Peak Power Spectral Density Research Articles

Mid-spatial frequency reduction via zero-depth of cut rapid-feed passes in face-turning

The single point diamond turning process (SPDT) is used widely in creating optical grade mirror surfaces on several engineering materials ranging from polymers, and metals, to brittle materials such as silicon and germanium. In visual optic mirror applications, mid-spatial frequency (MSF) errors generated during the SPDT process interfere with the visible spectrum of light thereby affecting the image quality. To overcome these errors, a post-processing operation of polishing the optical mirrors is required. The post-processing step not only increases the complexity of the manufacturing process but also leads to minor geometrical form changes in the mirror which affects performance. To avoid post-processing and minimize MSFs formed during turning- a novel method to modify the toolpath during the machining process has been proposed in this paper. The suggested toolpath strategy comprises two consecutive operations: i) employing variable low feed rates with the specified depth of cut (DoC) and ii) executing rapid traverse rates with zero depth of cut for a predetermined number of passes. The effectiveness of the proposed strategy is tested by carrying out facing experiments in a micro-precision CNC lathe. The power spectral density (PSD) content of the machined surface is then analyzed to check for any improvement in the frequency characteristics. The results show that the frequency errors generated by the toolpath in normal turning operations can be minimized, distributing the resulting PSD peak over a wide range of spatial frequencies. From the PSD plots, it is observed that there is a decrease of 77% and 85.82% in the peak intensity values when compared with surfaces machined at constant feedrates of 150 μm/rev and 200 μm/rev respectively. This method can be applied to nanoprecision SPDT machines to improve the surface quality and to eliminate the MSF errors of the visual optical grade mirrors without the need for post-processing.

Computations of energetic nearshore waves: Are weakly dispersive phase-resolving models telling the same story?

Three phase-resolving weakly dispersive wave models are used for 2DH (2D depth-integrated) computations of large-scale wave-by-wave processes induced by highly energetic sea/swell (SS) forcing near Haleʻiwa on the North Shore of Oʻahu, Hawaiʻi. The computed model results are compared to observations obtained over a nearshore cross-reef transect and from the basin of a small boat harbor. The level of agreement between the model results and observations in complex coastal environments under highly energetic wave forcing, along with the qualitative consistency among the three models, makes these models good candidates for operational applications in nearshore environments exposed to energetic wave forcing conditions.Spectral analyses inside the harbor and over the reef indicate that all three models generally account for infragravity (IG) spatial modal structures that are consistent with observations and the theory of edge and leaky waves. Over the reef, auto- and cross-spectral analyses reveal that the dominant waveforms are qualitatively reproduced by all three models, as indicated through: (i) the growth of IG wave amplitudes from deeper water to the shallow reef sites; (ii) the agreement of power spectral density peaks at the nearshore locations; and (iii) the remarkable similarity of spatial coherence functions among the models and between the models and observations. The computations of swell entering the small boat harbor at Haleʻiwa demonstrate that the models can successfully reproduce the variability in the narrow IG frequency bands that are spatially dependent and often subject to resonant amplifications.

