Wave Power Research Articles

Cosmologically consistent analysis of gravitational waves from hidden sectors

Production of gravitational waves in the early Universe is discussed in a cosmologically consistent analysis within a first-order phase transition involving a hidden sector feebly coupled with the visible sector. Each sector resides in its own heat bath leading to a potential dependent on two temperatures and on two fields: one a standard model Higgs field and the other a scalar arising from a hidden sector U(1) gauge theory. A synchronous evolution of the hidden and visible sector temperatures is carried out from the reheat temperature down to the electroweak scale. The hydrodynamics of two-field phase transitions, one for the visible and the other for the hidden is discussed, which leads to separate tunneling temperatures and different sound speeds for the two sectors. Gravitational waves emerging from the two sectors are computed and their imprint on the measured gravitational wave power spectrum vs frequency is analyzed in terms of bubble nucleation signature, i.e., detonation, deflagration, and hybrid. It is shown that the two-field model predicts gravitational waves accessible at several proposed gravitational wave detectors: LISA, DECIGO, BBO, and Taiji, and their discovery would probe specific regions of the hidden sector parameter space and may also shed light on the nature of bubble nucleation in the early Universe. The analysis presented here indicates that the cosmologically preferred models are those where the tunneling in the visible sector precedes the tunneling in the hidden sector and the sound speed cs lies below its maximum, i.e., cs2<13. It is of interest to investigate if these features are universal and applicable to a wider class of cosmologically consistent models. Published by the American Physical Society 2024

Impact resistance of recycled-PET fiber strengthened wave-dissipating concrete block considering rocking motion

This study was conducted to enhance the impact resistance of wave-dissipating concrete blocks by recycled-Polyethylene Terephthalate (rPET) fibers. The aim of this study is to address the structural vulnerabilities of maritime structures and contribute to environmental issue. Traditionally, the stability of marine structures has been largely dependent on self-weight, a characteristic that can be undermined by damage from sea waves. Wave-dissipating concrete blocks are engineered to reduce the power of waves, but they remain susceptible to fractures caused by hoisting and rocking motions after installation. Existing evaluations often neglect the impact of rocking motion, primarily concentrating on fractures due to lifting. To enhance impact resistance, ultra-slow speed experimental tests were conducted to determine the fracture energy of concrete block considering rPET. The results revealed a significant improvement in the fracture energy of rPET reinforced concrete. Based on these experimental test results, a numerical model was developed to simulate the behavior of wave-dissipating concrete blocks considering rocking motion. The developed Smoothed Particle Hydrodynamics (SPH) model proved to be more relevant than the Finite Element (FE) model. Furthermore, this newly developed numerical model was utilized to evaluate structural performance. The results of the numerical analysis indicated a relationship between weight and impact velocity on the occurrence of damage. This led to the proposal of fragility curves for Sealock and TTP under various impact velocities during rocking motion. Fragility curves, developed based on impact velocity, demonstrated enhanced impact resistance of wave-dissipating concrete blocks reinforced with rPET. In addition, the incorporation of PET fibers effectively controlled crack propagation and improved impact resistance, particularly with increasing block weight. The methodology employed in this study holds potential for predicting outcomes using simple data, making it applicable to other scenarios such as vehicle-bridge pier collisions.

Evolving scientific discovery by unifying data and background knowledge with AI Hilbert

The discovery of scientific formulae that parsimoniously explain natural phenomena and align with existing background theory is a key goal in science. Historically, scientists have derived natural laws by manipulating equations based on existing knowledge, forming new equations, and verifying them experimentally. However, this does not include experimental data within the discovery process, which may be inefficient. We propose a solution to this problem when all axioms and scientific laws are expressible as polynomials and argue our approach is widely applicable. We model notions of minimal complexity using binary variables and logical constraints, solve polynomial optimization problems via mixed-integer linear or semidefinite optimization, and prove the validity of our scientific discoveries in a principled manner using Positivstellensatz certificates. We demonstrate that some famous scientific laws, including Kepler’s Law of Planetary Motion and the Radiated Gravitational Wave Power equation, can be derived in a principled manner from axioms and experimental data.

