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In this study, the performance of a wave energy converter (WEC) rotor under regular and irregular wave conditions was investigated using 3D nonlinear numerical models. Factors such as the power take-off (PTO) load torque, wave periods, spacing of multiple WEC rotors, and wave steepness were analyzed. Two models were employed: a weakly nonlinear model formulated by incorporating the nonlinear restoring moment and Coulomb-type PTO load torque based on the potential flow theory, and a fully nonlinear model based on computational fluid dynamics. The results show that the average power estimated by both numerical models is consistent, with a wave steepness of 0.03 for the range of one-way and two-way PTO load torques, except for the deviations observed in the long range of the one-way PTO load torque. Furthermore, the average power of the WEC rotor under the applied PTO load torque exhibits a quadratic dependency, regardless of the wave steepness. In addition, adopting a one-way PTO load torque was more efficient than adopting a two-way PTO load torque. Therefore, the fully nonlinear model demonstrated its ability to handle a high degree of nonlinearity, surpassing the limitations of the weakly nonlinear model, which was limited to moderate wave steepness. [ABSTRACT FROM AUTHOR]

In recent years, whole-body vibration (WBV) training has received an increasing interest in the sports and medical fields. However, there has been inconsistency among several studies regarding the effect of WBV training on the human body, which is partly due to the lack of the existence of guidelines for using WBV training machines. To understand the effect of WBV training on the human body and build the needed regulations, it is essential first to understand the biodynamic responses to vibration which represent how vibration is transmitted to and through the human body. The purpose of this study is to systematically review previous studies that measured biodynamic responses when using WBV training machines to highlight inconsistencies in their results and provide possible reasons for them. An extensive literature search was performed on the SCOPUS database to obtain relevant studies. One hundred and fifty-six potentially relevant studies were obtained but after further screening, 23 papers from 2007 to 2020 met inclusion criteria and were included in the study. The papers were analysed with respect to acceleration, transmissibility, interface force, and apparent mass during different vibration settings, body posture, age, and sex. Results and conflicts among studies were highlighted and possible explanations for the inconsistency were provided. [ABSTRACT FROM AUTHOR]

This study tries to identify the effect of hydrodynamics on the absorbed wave power using a toroidal Oscillating Water Column (OWC) device. To this end, the fundamental hydrodynamic boundary value problem for an arbitrary shaped toroidal OWC device of revolution with vertical axis is solved. The described method is based on the discretization of the flow field around the device by means of ring-shaped macro-elements, in each of which axisymmetric eigenfunction expansions for the velocity potential is made. The solution sought for the corresponding diffraction and radiation velocity potentials is achieved using Galerkin's method. The applied formulation is generic and can be employed for arbitrary configurations of toroidal OWCs. Therefore, the numerical results shown and discussed in the present paper, in terms of the hydrodynamic loads and the air volume flows inside the OWC chamber, concern different types of OWCs. From the present analysis, it is demonstrated that the absorbed wave power by the examined toroidal devices is strongly affected by the geometrical parameters of the device; thus, these should be properly considered towards the maximization of the device's wave power efficiency. [ABSTRACT FROM AUTHOR]

In this study, the performance of a wave energy converter (WEC) rotor under regular and irregular wave conditions was investigated using 3D nonlinear numerical models. Factors such as the power take-off (PTO) load torque, wave periods, spacing of multiple WEC rotors, and wave steepness were analyzed. Two models were employed: a weakly nonlinear model formulated by incorporating the nonlinear restoring moment and Coulomb-type PTO load torque based on the potential flow theory, and a fully nonlinear model based on computational fluid dynamics. The results show that the average power estimated by both numerical models is consistent, with a wave steepness of 0.03 for the range of one-way and two-way PTO load torques, except for the deviations observed in the long range of the one-way PTO load torque. Furthermore, the average power of the WEC rotor under the applied PTO load torque exhibits a quadratic dependency, regardless of the wave steepness. In addition, adopting a one-way PTO load torque was more efficient than adopting a two-way PTO load torque. Therefore, the fully nonlinear model demonstrated its ability to handle a high degree of nonlinearity, surpassing the limitations of the weakly nonlinear model, which was limited to moderate wave steepness.

