Excitation Source Research Articles

Multisource ultrasound-excited thermography for detecting concrete microcracks in hydraulic structures

ABSTRACT Hydraulic concrete structures often suffer from cracking that could lead to engineering accidents. Thus, it is important to identify emerging concrete cracks so that the premonitory danger of the components can be comprehensively evaluated, and the disaster management level can be advanced to the initial stage of the hazard. This study investigated the use of ultrasound-excited thermography to detect surface microcracks in concrete engineering components. A detection system and method for the synergistic excitation of multiple excitation sources were developed, and self-adaptive pressure-loading sleeves containing back shafts made of glass fibre-reinforced nylon were developed to exert pressure on the transducers. Eighteen groups of in-situ experiments were conducted on important parts of the key component using a combination of 28-kHz and 40-kHz-transducers with a power of 100 W. The results demonstrate that ultrasound-excited thermography with the synergistic excitation of multiple excitation sources can be applied to detect surface cracks in approximately semi-infinite reinforced concrete members in-situ. The radius of the current investigation of cracks stimulated by one 100-W transducer pressed by the self-adaptive sleeve in reinforced concrete members is as far as 300 mm. The minimum widths of the detected cracks are 0.03 mm.

Review of linear flux-switching machines for variable speed applications

Purpose This paper aims to present an overview of permanent magnet linear flux-switching machines (PMLFSM), field excited LFSM and hybrid excited LFSM (HELFSM) topologies as presented in literature for transportation systems such as high-speed trains and maglev systems. Design/methodology/approach The structural designs of different configurations are thoroughly investigated, and their respective advantages and disadvantages are examined. Based on the geometry and excitation sources, a detailed survey is carried out. Specific design and space issues, such as solid and modular structures, structure strength, excitation sources placement, utilization of PM materials, and flux leakage are investigated. Findings PMLFSM provide higher power density and efficiency than induction and DC machines because of the superior excitation capability of PMs. The cost of rare-earth PMs has risen sharply in the past few decades because of their frequent use, so the manufacturing cost of PMLFSM is increasing. Owing to the influence of high-energy PMs and magnetic flux concentration, the efficiency and power density are higher in such machines. PM is the only excitation source in PMLFSM and has constant remanence, limiting its applications in a wide speed operation range. Therefore, the field winding is added in the PMLFSM to flexibly regulate the magnetic field, making it a hybrid excited one. The HELFSM possess better flux linkage, high thrust force density and better flux controlling ability, leading to a wide speed range. However, the HELFSM have problems with the crowded mover, as PM, field excited and armature excitation are housed on a short mover. So, for better performance, the area of each excitation component has to compete with each other. Originality/value Transportation of goods and people by vehicles is becoming increasingly prevalent. As railways play a significant role in the transportation system and are an integral part of intercity transportation. So, this paper presents an overview of various linear machines that are presented in literature for rail transit systems to promote sustainable urban planning practices.

Observation of acoustic meron textures

Merons, as a member of quasiparticle family characterized by half-integer of the skyrmion topological charge with nontrivial topological textures, are of great interest in various branches of physics. Here, we report the first experimental observation of a meron texture configuration in acoustic waves. A squared metastructure is designed to support the spoof acoustic surface wave, forming meron lattice patterns in the acoustic velocity field vectors. The experimental results indicate that the meron textures can be moved and shaped by tuning the phase and amplitude differences between the excited sound sources, respectively. To demonstrate the topologically protected character of meron against structure defects, we further measure the acoustic pressure and velocity field distributions on a defective surface. The acoustic meron texture not only provides potential applications toward topologically robust ways to manipulate vectorial characteristics of the acoustic waves but also instills confidence for exploring other members of the quasiparticle family, such as the acoustic hopfion in acoustic waves.

