Input Wave Research Articles

System Performance Characteristics of Darrieus Turbine with Tilted Blades in Current and Wave Conditions

Indonesia has abundant sources of renewable energy from ocean currents and waves, or a mixture of currents and waves at certain times to be used as an energy source for power plants. So at the Indonesian Hydrodynamics Laboratory, a study has been carried out to determine the performance of the Darrieus-type vertical axis turbine model to utilize the energy of ocean currents and waves. But the Darrieus Turbine with the turbine blades positioned perpendicular to the turbine axis cannot rotate if there is only wave force. Then several turbine models were made with the placement of the blades in an inclined position, to produce optimal rotor rotation in current conditions or a mixture of currents and waves. This paper describes the testing of 3 turbine models by varying the angle of inclination of the turbine blades (45°, 60°, and 75°), but still having the same turbine rotor area and giving different input currents and wave periods to produce the best efficiency and rotation in absorb current energy or a mixture of current and wave energy. The test results show that the 3 models of slanted blade turbines can absorb both wave and current energy, but turbines with 75° blade inclination produce the best performance compared to the others when exposed to currents and waves

Vascular Age Assessed From an Uncalibrated, Noninvasive Pressure Waveform by Using a Deep Learning Approach: The AI-VascularAge Model.

Aortic stiffness, assessed as carotid-femoral pulse wave velocity, provides a measure of vascular age and risk for adverse cardiovascular disease outcomes, but it is difficult to measure. The shape of arterial pressure waveforms conveys information regarding aortic stiffness; however, the best methods to extract and interpret waveform features remain controversial. We trained a convolutional neural network with fixed-scale (time and amplitude) brachial, radial, and carotid tonometry waveforms as input and negative inverse carotid-femoral pulse wave velocity as label. Models were trained with data from 2 community-based Icelandic samples (N=10 452 participants with 31 126 waveforms) and validated in the community-based Framingham Heart Study (N=7208 participants, 21 624 waveforms). Linear regression rescaled predicted negative inverse carotid-femoral pulse wave velocity to equivalent artificial intelligence vascular age (AI-VA). The AI-VascularAge model predicted negative inverse carotid-femoral pulse wave velocity with R2=0.64 in a randomly reserved Icelandic test group (n=5061, 16%) and R2=0.60 in the Framingham Heart Study. In the Framingham Heart Study (up to 18 years of follow-up; 479 cardiovascular disease, 200 coronary heart disease, and 213 heart failure events), brachial AI-VA was associated with incident cardiovascular disease adjusted for age and sex (model 1; hazard ratio, 1.79 [95% CI, 1.50-2.40] per SD; P<0.0001) or adjusted for age, sex, systolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, prevalent diabetes, hypertension treatment, and current smoking (model 2; hazard ratio, 1.50 [95% CI, 1.24-1.82] per SD; P<0.0001). Similar hazard ratios were demonstrated for incident coronary heart disease and heart failure events and for AI-VA values estimated from carotid or radial waveforms. Our results demonstrate that convolutional neural network-derived AI-VA is a powerful indicator of vascular health and cardiovascular disease risk in a broad community-based sample.

Projective Measurement-Based Quantum Phase Difference Estimation Algorithm for the Direct Computation of Eigenenergy Differences on a Quantum Computer.

Quantum computers are capable of calculating the energy difference of two electronic states using the quantum phase difference estimation (QPDE) algorithm. The Bayesian inference-based implementations for the QPDE have been reported so far, but in this approach, the quality of the calculated energy difference depends on the input wave functions being used. Here, we report the inverse quantum Fourier transformation-based QPDE with Na of ancillary qubits, which allows us to compute the difference of eigenenergies based on the single-shot projective measurement. As proof-of-concept demonstrations, we report numerical experiments for the singlet-triplet energy difference of the hydrogen molecule and the vertical excitation energies of halogen-substituted methylenes (CHF, CHCl, CF2, CFCl, and CCl2) and formaldehyde (HCHO).

