Wave Intensity Research Articles

Comparing the influence of Atlantic Multidecadal Variability and spring soil moisture on European summer heat waves

Abstract In this work, we study and compare the influence of the Atlantic Multidecadal Variability (AMV) and spring soil moisture in Southern Europe on the duration and intensity of European summer heat waves. We study heat waves with return times of a few years and also propose a new methodological approach, return time maps, that allows us to study rare heat waves with return times of 10 or 50 years. We use the outputs from three climate models, namely IPSL-CM6A-LR, EC-Earth3, and CNRM-CM6-1, in which North Atlantic sea surface temperatures are restored towards the observed AMV anomalies. The three models give consistent results, with the exception of EC-Earth simulating a much greater influence of soil moisture. Our main conclusion is that spring soil moisture in Southern Europe is a slow driver of greater importance than the AMV for European summer heat waves, both in terms of the extension of the region of influence and in terms of amplitude. While the influence of the AMV concentrates over the very south of Europe, around the Mediterranean Basin, spring soil moisture influence extends over large parts of Europe. As might be expected, a positive AMV phase or low soil moisture generally induces hotter and longer heat waves. For more extreme events, the influences of the AMV and soil moisture increase, according to regional patterns that seem to be the same as for typical heat waves. However, confirming this statement would require datasets with more extreme events.

The Effect of Contraction–Expansion Nozzle on High-Temperature Shock Tube Flow

To achieve higher enthalpy and pressure, the technique of variable cross-section drive is effectively combined with the heating of light gas to enhance the intensity of the incident shock wave. A study was conducted to predict the impact of variable cross-sections on the performance of high-temperature shock tube flow using a shock tube with a 2.6:1 diameter ratio between the driver and driven sections. The driver section was filled with a helium–argon gas mixture (mass ratio of 1:9), while the driven section contained dry air. Under total pressure conditions of 14.5 MPa and total temperature of 3404 K, as well as total pressure of 45 MPa and total temperature of 4845 K in the driver section, corresponding to driven section pressures of 10 kPa and 80 kPa, the results of chemical non-equilibrium numerical simulations were compared to experimental measurements of the incident shock Mach number and total pressure. The results indicated the following: First, after adding the contraction–expansion nozzle, the incident shock accelerated through the contraction section and reflected within the contraction section. Strong oscillations occurred during the flow, with increasing intensity as the throat size decreased. Second, without the nozzle, the shock velocity increased and then decreased. However, with the nozzle, the Mach number was highest near the nozzle exit and gradually decreased thereafter. Third, the presence of the nozzle led to the formation of a distinct fan-shaped wavefront, accompanied by significant variations in flow variables such as pressure, temperature, and Mach number in the region. This phenomenon was attributed to the interaction between the shock wave and the nozzle geometry, which altered the flow dynamics. Finally, as the throat size decreased, the intensity of the incident shock also decreased. After reflecting at the end of the shock tube, the total pressure in the driven section also decreased. The numerical simulations employed a multi-component, multi-temperature chemical non-equilibrium model, validated against experimental data, to accurately capture the complex flow behavior and wave interactions within the shock tube.

Study on time-frequency domain characteristics and cross-media communication of laser acoustic signals based on optical breakdown mechanism

Abstract Cross-media communication is a hot research issue at present. The use of sound waves generated by laser induced sound mechanism for cross-media communication is a new topic proposed in recent years. It is of great significance to study the characteristics of laser acoustic signal and the feasibility study for cross-media detection. The time-frequency characteristics and directivity of the laser induced sound signal are studied on the self-built experimental platform. The results show that the pulse duration of the laser acoustic signal is about 2 × 10−4 s, and the peak frequency is about 14.9 ± 0.75 kHz. And the signal strength perpendicular to the water surface is the weakest, so it has a good horizontal distance transmission ability. This paper verifies the detection system of trans-air-sea interface communication and trans-air-sea interface communication based on laser sound and conducts the communication experiment of laser acoustic signal. By modulating laser energy, the underwater acoustic signal is modulated in time domain, and the signal communication with 0-bit error rate of 8 bps within the meter is realized. The detection threshold of acoustic signal is calculated to be 44.9 dB re 1μpa after horizontal transmission of 1 km. The analysis and simulation of water surface micro-motion based on laser induced sound are carried out. The results show that the wave crest of water surface generated by laser acoustic signal through underwater reflection reaches the order of micron and can be detected by radar. The surface wave intensity is little affected by the depth of detection, so it could work in deep water. This study provides a certain experimental and theoretical basis for laser communication across the air and sea interface.

