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In this paper, we focus on addressing the air supply problem for fuel cells. The air supply system faces a challenge: operating at maximum load consumes a significant amount of power, while insufficient air can lead to oxygen starvation problems in fuel cells. An important metric, the oxygen excess ratio, indicates whether the fuel cell is receiving the appropriate amount of air. Unfortunately, directly measuring this ratio is generally impractical. To overcome this limitation, we propose a fixed-time observer that reconstructs the oxygen excess ratio within a short predetermined period. By utilizing this reconstructed index, we introduce a cascaded double-loop controller. Specifically, both the external and internal loops are regulated using a modified prescribed time control strategy. This approach enables the regulation of the oxygen excess ratio to the optimal value within a prescribed short time. The advantages of our proposed method are validated through hardware in-loop experiments, showcasing its superiority over conventional finite-time control techniques. • The controller ensures the oxygen excess ratio is regulated in a prescribed time. • The oxygen excess ratio is unmeasurable, so we estimate it by a Fixed-time observer. • A comparison with finite-time control is presented in a hardware-in-loop experiment. • The proposed method shows robustness against disturbance and parameter uncertainties. [ABSTRACT FROM AUTHOR]

This paper proposes a novel adaptive-gain generalized super twisting algorithm for permanent magnet synchronous motors. The stability of this algorithm is strict proof using the Lyapunov method. Both controllers of the speed-tracking loop and the current regulation loop are designed according to the proposed adaptive-gain generalized super twisting algorithm. Dynamically adjusted gains in the controllers can improve the transient performance and system's robustness while reducing chattering. A filtered high-gain observer is applied in the speed-tracking loop to estimate the lumped disturbances, including parameter uncertainties and external load torque disturbances. The estimates feeding forward to the controller further improve the robustness of the system. Meanwhile, the linear filtering subsystem reduces the sensitivity of the observer to the measurement noise. Finally, experiments are constructed using the adaptive gain generalized super twisting sliding mode algorithm and the fixed gain one, showing the effectiveness and advantages of the proposed control scheme. • An adaptive-gain generalized super twisting algorithm (GSTA) is proposed. • The stability of the proposed adaptive-gain GSTA is rigorously proven. • The proposed adaptive-gain GSTA is applied in the PMSM systems. • A filtered high-gain observer is constructed, which enhances the robustness of the system. • Experiments results show the effectiveness and advantages of the proposed control scheme. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-throughput experiments are proposed to measure the FCGR curve of soft material. • A high-throughput experiment can obtain more than 90 data points for one run of test. • The FCGR curve can be reasonably measured by only two high-throughput experiments. • Effect of storing temperature on the FCGR curve is studied by high-throughput tests. The fatigue properties of soft materials, including fatigue crack initiation and propagation, fatigue life and threshold, have been a significant concern in the past few decades. Measuring the fatigue crack growth rate (FCGR) curve is a standard method to characterize fatigue fracture and has been extensively studied in the literature. Conventional methods employing a pure shear configuration measure only one data point on the FCGR curve per test run. Thus, obtaining the whole FCGR curve with numerous data points becomes excessively time-consuming. This work proposes a high-throughput experimental method for measuring the FCGR curve of soft materials. We prepare ten thermoplastic polyurethane (TPU) specimens in single edge notch tensile configuration with different precut crack lengths, use a mechanical mechanism to apply the same cyclic loads to the ten specimens simultaneously, and identify the crack growth of each specimen by image processing. The proposed high-throughput experimental method enables the measurement of over 90 data points on the FCGR curve in a single test run, facilitating the acquisition of the entire curve with just two runs. The obtained FCGR curve exhibits a linear relationship within its middle region on double logarithmic coordinates. The proposed method is further applied to study the effect of temperature on the FCGR curve of TPU specimens. The current experimental setup can be further optimized to accommodate a wider range of soft materials with diverse mechanical properties and specific loading conditions. [ABSTRACT FROM AUTHOR]

