Spectral Intensity Research Articles

Separating source-intrinsic and Lorentz invariance violation induced delays in the very high-energy emission of blazar flares

The aim of the present study is to explore how to disentangle energy-dependent time delays due to a possible Lorentz invariance violation (LIV) at Planck scale from intrinsic delays expected in standard blazar flares. We first characterised the intrinsic time delays in BL Lacs and flat-spectrum radio quasars in standard one-zone time-dependent synchrotron self-Compton or external Compton models, during flares produced by particle acceleration and cooling processes. We simulated families of flares with both intrinsic and external LIV-induced energy-dependent delays. Discrimination between intrinsic and LIV delays is then investigated in two different ways. A technique based on Euclidean distance calculation between delays obtained in the synchrotron and in the inverse-Compton spectral bumps is used to assess their degree of correlation. A complementary study is performed using spectral hardness versus intensity diagrams in both energy ranges. We show that the presence of non-negligible LIV effects, which essentially act only at very high energy (VHE), can drastically reduce the strong correlation expected between the X-ray and the VHE gamma-ray emission in leptonic scenarios. The LIV phenomenon can then be hinted at measuring the Euclidean distance $d_ E $ from simultaneous X-ray and gamma-ray flare monitoring. Large values of minimum distance $d_ E,min $ would directly indicate the influence of non-intrinsic time delays possibly due to LIV in SSC flares. LIV effects can also significantly modify the VHE hysteresis patterns in hardness-intensity diagrams and even change their direction of rotation compared to the X-ray behaviour. Both observables could be used to discriminate between LIV and intrinsic delays, provided high-quality flare observations are available.

Leak Detection in Urban Hydraulic Systems Using the K-BiLSTM-Monte Carlo Dropout Model

Utility companies lose approximately 35 liters of water for every 100 produced due to incorrect, illegal connections and the poor condition of pipes. This study develops an intelligent model to detect leaks using the Kalman filter, BiLSTM neural networks, and the Monte Carlo Dropout algorithm. Using data from the Empresa de Acueductos y Alcantarillados de Bogotá (EAAB), Colombia, autocorrelation analysis, PCA, cluster analysis, ADF and Durbin-Watson tests, Hurst exponent, spectral analysis, and wavelet transform were performed. Then, Kalman filtering techniques were applied, and a BiLSTM architecture controlled with Monte Carlo dropout was implemented. The results showed an accuracy of 87.48% in training and 80.48% in validation. Temporal analysis revealed a stationary behavior in the flow series, and the decrease in spectral intensity around 0.25 Hz was related to pressure perturbations caused by leaks. A detailed evaluation of pressure and flow signals identified leak patterns with high precision, demonstrating the effectiveness of the wavelet spectrogram in detecting energy disturbances. The novelty of the study lies in the integration of advanced artificial intelligence and combinatorial optimization techniques to improve water resource management, allowing early and accurate detection of leaks, significantly improving compared to traditional methods. Doi: 10.28991/CEJ-2024-010-07-01 Full Text: PDF

Flexible Surface-Enhanced Raman Scattering (SERS) sensor for residue-free pesticide detection based on agriculture 4.0 concepts

Given the health and environmental risks associated with pesticide misuse, achieving zero pesticide residues is pivotal in Agriculture 4.0. Traditional detection methods such as HPLC and GC-MS are both complex and time-consuming. In contrast, surface-enhanced Raman scattering (SERS) offers rapid detection and high sensitivity, aligning with the efficiency and accuracy requirements of Agriculture 4.0. In this study, we developed a high-performance flexible substrate using a simple chemical synthesis method. We used material adsorption, anisotropic charge attraction and electron migration to facilitate the growth of the substrate material, which promoted more 'hot spots' and electron transfer, and continued optimisation of the preparation process, which resulted in a significant increase in spectral intensity. The substrate demonstrated outstanding detection capability, with a detection limit of 10−15 M for thiabendazole (TBZ). In practical fruit testing, TBZ residue concentrations on the surface of American cherries could be detected as low as 10−8 mg/mL, well below China's prescribed limit of 5 mg/kg. Relative to previous work in the field of pesticide detection, our study has lower detection limits and concentrations, as well as lower cost and simpler preparation, which provide more options for the detection of very low concentrations of hazardous substances. At the same time, it was confirmed that SERS is consistent with the zero pesticide residue goal of Agriculture 4.0, demonstrating practical efficacy and accuracy within this framework.

