Measurement Points Research Articles

Sensitivity analysis of landing and takeoff noise for conceptual low-boom supersonic aircraft using variable noise reduction system

This paper presents the results of an analysis of the sensitivity of the use of a variable noise reduction system (VNRS), considered in the new landing and takeoff (LTO) noise standard for supersonic aircraft, using a Japan Aerospace Exploration Agency (JAXA)-designed 66-ton twin-engine conceptual low-boom supersonic airliner as an example. The analysis was conducted using a tool developed by JAXA and examined the sensitivity of low-speed aerodynamic performance, the sensitivity of takeoff reference speed, the sensitivity of thrust control and flap control duration time ranges, and the sensitivity of noise level to takeoff profile uncertainty. The analyses showed that improving low-speed aerodynamic performance and increasing the takeoff reference speed significantly impact noise levels and the use of VNRS could reduce noise by 2.1 EPNLdB while maintaining the performance of the aircraft. Because the effective noise reduction method by changing the takeoff procedure considered differs for each noise measurement point, it is important to design a takeoff procedure that incorporates an appropriate VNRS. Uncertainty of the takeoff profile was also investigated using Monte Carlo simulations, and it was shown that noise reduction by VNRS is effective even with the assumed uncertainty in the takeoff profile.

The Influence of bogie cavity bottom plate on the aerodynamic noise characteristics of high speed trains

The bogie area with a complex structure is an extremely important source of noise for trains. Based on the large-eddy simulation(LES) and Ffowcs Williams-Hawkings(FW-H) analogy, aero-acoustic simulation was conducted on a 3-car high-speed train of a certain type with a bogie cavity bottom plate installed on the front and rear cars. The results show that bottom plate changes the flow field around the bogie, weakens the flow separation of airflow at the leading edge of the bogie cavity, mitigates the flow impact of airflow on various components of the bogie, suppresses the formation and detachment of large-scale vortices in the bogie area, and reduces the formation of pressure pulsations on the geometric surface of the bogie area. The bogie cavity bottom plate scheme reduces the far-field aerodynamic noise of the train by 1.63dBA, and the noise reduction effect is significant. The aerodynamic noise of the measurement point equipped with a bogie cavity bottom plate is lower than that of the conventional bogie cavity in all frequency bands, and the energy reduction is more significant at medium and low frequencies.

Far-field directivity estimation with a cube-shaped array of 256 MEMS microphones

The far-field directivity function (FFDF) of a sound source characterises the angular dependence of the acoustic fields far away from this source. This function can be estimated by performing a spherical wave expansion (SWE) of the sound field from pressure measurements distributed around the source. The truncation order of the SWE is a critical parameter that depends on the number of measurement points and on the spatial sampling scheme used for the measurements. Unfortunately, for irregular sampling schemes, no theoretical result allows to determine a truncation order. In this work, a surrounding cuboid microphone array composed of 256 MEMS microphones is deployed. A cross-validation framework is used in order to determine an optimal truncation order for the SWE of the field radiated by a test source. The quality of the reconstructed field is assessed on the frequency range 100-5000 Hz. Finally, the estimated SWEs and far-field directivities are compared to an analytical model of the test source.

Robotic arm, 3D vision and geometric matching for an efficient implementation of inverse Patch Transfer Function method

The inverse patch transfer function method was developed to reconstruct the acoustic fields (velocity, pressure, intensity) at the surface of a vibrating source with a complex geometry using the concept of a virtual acoustic domain. This method can be used to manage sources with complex shapes in a non-anechoic acoustic environment, even in the presence of masking objects. However, this method is quite demanding experimentally as it requires a large number of measurement positions with good spatial positioning accuracy. This article presents a dedicated experimental platform developed to simplify and automate the entire measurement process. First, a 3D camera placed on a robotic arm constructs a point cloud characterising the source and its environment. Using a geometric matching algorithm, the CAD of the object under test is detected in the cloud of points, enabling the different coordinate systems (CAD, robot and physical part) to be matched. Secondly, the measurement points required to apply iPTF can be defined directly in the CAD and reproduced in near-real time on the test rig, regardless of the type of antenna used, providing an efficient means of applying iPTF and opening the way to many advanced applications.

