Root Mean Square Velocity Research Articles

Ultra-subwavelength rect-particles for wideband phase velocity equalization in coupled lines

This paper presents a procedural approach for utilizing ultra-subwavelength rectangular chiral particles embedded in the substrate to eliminate the spurious response of the coupled transmission lines by equalizing the even and odd mode phase velocities in a large bandwidth, making it applicable to wideband coupled-line based structures. Even and odd mode phase velocities, is equalized with the BW of 4 GHz, spanning the range 0.5–4.5 GHz, the normalized phase velocity Root Mean Square Error is less than 0.005.

Imaging method of surface defect using leaky Rayleigh wave with ultrasonic phased array

ABSTRACT Leaky Rayleigh wave testing has the advantages of non-contact, high sensitivity, and good beam directivity. However, current leaky Rayleigh wave testing mostly uses monolithic transducers and is seriously affected by acoustic wave attenuation and diffusion, resulting in poor image quality, limited detection range and low imaging efficiency. In this paper, a novel leaky Rayleigh wave testing method using an ultrasonic phased array is developed, and the total focusing method (TFM) is used to achieve high-quality imaging of defects. To improve imaging efficiency, the root-mean-square velocity (RMSV) model is utilised to rapidly acquire an approximate analytical solution for the time of flight of the acoustic wave. To obtain more accurate defect images further, the amplitude of the total focusing imaging signal is calibrated. The experimental results demonstrate that the proposed method achieves a 48% improvement in the imaging accuracy of a 1 mm hole, compared to the traditional Synthetic Aperture Focusing Technique (SAFT) imaging method. The proposed method achieves an 92% reduction in imaging time compared to the conventional TFM. The proposed method provides a new non-contact approach for high-accuracy and high-efficiency defect imaging using leaky Rayleigh wave.

Response of second-mode instability to backward-facing steps in a high-speed flow

Stability in a Mach 4.5 boundary layer over backward-facing steps (BFSs) is investigated using numerical methods. Two types of cases are considered with different laminar inflow conditions, imposed with single-frequency or broadband-frequency modes, respectively. Compared with the typical K-type transition over a flat plate, the boundary layer transition initiated by 90 kHz-frequency second mode appears to follow the same pattern but with a noticeable delay over the step. A larger step height leads to a better inhibition of the downstream Λ-vortices and thus a later transition, providing the step height is smaller than the local boundary layer thickness. Moreover, both the frequency weighted power spectral density and the root mean square of the streamwise velocity indicate the presence of Kelvin–Helmholtz (K–H) instability when the step height is equivalent to the thickness of the nearby boundary layer. There may exist an optimal step height for suppressing single-frequency (90 kHz) mode without exciting significant K–H modes. Similar to the previous studies on roughness, BFS can act as an amplifier for the low-frequency second modes and a suppressor for the high-frequency second modes. The critical frequency is equal to that of the unstable mode whose synchronization point is exactly located at the step corner. Additionally, the correction effects of the step induce the change of the phase speed of the fast mode, which correspondingly results in the movement of the synchronization point. Generally, the BFS is not able to completely alleviate the transition initiated by the broadband-frequency second modes but can still delay the boundary layer transition in a certain degree by suppressing the high-frequency unstable waves.

Comparison of the Effects of Cognitive Dual-Task and Single-Task Balance Exercises on Static Balance among People with Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

