Energy Redistribution Research Articles

Noise mitigation in rectangular jets through plasma actuator-based shear layer control

A computational analysis is performed to study the three-dimensional response of rectangular shear layers to plasma actuator-based control, in the context of sound mitigation of supersonic non-axisymmetric jets. A Mach $1.5$ rectangular jet with an aspect ratio $2:1$ is controlled using experimentally informed actuation patterns, referred to as M0, M1, M2, M3, M ${\rm \pi}$ and M+/ $-$ 1. While the first five progressively increase the phase difference between successive actuators thus enhancing three-dimensionality of the shear layer structures, the latter corresponds to the flapping mode of the jet. A preliminary linear analysis identifies that the frequency, $St\sim 1$ , has a relatively high overall amplification within the baseline shear layer, and is hence utilized for control in the subsequent nonlinear simulations. Each actuation reveals unique near-field vortical and acoustic responses that have a profound impact on far-field noise levels. The M0 actuation induces circumferentially interconnected strong streamwise vortices, while M1 actuation enhances the circumferential variability in the coherent structures. The M2 actuation encompasses both these effects, and along with a very low tonal impact of forcing, produces the most desirable far-field noise mitigation ( ${\sim }2.6\,{\rm dB}$ ), contributed by a broadband reduction around the column-mode peak of the baseline jet. Beyond M2 actuation, effectiveness of control saturates, particularly along the direction of peak noise radiation. Through a near-field analysis of the acoustic component, the efficacy of M2 actuation is attributed to the attenuation of the radiative efficiency of the jet, including reduced energy in the supersonic phase speeds, and redistribution of energy into the higher helical modes. Further, it curtails the nonlinear difference interactions in the plume that energize column-mode frequencies, which often appear as strong intermittent sound-producing events. While the shear layer turbulent kinetic energy decreases with actuation, the controlled jets show minimal variations in mean flow properties, particularly under M2 actuation, suggesting this to be a promising small-perturbation-based noise control strategy.

Time-delayed characteristics of turbulence in pulsatile pipe flow

Direct numerical simulations are performed to study temporal variations of the wall shear stresses and flow dynamics in the turbulent pulsatile pipe flow. The mechanisms, responsible for the paradoxical phenomenon for which the amplitude of the oscillating wall shear stress in the turbulent flow is smaller than that in the laminar flow for the same pulsation conditions, are investigated. It is shown that the delayed response of turbulence in the buffer layer generates a large magnitude of the radial gradient of the Reynolds shear stress near the wall, which counteracts the effect of the oscillating pressure gradient on the change of the streamwise velocity and hence reduces the amplitude of the wall shear stress. Such a delayed response consists of two processes: the delayed development of near-wall streaks and the subsequent energy redistribution from the streamwise velocity fluctuation to the other two co-existing components. This is a dynamical manifestation of the viscoelasticity of turbulent eddies. As the frequency is reduced, the variation of the friction Reynolds number results in a phase-wise variation of the time scale and intensity of the turbulence response, causing the hysteresis of the wall shear stress. Such a phase asymmetry is amplified by the increase of the pulsation amplitude. An examination of the energy spectra reveals that the near-wall streaks are stretched in the streamwise direction during the acceleration phase, and then break up into small-scale structures in the deceleration phase, accompanied by the enhanced dissipation that transforms the turbulent kinetic energy into heat.

Research on energy redistribution of hybrid vehicle considering thermal constraints

Thermal management is one of the key factors affecting the performance of hybrid vehicles. However, most traditional energy management strategies lack the consideration of thermal constraints under harsh operating conditions. In this paper, taking a specific type of diesel-electric hybrid system as the research object, a strategy for energy redistribution under thermal management constraints is proposed. The diesel-electric hybrid system model is built and verified. Based on the model, the cooling capacity indexes are selected, and the weight coefficient of each cooling capacity index is determined by neighborhood component analysis. Then a comprehensive thermal evaluation system is obtained. Combined with the thermal evaluation system, the energy redistribution strategy based on the momentum gradient descent method is proposed. Two typical working conditions of high altitude and battery cooling system deterioration are selected, and the energy redistribution strategy is simulated and analyzed in real-time under both working conditions. The results show that the energy redistribution strategy can significantly improve the thermal state of the system at the expense of less overall energy consumption, take into account the economy and thermal balance, and ensure the reliable operation of the vehicle.