Specific EEG resting state biomarkers in FXS and ASD

BackgroundFragile X syndrome (FXS) and autism spectrum disorder (ASD) are neurodevelopmental conditions that often have a substantial impact on daily functioning and quality of life. FXS is the most common cause of inherited intellectual disability (ID) and the most common monogenetic cause of ASD. Previous literature has shown that electrophysiological activity measured by electroencephalogram (EEG) during resting state is perturbated in FXS and ASD. However, whether electrophysiological profiles of participants with FXS and ASD are similar remains unclear. The aim of this study was to compare EEG alterations found in these two clinical populations presenting varying degrees of cognitive and behavioral impairments.MethodsResting state EEG signal complexity, alpha peak frequency (APF) and power spectral density (PSD) were compared between 47 participants with FXS (aged between 5–20), 49 participants with ASD (aged between 6–17), and 52 neurotypical (NT) controls with a similar age distribution using MANCOVAs with age as covariate when appropriate. MANCOVAs controlling for age, when appropriate, and nonverbal intelligence quotient (NVIQ) score were subsequently performed to determine the impact of cognitive functioning on EEG alterations.ResultsOur results showed that FXS participants manifested decreased signal complexity and APF compared to ASD participants and NT controls, as well as altered power in the theta, alpha and low gamma frequency bands. ASD participants showed exaggerated beta power compared to FXS participants and NT controls, as well as enhanced low and high gamma power compared to NT controls. However, ASD participants did not manifest altered signal complexity or APF. Furthermore, when controlling for NVIQ, results of decreased complexity in higher scales and lower APF in FXS participants compared to NT controls and ASD participants were not replicated.ConclusionsThese findings suggest that signal complexity and APF might reflect cognitive functioning, while altered power in the low gamma frequency band might be associated with neurodevelopmental conditions, particularly FXS and ASD.

A mixer architecture using GaN-based split-gate nanowire transistor

Frequency mixer is an essential block in radio-frequency signal processing for frequency translation and phase comparison. The most common mixers are fabricated using passive elements which suffer from significant conversion loss and low isolation. Mixers using active devices are used less frequently and rather less matured on GaN technology. Here, we demonstrate a mixer based on GaN split-gate nanowire transistor, allowing low conversion loss and high isolation. A constriction is formed by electrostatic modulation of the effective gate width. The threshold voltage of the transistor is modified by one of the gate voltages through the width variation, while the other gate voltage biases the transistor in the saturation region. The nonlinear dependency of the transistor characteristics on the two gate voltages facilitates frequency translation. The mixing characteristics of this architecture are verified both experimentally and theoretically. The output power spectral density peaks at the difference frequency with a minimal conversion loss. Extremely high isolation is measured using three-port S-parameter measurements. The proposed architecture shows multiple benefits, additionally facilitating monolithic mixers on the GaN platform.

Evaluation Method of Magnetic Field Stability for Robotic Arc Welding Based on Sample Entropy and Probability Distribution

In this study, we analyzed the arc magnetic field to assess the stability of the arc welding process, particularly in robotic welding where direct measurement of welding current is challenging, such as under water. The characteristics of the magnetic field were evaluated based on low-frequency fluctuations and the symmetry of the signals. We used double-wire pulsed MIG welding for our experiments, employing Q235 steel with an 8.0 mm thickness as the material. Key parameters included an average voltage of 19.8 V, current of 120 A, and a wire feeding speed of 3.3 m/min. Our spectral analysis revealed significant correlations between welding stability and factors such as the direct current (DC) component and the peak power spectral density (PSD) frequency. To quantify this relationship, we introduced a novel approach using sample entropy and mix sample entropy (MSE) as new evaluation metrics. This method achieved a notable accuracy of 88%, demonstrating its effectiveness in assessing the stability of the robotic welding process.

Effects of windbreak types on aerodynamics of high-speed trains traversing from flat ground to semi-cutting and semi-embankment under crosswinds

