Variational Wave Research Articles

Resonant Excitation of Kelvin Waves by Interactions of Subtropical Rossby Waves and the Zonal Mean Flow

Abstract Equatorial Kelvin waves can be affected by subtropical Rossby wave dynamics. Previous research has demonstrated the Kelvin wave growth in response to subtropical forcing and the resonant growth due to eddy momentum flux convergence. However, the relative importance of the wave–mean flow and wave–wave interactions for the Kelvin wave growth compared to the direct wave excitation by the external forcing has not been made clear. This study demonstrates the resonant Kelvin wave excitation by interactions of subtropical Rossby waves and the mean flow using a spherical shallow-water model. The use of Hough harmonics as basis functions makes Rossby and Kelvin waves prognostic variables of the model and allows the quantification of terms contributing to their tendencies in physical and wave spaces. The simulations show that Kelvin waves are resonantly excited by interactions of Rossby waves and the balanced zonal mean flow in the subtropics, provided the Rossby and Kelvin wave frequencies, which are modified by the mean flow, match. The resonance mechanism is substantiated by analytical expressions. The Kelvin wave tendencies are caused by velocity and depth tendencies: The velocity tendencies due to the meridional advection of the zonal mean velocity can be outweighed by the zonal advection of the Rossby wave velocity or by the depth tendencies due to Rossby wave divergence. Identifying the resonant excitation mechanism in data should contribute to the quantification of Kelvin wave variability originating in the subtropics. Significance Statement This study seeks to understand how Kelvin waves, which are eastward-propagating disturbances in the tropical atmosphere, are connected to Rossby wave dynamics in the subtropics. Using idealized simulations, the Kelvin wave excitation is explained as a resonance effect due to interactions of Rossby waves and the zonal mean flow. The mechanism contributes to the understanding of atmospheric wave interactions and extratropical effects on the tropics. Further work searching for evidence of the new mechanism in atmospheric data may shed a new light on subseasonal variability in the tropics, such as the Madden–Julian oscillation.

Ultra-Low Frequency Waves of Foreshock Origin Upstream and Inside of the Magnetospheres of Earth, Mercury, and Saturn Related to Solar Wind–Magnetosphere Coupling

This review examines ultra-low frequency (ULF) waves across different planetary environments, focusing on Earth, Mercury, and Saturn. Data from spacecraft missions (CHAMP, Swarm, and Oersted for Earth; MESSENGER for Mercury; and Cassini for Saturn) provide insights into ULF wave dynamics. At Earth, compressional ULF waves, particularly Pc3 waves, show significant power near the equator and peak around Magnetic Local Time (MLT) = 11. These waves interact complexly with Alfvén waves, impacting ionospheric responses and geomagnetic field line resonances. At Mercury, ULF waves transition from circular to linear polarization, indicating resonant interactions influenced by compressional components. MESSENGER data reveal a lower occurrence rate of ULF waves in Mercury’s foreshock compared to Earth’s, attributed to reduced backstreaming protons and lower solar wind Alfvénic Mach numbers, as ULF wave activity increases with heliocentric distance. Short Large-Amplitude Magnetic Structures (SLAMS) observed at Mercury and Saturn show distinct characteristics compared to those of Earth, including the presence of whistler precursos waves. However, due to the large differences in heliospheric distances, SLAMS (their temporal scale size correlate with the ULF wave frequency) at Mercury are significantly shorter in duration than at Earth or Saturn, since the ULF wave frequency primarily depends on the strength of the interplanetary magnetic field. This review highlights the variability of ULF waves and SLAMS across planetary environments, emphasizing Earth’s well-understood ionospheric interactions and the unique behaviours observed for Mercury and Saturn. These findings enhance our understanding of space plasma dynamics and underline the need for further research regarding planetary magnetospheres.

A Whole-Brain Model of the Aging Brain During Slow Wave Sleep.

Age-related brain changes affect sleep and are reflected in properties of sleep slow-waves, however, the precise mechanisms behind these changes are still not completely understood. Here, we adapt a previously established whole-brain model relating structural connectivity changes to resting state dynamics, and extend it to a slow-wave sleep brain state. In particular, starting from a representative connectome at the beginning of the aging trajectory, we have gradually reduced the inter-hemispheric connections, and simulated sleep-like slow-wave activity. We show that the main empirically observed trends, namely a decrease in duration and increase in variability of the slow waves are captured by the model. Furthermore, comparing the simulated EEG activity to the source signals, we suggest that the empirically observed decrease in amplitude of the slow waves is caused by the decrease in synchrony between brain regions.