This review highlights the latest progress in the design and fabrication of soft network materials, as well as their representative applications. It focuses on fundamental principles, design concepts and fabrication techniques of soft network materials that consist of either periodically or randomly distributed microstructures. Finally, perspectives on the remaining challenges and open opportunities are provided. [Display omitted] Soft network materials represent a class of emerging cellular materials that have well-organized micro-architectures inspired by network microstructures found in many soft biological tissues. Apart from a good combination of low density, high stretchability and high air permeability, the high degree of design flexibility of soft network materials allows precise customization of mechanical properties by rationally tailoring their microstructural architecture and optimizing selections of constituent materials. These intriguing properties have enabled a range of promising applications in cutting-edge technologies, such as bio-integrated electronics and regenerative medicine. This review summarizes the latest progress in the design and fabrication of soft network materials, as well as their representative applications in biomedical devices, tissue engineering and other areas. It focuses on fundamental principles, design concepts and fabrication techniques of soft network materials that consist of either periodically or randomly distributed microstructures. Rational designs of these soft network materials result in customized mechanical properties that mimic or even exceed those of soft biological tissues. Finally, perspectives on the remaining challenges and open opportunities are provided. [ABSTRACT FROM AUTHOR]

Due to the increasing quantities of phenolic compounds present in wastewater, the use of enzymatic degradation with the laccase has attracted much attention as a green option for their removal. In this work, we developed a novel immobilization technology using 3D bioprinting for laccase immobilization. The hydrogel mechanism properties were optimized by experimenting with different component ratios of sodium alginate (SA), acrylamide (AM), and hydroxyapatite (HA). The improved mechanism properties were validated by morphology pictures and rheology characteristics. The optimal AM:HA:SA ratio was determined to be 4:1.2:1. We then employed an extrusion-based bioprinting technique to prepare the immobilized laccase. The substrate conversion was increased with the addition of HA, which improved the permeability of the matrix, and proved to be suitable for immobilization. The resulting immobilized laccase was used for the biodegradation of p-chlorophenol. The effects of the initial substrate concentration, pH, and temperature were evaluated. The immobilized laccase exhibited good storage stability and reusability, retaining over 80% of its initial activity after 72 h of storage, and was able to be reused for seven batches. These results highlight that the immobilized laccase prepared by 3D bioprinting has great potential for use in the biodegradation of phenolic compounds. [ABSTRACT FROM AUTHOR]

• The features of ballast silhouettes based on optimal ellipses and stretch curves are presented. • The suitable number of sampling points based on the optimal ellipses is presented. • A random batch generation method of ballast silhouettes is established. Research on the topological rule and random generation method of a ballast silhouette can realize different batch generations of ballast 2D topology under the condition of definite gradation, which can lay a foundation for the microscopic simulation and performance research of a railway ballast bed. Based on the analysis of ballast particle silhouette samples collected by digital image processing technology (DIPT), this paper presents a method of characterizing ballast silhouette features based on an optimal ellipse and surface stretch curve and achieves random batch generation of ballast silhouette 2D topology by establishing ballast particle reconstruction function libraries. The results show that the optimal ellipse processed by the least squares method can represent the holistic shape of ballast particles; the silhouette surface stretch curve based on the optimal ellipse can reflect the fluctuation degree of the silhouette; the function libraries can effectively support the reconstruction and random generation of ballast 2D topology; and the reconstructed ballast database passes the particle size gradation curve test and the main morphological characteristic parameter test, which shows that the method can be used in batch generation of ballast 2D silhouettes and related simulation. [ABSTRACT FROM AUTHOR]

Abstract This paper is concerned with the mean-square exponential stability and performance analysis, stabilization, dissipative control and dissipativity-based sliding mode control (SMC) problems for discrete-time switched stochastic hybrid systems. Such systems can be also regarded as switched hybrid systems with stochastic perturbation. Event detectors, which can save computational resource, are designed to determine whether the current data should be transmitted or not in the design process. Firstly, by proposing an average dwell time method combining with a switched (mode-dependent) Lyapunov function, a sufficient condition is established under the event-triggering scheme, which guarantees that the considered switched stochastic system is mean-square exponentially stable, and then an explicit parametrization of the desired stabilization controller is also given. Secondly, the event-triggering dissipativity analysis and the dissipative control problems are investigated. A dissipativity performance condition is proposed to guarantee the mean-square exponential stability and strict dissipativity for the discrete-time switched stochastic system, and then the dissipative controller is implemented by the state feedback. Thirdly, a switched observer is constructed to estimate unavailable state variables, based on which a differential-type sliding surface function is designed, with which the sliding mode dynamical equations can be easily obtained. The resulting closed-loop system with sliding mode dynamics is an autonomous switched stochastic system. Dissipativity analysis and synthesis are both investigated for the closed-loop system, and consequently sufficient conditions are derived, which pave the way for solving the event-triggering observer-based dissipative sliding mode control problem. Moreover, an event-triggering output-based SMC law is first synthesized to drive the system trajectories to enter a predefined sliding vicinity. Finally, illustrative examples are employed to validate the proposed controller design schemes. [ABSTRACT FROM AUTHOR]