Under the operation of strong crosswinds, the aerodynamic performance of high-speed trains (HSTs) will be seriously deteriorated when the transition section of flat ground and semi-cutting and semi-embankment (FGSCSE) is traversed, and the setting of windbreaks will help to slow down the impact of strong crosswinds on the trains. In this study, a three-dimensional coupled computational fluid dynamics numerical model to assess the aerodynamic performance of train–windbreak–FGSCSE–air system is developed. A comparative assessment is carried out to identify the variations in aerodynamic performance on the train carriage: no windbreak (NW), 50% ventilation windbreak (VW), and solid windbreak (SW), and the reasons for these variations are elucidated by examining the flow field structure's evolution. Furthermore, the operational safety of the train is discussed based on the indicator of wheel unloading ratio (fΔQ). Across the three distinct conditions, significant abrupt changes in aerodynamic load coefficients (ALCs) and the shedding of vortex structures are experienced by HSTs traversing the FGSCSE transition sections. Compared to the VW condition, the NW and SW conditions result in a greater number of shedding vortices on the leeward side and the tail of the train, and the VW condition results in the smallest magnitude of ALCs fluctuation. The power spectral density peak values of the aerodynamic loads follow the order: SW > NW > VW. Upon the train fully enters the subsequent operational environment, the VW condition has the smallest standard deviation of these coefficients. The standard deviations of CFy, CFz, CMx, CMy, and CMz for the head train in the VW condition are only 57.17% (46.81%), 55.85% (54.15%), 72.74% (34.62%), 57.99% (51.92%), and 44.60% (43.82%) of the corresponding values in the NW (SW) condition, respectively. In the NW, VW, and SW conditions, the fΔQ exceeds 0.9 when the wind speeds reach 30, 40, and 35 m/s, respectively. The windbreak with a ventilation rate of 30% performs the best, providing the most effective safety and stability for train operation.

Dexamethasone alleviates etomidate-induced myoclonus by reversing the inhibition of excitatory amino acid transporters.

Etomidate can induce myoclonus with an incidence of 50 ~ 85% during anesthesia induction. Dexamethasone, as a long-acting synthetic glucocorticoid, has neuroprotective effects. However, the effects of dexamethasone on the etomidate-induced myoclonus remain uncertain. Adult male Sprague-Dawley rats were randomly assigned to receive etomidate (1.5 mg/kg) plus dexamethasone (4 mg/kg) (etomidate plus dexamethasone group) or etomidate (1.5 mg/kg) plus the same volume of normal saline (NS) (etomidate plus NS group). The mean behavioral scores, local field potentials and muscular tension were recorded to explore the effects of dexamethasone on etomidate-induced myoclonus. Liquid chromatography coupled with tandem mass spectrometric system (LC-MS/MS), quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting were applied to analyze the levels of glutamate and γ-aminobutyric acid (GABA), the mRNA and protein expression of excitatory amino acid transporters (EAATs), and plasma corticosterone levels at different time points after anesthesia. Compared with the etomidate plus NS treatment, the etomidate plus dexamethasone treatment significantly decreased the mean behavioral score at 1, 3, 4, and 5 min after administration; the peak power spectral density (PSD) (p = 0.0197) in the analysis of ripple waves; and the glutamate level (p = 0.0139) in the neocortex. However, compared with etomidate plus NS, etomidate plus dexamethasone increased the expression of the neocortical proteins of EAAT1 (p = 0.0207) and EAAT2 (p = 0.0022) and aggravated the inhibition of corticosterone at 4 h (p = 0.0019), 5 h (p = 0.0041), and 6 h (p = 0.0009) after administration. Dexamethasone can attenuate the myoclonus, inhibit the glutamate accumulation, and reverse the suppression of EAATs in the neocortex induced by etomidate following myoclonus, while conversely aggravating etomidate-induced adrenal suppression.

Vessels and aircraft are chronic sources of anthropogenic noise in coastal marine and terrestrial soundscapes on Long Island, New York

Passive acoustic data collected during 2020 and 2021 were used to monitor changes in both terrestrial and underwater soundscapes, as well as human activity from aircraft and vessels. Passive acoustic data were collected at two artificial reefs south of Long Island, as well as along ocean beaches in Southampton, NY. At the artificial reefs, vessel noise was recorded more frequently during 2020 than in 2021. Commercial vessels and multi-user charter fishing vessels were more abundant during 2020. Peaks in power spectral density occurred at 60, 90 and 120 Hz in 2020 and 2021, which are frequencies consistent with noise generated by commercial vessels, suggesting that vessels are a significant contributor to the soundscape of the artificial reefs. In the terrestrial environment, noise generated by aircraft was more common during 2021. Peaks in power spectral density were measured around 160 and 290 Hz at one of the ocean beach sites. These frequencies are consistent with noise generated by aircraft. This study documents the chronic extent of anthropogenic noise in both the underwater and terrestrial environments of Long Island, NY, as well as quantifies the occurrence of various noise sources in these habitats.