THz Wave Power Enhancement Using a Microstrip Line-Based Combiner Integrated with Arrayed UTC-PDs

Advancements in semiconductor devices, such as Uni-travelling-carrier photodiodes (UTC-PDs), have played a significant role in the development of Terahertz communication technology. However, the persistent challenge is the limited output power from a single UTC-PD required for practical transmission distances. To enhance the output power, we propose and demonstrate a novel Terahertz wave power combining technique using a photomixer device comprising two arrayed UTC-PDs monolithically integrated with a microstrip line-based 2 × 1 Wilkinson power combiner and a patch antenna on a Silicon Carbide (SiC) substrate at 300 GHz. When the two UTC-PDs are activated at photocurrents of 8 mA and 10 mA, the device exhibits a 7.3 dB increase in power relative to the power obtained when only the 8 mA UTC-PD is activated, and a 4.4 dB increase in power relative to the power obtained with the 10 mA UTC-PD. This implies that power can be enhanced by a factor of N2 if the photocurrent is multiplied by N. Additionally, we demonstrate that the UTC-PD output saturation depends on the space charge effect, which modulates the electric field in the depletion region and results from critical charge density of about 80 kA/cm2 for the device in this work.

Effects of stratification on overshooting and waves atop the convective core of M⊙ main-sequence stars

ABSTRACT As a massive star evolves along the main sequence, its core contracts, leaving behind a stable stratification in helium. We simulate two-dimensional convection in the core at three different stages of evolution of a $5\,\mathrm{ M}_{\odot }$ star, with three different stratifications in helium atop the core. We study the propagation of internal gravity waves in the stably stratified envelope, along with the overshooting length of convective plumes above the convective boundary. We find that the stratification in helium in evolved stars hinders radial motions and effectively shields the radiative envelope against plume penetration. This prevents convective overshooting from being an efficient mixing process in the radiative envelope. In addition, internal gravity waves are less excited in evolved models compared to the zero-age-main-sequence model, and are also more damped in the stratified region above the core. As a result, the wave power is several orders of magnitude lower in mid- and terminal-main-sequence models compared to zero-age-main-sequence stars.

Oscillating surge wave energy converter using a novel above-water power takeoff with belt-arc speed amplification

We investigate the performance of a novel power takeoff (PTO) featuring belt-arc speed amplification for oscillating surge wave energy converters (OSWECs), aiming to address the PTO design challenges of extremely low rotary speed and large torque under the low-frequency and large energy density ocean wave excitations. The belt-arc design significantly increases the rotary speed of the generator, enabling generator downsizing and decreasing the powertrain friction losses. The design also allows for placing the generator above water, eliminating the need for high Ingress Protection ratings for the generator and powertrain, and potentially leading to substantial reductions in capital and maintenance costs. Using the potential flow theory, the dynamics of the integrated system are analyzed, and key parameters are identified. To validate the numerical analysis, a 1:10 scale model is designed, fabricated, and tested in a wave tank. Performance evaluations are conducted under regular and irregular wave conditions, with quantified effects of parameter tuning. The results reveal an optimal wave-to-electric efficiency of 48% under regular wave excitation and 20% under irregular excitation. These findings underscore the effectiveness of the proposed novel PTO design in addressing the challenges of low rotation speed and large torque inherent in OSWECs, demonstrating its ability to efficiently convert wave power into electricity.