The anterior cruciate ligament (ACL) reconstruction surgery improves mechanical stability; however, functional stability remains impaired. Balance exercises can help improve functional stability. The effect of cognitive dual-task balance exercises has not been studied in people with ACL reconstruction surgery; therefore, this study aimed to compare the effect of cognitive dual-task and single-task balance exercises on the static balance indices in these individuals. This study was a randomized clinical trial. After a period of conventional physiotherapy and applying inclusion criteria, 28 patients with ACL reconstruction surgery were randomly divided into two groups of cognitive dual-task and single-task balance exercises. Each group received the relevant exercises for four weeks, three times a week, with each session lasting 20 min. Center of pressure variables, including mean displacement in anterior-posterior and medial-lateral directions, total path length, mean velocity of displacement, root mean square of displacement and velocity, and the elliptical area, were measured using the FDM pressure platform before and after the interventions as the primary outcomes. Knee Injury and Osteoarthritis Outcome Score (KOOS) scale was completed by the participants before and after the interventions. The measured static balance variables and KOOS subscales had significant differences before and after intervention in both groups (P<0.05); however, no statistically significant difference was observed in these variables between the two groups. There was no significant correlation between KOOS subscales and measured static balance variables. Both cognitive dual-task and single-task balance exercises improved the indicators related to static balance and the level of functional disability of the knee. However, cognitive dual-task balance exercises had no superiority over single-task balance exercises in ACL-reconstructed individuals.

LDV measurements of boundary layer velocity profiles on flat plates with different surface roughnesses

The dynamics acting upon thin flat plates submerged in a fluid are chiefly governed by the delicate boundary layer enveloping their surfaces. Through a series of experiments, we investigated the impact of surface roughness elements on the boundary layer adjacent to a flat plate across a range of Reynolds numbers. The experiments were performed in the Chungnam National University-Cavitation Tunnel (CNU-CT). Three flat plates, each characterized by distinct surface roughness heights denoted by k, were subjected to scrutiny. One boasted a pristine smoothness, while the others bore the deliberate roughness of sandpaper, each with its own unique texture. With precision instrumentation, including Laser Doppler Velocimetry (LDV), we meticulously documented the axial velocity profile and the RMS (Root Mean Square) velocity at strategic points along the flat plates. Through these measurements, we unveiled the boundary layer's thickness, δ, and momentum thickness, θ, elucidating their variations under differing free-stream velocities. As our exploration deepened, the relationship between the local Reynolds number, Rnx, and the non-dimensional velocity profiles, u+ − y+, became apparent. A systematic shift along the log-law line ensued, with both u+ and y + increasing in tandem with the rise in Rnx. Yet, our inquiry did not conclude with observation alone. Employing empirical rigor, we quantified the drag forces acting upon flat plates of varying roughness heights, deriving them from the measured momentum thickness across a range of local Reynolds numbers, Rnx.

Orbit Determination of Chinese Rocket Bodies from the Picosecond Full-Rate Laser Measurements

Abstract In this paper, the results of the orbit determination of two Chinese rocket bodies from low earth orbit (LEO) regime based on the picosecond laser measurements provided by one laser sensor are presented. A new approach was implemented that involved using a set of single laser measurements known as full-rate measurements instead of normal points. The computation strategy was applied using three different scenarios, and several key parameters such as root mean square (RMS), RMS of position (RMSPOS), RMS of velocity (RMSVEL), and alert time were determined. The results obtained indicate that the most optimal solution is to use short orbital arcs that are 24 h long. In this case, the average RMSPOS is approximately 345–530 m, the average RMSVEL is approximately 1 m/s, and the average arc RMS is approximately 3.7–7.0 cm. The determined alert time parameter, which refers to the time during which the laser observation of a given object should be repeated, is on average approximately 19.5 h. If longer orbital arcs, such as 2 days or more, are used, RMSPOS and RMSVEL actually reach the level of single centimeters and single millimeters per second, respectively. However, the arc RMS increases significantly to at least decimeters and even above 1 m in some cases. This suggests that the long arc approach is not a favorable solution. In addition, an interesting discovery has been presented that some Chinese launchers are equipped likely with the laser retroreflectors that can easily reflect the laser beam.

