Excitation Source Research Articles

The Rapid Identification and Evaluation of the Resonant Noise of a Cooling Module Based on the Frequency Difference Sensitivity Method

The energy amplification factor transmitted from the excitation source to the response end cannot be identified quickly and accurately using the method of obtaining modal frequency combined with damping through modal frequency resonance. As a result, the above method cannot be used to further evaluate the effect of structural improvement. In this paper, a frequency difference sensitivity method is proposed in order to improve the efficiency of the above identification and evaluation processes while also guaranteeing accuracy. Firstly, a theoretical model suitable for the damping and rigid-body-mode frequency range of the cooling module is established according to the frequency difference between the excitation frequency, .system mode frequency, and vibration response sensitivity. Then, the accuracy and effect of the model are studied from the perspective of a simulation and experiment. The model can be used to identify and evaluate the resonance problem of the vehicle cooling module quickly and accurately. The energy amplification factor of the fan to the passive end of the cooling module can be efficiently predicted using the frequency difference sensitivity method proposed in this paper while ensuring accuracy. The quantized noise-reduction effect of the interior before and after the improvement can be efficiently predicted and evaluated using said model. The literature shows that the resonance of a vehicle cooling module can be identified and evaluated quickly and accurately via the frequency difference sensitivity method, which can overcome the problems that the conventional modal frequency resonance method encounters in identifying and evaluating quickly.

Cutoff wavenumber analysis of arbitrarily shaped waveguides using regularized method of fundamental solutions with excitation sources

AbstractThe method of fundamental solutions with excitation source (MFS‐ES) is a reliable method for determining the eigenvalues of a two‐dimensional hollow waveguide. However, the accuracy in MFS‐ES is extremely dependent on the choice of the auxiliary boundary. In this work, to avoid the problem, a regularized MFS‐ES (RMFS‐ES) is proposed. First, to overcome the shortcomings of MFS, a regularized method of fundamental Solutions (RMFS) is proposed by borrowing the ideas of singular boundary method (SBM) and single layer regularized meshless method (SRMM). Second, the expressions for the fundamental solutions at the singularities are given by utilizing the subtraction and adding‐back technique (SAB). Third, the excitation source method is introduced to overcome the problem that the RMFS may also have spurious frequencies. Finally, to improve the accuracy of RMFS‐ES in solving polygonal waveguide eigenvalue, a wedge scheme (WS) is given. Numerical results show that the meshless RMFS‐ES is a promising numerical method for waveguide eigenvalue problems.

AI – bedazzled by its allure, blinded to its risks

You can't escape generative AI. It is being applied to so many parts of our lives and is the source of much excitement and speculation. But how many organisations fully understand its ramifications? It seems that few have properly delineated policies and standards for its application, and this could lead to serious problems.

Multiplex fluorescence detection of single-cell droplet microfluidics and its application in quantifying protein expression levels.

This study presented a platform of multiplex fluorescence detection of single-cell droplet microfluidics with demonstrative applications in quantifying protein expression levels. The platform of multiplex fluorescence detection mainly included optical paths adopted from conventional microscopy enabling the generation of three optical spots from three laser sources for multiple fluorescence excitation and capture of multiple fluorescence signals by four photomultiplier tubes. As to platform characterization, microscopic images of three optical spots were obtained where clear Gaussian distributions of intensities without skewness confirmed the functionality of the scanning lens, while the controllable distances among three optical spots validated the functionality of fiber collimators and the reflector lens. As to demonstration, this platform was used to quantify single-cell protein expression within droplets where four-type protein expression of α-tubulin, Ras, c-Myc, and β-tubulin of CAL 27 (Ncell = 1921) vs WSU-HN6 (Ncell = 1881) were quantitatively estimated, which were (2.85 ± 0.72) × 105 vs (4.83 ± 1.58) × 105, (3.69 ± 1.41) × 104 vs (5.07 ± 2.13) × 104, (5.90 ± 1.45) × 104 vs (9.57 ± 2.85) × 104, and (3.84 ± 1.28) × 105 vs (3.30 ± 1.10) × 105, respectively. Neural pattern recognition was utilized for the classification of cell types, achieving successful rates of 69.0% (α-tubulin), 75.4% (Ras), 89.1% (c-Myc), 65.8% (β-tubulin), and 99.1% in combination, validating the capability of this platform of multiplex fluorescence detection to quantify various types of single-cell proteins, which could provide comprehensive evaluations on cell status.