Wave power in the Mediterranean Sea

Wave power in the Mediterranean Sea

Hydrodynamic performance of a pile-supported oscillating water column breakwater in front of a partially reflecting seawall

Integrating wave energy devices with breakwaters can offer an innovative and sustainable approach by combining wave power extraction with wave attenuation. The performance of this integrated system in offshore areas is influenced by the unique characteristics of the coastline. In this paper, a semi-analytical solution was developed using the matching eigenfunction method for the oscillating water column device integrated into a pile-supported breakwater in front of a partially reflective seawall. The model was validated through the energy conservation law, the Haskind relationship, and experimental data. Detailed examinations were conducted on the effects of the seawall's reflection coefficients, the distance between the system and the seawall, the wall draft, and the chamber breadth on hydrodynamic performance. Results show that the presence of the seawall significantly influences hydrodynamic coefficients (hydrodynamic efficiency, reflection coefficient, the relative transmitted amplitude, etc.), accompanied by the piston and sloshing mode resonances inside the chamber and the confined area between the system and the seawall. Due to energy dissipated by a partially reflective seawall, the magnitude of those hydrodynamic coefficients is mitigated, together with the piston and sloshing mode resonances inside the air chamber. The cancellation of the sloshing mode resonance inside the confined area is observed for the smaller seawall's reflection coefficient. The maximum and minimum hydrodynamic efficiency occur when the system is arranged at the wave nodes and antinodes of the formed standing wave field. Lower wave reflection and better wave power extraction can be achieved by properly adjusting the chamber drafts and breadths.

Conductive Hydrogel Tapes for Tripolar EEG: A Promising Solution to Paste-Related Challenges.

Electroencephalography (EEG) remains pivotal in neuroscience for its non-invasive exploration of brain activity, yet traditional electrodes are plagued with artifacts and the application of conductive paste poses practical challenges. Tripolar concentric ring electrode (TCRE) sensors used for EEG (tEEG) attenuate artifacts automatically, improving the signal quality. Hydrogel tapes offer a promising alternative to conductive paste, providing mess-free application and reliable electrode-skin contact in locations without hair. Since the electrodes of the TCRE sensors are only 1.0 mm apart, the impedance of the skin-to-electrode impedance-matching medium is critical. This study evaluates four hydrogel tapes' efficacies in EEG electrode application, comparing impedance and alpha wave characteristics. Healthy adult participants underwent tEEG recordings using different tapes. The results highlight varying impedances and successful alpha wave detection despite increased tape-induced impedance. MATLAB's EEGLab facilitated signal processing. This study underscores hydrogel tapes' potential as a convenient and effective alternative to traditional paste, enriching tEEG research methodologies. Two of the conductive hydrogel tapes had significantly higher alpha wave power than the other tapes, but were never significantly lower.

Expansion of measurement capabilities of the bolometric sensor of the terahertz wave power based on an inexpensive and stable measuring system

The paper discusses the results of a joint work of the Central Office of Measures in the Republic of Poland and the Military University of Technology in Warsaw within the framework of the project “Measurement Consistency in Electromagnetic Power Measurements in the Sub-THz Band”. The main problems in the study of electromagnetic radiation power in the terahertz range using a bolometric detector are considered. The design and parameters of the measuring system based on the use of a resistive bolometric detector, own signal amplifier, and measuring converter, which were designed and implemented at the Central Office of Measures in the Republic of Poland, are described. The results of metrological traceability to the SI units are presented. This paper is dedicated to expanding measurement capabilities of the bolometric detector based on a highly stable and inexpensive measuring system in the terahertz range. As a result of the joint work, a measuring system characterized by high parameter stability and a gain of more than 20 000 V/V was developed and tested.

Observation of topologically enhanced third harmonic generation in doubly resonant nonlinear topolectrical circuits

The ability to confine and guide wave makes topological physics a promising platform for large local field enhancement and strong scattering immunity, which enables efficient nonlinear processes. In this research, we employ a mirror-stacking approach to achieve resonance through two distinct frequency localized states (LSs) in one-dimensional topological circuits, introducing a novel method for validating topological states to facilitate harmonic enhancement. Experimental results reveal that the harmonic wave power increases significantly, by two orders of magnitude, when both the fundamental and harmonic waves are in LSs, in contrast to cases where only one wave is localized. The conversion efficiency is 15.7 times that when the fundamental wave is in a localized state and the harmonic is in a transmission mode. This method, leveraging double-resonance in topological LSs, not only advances harmonic generation in topolectrical circuits but also opens up possibilities for innovative applications in the broader field of photonic technology.