Changes in postural stability after cerebrospinal fluid tap test in patients with idiopathic normal pressure hydrocephalus.

In patients with idiopathic normal pressure hydrocephalus (iNPH), the characteristics of balance disturbance are not as well understood as those related to gait. This study examined changes in postural stability in quiet standing after the cerebrospinal fluid tap test (CSFTT) in these patients. Furthermore, the study explored the relationship between the amount of spontaneous body sway and both gait and executive function. All patients diagnosed with iNPH underwent CSFTT. We evaluated their center of pressure (COP) measurements on a force plate during quiet standing, both pre- and post-CSFTT. Following the COP measurements, we calculated COP parameters using time and frequency domain analysis and assessed changes in these parameters after CSFTT. At pre-CSFTT, we assessed the Timed Up and Go (TUG) and the Frontal Assessment Battery (FAB). We investigated the relationship between COP parameters and the TUG and FAB scores at pre-CSFTT. A total of 72 patients with iNPH were initially enrolled, and 56 patients who responded positively to CSFTT were finally included. Post-CSFTT, significant improvements were observed in COP parameters through time domain analysis. These included the velocity of COP (vCOP), root-mean-square of COP (rmsCOP), turn index, torque, and base of support (BOS), compared to the pre-CSFTT values (p < 0.05). In the frequency domain analysis of COP parameters post-CSFTT, there was a decrease in both the peak and average of power spectral density (PSD) values in both the anteroposterior (AP) and mediolateral (ML) directions below 0.5 Hz (p < 0.05). In addition, the TUG scores showed a positive correlation with vCOP, rmsCOP, turn index, torque, BOS, and both the peak and average PSD values in the AP and ML directions below 0.5 Hz (p < 0.05). The FAB scores demonstrated a negative correlation with vCOP, rmsCOP, turns index, BOS, and both peak and average PSD values in the AP direction below 0.5 Hz (p < 0.05). In patients with iNPH who responded to CSFTT, there was an improvement in spontaneous body sway during quiet standing after CSFTT. Increased spontaneous sway is associated with impaired gait and frontal lobe function. This may be linked to impaired cortico-cortical and cortico-subcortical circuits in patients with iNPH.

Measurement of pressure fluctuation distribution on a flat wall behind supported square cylinder with pressure-sensitive paint

The pressure fluctuation distribution on the floor surface behind a supported square cylinder in a turbulent boundary layer was measured by using pressure-sensitive paint (PSP). Specifically, the accuracy and frequency response of PSP at a Mach number around M = 0.3 were examined. Four square cylinders with different dimensions were investigated in the same turbulent boundary layer, and the detailed relationship between these conditions and Kármán vortex shedding structures was discussed. The values measured with PSP had a similar trend to those measured with a pressure transducer at up to 5 kHz. The peak power spectral density (PSD) of the pressure fluctuations due to Kármán vortex shedding was observed within an error of approximately 30 % at up to frequencies greater than 3 kHz. Moreover, the peak frequency of Kármán vortex shedding was found to decrease with the cylinder height in a manner similar to a previous empirical equation for the Strouhal number. The peak PSD value for the shortest square cylinder (h/w = 3.5, h/δ = 1.1) was twice as high as that for the other cylinders; also, the high-pressure fluctuation area in this case did not spread downstream, which suggests that the flow from the top of the cylinder affected the Kármán vortex shedding generated from the cylinder’s sides. One contour of the two main modes extracted for the highest PSD via the right singular vector vi at the Kármán vortex frequency had an asymmetric distribution behind the supported taller square cylinders (h/w ≥ 7.0, h/δ ≥ 2.3). This result is considered to be derived from the Kármán vortex shedding being mainly generated from the mainstream rather than the boundary-layer flow.

