (3), ISSN:0219-1377, ISSN:0219-3116

Due to the inner deteriorating mechanism or the mutant environmental stress, the degradation systems with multi-phase features have frequently been encountered in engineering practice. The key issue for prognostics of such systems is to account for the impact of the changing-point variability and the associated degradation state at this point on the progression of the degradation process. However, current studies usually treat the degradation state at the change point as a fixed value rather a random variable. Thus, it is still challenging to predict the lifetime of such multi-phase degrading systems. To this end, we first formulate a general degradation modeling framework based on a two-phase Wiener process. In prognostics, we take into full account the uncertainty of the degradation state at the changing point and then derive the analytical expressions of the lifetime and remaining useful life under the concept of the first passage time. The derived results are distinguished from existing results limited to the fixed state at the changing point. Furthermore, we extend our approach and results to cases with unit-to-unit variability and multiple phases. To facilitate the model implementation, we propose both offline and online methods for parameter identification, which make full use of the historical data and the in-service data. Finally, a numerical simulation and a practical case study are provided for illustration.

Pumping artesian water from porous media inevitably reduces the groundwater head and promotes soil consolidation, which may result in regional land subsidence. In this study, a fluid-mechanical coupled numerical model is developed to investigate the dewatering-induced groundwater drawdown and deformation responses for multi-layer strata. The relation between the stratum deformation and groundwater drawdown is discussed. The results show that the pumping process can be divided into four stages. The development of vertical deformation is inconsistent with the change of the pore pressure for the strata except for the confined aquifer at the early stage of pumping. The strata expand while the pore pressures reduce. This inconsistency may be due to the large unloading in the confined aquifer at the early stage of pumping. Soil arch comes into being owing to the constraint of the surrounding soils when the large unloading occurs in the confined aquifer; this can reduce the stratum compression and cause the expansion of the layers. It can be concluded that as the pumping continues, the decrease of the pore pressure dominates the vertical deformation and results in the soil compression in all strata.

By adding an EO–PO demulsifier, the interface between the asphaltene model compounds and water was changed. The adsorption replacement of C5Pe or C5PeC11 molecules by an EO–PO demulsifier and the competitive adsorption between them were compared. A reduction of the interfacial tension of the C5Pe or C5PeC11–water interface by EO–PO demulsifier addition for the water-in-oil (W/O) and oil-in-water (O/W) systems was observed, suggesting higher interfacial activities of the EO–PO demulsifier, especially at high EO–PO demulsifier concentrations. Crumpling ratios of the flat C5Pe–water interfacial film for W/O and O/W systems were also measured, and the results showed that the EO–PO demulsifier was capable of softening and weakening the interfacial films for both systems. The EO–PO demulsifier showed similar performance on changing the C5Pe interfacial film through both diffusion (simulating the W/O system) and spreading (simulating the O/W system) protocols. By investigating the Langmuir interfacial-area isoth...

It is currently a very active research area to develop multifunctional nanocomposites (NCs) which integrate the novel properties from various nanomaterials for multimodal imaging and simultaneous therapy. These theranostic nanoplatforms can provide complementary information from each imaging modality for accurate diagnosis and, at the same time, afford an imaging-guided focused tumor therapy. Among them, core/shell Fe₃O₄@Au NCs have attracted wide attention due to their unique advantages in magnetic targeting, multimodal imaging and photothermal therapy. This study developed a layer-by-layer assembling approach to synthesize Fe₃O₄@Au NCs with high photothermal conversion efficiency. The as-synthesized NCs showed significant photothermal ablation capability to HeLa cells in vitro under near infrared laser irradiation. To ensure the safety for medical applications, the bio-effects of Fe₃O₄@Au NCs on RAW264.7 cells were carefully assessed, in terms of cell viability, oxidative stress and apoptosis. We have demonstrated that Fe₃O₄@Au NCs had good biocompatibility in RAW264.7 cells and no significant cytotoxicity was found. Therefore, the Fe₃O₄@Au NCs synthesized in this study have great potential as an ideal candidate for CT/MR imaging and photothermal therapy.

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

The physiochemical properties of nanoparticles (NPs), including surface charge, will affect their uptake, transformation, translocation, and final fate in the environment. In this study, we compared the phytoxoxicity and transport behaviors of nano CeO2 (nCeO2) functionalized with positively charged (Cs-nCeO2) and negatively charged (PAA-nCeO2) coatings. Cucumber seedlings were hydroponically exposed to 0-1000 mg/L of Cs-nCeO2 and PAA-nCeO2 for 14 days and the contents, distribution, translocation, and transformation of Ce in plants were analyzed using inductively coupled plasma mass spectrometry, micro X-ray fluorescence (μ-XRF), and X-ray absorption near-edge spectroscopy (XANES), respectively. Results showed that the seedling growth and Ce contents in plant tissues were functions of exposure concentrations and surface charge. Cs-nCeO2 was adsorbed strongly on a negatively charged root surface, which led to significantly higher Ce contents in the roots and lower translocation factors of Ce from the roots to shoots in Cs-nCeO2 group than in PAA-nCeO2 group. The results of μ-XRF showed that Ce elements were mainly accumulated at the root tips and lateral roots, as well as in the veins and at the edge of leaves. XANES results revealed that the proportion of Ce(III) was comparable in the plant tissues of the two groups. We speculated that Cs-nCeO2 and PAA-nCeO2 were partially dissolved under the effect of root exudates, releasing Ce3+ ions as a result. Then, the Ce3+ ions were transported upward in the form of Ce(III) complexes along the vascular bundles and eventually accumulated in the veins. The other portion of Cs-nCeO2 and PAA-nCeO2 entered the roots through the gap of a Casparian strip at root tips/lateral roots and was transported upward as intact NPs and finally accumulated at the edge of the blade. This study will greatly advance our information on how the properties of NPs influence their phytotoxicity, uptake, and subsequent trophic transfer in terrestrial food webs.

Ba6Cu2GSn4S16 (G = Fe, Ni), and Sr6D2FeSn4S16 (D = Cu, Ag) were synthesized in an A-B-P-Q (A = Sr, Ba; B = Cu, Ag, Li; P = Sn, Ge; Q = S, Se, Te) system, through the introduction of the Fe and Ni atoms. The four compounds were found to be isostructural. They crystallize in space group I 4 3 d (no. 220) of the three-dimensional cubic structure. The structure is composed of SnS4 and (Cu|G)S4 by sharing corners with Ba2+ cations distributed in the channels of the Ba6Cu2GSn4S16 (G = Fe, Ni). The structure is composed of SnS4 and (D|Fe)S4 by sharing corners with Sr2+ cations distributed in the channels of the Sr6D2FeSn4S16 (D = Cu, Ag). The UV–vis diffuse reflectance spectra showed the Ba6Cu2FeSn4S16, Ba6Cu2NiSn4S16, Sr6Cu2FeSn4S16, and Sr6Ag2FeSn4S16 energy band gaps to be 1.20 eV, 0.82 eV, 1.53 eV and 1.87 eV, respectively.