Real Wave Research Articles

Platform motion minimization using model predictive control of a floating offshore wind turbine

Wind turbines are installed offshore with the assistance of a floating platform to help meet the world’s increasing energy needs. However, the incident wind and extra incident wave disturbances have an impact on the performance and operation of the floating offshore wind turbine (FOWT) in comparison to bottom-fixed wind turbines. In this paper, model predictive control (MPC) is utilized to overcome the limitation caused by platform motion. Due to the ease of control synthesis, the MPC is developed using a simplified model instead of high fidelity simulation model. The performance of the controller is verified in the presence of realistic wind and wave disturbances. The study demonstrates the effectiveness of MPC in reducing platform motions and rotor/generator speed regulation of FOWTs.

Ultimate strength analysis of longitudinal bending of hull girder based on image analysis

In the traditional code, the allowable stress method is used to check the total longitudinal strength of hull girder, which has the characteristics of simple and quick calculation. However, this method is based on the assumption of elastic materials, and can not truly reflect the actual bearing capacity of the structure. Based on image analysis, a practical method for calculating the ultimate longitudinal strength of ship hull is studied. The average stress-strain relationship of the elements constituting the cross section of the hull girder under axial pressure is given, and the progressive collapse behavior of the hull girder in longitudinal bending is analyzed. Finally, the reliability analysis method for the ultimate strength of the hull girder in longitudinal bending is put forward, and a real ship example is given. The research results show that the proposed method is not only suitable for the safety assessment of ship structures in the conceptual design stage, but also meets the requirements of rapid prediction of real ship wave loads and structural strength reliability analysis.

Arc‐Shaped Triboelectric Nanogenerator Based on Rolling Structure for Harvesting Low‐Frequency Water Wave Energy

AbstractOcean occupies about 71% of the global surface area and contains 97% of the total water on the earth. Ocean waves are regarded as one of the most promising renewable energy sources, but it is quite difficult to harvest such low‐quality and low‐frequency energy due to the technology limitations of traditional electromagnetic generators. In this work, a type of arc‐shaped triboelectric nanogenerator (AS‐TENG) with internal rolling structure is designed to harvest low‐frequency water wave energy. The freestanding roller with flexible surfaces can scroll freely with low friction along the arched track under external triggering, generating induced current between the complementary electrodes. The arc‐shaped design facilitates the high‐density integrating of multiple TENG units and effective packaging for potential large‐scope applications. One AS‐TENG can deliver an output power density of 5.47 W m−3 under regular triggering, while a power density of 2.34 W m−3 is achieved for an AS‐TENG array under real water wave triggering of 1.2 Hz. Moreover, through harvesting water wave energy by the AS‐TENG array, self‐powered temperature sensing and wireless transmission systems have been successfully constructed. This work demonstrates huge application prospects of the AS‐TENGs toward large‐scale ocean blue energy harvesting and environmental monitoring.

Realistic Dispersion of Plasmaspheric Hiss in the Inner Magnetosphere and Its Effect on Wave-induced Electron Scattering Rates

Abstract The cold plasma approximation is a common treatment to study wave–particle interactions between plasmaspheric hiss and magnetospheric electrons, which, however, can become a challenge during periods of disturbed geomagnetic activity. To assess the validity of the cold plasma dispersion relation of plasmaspheric hiss, we adopt the cold plasma theory to calculate the wave magnetic field intensities from the electric field intensities observed by Van Allen Probe A from 2012 October 1 to 2018 February 28. Comparisons between the observed and converted hiss magnetic field intensities capture pronounced differences with the enhancement of substorm activity, and exhibit the largest discrepancies on the nightside MLT sector for low-frequency hiss waves. We also use both the hiss dispersion curves derived from the observations and the cold plasma dispersion relation to evaluate hiss-induced electron diffusion coefficients under different substorm activity conditions. The results indicate that the profiles of electron diffusion rates vary considerably for the two hiss dispersion relations and that the differences between them become increasingly distinct with substorm activity intensification. Our study therefore demonstrates that the cold plasma theory can become less reliable for plasmaspheric hiss waves under disturbed geomagnetic circumstances and that the realistic wave dispersion is essential to better quantify the electron scattering effect of hiss waves, which needs to be carefully incorporated into future global simulations of the generation and propagation of plasmaspheric hiss and associated dynamic variability of radiation belt electrons.

