Search Results (864)

Nitrogen dioxide (NO₂) is broadly acknowledged as one of the six key air pollutants, posing a significant threat to environmental stability and human health. The profile of atmospheric nitrogen dioxide is required for quantifying NO₂ emissions from fossil fuel combustion and industry. In continuous-wave differential absorption lidar (CW-DIAL) systems, the laser sources employed are subject to the issues of varying output characteristics and poor instability. This study presents a CW-DIAL system for remote sensing of atmospheric NO₂ that employs a compact grating-based external cavity diode laser (ECDL) and Scheimpflug imaging. The laser in this system utilizes a piezoelectric transducer (PZT) for precise wavelength tuning, emitting at 448.1 nm and 449.7 nm with an output power of 2.97 W and a narrow linewidth of 0.16 nm. Signal capturing was achieved through a Newtonian telescope with a diameter of 200 mm and a 45° inclined CCD image sensor, satisfying the Scheimpflug principle. A case study near road traffic was used to verify the feasibility of ECDL-DIAL, which took place from 1 October to 2 October 2023 over an industrial park. The system generates precise NO₂ distribution maps with sub-50 m resolution over 3 km, updating every 10 min. Full article

Due to their compact sizes, low power consumption levels, and convenient integration capabilities, piezoelectric micromachined ultrasonic transducers (PMUTs) have gained significant attention for enabling environmental sensing functionalities. However, the frequency inconsistency of the PMUT arrays often leads to directional errors with the ultrasonic beams. Herein, we propose a reconfigurable PMUT array based on a Sc_0.2Al_0.8N piezoelectric thin film for in-air ranging. Each element of the reconfigurable PMUT array possesses the ability to be independently replaced, enabling matching of the required frequency characteristics, which enhances the reusability of the device. The experimental results show that the frequency uniformity of the 2 × 2 PMUT array reaches 0.38% and the half-power beam width (θ_−3dB) of the array measured at 20 cm is 60°. At a resonance of 69.7 kHz, the sound pressure output reaches 7.4 Pa (sound pressure level of 108.2 dB) at 19 mm, with a reception sensitivity of approximately 11.6 mV/Pa. Ultimately, the maximum sensing distance of the array is 7.9 m, and it extends to 14.1 m with a horn, with a signal-to-noise ratio (SNR) of 19.5 dB. This research significantly expands the ranging capability of PMUTs and showcases their great potential in environmental perception applications. Full article

Today’s ultrasonic transducers find broad application in diverse technology branches and most often cannot be replaced by other actuators. They are typically based on lead-containing piezoelectric ceramics. These should be replaced for environmental and health issues by lead-free alternatives. Multiple material alternatives are already known, but there is a lack of information about their technological readiness level. To fill this gap, a small series of prestressed longitudinally vibrating transducers was set up with a standard PZT material and two lead-free variants within this study. The entire process for building the transducers is documented: characteristics of individual ring ceramics, burn-in results, and free vibration and characteristics under load are shown. The main result is that the investigated lead-free materials are ready to use within ultrasonic bolted Langevin transducers (BLTs) for medium-power applications, when the geometrical setup of the transducer is adopted. Since lead-free ceramics need higher voltages to achieve the same power level, the driving electronics or the mechanical setup must be altered specifically for each material. Lower self-heating of the lead-free materials might be attractive for heat-sensitive processes. Full article

Surface acoustic wave-based (SAW) sensors are of great interest due to their high sensibility and fast and stable responses. They can be obtained at an overall low cost and with an intuitive and easy-to-use method. The chemical sensitization of a piezoelectric transducer plays a key role in defining the properties of SAW sensors. In this study, we investigate the structural and adhesion properties of a new class of coating material based on polyurethane polymeric composites. We used dark-field microscopy (DFM) and scanning electron microscopy (SEM) to observe the microstructure of polyurethane composite coatings on piezoelectric sensor elements and to analyze the effects of the chemical resistance and adhesion test (CAT) on the coating layers obtained with the polyurethane polymeric composites. The results of the microscopy showed that all polyurethane composite coatings exhibited excellent uniformity and stability after chemical adherence testing (CAT). All of the observations were correlated with the results of the ultrasonic analysis, which demonstrated the role of polyurethane as a binder to form the stable structure of the composites and, at the same time, as an adhesion promoter, increasing the chemical resistance and the adherence of the coating layer to the complex surface of the piezoelectric sensor element. Full article