Design and Optimization of a Partitioned Stator Hybrid Excited Machine With Inset PM From Perspective of Airgap Field Harmonics

In this paper, a novel partitioned stator hybrid excited machine with inset permanent magnet is proposed, which offers reduced flux leakage of permanent magnet and parallel flux paths. Also, the partitioned stator is introduced to alleviate the space conflict between multiple excitation sources. Thus, its torque and flux regulation capability can be improved. In order to understand the hybrid excited principle and improve the electromagnetic performances, the machine is analyzed and optimized from perspective of airgap field harmonics. First, airgap field harmonics produced by field modulation effect of the machine are analyzed and calculated by equivalent airgap model. Then, an optimization method based on airgap field harmonics is proposed and implemented to improve its electromagnetic performances. Finally, the machine design and optimization method are evaluated and verified by both finite element analysis and prototype experiments.

Fiber Optic Sensor-Based Bearing Defect Detection and Its Usages in Computer Vision

This work focuses on the investigation of surface defects in small bearings. Based on the theory of rough surface scattering and the dual-beam ratio measurement method, fiber optic sensing technology is applied in identifying surface defects in bearings. To facilitate the extraction of features for surface defects in bearings, a sensor probe fiber array with three concentric circles around the central emission is determined. A reflective intensity-modulated fiber optic sensor (FOS) is employed to detect surface defects on bearings. The structural parameters of the FOS are simulated through Matlab, considering the inner/outer diameter, numerical aperture, and axial spacing of the sensor. This work involves designing modulation light source excitation circuits, photoelectric conversion module circuits, pre-amplification differential amplifier circuits, infinite gain bandpass filtering circuits, and window function comparison circuits. This effectively amplifies the defect feature signals and eliminates noise interference. In experiments, the sensor probe is fixed on the support of a micro-displacement measurement platform. By adjusting the distance between the probe and the side surface through rotation, initial tests are conducted using standard roughness samples. The results indicate that installing the sensor probe at a distance of 0.92 mm from the side surface provides better measurement of surface roughness. The oscilloscope waveform reveals that the FOS can identify defects on different bearing surfaces. Furthermore, the bearing surface is divided into sections with engraved text (seal cover part) and without engraved text (inner and outer rings of the bearing). Using computer vision (CV) technology, a FOS detection system is designed, achieving a defect recognition rate of 99% for bearings, in line with the intended design goals.

Comparison of different methods to determine the sound reduction index R of walls

The laboratory method (ISO 10140-2:2021) is probably the most accurate method to determine the sound reduction index R of walls. Flanking noise (ISO 10848-1 and 4:2017) is almost fully eliminated in the laboratory setup whereas this is not the case for in situ measurements (ISO 10052:2021). The measurements are even more difficult for measurements in open air or in factory halls with mock-up setups. Manufactures of building elements, such as prefabricated walls, are interested in quick measurements of the sound reduction index R of their products. This paper compares the traditional laboratory measurements, the intensity method and the Sopranoise road barrier method (EN 1793-6) with the vibration velocity / sound pressure method (ISO 140-4:1998). Different setups were measured using different methods in laboratory and in open air. Most of the experiments were done with loudspeakers used as an excitation source, but some were also done with shakers and a tapping machine. The importance of the use of sound shielded accelerometers will be elucidated.

Theoretical analysis of conversion process of tire tread vibration to road noise exciting force

Tire tread vibration due to unevenness of the road surface, through some process, acts on the axle, which is the excitation source of solid-borne components of road noise. However, this conversion process has not been fully understood until now. Therefore, the author decomposed it into two parts and analyzed it theoretically. They are: a) variations in cavity pressure, b) variations in sidewall contact angle with the wheel rim. As a result, it is now possible to formulate the relationship between tread displacement/velocity and the force acting on the axle. This study enabled us to calculate the effect of these two processes on a typical tire shape, size and pressure.

