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Dynamic behaviour of the pneumatic muscle actuator (PMA) is conventionally modelled as a pressure-based first-order equation under discrete loads, which cannot exactly describe its dynamic features. Considering PMA's nonlinear, time-varying and hysteresis characteristics, we propose a novel high-order modified dynamic model of PMA based on its physical properties and working principle, with coefficients being identified under external dynamic loads. To tackle PMA's nonlinear hysteresis problem in high-frequency movements, a global fast terminal sliding mode controller with the modified model-based radial basis function (RBF) neural network disturbance compensator (RBF-GFTSMC) is designed. Comparison experimental studies are carried on a designed PMA platform that can provide continuously changing loads. Results show that the RBF-GFTSMC has superior trajectory tracking performance and disturbance compensation capability under wide-ranged frequencies and external loads, which can be potentially used to achieve precise control of PMA-actuated robots. • Modified model better describes pneumatic artificial muscle's dynamic behaviour. • Modelling under continuously changing and dynamic load conditions. • Novel controller adapts to high frequency applications with human interaction. • Model-based compensator improves control performance with dynamic external loads. [ABSTRACT FROM AUTHOR]

• A novel method of preparing the slippery lubricant-infused porous surface is proposed. • Condensation frosting is experimentally investigated on four typical substrates. • Directional icing propagation is impeded on the proposed slippery surface. • Molecular Dynamics simulation explores droplet wetting on slippery surfaces. Anti-propagation and enhanced icephobicity both are critical for anti-icing surfaces. In this work, four types of functional surfaces were prepared to investigate condensation frosting mechanisms (hydrophilic surfaces, hydrophobic slippery lubricant-infused porous surfaces, and two types of superhydrophobic surfaces). Experimental results indicated that no directional icing was identified on both the hydrophilic and slippery surfaces, while it was observed on superhydrophobic surfaces. The mechanisms were explained based on microscopic photos, together with theoretical analysis and Molecular Dynamics simulations. On the hydrophilic surfaces, the initially frozen droplets can induce the icing of some of their neighbours. However, these inter-droplet icing spreading failed to develop into a directional spreading for the whole field of view. On the slippery surfaces, most of the droplets had to freeze locally because the distances among them were beyond the effects of icing bridge. Moreover, the lubricant effects on droplet wetting were investigated using Molecular Dynamics simulation, and the results can support the existence of a lubricant layer beneath droplets. The surface icephobicity was experimentally investigated by measuring the critical shear stress of a frozen droplet. As a whole, the icephobicity of the slippery surface was significantly enhanced. Especially, when the substrate was chilled to −5 °C, the high icephobicity of the slippery surface was highlighted by an order of magnitude lower than that on the hydrophilic surface. Also, the slippery surfaces were fabricated based on silica nanoparticles via a commercially coating spray. This method can be of low economic cost for scalable preparation. Overall, the present work can be helpful for developing anti-icing functional surfaces. [ABSTRACT FROM AUTHOR]

