Current Issue : April-June Volume : 2024 Issue Number : 2 Articles : 5 Articles
The application field of space deployable antennas covers mobile communication, navigation, deep space exploration, etc. The traditional space deployable antenna mechanism deploys in a fixed way and mostly in a circular direction in order to expand the space deployable antenna configuration; this paper summarizes the bionic principle that can be used for antenna structure design by studying the tail feather deploying behavior of birds such as peacocks and proposes a new parabolic antenna configuration that imitates the tail feather deploying of birds. The kinematic model of the deployable mechanism is established, and kinematic analysis of the deployable process is carried out on the key rods. The simulation of the rod motion is carried out using ADAMS 2020 software, and the angle change results obtained from the simulation are compared with MATLAB 2020b to verify the correctness of the kinematic equations. The deployment trajectories of the innermost and outermost rib endpoints are analyzed, and the spatial arrangement of the antenna is determined to be in the range of 4 m × 3.5 m. This is a solid foundation for the development of spatially deployable antennas....
This study reports a novel Ni(OH)2/Co3O4 heterostructured nanomaterial synthesized through a simple two-step hydrothermal method combined with subsequent heat treatment. The Ni(OH)2/Co3O4 heterostructured nanomaterial showed excellent performance in the detection of xylene gas. XRD, SEM, and EDS characterized the crystal structure, microstructure, and composition elements of Co3O4 and Ni(OH)2/Co3O4, and the gas sensing properties of the Co3O4 sensor and Ni(OH)2/Co3O4 sensor were systematically tested. The test results indicate the Ni(OH)2/Co3O4 sensor has an optimal operating temperature of 175 ◦C, which is 10 ◦C lower than that of the Co3O4 sensor; has a response of 14.1 to 100 ppm xylene, which is 7-fold higher than that of the Co3O4 sensor; reduces the detection limit of xylene from 2 ppm to 100 ppb; and has at least a 4-fold higher response to xylene than other gases. The Ni(OH)2/Co3O4 nanocomposite exerts the excellent catalytic performance of two-dimensional nanomaterial Ni(OH)2, solves the deficiency in the electrical conductivity of Ni(OH)2 materials, and realizes the outstanding sensing performance of xylene, while the construction of the p–n heterojunction between Ni(OH)2 and Co3O4 also improves the sensing performance of the material. This study provides a strategy for designing high-performance xylene gas sensors using two-dimensional Ni(OH)2 materials....
In this study, an all-optical multiplexer (Mux) based on elliptical insulator-metal-insulator (IMI) plasmonic waveguides is designed. The area of the proposed structure is very small (400nm× 400 nm) which operates at a wavelength of 1,550 nm. The developed device utilizes constructive and destructive interferences between the input signals and the selector signal. This structure is less complex and has lower loss compared to the previous works. Transmission (T), contrast ratio (CR), modulation depth (MD), insertion loss (IL), and contrast loss (CL) are the five parameters that describe the performance of the plasmonic Mux. The transmission threshold between logic 0 and logic 1 is 0.5. Moreover, the maximum transmission efficiency of the device is 163%. Moreover, based on the MD value of 95.09%, the dimensions of the proposed structure are excellent and optimal. The proposed plasmonic Mux structure contributes substantially to developing an all-optical arithmetic logic unit (ALU) and alloptical signal processing nanocircuits. The finite element method (FEM) simulates the proposed plasmonic multiplexer with COMSOL Multiphysics 5.4 software....
Noise control has become one of the key issues to be considered in modern aeronautical machinery design. Many efforts have been devoted to noise reduction of airfoils and wings, including traditional flow control methods. In fact, some animals in wild nature exhibit superior aerodynamic and aeroacoustic performance, providing novel ideas for solving this engineering problem. In this research, bionic technology is used to obtain quiet and efficient wing. Inspired by the owl’s wing, we propose two bionic configurations, one coupled with leading edge waves and trailing edge serrations. The Large Eddy Simulation and the Ffowcs- Williams and Hawkings equation is applied to simulate the aerodynamic and aeroacoustic characteristics of wings at low-Reynolds number flow. Numerical results demonstrate that the bioinspired wings have excellent aerodynamic performances and remarkable lower overall sound pressure level compared to NACA 0016 which has similar relative thickness. In addition, the unsmooth structure of leading edge waves and trailing edge serrations provide an additional 4.27 dB noise suppression effect, with little impact on aerodynamic characteristics at small angle of attack. The detailed analysis reveals that, due to the special owl-based profile, the flow around two bioinspired wings is mainly turbulent on the upper and lower surfaces, and no laminar separation bubble is detected at the trailing edge. Moreover, the unsmooth structure modifications successfully weaken the scale and scope of coherent vortex structures. These factors contribute to reducing the associated pressure fluctuation, thereby controlling the aeroacoustic noise of wing. Consequently, a coupled bionic wing is presented with the excellent aerodynamic and aeroacoustic characteristics. The conclusions are envisioned to be beneficial to the design of new generation low-noise aeronautical machinery....
Silica nanostructured materials find application in different fields, since they are cheap, versatile, and easy to functionalize as materials. However, silica reactivity has not been deeply investigated yet, mainly due to a poor understanding of how it is affected by superficial defects. In the present study, the electronic and optical properties of nanoparticles have been investigated using bare silica nanoparticles (SNP) and amino- or phosphonate-functionalized silica nanoparticles (SNP–APTES and SNP-phosphonate), prepared by a sol-gel procedure, and their morphology has been investigated using transmission electron microscopy (TEM) analysis. The prepared silica nanomaterials were characterized by means of reflectance and emission spectroscopies to determine the types of defects that can be found on silica nanoparticles’ surface. In order to understand the effect of surface defects on the reactivity of silica, the nanoparticles were employed for the photocatalytic degradation of Rhodamine 6G (R6G), upon selective irradiation at 320 nm, where only silica colloids absorb. The photoreaction was carried out in ethanol and in water and was monitored following the fluorescence signal of the dye. The evaluation of the fluorescent intensities allowed for the determination of the degradation efficiencies....
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