Setting up light and noise maps to define the contours of a reserve of darkness and silence in Sherbrooke, Québec, Canada

Urban sprawl brings cities closer to natural areas, making them cohabit is a significant environmental challenge. Densification can also increase light and noise pollution, negatively affecting human and biodiversity well-being. Grounded on a collaboration between a college and a university, this work combines brightness and noise maps to establish the contours of a reserve of darkness and silence in Sherbrooke's Mont-Bellevue Park (Québec, Canada). The light and sound environments of the city are mapped by the research team using two devices mounted on vehicles or bicycles: a multispectral and multidirectional brightness sensor and a sound level meter. Long-term and fixed-point light and noise measurements were also conducted to develop the mobile measurement protocol. Wind tunnel measurements in an anechoic chamber were finally used to determine the effect of travel speed on measured noise levels, showing that speeds of less than 15 km/h ensure unbiased acoustic measurements using a windscreen. Perspectives include using the Noise Capture application to provide crowdsourced and additional noise levels at fixed measurement points. The open-source Noise Modelling tool will provide us with calculated environmental noise maps to be compared with measured data.

Optimization of an active device for global control of low-frequency wall reflections in a semi-anechoic room

An active device has been designed and built at LMA to control low-frequency reflections on the absorbing walls of a semi-anechoic room: the sound pressure reflected by the walls in the presence of an unknown source is estimated by linear filtering of the total sound pressure near the walls, then neutralized using acoustic sources placed on the walls. Here, we present 2D numerical simulations, involving monopole sources and series of damped analytic modes, which have enabled us to optimize the active device, in particular to (i) deal with resonance frequencies at which cancelling the diffracted pressure near the walls is not sufficient to cancel it inside the room, (ii) minimize the number of the total pressure measurement points required to estimate the pressure diffracted by the walls at each location, and (iii) select the strategy for minimizing the virtual signals corresponding to the diffracted pressure. Simulations show that with the optimized device, the control remains efficient up to frequencies corresponding to one wall source per wavelength and a little less than two pressure sensors per wavelength. Experiments are underway to compare measurements with simulations.

A fundamental study on energy-based assessment of Shinkansen railway noise in Japan

This study examines the assessment of environmental noise standards for the Shinkansen in Japan, which predominantly relies on averaging the highest noise levels, specifically L_(A,Smax) obtained from actual measurements taken at key locations along the Shinkansen routes. In contrast, the international approach, based on Europe, typically involves energy-based evaluations that calculate noise exposure over time using estimated values. By investigating the correlation between L_(A,Smax) and energy-based noise levels (L_AE), including data from the latest Shinkansen model, the N700S, this research aims to explore the potential for adopting energy-based noise assessments in Japan, aligning with international methodologies. Additionally, it compares the relationship between measured L_AE and L_(A,Smax) with that of estimated L_(A,Smax) and measured L_(A,Smax). The study also examines the calculation equations by derivingL_(A,Smax) from L_AE and considers factors contributing to the increase in Root Mean Square Error (RMSE), such as differences in routes, distances from the track surface to the measurement points, vehicle types, and the influence of building clusters.

Acoustic near field effects in distribution transformer noise measurement

This paper examines the near field effect, including the active and reactive acoustic field around a liquid-filled distribution transformer with heat-dissipating corrugated fins on the tank walls. The analysis was carried out on the basis of measurements of sound pressure and sound intensity levels along with acoustic maps including the phase correlation of acoustic waves. The acoustic field around the transformer was evaluated in the measurement planes showing normal direction radiation of up to 1,0 m distance. Discrete point measurements made with the PU (pressure - velocity) probe was used to obtain parameters such as particle velocity, active and reactive sound intensity as well as the transfer function associated with the reference microphone. The last parameter, the transfer function, allows to show the phase correlation between acoustic wave propagation, which contributes to a better understanding of acoustic near-field effects where energy circulates, creating a sound field that can have overestimated sound pressure and intensity levels.

Uncertainty study of two-phase flow distribution characteristics measurement based on bubble trajectory tracking method

Bubbles undergo complex motions such as nonlinear trajectories in two-phase flow, where the position, velocity magnitude, and direction of bubble centers continuously change as they evolve under the influence of forces. The complexity of bubble trajectory increases the difficulty in measuring the flow field distribution characteristics, which has been understudied in the previous. The bubble trajectory tracking model based on the Monte Carlo method is constructed to study the uncertainty of two-phase flow distribution characteristics measurement by the conductivity probe. The Monte Carlo method is adopted to randomly generate the bubble velocity at the initial moment and the bubble force characteristics are embedded to simulate the three-dimensional motion of the bubble. The influence of various factors on the distribution of effective bubble numbers and velocity relative error at the local point is quantitatively analyzed. It is found that the lateral spacing of the sensors has the greatest influence on the measurement results of small-sized bubbles, the accuracy is greatly reduced when the space is larger than the radius of the measured bubbles. Moreover, the measurement accuracy of the probe for medium-sized bubbles is high, and the effect of bubble lateral velocity and aspect ratio on the effective bubble ratio and velocity relative error is negligible. In addition, the maximum measurement range of the probe at local points is investigated which is found to be 4 mm in the lateral direction and 2 mm in the longitudinal direction. Finally, uniformly distributed bubbles are generated in a 20 mm × 10 mm transverse plane and the distribution of the effective bubble ratio of the probe is found to be consistent at different measurement points, which verifies the reliability of the probe measurement.