Electron cyclotron resonance heating is one of the methods of additional plasma heating in the T-15MD tokamak. The article considers the possibility of plasma heating using an extraordinary wave at the third harmonic of electron cyclotron resonance at a frequency of 140 GHz. It has been shown that, in accordance with the calculations by the quasi-linear OGRAY code, a high fraction of single-pass absorption (up to 96%) can be expected even when the ECR is turned on with an ohmic background. Increase in this fraction with the increase in plasma temperature agrees with the theoretical predictions. Vertical power launch seems to be the most attractive. Possible engineering solutions for implementation of such a scheme are proposed. [ABSTRACT FROM AUTHOR]

This work proposes an approach for the optimal sizing of a cylindrical heaving wave energy converter (WEC). The approach is based on maximising the absorbed power density (APD) of the buoy, with the diameter being the decision variable. Furthermore, two types of buoy shapes were compared to get the best option. The two buoy shapes are the cone cylinder buoy (CCB) and the hemisphere cylinder buoy (HCB). The aim was therefore to determine the best shape and as well as the optimal size of the cylindrical point absorber. To validate the approach, the simulation was performed under Durban (South Africa) sea characteristics of 3.6 m wave significant height and 8.5 s peak period, using the openWEC simulator. The buoy diameter range considered was from 0.5 m to 10 m for both shapes. Simulation results revealed that a diameter of 1 m was the optimal solution for both buoy shapes. Furthermore, the APD method revealed that the HCB was more efficient than the CCB. The power density of the HCB was 1070 W/m2, which was almost double the power density of the CCB, while the two shapes present almost the same absorbed power. [ABSTRACT FROM AUTHOR]

This work proposes an approach for the optimal sizing of a cylindrical heaving wave energy converter (WEC). The approach is based on maximising the absorbed power density (APD) of the buoy, with the diameter being the decision variable. Furthermore, two types of buoy shapes were compared to get the best option. The two buoy shapes are the cone cylinder buoy (CCB) and the hemisphere cylinder buoy (HCB). The aim was therefore to determine the best shape and as well as the optimal size of the cylindrical point absorber. To validate the approach, the simulation was performed under Durban (South Africa) sea characteristics of 3.6 m wave significant height and 8.5 s peak period, using the openWEC simulator. The buoy diameter range considered was from 0.5 m to 10 m for both shapes. Simulation results revealed that a diameter of 1 m was the optimal solution for both buoy shapes. Furthermore, the APD method revealed that the HCB was more efficient than the CCB. The power density of the HCB was 1070 W/m2, which was almost double the power density of the CCB, while the two shapes present almost the same absorbed power.

A two-dimensional computational fluid dynamics (CFD) numerical model is developed to study the power takeoff (PTO) efficiency of an Edinburgh duck wave energy converter (WEC) device by using the OpenFOAM source package. After the numerical validations and the convergent verifications, the characteristics of the duck WEC device for the power takeoff in various incident wave periods are examined. The present numerical investigation indicates that the maximum absorbed power of the duck WEC device is attained in its resonant period, while the maximum efficiency is achieved in a lower period. The influence of the damping coefficient on the PTO is also investigated. The optimal damping coefficient for acquiring more power and better efficiency is determined from a numerical examination. [ABSTRACT FROM AUTHOR]

The power performances of a point absorber wave energy converter (WEC) operating in a nonlinear multidirectional random sea are rigorously investigated. The absorbed power of the WEC Power-Take-Off system has been predicted by incorporating a second order random wave model into a nonlinear dynamic filter. This is a new approach, and, as the second order random wave model can be utilized to accurately simulate the nonlinear waves in an irregular sea, avoids the inaccuracies resulting from using a first order linear wave model in the simulation process. The predicted results have been systematically analyzed and compared, and the advantages of using this new approach have been convincingly substantiated. [ABSTRACT FROM AUTHOR]