To protect against soil secondary salinization, a desalination process for farmland drainage using wetlands was evaluated. In this study, the desalination effects of different plants in Chagan Lake were analyzed. A field experiment was conducted in the Qianguo irrigation district to choose the most efficient desalting plant by comparing the biomass contents and the ash rates of Typha spp., Phragmites communis , Phragmites japonica Steud. var. prostrata (Makino) L. Liu, Medicago sativa Linn., Lemna minor L. and Potamogeton crispus. Typha spp., Phragmites communis and Potamogeton crispus performed best among tested species in removing salt from saline farmland drainage. According to the calculated ash rates and ion contents, the amount of salt removed by reaping reed and cattail accounted for 10–26% of the salt in the drainage. The removal efficiencies of Ca 2+ , Mg 2+ , Na + , Cl − and SO 4 2− ions are 9–15% per year. A constructed wetland containing 233–288 km 2 of Typha spp. is required so that the removal efficiency of these six ions can be more than 80%. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To investigate the effects of autologous bone marrow mononuclear cells (BM-MNCs) implantation on regulation of cholangiocyte apoptosis in a model of intrahepatic ischemic type biliary lesion (ITBL) in rabbits. Materials and Methods: Thirty Japanese white rabbits were divided randomly into 3 groups (10 per group) including controls (group A), ITBL model (group B), and BM-MNCs implantation groups (group C). All rabbits underwent the same surgical procedure to prepare the liver for graft removal during transplantation. Subsequently, no additional vascular intervention was performed in group A. In group B, the hepatic artery and common bile duct were clamped with microvascular clips for 2 hours, where after the clips were removed to recover the blood supply. Group C received, BM-MNCs (108 cells per rabbit) injected through the hepatic artery after removing the clips. The animals were killed 4 weeks after operation. The survival rate, histopathologic examination, cholangiocyte apoptosis with terminal uridine nick-end labeling (TUNEL) staining and expressions of Bcl-2 and Bax proteins were examined using immunohistochemical staining. Results: Group A animals showed a survival of 100%; the rates in groups B and C were both 90%. Histopathologic examination revealed normal intrahepatic cholangiocytes in group A, obviously damaged ones in group B, and alleviated damage in group C. TUNEL staining indicated apoptosis of cholangiocytes in group B was more serious than that in group A or group C. Immunohistochemical staining demonstrated significantly decreased Bcl-2 expression in group B compared with that in group A; Bcl-2 expression in group C returned to the level of group A. Simultaneously, the Bax expression presented adverse results; the ratios of Bcl-2/Bax were ranked as group A > group C > group B. Conclusion: Implantation of autologous BM-MNCs significantly reduced apoptosis of intrahepatic cholangiocytes and prevented or abated intrahepatic ITBL. [Copyright &y& Elsevier]

Abstract: It is becoming evident that different dynamic derivatives play increasingly important roles in approximating functions and solutions of nonlinear differential equations for their great flexibility in grid designs. Different dynamic derivatives on time scales not only offer a convenient way in practical applications, but also show their distinctive features in approximations. It may be worthwhile to investigate if such useful features can be maintained or even improved in certain senses while different dynamic derivatives are used in the same application simultaneously. Under this consideration, we will introduce the combined delta (, or forward) and nabla (, or backward) dynamic derivatives, explore their basic properties, and investigate their applications for approximating classical derivative functions and for solving differential equation problems in this paper. Proper forward jump, backward jump and step functions will be introduced and utilized. It is found that while the combined dynamic derivatives possess similar properties as and derivatives, they offer more balanced approximations to the targeted functions and differential equations at satisfactory accuracy. The combined dynamic derivatives also reduce the unexpected computational spuriosity, and therefore lead to more reliable numerical algorithm designs. Computational examples are given to further illustrate our results. [Copyright &y& Elsevier]

Crossed symmetric solutions of nonlinear boundary value dynamic problems play an important role in many applications, in particular in adaptive algorithm designs. This article is devoted to the continuation of our investigation on second-order nonlinear companion dynamic boundary value problems on time scales. Monotonically convergent upper and lower solutions of the problems and their quasilinear approximations are investigated. It is shown that, under proper smoothness constraints, the iterative sequences constructed not only converge to the analytic solutions of the desired companion problems monotonically, but also preserve important crossed symmetry properties. The quasilinearization offers an efficient way in the solution approximation. Computational examples are given to illustrate our results. [Copyright &y& Elsevier]

This paper is concerned with modified adaptive difference schemes for solving degenerate nonlinear reaction–diffusion equations with singular source terms. The adaptive mechanisms both in space and time are considered. Modified monitor functions based on arc-lengths of the rate function ut are constructed. Further analyses are given on properties of the numerical schemes derived. We show that, under proper smoothness, consistency and step-size constraints, the numerical solution obtained preserves the monotonicity of the physical solution. Numerical experiments are given to demonstrate the monotonicity and convergence properties of the methods. [Copyright &y& Elsevier]

