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In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds.

The partial air cushion supported catamaran (PACSCAT) is a novel Surface Effect Ship (SES) and possesses distinctive resistance performance due to the presence of planing bottom. In this paper, the design of PACSCAT and air cushion system are described in detail. Model tests were carried out for Froude numbers ranging from 0.1 to 1.11, the focus is on the influence of air cushion system on resistance characteristics. Drag-reducing effect of air cushion system was proved by means of contrast tests in cuhionborne and non-cushionborne mode. Wave-making characteristics reflect that the PACSCAT would eventually enter planing regime, in which the air could just escape under the seals and the hull body could operate in a steady state. To acquire different air cushion pressure, air flow rate and leakage height were adjusted during tests. Experimental results show that the resistance performance in planing regime would decrease evidently as the increased air flow rate, however, the scheme with medium leakage height presents the best resistance performance in the hump region.

Aiming at the non-uniformity of the air film between the conveyor belt and the trough during the operation of the air-cushion belt conveyor, a comprehensive study was executed by means of simulation analysis. Firstly, the air cushion pressure was theoretically deduced according to the principle of force balance, and the theoretical distribution expression and curve of air cushion pressure were given. Then, by constructing a gas flow model around the stomata, the pressure and velocity distribution of the flow field near the stomata were deduced, by constructing a cross-sectional gas outflow model, the outflow velocity and pressure distribution of the air cushion along the cross-section were deduced. Finally, the air cushion field was simulated and analyzed based on the fluid dynamics analysis software Fluent, the effects of different pore velocity, pore arrangement and air cushion thickness on the characteristics of the air cushion flow field were studied. The results indicate that air cushion pressure decreases with increasing air cushion thickness. The bearing capacity of the air cushion has a linear relationship with the stomatal flow rate, and the linear ratio is K=41.57. The optimal design parameters for the arrangement of air holes is the aperture of 7 mm and the hole spacing of 75 mm. When the air cushion thickness is 3 mm ～5 mm, air cushion stiffness decreases with increasing air cushion thickness. [ABSTRACT FROM AUTHOR]

In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds. [ABSTRACT FROM AUTHOR]

In order to study the flow field characteristics of cushion system of partial air cushion support catamaran (PACSCAT) in waves, an analysis was carried out involving flexible treatment on the bow and stern air seals to simulate air seal shape under test conditions by means of computational fluid dynamics method and fluid structure interaction (FSI) method. On this basis, the pressure conditions of the air cushion chamber and the pressurized chamber at different wavelengths and different speeds are studied and compared with experimental results. The experimental results show that: for the air cushion pressure, the nonlinear characteristics of the numerical calculation results are more subtle than the experimental values, after linear transformation, the amplitudes of the experimental values are obviously greater than the calculated values after linear transformation, but the average values are not much different; At low speed of 2.0m/s, the spatial pressure distribution of the pressurized chamber and the air cushion chamber are uniformly distributed, at high speed of 3.6m/s, except for a certain pressure jump occurred in the air cushion chamber near the stern air seal, the pressure in other spaces is also evenly distributed, it proves that the pressurized chamber type of air intake can effectively meet the air cushion pressure balance. [ABSTRACT FROM AUTHOR]

This paper investigates the cushion lift dynamics of a polar hovercraft. The motion of the flexible skirt on the ice surface is simplified and a mathematical model is established to study the dynamic response characteristics of the hovercraft in the process of lifting and moving over ice. This model considers the pressure/flow characteristics, skirt pressure, air cushion pressure, and flow rate of the fan of the hovercraft, and establishes a simulation using a C++program. When the hovercraft is pushed by the propeller, a thrust of 10 kN will cause a pressure difference of about 450 Pa between the front and rear chambers, 0.06 m in the height of the upstream and downstream discharge flows, and a decrease of about 0.4° in the longitudinal inclination angle. Changing the pitch angle to 0.5° creates a pressure difference of about 500 Pa between the chambers and a height difference of 0.07 m between the discharge. When the hovercraft speed is low, the wind speed has a small impact on the air cushion pressure of the lift system. The results of this research provide important technical and experimental foundations for further studies on the ice surface kinematics and safety control strategy of polar hovercraft. • A cushion lift dynamics system of a polar hovercraft by flow balance equation. • The model studies air cushion pressure changes through the discharge height. • Air cushion pressure in the air chamber is affected by external influence. • The hovercraft tests on the ice proves the effectiveness of the simulation results. [ABSTRACT FROM AUTHOR]