CFD investigation on wind power harvesting from small-scale wind turbines for powering residential buildings in New Zealand

ABSTRACT As an alternative solution, wind power could be harnessed by designing and implementing small-scale wind turbines for distributed power generation. In this work, 3-dimensional time-domain numerical simulations, based on the Reynolds-Average Navier-Strokes (RANS) model, are conducted for two categories of small-scale wind turbines, i.e. drag force- (Savonius) and lift force-driven (Darrieus) ones, while placing them at a flat surface and a step height, respectively. The present results confirmed that placing a small-scale wind turbine at a step height can improve the maximum power output, respectively, approximately 219.2% for the Savonius wind turbine and 121.0% for the Darrieus wind turbine operating at their optimum stage; moreover, the corresponding peak power spectral density of the turbine torque is improved by 173.9% and 83.6%, respectively. In addition, the power generated from the wind flow could reduce the CO2 emission. It has been observed that the Savonius turbine could reduce the annual CO2 emission by 3,738.9–19,857.8 kg and that of Darrieus turbines by 4,919.6–26,128.8 kg. This study demonstrated the benefits of adopting forward facing steps to improve wind turbine performance in a typical urban environment.

Modelling and experimental characterization of double layer InP/AlGaInP quantum dot laser

Spectrum of an InP/AlGaInP self- assembled double-layer quantum dot (QD) laser fabricated by metal–organic vapor-phase epitaxy is theoretically and experimentally investigated. A bimodal QD size distribution (small and large QD groups) was detected which is formed during the fabrication. A model is proposed based on rate equations accounting for the superposition of two inhomogeneous QD groups. The total output power and the power spectral density (PSD) of the fabricated QD laser are experimentally characterized at room temperature. The output spectrum is segmented into the sum of two Gaussians curves (super Gaussian) belonging to the small and large QD groups. The peak PSD and the spectral width of each group are extracted and their dependency on the injected current density is analysed. The peak of the large QDs is found to be dominant at small current while the peak of the small QDs dominated at high current alongside a reduction in its spectral width leading to lasing based on them. This behaviour is attributed to the saturation of the large QDs energy levels due to its relatively long radiative lifetime. The experimental analysis is in a good agreement with the theoretical results.

The effects of non-Newtonian fluid material midsole footwear on tibial shock acceleration and attenuation.

Introduction: Given the possibility of higher ground temperatures in the future, the pursuit of a cushioning material that can effectively reduce sports injuries during exercise, particularly one that retains its properties at elevated temperatures, has emerged as a serious concern. Methods: A total of 18 man recreational runners were recruited from Ningbo University and local clubs for participation in this study. Frequency analysis was employed to investigate whether there is a distinction between non-Newtonian (NN) shoes and ethylene vinyl acetate (EVA) shoes. Results: The outcomes indicated that the utilization of NN shoes furnished participants with superior cushioning when engaging in a 90° cutting maneuver subsequent to an outdoor exercise, as opposed to the EVA material. Specifically, participants wearing NN shoes exhibited significantly lower peak resultant acceleration (p = 0.022) and power spectral density (p = 0.010) values at the distal tibia compared to those wearing EVA shoes. Moreover, shock attenuation was significantly greater in subjects wearing NN shoes (p = 0.023) in comparison to EVA shoes. Performing 90° cutting maneuver in NN shoes resulted in significantly lower peak ground reaction force (p = 0.010), vertical average loading rate (p < 0.010), and vertical instantaneous loading rate (p = 0.030) values compared to performing the same maneuvers in EVA shoes. Conclusion: The study found that the PRA and PSD of the distal tibia in NN footwear were significantly lower compared to EVA footwear. Additionally, participants exhibited more positive SA while using NN footwear compared to EVA. Furthermore, during the 90° CM, participants wearing NN shoes showed lower PGRF, VAIL, and VILR compared to those in EVA shoes. All these promising results support the capability of NN footwear to offer additional reductions in potential injury risk to runners, especially in high-temperature conditions.

