Excitation Source Research Articles

Enabling Visible-Light-Charged Near-Infrared Persistent Luminescence in Organics by Intermolecular Charge Transfer.

Visible light is a universal and user-friendly excitation source; however, its use to generate persistent luminescence (PersL) in materials remains a huge challenge. Herein, the concept of intermolecular charge transfer (xCT) is applied in typical host-guest molecular systems, which allows for a much lower energy requirement for charge separation, thus enabling efficient charging of near-infrared (NIR) PersL in organics by visible light (425-700nm). Importantly, NIR PersL in organics occurs via the trapping of electrons from charge-transfer aggregates (CTAs) into constructed trap states with trap depths of 0.63-1.17eV, followed by the detrapping of these electrons by thermal stimulation, resulting in a unique light-storage effect and long-lasting emission up to 4.6 h at room temperature. The xCT absorption range is modulated by changing the electron-donating ability of a series of acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile-based CTAs, and the organic PersL is tuned from 681 to 722nm. This study on xCT interaction-induced NIR PersL in organic materials provides a major step forward in understanding the underlying luminescence mechanism of organic semiconductors and these findings are expected to promote their applications in optoelectronics, energy storage, and medical diagnosis.

Shape and location recovery of laser excitation sources in photoacoustic imaging using topological gradient optimization

This study focuses on source term inversion in fractional partial differential equations, specifically applied to photoacoustic imaging. This work contributes to advancing imaging techniques and provides practical insights for medical diagnostics and materials characterization. Our aim in this paper is to develop an accurate method for recovering the location and the shape of a laser excitation source from partial boundary data. To achieve this, we reformulate our inverse problem as an optimization challenge. We utilize topological sensitivity analysis to establish an asymptotic expansion of a relevant shape function. These theoretical findings form the basis for a rapid and precise detection algorithm. Additionally, we present several numerical experiments that demonstrate the effectiveness and accuracy of our proposed approach.

Calculating torque, back-EMF, inductance, and unbalanced magnetic force for a hybrid electrical vehicle by in-wheel drive application

To use a Hybrid Excitation Synchronous Machine (HESM) in a hybrid electrical vehicle (HEV), its performance indicators such as back-EMF, inductance and unbalanced magnetic force should be computed preferably by an analytical method. First, the back-EMF is calculated by considering alternate-teeth and all-teeth non-overlapping and overlapping windings. The effects of three types of magnetization patterns including the radial, parallel and Halbach magnetizations on the back-EMF waveform have also been investigated. Then, the self-inductance of the stator and rotor windings, the mutual inductance between the stator and rotor windings, and the mutual inductance between the stator phases are computed. Next, the components of the unbalanced magnetic force (UMF) in the direction of the x and y axes and its amplitude are computed. Moreover, the effects of the magnetization patterns on those magnetic pulls are investigated. To minimize the UMFs, symmetry must be implemented in the excitation sources; therefore, first the stator winding then the permanent magnet and rotor winding are modified in such a way that the UMFs are reduced. Increasing the temperature leads to a weakening of the magnet’s residual flux density, which strongly affects the performance characteristics of the electric machine such as Back-EMF and UMF. Finally, the ratio of the permanent magnet flux to the rotor flux is determined in such a way that the average torque is maximized. In this section, the effects of three magnetization patterns will be investigated.

Research on acoustic methods for buried PE pipeline detection based on LSTM neural networks

As an essential component of urban infrastructure construction, polyethylene (PE) pipelines face the challenging task of underground detection due to the complex and dynamic nature of the subsurface environment, diverse installation paths, and the inherent insulating properties of PE materials. In order to address the non-excavation detection of buried PE pipelines, this paper proposes an acoustic method based on the long short-term memory (LSTM) neural network. The study begins by analyzing the propagation and reflection mechanisms of elastic waves in the pipe-soil coupling system, and a impact excitation source is designed to generate the excitation signal. After establishing the experimental environment and collecting experimental data, a comprehensive analysis is conducted, and the LSTM neural network is employed for data classification to determine the presence of buried PE pipelines. Through neural network training, accurate identification of the PE pipeline’s existence and prediction of its burial depth are achieved, providing an efficient and reliable solution for buried PE pipeline detection. The practical results demonstrate the significant application prospects of the combined acoustic method and LSTM neural network in buried PE pipeline detection. This research contributes a novel solution to the field of non-destructive PE pipeline detection, with both theoretical and practical implications.