ObjectiveThis paper aims to reveal the influence law of cushion pressure on the underwater noise radiation of air cushion vehicles (ACVs). MethodsAn ACV is taken as a computational example. First, the forming process of the skirt under cushion pressure is simulated according to the Newton–Raphson iteration method. Second, a numerical model considering skirt-air cushion-water coupling is established via the vibro-acoustic finite element method (FEM) and calibrated based on modal tests. Third, comparisons are made of the sound power level (SWL) of the ACV's underwater radiation noise under different pressure levels on the skirt and different cushion depression depths. ResultsUnderwater radiation noise is found to be positively correlated with air cushion pressure. The overall SWL increases by nearly 0.97 dB while the air cushion pressure increases by 1000 Pa. Increasing the stiffness of the skirt can effectively reduce the underwater radiation noise in the low frequency band, and increasing the cushion depression depth will increase the peak value of the SWL in the higher frequency band, and make the peak position shift to the low frequency direction. ConclusionThe influence law of air cushion pressure revealed in this paper has important guiding significance for evaluating and numerically predicting the acoustic performance of ACVs.

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The air film thickness is an important parameter of an air cushion belt conveyor, which directly affects the compressed air supply power and operating resistance of the system. Therefore, it is important to calculate the bottom thickness of the gas film accurately in the design stage. A calculation method for the thickness of a conveyor air cushion was derived based on the mathematical model of the air cushion flow field for a multi row uniformly distributed air cushion structure. Meanwhile, the algorithm was validated based on a Fluent 3D flow field numerical simulation and experiments. Through verification, it was found that due to the algorithm's assumption that the increase in the gas flow rate only existed at the axis of the gas hole, there was a sudden change in the calculation results of the gas flow rate at the axis of the gas hole. The sudden change in the gas flow rate had caused the calculation results of the air cushion thickness to experience abrupt and discontinuous changes. Furthermore, the calculation method for air cushion thickness was revised based on the verification results. Compared with the experimental test results, the average error of the calculation results of the algorithm proposed in this paper was 14.27%. [ABSTRACT FROM AUTHOR]

To study the performance of partial air cushion-supported catamaran (PACSCAT), which is sailing with a flexible air seal in waves, this paper uses the model tests, and research the motion characteristics of PACSCAT at different wavelengths, by monitoring the boundaries of heave, pitch, acceleration, air cushion pressure. Firstly this paper introduces the test situation of PACSCAT in the towing tank and introduces the test method, equipment, and test conditions. Second, this paper extracts the test data, analyzes the features of heave, pitch, acceleration, and air cushion pressure, and studies their linear and nonlinear changes in regular waves. Thirdly this paper analyzes the nonlinear air leakage flow of the bow of PACSCAT in detail under the test conditions and studies the internal and external free liquid surface under different conditions.

The prediction of the wave load on a hovercraft is essential for the design of the hull structure and safety. However, theoretical methods for the prediction of wave loads are still not mature enough due to the unique and complex nature of the air cushion structure, and numerical modeling and simulation are challenging due to the complexity of the gas-solid-liquid three-phase coupling, so the study of wave loads on hovercrafts still relies on experimentation. In this study, we aim to analyze the wave load response characteristics of a four-chamber hovercraft by conducting a wave load model test under medium/low sea states. The load components and amplitude-frequency response characteristics were thoroughly analyzed based on the acquired data of the cushion pressure, acceleration, and bending moment. The main characteristics of the wave-induced response of the hovercraft were described in detail, and an analytical relationship between the cushion pressure and hull acceleration was derived. The reliability of the experimental results was confirmed through a comparison with the derived results. The relationship between the cushion pressure and cushion volume was investigated in terms of the observed geometric volume of the air chamber, and the relationship between the cushion pressure and flow rate was analyzed to validate the derivation of the theory of wave loads on hovercrafts. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rheumatoid arthritis (RA) is a chronic disease, in which permanent joint deformation is largely preventable with the timely introduction of appropriate treatment strategies. However, there is no consensus for patients with RA to monitor their progress and communicate it to the rheumatologist till the condition progresses to remission. In response to this unmet need, we proposed the design of a self-measuring device based on bioelectrical impedance analysis (BIA) for regular monitoring of inflammation levels. Twenty joints of both hands were measured to monitor trends in inflammation levels. Three electrodes were used to measure two joints of each finger. A central electrode was used for two consecutive measurements. A suitable form factor for the device was proposed for the vertical placement of the hand. To ensure the stability of measurements, an air cushion was incorporated into the back of the hand, hand containers were designed on both sides, and a mobile application was designed. We conducted a convergence-assessment experiment with five air pressures to validate the consistency and convergence of bioimpedance measurements. A heuristic evaluation of the usability around the product and mobile application was conducted in parallel by six subject matter experts and validated the design. This study underscores the significance of considering patients' disease activity during intervals between hospital visits and introduces a novel approach to self-RA care. [ABSTRACT FROM AUTHOR]

