Receiver Positions Research Articles

Ultrasonic immersion testing of residual stress in plates using collinear Lamb wave mixing technique

Nondestructive estimation of residual stresses has been a major challenge in engineering. Herein, the collinear Lamb wave mixing method is proposed for residual stress measurement in metal plates under immersion ultrasonic testing. Numerical simulations have been conducted to investigate the influences of excitation parameters on the performance of the wave mixing method. The results showed that the receiver position and cycle numbers of primary waves affect the amplitude of the method, and optimal excitation parameters recommended. Ultrasonic immersion experiments are conducted on two types of plate-like specimens using the collinear Lamb wave mixing method. Experimental results showed that the proposed method is effective for measuring the residual stress in metal plates. The immersion ultrasonic testing can significantly reduce the influence of inconsistent coupling conditions between the transmitters and the specimen on experimental results, therefore it is more reliable than conventional contact testing.

Implementation and testing of single point positioning on IRNSS/NavIC receiver data

SummaryIndia has developed its own regional navigation satellite system called the Indian Regional Navigation Satellite System (IRNSS), also known as Navigation with Indian Constellation (NavIC). IRNSS/NavIC provides standard positioning and timing services for civilians and restricted services for authorized users. In this paper, single point positioning is implemented on the NavIC receiver data. Estimation techniques of the least squares method and extended Kalman filter are implemented after applying broadcast‐based clock corrections, orbit computation, relative time correction, and ionosphere delay correction for single and dual frequency. A data extraction and storage module is developed to store computed parameters at every intermediate stage in separate files. This is followed by an error plotter module to plot the extracted parameters for each satellite and to separately analyze their performance and the obtained errors. The estimated receiver position is visualized on Google Earth. The absolute error in both estimation techniques ranges between 5 and 15 m throughout the period.

Single-station single-frequency GNSS cycle slip estimation with receiver clock error increment and position increment constraints

Single-station single-frequency GNSS cycle slip estimation with receiver clock error increment and position increment constraints

Acoustic tracking of moving marine targets using a single autonomous surface receiver

AbstractWhile marine animal behavior is often studied in constrained lab setups, a more reliable exploration should be done in their natural environment and without human interference. This task becomes excessively more challenging when quantitative data are needed in large and unconstrained aquatic environments. Toward that end, researchers widely use acoustic positioning telemetry to remotely track their subjects, though this often requires an extensive network of receivers placed in the environment ahead of time. This study proposes a new tracking method that continuously tracks and reports the trajectory of a target in unconstrained marine environments using a single‐moving acoustic receiver. Instead of deploying an extensive array of static receivers, we use a single receiver mounted on an autonomous surface vehicle to obtain highly accurate results with much cheaper and simpler means. The receiver position and earlier target location estimations are used to calculate an optimal trajectory for the receiver, which in turn provides subsequent readings and target localizations based on a new variant of the Time Difference of Arrival approach. We demonstrate the performance of the proposed methods using both simulations and field experiments.

Global Navigation Satellite System Receiver Positioning in Harsh Environments via Clock Bias Prediction by Empirical Mode Decomposition and Back Propagation Neural Network Method.

This paper proposes a novel method to improve the clock bias short-term prediction accuracy of navigation receivers then solve the problem of low positioning accuracy when the satellite signal quality deteriorates. Considering that the clock bias of a navigation receiver is equivalent to a virtual satellite, the predicted value of clock bias is used to assist navigation receivers in positioning. Consequently, a combined prediction method for navigation receiver clock bias based on Empirical Mode Decomposition (EMD) and Back Propagation Neural Network (BPNN) analysis theory is demonstrated. In view of systematic errors and random errors in the clock bias data from navigation receivers, the EMD method is used to decompose the clock bias data; then, the BPNN prediction method is used to establish a high-precision clock bias prediction model; finally, based on the clock bias prediction value, the three-dimensional positioning of the navigation receiver is realized by expanding the observation equation. The experimental results show that the proposed model is suitable for clock bias time series prediction and providing three-dimensional positioning information meets the requirements of navigation application in the harsh environment of only three satellites.

