Re-Examination of Watson’s Microwave Yagi Aerial

A historical end-fire 34-slot travelling wave rectangular waveguide antenna has a more rigid structure than comparable travelling or leaky-wave end fire antennas. In simulation the published antenna design had peak directivity of 16.2dBi with 1dB directivity bandwidth of 12.2% but the matching was poor with S11≈-3dB. The feed section of the antenna was found to be independent of the travelling wave and front sections, enabling faster tuning. Changing the original narrow wall inclined slot feed to a narrow wall Z-slot gave S11≤-10dB bandwidth of 8% making the antenna of practical value. Comparison is made to a dielectric polyrod antenna which had comparable performance across an octave

Comparison and analysis of two natural adsorbents of Sorghum and Ziziphus nummularia pyrene for removal of Erythrosine dye from aquatic environments

One pollutant which seriously threatens water resources is dye. Therefore, finding a suitable method to separate the dye in water resources is very important. An adsorption process that uses low cost adsorbents is considered as an efficient strategy for this purpose. In this study, Erythrosine dye removal from an aquatic environment using natural absorbents, namely Sorghum and Ziziphus nummularia pyrene, was reviewed. The effects of different parameters such as pH, contact time, initial density, and the adsorbent amount in the batch system were investigated. The results indicated that increased temperature has no significant effect on the removal of Erythrosine dye, and the highest adsorption was achieved in the first 30 min of adsorbent- dye contact time. Also, most of the adsorption occurred at pH values of 4-8. Moreover, the highest amount of dye removal was observed in a concentration of 20 mg/L for the Ziziphus nummularia pyrene adsorbent and 5 mg/L of the Sorghum adsorbent. Also, the Langmuir and Freundlich equations were used to analyze the adsorption process, where both the Sorghum and Ziziphus nummularia pyrene adsorbents showed a better agreement with the Langmuir isotherm

A single feed dual-band circularly polarized millimeter-wave antenna for 5G communication

In this paper, one simple dual-band (28 and 38 GHz) circularly polarized slotted patch antenna, suitable for future millimeter wave mobile communication, is presented. The proposed monolayer circularly polarized patch antenna is considered without any 90\ub0 phase shifter and is excited by a single-feed microstrip line, which is very desirable for high gain antenna array implementation in millimeter wave band in order to compensate the link loss. From EM simulation, it has been found that the dimensions of the L-shaped slots significantly affect the performance of the antenna. The antenna has been prototyped and the measured results show that the antenna can simultaneously provide circular polarization in the two suggested millimeter-wave bands for the upcoming 5G mobile communications

Miniaturized Reflectarray Unit Cell Using Fractal-Shaped Patch-Slot Configuration

A large literature establishes the benefits of discussions for stimulating student engagement and critical thinking skills. However, we know considerably less about the differential effects of various discussion environments on student learning. In this study, we assess student perceptions concerning the benefits of discussions in an upper-level political science class. We compare how students evaluated discussions in the whole-class environment, in small face-to-face discussion groups, and in online discussion groups. Overall, according to student surveys, small discussion groups elicited the highest student satisfaction and scored highest in critical thinking skills, while online discussions provided the best forum to express thoughts. While they did not favor all-class discussions, students reported that this format, too, provided benefits