Search Results (21)

The performance of a high-frequency (HF) radar network situated within the Pearl River Estuary from 17 July to 13 August 2022 is described via a comparison with seven acoustic Doppler current profilers (ADCPs). The radar network consists of six OSMAR-S100 compact HF radars, with a transmitting frequency of 13–16 MHz and a direction-finding technique. Both the radial currents and vector velocities showed good agreement with the ADCP results (coefficient of determination r²: 0.42–0.78; RMS difference of radials: 11–21.6 $\mathrm{c}\mathrm{m} {\mathrm{s}}^{-1}$; bearing offset $\Delta \theta$: $-4.8°$–$16.1°$; complex correlation coefficient $\gamma$: 0.62–0.96; and phase angle $\alpha$: −24.3$°–$17.8$°$). For these radars, the $\Delta \theta$ values are not constant but vary with azimuthal angles. The relative positions between the HF radar and ADCPs, as well as factors such as the presence of island terrain obstructing the signal, significantly influence the errors. The results of spectral analysis also demonstrate a high level of consistency and the capability of HF radar to capture diurnal and semidiurnal tidal frequencies. The tidal characteristics and the Empirical Orthogonal Function (EOF) results measured by the HF radars also resemble the ADCPs and align with the characteristics of the estuarine current field. Full article

Because of its non-contact measurement characteristics, trackside acoustic technology is now utilized for train bearing fault diagnosis. However, the collected acoustic signal produces Doppler distortions that can impact the accuracy of bearing fault diagnosis. Additionally, when a fault occurs in the train bearing, it is analyzed using cyclostationary methods. In this study, we combine bearing fault characteristics with Doppler distortion correction and cyclostationary analysis methods. The trackside acoustic test platform is employed to collect and test the fault signals from bearings. These signals are processed and analyzed using Doppler distortion correction algorithms and cyclostationary techniques. A comparison between time domain maps and power spectrum maps before and after correction reveals an increase in SNR (signal to noise ratio) and a more concentrated energy distribution within the fault signals—at least a 50% improvement is observed. To further validate our method’s effectiveness, we select existing TADS equipment from a depot to collect bearing signals for analysis and processing using our proposed bearing fault diagnosis method. Comparison of time domain maps and power spectrum maps before and after correction shows clearer overall images and amplitude increase of nearly 125%. Therefore, we have successfully developed a stepwise method for bearing fault diagnosis based on cyclostationary Doppler distortion correction. Full article

This paper proposes a maximum-ratio combining sensor fusion scheme for using an extended Kalman filter in the underwater vehicle positioning task by means of communication devices (buoys) providing location information using a slant-range mechanism, inertial sensors, a Doppler velocity log, and a pressure sensor in the absence of bearing angle data. The parameter estimation methods for all navigation system components are described. The results of simulation modeling with corresponding quality metrics are presented. The outcomes were supported by conducted field experiments. The results obtained allowed us to obtain a position determination model for the underwater vehicle, which is still a relevant and complex task for seabed explorers. Full article

Trackside acoustic signals are useful for non-contact measurements as well as early warnings in the diagnosis of train wheelset bearing faults. However, there are two important problems when using roadside acoustic signals to diagnose wheel-to-wheel bearing faults; one is the presence of strong interference from strong noise and high harmonics in the signal, and the other is the low efficiency of bearing fault identification caused by it. Therefore, from the viewpoint of solving the two problems, a sparse operation method is proposed for denoising and detuning the modulation of the roadside acoustic signal, and a machine learning classifier with a Genetic Algorithm (GA)-optimized Radial Basis Neural Network (RBFNN) is proposed to improve the rate at which the features of roadside acoustic signal faults are recognized. Firstly, the background noise is filtered out from the Doppler-corrected acoustic signal using the Sparse Representation method, and the inverse wavelet transform is reconstructed into a noiseless signal. Secondly, the interference high-harmonic signal in the signal is filtered out using the Resonant Sparse Signal Decomposition (RSSD) method. Then, the GA is selected to optimize the parameters of the RBF neural network and build a fault diagnosis model. Finally, the extracted acoustic signal feature set is trained on the network model, and the trained model is used for testing. In summary, the sparse operation on the roadside acoustic signal processing and the GA-RBFNN diagnosis model were verified as being very effective in the diagnosis of roadside acoustic train wheel pair faults through the simulation experiment. Full article

