Wave Cycle Research Articles

Modelling the impact of trapped lee waves on offshore wind farm power output

Abstract. Mesoscale meteorological phenomena, including atmospheric gravity waves (AGWs) and including trapped lee waves (TLWs), can result from flow over topography or coastal transition in the presence of stable atmospheric stratification, particularly with strong capping inversions. Satellite images show that topographically forced TLWs frequently occur around near-coastal offshore wind farms. Yet current understanding of how they interact with individual turbines and whole farm energy output is limited. This parametric study investigates the potential impact of TLWs on a UK near-coastal offshore wind farm, Westermost Rough (WMR), resulting from westerly–southwesterly flow over topography in the southeast of England. Computational fluid dynamics (CFD) modelling (using Ansys CFX) of TLW situations based on real atmospheric conditions at WMR was used to better understand turbine level and whole wind farm performance in this parametric study based on real inflow conditions. These simulations indicated that TLWs have the potential to significantly alter the wind speeds experienced by and the resultant power output of individual turbines and the whole wind farm. The location of the wind farm in the TLW wave cycle was an important factor in determining the magnitude of TLW impacts, given the expected wavelength of the TLW. Where the TLW trough was coincident with the wind farm, the turbine wind speeds and power outputs were more substantially reduced compared with when the TLW peak was coincident with the location of the wind farm. These reductions were mediated by turbine wind speeds and wake losses being superimposed on the TLW. However, the same initial flow conditions interacting with topography under different atmospheric stability settings produce differing near-wind-farm flow. Factors influencing the flow within the wind farm under the different stability conditions include differing, hill and coastal transition recovery, wind farm blockage effects, and wake recovery. Determining how much of the differences in wind speed and power output in the wind farm resulted from the TLW is an area for future development.

Discrete electrocardiogram T amplitude detection based on cycle duration

In each cycle of the electrocardiogram wave there are P, Q, R, S and T amplitudes. Many studies have been conducted to obtain amplitude and QRS waves because they are related to ventricular depolarization, but to obtain T amplitude values related to ventricular repolarization are still rarely done, not even for the clinical standard (12 leads). This study aims to obtain the amplitude T value in each cycle and each electrocardiogram lead. Obtaining the amplitude T position on the reference lead will also find the amplitude T value on the other lead. Each cycle duration obtained from the duration RN to RN+1 is used to obtain the position of the endpoint of each cycle. The maximum value between the amplitude S position and the end point of the cycle is the amplitude T value. The results of research on 10 Physionet sinus rhythm samples and 10 Saiful Anwar Hospital Malang samples show that the duration of the cycle was successful in obtaining the amplitude T value for each lead. All samples can display a value. The amplitude in each cycle, where the values obtained in each cycle are still in normal conditions. The amplitude T value obtained is certainly accurate because there is only one positive value between the amplitude S position and the end of the cycle position. The position of the amplitude integer T found in a cycle in one lead will be the same as the position of the amplitude integer T in the cycle for the other lead. This occurs because of the simultaneous transmission of impulses that affect the atrial and ventricular muscle cells. The position of the amplitude T for each cycle can be found by filtering the maximum amplitude value between the amplitude position S and the final position of the cycle. Practically, this method can be programmed to be added to a digital electrocardiograph

Optimized Synchronous SPWM Modulation Strategy for Traction Inverters Based on Non-Equally Spaced Carriers

The switching frequency of high-power inverters, such as those used in rail transit traction systems, is low, due to switching loss and heat dissipation limitations. This can result in considerable output voltage harmonics. This paper proposes an optimal SPWM strategy for traction inverters based on non-equally spaced carriers to address this issue. By dividing the fundamental wave cycle into regions according to the principle of three-phase, half-wave, and quarter-wave symmetry, the carrier width is symmetrically changed in each region, and a switching angle sequence is generated by comparing the fundamental wave with the non-isometric carrier. The proposed optimal modulation strategy has lower harmonic content than traditional strategies within a specific modulation range. Enhancing the inverter output waveform leads to increased torque accuracy, lowering additional losses in the motor and avoiding overheating. This results in improved performance, enhanced efficiency, and extended service life of the motor system. To further reduce voltage harmonics across the full-speed range, a multi-mode segmented synchronous modulation strategy is designed based on the optimal modulation strategy for different modulation ranges. Appropriate switching points are selected to improve the stability of the traction drive system across the full-speed range. The effectiveness of the proposed method is verified through simulation and experimental results.