An Investigation of the Performance of the ANNMethod for Predicting the Base Shear and Overturning Moment Time-Series Datasets of an Offshore Jacket Structure

The primary purpose of the current study was to investigate the performance of artificial neural networks to predict the time series of the water surface level (WSL), base shear, and overturning moment using two types of ANN models: Nonlinear Autoregressive models with exogenous inputs (NARX) and Nonlinear Autoregressive models (NAR). After determining the suitable model, NARX, the possibility of predicting the time series of the base shear and the overturning moment data was investigated by considering the water surface level and time as the multivariable model inputs. A jacket model with a height of 4.55m was fabricated and tested in the 402m-long wave flume of the NIMALA marine laboratory. The jacket was tested at the water depth of 4m and subjected to random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20cm, 23cm, and 28cm. The findings showed that using the NARX neural network is a convenient method to predict the base shear and overturning moment values based on the water surface level data as input values. Finally, after suitable neural network determination, using the NARX neural network, the correlation value (R) for calculating water surface level (WSL), Base Shear, and Overturning Moment were obtained as 0.994, 0.97, and 0.94, respectively.

Analyzing the sensitivity of wave frequency responses of floating vessels to uncertain system variables utilizing Polynomial Chaos Expansion

Abstract From a mathematical viewpoint, the frequency domain analysis of vessel motion responses due to wave actions is based on integration of system dynamics idealized in terms of response amplitude operators (RAOs) for 6 DOF rigid body motions and an input wave spectrum in order to obtain the response spectrum. Various quantities of interest can be deduced from the response spectrum which are then used for deriving response-based operational limits for marine operations, also including extreme value and fatigue analysis. The variation of such quantities, owing to the uncertainties associated with the vessel system parameters, can be quantified by performing uncertainty propagation (UP) and consequent sensitivity analysis (SA). This study emphasizes and proposes a computational-efficient way of assessing the sensitivity of the system model output with respect to the uncertainties residing in the input parameters by operating on a surrogate model representation. In this respect, the global sensitivity analysis was effectively carried out by deploying an efficient non-intrusive polynomial chaos expansion (PCE) surrogate model built using a point collocation strategy. Successively, the Sobol' indices were obtained from the analytical decomposition of the polynomial coefficients. The indices, eventually, are employed to quantitatively measure the effects of input uncertainties on the output 6 DOF vessel Root Mean Square responses.

Pencil-drawn graphitic traces on sticky note paper for wearable electronics

Pencil-on-sticky note paper electrodes (PeoS) is a novel electrode fabrication method, using graphite from a pencil lead as an active material and sticky note paper as the substrate. This technique offers a low-cost and simple alternative for the fabrication of electrochemical sensors. In this paper, we aim to investigate the potential of PeoS as an effective electrode material for wearable electronic applications. The SEM images show overlapping graphite flakes, and the resistance of graphitic electrodes is found to be greater for xerox paper than for sticky note paper. An RC circuit based on sticky note paper yields the true nature for the square wave input. A bending test of the pencil-on-sticky note paper circuit shows an almost constant resistance value, showing PeoS has the potential to be used as a cost-effective alternative to traditional electrodes in wearable electronic applications, providing promising results for the future of non-invasive measurements of electrical signals.

Prediction of elastic wave propagation in composite bars using deep learning techniques

In this work, we developed a deep learning model based on a multilayer perceptron to predict the elastic wave output from composite bars. The model takes a vector representing the microstructure of the composite and the input wave applied at the left edge of the bar as features, with the target being the output elastic waves collected at the right edge of the bar. To train the model, we randomly generated composite bars with corresponding input waves and simulated them using finite element modeling. The results indicate that the proposed method can accurately and efficiently predict the output elastic waves.