Analysis of the Use of Ocean Wave Power Generation Technology as an Environmentally Friendly Energy Alternative in Indonesia

Indonesia is an archipelagic country that is geographically located between two continents and two oceans. As a country blessed with vast ocean expanses, Indonesia has great potential for marine energy sources. Ocean Wave Power Plants (PLTGL) are a type of energy that has advantages compared to other energy sources, namely that they are available throughout the ocean and are considered more environmentally friendly. However, in its use, Ocean Wave Power Plants require quite a lot of money. Apart from that, even though it is considered more environmentally friendly, ocean wave technology also has environmental impacts. This research aims to analyze the use of ocean wave power generation technology. The method used in this research is a qualitative research method with a literature study approach. The results of this research show that ocean wave power plants are a renewable energy source that has great potential to be used as an environmentally friendly alternative energy source in Indonesia

Study and analysis of high-power coupler failure due to asymmetric electric field distribution

Microwave vacuum electronics play a vital role in numerous applications, and high-power couplers are a critical component. However, coupler failure is a common problem in high-energy accelerators, especially in situations involving high continuous wave (CW) power operation, leading to costly downtime and reduced performance. This paper focuses on addressing the issue of coupler failure in high-power scenarios by studying the specific case of the Circular Electron-Positron Collider (CEPC) 650 MHz high-efficiency klystron, designed for a power of 800 kW and tested up to 700 kW. The failure was attributed to the cracking of the coupler ceramics due to asymmetric electric field distribution, a previously unnoticed issue. Consequently, this study describes the coupler testing process, analyzes the problem, and proposes corresponding solutions to achieve symmetrical electric field distribution and reduce thermal stress. After evaluating three approaches, we recommend the T-bar coupler with water cooling and forced air cooling as the most viable option. This research is significant for the future development of high-power couplers, as it offers references for overcoming technical challenges and optimizing structural designs. As a result, other high-power coupler designers may find inspiration in the suggested solutions as they strive for increased dependability and performance.

DELWAVE 1.0: deep learning surrogate model of surface wave climate in the Adriatic Basin

Abstract. We propose a new point-prediction model, the DEep Learning WAVe Emulating model (DELWAVE), which successfully emulates the behaviour of a numerical surface ocean wave model (Simulating WAves Nearshore, SWAN) at a sparse set of locations, thus enabling numerically cheap large-ensemble prediction over synoptic to climate timescales. DELWAVE was trained on COSMO-CLM (Climate Limited-area Model) and SWAN input data during the period of 1971–1998, tested during 1998–2000, and cross-evaluated over the far-future climate time window of 2071–2100. It is constructed from a convolutional atmospheric encoder block, followed by a temporal collapse block and, finally, a regression block. DELWAVE reproduces SWAN model significant wave heights with a mean absolute error (MAE) of between 5 and 10 cm, mean wave directions with a MAE of 10–25°, and a mean wave period with a MAE of 0.2 s. DELWAVE is able to accurately emulate multi-modal mean wave direction distributions related to dominant wind regimes in the basin. We use wave power analysis from linearised wave theory to explain prediction errors in the long-period limit during southeasterly conditions. We present a storm analysis of DELWAVE, employing threshold-based metrics of precision and recall to show that DELWAVE reaches a very high score (both metrics over 95 %) of storm detection. SWAN and DELWAVE time series are compared to each other in the end-of-century scenario (2071–2100) and compared to the control conditions in the 1971–2000 period. Good agreement between DELWAVE and SWAN is found when considering climatological statistics, with a small (≤ 5 %), though systematic, underestimate of 99th-percentile values. Compared to control climatology over all wind directions, the mismatch between DELWAVE and SWAN is generally small compared to the difference between scenario and control conditions, suggesting that the noise introduced by surrogate modelling is substantially weaker than the climate change signal.

Valine and Inflammation Drive Epilepsy in a Mouse Model of ECHS1 Deficiency.