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In this paper the power performances of a point absorber wave energy converter (WEC) operating in a nonlinear multi-directional mixed sea have been rigorously investigated. The absorbed power of the WEC Power Take Off (PTO) system has been calculated by incorporating a second order irregular wave model into a nonlinear dynamic filter. This is a new methodology that is uniquely proposed to the ocean wave energy research community. The predicted results of the WEC power performances have been rigorously analyzed and systematically compared, and the advantages of using our proposed new methodology under extreme wave states have been convincingly substantiated. The research findings in this paper highlight that it is important to employ a nonlinear wave theory under extreme wave states for studying the power performances of wave energy converters, but that linear wave theory gives good results under normal wave states. • A new methodology is proposed to the ocean wave energy research community. • The nonlinear multi-directional mixed sea has been considered. • A second order irregular wave model is incorporated into a nonlinear dynamic filter. • The proposed new methodology has been convincingly substantiated. [ABSTRACT FROM AUTHOR]

A novel wind-wave energy hybrid concept is presented in this paper, consists of a floating semi-submersible wind turbine and multiple point absorption wave energy converters (WECs). Numerical simulations are conducted using the hydrodynamic analysis program AQWA, based on the three-dimensional (3D) potential theory. To ensure the reliability of the numerical model, the hydrodynamic responses of the semi-submersible platform and the WECs are validated using available experimental data. Finally, three WECs with different shapes are designed to investigate the shape on the performance of this hybrid system, including platform motion, mooring line tension and power captured by the WECs. The results demonstrate that the hybrid system with the circular truncated conical WECs has the best performance compared to the other two shaped WECs. In addition, the influence of the platform motion on the performance of the WEC array is negative. Overall, this study could provide some insights for the design of other wind-wave integrated systems. • A novel wind-wave hybrid concept was presented. • A hinge articulation with damping was used to simulate the PTO system. • Three WECs with different shapes were designed to investigate the shape on the performance of the hybrid system. • A new variable is proposed to evaluate the WEC performance of unit displacement. • The effects of the platform motion on the performance of the WEC array are investigated. [ABSTRACT FROM AUTHOR]

Efforts by various researchers in recent years to design simple causal control laws that can be applied to WEC devices suggest that these controllers can yield similar levels of energy output as those of more complex non-causal controllers. However, most studies were established without adequately considering device and power conversion system constraints which are relevant design drivers from a cost and economic point of view. It is therefore imperative to understand the benefits of MPC compared to causal control from a performance and constraint handling perspective. In this paper, we compare linear MPC to a casual controller that incorporates constraint handling to benchmark its performance on a one DoF heaving point absorber in a range of wave conditions. Our analysis demonstrates that MPC provides significant performance advantages compared to an optimized causal controller, particularly if significant constraints on device motion and/or forces are imposed. We further demonstrate that distinct control performance regions can be established that correlate well with classical point absorber and volumetric limits of the wave energy conversion device.

This paper presents a novel catenary mooring system incorporating multiple clump weights (CWs) designed for a SPIC-Wavestar wind-wave energy hybrid system. To enhance the performance of the hybrid system, a parametric analysis was performed on mooring CWs. The motions of the SPIC platform, along with the power absorbed by the Wavestar wave energy converters (WECs), specifically in response to the operational regular wave, were simulated. The hydrodynamic analysis program AQWA was used for the analysis. The results indicated that the surge and pitch motions of the platform comprised low-frequency and wave-frequency components, whereas the heave motion only comprised a wave-frequency component. However, the low-frequency responses of the surge and pitch motions were substantially smaller than their wave-frequency counterparts. In addition, the properties of the CW exerted notable influence on both platform motion and the overall power absorption by the WEC array. The variation trends with respect to the CW weight, location, and number were complex. Overall, the results of this study provide valuable insights into the mooring design of ocean energy hybrid systems. [ABSTRACT FROM AUTHOR]