In this paper a new indirect type-2 fuzzy neural network predictive (T2FNNP) controller has been proposed for a class of nonlinear systems with input-delay in presence of unknown disturbance and uncertainties. In this method, the predictor has been utilized to estimate the future state variables of the controlled system to compensate for the time-varying delay. The T2FNN is used to estimate some unknown nonlinear functions to construct the controller. By introducing a new adaptive compensator for the predictor and controller, the effects of the external disturbance, estimation errors of the unknown nonlinear functions, and future sate estimation errors have been eliminated. In the proposed method, using an appropriate Lyapunov function, the stability analysis as well as the adaptation laws is carried out for the T2FNN parameters in a way that all the signals in the closed-loop system remain bounded and the tracking error converges to zero asymptotically. Moreover, compared to the related existence predictive controllers, as the number of T2FNN estimators are reduced, the computation time in the online applications decreases. In the proposed method, T2FNN is used due to its ability to effectively model uncertainties, which may exist in the rules and data measured by the sensors. The proposed T2FNNP controller is applied to a nonlinear inverted pendulum and single link robot manipulator systems with input time-varying delay and compared with a type-1 fuzzy sliding predictive (T1FSP) controller. Simulation results indicate the efficiency of the proposed T2FNNP controller. [ABSTRACT FROM AUTHOR]

Continental shelves serve as a bridge between the continent and ocean and sediments in this region are sensitive to land-sea interaction, sea-level variation and local subsidence. In this study, we present a comprehensive magnetic study of the longest sediment core (CSDP-1, 300.1 m) recovered from the South Yellow Sea. The major magnetic minerals in the studied sediments are magnetite, hematite and greigite. Greigite records a chemical remanent magnetization, which can be removed effectively by thermal demagnetization. The magnetostratigraphy defined in this study contains the Matuyama-Brunhes boundary (M/B, 781 ka) at ∼73.68 m, which is consistent with results from adjacent cores. The base of the Quaternary (∼2.6 Ma) in the Yellow Sea is recovered for the first time at a depth of 227.16 m. The basal age of the core is estimated to be ∼3.50 Ma. It indicates that the first transgression of the Yellow Sea occurred no later than ∼1.7 Ma. Succeeding large amplitude regressions occurred in some cold periods such as during MIS 20, MIS 18, and MIS 10. Our results provide the first chronology that brackets the entire Quaternary and we reconstruct the sedimentary evolution of the Yellow Sea with robust age constraints, which provides an important framework for further paleoenvironmental and tectonic studies. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear observer is proposed for a PEMFC system, based on Second Order Sliding Mode (SOSM) techniques. The goal is to estimate the hydrogen partial pressure in the anode channel of the PEMFC, using the measurements of stack voltage, stack current, anode pressure and anode inlet pressure. The proposed observer employs a nonlinear error injection term, where the error is obtained from the difference between the system voltage output obtained from an experimental validated nonlinear model and estimated voltage output obtained from the designed observer. The robustness of this observer against parametric uncertainties and load variations is studied, and the finite time convergence property is proved via Lyapunov analysis. Simulation results illustrate the effectiveness and robustness of the proposed approach. [ABSTRACT FROM AUTHOR]

The present work studied the softening and melting properties of different burden structures including pellet, sinter and mixed burden (pellet mixed with sinter) with a pellet ratio of 33.65%. The content of high chromic vanadium titano-magnetite in sinter and pellet was different. The experimental results indicated that the compositions of the burden have an important effect on the softening and melting properties. The softening and melting properties of pellet burden structure were improved when the high basicity sinter was added into the acid pellet forming mixed burden. The softening and melting properties of mixed burden with a pellet ratio of 33.65% were better than other burden structures. The initial softening temperature, the temperature interval of softening, the starting melting temperature, the temperature interval of melting, and maximum differential pressure were 1100 °C, 130 °C, 1250 °C, 130 °C and 15.7 kPa, respectively. By comparing the contents of Ti, V and Cr of iron that had dripped through the different burden structures, the content of valuable components (Ti 0.349%, V 0.244% and Cr 0.094%) was highest of the pig iron collected from the mixed burden. [ABSTRACT FROM AUTHOR]