Psychopathy checklist-youth version scores and recurring victimisation by an intimate partner in a justice-involved sample: A comparison of young men and women using longitudinal data.

People involved in the criminal justice system are at increased risk of recurring intimate partner violent (IPV) victimisation. Experience of trauma is linked to a variety of negative outcomes, including repeated experiences, so it is important to identify factors that may distinguish non-victims, single-event victims and recurring victims at an early stage as this could hold potential for intervention efforts. Research studies have identified individual-level risk factors for IPV victimisation but have not investigated psychopathy traits or sex differences. To examine sex differences in psychopathy scores and later IPV victimisation. Using the Pathways to Desistance study, a longitudinal study of 1354 adjudicated adolescent offenders, relationships between psychopathy checklist-youth version (PCL-YV) scores measured during the baseline wave, independent/control variables in wave 6 and self-reported IPV victimisation in wave 7 were explored using multinomial regression models. Among justice-involved young adults (average age 19), PCL-YV scores differentiated between non-victims, single-event victims and recurring victims. Higher total scores and higher ratings on the antisocial behaviours facet of psychopathy significantly increased the relative risk of recurring victimisation by an intimate partner overall, and specifically of emotional or physical intimate partner violence. For the young women but not the young men, a higher scoring on the interpersonal manipulation facet of psychopathy specifically increased the relative risk of being a recurring victim of any intimate partner violence. Sex-specific differences in relationships between high PVL-YV scores and recurring IPV victimisation can be used to screen for risk of repeated trauma for justice-involved young adults, which may change a trajectory of continued involvement in the criminal justice system to a trajectory of resilience and recovery.

PASS: A scoring system to evaluate persistent kidney injury in critically ill ICU adult patients

Background We evaluated if the course of recovery from sepsis-induced acute kidney injury (AKI) can be predicted using variables collected at admission. Methods A total of 63 patients admitted for sepsis-induced AKI in our Mangalore ICU were evaluated and baseline demographic and clinical/laboratory parameters, including serum creatinine (SCr), base excess (BE), Plethysmographic Variability Index (PVI), Caval Index, R wave variability index (RVI), mean arterial pressure (MAP) and renal resistivity index (RI) using renal doppler and need for inotropes were assessed on admission. Patients were managed as per standard protocol. After six hours of fluid resuscitation, patients were classified as volume responders or non-responders. Re-assessment was done at 24 hours and 72 hours after admission. Primary outcome was persistent AKI after 72 hours. Secondary outcome was initiation of dialysis or death within 15 days of admission. Results A total of 34 subjects recovered from AKI, of whom 32 patients were volume responders and 31 were non-responders. Response to fluid, MAP at admission and six hours, BE at admission, inotrope requirement, and PVI at admission did not correlate with recovery. Multiple logistic regression showed that SCr < 2.36 mg%, RVI > 14.45 and RI < 0.8 on admission correlated with recovery and they were evaluated further to model AKI recovery and develop PASS. PASS score = (SCr points × 5.4) + (RVI points × 4.0) + (RI points × 6.2). One point each was allotted if SCr was < 2.36, RVI was > 14.45 and RI was <0.8, and 0 otherwise. A score > 7.8 predicted recovery with a sensitivity of 79.4%, specificity of 72.4%, PPV 81.8%, NPV 76.7% and AuROC of 0.85. Conclusions The PASS score can be used to identify salvageable cases of sepsis-AKI, guiding fluid resuscitation and aiding early referral from rural to tertiary care centers for better management.

