| Millimeter Wave Holographical Inspection of Honeycomb Composites (Preprint) |
AUG 2007 |
9 pages |
| Authors:
J. T. Case; S. Kharkovsky; R. Zoughi; G. Steffes; F. L. Hepburn; MISSOURI UNIV-ROLLA
|
 | Multi-layered composite structures manufactured with honeycomb, foam, or balsa wood cores are finding increasing utility in a variety of aerospace, transportation, and infrastructure applications. Due to the low conductivity and inhomogeneity associated with these composites, standard nondestructive testing (NDT) methods are not always capable of inspecting their interior for various defects caused during the manufacturing process or as a result of in-service loading. On the contrary, microwave and millimeter wave ... |
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| Application of Millimeter Wave, Eddy Current and Thermographic Methods for Detection of Corrosion in Aluminum Substrate (Preprint) |
SEP 2006 |
10 pages |
| Authors:
A. C. Ryley; M. T. Ghasr; S. Kharkovsky; R. Zoughi; Gary Steffes; MISSOURI UNIV-ROLLA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Aluminum structures exposed to the elements are susceptible to corrosion. Corrosion may cause various mechanical and structural deficiencies such as material thinning. It is desirable to rapidly detect and evaluate the properties of an aluminum substrate early in the corrosion process to avoid costly maintenance actions later. There are several nondestructive, testing methods for this purpose. To investigate capabilities of millimeter wave, conventional eddy current, and flash thermography techniques for ... |
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| Comparison of X-Ray, Millimeter Wave, Shearography and Through-Transmission Ultrasonic Methods for Inspection of Honeycomb Composites (Preprint) |
AUG 2006 |
11 pages |
| Authors:
Mohamed A. Abou-Khousa; A. Ryley; S. Kharkovsky; R. Zoughi; D. Daniels; N. Kreitinger; G. Steffes; MISSOURI UNIV-ROLLA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Honeycomb composites are increasingly finding utility in a variety of environments and applications, such as structural components, radomes, etc. In-service and environmental stresses can produce unwanted flaws that adversely affect the structural integrity and functionality of these composites. These flaws may be in the forms of disbonds, delaminations, impact damage, crushed honeycomb, moisture intrusion, internal cracks, etc. There are several nondestructive testing (NDT) methods that may be used to inspect ... |
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| Disbond Thickness Evaluation Employing Multiple-Frequency Near-Field Microwave Measurements (Preprint) |
JUL 2006 |
19 pages |
| Authors:
M. Abou-Khousa; R. Zoughi; MISSOURI UNIV-ROLLA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Near-field microwave nondestructive evaluation (NDE) techniques have shown great potential for disbond detection in multi-layer dielectric composite structures. The high detection capability associated with these techniques stems from the fact that near-field microwave signals are sensitive to minute variations in the dielectric properties and geometry of the medium in which they propagate. In the past, the sensitivity of the near-field microwave NDE techniques to the presence and properties of disbonds ... |
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| Fusion of Microwave and Eddy Current Data for a Multi-Modal Approach in Evaluating Corrosion Under Paint and in Lap Joints (Preprint) |
JUL 2006 |
10 pages |
| Authors:
K. Gupta; M. T. Ghasr; S. Kharkovsky; R. Zoughi; R. J. Stanley; A. Padwal; M. O'Keefe; D. Palmer; James Blackshire; Gary Steffes; N. Wood; MISSOURI UNIV-ROLLA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Critical aircraft structures are susceptible to hidden corrosion. Find-it and fix-it approaches are inefficient as it relates to managing the problems associated with corrosion. More comprehensive corrosion information may be obtained using data fusion from several detection and evaluation methods. To this end, microwave, conventional and pulsed eddy current data from a multi-layer corroded panel, representing an aircraft lap joint, are fused and used as inputs to a structural analysis ... |
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| Disbond Thickness Evaluation Employing Multiple-Frequency Near-Field Microwave Measurements |
MAY 2006 |
19 pages |
| Authors:
M. Abou-Khasa; R. Zoughi; MISSOURI UNIV-ROLLA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Near-field microwave nondestructive evaluation (NDE) techniques have shown great potential for disbond detection in multi-layer dielectric composite structures. The high detection capability associated with these techniques stems from the fact that near-field microwave signals are sensitive to minute variations in the dielectric properties and geometry of the medium in which they propagate. In the past, the sensitivity of the near-field microwave NDE techniques to the presence and properties of disbonds ... |
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| Reduction of Sensitivity to Surface Roughness and Slight Standoff Distance Variations in Microwave Testing of Thick Composite Structures, |
2002 |
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| Authors:
