Bearing Fault Diagnosis Using Refined Composite Generalized Multiscale Dispersion Entropy-Based Skewness and Variance and Multiclass FCM-ANFIS

Bearing vibration signals typically have nonlinear components due to their interaction and coupling effects, friction, damping, and nonlinear stiffness. Bearing faults affect the signal complexity at various scales. Hence, measuring signal complexity at different scales is helpful to diagnosis of bearing faults. Numerous studies have investigated multiscale algorithms; nevertheless, multiscale algorithms using the first moment lose important complexity data. Accordingly, generalized multiscale algorithms have been recently introduced. The present research examined the use of refined composite generalized multiscale dispersion entropy (RCGMDispEn) based on the second moment (variance) and third moment (skewness) along with refined composite multiscale dispersion entropy (RCMDispEn) in bearing fault diagnosis. Moreover, multiclass FCM-ANFIS, which is a combination of adaptive network-based fuzzy inference systems (ANFIS), was developed to improve the efficiency of rotating machinery fault classification. According to the results, it is recommended that generalized multiscale algorithms based on variance and skewness be examined for diagnosis, along with multiscale algorithms, and be used to achieve an improvement in the results. The simultaneous usage of the multiscale algorithm and generalized multiscale algorithms improved the results in all three real datasets used in this study.

The method of measuring motion capture in wheelchairs during actual use – description of the method and model of measuring signal processing

The aim of the article is to verify the method of measuring motion capture in wheelchair during conditions of actual use and to formally describe how the measurement points are processed. The developed method and the measurement data processing process extract a set of parameters from the study that describe the kinematics of the human body while propelling a wheelchair. The method includes an algorithm to process data from video recorded with a sports camera to the coordinates of the marker position. For the selected marker positions, a data processing algorithm was proposed to determine universal parameters used in the assessment of the kinematics of the human body in terms of wheelchair use. The method has been verified with actual tests that analyzed the kinematics of the human body while propelling a wheelchair under various operating conditions. The proposed method of measuring motion capture involves inexpensive research equipment, offers the possibility of use in real conditions.

Delayed contrast and multiparametric MRI for treatment response assessment in brain metastases following stereotactic radiosurgery

Aims Following stereotactic radiosurgery (SRS), brain metastases can increase in size in up to a third of cases. Conventional magnetic resonance imaging (MRI) has a limited role to distinguish between tumour recurrence and SRS-induced changes, which can impact patient management. Delayed contrast MRI treatment response assessment maps (TRAM) use the principle of contrast clearance seen in other tumours, where high vascularity shows a rapid rise in contrast as well as rapid clearance, whereas areas of damaged or low vascularity show accumulation of contrast. We aimed to assess the ability of delayed contrast MRI and multiparametric MRI techniques of diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and MR spectroscopy (MRS) to distinguish between radiation-related effects and tumour tissue, as these techniques assess tissue physiological and metabolic information. Method A retrospective review was performed on 23 patients who had delayed contrast and multiparametric MRI between October 2018 to April 2020. Studies were restricted to cases with brain metastases enlarging post-SRS with uncertainty at the MDT meeting regarding progression or treatment-related change, impacting the patient’s management. MRI was performed at 3T including DWI, PWI, MRS with short and intermediate echo times, and 3D T1 MPRAGE at 3-5, 20-30 and 70-90 minutes after administration of intravenous contrast. Contrast clearance analysis was performed by selecting an enhancing region of interest (ROI), measuring signal intensities at the three different timepoints and taking apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV) values from the ROI. Choline/Creatine values were calculated from a single-voxel (10 mm isotropic) encompassing the entire contrast-enhancing lesion. Outcome was established from MRI follow-up at 6 months, with a stable or responding lesion considered treatment-related changes and increase considered progression. Results Across 23 patients, 24 metastases were assessed. Two patients were excluded as appropriate follow-up was not available. Sites of primary tumours included breast (n=8), lung (n=6), melanoma (n=4), neuroendocrine tumour from the lung (n=2) and renal cell carcinoma (n=2). Mean age was 56 years and 50% were female. In this cohort, 59% (n=13) were classified as having radiation-related changes on follow-up. Delayed MRI contrast clearance between the 3-5 and 70-90 minute imaging was significantly higher in cases of progression (23.6% vs. 2.5% decrease, p<0.05), as were the rCBV and Cho/Cr ratio (rCBV 3.1 vs. 1.5 and Cho/Cr ratio 2.3 vs. 1.4, p<0.05). Accuracy, sensitivity and specificity of using TRAM alone (contrast clearance decrease of >0%) for progression was 63%/100%/38%, PWI alone (rCBV cut-off 2.0) yielded results of 77%/75%/79% and for both Cho/Cr ratio alone (cut-off 1.8) and combined with TRAM, it was 90%/88%/92%. Neuroradiologist assessment of all techniques was 95%/100%/92%. Conclusion This study shows the effectiveness of delayed contrast and multiparametric MRI for treatment response assessment in patients with brain metastases treated by SRS in clinical practice. Although a delayed contrast MRI study is a very sensitive tool for detecting tumour progression, it lacks specificity. The accuracy of differentiating between tumour and treatment-related effects increases when delayed contrast MRI is used in combination with other advanced techniques such as MRS. By combining all these techniques, neuroradiologists had the highest accuracy, sensitivity and specificity for detecting progression in post-SRS brain metastases.