Controlling the morphology and surface defects is an effective strategy for enhancing photocatalytic performance. In this paper, we have successfully prepared zinc oxide (ZnO) microspheres with oxygen vacancies-enriched and porous hierarchical structures by hydrothermal annealing. The porous hierarchical structure of the ZnO microspheres was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other analytical techniques, and their photocatalytic properties were studied by the decomposition of methylene blue, tetracycline and phenol in condition simulated sunlight. The porous hierarchical structure of ZnO–SO 4 2- microspheres showed higher photocatalytic activity compared to ZnO–Cl- and ZnO–NO 3 - (ZnO from different sources of zinc as ZnO-X, where X is SO 4 2−, Cl− and NO 3 −, respectively.). Under sunlight, the photocatalytic removal rates of methylene blue, tetracycline and phenol by ZnO–SO 4 2- were 98%, 100% and 83%, respectively. Meanwhile, the photoelectrochemical tests showed that the porous hierarchical structures of ZnO–SO 4 2- microspheres had the best photocurrent response and the lowest charge transfer resistance. After five cycles of photocatalytic degradation of phenol, the synthesized ZnO microspheres also showed good durability and stability. In addition, superoxide radicals (•O 2 −) and hydroxyl radicals (•OH) were identified as the active species by the trapping experiments. This study showed that the improvement of photocatalytic performance of ZnO microspheres could be owing to abundant oxygen vacancies and the porous hierarchical structures. • The porous hierarchical structure of ZnO microspheres was synthesized. • The photocatalytic degradation property of ZnO was increased in the presence of OVs. • ZnO–SO 4 2- showed remarkable photocatalytic activity in the degradation of MB, TC and phenol. • The active species were identified in the photocatalytic degradation process. [ABSTRACT FROM AUTHOR]

This paper focus on the event-triggered sliding mode controller design for discrete-time switched genetic regulatory networks (GRNs) with persistent dwell time (PDT) switching. Firstly, the observation error dynamics of switched GRNs with PDT is constructed in the light of event-triggered sliding mode control (SMC) scheme. Next, sufficient conditions are derived to ensure the exponential stability of the augmented plant. Moreover, an event-triggered SMC law is synthesized to impel the system trajectories onto the sliding surface in a finite time. Finally, a verification example is provided to illustrate the effectiveness and potential of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive algebraic observer is proposed for a Polymer Electrolyte Membrane Fuel Cell (PEMFC) air-feed system, based on Higher Order Sliding Mode (HOSM) differentiators. The goal is to estimate oxygen and nitrogen partial pressures in the fuel cell cathode side, using measurements of supply manifold pressure and compressor mass flow rate. As the proposed technique requires the time derivatives of the states, Lyapunov-based adaptive HOSM differentiators are synthesized and implemented for estimating these derivatives without a-priori knowledge of the upper bounds of their higher order time derivatives. The performance of the proposed method is validated through experiments on a Hardware-In-Loop (HIL) test bench. These results illustrate the feasibility and effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Recovery of rare earth elements (REEs) from tailings is the solution to the waste of valuable resource and hazard of tailing dam. In order to lower the cost and increase the rate of REEs recovery, we investigated leaching kinetics and dissolution mechanisms of REE slag in hydrochloric acid (HCl) solution, and present a method for selectively recovering REEs directly from the leachate. Experiments were performed to elucidate the effects of the initial concentration of HCl, liquid–solid ratio, and reaction temperature on the leaching efficiency of REEs. The maximum leaching efficiency of REEs in this work exceeded 99%. The leaching kinetics and dissolution mechanism have also been analyzed by model fitting and microstructural observation. The leaching reaction was controlled by both of the interfacial transfer and diffusion across the product layer. The pitting corrosion and the colloidal silicic acid generated at the interface of REE-rich phase showed positive and negative effects on the leaching reaction rate, respectively. Finally, the selective recovery of REEs from the leachate was developed, and both the recovery of REEs and purity of the REE precipitate exceeded 99%. This study is expected to provide a feasible method for the recovery of REEs from the silicates containing slag. • Leaching recovery of RE exceeded 95% within 10 min. • Investigated leaching kinetics and dissolution mechanisms of RE slag in HCl sol. • Colloidal silicic acid generated at interface between RE-rich phase and HCl sol. • Developed novel method to selectively recover RE directly from the leachate. • The purity of RE precipitate exceeded 99% with a 100% RE recovery. [ABSTRACT FROM AUTHOR]

