Search Results (160)

The existing linear frequency increment cable defect detection method using frequency domain reflectometry suffers from severe pseudo-peak phenomena due to non-targeted frequency domain sampling, which interferes with diagnosis. To address this issue, this paper proposes an optimized frequency domain sampling method based on the exponential frequency increment reflection coefficient spectrum. This method optimizes the distribution of frequency domain sampling points, reducing the sampling of high-frequency noise signals, thereby effectively suppressing pseudo-peaks. Research indicates that the low-frequency band of the cable reflection coefficient spectrum contains richer information about the cable’s condition and has less noise compared to the high-frequency band. Therefore, an exponential frequency increment is used instead of the current linear frequency increment, resulting in a denser sampling in the low-frequency band and sparser sampling in the high-frequency band, better matching the information distribution characteristics of the cable reflection coefficient spectrum. To avoid spectral leakage caused by non-uniform sampling under exponential frequency increments, this method locally linearizes exponential sampling and uses interpolation to complete the overall frequency sampling rate, ensuring it meets the basic assumption of Fourier transform—uniform and equally spaced sampling signals. Finally, this method was validated on a 500 m laboratory test cable and a 2000 m operational cable. Experimental results show that this method can make the amplitude of regions other than impedance mismatch points in the positioning curve flatter and effectively suppress abnormal peak interference, significantly improving the accuracy of defect diagnosis. Full article

This paper presents a discrete Fourier transform (DFT)-based signal processing framework for eddy current non-destructive testing (NDT), aiming to enhance signal quality for precise defect characterization in critical nuclear components. By enforcing strict periodicity matching between sampling points and signal frequencies, the proposed approach mitigates DFT spectrum leakage, validated via phase linearity analysis with errors of ≤0.07° across the 20 Hz–1 MHz frequency range. A high-resolution 24-bit analog-to-digital converter (ADC) hardware architecture eliminates complex analog balancing circuits, reducing system-wide noise by overcoming the limitations of traditional 16-bit ADCs. A 6 × 6 mm application-specific integrated circuit (ASIC) for array sensors enables three-dimensional (3D) defect visualization, complemented by Gaussian filtering to suppress vibration-induced noise. Our experimental results demonstrate that the digital method yields smoother signal waveforms and superior 3D defect imaging for nuclear power plant tubes, enhancing result interpretability. Field tests confirm stable performance, showcasing clear 3D defect distributions and improved inspection performance compared to conventional techniques. By integrating DFT signal processing, hardware optimization, and array sensing, this study introduces a robust framework for precise defect localization and characterization in nuclear components, addressing key challenges in eddy current NDT through systematic signal integrity enhancement and hardware innovation. Full article

The beneficial role of melatonin (MT) as a potent broad-spectrum antioxidant and hormone-like regulator in plant protection against adverse environmental conditions is indisputable. However, the molecular networks underlying its unique scavenging capabilities are still far from understood. Herein, we show the ability of MT to maintain physiological functions under high light stress (HL) is mediated by photoreceptors. Melatonin treatment (50 μM) of the photoreceptor mutants phyA/B and cry1/2 augmented the deleterious effects of excess light (600 μmol m⁻² s⁻¹, 24 h), as evidenced by increased TBARs levels and electrolyte leakage, as well as decreased photosynthetic efficiency, in contrast to their parental form, Landsberg erecta, in which these parameters were significantly improved. The reduced stress resistance of the mutants was also confirmed by analysis of the transcript accumulation of ROS markers and enzymatic scavengers. Moreover, the increase in melatonin content in the mutants exposed to HL + MT contributed to increased ROS accumulation; therefore, the deleterious effect of MT could not be explained by an imbalance in ROS production below the cytostatic level. We hypothesize that the light-sensitive phenotypes of photoreceptor mutants under MT treatment may be due to the misregulation of stress-related genes that are targets for melatonin action. Full article