Formation of Efficient Microfilm Converters with Reproducible Parameters

The use of microfilm converters provides information in the field of processing, storage, transmission and presentation of information, especially in the process of control and measurement of physical quantities, as well as in the technology of manufacturing high technology products. Microfilm transducers form an equivalent output signal, which is a function of the measured quantity; their design and manufacturing technology are interrelated and highly correlated. Microfilm transducers are manufactured using microelectronic technology, in which group methods are used in the formation of a structure, which increases the reproducibility of parameters, are characterized by high sensitivity, low inertia, low power consumption, high reliability, and are combined with measuring signal processing devices. When creating microfilm converters, a structure is determined that most closely meets the requirements, design parameters, modes of manufacturing operations, the effect of operating conditions on characteristics, and optimal modes of operation. Structurally, a microfilm transducer consists of a base, an insulated structure, heat-generating and temperature-sensitive elements that provide the transmission of electrical signals, film conductors and contact pads, which provide a specified function of converting the measured value into an output signal. In microfilm converters, film thermocouples are used as thermosensitive elements, and adhesive sublayers are used in their manufacturing technology. The use of technological methods of microelectronics when creating microfilm converters can significantly improve their operational parameters.

Improved visualization of Liver Metastases Adjacent to Vessels using Hepatobiliary Phase Gadoxetic-acid-enhanced Single Shot Inversion-Recovery Gradient-Echo (IRGRE) MR Imaging

Objectives: To quantitatively compare contrast differences between liver metastases and vessels on Hepatobiliary Phase (HP) gadoxetic-acid-enhanced 2-Dimensional (2D) single-shot Inversion Recovery Gradient-Echo (IRGRE) and 3D Fat Saturated GRE (FSGRE) magnetic resonance images. Methods: The study included 55 consecutive patients who had HP FSGRE and IRGRE (39 at 1.5T, 16 at 3T) for liver metastases evaluation obtained 20 minutes after gadoxetic-acid administration. Thirty-eight patients had metastases (23 at 1.5T, 15 at 3T). Regions of interest were drawn measuring signal intensity (SI) of the largest lesion, normal liver, inferior vena cava, and background noise. Signal-to-noise (SNR) and contrast-to-noise ratio (CNR), respectively, were calculated as SI divided by standard deviation (SD) of background noise, and (S1-S2)/SD, where S1 and S2 represented SI for tissue 1 and tissue 2. Statistical analysis was via the Wilcoxon Sign Rank test. Results: Median liver-SNR for all 55 cases was greater for FSGRE than for IRGRE, as was lesion-SNR in the 38 with lesions (p<0.05). Vessel-SNR was greater for IRGRE than for FSGRE at 3T (p<0.05), with no difference between techniques at 1.5T (p>0.05). Median lesion/vessel contrast and CNR for the 38 cases with metastases at 1.5T and the 15 at 3T were, in absolute value, greater for IRGRE than for FSGRE (p<0.05). While both techniques yielded high lesion-liver contrast and CNR, only IRGRE provided consistently high lesion-vessel contrast and CNR (p<0.05). Conclusion: Hepatobiliary-phase contrast difference between liver metastases and vessels was significantly and substantially greater for IRGRE than for FSGRE, potentially facilitating improved lesion detection using IRGRE.

