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The immunoregulatory role of mesenchymal stem cells (MSCs) in inflammation is heterogeneous and can exhibit anti-inflammatory or proinflammatory properties depending on the microenvironment. We herein observed that the activation of Toll-like receptor 3 (TLR3) by polyinosinic : polycytidylic acid (poly(I : C)) stimulation facilitated the transformation of adipose-derived stem cells (ADSCs) into an anti-inflammatory phenotype. The enhanced anti-inflammatory properties were assessed in a taurocholate-induced pancreatitis model. The results demonstrated that poly(I : C) pretreated ADSCs exhibited enhanced anti-inflammatory properties than untreated ADSCs in taurocholate-induced pancreatitis. Mechanistically, poly(I : C)-treated ADSCs showed increased production and secretion of interleukin-10 (IL-10), which demonstrates a potent ability to alleviate inflammatory signaling cascades in acinar cells. Simultaneously, the heightened anti-inflammatory effects of poly(I : C)-treated ADSCs in pancreatitis were associated with the regulation of macrophage classical/alternative transformation, thereby mitigating inflammatory factor-mediated damage to the pancreatic acinar cell. We propose that TLR3 activation by poly(I : C) is an effective strategy to enhance the anti-inflammatory properties of MSCs, which offers a valuable consideration for improving the therapeutic efficacy of MSCs in inflammatory diseases. [ABSTRACT FROM AUTHOR]

Soft network materials (SNMs) represent one of the best candidates for the substrates and the encapsulation layers of stretchable inorganic electronics, because they are capable of precisely customizing the J-shaped stress-strain curves of biological tissues. Although a variety of microstructures and topologies have been exploited to adjust the nonlinear stress-strain responses of SNMs, the stretchability of most SNMs is hard to exceed 100%. Designing novel high-strength SNMs with much larger stretchability (e.g., >200%) than existing SNMs and conventional elastomers remains a challenge. This paper develops a class of hierarchical soft network materials (HSNMs) with developable lattice nodes, which can significantly improve the stretchability of SNMs without any loss of strength. The effects of geometric parameters, lattice topologies, and loading directions on the mechanical properties of HSNMs are systematically discussed by experiments and numerical simulations. The proposed node design strategy for SNMs is also proved to be widely applicable to different constituent materials, including polymers and metals. [ABSTRACT FROM AUTHOR]

Constructing heterojunction structures is an effective way to produce highly efficient photocatalysts with favorable charge transfer paths. In this study, TiO2 nanotube arrays were synthesized using an electrochemical anodization method, and g-C3N4 nanoparticles were grown in situ on TiO2 nanotubes using three thermal polymerization strategies. Compared with pure TiO2, the g-C3N4/TiO2 heterojunctions exhibited different degrees of enhancement in photoelectrochemical performance under stimulated solar light. The TNT-L heterojunction fabricated by urea solution exhibited excellent photoelectrochemical (PEC) activity and followed a Z-scheme mechanism, which is beneficial for carrier separation and maintaining the original redox capacity of each component. The crystallinity, morphology, chemical composition, and optical properties of the photocatalysts were also analyzed using a series of characterization techniques. [ABSTRACT FROM AUTHOR]

Due to the high-performance requirements of power converters in industrial applications, sliding-mode control has drawn extensive research attention for its insensitivity against external disturbances. In order to ensure this advantage while suppressing the chattering problem caused by discontinuous switching functions, in this article, a fuzzy sliding-mode control (FSMC) strategy consisting of three control loops is proposed for three-phase three-level neutral-point-clamped active front-end rectifiers. In the power tracking loop, an improved super-twisting algorithm is proposed to enforce the tracking errors of active power and reactive power to bounded regions in finite time and guarantee the transient performance. Next, in the dc-link voltage regulation loop, the regulation error of dc-link voltage converges to a bounded region with a super-twisting extended state observer-based FSMC strategy. A simple but efficient proportional-integral controller is employed in dc-link voltage balancing loop to reduce the voltage difference between two dc-link capacitors. The proposed controller is characterized by attenuated chattering phenomenon and improved the dc-link voltage regulation performance, disturbance rejection ability, and power tracking performance. Experimental results are provided to verify the effectiveness and superiority of the proposed strategy. [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]

