An efficient composite algorithm for rough surface reconstruction

For detection of a two-layered rough surface structure through ground-penetrating radar, the estimation of the profile of each layered rough surface is an important problem to be solved. In modeling and calculating the scattering of two-layered rough surfaces, we found that the profile of the upper rough surface can be observed directly through the figure of the echo from the upper surface. However, the echo of the lower rough surface has a quite different shape from its surface profile, because of the influence of the scattering of the upper rough surface. This is disadvantageous to the estimation and imaging of the profile of the lower rough surface. To solve this problem, a time-delay calibration method is proposed in this paper to be applied to the profile estimation of the lower rough surface in the case of two-layered rough interface detection. By introducing a smooth surface, the expression of time delay is derived to eliminate the influence of the scattering of the upper surface. Applying the derived expression of time delay to the echo data from the lower rough surface, the echo outline of the lower rough surface can be corrected to reflect the surface's profile shape. The calibrated B-scan echo shape shows good agreement with the profile of the lower rough surface. With this method, we can get the profile shape of the lower rough surface quickly and simply by calibrating the echo data directly. This method can be used for fast microwave imaging of two-layered rough surface and for eliminating the interference of scattering from rough surface on the echoes of nearby targets. The purpose of this paper is to solve the problem we have found in our previous work. The work of this paper is an extension of the previous work.

In this paper, we study the electromagnetic wave propagation in a parallel plate waveguide with rough surface walls, using a mode matching technique in combination with the method of moments (MoM). In the formulation, a line source in the smooth section of the waveguide excites a summation of modal fields. For each waveguide modal excitation, the modal response fields in the rough surface section of the waveguide are obtained by the solution of the governing surface integral equations through MoM. The total field distribution in the rough surface waveguide is a linear combination of the modal response fields. The coefficients are obtained by enforcing the continuity of tangential electric and magnetic fields at the junctions between smooth and rough surface waveguide sections. Results are illustrated for a variety of roughness spectra based on the parametric generalized power spectral density. The results are compared with the previously developed small perturbation method of second order (SPM2) results for the plane wave and waveguide models. With the numerical validation, the SPM2 waveguide model is proved to be able to capture the waveguide thickness effect especially for very rough surface profiles.

The electromagnetic wave transmission of the rough surface of Gaussian layered medium is studied with a hybrid algorithm which is based on MoM (method of moment) and combines with KA (Kirchhoff approximation). In the hybrid algorithm, the upper rough surface and the lower rough surface are placed in the MoM area and the KA area respectively, and the curve of transmission coefficient to change with the scattering angle of transmission wave is solved through numerical calculation. Finally, the relationships of transmission coefficient with the root-mean-square height, the dielectric constant and thickness of the middle-layer medium, and the frequency of incident wave of rough surface are discussed, and then a complete electromagnetic wave transmission characteristic is obtained.

The actual rough sea surface is described by Pierson-Moscowitz (PM) spectrum and Monte Carlo method; the composite electromagnetic scattering from the double rectangular crosssection conductor columns above the rough sea surface is investigated using the hybrid methodthe Method of Moment with the Kirchhoff approximation. Angular distribution curves of composite scattering coefficient are obtained; and this coefficient that varies with the parameter of sea surface, rectangular cross-section conductor columns and incident waves is calculated in detail. The characteristics of the composite scattering coefficient from the double rectangular cross-section conductor columns above the rough sea surface are also obtained. Results show that the hybrid methodthe Method of Moment with the Kirchhoff approximation, compared to the traditional Method of Moment, can obtain higher accuracy. Moreover, the hybrid method can effectively reduce the computation time and memory footprint, and the performance becomes more favorable with the increase of the sizes of rough surface.

This research focuses on the application of the spatial system of finite element modeling for the vehicle-bridge interaction on reinforced concrete US Girder Bridge in order to obtain the effect of surface roughness. Single vehicle and multiple vehicles on reinforced concrete T beam bridge were studied with variable surface roughness profiles. The effects of six different surface roughness profiles (very good, good, measured, average, poor, and very poor) were investigated for vehicle-bridge interaction. The values of the Dynamic Amplification Factor (DAF) were obtained for single and multiple vehicles on T Beam Bridge for different surface roughness profiles, along with the distances between the axles of heavy vehicle. It was observed that when the bridge has very good, good, measured, and average surface roughness, the DAF values for the single vehicle over the bridge were observed to be within acceptable limits specified by AASHTO. However, for the bridge with multiple vehicles only very good and measured surface roughness profiles showed a DAF and vehicle axle distances within the acceptable limits. From the current studies, it was observed that the spatial system showed reliable responses for predicting the behavior of the bridge under variable road surface roughness conditions and was reliable in vehicle axle detection, and therefore, it has a potential to be use for realistic simulations.