Creation of a Hardware-Software Dynamic Signal Simulator of the Upgraded Inter-Satellite Radio Link of the GLONASS System

This work is aimed at creating a hardware-software signal simulator of the upgraded inter-satellite radio link (ISRL) of the GLONASS system. The simulator shapes ISRL signals with dynamically changing parameters of the Doppler frequency shift and delay, which correspond to the mutual dynamics of spacecraft (SC) motion of the GLONASS system. The upgraded inter-satellite radio link will provide (as compared to the current ISRL) an increase in the information transfer rate of up to four times, as well as boost the accuracy of measuring the distance between satellites by two times. Modernization consists in complementing the radio signal of the second orthogonal (phase-shifted carrier frequency by 90 degrees relative to the existing one) component. To modernize the ISRL, it is necessary to create and verify new equipment for receiving and transmitting signals of the upgraded ISRL of the GLONASS system. The simulator is designed to process measurement algorithms embedded in the on-board equipment for inter-satellite measurements and assess their consistency. Consistency evaluation consists in measuring and analyzing the difference between the Doppler parameters and delay introduced into the signal and the estimation of these parameters in the receiving equipment of the ISRL. This difference will be the measurement error. Dynamic simulation is performed for 24 system points, corresponding to GLONASS satellites, on the half-period of satellite revolution (20 280 seconds). The signal is generated at the input of the antenna-feeder device of one of the satellites in accordance with the information for generating the measuring signal, parameters of the transmitters of the signals of the upgraded ISRL and the almanac of the satellite constellation (because the signal at the input of the antenna-feeder device of the navigation receiver incomes from several SC) specified by the user.

Diagnostics, measurement and control of electrical parameters supercapacitors

This article considers possible approaches to diagnostics and measurement electrical parameters of supercapacitors. The analysis the results of diagnostics and measurement the parameters of supercapacitors has determined a significant frequency dependence of theirs. The discrepancy between the two-element equivalent circuit of supercapacitors has been established. Diagnostics and control electrical parameters of supercapacitors in the infralow frequency range can be performed by direct conversion methods. In this case, high-precision low-resistance resistors can be used as an exemplary measure. For the diagnostics and design of meters for the electrical parameters of supercapacitors of capacitors, the authors propose an iterative-recursive method for determining the numerical values of the electrical parameters of the equivalent circuit of such objects. The essence of the proposed iterative-recursive method is that at the first stage, the iterative approximation determines the number of n-absorption links, which it is enough to know when developing, manufacturing and operating supercapacitors. Theoretical and experimental studies of the equivalent circuit of supercapacitors show that the equivalent resistance of such capacitors and their capacitance increase with decreasing frequency of the measuring signal, and the nature of these dependences is determined by the number of n-absorption links and the numerical values of the elements of each link.

The efficiency of using wavelet transforms for filtering noise in the signals of measuring transducers

Methods of wavelet filtering of noise in signals of measuring transducers using the threshold method of discrete wavelet transform are considered. To study the methods of wavelet filtering of noise, special model signals were used to estimate the filtering errors. A method has been developed for determining the parameters of wavelet filtering of noise with a threshold for all levels of decomposition, which makes it possible to determine the wavelet function, threshold function and filtering threshold of the detailing coefficients of the discrete wavelet decomposition. The influence of the parameters of the noise distribution, the noise level, the number of vanishing moments of the Daubechies wavelet function, the nature of the threshold function and the threshold value on the filtering error caused by the noises of non-stationary measuring signals has been investigated by the method of a computational experiment. The results of the study of six threshold functions are given with the addition of noise to the measuring signal with nonstationary amplitude, frequency and duty cycle of rectangular pulses. The signal of the Doppler sensors is investigated, the wavelet filtering parameters are calculated, which provide the minimum error. The obtained parameters are used to construct graphs of signals before and after filtering directly in the time domain using the inverse wavelet transform.