Search Results (1,420)

Seasonal dynamics of dissolved organic matter (DOM) in agricultural ditches significantly impact carbon cycling and water quality in connected rivers. This study aimed to characterize seasonal variations in DOM composition and dynamics within hierarchical agricultural ditch systems in Tianjin, northern China. Surface water samples were collected from river channels, main ditches, branch ditches, lateral ditches, and field ditches during wet (June 2021) and dry (December 2021) seasons. DOM characteristics were analyzed using dissolved organic carbon (DOC) quantification, ultraviolet-visible (UV-Vis) absorption spectroscopy, and three-dimensional excitation–emission matrix spectroscopy (3D-EEMs) coupled with parallel factor analysis (PARAFAC). The concentration of DOC in ditch surface water exhibited significant seasonal variations, with significantly higher levels observed during the wet season (Huangzhuang: 6.72 ± 0.7 mg/L; Weixing: 13.15 ± 3.1 mg/L) compared to the dry season (Huangzhuang: 5.93 ± 0.3 mg/L; Weixing: 9.35 ± 2.6 mg/L). Both UV-Vis spectral and EEM-PARAFAC analysis revealed that DOM in ditch systems was predominantly composed of fulvic-like and tryptophan-like components, representing the portion of organic matter in water bodies that is highly biologically active, highly mobile, relatively “fresh”, or “not fully humified”. PARAFAC identified microbial humic-like (C1: wet season 40.36%, dry season 34.42%) and protein-like (C3: wet season 40.3%, dry season 49.87%) components as dominant. DOM sources were influenced by dual inputs from terrestrial and autochthonous origins during the wet season, while primarily deriving from autochthonous sources in the dry season. This study elucidates the advances of spectroscopic techniques in deciphering the composition, sources, and influencing factors of DOM in aquatic systems. The findings support implementing riparian buffer strips and optimized fertilizer management to mitigate seasonal peaks of bioavailable DOM in agricultural ditch systems. Full article

This paper presents the initial design of a permanent magnet synchronous machine with mechanically controlled excitation flux using the linear sliding motion of an additional excitation source placed inside a hollow shaft in the rotor. A new rotor design concept and assembling method are described and presented in detail. On the basis of 3D-FE analysis results, the principle of adjusting reluctance, magnetic flux distribution, flux linkage, field weakening rate, no-load back EMF waveforms, electromagnetic torque, magnetic tension, and the effectiveness of the excitation adjustment of the presented machine design are discussed. The presented machine concept enables the design of permanent magnet excited machines with a good flux control range operating in changing load conditions under variable rotor speed. Full article

Biodetection, the basis of many biotechnologies, has rapidly developed in recent years. Among various biodetection methods, the photoelectrochemical (PEC) sensor is an emerging analytical method and has been applied in biodetection widely because of its high sensitivity, low cost, expandability into multichannel sensor arrays, and many other superior properties. Unlike conventional electrochemical aptasensors, the PEC aptasensor uses light as the excitation and an electrical photocurrent as the readout, which separates the stimulus from the measurement and reduces the excitation-related background. By modulating the light and demodulating the current, the PEC aptasensor improves the signal-to-noise ratio and lowers the limit of detection in complex matrices. Compared with optical aptasensors, the PEC aptasensor relies on simple light sources and electrodes rather than bulky imaging optics, enabling easier miniaturization and light-addressed multiplexed arrays. Therefore, aptamer-based PEC aptasensors have become a new hotspot in the field of biodetection. In this review, the development history of PEC aptasensors was presented. Then, this paper focuses on the photoactive nanomaterials, aptamers as sensing films, and sensing strategies of PEC aptasensors. The applications of PEC aptasensors in biodetection were also discussed. Finally, current challenges are discussed and opportunities in the future are prospected. Full article

