Mohamed K. Abdelazeez

Measurements of the “Magnex DC” characteristics at microwave frequencies

This paper deals with the measurements of the equivalent impedance, insertion loss (IL), and return loss (RL) of a conductive composite material called “Magnex DC”, performed at microwave frequencies. It is found that the equivalent impedance of this composite material decreases as the frequency increases in the X-band (8–12.4 GHZ) and the IL of a 1.4 mm thick specimen is greater than 9 dB over the whole band. The utilization of this material in electromagnetic shielding is considered. Furthermore, results of the measurements performed on a tapered specimen are also reported.

Microwave properties of the talc filled polypropylene

A microwave bench operating in the frequency range 8–12 GHz (X-band) was used to investigate some of the electrical characteristics of the talc filled polypropylene composite. The impedance, return loss, and insertion loss are measured as a function of frequency in the X-band range. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composite. The impedance, return loss and insertion loss show relatively low frequency dependence. Also, the return loss and the impedance exhibit a resonance behaviour at 11.91 GHz. The results suggest that this composite material could be used in some microwave applications.

Some properties of nickel-coated carbon fibre-polypropylene composite at microwave frequencies

Some properties of nickel-coated carbon fibre-polypropylene composite are considered at microwave frequencies in the range 8 to 12 GHz. The paper presents the measured values of the insertion and return losses and the equivalent input impedance in the above frequency band. Measurements were performed on composite material for different nickel-coated fibre concentrations of 0, 5, 10, 16 and 28 wt%. The filler effects shows a transition region and identifies the dependency of the electrical properties on these concentrations. Furthermore, shielding effectiveness is calculated for the given concentrations and it is found that its value could reach more than 30 dB over the whole frequency band for a specimen of 2.6 mm thickness and with 28 wt% concentration.

Acoustics of King Abdullah Mosque

This paper presents the acoustical problems associated with a huge mosque that has been built recently in Amman, Jordan. These problems include very high reverberation time values inside the mosque, reaching more than 15 s at midfrequencies, and more than 22 s for all frequencies below 500 Hz. In addition, the articulation index was very low and the ambient noise level was very high. These conditions produced an unacceptable acoustic environment for this place, and their reduction was essential. To remedy these problems, most of the interior surfaces of the mosque were treated using appropriate types of materials. Final measurements indicate that the reverberation time in the midfrequencies is around 1 s. Furthermore, the use of an electroacoustic system provides an almost uniform sound level inside the mosque. The articulation index measurements show good to excellent response.

Measurements and analysis of the traffic noise in amman, jordan and its effects

Abstract This paper gives the measured values of the sound pressure level (L10) resulting from traffic noise measurements over periods of 1 h and 18 h. These measurements were done daily over long and difficult periods, and at different periods and at different locations, in the greater Amman (Jordan) area. Measured values are presented versus the numbers of vehicles accounted for at the time of measurement. Comparisons between calculated and measured levels for both Amman and other cities are given. Annoyance, from the traffic noise, to the people living around the measurement sites is given in a percentage form.

Electrical properties of oilshale rocks

The characterization of electric properties of oilshale deposit is reported. The scanning electron microscopy and the results of the dielectric constants show that the deposit is a heterogeneous composite material containing some conducting and insulating microstructural units. The components of the equivalent input impedance measured at microwave frequencies (8 to 12 GHz) and the impedance at low frequencies (0.5 Hz to 30 kHz) showed frequency dependence. The real and imaginary components of the permittivity determined from the impedance data obtained at low frequencies showed an exponential decrease with frequency. The observed frequency dependence of the rock permittivity is ascribed generally to a Maxwell-Wagner type of mechanism. Also it was observed that the conductivity is almost independent of the frequency below 1 kHz and increases with frequency above this range. The values obtained for the conductivity at low frequencies indicate that the rock has an intermediate electrical conduction due to some mineralized metallic complexes and carbon content.

Some electrical properties of aluminum-epoxy composite

Abstract The dependence of some electrical properties of aluminum flake-epoxy composites on frequency and filler content is studied. The insertion loss as well as the shielding effectiveness (SE) show great dependence on filler concentration. The SE for the composites varies linearly with the microwave frequency and reaches up to 50 dB for a 90 wt.% composite specimen. The dependence of the electrical conductivity on the filler content shows that the composite changes from an insulating to a conductive behavior. The composite structure revealed by scanning electron microscopy supports the observed variations of the electrical conductivity.

Microwave measurements on oilshale rocks

Characterization of some structural and electrical properties of oilshale deposit are studied in the X-band (8 to 12 GHz) through measuring the insertion loss (IL), return loss (RL), and the material equivalent input impedance, Zm. X-ray diffraction and scanning electron microscopy show that the deposit contains a number of minerals and oil pores. Measurements at microwave frequency show that the IL for the rock specimen of 5.1 mm thickness ranges between 2 and 4.5 dB; and the value of the RL for the same specimen ranges between 2 and 5.8 dB over the whole X-band. A particular surface deposit specimen of thickness 7.15 mm shows a high value of RL of about 38 dB at around 11.2 GHz, which seems almost transparent at this frequency. The overall behaviour of the measured impedance as a function of frequency shows a relatively strong dependence on the specimen thickness and weak dependence on both deposit depth and composition. Analysis of the obtained data of impedance indicates that the deposit has an inductive behaviour.

Mechanical and electrical behaviour of “Magnex DC” conductive polymer composite

Mechanical and electrical behaviour of the “Magnex DC” conductive polymer composite is reported. X-ray diffraction patterns and scanning electron microscopy (SEM) show that the composite has a semicrystalline, isotropic, and defected structure. It was found that both the elastic modulus and yield stress increase with decreasing temperature; the yield stress increases nonlinearly with increasing strain rate due to the voids in the composite. In addition, the activation energy and the activation volume of a single rate-activated process observed at relatively high strain rates are determined. The dependence of the impedance behaviour on frequency is investigated. It was observed that the a.c. conductivity is almost independent of frequency below 10 kHz and increases with frequency above this range. The values obtained for the conductivity indicate that the composite has a relatively small electrical conduction which is rather less than that for the pure semiconductors.

Bluetooth/uwb circular patch antenna with dual band notches

In this paper, we propose a new planar antenna for Ultra Wide-Band (UWB) and Bluetooth applications with two band notches. The band notch are designed to reject the Worldwide Interoperability for Microwave Access (WiMAX) applications based on the IEEE 802.16 standards for the frequency band 3.3-3.8 GHz and the Wireless Local Area Network (WLAN) applications band that based on the IEEE 802.11 standard for the frequency band of 5.15-5.825 GHz. The antenna consists of a circular patch, co-planner waveguide (CPW) feed line with 50 Ω input impedance, T-strip connected to the top of the patch and complementary circular slot type split ring resonator (SRR) is etched at the bottom edge of the patch. The antenna covers the UWB frequency band (3.1-10.6) GHz beside extra band for Bluetooth frequency range (2.4-2.48) GHz. The characteristics of the designed structure are investigated using finite element method based electromagnetic solver, HFSS. Promising return loss data with good matching, good gain, high efficiency and omni-directional radiation pattern are obtained.