Study on Thermal Characteristics of Winding under Inter-Turn Fault of Oil-Immersed Transformer

The inter-turn fault is a common fault of oil-immersed transformers. Due to the deterioration of inter-turn insulation, its resistance decreases, which leads to an increase in the winding coil current and loss, causing the winding temperature to rise. Therefore, analyzing the electrothermal characteristics of inter-turn short circuit faults in oil-immersed transformers can provide a theoretical basis for the diagnosis of inter-turn faults in transformers. This paper studies the equivalent circuit under inter-turn faults and establishes a field–circuit coupling model to calculate the current characteristics under different inter-turn short circuit faults of transformers. The distribution of coil losses under faults is calculated as thermal source excitations, and a thermal–fluid-coupled calculation model for oil-immersed transformers is established. After the experimental verification, it is found that both the errors between the winding and tank surface temperatures do not exceed the acceptable limits, validating the effectiveness of this model. Using this model to calculate the temperature distribution for various inter-turn short circuit faults in transformers reveals their hot-spot characteristics. The results indicate that under inter-turn fault conditions, the temperature at faulty turns will gradually increase towards a limit, eventually leading to coil damage. This research provides theoretical support for enhancing transformer detection and diagnostic capabilities.

Influence of quantum well thickness on the Cathodoluminescent properties of AlGaN-based UVC light source tube with CNT field emitters

Far ultraviolet C (UVC) light sources work well for a variety of applications, such as water purification, bacteria and virus sterilization, and sensing, because of their short wavelength. Herein, the recognized problems with a conventional UVC-LED are solved by creating a triode structure UVC light source tube (UVC-LST) operating at ∼268 nm employing a carbon nanotube (CNT) electron emitter as an excitation source. The UVC light emission of an aluminum reflector-capped AlGaN multiple quantum well (MQW) heterostructures synthesized on a nanopatterned sapphire substrate based on a cathodoluminescence (CL) layer is assessed. For luminescence results comparison, the heterostructure of AlGaN-based MQWs was fabricated with various QW layer thicknesses of 1, 1.5, and 2 nm. The utilization of a thinner QW layer with a thickness of 1 nm significantly improved the UVC light emission efficiency compared to the UVC-LSTs fabricated with thicker QW layers of 1.5 nm and 2 nm. The UVC-LST with the 1 nm QW layer exhibited approximately a 30 % improvement in light output power compared to the UVC-LST with a 1.5 nm QW layer, and closely a 33 % improvement compared to the UVC-LST with a 2 nm QW layer. Moreover, the UVC-LST with the thinner QW layer demonstrated a high power efficiency of 5.24 % when operating on a 2-inch light-emitting area, while consuming a low power of 7 W. This high power efficiency indicates that a significant portion of the input electrical power is effectively converted into UVC light output, highlighting the superior performance of the UVC-LST based on the 1 nm QW layer design.

Co-doping Sm3+ transforms Y2Ge2O7:Pr3+ into a novel orange-reddish long afterglow phosphor

Red long afterglow phosphors have significant implications for the realization of multicolor long-afterglow phosphors, but their insufficient luminescence intensity and afterglow duration still cannot meet the demands of practical applications. In this study, a novel orange-red phosphor, Y2Ge2O7:Pr3+, was synthesized for the first time. This phosphor not only exhibits exceptional thermal resistance but also shows a marked enhancement in long-afterglow performance upon co-doping with Sm3+. Remarkably, an orange-red afterglow can still be distinctly observed with the naked eye even 5 min after the removal of the excitation source in darkness. Further investigations involving thermoluminescence spectrum tests and the construction of an independent host-referred binding energy (HRBE) diagram reveal that the introduction of Sm3+ effectively mitigates the trap depth (1.02 eV) of the Y2Ge2O7:Pr3+ phosphor and significantly augments the quantity of electrons in shallow traps. This modification facilitates the effective release of electrons under room temperature conditions by the improved phosphor, thereby actualizing the long-afterglow luminescence phenomenon. Additionally, our findings indicate that a trap depth within the range of 0.60–0.80 eV is the optimal range for releasing electrons at room temperature. This research offers a crucial reference for future endeavors aimed at enhancing the performance of long-afterglow phosphors.

Varroa Mite Counting Based on Hyperspectral Imaging.