N. Qaddoumi; T. Bigelow; R. Zoughi; L. Brown; M. Novack
|
 | Testing of thick sandwich composite structures is an important and challenging issue. Standard NDT methods are not always capable of testing these structures for the presence of thin disbonds and delaminations. However, near field microwave NDT methods have shown great potential for this purpose. Although these methods are very sensitive to the presence of thin disbonds and delaminations, they are also very sensitive to changes in the standoff distance. This ... |
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| A Brief Review of Microwave Testing of Stratified Composite Structures: A Comparison Between Plane Wave and Near Field Approaches, |
2002 |
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| Authors:
R. Zoughi; J. Lai; K. Munoz
|
| Stratified composite structures are increasingly being used in many critical applications. The composites are commonly manufactured from an array of dielectric or insulating materials. Depending on their thickness, layer structure or inhomogeneity, standard NDT techniques may not always be able to effectively test these stratified structures for disbond, delamination or coating thickness variation. On the other hand, microwave signals can penetrate inside of dielectric materials and interact with their inner ... |
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| Microwave Corrosion Detection Using Open Ended Rectangular Waveguide Sensors, |
2000 |
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| Authors:
N. Qaddoumi; L. Handjojo; T. Bigelow; J. Easter; A. Bray; R. Zoughi
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| In this paper the dielectric properties of several different rust samples from different environments are measured. |
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| Microwave Detection of Covered Surface Cracks in Metals, |
2000 |
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| Authors:
N. Wang; K. Donnell; M. Castle; R. Zoughi; M. Novack
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| This paper presents the results of detecting tight cracks under thin coatings, such as primer and paint, using open-ended coaxial probes and open-ended rectangular waveguide probes. For the latter case the properties of higher-order modes are utilized. Influences of crack size, probe size, operating frequency and coating thickness are investigated. Some of the issues related to the coaxial probe are also investigated theoretically. |
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| Microwave Inspection of Bridge Fatigue Cracks in Railroad Overpass, |
2000 |
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| Authors:
H. Campbell; E. Winkler; N. Qaddoumi; R. Zoughi; D. Raymond; D. Williams; J. Meheen
|
| This paper presents the results of an investigation using microwave nondestructive testing techniques for detection of fatigue cracks in a railroad overpass bridge. Specifically, crack detection in this bridge structure using open-ended rectangular waveguide probes is examined. A dominant mode and a higher-order mode probe were used in this investigation, the objective of which was to investigate the capabilities of these microwave probes on-site. Crack detection was performed at one ... |
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| Detection of Corrosion in Aluminum Panels Under Paint and Primer, |
2000 |
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| Authors:
D. Hughes; N. Wang; T. Case; K. Donnell; R. Zoughi; R. Austin; M. Novack
|
| Microwave nondestructive techniques have been used in the past to detect the presence of corrosion in steel plates under layers of paint and primer. This paper describes a similar investigation for the detection of corrosion in aluminum plates. Dielectric properties of paint, primer and aluminum oxide were determined. Theoretical calculations produced promising results. Experimental measurements on specially prepared panels showed that, using a multi-layer code simulating the reflection coefficient at ... |
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| Microwave Evaluation of Accelerated Chloride Ingress in Mortar, |
2000 |
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| Authors:
C. Hu; T. Case; M. Castle; R. Zoughi; K. Kurtis
|
| Corrosion of steel in reinforced concrete structures can be induced by the presence of chloride ions near the steel/concrete interface. To show the potential of microwave nondestructive testing techniques for evaluating chloride ingress, 8"x8"x8" mortar specimens with different mixture designs were prepared. To accelerate chloride ingress, they were exposed to cyclical wet/dry conditions, where the wet condition included exposure to salt bath. A complete discussion of the results will be ... |
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| Interaction of Surface Cracks in Metal with Open Ended Coaxial Probes at Microwave Frequencies, |
2000 |
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| Authors:
Y. Wang; R. Zoughi
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| Detection and evaluation of stress induced surface cracks in metals is an important issue in many critical environments. There exist several conventional NDT techniques for detecting such cracks, although each has its limitations and advantages. Recent developments in using microwave based techniques have also shown great promise. One of these microwave NDT techniques makes effective use of open ended coaxial probes for detecting and evaluating tight surface cracks. The potential ... |
