Vibrational Communication of Scolypopa australis (Walker, 1851) (Hemiptera: Ricaniidae)—Towards a Novel Sustainable Pest Management Tool

A study was undertaken to determine whether Scolypopa australis, the passionvine hopper, communicates using substrate-borne vibrations, as its use of such signals for communication is currently unknown. This insect is a costly pest to the kiwifruit industry in New Zealand, where few pest management tools can be used during the growing season. Vibrations emitted by virgin females and males of S. australis released alone on leaves of Griselinia littoralis were recorded with a laser vibrometer to identify and characterise potential spontaneous calling signals produced by either sex. In addition to single-insect trials, preliminary tests were conducted with female–male pair trials to determine whether individuals exchanged signals. The signal repertoire of S. australis includes a male calling signal and two female calling signals. However, no evidence of duetting behaviour that is potentially necessary for pair formation has been found to date. Our outcome suggests that a deeper understanding of the role of vibrational communication employed by S. australis is needed, and by disclosing the pair formation process, a new residue-free pest management tool against this pest may be developed. In addition, this vibration-based tool could contribute to future biosecurity preparedness and response initiatives.

Effects of Vibration Characteristics on the Atomization Performance in the Medical Piezoelectric Atomization Device Induced by Intra-Hole Fluctuation

Oral inhalation of aerosolized drugs has be widely applied in healing the affected body organs including lesions of the throat and lungs and it is more efficient than those conventional therapies, such as intravenous drip, intramuscular injection and external topical administration in the aspects of the dosage reduction and side effects of drugs. Nevertheless, the traditional atomization devices always exhibit many drawbacks. For example, non-uniformed atomization particle distribution, the instability of transient atomization quantity and difficulties in precise energy control would seriously restrict an extensive use of atomization inhalation therapy. In this study, the principle of intra-hole fluctuation phenomenon occurred in the hole is fully explained, and the produced volume change is also estimated. Additionally, the mathematical expression of the atomization rate of the atomizing device is well established. The mechanism of the micro-pump is further clarified, and the influence of the vibration characteristics of the atomizing film on the atomization behavior is analyzed theoretically. The curves of sweep frequency against the velocity and amplitude of the piezoelectric vibrator are obtained by the Doppler laser vibrometer, and the corresponding mode shapes of the resonance point are achieved. The influence of vibration characteristics on atomization rate, atomization height and atomization particle size are also verified by experiments, respectively. Both the experimental results and theoretical calculation are expected to provide a guidance for the design of this kind of atomization device in the future.

The Effect of Flow-Induced Vibration on Heat and Mass Transfer Performance of Hollow Fiber Membranes in the Humidification/Dehumidification Process

Cross-flow hollow fiber membranes are commonly applied in humidification/dehumidification. Hollow fiber membranes vibrate and deform under the impinging force of incoming air and the gravity of liquid in the inner tube. In this study, fiber deformation was caused by the pulsating flow of air. With varied pulsating amplitudes and frequencies, single-fiber deformation was investigated numerically using the fluid–structure interaction technique and verified with experimental data testing with a laser vibrometer. Then, the effect of pulsating amplitude and frequency on heat and mass transfer performance of the hollow fiber membrane was analyzed. The maximum fiber deformation along the airflow direction was far larger than that perpendicular to the flow direction. Compared with the case where the fiber did not vibrate, increasing the pulsation amplitude could strengthen Nu by 14–87%. Flow-induced fiber vibration could raise the heat transfer enhancement index from 13.8% to 80%. The pulsating frequency could also enhance the heat transfer of hollow fiber membranes due to the continuously weakened thermal boundary layer. With the increase in pulsating amplitude or frequency, the Sh number or Em under vibrating conditions can reach about twice its value under non-vibrating conditions.

