Nasser Qaddoumi

Innovative Near-Field Microwave Nondestructive Testing of Corroded Metallic Structures Utilizing Open-Ended Rectangular Waveguide Probes

An innovative method utilizing microwave nondestructive testing and evaluation (NDT&E) techniques for enhanced detection and evaluation of rust under paint has been developed. The results are promising, and they show that the use of a layer of dielectric material with known properties to replace the standoff layer (air) yields significant improvements in the measurement sensitivity and resolution for some microwave NDT applications. The goals of this investigation were pursued and achieved using theoretical electromagnetic computer programs describing the interaction of microwave signals radiated out of an open-ended rectangular waveguide with any layered medium. One of the computer programs calculates the aperture reflection coefficient (simulating measurements), and the other computer program calculates the field distribution in any layered media. The experimental results were obtained using an inspection system that was built according to the results of the theoretical investigation, and they confirmed the theoretical results.

Near-field microwave imaging utilizing tapered rectangular waveguides

This paper is focused on utilizing tapered rectangular waveguides for near-field microwave-imaging purposes. Conventionally, the standard rectangular waveguides have been used as imaging probes to capture images of subsurface inclusions/defects in various dielectric media. The lateral resolution provided by the standard probes is inversely proportional to the waveguides aperture size. Consequently, seeking high-resolution images dictates the operation in higher microwave frequency bands. For many applications, however, the probes sensitivity is not optimum in these frequency bands, and hence, there is a tradeoff between sensitivity and resolution. In this paper, the authors propose the employment of tapered waveguides in the near-field imaging systems as an effort to attain higher resolution while maintaining an acceptable sensitivity. It will be shown that tapering the rectangular waveguide significantly enhances the spatial resolution of the obtained images as opposed to the standard waveguides operating at the same frequency

Detecting defects in outdoor non-ceramic insulators using near-field microwave non-destructive testing

This paper presents a novel near-field microwave nondestructive testing technique for defect detection in non-ceramic insulators (NCI). In this work, distribution class 33 kV NCI samples with no defects, air voids in silicone rubber, cracks in the fiberglass core and small metallic inclusion between the fiber core and shank were inspected. The microwave inspection system utilizes an open-ended rectangular waveguide sensor operating in the near-field at a frequency of 24 GHz. The used inspection system is simple, safe and relatively inexpensive. A data acquisition system was used to record the measured data. The results showed that all defects were repeatedly detected with high sensitivity. Line scans of the samples were obtained revealing the presence of different defects and their location. The technique also demonstrated ability to detect thickness variations in the silicon rubber shank.

An Underwater Wireless Sensor Network with Realistic Radio Frequency Path Loss Model

We propose an Underwater Wireless Sensor Network (UWSN) for near-shore applications using electromagnetic waves (EM). We also introduce a realistic path loss model for estimating the attenuation encountered by EM waves in underwater environments. The proposed model takes into account the variation of the seawater complex-valued relative permittivity with frequency in contrast to previous work that treats the permittivity as a real-valued constant parameter. Furthermore, the proposed model accounts for the impedance mismatch at the seawater-air boundary, which results in a more realistic estimate of the signal attenuation. Simulation results show the expected signal levels underwater for different scenarios. A prototype implementation to measure the path loss is also presented.

Potential of near-field microwave imaging in breast cancer detection utilizing tapered rectangular waveguide probes

Microwave imaging for medical applications has been of interest for many years. A novel near-field microwave non-invasive testing and evaluation (NIT&E) technique utilizing tapered rectangular waveguide probes is presented for breast cancer detection. Near-field microwave NIT&E techniques can be a successful candidate for the detection of breast cancer because of their potential in dealing with materials of low conductivity (i.e. lossy dielectrics like the breast tissue). The physical basis for breast tumor detection with microwave imaging is the contrast in dielectric properties of normal and malignant breast tissues. A method adopting Fourier transform matching (FTM) technique and utilizing the reflection coefficient at the aperture of a tapered rectangular waveguide sensor radiating into a breast is described resulting in microwave images that indicate the presence of a tumor. These images demonstrate the feasibility of detecting breast tumors using this approach.

Outdoor Insulators Testing Using Artificial Neural Network-Based Near-Field Microwave Technique

This paper presents a novel artificial neural network (ANN)-based near-field microwave nondestructive testing technique for defect detection and classification in nonceramic insulators (NCI). In this paper, distribution class 33-kV NCI samples with no defects, air voids in silicone rubber and fiber glass core, cracks in the fiberglass core, and small metallic inclusion between the fiber core and shank were inspected. The microwave inspection system uses an open-ended rectangular waveguide sensor operating in the near-field at a frequency of 24 GHz. A data acquisition system was used to record the measured data. ANN was trained to classify the different types of defects. The results showed that all defects were detected and classified correctly with high recognition rates.

RF energy harvesting for autonomous wireless sensor networks

The system specifications of RF energy harvesting are outlined, indicating the general guideline of low power circuit and system design as well as the frequency set to be used in the system. Four frequency bands representing five wireless standards were chosen namely, GSM, DTV, Wi-Fi, Bluetooth and road tolling system. A harvesting system has been designed and simulated. A microstrip line antenna, RF-DC rectifier circuit and a voltage doubler circuit were designed. The simulations show promising preliminary results for the RF energy harvesting system compared to similar work in literature.

Partial discharge and oil quality monitoring using an RF antenna [2009 Myron Zucker prize winner]

Partial discharge (PD) is a small electrical spark that occurs within the electrical insulation of transformers, switchgears, cables, and windings in large motors and generators. The objective of this work is to design and use a multipurpose radiofrequency (RF) antenna that can detect the PD in transformers oil and monitor the oils quality. Upon the occurrence of a PD, an electromagnetic wave is generated. This wave travels in different directions and propagates through the transformers oil. Additionally, the same antenna can be connected to a simple microwave radiometer circuit to evaluate the oil quality.

Improving electrical engineering education at the American University of Sharjah through continuous assessment

The electrical engineering (ELE) program at the American University of Sharjah (AUS) is designed to fulfill the ABET criteria. Several assessment tools are used to qualitatively and quantitatively measure the level of achievement of the programs educational objectives and outcomes. These tools include alumni, employer, and graduate advisor surveys. Results of such surveys are used to continuously improve the program curriculum, design activities, and the overall educational experience of the students. We believe that the techniques utilised in this process are crucial to the level of success that the ELE program at AUS has achieved over a relatively short-time frame. This has been reflected in the excellent academic reputation of AUS in the Middle East. Furthermore, the ELE program at AUS has received ABET accreditation in 2006 for a period of six years, which makes it the first ELE program to be fully accredited by ABET outside the USA.

Conductive Concrete for Electromagnetic Shielding Applications

Conventional concrete is a dielectric whose properties change based on the constituents of the mixture. Consequently, it is not an effective electromagnetic shield since radio frequency (RF) waves can still propagate through it with relatively low attenuation. Recently, conductive concrete, which is a cement-based mix, was developed to achieve high electrical conductivity and high mechanical strength. Petroleum coke with different particle sizes, synthetic graphite, and steel fibers were used to improve the electrical properties of the concrete. In this paper, the effectiveness of conductive concrete as an electromagnetic shield is investigated. Steel fiber configuration and sample thickness were the parameters used in the evaluation. Frequencies between 0.3 to 11 GHz were considered in the investigation. The free space measurement method was used to measure the electromagnetic shielding effectiveness and the results showed that attenuation up to 50 dB could be achieved for the frequency range considered in the investigation.