Fluctuation Level Research Articles

The effect of scattering instability induced by high intensity seed on backward Raman amplification

Backward Raman amplification (BRA) in plasma has become one of the most promising techniques for further promoting light intensity. In this work, BRA in plasma is simulated using one-dimensional particle-in-cell code with different seed intensity, showing that higher seed intensity (in the range of 2×1011–2×1015 W/cm2) will increase energy conversion efficiency with pump pulse of fixed intensity (2×1014 W/cm2), which is pre-depleted by spontaneous Raman scattering. We find that the scattering instability of amplified seed pulse is enhanced and the plasma wave fluctuation level is promoted with seed intensity at 2×1016 W/cm2 because the local plasma density changes in the pump scattering depletion region. In the simulations, we also found that the enhanced Raman scattering and secondary Raman scattering of amplified seed pulse causes a rapid energy consumption and earlier saturation of the amplification, which significantly affects the temporal shape of the amplified seed pulse to form a double peak shape. In addition, we explore the evolution of the energy and the pulse duration of the double peaks in detail and reveal the law of pulse energy growth with different pulse durations in a Raman amplifier.

Dietary supplementation of vitamin D3 and calcium partially recover the compromised time budget and circadian rhythm of lying behavior in lactating cows under heat stress

Heat stress (HS) impedes cattle behavior and performance and is an animal comfort and welfare issue. The objective of this study was to characterize the time budget and circadian rhythm of lying behavior in dairy cows during HS and to assess the effect of dietary supplementation of vitamin D3 and Ca. Twelve multiparous Holstein cows (42.2 ± 5.6 kg milk/d; 83 ± 27 d in milk) housed in tiestalls were used in a split-plot design with the concentration of dietary vitamin E and Se as main plots (LESe: 11.1 IU/kg and 0.55 mg/kg, and HESe: 223 IU/kg and 1.8 mg/kg, respectively). Within each plot cows were randomly assigned to (1) HS with low concentrations of vitamin D3 and Ca (HS, 1,012 IU/kg and 0.73%, respectively), (2) HS with high concentrations of vitamin D3 and Ca (HS+D3/Ca; 3,764 IU/kg and 0.97%, respectively), or (3) thermoneutral pair-fed (TNPF) with low concentrations of vitamin D3 and Ca (1,012 IU/kg and 0.73%, respectively) in a Latin square design with 14-d periods and 7-d washouts. Lying behavior was measured with HOBO Loggers in 15-min intervals. Overall, cows in HS spent less time lying per day relative to TNPF from d 7 to 14. Daily lying time was positively correlated with milk yield, energy-corrected milk yield, and feed efficiency, and was negatively correlated with rectal temperature, respiratory rate, fecal calprotectin, tumor necrosis factor-α, and C-reactive protein. A treatment by time interaction was observed for lying behavior: the time spent lying was lesser for cows in HS than in TNPF in the early morning (0000-0600 h) and in the night (1800-2400 h). The circadian rhythm of lying behavior was characterized by fitting a cosine function of time into linear mixed model. Daily rhythmicity of lying was detected for cows in TNPF and HS+D3/Ca, whereas only a tendency in HS cows was observed. Cows in TNPF had the highest mesor (the average level of diurnal fluctuations; 34.2 min/h) and amplitude (the distance between the peak and mesor; 17.9 min/h). Both the mesor and amplitude were higher in HS+D3/Ca relative to HS (26.6 vs. 25.2 min/h and 3.91 min/h vs. 2.18 min/h, respectively). The acrophase (time of the peak) of lying time in TNPF, HS, and HS+D3/Ca were 0028, 0152, and 0054 h, respectively. Lastly, a continuous increase in daily lying time in TNPF was observed during the first 4 d of the experimental period in which DMI was gradually restricted, suggesting that intake restrictions may shift feeding behavior and introduce biases in the behavior of animals. In conclusion, lying behavior was compromised in dairy cows under HS, characterizing reduced daily lying time and disrupted circadian rhythms, and the compromised lying behavior can be partially restored by supplementation of vitamin D3 and Ca. Further research may be required for a more suitable model to study behavior of cows under HS.