Experimental study for evaluating the response of the power take off of a point absorber wave energy generation system using a hydraulic wave simulator

The increase in energy prices and the need to control the rate of climate change are two of the biggest challenges facing the planet. Despite the fact that the wave energy technology is still in its infancy, it is considered one of the most promising renewable energy sources that exhibits a large potential for sustainable growth towards Net Zero. In this paper, a novel design methodology for a new wave energy generation system is presented and the performance of its power take-off (PTO) or drivetrain is analysed. A complete description of the wave energy generation system is presented including the general concept of the power take-off, configuration, mechanical design, electrical system, simulation test-rig, expected power out and the force load on the system. The results from the power take-off system obtained from the simulation process of the test-rig using a hydraulic linear wave simulator, show that the change in the electric load produces different power and force values and consequently a wide range of efficiencies. It has been noticed that increasing the electric load leads to a better efficiency, i.e., high power and force values. However, there is a certain threshold where the system stops behaving in its high performance and its efficiency drops notably. This threshold depends not only on the electric load, but also on the values of the fixed parameters, i.e., wave cycle time, wave height and frequency. The finding will support the complete design of a point absorber system, including the buoy design, to interact with the expected level of wave patterns.

Attosecond electron microscopy of sub-cycle optical dynamics.

The primary step of almost any interaction between light and materials is the electrodynamic response of the electrons to the optical cycles of the impinging light wave on sub-wavelength and sub-cycle dimensions1. Understanding and controlling the electromagnetic responses of a material2-11 is therefore essential for modern optics and nanophotonics12-19. Although the small de Broglie wavelength of electron beams should allow access to attosecond and ångström dimensions20, the time resolution of ultrafast electron microscopy21 and diffraction22 has so far been limited to the femtosecond domain16-18, which is insufficient for recording fundamental material responses on the scale ofthe cycles of light1,2,10. Here we advance transmission electron microscopy to attosecond time resolution of optical responses within one cycle of excitation light23. We apply a continuous-wave laser24 to modulate the electron wave function into a rapid sequence of electron pulses, and use an energy filter to resolve electromagnetic near-fields in and around a material as a movie in space and time. Experiments on nanostructured needle tips, dielectric resonators and metamaterial antennas reveal a directional launch of chiral surface waves, a delay between dipole and quadrupole dynamics, a subluminal buried waveguide field and a symmetry-broken multi-antenna response. These results signify the value of combining electron microscopy and attosecond laser science to understand light-matter interactions in terms of their fundamental dimensions in spaceand time.

Evaluation of wave-induced instability of nearly saturated sandy slopes under partially undrained condition: A case study of landslide in Fraser River delta front

A significant amount of Methane gas in soil deposits at Fraser River Delta (FRD), Canada, was identified as it adversely impacted the stability of the sloping seabed in the area under waves and tides. In this study, an integrated FEM model is utilized to investigate the instability of FRD front due to 1985 storm waves. Despite earlier studies that focused only on the role of residual pore pressure reached at late wave cycles in inducing the slide of FRD front (using empirical correlations), the transient response of sediments at early wave cycles is considered herein. The effect of coupled-flow-and-deformation processes within the sediments on the extent of the sliding plane is considered. For wave-seabed interaction modeling, Biot’s poroelasticity and linear wave theory are employed to represent the fluid and seabed domains, respectively. The slide evaluation of the sloping seabed is conducted using Strength Reduction Technique with Mohr-Coulomb failure criterion. The results indicate that the storm waves cause a shallow slide within the slope, and the proximity of the unsaturated layer to mudline exacerbated the instability condition. Moreover, instantaneous liquefaction zones are found to emerge away from the slope; thus, they may not lead to an exacerbated sliding of the slope.