Color Digital Holography Based on Generalized Phase-Shifting Algorithm with Monitoring Phase-Shift

Color digital holography (DH) has been researched in various fields such as the holographic camera and holographic microscope because it acquires a realistic color object wave by measuring both amplitude and phase. Among the methods for color DH, the phase-shifting DH has an advantage of obtaining a signal wave of objects without the autocorrelation and conjugate noises. However, this method usually requires many interferograms to obtain signals for all wavelengths. In addition, the phase-shift algorithm is sensitive to the phase-shift error caused by the instability or hysteresis of the phase shifter. In this paper, we propose a new method of color phase-shifting digital holography with monitoring the phase-shift. The color interferograms are recorded by using a focal plane array (FPA) with a Bayer color filter. In order to obtain the color signal wave from the interferograms with unexpected phase-shift values, we devise a generalized phase-shifting DH algorithm. The proposed method enables the robust measurement in the interferograms. Experimentally, we demonstrate the proposed algorithm to reconstruct the object image with negligibly small conjugate noises.

Ultra-hard rhombohedral carbon by crystal chemistry and ab initio investigations

A new ultra-hard rhombohedral carbon rh-C4 (or hexagonal h-C12) is reported as derived from 3R graphite through crystal chemistry construction and ground state energy within the density functional theory. A resulting cohesive extended hexagonal three-dimensional network of h-C12 is identified as formed of C4 tetrahedra like in cubic and hexagonal diamond. The electronic band structure of rh-C4 is characteristic of insulator with Egap ​= ​4 ​eV similarly to diamond. From the energy-volume equations of state and the set of elastic constants a larger value of bulk modulus versus lonsdaleite, and the largest Vickers hardness (HV) versus both forms of diamond were revealed. The phonon band structure showing only real wave numbers further confirms the stability of the new carbon phase.

STATIC PROPERTIES OF THE 6Li NUCLEUS IN THE THREE-CLUSTER MODEL

This scientific work is devoted to a deep study of the structure of the weakly bound light 6Li nucleus in the framework of the three-cluster α+p+n-model. The realistic Reid soft core potential (RSC-potential) have been utilized as the nucleon-nucleon interaction. The potential with even-odd splitting in waves is used for describing the interaction of the alpha-particle and nucleons. The spectrum of low-lying energy levels of the 6Li nucleus has been calculated, and realistic wave functions of the relative motion of the clusters in this nucleus have been defined. The matrix elements and operators of the main static characteristics of the 6Li nucleus are presented. In particular, the root-mean-square charge and material radii, magnetic dipole and electric quadrupole moments of the 6Li nucleus have been calculated.

PROPERTIES OF LIGHT NUCLEI 6He AND 6Be IN THE FRAMEWORK OF THE THREE-CLUSTER MODEL

This scientific work is the study of the structure of light nuclei 6He and 6Be in the framework of the three-cluster α+2n-model. The calculation methods have been based on the variational solution of the stationary Schrödinger equation for the relative motion of three clusters in 6He and 6Be nuclei, respectively. The realistic Reid potential has been chosen as the nucleon-nucleon interaction potential, and the potential with even-odd wave splitting has been used for the interaction of the alpha-particle and nucleons. Realistic wave functions of the relative motion of the alpha particle and nucleons in these nuclei and low-lying energy levels have been calculated. The static observables of the 0+ ground state of 6He and 6Be nuclei, in particular, the root-mean-square charge and material radii and binding energies, have been determined. The obtained values of the root-mean-square charge and material radii of the 6He nucleus confirm the hypothesis of the presence of a neutron halo structure of this nucleus.

ECG Analysis for HRV Detection

In this paper an algorithm is proposed for estimation of HRV with better accuracy and results. We are making use of Auto Regressive Model (AR Model) for the estimation. Since ECG wave is also contaminated with a lot of noise such as Power Line Interference (PLI), EMG and just some common artifacts like breathing disturbance’s, so to filter out all this noise from the wave we are using Cumulant based AR model for filtering the wave. Using IoT we will later use real time ECG waves to estimate HRV.

Introducing envelope soliton solutions for wave–structure investigations

This paper explores the applicability of envelope soliton solutions of the non-linear Schrödinger-type equation as an innovative design wave for wave–structure interaction investigations. The major benefits of envelope solitons are the potential to generate non-linear wave groups of certain frequency and (physically possible) wave steepness as well as the availability of an analytical solution. Furthermore, the fact that envelope solitons are characterized by a limiting frequency bandwidth enables the tailor-made generation of critical wave conditions for task-specific wave–structure investigations. For the evaluation of the applicability of envelope solitons, wave–structure investigations with a chemical tanker were performed in a set of envelope solitons at certain frequencies and wave steepness. The applicability of envelope solitons as design waves as well as their impact on the chemical tanker are compared to classical design wave concepts and tailored extreme wave events. For the extreme wave events, the Peregrine breather solution and a real world abnormal wave reproduction, the famous ‘New Year Wave’, were selected. The investigations comprised model tests as well as numerical simulations. Altogether, this paper shows that envelope solitons are excellent design waves for extreme response investigations suitable for model tests as well as numerical investigations.