To address the dynamic characteristics of vehicle semi-active suspension systems under special operating conditions and multi-source excitations, this paper proposes a fuzzy adaptive proportional–integral–derivative model predictive control (PID-MPC) strategy aimed at enhancing ride comfort during vehicle operation. The proposed approach employs MPC as the primary controller to optimize suspension performance, incorporating a fuzzy adaptive PID compensation mechanism for real-time adjustment of PID parameters, thereby improving control efficacy. A half-car semi-active suspension model was established on the MATLAB/Simulink (2020b) platform, with simulation validation conducted across diverse road profiles, including speed bump road surface, Class B road surface, and Class C road surface. Simulation results demonstrate that the proposed strategy achieves a significant reduction in both vehicle vertical acceleration and vehicle pitch angle acceleration while maintaining appropriate suspension deflection and tire dynamic loads, effectively elevating occupant ride comfort. Research demonstrates that the fuzzy adaptive PID-MPC control strategy exhibits commendable performance under typical road operating conditions, possessing notable potential for practical engineering implementation. Full article

This paper describes an improved version of a sampling-based bridge designed for impedance calibration. Based on the original concept of the new multiplexer, which constitutes a key element of the improved impedance bridge, we propose a new procedure for determining the complex voltage ratio using both successive and simultaneous sampling. The procedure significantly improves the accuracy of impedance comparisons by eliminating digitizer gain errors and reducing errors caused by instabilities in the excitation voltages supplied by the precision sources driving the bridge arms. An implementation of the new procedure, employing an innovative cross-multiplexer together with modified software, is presented. We also provide an analysis of selected error sources, including the effects of digitizer nonlinearity, which is crucial when applying the modified method for determining the impedance ratio. Finally, validation results are presented, demonstrating the performance and accuracy of the SUT sampling-based bridge in comparison with another validated bridge used at the Italian National Metrology Institute (INRIM) in Turin. Full article

Simulated (or measured) photoabsorption spectra often provide the first indication of how matter interacts with light when irradiated by some radiation source. In addition to the direct, often slowly varying photoabsorption cross-section as a function of the incident photon frequency, such spectra typically exhibit numerous resonances and edges arising from the interaction of the radiation field with the subvalence or even inner-shell electrons. Broadly speaking, these resonances reflect photoexcitation, with its subsequent fluorescence, or the autoionization of bound electrons. Here, a (relativistic) cascade model is developed for estimating the photoabsorption of (many) atoms and multiply charged ions with a complex shell structure across the periodic table. This model helps distinguish between level- and shell-resolved, as well as total photoabsorption, cross-sections, starting from admixtures of selected initial-level populations. Examples are shown for the photoabsorption of C⁺ ions near the 1s − 2p excitation threshold and for Xe²⁺ ions in the photon energy range from 10 to 200 eV. While the accuracy and resolution of the predicted photoabsortion spectra remain limited due to the additive treatment of resonances and because of missing electronic correlations in the representation of the levels involved, the present implementation is suitable for ions with quite different open-shell structures and may support smart surveys of resonances along different isoelectronic sequences. Full article

This study investigates the electromagnetic and NVH characteristics of an outer-rotor surface-mounted permanent magnet synchronous generator (SPMSG) for wave energy applications, focusing on the effect of rotor eccentricity. To reflect potential fault due to manufacturing or assembly defects, a 0.5 mm rotor eccentricity was introduced in finite element method (FEM) simulations. The torque ripple waveform was analyzed using fast Fourier transform (FFT) to identify dominant harmonic components that generate unbalanced electromagnetic forces and induce structural vibration. These harmonic components were further examined under variable marine operating conditions to evaluate their impact on acoustic radiation and vibration responses. Based on the simulation and analysis results, a design-stage methodology is proposed for predicting vibration and noise by targeting critical harmonic excitations, providing practical insights for marine generator design and improving long-term operational reliability in wave energy systems. Full article

The asymmetry of seismic rupture significantly dictates the intensity and spatial distribution of the radiated stress waves during mining-induced tremors, exerting a pivotal influence on the dynamic instability of roadways triggered by mining-induced tremors. In this study, a method for simulating arbitrary rupture patterns based on the theory of moment tensors is proposed. Based on the engineering context of strong seismicity-induced roadway dynamic instability at the Xinjulong coal mine, the entire process, from the excitation and propagation of seismic stress waves to the subsequent destabilization and destruction of the roadway, is reproduced. The effects of seismic source, including rupture patterns, seismic energy, fault plane angles, and the dominant frequency of stress waves, on the stability of a roadway are analyzed. Research indicates that a strong mining-induced tremor is characterized by tensile failure, with the radiated P-waves playing a predominant role in the destabilization and collapse of the roadway compared to S-waves. The P-waves exert a repetitive tensile and compressive effect on the perturbed medium, whereas S-waves contribute through compressive shear actions. The stability of a roadway is influenced by various characteristics of the seismic source. The rupture pattern of the seismic source affects the spatial distribution of stress waves. The seismic energy influences the kinetic energy transmitted to the roadway, with an increase in energy leading to a greater contribution of S-waves to roadway destruction. The fault plane angle similarly affects the propagation pattern of stress waves, particularly at 45° and 60° angles, where the maximum radiation of P-waves is directed towards the roadway, causing the most severe damage. The dominant frequency affects the attenuation of stress waves, with lower frequencies resulting in less attenuation and a higher likelihood of roadway damage. Full article