Experimental comparisons of speech transmission index prediction methods

Good speech intelligibility is the primary goal of acoustic environment control in lecture rooms and auditoria. The speech transmission index (STI) is the primary objective evaluation metric for speech intelligibility. Therefore, accurate prediction of the STI during the design stage is important for acoustic environment control in lecture rooms and auditoria. Two types of STI prediction methods based on simulated impulse responses and statistical are recommended by the IEC standard. In this study, the prediction accuracy and influencing factors of these two types of prediction methods were systematically analysed using STI measurements collected at 25 receiver positions in six rooms. The results reveal the following. (1) When the influence of the signal-to-noise ratio (SNR) is not considered, for the STI prediction method based on simulated impulse responses, the prediction accuracy is in an acceptable range with the average predicted STI discrepancy of the 25 receiver positions being −0.004 and the maximum discrepancy being 0.046. For the STI prediction method based on statistical, the average predicted STI discrepancy of the 25 receiver positions was −0.015, and the maximum discrepancy was −0.091. STI prediction based on statistical exhibited a larger prediction error at the receiver positions close to the sound source and smaller prediction error at the receiver positions farther away from the sound source. (2) When the influence of the SNR was considered, the errors of both prediction methods increased significantly. For the STI prediction method based on simulated impulse responses, the average predicted STI discrepancy of the 25 receiver positions was −0.035 and the maximum discrepancy was −0.088. For the STI prediction method based on statistical, the average predicted STI discrepancy of the 25 receiver positions was −0.030 and the maximum discrepancy was −0.112. (3) Using a sound source that is different from the onsite measurement sound source can induce noticeable errors in both methods. (4) For the STI prediction method based on statistical using the actual Q value of the sound source, the prediction accuracy of receiver positions close to the sound source can be significantly improved and the effect on receiver positions farther away from the sound source is relatively small. (5) Both methods require significant technical expertise from users, rendering it difficult to obtain accurate prediction results during the design stage.

Effect of satellite availability and time delay of corrections on position accuracy of differential NavIC

Abstract The position accuracy of standalone Navigation with Indian Constellation (NavIC) may not be met for certain applications like civil aviation. To improve the position accuracy of the user receiver, the technique used is Differential NavIC, which makes use of Differential corrections. The position accuracy of the user receiver also depends on the satellite availability (i.e. number of satellites available at a certain time instant to estimate the user position) and delay in transmission of differential corrections. In this article, the analysis of differential NavIC using different numbers of visible satellites (satellite availability) and different time delays for transmission of corrections is carried out. For this analysis, three cases are considered, Case I is when all (six) NavIC satellites are visible, Case II is when five satellites (3 Geosynchronous Orbit (GSO) and 2 Geostationary Earth Orbit (GEO)) are visible, and Case III is when five satellites (3 GEO and 2 GSO) are visible. The comparative analysis for these three cases is carried out with respect to the position accuracy parameters and Geometric Dilution of Precision. It is observed that, with the satellite availability in case I and case III, the user receiver accuracy is approximately the same. In case III, the accuracy of the user receiver (3.08 m) is similar to the accuracy (3.09 m) in case I. For time delay in transmission of corrections, different time delays (0, 5, 10, 20, …, 300 s) are considered to observe the effect on the positional accuracy of the user receiver. Due to the increase in this time delay, there is a significant degradation in the user receiver position accuracy of differential NavIC.

Wireless vision-based digital media fixed-point DSP processor depending robots for natural calamities

AbstractNatural calamities are affecting many parts of the world. Natural disasters, terrorist attacks, earthquakes, wildfires, floods and all unpredicted phenomena. Disasters cause emergency conditions, so imperative to coordinate the prompt delivery of essential services to the sufferers. Often, disasters lead many people to perish by becoming trapped inside, but many more also perish as a result of individuals receiving rescue either too late or not at all. The implementation and design of a Receiver module utilizing Davinci code processor DVM6437, Wireless camera receiver, Zigbee Transceiver and Global Positioning System (GPS) is proposed in this manuscript for Wireless Vision-based Semi-Autonomous rescue robots that are employed in rough terrain. The receiver side’s Zigbee transceiver module eliminates the limitations of tele-operating rescue robots by enabling the control station to receive GPS data signals and aids in robot management by sending control signals wirelessly. Half and full-duplex communication are supported by the Davinci processor DVM6437, a digital media fixed-point DSP processor that relies on Very Long Instruction Words. It includes an extensive instruction set that is ideal for real-time salvage operations. DVM processor is coded utilizing MATLAB Simulink. MATLAB codes and Simulink blocks are employed under Embedded IDE link.