The credit cycle and corporate strategy: challenges and solutions

PurposeThis paper offers a practical overview of the U.S. credit cycle and the challenges it poses, along with a perspective on where we seem to be in the cycle in early 2023. Suggestions are then offered for how corporate executives can address cyclical challenges from a corporate strategy perspective.Design/methodology/approachThe United States credit cycle was out into context by following the trend of Moody’s Baa corporate bond yields from January 1919 to November 2022. Under the Moody’s rating system, Baa is the lowest level of investment grade credit, and as such it possesses speculative characteristics that are sensitive to cyclical dynamics. Another reason for choosing Baa credit patterns for analysis is data availability: over 100-years of continuous Baa data is searchable at the U.S. Federal Reserve.FindingsThe prior credit cycle wave of progressively lower inflation and interest rates began in 1982 and ended in 2020. The current credit cycle of wave of progressively higher inflation and interest rates will present strategic risks and opportunities that executives will increasingly have to deal with.Originality/valueThis is the first corporate strategy paper we are aware that practically addresses the credit cycle change. It is also the first paper we are aware that provides practical suggestions on how to address that change from a corporate strategy perspective.

Motivation states to move, be physically active and sedentary vary like circadian rhythms and are associated with affect and arousal.

Motivation to be physically active and sedentary is a transient state that varies in response to previous behavior. It is not known: (a) if motivational states vary from morning to evening, (b) if they are related to feeling states (arousal/hedonic tone), and (c) whether they predict current behavior and intentions. The primary purpose of this study was to determine if motivation states vary across the day and in what pattern. Thirty adults from the United States were recruited from Amazon MTurk. Participants completed 6 identical online surveys each day for 8 days beginning after waking and every 2-3 h thereafter until bedtime. Participants completed: (a) the CRAVE scale (Right now version) to measure motivation states for Move and Rest, (b) Feeling Scale, (c) Felt Arousal Scale, and (d) surveys about current movement behavior (e.g., currently sitting, standing, laying down) and intentions for exercise and sleep. Of these, 21 participants (mean age 37.7 y; 52.4% female) had complete and valid data. Visual inspection of data determined that: a) motivation states varied widely across the day, and b) most participants had a single wave cycle each day. Hierarchical linear modelling revealed that there were significant linear and quadratic time trends for both Move and Rest. Move peaked near 1500 h when Rest was at its nadir. Cosinor analysis determined that the functional waveform was circadian for Move for 81% of participants and 62% for Rest. Pleasure/displeasure and arousal independently predicted motivation states (all p's < .001), but arousal had an association twice as large. Eating, exercise and sleep behaviors, especially those over 2 h before assessment, predicted current motivation states. Move-motivation predicted current body position (e.g., laying down, sitting, walking) and intentions for exercise and sleep more consistently than rest, with the strongest prediction of behaviors planned for the next 30 min. While these data must be replicated with a larger sample, results suggest that motivation states to be active or sedentary have a circadian waveform for most people and influence future behavioral intentions. These novel results highlight the need to rethink the traditional approaches typically utilized to increase physical activity levels.

Recovering density disturbance spectra from FLDI. Part 1.

Focused laser differential interferometry (FLDI) measures the phase shift corresponding to localized fluctuations in the refractive index of a medium. The sensitivity, bandwidth, and spatial filtering properties of FLDI make it particularly suited to applications in high-speed gas flows. Such applications often require the quantitative measurement of density fluctuations, which are related to changes in the refractive index. In a two-part paper, a method is presented for the recovery of a spectral representation of density disturbances from the measured time-dependent phase shift for a particular class of flows able to be modeled using sinusoidal plane waves. The approach is based on the ray-tracing model of FLDI due to Schmidt and Shepherd [Appl. Opt.54, 8459 (2015)APOPAI0003-693510.1364/AO.54.008459]. In this first part, the analytical results for FLDI response to single- and multiple-frequency plane waves are derived and validated against a numerical implementation of the instrument. A spectral inversion method is then developed and validated, including consideration for the frequency-shifting effects of any underlying convective flows. In the second part [Appl. Opt.62, 3054 (2023)APOPAI0003-693510.1364/AO.480354], results from the present model are compared with previous exact solutions temporally averaged over a wave cycle and with an approximate method.

