Maximum Amplitude Research Articles

Nonlinear free vibration analysis of multi-directional functionally graded porous sandwich plates

Multi-directional functionally graded materials (MFGMs) have attracted significant research attention due to their advantages over one-directional FGMs. In MFGM structures, material properties can be tailored to grade in the required direction, overcoming practical problems like excessive temperature gradients or extreme deflections. This paper aims to investigate the nonlinear free vibration of MFG porous sandwich plates to improve their application in sandwich structures. The two outer layers of the plates are composed of three-directional functionally graded material (3D-FGM), with a bi-directional functionally graded material (2D-FGM) core layer. Additionally, the porosity distribution within the material matrix is assumed to be either even or uneven across the plate thickness. A higher-order finite element model based on Shi's plate theory and the von Kármán assumption is developed. The nonlinear free vibration frequencies are determined through the maximum vibrational amplitude using an iterative algorithm with a displacement control strategy. The accuracy and effectiveness of the proposed model are demonstrated through a comparison with published data. The results show that the vibration response is significantly influenced by various parameters. Specifically, increasing the material gradient indexes in the thickness direction enhances the frequency ratio, while increasing the gradient indexes in the length and width directions reduces it. Higher porosity coefficients in the core layer decrease the frequency ratio, whereas higher pore coefficients in the outer layers increase it. The additional knowledge gained from this study can help with future analysis and design procedures related to the nonlinear responses of these complex structures.

Design optimization and experimental verification of ultrasonic stack for micro hot embossing of polymers

Ultrasonic micro hot embossing (UMHE) is a prominent technique used in numerous sectors to produce micro parts since it is cheaper, faster, and more accurate. Amplitude uniformity is a crucial parameter in UMHE in order to manufacture micro parts with accurate dimensions and high-quality surfaces, even though limited research has been conducted on the uniformity of ultrasonic amplitude at the horn face during the embossing process. This paper presents an experimental and numerical study for designing an ultrasonic transducer and horn tailored to the micro hot embossing of polymer micro parts. A finite element (FE) simulation model combined with the Taguchi method has been developed to optimize the horn geometry and maximum amplitude uniformity. The Taguchi orthogonal array of 25 design runs has been generated and simulated using the developed FE modal analysis model, and then the optimized geometry was used to fabricate the horn. Applied torque and operating time calibrate and evaluate the transducer vibration characteristics. Experimental and simulation results revealed that the fabricated ultrasonic transducer and horn of a straight microfeature has a natural frequency of 28.8 kHz and has an 11 µm average peak-to-peak amplitude with 0.963 amplitude homogeneity along the microfeature face. The achieved frequency separation was greater than 0.85 kHz, whereas the gain ratio was 1.2. The design methodology developed in this paper showed great potential and has been numerically validated for various microfeature shapes across the horn face. Consequently, it can be applied to various ultrasonic applications beyond UMHE.

Lead and calcium crosstalk tempted acrosome damage and hyperpolarization of spermatozoa: signaling and ultra-structural evidences

BackgroundExposure of humans and animals to heavy metals is increasing day-by-day; thus, lead even today remains of significant public health concern. According to CDC, blood lead reference value (BLRV) ranges from 3.5 µg/dl to 5 μg/dl in adults. Recently, almost 2.6% decline in male fertility per year has been reported but the cause is not well established. Lead (Pb2+) affects the size of testis, semen quality, and secretory functions of prostate. But the molecular mechanism(s) of lead toxicity in sperm cells is not clear. Thus, present study was undertaken to evaluate the adverse effects of lead acetate at environmentally relevant exposure levels (0.5, 5, 10 and 20 ppm) on functional and molecular dynamics of spermatozoa of bucks following in vitro exposure for 15 min and 3 h.ResultsLead significantly decreased motility, viable count, and motion kinematic patterns of spermatozoa like curvilinear velocity, straight-line velocity, average path velocity, beat cross frequency and maximum amplitude of head lateral displacement even at 5 ppm concentration. Pb2+ modulated intracellular cAMP and Ca2+ levels in sperm cells through L-type calcium channels and induced spontaneous or premature acrosome reaction (AR) by increasing tyrosine phosphorylation of sperm proteins and downregulated mitochondrial transmembrane potential. Lead significantly increased DNA damage and apoptosis as well. Electron microscopy studies revealed Pb2+ -induced deleterious effects on plasma membrane of head and acrosome including collapsed cristae in mitochondria.ConclusionsPb2+ not only mimics Ca2+ but also affects cellular targets involved in generation of cAMP, mitochondrial transmembrane potential, and ionic exchange. Lead seems to interact with Ca2+ channels because of charge similarity and probably enters the sperm cell through these channels and results in hyperpolarization. Our findings also indicate lead-induced TP and intracellular Ca2+ release in spermatozoa which in turn may be responsible for premature acrosome exocytosis which is essential feature of capacitation for fertilization. Thus, lead seems to reduce the fertilizing capacity of spermatozoa even at 0.5 ppm concentrations.Graphical