Various models of ionization and fission chambers for ionizing radiation detection, designed to operate under harsh conditions such as those found in fusion reactors or particle accelerators, have been experimentally characterized and numerically simulated. These models were calibrated using a photon beam in the X-ray spectrum. Irradiations were performed at the Biomedical Research Center of the University of Granada (CIBM) with a bipolar metal-ceramic X-ray tube operating at a voltage of 150 kV and a dose rate ranging from 0.05 to 2.28 Gy/min. All detectors under study featured identical external structures but varied in detection volume, anode configuration, and filling gas composition. To assess inter- and intra-model response variations, the tested models included 12 micro-ionization chambers (CRGR10/C5B/UG2), 3 micro-fission chambers (CFUR43/C5B-U5/UG2), 8 micro-fission chambers (CFUR43/C5B-U8/UG2), and 3 micro-fission chambers (CFUR44/C5B-U8/UG2), all manufactured by Photonis (Merignac, France). The experimental setup was considered suitable for the tests, as the leakage current was below 20 pA. The optimal operating voltage range was determined to be 130–150 V, and the photon sensitivities for the chambers were measured as 29.8 ± 0.3 pA/(Gy/h), 43.0 ± 0.8 pA/(Gy/h), 39.2 ± 0.3 pA/(Gy/h), and 96.0 ± 0.9 pA/(Gy/h), respectively. Monte Carlo numerical simulations revealed that the U layer in the fission chambers was primarily responsible for their higher sensitivities due to photoelectric photon absorption. Additionally, the simulations explained the observed differences in sensitivity based on the filling gas pressure. The detectors demonstrated linear responses to dose rates and high reproducibility, making them reliable tools for accurate determination of ionizing photon beams across a range of applications. Full article

Photodynamic and photothermal therapies with IR780 have gained exponential interest, and their photophysical properties have demonstrated promise for use in antitumor and antimicrobial chemotherapy. IR780 and its derivatives are valuable in labeling nanostructures with different chemical compositions for in vitro and in vivo fluorescence monitoring studies in the near-infrared (NIR) spectrum. The current literature is abundant on this topic, particularly with applications in the treatment of different types of cancer using laser illumination to produce photodynamic (PDT), photothermal (PTT), and, more recently, sonodynamic therapy (SDT) approaches for cell death. This review aims to update the state of the art concerning IR780 photosensitizer as a theranostic agent for PDT, PTT, SDT, and photoacoustic (PA) effects, and fluorescence imaging monitoring associated with different types of nanocarriers. The literature update concerns a period from 2017 to 2024, considering, more specifically, the in vivo effects found in preclinical experiments. Some aspects of the labeling stability of nanostructured systems will be discussed based on the evidence of IR780 leakage from the nanocarrier and its consequences for the reliable analysis of biological data. Full article

Effective noise management and control of periodic fluctuations in spaceborne atomic clocks are essential for the accuracy and reliability of Global Navigation Satellite Systems. Time-varying periodic terms can impact both the performance evaluation and prediction accuracy of satellite clocks, making it crucial to mitigate these influences in the clock bias. We propose methods based on the Fourier dictionary and basis pursuit, namely the Fourier basis pursuit (FBP) spectrum and the Fourier basis pursuit bandpass filter (FBPBPF), to analyze and extract periodic terms in the satellite clock bias. The FBP method minimizes the L1-norm to improve spectral quality, while the FBPBPF reduces boundary effects and noise. Our experimental results show that the FBP spectrum has a more obvious main lobe and reduces spectral leakage compared to traditional windowed Fourier transforms. In simulation experiments, the FBPBPF achieves periodic term extraction with errors reduced by 6.81% to 26.55% compared to traditional signal processing methods, and boundary extraction errors reduced by up to 63.67%. Using the BeiDou Navigation Satellite System’s precise clock bias for verification, the FBP-based prediction method has significantly improved the prediction accuracy compared to the spectral analysis model. For 6, 12, 18, and 24 h predictions, the average root mean square error of the FBP prediction method is reduced by 15.85%, 11.04%, 6.45%, and 4.01%, respectively. Full article

This study investigates wellbore leakage accidents associated with Carbon Capture, Utilization, and Storage Enhanced Oil Recovery (CCUS-EOR) to identify causal factors, clarify their degrees of influence, hierarchical structures, and substantive roles, while revealing the causal mechanisms behind these incidents to promote the safe development of CCUS-EOR. A distinctive aspect of this research is its integrated framework, which effectively combines the theory of integrated safety management with advanced methodologies such as the Decision-Making Trial and Evaluation Laboratory (DEMATEL), Interpretive Structural Models (ISM), and Cross-Impact Matrix Multiplication (MICMAC) to systematically analyze the interdependencies among risk factors. This comprehensive approach provides a nuanced understanding of the interactions among the 20 identified influencing factors across four domains, organized into a multilayered, three-stage structure. Furthermore, the study uncovers two critical causal pathways for wellbore leakage, namely F17 (lack of supervision and feedback) → F20 (inadequate safety investment) → F16 (lack of education and training) → F3 (weak safety awareness) → F9 (improper material selection) and F13 (high geological activity) → F11 (poor reservoir properties) → F6 (corrosion and aging failure), offering unique insights into risk dynamics that remain underexplored in the existing literature. This study could be enhanced in future research by taking into account a broader spectrum of causal factors, incorporating scenario simulations to facilitate a more comprehensive analysis, and involving a greater number of experts from diverse fields to enrich the insights derived. Full article