Numerical investigation on the mechanism of cascade unsteady force control based on pre-stator actuated oscillating trailing edge flaps

Unsteady force caused by rotor - stator interaction is one of the main excitation sources of impeller machinery vibration. To suppress the unsteady force, the stator wakes are conducted by the secondary flow generated by stator actuated oscillating trailing edge flaps (AOTEF). The unsteady Reynolds averaged Navier-Stokes equation (RANS) method based on the shear transport turbulence k-ω model and the improved delayed detached eddy simulation (IDDES) method are employed to numerically study a single cascade with AOTEF. The results show that the AOTEF oscillating phase angle determines the phase relationship between the stator wake and the rotor blade, and then affects the strength of the interaction between the stator wake and the rotor blade. Under the optimal phase of AOTEF, the rotor unsteady force decreases by 3 dB at rotor-stator blade passing frequency. The AOTEF significantly rises the peak value of the stator wake deficit. The amplitude of stator wake vorticity is significantly weakened by AOTEF, and the vortex shedding phase is regulated by AOTEF actuating phase. This study provides a new idea for the vibration and noise reduction of turbomachinery.

A subwavelength insulation panel for acoustic and aeroacoustic sources

A new kind of panel with strong transmission loss, breaking the mass law by 15 dB and composed by a soft solid plate with embedded solid cylindrical inclusions is studied numerically and experimentally. The presence of the inclusions introduces resonant and antiresonant phenomena in the subwavelength regime (the thickness is 30 times smaller than the equivalent wavelength in air), leading to an elastic band-gap and a destructive modal interference able to interact with each other. We also report on an experimental campaign demonstrating that the panel is very effective at insulating aeroacoustic sources (tested up to Mach 0.6), showing even better performance than with an acoustic source excitation. A new analysis tool, the vibroacoustic band diagram, is introduced to better apprehend theoretically all these results.

Measurement of nano molar ammonium with a cyclic olefin copolymer microchip and low-power LED

In oligotrophic regions, ammonium (NH4+) concentrations can be below 50 nM, however, few existing instruments can measure below this level with high confidence. This work, based on the o-pthaldialdehyde (OPA) fluorescence assay, is applied to measure nanomolar NH4+ in a novel optofluidic Cyclic Olefin Copolymer (COC) microchip using a low-power (20 mW) Light Emitting Diode (LED) as the excitation source. The optical arrangement was first modeled using ray tracing software to determine the initial detection volume size. Ammonium standards made with artificial seawater of 5 nM to 1000 nM, were run in triplicates. The limit of detection (LOD) obtained was 1.5 nM (3 x σ of the blank) or a LOD of 15 nM when the y-intercept and the vertical variation of each measured concentration on the calibration curve were taken into consideration (y-intercept +3. S y/x). Precision at 5 nM and 1000 nM was 3.3% and 0.5% respectively. The optofluidic system was also compared to an off-the-shelf fluorometer (Jasco FP2020) and an existing high-resolution shipboard analyser using five different standard concentrations. The LOD and the ammonium concentrations uncertainty for the Jasco FP2020, shipboard analyser, and current microsystem were 217 nM, 39 nM, and 15 nM and ± 232 nM, ± 48 nM, and ± 16 nM respectively. The optical setup was also validated using real samples from the Atlantic. This optical design, without optical fibres, makes the system simple and suitable for use with other fluorescent assays when compact, rugged, low-cost, and low-power consumption instrumentation is required.

Large‐Scale Daylight Photoluminescence: Automated Photovoltaic Module Operating Point Detection and Performance Loss Assessment by Quantitative Signal Analysis

Daylight photoluminescence (DPL) is a relatively novel imaging technique utilized in photovoltaic (PV) system inspection, using the sun as excitation source. Filtering the luminescence signal from the strong sun irradiation is its main challenge. Images acquired at two different operating points (OPs) of the module, allow subtraction of the background radiation while maintaining the luminescence signal. A DPL‐ready inverter, which is able to toggle between manually selectable OPs of connected PV modules, is presented in this work. Synchronization of image acquisition and OP switching becomes particularly challenging if the camera is applied to unmanned aerial vehicles. To overcome this challenge, an algorithm is developed to identify OP switches in a set of images taken in the field by investigating image intensities. Further, by working out the detailed dependencies of the signal recorded during DPL, the temperature coefficient of photoluminescence intensity is derived theoretically, and its impact on quantitative inspections. The potential field application of DPL images to identify performance loss in PV modules is investigated by two approaches: recording the signal intensity of images over time and comparing the signal intensity of different PV modules in one image. For both approaches, their hypothetical applicability is shown experimentally.