Side-Opened Hollow Fiber-Based SPR Sensor for High Refractive Index Detection.

To facilitate the sensor fabrication and sensing operation in microstructured optical fiber-based surface plasmon resonance (SPR) sensors for high refractive index (RI) detection, we propose a special hollow fiber-based SPR sensor that comprises an opening on its body side and a thin gold layer coated on its outer surface. The analyte is able to flow into the hollow core through the side-opening to form new fiber core, with the Gaussian-like mode propagating in it. We investigate the sensing performance of the proposed sensor in a higher RI range of 1.48 to 1.54 at two feasible schemes: one is to only fill the fiber core with analyte (Scheme A), and the other is to directly immerse the sensor in the analyte (Scheme B). The results demonstrate that our sensor exhibits higher wavelength sensitivity at Scheme A with a maximum wavelength sensitivity of 12,320 nm/RIU, while a greater amplitude sensitivity was found at Scheme B with a maximum amplitude sensitivity of 1146 RIU-1. Our proposed sensor features the advantages of simple fabrication, flexible operation, easy analyte filling and replacing, enhanced real-time detection capabilities, high RI detection, and very high wavelength sensitivity and amplitude sensitivity, which makes it more competitive in SPR sensing applications.

Novel Phononic-Like Crystal Wave Barrier Structure for Vibration Isolation

As an efficient, environmentally friendly, and economical urban public transportation tool, the subway has significant advantages compared to other urban public transportation tools and plays an irreplaceable role in the urban rail transit system. While the subway brings many conveniences to people, its operation has also brought a series of problems to urban development and residents’ lives, especially the vibration and noise problems generated by the subway have become unavoidable and urgent problems to be solved. The traditional wave barriers have a certain effect on attenuating and suppressing the vibration generated by the subway, but it has shortcomings in terms of the width and quantity of elastic wave bandgap (BG), so its application in low-frequency vibration reduction and isolation of subway systems is greatly limited. In order to broaden the elastic BG width and quantity of the wave barrier, this paper designs a novel phononic-like crystal subway wave barrier (PLCSWB) for subway vibration isolation based on locally resonant theory. Firstly, the dispersion curves of the novel PLCSWB are calculated using the improved plane wave expansion method and finite element method (FEM), and compared with the dispersion curves of traditional phononic crystal (PC) wave barriers. Secondly, the frequency response function of the novel PLCSWB is calculated using FEM to evaluate its attenuation effect on vibration, and the energy distribution characteristics at its BG boundary are analyzed. Then, the main factors affecting the BG of the novel PLCSWB are analyzed, and a spring–mass system equivalent model of the novel PLCSWB is established to theoretically estimate its BG range. Finally, the vibration data of the tunnel wall monitored on site are used to analyze and verify the vibration isolation effect of the novel PLCSWB. The results show that the novel PLCSWB opens five low-frequency BGs in the 200[Formula: see text]Hz frequency band, which increased the total width of the opened BGs by 49% compared to traditional PC wave barriers. In the frequency range of the BG, the attenuation value of the novel PLCSWB to vibration is mostly above 30[Formula: see text]dB, and the energy distribution inside the structure is mainly concentrated in the primitive cell that controls the BG, indicating good attenuation and control effects on vibration. The main factors affecting the BG of the novel PLCSWB are the density of the scatterer material, the elastic modulus, and the thickness of the wrapping layer material. Moreover, during subway operation, the novel PLCSWB has a good attenuation effect on the vibration transmitted from the tunnel wall to the soil. Among them, the maximum vibration acceleration amplitude of the novel PLCSWB with nine rows is reduced by 47%, and the vibration isolation performance is remarkable. The relevant research results of this paper provide a novel approach and method for the study of subway vibration reduction and isolation, and can also provide specific references for the design and development of wave barriers.