Large focal length planar focusing of Dyakonov polaritons in hyperbolic metamaterial

Achieving subwavelength optical focusing is of great importance in nanophotonics. However, achieving focusing with both a small focal spot size and a large focal length remains elusive so far. Here, a large focal length planar focusing device is presented, utilizing highly oriented Dyakonov polaritons in hyperbolic metamaterial with periodic silver rings as the excitation source. Experimental results show that by controlling the size of the excitation sources, the focal length can reach 6λ0 (where λ0 is the illumination wavelength), and the focal spot size can be reduced to λ0/10. This method provides new prospects for planar polariton optical applications.

Elemental analysis of “kampong” chicken egg shell content using a Nd-YAG laser induced breakdown spectroscopy

Abstract Distinguishing between eggs laid by chickens fed organic versus chemical feed poses a formidable challenge, particularly when relying on eggshell characteristics alone. As such, this investigation was undertaken to conduct a qualitative exploration of the eggshell composition in free-range chickens, employing laser induced breakdown spectroscopy (LIBS) to discern varying feed treatments within the samples. To initiate the formation of micro-plasma, a Nd:YAG LIBS system has been utilized as the excitation source. The eggshells used in the study were sourced from seven distinct chicken groups subjected to diverse feeding protocols, including 100% industrial feed, 100% village feed, and its combination, and also along with eggshells from purebred chickens purchased from traditional markets. Based on the spectroscopic analysis, the seven samples utilized in this study exhibit a uniform chemical composition, encompassing both organic and inorganic elements, specifically C, O, H, Ca, Mg, Fe, Al, K, Si, and S.

Some results from a transversely excited atmospheric carbon dioxide-laser induced breakdown spectroscopy investigation of tsunami deposit cored from Aceh Besar coastal region

Abstract We undertook an extensive analysis to examine the geochemical imprints encapsulated within the samples of the 2004 Indian Ocean tsunami deposits procured from the Seungko Mulat coastal region, nestled in the western section of Aceh Besar Regency, Aceh Province, Indonesia. In order to induce the formation of micro-plasma, a Transversely Excited Atmospheric Carbon Dioxide-Laser Induced Breakdown Spectroscopy (TEA CO2-LIBS) has been employed as the excitation source. Our investigation unveils distinct spectral signatures within every layer of the stratified tsunami deposit. We observed the unmistakable presence of salt elements (Ca, K, Mg, Na, Al), transition metals, heavy metals (Si, Fe, Ti, Ba, Sr, Cu, Cr, Pb, Mn, Ni, V), and also organic constituents (C, H, O, and N). The emission intensities of these elements exhibited a significant increase within the layers of the tsunami deposit, unequivocally setting them apart from their non-tsunami equivalents. In addition, we performed a vertical analysis of LIBS elemental emission intensity ratios, unveiling unique values for the Ca/Ti, and Si/Ti, ratios, which significantly distinguish them from all other ratios scrutinized in this exhaustive investigation. This research serves to highlight the effectiveness of TEA-LIBS as a promising and efficient optical technique for discerning the chemical profile associated with the renowned 2004 Indian Ocean tsunami deposits from Seungko Mulat Village in Aceh Province.

