Occurrence Of Waves Research Articles

Mathematical Modelling of Virus Spreading in COVID-19.

A mathematical model is proposed to analyze the spreading dynamics of COVID-19. By using the parameters of the model, namely the basic reproduction number (R0) and the attenuation constant (k), the daily number of infections (DNI) and the cumulative number of infections (CNI) over time (m) are deduced and shown to be in good agreement with experimental data. This model effectively addresses three key issues: (1) inferring the conditions under which virus infections die out for a specific strain given R0; (2) explaining the occurrence of second waves of infection and developing preventive measures; and (3) understanding the competitive spread of two viruses within a region and devising control strategies. The findings highlight the potential of this simple mathematical framework in comprehensively addressing these challenges. The theoretical insights derived from this model can guide the evaluation of infection wave severity and the formulation of effective strategies for controlling and mitigating epidemic outbreaks.

Prediction of maximum air temperature for defining heat wave in Rajasthan and Karnataka states of India using machine learning approach

Temperature rise, associated with global warming, has increased the severity and frequency of heat waves around the world. Rajasthan and Karnataka are two major states of India and these have been facing frequent heat waves in the past few years. The present study used machine learning approach to predict the maximum air temperature (AT) for defining the heat wave occurrences in these two states. The analysis was based on the monthly data of 13 parameters, collected from NASA's Giovanni and ERA5 reanalysis data during the summer season for the past 10-years (2013–2022). The data obtained were at different resolutions, which was resampled to 5 km × 5 km spatial resolution. Pearson's correlation and sensitivity analysis were used to check the dominant input parameters. Three machine learning approaches were used in the study: multiple linear regression (MLR), support vector regression (SVR), and random forest (RF). 3-fold cross validation was used to evaluate the model performance. The data was divided into three periods for the purpose of testing, training and validation. It was observed that the maximum AT in both states was above the limits of IMD criteria for defining heat wave occurrences. The performance of the models was evaluated using statistical metrics, comprising of root mean square error (RMSE) and coefficient of determination (R2). Good correlation of AT with land surface temperature (LST), black carbon (BC), AOD, and CO was found for both the states. AT was found to be more sensitive to the change in LST and BC compared to other parameters. The machine learning results indicated that RF outperformed MLR and SVR in predicting AT in both states. The adjusted R2 was 0.90 and 0.92, for Rajasthan and Karnataka, respectively while RMSE was 2.36% and 1.44%, for Rajasthan and Karnataka, respectively. Overall, the study shows that machine learning-based approaches can predict maximum AT for defining heat wave conditions with high accuracy. The study can have significantly applications in different fields like climate modelling studies, urban planning and infrastructure, agriculture etc. and it can help to implement appropriate measures to mitigate the adverse impacts of temperature rise.

Heat Stress Effects on Leaf Physiological Performances, Vegetative Growth and Grain Yield of Grain Corn (Zea mays L.)

The impact of climate change on agricultural production will be most pronounced in tropical and subtropical regions, with numerous climate modeling studies predicting more occurrences of heat waves in the future. Elevated temperatures resulting from global warming pose a significant threat to the agricultural sector, as warmer conditions can hinder plant growth and development, leading to reduced crop yields or even crop failure under extreme circumstances. Therefore, this study aimed to determine the effects of ambient, non-heated (30 °C) and heat stress conditions (38 °C) on the plant physiological responses, growth and yield of grain corn during both the vegetative and reproductive stages. The results demonstrated that exposure to heat stress for 7 days significantly impacted the physiological performance of the plants, resulting in a substantial 46.9% reduction in net photosynthetic rate. However, prolonged exposure to heat for 28 days caused even more severe effects, with a 72.5% reduction in net photosynthetic rate. Although the effects of heat stress on vegetative growth were not apparent after 7 days, the plants exhibited severe damage after 28 days of heat stress treatment. During the flowering stage, heat stress led to significant reduction in kernel set, total kernel number, and grain weight of grain corn by 45%, 41%, and 46%, respectively. Poor and scattered kernel set on cobs during the heat stress treatment at the anthesis period indicated damage to pollen grains, failed pollination, and fertilization. These findings highlight the vulnerability of grain corn varieties cultivated in Malaysia to the negative impacts of heat stress, leading to potential losses in production yield.