Varroa mite infestation poses a severe threat to honeybee colonies globally. This study investigates the feasibility of utilizing the HS-Cam and machine learning techniques for Varroa mite counting. The methodology involves image acquisition, dimensionality reduction through Principal Component Analysis (PCA), and machine learning-based segmentation and classification algorithms. Specifically, a k-Nearest Neighbors (kNNs) model distinguishes Varroa mites from other objects in the images, while a Support Vector Machine (SVM) classifier enhances shape detection. The final phase integrates a dedicated counting algorithm, leveraging outputs from the SVM classifier to quantify Varroa mite populations in hyperspectral images. The preliminary results demonstrate segmentation accuracy exceeding 99% and an average precision of 0.9983 and recall of 0.9947 across all the classes. The results obtained from our machine learning-based approach for Varroa mite counting were compared against ground-truth labels obtained through manual counting, demonstrating a high degree of agreement between the automated counting and manual ground truth. Despite working with a limited dataset, the HS-Cam showcases its potential for Varroa counting, delivering superior performance compared to traditional RGB images. Future research directions include validating the proposed hyperspectral imaging methodology with a more extensive and diverse dataset. Additionally, the effectiveness of using a near-infrared (NIR) excitation source for Varroa detection will be explored, along with assessing smartphone integration feasibility.

Hybridly Packaged White Light Emitting Diode Composed of Fluorescent SiC and Nitride‐Based Near‐Ultraviolet Light Emitting Diode

A combination of fluorescent SiC (f‐SiC) and porous f‐SiC is a promising phosphor material for pure white light emission. Herein, the anodic oxidation condition is optimized to produce porous f‐SiC. Furthermore, a hybridly packaged white light emitting diode (LED) package composed of f‐SiC/porous f‐SiC stacks with a nitride‐based NUV‐LED as an excitation source is fabricated. A distinct pure white light emission and the peak luminous efficacy of 11.6 lm W−1 at a forward current of 10 mA in the NUV‐LED are observed. At the peak luminous efficacy, the estimated internal quantum efficiency of the f‐SiC/porous f‐SiC stacks is ≈80% as the package involved several types of optical and energy losses.

VO2-Based metasurface for dynamically tunable terahertz surface plasmonic waves

Surface plasmonic waves (SPWs), which propagate along metal-dielectric interfaces, play a pivotal role in various photonic applications such as highly integrated photonic devices, super-resolution imaging, high-sensitivity sensing, on-chip integrated systems, etc. The ability to control the excitation direction of the SPWs is of great importance in these applications. In this work, we propose a terahertz on-chip metasurface device whose SPWs propagation direction can be dynamically tuned at the excitation source by exploiting the vanadium dioxide (VO2). Under circularly polarized light incidence, destructive or constructive interference formed in the subwavelength square ring slit resonators (SRSRs) arrays, resulting in the unidirectional propagation of terahertz SPWs. By adjusting the conductivity of VO2, the flexible control over the propagation direction of SPWs is realized. This approach significantly enhances the level of control compared to previous traditional polarization control method which can only be modulated by the polarization state, marking a notable advancement in the development of functional devices that harness the power of SPWs.

Sensitive and High-Throughput Time-Resolved Luminescence Detection of Tetracycline in Milk for Eliminating Background Fluorescence on a Miniaturized Apparatus.

Fluorescence detection has always suffered from high background fluorescence from real samples such as milk. Therefore, cumbersome pretreatments of samples were necessary to remove the fluorescent substances but led to long processing times and low efficiency. Time-resolved luminescence detection is a powerful technique for eliminating short-lived background fluorescence without additional pretreatments. However, the related instruments are usually equipped with high-speed excitation sources and detectors, which are always bulky and expensive. Herein, we developed a low-cost and miniaturized imaging system for high-throughput time-gated luminescence detection. An UV LED array was used to excite multiple samples, the luminescence of which could be detected by a smartphone simultaneously. An analog circuit was designed to synchronize the LED to the mechanical chopper to eliminate the background signals resulting from scattering and short-lived autofluorescence. Compared to other synchronous circuits based on FPGAs and microcontrollers, this analog circuit required no programming and memory. For the first time, high-throughput time-resolved luminescence detection of tetracycline in milk without any separation or enrichment was achieved by utilizing a smartphone as a camera, and the scattered signals and the background fluorescence were eliminated efficiently. The limit of detection reached as low as 53 nM (∼0.024 ppm), lower than the residue limit set by the European Union. This high-throughput time-gated luminescence detection method can be used for quantitative analysis of many real samples with high background fluorescence.