The 2 × 25 kV flexible traction power supply system (FTPSS), using a three-phase-single-phase converter as its power source, effectively addresses the challenges of neutral section transitions and power quality issues inherent in traditional power supply systems (TPSSs). However, the bidirectional fault current and low short-circuit current characteristics degrade the effectiveness of traditional TPSS protection schemes. This paper analyzes the fault characteristics of FTPSS and proposes a fault identification method based on empirical wavelet transform (EWT) and 1-sequence faulty energy. First, a composite sequence network model is developed to reveal the characteristics of three typical fault types, including ground faults and inter-line short circuits. The 1-sequence differential faulty energy is then calculated. Since the 1-sequence component is unaffected by the leakage impedance of autotransformers (ATs), the proposed method uses this feature to distinguish the TPSS faults from disturbances caused by electric multiple units (EMUs). Second, EWT is used to decompose the 1-sequence faulty energy, and relevant components are selected by permutation entropy. The fault variance derived from these components enables reliable identification of TPSS faults, effectively avoiding misjudgment caused by AT excitation inrush or harmonic disturbances from EMUs. Finally, real-time digital simulator experimental results verify the effectiveness of the proposed method. The fault identification method possesses high tolerance to transition impedance performance and does not require synchronized current measurements from both sides of the TPSS. Full article

The performance and beam quality of the new fourth-generation synchrotron light source with ultra-low emittance are highly susceptible to coupled-bunch instabilities. These instabilities arise from the interaction between the bunched electron beam and the surrounding vacuum chamber installations. To mitigate these effects, the installation of a transverse bunch-by-bunch feedback system is planned. This system will comprise a button-type beam position monitor (BPM) for beam signal detection, a digital feedback controller, a broadband power amplifier, and a broadband stripline kicker as the primary actuator. One of the critical challenges lies in the development of the stripline kicker, which must be optimized for high shunt impedance and wide bandwidth while minimizing beam-coupling impedance. This work focuses on the comprehensive design of the stripline kicker intended for transverse (horizontal and vertical) bunch-by-bunch feedback in the Siam Photon Source II (SPS-II) storage ring. The stripline kicker design also incorporates features to enable its use for beam excitation in the SPS-II tune measurement system. The optimization process involves analytical approximations and detailed numerical electromagnetic field analysis of the stripline’s 3D geometry, focusing on impedance matching, field homogeneity, power transmission, and beam-coupling impedance. The details of engineering design are discussed to ensure that it meets the fabrication possibilities and stringent requirements of the SPS-II accelerator. Full article

Spherical acoustic resonant cavities have been increasingly reported in photoacoustic spectroscopy due to their small volume and enhanced effective gas absorption path length. For further reducing the acoustic cavity volume and exploiting broadband LED as a light source, this paper reports a low-cost, LED-based photoacoustic gas-sensing system using a hemispherical acoustic resonant (HAR) cavity with a radius of 15 mm and a volume of 7.07 mL. The placement of both the excitation light source and transducer, as important elements in photoacoustic spectroscopy, was systematically optimized for improving the generation efficient of photoacoustic signal. The frequency response of the HAR cavity was thoroughly characterized for exploring an optimal operation frequency of the light source. Through positional and frequency optimization, the developed low-cost, LED-based photoacoustic spectrophone realized highly sensitive measurements of hydrocarbon gases with measurement sensitivities of 111.6 ppm (3σ) for isobutane, 140.1 ppm (3σ) for propane, and 866.4 ppm (3σ) for ethylene at an integration time of 1 s. These results demonstrate the strong potential of low-cost, LED-HAR-based PA-sensing systems in the field of gas sensing for widespread deployment in distributed sensor networks and atmospheric monitoring platforms. Full article