Stochastic modeling of spatially-dependent elastoplastic parameters in 316L stainless steel produced by direct energy deposition

The stochastic modeling and calibration of an anisotropic elasto-plastic model for additive manufacturing materials are addressed in this work. We specifically focus on 316L stainless steel, produced by directed energy deposition. Tensile specimens machined from two additive manufactured (AM) box-structures were used to characterize material anisotropy and random spatial variations in elasticity and plasticity material parameters. Tensile specimens were cut parallel (horizontal) and perpendicular (vertical) to the AM deposition plane and were indexed by location. These results show substantial variability in both regimes, with fluctuation levels that differ between specimens loaded in the parallel and perpendicular build directions. Stochastic representations for the stiffness and Hill’s criterion coefficients random fields are presented next. Information-theoretic models are derived within the class of translation random fields, with the aim of promoting identifiability with limited data. The approach allows for the constitutive models to be generated on arbitrary geometries, using the so-called stochastic partial differential approach (to sampling). These representations are then partially calibrated using the aforementioned experimental results, hence enabling subsequent propagation analyses. Sampling is finally exemplified on the considered structure.

An Anisotropic Density Turbulence Model from the Sun to 1 au Derived from Radio Observations

Solar radio bursts are strongly affected by radio-wave scattering on density inhomogeneities, changing their observed time characteristics, sizes, and positions. The same turbulence causes angular broadening and scintillation of galactic and extragalactic compact radio sources observed through the solar atmosphere. Using large-scale simulations of radio-wave transport, the characteristics of anisotropic density turbulence from 0.1 R ⊙ to 1 au are explored. For the first time, a profile of heliospheric density fluctuations is deduced that accounts for the properties of extrasolar radio sources, solar radio bursts, and in situ density fluctuation measurements in the solar wind at 1 au. The radial profile of the spectrum-weighted mean wavenumber of density fluctuations (a quantity proportional to the scattering rate of radio waves) is found to have a broad maximum at around (4–7) R ⊙, where the slow solar wind becomes supersonic. The level of density fluctuations at the inner scale (which is consistent with the proton resonance scale) decreases with heliocentric distance as cm−6. Due to scattering, the apparent positions of solar burst sources observed at frequencies between 0.1 and 300 MHz are computed to be essentially cospatial and to have comparable sizes, for both fundamental and harmonic emission. Anisotropic scattering is found to account for the shortest solar radio burst decay times observed, and the required wavenumber anisotropy is q ∥/q ⊥ = 0.25–0.4, depending on whether fundamental or harmonic emission is involved. The deduced radio-wave scattering rate paves the way to quantify intrinsic solar radio burst characteristics.

Unusually long path length for a nearly scatter-free solar particle event observed by Solar Orbiter at 0.43 au

Context. After their acceleration and release at the Sun, solar energetic particles (SEPs) are injected into the interplanetary medium and are bound to the interplanetary magnetic field (IMF) by the Lorentz force. The expansion of the IMF close to the Sun focuses the particle pitch-angle distribution, and scattering counteracts this focusing. Solar Orbiter observed an unusual solar particle event on 9 April 2022 when it was at 0.43 astronomical units (au) from the Sun. Aims. We show that the inferred IMF along which the SEPs traveled was about three times longer than the nominal length of the Parker spiral and provide an explanation for this apparently long path. Methods. We used velocity dispersion analysis (VDA) information to infer the spiral length along which the electrons and ions traveled and infer their solar release times and arrival direction. Results. The path length inferred from VDA is approximately three times longer than the nominal Parker spiral. Nevertheless, the pitch-angle distribution of the particles of this event is highly anisotropic, and the electrons and ions appear to be streaming along the same IMF structures. The angular width of the streaming population is estimated to be approximately 30 degrees. The highly anisotropic ion beam was observed for more than 12 h. This may be due to the low level of fluctuations in the IMF, which in turn is very probably due to this event being inside an interplanetary coronal mass ejection The slow and small rotation in the IMF suggests a flux-rope structure. Small flux dropouts are associated with very small changes in pitch angle, which may be explained by different flux tubes connecting to different locations in the flare region. Conclusions. The unusually long path length along which the electrons and ions have propagated virtually scatter-free together with the short-term flux dropouts offer excellent opportunities to study the transport of SEPs within interplanetary structures. The 9 April 2022 solar particle event offers an especially rich number of unique observations that can be used to limit SEP transport models.