ECHS1 Deficiency (ECHS1D) is a rare and devastating pediatric disease that currently has no defined treatments. This disorder results from missense loss-of-function mutations in the ECHS1 gene that result in severe developmental delays, encephalopathy, hypotonia, and early death. ECHS1 enzymatic activity is necessary for the beta-oxidation of fatty acids and the oxidation of branched-chain amino acids within the inner mitochondrial matrix. The pathogenesis of disease remains unknown, however it is hypothesized that disease is driven by an accumulation of toxic metabolites from impaired valine oxidation. To expand our knowledge on disease mechanisms, a novel mouse model of ECHS1D was generated that possesses a disease-associated knock-in (KI) allele and a knock-out (KO) allele. To investigate the behavioral phenotype, a battery of testing was performed at multiple time points, which included assessments of learning, motor function, endurance, sensory responses, and anxiety. Neurological abnormalities were assessed using wireless telemetry EEG recordings, pentylenetetrazol (PTZ) seizure induction, and immunohistochemistry. Metabolic perturbations were measured within the liver, serum, and brain using mass spectrometry and magnetic resonance spectroscopy. To test disease mechanisms, mice were subjected to disease pathway stressors and then survival, body weight gain, and epilepsy were assessed. Mice containing KI/KI or KI/KO alleles were viable with normal development and survival, and the presence of KI and KO alleles resulted in a significant reduction in ECHS1 protein. ECHS1D mice displayed reduced exercise capacity and pain sensation. EEG analysis revealed increased slow wave power that was associated with perturbations in sleep. ECHS1D mice had significantly increased epileptiform EEG discharges, and were sensitive to seizure induction, which resulted in death of 60% of ECHS1D mice. Under basal conditions, brain structure was grossly normal, although histological analysis revealed increased microglial activation in aged ECHS1D mice. Increased dietary valine only affected ECHS1D mice, which significantly exacerbated seizure susceptibility and resulted in death. Lastly, acute inflammatory challenge drove regression and early lethality in ECHS1D mice. In conclusion, we developed a novel model of ECHS1D that may be used to further knowledge on disease mechanisms and to develop therapeutics. Our data suggests altered metabolic signaling and inflammation may contribute to epilepsy in ECHS1D, and these alterations may be attributed to impaired valine metabolism.

Design comparison and effects of a chamber structure on wave dissipation

ABSTRACT Among all the ocean energy sources that have been widely studied, chamber structures such as oscillating water column (OWC) technologies are effective and low-cost methods to develop hundreds of wave power generation devices as the disadvantage is its lack of efficiency. Even if the OWC system does not perform any power generation operations, it is a wave-absorbing structure. A large part of the wave energy may be blocked by the structure’s acting chamber or could be dissipated during the interaction of the waves in the air chamber, which affects the actual power generation benefit evaluation. Nevertheless, a better wave attenuation structure may present a relatively poor design of the OWC generator chamber. A series of experiments were conducted with regular and irregular wave conditions to study the effects of energy dissipation caused by a chamber structure under varied barrier and orifice designs.

Effect of Lemongrass (Cymbopogon Citratus) Essential Oil Inhalation on Brain Waves in Healthy Female Adults in Awake State by Power Spectral Analysis of Quantitative Electro-encephalogram: A Self-controlled Study

Background: Industrialization of society and competitive lifestyle have made our daily life full of stress and people are searching for a convenient way to cope with this. Effect of lemongrass fragrance on brain functions can be analyzed through power spectral analysis of quantitative electroencephalogram (EEG). Objective: To assess the effects of lemongrass (Cymbopogon Citratus) essential oil aroma inhalation on EEG in healthy female adults in awake state by power spectral analysis. Methods: This self-controlled trial was conducted in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka from March 2022 to February 2023. Thirty healthy female volunteers from this campus participated in this study. Each subject had undergone three successive sessions of baseline, water and essential oil mist inhalation and EEG recording afterwards. Statistical test was done by Student’s paired ‘t’ test and Wilcoxon matched pair signed rank test by using SPSS v.25. Results: Mean ± SD of absolute power of alpha brain wave were significantly higher (p˂0.0001) after inhalation of essential oil mist compared to both baseline and water mist inhalation in all brain regions. The absolute power of beta wave after essential oil mist exposure was significantly higher compared to baseline and water mist exposure in frontal (p=0.0001; p=0.0005), parietal (p=0.0009; p=0.005) and occipital regions (p<0.001). No significant change after inhalation of water mist compared to baseline. Conclusion: Lemongrass essential oil inhalation is effective to induce conscious relaxation, calmness with increased attention and vigilance by increasing power of alpha and beta waves in healthy female adults. JAFMC Bangladesh, Vol 19, No 2 (December) 2023: 32-36