In this article, a nonlinear high-gain observer (NHGO)-based second-order sliding mode (SOSM) control strategy is proposed for the three-phase three-level neutral-point-clamped (NPC) converter. This controller applies the advanced SOSM algorithm both in the voltage regulation loop and in the power tracking loop, which provides a fast dynamic for the dc-link voltage, and also assures a good steady-state behavior for the NPC converter. Additionally, an NHGO technique is implemented in the voltage regulator combining with the SOSM algorithm. The conventional observer-based controllers suffer from the destructive effects of measurement noise, and it can only be addressed by diminishing the observer gain, which sacrifices the observer property. The NHGO technique adopts a time varying gain, that is, high gain in transient while low gain in steady state, which minimizes the adverse influence of measurement noise. The tuning method of the proposed NHGO-based SOSM controller is given to simplify the implementation process. Finally, the simulation and experimental results of the proposed control scheme for the NPC converter are given and compared with the conventional PI controller as well as the well-known linear extended state observer-based control method, which validates the feasibility and superiority of the proposed controller. [ABSTRACT FROM AUTHOR]

In this article, a two-stage control scheme consisting of an adaptive-gain second-order sliding mode (SOSM) controller and a switched high-gain observer (HGO) is proposed for the three-level neutral-point-clamped (NPC) converter. The adaptive-gain SOSM control method is applied both in the voltage regulation loop and instantaneous power tracking loop, thus, the boundary of the disturbance derivative does not need to be known a priori. Compared with the fixed-gain SOSM, it provides a faster dynamic and a better steady-state response for the NPC converter. On the other hand, the conventional disturbance compensation observer used in the power system suffers from the adverse effects of measurement noise, which limits the performance of the observer. A switched HGO is combined with the adaptive-gain SOSM controller in the voltage regulation loop to address this issue. By using a switched observer gain, the switched HGO greatly diminishes the performance degradation induced by the inevitable measurement noise. Finally, several experiments between the representative extended state observer-based SOSM control scheme and the proposed control method are carried out for a comparison. The results demonstrate the feasibility and effectiveness of the proposed approach. [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]

Developments of soft network materials with rationally distributed wavy microstructures have enabled many promising applications in bio-integrated electronic devices, due to their abilities to reproduce precisely nonlinear mechanical properties of human tissues/organs. In practical applications, the soft network materials usually serve as the encapsulation layer and/or substrate of bio-integrated electronic devices, where deterministic holes can be utilized to accommodate hard chips, thereby increasing the filling ratio of the device system. Therefore, it is essential to understand how the hole-type imperfection affects the stretchability of soft network materials with various geometric constructions. This work presents a systematic investigation of the imperfection sensitivity of mechanical properties in soft network materials consisting of horseshoe microstructures, through combined computational and experimental studies. A factor of imperfection insensitivity of stretchability is introduced to quantify the influence of hole imperfections, as compared to the case of perfect soft network materials. Such factor is shown to have different dependences on the arc angle and normalized width of horseshoe microstructures for triangular network materials. The soft triangular and Kagome network materials, especially with the arc angle in the range of (30 ∘ , 60 ∘ ), are found to be much more imperfection insensitive than corresponding traditional lattice materials with straight microstructures. Differently, the soft honeycomb network materials are not as imperfection insensitive as traditional honeycomb lattice materials. [ABSTRACT FROM AUTHOR]