Research and application of joint-constrained inversion of transient electromagnetic multivariate parameter

Due to the phenomena of stratigraphic inclination, complex structure, and lateral discontinuity of resistivity or layer thickness in most of the coal seams, the traditional one-dimensional transient electromagnetic inversion method has limitations in interpretation accuracy. In addition, two- and three-dimensional inversion and artificial intelligence inversion have problems of large computation and large sample size, respectively, which limit their application in small- and medium-sized engineering exploration. To improve the inversion effect, this study proposes a method of joint-constrained inversion of transient electromagnetic multivariate parameters. This method achieves the joint constraint inversion of the transient electromagnetic multi-parameter by making full use of the geological data and a priori information to construct the initial model and adding the constraints such as the resistivity, the thickness, and the layer interface of each layer in the inversion objective function, and at the same time, taking into account the spatial correlation of the stratigraphic structure between the neighboring measurement points, as well as the transverse and vertical constraints between the measurement points along the direction of the survey line and perpendicular to the survey line. First, a series of typical geoelectric models are established and numerically simulated, and the results are compared with those of the traditional inversion method to verify the applicability and effectiveness of the method. Then, the constrained inversion is carried out on the physical simulation and measured data, and the results are in good agreement with the actual geological conditions. The numerical simulation, physical simulation and measured data inversion results consistently prove that this method can effectively reduce the uncertainty of the inversion at the isolated measuring points, improve the spatial continuity of the formation boundary, and better reflect the actual geoelectric characteristics of the formation.

A novel electromagnetic-navigated maxillary repositioning system for Le Fort I osteotomy: Preclinical evaluation

PurposeAdvancements in surgical assistive technologies for orthognathic surgery have increased the prevalence of guided surgeries. This study developed and evaluated a novel system utilizing electromagnetic (EM) navigation for maxillary positioning. MethodsLe Fort I osteotomies were performed on three skull models. The three-dimensional position of two sensors, facilitated by an EM tracking system, was used to move and fix the maxilla in its planned position, shifted 3 mm forward. The first sensor was placed on the lateral border of the pyriform aperture on the cranial side, while the second sensor was affixed as a splint on the maxillary dentition. Surface data from scans of the experimental skull bone were obtained using an optical scanner and superimposed on the pre-planned data to assess accuracy. ResultsThe discrepancy between the maxilla positioned with EM navigation and the planned position was within 1.0 mm in the vertical, horizontal, and anteroposterior directions. Error at the A and ANS measurement points was 0.44 and 0.54 mm, respectively (average = 0.49 mm). ConclusionThis experimental study represents a paradigm shift from guided to navigation surgery. Meticulous maxillary repositioning achieved through EM navigation enhances the reproducibility of preoperative simulations during surgery.

Study protocol for a multicentre randomised controlled trial evaluating the efficacy of an online yoga intervention in high-grade glioma patients and their caregivers: the YINOTA-O-trial

IntroductionHigh-grade glioma patients and their caregivers often suffer from distress and a lower quality of life. Results from studies with patients with mixed cancer entities suggest that yoga can be...

Tsunami Data Assimilation Using High‐Frequency Radar‐Derived Surface Currents by Considering Beam Angle‐Dependent Measurement Error Distributions

AbstractThe application of high‐frequency radar as an instrument for assimilating tsunami‐induced current fields is garnering increasing interest. The performance of surface current velocity measurements depends on the azimuthal differences between the crossing radar beams at the measurement points. This study aimed to incorporate the measurement error distributions of the east‐west and north‐south velocity components into tsunami data assimilation based on an optimal interpolation method, assuming Gaussian noise with the time‐invariant and a uniform standard deviation (STD = 5 cm/s) of radial velocity measurements. Through the empirical orthogonal function (EOF) analysis of radar‐derived surface currents in the Kii Channel, Japan, the velocities reconstructed using higher modes (EOFs 16–274) were associated with measurement errors, portraying nonuniform distribution depending on the crossing beam angle of two radar beams. Based on independent fifteen‐time assimilation experiments for two different tsunami scenarios, for a uniform water depth of 500 m, we observed a significant improvement of up to 29% and 0.9% in the assimilation performance (on average) over the along‐coast stations for scenarios with 1‐ and 5‐m maximum initial sea surface heights, respectively. The measurement errors dependent on the crossing beam angle reduced the error‐induced tsunamis, resulting in stable assimilations, with lower STDs in the fifteen‐time assimilation performances. When the STD of Gaussian noise varies with time, it is important to consider the temporal change in the radial velocity measurement errors and/or noise‐filtering techniques, to maintain a certain level of noise intensity.