Dynamic Fluctuation Measurement and Factor Decomposition of China’s Export Growth to Japan and South Korea in the Context of COVID-19

In the context of the COVID-19, it is very significant to explore the dynamic fluctuation of China’s export growth to the international market and examine the causes of this fluctuation in a multi-dimensional way. The dynamic fluctuation level is measured in the short and medium-long cycle respectively based on monthly data. Factor decomposition of the dynamic fluctuation is made from the growth effect, the structure effect and the competitiveness effect by the improved CMS model, which results show that the growth effect has decreased first and then increased; The structure effects include market structure effects and commodity structure effects, and the former effect basically fluctuates around the X-axis while there is a negative commodity structure effect; There are different specific competitiveness effects on 21 categories of goods. China should rely on the RCEP agreement to strengthen and stabilize trade cooperation other countries, and strengthen its core position in the industry chain and value chain in the Asia Pacific region. The current paper creatively introduce the trade expansion margin including the ternary margin and product structure into the CMS model, explaining the internal relationship between the trade expansion margin analysis at the product- market level and the CMS analysis at the overall level; meanwhile, this paper analyses the dynamic fluctuation structure of China’s export growth to Japan and South Korea through a CMS factor decomposition from the perspective of technological structure and factor ladder, and studies the source and dynamic distribution evolution of this growth pattern.

실증적 분석을 통한 지방교육재정교부금의 다원화 방안 탐색

The purpose of this study is to propose a plan to diversify grants in order to effectively respond to the conflicting demand forecasts of the education community and fiscal authorities at a time when the school-age population is continuously declining, and to secure the stability of local education finance. In particular, we focused on examining how to separate salary grants in light of the high proportion of labor costs as a fixed expense due to the nature of educational activities. To this end, the study empirically compares and analyzes the future outlook of local education finance under the unified funding structure linked to national taxes following the reorganization of the local education finance grant system in 2004, and under the separate funding structure linked to national taxes for salary grants, which was operated until then.
 The research findings are as follows: First, when comparing the combined results of the salary grant and other national tax grants calculated based on labor costs by school level with the current national tax grant, the current national tax grant is less from 2005 to 2016, but the current national tax grant is more from 2017 onwards. Second, when the salary grant was separated from the national tax grant, the financial stability of the grant was found to be greater. In other words, the level of fluctuation was not as large as that of the national tax-linked grant, which is currently unified, and the size of the overall grant was somewhat reduced.

Comparison of Motor Evoked Potentials Neuromonitoring Following Pre- and Postoperative Transcranial Magnetic Stimulation and Intraoperative Electrical Stimulation in Patients Undergoing Surgical Correction of Idiopathic Scoliosis.