Coupling Indoor and Outdoor Heat Stress During the Hot Summer of 2022: A Case Study of Freiburg, Germany

Indoor and outdoor heat stress, which can appear during warm periods of the year, often has a negative impact on health and reduces productivity at work and study. Intense heat waves (HWs) are causing increasing rates of morbidity and mortality. This study aimed to analyze the coupling and delay of indoor and outdoor heat stress during HW events, using the example of ten workplaces (WPs) situated in different offices and buildings in the medium-sized city of Freiburg, Germany. The relationships between air temperature, humidity, and thermal stress intensity in the WPs were explored during HW periods. It was found that the level of thermal load in the investigated WPs was very different compared to that outdoors (during HWs and the entire summer). The mean physiologically equivalent temperature (PET) for the summer of 2022 inside the investigated offices was 2 °C higher than outside. All classes of thermo-physiological stress were observed outdoors at a meteorological station during the study period. While at eight of the ten workplaces, the most frequent physiological stress was slight heat stress (ranging between 62.4% and 97.4% of the time), the other two WPs were dominated by moderate heat stress (53.7% and 60.6% of the time). The daily amplitudes as well as diurnal courses of air temperature, humidity, and PET during the summer differed significantly at the ten different WPs. It is suggested to use vapor pressure instead of relative humidity to characterize and compare different HWs both outside and inside. It is proposed for future work research to analyze not only room and building characteristics but also the characteristics of the surroundings of the building for a better understanding of the key factors that influence human thermal comfort in different workplaces. A framework of the drivers affecting the coupling of outdoor and indoor heat stress is proposed.

Vibration control and energy harvesting of adjacent structures by electromagnetic dampers considering soil-structure interaction

With rapid urbanization, the increasing density of buildings in urban areas has forced us to consider interactions between adjacent structures. However, most studies have focused on fixed foundations, neglecting soil-structure interactions (SSI). This paper addresses this gap by investigating the optimization of two adjacent structures using electromagnetic inerter dampers (EMID) under SSI. The EMID system, equipped with energy harvesting capabilities, was optimized using the Monte Carlo search method, with results demonstrating a significant reduction in dynamic response. Specifically, frequency and time domain analyses show that the EMID system reduces peak displacement and acceleration by up to 41.23% compared to uncontrolled structures. Additionally, the system efficiently converts seismic energy into electrical energy, with energy harvesting reaching peak values under intense seismic waves, such as those observed in Mexico City earthquake conditions. This innovative system not only enhances seismic performance, particularly in soft soil conditions, but also offers energy resilience by supplying emergency power, thus highlighting its potential for sustainable urban infrastructure.

Maternal exposure to ambient temperature and risk of preterm birth in Chengdu, China, from 2017 to 2020: a cohort study