Study on seismic wave propagation regularity and dam-foundation interaction characteristics of earth-rock dam on deep overburden

Many dams have to be constructed on deep overburden in meizoseismal areas, so it is vital to understand the seismic performance of these dams. Current research primarily focuses on the whole seismic response of dams, in which the analysis can be relatively imprecise. Nevertheless, an in-depth understanding of the propagation regularity of seismic waves in earth-rock dams on deep overburden, as well as the interaction characteristics between the dam and overburden, is critical. In this paper, based on a planning soil core wall dam with over 500 m of overburden, the seismic wave input method is employed to conduct a detailed and in-depth study from the perspectives of the spatial distribution of seismic acceleration and the Fourier spectra of acceleration time history. The results indicate that the spatial distribution of the peak acceleration of the dam is significantly inconsistent. The horizontal peak acceleration of the upstream side of the dam is greater than that of the downstream side because the dynamic modulus of the dam is significantly inconsistently distributed. In addition, the amplification behaviours of the seismic wave are different in the overburden and dam body, and the low-frequency and high-frequency components are amplified. The dynamic interaction between the dam body and the overburden significantly reduces the acceleration response at the dam-foundation interface by 44 % and 50 % in horizontal and vertical accelerations, respectively, because of the absorption of seismic wave energy by the dam body and the inconsistency of the dynamic modulus distribution of the overburden. The findings of this study provide robust theoretical support for evaluating the seismic performance and designing measures for the seismic resistance of earth-rock dams on deep overburden.

Transparent Bilayer ITO Metasurface with Bidirectional and Coherently Controlled Microwave Absorption

AbstractMetasurface absorbers (meta‐absorbers) are highly compelling in modern optoelectronic devices. However, owing to the limitations of the sandwiched design framework, conventional meta‐absorbers are restricted to fully absorbing only one‐sided incident waves while completely reflecting the electromagnetic (EM) waves from the opposite direction. In addition, the existing absorbers are opaque and their absorption performances are fixed after the initial design. Here, an optically transparent meta‐absorber consisting of bilayer indium tin oxide patterned layers that can achieve bidirectional and broadband absorption in the microwave frequency range is demonstrated. The inherent physics of bidirectional absorption can be attributed to the interference between multiple reflections and transmissions of EM waves. Furthermore, it is demonstrated that the absorption properties of the proposed meta‐absorber can be continuously switched via coherent control by adding another microwave beam to the other side of the meta‐absorber and manipulating the phase difference between the two input waves. The results indicate that the proposed design can enrich the functionalities of few‐layer metasurfaces and break new ground for EM shielding optical windows.

Controlling optical bistability, multistability and all-optical switching through multi-photon excitation process

We present a theoretical study on optical bistability (OB), optical multistability (OM) and tunable all-optical switching in a four-level cascade type atomic system. The density matrix formalism is used to find out the response of the probe laser field. We explore OB and OM under unidirectional optical ring cavity configuration. A comparison between the effects of electromagnetically induced transparency and electromagnetically induced absorption windows on OB is presented. The threshold of OB and the hysteresis width can be tuned effectively by adjusting the applied coherent fields. A transition from OB to OM and vice-versa can be easily achieved by tuning the field parameters and the atomic cooperation parameter. Dynamic control of the probe laser propagating through the medium has been investigated. We also demonstrate conversion of a continuous wave input probe field into output switched pulse. The ON/OFF time of the switched probe pulse can also be controlled by tuning the field parameters.