We introduce the concept of ergodicity and explore its deviation caused by quantum scars in an isolated quantum system, employing a pedagogical approach based on a toy model. Quantum scars, originally identified as traces of classically unstable orbits in certain wavefunctions of chaotic systems, have recently regained interest for their role in non-ergodic dynamics, as they retain memory of their initial states. We elucidate these features of quantum scars within the same framework of this toy model. The integrable part of the model consists of two large spins, with a classical counterpart, which we combine with a random matrix to induce ergodic behavior. Scarred states can be selectively generated from the integrable spin Hamiltonian by protecting them from the ergodic states using a projector method. Deformed projectors mimic the ‘quantum leakage’ of scarred states, enabling tunable mixing with ergodic states and thereby controlling the degree of scarring. In this simple model, we investigate various properties of quantum scarring and shed light on different aspects of many-body quantum scars observed in more complex quantum systems. Notably, the underlying classicality can be revealed through the entanglement spectrum and the dynamics of ‘out-of-time-ordered correlators’. Full article

Wavelet analysis (WA) decomposes laser Doppler (LD) microcirculatory signals into characteristic frequency intervals related to endothelial nitric oxide (NO)-independent, endothelial NO-dependent, neurogenic, myogenic, respiratory, and cardiac physiological influences. Since LD signals have a finite length, the WA results suffer from spectral leakage due to edge effects. The cone of influence (COI) delineates the regions of the wavelet scalogram where these effects become important. We aimed to determine whether accounting for the COI leads to significant differences in the WA results. Two typical patterns of LD signals were analysed: a baseline and a post-occlusive reactive hyperemia (PORH) signal. The WA spectra were constructed without and with excluding data affected by the COI. The relative power (RP = median power of each frequency interval/median power of the total spectrum) of the spectral components obtained without and with the COI was compared. Applying the COI correction did not significantly affect the baseline signals. On the contrary, in PORH, accounting for the COI resulted in significant differences in the RP of the endothelial NO-independent (p = 0.0005; Wilcoxon signed-rank test), endothelial NO-dependent (p = 0.0005), neurogenic (p = 0.0038), myogenic (p = 0.001), respiratory (p = 0.0002), and cardiac frequency bands (p = 0.0002). The results suggest that applying the COI correction to the WA results obtained from the LD signals is desirable, especially for transient signals. Full article

This paper proposes an improved algorithm based on the phase extraction of the Moiré fringe for wafer-mask alignment in nanoimprint lithography. The algorithm combines the strengths of the two-dimensional fast Fourier transform (2D-FFT) and two-dimensional window Fourier filtering (2D-WFF) to quickly and accurately extract the fundamental frequencies of interest, eliminate noise in the fundamental frequency band by using the threshold of the local spectrum, and effectively suppress spectral leakage by using a Gaussian window with outstanding sidelobe characteristics while overcoming their limitations, such as avoiding the time-consuming parameter adjustment. The phase extraction accuracy determines the misalignment measurement accuracy, and the alignment accuracy is enhanced to the nanometer level, which is 15.8% and 6.6% higher than 2D-FFT and 2D-WFF, respectively. The results of simulations and experiments confirm the feasibility and rationality of the algorithm. Full article

Dill is a fragrant vegetable containing various beneficial compounds for health. This research aims to evaluate the impact of various spectra of LED light on essential oil composition and morphological and physiological characteristics of three dill cultivars. LED light treatments included greenhouse light as control (C), blue (B), red (R), red + blue (RB), and white (W). RB light enhanced most physiological indicators investigated in this study, including photosynthetic pigments, phenols, flavonoids, and antioxidant capacity. Furthermore, electrolyte leakage in the three cultivars of Khomein, Isfahan, and Varamin decreased when exposed to RB light compared with C light. Under RB light, the essential oil contained more dill ether and α-phellandrene than in other light conditions. In general, light treatment with 75% R light and 25% B light had a noticeable impact on enhancing physiological features compared with other light spectrums. α-phellandrene levels increased in the Isfahan and Varamin cultivars under RB and B light conditions. Finally, the RB light and Khomein cultivars improved physiological features, whereas RB and R light in the Varamin and Isfahan cultivars are recommended for more essential oil compositions in functional food production. Full article