Transient-absorption spectroscopy of dendrimers via nonadiabatic excited-state dynamics simulations.

The efficiency of light-harvesting and energy transfer in multi-chromophore ensembles underpins natural photosynthesis. Dendrimers are highly branched synthetic multi-chromophoric conjugated supra-molecules that mimic these natural processes. After photoexcitation, their repeated units participate in a number of intramolecular electronic energy relaxation and redistribution pathways that ultimately funnel to a sink. Here, a model four-branched dendrimer with a pyrene core is theoretically studied using nonadiabatic molecular dynamics simulations. We evaluate excited-state photoinduced dynamics of the dendrimer, and demonstrate on-the-fly simulations of its transient absorption pump-probe (TA-PP) spectra. We show how the evolutions of the simulated TA-PP spectra monitor in real time photoinduced energy relaxation and redistribution, and provide a detailed microscopic picture of the relevant energy-transfer pathways. To the best of our knowledge, this is the first of this kind of on-the-fly atomistic simulation of TA-PP signals reported for a large molecular system.

Probing parton propagation in heavy-ion collisions with ALICE heavy-flavour measurements

Heavy quarks (charm and beauty) are valuable probes for investigating the properties of the quark–gluon plasma (QGP) formed in ultra-relativistic heavy-ion collisions, as they are mainly produced through hard-scattering processes prior to the formation of the QGP, and their number is conserved during the subsequent QGP evolution. Measurements of the nuclear modification factor RAA of charm and beauty hadrons allow us to characterise the in-medium energy loss of heavy quarks while traversing the QGP. Information on their diffusion and degree of participation in the collective motion of the medium can be obtained by measuring the elliptic-flow coefficient v2 of heavy-flavour particles. Complementary insights into heavy-quark fragmentation and energy redistribution can be obtained by measuring angular correlations involving heavy-flavour particles. In this contribution, the recently published results on the non-prompt v2 coefficient of D0 mesons are presented, comparing them with those of other particle species in Pb–Pb collisions at √SNN = 5.02 TeV. Additionally, we report the recent findings on the RAA of prompt D mesons and Λc+ baryons in Pb–Pb collisions at the same energy. Furthermore, we discuss the new Pb–Pb results on angular correlations between heavy-flavour decay electrons and charged particles in the same collision system.

Electronic energy transfer ionization in naphthalene-CO2 clusters reveals excited states of dry ice.

Electronic energy relaxation and transfer shapes the photochemistry in molecules and materials that are exposed to UV radiation in areas ranging from astrochemistry to biology. The interaction between CO2 and polycyclic aromatic hydrocarbons (PAHs) specifically, is of paramount interest in astrochemically relevant ices, the transition to renewable energy and the development of green chemistry. We investigate the vacuum UV excitation of the naphthalene-CO2 complex and observe excited states of CO2 through a newly identified molecular electronic energy transfer ionization mechanism. We evaluate the spectral development upon cluster growth with time-dependent density functional theory and show that the photoionization spectrum of naphthalene-CO2 closely resembles the photon-stimulated desorption spectrum of CO2 ice. The molecular electronic energy transfer ionization mechanism may affect the energy redistribution and charge balance in the interstellar medium significantly and therefore we discuss its implications for astrochemical models.

