Verification of the Radio Wave Absorption Effect in the Millimeter Wave Band of SWCNTs and Conventional Carbon-Based Materials

Using a sample coated with three types of carbon-based paints, namely single-wall carbon nanotube (SWCNTs), carbon black, and graphite, the amount of radio wave absorption for each was measured. SWCNTs proved to have the superior radio wave absorption effect in the millimeter band. Considering the change in the amount of radio wave absorption depending on the coating amount, three different coating thicknesses were prepared for each test material. The measurement frequency was set to two frequency bands of 28 GHz and 75 GHz, and the measurement method was carried out based on Japanese Industrial Standard (JIS) R1679 “Radio wave absorption characteristic measurement method in the millimeter wave band of the radio wave absorber.” As for the amount of radio wave absorption in the 28 GHz band, a maximum amount of radio wave absorption of about 6 dB was obtained when 35 m of CNT spray paint was applied. It was confirmed that the carbon black paint came to about 60% that of the SWCNT, and the graphite paint did not obtain much radio wave absorption even when the coating thickness was changed. Furthermore, even in the 75 GHz band, the radio wave absorption was about 7 dB when 16 μm of CNT spray paint was applied, showing the maximum value. Within these experimental results, the CNT spray paint has a higher amount of radio wave absorption in the millimeter wave band than paints using general carbon materials. Its effectiveness could be confirmed even with a very thin coating thickness of 35 μm or less. It was also confirmed that even with the same paint, the radio wave absorption effect changes depending on the difference in coating thickness and the condition of the coated surface.

Optimized Neural Network Prediction Model of Shape Memory Alloy and Its Application for Structural Vibration Control

The traditional mathematical model of shape memory alloy (SMA) is complicated and difficult to program in numerical analysis. The artificial neural network is a nonlinear modeling method which does not depend on the mathematical model and avoids the inevitable error in the traditional modeling method. In this paper, an optimized neural network prediction model of shape memory alloy and its application for structural vibration control are discussed. The superelastic properties of austenitic SMA wires were tested by experiments. The material property test data were taken as the training samples of the BP neural network, and a prediction model optimized by the genetic algorithm was established. By using the improved genetic algorithm, the position and quantity of the SMA wires were optimized in a three-storey spatial structure, and the dynamic response analysis of the optimal arrangement was carried out. The results show that, compared with the unoptimized neural network prediction model of SMA, the optimized prediction model is in better agreement with the test curve and has higher stability, it can well reflect the effect of loading rate on the superelastic properties of SMA, and is a high precision rate-dependent dynamic prediction model. Moreover, the BP network constitutive model is simple to use and convenient for dynamic simulation analysis of an SMA passive control structure. The controlled structure with optimized SMA wires can inhibit the structural seismic responses more effectively. However, it is not the case that the more SMA wires, the better the shock absorption effect. When SMA wires exceed a certain number, the vibration reduction effect gradually decreases. Therefore, the seismic effect can be reduced economically and effectively only when the number and location of SMA wires are properly configured. When four SMA wires are arranged, the acceptable shock absorption effect is obtained, and the sum of the structural storey drift can be reduced by 44.51%.

Effect of Reaction Temperature on Adsorption Efficiency using Computer Mathematical Statistics Visible Spectorphotometer

In this paper, waste shrimp shells extracted from the head of the chitosan material; static adsorption experiments manner by wastewater containing Fe(III) added chitosan, vis spectrophotometer absorbance before and after the measurement experiment was obtained by reacting the size of the metal ion concentration, adsorption conditions whereby chitosan Fe(III) and the ability to explore. Experiments show that. In the case where the reaction temperature is less than 55°C, chitosan has adsorption rate Fe(III) smaller rise, the optimum temperature was 55°C, but the effects on the reaction temperature adsorption rate is not large; Adsorption when control time 30 min to 50 min, the absorption effect is increased with increase in the time, to reach the optimal reaction time 50 min.

Viscous Dissipation Effect in the Free Convection of Non-Newtonian Fluid with Heat Generation or Absorption Effect on the Vertical Wavy Surface

The present article analyzes the effect of viscous dissipations on natural convection heat transfer. The power law model for non-Newtonian fluid with heat generation or absorption effect along a sinusoidal wavy surface with isothermal boundary condition is investigated. A simple coordinate transform is employed to map the wavy surface into a flat surface, and also, the fully implicit finite difference method is incorporated for the numerical solution. The findings of this study can help better understand the effect of parameters such as the Brinkman number, heat generation/absorption, wave amplitude magnitude, and generalized Prandtl number on convective heat transfer in dilatant and pseudoplastic non-Newtonian. Results show that as the Brinkman number increases, the amount of heat transfer decreases. This is physically justifiable considering that the fluid becomes warmer due to the viscous dissipation, decreasing its temperature difference with the constant temperature surface. Also, the effect of the power law viscosity index is surveyed. It is demonstrated that the magnitude of the local Nusselt number in the plane leading edge has the smallest quantity for pseudoplastic fluids compared to dilatant Newtonian fluids. Additionally, as the distance from the plane leading edge increases, the heat transfer declines.

Unsteady MHD Rear Stagnation-Point Flow of a Hybrid Nanofluid with Heat Generation/Absorption Effect

The study of unsteady flow is essential in various engineering systems, for instance, the periodic fluid motion and start-up process. Therefore, this numerical study focuses on examining the unsteady magnetohydrodynamics (MHD) rear stagnation-point flow in Al2O3-Cu/H2O hybrid nanofluid past a permeable stretching/shrinking surface with the impact of heat generation/absorption. By choosing a suitable similarity transformation, partial differential equations are transformed into a system of nonlinear ordinary differential equations and solved using the bvp4c function in the MATLAB package. The effects of the solution domain’s operating parameters are analysed, and dual solutions are observable as the sheet shrinks. It is found that the addition of the suction parameter escalates the heat transfer efficiency. Eventually, the existence of the unsteadiness parameter and the heat generation/absorption effect significantly encourage heat transfer deterioration.