Control co-design and uncertainty analysis of the LUPA’s PTO using WecOptTool

Control co-design has been shown to significantly improve the performance of wave energy converters (WEC). By considering the control and WEC design concurrently, the space searched by the optimization routine is greatly expanded which results in better performing devices. Recently, an open-source WEC co-design code, WecOptTool, was released to perform control co-design research and facilitate its adoption in the community. In this study, we use WecOptTool to perform control co-optimization and uncertainty analysis of the LUPA device. The Laboratory Upgrade Point Absorber (LUPA) is a new open-source laboratory-scale WEC that provides a platform for testing new concepts, innovating control schemes, and validating numerical models. The LUPA can be adjusted to different configurations, including changing the number of bodies, the degrees of freedom (DOF), the float and spar geometry, and the diameter of the drive sprocket pulley in the power take off (PTO) system, as well as providing different control algorithms and input waves. The drive sprocket diameter influences the torque vs speed of the generator, which allows for more flexibility in operating under different wave conditions or with different control schemes. In this study we optimize the drive sprocket diameter, while considering the optimal control algorithm for each potential design, to identify the optimal diameter for electric power production at the PacWave South WEC test site. This case study demonstrates several new capabilities of WecOptTool including a multi-body multi-DOF system and multi-directional irregular waves. The PTO dynamics are modeled using first principle methods for a parametrized model of the mechanical subcomponents in combination with generator model obtained using a power-invariant Park transform. The case-study will be made available to serve as a design tool along the LUPA hardware. Users can readily use this model to perform their own design optimization prior to testing with the physical LUPA device. Finally, we use the automatic differentiation capability of WecOptTool to perform a sensitivity and uncertainty analysis of the LUPA device.

Experimental passive and reactive control of a Laboratory Scale WEC Point Absorber

Scaled testing is an important and valuable step in the process of determining best practices of WEC development, validating numerical models of WEC systems, and/or preparing for larger scale testing. Validation and verification of numerical models are very important as there are physical phenomena that are hard to numerically model such as non-linear frictional effects. This paper builds on the 2021 EWTEC paper [1] in performing and evaluating experimental testing of the Laboratory Upgrade Point Absorber (LUPA). Since this last paper, LUPA has been fabricated and deployed and an initial characterization has been performed. Particularly passive (damping), and reactive (damping and stiffness) control methodologies are employed in regular waves to characterize and evaluate the mechanical power extracted from the waves. Reactive control allows us to invest energyin the system to get a greater average energy out as compared to damping control.&#x0D; The LUPA project has just finished its first deployment in the Large Wave Flume at the O.H. Hinsdale Wave Research Laboratory at Oregon State University as shown in Figure 1. Three modes of operation were tested, namely one body heave only, two body heave only, and six degrees of freedom. The one body heave only mode restricts the motion to linear and vertical and fixes the spar body so that the float is the only body free to move. The two body heave only maintains the vertical linear motion, but unlocks the float such that the float and spar are free to heave. The six degrees of freedom case is a floating moored mode with no restrictions on motion.&#x0D; This paper will focus on comparing passive and reactive control for the one body heave only case and the six degreesof freedom case with preliminary results shown in Figure 2. Regular waves were tested, focusing on a single wave heightand sweeping the wave period. Results will be presented in power (W) units and in capture width (m). Fig. 2. Top shows max power output vs input wave period for one body and two body configurations and just damping and damping and stiffness cases.Take note of differing input wave height. Bottom shows capture width.&#x0D; The LUPA project will provide a valuable testing platform for students and researchers. It will also provide a publicly available open source design and dataset for the research community here: https://github.com/PMECOSU/LUPA. This paper will serve as documentation of the initial testing of the system, providing baseline control results to be compared in future testing.

Evaluation of nearshore bathymetric inversion algorithms using camera observations and synthetic numerical input of surface waves during storms

Nearshore bathymetry is difficult to measure using survey methods when wave heights approach the breaking limit. Remote sensing using digital cameras offers a way to observe the surf zone and calculate water depths based on phase speed but comes with its challenges of potentially noisy data that can introduce error into estimates of frequency and wavenumber used in phase speed calculation. This study investigates the robustness of a new version of a bathymetric inversion algorithm (cBathy, version 2.0) in moderate to energetic wave conditions by comparing depth estimates from timeseries’ of pixel intensity with depth estimates from synthetic water level data. The synthetic data are generated by the phase-resolving numerical model, SWASH, and optical data were collected during a field experiment in 2015. Model results from SWASH computed with known bathymetry are used as input to cBathy, and depth estimates are compared to nearshore surveys. Argus camera observations are also used as input to cBathy for the same times as the SWASH simulations. The SWASH simulations resolve breaking waves and do not include (optical) changes to the relation between water surface slope and pixel intensity, termed modulation transfer function, that occur during wave breaking, enabling better estimates from bathymetric inversion algorithms near morphologic features like sand bars. The results indicate that improvements result from eliminating of disruptions to the modulation transfer function caused by wave breaking and residual foam. We show that the use of synthetic wave data is a valuable means of isolating errors in bathymetric inversion algorithms.