Scattering kernel of an array of floating ice floes: application to water wave transport in the marginal ice zone

A radiative transfer model of water wave scattering in the marginal ice zone is considered. In this context, wave energy redistribution across the directional components of the spectrum as a result of scattering by the constituent ice floes is typically modelled via a scattering kernel describing the far-field directionality of the scattered wave field produced by a single floe in isolation. Recognizing the potential importance of the floe size distribution (FSD) on wave scattering, we propose an enhanced scattering kernel constructed from the far-field scattering pattern of a circular array of floes. This is achieved by solving the self-consistent multiple scattering of a time-harmonic plane wave by a large array of floating circular floes with radii sampled from a prescribed FSD. A fast multipole method is implemented to accelerate the numerical estimation of the solution. Simulations are then conducted to characterize the properties of the scattering kernel for a range of configurations. It is found that the scattering kernel obtained for a wide array has a large, narrow transmission peak in the forward direction, while it uniformizes low-amplitude scattered waves in other directions. An idealized application to radiative transfer theory is also considered.

Jet energy redistribution and broadening using hadron+jet measurements in pp and Pb–Pb collisions with ALICE

In this contribution we present measurements of the semi-inclusive distributions of charged jets recoiling from a trigger hadron (hadron+jet) in pp and Pb–Pb collisions, which provide unique probes of medium-induced modification of jet production. We observe that the jet yield at low pT and at large azimuthal angle between the trigger hadron and jet is significantly enhanced in Pb–Pb collisions with respect to pp collisions, which we interpret through comparisons to model calculations.

Optimizing Energy Distribution and Utilization in Multi-Building Complexes Using Effective Thermal Storage Systems and Renewable Energy Sharing

An increase in renewable energy sources and a subsequent need for more energy-efficient construction practices have prompted efforts to optimize energy distribution networks. Various building types, including residential, hotel, and hospital structures, may benefit from solar-based integrated energy systems (SIES) that include energy-sharing mechanisms and Effective Thermal Storage Systems (ETSS). This new approach is presented in the present research. In this paper a new optimization model is proposed that consider the correlation of energy storage system with fluctuating load demands of the building (BL). This theology makes it possible for any building with high energy demand in the day to trade excess power with another building which has low demand during the same time. From the simulation we get that grid power consumption is reduced from homes by 15%, hotels by 12% and hospitals by 18% through use of energy-sharing and Energy Transfer System (ETSS). Efficient energy redistribution management also helps increase the consumption of renewable resources by 20%. The proposed method led to a cumulative increase in the overall efficiency by 12% compared to the control strategy by optimizing the energy supply and demand in various sorts of buildings. Comparing our method with the previous work clearly shows that using the proposed approach yields better energy saving and higher usage of renewable energy sources because the method takes into consideration building plan and load profile. These results serve as a foundation for integrated energy systems of a smart city solution that incorporates ETSS and energy sharing.

Probing the amplitude modulation and pulsational energy re-distribution in the oscillation of HD 137949

We present the result of over 50-h of Johnson-B photometric observation of HD 137949. These high-speed photometric data were acquired between June 12 and August 19 2013 using the 0.5-m telescope of the South African Astronomical Observatory (SAAO). The result of our frequency analysis when compared with that of similar B-light photometric data obtained in 1981 and 1987 using the same telescope reveals the existence of a long-term stability in its principal frequency of oscillation at ν1=2.014781±0.000003 mHz; even with the excitation of two new secondary oscillations (ν2=2.016787±0.000006 mHz; ν3=2.012628±0.000009 mHz). On the contrary, the signature of its principal amplitude of oscillation (A) was found to have changed drastically within a time-span of about three decades. However, the aggregate amplitude (∑A) of all the detected oscillations was observed to have remained constant within the period under investigation. In addition, HD 137949 was observed to have undergone pulsational energy re-distribution within this time-span of about three decades; with a signature that is suggestive of non-conservation of its total energy (pulsational). We discuss the possible implications of the recently observed dynamics in the oscillation-signature of HD 137949.