Numerical Study on the Unusual Vibration Load Characteristics and Mechanisms of the Front Landing Gear Compartment

Civilian aircraft can experience noticeable vibrations in the cockpit and cabin due to mechanical faults during flight. To address this issue, a hybrid approach was utilized to investigate fluid-induced vibration load characteristics in the front landing gear compartment under different hatch opening angles. The results reveal that the root mean square (RMS) of cumulative pressure loads on both small and large hatches under different opening angles is largest at a 15°. For all the simulated cases (0°, 5°, 10°, 15°, 20°), the power spectral density (PSD) results of the chosen monitoring points on the inner wall of the large hatch exhibit broadband frequency characteristics, and the peak PSD values for the chosen monitoring points on the outer wall of the small hatch exhibit a significant concentration of energy at approximately 75 Hz. The peak PSD values for the selected monitoring points on the inner wall of the small hatch demonstrate a more uniform distribution of energy. Utilizing the iso-surface of Q-criterion, spatial streamlines, and streamlines at different cross-sections to analyze flow characteristics, the study investigates the fluctuating load mechanisms of the compartments. The results indicate that unsteady loads stem from the blunt edges of the hatches, which induce unsteady flow and spanwise flow. Geometric gaps between different locations cause flow separation, and the flows inside the compartment exhibit characteristics similar to those of a clean cavity. Furthermore, the mutual interference can be described using circulating flow and spanwise flow, resulting in flow unsteadiness. The flow separation zones enlarge and vortex intensity increases with the increase of the hatch opening angle from 0° to 15°; then, their values decrease as the hatch opening angle increases from 15° to 20°. These variations explain the maximum RMS of cumulative pressure loads at 15°.

Simulation of ground motion emissions from wind turbines in low mountain ranges: implications for amplitude decay prediction

The characterization and prediction of wind turbine (WT) emissions are important steps in reducing their impact on humans or sensitive technologies such as seismic stations or physics experiments. Here, WT ground motion emissions are studied along two measurement lines set up at two wind farms on the Eastern Swabian Alb, southwest Germany. The main purpose of the data analysis is to estimate amplitude decay rates from vertical component data and surface wave phase velocities excited by the permanent motion of the WT towers. Phase velocities as well as geological information serve as input to build realistic subsurface models for numerical wave field simulations. Amplitude A decay rates are characterized by b-values through Asim 1/r^b depending on distance r and are derived from peaks in power spectral density (PSD). We find an increase of b_text {PSD} with frequency from 0.5 to 3.2 for field data. For low frequencies (1.2 Hz and 3.6 Hz), b_text {PSD} ranges from 0.5 to 1.1, hence close to the geometrical spreading factor of surface waves (b_text {PSD}=1). Anelastic damping and scattering seem not to be significant at these frequencies which also shows in numerical simulations for quality factors Q=50-200. We also find that the emitted wavefields from several WTs interfere, especially in the near-field, and produce strong local ground motion amplitudes. The inclusion of a steep topography present in low mountain ranges adds more wave field distortions which can further increase the amplitudes. This needs to be considered when predicting WT induced ground motions.