Sub-Array-Based Millimeter Wave Massive MIMO Channel Estimation

Combination of millimeter wave (mmWave) and massive multiple input multiple output (MIMO) forms a promising technology for future sixth generation networks. As the number of antennas increases, propagation channel starts yielding spherical wavefronts, for which the traditional channel estimation algorithms are no longer applicable. To overcome this technical gap, a novel MIMO channel estimation scheme based on the assumption of spherical wavefront is proposed in this work. The large antenna array is first divided into several sub-arrays, and then the channel estimation is performed for each sub-array based on the orthogonal matching pursuit algorithm. In addition, the joint estimation of angle of arrivals and departures (AoAs and AoDs) of each uniform planar sub-array is transformed into separate estimation by dimensionality reduction. Next, an iterative estimation is performed using Taylor expansion to continuously approximate the real grid points to recover the AoAs/AoDs. Lastly, the superiority of the proposed algorithm is verified by numerical simulations, where the proposed algorithm exhibits the best NMSE performance, compared with the existing MIMO channel estimation methods.

Earthquake response control effects of coupled structural systems incorporating a negative stiffness connector: Experimental and numerical investigation

Coupled vibration control (CVC) systems, which typically consist of two frames and connectors, such as stiffness and damping elements, can be used for the seismic protection of coupled or adjacent structures. This study aims to experimentally and numerically elucidate the response behavior and control effects of CVC structural systems comprising a mainframe and subframe incorporating passive negative stiffness (PNS) at the connection subjected to earthquakes. Shake table experiments were conducted using CVC system specimens incorporating a PNS device (PNSD) consisting of curved-leaf springs under dynamic excitations. A significant seismic response reduction for the mainframe of the CVC specimen under simulated waves was achieved by incorporating the PNSD at the connection. Moreover, a response simulation was performed using six-story CVC structure models connected by negative stiffness and viscous damping elements subjected to simulated and observed seismic wave inputs. The displacement and acceleration peak response of the mainframe using the numerical CVC models was lower than that of the uncontrolled model. Therefore, incorporating negative stiffness and viscous damping connectors into CVC systems can reduce the seismic response. This study contributes to the advancement of aseismic technologies for coupled or adjacent buildings utilizing the PNS.

High-Efficiency GaN Frequency Doubler Based on Thermal Resistance Analysis for Continuous Wave Input

High-Efficiency GaN Frequency Doubler Based on Thermal Resistance Analysis for Continuous Wave Input

A random non-uniform wave input method based on complex incident site waves

To improve the deficiency of the wave input method (WIM) in expressing complex incident site waves, in this paper, a random non-uniform wave input method (RNUWIM) is derived from the use of the random incident waves and the visco-elastic boundary condition. The random incident waves are generated and adjusted by the comparison of the horizontal ground motion’s response spectrum and the target spectrum, so that they are representative of the actual wavefield in project sites. Furthermore, the RNUWIM is implemented and verified by the finite element method. The result shows that the RNUWIM inherits the advantages of the WIM in simulating the wave propagation effect and the radiation damping effect. In the new method, the spatial variation of ground motions such as time delays, peak variation, and time-history shape differences can be simulated synthetically. The errors of RNUWIM in ground acceleration, velocity, and displacement at the reference point are respectively 3.23%, 0.66%, and 0.07% in one case, which proves the efficiency of the RNUWIM in seismic response analyses.