New theoretical approach to dynamics of heat-mass-transfer, thermal turbulence and air ventilation in atmosphere of an industrial city II. Spectrum of thermal turbulence

In this paper we go on a development of consistent theoretical approach to modelling the turbulent regime in the atmosphere of the industrial cities and present the analytical foundations of a new model of thermal turbulence spectrum for atmosphere of an industrial city. Special attention is paid to general analytical aspects for accounting of the phenomenon of wave or vortex diffusion, which is usually ignored in most works on atmospheric ventilation modelling. Redistribution of energy over the spectrum of eddy sizes is usually called a spectral transformation, the study of which is possible only under the condition of real introduction of nonlinearity into the equation of turbulent motion. The approach presented is implemented into the general theory of heat-mass-transfer, thermal turbulence and air ventilation in atmosphere of an industrial city, including an improved theory of atmospheric circulation in combination with the hydrodynamic modelling, method of a complex geophysical plane field and the Arakawa-Schubert approach to a quantitative description of convective instability in the city’s atmosphere.

The method of virtual bench tests conducting to analyze the vehicle technical characteristics compatibility to detect and prevent the risk of resonant phenomena in the sprung cab

BACKGROUND: A relevant issue when designing vehicles with multiple levels of suspension systems is collaborative operation of these systems, which ensures the required vehicle dynamics and smoothness parameters, as well as the absence of risk for the occurrence of resonance phenomena. The vehicle cab is a dynamic system with 6 degrees of freedom, so its oscillatory motions have a complex spatial character with the oscillation energies overflow from one direction to another. The solving of problems of the sprung cab dynamics should be conducted in a spatial nonlinear formulation, which makes it possible to take into account the phenomena of redistribution of oscillation energy between the directions of space. This approach can be put into operation with simulation modeling methods through creating a spatial virtual rig of the cab with a suspension system and modeling its dynamics with the application of appropriate external inputs.
 AIM: Development of the method of using virtual tests to analyze the compatibility of technical characteristics of the cab suspension system, the frame system and the primary vehicle suspension systems to detect and prevent the risk of resonant phenomena in the cab.
 METHODS: Building a virtual test rig of a vehicle cab as a multibody dynamics system of connected bodies in space, mounted at the movable vehicle frame with spring-dampers. Virtual tests are conducted by simulation modeling methods according to the method for analyzing nonlinear phenomena when spatial resonances occur in the secondary suspension system of a vehicle cab.
 RESULTS: The method of vehicle cab virtual tests conducting for analyzing oscillatory processes occurring in the cab, including resonances, using a virtual test rig in a multibody dyamics software package.
 CONCLUSION: The developed method ensures an ability to take measures to detect and prevent the risk of spatial resonance phenomena in the vehicle cab at all stages of the components design and the cab suspension systems study.

Effect of friction and obstruction on the dynamics of a curved pipe conveying fluid with fixed ends

A dynamic model for a curved pipe conveying fluid with fixed ends is formulated using the extended Hamilton’s principle. The external work done by the pump to overcome the frictional head loss and a semi-venturi model for the obstruction to the flow in the pipe are modelled. An eigenvalue analysis is conducted followed by a convergence study of the natural frequencies. The pipe vibration experiments are performed for a pulse velocity excitation to validate the computed natural frequencies. The influence of friction, curvature and obstruction on the eigenvalues of the system are studied using the developed model. In the absence of friction, the effect of small curvature on the dynamics of the pipe is found to be negligible and the higher curvature is observed to delay divergence instability. The presence of friction induces stiffness which delays divergence and flutter instability velocity, prominently at higher curvature. Similarly, the obstruction also delays flutter for higher curvature pipes. Both friction and obstruction have a stabilising effect at higher curvature at higher flow velocity. The presence of sharp bend or a sharp change in curvature is observed to initiate dynamic instability at very low flow velocity compared to the pipes without sharp bends. The influence of curvature and obstruction on the vibration of the pipe is studied from the experiments. The curvature and obstruction enhance energy redistribution and excitation in the experiments. The trends observed in the computed acceleration responses are in close comparison with the experimental responses. The effect of flutter instability is also observed at higher flow velocity in the experimental responses as predicted by the model.