Background and Objectives: Chronic painful midportion Achilles combined with plantaris tendinopathy can be a troublesome condition to treat. The objective was to prospectively follow patients subjected to ultrasound (US)- and color doppler (CD)-guided wide awake, local anesthetic, no-tourniquet (WALANT) surgery in a private setting. Material and Methods: Twenty-six Swedish patients (17 men and 9 women, mean age 50 years (range 29–62)) and eight international male patients (mean age of 38 years (range 25–71)) with combined midportion Achilles and plantaris tendinopathy in 45 tendons altogether were included. All patients had had >6 months of pain and had tried non-surgical treatment with eccentric training, without effect. US + CD-guided surgical scraping of the ventral Achilles tendon and plantaris removal under local anesthesia was performed on all patients. A 4–6-week rehabilitation protocol with an immediate full-weight-bearing tendon loading regime was used. The VISA-A score and a study-specific questionnaire evaluating physical activity level and subjective satisfaction with the treatment were used for evaluation. Results: At the 1-year follow-up, 32/34 patients (43 tendons) were satisfied with the treatment result and had returned to their pre-injury Achilles tendon loading activity. There were two dropouts (two tendons). For the Swedish patients, the mean VISA-A score increased from 34 (0–64) before surgery to 93 (61–100) after surgery (p < 0.001). There were two complications, one wound rupture and one superficial skin infection. Conclusions: For patients suffering from painful midportion Achilles tendinopathy and plantaris tendinopathy, US + CD-guided surgical Achilles tendon scraping and plantaris tendon removal showed a high satisfaction rate and good functional results 1 year after surgery. Full article

The article provides a discussion on a methodology intended for testing of power transmission systems featuring an innovative highly torsionally flexible metal clutch patented by the co-authors of this paper. What this methodology takes into account is the amplitude and frequency analyses discussed in the article, as well as a sensing system based on diverse piezoelectric and magnetic phenomena, the Doppler effect, etc. Both contact and non-contact (laser measurement) methods were used during the tests. The purpose of the tests conducted at the stand, originally designed by the authors in accordance with the methodology proposed, was to evidence that using the innovative and patented, highly torsionally flexible metal clutch makes it possible to reduce the vibrations of multi-stage toothed gears, consequently reducing the forces affecting the gear bearings and those acting at the tooth space, which is to enable the service life of individual components of the power transmission systems intended for mining scraper conveyors to be significantly extended. Based on the studies and analyses performed by the authors, one can observe and conclude that the methodology proposed in the paper makes it possible to use an example of a relatively complex power transmission system in order to examine the relationships between the processes at work, i.e., the decline of the linear vibrations of the gear housing (which is undoubtedly positive in power transmission systems) at the expense of increasing torsional vibrations of the innovative clutch, the latter not to be considered unfavourable to users in the case analysed. Full article

In this manuscript, an underwater target tracking problem with passive sensors is considered. The measurements used to track the target trajectories are (i) only bearing angles, and (ii) Doppler-shifted frequencies and bearing angles. Measurement noise is assumed to follow a zero mean Gaussian probability density function with unknown noise covariance. A method is developed which can estimate the position and velocity of the target along with the unknown measurement noise covariance at each time step. The proposed estimator linearises the nonlinear measurement using an orthogonal polynomial of first order, and the coefficients of the polynomial are evaluated using numerical integration. The unknown sensor noise covariance is estimated online from residual measurements. Compared to available adaptive sigma point filters, it is free from the Cholesky decomposition error. The developed method is applied to two underwater tracking scenarios which consider a nearly constant velocity target. The filter’s efficacy is evaluated using (i) root mean square error (RMSE), (ii) percentage of track loss, (iii) normalised (state) estimation error squared (NEES), (iv) bias norm, and (v) floating point operations (flops) count. From the simulation results, it is observed that the proposed method tracks the target in both scenarios, even for the unknown and time-varying measurement noise covariance case. Furthermore, the tracking accuracy increases with the incorporation of Doppler frequency measurements. The performance of the proposed method is comparable to the adaptive deterministic support point filters, with the advantage of a considerably reduced flops requirement. Full article