Hyperloop, a very high-speed transportation system including a pod transporting the passengers in a tube, forms the core debate in numerous recent investigations. The present paper, furthering the current advanced findings, proposes a novel hybrid levitation including Electro-Dynamic Suspension (EDS) and air cushions for the pod in the hyperloop system. It also presents a vibrational model for the hybrid levitation pod to predict the vibration behavior of the pod in accelerating and braking maneuvers. In this regard, an industrial pod is designed conceptually by performing preliminary calculations. Via CFD simulations in Ansys Fluent software, we hold forth a nonlinear dynamic model for the air cushions. Then, the paper analyzes a 3-DOF vibration model of the pod and verifies it by comparing the related results with obtained ones from the MSc ADAMS software. Afterward, the mentioned vibration model is developed into a 7-DOF model to predict the vibration behavior of the pod in accelerating and braking maneuvers. Also, the governing dynamic equations of the system are derived and numerically solved. Finally, the vibration behavior of the pod in different accelerating and braking conditions is investigated. [ABSTRACT FROM AUTHOR]

In this paper, the motion of partial air cushion support catamaran (PACSCAT) sailing in regular waves was firstly investigated by the experimental method. The monitored histories of heave, pitch, midship acceleration, and air cushion pressure in towing tests are performed to analyze the influence of air cushion on the periodicity feature of hull body motion. Subsequently, using the finite volume method (FVM)-based CFD software Star-ccm, numerical simulations are carried out for the PACSCAT model with a simplification of the air cushion system. The detailed flow information of wave evolution, pressure, and velocity distribution is investigated. The calculated oscillation characteristics of different motion parameters are compared with those from experiment and show good agreement. The numerical method also has good capacity in the prediction of amplitude response of heave and midship acceleration; however, large error is found when calculating resistance and amplitude response of pitch. [ABSTRACT FROM AUTHOR]

This paper presents the control system of cushion pressure for the developed intelligent air-cushion track vehicle (IACTV) for operating on swamp terrain and wet fields. A novel auto-adjusting supporting system is designed for the vehicle's intelligent air-cushion system. Focusing on minimizing the total power demand of the vehicle, an optimization model has been established, for examining the effects of vehicle parameters and load distribution on power consumption by controlling air-cushion pressure. Then optimum cushion pressure is determined based on the developed optimum pressure - sinkage relationship and the pressure in the cushion chamber is controlled by the Fuzzy controller by maintaining volume flow rate and continuously monitored by the pressure sensor attached with the cushion chamber. The ultrasonic displacement sensor is used to measure the sinkage of the vehicle. The output voltages of the ultrasonic displacement are used to operate the pull-in solenoid switch through the microcontroller which closes the circuit of the compressor motor. Distribution of vehicle load to the air-cushion system is controlled by Fuzzy Logic controller by maintaining the inside pressure of the cushion. [ABSTRACT FROM AUTHOR]

Automatic assembly with a part vibrating on incompressible air cushion is considered. The equation of pressure distribution in air cushion between the part and the supporting surface of a pneumatic track is derived. To solve the equation of pressure distribution, a finite element model is constructed. The equation of part motion on air cushion and the equation of pressure distribution are solved. The zones of parameter combinations of air flow and the part motion are defined in cases of slowly damping process, slowly increasing vibrations amplitude or constant amplitude vibrations of the part on the air cushion. Dependencies of vibrations amplitude and air cushion pressure, both on air flow and the system parameters are determined. [ABSTRACT FROM AUTHOR]