The Stagger Code for Accurate and Efficient, Radiation-coupled Magnetohydrodynamic Simulations

We describe the Stagger code for simulations of magnetohydrodynamic (MHD) systems. This is a modular code with a variety of physics modules that will let the user run simulations of deep stellar atmospheres, sunspot formation, stellar chromospheres and coronae, proto-stellar disks, star formation from giant molecular clouds, and even galaxy formation. The Stagger code is efficiently and highly parallelizable, enabling such simulations with large ranges of both spatial and temporal scales. We describe the methodology of the code and present the most important of the physics modules, as well as its input and output variables. We show results of a number of standard MHD tests to enable comparison with other, similar codes. In addition, we provide an overview of tests that have been carried out against solar observations, ranging from spectral line shapes, spectral flux distribution, limb darkening, intensity and velocity distributions of granulation, to seismic power spectra and the excitation of p-modes. The Stagger code has proven to be a high-fidelity code with a large range of uses.

Optimal intensity measure for seismic performance assessment of shield tunnels in liquefiable and non-liquefiable soils

Relating the ground motion intensity measure (IM) and the structural engineering demand parameter is a crucial step in the performance-based earthquake engineering framework. This study investigates the selection of IM for development of probabilistic seismic demand model of urban shield tunnels subjected to earthquake ground motions in liquefiable and non-liquefiable soils. Nonlinear dynamic effective stress analyses are conducted to develop a database of the intensity measures and structural seismic responses exposed to ground shaking and soil liquefaction. Two advanced soil constitutive models (i.e., Pressure DependMultiYield03 and PressureIndependMultiYield for liquefiable and non-liquefiable soils, respectively) are employed to capture the nonlinear behavior. A suite of 23ground motion intensity measures is selected and assessed based on the evaluation criteria of correlation, efficiency, practicality and proficiency. Eventually, the multi-level fuzzy comprehensive evaluation method is employed to comprehensively consider the four evaluation criteria and establish the optimal ground motion IM suitable for probabilistic seismic demand analysis of shield tunnel structures. The obtained results show that the sustained maximum acceleration is the optimal IM for evaluating the structural seismic response, followed by the peak ground acceleration in both liquefiable and non-liquefiable soils. Peak pseudo velocity spectrum, displacement square integral and Housner spectral intensity are found to be not suitable for the probabilistic seismic demand analysis of shield tunnel structures.

Interference correction for polarization spectral intensity modulation (PSIM) with spatial heterodyne spectroscopy (SHS)

Spectropolarimetry, capable of measuring both the polarization parameters and spectral information of light, is widely utilized in astrophysical research and atmospheric remote sensing. Spatial Static Polarization Modulation Interferometric Spectroscopy merges polarization spectral intensity modulation (PSIM) with spatial heterodyne spectroscopy to achieve high spectral resolution and static synchronous measurement of continuous band polarization spectral information. This article is based on spatial static polarization modulation interferometric spectroscopy principles and describes correction techniques for non-uniform response and phase errors observed in interferograms. A quantitative relationship was established through simulation between the non-uniform response, phase errors in the interferograms, and the demodulation accuracy of polarization parameters. An experimental setup based on these principles was constructed to validate the effectiveness of the correction. The experimental results demonstrated that by using the reported data processing workflow the error in the degree of polarization was reduced from 0.1354 to 0.0095.

Thermal radiation and soot in buoyant turbulent diffusion flames under different oxygen concentrations: Measurements and implications to radiation modeling