The stability and deformation of the permanent shiplock slopes are among the key issues in the design and construction of the Three Gorges Project. The permanent shiplock slopes, formed by deeply and steeply cutting into weathered and fresh granites, are 1607 m in length and 50–170 m in height. The disturbed zone in the permanent cut slopes induced by excavation is therefore one of the most important aspects in slope stability and deformation evaluation. A comprehensive investigation including non-linear finite element analysis, in-situ testing, instrumentation and monitoring, back analysis and rock mass quality rating has been carried out for the identification and evaluation of the excavation disturbed zone in the permanent cut slopes. The results of the investigation confirmed the existence of such an excavation disturbed zone in the permanent cut slopes. This zone is characterized by a considerable weakening in the mechanical properties of the rock mass. From the cut surface to the deeper region of the permanent cut slopes, the excavation disturbed zone can be further divided into a damaged zone, an affected zone and a slightly affected zone according to the extent of weakening in the rock mass. The damaged zone and the affected zone have thicknesses of 5–10 m and 10–20 m, respectively. The exact pattern of the excavation disturbed zone is variable in different parts of the permanent cut slopes and are generally similar to that of the plastic zones estimated by using the non-linear finite element analysis. The present investigation has provided both factual data and insights for the stability and deformation evaluation of the permanent shiplock slopes. The approach and methodology developed in the paper can be used to assess similar excavation disturbed zones in other large cut slopes. [Copyright &y& Elsevier]

Compressed carbon dioxide is a promising energy storage technology. However, renewable energy variability can lead to insufficiency during charging and discharging. The present work systematically investigates the effect of charging/discharging insufficiency on compressed carbon dioxide energy storage systems from the viewpoint of transient thermodynamic cycles. The insufficiency extent is defined based on the pressure at the high-pressure tank when disturbances occur. Then the effects of insufficiency extent are investigated in three typical scenarios. In the results, the effects of charging/discharging insufficiency on the efficiency, storage density and power output of the energy storage system during long-term operation are demonstrated. The efficiency of the system during the whole working period is 57.78%, lower than the design efficiency of 59.66%. In particular, the energy storage density is reduced dramatically to 197.60 kJ·m−3, which is 78.2% of the storage density of 252.68 kJ·m−3 at design conditions. Besides, the average output power of the turbine is reduced to 95.70% of the design value. The present work provides an improved understanding of the charging and discharging for compressed carbon dioxide energy storage, especially when renewables are integrated. • Problem on renewable energy variability effects on carbon dioxide energy storage is proposed and formulated. • Insufficient charging/discharging effects on efficiency, power and energy storage density are evaluated. • Cycle efficiency can be maintained at 57.78% but energy storage density reduced to 78.2%. • Necessity to consider renewable energy efficiency in economic analysis is suggested. [ABSTRACT FROM AUTHOR]

The supercritical-CO 2 (S–CO 2) cooler is one of the main components in S–CO 2 power system. This work aims at revealing the cooling mechanism of S–CO 2 under wide working conditions to assist the S–CO 2 cooler design. The pseudo-condensation is proposed with the analogy between supercritical cooling and subcritical condensation. From the pseudo-condensation and the traditional turbulent field analysis, the specific heat is found to be the dominant parameter for the enhanced heat transfer in S–CO 2 cooling. The disappearing of enhanced cooling heat transfer, in the view of pseudo-condensation, is mainly due to the thickening of pseudo liquid film, which is dominated by the gravity force, inertial force and interfacial force in low mass flux flow while the gravity force effect is negligible in high mass flux flow. However, from the turbulent field analysis, the disappearing of enhanced cooling heat transfer is mainly caused by the thickening boundary layer due to the local increase in density and viscosity in addition to the decrease in specific heat. Finally, based on the S–CO 2 cooling mechanism, two correlations for predicting heat transfer are proposed and evaluated. The present work can significantly enhance in-depth understanding on S–CO 2 cooling and promote engineering application. • The S–CO 2 cooling mechanism is analyzed with pseudo-condensation and turbulent field. • Pseudo-condensation is based on analogy between supercritical cooling and subcritical condensation. • Turbulent field analysis focuses on selection of key influencing thermophysical properties. • Two more accurate correlations are developed based on the obtained cooling mechanism. • The pseudo-condensation for S–CO 2 cooling process is proved to be with high reliability. [ABSTRACT FROM AUTHOR]