This study explores the effects of ultrasonic treatment on the quality of potatoes processed into fries. Ultrasonic waves generate rapid pressure changes and cavitation effects, which can enhance seed vigor and growth. Over a three-year period (2015–2017) in east-central Poland, a field experiment was conducted using a randomized block design with split-plot divisions with three replications. The study compared two cultivation technologies: (a) with ultrasonic treatment of seed potatoes before planting, and (b) traditional technology. The second-order factor consisted of eight edible potato cultivars from all earliness groups (‘Denar’, ‘Lord’, ‘Owacja’, ‘Vineta’, ‘Satina’, ‘Tajfun’, ‘Syrena’, and ‘Zagłoba’). The sonication process was carried out using an ultrasonic bath with piezoelectric transducers. The results demonstrated significant impacts of the cultivation technology, potato variety, and weather conditions on the quality of fries. This research underscores the potential of ultrasonic treatment to improve the quality and consistency of potato products in the food industry. The use of ultrasound treatment on potato tubers before planting aligns with sustainable development by enhancing agricultural efficiency, reducing the environmental impact, and supporting socio-economic aspects of sustainable farming. It also aids in developing tools and methods for monitoring and quantifying sustainability efforts in potato processing, such as in the production of French fries. Future research should focus on optimizing ultrasonic parameters and exploring the long-term effects of sonication on potato storage and processing qualities. Full article

Due to the uncertainty of material properties of plate-like structures, many traditional methods are unable to locate the impact source on their surface in real time. It is important to study the impact source-localization problem for plate structures. In this paper, a data-driven machine learning method is proposed to detect impact sources in plate-like structures and its effectiveness is tested on three plate-like structures with different material properties. In order to collect data on the localization of the impact source, four piezoelectric transducers and an oscilloscope were utilized to construct an experimental platform for impulse response testing. Meanwhile, the position of the impact source on the surface of the test plate is generated by manually releasing the steel ball. The eigenvalue of arrival time in the time domain signal is extracted to build data sets for machine learning. This paper uses the Back Propagation (BP) neural network to learn the difference in the arrival time of each sensor and predict the location of the impact source. The results demonstrate that the machine learning method proposed in this paper can predict the location of the impact source in the plate-like structure without relying on the material properties, with high test accuracy and robustness. The research work in this paper can provide experimental methods and testing techniques for locating impact damage in composite material structures. Full article

This study investigates the optimal design and operation of an underwater ultrasonic system for algae removal, focusing on the electromechanical load of Langevin-type piezoelectric transducers. These piezoelectric transducers, which operate in underwater environments, exhibit variations in electrical–mechanical impedance due to practical environmental factors, such as waterproof molding structures or variations in pressure and flow rates depending on the water depth. To address these challenges, we modeled the underwater load conditions using the finite element method and analyzed the impedance characteristics of the piezoelectric transducer under realistic environmental conditions. Based on this analysis, we developed an ultrasound-driven system capable of efficient output control by incorporating the impedance characteristics of the transducer under load variations and subaquatic conditions. This study proposes analytical and experimental methods for modeling and analyzing practical ultrasound-driven systems for algae removal. Full article