Polyurethane reinforcement technology can improve the stiffness and the stability of ballast beds. In this study, the performances of the uniaxial compression and fatigue of polyurethane-reinforced ballast with different amplitudes of cyclic loading were studied. The corresponding simulation models were established by the discrete element method (DEM). Then those simulation models were compared and verified with the tests in the laboratory. The mesoscopic mechanical properties of polyurethane-reinforced ballast during compression were analyzed. The uniaxial compression results showed that during the compression process, the stiffness modulus of the samples increased from low to high (increased by 119.93%), and then decreased gradually and gently at the later stage of loading (the stiffness modulus at the turning point was approximately 2.86 MPa) until failure. The mesoscopic results based on the DEM showed that the polyurethane materials not only bore the normal force of the structure but also substantially bore the tangential force. The stiffness modulus of the polyurethane-reinforced ballast decreased with the increase of the loading times but gradually tended to be stable. The cyclic loading results showed that the deformation of the structure did not increase linearly with the increase of the cyclic loading amplitude. The DEM showed that the stiffness modulus of the polyurethane-reinforced ballast was small when the cyclic loading amplitude was large. However, as long as the cyclic loading did not exceed the bearing limit of the structure, the structure could recover to the initial deformation after the cyclic loading was removed. • The uniaxial compression performance of the polyurethane-reinforced ballast is monitored. • The bonding performance of the polyurethane-reinforced ballast during compression is analyzed with the DEM. • The fatigue properties of the polyurethane-reinforced ballast with different cyclic loads are investigated. • The fatigue reasons of the polyurethane-reinforced ballast under cyclic loads were analyzed with the DEM. [ABSTRACT FROM AUTHOR]

• The vibration characteristics of a ballast bed under different temperature and humidity environments were analyzed. • The influence of different environments on damping and stiffness of a ballasted track was analyzed. • The longitudinal vibration transmission characteristics of a ballast bed under different environments were obtained. • The modal analysis of a ballasted track under different frozen environments was carried out. Studying the dynamic characteristics and evolution laws of the ballast bed under low-temperature, rain and snow environments has practical significance for the driving stability of railways in alpine. In this paper, a full-scale ballasted track model was constructed in a programmable temperature control laboratory, and the frequency response function (FRF) curves of the ballast bed under different temperature and humidity conditions were measured. Then the vibration characteristics and the evolution laws of the ballast bed under different conditions were analyzed. The longitudinal transfer behavior and the dissipation of the vibration energy in the ballast bed under different humidity and temperature environments were discussed combined with the finite element method. The results show that the influence of temperature on the vibration characteristics of the ballast bed is not significant in the dry and water-rich environments, but the vibration characteristics of the ballast bed in the frozen environment change dramatically with the decrease of temperature. The vibration energy is harder to dissipate in the frozen ballast bed than in the dry and water-rich ballast beds, and the frozen ballast bed is more prone to be sudden damaged when a train passes due to the significant increase in its stiffness. Thus, the performance monitoring and emergency maintenance of the ballast bed in those environments should be strengthened. [ABSTRACT FROM AUTHOR]

The catalytic activities of pyrite in the heterogeneous Photo-Fenton processes for oxidation of methylene blue (MB) were systematically investigated. Experimental results revealed that nearly 100% MB (50 mg/L)could be completely degraded after 20 min under the optimum conditions. The excellent oxidation ability could be attributed to the photocatalytic activity of pyrite under visible light illumination, and the Fenton catalytic reaction occurring at the surface of FeS 2 together with dissolved iron ions in the aqueous phase. Most importantly, the FeS 2 nanoparticles assembled on graphene sheets were synthesized via a one-step solvothermal method with higher photocurrent response, reduced charge transferring resistance, and superior cycling stability. The obtained materials were also characterized by XRD, SEM, TEM, XPS, TG, and ESR for structural, morphological, chemical, and reaction mechanism studies. • Spherical FeS 2 nanoparticles were prepared by the solvothermal method and FeS 2 /graphene obtained by in-situ composite. • The influence factors in heterogeneous FeS 2 photo Fenton system and catalytic reaction mechanism were investigated. • The photoelectrochemical properties of FeS 2 and FeS 2 /graphene were tested and analyzed. [ABSTRACT FROM AUTHOR]