Analysis of the Repeatability of the Pencil Lead Break in Comparison to the Ball Impact and Electromagnetic Body-Noise Actuator

Acoustic emission testing is used to monitor the structural health by recording and analyzing sound signals originating from within a structure. Usually, sensors are attached at key positions on a structure under test to record and analyze these acoustic signals. For reliable measurements, the coupling of these sensors has to be assessed. For this purpose, artificial sound sources are commonly used which induce signals in the form of elastic waves into a structure allowing to approximately assess the frequency response function of the sensor coupling. To assess the coupling of sensors reliably by means of an artificial sound source, it has to exhibit high repeatability, i.e. small relative standard deviation (RSTD) with respect to some characteristic of interest. In this work, the repeatability of the pencil lead break, ball impact and an electromagnetic body-noise actuator is assessed across several repetitions. Through controlled and repeated excitation of the respective artificial sound sources on a concrete girder, the RSTD of the magnitude spectra of the artificial sound sources across frequency is assessed in the frequency range of about 0 kHz to 650 kHz. The ball impact and the actuator exhibited a RSTD of below 5 % of their magnitude spectra for frequencies below about 20 kHz, the maximum frequency for the actuator, whereas for the pencil lead break a RSTD of above 11 % was observed across the entire frequency range. An increase of the RSTD with increasing frequency was observed for the ball impact and the pencil lead break. The repeatability of the pencil lead break, for which a RSTD between 15 % to 40 % was observed for a broad frequency range of its amplitude spectrum, usually achieved a lower relative standard deviation than the ball impacts with 4 mm and 5 mm balls above a frequency of about 60 kHz. A significant increase of the relative standard deviation for the 4 mm and 5 mm ball was observed starting at about 20 kHz. Above about 60 kHz, the relative standard deviation of the 5 mm ball impact had risen to 30 % and more oscillating between about 30 - 50 %. At 200 kHz and more all signals were attenuated to background noise level by the concrete girder. It is concluded, that the pencil lead break is inferior with respect to repeatability below 40 kHz compared to the 4 mm and 5 mm ball impact and electromagnetic body-noise actuator, but performs equally well or better above 60 kHz. The repeatability of the investigated artificial sound sources depends on the investigated frequency range with no unique best. The most important finding is the increasing relative standard deviation of the ball impact with increasing frequency. As a result, the repeatability of the ball impact is questionable and should be investigated before using it in high precision experiments.

PRODIGE – envelope to disk with NOEMA

Context. Complex organic molecules (COMs) have been found toward low-mass protostars, but the origins of the COM emission are still unclear. It can be associated with, for example, hot corinos, outflows, and/or accretion shock and disk atmospheres. Aims. We aim to disentangle the origin of the COM emission toward the chemically rich protobinary system SVS13A using six O-bearing COMs. Methods. We conducted NOrthern Extended Millimeter Array observations toward SVS13A as part of the PROtostars & DIsks: Global Evolution (PRODIGE) program. Our previous DCN observations reveal a possible infalling streamer, which may affect the chemistry of the central protobinary by inducing accretion outbursts and/or shocked gas. We further analyzed six O-bearing COMs: CH3OH, aGg’- (CH2OH)2, C2H5OH, CH2(OH)CHO, CH3CHO, and CH3OCHO. Although the COM emission is not spatially resolved, we constrained the source sizes to ≲0.3–0.4 arcsec (90–120 au) by conducting uv-domain Gaussian fitting. Interestingly, the high-spectral-resolution data reveal complex line profiles with multiple peaks; although the line emission is likely dominated by the secondary, VLA4A, at VLSR = 7.36 km s−1, the numbers of peaks (~2–5), the velocities, and the linewidths of these six O-bearing COMs are different. The local thermodynamic equilibrium (LTE) fitting unveils differences in excitation temperatures and emitting areas among these COMs. We further conducted multiple-velocity-component LTE fitting to decompose the line emission into different kinematic components. As a result, the emission of these COMs is decomposed into up to six velocity components from the LTE modeling. The physical conditions (temperature, column density, and source size) of these components from each COM are obtained, and Markov chain Monte Carlo sampling was performed to test the fitting results. Results. We find a variety in excitation temperatures (100–500 K) and source sizes (D ~ 10–70 au) from these kinematic components from different COMs. The emission of each COM can trace several components, and different COMs most likely trace different regions. Conclusions. Given this complex structure, we suggest that the central region is inhomogeneous and unlikely to be heated by only protostellar radiation. We conclude that accretion shocks induced by the large-scale infalling streamer likely exist and contribute to the complexity of the COM emission. This underlines the importance of high-spectral-resolution data when analyzing COM emission in protostars and deriving relative COM abundances.