Rotational effect of a cylinder on hydro-thermal characteristics in a partially heated square enclosure using CNT-water nanofluid

Rotating cylinder movement in a cavity flow is an exciting field of study in heat transfer. Considerable research has been carried out on rotating cylinders under MHD mixed convection in various types of enclosures. However, considering partially heated square enclosure and magnetic field using CNT-water nanofluid is very limited. This study's goal is to assess the hydrothermal phenomena in a square enclosure with a rotating cylinder. Simulation has been conducted for different rotational speeds (Ω) and dimensionless times (τ) to observe the thermal and fluid flow behaviour. The Galerkin Residual based finite element method has been used to conduct numerical calculations. The results are shown as isotherms, streamlines, and average Nusselt number at the cylinder wall. Moreover, the drag force at the moving wall, and the fluid properties such as the root mean square (rms) of velocity, the temperature, the vorticity functions, and the average fluid temperature are also presented. The heat transfer rate, drag force, rms velocity, and temperature increase with the rise of rotational speed and dimensionless time rise. Maximum vorticity occurs at Ω = 8 and τ = 1. The maximum vorticity function increases 12 times with the increasing rotational speed. Higher rotational speed leads to increased average fluid temperature. The case of Ω = 8, τ = 1 shows the most temperature variance, while Ω = 1, τ = 0.1 has the least. Increasing rotational speed results in higher drag force on the cylinder's surface. At Ω = 4, the drag force is 2.8 times greater than at Ω = 2. Overall, the fluid flow and thermal performance boost up while the rotating speed of the cylinder is higher.

Based on the Feedforward Inputs Obtained by the Intelligent Algorithm the Moving Mirror Control System of the Fourier Transform Spectrometer

A moving mirror control system of the Fourier transform spectrometer (FTS) based on the feedforward inputs obtained by the intelligent algorithm is proposed in this paper. Feedforward control is an important part of the moving mirror speed control system of the FTS. And it is always difficult to quantitatively calculate the feedforward inputs through a precise mathematical model of the controlled object. Therefore, based on the expected motion law, an intelligent adaptive algorithm for obtaining feedforward inputs of the moving mirror system was designed. The algorithm decomposed the motion stroke into several position points, iteratively obtained the driving quantity of the moving mirror that met the expected instantaneous speed of each position point, and finally obtained the feedforward inputs of the whole motion stroke. The feedforward inputs obtained by the intelligent algorithm combined with the speed loop PID control constitute the complete moving mirror speed control system. Then, we applied the control system to the moving mirror of the FTS and acquired the velocity of the moving mirror. The experimental results show that the control system is feasible, the error of the peak-to-peak velocity is 0.047, and the error of the root mean square (RMS) velocity is 0.003. Compared with the single-speed-loop control system without feedforward inputs, the error of the peak-to-peak velocity is reduced by 43.3%, and the error of the RMS velocity is reduced by 67.7%, realizing a more accurate control of the moving mirror. Therefore, the control system based on the feedforward inputs obtained by the intelligent algorithm is a feasible and effective moving mirror speed control scheme of the FTS.

Hypersonic FLEET velocimetry and uncertainty characterization in a tripped boundary layer

Femtosecond laser electronic excitation tagging (FLEET) velocimetry is applied in a hypersonic boundary layer behind an array of turbulence-inducing trips. One-dimensional mean velocity and root-mean-square (RMS) of velocity fluctuation profiles are extracted from FLEET emissions oriented across a 2.75∘ wedge and through a boundary layer above a flat plate in two test campaigns spanning 21 tunnel runs. The experiment was performed in the Texas A&M University Actively Controlled Expansion tunnel that operated near Mach 6.0 with a Reynolds number near 6 × 106 m−1 and a working fluid of air at a density near 2.5 × 10−2 kg m−3. Detailed analysis of random and systematic errors was performed using synthetic curves for error in the mean velocity due to emission decay and the error in the RMS velocity fluctuation due to random error. The boundary layer behind an array of turbulence-inducing trips is documented to show the breakdown of coherent structures. FLEET velocimetry is compared to the tunnel Data Acquisition System, Vibrationally Excited Nitric Oxide Monitoring results, and Reynolds-Averaged Navier–Stokes computational fluid dynamics to verify results.