For those piezoelectric materials that operate under high-power conditions, the piezoelectric and dielectric properties obtained under small signal conditions cannot be directly applied to high-power transducers. There are three mainstream high-power characterization methods: the constant voltage method, the constant current method, and the transient method. In this study, we developed and verified a combined impedance method that integrated the advantages of the constant voltage and current methods, along with an improved transient method, for high-power testing of PZT-5H piezoelectric ceramics. The results from both methods indicated that with increasing power, the electromechanical coupling coefficient $k_{31}$ , the piezoelectric constant $d_{31}$, and the elastic compliance $s_{11}^{\mathrm{E}}$ of the PZT-5H showed increasing trends, while the mechanical quality factor $Q_{\mathrm{m}}$ first decayed rapidly and then stabilized at a fixed level. Additionally, under the combined impedance method, the temperature of the vibrators rose significantly due to self-heating, whereas the transient method generated almost no heat, and the vibrators remained at room temperature. By comparing the results from the two methods, we decoupled the effects of temperature and power on the high-power piezoelectric performance. The results showed that the self-heating temperature amplified the effects of power on $k_{31}$, $d_{31}$, and $s_{11}^{\mathrm{E}}$, while its influence on $Q_{\mathrm{m}}$ remained negligible. Full article

The synthesis of reliable, cost-effective, and eco-friendly ZnO piezoelectric nanoparticles (NPs) can contribute to nanotechnology applications in electronics, sensors, and energy harvesting. Herein, ZnO NPs were synthesized using a hydrothermal method under varied reaction times and adding ammonium hydroxide, which provided an advantage of a low-cost, scalable, low-temperature, and environmentally friendly process. Characterization through UV–Vis spectroscopy revealed absorption peaks between 374 and 397 nm, showing a blue shift compared to bulk ZnO (400 nm) attributable to nanoscale dimensions. Transmission Electron Microscopy (TEM) analysis indicated particle dimensions with length and width ranges from 150 to 341 nm and from 83 to 120 nm, respectively. X-ray diffraction (XRD) confirmed high-crystalline quality, with crystallite sizes calculated using the Scherrer equation. In addition, the effective mass model provided an estimated band gap that matched with the reported data. Also, the lattice parameters, interplanar distances, and Zn-O bond lengths were consistent with Joint Committee on Powder Diffraction Standards (JCPDS). Finally, a ZnO NP film was deposited on a steel substrate, which generated a displacement of 150 nm under a square wave voltage of 10 V. The piezoelectric behavior of the synthesized ZnO NPs can be useful for fabrication of piezoelectric nanogenerators. The proposed synthesis can allow ZnO NPs with potential application in electronic devices, energy harvesters, and transducers. Full article

Piezoelectric micromachined ultrasonic transducers (PMUTs) show considerable promise for application in ultrasound imaging, but the limited bandwidth of the traditional PMUTs largely affects the imaging quality. This paper focuses on how to arrange cells with different frequencies to maximize the bandwidth and proposes a multi-frequency PMUT (MF-PMUT) linear array. Seven cells with gradually changing frequencies are arranged in a monotonic trend to form a unit, and 32 units are distributed across four lines, forming one element. To investigate how the arrangement of cells affects the bandwidth, three different arrays were designed according to the extent of unit aggregation from the same frequency. Underwater experiments were conducted to assess the acoustic performance, especially the bandwidth. We found that the densest arrangement of the same cells produced the largest bandwidth, achieving a 92% transmission bandwidth and a 50% burst-echo bandwidth at 6 MHz. The mechanism was investigated from the coupling point of view by finite element analysis and laser Doppler vibrometry, focusing on the cell displacements. The results demonstrated strong ultrasound coupling in the devices, resulting in larger bandwidths. To exploit the advanced bandwidth but reduce the crosstalk, grooves for isolation were fabricated between elements. This work proposes an effective strategy for developing advanced PMUT arrays that would benefit ultrasound imaging applications. Full article

The effect of residual stress or heat on ferroelectrics used to convert photons into electricity was investigated. The data analysis reveals that when the PET-PZT piezoelectric transducer is UV-irradiated with a 405 nm wavelength, it becomes a photon–heat–stress electric energy converter and capacitator. Our objective was to evaluate the PET-PZT photon–heat–stress electric energy conversion performance and the role of the light’s wavelength and intensity. Converting waste energy from energy-intensive processes and systems is crucial to reducing the environmental impact and achieving net-zero emissions. To achieve these, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. Full article