Possible influences of spring Barents Sea ice shrinking on Chinese heat wave events

AbstractHeat waves have a catastrophic impact on ecosystems, economy, society and human health. Revealing the underlying physical drivers of heat waves is essential for improving extreme event forecasts and disaster prevention capabilities under climate change. Thus, this study provides an analysis of the maximum temperature, and heat wave frequency and duration during July–August in China from 1961 to 2022. Significant upward trends of different heat wave indexes were observed and broke the historical record in 2022. The influence of large‐scale circulation on heat waves illustrates that the eastward South Asia High (SAH) and anomalously westward Western Pacific Subtropical High (WPSH) are closely associated with increased heat wave events, especially in 2022. We further demonstrate using reanalysis data that the Barents Sea ice shrinkage is associated with increased heat waves in China by modulating favourable atmospheric circulations. In addition, the North Atlantic Oscillation (NAO), which is closely linked to Arctic Sea ice, can provoke large‐scale Rossby waves, which in turn can cause extreme heat events in China. In particular, the reduced sea ice coupled with NAO strengthens the anomalous eastward SAH and anomalous westward WPSH of their position and intensity especially in 2022 and provides favourable atmospheric circulation patterns for the occurrence of heat waves.

Understanding Quiet and Storm Time EMIC Waves—Van Allen Probes Results

AbstractGeomagnetic indices have been used as a proxy for studying electromagnetic ion cyclotron (EMIC) wave occurrences under different geomagnetic conditions. However, the drivers of EMIC waves are different during non‐storm, storm time and during individual storm phases. Using ∼7 years of data from the twin Van Allen Probes, we demonstrate that the occurrence probability of EMIC waves are not well captured by a specific geomagnetic activity index alone, but is rather well manifested by considering individual storm phases. We show EMIC wave occurrence statistics during different storm phases (pre‐onset, main and recovery) for geomagnetic activity indices Sym‐H, AE, and Kp and solar wind dynamic pressure Pdyn, illustrating that the occurrence rates vary significantly during different storm phases even for a given geomagnetic index. We also utilize this large database to show EMIC wave occurrence distribution, and how various wave and plasma parameters behave under different geomagnetic conditions. EMIC waves occur 2.9 times more often during geomagnetic storms than during non‐storm times. The majority (72%) of storm time EMIC waves occur during the recovery phase due to long recovering time, while the highest occurrence rates are in the pre‐onset phase, followed by main and recovery phases. EMIC waves in the main phase have occurrence peaks in the dusk to pre‐midnight sectors while recovery phase events spread to more Magnetic Local Time (MLT) sectors with peaks in the morning sector. Wave amplitudes are found to be evenly distributed across different MLT sectors during all geomagnetic conditions.

Trends in Prescription Chronic Pain Medication Use before and during the First Wave of the COVID-19 Pandemic in Québec, Canada: An Interrupted Time Series Analysis.

In Canada, a state of health emergency was declared in May 2020 as a result of the COVID-19 pandemic. This study aimed to assess trends in the use of prescription medication for pain management by people living with chronic pain before and during the first wave of the pandemic. Participants (n = 177) were adults reporting chronic pain who had completed a web-based questionnaire in 2019 and for whom complete longitudinal private and public insurance prescription claims were available. The monthly prevalence of medication use for nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, and prescribed cannabinoids was assessed. An interrupted time series analysis was then performed to evaluate if the COVID-19 pandemic had had an impact on trends in pain medication use. The beginning of the first wave of the pandemic was associated with the onset of a downward trend in opioid use (p < 0.05); no such association was found regarding NSAIDs. However, point prevalence of opioid use at the beginning (Nov. 2019) and at the end (Mai 2020) of the study period remained somewhat stable (17.0% vs. 16.4%). Regarding prescribed cannabinoids, a gradual increase in use was observed over the entire study period independently from the impact of the first wave of the pandemic (15.3% vs. 22.6%, p < 0.05). While the occurrence of the first wave did have an impact on opioid use among people living with chronic pain, access to and use of opioids appear to have returned to normal before the end of the first wave of COVID-19.