BackgroundDue to climate change, the frequency and intensity of heat waves and other extreme weather events are rapidly increasing. Compared to the general population, pregnant women and fetuses are increasingly vulnerable to the effects of extreme temperatures and are associated with the occurrence of adverse birth outcomes, including preterm birth (PTB). However, its risk of preterm birth is currently uncertain. The objective of the research is to examine the effect of ambient temperature on PTB in pregnant women.MethodsThis study included 6,850 pregnant women from the Tongji-Shuangliu Birth Cohort. Meteorological data for Chengdu through the European Centre for Medium-Range Weather Forecasts. The main exposure assessment was conducted during eight different exposure windows, including the first three months of pregnancy, 7 weeks periods during the first two trimesters, throughout pregnancy, 1-week preceding delivery, and 4 weeks preceding delivery. The effect of environmental temperature on PTB during different exposure windows was assessed using the logistic regression based on the percentile of the mean temperature in different exposure cycles. Additionally, the lagged effect of environmental temperature on preterm births throughout the study period was analyzed using a distributed lag non-linear model.ResultsAmong the 6850 pregnant women, 301 (4.4%) were diagnosed with PTB. Compared to mild temperature (10th to 90th percentile), exposure to extreme cold (< 10th percentile) temperature during the 4 weeks preceding delivery (RR = 2.45, 95% CI:1.11,5.40) and throughout pregnancy (RR = 3.85, 95% CI:1.56,9.53) increased the risk of PTB. In addition, hot temperature (> 90th percentile) at 4 weeks preceding delivery (RR = 0.33, 95% CI:0.13,0.86) and 22–28 weeks of pregnancy (RR = 0.25, 95% CI:0.11,0.59), and cold exposure at 1-week preceding delivery(RR = 0.51, 95% CI:0.27,0.96), reduced risk of PTB. In the lagged model, compared with 18° C (50th percentile), 7 °C (10th percentile) had the strongest effect on lag day 21 and lag 22 (RR = 1.20, 95% CI:1.03,1.40; RR = 1.20, 95% CI:1.03,1.39). A temperature of 27° C (90th percentile) was protective for PTB from the 22nd day of lag(RR = 0.86, 95% CI:0.75,0.99).ConclusionsThis study indicates that high temperature may be a protective factor for PTB, while low temperature may be a risk factor, with an obvious lag effect.

Nonlinear Airy beam propagation in defected photonic lattices.

This work theoretically investigates the interplay of nonlinear Airy beams (AB) propagation and optically induced waveguide arrays in a photorefractive (PR) crystal. By introducing defect guides within the photonic lattice, we control the trajectory and self-bending properties and mostly the complex photoinduced waveguiding structures of these unconventional beams. Positive defects within the lattice induce the formation of solitary-like waves, while negative defects result in strong repulsion effects. In the nonlinear regime, these phenomena are further enhanced, with higher solitonic wave intensity in the case of a positive defect. Our simulations further demonstrate that at a lattice period of 20 µm, a specific defect guide modulation depth, and proper nonlinearity strength, a single laser beam injected in a negatively defected waveguide splits into up to seven distinct output channels. By judiciously adjusting the parameters, we can generate output channels that are spatially separated by up to 19 times the beam waist, thereby offering precise control over both the position and intensity of the output channels.

Metal Powder Production by Atomization of Free-Falling Melt Streams Using Pulsed Gaseous Shock and Detonation Waves

A new method of producing metal powders for additive manufacturing by the atomization of free-falling melt streams using pulsed cross-flow gaseous shock or detonation waves is proposed. The method allows the control of shock/detonation wave intensity (from Mach number 4 to about 7), as well as the composition and temperature of the detonation products by choosing proper fuels and oxidizers. The method is implemented in laboratory and industrial setups and preliminarily tested for melts of three materials, namely zinc, aluminum alloy AlMg5, and stainless steel AISI 304, possessing significantly different properties in terms of density, surface tension, and viscosity. Pulsed shock and detonation waves used for the atomization of free-falling melt streams are generated by the pulsed detonation gun (PDG) operating on the stoichiometric mixture of liquid hydrocarbon fuel and gaseous oxygen. The analysis of solidified particles and particle size distribution in the powder is studied by sifting on sieves, optical microscopy, laser diffraction wet dispersion method (WDM), and atomic force microscopy (AFM). The operation process is visualized by a video camera. The minimal size of the powders obtained by the method is shown to be as low as 0.1 to 1 μm, while the maximum size of particles exceeds 400–800 μm. The latter is explained by the deficit of energy in the shock-induced cross-flow for the complete atomization of the melt stream, in particular dense and thick (8 mm) streams of the stainless-steel melt. The mass share of particles with a fraction of 0–10 μm can be at least 20%. The shape of the particles of the finest fractions (0–30 and 30–70 μm) is close to spherical (zinc, aluminum) or perfectly spherical (stainless steel). The shape of particles of coarser fractions (70–140 μm and larger) is more irregular. Zinc and aluminum powders contain agglomerates in the form of particles with fine satellites. The content of agglomerates in stainless-steel powders is very low. In general, the preliminary experiments show that the proposed method for the production of finely dispersed metal powders demonstrates potential in terms of powder characteristics.