Heart rate variability in children of younger school age in the speleoclimatotherapy

The autonomic nervous system is a key link in the course of adaptation and adaptive reactions of the organism to various environmental factors. The aim of this study was to assess the heart rate variability of primary school children during a course of speleoclimatotherapy. The heart rate variability were evaluated in 175 practically healthy children aged 7–10 years. In the course of the study the effect of speleoclimatotherapy on the balance sympathetic and parasympathetic nervoussystem was studied using the parameters of spectral analysis of heart rate variability (HRV). HRV data were analysed in the frequency domain: total wave power (TP), high frequency waves (HF), low frequency waves (LF), very low frequency waves (VLF), vagosympathetic index LF/HF. After a course of speleoclimatotherapy the analysis of the obtained results allowed us to establish statistically significant differences in the groups of boy and girls with vagotonic and normotonic type of regulation. After a course of speleoclimatotherapy reduction of the indexe of a vagosympathetic balance (LF/HF) to normal values was found in the groups of sympathotonic boys and sympathotonic girls, while in sympathotonic girls there was an increase in the value of the total power (TP). It is possible to speak about the restoration of vegetative equilibrium and increase of adaptive capabilities of the child’s organism due to adaptation to the microclimate of speleo-chambers.

Power-modulated reconfigurable nonlinear plasmonic devices without DC power supply and feed circuit

High-power electromagnetic (EM) waves can directly modulate the parameters of nonlinear varactor diodes through the rectification and Kerr effects without relying on external sources. Based on this principle, we propose a power-modulated reconfigurable nonlinear device based on spoof surface plasmon polariton (SSPP) waveguide loaded by varactor diodes, without applying DC power supply or feed circuit. Increasing the input power level reduces the effective capacitance of the varactor diode, leading to a blueshift in the cutoff frequency of the SSPP waveguide. This feature can be employed to realize the switching on/off of the input signal depending on the signal power. On the other hand, the transmission state of a low-power signal can be controlled by inputting another independent high-power EM wave simultaneously. Increasing the power of the control wave will enable the low-power signal within a wider bandwidth switched from off to on states. Experimental results are presented to show the excellent performance of the power-modulated reconfigurable SSPP device. This method can reduce the system complexity and provide inspiration for reconfigurable all-passive multifunctional devices and systems.

A bionic design of oscillating wave surge energy converter based on scallops

Oscillating wave surge converters (OWSCs) are generally of rectangular geometries. What kind of flap shape is better is still not clear. Thus, this study proposes some bionic flaps by mimicking the scallops. Eight scallop-based bionic flaps were compared. The fluid pressure and velocity surrounding the bionic and the original flaps were compared to examine why the bionic flap was better. Then, a Sobol sensitivity analysis was conducted, which found that the wave period, water depth, OWSC damping, Bezier length ratio, and Bezier height ratio have notable influences on the OWSC. Parametric study of the OWSC tells that as the increase of the Bezier length ratio, the capture factor increases first and then converges. As the increases of the remaining parameters, the capture factor increases first and then decreases. Radial basis function neural network and genetic algorithm were utilized to optimize the OWSC under different environmental conditions, and the optimized OWSC structural parameters are presented. The Bezier length ratio can always be 1.0 when in real engineering. The seaside outward curved and leeside flat bionic flap performed the best, the maximum capture factor of which is 0.48. The bionic flap improved the capture factor by 30 % compared with the original flap.