О проблеме дисбаланса рисков ответственности и вознаграждения финансового управляющего по делам о несостоятельности (банкротстве) граждан

The article shows the problem of imbalance of high liability risks and the amount of remuneration of a financial receiver as a reason for refusal to get involved in personal bankruptcy cases. The author evaluates the explanation of the Supreme Court of the Russian Federation that a citizen may be released of any debts if no candidate to the receiver position is submitted to court. The paper points out that such explanation can be used in exceptional cases only.

Reciprocal sensitivity kernels for receiver positioning

In their classical formulation, sensitivity kernels aim to evaluate the points where an infinitesimal variation in the properties of the medium would most affect a pressure (or displacement) measurement at a fixed location. These kernels feature typical cigar shapes, with characteristically low sensitivity on the direct path. In this presentation, the same approach is applied to the reciprocal problem, where we want to evaluate, at a constant source position, which points are the most (or least) sensitive to a given model change. These reciprocal kernels exhibit flared shapes centered on the areas where the model is perturbed. Applications to receiver positioning in acoustic are discussed.

Rotation-Tolerant Wireless Power Transmission Scheme with Smart Positioning for Cognitive Research on Moving Animals.

This article presents a novel wireless power transmission scheme designed for moving loads. Specifically focused on compensating for the tilt misalignment of the receiver. By utilizing phase-shifted excitation signals from an array of transmitters, the proposed scheme effectively mitigates the impact of misalignment, locally. The application of this scheme holds particular relevance for studying the behavior of moving animals in cognitive research. The system incorporates a cage with two transmitter arrays positioned on the top and bottom sides. To smart determining the receiver's position, the proposed structure utilizes current feedback from the driving circuits and employs SVM (Support Vector Machine) classification algorithms for positioning. Furthermore, when the receiver coil is tilted, a phase shift mechanism significantly enhances the power delivered to the receiver. Additionally, the use of an overlapped transmitter array enhances rotation tolerance and improves the uniformity of the magnetic fields for moving objects. The performance of the proposed scheme is validated through extensive simulations and measurements using a fabricated prototype. Notably, the designed system achieves a power delivery of 296 mW to the load at a 90° angular misalignment, compared to 1.67 µW delivered by conventional array system.

The effect of spatial orientation of solar energy receiver on the energetic gain

The angle of incidence of solar radiation on the PV panel is a function of many factors: the angle of solar declination, the angle of latitude, the hour angle, the azimuth angle and the angle of receiver inclination to the ground. Optimization of the positioning of a solar energy receiver, considering the possible energetic gain, with the Liu-Jordan isothropic mathematical model has been made. The influence reflectivity coefficient of the ground and transparency coefficient of the atmosphere on the investigated angle has been taken into account. The computer simulation results have been presented and compared with those obtained by other authors.

Sound propagation in realistic interactive 3D scenes with parameterized sources using deep neural operators.

We address the challenge of acoustic simulations in three-dimensional (3D) virtual rooms with parametric source positions, which have applications in virtual/augmented reality, game audio, and spatial computing. The wave equation can fully describe wave phenomena such as diffraction and interference. However, conventional numerical discretization methods are computationally expensive when simulating hundreds of source and receiver positions, making simulations with parametric source positions impractical. To overcome this limitation, we propose using deep operator networks to approximate linear wave-equation operators. This enables the rapid prediction of sound propagation in realistic 3D acoustic scenes with parametric source positions, achieving millisecond-scale computations. By learning a compact surrogate model, we avoid the offline calculation and storage of impulse responses for all relevant source/listener pairs. Our experiments, including various complex scene geometries, show good agreement with reference solutions, with root mean squared errors ranging from 0.02 to 0.10 Pa. Notably, our method signifies a paradigm shift as-to our knowledge-no prior machine learning approach has achieved precise predictions of complete wave fields within realistic domains.

Efficient calculation of the three-dimensional sound pressure field around a slab track

The wavenumber domain Boundary Element (2.5D BE) method is well suited to calculate the acoustic sound field around structures with a constant cross-section along one dimension, such as noise barriers or railway track. By expressing the sound field along this dimension in wavenumber domain, the numerical model is reduced from a 3D model to 2D model at each wavenumber. A consequence of the required discrete Fourier domain representation is that the sound field is represented by periodically repeating sections, of which only one section is physically meaningful. The resolution and the number of required wavenumbers increases with the desired length and spatial discretisation of this section. Describing the sound field adequately to auralise the sound without disturbing artefacts requires a large number of wavenumbers (and thus 2D BE computations), which is not feasible for large geometries. Here, a method is introduced that allows the calculation of the 3D sound field by solving a single 2D BE problem for a dense frequency spectrum and interpolating at higher wavenumbers. The calculation efficiency is further increased by precalculating the acoustic transfer functions between each BE surface element and receiver positions. Combining these two methods allows for efficient calculation of the 3D sound field around acoustically rigid structures such as slab tracks. The numerical approach is validated by comparison with a standard 2.5D BEM calculation and an analytical solution. Precalculated transfer functions to calculate the sound radiation from railway track, which are made available online, are illustrated. An example application is presented.