To develop and validate numerical models for sooty fires, we have established a dataset of the thermal radiation and soot in 15 kW buoyant turbulent ethylene flames. The flames are stabilized on a water-cooled round burner with a 15.2 cm outer diameter (D) and 13.7 cm inner diameter at three oxygen concentrations (OC) of 15.2 %, 16.8 %, and 20.9 %. A two-color optical probe is used to measure the spectral radiative intensities at two wavelengths, from which soot volume fraction and temperature are determined. The overall mean soot volume fractions are consistent with results from laser induced incandescence and laser extinction measurements. For a given OC, the mean soot temperature and volume fraction conditioned on the radiative intensity greater than a threshold value (instrumental detection limit) are relatively independent of spatial location. When OC decreases from 20.9 % to 15.2 %, the conditional mean soot volume fraction decreases by a factor of two. However, the conditional mean soot temperature at different locations and OCs are within a narrow range (with a standard deviation of only 22 K). The effect of detection limit is discussed, and the results show that the correlation between soot volume fraction and temperature is weak with a sufficiently low detection limit. Based on the experimental findings, a simplified model for the turbulence-radiation interaction (TRI) is proposed for application in the numerical modeling of soot radiation. The model approximates the turbulent closure term for radiation by taking advantage of the fact that the soot temperature has a relatively unchanged mean value and a narrow quasi-normal distribution within the buoyant turbulent flame, regardless of the spatial location and oxygen concentration. Therefore, the soot emission power can be directly calculated from the mean soot volume fraction and conditional mean soot temperature in a decoupled manner.

An alternative macro‐Raman mapping algorithm, adapting the numbers of accumulations

AbstractMacro‐Raman mapping is an approach that is well suited to study the distribution of molecules over a surface of typically several cm2, such as the pigment distribution on a painting. During such an experiment, thousands Raman spectra are recorded in a predefined array of points. As there can be a huge difference in Raman sensitivity between different molecules, an alternative approach is proposed, where measurement times are adapted according to the quality of the Raman scatterer. Therefore, an iterative process is implemented, involving recording short accumulations, followed by a quick evaluation. As soon as the accumulated spectrum reaches a quality criterium, measurement of the next point is started, while in the other case further accumulations are added. The influence of using multiple accumulations opposite to a single measurement for a prolonged period has been assessed by comparing the overall measurement time and the spectral intensity of the main Raman band (520.5 cm−1) of silicon. Another prerequisite for this algorithm to be successful is the need for a quick and reliable evaluation of the spectral quality. This was examined by applying this function on the accumulations of Raman spectra of 49 paint samples from a colour chart. Finally, the variable‐accumulation algorithm is applied during a macro‐Raman mapping experiment of a watercolour painting on paper. Despite a significant gain in overall measuring time, this novel approach yields a qualitative data set that can be used for creating clear Raman maps, using different data processing methods.

Tailoring the visible light band of Watt-level SCs pumped via picosecond pulse with different Raman extent

We investigate the supercontinuum (SC) tailoring property by varying the transmission fiber length after the master oscillator power amplifier system. The conversion efficiency of the visible light band is effectively enhanced via tailoring the Raman extent of the injected 30 ps pulse into the nonlinear photonic crystal fiber (PCF). Experimentally, a 3.6 W all-fiber SC spanning from 414 nm to over 1750 nm (@20 dB) is accomplished by using a high duty cycle domestic PCF through precisely controlling the extent of Raman effect. The proposed method is instructive for the further realization of high power SC with an enhanced spectral intensity in the visible light band.

Experimental and theoretical investigation of a miniature simple pressure pulsation attenuator lined with porous polyurethane material

A miniature simple pressure pulsation attenuator (PPA) lined with porous polyurethane material is designed and a theorical model is established for analyzing the pressure pulsation attenuation performance of PPA. The effect of internal structural parameters of PPA and external operating conditions on attenuation performance is investigated theoretically and experimentally. Spectral intensity is used as a new method to evaluate the pressure pulsation attenuation, and other common index such as pressure pulsation rate and frequency spectrum are also compared in detail. The results show that spectral intensity can more accurately reflect the overall effect of pressure pulsation and the attenuation effect at a specific frequency. The present PPA is more suitable for low static pressure and can effectively eliminate low-frequency and high-frequency pressure pulsation. In addition, the diameter and number of pores can affect the pressure pulsation attenuation. Insertion loss of PPA exhibits multiple peaks, which are mainly influenced by liner length and liner material. Furthermore, the flow rate increases as the pulsation frequency increases for the piston pump based on frequency control, which can cause the pulsation attenuation performance to basically remain unchanged. The research offers valuable insights for the design, optimization, and analysis of PPA in seawater hydraulic system.