Although sea‐level is the primary control over sedimentary architectures on continental shelves, deciphering such changes is still challenging, except for the easily recognized transgression‐regression cycles. This problem becomes more prominent in sedimentary units with relatively homogenous and fine‐grained lithologies that have been deposited over short periods. Here, we focus on a dominantly clayey silt section of a sediment core from the outer shelf of the East China Sea. Detailed rock magnetic and electron microscopy analyses indicate that authigenic greigite (Fe3S4) is the major magnetic component in an almost 4‐m‐thick interval that was deposited during the late Marine Isotope Stage (MIS) 3, while pyrite (FeS2) is enriched in the underlying middle MIS 3 sediments. According to microfossil analyses, the identified greigite formed in a prodelta setting that was affected by cold coastal currents after the middle MIS 3, when the Taiwan Warm Current and its associated upwelling were prevailing within a middle‐outer shelf setting favorable for pyrite formation. Large‐amplitude regression occurred subsequently during the MIS 2, limiting sulfate supply and favoring the greigite preservation. Our results, along with the previous studies, demonstrate that both the material and environmental conditions that are crucial to iron sulfide survival have been largely controlled by sea‐level change. Moreover, we make a preliminary proposition that a water depth range of 30–60 m is more likely to lead to the enrichment of greigite on continental shelves. We, therefore, provide a promising avenue for the assessment of sea‐level change on continental shelves over orbital and even suborbital timescales. Key Points: Greigite was identified as the major magnetic mineral in almost 4‐m‐thick late MIS 3 sediments from the outer shelf of the East China SeaAuthigenic greigite and pyrite have great potential to indicate sea‐level change on continental shelves even on suborbital timescalesWater depths of 30–60 m are likely to be more suitable for extensive formation and preservation of greigite in continental shelf sediments [ABSTRACT FROM AUTHOR]

This paper presents a tracking control scheme with quantization mechanism for hypersonic flight vehicles (HFVs) with prescribed performance using an interval type-2 fuzzy neural network (IT2FNN). A parameterized tracking error model of the HFV is derived with some considered uncertainties, which are approximated by an IT2FNN. The tracking control of the velocity and altitude of the HFV is designed by using a prescribed performance control technique. It allows that transient characteristics of the tracking errors can be improved and adjusted by some prescribed performance functions. According to an adaptive backstepping control design procedure, novel continuous control laws of the fuel equivalency ratio, canard deflection, and elevator deflection are designed with logarithmic quantization mechanism, for the sake of avoiding inadvertently increasing the effective gains of continuous controllers as well as reducing loads of the communication from controller unit to actuator unit. Besides, the limited tracking errors of the flight path angle and angle-of-attack can be achieved by applying the designed controllers. Finally, the presented tracking controllers with quantization mechanism are validated by comparative simulations. [ABSTRACT FROM AUTHOR]

This paper presents voltage regulation and current tracking control strategies for three phase two-level grid-connected power converters. By using power-invariant Park’s transformation, an averaged mathematical model of power converters is obtained in dq synchronous reference frame. Then a novel control strategy using adaptive control and ${H}_{\infty }$ technique is proposed to regulate the dc-link output voltage as well as track a desired current reference for three-phase power rectifiers. More specifically, an efficient adaptive controller is established in the external loop for regulating dc-link output voltage in the presence of external disturbances. A set of ${H}_{\infty }$ controllers are designed in the internal loop to force the input currents track their desired values. Finally, simulation results obtained from the proposed control method are presented, analyzed, and compared with that of sliding mode control, and the superiority of the proposed control laws is verified. [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]