SALT-DOME STRUCTURES MODELING IN DEPTH DOMAIN USING RAY TRACING AND SEISMIC ATTRIBUTE ANALYSIS

Background. Increasing the resource base and hydrocarbon exploration is the main goal of performing seismic data acquisition. Due to the presence of salt diapirs, normal and reverse faults as well as other discontinuities in the geological subsurface, there appear characteristic features of seismic signals – a break in phase continuity and significant attenuation of the amplitude without a break in phase continuity. These geological features are sometimes distinguished by attenuation of the seismic signal or even an absence of wave field reflections. In areas of salt-dome tectonics, it is often completely impossible to trace any reflective horizons. To accurately map the fault location, deep or vertical horizons, it is necessary to improve the approach to obtaining and interpreting data in faulted areas with complex geology. Methods. The research presents an integrated approach to modeling the rays from each receiver of seismic signals to each bin on the reflective boundary. The reflected beams then propagate from the reflective boundary to the simulated position of the seismic receiver. Since the nature and velocity of beam propagation vary, it is possible to obtain additional information from zones shielded by faults or sub-vertical horizons, to trace the trajectories of seismic energy propagation and its focusing/defocusing zones. Verification of the seismic image and its geological content was performed using seismic attribute analysis. Results. Ray tracing allowed analyzing poor illumination zones below salt wings. During further steps such as processing and interpretation, ray tracing provided additional information for diapir mapping. Seismic attribute analysis was used as an additional tool to define the boundaries of the salt structure. This makes it possible to analyze the dynamic and kinematic parameters of the seismic field and map the salt body's boundaries based on these characteristics. Conclusions. An integrated approach involving several methods will solve the problem of mapping seismic horizons in areas surrounding fault zones with a weak seismic signal. A more reliable geological image can only be obtained by using complex sequences, including seismic processing, ray tracing, and seismic attribute analysis. The integrated application of the techniques demonstrates consistent geological results and has implications for discovering new deposits and hydrocarbon traps confined to the zones of development of salt-dome tectonics in the Dnipro-Donets basin.

A fast algorithm for simulation and analysis of wavefields in acoustic single-well imaging of logging-while-drilling considering arbitrary types of sources

Acoustic single-well imaging (SWI) of logging-while-drilling (LWD) is an advanced logging method in reservoir exploration, which uses reflected waves to detect the around-borehole geologic structures and quickly determines the drilling direction for enhancing the drilling-encounter ratio and reducing the drilling risk. Forward acoustic modeling is a fundamental problem for SWI in LWD. Due to the complex structures, it is a challenge to simulate the wave propagation and investigate wavefield characteristics based on the forward model. Numerical modeling is a commonly used method for calculating wavefields; however, it is too computationally expensive. In this study, we develop a fast method for calculating the full reflected pressure and displacement waves (i.e., P-P, SV-SV, SH-SH, and P-SV/SV-P) in SWI of LWD considering different types of sources such as arcuate, monopole, and dipole transmitters. The analytical algorithm is developed by applying the reciprocity relation between the virtual force (displacement) sources located at the receiver position and the outside-borehole virtual forces that are equivalent to the reflections from the formation interfaces. Numerical experiments indicate that the analytical solutions agree well with the reference solutions from the 3D finite-difference time-domain method, demonstrating the accuracy and high efficiency of the analytical method. Based on the analytical solutions, we find that LWD reflected waves are much more sensitive to the azimuth than those in the wireline case, indicating that the availability of LWD is important for identifying the reflector azimuth. Furthermore, to enhance the reception efficiency of reflected waves, the LWD parameters are optimized. For slow formations, we suggest using a dipole source with dominant excitation-frequency band being from 1 kHz to 3 kHz. For fast formations, a dipole with wider excitation-frequency band from 1 kHz to 5 kHz is recommended. For all formations, recording pressure signals indicates much higher reception efficiency than the displacement signals.