Success of the small mass-ratio approximation during the final orbits of binary black hole simulations

Recent studies have shown the surprising effectiveness of the small mass-ratio approximation (SMR) in modeling the relativistic two-body problem even at comparable masses. Up to now this effectiveness has been demonstrated only during inspiral, before the binary transitions into plunge and merger. Here we examine the binding energy of nonspinning binary black hole simulations with mass ratios from $20\ensuremath{\mathbin:}1$ to equal mass. We show for the first time that the binaries undergo a transition to plunge as predicted by analytic theory, and estimate the size of the transition region, which is $\ensuremath{\sim}10$ gravitational wave cycles for equal mass binaries. By including transition, the SMR expansion of the binding energy is accurate until the last cycle of gravitational wave emission. This is true even for comparable mass binaries such as those observed by current gravitational wave detectors, where the transition often makes up much of the observed signal. Our work provides further evidence that the SMR approximation can be directly applied to current gravitational wave observations.

Wind-current feedback is an energy sink for oceanic internal waves

Internal waves contain a large amount of energy in the ocean and are an important source of turbulent mixing. Ocean mixing is relevant for climate because it drives vertical transport of water, heat, carbon and other tracers. Understanding the life cycle of internal waves, from generation to dissipation, is therefore important for improving the representation of ocean mixing in climate models. Here, we provide evidence from a regional realistic numerical simulation in the northeastern Pacific that the wind can play an important role in damping internal waves through current feedback. This results in a reduction of 67% of wind power input at near-inertial frequencies in the region of study. Wind-current feedback also provides a net energy sink for internal tides, removing energy at a rate of 0.2 mW/m^2 on average, corresponding to 8% of the local internal tide generation at the Mendocino ridge. The temporal variability and modal distribution of this energy sink are also investigated.

Research on portable constant pulse current source device

A set of portable constant pulse current sources with STM32 as the control core is developed, which mainly involves the SCM control module, operational amplifier circuit module, pulse output module, power module, key module, and display module. Based on the traditional constant-current source circuit design, the real-time display control system is constructed by software programming optimization, which has the characteristics of portable and strong stability. By connecting the field effect tube and operational amplifier in series to form a feedback loop, the current output accuracy is improved and the stability of the current output is ensured. The experimental results show that after the op-amp circuit is introduced into the series feedback system, the front and rear order circuit can be more stable, and ensure the reference voltage is stable at the same time, through the duty cycle of PWM wave to adjust the current output, so that the constant current source output 0~2mA adjustable low-frequency stable current. At the same time, in terms of human-computer interaction, in addition to the use of buttons to adjust the current at both ends of the load, a small OLED display screen is used to display the current, voltage, and pulse frequency in real time. The experiment shows that the instrument has high stability and load adaptability, and has high practical value.

Spatial distribution characteristics of soil liquefaction potential in the Yellow River Subaquatic Delta, China

This paper aims to provide a design basis for engineering disaster prevention and mitigation by accurately describing the spatial distribution of soil liquefaction. A group of in-situ Cone Penetration Tests (CPT) was conducted to evaluate the seabed soil properties and liquefaction potential of the Yellow River Subaquatic Delta. The factor of safety against liquefaction (FSL) and liquefaction potential index (LPI) were utilized to investigate the liquefaction characteristics of seabed soils. The findings are as follows: (1) The delta is "near coarse and far fine," with sand and silt dominating the onshore direction and silt and silty clay dominating the offshore direction; (2) Silt, as a structured soil, has a maximum sensitivity of 10, and there are local liquefaction phenomena. The size of a Soil behavior type index can be used as the limit value of liquefaction discrimination in the region; (3) The FSL of the shallow layer is smaller, while that of the deep layer is generally larger. The FSL near the coast is smaller than that far from the coast, but its variation range is large, indicating that the shallow soil layer near the coast is more prone to liquefaction; (4) The LPI of the delta is less than 5, which is significantly affected by the wave cycle loads and geographical environment. Liquefaction can occur, but the probability of large-scale liquefaction is low.