Estimating turbulent kinetic energy with an acoustic Doppler current profiler

A new method for estimating turbulent kinetic energy (TKE) from acoustic Doppler current profiler (ADCP) measurements is presented. Current methods of estimating TKE from ADCP measurements require assumptions regarding the flow being measured. Combining the geometric orientation of ADCP sampling beams and the relative contributions of root mean square (RMS) velocities to the total TKE results in a formula that can be written for any ADCP. Data from a direct numerical simulation (DNS) are used with a virtual ADCP to assess the success of this method, and laboratory experiments are used to test the new method in a physical setting. The proposed approach measures TKE with an average RMS error of 15.2%, which is less than that from previous methods. Error caused by the ADCP sampling in different spatial locations contributes most to overall error; commercially available ADCPs typically sample at a high enough frequency and fine enough resolution to measure the RMS velocities needed to calculate TKE. Guidelines for measuring TKE with an ADCP are proposed, and published data on rivers are used to estimate the applicability of this method in practice.

Translational and angular velocities statistics of inertial prolate ellipsoids in a turbulent channel flow up to Re τ = 1000

Direct numerical simulations of the turbulent flow in a channel are conducted up to $Re_{\tau }=1000$ to examine the influence of the friction Reynolds number on the translational and angular velocities of inertial, prolate ellipsoids. The quadrant distribution of the turbulent events seen by the particles is not significantly affected by the value of $Re_{\tau }$ , but subtle modifications take place, depending on the position in the channel and on the particle relaxation time. Overall, the influence of $Re_{\tau }$ on the first and second statistical moments of the ellipsoids translational velocity is the same as that observed for the fluid velocity. The weak dependence of these statistics to the particle shape previously observed at low Reynolds number remains at higher values of $Re_{\tau }$ . Similarly, the mean and root mean square (r.m.s.) of the angular velocity of the fluid seen by the particles weakly depend on particle shape and they have the same dependence to $Re_{\tau }$ as the angular velocity statistics of the carrier fluid. Particle angular velocity statistics are more strongly affected by the flow Reynolds number due to the evolution of the complex shape and inertia dependent rotation orbits with $Re_{\tau }$ . In the near-wall region the average angular velocity of weakly inertial ellipsoids increases with $Re_{\tau }$ due to their stronger alignment with the mean fluid vorticity. Furthermore, the r.m.s. of the wall-normal component of the angular velocity of more inertial ellipsoids increases with $Re_{\tau }$ owing to the larger fluctuations of the angle between the particle major axis and the velocity-gradient plane.

Variation between individuals in sensorimotor feedback control of standing balance.

We examined intersubject variation in human balance, focusing on sensorimotor feedback. Our central hypothesis was that intersubject variation in balance characteristics arises from differences in central sensorimotor processing. Our second hypothesis was that similar sensorimotor feedback mechanisms are used for sagittal and frontal balance. Twenty-one adults stood on a continuously rotating platform with their eyes closed in the sagittal or frontal plane. Plant dynamics (mass, height, and inertia) and feedback control were included in a model of sensory weight, neural time delays, and sensory-to-motor scaling (stiffness, damping, and integral gains). Sway metrics [root-mean-square (RMS) sway and velocity] were moderately correlated between planes of motion (RMS: R = 0.66-0.69 and RMS velocity: R = 0.53-0.58). Sensory weight and integral gain exhibited the highest correlations between the plane of motion (R = 0.59 for sensory weight and R = 0.75 for integral gain during large stimuli). Compared with other subjects, people who adopted a high vestibular weight or large integral gain in one condition did so across all tests. Intersubject variation in sensory weight, stiffness, and integral gain were significantly associated with intersubject variation in RMS sway whereas sensory weight and time delay were the strongest significant predictors of RMS velocity. Multiple linear regression showed that intersubject variation in sway metrics was predicted better by intersubject variation in central feedback mechanisms vs. plant dynamics. Together, results supported the first hypothesis and partially supported the second hypothesis because only a subset of feedback processes was moderately or strongly correlated (mostly during large surface tilts) between planes of motion.NEW & NOTEWORTHY This study details naturally occurring intersubject variation in healthy adults' balance control. Experimental surface tilts evoked postural sway and sensorimotor modeling defined feedback control parameters. We determined the relation between intersubject variation in feedback control (vestibular and proprioceptive reliance, neural time delay, sensory-to-motor scaling) and intersubject variation in postural sway between planes of motion and between stimulus amplitudes.