The real-time control and prediction of attitude and moving trajectory in shield tunneling is challenging, especially in the small radius of curvature. The present study focuses on developing a method for predicting the attitude of a shield based on a new model that incorporates a wavelet transform (WT) into a random forest (RF) deep learning method. Daubechies (dbN) is selected among several wavelet bases to denoise the original tunneling parameters in the time and frequency domains, and optimal wavelet parameters for different input variables are obtained. The proposed WT–RF model was implemented and validated by a case study of the Shizimen Tunnel in Zhuhai, China. Sorted by the correlation coefficient between the input parameters and the output parameters, eight cases with different input parameter combinations were also selected for comparison. The results revealed that the developed wavelet signal denoiser-RF model can successfully predict the shield attitude parameters and that using a suitable combination of input parameters can greatly improve the prediction accuracy of the model. The number of input parameters is not a key factor for determining the prediction accuracy of the model, and adding less relevant input parameters will greatly reduce the prediction performance of the model. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of safely cargo transfer over a ramp between a cargo vessel and a lighter surface effect ship (SES). For this purpose, an adaptive neural network (NN) controller is proposed to control of ramp motions in the presence of entirely unknown dynamics and disturbances wherein the controller is subject to input saturation constraint. In this regard, we develop a novel non-affine nonlinear SES model by considering the nonlinear relationship among the air cushion pressure, the air flow into and out of the air cushion and the air cushion volume. To deal with the saturation constraint, an auxiliary system is proposed. To ensure the system stability, Lyapunov’s direct method is employed to investigate the uniformly ultimately boundedness (UUB) of all closed-loop system states. The simulation results demonstrate the effectiveness of the proposed controller in critical sea conditions, including regular and irregular waves with high frequencies and large amplitudes. A comparative analysis with model-based approaches including Proportional Integral Derivative (PID) and Linear-Quadratic Regulator (LQR) control systems are given to highlight the performance of the controller. [ABSTRACT FROM AUTHOR]

Water–air interaction (mixing of gas and water and gas dissolution into water) is one of the main reasons for gas loss in air cushion surge chambers. With the increase of water head in hydraulic power generation systems, the heat and mass transfer process at the water–air interface under high-pressure conditions intensifies, and the water–air interaction is further strengthened. If some gas is mixed/dissolved in water and enters downstream pipelines, it will affect the safety of the unit. At present, there has been no theoretical or systematic research on gas loss and related water gas two-phase flow in air cushion surge chambers under high-pressure conditions. Therefore, this article established an air loss model for an air cushion surge chamber based on the VOF model and gas–liquid mass transfer theory. We analyzed the mechanism of gas loss in the gas chamber through simulation and quantitatively expressed the gas loss. The results indicate that during a typical large fluctuation process, the gas–liquid mass transfer process at the water–air interface, air mass, and vortex is very strong, with a pressure chamber of approximately 923.89 m3. The gas dissolved in water enters the water diversion system, with a length of 28.75 m3. High pressure gas enters the water diversion system in the form of air masses. When considering the water inlet on the right side of the air chamber, the total gas loss in the air chamber is slightly lower (854.18 m3) and no mixed air mass was detected entering the connecting pipe. [ABSTRACT FROM AUTHOR]

The mathematical model of the dynamics of an Air Cushion Vehicle with a ballonet type skirt is presented. This model incorporates a number of interrelated submodels representing different constituents of ship dynamics: rigid body, air cushion, propulsion system, ballonet, underlying surface, aerodynamics, yaw rudder. The proposed model is capable of predicting all major characteristics of the ship movement such as trajectory, forces, moments, air cushion pressure, subject to different operating conditions. Both controlled and uncontrolled movement may be simulated. The suggested approach is based on the numerical integration of the equations of motion as well as the equation describing the pressure evolution in the air cushion. The verification of the model was carried out and the results of model towing tests are presented. [ABSTRACT FROM AUTHOR]