Multi-component quantitative analysis of LIBS using adaptively optimized multi-branch CNN

Multi-component quantitative analysis of laser-induced breakdown spectroscopy (LIBS) is very important for industrial process control, food safety and space exploration. Due to the strong background interference and complex matrix effect, traditional quantitative analysis methods are difficult to realize accurate multi-component regression. Deep learning has the advantages of automatically extracting full-spectrum features and strong nonlinear modeling capabilities, which provides new opportunities for advancing the progress of LIBS quantitative analysis. However, due to the large difference of spectral line intensity and spectral cross-interference, existing deep learning models have limited performance for simultaneous multi-component regression. To this end, a novel adaptively optimized multi-branch convolution neural network (AOMB-CNN) framework is proposed for multi-component quantitative analysis of LIBS. Multi-branch structure is adopted to ensure the accuracy of multi-component content simultaneously. Dynamic weighted loss function and Bayesian optimization algorithm are used to adaptively optimize the deep learning model. The results demonstrate that the AOMB-CNN can effectively improve the performance of multi-component regression on 2 LIBS datasets compared with the traditional quantitative analysis methods. The root mean square error (RMSE) of 8 components of the ChemCam test set are 2.4465, 0.3486, 1.2481, 1.3909, 0.9010, 0.8892, 0.6700, and 0.5498 respectively, and the RMSE of 4 components of the steel test sets are 1.9787, 0.3455, 0.6025 and 1.6631 respectively. The proposed method provides an end-to-end, adaptively optimized, full-spectrum deep learning solution for LIBS multi-component content measurement without human intervention.

A Study on the Behavior of Smart Starch-co-poly(N-isopropylacrylamide) Hybrid Microgels for Encapsulation of Methylene Blue.

Hybrid microgels made from starch nanoparticles (SNPs) and poly(N-isopropylacrylamide) p(NIPAM) were used as promising hosts for the methylene blue (MB) dye. In this paper, these thermoresponsive microgels were characterized by dynamic light scattering (DLS), zeta potential measurements (ZP), and scanning electron microscopy (SEM) and evaluated as carriers for skin-targeted drug delivery. The hybrid microgel-MB systems in PBS solution were also studied by UV-vis spectroscopy and DLS, revealing discernible differences in spectral intensity and absorption shifts compared to microgels devoid of MB. This underscores the successful integration of methylene blue within the SNPs-co-p(NIPAM) microgels, signifying their potential as efficacious drug delivery vehicles.

Mid-infrared dual-wavelength operation of a diode-pumped Tm:YScO3 laser

A simultaneous continuous-wave (CW) dual-wavelength Tm:YScO3 laser using a single birefringent filter (BF) was experimentally demonstrated. We calculated the wavelength-dependent loss property of the BF. By adjusting the BF plate, the spectral intensity ratio of the generated wavelengths can be maintained to be 1:1. A simultaneous CW dual-wavelength Tm:YScO3 laser at 1948 and 2098 nm is experimentally realized. For a pump power of 15.2 W, mid-infrared dual-wavelength laser radiation at 1948 and 2098 nm and 5.9 W of output power using a 5% output coupler could be generated. A slope efficiency of 42.2% with respect to the absorbed pump power and optical-to-optical efficiency of 38.8% for the highest-incident pump power were obtained. To our knowledge, this is the first study that has realized the dual-wavelength in a Tm:YScO3 laser.

Enhancing elemental quantification in LIBS with SHAP-guided emission line analysis: A soil carbon study

In laser-induced breakdown spectroscopy (LIBS), identifying key emission lines for accurate elemental quantification has long posed a challenge. Traditional methods rely on experimental knowledge, atomic databases, and intricate spectral analyses. Although machine learning techniques – such as boosting algorithms and neural networks – offer efficient processing for large datasets, the complexity of these techniques often compromises interpretability. To address this issue, our study integrates the SHapley Additive exPlanations (SHAP) algorithm with gradient boosting models in order to interpret the most important spectral features, thus enhancing our understanding of how specific emission lines contribute to the carbon (C) concentration predictions in soils. Deployed on a large dataset of 1019 soil samples, a wrapper method with a random forest regressor reduced the initial spectral intensity features from 13,748 to 1098. Subsequent application of a LightGBM regression model calibrated via the Optuna framework yielded R2 of 0.98 and 0.77, and RMSE values of 1.55 and 4.54 g kg−1 for training and validation sets, respectively. The SHAP summary plot showed that C emission lines influenced the model's predictions positively, as anticipated, whereas silicon (Si) emission lines produced a negative impact, suggesting a lower C concentration in sandy soils. Our findings not only validate the efficacy of SHAP in improving LIBS-based soil C quantification, but they also offer a sophisticated framework for decoding the complex interplay between emission lines and target elemental concentrations.