This project presents the development of an open-source educational platform based on an automotive Electrically Excited Synchronous Machine (EESM) repurposed from a KIA Sportage mild-hybrid vehicle. The introduction provides an overview of hybrid drive systems and the primary configurations employed in automotive applications, including classifications based on power flow and the placement of electric motors. The focus is placed on the parallel hybrid configuration, where a belt-driven starter-generator assists the internal combustion engine (ICE). Due to the proprietary nature of the original control system, the unit was disassembled, and a custom control board was designed using a Texas Instruments C2000 Digital Signal Processor (DSP). The motor features a six-phase dual three-phase stator, offering improved torque smoothness, fault tolerance, and reduced current per phase. A compact Anisotropic Magneto Resistive (AMR) position sensor was implemented for position and speed measurements. Current sensing was achieved using both direct and magnetic field-based methods. The control algorithm was verified on a modified six-phase inverter under simulated vehicle conditions utilizing a dynamometer. Results confirmed reliable operation and validated the control approach. Future work will involve complete hardware testing with the new control board to finalize the platform as a flexible, open-source tool for research and education in hybrid drive technologies. Full article

Persistent luminescence nanoparticles (PLNPs) represent a unique class of optical materials. They possess the ability to absorb and store energy from external excitation sources and emit light persistently once excitation terminates. Because of this distinctive property, PLNPs have attracted considerable attention in various areas. Especially in recent years, PLNPs have revealed marked benefits and extensive application potential in fields such as biological detection, imaging, targeted delivery, as well as integrated diagnosis and treatment. Not only do they potently attenuate autofluorescence interference arising from biological tissues, but they also demonstrate superior signal-to-noise ratio and sensitivity in in vivo imaging scenarios. Therefore, regarding the current research, this paper firstly introduces the classification, synthesis methods, and luminescence mechanism of the materials. Subsequently, the research progress of PLNPs in biological detection and imaging and medical treatment in recent years is reviewed. The challenges faced by materials in biomedical applications and the outlook of future development trends are further discussed, which delivers an innovative thought pattern for developing and designing new PLNPs to cater to more practical requirements. Full article

This study demonstrates the feasibility of exciting NV centers using ITO-anode OLED devices, followed by the fabrication of GO/PEDOT:PSS hybrid anodes via spin-coating. Through interfacial modification, the OLED devices exhibit significantly enhanced luminescence intensity, leading to improved NV center excitation efficiency. Experimental results show that the optimized GO/PEDOT:PSS (40%) hybrid anode device achieves a lower turn-on voltage, with the NV center fluorescence peak intensity reaching 3.7 times that of the ITO-anode device, confirming the enhanced excitation effect through interfacial engineering of the light source. By integrating NV centers with OLED technology, this work establishes a new approach for efficient excitation. This integration approach provides a new pathway for applications such as quantum sensing. Full article

Weeds are among the primary factors that adversely affect crop yields. Chlorophyll fluorescence, as a sensitive indicator of photosynthetic activity in green plants, provides direct insight into photosynthetic efficiency and the functional status of the photosynthetic apparatus. This makes it a valuable tool for assessing plant health and stress responses. Active chlorophyll fluorescence technology uses an external light source to excite plant leaves, enabling the rapid acquisition of fluorescence signals for real-time monitoring of vegetation in the field. This technology shows great potential for weed detection, as it allows for accurate discrimination between crops and weeds. Furthermore, since weed-induced stress affects the photosynthetic process of plants, resulting in changes in fluorescence characteristics, chlorophyll fluorescence can also be used to detect herbicide resistance in weeds. This paper reviews the progress in using active chlorophyll fluorescence sensor technology for weed detection. It specifically outlines the principles and structure of active fluorescence sensors and their applications at different stages of field operations, including rapid classification of soil and weeds during the seedling stage, identification of in-row weeds during cultivation, and assessment of herbicide efficacy after application. By monitoring changes in fluorescence parameters, herbicide-resistant weeds can be detected early, providing a scientific basis for precision herbicide application. Full article