An Evaluation of the Autonomic Nervous Activity and Psychomotor Vigilance Level for Smells in the Work Booth

In this study, we investigated the effects of the smell environment in the work booth on autonomic nervous activity (ANS) and psychomotor vigilance levels (PVLs) using linalool (LNL) and trans-2-nonenal (T2N). The subjects were six healthy males (31 ± 6 years old) and six healthy females (24 ± 5 years old). They sat in the work booth filled with the smells of LNL and T2N for 10 min, and their electrocardiograms (ECGs), skin conductance levels, pulse wave variabilities, skin temperatures, and seat pressure distributions were measured. In addition, the orthostatic load test (OLT) and psychomotor vigilance test (PVT) were performed before and after entering the work booth, and a subjective evaluation of the smell was also performed after the experiment. This paper focused on ECG and PVT data and analyzed changes in heart rate variability indices and PVT scores. Males felt slightly comfortable with the LNL smell and showed promoted sympathetic nerve activity in the OLT after the smell presentation. Females felt slightly uncomfortable with the T2N smell and showed promoted sympathetic nerve activity and a decrease in PVT scores in the OLT after the smell presentation. Gender differences were observed in ANS and PVLs, and it is possible that the comfort of LNL increased sympathetic nervous activity in males, while the uncomfortableness of T2N may have reduced work performance in females.

Consequences of delaying non-urgent surgeries during COVID-19: a population-based retrospective cohort study in Alberta, Canada

ObjectivesTo ensure sufficient resources to care for patients with COVID-19, healthcare systems delayed non-urgent surgeries to free capacity. This study explores the consequences of delaying non-urgent surgery on surgical care...

Evaluation of Equatorial Westerly Wind Events in the Pacific Ocean in CMIP6 Models

Abstract Westerly wind events (WWEs) are anomalously strong, long-lasting westerlies over the Indian or Pacific Oceans that are capable of forcing oceanic wave modes, which in turn can impact the evolution of coupled ocean-atmosphere phenomena such as the El Niño Southern Oscillation (ENSO). This work examines the fidelity of equatorial WWEs over the Pacific Ocean in 30 CMIP6 historical simulations against observations. WWEs are identified using equatorially-averaged zonal wind stress anomaly duration, zonal extent, and intensity criteria. Most simulations correctly place the majority of WWEs over the west Pacific, although they are skewed westward and generally occur less frequently compared to observations. Simulated WWEs tend to be weaker than observations for a given duration and zonal extent with several models having shorter durations and zonal extents than observations. Biases in simulated WWEs are associated with biases in Madden-Julian Oscillation (MJO) and convectively-coupled Rossby wave (CRW) variability. Models that underpredict WWE forcing in the west Pacific also severely underpredict MJO and CRW variance. Further, the multi-model mean shows a smaller fraction of WWEs associated with both the MJO and CRW than observations.

Maternal emotion regulation abilities affect adolescent depressive symptoms by mediating their emotion regulation ability: An ERP study

Adolescents with major depressive disorder (MDD) experience significant difficulties in emotion regulation. This study aimed to explore emotion regulation in adolescents with depression using an emotion regulation paradigm combined with event-related potentials (ERP) while investigating the relationship between maternal emotion regulation and adolescent depressive symptoms through a mediation model. Overall, 38 healthy controls (HC) and 57 adolescents with depression (MDD) rated the pictures they saw according to aversive reappraisal (reappraisal of an aversive picture or down-regulate aversive emotions), aversive watch, and neutral conditions. Adolescents with depression gave more negative ratings to aversive images, and the emotional regulation success index (ERSI) of adolescents with depression was lower than that of healthy individuals. ERP data revealed an elevation in late positive potential (LPP) amplitude during the aversive reappraisal and aversive watch conditions compared with that in the neutral condition in the MDD group. Compared with the HC group, adolescents with depression showed larger LPP amplitudes under aversive watch conditions. The aversive reappraisal condition evoked a larger LPP than that in the other conditions in the HC group in the late time windows. The ΔLPP (separating the variability in the ERP wave associated with emotion regulation) was larger in the HC group than in the MDD group. Mediation analysis revealed that maternal emotion regulation influenced adolescent depression levels through its effect on the adolescent’s emotion regulation. These findings provide important insights into the emotion regulation process in adolescents with depression and offer suggestions for clinical interventions.