With excess slurry pressures exerted on the tunnel face, slurry particles tend to infiltrate into the soil in front of the tunnel. There will be excess pore pressure ahead of the tunnel in the case of infiltration, leading to an impairment in the supporting effect contributed by the excess slurry pressure. Corresponding to three slurry infiltration scenarios distinguished by the forms of the filter cake, different pressure transfer models are employed to describe the pore pressure distribution. Using the kinematic approach of limit analysis and the numerically simulated seepage field, the study of tunnel face stability under different slurry infiltration cases is extended by employing a 3D discretization-based failure mechanism. In addition, two simple empirical formulas describing the pore pressure distributions above the tunnel and in advance of the tunnel are established and verified. Combined with the dichotomy method and strength reduction method, the safety factors yielding rigorous upper-bound solutions are obtained by optimization. The proposed method is validated by a comparative analysis. The developed framework allows considering the influence of excess pore pressure on the whole failure mechanism and the three-dimensional characteristics of seepage. A parameter analysis is performed to study the effect of the excess slurry pressure, hydraulic conditions, soil strength properties, and pressure drop coefficient. The results show that the steady-state flow model leads to much more conservative results than the full-membrane model. The safety factor increases with the increasing excess slurry pressure and the decreasing pressure drop coefficient. The present work provides an effective framework to quickly assess the face stability of tunnels under excess slurry pressure considering different filter cake scenarios. [ABSTRACT FROM AUTHOR]

Researching the control of cumulative risk for submarine tunnel shield construction is of great significance for improving risk management capability. Firstly, the concepts of cumulative risk, fragility, and the theory of system dynamics (SD) are introduced. Secondly, the risk conduction network is established, and the risk conduction mechanism based on fragility is analyzed. Then, the cumulative risk control model is established by SD. Finally, Dalian Metro Line 5 Cross-sea Large Diameter Shield Construction Project is used to verify the model. Simulations of cumulative risk with and without control measures are compared, and the result is in line with objective facts. The correctness and effectiveness of the model are verified. [ABSTRACT FROM AUTHOR]

The natural fiber-reinforced thermoplastic tape was produced using a novel process assembly that involves a drawframe and a double belt press. First, the state-of-the-art film-stacking process was modified through the integration of a drawframe to supply the natural fiber preforms for reinforcement, adding thermoplastics films as matrix material and processing them to a unidirectional tape (UD tapes) using a double belt press. Based on that, a new approach was investigated using a commingled sliver containing natural reinforcing and polymer matrix fibers to manufacture UD tapes. This leads to a reduced flow path of the matrix polymer, which is a decisive parameter for production efficiency. To ensure a homogeneous distribution and alignment of the fibers after gilling, the influence of various processing parameters on one another and the resulting UD tape quality were examined. As result, a draft ratio in the range of 10 ± 2, a low linear density (here 12 ktex) and general use of many thin in contrast to fewer heavier slivers is advisable. The differences in impregnation quality and thus the mechanical performances of the UD tapes from both processes were validated using scanning electron microscopy and mechanical testing. It was found that the commingled sliver composite had 10% higher flexural modulus and 34% higher flexural strength compared to the film-stacking-based composites. In conclusion, using commingled sliver could enable the increase in productivity and fiber volume fraction compared to film-stacking-based composites. [ABSTRACT FROM AUTHOR]

In this paper, a novel global sliding mode controller (GSMC) with a comprehensive observer is used to solve the problems of time-varying coefficients, modeling errors and disturbance with unknown upper bound in the trajectory tracking control of the air-cushion vehicle (ACV). Considering the multiple resistance coefficients that change with the motion state in the ACV's dynamic model, a comprehensive observer is used to estimate and compensate for the model uncertainty in real time. An adaptive disturbance estimation law without disturbance upper bound is given to compensate for the total disturbance. On the basis of real-time compensation of model uncertainty by adaptive estimation law, a new GSMC with hyperbolic tangent function is proposed to track the ACV's trajectory. The interconnected system of observer and trajectory tracking controller is shown to have enhanced robustness. Finally, simulations verify the effectiveness of the proposed control approaches. [ABSTRACT FROM AUTHOR]