Seismic response of granites with different grain sizes after thermal treatment: an experimental study

Understanding the wave propagation behaviour in rock masses with different temperatures and geological conditions is of great significance for the stability and safety evaluation of deep rock engineering, e.g., enhanced geothermal system, nuclear waste disposal. However, the response and mechanism of ultrasonic waves through granites after thermal treatment are still poorly understood. In order to determine the combined effects of heating temperature and grain size on wave propagation across granites, a series of laboratory ultrasonic tests were performed with the pulse transmission method, combined with scanning electron microscopy observation. The testing results indicate that heating temperature and grain size have a combined impact on wave propagation across the tested granites. The wave velocity, transmitted coefficient, peak power spectral density and accumulative energy are generally negatively correlated with heating temperature regardless of grain size. The effect of grain size on wave propagation is more pronounced at low temperatures. Basically, the crack evolution is the main reason for the seismic response of granite after thermal treatment. A damage factor defined by the change of microcrack area in this paper is proposed and adopted to consider the combined effect of heating temperature and grain size. The peak power spectral density of the low-frequency wave and the transmission coefficient of the high-frequency wave are appropriate as the optimal wave indicators for evaluating the deterioration of granites at high- and low-damage stages, respectively. The findings in this study are of great importance for site selection and stability assessment in rock engineering activities under high temperatures, especially for the development of deep-seated hot dry rock.

481-P: 10kHz SCS Restores Mechanical and Thermal Neural Processing in a Rodent Model of Painful Diabetic Neuropathy

A recent randomized controlled trial of 10 kHz spinal cord stimulation (SCS) in patients with painful diabetic neuropathy (PDN) has demonstrated significant and durable improvements in neurologic status, particularly sensory restoration of the foot (Petersen et al 2021, Argoff et al 2023). In order to gain further mechanistic insight into the improvements in sensory processing by 10kHz SCS, we analyzed the receptive field (RF) size and responses of spinal dorsal horn (DH) neurons to mechanical and thermal stimuli of the paw in a PDN rat model. For PDN-model, Rats were given a single effective dose of streptozotocin (STZ), while Naïve animals were injected with 0.9% saline. Four groups were studied: Naïve, STZ, STZ+ShamSCS, and STZ+10kHzSCS. Rats were anesthetized with urethane and a laminectomy was performed for DH neurons recording. We analyzed RF size and the response of DH neurons to vibrotactile stimulation and thermal sensation. Both the Naïve and STZ+10kHzSCS groups had significantly smaller RFs than the STZ Control and STZ+ShamSCS groups. In response to a 1 Hz vibration frequency, Naïve and STZ+10kHzSCS groups had higher peak power spectral density (PSD) of DH firing than STZ+ShamSCS, and PSD for the STZ+10kHzSCS group was statistically higher than for the STZ Control group. Response of DH neurons showed no significant differences between groups during the thermal stimulation, but the post-stimulus firing rates for the STZ+10kHzSCS group were significantly higher compared to STZ Control and STZ+ShamSCS. These data suggest that 10 kHz SCS amplified the DH response to large fiber (vibration) and small fiber (warm) signals and normalized the receptive field of the paw (acuity) in PDN rats. In diabetes, where peripheral sensory compromise from chronic hyperglycemia can lead to loss of protective sensation, such ‘tuned amplification’ as provided by 10 kHz SCS in the central nervous system may compensate for the reduced functionality seen in the peripheral sensory systems. Disclosure K.Lee: Employee; Nevro Corp. D.Lee: Employee; Nevro Corp. D.Wang: Employee; Nevro Corp. Z.B.Kagan: Employee; Nevro Corp. K.Bradley: Employee; Nevro Corp.

Experimental investigation of strut effects on slanted cylinder afterbody aerodynamics using magnetic suspension and balance system

In this study, strut support effects on a slanted cylinder afterbody were investigated by a magnetic suspension and balance system installed in a wind tunnel. The results showed that the aerodynamic characteristics with respect to the critical Reynolds number where the flow field and aerodynamic forces change significantly. In the cases with the dummy strut, the range of the critical Reynolds number decreases, and the variation depends on the location of the strut. The size of the recirculation region and the separation bubble on the wake center plane also changes depending on the location of the strut. Moreover, additional weak vortices are observed to be formed behind the strut, which changes the wake structure. That change affects the variation of the vortex core wandering, and is a factor in the power spectral density peaks observed in previous studies. It is suggested that the strut support strongly interferes with the flow around the test model and should be carefully considered.