Study of LC oscillation based on excitation source of two-stage full-bridge structure

Abstract Nuclear magnetic resonance logging transmitting circuits must face the harsh operating environment of high voltage and high frequency. To reduce the voltage and current tolerated by the switching devices in the circuit and minimize the circuit loss, a high-frequency, high-voltage pulse transmitting circuit based on a two-stage full-bridge structure is designed in this paper. A new strategy for pulse excitation oscillation is proposed. The proposed strategy is based on the decision to end the excitation at the moment of peak voltage and the condition for limiting peak charging current (3.2). Finally, the circuit topology and excitation strategy proposed to achieve the overall optimal performance of sustained voltage oscillation with a peak voltage of 1180 V, precisely matching the transmitting frequency of 481 kHz and suppressing the charging current below 10 A.

A Gravity-Assisted Piezoelectric Inertial Actuator for Bidirectional Smooth Drives by Single Excitation Source

A Gravity-Assisted Piezoelectric Inertial Actuator for Bidirectional Smooth Drives by Single Excitation Source

Inspection of defects in composite structures using long pulse thermography and shearography

Long pulse thermography (LPT) and shearography have been developed as primary methods for detecting debonding or delamination defects in composites due to their full-field imaging, non-contact operation, and high detection efficiency. Both methods utilize halogen lamps as the excitation source for thermal loading. However, the defects detected by the two techniques differ due to their distinct inspection mechanisms. In this study, LPT and shearography are employed to evaluate internal damage in various composite structures. The experimental results demonstrate that LPT, when combined with thermal signal processing algorithms, can clearly detect debonding defects in rubber-to-metal bonded plates, whereas excessive adhesive defects can only be identified by shearography. Flat-bottom holes in the CFRP panel can only be detected by LPT, and shearography is particularly effective for detecting composite materials with a metal skin. For the quantitative measurement of defect sizes, the average errors of the rubber-to-metal bonded plate and CFRP panel using LPT are 4.9 % and 2.2 %, respectively, whereas the average errors of the rubber-to-metal bonded plate and aluminum honeycomb panel using shearography are 15.12 % and 95.4 %, respectively. This indicates that LPT is superior to shearography in quantitatively measuring defect sizes. These two nondestructive testing methods, based on different principles, each have their own advantages and disadvantages. Employing a multi-modal inspection method can leverage their complementary advantages, preventing misdetection and leakage of internal defects in composites.

Finite element numerical analysis of structural vibration of a certain pump station

Abstract In the process of pump station operation, the vibration of factory structure caused by hydraulic or mechanical factors will seriously threaten the ordinary operation of pump station; reduce the efficiency of units; shorten the service lifespan of equipment, and even lead to failure of units. In this paper, ANSYS software and modal analysis method are applied to simulate the vibration effect on pump station under natural vibration, unit vibration excitation and hydraulic excitation. The intrinsic vibration features of pump station structure under diverse boundary conditions, different working conditions and distinct external excitation sources are studied. According to the results of modal and harmonic response analysis, it can be concluded that: 1. A cross relationship has been found existing between pump station structure and unit excitation of speed frequency. 2. In addition to the upper part of the pump station fragile structure, the vibration of the pier is more noteworthy. 3. The vibration amplitude of the whole pump station along vertical direction is larger than that in other directions while the deformation following the unit axis and flow direction presents a strong tendency. 4. In general, the influence of hydraulic load on the structural force of pump station is relatively small.