Investigation of the long-term variation of gravity waves over South America using empirical orthogonal function analysis

The spatial and temporal variability of gravity waves (GWs) potential energy (Ep) over South America (SA) was examined by analyzing temperature profiles obtained through the utilization of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) from January 2002 to December 2021. We used the empirical orthogonal function (EOF) analysis to decompose GWs parameters and to analyze the GW variations over SA. We considered the first three eigenmodes (EOF1, EOF2, and EOF3) and their principal components (PC1, PC2, and PC3) of the EOF decomposition, which accounts for ∼80–90% of the total GWs variation over SA. Further, we analyzed the coupled variation of Ep and zonal mean wind (U) to verify their inter-dependencies using the singular value decomposition (SVD). The spatial variation showed that different localized mechanisms generate GWs at different sectors of the continent. The EOF1 of Ep comprised more than 50%, the EOF2 ∼20–25%, and the third ∼10–15% of the total GWs variation. The positive variation of GWs energy in the EOF1 is localized in the tropical region from the lower stratosphere to the lower mesosphere and southward below 1.5° S in the upper mesosphere. The spectral analysis of GWs energy showed biannual, annual, semiannual, and 11-year variations at different eigenvectors. Relative Ep (REp) showed an asymmetric hemispheric response to solar flux over South America. The REp response to QBO showed a modulating effect below 70 km and a positive response above 70 km. There is a good positive correlation between the temporal component of EOF2 of Ep and the quasi-biennial oscillation (QBO) at 30 mb and 50 mb in the PC2 temporal variation.Graphical

Observation and modelling of infragravity waves at a large meso-tidal inlet and lagoon

The role of infragravity waves (IG waves) in beach and dune erosion or in flood hazard has been extensively studied on open beaches. In contrast, the detailed characterization of IG waves and their contribution to the Total Water Level (TWL) along the shore of inlets received little attention so far. In such environment, there is a real lack of in situ observations of waves and hydrodynamics conditions at appropriate spatial and temporal coverage to study the role of infragravity (IG) waves (long waves of frequency typically ranging between 0.004 Hz and 0.04–0.05 Hz) on coastal hazards. This contribution is based on field observations collected at the Arcachon Lagoon, a shallow semi-enclosed lagoon connected to the ocean by a large tidal inlet, located in southwest France. Analyses combine observations made at several locations during storm events within the inlet and the lagoon with numerical simulation with the XBeach surfbeat model to explore the spatial variability of IG waves and simulate observed, historical, and idealized storm conditions. The results show that IG waves are substantial during typical winter storms at the inlet and range from Hm0 = 0.8 to over 1 m across the ebb delta and about 0.4–0.6 m in the inner part of the inlet. At the lagoon entrance, IG waves remain substantial (about 0.1–0.2 m) and decrease to a few centimeters at the lagoon shore. The spatial variability and magnitude of IG waves along the inlet coast, simulated for the historical storms, are quite comparable to those observed during classical winter, and do not increase linearly with offshore wave energy. However, both observations and simulations reveal local amplifications of IG waves in the inner part of the inlet, especially along the sheltered coast were IG waves dominate the variance of free surface elevation, reaching about 0.6–0.7 m during common storms and more than 1 m for an extreme storm scenario. A numerical experiment indicates that IG wave reflection from one coast to the other contributes up to 35–40% of the measured IG wave height at a hot spot located along the sheltered coast. Finally, the contribution of IG waves to TWL at the shore on both sides of the inlet has been estimated to be about 0.4–0.6 m for a common storm and 0.6–0.9 m for an extreme scenario, locally peaking at 0.74 and 1.1 m respectively and overpassing the contribution of wave-induced setup. This work provides new insights into the contribution of IG waves to TWL and its implications for overtopping flooding hazard and overwash processes at large inlets, highlighting the need to consider IG waves in Early Warning Systems or hazard mapping for flood prevention plans in these environments.

Effects of wave breaking on moisture flux

Wave breaking is a ubiquitous phenomenon in ocean dynamics, serving as a critical conduit for the exchange of momentum, heat, and energy between the atmosphere and the ocean. Although its vital role in air-sea moisture exchange is widely acknowledged, quantifying its exact impact on moisture flux remained quite challenging due to data limitations and the inherently turbulent nature of the process. To overcome these challenges, we construct a comprehensive 10-year global dataset that incorporates multiple breaking wave variables, informed by statistical breaking theories, to capture the intricacies of the breaking process and its consequential effects. We then employ a stacked machine learning model to elucidate the complex relationships between wave breaking and moisture flux. The performance of our stacked model, which is enriched with breaking wave variables, is validated against the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis data (ERA5). The results offer excellent predictions and highlight the importance of breaking-wave-related variables in regulating moisture flux, thereby substantiating the integral role of wave breaking in modulating air-sea interactions and moisture transport.