The impact of pulse repetition frequency on microbubble activity and drug delivery during focused ultrasound-mediated blood-brain barrier opening

Objective. Pulsed focused ultrasound (FUS) can deliver therapeutics to the brain by using intravenous microbubbles (MBs) to open the blood-brain barrier (BBB). MB emissions indicate treatment outcomes, like BBB opening (harmonics) and damage (broadband). Typically, a pulse repetition frequency (PRF) of 1 Hz is used, but the effect of PRF on MBs is not fully understood. We investigated the effect of PRF on MB activity and tracer delivery. Approach. The effect of PRF (0.125, 0.25, 0.5, 1, and 2 Hz) on MB activity was monitored through harmonic and wideband emissions during FUS sonications of the rat brain at 274.3 kHz. BBB opening was quantified through fluorescence imaging to estimate the concentration of Trypan Blue (TB) dye following a 75-pulse FUS exposure for PRFs of 1 and 0.25 Hz. Main results. At a fixed acoustic pressure, the percentage change in maximum harmonic amplitude compared to the control (PRF = 1 Hz) decreased with increasing PRF, with a median change of 73.8% at 0.125 Hz and −38.3% at 2 Hz. There was no difference in the pressure threshold for broadband emissions between PRFs of 0.25 and 1 Hz. PRF = 0.25 Hz, led to a 68.2% increase in the mean concentration of TB measured after FUS, with a 53.9% increase in the mean harmonic sum, compared with PRF = 1 Hz. Harmonic emissions-based control at PRF = 0.25 Hz yielded similar TB delivery, with less damage at histology, compared with 1 Hz. Significance. For a fixed number of FUS pulses, reducing the PRF was shown to increase the magnitude of harmonic emissions and TB delivery, but not the threshold for broadband emissions. While further research is necessary to understand the mechanisms involved, these results may be useful to improve clinical safety margins and sensitivity to detecting small harmonic signals from cavitating MBs.

A Flexural Ultrasonic Transducer for Inducing Acoustic Cavitation on Material Surfaces

Abstract Purpose This paper proposes a flexural ultrasonic transducer specifically designed for surface treatment of materials with delicate surfaces such as skin by acoustic cavitation at low frequencies. The goal of this preliminary study is to assess the resonance frequencies and the output sound pressure of the proposed transducer and confirm generation of acoustic cavitation on the surface of an artificial skin phantom. Methods A transducer prototype was designed based on structural-acoustic simulation and fabricated. The proposed design employs a concave-shaped acoustic resonator with a spherical cavity, which is driven by flexural vibration of a piezoelectric ceramic disk actuator. The transducer prototype has compact dimensions of 15 mm in diameter and 8 mm in axial length, working at frequencies around flexural vibration modes of the piezoelectric disk with a thickness of 1 mm. Results The maximum sound pressure amplitude reached 125 kPa with an input voltage amplitude of 10 V at the second resonance frequency of 167 kHz, where the third axisymmetric eigenmode was excited. Despite enhancing the maximum pressure, the sound pressure outside the resonator attenuates because the near-field distance of the irradiated sound wave is smaller than the height of the resonator. This implies that the proposed method provides the cavitation effect on material surfaces, possibly minimizing the side effect of ultrasound irradiation on the underlying structure. Cavitation generation on a urethane gel surface was directly observed by using a high-speed video camera. Conclusion We confirmed that acoustic cavitation was generated and propelled to the target surface. It concludes that ultrasound irradiation using the proposed ultrasonic transducer could be a promising alternative for effective and safe ultrasound treatment of material surfaces.