A Novel Wave Energy Equivalence Based Lumping Block Method for Efficiently Predicting the Fatigue Damage of Mooring Lines

The lumping block equivalent method (LBEM) is widely used to reduce the computational effort in the fatigue damage assessment of offshore structures, and the wave parameters of the representative sea states (RSSs) resulting from LBEM are of vital importance for the accurate prediction of offshore structures’ fatigue damage. In this study, a novel wave energy equivalence (WEE)-based LBEM is proposed to determine the wave parameters of the RSS accurately. The novelty of the proposed method is that a compact relationship between the input wave energy component and mooring lines’ fatigue damage is derived, and the modified statistical relationships between the wave parameters and spectral moments are provided by incorporating the effects of the peak enhancement factor of the input wave spectrum, the number of original sea states (OSSs) and the equivalence bandwidth of the OSSs. Based on the compact relationship, the wave energy component of the RSS can be determined from the wave energy component of the OSSs for each wave frequency from the viewpoint of the fatigue damage equivalence criterion. The wave energy distribution of the RSS can be accurately characterized with the wave energy distribution of the OSSs, and the spectral moments of the RSS can be calculated by its energy distribution directly, without any approximation. Moreover, the wave parameters of the RSS can be determined from the modified statistical relationships easily. The effectiveness of the proposed WEE LBEM is numerically investigated with a moored semi-submersible platform. Results show that the proposed WEE LBEM is robust, efficient and accurate within engineering expectations, and it outperforms the conventional LBEMs both in accuracy and robustness.

Acoustic and mechanical metamaterials for energy harvesting and self-powered sensing applications

Metamaterials are artificially engineered structures that exhibit extraordinary properties beyond the constituent materials, making them attractive for various applications in optics, acoustics, and mechanics. Energy harvesting is an eco-friendly technology that recycles ambient wave and mechanical energy by converting it into valuable electricity. The unique properties of metamaterials offer exciting opportunities to enhance energy harvesting performance by manipulating input wave direction and amplitude or increasing strain levels on energy conversion materials and devices. Recently, there has been a surge in research on incorporating energy manipulation capabilities of phononic crystals, locally-resonant acoustic metamaterials, and mechanical metamaterials into energy harvesting systems, including acoustic and elastic wave focusing and localization and mechanical energy trapping phenomena. In this review, we provide a classification of acoustic and mechanical metamaterials utilized for energy harvesting and self-powered sensing, followed by a comprehensive comparison of how each metamaterial has been integrated and the extent to which it contributes to quantitative improvements in energy and sensing performance. We also discuss the potential of unexplored metamaterials whose concepts are intriguing but have not yet been applied to energy harvesting or self-powered sensing, and discuss the vision and future direction of metamaterial research in this exciting field.

Nonlinear dynamic analysis of soil-pile interactions of nuclear power plants with nonlithological foundation

PurposeThe dynamic response of the nuclear power plants (NPPs) with pile foundation reinforcement have not yet been systemically investigated in detail. Thus, there is an urgent need to improve evaluation methods for nonlithological foundation reinforcements, as this issue is bound to become an unavoidable task.Design/methodology/approachA nonlinear seismic wave input method is adopted to consider both a nonlinear viscoelastic artificial boundary and the nonlinear properties of the overburden layer soil. Subsequently, the effects of certain vital parameters on the structural response are analyzed.FindingsA suitable range for the size of the overburden foundation is suggested. Then, when piles are used to reinforce the overburden foundation, the peak frequencies in the floor response spectra (FRS) in the horizontal direction becomes higher (38%). Finally, the Poisson ratio of the foundation soil has a significant influence on the FRS peak frequency in the vertical direction (reduce 35%–48%).Originality/valueThe quantifiable results are performed to demonstrate the seismic responses with respect to key design parameters, including foundational dimensions, the Poisson Ratio of the soil and the depth of the foundation. The results can help guide the development of seismic safety requirements for NPPs.