Application of KBaYSi2O7:Bi3+,Eu3+ Phosphor for White Light-Emitting Diodes with Excellent Color Quality

This paper examines the properties of two phosphor materials synthesized via utilizing the sol gel method: KBaYSi2O7:Bi3+ (KBYS:Bi) phosphor providing cyan/deep-blue emission and KBaYSi2O7:Bi3+,Eu3+ (KBYS:Bi,Eu) phosphor exhibiting tunable emission from near-UV to red. The optimal doping concentrations for Bi3+ and Eu3+ are 0.2% and 3.5%, respectively. It is found that the ability to give discrepant emission peaks under different excitation sources of the KBYS:Bi phosphor is attributed to the occupancy of Bi3+ in different cation hosts. Meanwhile, co doping the Eu3+ and Bi3+ into the KBYS host leads to red and cyan emission regions, enabling the emission tunability of the KBYS:Bi,Eu phosphor. KBYS:Bi,Eu phosphor was then used in combination with YAG:Ce3+ and blue chips to fabricate a white light emitting diode (LED) model. The particle sizes of KBYS:Bi,Eu phosphor are adjusted to examine its influences on the LED properties. With increasing particle sizes (≥12 µm), the KBYS:Bi,Eu phosphor can improve the scatter efficacy, transmission power, lumen output, and color performance (rendition and uniformity). Both KBYS:Bi and KBYS:Bi,Eu phosphors are promising luminescent phosphors that can be combined with other phosphor with different emission colors to obtain the full-spectrum or tunable white light for LEDs.

UV and X-ray induced photochromic material based on defect state exchanges

Inorganic photochromic (PC) materials are gaining increasing recognition as promising candidates for applications in optical storage and information display. However, conventional photochromic materials exhibit sluggish coding rates and a deficiency in intelligent response for writing and erasing under multiple excitation sources. This deficiency contributes to suboptimal readout/decoding efficiency and storage security. Here, we show a Ba2NaNb5O15:Er3+ photochromic material with photoluminescence reversible modulation that can fast respond to both ultraviolet light and 532 nm laser within about 1 s, which accompanied by thermal bleaching. The PC mechanism which is based on defect state exchanges between oxygen vacancy defects and color centers is attributed to the structural flexibility of Nb-O systems and oxygen vacancy increased under irradiation. More importantly, it shows differential PC decay behavior in response to X-ray and UV light due to the difference in the number of trapped carriers. Therefore, a simple strategy based on different self-recovery levels induced by double excitation is constructed to develop an encrypted optical memory model. This fast and differential excitation source response behavior hopefully stimulates the development of new encrypted optical memory.

Comparative study on photocatalytic activity: Ni ferrite/Mg ferrite vs. Z-scheme Ni ferrite/silver/Mg ferrite heterojunction under solar radiation

This study investigates the photodegradation efficiency of core/shell structures comprising NiFe2O4/MgFe2O4 (NiF/MgF) and Z-scheme NiFe2O4/Ag/MgFe2O4 (NiF/Ag/MgF) heterojunctions for Methylene Blue dye degradation. In this study, solar radiation was used as a source of excitation. X-ray diffraction analysis reveals an increase in particle size and micro-strain for NiF/MgF and NiF/Ag/MgF, confirming the formation of core/shell structures. The NiF/Ag/MgF sample exhibits the highest magnetization, attributed to the RKKY magnetic interaction between NiF and MgF moments via the conduction electron of the Ag metal layer. Optical measurements indicate increased absorption coefficient and absorption bandwidth for core–shell structures. Photocatalytic activity measurements demonstrate that while bare MgFe2O4 MgF shows limited photodegradation efficiency, NiF/MgF and NiF/Ag/MgF heterojunctions significantly enhance photodegradation. The presence of the Ag metal layer in the NiF/Ag/MgF heterojunction reduces electron-hole pair recombination and enhances their separation, leading to exceptional photodegradation efficiency. These results highlight the significance of Z-scheme heterojunction configurations in augmenting photodegradation processes under solar radiation, offering notable economic advantages. Additionally, the high magnetization observed in the studied samples presents an opportunity for efficient waste material retrieval using a simple magnetic extraction method.