Emission Characteristics of Energetic Electrons with Crescent-shaped Velocity Distributions

Abstract Solar flares release magnetic energy through reconnection, accelerating electrons into nonthermal velocity distributions, including crescent-shaped electron populations. These energetic electron distributions are crucial in driving instabilities that can lead to distinct electromagnetic emissions. This study investigates the emission properties of crescent-shaped electron velocity distribution functions under different frequency ratios (ω pe /Ω ce ), critical for understanding plasma conditions in various astrophysical environments, by comparing the emissions and intensities of waves among different cases. Here, we study and analyze three distinct frequency ratio conditions (2.2, 10, and 1, designated as cases A, B, and C, respectively). We find that the beam-Langmuir and upper-hybrid modes can be efficiently excited, leading to further plasma emissions in different cases. Our study reveals that the fundamental (O/F) emission can reach a maximum value of ∼10−4 E k0, while the harmonics (H) can extend to ∼1.5 × 10−5 E k0, depending on the frequency ratio of the environment. The intensity of the fundamental mode exceeds previous findings for pure-ring, pure-beam, and ring–beam distributions, highlighting the impact of crescent-shaped electron velocity distributions on wave excitation and emission processes. This effect is notably influenced by different frequency ratios, offering new insights into the way that nonthermal electron distributions affect the plasma emission process.

Study on the resistance characteristics of corrugated flame arrester for hydrogen explosion

Abstract The resistance characteristics of a corrugated flame arrester in hydrogen explosions were investigated using a visual explosion-retardant system. By varying the structural parameters of the corrugated flame-retardant system and the concentration of hydrogen, the flame resistance characteristics and the mechanisms affecting hydrogen explosions were summarized. The results indicate that there was a clear correlation between the flame propagation and pressure rise during explosion resistance. When the flame resistance failed, a significant enhancement effect was observed at the backend of the flame-retardant system. Additionally, a noticeable oscillation occurred in the initial stage of flame propagation due to the obstruction caused by the flame-retardant system. The thickness and porosity of the flame-retardant system, along with the hydrogen concentration, influenced the intensities of shock waves and flames entering the narrow channel, as well as the physical and chemical effects during internal propagation, thereby affecting the overall flame resistance.

Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?