Propagation of a vector wavelet through von Kármán-type random elastic media: Monte Carlo simulation by using the spectrum division method

SUMMARY For the study of the random velocity fluctuation of the solid Earth medium, it is useful to measure the collapse of a seismic wavelet with increasing travel distance and the excitation of coda waves. Radiative transfer theory (RTT) is a powerful tool for synthesizing the propagation of a seismic wavelet in random media statistically characterized by the power spectral density function (PSDF) of the fractional velocity fluctuation. The Born scattering coefficient is a key building block of RTT. As the centre wavenumber of a wavelet increases, the phase shift across the correlation length increases and the Born approximation leads to an extremely large forward scattering exceeding the applicable range of the perturbation method. In such a case, the Eikonal approximation is able to explain the envelope broadening with increasing travel distance; however, it can not explain the coda excitation. To overcome the difficulty, we have proposed a hybrid Monte Carlo (MC) simulation for scalar waves. In the case of von Kármán-type random media, when the centre wavenumber is higher than the corner wavenumber, taking the centre wavenumber as a reference, we divide the PSDF into two spectral components. Applying the Born and Eikonal approximations to the high- and low-wavenumber spectral components, we statistically evaluate the wide-angle scattering and the narrow-angle ray bending, respectively. The proposed MC simulation serially using two kinds of scattering processes successfully synthesizes the time trace of the wave energy density from the onset to the late coda. The travel-distance fluctuation derived from the one-way propagation of the Eikonal approximation is also important. This paper extends this method for the propagation of a vector wavelet in random elastic media. We suppose that random fractional fluctuations of the P- and S-wave velocities and the mass density are linearly proportional to each other, which maintains the linear polarization of an Swave throughout the scattering process. Using the hybrid MC simulation with the spectrum division, we synthesize three-component energy density time traces for the anisotropic radiation from a moment tensor source, from which we derive three-component root mean square (RMS) velocity amplitude time traces at different azimuths. In parallel, we synthesize the propagation of a vector wavelet in many realized random elastic media by the finite-difference simulation, then we calculate three-component RMS velocity amplitude time traces. Using them as a benchmark, we confirm the validity of the proposed MC simulation for specific cases.

Experimental Investigation on Velocity Fluctuation in a Vaned Diffuser Centrifugal Pump Measured by Laser Doppler Anemometry

Turbulent flow, mainly originating from the rotor-stator interaction (RSI), is closely associated with the normal and safe operation of the centrifugal pump. In the current research, to clarify turbulent flow in the centrifugal pump with a vaned diffuser, the non-intrusive LDA (Laser Doppler Anemometry) system is applied to measure velocity pulsation signals at different regions when the pump operates at various flow rates. Time and frequency domain analysis methods are combined to investigate the velocity signals, and the velocity distribution around the volute tongue region is reconstructed from twenty measuring points. Results show that the velocity spectrum is characterized by the discrete components at the blade passing frequency and its higher harmonics, and it is caused by the RSI between the impeller and the diffuser. For the points in the volute spiral and diffusion sections, due to the significantly reduced RSI effect, the velocity spectrum shows an evident difference from comparison with the points between the impeller and diffuser, and the blade passing frequency is not always the dominant frequency. The comparison of velocity amplitudes and RMS* (root mean square of velocity) values at different points proves that the measuring position and flow rate affect velocity pulsations. As observed from velocity distribution reconstructed by LDA signals, high velocity regions are developed downstream of the diffuser channel for all the measured flow rates.

Evaluation of the Hand Motion and Peeling Force in Inner Limiting Membrane Peeling.