Impact of Water-Cement Ratio on Concrete Mechanical Performance: Insights into Energy Evolution and Ultrasonic Wave Velocity.

The water-cement ratio significantly affects the mechanical properties of concrete with changes in porosity serving as a key indicator of these properties, which are correlated with the ultrasonic wave velocity and energy evolution. This study conducts uniaxial compression tests on concrete with varying water-cement ratios, analyzing energy evolution and ultrasonic wave velocity variations during the pore compaction stage and comparing damage variables defined by dissipated energy and ultrasonic wave velocity. The results indicate the following findings. (1) Higher water-cement ratios lead to more complete hydration, lower initial porosity, and a less pronounced pore compaction stage, but they deteriorate mechanical properties. (2) In the pore compaction stage, damage variables defined by dissipated energy are more regular than those defined by ultrasonic wave velocity, showing a nearly linear increase with stress (D = 0~0.025); ultrasonic wave variables fluctuate within -0.06 to 0.04 due to diffraction caused by changes in the pore medium. (3) In the pre-peak stress stage, damage variables defined by ultrasonic wave velocity show a distinct threshold. When the stress ratio exceeds about 0.3, the damage variable curve's growth shows clear regularity, significantly reflecting porosity changes. In conclusion, for studying porosity changes during the pore compaction stage, damage variables defined by dissipated energy are more effective.

Movie-related Korean Wave and intention to visit: The role of country image as a mediating factor

The Korean Wave, also known as Hallyu, is a phenomenon of globalization of South Korean culture that has influenced many aspects of life in various countries. Indonesia is a country affected by the Korean Wave due to globalization through the media. This paper aims to analyze the impacts of four detailed movie-related Korean Wave variables (visual, vocal, celebrity, and language) on intention to visit South Korea, with country image as a mediating variable. The research sample consisted of 302 fans and non-fans of the Korean Wave who either experienced or were interested in Korean Wave cultural contents. Data were collected from September to October 2023. The results were analyzed using the Partial Least Squared Structural Equation Model (PLS-SEM). The results confirm that four Korean Wave traits positively affect Indonesian tourists’ desire to travel to Korea. Improving the movie quality, including visuals, voice, celebrity, and language, might motivate Indonesian tourists to visit Korea. Likewise, the country’s image is positively and significantly influenced by each of the four Korean Wave variables. The findings were statistically significant at 5% significance level. Moreover, the study discovered that the perception of the country considerably affected the desire to travel and served as a go-between for the effects of film visuals, celebrity presence, and language on the decision to visit.

Attack detection method for encrypted wave‐variable‐based bilateral control systems

AbstractThis study presents an energy‐based attack detection method involving an encrypted bilateral control system using wave variables. In the considered bilateral control system, the leader and follower receive the follower's force information and the leader's velocity information, respectively, through the wave variables. The considered attack model multiplies the wave variables by an attack parameter, which is possible due to the malleability of the encryption scheme. The bilateral control system will be destabilized if the attacker chooses a relatively large parameter value. This motivates in developing a passivity observer for each leader and follower side to compute the total energy and constructing an energy‐based detection method that can be incorporated into the encrypted bilateral control system and is summarized in the presented theorem. Furthermore, this study provides a specific design for reasonable threshold parameters concerning the control system energy. The theorem and the experimental validation confirm that the developed encrypted wave‐variable‐based bilateral control system with the proposed attack detector is secure and effective as a countermeasure against malleability‐based attacks.

The Impact of Korean Wave on South Korea’s Export of Consumer Goods to ASEAN-5 Country

This study aims to assess the impact of the Korean Wave on the export of consumer goods from South Korea to the ASEAN-5 countries (Indonesia, Malaysia, Thailand, Singapore, and the Philippines) from 2010 to 2020. This study took into account various factors to analyze the export dynamics, such as gross domestic product (GDP) per capita, interest rates, Google search trends, and the geographical distance between countries. Cultural goods exported from South Korea were used as a measure of the Korean Wave, employing the gravity model and the fixed effects model (FEM) for analysis. The results of this study indicated a positive impact of the Korean Wave variable on the export of South Korean consumer goods. Additionally, the findings revealed that variables such as South Korea’s GDP per capita, distance, and exchange rates had a negative impact on the export of such goods. Furthermore, this study highlights the positive impacts of the ASEAN-5 countries’ GDP per capita and Google search trends on the export of South Korean consumer goods.

