Ultra-Wideband FSS-Based Antennas

As antennas are indispensable elements in wireless systems, it is necessary to provide UWB antennas suitable for UWB systems. The most proposed UWB antennas have omnidirectional radiation, which provides the wide coverage area that is highly demanded by many conventional UWB applications. However, directional radiation is more beneficial for other UWB applications and it may even be beneficial for the conventional UWB omnidirectional applications in some environments that contain many sources of interference and distorting objects, where the omnidirectional radiation leads to high interference and loss of power in undesirable directions. Consequently, an immense research has addressed the issue of realizing UWB planar antennas with unidirectional radiation characteristics. Basically, the main technique used to create unidirectional radiation patterns is employing cavity-baking reflectors to redirect the back radiation, hence increasing the gain of the radiators. In addition, these reflectors can decouple the mounted radiator from the surroundings that can damage its characteristics. Therefore, we suggest the employment of UWB reflectors to achieve UWB planar antennas with directional radiation. Our research for designing optimal UWB reflectors has led to the investigation in the field of frequency selective surfaces (FSSs), which are valuable structures and can be of great interest to a wide range of applications especially UWB applications. Subsequently, the main aim of this chapter is to give a review of the fundamental uses of FSSs in antenna engineering and the basic physical concepts that have been employed to serve the purpose of enhancing antennas’ performances using FSSs with a variety of features and characteristics. Furthermore, it is geared toward the presentation of our proposed UWB FSS-based antennas. First, we use basic FSSs such as the capacitive and its complementary inductive FSSs to design UWB reflectors that can serve improving and stabilizing the gain of UWB antennas. Thereafter, a proposed UWB single-layer FSS is used to serve the same purpose. Then, the FSS is integrated and designed together with UWB radiator, which resulted in lower profile along with good performance

Stndies on the Pneumoconiosis of Electric Welders

Sadatoshi, one of the authors, had reported previously that he had found 26% of electric welders at a certain heavy industrial plant suffered from pneumoconiosis by roentgenological examination. In this time investigation was done upon 78 electric welders carrying pneumoconiosis without pulmonary tuberculosis and the result was as follows: 1) Chest X-ray findings approved granulated type. No fibrosis, tendency of confluence, emphysema and eggshell calcification. Changes in hilus could not be found at the begining. 2) No visible changes in blood findings. Except, as the type advanced, a tendency of a slight decrease in neutrophil leukocytes and increase in lymphocytes could be seen. 3) No remarkable changes admitted in lung vital capacity and maximum ventulating volume. Expiratory impediment appeared in the third type. 4) Though welding dust contains SiO(2), welder's pneumoconiosis is innocent compared with silicosis. It also seems a little different from siderosis and so is suitable to classify it as "welder's Pneumoconiosis". 5) Occupational career should be cared when taking routine X-rayphotographs

Treatment planning comparison of high-dose-rate brachytherapy vs. robotic and conventional stereotactic body radiotherapy for ultrahypofractionated treatment of prostate cancer

Background and purpose: Ultrahypofractionated radiation therapy is increasingly used in the treatment of prostate cancer. High-dose-rate brachytherapy (HDR-BT) and stereotactic body radiotherapy (SBRT) are representative methods of ultrahypofractionation. This study was performed to compare clinically applied treatment plans for patients who had been treated using HDR-BT vs. conventional or robotic SBRT. Materials and methods: Calculated dose-volume indices between HDR-BT without a perirectal spacer (n = 20), robotic SBRT without a spacer (n = 40), and conventional (non-robotic) SBRT with a spacer (n = 40) were compared. Percentages against the prescription dose regarding the planning target volume (PTV), bladder, rectum, and urethra were statistically compared. Results: The D50% of the PTV with HDR-BT (140.5% ± 4.9%) was significantly higher than that with robotic or conventional SBRT (116.2% ± 1.6%, 101.0% ± 0.4%, p < 0.01). The D2cm3 of the bladder with HDR-BT (65.6% ± 6.4%) was significantly lower than those with SBRT (105.3% ± 2.9%, 98.0% ± 1.3%, p < 0.01). The D2cm3 of the rectum with HDR-BT (60.6% ± 6.2%) was also significantly lower than those with SBRT (85.1% ± 8.8%, 70.4% ± 9.6%, p < 0.01). By contrast, the D0.1cm3 of the urethra with HDR-BT (117.1% ± 3.6%) was significantly higher than those with SBRT (100.2% ± 0.7%, 104.5% ± 0.6%, p < 0.01). Conclusions: HDR-BT could administer a higher dose to the PTV and a lower dose to the bladder and rectum, at the cost of a slightly higher dose to the urethra compared with SBRT