Robot assistance in membrane peeling may improve precision and dexterity or prevent complications by task automation. To design robotic devices, surgical instruments' velocity, acceptable position/pose error, and load ability need to be precisely quantified. A fiber Bragg grating and inertial sensors are attached to forceps. Data collected from forceps and microscope images are used to quantify a surgeon's hand motion (tremor, velocity, posture perturbation) and operation force (voluntary and involuntary) in inner limiting membrane peeling. All peeling attempts are performed on rabbit eyes in vivo by expert surgeons. The root mean square (RMS) of the tremor amplitude is 20.14 µm (transverse, X), 23.99 µm (transverse, Y), and 11.68 µm (axial, Z). The RMS posture perturbation is 0.43° (around X), 0.74° (around Y), and 0.46° (around Z). The RMS angular velocities are 1.74°/s (around X), 1.66°/s (around Y), and 1.46°/s (around Z), whereas the RMS velocities are 1.05 mm/s (transverse) and 1.44 mm/s (axial). The RMS force is 7.39 mN (voluntary force), 7.41 mN (operation force), and 0.5 mN (involuntary force). Hand motion and operation force are measured in membrane peeling. These parameters provide a potential baseline for determining a surgical robot's accuracy, velocity, and load capacity. Baseline data are obtained that can be used to guide ophthalmic robot design/evaluation.

Differing postural control patterns in individuals with bilateral and unilateral hearing loss

ObjectivesHearing loss (HL) is associated with imbalance and increased fall risk. The mechanism underlying this relationship and differences across types of hearing loss remains unclear. Head mounted displays (HMD) can shed light on postural control mechanisms via an analysis of head sway. PurposeThe purpose of this study was to evaluate head sway in response to sensory perturbations in individuals with bilateral (BHL) or unilateral hearing loss (UHL) and compare them to controls. Materials and methodsWe recruited 36 controls, 23 individuals with UHL and 14 with BHL. An HMD (HTC Vive) measured head sway while participants stood on the floor, hips-width apart. Stimuli included two levels of visuals and sound. Root Mean Square Velocity (RMSV) and Power Spectral Density (PSD) were used to quantify head sway. ResultsAdjusting for age, individuals with BHL had significantly higher anterior-posterior and medio-lateral RMSV than controls and individuals with UHL. Individuals with UHL demonstrated significantly lower response to visual perturbations in RMSV AP and in all 3 frequency segments of PSD compared to controls. Individuals with UHL showed significantly lower movements at high frequencies compared to controls. Sounds or severity of HL did not impact head sway. ConclusionsIndividuals with BHL demonstrated increased sway with visual perturbations and should be clinically assessed for balance performance and fall risk. Individuals with UHL exhibited reduced responses to visual stimuli compared with controls, which may reflect conscious movement processing. Additional studies are needed to further understand the mechanistic relationship between hearing loss and imbalance.

Test Investigation and Rule Analysis of Bearing Fault Diagnosis in Induction Motors

In this paper, a series of tests were conducted on the bearings of induction motors to investigate vibration signal analysis-based diagnosis of bearing faults, and a thorough analysis was also conducted. In the engineering field, the kurtosis coefficient of vibration acceleration and the root mean square of vibration velocity, as well as resonant demodulated spectrum analysis of vibration acceleration, have been widely used for bearing fault diagnosis. These are integrated in almost any commercially available device for diagnosing bearing faults. However, the unsuitable use of these devices results in many false diagnoses. In light of this, they were selected as research objects and were investigated experimentally. In three induction motors, faults of different severity in the bearing outer race and cage were modeled for tests, and the corresponding results were used to evaluate the performance of the selected diagnosis methods. Some vague information in engineering was clarified, and some instructive rules were outlined to improve the bearing fault diagnosis performance. Taking the kurtosis coefficient of vibration acceleration (Ku) as an example, in engineering, Ku = 4 is generally taken as the diagnostic threshold of bearing faults. This means the following rule applies: if Ku ≤ 4, the bearing is healthy; otherwise, the bearing is faulty. However, the test results in this paper show that even if Ku ≤ 4, the bearing might be faulty; if Ku &gt; 4, the bearing is indeed faulty. Therefore, the diagnostic rule should be improved as follows: if Ku &gt; 4, the bearing is faulty (which can be assured), and if Ku ≤ 4, the status of the bearing is still undetermined. Thus, this paper can be helpful for researchers to gain an experimental understanding of the selected diagnosis methods and provides some improved rules on their use for reducing false diagnoses.

