In order to improve the radiation performance of low-frequency sound device, a design method for a long-stroke low-frequency sound device is proposed, which mainly involves the design of the drive structure and radiation structure and the drive structure is designed with an electric long stoke. The flat plate and conical structures of piston plate of radiation structure are compared, and a long-stroke radiation structure with a low-damping guide support motion pair uniformly distributed in the circumferential direction is proposed. The numerical simulation results show that, with six straight-line bearings circumferentially and uniformly distributed, the displacement and stress distribution of piston plate are better than those of piston plate with three straight-line bearings installed in the same manner. The sound device is further tested in the experiment, and it is found that the vibration displacement amplitude at the center of piston plate is 3.9 mm (20 Hz), and the maximum sound pressure level of 40 Hz is found at the location 10 m from the center of sound device along the axial direction, reaching 105.3 dB.
Prestress has a great bearing on the performance of flextensional transducer. In order to enhance the adjustability of prestress, a design method for the flextensional transducer with adjustable prestress was proposed in this study. Through the conversion design of rotational and rectilinear motions of the transition block, the clamping length of major axis of class IV flextensional transducer shell was changed, enabling the adjustment of prestress. Next, the related experiment was further carried out. The results show that the return displacement of adjustable transition block is slightly greater than the travel displacement, and both displacements show high overlap ratios in the two tests. Because of the prestress adjustment, the frequency response of flextensional transducer is reduced to some extent, within one frequency band (40-63 Hz), but its sound pressure level (SPL) substantially increases nearby the resonant frequency (about 75 Hz).
A micromechanical target tracking system based on polarization grating (PG) is designed to meet the conformal design of laser communication systems and to realize the lightweight and miniaturization of space laser communication networking. The rotating dual PGs are applied to the dynamic tracking of laser targets for the first time, the relationship between the target position and the dual polarization gratings (PGs) angles is defined, and the PG beam deflection multi-coordinate construction and decoupling are carried out. A dual PGs mathematical model was established, and a controller based on the dual PGs system loop was designed. After calibration and dynamic verification of the dual PGs, the unmanned aerial vehicle (UAV) tracking experiment is conducted for the first time, and the dual axis closed-loop tracking error of the dynamic target is within 300µrad (RMSE). The feasibility of dual PGs tracking formula, the feasibility of laser target fixed-point closed-loop control, and the dynamic closed-loop tracking performance are verified. In engineering applications, the dual PGs tracking system has guiding significance for realizing the lightweight and miniaturization of system integration, as well as the possibility to replace the traditional tracking control system.
The parabolic reflector provides one of the common sound wave convergence methods in acoustic engineering. To reduce the difficulty of fabricating large-size reflectors and improve the convergence effect, this paper proposes a multi-segment linear reflector design method. Through the normal vibration radiation analysis of the flextensional transducer shell, the reflector interface reflection was optimized, the reflection effect was improved and the reflector size was reduced. The transmission theory was used to analyze the impact of different material parameters and sound wave frequency on the reflector transmission coefficient, and the gain effect of the multi-segment linear reflector was further tested. The research results show that the reflector has a significant gain effect in the test frequency band of 20∼100Hz, and the gain at 70Hz I reaches the maximum of 11.2dB.
The incident wave pressure acting on the wall of the spherical charge in the rock and soil is an important factor affecting the size of the explosion cavity, and the pressure of the incident wave is related to the impedance of both the explosive and the rock and soil. In this paper, based on the quasi-static model of explosive spherical charge in rock and soil, the impact impedance was introduced to calculate the size of explosion cavity in rock and soil medium. Through the field underground explosion experiment, it is found that the calculation result of the impact impedance model is 6.15% higher than the original model, and the influence rule of several geotechnical medium parameters on the cavity size was also analyzed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.