• The novel waterproof form of the underwater shaking tables is researched. • Mechanism of the air cushion during motion. • The theoretical and simulation analysis method of liquid-solid-gas coupling. • Selection and analysis method of the air cushion pressure for the underwater shaking tables. Underwater machinery usually involves waterproof problems. An inflatable waterproof system, a type of waterproof equipment for underwater shaking tables is studied in this paper. The inflatable waterproof system used an air cushion, made of rubber-coated woven fabric reinforced composites, to cover the gap between the shaking table and the floor and provide sealing and waterproofing. The water load is borne by the pressure air inside the closed flexible membrane structure. The mechanism of the movement process of the air cushion was analyzed, and the differential equations are obtained through theoretical analysis. The evolution in air pressure of the air cushion and the velocity potential in the shaking water are the necessary conditions for solving the motion equation. Based on this, a 1:4 scaled model was made and tested. The finite element model combining the CEL(Coupled Eulerian-Lagrangian) method and fluid cavity method was verified by the test results, which provides a research method for the problems involving the coupling of liquid-solid-gas. The motion equation was solved and verified by the test and simulated results. The results show that the air cushion is in the state of force balance in the moving process and the change of force of the air cushion is related to the evolution of the cross-section profile of the air cushion, the evolution of air pressure, and the velocity potential of the shaking water. The velocity potential of the shaking water can be ignored in the horizontal motion. The cross-section profile of the air cushion is related to the inflation pressure and can maintain a stable circular-arc shape when the inflation pressure is greater than 35.00 kPa under 3.0 m water. The inflation pressure of the air cushion should be 35.00 kPa-40.00 kPa under 3.0 m water in consideration of safety and stability. The research results reference the design and application of the waterproof air cushion for underwater shaking tables and other underwater machinery. [Display omitted] [ABSTRACT FROM AUTHOR]

The Partial Air Cushion Supported Catamaran (PACSCAT) is an innovative design which combines both the characteristics of hovercraft and catamaran. Further, it provides a high-speed and efficient solution with excellent performance, particularly for shallow water. In this paper, experimental and numerical method are carried out for research of motion attitude and resistance characteristics, which provide a reference for further research and hull optimization work. By model towing test and data interpretation, and the resistance, trim, and heave varying law with increasing speed is summarized. From the view of total resistance, the impacts of the cushion pressure and air flow on resistance performance of PACSCAT are analyzed. Based on the theory of viscous fluid mechanics, a numerical simulation method with high prediction accuracy is established. The flow field around and inside the hull is simulated, the simulating results show good agreements with the testing data. Finally, the effect of the cushion compartment improving the resistance performance is studied. The results show that the cushion compartment is significant for adjusting the pressure distribution of the air cushion. And the average resistance reduction ratio at the high-speed segment can even reach 22%. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Air-cushion-assisted platforms (ACAPs) are floating platforms supported by both buoyancy pontoon and air cushion, which have merits of wave bending moment reduction, better stability, and hydrodynamic performance. However, there is barely a concise method that can quickly predict the motion response of ACAPs. In this paper, a simplified panel method (sPM) was presented for evaluating the hydrodynamics of ACAPs. The sPM extends the conventional boundary integral equation (BIE) to include the radiation solutions of pulsating air pressure but ignores some unimportant air-water cross terms in motion equations whose coefficients cannot be directly derived from conventional Green's function methods. The effectiveness of the sPM was validated by experimental data from an ACAP model with one air chamber and analytical results from an oscillating water column (OWC). The numerical results demonstrate that the sPM can give desirable predictions for motion responses of the ACAP and inner pressure of the OWC as compared with results from the literature, which suggests the sPM could be approximately applied to evaluation of hydrodynamic performance of ACAPs and OWCs. [ABSTRACT FROM AUTHOR]

In this work, the applicability of Sequential Injection Chromatography for the determination of transition metals in water is evaluated for the separation of copper(II), zinc(II), and iron(II) cations. Separations were performed using a Dionex IonPAC TM guard column (50 mm×2 mm i.d., 9 µm). Mobile phase composition and post-column reaction were optimized by modified SIMPLEX method with subsequent study of the concentration of each component. The mobile phase consisted of 2,6-pyridinedicarboxylic acid as analyte-selective compound, sodium sulfate, and formic acid/sodium formate buffer. Post-column addition of 4-(2-pyridylazo)resorcinol was carried out for spectrophotometric detection of the analytes׳ complexes at 530 nm. Approaches to achieve higher robustness, baseline stability, and detection sensitivity by on-column stacking of the analytes and initial gradient implementation as well as air-cushion pressure damping for post-column reagent addition were studied. The method allowed the rapid separation of copper(II), zinc(II), and iron(II) within 6.5 min including pump refilling and aspiration of sample and 1 mmol HNO 3 for analyte stacking on the separation column. High sensitivity was achieved applying an injection volume of up to 90 µL. A signal repeatability of<2% RSD of peak height was found. Analyte recovery evaluated by spiking of different natural water samples was well suited for routine analysis with sub-micromolar limits of detection. [ABSTRACT FROM AUTHOR]