Analysis of the cause of the 40Hz frequency component in spiral casing of a high-head pump turbine

Abstract Vibration and noise problems affect the safe and stable operation of pump turbines. For the design of pump turbines, it is crucial to accurately identify the excitation sources and their evolution laws that cause vibration and noise. Based on numerical calculation methods, this paper studies the 40Hz frequency component that occurs in the spiral case of a prototype pump turbine during operation in a power plant. Upon analysis of the internal flow characteristics of the spiral case, the study examines the causes for the formation of pressure pulsations at this frequency component and their transmission laws.

Developmental and Experimental Study on a Double-Excitation Ultrasonic Elliptical Vibration-Assisted Cutting Device

Ultrasonic elliptical vibration-assisted cutting (UEVC) has been successfully applied in the precision and ultra-precision machining of hard and brittle materials due to its advantages of a low cutting force and minimal tool wear. This study developed a novel double-excitation ultrasonic elliptic vibration-assisted cutting (D-UEVC) device by coupling ultrasonic vibrations in orthogonal dual paths. A two-degree-of-freedom vibration system of the D-UEVC was modeled, form which the elliptical trajectory of the end under different phase angle φ values was derived. The initial dimensions of the D-UEVC device were obtained through theoretical calculations. Subsequently, with the aid of finite element analysis methods, structural dynamic analysis of the device was conducted to obtain the elliptical vibration trajectory under different phase differences of the excitation source. In order to verify the cutting trajectory and cutting performance of the D-UEVC device, a prototype of the device was developed, and a series of vibration performance tests as well as the Inconel 718 cutting experiment were conducted. The experimental results illustrated that the D-UEVC device can achieve the elliptical vibration trajectory at the tool tip with a resonant frequency of 36.5 KHz. The adjustable elliptical vibration trajectories covered a range of ±4 μm in the axial and radial directions. Compared with the surface roughness Ra = 0.36 μm under the conventional cutting, the surface roughness of Inconel 718 under D-UEVC was Ra = 0.215 μm. Thus, the surface quality can be significant improved by utilizing the D-UEVC device.

Threshing cylinder unbalance detection using a signal extraction method based on parameter-adaptive variational mode decomposition

The threshing cylinder will wear and deform during the threshing process, causing dynamic balance problems. The combine harvester has multiple vibration excitation sources and a complex vibration environment, making it challenging to extract weak unbalanced signals from strong background noise. A novel three-step filtering framework is proposed in this paper. A zero phase filter was used as the pre-processing layer to filter out the high frequency components in the original signal and reduce the number of parameter-adaptive variational mode decompositions (PAVMD) needed. The PAVMD was used to decompose the non-stationary vibration signal before Adaptive Neuron Linear (Adaline) function was used to fit sinusoidal signal parameters. A measurement index, termed the correlation amplitude (CA) index, is constructed. The parameterisation of PAVMD was guided by the CA index, and the modal component of the unbalanced fault features were located. The simulation and real cylinder signals proved that the proposed method could effectively extract unbalanced signals under noise interference, and the unbalance was identified accurately by the influence coefficient method. Experiments on a threshing cylinder showed that the amplitude identification error was <24 g in single-sided unbalance identification, and the amplitude identification error was <27 g in double-sided unbalance identification. The proposed method had high robustness and small identification error, especially under short-time working conditions, compared with other similar approaches.

Off-plane quartz-enhanced photoacoustic spectroscopy.

In this work, we developed off-plane quartz-enhanced photoacoustic spectroscopy (OP-QEPAS). In the OP-QEPAS the light beam went neither through the prong spacing of the quartz tuning fork (QTF) nor in the QTF plane. The light beam is in parallel with the QTF with an optimal distance, resulting in low background noise. A radial-cavity (RC) resonator was coupled with the QTF to enhance the photoacoustic signal by the radial resonance mode. By offsetting both the QTF and the laser position from the central axis, we enhance the effect of the acoustic radial resonance and prevent the noise generated by direct laser irradiation of the QTF. Compared to IP-QEPAS based on a bare QTF, the developed OP-QEPAS with a RC resonator showed a >10× signal-to-noise ratio (SNR) enhancement. The OP-QEPAS system has great advantages in the use of light emitting devices (LEDs), long-wavelength laser sources such as mid-infrared quantum cascade lasers, and terahertz sources. When employing a LED as the excitation source, the noise level was suppressed by ∼2 orders of magnitude. Furthermore, the radial and longitudinal resonance modes can be combined to further improve the sensor performance.