White‐Color Generation Using Blue Top‐Emission Organic Light‐Emitting Diode and Nanocrystalline Materials

White light is of great technical interest in many photonic applications. In this work, colloidal solutions containing mutually immiscible green perovskite nanocrystals and red InP quantum dots are developed as color‐conversion (CC) materials for generating white light. By combining the green/red CC materials and a blue top‐emission organic light‐emitting diode as an excitation source, it is possible to generate white light with a range of color temperatures (CTs). The technical approach can be extended to a wide variety of photonic applications where controllable CT is desirable.

Enhanced Catalytic Performance of Ag NP/0.95AgNbO3-0.05LiTaO3 Heterojunction from the Combination of Surface Plasma Resonance Effect and Piezoelectric Effect Using Facile Mechanical Milling.

An internal built electric field can suppress the recombination of electron-hole pairs and distinctly enhance the catalytic activity of a photocatalyst. Novel t-Ag/0.95AgNbO3-0.05LiTaO3 heterojunction was prepared by reducing silver nanoparticles (Ag NPs) on the surface of the piezoelectric powder 0.95AgNbO3-0.05LiTaO3 (0.05-ANLT) using a simple mechanical milling method. The effects of milling time and excitation source used for the degradation of organic dye by heterojunction catalysts were investigated. The results demonstrate that the optimized 1.5-Ag/0.05-ANLT heterojunction removes 97% RhB within 40 min, which is 7.8 times higher than that of single piezoelectric catalysis and 25.4 times higher than that of single photocatalysis. The significant enhancement of photocatalytic activity can be attributed to the synergistic coupling of the surface plasmon resonance (SPR) effect and the piezoelectric effect.

Research on X-ray-based energy conversion technology and assessment of application prospect

A new type of wireless energy transfer (radiation energy to electricity) power system is proposed for small-scale distributed energy utilization. To utilize radiation energy efficiently, energy conversion technologies based on different conversion modules and dissimilar material combination schemes are used. A variety of schemes such as single photovoltaic cell and single/multilayer fluorescent layer integrated with photovoltaic cell are designed. The maximum power density ranges from 7.93 nW/cm3 (tube voltage: 30 kV, tube current: 1 mA) to 6.7 µW/cm3 (tube voltage: 110 kV, tube current: 1 mA). After the structure layout of the system is matched and optimized, the maximum output power in radio-luminescent mode can be much higher than that in radio-voltaic mode. In particular, the maximum output power of conversion modules with a stacked layer can be increased by more than 36 times in radio-luminescent mode compared to radio-voltaic mode. At the same time, the effect of the distance of wireless energy transfer on the output performance of the energy conversion module is analyzed. To adjust the radiation intensity and field parameters better, X-ray tube is used as the radiation excitation source for performance testing and analysis. The performance attenuation of different energy conversion modules is similar when responding to X-ray over long distances. Compared with the radio-voltaic mode, the findings of this paper show that the output power of the system based on the radio-luminescent mode can be an order of magnitude higher.

A non-excavation detection method for buried PE pipelines based on 3D time-domain stacking focusing of elastic wave reflection

This paper proposed a method for locating buried polyethylene (PE) pipelines based on three-dimensional time-domain stacking focusing on elastic wave reflections. Research is conducted on the elastic wave propagation mechanism in solids. A finite element model of the propagation of elastic waves in a pipe–soil coupling system excited by a vertically oriented source is established. The transverse wave energy component below the excitation source is zero for elastic waves excited by a vertically oriented source. Based on this characteristic, an elastic wave probe array is first used, circularly distributed around the excitation source. The symmetry of the probe array is utilized to locate the buried PE pipes in the horizontal direction. Then, interference from the transverse waves is reduced by placing the excitation source directly above the buried PE pipeline. A three-dimensional image of the buried PE pipeline is formed using high-frequency elastic wave reflection signals and three-dimensional time-domain stacking. The results show that the proposed method can determine the horizontal position and burial depth of buried PE pipes without excavation. In addition, this work is significant for the localization methods of other buried pipe materials. The related detection systems and imaging methods have certain universality and reference value for detecting other buried public facilities.

