Single-, Dual- and Triple-band Frequency Reconfigurable Antenna

The paper presents a frequency reconfigurable slot dipole antenna. The antenna is capable of being switched between single-band, dual-band or triple-band operation. The antenna incorporates three pairs of pin-diodes which are located within the dipole arms. The antenna was designed to operate at 2.4 GHz, 3.5 GHz and 5.2 GHz using the aid of CST Microwave Studio. The average measured gains are 1.54, 2.92 and 1.89 dBi for low, mid and high band respectively. A prototype was then constructed in order to verify the performance of the device. A good level of agreement was observed between simulation and measurement

An Electronically Reconfigurable Patch Antenna Design for Polarization Diversity with Fixed Resonant Frequency

In this paper, an electronically polarization reconfigurable circular patch antenna with fixed resonant frequency operating at Wireless Local Area Network (WLAN) frequency band (2.4-2.48 GHz) is presented. The structure of the proposed design consists of a circular patch as a radiating element fed by coaxial probe, cooperated with four equal-length slits etched on the edge along x-axis and y-axis. A total of four switches was used and embedded across the slits at specific locations, thus controlled the length of the slits. By activating and deactivating the switches (ON and OFF) across the slits, the current on the patch is changed, thus modifying the electric field and polarization of the antenna. Consequently, the polarization excited by the proposed antenna can be switched into three types, either linear polarization, left-hand circular polarization or right-hand circular polarization. This paper proposes a simple approach that able to switch the polarizations and excited at the same operating frequency. Simulated and measured results of ideal case (using copper strip switches) and real case (using PIN diode switches) are compared and presented to demonstrate the performance of the antenna

Design and Modeling of an Integrated Micro-Transformer in a Flyback Converter

This paper presents the design and modeling of a square micro-transformer for its integration in a flyback converter. From the specifications of the switching power supply, we determined the geometric parameters of this micro-transformer. The π-electrical model of this micro-transformer highlights all parasitic effects generated by stacking of different material layers and permits to calculate the technological parameters by using the S-parameters. A good dimensioning of the geometrical parameters reduces efficiently the energy losses in the micro-transformer and permits to reach the desirable value of the converter output voltage. We have also simulated the electromagnetic effects with the help of the software FEMLAB3.1 in two cases. The first case, without ferromagnetic core, the second case with ferromagnetic core, in order to choose the micro-transformer that has better electromagnetic compatibility with the vicinity components. To validate dimensioning of the geometrical and technological parameters, we have simulated with the help of the software PSIM6.0, the equivalent electrical circuit of the converter containing the electrical circuit of the dimensioned planar micro-transformer

Experimental study on mechanical properties of elastomer containing carbon nanotubes

Recently, elastomer reinforced with nanofillers have attracted great interest due to their properties. The incorporation of carbon nanotubes into elastomers improves significantly their mechanical and dynamic mechanical properties. Carbon nanotubes (CNTs) were used to prepare natural rubber (NR) nanocomposites. Four different NR compounds containing CNTs were investigated. Compounds were prepared by a two roll mill with conventional and efficient cure systems. The properties of the nanocomposites such as tensile strength, tensile modulus and elongation at break were studied. Results obtained show that a smaller amount of CNTs can effectively improve the performance of NR. NR with 1% CNTs composites exhibited better tensile strength compared to other compounds. The study also indicated that filler materials effect on the mechanical properties of the blends

Wide to multiband elliptical monopole reconfigurable antenna for multimode systems applications

Wideband-multiband reconfigurable elliptical monopole antenna is investigated in this paper. By having conventional elliptical monopole antenna, wideband operating frequency is obtained. With the combination of dual pairs of slotted arms and a band-pass filter on the ground plane of the elliptical monopole, multiband is achieved. Dual-band operating frequencies at 1.6 GHz and 2.6 GHz while wideband operates from 3.35 GHz to 9 GHz. Therefore, wide range of wireless communication systems is obtained from the proposed antenna to support the multiband mode (i.e. GPS and LTE) and UWB systems. Frequency reconfigurable is achieved by controlling the switches integrated on the antenna structure. Simulated results of reflection coefficient, radiation patterns and gain performance are presented. The proposed antenna design is suitable candidate for different wireless communication applications

Preparation and Elastic Moduli of Germanate Glass Containing Lead and Bismuth

This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO2)60–(PbO)40−x–(½Bi2O3)x where x = 0 to 40 mol%. Their densities with respect of Bi2O3 concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B2O3)20–(PbO)80−x–(Bi2O3)x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi2O3 content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi2O3 but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi2O3 concentration

Septic Shock, Adult Respiratory Distress Syndrome, and Disseminated Intravascular Coagulopathy Following Midtrimester Genetic Amniocentesis

Background: Midtrimester genetic amniocentesis is a commonly performed procedure, with acknowledgment of some risk to mother and fetus

A Review of Forensic Entomology Cases at Ipoh Hospital and Hospital Universiti Kebangsaan Malaysia for the Year 2003

Forensic entomology was utilized to determine the postmortem interval of eleven forensic cases sentfor autopsy examination at Ipoh Hospital and Hospital University Kebangsaan Malaysia between of Januaryto December 2003. Sixth species of sarcosaprophagous flies: Chrysomya megacephala, Chrysomya rufifacies,Chrysomya villeneuvi, Chrysomya nigripes, Synthesiomya nudiseta and a sarcophagid fly were found amongthe maggot specimens received by the Forensic Entomology Laboratory, Department of Parasitology &Medical Entomology, Universiti Kebangsaan Malaysia. Those maggots were collected from dead bodiesfound among others in wrapped in gunny bags, around water tank, hanged with black nylon clothes, insidehome, beside road, drowning in lombong and an estate. Ch. megacephala was the main species found in eightcases examined. Postmortem Interval (PMI) estimated from the cases varied from one day to 10 days