Study of The Impact of Convectively Coupled Equatorial Kelvin and Rossby Waves on Rainfall Extremes in Sulawesi, Indonesia

This study examined the impact of Equatorial Kelvin and Equatorial Rossby (ER) waves on rainfall extremes over Sulawesi Island, Indonesia. Impacts are assessed by changes in the probability of rainfall events that exceeded extreme value and changes in the fraction of wet days. Using Asian Precipitation – Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) rainfall data and Outgoing Longwave Radiation (OLR) from NOAA, impacts are quantified with the respect to wave’s local phase grouping. The local wave phase is based on the standardized OLR anomalies and their temporal tendency. Results showed that Kelvin and ER wave can modulate daily rainfall extremes over Sulawesi Island. Kelvin wave has the strongest impact with changes in the probability of extreme rainfall by up to +100% (-70%) in phases 5 and 6 (1 and 2) and increases the value of wet day fraction by up to > 0.04. Followed by the ER wave with changes in the probability of extreme rainfall by up to +50% (-50%) in phase 4 (1 and 2) and increases the value of the wet day fraction by up to 0.05. The superposition between ER and Kelvin wave occurrence increases the possibility of extreme rainfall occurrence by up to 100 % in almost every part of Sulawesi island in phases 4,5 and 6. The results suggest that Kelvin and ER waves can be another important source of predictability for extreme rainfall on Sulawesi Island.

Evaluation of the Implementation of Traditional Market Health Protocols in East Java

The occurrence of the Second Wave of the Covid-19 Pandemic has made the Indonesian government issued a new policy called the Emergency PPKM Policy with Health Protocols (Prokes). A policy must have an impact on people's lives, as well as scrap metal traders at Setono Betek Market in Kediri City and PKL Culinary Center and traditional market in Rungkut District, Surabaya City. This research was conducted with the aim of knowing how the impact of PPKM Darurat in the control of health protocols on the lives of iron traders who had to close their stalls for two weeks according to applicable regulations and controlling prokes by Satpol PP at the PKL at the Culinary Center in Rungkut District, Surabaya City. This type of research is descriptive research with a qualitative approach. With data collection methods through interviews, documentation, field studies, and literature studies. Technical Data analysis in this study uses interactive methods through data reduction, data presentation, and conclusion drawing. The results of this study show that the Emergency PPKM regulation makes these iron traders must close their stalls for two weeks, namely in the initial period of July 3-July 20, 2021. As a result of this closure, scrap metal traders experienced a decrease in an average turnover of almost 90%. The social impact these iron merchants feel is also complex, especially on behavior change. An appeal to do marketing online, but still, not all merchants can take advantage of existing technology. While the control of the health process by Satpol PP, Effectiveness, Efficiency, Adequacy, Equity, Responsiveness, and Accuracy

Theoretical prediction of early afterdepolarization-evoked triggered activity formation initiating ventricular reentrant arrhythmias

Background and ObjectiveExcessive prolongation of QT interval on ECGs in patients with congenital/acquired long QT syndrome and heart failure is a sign suggesting the development of early afterdepolarization (EAD), an abnormal repolarization in the action potential of ventricular cardiomyocytes. The development of EAD has been believed to be a trigger for fatal tachyarrhythmia, which can be a risk for sudden cardiac death. The role of EAD in triggering ventricular tachycardia (VT) remains unclear. The aim of this study was to elucidate the mechanism of EAD-induced triggered activity formation that leads to the VT such as Torsades de Pointes. MethodsWe investigated the relationship between EAD and tachyarrhythmia initiation by constructing homogeneous myocardial sheet models consisting of the mid-myocardial cell version of a human ventricular myocyte model and performing simulations of excitation propagation. ResultsA solitary island-like (clustering) occurrence of EADs in the homogeneous myocardial sheet could induce a focal excitation wave. However, reentrant excitation, an entity of tachyarrhythmia, was not able to be triggered regardless of the EAD cluster size when the focal excitation wave formed a repolarization potential difference boundary consisting of only a convex surface. The discontinuous distribution of multiple EAD clusters in the ventricular tissue formed a specific repolarization heterogeneity due to the repolarization potential difference, the shape of which depended on EAD cluster size and placed intervals. We found that the triggered activity was formed in such a manner that the repolarization potential difference boundary included a concave surface. ConclusionsThe formation of triggered activity that led to tachyarrhythmia required not only the occurrence of EAD onset-mediated focal excitation wave but also a repolarization heterogeneity-based specific repolarization potential difference boundary shape formed within the tissue.