Historical Pigments and Paint Layers: Raman Spectral Library with 852 nm Excitation Laser

Raman spectroscopy (RS), for its robust analytical capabilities under constant development, is a powerful method for the identification of various materials, in particular pigments in cultural heritage. Characterization of the artist’s palette is of fundamental importance for the correct formulation of restoration intervention as well as for preventive conservation of artworks. Here we examine the number and variability of research studies exploiting Bravo handheld Raman spectrophotometer relying on the excitation of Raman signal with temperature-shifted diode lasers emitting at 852 and 785 nm. To this end, we explore the spectral features of common historical pigments examined as powders and in the paint layer. We show that some materials may exhibit slightly different spectra as concerns especially the relative intensity of Raman lines with 852 nm laser excitation wavelength as compared to the standard 785 nm. The aim is to provide the research community with a reference spectral database that facilitates the identification of unknown pigments using the 852 nm excitation source.

Widefield Super-Resolution Infrared Spectroscopy and Imaging of Autofluorescent Biological Materials and Photosynthetic Microorganisms Using Fluorescence Detected Photothermal Infrared (FL-PTIR).

We have demonstrated high-speed, super-resolution infrared (IR) spectroscopy and chemical imaging of autofluorescent biomaterials and organisms using camera-based widefield photothermal detection that takes advantage of temperature-dependent modulations of autofluorescent emission. A variety of biological materials and photosynthetic organisms exhibit strong autofluorescence emission under ultraviolet excitation and the autofluorescent emission has a very strong temperature dependence, of order 1%/K. Illuminating a sample with pulses of IR light from a wavelength-tunable laser source causes periodic localized sample temperature increases that result in a corresponding transient decrease in autofluorescent emission. A low-cost light-emitting diode-based fluorescence excitation source was used in combination with a conventional fluorescence microscopy camera to detect localized variations in autofluorescent emission over a wide area as an indicator of localized IR absorption. IR absorption image stacks were acquired over a range of IR wavelengths, including the fingerprint spectral range, enabling extraction of localized IR absorption spectra. We have applied widefield fluorescence detected photothermal IR (FL-PTIR) to an analysis of autofluorescent biological materials including collagen, leaf tissue, and photosynthetic organisms including diatoms and green microalgae cells. We have also demonstrated the FL-PTIR on live microalgae in water, demonstrating the potential for label-free dynamic chemical imaging of autofluorescent cells.

Detection of gunshot residue by flash-pulse and long-pulse infrared thermography

Detection of gunshot residues (GSR) in a bullet hole area is one of the forensic investigations aiding in the reconstruction of crime scenes. Traditionally, chromogenic methods based on chemical exposure or microscopic/spectroscopic methods are used for this purpose. In this study, we explore the applicability of active excitation infrared thermography methods for GSR detection in the bullet hole area on fabric samples. A standard 9 mm full metal jacket ammunition with a nickel-plated shell and natural cotton fabric samples were used for experiments in this study. The applicability of active thermography methods based on two different light/heat excitation sources to detect the GSR was investigated. Flash-pulse and long-pulse thermography were compared through an experimental investigation. We evaluated the effectiveness of various thermographic data processing methods, including background subtraction, temperature derivative analysis, Fourier transform phase analysis, principal component analysis, and higher-order statistics for GSR evaluation. Our findings demonstrate that flash-pulse thermography and kurtosis analysis yield the highest contrast-to-noise ratio (CNR) and produce sharp, clear images of GSR, making it the optimal method for thermographic GSR detection. Our study indicates that even though the GSR particles are tiny, they can produce sufficient contrast to be detected by the thermographic methods if appropriate experimental and post-processing procedures are used. Thus, these methods could complement GSR detection as they are non-destructive and offer rapid inspection.