Copyright of INMATEH - Agricultural Engineering is the property of INMATEH - Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The power loss generated by the air cushion belt conveyor when transporting materials mainly depends on the diameter of the orifice, the form of arrangement, and the thickness of the air film. A mathematical model of an air cushion belt conveyor is established through mechanical analysis, and the relationship between load distribution, air film thickness, air film carrying capacity, and power consumption is found. Numerical simulations of orifices of different diameters on the disk groove and the formed air film are carried out, and the loading capacity of the air film was analyzed by observing the stress and deformation of the wire rope core. The results show that the air film formed by the selected type of orifice arrangement in this paper carries the load, which causes the least amount of deformation and stress change in the wire rope core, and the stability of the air film loading capacity is also verified by experiments. [ABSTRACT FROM AUTHOR]

Due to the increasing use of renewable energy sources, and to counter the effects of fossil fuels, renewable dispatchable hydro power can be used for balancing load and generation from intermittent sources (solar and wind). During higher percentage change in load acceptance or rejection in the intermittent grid, the operations of surge tanks are crucial in terms of water mass oscillation and water hammer pressure, and to avoid wear and tear in actuators and other equipment, such as hydro turbines. Surge tanks are broadly classified as open types, with access to open air, and closed types, with a closed volume of pressurized air. Closed surge tanks are considered to have a more flexible operation in terms of suppressing water mass oscillation and water hammer pressure. In this paper, a mechanistic model of an air cushion surge tank (ACST) for hydro power plants is developed based on the ordinary differential equations (ODEs) for mass and momentum balances. The developed mechanistic model of the ACST is a feature extension to an existing open-source hydro power library—OpenHPL. The developed model is validated with experimental data from the Torpa hydro power plant (HPP) in Norway. Results show that the air friction inside the ACST is negligible as compared to the water friction. The results also indicate that a hydro power plant with an ACST is a potential candidate as a flexible hydro power in an interconnected power system grid supplied with intermittent energy sources. Conclusions are drawn based on the simulation results from hydraulic performance of the ACST. [ABSTRACT FROM AUTHOR]

This article presents an overview of breaking waves and liquid sloshing impact acting on rigid walls and in liquid containers. The physics of breaking waves against rigid walls can be understood through the Bagnold/Mitsuyasu piston theory. The flip-through is a major feature associated with the occurrence of violent waves without any actual impact on the wall. The physics of the phase transition during liquid impacts involves two- and multi-phase flows due to the entrapped gas pockets is addressed. The liquid sloshing assessment of liquefied natural gas tanks together with the dimensionless parameters governing the design of small-scale models is discussed. The nonlinear liquid sloshing dynamics under sway and rotational excitations is described for different container geometries. This article will discuss recent developments of numerical algorithms and computer codes capable to describe breaking waves and extreme sloshing impacts. Moreover, recent advances in breaking Faraday waves are also addressed together with an assessment of breaking interfacial gravity waves, in which a multilayer or stratified medium is a stack of different thin layers. [ABSTRACT FROM AUTHOR]

A new apparatus for a moving induction heating and gas-assisted hot embossing apparatus has been developed. A mechanism was designed and implemented to move the platform in and out the wrapped coil, on which the sealed box for substrate/mold was placed. A chamber of 195 mm diameter and 221 mm length was machined. The movable platform, the sealed box with substrate/mold stack, wrapped coil and cooling fan were all implemented in the high pressure chamber. The nine-point thermocouples attached on the mold, thus, a temperature history of the moving induction heating can be obtained and study the influence of the moving path and power on the heating rate and temperature distribution. The micro V-cut structure hot embossing experiment were performed to prove the potential of this moving induction heating and gas-assisted pressuring hot embossing for fast fabrication of microstructure onto polymeric substrates. As a results, replication rates were all above 95% at 200 °C and 5 kgf/cm2 and the cycle time was less than 4 min and the optic measurement shows the replicated V-cut film can enhance the 36.8% illuminance. The experiment results show the manufacturing potential of this apparatus. [ABSTRACT FROM AUTHOR]