Global temperature leaped more than 0.4°C (0.7°F) during the past two years, the 12-month average peaking in August 2024 at +1.6°C relative to the temperature at the beginning of last century (the 1880-1920 average). This temperature jump was spurred by one of the periodic tropical El Niño warming events, but many Earth scientists were baffled by the magnitude of the global warming, which was twice as large as expected for the weak 2023-2024 El Niño. We find that most of the other half of the warming was caused by a restriction on aerosol emissions by ships, which was imposed in 2020 by the International Maritime Organization to combat the effect of aerosol pollutants on human health. Aerosols are small particles that serve as cloud formation nuclei. Their most important effect is to increase the extent and brightness of clouds, which reflect sunlight and have a cooling effect on Earth. When aerosols – and thus clouds – are reduced, Earth is darker and absorbs more sunlight, thus enhancing global warming. Ships are the main aerosol source in the North Pacific and North Atlantic Oceans. We quantify the aerosol effect from the geographical distribution of sunlight reflected by Earth as measured by satellites, with the largest expected and observed effects in the North Pacific and North Atlantic Oceans. We find that aerosol cooling, and thus climate sensitivity, are understated in the best estimate of the United Nations Intergovernmental Panel on Climate Change (IPCC). Global warming caused by reduced ship aerosols will not go away as tropical climate moves into its cool La Niña phase. Therefore, we expect that global temperature will not fall much below +1.5°C level, instead oscillating near or above that level for the next few years, which will help confirm our interpretation of the sudden global warming. High sea surface temperatures and increasing ocean hotspots will continue, with harmful effects on coral reefs and other ocean life. The largest practical effect on humans today is increase of the frequency and severity of climate extremes. More powerful tropical storms, tornadoes, and thunderstorms, and thus more extreme floods, are driven by high sea surface temperature and a warmer atmosphere that holds more water vapor. Higher global temperature also increases the intensity of heat waves and – at the times and places of dry weather – high temperature increases drought intensity, including “flash droughts” that develop rapidly, even in regions with adequate average rainfall. Polar climate change has the greatest long-term effect on humanity, with impacts accelerated by the jump in global temperature. We find that polar ice melt and freshwater injection onto the North Atlantic Ocean exceed prior estimates and, because of accelerated global warming, the melt will increase. As a result, shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is likely within the next 20-30 years, unless actions are taken to reduce global warming – in contradiction to conclusions of IPCC. If AMOC is allowed to shut down, it will lock in major problems including sea level rise of several meters – thus, we describe AMOC shutdown as the “point of no return.” We suggest that an alternative perspective – a complement to the IPCC approach – is needed to assess these issues and actions that are needed to avoid handing young people a dire situation that is out of their control. This alternative approach will make more use of ongoing observations to drive modeling and more use of paleoclimate to test modeling and test our understanding. As of today, the threats of AMOC shutdown and sea level rise are poorly understood, but better observations of polar ocean and ice changes in response to the present accelerated global warming have the potential to greatly improve our understanding.

Impact of foam metal hoods on pressure waves generated by high-speed trains traversing tunnels

The high-speed trains traveling at 400 km/h will generate severe alternating pressure and potential sonic boom when passing through tunnels. This paper proposed foam metal hoods (FMH) to mitigate the pressure waves induced by trains traversing tunnels. 1:20 scaled moving-model experiments were conducted to investigate the mitigation mechanisms of FMH on micro-pressure waves (MPW), residual pressure, and aerodynamic loads on the train and tunnel. The impact of FMH's installation position and length on MPW and residual pressure were discussed. The results indicate that the entrance FMH can weaken the expansion wave generated by the tail train entering the tunnel, thereby reducing the pressure amplitude on the train surface and tunnel wall. FMH can reduce the reflection intensity of pressure waves, effectively lowering the root mean square (RMS) of residual pressure. Installing FMH at both ends can reduce the RMS of residual pressure in the middle of the tunnel by 25%. The exit FMH enables the initial wavefront to gradually release pressure outward, thereby reducing MPW intensity. The radiation range of the MPW iso-surface is narrowed by energy consumption as the wavefront passes through the porous structures. The mitigation ratio of MPW intensifies as the length of the exit FMH increases. Using a 4-m-long exit FMH can decrease the MPW amplitude by 83.2% at 20 m from the FMH exit. The FMH facilitates a low-noise environment near tunnel portals, reducing the aerodynamic loads on the tunnel structures, and mitigating the train aerodynamic loads.

Cold waves in the Amazon rainforest and their ecological impact.

Cold waves crossing the Amazon rainforest are an extraordinary phenomenon likely to be affected by climate change. We here describe an extensive cold wave that occurred in June 2023 in Amazonian-Andean forests and compare environmental temperatures to experimentally measured thermal tolerances and their impact on lowland animal communities (insects and wild mammals). While we found strong reductions in activity abundance of all animal groups under the cold wave, tropical lowland animals showed thermal tolerance limits below the lowest environmental temperatures measured during the cold wave. While mammal activity and the biomass of most insects recovered over the next season, dung beetle biomass remained low. A quarter of all insects showed very small thermal safety margins (0.62 °C) with respect to the recorded minimum temperature of 10.5 °C, suggesting that an increased intensity of cold waves in the future could imperil cold-sensitive taxa of Amazonian animal communities.