• The resistance values of ballast beds with concrete sleepers and composite sleepers were tested. • The resistance variation laws of ballast beds with the 2 types of sleepers were studied. • The 'rebounding' of ballast particles in the ballast bed with composite sleepers was discovered. • The moving differences of the ballast around the 2 types of sleepers were explained. A composite sleeper has a similar shape, stiffness, and weight to that of an existing wood sleeper with additional benefits including excellent durability, extended design life like a prestressed concrete sleeper, environmentally friendliness, and cost effectiveness. Therefore, in some cases, composite sleepers are considered as an alternative for wooden or concrete sleepers. In this study, the longitudinal- and lateral-displacement resistance changes of the fiber reinforced foamed urethane (FFU) composite sleepers and the concrete sleepers in ballast beds were tested. The application conditions of the composite sleeper in a ballast bed were analyzed. The results show that the resistance of the composite sleeper changed more sharply, and its value was greater than that of the concrete sleeper during the initial stage of their displacements. The longitudinal and lateral resistance of the composite sleeper was lower than that of the concrete sleeper with an increase in displacement (at 2 mm, longitudinal: 41.35% of the concrete sleeper, lateral: 35.64% of the concrete sleeper). Using the discrete element method (DEM), it was found that when the composite sleeper moves, the ballast around it may 'rebound.' The force and its transfer of the ballast near the displacement end of the concrete sleeper was an upward arc, while that of the composite sleeper was a downward arc. The ballast on the side of the concrete sleeper moved upward (tending to be horizontal) along the lateral-displacement direction of the sleeper, while that of the composite sleeper moved downward (tending to be vertical). [ABSTRACT FROM AUTHOR]

• The resistance characteristics of ballast bed in different temperature and humidity were explored. • The characteristics of ballast bed resistance in freezing environment were explored. • The variation rule of ballast bed resistance during melting process of ice and snow was explored. A ballasted track structure is one of the most representative types of railway construction. Due to the influences of low-temperature rain and snow environments in alpine regions, an in-depth study of the resistance characteristics and evolution patterns of ballasted track beds is urgently needed. A full-scale ballasted track model was constructed in an insulated test chamber with a programmable temperature-controlled environment. The longitudinal and lateral resistances of the ballast bed were tested for different temperature and humidity conditions, and the performance evolution patterns were analyzed. After the failure of the internal ice layers, a resistance test was carried out for the ballast bed in a low-temperature freezing environment, and the influence of the ice destruction on the characteristics of the ballast bed resistance was analyzed. By simulating the low temperature rise environment, the variation patterns of the ballast bed resistance during the freeze–thaw process were tested and analyzed. The results showed the following. The ballast bed resistance in a dry and low-temperature environment was different from that at normal temperature, and the variation with temperature was greater than that at a normal temperature. The resistance of the ballast bed in a wet state decreased compared to that in a dry condition; as the humidity increased from 34% (dry) to 91% (wet), the longitudinal resistance decreased by 22% and the lateral resistance decreased by 17%. The freezing environment could increase the ballast bed resistance when the sleepers had small displacements. However, after the displacement exceeded a certain value (3.8 mm longitudinally and 2.9 mm laterally under the test conditions), the ballast bed resistance was reduced, with the average reduction rates of the longitudinal and lateral resistances reaching 4.55 kN/mm and 2.90 kN/mm, respectively. The rapid rise and fall of the ambient temperature had an enormous influence on the ballast bed resistance. When an ice-water mixture appeared inside the ballast bed at about 0 °C, the longitudinal and lateral resistances were reduced to 31.64% and 30.28%, respectively, of the resistances in a normal situation. The state dependence of the ballast bed resistance on the low-temperature rain and snow environment indicated that more attention is necessary for the complex service characteristics of the ballasted track under similar conditions. [ABSTRACT FROM AUTHOR]

• The compressive strengths of ballast-ice combinations at different freezing temperatures were obtained. • The strength evolution patterns of ballast-ice combinations during compression were explored. • The internal meso -mechanical states of ballast-ice combinations at the failure moment were analyzed. The mechanical properties of railway ballast in a freezing environment are different from those in a normal environment, and these properties need special attention. In this work, uniaxial compression ballast-ice specimens with the same size were made, and the compressive strengths of the specimens for the temperature conditions of –10 °C, –20 °C, and –30 °C were measured using a pressure testing machine. Then the evolution patterns of the compressive strengths of the ballast-ice combinations with temperature were analyzed. The discrete element models for the uniaxial compression tests of the ballast-ice combinations were established, and the meso -mechanical changes of the ballast-ice combinations at different freezing temperatures were analyzed at the failure moment. The results showed that with the decrease of temperature, the compressive strength, and the brittleness of the ballast-ice combinations gradually increased. The main manifestations were as follows. When the temperature was below –10 °C, the compressive strength of the ballast-ice combinations increased with the decrease of temperature (49.150 kPa at –10 °C, 154.625 kPa at –30 °C). The elastic modulus of the ballast-ice combinations increased with the decrease of temperature (5.118 MPa at –10 °C, 29.330 MPa at –30 °C), and their compression distances decreased when the failure occurred (1.96 mm and 1.09 mm). At the failure moment, the ice layer inside the ballast-ice combinations with a higher temperature (–10 °C) was more complete (the number of bonding keys was more than 2400, and the keys were agminated), but the force it could bear was lower (the bonding keys were numerous and concentrated, but their force values were small). When the temperature was lower (–30 °C), the separation was more serious at the failure moment (the number of bonding keys was fewer than 1500), but the overall force that the combination could bear was higher (there were five bonding forces more than 500 N). It is hoped that the test methods of this work can provide a reference for the further study of the mechanical properties of ballast in a freezing environment. [ABSTRACT FROM AUTHOR]