Optimal design of experiments for computing the fatigue life of an offshore wind turbine based on stepwise uncertainty reduction

The design of an offshore wind turbine to resist fatigue damage during its whole service life requires to estimate an expectation over the pluri-annual joint statistics of wind and wave variables. Using a full factorial-based integration for the estimation of the cumulative fatigue damage represents a tremendous computational cost with aero-servo-hydro-elastic solvers which is generally not affordable by industrial designers. To overcome this limitation, strong approximations with lumping of environmental discretized joint probability (scatter diagram) are generally employed. We present in this paper a new method, called MAKSUR, involving the iterative enrichment of a design of experiments tailored to provide a good approximation of the long term mean damage. This method relies on a Kriging response surface with a learning criterion defined as the variance of the mean damage integral. It is compared to another previous similar approach called AK-DA, also dedicated to damage prediction, but is shown to converge more efficiently and with less numerical parameters to define by the user. The potential of the method for offshore wind turbine is demonstrated by a realistic 6D floating wind turbine case study with six wind and wave input variables.

Wave energy converter arrays: A methodology to assess performance considering the disturbed wave field

Wave Energy Converters (WECs) often face power fluctuations due to wave variability, making grid integration costly. To mitigate this, placing multiple WECs in an array can reduce both power variability and expenses. Prior research has limited consideration of the impact of individual WECs on the disturbed wave field. Therefore, a novel simulation framework is proposed which is capable of evaluating the disturbed wave field by coupling a time domain hydrodynamics solver (ProteusDS) and a spectral wave field propagation model (Simulating WAves Nearshore (SWAN)).Numerical simulations are conducted for three different WEC archetypes (RM3, RM5, and Triton) under four representative sea states. The framework is compared with two lower-fidelity models to highlight key array effects. Results show that (a) placing WECs in an array significantly improves power quality (e.g., Triton reduces CoV by up to 37%); (b) WECs notably impact the wave field (e.g., RM3 up to 14%, RM5 up to 39%, Triton up to 29% diffraction); (c) Wave refraction, alongside attenuation, is crucial, or array power may be underpredicted (e.g., RM5 by 40% and Triton by 26%); (d) Constructive array effects can be found (e.g., Triton Q-factor up to 1.07) even without optimization, emphasizing the potential for further improvements.

Painlevé Analysis of the Traveling Wave Reduction of the Third-Order Derivative Nonlinear Schrödinger Equation

The second partial differential equation from the Kaup–Newell hierarchy is considered. This equation can be employed to model pulse propagation in optical fiber, wave propagation in plasma, or high waves in the deep ocean. The integrability of the explored equation in traveling wave variables is investigated using the Painlevé test. Periodic and solitary wave solutions of the studied equation are presented. The investigated equation belongs to the class of generalized nonlinear Schrödinger equations and may be used for the description of optical solitons in a nonlinear medium.

Investigating wave solutions and impact of nonlinearity: Comprehensive study of the KP-BBM model with bifurcation analysis.

In this paper, we investigate the (2+1)-dimensional Kadomtsev-Petviashvili-Benjamin-Bona Mahony equation using two effective methods: the unified scheme and the advanced auxiliary equation scheme, aiming to derive precise wave solutions. These solutions are expressed as combinations of trigonometric, rational, hyperbolic, and exponential functions. Visual representations, including three-dimensional (3D) and two-dimensional (2D) combined charts, are provided for some of these solutions. The influence of the nonlinear parameter p on the wave type is thoroughly examined through diverse figures, illustrating the profound impact of nonlinearity. Additionally, we briefly investigate the Hamiltonian function and the stability of the model using a planar dynamical system approach. This involves examining trajectories, isoclines, and nullclines to illustrate stable solution paths for the wave variables. Numerical results demonstrate that these methods are reliable, straightforward, and potent tools for analyzing various nonlinear evolution equations found in physics, applied mathematics, and engineering.