Two-mode dissipation of oscillating tuning fork in 3He–4He superfluid mixtures

In this paper, we present the results of theoretical studies of the possible mechanism of energy dissipation that takes place in the experiments with vibrating quartz fork in superfluid 3He–4He mixtures with high concentration. The possibility and efficiency of the tuning fork radiation of both the second sound wave and the diffusion dissipative wave were investigated. The relationships between the amplitudes of temperature and concentration oscillations in these waves were found and the relative wave intensities were determined. This allowed us to give a possible explanation for observed additional mechanisms of tuning fork attenuation in helium solutions.

TEVAR versus open aortic arch replacement in ex vivo perfused human thoracic aortas.

This study aims to assess the outcomes of therapeutic options for aortic arch pathologies by comparing thoracic endovascular aortic repair (TEVAR) with open arch replacement (OAR) using woven polyester grafts from a mechanical and biomechanical perspective, with emphasis on ex vivo perfused human thoracic aortas reproducing heart rate and stroke volume conditions. Eleven non-diseased thoracic aortas from human cadavers were divided into TEVAR (n=5) and OAR (n=6) and tested using a custom-built mock circulation loop. Pressure, diameter, and stroke volume were monitored during perfusion before and after the intervention. Samples undergoing TEVAR showed a higher ascending systolic pressure post-intervention than OAR (TEVAR: 137±9mmHg vs OAR: 126±6mmHg, p=0.017). After the intervention, a significant discrepancy in the mean pressure differences between the ascending and descending aorta ΔP was observed (TEVAR: 9±3mmHg vs OAR: 1±2mmHg, p=0.004). Input impedance at zero frequency, approximating Windkessel resistance, was higher for TEVAR than for OAR (TEVAR: 1.78±0.04 vs OAR: 1.66±0.03mmHgs/ml, p=0.004). A correlation was found between the resistance and the negative peak of the time-normalized wave intensity analysis (Kendall's coefficient τ=-0.35 and p=0.023). Another correlation was observed between resistance and ΔP (τ=0.51, p=0.001). Looking at the replication of heart rate and stroke volume over the course of the study, the observed differences can largely be attributed to the type of intervention. The results suggest that TEVAR has adverse effects compared to OAR, particularly with regard to left ventricular afterload. Clinicians should consider the possibility of increased afterload and altered wave dynamics when deciding on TEVAR, particularly in patients with pre-existing impaired cardiovascular conditions.

Luddism, Machine-Breaking and the Swing Riots

If the eighteenth century in England was the age of the riot, the early decades of the nineteenth century might usefully be labelled as the age of machine breaking. Between 1811 and 1830, several extraordinarily intensive waves of machine breaking swept both rural and urban England alike. Against popular misconceptions, such protests – including the Luddite movement of 1811-12, the Bread or Blood riots of 1816, and the Swing quasi-insurrection of 1830 – tended not to oppose technological innovation but rather challenged the ways in which machinery impacted upon labour and wider social relations. Further, the paper shows that machine breaking, especially in the countryside, had a deeper history going back into the late seventeenth century. It also argues that the history of machine breaking in Wales and Scotland has received remarkably little scholarly attention, something the paper begins to address.

Wave-breaking phenomena around a wedge-shaped bow

Bow wave breaking has long been a research challenge in the research field of ship hydrodynamic. This study simplifies the ship's bow as a three-dimensional wedge-shaped structure and conducts experimental measurements to investigate the dynamic characteristics of bow wave breaking. The experiments are carried out in a recirculating water channel, with the force transducer and wave height probes used for measurement. The complex mechanisms influencing bow wave breaking in real-world scenarios can be influenced by factors such as flow velocity, draft, flooding angle, flare angle, and yaw angle. Experiments are carried out under various conditions by controlling one factor at a time. The results show that more intense wave breaking not only increases the resistance force on the wedge but also raises the wave height of the measuring point in the non-breaking region and the nonlinearity in the breaking region. The high-frequency fluctuations of wave height in the breaking region become more obvious. Through a quantitative comparison of different factors on the wave-breaking phenomena, it can be found that the flooding angle has a significant impact on resistance, which helps explain why slender hull designs are commonly used for fast ships. The yaw angle plays a crucial role in affecting the bow waves, influencing both stable wave height and nonlinear breaking waves. The measurement results presented in this paper can provide valuable validation data and flow insights for studies on ship bow wave breaking.