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| Microwave Detection of Stress-Induced Fatigue Cracks in Steel and Potential of Crack Opening Determination Using A New Phase Sensitive Approach Based on a Waveguide Magic Tee, |
1999 |
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| Authors:
N. Qaddoumi; E. Ranu; R. Zoughi; J. D. McColskey
|
| Detection and evaluation of surface cracks in metals is an important facet of nondestructive testing and evaluation (NDT&E). Cracks in bridges, aircraft wings and other metal structures can pose serious danger to the structure and ultimately human lives. Detection, being the first step in NDT&T, has been accomplished on a variety of cracks using several recently developed microwave techniques, namely dominant mode, higher-order mode and open-ended coaxial lines 1-4. Evaluation ... |
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| Microwave Detection of Machined Notches in Stainless Steel with Rough Surface, |
1999 |
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| Authors:
Y. Wang; N. Qaddoumi; M. Frank; R. Mirshahi; V. Otashevich; R. Zoughi
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| In this paper the results of measurements conducted at three microwave and millimeter wave frequency bands (K-, Ka and V-bands) will be presented along with a discussion of these results. |
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| Application of Near-Field Microwave Sensing Techniques for Segregation Detection in Concrete Members, |
1999 |
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| Authors:
K.J. Bois; A.D. Benally; R. Zoughi; P.S. Nowak
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| In this presentation, a simple, low-cost near-field microwave nondestructive inspection technique for segregation detection in concrete members is presented. This process employs information from the measured magnitude of reflection coefficient at the aperture of an open-ended rectangular waveguide sensor. These measurements, whose results will be presented, were conducted using a Hewlett-Packard HP8510B network analyzer. However, in practice a simple and relatively inexpensive inspection apparatus constructed from discrete microwave components can ... |
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| Microwave NDE of Impact Damaged Fiberglass and Elastomer Layered Composites, |
1999 |
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| Authors:
E.C. Greenwald; L.J. Levenberry; N. Qaddoumi; A. McHardy; R. Zoughi; C.F. Poranski
|
| Layered composites have been proposed as advanced materials for future use in large naval sonar domes. Unlike today's steel/rubber composite domes, such materials promise engineered acoustic properties and less costly resin-transfer fabrication methods. The development and deployment of these large and complex composite structures will result in challenging NDE requirements for both manufacturing quality assurance and in-service needs. Among the anticipated in-service requirements is the detection and characterization of the ... |
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| Microwave Detection of Surface Cracks in Metals Under Dielectric Coatings Using Open-Ended Coaxial Sensors: Preliminary Results, |
1998 |
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| Authors:
R. Zoughi; C. Huber; J. Easter; K. Hayes
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| This paper presents some preliminary experimental results of using this sensor for surface crack detection in metals under thin dielectric coatings. |
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| A Microwave Method For Detection Of Finite Surface Cracks In Metals, |
1997 |
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| Authors:
C. Yeh; R. Zoughi
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| The application of microwaves for detecting surface cracks receives great attention recently. An electromagnetic model for finite surface crack detection was developed and its results are compared with some experimental results to verify its integrity. An open-ended waveguide sensor is used to scan a metal surface with a crack in it. The crack is modeled as a small waveguide being fed by a larger one. The presence of the crack ... |
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| Preliminary Results of Microwave Non-Contact Detection and Depth Determination of Disbonds in Low Permitivity and Low Loss Thick Sandwich Composites, |
1996 |
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| Authors:
N. Qaddoumi; S. Ganchev; R. Zoughi; G.W. Carriveau
|
| To ensure manufacturing quality and safe use of thick dielectric composite structures it is essential to utilize a nondestructive testing technique for inspecting the structural integrity. As the thickness of these composite structures increase, most of the nondestructive testing (NDT) techniques become less capable of detecting defects. Microwave signals can penetrate deep inside dielectric materials and interact with their inner structure. They are also sensitive to changes associated with boundary ... |