A piezoelectric cantilever-beam-spring-pendulum oscillator for multi-directional vibration energy harvesting

Harvesting energy from environmental vibrations holds significance for powering wireless sensors and transducers. However, the current vibration energy harvesting methods still have room for improvement, especially in the field of low-frequency vibration, where the performance of output voltage is relatively insufficient. This paper proposes a novel piezoelectric energy harvester consisting of a piezoelectric cantilever beam and a spring pendulum in order to address this challenge. Under external excitation, energy exchange is generated between the internal parts of the system, so that the swinging of the pendulum is interchanged with the extension and contraction motion of the spring and the bending motion of the cantilever beam to realize multidirectional energy harvesting. Firstly, the energy equation of system is obtained and the dynamics model of system is derived based on Lagrange's theorem. In addition, the response characteristics of system under harmonic excitation and the effects of different parameters on the system performance are investigated by simulation. With proper parameter selection, the system can produce higher output voltages. Compared to a piezoelectric cantilever-single-pendulum, the proposed structure demonstrates superior performance, especially in low-frequency vibration. The maximum voltage amplitudes in the x- and z-directions were 106.6% and 187.3% of those of the piezoelectric cantilever-single-pendulum, respectively. This paper proves the superior energy harvesting performance of the proposed structure.

Trunk muscle activation of core stabilization exercises in subjects with and without chronic low back pain.

Weakness and atrophy in trunk muscles have been associated with chronic low back pain (CLBP). This study aimed to identify isometric exercises resulting the highest trunk muscle activity for individuals with and without CLBP. Fourteen males with CLBP and 15 healthy age-matched healthy subjects were recruited for this study. Muscle activity during maximal voluntary isometric contraction (MVIC) was measured for a comparative reference with surface electromyography (sEMG) from six trunk muscles. Thereafter maximum EMG amplitude values were measured during eleven trunk stability exercises. The maximal EMG activity in each exercise relative to the MVICs was analyzed using generalizing estimating equations (GEE) models with the unstructured correlation structure. The GEE models showed statistically significant differences in muscle activity between exercises within both groups (p< 0.001), with no significant differences between groups (p> 0.05). The highest muscle activity was achieved with the hip flexion machine for multifidus, side pull with a resistance band for lumbar extensors, side and single-arm cable pull exercises for thoracic extensors, rotary plank and the hip flexion machine for abdominal. This study found five isometric trunk exercises that exhibited highest muscle activity depending on muscle tested, with no significant difference between individuals with and without CLBP.

Liner orientation change of dual mobility cup determined via 3D ultrasound imaging and motion analysis: A cadaver study

BackgroundA mobile polyethylene liner enables the dual mobility cup (DMC) to contribute to restoring hip joint range-of-motion, decreasing wear and increasing implant stability. However, more data is required on how liner orientation changes with hip joint movement. As a first step towards better understanding liner orientation change in vivo, this cadaver study focuses on quantifying DMC liner orientation change after different hip passive movements, using ultrasound imaging and motion analysis. HypothesisThe liner does not always go back to its initial orientation and its final orientation depends mainly on hip movement amplitude. Methods3D ultrasound imaging and motion analysis were used to define liner and hip movements for four fresh post-mortem human subjects with six implanted DMC. Abduction and anteversion angles of the liner plane relative to the pelvis were measured before and after hip flexion, internal rotation, external rotation, abduction, adduction. ResultsLiner orientation changes were generally defined by angle variation smaller than 5°, with the liner nearly going back to its initial orientation. However, hip flexion caused liner abduction and anteversion angle variations greater than 15°. Except for hip adduction, only weak or no correlation was found between the final angle of the liner and the maximal hip joint movement amplitude. DiscussionThis study is the first attempt to quantify liner orientation change for implanted DMC via ultrasound imaging and constitutes a step forward in the understanding of liner orientation change and its relationship with hip joint movement. The hypothesis that the final liner abduction and anteversion angles depend mainly on hip movement amplitude was not confirmed, even if hip flexion was the movement generating the most liner orientation changes over 15°. This approach should be extended to in vivo clinical investigations, as measured liner angle variation could provide important support for the wear and stability claims made for DMC. Level of evidenceIV; cadaveric study.