Perineural treatment of peripheral nerves with capsaicin produces a long-lasting selective regional thermo- and chemo-analgesia and elimination of the neurogenic inflammatory response involving degeneration of nociceptive afferent fibers. In this study, we examined longitudinal changes in mustard oil–induced sensory neurogenic vasodilatation and plasma extravasation following perineural capsaicin treatment of the rat saphenous nerve utilizing scanning laser Doppler imaging and vascular labeling with colloidal silver. Capsaicin treatment resulted in a marked decrease in mustard oil–induced vasodilatation in the skin area served by the saphenous nerve. Repeated imaging of the vasodilatatory response showed no recovery for at least 7 weeks. However, following transection and ligation of the capsaicin-treated saphenous nerve, a substantial recovery of the vasodilatatory response was observed, suggesting a reinnervation of the chemodenervated skin area by collateral sprouting of neighboring intact sciatic nerve afferents. Elimination of the recovered vascular reaction by capsaicin treatment of the sciatic nerve supported this conclusion. Similar results have been obtained by using the vascular labeling technique. These findings indicate an inhibitory effect of persisting cutaneous nerve fibers on the collateral sprouting of intact nerve fibers into the chemodenervated skin area. These observations may bear implications for the development of sensory disturbances following peripheral nerve injuries. Full article

An investigation of vascularity of ovarian and uterine arteries after hormonal treatment for inactive ovaries using the short-term progesterone-based programme had not yet been explored in repeat-breeder crossbred dairy cows. To investigate the in vivo follicular and uterine arterial indices as an indicator of successful hormonal stimulation for inactive ovaries in repeat-breeder crossbred dairy cattle, 59 cows with inactive ovaries were induced with a 5-day progesterone-based protocol. At the completion of hormonal synchronisation, cows were divided into two groups according to the size of the largest follicle (LF) on their ovary: small (≤10.0 mm) and large (>10.0 mm) LFs. Vascularities of LF and uterine artery (UtA) were evaluated using a colour Doppler tool. Cows that presented with large LF had greater follicular and UtA vascular indices (p < 0.001) and pregnancy rate (p < 0.01) than cows bearing small LF on their ovary. There was a positive correlation (p < 0.001) between follicular size and LF and UtA vascular indices. Our findings highlighted that in vivo LF and UtA vascular indices at the completion of hormonal stimulation might be a promising indicator for predicting success in ovarian response to hormonal stimulation for inactive ovaries of infertile crossbred dairy cows. Full article

A major advantage of the use of passive sonar in the tracking multiple underwater targets is that they can be kept covert, which reduces the risk of being attacked. However, the nonlinearity of the passive Doppler and bearing measurements, the range unobservability problem, and the complexity of data association between measurements and targets make the problem of underwater passive multiple target tracking challenging. To deal with these problems, the cardinalized probability hypothesis density (CPHD) recursion, which is based on Bayesian information theory, is developed to handle the data association uncertainty, and to acquire existing targets’ numbers and states (e.g., position and velocity). The key idea of the CPHD recursion is to simultaneously estimate the targets’ intensity and the probability distribution of the number of targets. The CPHD recursion is the first moment approximation of the Bayesian multiple targets filter, which avoids the data association procedure between the targets and measurements including clutter. The Bayesian-filter-based extended Kalman filter (EKF) is applied to deal with the nonlinear bearing and Doppler measurements. The experimental results show that the EKF-based CPHD recursion works well in the underwater passive multiple target tracking system in cluttered and noisy environments. Full article

This contribution investigates fatigue crack detection, localization and quantification in idealized necked double shear lugs using piezoelectric transducers attached to the lug shaft and analyzed by the electro-mechanical impedance (EMI) method. The considered idealized necked lug sample has a simplified geometry and does not includes the typical bearing. Numerical simulations with coupled-field finite element (FE) models are used to study the frequency response behavior of necked lugs. These numerical analyses include both pristine and cracked lug models. Through-cracks are located at 90${}^{\circ }$ and 145${}^{\circ }$ to the lug axis, which are critical spots for damage initiation. The results of FE simulations with a crack location at 90${}^{\circ }$ are validated with experiments using an impedance analyzer and a scanning laser Doppler vibrometer. For both experiments, the lug specimen is excited and measured using a piezoelectric active wafer sensor in a frequency range of 1 kHz to 100 kHz. The dynamic response of both numerical calculations and experimental measurements show good agreement. To identify (i.e., detect, locate, and quantify) cracks in necked lugs a two-step analysis is performed. In the first step, a crack is detected data-based by calculating damage metrics between pristine and damaged state frequency spectra and comparing the resulting values to a pre-defined threshold. In the second step the location and size of the detected crack is identified by evaluation of specific resonance frequency shifts of the necked lug. Both the search for frequencies sensitive to through-cracks that allow a distinction between the two critical locations and the evaluation of the crack size are model-based. This two-step analysis based on the EMI method is demonstrated experimentally at the considered idealized necked lug, and thus, represents a promising way to reliably detect, locate and quantify fatigue cracks at critical locations of real necked double shear lugs. Full article