There are two distinctly different views on Quaternary sedimentation rates in the central Arctic Ocean, namely, that they were on cm/kyr or on mm/kyr scales, largely as a result of divergent interpretations of magnetic reversal stratigraphy. This study provides new evidence to help resolve this controversy in the form of an almost 1‐m‐thick negative polarity interval located at ~1.15 m below the seafloor in a 4.15‐m‐long sediment core from the Lomonosov Ridge, central Arctic Ocean. This thick polarity anomaly was first revealed through alternating field demagnetization of natural remanent magnetization on u‐channel samples. It was subsequently confirmed to be an authentic signal of a syndepositional geomagnetic field by integrating detailed rock magnetic studies, transmission electron microscopy with energy‐dispersive X‐ray spectroscopy analyses of magnetic extracts, and both alternating field and thermal demagnetization of discrete paleomagnetic samples. Here we conclude that it is more reasonable to interpret the reversed interval as a record of the Matuyama Chron rather than a Brunhes‐aged excursion, which yields mean sedimentation rates of ~1.5 mm/kyr and ~0.5 mm/kyr in the Brunhes and Matuyama Chrons, respectively. These estimates are remarkably lower than assumed in most recent studies, but in good agreement with both previous magnetostratigraphic and recent geochemical studies relative to the decay of Be and U‐series isotopes, which might indicate "sediment‐starved" environments at least in some parts of this region. Overall, our results not only imply that chronostratigraphy in the central Arctic Ocean remains open to debate but also warrant further investigations in this microfossil‐barren region. Key Points: The effects of self‐reversed CRM of diagenetic titanomaghemite are probably only regional in the central Arctic sedimentsThe "reversal" interpretation supports "sediment starved" environments at least in some regions of the central Arctic OceanThe chronostratigraphy and usability of paleomagnetism in the central Arctic Ocean remains open to debate and further studies are warranted [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]

A series of soft magnetic nickel ferrite (NiFe 2 O 4) samples were successfully synthesised at 1000 °C over a period of 2 h through the molten salt synthesis method using iron oxide red as iron-bearing raw materials. After the cubic spinel structured NiFe 2 O 4 was prepared, the lattice parameter, oxygen positional parameter, M (Fe, Ni)-O bond length, and distribution of cations at tetrahedral and octahedral sites were determined using XRD. The fitting results of Raman spectroscopy demonstrated that the cations of Fe and Ni constituted complex compounds (MO 4) at the tetrahedral site. The morphologies of the synthesised NiFe 2 O 4 samples displayed different shapes and sizes when different molten salts were used as the medium. In addition, energy dispersive spectroscopy was used to analyse the composition of the samples, which indicated the samples were composed of Ni, Fe, and O. The highest value of saturation magnetisation (44 emu/g) was obtained with the NaCl-Na 2 SO 4 molten salts. Unlabelled Image • NiFe 2 O 4 were successfully synthesised by the molten salts method with different eutectic molten salts as intermediate medium. • The cations distribution of prepared NiFe 2 O 4 at tetrahedral and octahedral sites have been obtained from XRD. • The highest value of the saturation magnetization (44 emu/g) was obtained with NaCl-Na 2 SO 4 molten salts. [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]

This paper proposes a novel control strategy for three-level neutral-point-clamped (NPC) power converter. The proposed control scheme consists of three control loops, i.e., instantaneous power tracking control loop, voltage regulation loop, and voltage balancing loop. First, in the power tracking control loop, a set of adaptive sliding mode controllers are established to drive the active and reactive power tracking to their desired values via radial basis function neural network technology. In the voltage regulation loop, an efficient but simple adaptive controller is designed to regulate dc-link output voltage where the load is considered as an external disturbance. Moreover, a composite controller is developed in the voltage balancing loop to ensure imbalance voltages between two dc-link capacitors close to zero, in which a reduced-order observer is used to estimate sinusoidal disturbance improving the converter performance. The effectiveness and superiority of the proposed control strategy for the NPC power converter are compared with other control schemes through experimental results. [ABSTRACT FROM AUTHOR]

Using anions (OH−, Cl−, SO42−, NO3− and CH3COOH−) as structure and surface directing agents, α-Fe2O3 nanoparticles with quasi cube, parallel hexahedron, irregular sphere, nanosheet and hexagon shapes were successfully prepared by utilizing larger particles of iron oxide red. The results revealed that the shape of the α-Fe2O3 nanoparticles had a remarkable effect on the optical and magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract This paper is concerned with the problems of observer-based sliding mode control and fault estimation for Lipschitz nonlinear systems. The concerned plants are characterized with an actuator fault deviation existing in state dynamics and measured outputs. It represents a more general faulty plant case than those considered in the existing literature. Comparing with existing results on the sliding mode control procedure design, we propose new techniques to overcome the difficulty caused by parametric perturbation and measured noise existing in system output. For precisely estimating the plant states and the faults simultaneously, a novel estimation technique is developed to tackle the influence from the fault deviation. Based on the state estimation, an integral-type sliding mode control scheme by the utilization of an augmented sliding mode observer is presented for the stabilization of the faulty plants. Finally, an electromechanical system is applied to validate the availability and applicability of the presented control methods. [ABSTRACT FROM AUTHOR]