Wave climate characteristics and effects of tropical cyclones on high wave occurrences in Indonesian waters: Strengthening sea transportation safety management

Tropical cyclones can cause bad weather and high waves that can endanger maritime activities, especially in the waters of Indonesia, which is a maritime country. Understanding ocean wave climate characteristics and the effect of Tropical Cyclones (TCs) on high wave occurrences is important, particularly to ensure the safety of fisheries activities in Indonesian seas. We aim to do so by focusing on Indonesia's 11 Fisheries Management Areas (IFMAs) using descriptive and inferential statistics. Wind and wave data were taken from the European Center for Medium-Range Weather Forecast (ECMWF), namely ECMWF Reanalysis v5 (ERA5) within the range of 42 years (1979–2020), whereas the TC data were from the International Best Track Archive for Climate Stewardship (IBTrACS). We found that significant wave heights (SWHs) in the inner seas are strongly related to monsoonal wind fields. The maximum SWH occurred in northern Indonesian seas during December–February (DJF), while occurring in southern and inner seas between June–August (JJA). The highest extreme SWH and probability of exceedance (PE) for SWH >2 m were found in IFMAs facing the open ocean, such as Malacca Strait, Western Sumatra waters, Southern Java waters, Natuna Sea, Sulawesi Sea, and Northern Papua waters. We found that TCs activity in adjacent Indonesian waters could increase anomalous SWH occurrences. Positive SWH anomalies ranged from 0.1 to 0.4 m and varied depending on TC location and season. TC that forms in the following areas increase the PE for SWH >2 m: (1) Bay of Bengal: Western Sumatra waters (March–May, MAM) around 20%; (2) Western Pacific Ocean: Northern Papua waters (DJF) around 5%; (3) Northeastern Indian Ocean: Western Sumatra waters (DJF) about 3%; and (4) Western and Northern Australian waters: Southern Java waters (DJF) about 20%. The results of this study can serve as an early assessment for investigating wave climate characteristics and identifying the areas in Indonesian waters that are most susceptible to the impact of TCs, particularly in IFMAs. These findings hold significant value for managers and policy authorities, such as the Ministry of Transportation and the Ministry of Marine Affairs and Fisheries of the Republic of Indonesia. They can utilize this information to develop measures aimed at reducing vulnerabilities among marine resource users, specifically fishers, and improving fishing vessel safety. Additionally, these findings can be utilized to enhance advance warnings and forecasts, enabling marine managers to implement strategies that minimize the impact of extreme events and increase resilience in the face of ocean and coastal disasters.

Impact assessment of air pollutants and greenhouse gases on urban heat wave events in the Beijing-Tianjin-Hebei region.

The production and quality of human life have been impacted by the extreme heat wave events caused by global warming and urbanization. This study analyzed the prevention of air pollution and the strategies of emission reduction based on decision trees (DT), random forests (RF), and extreme random trees (ERT). Additionally, we quantitatively investigated the contribution rate of atmospheric particulate pollutants and greenhouse gases to urban heat wave occurrences by combining numerical models and big data mining technology. This study focuses on changes in the urban environment and climate. The main findings of this study are as follows.The average concentrations of PM2.5 in the northeast of Beijing-Tianjin-Hebei in 2020 were 7.4%, 0.9%, and 9.6% lower than those in the corresponding years of 2017, 2018, and 2019, respectively. The carbon emissions in the Beijing-Tianjin-Hebei region showed an increasing trend during the previous 4years, which was consistent with the spatial distribution of PM2.5. In 2020, there were fewer urban heat waves, which was attributable to a reduction of 75.7% in emissions and an improvement of 24.3% in the prevention and management of air pollution. These results suggest that the government and environmental protection agencies need to pay attention to changes in the urban environment and climate to diminish the negative effects of heatwaves on the health and economic growth of the urban population.

Role of spin-orbit coupling on crystal-field splitting and phase-stability of rare-earth based layered intermetallic

Layered and incommensurate heterostructures have attracted much attention for the occurrence of superconductivity and charge density waves with the possibility of intercalating foreign atoms. However, lanthanide-based heterostructures where (EuxSm1-x)S and TaS2 are alternatively stacked have been scarcely investigated. In this work, we performed phase stability, bonding behavior and electronic-structure analysis of (EuxSm1-x)TaS3 using first-principles density-functional theory methods. Our phase stability analysis suggests 50 at.% solubility of Eu in (EuxSm1-x)TaS3 compared to Eu solubility in all proportions in cubic SmS. The instability of Eu beyond 50 at.% in (EuxSm1-x)TaS3 was attributed to higher density of Eu-4f states at the Fermi-level. Based on band position calculated from spin-orbit coupling effect, we constructed a qualitative schematic of possible crystal-field analysis. The local change in bond-length and bond-angle around Eu-S in (EuxSm1-x)TaS3 correlate well with our crystal-field analysis. We believe that quantum mechanical insights provided in this work will be useful to understand other complex heterostructures.