Numerical Study on Wave Attenuation of Tsunami-Like Wave by Emergent Rigid Vegetation

The extreme surges and waves generated in tsunamis can cause devastating damages to coastal infrastructures and threaten the intactness of coastal communities. After the 2004 Indian Ocean tsunami, extensive physical experiments and numerical simulations have been conducted to understand the wave attenuation of tsunami waves due to coastal forests. Nearly all prior works used solitary waves as the tsunami wave model, but the spatial-temporal scales of realistic tsunamis differ drastically from that of solitary waves in both wave period and wavelength. More recent work has questioned the applicability of solitary waves and been looking towards more realistic tsunami wave models. Therefore, aiming to achieve more realistic and accurate results, this study will use a parameterized tsunami-like wave based on wave observations during the 2011 Japan tsunami to study the wave attenuation of a tsunami wave by emergent rigid vegetation. This study uses a high-resolution numerical wave tank based on the non-hydrostatic wave model (NHWAVE). This work examines effects of prominent factors, such as wave height, water depth, vegetation density and width, on the wave attenuation efficiency of emergent rigid vegetation. Results indicate that the vegetation patch can dissipate a considerable amount of the total wave energy of the tsunami-like wave. However, the tsunami-like wave has a higher total wave energy, but also a lower wave energy dissipation rate. Results show that using a solitary instead of a tsunami-like wave profile can overestimate the wave attenuation efficiency of the coastal forest.

Ultra-thin and broadband surface wave meta-absorber.

Perfect absorbers are highly desired in many engineering and military applications, including radar cross section (RCS) reduction, cloaking devices, and sensor detectors. However, most types of present absorbers can only absorb space propagation waves, but absorption for surface waves has not been researched intensively. Surface waves are easily excited on the interfaces between metal and dielectrics for electronic devices, which decreases their working performances due to the electromagnetic disturbances. Thus, it is of great significance to design appropriate absorbers to dissipate undesirable surface waves. Here, we propose the concept of a surface wave absorber, analyze its working principle, and prove its good performances experimentally. To demonstrate our concept, we design and fabricate a realistic surface wave absorber that is fixed on a metal surface. Experiments are performed to verify its electromagnetic characteristics. The results show that our designed meta-absorber can achieve an excellent surface wave absorption within a wide frequency window (5.8-11.2 GHz) and exhibit a very high efficiency over than 90%, but only with the thickness of 1 mm (0.028 λ). Our device can help to solve the issues of absorption at large angles, and it can find wide applications in large antenna array design and other communication systems.

Rayleigh Wave Dispersion Curve Inversion with the Artificial Bee Colony Algorithm

Rayleigh wave dispersion curve inversion is a non-linear iterative optimization process with multi-parameter and multi-extrema. It is difficult to carry out inversion and reconstruction of stratigraphic parameters quickly and accurately with a single linear or non-linear inversion for the data processing of Rayleigh waves with complex seismic geological conditions. We proposed a new method that combines artificial bee colony algorithm (ABC) and damped least squares algorithm (DLS) to invert Rayleigh wave dispersion curve. First, food sources are initialized in a large scale of the model based on the prior geological information. Then, after three kinds of bee operators (employed bees, onlooker bees and scout bees) transform each other and perform search optimization with several iterations, the targets are converged near the optimal solution to obtain an initial S-wave velocity model. Finally, the final S-wave velocity model is obtained by local optimization of DLS inversion with fast convergence and strong stability. The correctness of the method has been verified by one high-velocity interlayer model, and it was further applied to a real Rayleigh wave dataset. The results show that our method not only absorbs the advantages of ABC global search optimization and strong adaptability, but also makes full use of the advantages of DLS inversion, such as high accuracy and fast convergence speed. The inversion strategy can effectively suppress the inversion falling into local extrema, get rid of the dependence on an initial model, enhance the inversion stability, further improve the convergence speed and inversion accuracy, while has good anti-noise ability.