Herein we demonstrate a new, reproducible, and facile strategy to prepare γ-Fe 2 O 3 with iron oxide scale by pre-treated with molten sodium hydrate, hydrolysis and subsequent heat treatment method. The structural, chemical composition, morphological, optical, magnetic properties as well as possible transformation mechanism were investigated. X-ray diffraction (XRD), UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy (XPS) confirm that the tetragonal γ-Fe 2 O 3 phase with lattice parameters a = 8.3477 Å and c = 25.1823 Å was prepared. For the phase transformation process, the mixture of iron oxide scale and NaOH formed intermediate α-NaFeO 2 in the calcined process, then the structure of FeO 4 was generated in the hydrolysis procedure. The prepared γ-Fe 2 O 3 have saturation magnetization of 9.03 emu/g and coercivity 322.8 Oe. [ABSTRACT FROM AUTHOR]

A new approach to the control of three-phase two-level grid-connected power converters is proposed in this paper. The proposed control is an extended state observer (ESO)-based second order sliding mode (SOSM), which comprises two control loops: the outer loop is a voltage regulation loop, as well as inner loop is an instantaneous power tracking loop. The outer loop is accomplished by an ${H}_{\infty }$ controller plus an ESO, which is designed to regulate dc-link capacitor voltage of the converter and asymptotically reject external disturbances and parameter perturbations. The SOSM strategy is employed in the inner loop to drive the active and reactive power convergence to their desired values. Control objectives of nearly unity power factor and dc-link capacitor voltage regulation are simultaneously satisfied. Availability of the ESO-based SOSM is compared with the classic proportional-integral control in simulations, and the comparison implies that the proposed strategy not merely achieves an almost perfect tracking performance, but also provides a complete robustness against resistance load variation. [ABSTRACT FROM AUTHOR]

This paper concentrates on the problem of control of a hybrid energy storage system (HESS) for an improved and optimized operation of load-frequency control applications. The HESS consists of a supercapacitor serving as the main power source and a fuel cell serving as the auxiliary power source. First, a Hammerstein-type neural network is proposed to identify the HESS, which formulates the Hammerstein model with a nonlinear static gain in cascade with a linear dynamic block. It provides the model information for the controller to achieve the adaptive performance. Second, a feedforward neural network based on a back-propagation training algorithm is designed to formulate the proportional-integral-derivative (PID)-type neural network, which is used for the adaptive control of the HESS. Meanwhile, a dynamic antiwindup signal is designed to solve the operational constraint of the HESS. Then, an appropriate power reference signal for the HESS can be generated. Third, the stability and the convergence of the whole system are proved based on the Lyapunov stability theory. Finally, simulation experiments are followed through on a four-area interconnected power system to demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

This paper studies the problem of adaptive fuzzy control for a category of single-input single-output nonlinear networked control systems with network-induced delay and data loss based on adaptive backstepping control approach. Fuzzy logic systems are used to approximate the unknown nonlinear characteristics existing in the system, while Pade approximation is introduced to handle network-induced delay. Data loss occurs intermittently and stochastically in the data transmitting process, which is regarded as the delay in the controller design. In the framework of adaptive fuzzy backstepping technique, a novel state-feedback adaptive controller is constructed to ensure all signals in the resulting closed-loop system to be bounded and the state variables can be regulated to the origin. Finally, two examples are given to show the validity of the proposed results. [ABSTRACT FROM PUBLISHER]