Non-homogeneous approximation for the kurtosis evolution of shoaling rogue waves

Bathymetric changes have been experimentally shown to affect the occurrence of rogue waves. We recently derived a non-homogeneous correction to the spectral analysis, allowing us to describe the evolution of the rogue wave probability over a shoal. Here, we extend this work to the evolution of the excess kurtosis of the surface elevation, that plays a central role in estimating rare event probabilities. Furthermore, we provide an upper bound to the excess kurtosis. In intermediate and deep water regimes, a shoal does not affect wave steepness nor bandwidth significantly, so that the vertical asymmetry between crests and troughs, the excess kurtosis and the exceedance probability of wave height stay rather constant. In contrast, in shallower water, a sharp increase in wave steepness increases the vertical asymmetry, resulting in a growth of both the tail of the exceedance probability and the excess kurtosis.

On the modulational of Schamel nonlinear Schrödinger equation and the associated envelope excitations in a degenerate relativistic quantum complex plasma

The modulational instability (MI) of Schamel/modified nonlinear Schrödinger equation (SNLSE) or (mNLSE) and the associated envelope excitations, including bright solitons in a multicomponent dense plasma consisting of relativistically degenerate electrons, trapped ions, and non-degenerate dust species are reported. A conventional multiple scales perturbative technique is utilized to get a SNLSE. This equation is different from the standard NLSE which the SNLSE has a nonlinear term with fractional order (3/2). The MI criteria are derived in detail. Also, the occurrence of envelope solitary wave and the effects of the different physical parameters on its profile are briefly discussed. The current results are advantageous to understand the mechanism of the propagation of the envelope excitations in complex plasmas with trapped ions and relativistically degenerate electrons, such as those observed in space observations and laboratory complex plasma.

The Impact of SARS-CoV-2 Lineages (Variants) and COVID-19 Vaccination on the COVID-19 Epidemic in South Africa: Regression Study.

Emerging SARS-CoV-2 variants have been attributed to the occurrence of secondary, tertiary, quaternary, and quinary COVID-19 epidemic waves threatening vaccine efforts owing to their immune invasiveness. Since the importation of SARS-CoV-2 in South Africa, with the first reported COVID-19 case on March 5, 2020, South Africa has observed 5 consecutive COVID-19 epidemic waves. The evolution of SARS-CoV-2 has played a major role in the resurgence of COVID-19 epidemic waves in South Africa and across the globe. We aimed to conduct descriptive and inferential statistical analysis on South African COVID-19 epidemiological data to investigate the impact of SARS-CoV-2 lineages and COVID-19 vaccinations in South African COVID-19 epidemiology. The general methodology involved the collation and stratification, covariance, regression analysis, normalization, and comparative inferential statistical analysis through null hypothesis testing (paired 2-tailed t tests) of South African COVID-19 epidemiological data. The mean daily positive COVID-19 tests in South Africa's first, second, third, fourth, and fifth COVID-19 epidemic wave periods were 11.5% (SD 8.58%), 11.5% (SD 8.45%), 13.3% (SD 9.72%), 13.1% (SD 9.91%), and 14.3% (SD 8.49%), respectively. The COVID-19 transmission rate in the first and second COVID-19 epidemic waves in South Africa was similar, while the COVID-19 transmission rate was higher in the third, fourth, and fifth COVID-19 epidemic waves than in the aforementioned waves. Most COVID-19 hospitalized cases in South Africa were in the general ward (60%-79.1%). Patients with COVID-19 on oxygen were the second-largest admission status (11.2%-16.8%), followed by patients with COVID-19 in the intensive care unit (8.07%-16.7%). Most patients hospitalized owing to COVID-19 in South Africa's first, second, third, and fourth COVID-19 epidemic waves were aged between 40 and 49 years (16.8%-20.4%) and 50 and 59 years (19.8%-25.3%). Patients admitted to the hospital owing to COVID-19 in the age groups of 0 to 19 years were relatively low (1.98%-4.59%). In general, COVID-19 hospital admissions in South Africa for the age groups between 0 and 29 years increased after each consecutive COVID-19 epidemic wave, while for age groups between 30 and 79 years, hospital admissions decreased. Most COVID-19 hospitalization deaths in South Africa in the first, second, third, fourth, and fifth COVID-19 epidemic waves were in the ages of 50 to 59 years (15.8%-24.8%), 60 to 69 years (15.9%-29.5%), and 70 to 79 years (16.6%-20.7%). The relaxation of COVID-19 nonpharmaceutical intervention health policies in South Africa and the evolution of SARS-CoV-2 were associated with increased COVID-19 transmission and severity in the South African population. COVID-19 vaccination in South Africa was strongly associated with a decrease in COVID-19 hospitalization and severity in South Africa.