Modern trends in higher education are aimed at the fact that the educational process should become more dynamic and flexible, including the training of engineering specialists in higher educational institutions. During the pandemic caused by COVID-19, most institutions switched to distance learning, in connection with this, the use of virtual instruments created using the LabVIEW graphical programming environment is of particular relevance for practical and laboratory work. Such instruments allow you to conduct classes remotely. The article describes the designed virtual instrument for simulation modeling of the process of determining the surface roughness parameters. To implement this task, a model for calculating the surface roughness parameters is proposed, which takes into account the influence of the geometric parameters of the metal cutting tool and the physic of cutting process during workpiece processing. The modeling process of roughness measurement is carried out in two stages. At the first stage, the movement of the sensor of device the along the scanned surface and the sound of the device drive are simulated. At the second stage, the surface roughness parameters are calculated. The surface roughness profile is a superposition of the theoretical profile which is obtained by copying the profile of the cutting tool tip on the machined surface and random distortion of the profile due to the physic of cutting process. For the purpose of obtaining the coordinates of the theoretical profile points of the workpiece after processing it, an algorithm has been developed for calculating the current position of the profile point depending on the ratio of the feed values and the curvature radius tip of the cutting tool. Changing the position of the current point of the theoretical surface profile due to the impact of the physic of cutting process is taken into account by introducing random oscillations superimposed on the surface profile, which are generated by a random number generator according to the law of equal probability. A technique for processing an array of profile points coordinates to obtain surface roughness numerical parameters Rz, Ra and Rmax is described. The use of computer measuring technologies for solving tasks in the field of engineering using information and measuring equipment allows students to develop the skills to perform technical measurements, receive, analyze and critically evaluate the obtained measurement results

In high voltage equipment, gases are often used as insulation material. Several parameters can influence the dielectric withstand voltage of gaseous insulation systems, such as the degree of inhomogeneity, gas pressure and type as well as surface roughness. This study focuses on the influence of surface roughness on the withstand voltage of atmospheric pressure air gaps under lightning impulse stresses. For this purpose, surface profiles of different rough metallic surfaces have been characterized using an optical surface scanner with a resolution of 3nm. Based on the extracted features of the surface roughness, axial symmetric random surface profiles have been generated in a multi-physics simulation tool, electric field simulations performed, and streamer criterion applied to estimate the breakdown voltage. To verify the simulation results, lightning impulse breakdown voltage measurements have been carried out in simple configurations (sphere plate and rod plate) for four different degrees of surface roughness of the plate electrode. The experimental results confirm the observed trend in simulations, where the breakdown voltage is only to a limited extend reduced even for considerably rough surface profiles.

In this paper we investigate a method to measure plastic strain of metals with no contact using the laser speckle method. This method is based on observation of the change in laser speckle pattern depending on surface profile change occurring due to plastic deformation. The analysis of the laser speckle pattern is performed using an image-processing system. The relationships between speckle pattern and surface roughness or frequency characteristics of the surface profile were investigated in this study. Surface roughness and surface profile were observed for steel specimens polished with emery papers or plastically deformed. The surface profile diagram was analyzed by means of the Fast Fourier Transform with a computer and the distribution of frequency was obtained. The results show that distribution of light intensity of the speckle is related to frequency distribution of the surface profile, but the distribution of the laser speckle is not always related to surface roughness. It was also clarified that the laser speckle pattern is closely related to the magnitude of plastic strain.

As the turning process is one of the most necessary process. The surface roughness has been considered for the quality of workpiece. There are many factors which affect the surface roughness. Hence, the objective of this research is to monitor the relation between the surface roughness and the cutting forces in aluminium turning process with a wide range of cutting conditions. The coated carbide tool and aluminium alloy (Al 6063) are used for this experiment. The cutting parameters are investigated to analyze the effects of them on the surface roughness which are the cutting speed, the feed rate, the tool nose radius and the depth of cut. In the case of this research, the dynamometer is installed in the turret of CNC turning machine to generate a signal while turning. The relation between dynamic cutting forces and the surface roughness profile is examined by applying the Fast Fourier Transform (FFT). The experimentally obtained results showed that the cutting force depends on the cutting condition. The surface roughness can be improved when increasing the cutting speed and the tool nose radius in contrast to the feed rate and the depth of cut. The relation between the cutting parameters and the surface roughness can be explained by the in-process cutting forces. It is understood that the in-process cutting forces are able to predict the surface roughness in the further research.