Magnetic greigite may be a valuable indicator for methane emissions in the geological past, if its formation pathway and diagenetic environment can be unambiguously defined. Here, we investigate sulfur isotopic compositions of iron sulfides and ferrous iron concentrations of thick greigite‐bearing sediments (TGBSs) in the South Yellow Sea, a shallow marginal sea with strong methane emissions. For the first time, isotopically heavy iron sulfides (up to 28.7‰ in δ34S and 0.19‰ in Δ33S) and enrichments of ferrous iron in the TGBSs are observed. We interpret the data as indicating synchronic occurrences of anaerobic oxidation of methane coupled to sulfate and iron reductions, which occur in coastal methanic zones with limited sulfate availability and therefore probably imply leakages of methane. Consequently, we suggest that greigite is a promising geological indicator for tracing methane liberated from coastal sediments, accounting for ∼60% of the currently rising global marine methane budget. Plain Language Summary: Greigite (Fe3S4) is an easily detected ferromagnetic mineral and extensively observed in shallow coastal sediments, where strong methane emissions to the atmosphere prevail. It probably forms in a relatively sulfur‐poor environment associated with the consumption of methane by sulfate reduction. Here, we found a unique sulfur isotope fingerprinting in iron sulfides and enrichment of ferrous iron in these greigite‐bearing sediments, likely defining a methanic condition associated with potential coastal methane leakages. Our study highlights the intrinsic linkage between methane and greigite formation, supports that greigite may be a potential indicator for quantifying the global natural methane budget, and therefore has paleoenvironmental implications for geological global warming events. Key Points: Isotopically heavy sulfides (both δ34S and Δ33S) and enrichment of ferrous iron are synchronically observed in greigite‐bearing sedimentsPyrite with elevated Δ33S in thick greigite‐bearing sediments likely formed under a methanic conditionGreigite is a potentially useful tracer for methane leakages from coastal sediments [ABSTRACT FROM AUTHOR]

This study presents an adaptive sliding mode control (SMC) scheme for the output voltage regulation of the three‐phase AC/DC voltage source converters, based on interval type‐2 (IT2) Takagi–Sugeno (T–S) fuzzy model. Parameters of the whole system are considered with bounded perturbations, and the non‐linearities together with corresponding uncertain parameters existing in the input term are dealt with lower and upper membership functions of type‐2 firing intervals. SMC technique is employed to control the output capacitor voltage while keeping the power factor close to one, using the T–S fuzzy model. An integral sliding mode surface, in terms of the error dynamics generated by the system states and their references, is first designed with normalised central membership functions. Then, adaptive technique is applied to compensate the uncertain coefficients in the IT2 membership grades. Finite‐time reachability of the sliding mode is guaranteed under the resulting adaptive SMC. Finally, the robust and effective tracking performance of the proposed controller is tested and validated in the presence of the uncertain parameter perturbations. [ABSTRACT FROM AUTHOR]

This paper proposes an extended state observer (ESO) based second-order sliding-mode (SOSM) control for three-phase two-level grid-connected power converters. The proposed control technique forces the input currents to track the desired values, which can indirectly regulate the output voltage while achieving a user-defined power factor. The presented approach has two control loops. A current control loop based on an SOSM and a dc-link voltage regulation loop which consists of an ESO plus SOSM. In this work, the load connected to the dc-link capacitor is considered as an external disturbance. An ESO is used to asymptotically reject this external disturbance. Therefore, its design is considered in the control law derivation to achieve a high performance. Theoretical analysis is given to show the closed-loop behavior of the proposed controller and experimental results are presented to validate the control algorithm under a real power converter prototype. [ABSTRACT FROM PUBLISHER]

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, the design of a nonlinear observer-based fault diagnosis approach for polymer electrolyte membrane (PEM) fuel cell air-feed systems is presented, taking into account a fault scenario of sudden air leak in the air supply manifold. Based on a simplified nonlinear model proposed in the literature, a modified super-twisting (ST) sliding mode algorithm is employed to the observer design. The proposed ST observer can estimate not only the system states, but also the fault signal. Then, the residual signal is computed online from comparisons between the oxygen excess ratio obtained from the system model and the observer system, respectively. Equivalent output error injection using the residual signal is able to reconstruct the fault signal, which is critical in both fuel cell control design and fault detection. Finally, the proposed observer-based fault diagnosis approach is implemented on the MATLAB/Simulink environment in order to verify its effectiveness and robustness in the presence of load variation. [ABSTRACT FROM PUBLISHER]

