Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
A new model-free output-only signal processing-based damage detection procedure was carried out in this paper. First of all, a finite element model as the representative of reinforced concrete (RC) frames was constructed and subjected to a specific loading protocol in OpenSees. The protocol consisted of 9 consequent different near-fault fling-step pulse-type earthquake records with low-amplitude white noises among them to simulate the collapse procedure. The analysis process was complemented in three levels: (a) the Fourier transform was utilized to extract the vibration frequency, (b) the time instants of damage occurrence were detected by using the discrete wavelet transform, and (c) accurate damage detection was made by using the extracted pulse components of the records as loading protocol for earthquake simulation and the discrete wavelet transform. The results revealed that the proposed combinatorial method could efficiently diagnose the damage in the RC frames. Also, applying a pulse component instead of an original record increases the accuracy of damage detection by 70%....
A field-programmable gate array (FPGA) based system for digital filtering in a neonatal heart rate monitoring system is presented. The system employs electric potential sensors (EPS) and contains a single hardware filter stage for antialiasing. The remaining digital signal processing required to provide a clinical standard electrocardiogram (ECG) is performed on the FPGA (myRIO 1900, National Instruments Corporation of Austin, Austin, TX, USA). This is compared with a previous microprocessor version (Raspberry Pi 3, BCM2837 processor, Raspberry Pi Ltd, Cambridge, UK) containing a dual hardware/software filtering scheme, with the aim of simplifying the analog front end and allowing for reconfigurable filtering in the digital domain. A custom neonate phantom was employed to emulate real world conditions and ambient noise. The developed FPGA system was shown to have a signal quality comparable with the microprocessor implementation, with an average signal-to-noise ratio loss of 2%. A 12 dB increase in the attenuation of the predominant 50 Hz noise was shown, indicating filter effectiveness gains. The phantom was used to broadcast data from the preterm infant cardio-respiratory signals database (PICSDB) and the FPGA filtering scheme was shown to remove the majority of the ambient 50 Hz noise with an average reduction of 30 dB, and provided a clean ECG signal. These results demonstrate that FPGA-filtered EPS ECGs have comparable signal quality to the combined HW/SW filtering implementation, with a reduction in complexity and power consumption....
Image perceptual hashing is broadly applied in image content authentication, recognition, retrieval, and social media hotspot event detection. An image authentication algorithm is put forward based on the Itti visual saliency model and geometric invariant vector distance. To begin with, the image is preprocessed and weighted by the Itti model and contourlet transform. After that, the weighted image is randomly divided into blocks, and the image feature vector is constructed by calculating the geometric invariant vector distance on both Hu invariant moment vector and maximum singular value vector of the random blocks. In the end, the feature vector is quantized and encrypted to generate the ultimate hash. Experimental results illustrate that when the threshold T 70, the true positive rate PTPR for duplicate images stands at 0.96574, while the false rate PFPR of different images is merely 0.0224, with the total error rate reaching the minimum value (0.0566). Furthermore, the AUC value of the proposed algorithm is 0.9951, which is higher than that of the comparison algorithms, indicating that the algorithm has better performance than other state-of-the-art algorithms in terms of various visual content-preserving attacks....
This study presents three different sinc estimators and a method to estimate complex-valued exponential tone signal frequency using three DFT samples. The proposed method suggests using sinc interpolation together with the well-known Jacobsen estimator. According to simulation results, the root mean square error (RMSE) of the proposed algorithm is lower than those of the Jacobsen estimator and its improved version suggested by Candan. The price paid for improvements in the RMSE is a slight increase in computation time....
Background: In recent years the use of sample entropy (SampEn) to evaluate the complexity of the locomotor system in human gait data has gained in popularity. However, it has been suggested that SampEn is sensitive to various input parameters and signal preprocessing methods. This study quantified the effects of different temporal and spatial normalization approaches and various lengths of the template vector (m) on SampEn calculations. The discriminatory ability of SampEn was studied by comparing two walking conditions. Methods: Twenty-three participants (seven males, 55.7 ± 8.5 years, 165.7 ± 7.9 cm, 80.5 ± 16.7 kg) walked on a treadmill with preferred (Vpref ) and maximum (Vmax) speed. Data were segmented and resampled (SEGM), resampled and spatially normalized (NORM), resampled and detrended (ZERO). Results: For vertical ground reaction force (vGRF) and center of pressure in anterio-posterior direction (COPap), in both walking conditions, SampEn was generally sensitive to the vector length and not to the data processing, except for COPap in ZERO, m = 2, 4. For the COPml SampEn behaved oppositely, it was sensitive to preprocessing method and not to the m length. The regularity of COPap and vGRF in all processed signals increased in Vmax condition. For the COPml only two signals, WHOLE and ZERO, revealed increased complexity caused by more demanding walking conditions. Conclusions: SampEn was able to discriminate between different walking conditions in all analyzed variables, but not in all signals. Depending on evaluated variable, SampEn was susceptible in different way for the m level and processing method. Hence, these should be checked and selected for each variable independently. For future studies evaluating influence of walking velocity on COP and vGRF regularity during treadmill walking it is advised to use raw time series. Furthermore, to maintain template vector which represents biological relevance it is advised to detect highest frequencies present in analyzed signals and evaluate minimal time interval which can reflect change caused by response of a neuromuscular system. During evaluating treadmill walking measured with 100 Hz sampling frequency it is recommended to adopt m from 6 to 10, when average stride time is up to about 1 s....
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