Analytical Techniques for Elemental Analysis: LIBS, LA-TOF-MS, EDX, PIXE, and XRF: A Review

This contribution presents the applications of laser-induced breakdown spectroscopy (LIBS) for qualitative and quantitative elemental analysis of several samples such as geological ores, cement, and industrial materials. A combination of LIBS with the laser ablation time‒of‒flight mass spectrometer (LA-TOF-MS) assists in elemental quantification and isotopic abundance analysis. Different elemental components such as aluminum (Al), calcium (Ca), iron (Fe), potassium (K), lithium (Li), magnesium (Mg), sodium (Na), rubidium (Rb), silicon (Si), strontium (Sr), and titanium (Ti) in cement varieties, as well as rare earth metals, lanthanum (La), cerium (Ce), and neodymium (Nd) in geological ore samples, and cobalt (Co), chromium (Cr), nickel (Ni), iron (Fe), and molybdenum (Mo) in industrial standard material samples, have been precisely identified and their relative weight percentages estimated using CF-LIBS and LA-TOF-MS diagnostic techniques. To ensure the reliability of LIBS for the elemental analysis of industrial materials, a comparative study with other compatible techniques, including EDX, PIXE, and XRF, utilizing different excitation sources is presented. The results suggest that LIBS offers unique advantages, enabling rapid elemental analysis in circumstances where other techniques may face certain limitations.

Autofluorescence lifetime flow cytometry with time-correlated single photon counting.

Autofluorescence lifetime imaging microscopy (FLIM) is sensitive to metabolic changes in single cells based on changes in the protein-binding activities of the metabolic co-enzymes NAD(P)H. However, FLIM typically relies on time-correlated single-photon counting (TCSPC) detection electronics on laser-scanning microscopes, which are expensive, low-throughput, and require substantial post-processing time for cell segmentation and analysis. Here, we present a fluorescence lifetime-sensitive flow cytometer that offers the same TCSPC temporal resolution in a flow geometry, with low-cost single-photon excitation sources, a throughput of tens of cells per second, and real-time single-cell analysis. The system uses a 375 nm picosecond-pulsed diode laser operating at 50 MHz, alkali photomultiplier tubes, an FPGA-based time tagger, and can provide real-time phasor-based classification (i.e., gating) of flowing cells. A CMOS camera produces simultaneous brightfield images using far-red illumination. A second PMT provides two-color analysis. Cells are injected into the microfluidic channel using a syringe pump at 2-5 mm/s with nearly 5 ms integration time per cell, resulting in a light dose of 2.65 J/cm2 that is well below damage thresholds (25 J/cm2 at 375 nm). Our results show that cells remain viable after measurement, and the system is sensitive to autofluorescence lifetime changes in Jurkat T cells with metabolic perturbation (sodium cyanide), quiescent versus activated (CD3/CD28/CD2) primary human T cells, and quiescent versus activated primary adult mouse neural stem cells, consistent with prior studies using multiphoton FLIM. This TCSPC-based autofluorescence lifetime flow cytometer provides a valuable label-free method for real-time analysis of single-cell function and metabolism with higher throughput than laser-scanning microscopy systems.

Experimental Validation of a Coupled Acoustic Fluid-Poroelastic-Plate Model with Frontal and Lateral Source Excitations

This work deals with a coupled acoustic problem involving a compressible fluid and a poroelastic material contained in a cavity whose walls are all rigid except for the top, where a flexible plate is placed. The fluid is described utilizing its acoustic pressure, whereas, for the plate, the Naghdi shell model is used. The mechanical behaviour of the absorbing layer attached to the plate is described by using the Biot-Allard model, where the governing equations are written in the displacement-based formulation. The main novelty of this work lies in addressing the coupling between the plate and the poroelastic medium using the Reissner-Mindlin formulation for the Naghdi’s shell model and the displacement-based formulation for the Biot-Allard model. A comprehensive three-dimensional analysis is performed, comparing numerical and experimental results and showing the advantages of using the Biot-Allard poroelastic model in combination with the Naghdi shell model to predict the in-plane displacements of the plate structure over other fluid-equivalent formulations, such as the Allard-Champoux model.