Heterogeneities of Short-Period S-Waves Attenuation Field in the Kuril-Kamchatka Region and their Relation to Large and Great Earthquakes

We study characteristics of short-period shear wave attenuation field in the lithosphere to pick out areas of possible preparation for large and great shallow earthquakes. We have processed more than 360 seismograms of events with source depths of 0–33 km recorded by station PET from two areas limited by coordinates of 45.0˚–50.5˚ N and 54.0˚–56.5˚ N, respectively (for brevity, we will call the areas as the southern and the northern ones). Besides, for the purposes of comparison we have analyzed seismograms by station KGB that recorded earthquakes from the area located between 52˚ и 54˚ N. We used the method based on analysis of Sn and Pn maximum amplitude ratio. We find that attenuation in the lithosphere of the northern area is generally much higher than in the southern one. At the same time attenuation in both areas is weaker than in the region of north-eastern Japan. Relatively lower attenuation corresponds to rupture zones of the great earthquakes of 1952 (Mw = 9.0) and 1963 (Mw = 8.6) occurred in the southern area more than 50 years ago. Higher attenuation is observed in the rupture zones of the recent events dated 1997 (Mw = 7.8), 2006 (Mw = 8.3) and 2018 (Mw = 7.3). The obtained data are in agreement with earlier conclusions stating that typical large subduction type earthquakes occur in the areas characterized by higher fluid content in the uppermost mantle; and large and great earthquakes are followed by deep fluids ascent during a few decades, which leads to attenuation decrease in the uppermost mantle. We also pick out the high attenuation zones where no large and great earthquakes (Mw ≥7.8) have occurred for quite a long time. We suggest that active processes of preparation for large earthquakes can be observed in these zones (first of all in the area of the Avacha Bay and to the east of it).

The Influence of Diabetes on Thrombotic Profiles and Outcomes on Patients with Peripheral Artery Disease

BackgroundElevated glycated hemoglobin (HbA1c) is associated with vascular complications, including arterial thrombosis post-revascularization. However, the objective relationship between levels of HbA1c and coagulation profiles has not been established. This study aims to determine the association between specific coagulation parameters and variations in HbA1c in patients undergoing lower extremity revascularization. MethodsPatients with Peripheral Artery Disease (PAD) undergoing revascularization were prospectively evaluated between December 2020 and July 2023. Patients were categorized based on their HbA1c levels, and their thromboelastography with platelet mapping (TEG-PM) results were compared at baseline, post-operatively day 1, 1 month, 3 months and 6 months. The parameters included Maximum Amplitude (MA) with both adenosine diphosphate (ADP) and arachidonic acid (AA), as well as ADP and AA percent aggregation indicating clot strength. The study further assessed the differences in these parameters between groups with varying HbA1c levels through the use of unpaired Student t test for pairwise analysis and Mann-Whitney U tests. ResultsAmong 830 samples, those with HbA1c above 6.5 demonstrated a significant increase in ADP MA (52.6 vs. 43.5, p<0.01), AA MA (36.6 vs. 29.65, p<0.05), clot strength without platelets ActF MA (activator F: 13.10 vs. 10.80, p<0.01), and heparin neutralized uninhibited clot strength from thrombin activation HKH MA (heparinized kaolin with heparinase: 61.10 vs. 57.70, p<0.01) values at baseline. Post-operatively, patients with HbA1c levels greater than 6.5 had higher median functional fibrinogen CFF FLEV levels (citrated functional fibrinogen: 40.95 vs. 371.35, p<0.05) and higher formation of fibrin in response to stimulation of thrombin by tissue factor CFF MA values (22.90 vs. 20.40, p<0.05) when measured within 36 hours of intervention, with these trends staying consistent during the 1-month follow-up visit. The trend analysis revealed a progressive increase in ADP MA values with rising HbA1c values, indicating a unit increase in the thrombotic risk relationship. Regression analysis showed a positive relationship between HbA1c and both ADP MA (a 2.261 unit increase for each unit increase in HbA1c) and AA MA. The R-square values indicate that HbA1c only explains a small percentage of the variance in these parameters, suggesting the confounding influence of other factors contributing to thrombosis. ConclusionElevated HbA1c levels appear to be associated with pro-thrombotic tendencies in clot dynamics as measured by TEG-PM, particularly in parameters related to platelet function. HbA1c explains a limited proportion of the variability in these measures, emphasizing the need for a comprehensive approach to evaluating clotting profiles in patients. This study lays the groundwork for further investigation into personalized antithrombotic strategies for patients with varying HbA1c levels.