A combined wind turbine and wave energy converter (WEC) into one unit can harvest more power from marine renewable energy and reduce the cost of energy produced. This paper focuses on the WEC of the semi-submersible yaw-drive flap combination (SYFC) concept and presents the novel hybrid system of flap WEC with a yaw control system to avoid the yaw misalignment of flaps and increase the absorbed power by all WECs. The boundary element method (BEM) is employed to predict the semi-submersible platform hydrodynamics response and flap power under different regular sea state conditions. The validation was first carried out for the response amplitude operator (RAO) and spectral density function (SDF) of the semi-submersible flap combination (SFC) for surge, heave and pitch and line tension in the frequency domain. Afterward, the total absorbed power and capture width ratio (CWR) of the SYFC and SFC at different wave periods and wave heights are presented using the optimum damping coefficient. It is found that the CWR of the SYFC is almost 2–2.5 times more than the CWR of the SFC in almost all wave periods. Finally, the hydrodynamic interaction between the flap and braceless semi-submersible of the SFC and SFYC was presented and discussed. [ABSTRACT FROM AUTHOR]

The present paper deals with the theoretical evaluation of the efficiency of an array of cylindrical Wave Energy Converters (WECs) having a vertical symmetry axis and placed in front of a reflecting vertical breakwater. Linear potential theory is assumed, and the associated diffraction and motion radiation problems are solved in the frequency domain. Axisymmetric eigenfunction expansions of the velocity potential are introduced into properly defined ring-shaped fluid regions surrounding each body of the array. The potential solutions are matched at the boundaries of adjacent fluid regions by enforcing continuity of the hydrodynamic pressures and redial velocities. A theoretical model for the evaluation of the WECs’ performance is developed. The model properly accounts for the effect of the breakwater on each body’s hydrodynamic characteristics and the coupling between the bodies’ motions and the power take-off mechanism. Numerical results are presented and discussed in terms of the expected power absorption. The results show how the efficiency of the array is affected by (a) the distance between the devices and the wall, (b) the shape of the WEC array configuration, as well as (c) the angle of the incoming incident wave.

This paper presents the modelling of over-finishing grinding with abrasive brushes and also a comparative study between the absorbed power when over-finishing grinding the beech, the spruce and the MDF with this kind of tools as compared to the absorbed power when over-finishing grinding under similar conditions using the wide belt sanding (grinding) technology, presenting the advantages of reconsidering such a technological process.

A visible Q-switched pulse train at 639 nm was successfully generated in a Pr-doped double-clad structured waterproof fluoride glass fibre with a semiconductor saturable absorber mirror. The slope efficiency was calculated as 36.3%. The pulse duration and the radio frequency were measured as 270 ns and 107 kHz at 596 mW of absorbed power, respectively. The pulse energy and the pulse peak power were calculated as 1.32 μJ and 4.87 W, respectively.

The paper work presents the particularities grinding rubber of paper industry. An analysis of variance cutting power at roller with rubber coat and presents cutting data used for processing by machine grinding rollers. It also present some directions to processing by grindig rubber with porous grinding wheel and cooling flow abundantly. [ABSTRACT FROM AUTHOR]

To improve power generation efficiency and reduce costs in the industry of ocean renewable energy, one of the optimal strategies is the addition of wave energy converters (WECs) into the floating wind turbine. This paper proposes a novel hybrid wind-wave energy concept that comprises multiple Wavestar point absorption wave energy converters (WECs) and a SPIC semi-submersible floating wind turbine (FWT). ANSYS/AQWA software is used to perform numerical simulations based on three-dimensional potential flow theory. Three hybrid systems are designed with different numbers of Wavestar WECs, which are symmetrically arranged on the platform. Before the study, the hydrodynamic responses of the Wavestar WEC and the SPIC concept platform are simulated separately and compared with existing experimental data. After the validation of numerical models, the platform motions and the absorbed power of the WECs are investigated, which are the main factors in evaluating the performance of a hybrid system. After a series of numerical simulations, the results show that the absorbed power increase significantly with the increase in the number of the Wavestar WECs, while the platform motions also increase. It can be concluded that the wind-wave energy hybrid design needs to find a balance between the platform motions and the absorbed power of the WECs. Overall, this study can be used as a reference for the design of other novel hybrid ocean energy concepts. [ABSTRACT FROM AUTHOR]