Évaluation de la formation théorique et pratique des internes en Île-de-France sur les connaissances et l’accompagnement de la transidentité chez l’enfant et l’adolescent

IntroductionGender dysphoria, non-binarity, trans-identity, neutrality, gender fluid. faced with the emergence of a redefinition and reaffirmation of gender, what place and training are there for the doctors of tomorrow? A public health issue is coming to the fore as the suicide rate among these adolescents is seven times higher than among so-called “cisgender” adolescents. So how do you take care of these patients and their families, for whom access to care is so difficult? Several doctors have found themselves confronted with this real tidal wave of requests for gender consultations without any training or clear recommendations. MethodThis survey, carried out among resident doctors in the Île-de-France region, aims to assess the current practical and theoretical training concerning the care of children and adolescents with a trans-identity status. This survey was carried out during the month of June 2020, using an anonymous online questionnaire consisting of 16 questions including multiple choices as well as open-ended ones. The questions concerned a self-assessment of practical and theoretical knowledge according to the year and specialty of the residency. It also addressed the issue of training programs implemented by medical faculties and university hospitals as well as the confrontation to trans-identity in clinical practice and the reflections emerging from it. ResultsThe findings, collected from the answers of 143 resident doctors, show an overall lack of knowledge, theoretical and practical, without medical specialization distinction. It includes pediatric and child psychiatric specialties that are all the more directly concerned. This gap is mostly attributed to the lack of training and teaching in medical universities and hospitals, as well as to a subject still considered taboo within the medical profession itself. The overwhelming majority of doctors are thus in demand for more comprehensive education on the issue as part of their general medical training curriculum. ConclusionIt appears more than important to consider trans-identity status a real public health issue. This matter is taking on an increasingly crucial role in child and adolescent medical counselling. In the coming years, this will enable better patient support and better access to care within a population weakened by years of discrimination and inequality in relation to the fundamental right to health.

Analysis of the rogue waves in the blood based on the high-order NLS equations with variable coefficients* *Project supported by the National Natural Science Foundation of China (Grant No. 11975143), Nature Science Foundation of Shandong Province of China (Grant No. ZR2018MA017), the Taishan Scholars Program of Shandong Province, China (Grant No. ts20190936), and the Shandong University of Science and Technology

The research of rogue waves is an advanced field which has important practical and theoretical significances in mathematics, physics, biological fluid mechanics, oceanography, etc. Using the reductive perturbation theory and long wave approximation, the equations governing the movement of blood vessel walls and the flow of blood are transformed into high-order nonlinear Schrödinger (NLS) equations with variable coefficients. The third-order nonlinear Schrödinger equation is degenerated into a completely integrable Sasa–Satsuma equation (SSE) whose solutions can be used to approximately simulate the real rogue waves in the vessels. For the first time, we discuss the conditions for generating rogue waves in the blood vessels and effects of some physiological parameters on the rogue waves. Based on the traveling wave solutions of the fourth-order nonlinear Schrödinger equation, we analyze the effects of the higher order terms and the initial deformations of the blood vessel on the wave propagation and the displacement of the tube wall. Our results reveal that the amplitude of the rogue waves are proportional to the initial stretching ratio of the tube. The high-order nonlinear and dispersion terms lead to the distortion of the wave, while the initial deformation of the tube wall will influence the wave amplitude and wave steepness.

Nodding Duck Structure Multi-track Directional Freestanding Triboelectric Nanogenerator toward Low-Frequency Ocean Wave Energy Harvesting.

Development of ocean energy conversion technique is a strategic requirement to optimize the energy structure and expand the "blue economic" space. Triboelectric nanogenerator (TENG) provides a potential approach for efficiently capturing wave energy with its unique advantages. Herein, a nodding duck structure multi-track freestanding triboelectric-layer nanogenerator (NDM-FTENG) is developed for ocean wave energy harvesting at a low-frequency range. Configuration parameters including track numbers, connection approach, oscillation frequency, and swing amplitude on electrical output performances of NDM-FTENG are systematically investigated and optimized; the maximum instantaneous power density of 4 W/m3 is obtained by one NDM-FTENG block with 320 LEDs lighted up simultaneously. Overall, NDM-FTENG is proved to be an efficient device for driving small electronics with excellent stability and durability in a real water wave environment, and the power potential can be further magnified by combining more NDM-FTENG devices in parallel to form a network toward large-scale blue energy harvesting.