Empirical and modified hemostatic resuscitation for liver blast injury combined with seawater immersion: A preliminary study

PurposeTo compare the effects of empirical and modified hemostatic resuscitation for liver blast injury combined with seawater immersion. MethodsThirty rabbits were subjected to liver blast injury combined with seawater immersion, and were then divided into 3 groups randomly (n = 10 each): group A (no treatment after immersion), group B (empirical resuscitation with 20 mL hydroxyethyl starch, 50 mg tranexamic acid, 25 IU prothrombin complex concentrate and 50 mg/kg body weight fibrinogen concentrate), and group C (modified resuscitation with additional 10 IU prothrombin complex concentrate and 20 mg/kg body weight fibrinogen concentrate based on group B). Blood samples were gathered at specified moments for assessment of thromboelastography, routine coagulation test, and biochemistry. Mean arterial pressure, heart rate, and survival rate were also documented at each time point. The Kolmogorov-Smirnov test was used to examine the normality of data distribution. Multigroup comparisons were conducted with one-way ANOVA. ResultsLiver blast injury combined with seawater immersion resulted in severe coagulo-fibrinolytic derangement as indicated by prolonged prothrombin time (s) (11.53 ± 0.98 vs. 7.61 ± 0.28, p＜0.001), activated partial thromboplastin time (APTT) (s) (33.48 ± 6.66 vs. 18.23 ± 0.89, p＜0.001), reaction time (R) (min) (5.85 ± 0.96 vs. 2.47 ± 0.53, p＜0.001), decreased maximum amplitude (MA) (mm) (53.20 ± 5.99 vs. 74.92 ± 5.76, p＜0.001) and fibrinogen concentration (g/L) (1.188 ± 0.29 vs. 1.890 ± 0.32, p = 0.003), and increased D-dimer concentration (mg/L) (0.379 ± 0.32 vs. 0.051 ± 0.03, p = 0.005). Both empirical and modified hemostatic resuscitation could improve the coagulo-fibrinolytic states and organ function, as indicated by shortened APTT and R values, decreased D-dimer concentration, increased fibrinogen concentration and MA values, lower concentration of blood urea nitrogen and creatine kinase-MB in group B and group C rabbits in comparison to that observed in group A. Further analysis found that the R values (min) (4.67 ± 0.84 vs. 3.66 ± 0.98, p = 0.038), APTT (s) (23.16 ± 2.75 vs. 18.94 ± 1.05, p = 0.001), MA (mm) (60.10 ± 4.74 vs. 70.21 ± 3.01, p < 0.001), and fibrinogen concentration (g/L) (1.675 ± 0.21 vs. 1.937 ± 0.16, p = 0.013) were remarkably improved in group C than in group B at 2 h and 4 h after injury. In addition, the concentration of blood urea nitrogen (mmol/L) (24.11 ± 1.96 vs. 21.00 ± 3.78, p = 0.047) and creatine kinase-MB (U/L) (85.50 ± 13.60 vs. 69.74 ± 8.56, p = 0.013) were lower in group C than in group B at 6 h after injury. The survival rates in group B and group C were significantly higher than those in group A at 4 h and 6 h after injury (p < 0.001), however, there were no statistical differences in survival rates between group B and group C at each time point. ConclusionsModified hemostatic resuscitation could improve the coagulation parameters and organ function better than empirical hemostatic resuscitation.

The wave passage over a seamount without reflection: Analytical results using the generalized Carrier–Greenspan transform

A method for the transformation of linear shallow water equations based on a generalization of the Carrier–Greenspan transform, well known in the theory of wave rolling on a flat slope, is presented. Thanks to it, the initial equations for waves over arbitrary bathymetry are reduced to a wave equation, from which both the displacement of the free surface and the flow velocity can be obtained simultaneously. Exact solutions in the sum of traveling waves have been obtained for certain configurations of the seabed in the form of seamounts. It is shown that when moving from a more gentle slope to a sharper one, the waveform will integrate a certain number of times, and the maximum amplitude is not reached at the very top of the mountain.