Integration of piezoelectric stacks in components using powder bed fusion

Laser-based powder bed fusion of metals (PBF-LB/M) is the most commonly used additive manufacturing process for fabricating complex metal parts by selective, layer-wise melting of metallic powder using a laser beam. This manufacturing technique can easily fabricate parts with complex geometries that cannot be fabricated using conventional manufacturing processes. These parts with complex geometries are generally used by aerospace and space industries, and advancement in functionalization of additive manufactured parts is highly beneficial to these industries. However, the parts constructed using additive manufacturing are monolithic, stiff, and lightweight and hence, they are vulnerable to high amplitude resonant vibrations. This is due to the low damping factor of the materials used and the absence of interfaces and connections that contribute to structural damping in conventional structures. The integration of piezoelectric materials within these structures would enable the control of vibration characteristics. The techniques presented in this study will enable a high level of freedom in the placement of piezoelectric materials and investigate the potential of merging parts constructed using additive manufacturing with piezoelectric materials. Furthermore, a technique to track the stress state during the integration process, which is crucial for the pre-stress evaluation of integrated piezoelectric stacks, is presented and shows characteristics similar to a force cell. Pre-stress is successfully tracked during integration and in some concepts tensile stress onto the piezoelectric material is occurring. Finally, to verify the functionality for potential piezoelectric damping, power conversion was reported with laser vibrometer measurements and FE validation.

Identification of Multiple Cracks in Composite Laminated Beams Using Perturbation to Dynamic Equilibrium

Identification of cracks in beam-type components is significant to ensure the safety of structures. Among the approaches relying on mode shapes, the concept of transverse pseudo-force (TPF) has been well proved for single and multiple crack identification in beams made of isotropic materials; however, there is a noticeable gap between the concept of TPF and its applications in composite laminated beams. To fill this gap, an enhanced TPF approach that relies on perturbation to dynamic equilibrium is proposed for the identification of multiple cracks in composite laminated beams. Starting from the transverse equation of motion, this study formulates the TPF in a composite laminated beam for the identification of multiple cracks. The capability of the approach is numerically verified using the FE method. The applicability of the approach is experimentally validated on a carbon fiber-reinforced polymer laminated beam with three cracks, the mode shapes of which are acquired through non-contact vibration measurement using a scanning laser vibrometer. In particular, a statistic manner is utilized to enable the approach to be feasible to real scenarios in the absence of material and structural information; besides, an integrating scheme is utilized to enable the approach to be capable of identifying cracks even in the vicinity of nodes of mode shapes.

Modelling Anisotropy Influence on Guided Wave Scattering at Composite Delaminations

Carbon fibre reinforced composite laminates are widely used in aerospace structures but are prone to barely visible impact damage (BVID). Depending on impact severity, delaminations can form below the surface of the laminate, reducing the load bearing capacity. Efficient structural health monitoring (SHM) of composite panels can be achieved using guided waves propagating along the structure. Propagation and scattering of the A0 Lamb wave mode in a quasi-isotropic composite laminate was modelled using full three-dimensional (3D) Finite Element (FE) simulations. Individual ply layers were modelled using homogeneous unidirectional composite material properties to accurately capture the anisotropy effects. FE predictions for scattering and energy trapping at delaminations were compared to experimental measurements. Noncontact, full-wavefield guided wave measurements were obtained using a laser vibrometer. Good agreement was found between experiments and FE predictions. The effect of delamination shape and depth was investigated through a numerical parameter study. The angular dependency of the amplitude of the scattered wave was calculated. The influence of ply layer anisotropy on wave propagation in an undamaged laminate was investigated numerically. The sensitivity of guided waves for the detection of delaminations due to barely visible impact damage (BVID) in composite panels has been verified.

Contactless laser control and measuring complex for determining the level of winding pressure and magnetic conductor of power transformer

TARGET. The purpose of this work is to develop a non-contact laser control and measuring complex (LCMC) for vibration control of the level of pressing of windings and magnetic circuit of a power transformer. A laser vibrometer is used as a measuring element, the developed software in the LabVIEW graphical programming environment serves as a tool for processing vibration signals. The technical condition of the power transformer is analyzed by the amplitude spectra of the vibration of the tank of the transformer under study, formed using the fast Fourier transform algorithm in the LabVIEW software.METHODS. The vibration control method makes it possible to control a power transformer during its operation under voltage, which makes it possible to move from a planned system of transformer repairs to a system for taking out for repair according to the current technical condition.RESULTS. The developed LCMC allows to carry out non-contact measurements of vibration parameters of a power transformer under voltage and to establish the current level of pressing of windings and magnetic circuit.CONCLUSION. The developed LCMC with software allows contactless control of the technical condition of the magnetic circuit and the windings of the power transformer according to the amplitude-frequency characteristics of the vibration parameters, as well as the use of statistical methods for processing and analyzing signals received from the transformer.