On the performance of outage probability in cognitive NOMA random networks with hardware impairments

ABSTRACT The performance of the cognitive non-orthogonal multiple access (NOMA) systems with random locations is examined in the present paper. More precisely, the positions of the secondary receivers (SRs) are randomly distributed inside a disk with the centre at the secondary transmitter (ST). The primary networks (PNs), on the other hand, are not necessarily inside the transmission range of the ST. Two user selection schemes namely, path-loss-based and channel-gain-based approaches, are adopted to serve two SRs according to the power domain NOMA technique. Additionally, the impact of the imperfect hardware impairments (HIs) on both transmitters and receivers is also taken into consideration. Furthermore, a recently proposed transmit power allocation at the ST is employed to concurrently maximize the system performance of the secondary networks (SNs) and to strictly protect the quality-of-service (QoS) of the PNs. The correctness of the developed mathematical frameworks is corroborated by simulation results based on the Monte Carlo method. Finally, we unveil that there is no scheme that always outperforms another. Thus, an adaptive scheme can be proposed to optimize the networks' performance. Our findings also reveal that the outage probability (OP) under the harmful effect of HI can be effectively mitigated by increasing the transmit power of the ST. Additionally, increasing the transmit power of the PT is also beneficial for the SNs with the adopted transmit power allocation at the ST.

Adverse effects of receiver clock bias and drift on NavIC user position coordinates and their mitigation

We investigated the effects of receiver clock bias and drift on NavIC receiver position coordinates at a low latitude station and proposed a mitigation technique. For this, Five weeks data of Accord IRNSS-GPS-SPS (AIGS) receiver are considered. Error in each position coordinates (X, Y and Z) is estimated and observed that the maximum error occurred in user position Z-coordinate. CEP for 2D position is analyzed and observed that the Circular Error Probability (CEP) values are high in Z coordinate of YZ and ZX planes. Further, it is noticed that the timing of sudden enhancement of both clock bias and drift parameters coincides with the periodic anomaly of the X, Y and Z coordinates. The error in individual position coordinates is minimized by applying 6th order Butterworth low pass filter resulting in improved position accuracy. If such errors are not mitigated, the position estimation of the receiver becomes highly erroneous.

Auralization and Visualization for Infrastructure Planning in the Joint Project "EAV-Infra"

Within the joint research project "Real-time Calculation, Auralization and Visualization of Sound Propagation and Noise Protection Measures for Infrastructure Projects" (EAV-Infra), funded by the Federal Ministry for Economic Affairs, the potentials of digital infrastructure planning based on Building Information Modeling (BIM) and the auralization of different states of planning will be combined. In this contribution, the objectives of the project will be presented with particular focus on the auralization. Currently, the effectiveness of noise mitigation measures like acoustic barriers or rail dampers is evaluated and communicated mostly by means of SPL values. Through auralization, a more vivid impression of different states of planning can be given during the whole planning process. In EAV-Infra, the auralization will be based on audio data of partial sound sources taken from real train passings. The data will be collected at various sites using a newly developed MEMS microphone array. To achieve a realistic hearing impression at the receiver position, a suitable model of the sound propagation will be implemented, which allows for a simulation in real time. In a last step, the partial sound source's signals will be convolved with the calculated sound propagation to synthesize the signal at the receiver position.

Dynamic positioning method and precision analysis of marine seismic vertical cables

AbstractSimilar to conventional ocean bottom seismometers and ocean bottom cables, the attitude and position of vertical cables deployed on the seafloor should be calibrated. However, due to the effect of ocean currents, the cable attitude is not stationary. Therefore, a new method for the dynamic repositioning of vertical cables is required. The dynamic repositioning of the hydrophones on vertical cables plays an important role in accurately describing the structure of the stratum and establishing an accurate velocity model. To realize the dynamic positioning of marine vertical cables, the shot lines are divided according to time, the first break time objective equation is established and the receiver position in each time period is obtained using the inversion methods outlined in this work. By analysing the trace spacing, first break time, shot point coordinate accuracy, temporal resolution, shot line spacing and other factors after repositioning, it is found that the first break time pickup accuracy and shot line spacing are the main factors that affect the repositioning accuracy. Furthermore, the resolution is limited by the timing of a single shot line. Additionally, the trace spacing after repositioning is consistent with the actual situation, which verifies the correctness and feasibility of this method.