Lac Cultivation as a Pathway to Prosperity: A Success Story from Ranchi, Jharkhand

Lac is a commercially significant cash crop that serves as a vital source of income for millions of economically disadvantaged farmers residing in tribal-dominated forest and sub-forest regions of the country. Due to the worldwide trend towards the usage of natural products, there is a consistent demand for bio-degradable and non-toxic products made from lac in the market. However, production of this economically vital commodity is declining over the years because of alterations in precipitation patterns, recurrent droughts and floods, heightened intensity and frequency of cold waves, and surges in insect pests and diseases. Jharkhand, the largest lac producer state in the country has reflected a disappointing growth rate at -0.33% over the period of 2011-12 to 2021-22. The benefit cost ratio of 2.43 by selling stick lac to middlemen, clearly reflects the high profitability nature of lac cultivation. Considering the economic benefits of the producers and the global demand for safe natural lac cultivation, enhancement in various aspect is required.

Absorption of electromagnetic waves at oblique resonance in plasmas threaded by inhomogenous magnetic fields.

There has been of significant interest lately in the study of electromagnetic (EM) waves interacting with magnetized plasmas. The variety of resonances and the existence of several pass and stop bands in the dispersion curve for different orientations of the magnetic field offer new mechanisms of EM wave energy absorption [1-3]. However, earlier studies have investigated only special cases of magnetized plasma geometry [e.g., RL mode (k[over ⃗]||B[over ⃗]_{ext}) or (k[over ⃗]⊥B[over ⃗]_{ext}) X,O-mode configuration]. In these specific cases, EM waves encounter specific resonances [e.g., for (θ=0) cyclotron resonances, and for (θ=π/2), hybrid resonances]. A general case of EM wave propagation is at an oblique angle with respect to the externally applied magnetic field B[over ⃗]_{ext} considered here. Furthermore, the magnetic field is chosen to be inhomogeneous such that the EM wave pulse encounters a resonance layer within the plasma medium. A 2D particle-in-cell (PIC) simulation using the OSIRIS 4.0 platform has been carried out for these studies. A significant enhancement in absorption leading to almost complete absorption of laser energy by the plasma has been observed. A detailed study characterizing the role of the external magnetic field profile, EM wave intensity, etc., has also been carried out.

Comparison of Extremely Low Frequency Electromagnetic Waves in Different Parts of Residential Houses in Yazd City

Introduction: Extremely low frequency (ELF) waves are less than 300 Hz. Electrical devices with city electricity are one of the most important sources of generating ELF waves. The main objective of this research was to investigate and compare the magnetic fields produced by ELF electromagnetic fields (ELF-EMF) waves in different parts of residential houses in Yazd city. Material and Methods: Thirty-three houses were selected, and an EMF-828 was used (made in Taiwan) for ELF-EMF intensity measurement in three parts of the kitchen, living room, and bedroom and three modes of Normal, OFF, and ON electrical instruments. Results: Two-way ANOVA was used to compare two-by-two ELF waves in three modes: OFF, Normal, and ON. A significant value was obtained (p-value=0.036) in OFF and ON modes in the living room. Similar results were for kitchen (p-value=0.014) in two modes of ON and OFF. However, there was not a significant relationship (p&gt;0.05) between the mean intensity of ELF-EMF waves and the studied building parameters. Conclusion: The mean intensity of the ELF waves in different modes was not the same in kitchen and was in the order of ON&gt; Normal&gt; OFF that could be related to high-wave generation equipment. The comparison of mean intensity ​​of ELF-EMF waves in different locations of the investigated houses was much lower than the standard level set by ICNIRP. Preventing the simultaneous use of high-power electrical instruments led to both save consumption and reduce EMF-ELF waves exposure risk.