Extending the operational range of Francis turbines: A case study of a 200 MW prototype

Francis turbines are now widely used to support the integration of renewable and intermittent energy sources such as solar and wind power. Consequently, these turbines often operate away from their best efficiency point (BEP). Such operations cause detrimental pressure fluctuations in the runner and draft tube, leading to early fatigue failures. To address these harmful flow conditions and extend the operating range of Francis turbines, a mitigation system was developed and tested on a large-scale, high-head 200 MW Francis turbine. The system consists of four circular rods placed in the draft tube with variable radial protrusion lengths, adjustable using linear actuators. Pressure, accelerometer, and vibration sensors installed on the turbine allowed quantification of the rod system performance. The results demonstrate the system’s capability to reduce pressure pulsations by up to 80 % in terms of maximum pressure amplitude and 100 % in terms of fatigue cycle in both low and high-frequency ranges, up to ten times the runner frequency, based on pressure analysis. The optimal rod protrusion ranges from 5 to 20 % of the runner outlet diameter function of the operating load. The impact of the rods’ protrusion on the turbine structure appears negligible from the accelerometer measurements performed on the draft tube and spiral casing. The hydraulic efficiency is reduced by up to 1 %. These findings are significant across a wide range of part-load operations, from 40 % to 60 % load, indicating the potential to extend the operational range of existing Francis turbines. The research presented here is a novel attempt to enhance the existing Francis turbines with a new degree of freedom using protruding rods.

Soil flooding filters evolutionary lineages of tree communities in Amazonian riparian forests.

Inundations in Amazonian black-water river floodplain result in the selection of different tree lineages, thus promoting coexistence between species. We investigated whether Amazonian tree communities are phylogenetically structured and distributed along a flooding gradient from irregularly flooded forests along streams embedded within upland (terra-firme) forest to seasonally flooded floodplains of large rivers (igapós). Floristic inventories and hydrological monitoring were performed along the Falsino River, a black-water river in the eastern Amazon within the Amapá National Forest. We constructed a presence-and-absence matrix and generated a phylogeny using the vascular plant database available in GenBank. We calculated the standardized values of the metrics of phylogenetic diversity (ses.PD), average phylogenetic distance (ses.MPD), and average nearest-neighbor distance (ses.MNTD) to test whether the history of relationships between species in the community is influenced by inundation. We used the phylogenetic endemism (PE) metric to verify the existence of taxa with restricted distribution. Linear regressions were used to test whether phylogenetic metrics have a significant relationship with the variables: maximum flood height, maximum water table depth, and maximum flood amplitude. The results show that forests subject to prolonged seasonal flooding have reduced taxon richness, low phylogenetic diversity, and random distribution of lineages within communities. On the other hand, terra-firme riparian forests showed higher rates of taxon richness, diversity, and phylogenetic dispersion, in addition to greater phylogenetic endemism. These results indicate that seasonal and predictable soil flooding filters tree lineages along the hydrographic gradient. Different adaptations to root waterlogging are likely requirements for colonization in these environments and may represent an important factor in the diversification of tree lineages in the Amazon biome.

Design of a real-time frequency stabilization system for dual laser-based interferometer on EAST.

This study addresses the challenge of intermediate frequency (IF) instability in the far-infrared polarimeter/interferometer (POINT) of the Experimental Advanced Superconducting Tokamak (EAST) to ensure the accuracy and stability of electron density measurements. Sudden and extensive IF shifts of the lasers can cause instability and even measurement errors of the diagnostic system. This paper introduces a comprehensive solution for stabilizing IF fluctuations. First, analog IF is converted into digital form using an analog-to-digital converter, and the digitalized signal is processed by a digital signal system based on a ZYNQ processor. The exact value of the IF is obtained by acquiring the point of maximum amplitude through the fast Fourier transform method, while the ZYNQ processor loaded with a fuzzy control algorithm will precisely adjust the laser cavity length via piezoelectric ceramics, achieving frequency stabilization within a target range. Comparative analyses confirm the method's efficacy in managing sudden frequency shifts, maintaining stability within 850 ± 100kHz (a central frequency of 850kHz, fluctuating within a range of ±100kHz), with a control speed of 0.5s per action and robust against variations up to 270kHz. This efficient and rapid control mechanism fulfills the critical need for IF stabilization, ensuring the stability and precision of the POINT system in the EAST discharge experiments.