• The influence of tamping times on damping and stiffness of ballast bed was revealed. • The longitudinal vibration transmission attenuation of ballast bed was studied. • The correlation between the ballast bed resistance, damping and stiffness was studied. • The "resistance work" was used to determine the resistance variation of ballast bed. A ballast bed provides a stable foundation and a sufficient vibration-damping performance for a railway line due to its loose and porous structure. Tamping operations change the compactness of ballast stacks and improve and maintain the state of ballast beds, which also affect the vibration-transfer characteristics and resistance performance of ballast beds. In the present study, impact excitation technology was used to test and analyze the influence of the number of tamping operations performed by a tamping car on the damping and stiffness of a ballast bed. Additionally, the influence of different tamping operations on the longitudinal vibration-transmission characteristics of the ballast bed was obtained by the methods of "single-point excitation and multi-point pick-up". The mode of analysis of the railway structure was carried out by numerical simulation, and the resistance test on site was used to study the evolution law of the longitudinal and lateral resistance of the ballast bed during three tamping operations. The results showed that a large machine tamping operation changed the values of the two dominant resonances (140.75 Hz to 202.35 Hz and 381.25 Hz to 418.75 Hz) of track structure in the range of 0–600 Hz. The tamping operation also affected the resistance, damping, and stiffness of the ballast bed (the longitudinal and lateral resistances decreased by 17.39% and 20.34%, respectively, and the damping and stiffness increased by 204.07% and 148.80%, respectively), which suggests that the longitudinal/lateral resistances, damping, and stiffness of the ballast bed were strongly negatively correlated with one another. The modal shapes of the track structure caused by the first tamping and the second tamping were obviously different, and the positions and values of the maximum displacement changed (1.92 mm to 1.71 mm). The tamping also affected the longitudinal vibration transmission between the sleepers, and the maximum attenuation rate between adjacent sleepers was 81.25%. The change of the resistance work of the ballast bed with the displacement was more significant than the change of the resistance of the ballast bed with the displacement (when the ballast bed resistance decrement rates were 4.34%, 16.19%, and 20.34%, the track bed resistance work decrement rates were 13.14%, 28.15%, and 39.35%, respectively). Thus, the resistance work was more applicable when describing the variational degree of the stability of the ballast bed. [ABSTRACT FROM AUTHOR]

• An enzymatic route for the epoxidation of vegetable oil methyl ester was established. • An acid-base pair MOFs (UiO-66-NH 2) was prepared for CO 2 fixation with epoxides. • The epoxide conversion reached 94.4 % with CO 2 using UiO-66-NH 2. • The applicability of vegetable oil for epoxidation and CO 2 fixation were tested. Bio-based five-membered cyclic carbonates were synthesized from renewable O-acetyl methyl ricinoleate that from crops and CO 2 via two steps and the products after each reaction step were characterized by fourier transform infrared spectroscopy. For the acid-catalyzed process, O-acetyl methyl ricinoleate epoxidation of unsaturated double bonds was accomplished using lipase as a sustainable replacement. The effect of different experimental conditions, including the solvent, initiator types, initiator ratios, enzyme amount, reaction temperature, and reaction time, on epoxide conversion was analyzed. O-acetyl methyl ricinoleate conversion reached 95 % under the optimized reaction conditions and the resulting epoxide was subsequently reacted with CO 2 using the acid-base pair UiO-66-NH 2 to produce cyclic carbonate. CO 2 adsorption and fixation occurred simultaneously due to the use of bifunctional UiO-66-NH 2 and epoxide conversion reached 94.4 % with CO 2 using UiO-66-NH 2. The substrates applicability was tested after each step and it was found that more than 92 % of the fatty acid methyl esters were converted into their corresponding epoxides and more than 90 % epoxide conversion occurred, with the exception of epoxy methyl linolenate (85.4 %) due to the presence of multiple double bonds in methyl linolenate. These results demonstrate this reaction scheme can be efficiently adopted for vegetable oil methyl esters. [ABSTRACT FROM AUTHOR]