Contribution Ratio of Excitation Sources to the Underwater Acoustic Radiation of the X-BOW Polar Exploration Cruise Ship

Contribution Ratio of Excitation Sources to the Underwater Acoustic Radiation of the X-BOW Polar Exploration Cruise Ship

Dynamic response analysis of high-speed train gearboxes excited by wheel out-of-round: experiment and simulation

Due to the special characteristics of rail vehicles, wheel–rail excitation has always had a huge impact on the stable operation of the vehicle system and the dynamic performance of each component structure. This paper takes high-speed train gearbox as the research object and establishes a rigid-flexible coupling dynamics model and analyses the dynamic response and fatigue damage of the gearbox under the excitation of wheel flat and wheel polygon. Combined with the analysis of test data from the gear transmission testrig and actual line operation of high-speed trains, it shows that high-speed train gearboxes are different from those applied in other fields, where the gear meshing excitation is no longer its main excitation source, but the wheel–rail excitation instead. The comparison analysis between the wheel flat and wheel polygon conditions indicates that the response of the gearbox to the wheel flat excitation is similar to the operational modal test and is capable of causing multi-order modal vibration of the gearbox. The effect of the wheel polygon on the gearbox is similar to that of single-frequency excitation, which lead to certain order modal resonance in the gearbox under frequency coupling situations. The impact of both conditions on gear box fatigue damage increases with the vehicle operating speed.

P-EcStat: A Versatile Design of Photoelectrochemical and Electrochemical Sensing System with Smartphone Interface via Bluetooth Low Energy

Electrochemical and photoelectrochemical sensors are a rapidly developing field in analytical chemistry. However, commercial systems often lack versatility and affordability, hindering wider adoption. Additionally, the absence of integrated excitation light sources limits their application in photoelectrochemical sensing. Here, we present a highly precise, versatile, affordable measurement system for both electrochemical and photoelectrochemical sensing applications. The system incorporates a three-electrode potentiostat with a synchronized excitation light source. This design enables the system to perform conventional electrochemical measurements like cyclic voltammetry, chronoamperometry, and photoelectrochemical amperometric measurements with controlled light excitation. The developed measurement system operates within a voltage range suitable for a measurable current range of 1 nA to 18 mA, with a high precision of 99%. The excitation source is a monochromatic LED system offering seven distinct wavelengths with digitally controlled intensity via a digital-to-analog converter. Furthermore, an Android-based user interface allows wireless system control via Bluetooth Low Energy. The report also details the construction of a photoelectrochemical experiment using copper (II) oxide nanorods synthesized by the hydrothermal process as the photoactive material employed to test the experiment on a potassium ferricyanide/potassium ferrocyanide solution. This user-friendly system allows broader exploration of electrochemical and photoelectrochemical sensing applications.

Active vibration control using minimum actuation power: Multiple primary sources controlled by multiple secondary sources

Minimum Actuation Power (MAP) is a novel active vibration control strategy that minimizes the total input power into the structure by monitoring the input power from the secondary source. In a previous paper, we presented the theory for MAP for a single primary source controlled by a single secondary source and demonstrated the application of MAP for rotorcraft interior noise control. In this paper, we extend the theoretical framework for MAP for multiple primary sources (excitation) controlled by multiple secondary sources (control). We show that the input power from the secondary sources is zero only when the secondary sources are located such that the phase of the cross-mobility term for each primary–secondary pair is same. This condition puts a constraint on the location of the secondary sources with respect to the primary sources so that the input power from the secondary sources is zero. We present simulations for a simply supported plate excited by two primary sources and controlled by a single secondary source that validate the theoretical findings. We also study the effect of phasing between the primary sources on MAP control performance and show that the maximum power reduction is obtained when the phase difference between the primary sources is zero. Experimental results are provided that demonstrate the feasibility of the MAP theory.