In this paper, a combination of feedback linearization and disturbance observer-based control (DOBC) is adopted for the design of a state-feedback controller that regulates the velocity and altitude of air-breathing hypersonic vehicles (AHVs) subject to constrained inputs. First, a disturbance observer is established to estimate the overall effect of possible uncertainties and disturbances on the nominal vehicle model which is called the lumped disturbance. Then, a compensation method is proposed based on disturbance observer and feedback linearization control to counteract the mismatched lumped disturbance. Furthermore, a novel antiwindup modification is implemented on the baseline control to handle the possible input saturation. The designed controller addresses the issue of stability robustness with respect to system uncertainties and disturbances, and achieves zero-error tracking with good performance and antiwindup property meanwhile, which is the major merit compared with other existing AHV controllers. Finally, simulation is presented to verify the effectiveness of this control scheme. [ABSTRACT FROM PUBLISHER]

A series of Strontium hexaferrite (SrFe 12 O 19 ) were successfully synthesized at 1100 °C for 2 h by the molten-salt synthesis method using SrCO 3 and oxidized scale as raw materials. The characteristics morphology and magnetic properties of as-prepared SrFe 12 O 19 powders in different eutectic molten salt mixtures were discussed. The morphology feature has an important influence on magnetic properties of SrFe 12 O 19 , in particular of the coercivity. Because the basal plane of M-type strontium hexaferrite is easily magnetized, the obtained samples of platelet-shaped with large ratio of width to thickness in KCl–Na 2 SO 4 and KCl–K 2 SO 4 molten salts display a low coercivity which is 2862 Oe and 2687 Oe, respectively. The H c , M s , M r and (BH) max of the obtained SrFe 12 O 19 with irregular elliptical shape in NaCl–KCl molten salt are 4043 Oe, 60.77 emu/g, 33.75 emu/g, 0.61 MG Oe. The multi-domain structure of all samples may cause the coercivity lower than the theoretical value. [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]

An adaptive second-order sliding mode controller is proposed for a class of nonlinear systems with unknown input. The proposed controller continuously drives the sliding variable and its time derivative to zero in the presence of disturbances with unknown boundaries. A Lyapunov approach is used to show finite time stability for the system in the presence of a class of uncertainty. An illustrative simulation example is presented to demonstrate the performance and robustness of the proposed controller. [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]

In the present study, the reduction process of pellet containing high chromic vanadium-titanium magnetite in cohesive zone has been investigated. To elucidate the reduction process including the softening and melting properties, structure changes and migration processes of valuable components (Fe, V, Ti, and Cr) in pellet containing high chromic vanadium-titanium magnetite in cohesive zone, the experiment was carried out at different temperatures and the pellet samples were analyzed by the methods of XRD, SEM, and chemical analysis. The results of reduction process show that the temperature range of cohesive zone of pellet is from 1087.9 to 1338.3 °C and the maximum differential pressure of the burden is 15 859 Pa at the temperature of 1291 °C. The reduction process of pellet was gradually conducted from outside to inside, which could form a layer of iron shell on the outer surface of the pellet. A lot of wustite could be generated in the core of pellet when the reduction temperature exceeded 1100 °C. The migration process of iron is Fe2O3→Fe3O4→FeO→Fe, while the generated FeO could react with SO2 forming 2FeO·SO2. The reduction process of titanium is Fe2O3·3TiO2→Fe5TiO8→Fe2TiO4→FeTiO3→Ti(O0.19C0.53N0.32)→Ti(C,N)→[Ti] and MgO·TiO2→Ti(C,N)→[Ti]. The migration process of vanadium is V2O3→VN, VC→[V] and the chromium oxide was reduced as follows: (Fe0.6Cr0.4)2O3→FeCr2O4→[Cr]. [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]