• Molecular potential functions are examined for silica simulations under high temperature. • Molecular Dynamics simulations illustrate the sintering mechanism of silica nanoparticles. • The proposed method of "solid-liquid" coexistence can effectively analyse sintering process. • High temperature effects on nanoparticle contact are substantially identified and quantified. • The proposed model of thermal conductivity can accurate capture available experimental data. Silica aerogels are extensively used for thermal insulation at high temperatures. However, it has been experimentally found that high temperature can change the pore structure and undermine thermal insulation. The mechanism of high temperature influence is unclear due to the limited resolution of experimental observations. In the present work, molecular dynamics simulations and theoretical modeling were combined to investigate the effects of high temperature on pore structures and heat conduction. At the scale of nanoparticles, the structural evolution induced by the sintering process of silica aerogels was numerically investigated. The melting process of a single silica nanoparticle can be divided into three stages, and it was found that extending the stage of surface diffusion can improve the thermal stability of silica nanoparticles. At the scale of particle assembly, the contact diameter between adjacent particles was identified and numerically evaluated. At the scale of bulk material, a theoretical model was developed to predict the solid thermal conductivity by considering both the temperature effect on the intrinsic thermal conductivity of backbone and the effect of nanoparticle size. A good agreement was found between the present model and available experimental data. An insightful discussion of the existing theoretical models and experimental data was also presented. The present work can inspire further cross-scale modeling of silica aerogels and may pave the way for the development of silica aerogels with high stability and thermal insulation at high temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Stretching computation strategies, including the hyperbolic exponential fittings along the lens interface, stretching transformations in z- and r-directions are discussed in this paper. The resulted adapted finite difference schemes are not only simple in structure, but also highly effective and efficient in the solution of paraxial Helmholtz equations for light beam propagation simulations and high performance lens designs. Cylindrically symmetric lens domains are assumed. Simulation results are given to illustrate the aforementioned numerical strategies with laboratory applications. Detailed algorithmic structures are given for immediate programming implementations and for similar lightwave propagation computation issues. [Copyright &y& Elsevier]

• Rough surface promotes ice nucleation if accessible groove width and ice lattice constant match. • Ice nucleation is significantly inhibited by decreasing solid surface free energy. • A quenching-induced wandering or jumping-up of nanodroplet is observed. It is significant to inhibit the formation of ice on solid surface under some occasions in industry. The origin of ice formation on solid surface is the heterogeneous ice nucleation, which has drawn a lot of research attention in the last decade. In this work, we investigated the effects of surface fraction, pillar height, and solid surface wettability on ice nucleation using molecular dynamics simulation. Compared with that of smooth surface, the ice nucleation rates on rough surface can be enhanced or inhibited depending on the groove size, which can be attributed to the status of water molecules confined between pillars. In addition, it is found that the ice nucleation rate can be significantly weakened by reducing the solid surface free energy. More importantly, when the surface free energy is low enough, a quenching-induced mobility of nanodroplet is observed, including wandering on the solid surface or jumping away. These findings can address the importance of the coupling effect of the gap width and height of pillars, together with the quenching-induced mobility, which we believe will be helpful to understand more molecular mechanisms of heterogeneous ice nucleation. [ABSTRACT FROM AUTHOR]

• This study proposed a new assessment technique with admittance control for measuring active ranges of motion of wrists. • The robotic system has a reconfigurable handle structure that allows for multi-dimensional wrist motions. • The reliability was validated on 11 subjects by measuring wrist flexion/extension and radial/ulnar deviation. The measurement of wrist active range of motion (ROM) is essential for determining the progress of hand functional recovery, which can provide insight into quantitative improvements and enable effective monitoring during hand rehabilitation. Compared with manual methods, which depend on the experience of the therapist, the proposed robot-assisted assessment technique can measure active ROM of human wrists. The robot with a reconfigurable handle design allows for multiple wrist motions. Experiments were conducted with 11 human subjects to measure ROMs of human wrist flexion/extension and radial/ulnar deviation. Reliability analysis was conducted by calculating the intra-class correlation coefficients (ICC), standard error of measurement (SEM) and SEM%. Results showed high reliability (ICC 2,1 ≥ 0.89, SEM ≤ 2.36°, SEM% ≤ 6.81%). Future will focus on adaptive joint self-alignment design between human users and robots to further improve its assessment accuracy. [ABSTRACT FROM AUTHOR]