An entropy model for Carreau nanofluid ciliary flow with electroosmosis and thermal radiations: A numerical study.

In order to localize heat production and drug activation, it is possible for drug delivery to make use of nanofluids containing thermal radiation. By limiting the amount of medication that is administered to healthy tissues, this approach increases drug distribution. We explore the effect that thermal radiation has on the flow of a ternary-hybrid nanofluid composed of titanium oxide (TiO2), silica (SiO2), and aluminum oxide (AI2O3). The base liquid that we use for our Carreau constitutive model is blood. Entropy and electroosmosis are both taken into account when the conduit is connected to the battery terminals outside. Following the step of translating the observation model into a wave frame, the physical restrictions of the lubrication theory are used in order to provide a more complete explanation for the wave occurrences. In this work, shooting is used to simulate boundary value issues that are solved with Mathematica NDSolve. The production of the least amount of entropy and a rise in thermodynamic efficiency are achieved by the motion of cilia and elastic electroosmotic pumping. It is also observed that heat transfer is proportional to the length of cilia. Nusselt number is increased by large cilia but skin friction got a reduction.

The Radial Distribution of Ion-scale Waves in the Inner Heliosphere

Determining the mechanism responsible for plasma heating and particle acceleration is a fundamental problem in the study of the heliosphere. Due to efficient wave–particle interactions of ion-scale waves with charged particles, these waves are widely believed to be a major contributor to ion energization, and their contribution considerably depends on the wave occurrence rate. By analyzing the radial distribution of quasi-monochromatic ion-scale waves observed by the Parker Solar Probe, this work shows that the wave occurrence rate is significantly enhanced in the near-Sun solar wind, specifically 21%–29% below 0.3 au, in comparison to 6%–14% beyond 0.3 au. The radial decrease of the wave occurrence rate is not only induced by the sampling effect of a single spacecraft detection, but also by the physics relating to the wave excitation, such as the enhanced ion beam instability in the near-Sun solar wind. This work also shows that the wave normal angle θ, the absolute value of ellipticity ϵ, the wave frequency f normalized by the proton cyclotron frequency f cp, and the wave amplitude δ B normalized by the local background magnetic field B 0 slightly vary with the radial distance. The median values of θ, ∣ϵ∣, f, and δ B are about 9°, 0.73, 3f cp, and 0.01B 0, respectively. Furthermore, this study proposes that the wave mode natures of the observed left-handed and right-handed polarized waves correspond to the Alfvén ion cyclotron mode wave and the fast magnetosonic whistler mode wave, respectively.

Amplitude‐Dependent Properties and Excitation Mechanisms of EMIC Waves in the Earth's Inner Magnetosphere

AbstractLarge‐amplitude (Bw &gt; 1 nT) electromagnetic ion cyclotron (EMIC) waves can cause the rapid loss of &gt;1 MeV electrons, greatly impacting radiation belt dynamics. With long‐term Van Allen Probe B observations from 2013 to 2018, we conducted a statistical survey to reveal the amplitude‐dependent EMIC wave properties and excitation mechanisms in the Earth's inner magnetosphere. Statistical results show that large‐amplitude EMIC waves prefer to occur in the afternoon‐dusk sector in the northern hemisphere and tend to be more left‐hand polarized with smaller wave normal angles. In addition, the high proton beta parallel conditions also favor the generation of larger‐amplitude EMIC waves. From the variations of EMIC wave occurrence rate as a function of SuperMAG electrojet (SME) index and solar wind dynamic pressure, we find that the small‐amplitude EMIC waves are generally triggered by high solar wind dynamic pressure, while large‐amplitude EMIC wave generation is both affected by substorm activity and solar wind dynamic pressure. The normalized magnetic field perturbations during EMIC wave appearance, which enable us to distinguish the relative roles of magnetospheric compression and substorm injection in the excitation of different‐amplitude EMIC waves, provide further evidence that as wave amplitude increases, substorm injection plays a more important role in EMIC wave excitation, and magnetospheric compression is also an indispensable trigger.