In composite structures, the precise identification and localization of damage is necessary to preserve structural integrity in applications across such fields as aeronautical, civil, and mechanical engineering. This study presents a deep learning (DL)-assisted framework for simultaneous damage localization and severity assessment in composite structures using Lamb waves (LWs). Previous studies have often focused on either damage detection or localization in composite structures. In contrast, this study aims to perform damage detection, severity assessment, and localization using independent DL models. Three DL models, namely the artificial neural network (ANN), convolutional neural network (CNN), and gated recurrent unit (GRU), are compared. To assess their damage detection and localization capabilities. Moreover, zero-mean Gaussian noise is introduced as a data augmentation technique to address the variability and noise inherent in LW signals, improving the generalization capability of the DL models. The proposed framework is validated on a composite plate with four piezoelectric transducers, one at each corner, and achieves high accuracy in both damage localization and severity assessment, offering an effective solution for real-time structural health monitoring. This dual-function approach provides a scalable data-driven method to evaluate composite structures, with applications in predictive maintenance and reliability assurance in critical engineering systems. Full article

The analysis conducted herein has shown that the efficiency of smoke precipitation can be improved by additionally making smoke particles interact with ultrasonic (US) oscillations. Because the efficiency of US coagulation lowers when small particles assemble into agglomerates, the authors of this work have suggested studying how smoke particles interact with complex sound fields. The fields are formed by at least two US transducers which work at a similar frequency or on frequencies with small deviations. To form these fields, high-efficiency bending wave ultrasonic transducers have been developed and suggested. It has been shown that a complex ultrasonic field significantly enhances smoke precipitation. The field in question was constructed by simultaneously emitting 22 kHz US oscillations with a sound pressure level no lower than 140 dB at a distance of 1 m. The difference in US oscillations’ frequencies was no more than 300 Hz. Due to the effect of multi-frequency ultrasonic oscillations induced in the experimental smoke chamber, it was possible to provide a transmissivity value of 0.8 at a distance of 1 m from the transducers and 0.9 at a distance of 2 m. Thus, the uniform visibility improvement and complete suppression of incoming smoke was achieved. At the same time, the dual-frequency effect does not require an increase in ultrasonic energy for smoke due to the agglomeration of small particles under the influence of high-frequency ultrasonic vibrations and the further aggregation of the formed agglomerates by creating conditions for the additional rotational movement of the agglomerates due to low-frequency vibrations. Full article

Ultrasonic pulse velocity (UPV) has shown effectiveness in determining the depth of surface-open cracks in concrete structures. The type of transducer and the algorithm for extracting the arrival time of the ultrasonic signal significantly impact the accuracy of crack depth detection. To reduce the energy loss in piezoceramic-based sensors, a high-performance piezoceramic-enabled smart aggregate (SA) was employed as the ultrasonic transducer. For the extraction of ultrasonic signal arrival time in concrete, a novel characteristic equation was proposed, utilizing the slope of the signal within a shifting window. This equation was subsequently applied to modify Maeda’s function, with the arrival time of ultrasonic waves defined as the moment corresponding to the minimum Akaike information criterion (AIC) value. Six plain concrete specimens with artificial cracks were prepared and one reinforced concrete beam with a load-induced crack was used for validation. The average deviation of the testing of 492 points on 12 human-made cracks was around 5%. The detection results of 11 measurement points of a crack in a reinforced concrete beam show that three measurement points have a deviation of about 17%. The experimental results demonstrated that the novel piezoelectric transducer and improved AIC algorithm exhibit high accuracy in detecting the depth of concrete cracks. Full article

Vibration is a major problem that can cause structures to wear out prematurely and even fail. Smart structures are a promising solution to this problem because they can be equipped with actuators, sensors, and controllers to reduce or eliminate vibration. The primary objective of this paper is to explore and compare two deep learning-based approaches for vibration control in cantilever beams. The first approach involves the direct application of deep learning techniques, specifically multi-layer neural networks and RNNs, to control the beam’s dynamic behavior. The second approach integrates deep learning into the tuning process of a PID controller, optimizing its parameters for improved control performance. To activate the structure, two different input signals are used, an impulse signal at time zero and a random one. Through this comparative analysis, the paper aims to evaluate the effectiveness, strengths, and limitations of each method, offering insights into their potential applications in the field of smart structure control. Full article