The thermoelectric effect can convert waste heat into electricity. The present work presents an integrated system of Thermoelectric Generators (TEG) and Phase Change Materials (PCMs) for thermal insulation of high-speed vehicles, where high heat fluxes of large fluctuations make thermal protection and energy harvest challenging. A single-stage thermoelectric generator is prepared with phase-change materials embedded to absorb and convert excessive heat. The performance is evaluated experimentally and numerically, between which a reasonable agreement is observed. The maximum temperature at the outside surface is reduced by 200 K, and the temperature curves are flattered. Furthermore, two-stage and two-segment integrated systems are numerically evaluated, generating a data set of thermoelectric performance. An artificial neural network is developed for prediction and a genetic algorithm is employed for optimization. The maximum specific power can be improved to 570 W/m2 in the two-segment system, while the temperature variation at the hot side of TEG in the two-stage system can be reduced to 230 K. Finally, a discussion on the effects of PCMs parameters is performed. Overall, the present work not only demonstrates the feasibility of such an integrated system but also illustrates the whole procedure of the predictions and optimizations. This could inspire more development for advanced integrated systems for thermal management. • Experiments of integrated thermoelectric conversion system and COMSOL simulations are mutually validated. • Phase change materials integrate with thermal insulation and thermoelectric conversion. • The high fidelity of proposed neural network prediction and optimization is demonstrated. • The maximum temperature is reduced to 540 K in a two-stage system. • The maximum specific power is improved to 570 W m−2 in a two-segment system. [ABSTRACT FROM AUTHOR]

The measurement of wrist passive ranges of motion (ROMs) can provide insight into improvements and allow for effective monitoring during a rehabilitation program. Compared with conventional methods, this study proposed a new robotic assessment technique for measuring passive ROMs of the wrist. The robotic system has a reconfigurable handle structure that allows for multi-dimensional applications of wrist motions. The assessment reliability of this robotic system was analysed on 11 subjects for measuring wrist extension/flexion and radial/ulnar deviation. Preliminary data demonstrated its potential with intraclass correlation coefficient (ICC 2,1 ) all greater than 0.857 and standard error of measurement (SEM) less than 3.38°. Future work will focus on the standardization of the assessment protocol of this robotic system for assessment purposes, paving the way for its clinical application. [ABSTRACT FROM AUTHOR]

The novelty of this paper is the adjustable workspace and torque capacity of a compliant ankle rehabilitation robot (CARR). The robot has three rotational degrees of freedom (DOFs) redundantly actuated by four compliant actuators. It suffers from conflicting workspace and actuation torque due to the use of a parallel mechanism and compliant actuators. To address this issue, also considering physical constraints imposed by human users, the CARR is designed with reconfigurability to make a trade-off between workspace and torque capacity for meeting different training requirements. Theoretical analysis indicates that varying kinematic and dynamic performance of the robot can be achieved by reconfiguring the layout of the actuators. Experiments with/without load also demonstrate the validity of the reconfigurable robotic design for practical applications. [ABSTRACT FROM AUTHOR]