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| Electromagnetic Modeling of the Interaction of Cracks in Metallic Surfaces with Open-Ended Waveguides Using an Equivalent Magnetic Current, |
1996 |
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| Authors:
C. Huber; H. Abiri; S. Ganchev; R. Zoughi
|
| In previous research a mode matching approach was used to describe the electromagnetic properties of a system formed by an open-ended waveguide and a crack. A more versatile formulation for evaluating the electromagnetic properties in such a system is possible by using a moment solution approach, which eliminates the necessary distinction between empty, filled and finite length cracks, independent of the relative position of the crack within the probing waveguide ... |
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| Near-Field Analysis of Rectangular Waveguide Probes Used for Imaging, |
1996 |
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| Authors:
N. Qaddoumi; H. Abiri; S. Ganchev; R. Zoughi
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| Near-field microwave imaging of composite structures has received considerable attention recently. The success achieved on the experimental level motivated the development of a theoretical model to describe the high quality images obtained using near-field microwave imaging. This theoretical model will also help in building an intuitive understanding of the behavior of the fields inside dielectric materials in the near-field of an open-ended rectangular waveguide probe. A near-field microwave image is ... |
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| Microwave Diagnosis of Low-Density Fiberglass Composites with Resin Binder, |
1996 |
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| Authors:
N. Qaddoumi; S. Ganchev; R. Zoughi
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| Dielectric properties of low-density fiberglass composites are studied at microwave frequencies and are related to the resin binder content and state of cure. A completely filled short-circuited waveguide method is used to study the dielectric properties of fresh and slightly cured resin binder (used in the production of low-density fiberglass composite materials) in the frequency range of 4-18 GHz. The preliminary results indicate that the dielectric properties of resin binder ... |
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| Microwave Detection and Depth Determination of Disbonds in Low-Permittivity and Low-Loss Thick Sandwich Composites, |
1996 |
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| Authors:
N. Qaddoumi; R. Zoughi; G.W. Carriveau
|
| Nondestructive evaluation (NDE) of disbonded low-permittivity and low-loss dielelectric multilayered composite media is of considerable interest in many applications. The ability of microwaves to penetrate inside dielectric materials makes microwave NDE techniques very suitable for interrogating structures made of multilayered dielectric composites. Additionally, the sensitivity of microwaves to the presence of dissimilar layers in such materials allows for accurate detection of a disbonded layer. In a multilayered composite, a disbond ... |
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| Microwave Nondestructive Evaluation. |
FEB 1995 |
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| Authors:
R. Zoughi; S. Ganchev; NONDESTRUCTIVE TESTING INFORMATION ANALYSIS CENTER AUSTIN TX
|
| This State-of-the-Art Review contains information on both the fundamental science and general applications of microwave nondestructive evaluation. Chapter contents include: introductory background on microwave and millimeter wave spectra, definition and scope of microwave NDE, dielectric properties of materials, material characterization using microwaves, thickness and disbond measurements, microwave techniques for surface cracks, defect detection in thick composites, and concluding remarks and the future of microwave NDE. The publication contains 553 references ... |
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| A General Formulation for Admittance of an Open-Ended Rectangular Waveguide Radiating into Stratified Dielectrics, |
1995 |
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| Authors:
S. Bakhtiari; S. Ganchev; R. Zoughi
|
| A general approach is presented for calculating the aperture admittance of a rectangular waveguide radiating into layered dielectric media. The two specific geometries of stratified, lossy dielectric media that are addressed terminate into either an infinite half-space or a perfectly conducting surface. The geometries describe two prevalent categories of layered dielectric composites and coatings that often are encountered in practical microwave nondestructive evaluation applications. Solutions are found initially by constructing ... |
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| Microwave Compressive Strength Estimation of Cement Paste Using Monopole Probes, |
1995 |
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| Authors:
W. Shalaby; R. Zoughi