ZnO thin films were deposited using RF sputtering by varying the argon:oxygen gas flow rates and substrate temperatures. Structural, optical and electrical characterization of ZnO thin films were systematically carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, X-Ray photoelectron spectroscopy (XPS) and Hall measurements. Film deposited at room temperature and annealed at 300 °C exhibited low O₂ incorporation with localized defects and a high percentage of Zn interstitials. A large crystalline size and fewer grain boundaries resulted in a high Hall mobility of 46.09 cm²/V-s Deposition at higher substrate temperatures resulted in improvement in O₂ incorporation through the annihilation of localized defects and decrease in oxygen vacancies and Zn interstitials. Urbach tails within the bandgap were identified using the absorption spectrum and compared with the % defects from XPS. Bottom-gate thin-film transistors were subsequently fabricated on a SiO₂/p-Si substrate using the combination of RF sputtering, wet etching and photolithography. Variation in the substrate temperature showed performance enhancement in terms of the leakage current, threshold voltage, sub-threshold swing and I_ON/I_OFF ratio. Thin-film transistor (TFT) devices deposited at 300 °C resulted in an O₂-rich surface through chemisorption, which led to a reduction in the leakage current of up to 10⁻¹² A and a 10-fold reduction in the sub-threshold swing (SS) from 30 V to 2.8 V. Further TFT optimization was carried out by reducing the ZnO thickness to 50 nm, which resulted in a field-effect mobility of 1.1 cm²/V-s and I_ON/I_OFF ratio of 10⁵. Full article

In order to ensure the safety of steel wire rope in various application scenarios, it is particularly important to quantitatively detect the defects of wire rope. Complex detection conditions affect the detection efficiency of wire rope. Therefore, based on the magnetic flux leakage method, this study proposes a method to identify the damage width of steel wire rope for multi-channel fusion of a Hall sensor array. Firstly, the Hall sensor array is used to capture the magnetic flux leakage data of steel wire rope; then, continuous wavelet transform is used to decompose the original data, and moving average filtering is used to denoise each component; the denoised components are merged and converted into a time spectrum, and the time spectrum is classified by ResNet50 image classification model to realize the detection of wire rope damage width. According to the dataset used in this study, the results show that the proposed method performs best in the mainstream noise reduction model; detection accuracy for the width of damage in steel wire ropes is 97%, which proves that the proposed method is effective and feasible. Full article

The electromagnetic spectrum is a limited resource. With the widespread application of the electromagnetic spectrum in various fields, the contradiction between the demand for the electromagnetic spectrum and electromagnetic spectrum resources has become increasingly prominent. Spectrum sharing is an effective way to improve the utilization of the electromagnetic spectrum. However, there are many challenges in existing distributed electromagnetic spectrum trading based on blockchain technology. Since a blockchain does not provide privacy protection, the risk of privacy leakage during the trading process makes electromagnetic spectrum owners unwilling to share. In addition, a blockchain only guarantees integrity, and the imperfect trading dispute resolution mechanism causes electromagnetic spectrum owners to be afraid to share. Therefore, we propose a privacy-preserving electromagnetic-spectrum-sharing trading scheme based on blockchain and ABE. The scheme not only designs an ABE fine-grained access control model in ciphertext form but also constructs a re-encryption algorithm that supports trading arbitration to achieve privacy protection for electromagnetic spectrum trading. Finally, we experimentally evaluated the efficiency of the proposed electromagnetic spectrum trading scheme. The experimental results show that the electromagnetic spectrum trading scheme we propose was highly efficient. Full article

This paper presents Z-OFDM, a high-performance solution for underwater acoustic communication. Traditional underwater orthogonal frequency division multiplexing (OFDM) systems suffer from spectrum leakage and distortion due to the narrowband nature of underwater acoustic signals and the picket fence effect of the fast Fourier transform (FFT). Z-OFDM addresses these issues by integrating zoom-fast Fourier transform (ZoomFFT) with OFDM and redesigning the modulator and demodulator to replace the conventional FFT. This integration enhances spectral resolution, resulting in higher channel capacity, improved Signal to Interference plus Noise Ratio (SINR), and reduced Bit Error Rate (BER). Computer simulations using underwater acoustic channels from Fuxian Lake and Wuyuan Bay demonstrate that the Z-OFDM system achieves a 6 dB gain compared to conventional OFDM systems at a BER of ${10}^{-3}$. These results demonstrate the effectiveness of Z-OFDM in overcoming the limitations of traditional FFT-based OFDM systems in underwater environments. Full article