Quasi‐Diurnal Lunar Tide O1 in Ionospheric Total Electron Content at Solar Minimum

AbstractFor the first time, characteristics of the geographical and seasonal distribution of the quasi‐diurnal lunar O1 tide were derived from a time series of ionospheric total electron content (TEC) maps provided by International Global Navigation Satellite System Service (IGS). The data analysis is focused on solar minimum in 2008 and 2009 where disturbing influences of geomagnetic and solar activity were minimal. We found that the magnitude of the O1 tide is as strong as the “dominant” semidiurnal lunar M2 tide. Relative amplitudes of 10% and larger are observed in some regions for the O1 component in TEC. The O1 component is particularly strong in northern hemispheric winter over the west coast of South America. There, two maxima occur which are northward and southward of the magnetic equator in the Equatorial Ionization Anomaly (EIA) crest regions. Following Yamazaki et al. (2017, https://doi.org/10.1002/2017ja024601), it might be assumed that a longitudinal anomaly of ionospheric conductivities in the Peruvian sector leads to a stronger modulation of the equatorial electrojet by the lunar tides. Electrodynamic lifting of plasma and transport to the EIA crests may explain the variations of the O1 component in TEC. Contrary to many studies, we find the O1 component (period 25.82 hr) more important than the M1 component (period 24.84 hr, a lunar day). We show that the geographical distribution of the O1 component is totally different from that of the M1 component which is smaller. The seasonal variation of O1 shows maximal amplitudes in northern hemispheric winter and minimal amplitudes in southern hemispheric winter.

The vitals for steady nucleation maps of spontaneous spiking coherence in autonomous two-dimensional neuronal networks

Thin pancake-like neuronal networks cultured on top of a planar microelectrode array have been extensively tried out in neuroengineering, as a substrate for the mobile robot’s control unit, i.e., as a cyborg’s brain. Most of these attempts failed due to intricate self-organizing dynamics in the neuronal systems. In particular, the networks may exhibit an emergent spatial map of steady nucleation sites (“n-sites”) of spontaneous population spikes. Being unpredictable and independent of the surface electrode locations, the n-sites drastically change local ability of the network to generate spikes. Here, using a spiking neuronal network model with generative spatially-embedded connectome, we systematically show in simulations that the number, location, and relative activity of spontaneously formed n-sites (“the vitals”) crucially depend on the samplings of three distributions: (1) the network distribution of neuronal excitability, (2) the distribution of connections between neurons of the network, and (3) the distribution of maximal amplitudes of a single synaptic current pulse. Moreover, blocking the dynamics of a small fraction (about 4%) of non-pacemaker neurons having the highest excitability was enough to completely suppress the occurrence of population spikes and their n-sites. This key result is explained theoretically. Remarkably, the n-sites occur taking into account only short-term synaptic plasticity, i.e., without a Hebbian-type plasticity. As the spiking network model used in this study is strictly deterministic, all simulation results can be accurately reproduced. The model, which has already demonstrated a very high richness-to-complexity ratio, can also be directly extended into the three-dimensional case, e.g., for targeting peculiarities of spiking dynamics in cerebral (or brain) organoids. We recommend the model as an excellent illustrative tool for teaching network-level computational neuroscience, complementing a few benchmark models.

Low-Frequency Flexural Wave Acoustic Insulation Characteristics of a Double-Layer Metamaterial Plate

The effects of geometric parameters and constituent material parameters on the flexural wave bandgap of a locally resonant double-layer metamaterial plate are investigated using the finite element method. Reasonable parameters are obtained through optimization; then, a double-layer plate made of ABS material with added aluminum mass blocks is designed. The results show that it can open the low-frequency (112--124 Hz) flexural wave bandgap at a subwavelength size. The metamaterial plate is modeled as an equivalent spring-mass system, and the frequency range with negative density for the equivalent dynamic mass is consistent with the width of the flexural wave bandgap. The bandgap generation mechanism is further elucidated. Sound insulation performance of double-layer metamaterial panels verified in an acoustic chamber. The maximum amplitude of STL is achieved at the 112 Hz point in the bandgap frequency range, which indicates that the low-frequency bandgap can effectively reduce vibration and noise. These results demonstrate that this novel double-layer metamaterial plate has wide applications in engineering.