The impact of dissipative algorithms on assessment of high-speed train running safety on railway bridges

The global expansion of high-speed railway networks has elevated their significance as a primary mode of transportation, particularly concerning train running safety (TRS) on bridges during seismic events. Achieving an accurate simulation model for train-bridge coupled (TBC) systems is often hindered by oversimplified assumptions. Refined TBC modeling adds complexity to the relationship between train wheels and tracks, necessitating the discretization of continuous models. However, this process leads to numerical errors and overshooting phenomena, significantly affecting TRS assessment. To tackle these challenges, an efficient unconditionally stable explicit numerical dissipation algorithm is designed to minimize errors and mitigate overshooting in TRS calculations. Furthermore, three TRS indices, the derailment factor, offload factor, and velocity-related spectral intensity, are investigated using spectral radii. The results show that adjusting the spectral radius can effectively reduce false peaks in these indices. Nonetheless, excessively small values may lead to inaccurate TRS assessments. Comparative analysis reveals that setting the spectral radius to 0.5 achieves relatively precise TRS assessments. This study underscores the pivotal role of dissipative algorithms in the safety assessment of TBC systems, an aspect overlooked in previous research.

Analysis of the effects of various light spectra on microgreen species

ABSTRACT Light conditions, such as spectral composition, intensity and photoperiod, can affect the photosynthetic apparatus and content of beneficial bioactive compounds. The experiments realised under randomised experimental design tested seedlings of 21 genotypes, including 12 genotypes of the Brassicaceae family, lettuce, amaranth, onion, spinach, fenugreek and two beet and two basil genotypes, which were cultivated in three light environments under narrow-band red and blue light-emitting diodes (LEDs) and broad-band white LEDs. Responsiveness to light spectra was assessed based on fresh and dry weight, total chlorophyll and carotenoid contents and non-invasive assessment of specific compounds using fluorescence excitation ratios. In white light, we observed a higher fresh weight compared to that in monochromatic environments, especially compared to blue light. In most of the species, blue and white light had a positive effect on the concentration of chlorophyll and carotene in plants compared to red light. Blue light was associated with the highest values of chlorophyll excitation ratios, indicating a significant increase in flavonoids and anthocyanin contents. Individual microgreens responded differently in all assessed traits, especially in fluorescence ratios. We also observed the clustering of microgreens with similar responses to LED light spectra. In conclusion, in most plant species, multispectral white LEDs positively influenced quantitative and qualitative traits compared to the most frequently used red LEDs. Blue light slightly improved quality, but suppressed growth. Nevertheless, some species responded differently, emphasising the need to optimise the light to improve the microgreens’ production and nutritional value.

Criticality of Spray Solvent Choice on the Performance of Next Generation, Spray-Based Ambient Mass Spectrometric Ionization Sources: A Case Study Based on Synthetic Cannabinoid Forensic Evidence

Mass spectrometry (MS) is a highly selective and sensitive analytical tool with a myriad of applications, but such techniques are typically used in laboratory settings due to the handling and preparations that are necessary. The merging of two streams of robust research, portable MS systems and next-generation ambient ionization methods, now provides the ability to perform high-performance chemical screening in an on-site and on-demand manner, with natural applications in disciplines such as forensic science, where samples of interest are typically found in field environments (i.e., traffic stops, crime scenes, etc.). Correspondingly, investigations regarding the suitability and robustness of these methodologies when they are utilized for authentic forensic evidence processing are prudent. This work reports critical insights into the role that choice of spray solvent system plays regarding analytical performance of two spray-based ambient ionization sources, paper spray ionization (PSI) and filter cone spray ionization (FCSI), when employed for evidence types containing emerging synthetic cannabinoids. The systematic characterization studies reported herein show that the applied spray solvent can dramatically affect both spectral intensity and signal duration, and in some circumstances, yield deleterious false negative responses. Overall, acetonitrile-based systems are shown to strike a balance between analyte solubility concerns and spray ionization dynamics of the novel ion sources employed on portable MS systems.