The relationships between the results of pre- and intraoperative motor evoked potential recordings during neuromonitoring and whether idiopathic scoliosis (IS) surgical correction improves the spinal efferent transmission have not been specified in detail. This study aims to compare the results of surface-recorded electromyography (EMG), electroneurography (ENG, M, and F-waves), and especially motor evoked potential (MEP) recordings from tibialis anterior muscle (TA) bilaterally in 353 girls with right idiopathic scoliosis (types 1-3 according to Lenke classification). It has not yet been documented whether the results of MEP recordings induced by transcranial single magnetic stimulus (TMS, pre- and postoperatively) and trains of electrical stimuli (TES; intraoperatively in T0-before surgery, T1-after pedicle screws implantation, and T2-after scoliosis curvature distraction and derotation following two-rod implantation) can be compared for diagnostic verification of the improvement of spinal cord neural transmission. We attempted to determine whether the constant level of optimal anesthesia during certain surgical steps of scoliosis treatment affects the parameters of MEPs recorded during neuromonitoring procedures. No neurological deficits have been observed postoperatively. The values of amplitudes but not latencies in MEP recordings evoked with TMS in IS patients compared before and after surgery indicated a slight improvement in efferent neural transmission. The results of all neurophysiological studies in IS patients were significantly asymmetrical and recorded worse on the concave side, suggesting greater neurological motor deficits at p = 0.04. The surgeries brought significant improvement (p = 0.04) in the parameters of amplitudes of sEMG recordings; however, the consequences of abnormalities in the activity of TA motor units were still reflected. ENG study results showed the symptoms of the axonal-type injury in peroneal motor fibers improving only on the concave side at p = 0.04, in parallel with F-wave parameters, which suggests that derotation and distraction might result in restoring the proper relations of the lumbar ventral roots in the spinal central canal, resembling their decompression. There were no significant differences detected in the amplitudes or latencies of MEPs induced with TMS or TES when comparing the parameters recorded preoperatively and intraoperatively in T0. The amplitudes of TES-evoked MEPs increased gradually at p = 0.04 in the subsequent periods (T1 and T2) of observation. A reduction in MEP latency at p = 0.05 was observed only at the end of the IS surgery. Studies on the possible connections between the level of anesthesia fluctuations and the required TMS stimulus strength, as well as the MEP amplitude changes measured in T0-T2, revealed a lack of relationships. These might not be the factors influencing the efferent transmission in spinal pathways beside the surgical procedures. Pre- (TMS-evoked) and intraoperative (TES-evoked) recordings are reliable for evaluating the patient's neurological status before and during surgical scoliosis correction procedures. An increase in MEP amplitude parameters recorded on both sides after scoliosis surgery proves the immediate improvement of the total efferent spinal cord transmission. Considering comparative pre- and postoperative sEMG and ENG recordings, it can be concluded that surgeries might directly result in additional lumbar ventral root decompression. We can conclude that MEP parameter changes are determined by the surgery procedures during neuromonitoring, not the anesthesia conditions if they are kept stable, which influences a decrease in the number of false-positive neuromonitoring warnings.

Fluid-Dynamic and Aeroacoustic Characterization of Side-by-Side Rotor Interaction

An investigation of twin corotating rotors’ interaction effects was performed by load (thrust and torque) measurements, flow field dynamics through Time-Resolved Particle Image Velocimetry, and acoustic emissions using a microphone array. Two rotors, each with a diameter of D = 393.7 mm and equipped with three blades, were investigated in a side-by-side configuration, to simulate a multirotor propulsion system. The mutual distance between the propellers is 1.02 D, and four different rotating speeds, i.e., 2620, 3500, 4360, and 5200 RPM, were explored. In such a configuration, thrust and torque undergo a reduction compared to that found for a single propeller configuration. The level of aerodynamic load fluctuations increases as well. The interaction of the wakes produces a recirculation region at the external periphery of the shear layers. An innovative approach involving the coupling of Proper Orthogonal Decomposition (POD) and Wavelet Transform has been employed to investigate the dominant structures within the flow and their mutual influence. The results reveal that the interacting wakes are dominated by a wave-like motion pulsating at Harmonics of the Blade Passing Frequency (HBPF) of 1/3. Higher orders of POD modes capture coherent vortical structures, including tip vortices pulsating at HBPF = 1. The aeroacoustic investigation shows that the noise level, in terms of the Over All Sound Pressure Level, presents a remarkable increment concerning that generated by the single propeller.

A model of correlated interval–probabilistic conditional value-at-risk and optimal dispatch with spatial correlation of multiple wind power generations

The correlated uncertain variables with the probability density function have been conducted in previous studies. However, the probability density functions of random variables are not always available, but their boundaries are more readily obtained. Accordingly, this paper adopts the interval variables with spatial correlation in multiple wind generations to achieve more practical scheduling. First, a novel risk qualification model, that is, correlated interval-probabilistic-based conditional value-at-risk, can be proposed to reduce the conservativeness of the traditional risk assessment methods. Then, an uncertain optimization model is built that considers multiple uncertainties, including probabilistic uncertainties of the load and interval uncertainties of coupled adjacent wind farms. Moreover, two spinning reserves are developed and integrated into the dispatch model. Finally, the influence of the wind power generation's correlation and fluctuation levels on the dispatch results is also investigated. Simulations on IEEE-39 and IEEE-118 bus systems validate the accuracy of the proposed risk assessment method.

