scholarly journals Application of GO Management in Bistatic RCS Computation Using the Vector Parabolic Equation Method

2013 ◽  
Vol 2013 ◽  
pp. 1-4
Author(s):  
X. J. Zhong ◽  
T. J. Cui ◽  
J. F. Zhang ◽  
W. M. Yu
Keyword(s):  
Parabolic Equation ◽  
Cross Sections ◽  
Large Scale ◽  
Three Dimensional ◽  
Original Method ◽  
Good Choice ◽  
Bistatic Radar ◽  
Large Scale Problems ◽  
Radar Cross Sections ◽  
Resultant Matrix

The parabolic equation (PE) method is a good choice in solving large-scale problems, but the resultant matrix is usually ill conditioned. In this letter, we introduce the geometric optics (GO) management in the calculation of bistatic radar cross sections using three-dimensional vector PE method. This method manages the object surface by GO, and hence the ill-conditioned problem can be avoided. Examples are given using the presented method, original method, and the method of moments. Results show the validity and stability of the presented method.

scholarly journals Analysis of RCS of Low Observable Aircraft in VHF Band

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yi-Ru Jeong ◽  
Chan-Sun Park ◽  
Young-Kwan Ko ◽  
Jong-Gwan Yook
Keyword(s):  
Method Of Moments ◽  
Cross Sections ◽  
Incident Wave ◽  
Specular Reflection ◽  
Three Dimensional ◽  
Bistatic Radar ◽  
Three Dimensional Model ◽  
Maximum Value ◽  
Radar Cross Sections ◽  
Fast Multipole Algorithm

Electromagnetic signatures of a low observable aircraft have been studied in VHF band. First of all, a three-dimensional model of the aircraft has been established for numerical computation. Then, monostatic and bistatic radar cross sections (RCS) have been calculated. The model of the aircraft is made by a curved surface, and commercial as well as in-house three-dimensional electromagnetic code which is based on the method of moments (MoM) is utilized to calculate the RCS. A characteristic basis function method (CBFM) and a multilevel fast multipole algorithm (MLFMA) have been applied to analyze electrically large objects. The change of the monostatic RCS is very large depending on the direction of the incident wave. The maximum value is about 42 dBsm at the top and bottom of the aircraft, and the minimum value is about −10 dBsm at the front and back of the aircraft. It is found that the bistatic RCS also changes dramatically depending on the direction of the incident wave. The direction of maximum RCS occurs around specular reflection, and the value of maximum RCS ranges from 27 dBsm to 43 dBsm. On the other hand, the direction of the minimum RCS occurs irregularly, and the value is in the level of −30 dBsm.

scholarly journals Stereological Estimation of Orientation Distribution of Generalized Cylinders from a Unique 2D Slice

2013 ◽  
Vol 19 (6) ◽  
pp. 1678-1687 ◽  
Author(s):  
Jean-Pierre Da Costa ◽  
Stefan Oprean ◽  
Pierre Baylou ◽  
Christian Germain
Keyword(s):  
Cross Sections ◽  
Composite Structures ◽  
Large Scale ◽  
Fibrous Composite ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Inequality Constraints ◽  
Orientation Distribution ◽  
Industrial Applications ◽  
Cost Constraints

AbstractThough three-dimensional (3D) imaging gives deep insight into the inner structure of complex materials, the stereological analysis of 2D snapshots of material sections is still necessary for large-scale industrial applications for reasons related to time and cost constraints. In this paper, we propose an original framework to estimate the orientation distribution of generalized cylindrical structures from a single 2D section. Contrary to existing approaches, knowledge of the cylinder cross-section shape is not necessary. The only requirement is to know the area distribution of the cross-sections. The approach relies on minimization of a least squares criterion under linear equality and inequality constraints that can be solved with standard optimization solvers. It is evaluated on synthetic data, including simulated images, and is applied to experimental microscopy images of fibrous composite structures. The results show the relevance and capabilities of the approach though some limitations have been identified regarding sensitivity to deviations from the assumed model.

scholarly journals Performance Assessment of Reference Modelling Methods for Defect Evaluation in Asphalt Concrete

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8190
Author(s):  
Pauli Putkiranta ◽  
Matti Kurkela ◽  
Matias Ingman ◽  
Aino Keitaanniemi ◽  
Aimad El Issaoui ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Laser Scanning ◽  
Large Scale ◽  
Three Dimensional ◽  
Qualitative Assessment ◽  
Three Dimensional Mapping ◽  
Road Surfaces ◽  
Three Dimensional Measurement ◽  
Mobile Methods