A temperature-sensitive points selection method for machine tool based on rough set and multi-objective adaptive hybrid evolutionary algorithm

Reasonable deployment of temperature sensors is the key to accurately monitoring the temperature field of machine tools and improving the accuracy of thermal error prediction and compensation models. To determine the optimal deployment location of sensors, this paper proposes a temperature-sensitive points selection method tightly coupled with rough set and multi-objective optimization. Firstly, the importance of each temperature measurement point to the thermal error is calculated based on the rough set, and information entropy is introduced to amplify the importance difference among adjacent measurement points at the same heat source. Then, with the temperature measurement points groups as the variables, the number of temperature measurement points in the group, and the information importance of the group as the objectives, a multi-objective attribute reduction model is established, which transforms the temperature-sensitive points selection problem into a discrete multi-objective optimization problem. Finally, a multi-objective adaptive hybrid evolutionary algorithm is proposed, which designs a population initialization method based on mutual information and interval probability, and dynamic adaptive evolutionary parameters to achieve optimal temperature-sensitive points selection. Experiments on the high-speed dry hobbing machine verify the superiority and effectiveness of the proposed method.

Development of nursing students' professional identity in different mentoring approaches during clinical training: A quasi-experimental study

BackgroundThe professional identity (PI) of nursing students' is essential for high quality performance and safe healthcare. Clinical training plays a key role in the development of professional identity during nursing studies. AimThe aim of this study was to investigate the impact of individual and group mentoring approaches on the development of PI during clinical training, as well as the influence of the order in which these approaches are applied, and the effect of time on the development of PI. DesignThis study used a quasi-experimental design. SettingsThe study was conducted at the Department of Health Studies in Croatia. ParticipantsThe 119 first, second, and third year ungraduate nursing students. MethodsStudents were divided into two groups. Each group performed clinical training in group and individual mentoring approaches, but in different order. The Professional Identity Five Factor Scale (PIFFS) was used to measure PI levels at four different time points: immediately before and after the first and second rounds of clinical exercises. ResultsBoth groups of students, achieved approximately average results in all three dimensions of the PI. There was no statistically significant main effect of the group/individual mentoring approach on the dimensions of knowledge (P = 0.471), experience (P = 0.865) or perception of role model and professional future (P = 0.565). The levels of the dimensions knowledge (P = 0.001), experience (P = 0.001) or perception of the role model and professional future (P = 0.002) differed in four measurement points, which indicates a general increase in all three PI dimensions. ConclusionsDuring the performance of the clinical training, the level of PI increased. The group mentoring approach has an immediate effect on increasing knowledge, but this effect diminishes over time. In terms of experience, both mentoring approaches have similar reinforcing effects. However, the individual approach seems to be more suitable for improving the perception of role models and the professional future.

A simple hot wire temperature drift correction based on temperature sensitivity applied to a turbulent shear layer

A procedure is proposed to correct temperature drift for hot wire anemometry measurements in turbulent fields where the facility is not equipped with temperature control. The procedure consists of evaluating the wire sensitivity to the temperature by building a voltage-temperature curve. The voltages of both the calibration points and the measurement points are corrected, shifting the voltage values to an arbitrary reference temperature. The correction can be applied to the instantaneous voltages by performing synced temperature measurements with constant current anemometry or constant voltage anemometry cold wire. The efficacy of the method is tested on a turbulent shear layer that develops on the side of an open jet wind tunnel not equipped with temperature control. The velocity statistics show a good match with respect to reference particle image velocimetry measurements, evidencing the self-similarity of the shear layer in contrast with the non-corrected data and the data corrected using the semi-empirical and analytical relation based on King's law modification. A correction based only on the temperature statistics shows indistinguishable results with respect to the instantaneous correction.