Experimental and numerical investigations of electron transport enhancement by electron-cyclotron plasma-wave interaction in tokamaks

Energy transfer from electron-cyclotron (EC) waves to the plasma is being routinely used in tokamaks to heat and drive current through the electron channel. Technical applications such as magnetohydrodynamic mode mitigation require power deposition with a high degree of localization. However, observations made in tokamaks show a broader distribution of suprathermal electrons than predicted by standard drift-kinetic codes. The present paper explores a possible wave-induced increase of electron turbulent transport that may explain the experimental data, using power-modulated EC waves in the Tokamak à Configuration Variable (TCV). In particular, an indirect measurement of the suprathermal electron population via hard x-rays exhibits an enhanced radial transport with increased wave power. This correlates well with the measured increase of the density fluctuation level during the power pulses, associated with the destabilization of ion temperature gradient modes and trapped electron modes and with stiff electron profiles. Forward bounce-averaged drift-kinetic simulations show that a radial diffusion model directly proportional to the wave power deposition is required to match the experimental data. The power dependency is confirmed by global flux-driven gyro-kinetic simulations using a realistic EC power source, computing turbulent transport from first principles and showing a radial increase of electron transport with increased wave power.

Interplay of degeneracy and non-degeneracy in fluctuation propagation in coherent feed-forward loop motif

We present a stochastic framework to decipher fluctuation propagation in classes of coherent feed-forward loops (CFFLs). The systematic contribution of the direct (one-step) and indirect (two-step) pathways is considered to quantify fluctuations of the output node. We also consider both additive and multiplicative integration mechanisms of the two parallel pathways (one-step and two-step). Analytical expression of the output node’s coefficient of variation shows contributions of intrinsic, one-step, two-step, and cross-interaction in closed form. We observe a diverse range of degeneracy and non-degeneracy in each of the decomposed fluctuation terms and their contribution to the overall output fluctuations of each CFFL motif. The analysis of output fluctuations reveals a maximal level of fluctuations of the CFFL motif of type 1.

Exploring the dynamics of arrivals and prices volatility in onion (Allium cepa) using advanced time series techniques

Modeling the arrivals and prices of agricultural commodities is an essential requirement for farmers, consumers, and governmental organizations to make informed decisions. This is particularly important for perishable commodities such as vegetables, where spoilage can lead to significant losses for farmers and have a ripple effect on supply and demand dynamics. Volatility in the arrivals and prices of vegetables like onion is a serious issue affecting the common person in different ways. The study attempts to employ different time series models like the autoregressive integrated moving average (ARIMA), Artificial neural network (ANN), hybrid, and ensemble empirical mode decomposition (EEMD) techniques to analyze the pattern and trend of onions in Chandigarh and Delhi markets. From the results of the study, the amount of volatility in the data was found to range from medium to high among the markets. Decomposition techniques such as EEMD-ARIMA and EEMD-ANN performed better for the study data with the least mean absolute percentage error (MAPE) values, such as 17.74 and 6.78% for arrivals and 9.76 and 10.24% for prices at Chandigarh and Delhi markets, respectively. The EEMD techniques exceled in handling the non-linearity and non-stationarity by decomposing the data into different intrinsic modes and a residual, providing a better understanding of the fluctuation levels of data.

Adaptive error bounded piecewise linear approximation for time-series representation

Error-bounded piecewise linear approximation (l∞-PLA) has been proven effective in addressing challenges in data management and analytics. It works by approximating the original time series with linear segments such that the approximation error on each data point does not exceed a pre-defined threshold. To achieve this goal, most prior works on l∞-PLA use a fixed error threshold during the entire approximation process, assuming a stable time series. However, in many real-world applications, the distribution of values on the time series undergoes substantial changes in different temporal stages. This introduces a need to adaptively tune the error threshold based on the properties of the time series while considering the trade-off between representation error and storage resources. In this work, we propose a general framework for constructing l∞-PLA with adaptive error bounds (AEPLA). It works by dividing the original time series into a set of intervals and assigns adaptive error bounds to these sub-sequences based on their fluctuation levels. Next, these sub-sequences are approximated using a user-defined l∞-PLA method. We implement this framework by employing three different types of l∞-PLA methods and evaluate the performance of our approach on an extensive set of real-world time-series datasets from industrial and scientific domains. Our experiments show that constructing l∞-PLA using the AEPLA framework can provide better a trade-off between representation error and storage resources and achieves lower time and space costs than applying the original l∞-PLA methods.