An experiment generates a specified mean strained rate turbulent flow: Dynamics of particles

This study aimed to simulate straining turbulent flow empirically, having direct similarities with vast naturally occurring flows and engineering applications. The flow was generated in 100&amp;lt;Reλ&amp;lt;500 and seeded with passive and inertial particles. Lagrangian particle tracking and particle image velocimetry were employed to extract the dynamics of particle statistics and flow features, respectively. The studies for axisymmetric straining turbulent flow reported that the strain rate, flow geometry, and gravity affect particle statistics. To practically investigate mentioned effects in the literature, we present the behavior of both passive and inertial particles from the novel experiment conducted on initially homogeneous turbulence undergoing a sudden axisymmetric expansion. We represent the result with two different mean strains and Reynolds–Taylor microscales. However, this study, in contrast to the previous studies, considers the fields of inertial particles in the presence of gravity. The result discloses that the novel designed and conducted experiments simulated the flow satisfactorily. Then, the particle behavior in such flow showed the effectiveness of the flow distortion on particle dynamics such as velocity root mean square and Reynolds stress. Straining turbulence flow is subject to many industrial applications and physics studies, such as stagnation points, external flow around an airfoil, internal flow in changeable cross section pipe, expansion in the engine mixing chamber, and leading edge erosion. This study's conclusion could apply constructively to these areas.

Measurement and compensation of spillover effect in underwater acoustic sensor networks during target localization

Localization in underwater acoustic sensor networks (UWASNs) depends critically on the mobility pattern of the topology as well as the target node. Prior literature has attempted to localize static as well as dynamic sensors. However, unintentional movement of the sensor network introduces localization errors which add up cumulatively and disrupt the normal functioning of an underwater sensor network. In the present work, the concept of spillover has been defined to denote these unintentional movements. The genesis of spillover has been discussed with respect to the signal model. A theorem is proposed to describe the consequence of spillover on the UWASN. The problem of spillover is quantified mathematically. The loss of localization performance due to the spillover effect is then measured with the formulation of a control function which incorporates delay time. To mitigate the losses, a spillover compensation (SoC) algorithm is proposed. SoC utilizes a discretization technique to reduce the variance of sensor position and to enhance localization accuracy. It improves the performance of localization by at least 23.15% and reduces the localization error by 31% up to 600 m. Through a series of computations using parameters such as root mean square (RMS) positioning error and RMS velocity error, the theoretical findings are verified and compared with standard techniques. Diversity in deployment scenarios is taken care of using variance and sensor speed. The proposed technique shall be useful to create spillover-aware systems in underwater cybernetic localization and UWASNs in general.

Rating of perceived difficulty scale for measuring intensity of standing balance exercises in individuals with vestibular disorders.

A method for prescribing the difficulty or intensity of standing balance exercises has been validated in a healthy population, but requires additional validation in individuals with vestibular disorders. This study validated the use of ratings of perceived difficulty for estimation of balance exercise intensity in individuals with vestibular disorders. Eight participants with a confirmed diagnosis of a vestibular disorder and 16 healthy participants performed two sets of 16 randomized static standing exercises across varying levels of difficulty. Root Mean Square (RMS) of trunk angular velocity was recorded using an inertial measurement unit. In addition, participants rated the perceived difficulty of each exercise using a numerical scale ranging from 0 (very easy) to 10 (very difficult). To explore the concurrent validity of rating of perceived difficulty scale, the relationship between ratings of perceived difficulty and sway velocity was assessed using multiple linear regression for each group. The rating of perceived difficulty scale demonstrated moderate positive correlations RMS of trunk velocity in the pitch (r = 0.51, p < 0.001) and roll (r = 0.73, p < 0.001) directions in participants with vestibular disorders demonstrating acceptable concurrent validity. Ratings of perceived difficulty can be used to estimate the intensity of standing balance exercises in individuals with vestibular disorders.