Simulations of the Surf Zone Eddy Field and Cross‐Shore Exchange on a Nonidealized Bathymetry

AbstractX‐band radar observations from the 2017 Inner Shelf Dynamics Experiment (ISDE) in central California show multiple persistent and pulsatory rip currents on a relatively straight coastline with alongshore‐varying bathymetry. Although past studies have assessed the characteristics of transient rip currents on alongshore uniform beaches, the relative balance of transient versus steady rip current behavior on nonuniform beaches in realistic wave conditions remains poorly understood. Here, a phase‐resolving Boussinesq‐type wave model (funwaveC) is used to assess the role of alongshore‐varying bathymetry and incident conditions in controlling mean and transient surf zone vorticity and velocity fields and their effect on surf zone exchange. The model simulates wave conditions chosen from the ISDE observations and utilizes both an alongshore‐varying bathymetry estimated from the ISDE radar observations and a uniform bathymetry. Results show that the variable bathymetry significantly increases the alongshore‐ and time‐averaged kinetic energy but that this increase is primarily due to the increase in the standing component resulting from mean circulation patterns, with only small changes in the transient component. A variable bathymetry also increases the spectral energy of surf zone vorticity and time‐averaged vorticity forcing at large spatial scales (>100 m). Wave directional spreading has a large impact on the alongshore‐ and time‐averaged enstrophy and on the spectral energy of surf zone vorticity and vorticity forcing at smaller spatial scales (<100 m). In the presence of a directionally spread wavefield, an alongshore‐varying bathymetry slightly increases the total exchange velocity but has little effect on its transient component.

A Comparative Study of Metaheuristic Algorithms for Wave Energy Converter Power Take-Off Optimisation: A Case Study for Eastern Australia

One of the most encouraging sorts of renewable energy is ocean wave energy. In spite of a large number of investigations in this field during the last decade, wave energy technologies are recognised as neither mature nor broadly commercialised compared to other renewable energy technologies. In this paper, we develop and optimise Power Take-off (PTO) configurations of a well-known wave energy converter (WEC) called a point absorber. This WEC is a fully submerged buoy with three tethers, which was proposed and developed by Carnegie Clean Energy Company in Australia. Optimising the WEC’s PTO parameters is a challenging engineering problem due to the high dimensionality and complexity of the search space. This research compares the performance of five state-of-the-art metaheuristics (including Covariance Matrix Adaptation Evolution Strategy, Gray Wolf optimiser, Harris Hawks optimisation, and Grasshopper Optimisation Algorithm) based on the real wave scenario in Sydney sea state. The experimental achievements show that the Multiverse optimisation (MVO) algorithm performs better than the other metaheuristics applied in this work.

Metal-organic framework-derived NiSe2-CoSe2@C/Ti3C2Tx composites as electromagnetic wave absorbers

• A novel accordion-like structure was synthesized by ZIF-67 derivation strategy. • Their morphological evolution in various stages is clarified. • Revealing the contribution of dielectric property modulation to absorption performance. • The EAB reached 5.68 GHz at a thickness of 2.6 mm for NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composite. Two-dimensional metal carbide or nitride materials are considered as a new class of electromagnetic wave absorbing materials due to their unique multilayer structure and metal-like properties. The NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composites were prepared through a facile hydrothermal treatment and selenization reaction. Distinctly, the maximum reflection loss ( RL ) is −60.46 dB with the mass fraction of NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x of 40 wt% at 2.6 mm. The bandwidth of RL < −10 dB reaches up to 5.68 GHz (10.32–16 GHz). The synergistic mechanism of the multiple scattering and multi-interface polarization effects of NiSe 2 -CoSe 2 @C compounded with Ti 3 C 2 T x is reviewed to interpret the significant improvement of electromagnetic wave absorption performance. The results indicate that NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composites have potential applications as realistic electromagnetic wave absorbing materials.

Elastic wave field simulation of a three-dimensional sedimentary basin for incident spherical P, SV, and SH waves

In this paper, the source is assumed to be a more realistic spherical wave than plane wave, and the scattering of spherical P, SV and SH waves by 3D sedimentary basins is studied by using IBEM. The total wave field is decomposed into free wave field and scattered wave field. The free wave field is solved by direct stiffness method combined with Hankel transformation, while the scattered wave field is simulated by dynamic Green's function. The correctness of the method is verified by comparing the results calculated by this method with those in published literature. Taking the model of a semi elliptical sedimentary basin as an example, the effects of source location, incident wave frequency, shear wave velocity ratio between bedrock and single rock on surface displacement amplitude are studied. The results show that: under the incident of spherical wave source, the sedimentary basin has obvious amplification effect on the surface displacement for different source location, and the larger the incident frequency, more obvious the amplification effect is; in the layered half-space, when the incident frequency is low, the shear wave velocity ratio has a significant effect on the basin surface displacement.