A challenge in the field of material science and concrete technology is to associate material properties and behavior with changes in internal microstructure. A fundamental issue for planning, implementation, and quality control of construction projects is the fundamental understanding of the hardening process in freshly poured cement-based materials. Shortly after the mixing process, cementitious materials exhibit a substantial damping effect on ultrasonic wave propagation along with low-pulse velocity. The way a wave reflects and diffuses in the volume of a solid material can provide important information about internal heterogeneities. An important application of the wave propagation technique is the determination of layers within the material distinguished by unlike elastic properties. During the hardening process, the ultrasonic wave propagation exhibits a noticeable sensitivity at the point of phase change of the material, that is, the critical point at which the state of the suspension transforms from liquid to solid state. After that point, there is a continuous increase of pulse velocity and ultrasonic signal amplitude. The solidification point is of practical importance since at this point the load-bearing capacity of the composite material and its long-term behavior are based on the connectivity of the solid phase. This study aims to develop a nondestructive tool to monitor freshly poured cement-paste composites at early stages, during the hydration process, by means of nonlinear elastic waves. The measurement setup combined a contact ultrasonic transducer with a noncontact optical detection system, in which the principle of operation is based on the Doppler effect. This methodology enabled us to assess the amplitudes of harmonic vibrations of an acoustic wave propagating through the material with a specific fundamental frequency. This enabled the evaluation of important material properties, such as minute changes in the internal microstructure of fresh concrete during hardening, the evolution of nonlinearity parameters that relate to higher-order elastic constants of the material, as well as the ultrasonic wave velocity. Full article

The paper presents an application of the Conditionally-Minimax Nonlinear Filtering (CMNF) algorithm to the online estimation of underwater vehicle movement given a combination of sonar and Doppler discrete-time noisy sensor observations. The proposed filter postulates recurrent “prediction–correction” form with some predefined basic prediction and correction terms, and then they are optimally fused. The CMNF estimates have the following advantageous features. First, the obtained estimates are unbiased. Second, the theoretical covariance matrix of CMNF errors meets the real values. Third, the CMNF algorithm gives a possibility to choose the preliminary observation transform, basic prediction, and correction functions in any specific case of the observation system to improve the estimate accuracy significantly. All the features of conditionally-minimax estimates are demonstrated by the regression example of random position estimate given the noisy bearing observations. The contribution of the paper is the numerical study of the CMNF algorithm applied to the underwater target tracking given bearing-only and bearing-Doppler observations. Full article

Underwater target tracking system can be kept covert using the bearing-only or the bearing-Doppler measurements (passive measurements), which will reduce the risk of been detected. According to the characteristics of underwater target tracking, the square root unscented Kalman filter (SRUKF) algorithm, which is based on the Bayesian theory, was applied to the underwater bearing-only and bearing-Doppler non-maneuverable target tracking problem. Aiming at the shortcomings of the unscented Kalman filter (UKF), the SRUKF uses the QR decomposition and the Cholesky factor updating, in order to avoid that the process noise covariance matrix loses its positive definiteness during the target tracking period. The SRUKF uses sigma sampling to avoid the linearization of the nonlinear bearing-only and the bearing-Doppler measurements. To ensure the target state observability in underwater target tracking, the paper uses single maneuvering observer to track the single non-maneuverable target. The simulation results show that the SRUKF has better tracking performance than the extended Kalman filter (EKF) and the UKF in tracking accuracy and stability, and the computational complexity of the SRUKF algorithm is low. Full article

Function-integrative textiles bear the potential for a variety of applications in the medical field. Recent clinical investigations suggest that the application of a function-integrative fabric could have a positive impact on currently applied diagnostic procedures of a specific type of tumour. In this context, the fabric should enable local warming of a patient’s upper extremity as well as blood flow measurement. Existing solutions comprise a warming system but lack a measuring apparatus for blood flow determination. With regard to the quality of results of current diagnostic procedures, the local warming of the patients’ upper extremity and the simultaneous determination of the blood flow plateau are crucial. In the present paper, the development process of a function-integrative sleeve is introduced. Besides the development of an adaptable sleeve-design, the manufacturing process of an integrated warming system was also addressed. Furthermore, the identification of crucial physiological effects, using a Laser Doppler Perfusion Monitor, is introduced. During testing of the function-integrative sleeve, modulation of the desired physiological effects was observed. The results support the initial assumptions and dictate further investigations on increasing user-friendliness and cost-efficiency during adjusting and determining the physiological effects in the course of tumour diagnosis. Full article