Comparison of aerodynamic performance of moving train model at bridge–tunnel section in wind tunnel with or without tunnel portal

The moving train model test for wind tunnels is an advanced and effective research method for studying the aerodynamic effect of trains passing through tunnel portals in crosswind environments. However, the modelling of tunnel portal structures is cumbersome, and its influence on test results remains unclear. Here, the influence law of the presence and absence of a tunnel portal on the aerodynamic performance of a train was investigated via a wind tunnel test and an improved delayed eddy simulation turbulence model with “mosaic” mesh technology. First, the difference between train locomotion on the windward and leeward side lines with and without a portal was compared from the perspectives of aerodynamic load amplitude, power spectral density (PSD), and standard deviation. Second, the influence of vehicle speed on the amplitude of the train’s aerodynamic load was studied, and the recommended critical speed was determined. Finally, the applicability of the moving model test results under different scale ratios (Reynolds numbers) was explored. Key results show that the aerodynamic load amplitude, PSD peak and standard deviation of the train on the leeward side line are generally higher than those on the windward side line. As indicated by the lift force in the ‘EX’ process without the tunnel portal, the amplitude on the leeward side line is 1.73 time the corresponding values on the windward side line. At speeds of 6, 12 and 18 m/s, when the moving train model speed reaches 12 m/s, the influence of the tunnel portal on the aerodynamic load amplitude can be ignored. The results imply a serious distortion of the aerodynamic load amplitude for the 1:20 model scale, whereas it appears to be appropriate at the 1:16.8 and 1:10 scales. The model test with a Reynolds number of 2.67 × 105 offers an ideal reference value for real trains.

Learning a novel rhythmic stepping task in children with probable developmental coordination disorder

BackgroundDevelopmental coordination disorder affects approximately 6% of children, interfering with participation in physical activity and can persist through adulthood. However, no studies have investigated the neuromotor mechanisms of learning of a novel task with rhythmic cueing. MethodsMovement Assessment Battery for Children-2nd edition was used to identify 48 children with probable developmental coordination disorder (13.9 ± 0.05 yrs., 27% male) and 37 typically developed (13.9 ± 0.10 yrs., 54% male). While instrumented with an inertial measurement unit, both groups performed a novel rhythmic stepping task and with a concurrent auditory stroop test (dual-task), underwent seven weeks of intervention with step training with rhythmic cuing and were tested for retention five weeks post-intervention. FindingsInitially, the group with probable developmental coordination disorder had a higher variability of step timing (coefficient of variation: 0.08 ± 0.003-typically developed – 0.09 ± 0.004-probable developmental coordination disorder, p < 0.05) and a frequency of peak power spectral density further from the target 0.5 Hz (0.50 ± 0.002 Hz-typically developed – 0.51 ± 0.003 Hz-probable developmental coordination disorder, p < 0.05), and were more affected by the dual-task: power spectral density at 0.5 Hz (−7.2 ± 3.3%-typically developed – -13.4 ± 4.6%- prob_DCD, p < 0.05) and stroop test errors (6.4 ± 1.1%-typically developed – -11.1 ± 2.4%- probable developmental coordination disorder, p < 0.05). The intervention led to similar improvements in both groups in coefficient of variation of step timing (0.12 ± 0.01-Pre – 0.07 ± 0.002-Post, p < 0.05), frequency of the peak power spectral density (0.51 ± 0.005 Hz-Pre – 0.50 ± 0.001 Hz-Post, p < 0.05) and relative power spectral density bandpower (3.2 ± 0.2%-Pre – 5.9 ± 0.3%-Post, p < 0.05). All improvements were retained after five weeks post-training. InterpretationRhythmic cueing shows strong promise for enhancing motor learning in children with probable developmental coordination disorder. Trial registrationRetrospectively registered on ClinicalTrials.gov with reference: NCT03150784