Investigation of structural, physical and optical properties of sodium boro-tellurite glasses doped with iron oxide

In this work, we demonstrate systematic studies on the influence of Fe2O3 on the structural and optical properties of transparent B2O3–TeO2–Na2O glasses containing the different concentrations of Fe2O3. The glasses were prepared via the standard melt quenching method, and the prepared glasses were characterized using, XRD, electron paramagnetic resonance (EPR), FTIR, and UV–visible spectroscopic techniques. Furthermore, we evaluated several physical properties of the glasses, including densities, molar volume, boron-boron separation, and oxygen packing density, with respect to the concentration of Fe2O3 in the host glass matrix. It is observed that the density of the glasses and the average boron-boron distance found increase with Fe2O3 concentration due to the modification in the glass network induced by the dopant ions. EPR spectra reveals the presence resonance signals at g ∼2.04 and g ∼4.26, hence it proves the existence of Fe3+ in distorted octahedral coordination and supported by UV–Vis absorption bands. The FTIR spectra revealed an increase in spectral intensity with the concentration of Fe2O3. This was attributed to the formation of non-bridging oxygens through converting BO4 units into BO3 units, which Fe2O3 mediated. The UV–visible spectral analysis showed a decreased energy band gap from 2.26 to 1.51 eV with increased Fe2O3 concentration. Additionally, we determined the Urbach energy, refractive index, optical basicity, and electronegativity, which are presented in detail.

Transition probabilities and suitable coupling scheme for 6p→6s transition array of neutral xenon using hollow cathode discharge lamp technique

In the present work, analyses have been performed to determine spectroscopic parameters, including transition probabilities, and relative line strengths of discharge-produced xenon plasma. We present the transition probabilities of twenty-three emission lines originating from the 5p56p →5p56s transition array of neutral xenon covering the wavelength range from 450 to 1100 nm using a xenon-filled hollow cathode discharge lamp. The experimental absolute transition probabilities have been measured by combining the reported lifetimes of upper levels with the integrated spectral intensities of xenon transitions. The results agree well with the reported data in the NIST database, where available. The theoretical line strengths for all spectral transitions originating from the 5p56p→5p56s transition array have been calculated in the LS, LK, jj, and jck coupling schemes using the 3j, 6j, and 9j symbol relations. Furthermore, the normalized experimental line strengths have also been measured and compared with theoretical line strengths, which confirm that the jj and jck coupling scheme is more appropriate for the level designation of xenon.

Characteristics of laser induced plasma near a flat gas-liquid interface and its effect on the performance of laser induced breakdown spectroscopy (LIBS) detection

Moving the laser focus to the vicinity of the gas-liquid interface is the key point for many new enhanced and new methods to improve the quality of spectral signals in water Laser induced breakdown spectroscopy (LIBS) detection. Understanding the generation and evolution characteristics of the plasma induced by pulsed laser near the gas–liquid interface is of great significance for the establishment of evolution models and improvement of these new LIBS methods. In this paper, a set of slow horizontal flow auxiliary system is established to provide an ideal flat gas–liquid two-phase interface experimental condition. Experimental research on vertical incidence flat system was conducted using techniques such as time-resolved imaging, plasma characterization diagnosis, and spectral analysis. And the detection capabilities of the system were also tested. The characteristics and mechanisms of LIBS near the gas-liquid two-phase interface were investigated with the laser incident on the sample along the vertical direction. Simulation of the laser beam focusing process and observation of laser beam spot images show that the shift of plasma generation position relative to the focal point results from the refraction of the laser beam entering the solution from the air and the ‘interface effect’ of propagation on the vertical direction. Moreover, the plasma forms only the optical power density surpasses the breakdown threshold. In this work, plasma with smaller size, rounder shape, stronger radiation, higher temperature, and higher density can be produced when the focus position is in the liquid column 0.3 mm away from the upper interface. Simultaneously, for example, the Mg ion line at 285.213 nm, the obtained spectral intensity to signal-to-background ratio reaches the maximum value, and a better spectral signal can be obtained, which is 2–4 times of other positions, and the detection limits of the elements Na, Mg, and Ca also reach the lowest level, with 1.6–2.4 times of the detection limit of other focusing positions for Mg and 1.4–1.7 times for Ca, respectively.