• Integration and conversion of supercritical carbon dioxide coal-fired power cycle and high efficiency energy storage cycle are discussed. • A three-step strategy is proposed and various cycles are presented and assessed. • First step: the tri-compression coal-fired integrated energy storage cycle has a high efficiency. • Second step: the integrated energy storage cycle with various heat sources needs to consider the trade-off of performance criteria. • Third step: the high efficiency split expansion adiabatic energy storage cycle is proposed. The emission peak/carbon neutrality calls for significantly improved coal-fired power plants. Sustainability of the power plants is critical to meeting the net zero targets in 2050/2060. In this context, it is necessary to investigate the integration and conversion of the supercritical carbon dioxide coal-fired power cycle and the supercritical carbon dioxide energy storage cycle. In this work, the thermodynamic model and performance criteria are firstly presented. After comparison of the two cycles, a three-step strategy for the development of the power cycle is proposed and assessed. First step: when coal still plays an important role as a main energy resource, the integrated tri-compression coal-fired supercritical compressed carbon dioxide energy storage cycle has the highest round-trip efficiency of 56.37%. Second step: with the challenge in utilization of coal energy, a trade-off among the performance criteria must be struck in the integrated cycle with various heat sources. Third step: the adiabatic supercritical compressed carbon dioxide energy storage cycle is proposed, and a high round-trip efficiency of 72.34% is achieved in the split expansion cycle. The present research provides not only a new prospect of the conventional power plants but also design guidance for the supercritical carbon dioxide energy storage cycle. [ABSTRACT FROM AUTHOR]

This work presents a design of 1000 MW S–CO 2 coal-fired power system, containing not only a new methodology of S–CO 2 power system modeling, but also the specific directions for engineering design. The coupling between computational fluid dynamic simulations at boiler scale and the mathematical modeling of the thermal cycle facilitates a high reliability of the comprehensive design. Our analysis helps identify key questions and then delivers specific directions for engineering design, especially for the pressure drop penalty in tail flue and thermal-hydraulic performance of cooling wall. The proposed flue split method coupled with parallel utilization method can not only effectively reduce the pressure drop penalty but also simplify the system heater configuration. Moreover, the thermal performance of S–CO 2 cooling wall is improved by using the flue gas recirculation and cooling wall arrangement optimization. The optimized position and proportion of flue gas extraction are further obtained. Comprehensively, the proposed design of S–CO 2 coal-fired power system enhances the system net efficiency up to 51.00%, with an efficient utilization of residual heat and cooling wall temperature below 700 °C. • A multiscale modelling platform is proposed for S–CO 2 coal-fired power system. • An improved system is obtained with system net efficiency up to 51.00% and cooling wall temperature all below 700 °C. • Flue split method and parallel utilization are developed for efficient recovery of tail flue heat. • Flue gas recirculation and cooling wall optimization are used to improve thermal safety of S–CO 2 cooling wall. [ABSTRACT FROM AUTHOR]

• Use partial differential equations (PDEs) modeling the fair price of Asian options. • The combination of aPC and a system of PDEs with moving boundary conditions. • The application of probability distributions constructed from real data of historic volatilities. This paper concerns accurate and efficient polynomial chaos expansions (PCEs) for Asian option pricing with uncertain volatilities. While arbitrary distributions of the volatility parameter are applied for estimating real-world option prices, arbitrary polynomial chaos (aPC) are incorporated for approximating raw data of the historical volatility distributions. Rigorous analysis is carried out to ensure the numerical stability of the compact aPC Crank-Nicolson finite difference method accomplished. Numerical results acquired are compared with solutions via standard Monte Carlo schemes (MCSs) and generalized polynomial chaos (gPC) with different random volatilities. Stock data from Asian financial industry are used. It is evident that the novel schemes derived are highly accurate and efficient for evaluating means and variances of uncertain volatility and stochastic Asian option pricing. [ABSTRACT FROM AUTHOR]

This paper proposes a new robot-assisted bilateral upper limb training strategy, focusing on the bilateral coordination of users' upper limbs. The strategy is implemented and evaluated on a bilateral upper limb rehabilitation device (BULReD) that is an H-bot mechanism actuated by two Maxon DC motors. The control system consists of a position controller, an admittance controller and an adaptive algorithm, where the BULReD stiffness is modified session by session based on training performance. This strategy is also integrated with subject-specific workspace for enhanced training safety. Experiments were carried out with five subjects through active reaching tasks. Results indicate that the proposed training strategy requires significant coordination of bilateral upper limbs for task completion, and is able to tune control parameters to an appropriate difficulty level based on participants' training performance. Future work will focus on its clinical evaluation on patients with upper limb disabilities. • A robot-assisted bilateral upper limb coordination training strategy. • The strategy enables subject-specific workspace determination. • Experimental results support its potential for upper limb coordination training. [ABSTRACT FROM AUTHOR]