Dynamic process and dynamic-stall phenomenon on blade sections of a floating horizontal-axis wind turbine caused by the platform's pitch motion

Floating horizontal-axis wind turbines (FHAWTs) experience six degrees of freedom motion in space with their floating platforms. Such dynamic process may induce complex dynamic flow and variable local load on the blades, however, still insufficiently understood from a perspective of unsteady aerodynamics. In this study, the local aerodynamic load in the dynamic process induced by the platforms’ pitch motion is investigated by computational fluid dynamics. Our results indicate that the axial force of each blade section fluctuates significantly over time, with varying levels of fluctuation among the blade sections. The pressure distributions around the blade sections also vary significantly. Additionally, we observe the light dynamic stall phenomenon that cause stronger lift in upstroke and weaker lift in downstroke, and the flow separation and reattachment process during the dynamic stall demonstrates a delayed response relative to instantaneous changes in the angle of attack. The load variations due to the dynamic process and dynamic stall can lead to severe fatigue and extreme loads on the surface and structure of the blades. These findings suggest that quasi-steady analysis, which neglects the dynamic process, is not sufficient for accurately predicting the blade loads under pitch motion. Furthermore, we find that the fatigue-load properties vary with location on a blade section, with the leading and trailing edges being more susceptible to fatigue problems. These results highlight the importance of considering the potential harmful effects of pitch motion in the design of FHAWTs.

Three-dimensional modelling of the shock–turbulence interaction

ABSTRACTThe complex interaction between shocks and plasma turbulence is extremely important to address crucial features of energy conversion in a broad range of astrophysical systems. We study the interaction between a supercritical, perpendicular shock and pre-existing, fully developed plasma turbulence, employing a novel combination of magnetohydrodynamic and small-scale, hybrid-kinetic simulations where a shock is propagating through a turbulent medium. The variability of the shock front in the unperturbed case and for two levels of upstream fluctuations is addressed. We find that the behaviour of shock ripples, i.e. shock surface fluctuations with short (a few ion skin depths, di) wavelengths, is modified by the presence of pre-existing turbulence, which also induces strong corrugations of the shock front at larger scales. We link this complex behaviour of the shock front and the shock downstream structuring with the proton temperature anisotropies produced in the shock–turbulence system. Finally, we put our modelling effort in the context of spacecraft observations, elucidating the role of novel cross-scale, multispacecraft measurements in resolving shock front irregularities at different scales. These results are relevant for a broad range of astrophysical systems characterized by the presence of shock waves interacting with plasma turbulence.

Study of physiological and pathological information mining with biological information similarity analysis

Chronic diseases, such as sleep apnea and Parkinson's disease, are characterized by insidious onset, complex etiology, slow course, and easy-to-cause other complications, which seriously affect life quality of the patients. Real-time monitoring of biological information can effectively reveal the occurrence and development of chronic diseases. It also helps in aspects of early diagnosis and treating options. In current study, the dynamic change rules of biological signals caused by chronic diseases have been explored, from which one can realize the auxiliary diagnosis and evaluation of these diseases. Attention has been focused on physiological fluctuation and coordination of biological information similarity, including pulse fluctuation detection in patients with sleep apnea and plantar pressure coordination assessment in patients with Parkinson's disease. In the biological similarity study, the heart rate from sleep apnea patients has been recorded two minutes before and after breath pulse. Information of the average plantar pressure from both foot of Parkinson patients has also been recorded and analyzed. Results show that: for sleep apnea patients, their heart rate fluctuation level has significantly reduced. That is because the human body enhances its sympathetic nerve activity to open the airway. The heart rate starts to change periodically, resulting in its fluctuations tending to be consistent. Compared with ordinary people, PD patients have weaker biological information similarities of plantar pressure on one foot. Also, information similarity between left and right feet of PD patients was more diversified. It revealed that the left and right foot plantar pressure fluctuated more and tended to be more consistent together with gait disorder and weakened balance. Such results show that the similarity of biological information can effectively excavate the fluctuation and coordination of physiological signals, and effectively contribute to the recognition and auxiliary diagnosis of chronic diseases. Data mining methods applied here helps to explore the physiological and pathological mechanism of the studied chronic diseases and sheds light on early diagnosis and severity assessment. It becomes more promising to develop algorithms, software, and hardware systems that is helpful for patients and facilitate promotion of human life quality and health cause.