Multi‐Instruments Observation of Ionospheric‐Thermospheric Dynamic Coupling Over Mohe (53.5°N, 122.3°E) During the April 2023 Geomagnetic Storm

AbstractThe state and variations of the Ionosphere‐Thermosphere (I‐T) system are strongly influenced by dynamical processes, with these effects being amplified during intense space environment disturbances such as geomagnetic storms, producing multi‐scale disturbance features in the I‐T system. The redistribution of energy and momentum through the dynamical processes is currently not well understood. Unfortunately, the dearth of thermospheric observations has yielded limited studies capable of monitoring and analyzing the I‐T dynamical coupling during storms using co‐located measurements. This work examines the responses of the I‐T system during the April 2023 geomagnetic storm based on high‐resolution continuous I‐T system observations at Mohe observatory, a middle latitude station. Both large‐scale features and short‐period oscillations were identified in multiple key parameters of the I‐T system. Similar disturbed patterns in thermospheric winds occurred during the main and recovery phases of the geomagnetic storm. However, the oscillation features in many parameters of the I‐T system are only observed during the main phase. The results of concurrent I‐T system observations unveil the oscillation features of thermospheric winds, temperatures, the ionospheric F2 peak height, electron density, and total electron content. These findings reveal the important influence of wind divergence on thermospheric temperature disturbances and its modulatory effect on ionospheric disturbances.

Turbulent kinetic energy redistribution in a gravity current interacting with an emergent cylinder

Gravity currents are flows driven by density gradients between two or more contacting fluids and play a key role in nature and industrial environments via global ocean circulations, climate variability and the distribution of airborne pollutants. In the present work, we study, experimentally, the changes induced by an emergent vertical PVC cylinder on the mean and turbulent flow fields of an unsteady bottom-generated lock release gravity current. Tests were carried out, with and without the cylinder, in refractive index matching conditions and instantaneous velocities were acquired with a Particle Image Velocimetry system. The mean velocity field, Reynolds stresses and terms of turbulent kinetic energy (TKE) budget for the currents head were presented and discussed. The results show that the adverse pressure gradient generated by the cylinder induces a uniform deceleration of the current head. Hence, there are no appreciable differences on the spatial distribution of the mean velocities in the current head, compared to the undisturbed current. On the other hand, the changes on the turbulent flow field are remarkable. The total diffusion of TKE decays in the inner part of the head while becoming stronger at the interface between the two fluids, as the current approaches the cylinder. This is associated to an increase of the diffusion term due to pressure fluctuations, that acts against diffusion due to velocity fluctuations and contributes to disrupt the transport of TKE from the interface between the fluids and the inner part of the current. As a result, in the presence of an obstacle, Reynolds stresses are suppressed in the inner part of the current head and enhanced at the interface.

Evolution processes and diagenetic response of paleo-pore fluids in continental rift basin: A case study of Bonan Sag

Evolution and transport processes of pore fluids are accompanying with the burial process of sedimentary basins. Those processes lead to redistribution of materials and energies, and control the distribution of favorable reservoirs in sedimentary basins too. For petroliferous basins, confirming the evolution processes of pore fluids is useful for favorable reservoirs prediction. In this study, formation waters chemistry characteristics, skeleton particle compositions, and diagenetic products of sandstones were all take into consideration. It is to invert the evolution processes of pore fluids in continental rift basin. This study shows the changes of formation waters, diagenetic products and skeleton particle compositions are regularly with depth. The evolution processes of pore fluids are mainly controlled by basin sinking and uplifting, fluids concentration, mudstones compaction, organic matter evolution, diagenesis. The evolution of pore fluids in Bonan Sag have experienced seven stage: firstly, primary lake water; and then alkaline fluids from mudstone, which is caused by compaction; and then acidic fluids with organic acids; and then the alkaline fluids, which is caused by basin uplifting and water-rock interactions; and then acidic fluids with CO2, which is from cracking of organic matters; and then acidic fluids with CO2/H2S which caused by TSR; at last, alkaline fluids caused by deep buried and water-rock interactions. Changes of pore fluids (physical or chemical) lead parts of minerals in sandstones be unstable, and then dissolved by pore fluids. At the same time, part of dissolved particles in pore fluids reacted with each other, and then precipitated as diagenetic products.