A three-dimensional transient numerical code ITU-WAVE based on potential theory and Neumann-Kelvin approximation is extended to take into account wave interaction in an array system using two and four truncated vertical cylinder arrays. ITU-WAVE panel code is validated against analytical array results before applied to power absorption from ocean waves for different array configurations. The effects of the separation distances between array system and heading angles on energy absorption in both sway and heave modes are studied by the support of numerical simulations which show sway mode has wider bandwidth than heave mode for energy absorption. It is also shown that wave interactions are stronger when the array systems are close and these wave interactions are reduced significantly and shifted to larger times when the separation distance is increased. The wave interaction is much stronger at the same separation distance and heading angle in heave mode than in sway mode. Numerical experience also shows that more power is absorbed in sway mode than in heave mode in both two and four array systems at any separation distances and heading angles when the bodies in array system have the same displacement in both sway and heave modes. [ABSTRACT FROM AUTHOR]

The electric activities of neurons serve as a foundation for normal brain functions. Electromagnetic radiation has a significant impact on neuronal activity in the brain, especially when cell phone is used extensively. To understand this mechanism, we developed a mathematical model aiming at describing the effect of electromagnetic radiation on neuronal firing activity by introducing an additional membrane current into the Hodgkin-Huxley neuron model. The results show that the neuronal firing activity of a single neuron can be suppressed by electromagnetic radiation. Besides, the spatiotemporal patterns of neuronal network are also suppressed from the stable propagating wave state to a homogeneous resting state. Our studies suggest that the electromagnetic radiation has a suppressive effect on neuronal firing activities, especially on the collective electric activities of neuronal network that is related to information processing. [ABSTRACT FROM AUTHOR]

This paper deals with the novel composition of the Wavestar (WS) wave energy converter (WEC) and a floating offshore wind turbine (FOWT) as a hybrid wave-wind energy concept. Two hybrid systems with different WS diameters and numbers (namely N12D5.725 and N18D5) have been considered, in which the total WSs volume displacement for both concepts is equal. In both concepts, two rectilinear arrays of WS in three groups have been proposed. In the present study, the ANSYS-AQWA software is used to estimate the WSs performance considering hydrodynamics interaction between floating bodies. Firstly, the validation was carried out for the WS heave position and velocity response in the time domain and for the FOWT response in the frequency domain. Then, the power take-off (PTO) optimum damping coefficient for two WSs systems was obtained. Afterward, total absorbed power and capture width ratio (CWR) at various wave heights and periods are presented using the optimum damping coefficient. It is concluded that the system of N18D5 is absorbed about 12.85% more power than N12D5.725 for all wave directions. The highest and lowest power occurs in the wave direction of 75 and 0°, respectively. The hydrodynamic interaction decreases average WSs power, especially in larger wave periods. • Hybrid Wind-Wave energy coupling concept were proposed using braceless semi-submersible FOWT-Wavestars (N12D5.725 and N18D5). • Time domain and frequency domain responses of the Wavestars and braceless semi-submersible FOWT platform were analyzed. • Total absorbed power and capture width ratio (CWR) were presented and discussed under different wave heights and wave periods. • Hydrodynamic interaction between Wavestars and braceless semi-submersible FOWT are studied. [ABSTRACT FROM AUTHOR]