Usefulness of glottal excitation source information for audio-visual speech recognition system

Usefulness of glottal excitation source information for audio-visual speech recognition system

The impact of a two-dimensional vibration excitation on the critical incident flow velocity of a sessile droplet

The movement of a sessile droplet can be initiated by different mechanisms. In addition to an incident flow, a vibration or differences in the surface properties can initiate the movement of a droplet. In many cases, the mechanisms occur in combination and their interaction is not well understood. We report on the investigation of superposition of an incident flow and a two-dimensional vibration excitation acting simultaneously. The focus is on the analysis of the critical air flow velocity required for the detachment of a droplet. More precisely, it is investigated how a simultaneous two-dimensional vibration affects the critical incident flow velocity. In particular, the influence of a phase shift of both excitation sources with respect to each other is investigated. For this purpose a rectangular Plexiglas flow channel equipped with two electromagnetic shaker is used. One oscillation source acts vertical to flow direction, while the second shaker operates simultaneously in horizontal direction. Two scenarios are considered for the orientation of the horizontal vibration excitation. Case 1: the horizontal vibration excitation is in the direction of the incident flow. Case 2: the horizontal vibration is transverse to the incident flow. The excitation frequency and acceleration are varied within the series of experiments. Water droplets of different volumes (7.8 – 23.4 μl) are studied. The substrate is polymethylmethacrylate (PMMA), which has a hydrophilic character, at static contact angles of about 74°for a water droplet. The data obtained reveal that the critical velocity for detachment of a sessile droplet can be significantly reduced by superimposing an oscillatory excitation only for certain frequencies. A significant decrease in the critical velocity is observed for an excitation in the range of the first and second eigenfrequencies. The phase offset of the two vibration sources will also affect the critical droplet detachment velocity if the horizontal excitation source is parallel to the incident flow. However, if the excitation is in the horizontal plane perpendicular to the incident flow, a phase shift between the two vibration sources has no effect.

Second-order optical nonlinearity of two 1,3,4-oxadiazole derivatives: An experimental and theoretical study

Measurements and theoretical modeling of the second-order optical nonlinearity of 2-(4-(dodecyloxy)phenyl)-5-(pyridin-3-yl)-1,3,4-oxadiazole (Oxa-4-Py) and 2-(4-(dodecyloxy)phenyl)-5-(4-(5-(thiophen-2-yl)-1,3,4-oxadiazol-2-yl)phenyl)-1,3,4-oxadiazole (DiOxaBn-2-Tio) are reported here. The hyper-Rayleigh scattering technique was applied to measure the dynamic first hyperpolarizability, βexpλ=1064, of the samples. The excitation source was a Nd:YAG laser operating at 1064 nm, 6 ns and 10 Hz, and a two-level approximation was applied to estimate the static first hyperpolarizability, βexpλ=0, of the samples. The obtained values for βexpλ=1064 were 173×10−30 esu (Oxa-4-Py) and 226×10−30 esu (DiOxaBn-2-Tio), and the calculated values for static first hyperpolarizability, βexpλ=0 were 106×10−30 esu (Oxa-4-Py) and 126×10−30 esu (DiOxaBn-2-Tio). The βexpλ=1064 value determined for the DiOxaBn-2-Tio is among the largest experimental values reported so far for a 1,3,4-oxadiazole derivative. The calculations based on a density functional method confirmed the trend of the βexpλ=1064 values among the samples, i.e. the first hyperpolarizability of DiOxaBn-2-Tio is approximately 30% larger than βexpλ=1064 for Oxa-4-Py.

Chemiluminescence‐driven photoelectrochemical sensor: A mini review

AbstractIn recent years, photoelectrochemical (PEC) sensors have attracted much attention due to their inherent advantages, such as ease of operation, high sensitivity, and structural diversity. Compared with conventional PEC detection methods, self‐illuminated PEC sensors do not require an external light source, which makes them more attractive in terms of instrument miniaturization and simplified operation. Chemiluminescence (CL), a straightforward and efficient excitation source, can be harnessed for PEC sensors. In this review, we provide a summary on the recently reported chemiluminescence‐driven PEC sensors. Initially, we briefly describe the current chemiluminescent systems employed in PEC sensors, including luminol and peroxyoxalate CL systems. Subsequently, the CL‐exciting modes and the design strategies for self‐excited PEC sensors are explored. The subsequent sections of the paper predominantly focus on discussing the applications of such PEC sensors in the detection of various target analytes. Furthermore, future prospects for advancing these PEC sensors are discussed.