Evolution Law of Wellbore Instability Risk under Fluctuating Pressure

The bottom hole fluctuating pressure has a large influence on the wellbore instability. To address this problem, firstly, according to the principle of seepage mechanics, we established a calculation model of the change in pore pressure around the wellbore radius under fluctuating pressure; then, through laboratory rock mechanics test and rock damage mechanics theory analysis, the change law of formation strength under the action of static hydration and dynamic damage are determined; finally, based on the theory of rock mechanics in porous media, a quantitative evaluation method for the risk of wellbore instability under fluctuating pressure is established and the changing pattern of wellbore instability risk is analyzed. The results show that the pore pressure around the well shows a trend of fluctuation increase under fluctuating pressure, and there is a certain lag in the fluctuation of pore pressure inside the formation; the longer the muddy shale is immersed in drilling fluid, the greater the reduction in strength; the reduction is greater in the early stage of immersion, and the reduction in strength in water-based drilling fluid is greater than that in oil-based drilling fluid. At the beginning of the pressure cycle, the formation damage variable and compressive strength gradually increase and decrease with the increase of the pressure cycle number; after several cycles, the magnitude of change gradually decreases with the increase of the cycle number. When the bottom hole pressure fluctuates at a certain period, the greater the fluctuation, the shorter the period of wellbore stability; when the bottom hole pressure fluctuates at a certain range, the smaller the fluctuation period, the faster the borehole enters the high-risk period, while the shortest period of wellbore stability occurs when the fluctuation period is smallest; and when the wave cycle is in the middle, the wellbore stability period is the longest.

Classical Interpretation of Quantum Mechanical Concepts

All of the mathematical formulations of quantum mechanics describe the interaction between radiation and atoms, but we show here that only Einstein has been able to establish a solid logical connection with classical theory. His methods are used to interpret the other mathematical models by requiring that observables be described in a physically-defined coordinate system and that there be strict adherence to the conservation of momentum. The properties of momentum exchange are included in a quantum oscillator, or clock, by replacing the non-relativistic Hamiltonian model with a relativistically correct Lagrangian model. Equal contributions are assigned to photon, electron, and nucleus; and field boundaries are defined that coincide with the electron shells. The fields of the particles superpose linearly, but otherwise their physical integrity is maintained throughout. The Lagrangian model accounts for the 720 degree rotation of a wave function as an initial 360 degree electromagnetic wave cycle (photon absorption) followed by a second wave cycle (photon emission), yielding two wave cycles to correspond with one complete electron cycle. The abstract space of quantum mechanics is replaced by a real classical space.

A Distortion-Free All-Digital Transmitter Based on Noise-Shaped PWM

A novel pulse-width modulation (PWM) architecture for all-digital transmitters (ADT) that achieves good in-band and out-band performance with a very low ratio between the modulated signal frequency and the carrier frequency is presented in this paper. The proposed scheme reduces the harmonics leaving only those corresponding to multiples of the carrier frequency, overcoming the spectral limitations of other PWM implementations and relaxing the filter requirements. The binary signal is obtained using a table-based approach with very low computational complexity, mapping the complex I/Q baseband signal to duty cycles of a square wave with low distortion. In addition, a new parallelized noise shaping circuit to reduce the distortion caused by the discretization of the duty-time intervals is presented. The digital radio frequency signal is generated using a high-speed serializer and a standard pulse former. The ADT is simulated under different scenarios to evaluate the influence of time resolution in terms of Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM). The transmitter performance is verified by an FPGA implementation using 64-QAM modulated signals, achieving values of ACPR1, ACPR2, and EVM better than −47 dBc, −53 dBc, and −35 dB, respectively, using 64 quantization levels for the PWM signal.

Application of swarm intelligence for dynamic properties of moored floating structures using two-dimensional fluid dynamic program

This paper presents a numerical investigation into interactions between oscillatory waves and moored floating structures by through applying Swarm Intelligence (SI). The effects of small and large incident waves placing a force on the obstacles were studied using two floating structures composed of a rectangle and a cage kind with taut-moored and slack-moored situations. The aforementioned problem was reduced to solve systems of sparse-nonlinear equations for surge, heave, and pitch responses, as well as mooring forces considering that there is a distorted wave motion due to the presence of the movable obstacle boundary. The particle swarm optimization (PSO) algorithm is proposed here to provide insight into computational intelligence factors affecting calculation results and efficiency. Besides that, a computational fluid dynamic (CFD) program is based on a full Navier-Stokes solver. A series of numerical examinations for selected wave heights and wavelengths including a set of optimization procedures have been taken into account in the evaluation of formulated objective function, F, where the best potential solution is computed at each computational step. Meanwhile, a collection of empirical benchmarks were also developed based on reported measurements in the literature to provide sound empirical support for the theoretical findings. The results show that the optimization method exhibits a favorable convergent behavior (F≈0), where the computed results agree well with the measurements in terms of mean amplitudes of the surge, heave, and pitch responses and peak values of mooring-line tensions. The approach would firmly converge on benchmarks with improved computational steps of 18,321 running for 20.1 wave cycles in the case of the taut-moored rectangular structure. For the slack-moored cage, a satisfactory convergence was achieved using a series of data calibrations into an algorithm that took 27,976 iterations and 24.5 s to complete. Furthermore, CFD captures of wave deformations, dynamic forces, and streamlines were able to qualitatively corroborate the results.