Carbon and water relationships change nonlinearly along elevation gradient in the Qinghai Tibet Plateau

The influence of terrain elevation on carbon and water ecosystem services, mediated by heat and energy redistribution, has significant implications for the Qinghai Tibet Plateau (QTP). Renowned as the “Third Pole of the Earth” and the “Water Tower of Asia,” the QTP boasts the planet’s most extensive elevation range. However, understanding the intricate effects of the elevation gradient (EG) on carbon and water services and their interrelationships remains limited. In this study, we deploy the moving window method (MWM), the generalized additive model (GAM), and the structural equation model (SEM) to explain the dynamics of ecosystem service relationship across the EG. Our analysis, spanning 2000 to 2018, reveals annual mean values of carbon storage (CS) at 50.45 tC/ha and water yield (WY) at 246.14 mm for the QTP. The results highlight the importance of the carbon–water trade-off and the pronounced CS reduction in the south-central plateau under varying EG, alongside the harmonized interactions in the northeast and southern sectors. GAM outcomes show a non-linear association between ecosystem service relationship and EG. With elevational ascent, the correlation between the digital elevation model (DEM) and CS transitions from positive to negative, and the ecosystem service relationship transitions from synergy to trade-off. In the QTP, the explanatory force of inherent meteorological factors in shaping CS and WY surpasses that of all socio-economic factors, with the latter wielding greater influence over ecosystem service relationship dynamics. The insights from this investigation provide a foundation for integrating intricate terrain gradients into strategies aimed at alleviating potential adverse ramifications for human well-being.

Photodissociation dynamics of m- and p-cresol in the S1 state: Interplay between the mode-randomization and H atom tunneling reaction.

The H atom tunneling dissociation dynamics of the S1 state of meta- or para-cresol has been investigated by using the picosecond time-resolved pump-probe spectroscopy in a state-specific manner. The S1 state lifetime (mainly due to the H atom tunneling reaction) is found to be mode-dependent whereas it quickly converges and remains constant as the rapid intramolecular vibrational energy redistribution (IVR) starts to participate in the S1 state relaxation with the increase of the S1 internal energy (Eint). The IVR rate and its change with increasing Eint have been reflected in the parent ion transients taken by tuning the total energy (hνpump + hνprobe) just above the adiabatic ionization threshold (so that the dissipation of the initial mode-character could be monitored as a function of the reaction time), indicating that the mode randomization rate into the S1 isoenergetic manifolds exceeds the tunneling rate quite early in terms of Eint for m-cresol (≤∼1200cm-1) or p-cresol (≤∼800cm-1) compared to the case of phenol (≤∼1800cm-1). Though the H atom tunneling dynamics of phenol (S1) seems to be little influenced by the methyl substitution on the either m- or p-position, the IVR rate has been found to be strongly accelerated due to the sharply-increasing (S1) density of states with increasing Eint due to the pivotal role of the low-frequency CH3 torsional mode.

