Papers by Keyword: DRA

Abstract: The regular shape of a circular dielectric resonating antenna (DRA) is changed in this paper. The proposed dielectric resonator has a perturbed circular shape in which the least arc to arc distance is same as that of the wavelength (λ) that is calculated from the design frequency. The proposed structure has a substrate and a dielectric resonator which include dielectric materials. In this paper different dielectric materials have been used both for substrate as well as dielectric resonator and the performance of the proposed DRA has been evaluated in terms of S-Parameter ( <-10 dB) , antenna gain , radiation efficiency , directivity . The dielectric materials like FR4 epoxy and GaAs have been used for the substrate. For perturbed shaped dielectric resonator, the materials having high dielectric constant like silicon, alumina 92_pct.

Abstract: Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from SrTi_1-xZr_xO₃ ceramic with different substitution of Zr in place of Ti for (0 ≤ x ≤1). Ceramic powder were prepared using conventional solid state reaction method. X-ray Diffraction exposes physical properties Zr-doped SrTiO₃ which exhibit phase transition from cubic, tetragonal to orthorhombic phase. The electrical properties such as dielectric constant (ε_r) and dielectric loss (tan δ) were studied in variation of temperatures and frequencies. At room temperature the dielectric constant decreased from 240 to 21 with increase of Zr content however the amazing result was obtained for multiband antenna by Zr content. The dielectric loss obtain shows very low loss value roughly below 0.07 for all samples. The variations of return loss, resonance frequency and bandwidth of CDRAs at their respective resonant frequencies are studied experimentally.

Abstract: To solve the single tube gathering process paraffin oil viscosity reduction shaft and gathering the problem of high back pressure. Technical application of crude oil pour point depressant, mixed ester, benzene, ethylene oxide such as octylphenol ether compound by an oil-soluble DRA. Dosage in the 50 ~ 100mg/l to meet the water when the wellbore is less than 25% of the wax viscosity and single-tube process requirements gathering, can be compared to the multi-port wells, monitoring data before and after dosing showed that the crude oil after dosing freezing point decreased 5.6 °C, the average rate of 87.4% viscosity reduction, the average rate of 91.5% paraffin. Pipeline wellhead back pressure reduced by 20 to 30 percentage points

Abstract: We present a new concept for compact, tunable antennas. Traditional approaches have circuits and switchable elements which can be bulky and lossy. Here we investigate structures which offer direct tuning through voltage-controlled deformation of the radiating structure itself. The antenna is a dielectric resonator (DRA), where the antenna impedance and tuning depends on the shape of the dielectric. The deformation action is through using electro-active polymer (EAP) for the dielectric. EAPs have promising properties for smart antennas and ongoing developments are continuing to improve its suitability.

Abstract: Discontinuously reinforced aluminum (DRA) composites are attractive for a large range of engineering applications because of its excellent wear-resistance, high thermal conductivity and light weight etc. In this paper, DRA composites were designed and fabricated especially for automotive application, and their properties were measured. Brake discs of DRA composites were manufactured and their braking performances were investigated, including brake velocity, brake pressure, brake torque, brake deceleration, brake time and surface temperature etc. The test results show DRA composites exhibit an excellent braking performance.