The Life Cycle of Innovations and Kondratiev Waves in the Context of the Conception of Industry 4.0

The nature of long Kondratiev waves, reflecting the cyclical nature of economic development, has attracted the attention of scholars for more than a hundred years. This problem becomes especially relevant in times of global crises. And although this theory do not belong to the mainstream of economic thought, the great theorists of the twentieth century have tried to either prove or disprove the reality of the very existence of long waves. The very idea of the non-linearity of the development of a system of any nature was impossible within the framework of the science of the nineteenth century, therefore, in order to understand the revolutionary nature of Kondratiev?s ideas and his contribution to changing the paradigm of economic science, the work compares the epistemological principles that were inherent in the science of the nineteenth century and at the beginning of the twentieth century. In particular, the main attention is paid to consideration of the fundamentals of thermodynamics of non-equilibrium processes, which examines the processes of self-organization in open systems, and synergetics, one of the cornerstones of which is the axiom of the non-additivity of the properties of the whole as an aggregate of the properties of its parts. The paper demonstrates the application of such a system of scientific views to determine the features of the life cycle of innovations. This approach makes it possible to apply the mathematical apparatus of non-linear dynamics to study the evolution of non-equilibrium economic systems and to determine the final state of the system by studying its possible trajectories in phase space. The respective analysis of the development of endogenous theories of long cycles made it possible to investigate how views on the place of innovations in determining the nature of Kondratiev waves changed. It is shown that it is not the presence of innovations that is essential, but the formation of an innovation cluster. Such a cluster consists of the so-called improving innovations, the use of which contributes only to the quantitative growth of economic indicators, and the catalyst is the basic (or systemic) innovations, the implementation of which determines the transition of the economic system to a new industrial type. In further research, it is expedient to use such an approach to the analysis of the ways of evolution of the economy in the context of sustainable development.

Doublet structure in the optical spectrum of a semiconductor laser with optoelectronic feedback in a square-wave regime

We observe an optical spectrum consisting of a doublet in the output of a semiconductor laser diode with optoelectronic feedback in a dynamical regime in which a self-sustained square-wave modulation is observed, depending on injection current and feedback strength. The doublet frequency splitting is strongly correlated with the duty cycle of the square wave; both parameters as well as the relative magnitude of the peaks are observed to vary with the feedback level. A rate equation model reproduces the spectral doublets. The appearance of the doublet is attributed to active medium gain saturation and refractive index dependence on the carrier density.

Effects of inlet and secondary flow conditions on the flow field of rotating detonation engines with film cooling

A three-dimensional simulation of the rotating detonation engine (RDE) with film cooling is conducted. The aim of this study is to analyze the fluid dynamics and heat transfer of the detonation flow field under the influence of cooling flow from the film holes. Results suggest that when the rotating detonation wave sweeps the film holes, the shape of the wave structure will deform, and the detonation products will invade and block the outflow from the film holes; however, this only occurs temporarily. The structure of the detonation wave will quickly restore to its stable form and, meanwhile, the cooling flow also recovers rapidly and provides adequate protected area on the wall surface and effective thermal protection time in a full propagation cycle of the detonation wave. A parametric analysis indicates that the effective outflow time improves with the increase of the mass flow rate of the cooling flow; on the other hand, the cooling efficiency is more significant downstream from the inlet of the combustor to the outlet. In addition, the thrust and specific impulse of the RDE are also examined under the influence of film cooling.