Liquid-metal divertor consisting of liquid Sn and Mo meshes would face high-flux plasma environments during service. In this work, the Sn corrosion behaviors on initial and pre-irradiated Mo meshes under hydrogen plasma irradiation were investigated to evaluate the reliability of the porous structure. According to the analysis and computation of XRD spectrum, the sub-grain size of the initial meshes would continuously grow during the corrosion process. The SEM images showed that after corrosion, the appearance and disappearance of prismatic Mo grains occurred alternately with the increase of plasma fluence. The thicknesses of corroded wires in the longitudinal and transverse directions displayed a similar repeatable change. In comparison to initial meshes, surface sub-grain growth and damage induced by the pre-irradiation treatment would result in differences in the corrosion process under hydrogen plasma irradiation. The pre-irradiated surface Mo grains with obvious grain boundaries were first dissolved to pebble-like Mo particles by liquid Sn and then stripped from the surface after corrosion. Sub-grain size was reduced from 72.5 nm to 41.1 nm at the fluence of 1.07 × 1026 ions/m2, which was inverse to the increasing phenomenon of the initial sample under same corrosion conditions. Additionally, the corrosion phenomenon, i.e., the presence and subsequent disappearance of prismatic Mo grains, occurred similarly on the surface of pre-irradiated samples. Based on the analysis of initial and pre-irradiated surface morphologies and wire thickness, Mo grains might go through an onion-peeling-like cycle of growth and fracture during the corrosion process. Besides, the wire thicknesses of all pre-irradiated Mo meshes were slightly less than that of the initial samples under the same corrosion conditions. Somehow, the comparative result reflected that the pre-irradiated samples were corroded more severely. Thus, the pre-irradiation of hydrogen plasma in this work would weaken corrosion resistance of Mo meshes in liquid Sn. • Growth and fracture of Mo grains might repeatedly happen during the corrosion process under hydrogen plasma irradiation. • Brief H 2 plasma irradiation could accelerate the growth of Mo grains compared with annealing under the same conditions. • The corrosion resistance of Mo wires was weakened during the corrosion process as a result of hydrogen bubbles burst. [ABSTRACT FROM AUTHOR]

This paper is concerned with the event-triggered fuzzy control design and its application to an inverted pendulum system. First, all of the introduced time-varying delay information from the inverted pendulum system and event-triggered mechanism is considered in the stability analysis. The interval of the time-varying delay is then divided into l nonuniform subintervals by utilizing an improved delay-partitioning technique. Information on each subinterval is processed by employing a reciprocally convex method. The proposed delay-dependent stability condition of the inverted pendulum system is determined to be considerably less conservative than the existing results in the literature, and the reduction in the conservativeness becomes progressively noticeable as the delay partitioning number l becomes progressively thinner. Moreover, by employing the parallel distributed compensation law, conditions sufficient for the resulting fuzzy controller and the event-triggering fuzzy controller are presented for the nonlinear inverted pendulum system. Finally, the advantages and effectiveness of the proposed design schemes are demonstrated by three simulation examples. [ABSTRACT FROM AUTHOR]

Motivated by the paper of Ward [5] , we use variational minimizing methods and Rabinowitz's Saddle Point theorem [1–4] to study the existence of the solution for the boundary value problem (1.2) with a parameter a , we notice that two cases: a < 1 and a = 1 are totally different. [ABSTRACT FROM AUTHOR]

This paper is concerned with event-triggered sliding mode control (SMC) for uncertain stochastic systems subject to limited communication capacity. We consider the stochastic perturbation, exogenous disturbance and the network-induced communication constraints in a whole framework of SMC design. The measurable output is adequately sampled for periodic computation of a designed event trigger. Network-induced delays are characterized in the transmission over a shared network communication from sensor to controller. An event-triggered zero-order-hold (ZOH) is employed to keep receiving and sending the delayed measurement for control updating, and a state observer is designed to estimate the system state and to facilitate the design of sliding surface. Then, based on the measurement and observer’s outputs, a novel SMC law is presented. The stochastic stability for the overall closed-loop system is analyzed, and the exogenous disturbance is attenuated in an H ∞ sense. Furthermore, the presented event-triggered SMC methods are successfully applied to multi-loop control case considering shared communication limitation. Simulation results are provided to verify the effectiveness of the proposed design scheme. [ABSTRACT FROM AUTHOR]