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| In-situ evaluation of the compressive strength of existing concrete structures using a direct approach is the objective of this investigation. The principle factor affecting the compressive strength of a concrete structure is its water/cement (w/c) ratio. The reflection properties of four cement paste samples with w/c of 0.35, 0.40, 0.50, and 0.55 were measured using several monopole probes at microwave frequencies of 5, 9, and 12 GHz. The effect of ... |
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| Application of Open-Ended Rectangular Waveguides for Detecting Surface Cracks, |
1995 |
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| Authors:
R. Zoughi; R. Salem; C. Huber; S. Ganchev; H. Abiri
|
| Surface crack detection in metallic structures is an important issue in many environments (such as steel bridge members) and industries. A relatively new microwave method of detection using an open-ended rectangular waveguide has shown great practical promise. This method is quite versatile and may be applied to long, finite, filled and covered cracks. Furthermore, crack dimensional analysis is also possible with this method. The measured and theoretical results of several ... |
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| Higher Order Modes as Indicators of Surface Cracks Under Stratified Dielectric Coatings Using an Open-Ended Waveguide, |
1995 |
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| Authors:
C. Huber; R. Zoughi
|
| Detection of fatigue/surface cracks on metal surfaces under stratified dielectric coatings is an important practical issue. Some conventional NDE techniques, such as dye penetrant, are not applicable in testing coated surfaces. Microwave signals penetrate inside a dielectric media and can interrogate interior flaws. A rectangular waveguide is used to detect such cracks. Higher order modes at the aperture of the waveguide can be used as a detection tool. Outside the ... |
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| Microwave Detection of Finite Surface Cracks in Metals Using Rectangular Waveguides, |
1994 |
|
| Authors:
C. Yeh; R. Zoughi
|
| An electromagnetic model for finite surface crack detection is developed and its results are compared with those of the existing long crack model and some experimental results to verify its integrity. An open-ended waveguide sensor is used to scan a metal surface with a crack in it. The crack is then modelled as a small waveguide being fed by a larger one. The presence of the crack causes higher order ... |
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| Microwave Nondestructive Thickness Monitoring of Dielectric Slabs Backed by Conducting Plates, |
1994 |
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| Authors:
R. Zoughi; S. Bakhtiari
|
| The techniques outlined here are brief presentation of some of the work that the authors have been engaged in during the past few years. The detailed explanation of these approaches are given elsewhere. The focus of the discussion given here is on three techniques for measuring the thickness of a single dielectric layer backed by a conducting plate. The first two techniques involve the measurement of the magnitude and phase ... |
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| Microwave Scattering Characteristics of Defective Dielectric Cylinders, |
1994 |
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| Authors:
N. Qaddoumi; R. Zoughi
|
| Microwave scattering properties (radar cross-section, RCS) of inhomogeneous dielectric (composite) cylinders with finite lengths and radii are used to determine the presence of defects of various shapes, sizes and dielectric properties. These cylinders are assumed to be irradiated by a uniform plane wave with arbitrary linear polarization and incidence angle. The induced and scattered fields are numerically obtained using the method of moments. This technique is used to optimize defect ... |
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| Terrain Classification in SAR Images Using Principal Components Analysis and Neural Networks. |
MAR 1993 |
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| Authors:
M. R. Azimisadjadi; S. Ghaloum; R. Zoughi; COLORADO STATE UNIV FORT COLLINS DEPT OF ELECTRICAL ENGINEERING
|
| The development of a neural network-based classifier for classifying three distinct scenes (urban, park and water) from several polarized SAR images of San Francisco Bay area is discussed. The principal component (PC) scheme or Karhunen-Loeve (KL) transform is used to extract the salient features of the input data, and to reduce the dimensionality of the feature space prior to the application to the neural networks. Employing PC scheme along with ... |
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| Nondestructive Microwave Thickness Measurements of Dielectric Slabs, |
SEP 1990 |
|
| Authors:
R. Zoughi; M. Lujan
|
| Nondestructive evaluation of material using microwaves is receiving more attention because microwaves are capable of penetrating into lossless material; other characteristics, such as detecting reflections from boundaries, phase detection, etc., make microwaves very attractive for certain applications. This paper discusses two techniques (transmission and reflection) for measuring thickness of dielectric slabs and slabs backed by conducting plates. Theoretical and experimental aspects of each technique are outlined in detail along with ... |
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Reports by Author