The importance of terrain factors in the spatial variability of plant cover diversity in a steppe gully

Information about the slope angle and its exposure is often given when describing plant communities. However, the slope angle should be noted to affect a complex of different phenomena and processes. The slope angle affects the albedo and thermal regime of the soil. The slope angle affects the redistribution of moisture and determines the moisture availability of a particular area. The slope angle also determines the risks of erosion processes. In turn, erosion processes determine the depth of the soil layer and the content of organic matter in it, which greatly affects the conditions for plant life and their dynamics. Therefore, the slope angle of the relief is a complex environmental indicator, which is its most important weakness. The information on the slope angle of the relief surface does not indicate which environmental factor is limiting and determines the characteristics of the vegetation cover. Similarly, the quantitative orientation of a slope using rhumb lines is a rather crude way to indicate the role of terrain in the redistribution of solar energy. With a certain degree of accuracy, rhumbs characterize incoming solar radiation, but are not sensitive to estimating the amount of diffuse radiation. Modern geoinformation technologies make it possible to determine the amount of solar radiation reaching the terrain surface using a digital elevation model. The aim of the article was to identify the role of relief factors in terms of topographic wetness index, erosion index, and solar radiation in the spatial variability of the vegetation diversity of a steppe gully. There was no linear correlation between the other predictors. Some correlations can be interpreted as the result of certain nonlinear patterns. In this sense, the geomorphological predictors are mostly linearly independent and thus each of them carries independent information for characterizing environmental conditions. The vegetation cover of the gully system was represented by 263 plant species. The analysis of the synoptic phytosociological table allowed us to find out that the vegetation cover of the studied gully system is represented by six classes of vegetation. The geomorphological predictors allowed for a classification of vegetation types with an accuracy of 23.8% to 100%. The topographic wetness index was the most important for classification. Altitude and insolation were also important for classification (94 and 95 respectively). The topographic wetness index provided an accurate identification of wetland vegetation of the Phragmito-Magnocaricetea class. Naturally, this type of vegetation preferred biotopes with the highest level of soil moisture. High insolation accurately labeled the locations where Festuco-Brometea steppe vegetation was most likely to be found. Some of the artificial tree plantations that occurred in the thalweg of the gully can be clearly identified by the high level of the topographic wetness index. Another group of artificial tree plantations is located on relatively high relief areas and should be differentiated from Galio-Urticetea communities, which prefer locations with higher light levels, and from Molinio-Arrhenatheretea, which prefer locations with a higher risk of erosion. The most arid locations are preferred by Agropyretalia intermedio-repentis vegetation. Steppe and meadow vegetation located at altitudes less than 116 meters also differ in their preferred height. Steppe vegetation is usually located at a level higher than 95 meters. Natural steppe and meadow vegetation at elevations below 116 meters differs from semi-natural Galio-Urticetea vegetation in that the latter usually prefers more well lit locations. Steppe communities are misclassified as meadow in 15.3% of cases, and meadow is misclassified as steppe in 18.5% of cases. Artificial tree plantations are misclassified as steppe in 42.9% of cases and 14.3% are misclassified as Agropyretalia intermedio-repentis. In its turn, Agropyretalia intermedio-repentis is misclassified as Festuco-Brometea in 6.7% of cases, as Molinio-Arrhenatheretea or Onopordetalia acanthii in 3.3% of cases, and as Galio-Urticetea in 10.0% of cases. The Onopordetalia acanthii community was misclassified as Festuco-Brometea, Molinio-Arrhenatheretea and Galio-Urticetea in 6.7% of cases, respectively.

Scattering and enhancement of electromagnetic waves energy by coaxial plasma cylinders

The scattering of plane electromagnetic waves by three configurations of coaxial plasma cylinders is investigated in perpendicular incidence.‏ The results show that the electromagnetic energy enhancement and redistribution of energy are significantly affected by plasma frequency, electron neutral collision frequency, incident wave frequency, and the configuration of coaxial plasma cylinders. With increasing the collision frequency at fixed plasma frequency and incident wave frequency, the maximum relative energy density of the focal spot increases, and with a further increase in the collision frequency, the maximum relative energy density of the focal spot reaches some maximum value and begins to decrease. Furthermore, for fixed values of collision and plasma frequencies, at incident frequencies where the focal length is large, the maximum relative energy density is small. One main result obtained in this research indicates that the energy enhancement at the focal spot for TM polarization scattering is more than for TE mode. The results of this paper may be used for applications related to the redistribution and enhancement of electromagnetic energy.