The deterioration of road conditions and increasing repair deficits pose challenges for the maintenance of reliable road infrastructure, and thus threaten, for example, safety and the fluent flow of traffic. Improved and more efficient procedures for maintenance are required, and these require improved knowledge of road conditions, i.e., improved data. Three-dimensional mapping presents possibilities for large-scale collection of data on road surfaces and automatic evaluation of maintenance needs. However, the development and, specifically, evaluation of large-scale mobile methods requires reliable references. To evaluate possibilities for close-range, static, high-resolution, three-dimensional measurement of road surfaces for reference use, three measurement methods and five instrumentations are investigated: terrestrial laser scanning (TLS, Leica RTC360), photogrammetry using high-resolution professional-grade cameras (Nikon D800 and D810E), photogrammetry using an industrial camera (FLIR Grasshopper GS3-U3-120S6C-C), and structured-light handheld scanners Artec Leo and Faro Freestyle. High-resolution photogrammetry is established as reference based on laboratory measurements and point density. The instrumentations are compared against one another using cross-sections, point–point distances, and ability to obtain key metrics of defects, and a qualitative assessment of the processing procedures for each is carried out. It is found that photogrammetric models provide the highest resolutions (10–50 million points per m2) and photogrammetric and TLS approaches perform robustly in precision with consistent sub-millimeter offsets relative to one another, while handheld scanners perform relatively inconsistently. A discussion on the practical implications of using each of the examined instrumentations is presented.

Subsurface temperature maps in French sedimentary basins: new data compilation and interpolation

2010 ◽  
Vol 181 (4) ◽  
pp. 377-390 ◽  
Author(s):  
Damien Bonté ◽  
Laurent Guillou-Frottier ◽  
Cynthia Garibaldi ◽  
Bernard Bourgine ◽  
Simon Lopez ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Surface Temperature ◽  
Cross Sections ◽  
Large Scale ◽  
Thermal Structure ◽  
Three Dimensional ◽  
Sedimentary Basins ◽  
Local Character ◽  
Data Compilation ◽  
Temperature Maps

Abstract Assessment of the underground geothermal potential requires the knowledge of deep temperatures (1–5 km). Here, we present new temperature maps obtained from oil boreholes in the French sedimentary basins. Because of their origin, the data need to be corrected, and their local character necessitates spatial interpolation. Previous maps were obtained in the 1970s using empirical corrections and manual interpolation. In this study, we update the number of measurements by using values collected during the last thirty years, correct the temperatures for transient perturbations and carry out statistical analyses before modelling the 3D distribution of temperatures. This dataset provides 977 temperatures corrected for transient perturbations in 593 boreholes located in the French sedimentary basins. An average temperature gradient of 30.6°C/km is obtained for a representative surface temperature of 10°C. When surface temperature is not accounted for, deep measurements are best fitted with a temperature gradient of 25.7°C/km. We perform a geostatistical analysis on a residual temperature dataset (using a drift of 25.7°C/km) to constrain the 3D interpolation kriging procedure with horizontal and vertical models of variograms. The interpolated residual temperatures are added to the country-scale averaged drift in order to get a three dimensional thermal structure of the French sedimentary basins. The 3D thermal block enables us to extract isothermal surfaces and 2D sections (iso-depth maps and iso-longitude cross-sections). A number of anomalies with a limited depth and spatial extension have been identified, from shallow in the Rhine graben and Aquitanian basin, to deep in the Provence basin. Some of these anomalies (Paris basin, Alsace, south of the Provence basin) may be partly related to thick insulating sediments, while for some others (southwestern Aquitanian basin, part of the Provence basin) large-scale fluid circulation may explain superimposed cold and warm anomalies.

scholarly journals The Investigation of EM Scattering from the Time-Varying Overturning Wave Crest Model by the IEM

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Xiao Meng ◽  
Li-xin Guo ◽  
Tian-qi Fan
Keyword(s):  
Cross Sections ◽  
3D Model ◽  
Three Dimensional ◽  
Integral Equation Method ◽  
Wave Crest ◽  
Time Varying ◽  
Spike Generation ◽  
Horizontal Polarization ◽  
Em Scattering ◽  
Radar Cross Sections

Investigation of the electromagnetic (EM) scattering of time-varying overturning wave crests is a worthwhile endeavor. Overturning wave crest is one of the reasons of sea spike generation, which increases the probability of false radar alarms and reduces the performance of multitarget detection in the environment. A three-dimensional (3D) time-varying overturning wave crest model is presented in this paper; this 3D model is an improvement of the traditional two-dimensional (2D) time-varying overturning wave crest model. The integral equation method (IEM) was employed to investigate backward scattering radar cross sections (RCS) at various incident angles of the 3D overturning wave crest model. The super phenomenon, where the intensity of horizontal polarization scattering is greater than that of vertical polarization scattering, is an important feature of sea spikes. Simulation results demonstrate that super phenomena may occur in some time samples as variations in the overturning wave crest.

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