At present, with the advances in satellite communication systems and their increasing importance, wideband antennas are in great demand for both military and commercial applications. Most of the communication systems need a wideband antenna that operates on multi-octave frequencies. In patch antenna, diverse techniques played a vital role in enhancing the antenna parameters such as gain or bandwidth. A new design concept of a compact rectangular dual patch antenna has been developed for both high gain and wider bandwidth. In this work, a compact rectangular dual patch antenna is proposed as a wideband antenna for multiple satellite communication applications such as Global Positioning System, Global Navigation Satellite System, Indian Regional Navigation Satellite System, and S-Band Satellite Communication. The designed rectangular dual patch antenna is simulated and fabricated. Based on the performance, the fabricated antenna is compared with the simulated results in terms of VSWR, gain, axial ratio, and 3 dB beam width. Increased gain and wider bandwidth have been achieved with the developed rectangular patches and their energy distributed on the surface of the dual patches simultaneously. Finally, the proposed rectangular dual patch antenna shows improved performance for the multiple satellite communication applications.
The finite element method entails several approximations. Hence it is essential to subject all new finite elements to an adequate
set of pathological tests in order to assess their performance. Many such tests have been proposed by researchers from time
to time. We present an adequate set of tests, which every new finite element should pass. A thorough account of the patch
test is also included in view of its significance in the validation of new elements. 相似文献
Correlations between the energy gap, optical electronegativity and bulk modulus are given for compound and ternary chalcopyrite semiconductors. Bulk modulus and electronic polarizability values have been evaluated from the optical electronegativity. The estimated values of these parameters are in good agreement with the available experimental data. 相似文献
In this work, a single cylinder conventional spark ignition engine was converted to operate with hydrogen using the timed manifold fuel injection technique. A solenoid operated gas injector was used to inject hydrogen into the inlet manifold at the specified time. A dedicated electronic circuit developed for this work was used to control the injection timing and duration. The spark timing was set to minimum advance for best torque (MBT). The engine was operated at the wide-open throttle condition. For comparison of results, the same engine was also run on gasoline.The performance and emission characteristics with hydrogen and gasoline are compared. From the results, it is found that there is a reduction of about 20% in the peak power output of the engine when operating with hydrogen. The brake thermal efficiency with hydrogen is about 2% greater than that of gasoline. A lean limit equivalence ratio of about 0.3 could be attained with hydrogen as compared to 0.83 with gasoline. CO, CO2 and HC emissions were negligible with hydrogen operation. However, for hydrogen operation, NOx emission was four times higher than that of gasoline at full load power. The best ignition timing for hydrogen was much retarded when compared to gasoline. The effect of hydrogen injection pressure was also studied and no specific changes were observed. The effect of operating speed was also studied. 相似文献
In recent years, aluminium based cast composites have gained popularity in all the emerging fields of technology owing to their superior high stiffness and strength. The properties of cast composites are dictated largely by the solidification phenomenon, which needs to be well understood by foundry technologists. Information on the solidification studies of cast composites is scarce. However, the theoretical prediction of the solidification behaviour of cast composites by the use of commercially available finite element analysis (FEA) software has not yet been reported. The theoretical prediction can definitely yield good lot of information as regards the cooling rates of the cast composites saving enormous time in experimentation. In light of the above, the present investigation is aimed at the prediction of cooling curves of Al 6061–SiCp composites using finite element analysis. L-shaped composite castings were prepared using stir cast technique. The temperature of the composite during solidification was measured by K-type thermocouple, from which the cooling curves were constructed. Experiments were carried out over a range of particle weight percentage of 2–6 wt% in steps of 2 wt%. Comparison of the cooling curves of Al 6061–SiCp composite with the un-reinforced alloy reveals significant decrease in cooling rate with the addition of SiC particles. A two-dimensional transient heat transfer model was used in commercial finite element analysis software to predict the cooling curves of composite castings. The predicted cooling curves are compared with results obtained from experiments and found to be in good agreement. 相似文献
A simple and convenient method has been developed for the synthesis of 1,3,8,10,15,17,22,24-octanitrophthalocyanine derivatives MPcON's [M = Fe(III)Cl, Zn(II), Co(II), Cu(II) and Ni(II)]. The compounds were prepared from 3,5-dinitrophthalic acid in the presence of ammonium chloride, urea and catalytic quantity of ammonium molybdate in nitrobenzene solvent; the complexes were characterized by elemental analysis, electronic and IR spectra and powder XRD. The electrochemical redox properties of the complexes were studied using glassy carbon and platinum electrodes in non-aqueous media employing tetra butyl ammonium perchlorate as supporting electrolyte. 相似文献