Magnetic minerals in sediments of the continental shelf are sensitive to environmental changes. Therefore, to determine the exact phases of magnetic minerals is the prerequisite to investigate the paleoenvironmental significances. In this study, a comprehensive rock magnetic investigation, coupled with mineralogical studies, was carried out on the long core NHH01 (with a length of 125.64 m) from the central continental shelf of the South Yellow Sea. Single-domain greigite was identified as the dominant magnetic carrier in sediments between 44.90 and 51.80 m, and terrigenous magnetite is the major magnetic phase in the adjacent layers. The existence of greigite unambiguously indicates an anoxic environment. We tentatively interpreted that such an environment could be formed by the fast sea level changes, long-existing of the cold eddies during warm stages, or in a lake which might be related to locally tectonic uplifting. Therefore, the occurrence of the thick-layer greigite could supply a new perspective to paleoenvironmental or even tectonic studies. [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]

In this paper, a full-bridge boost power converter topology is studied for power factor control, using output higher order sliding mode control. The AC/DC converters are used for charging the battery and super-capacitor in hybrid electric vehicles from the utility. The proposed control forces the input currents to track the desired values, which can control the output voltage while keeping the power factor close to one. Super-twisting sliding mode observer is employed to estimate the input currents and load resistance only from the measurement of output voltage. Lyapunov analysis shows the asymptotic convergence of the closed-loop system to zero. Multi-rate simulation illustrates the effectiveness and robustness of the proposed controller in the presence of measurement noise. [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]

• Carbothermal reduction–H 2 SO 4 leaching of high-fluorine Bayan Obo tailings is studied. • More than 99% of Fe is reduced to the metallic state as the basicity increases to 1.87. • Approximately 97% of Fe and 83% of the REEs were separated and extracted. • Leaching temperature (>25 °C) and H 2 SO 4 concentration (>2 mol/L) hinder the leaching of rare earth elements. In this work, carbothermal reduction followed by sulfuric acid (H 2 SO 4) leaching of Bayan Obo tailings has been studied for the selective concentration of Fe and rare earth (RE) minerals. The effect of basicity on the metallization rate of Fe, transfer behaviors of metallic Fe and RE elements, phase composition, and element migration was investigated using XRD, SEM-EDS, EDS mapping, and FT-IR spectroscopy. At a roasting temperature of 1100–1200 °C and a basicity of 1.87, more than 99% of Fe was metallized and 97.91% of Fe and 94.94% of RE were separated magnetically. After roasting, the RE elements mainly existed in Ca 2 RE 8 (SiO 4) 6 O 2 and Ca 8 RE 2 (PO 4) 6 O 2 , 88% of which were leached out by H 2 SO 4 at 25 °C with an initial concentration of 2 mol/L and a stirring speed of 900 r/min. The precipitation of RE 2 (SO 4) 3 was responsible for the incomplete recovery of RE elements during leaching. [ABSTRACT FROM AUTHOR]

In previous study, we have found the catechol- O-methyltransferase (COMT) Val158Met polymorphism may be associated with the risk of Parkinson's disease (PD) in Asians, especially Japanese population. In this study, we further evaluated the associations of PD wearing-off susceptibility with COMT polymorphisms. We carried out a retrieval of studies and included the relevant studies which met the criteria. After the data were extracted, the Stata software 11.0 was used to analyse the genotype frequencies. A total of five studies were included. The pooled result indicated that genotype AA was significantly associated with the wearing-off risk of PD (AA vs. others: OR = 2.52, 95 % CI 1.21-5.26, P = 0.013; AA vs. GA: OR = 2.51, 95 % CI 1.18-5.34, P = 0.017; AA vs. GG: OR = 2.17, 95 % CI 1.09-4.33, P = 0.027). The results also showed allele A was correlated with PD wearing-off risk (A vs. G: OR = 1.95, 95 % CI 1.18-3.22, P = 0.009). In conclusion, this study suggested that Val158Met polymorphisms in COMT may increase the risk of wearing-off. Further studies with larger sample sizes are needed to confirm our results. [ABSTRACT FROM AUTHOR]