HYDROACOUSTICS OF THE MECHANICAL BILEAFLET HEART VALVE

The results of experimental researches of hydrodynamic noise generated by a jet flow through the mechanical bileaflet mitral valve prosthesis of the Italian company Sorin are given. Physical simulation was carried out in laboratory conditions on the model of the left atrial chamber and the left ventricular chamber of the heart. The hydrodynamic noise of the flow through the artificial bileaflet mitral valve increased with increasing water flow. It was found that the greatest intensity of hydrodynamic noise and its spectral components was observed near the central jet of the bileaflet mitral valve. The obtained average pressure values in the near wake of the open mitral valve near the side jet are (10 – 20) % higher than near the central jet. It was determined that the power spectral densities of pressure fluctuations near the central jet are higher than near the side jet, especially in the frequency range (10 – 100) Hz. It was established that the small-scale vortex structures, which broke away from its leaflets and generated pressure fluctuations in the frequency range (20 – 70) Hz, degenerated starting from a distance of 2.5 valve diameters downstream. Increased levels of pressure fluctuations were observed near the central jet by more than (12 – 13) dB relative to hydrodynamic noise inside the atrial chamber and by more than (5 – 7) dB higher relative to pressure fluctuations near the side jet inside the left ventricular chamber in the frequency range (12 – 15) Hz. With an increase in water flow in the near wake of the mitral valve, an increase in the spectral levels of pressure fluctuations in the frequency range (60 – 80) Hz was observed. At a distance of more than below the open mechanical bileaflet mitral valve, the hydrodynamic noises near the central and side jets became approximately equal in the entire frequency range under consideration. The research results showed that hydroacoustic diagnostics of the operation of the mechanical bileaflet heart valve can be an effective means of diagnosing thrombus formation on the artificial valve leaflets.

Application of the 2D Code Tamic Analyzer Based on the Method of Impedance Analog of the Sestroretskii Electromagnetic Space for Problems of Plasma Diagnostics in Tokamak Fusion Facilities

Applications of the two-dimensional full-wave electromagnetic code Tamic Analyzer, developed by B.V. Sestroretskii to study the limiting possibilities of diagnostics of reflectometry in tokamak plasma. It is shown that by comparing experimental reflectometry data with calculations using this code, it is possible to determine the structure of density fluctuations in a tokamak, but the experimental radial correlation lengths can be significantly overestimated. Simulation using the Taimic Anylyser code made it possible to determine the limiting level of density fluctuations at which it is possible to measure the plasma density profile and observe Alfven fluctuations in the International Experimental Thermonuclear Reactor of the tokamak type (ITER) under construction. Possible ways to increase the speed and counting field of the code are considered.

Energetic ion enhancements in sheaths driven by interplanetary coronal mass ejections

We analyze here an energetic proton enhancement in a sheath ahead of a slow interplanetry coronal mass ejection (ICME) detected by Parker Solar Probe on June 30, 2021 at the heliospheric distance of 0.76 AU. The shock was likely quasi-parallel and had a high Mach number. However, the proton fluxes were not enhanced at the shock but about an hour later. The fluxes stayed elevated with a sporadic behaviour throughout the sheath. We suggest that some mechanism internal to the sheath was responsible for the energization. The observations show enhanced levels of magnetic field fluctuations in the sheath and frequent presence of highly reduced magnetic helicity structures (sigma _{m}) at various time scales, representing either small-scale flux ropes or Alfvénic fluctuations that could have contributed to the energization. The correlation between the energetic proton fluxes and normalized fluctuation amplitudes/occurrence of high sigma _{m} structures was generally weak or negligible. The most striking feature of the sheath was a strong enhancement of density (up to 50 cm−3) that implies the importance of compressive acceleration in the sheath. A statistical analysis of ion enhancements of 73 sheaths detected by ACE at {sim} 1 AU reveals that this sheath was peculiar as in ICME-driven sheaths preceded by strong shocks the ion fluxes typically peak at the shock and strongly decline through the sheath.