Based on the Propagation-Inside-Layer Expansion (PILE) and Forward-Backward method (FBM), the composite scattering from the target below a dielectric rough soil surface using the extended PILE (EPILE) combined with the Forward-Backward method (FBM) is studied. The accuracy and e-ciency of the EPILE + FBM for this speciflc type of composite scattering is researched by comparing with the method of moments (MOM), the in∞uences of the target size, target depth, target horizontal distance, the rms height, the correlation length, the incident angle and the soil moisture content, etc., to the bistatic scattering coe-cient (BSC) are also investigated.

Compared with scattering from a rough surface only, composite scattering from a target above a rough surface has become so practical that it is a subject of great interest. At present, this problem has been solved by some numerical methods which will produce an enormous calculation amount. In order to overcome this shortcoming, the reciprocity theorem (RT) and the method of equivalent edge currents (MEC) are used in this paper. Due to the advantage of RT, the difficulty in computing the secondary scattered fields is reduced. Simultaneously, MEC, a high-frequency method with edge diffraction considered, is used to calculate the scattered field from the cone-cylinder target with a high accuracy and efficiency. The backscattered field and the polarization currents of the rough sea surface are evaluated by the Kirchhoff approximation (KA) method and physical optics (PO) method, respectively. The effects of the backscattering radar cross section (RCS) and the Doppler spectrum on the size of the target and the windspeed of the sea surface for different incident angles are analysed in detail.

One of the most popular methods for calculating the scattering of light from rough surfaces is the Kirchhoff approximation. A recent modification of the Kirchhoff approximation allows calculation of the scattering of electromagnetic radiation from rough surfaces with very high, or even infinite, slopes, which occurs frequently in, for example, imaging or testing of printed circuits or remote sensing applications. The modification involves a simple change in the way the surface normal is described which removes the explicit dependence of the resulting integral equations on the surface slope, and changing the sampling of the surface, removing the requirement of small slopes for application of the method. In this paper we present the application of the method to vector electromagnetic scattering, using the Stratton-Chu equation, from 2D rough metallic surfaces with infinite slope. The single and double scatter contributions to the total scattered intensity are calculated numerically with this new formulation. Geometrical shadowing is included by using ray tracing directly on the surface. The theoretical basis and preliminary numerical results of the application of this method to vector electromagnetic scattering from simple rough metallic surfaces (plane surfaces with single grooves or with a small number of identical grooves) with infinitely sloped structure are presented.

To analyze EM scattering of a dielectric Target above the dielectric Gauss rough surface, a fast Cross Coupling iterative Approach is present in this paper. This algorithm combines the merit of both the bi-conjugate gradient method (Bi-CG) and forward backward method (FBM). At first, the electric field integral equations (EFIE) of the induced currents on the rough surface and the target are derived. An iterative approach was developed to solve the two EFIEs and scattering from both the target and underlying surface. The EFIE of the rough surface and the target are solved by using FBM and bi-conjugate gradient method (Bi-CG), respectively. The mutual effect between the rough surface and the target are implemented by iterative Calculation. The results of EM scattering form a dielectric cylinder above the dielectric Gauss rough surface showed that CCIA was well agreement with MOM. The accuracy, efficiency, and convergence of the method are then studied for rough surfaces with various parameters. The effect of these parameters for the scattering pattern was also discussed.

A robust and accurate iterative algorithm is proposed for the solution of electromagnetic wave scattering from 1-D layered rough surfaces. The forward–backward method (FBM) has been applied extensively for solving electromagnetic scattering from single-layer rough surfaces due to its rapid convergence rate. Nevertheless, the performance of the FBM deteriorates, as it is applied to layered random rough surface problems. The proposed method greatly improves the convergence rate of the FBM by applying a residual minimization step. The computational cost of the minimization step and the forward–backward sweeps is expedited by using the spectral acceleration. In this communication, the proposed algorithm is applied as a solution to the problem of electromagnetic wave scattering from layered rough surfaces. Numerical results are presented to demonstrate the better convergence properties of the proposed method as compared with the standard FBM. In addition, the proposed method is shown to be more robust than the FBM, especially as the distance between interfaces decreases. The computational complexity of the proposed algorithm is also presented and discussed.

Surface roughness measurement using an optical system