The human lower leg muscle pump functions as a flow diverter pump, maintaining low ambulatory venous pressures during locomotion

ObjectiveAmbulatory venous pressure (AVP) is the drop of pressure observed in the superficial veins of the lower leg during movement. This phenomenon has been linked to the function of the calf muscle pump (CMP) and the competence of venous valves. Nevertheless, the concept of the CMP function remains controversial. This study aimed to elucidate the association between lower leg muscles activity, changes in pressure in distinct venous segments, and lower extremity arterial blood supply in healthy subjects during various types and intensities of exercise. MethodsTwelve legs of nine healthy volunteers were enrolled in the study. Continuous pressure (intramuscular vein [IV] and three great saphenous vein [GSV] points) and surface electromyography data (gastrocnemius and anterior tibial [ATM] muscles) were recorded during treadmill walking, running, and plantar flexion exercises. The pressure gradient (ΔP, mmHg) between adjacent points of measurement was calculated. Minute unit power of muscle pump ejection and suction (NE, and NS, MPa/min) were calculated and compared with the arterial blood supply of the lower extremity (LBF, L/min). ResultsΔP demonstrated a consistent pattern of changes during walking and running. In GSV, the ΔP was observed to be directed from the thigh to the mid-calf (retrogradely) and from the ankle to the mid-calf (anterogradely) throughout the entire stride cycle. However, its value decreased with increasing stride cycle frequency. The dynamics of ΔP between the IV and GSV were as follows: It was directed from the IV to GSV during gastrocnemius contraction and was reversed during anterior tibial muscle contraction and gastrocnemius relaxation (swing phase). LBF, NE, and NS demonstrated similar exponential growth with increasing stride frequency during walking and running. ConclusionsDuring natural locomotion, the muscle pump acts as a flow diverter pump, redirecting the flow of blood from the superficial veins to the intramuscular veins via the perforating veins. During ambulation, the pressure in the superficial venous network depends upon the capacity of the muscle pump to provide output that matches the changes in arterial blood flow.

Experimental research of helicopter blade load in flight based on optical sensing

Abstract The actual flight measurement of blade load is an extremely important part of the new helicopter. In order to solve the problems existing in the traditional electrical measurement method, such as weak anti-interference ability, short life, and large added mass, a flight measurement method of blade load based on optical sensing is proposed. Firstly, the strain mode distribution law is obtained by calculating the dynamic response of the real blade. The optimal layout of the optical fiber measurement points is determined. Through theoretical analysis of strain transferring and experimental verification, a highly reliable fusion scheme of blade and fiber is designed to meet the flight requirements. Based on the power line carrier technology, the optical sensing test system for helicopter flight test is developed. The flight test of blade load is completed successfully. The results of optical fiber measurement are consistent with the results of traditional electrical measurement, which indicates that the optical sensing technology has good applicability in the measurement of helicopter blade load. At the same time, it has been proved that the optical measurement system set is reliable and durable. It is of great significance for the leap from electric measurement to optical measurement.

Interferometric Rayleigh Scattering for Flow Temperature and Velocity Analysis

A new processing method is developed to analyze images from a Fabry–Pérot interferometer in order to extract point measurements of temperature and velocity within a gas flow, using Rayleigh scattering. Two types of interferograms are generated from a Fabry–Pérot model combined with a simulated light source. The first type is obtained from a diffuse coherent light source, namely, a laser beam on a diffuser. The interferometer characteristics, defined by only two independent parameters, are retrieved within 0.1% accuracy. The knowledge of these parameters is mandatory to analyze interferograms from Rayleigh scattered light. The second type corresponds to Rayleigh scattered light from a small volume under flow conditions, lighted with a focused laser beam and captured with long exposure time. Several flow parameters are chosen to generate these interferograms. The relative errors on the temperature and velocity estimates are found to be weak. Noise is also added to assess the robustness of the processing method. The error induced by the estimates of the instrument function is found to be of second order compared to the error induced by the image analysis.

Uncertainties in exposure predictions arising from point measurements of carbon dioxide in classroom environments.

Predictions of airborne infection risk can be made based on the fraction of rebreathed air inferred from point measurements of carbon dioxide (CO[Formula: see text]). We investigate the extent to which environmental factors, particularly spatial variations due to the ventilation provision, affect the uncertainty in these predictions. Spatial variations are expected to be especially problematic in naturally ventilated spaces, which include the majority of classrooms in the UK. An idealized classroom, broadly representative of the physics of (buoyancy-driven) displacement ventilation, is examined using computational fluid dynamics, with different ventilation configurations. Passive tracers are used to model both the CO[Formula: see text] generated by all 32 occupants and the breath of a single infectious individual (located in nine different regions). The distribution of infected breath is shown to depend strongly on the distance from the release location but is also affected by the pattern of the ventilating flow, including the presence of stagnating regions. However, far-field exposure predictions based on single point measurements of CO[Formula: see text] within the breathing zone are shown to rarely differ from the actual exposure to infected breath by more than a factor of two-we argue this uncertainty is small compared with other uncertainties inherent in modelling airborne infection risk.