Обоснование безопасных расстояний по отношению к окружающим объектам при проведении камуфлетных взрывов в горных породах

Introduction. Despite the simplicity and accessibility of camouflage blasting, the issues of ensuring the safe conduct of such work are important. A camouflage explosion eliminates the occurrence of an air shock wave and the harmful effects of the explosion products on the environment, but leads to strong seismic vibrations. The impact of seismic loads on nearby objects can lead to the loss of their carrying capacity, damage and destruction, therefore, when choosing a place for installing camouflage charges, the task arises of assessing the field of environmental velocities during an explosion and determining the distances at which the velocities do not exceed the maximum allowable values established for objects under consideration. The aim of the study is to solve the problem of determining the velocity field in a continuous elastic-plastic medium during a camouflage explosion. Research methodology. The solution of the central symmetric problem of the propagation of explosive disturbances in solid media is based on the assumption that a deep spherical charge of a certain radius is placed in an unbounded half-space, which instantly turns into a high-pressure gas without changing the volume. It is assumed that the pressure in the cavity decreases according to a power law, and the relationship of pressure with the radius, velocity and acceleration of the expanding cavity is determined by the camouflage equation , whose constants A, B and C are functions of the parameters of rocks and soils. The perturbed state of the medium caused by the expanding cavity is also characterized by densities ρ0 and ρ respectively, in the elastic and plastic regions of its deformation, and the transition from the elastic state to the plastic state is accompanied by an instantaneous change in the density of the medium from ρ0 to ρ, introduced to approximately take into account the actual compressibility. Results. The determination of the velocity field in the medium surrounding the charge during the explosion is reduced to solving the ordinary differential equation of motion of a spherical cavity expanding due to internal pressure. It is shown that the unknown constant included in the obtained relation can be determined from the condition of conservation of the energy released during the explosion in the entire elastoplastic region of the medium motion. Discussion. The novelty of the result obtained lies in the substantiation of the possibility of using the assumptions about the vibrationless nature of the movement of the camouflage cavity and the incompressibility of the medium in the plastic and elastic regions to determine the velocity field that forms in a continuous medium during the explosion of a camouflage charge. Conclusion. Under the assumption of the vibrationless nature of the motion and the incompressibility of the medium in the plastic and elastic regions, a solution is obtained for the centrally symmetric problem of determining the velocity field in a continuous elastoplastic medium during a camouflage explosion. The solution obtained makes it possible to estimate the sizes of expansion zones, plastic deformation of the medium, and the impact of explosive disturbances on various objects.

Electrohydraulic Yutkin effect and electrospark discharges in liquids

Electrospark discharges in liquids are the subject of numerous studies, as they are a source of powerful wave pulses that can be used in various technological processes. One of the first researchers of this phenomenon was L.O. Yutkin, who substantiated and investigated the electrohydraulic effect (EHE). This effect allows to transform electrical energy into mechanical energy of powerful shock waves, which opens up great opportunities for increasing the efficiency of various technologies. The purpose of the study is to analyze the history of the study of electric spark discharges in liquids, the contribution of L.O. Yutkin to the development of the theory and practical application of the EHE, and to highlight the advantages of wave treatments based on this effect. In the course of the study, scientific papers and experimental data obtained in the study of electrospark discharges in liquids and the electrohydraulic effect were analyzed. The theoretical foundations of these phenomena were considered, as well as practical applications of EHE in various industries. The electrohydraulic effect (EHE), discovered by L.O. Yutkin, is a unique phenomenon that allows converting electrical energy into mechanical energy of powerful shock waves. This is achieved by generating an electric discharge in a liquid, which leads to the formation of a plasma channel and the subsequent occurrence of a shock wave. The main advantage of wave treatments based on EHE is the ability to introduce large amounts of energy into the medium, which allows to increase the efficiency of numerous technological processes. The electrohydraulic Yutkin effect remains an inexhaustible source for the creation of advanced technologies that are already widely used in many industries