The renewable energy technologies produced 20% of EU’s electricity consumption in 2010. The share of renewables for electricity generation is expected to increase to about 40% in 2020 to meet the EU target of 20% overall energy consumption from renewables, and it should further increase to 66% in 2030 and 100% in 2050, according to the European Renewable Energy Council (EREC, 2010). A wide variety of wave energy conversion technologies are currently being developed. A new wave energy converter (WEC) - CECO, aims at converting in electricity both the kinetic and the potential wave energy, and is composed of a central element and two lateral movable modules (LMM), which move, upward and downward, under the action of incident waves, Figure 1. The proof of concept of this patented WEC was carried out at the Hydraulics Laboratory of the Faculty of Engineering of the University of Porto, on a geometrical scale of 1:20. The paper presents some results of those tests and analyses the CECO response for different wave conditions and modes of operation (power take-off damping level and WEC inclination). Two different techniques were used to evaluate the power absorbed. The analysis is based on the measured motion, velocity and acceleration time series, the mean absorbed power and corresponding relative capture widths. The potential of this new concept was confirmed, as relative capture widths of up to 30% were obtained. In addition, these results are expected to improve after optimizing some components of this WEC. Figure 1. Representation of CECO (a) and its mode of operation: (b) upward motion - the wave crest passes by the LMM; (c) downward motion - the wave trough passes by LMM.

This paper presents the modelling of over-finishing grinding with abrasive brushes and also a comparative study between the absorbed power when over-finishing grinding the beech, the spruce and the MDF with this kind of tools as compared to the absorbed power when over-finishing grinding under similar conditions using the wide belt sanding (grinding) technology, presenting the advantages of reconsidering such a technological process. [ABSTRACT FROM AUTHOR]

One of the most significant factors in ride quality in cycling sports are the vibrations generated by road surface defects passing through the bicycle and transmitted to the cyclist's hands and buttocks. To study comfort, one metric that has been put forward is the measurement of the power absorbed at the cyclist's hands. Measuring absorbed power requires the use of the force and the velocity at the hands and provides an overall energy-based quantity. The aim of this study is to dynamically calibrate an instrumented brake hood transducer to measure the power absorbed at the cyclist's hands. Using a base excitation technique involving suspended masses, dynamic calibration of the brake hood was conducted in the 3-100 Hz frequency range, and the force transducer sensitivity and seismic mass were measured. An accelerometer attached to the brake hood enabled measurements of acceleration and calculation of velocity. A frequency-dependent phase mismatch between the force signal and the acceleration was obtained by measuring the accelerance at the hand-bike interface. A device called the Power Calibrator equipped with an impedance head was developed to assess the accuracy of the power measured by the instrumented brake hood. The results show that the instrumented brake hood can accurately measure the absorbed power at the cyclist's hands. Phase mismatch between the force and the velocity signals must be corrected to improve the accuracy of measurements. To implement the measurements, it is recommended that the calculations be done in the frequency domain. [ABSTRACT FROM AUTHOR]

The absorbed power characteristics of seated body exposed to whole-body vibration along the individual and combined fore-aft (x), lateral (y) and vertical (z) axes are investigated through measurements of body-seat interactions at the two driving-points formed by the body and the seat-pan, and upper body and the seat backrest. The experiments involved two levels of back support (no back support and vertical backrest) and two levels of broad-band vibration with nearly constant acceleration power spectral density in the 0.5-20 Hz frequency range applied along the individual x-, y- and z- axis (0.25 and 0.4 m/s2 rms acceleration), and along the three-axis (0.23 and 0.4 m/s2 rms acceleration along each axis). The biodynamic responses, measured at the seat-pan and the backrest are applied to characterize the total seated body's energy transfer along each axis. Furthermore, an alternative frequency response function method Hv is employed to capture the coupling in the seated body responses to uncorrelated multi-axis vibration. The total vibration absorbed power responses to simultaneous x, y and z -axis vibration are subsequently derived as the summation of vibration absorbed power along the individual axis within each one-third frequency band. The mean responses measured at the seat-pan suggest strong effects of the back support, and the direction and magnitude of vibration. The total vibration power absorbed by the seated body is further estimated under a multi-axis vibration environment of four different work vehicles. The results suggest that total average power absorbed under reported vehicular vibration varies with the effective acceleration in a nearly quadratic manner. [ABSTRACT FROM AUTHOR]

We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power takeoff (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000m³ and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s. [ABSTRACT FROM AUTHOR]