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A new adaptive frequency selective surface (AFSS) has been presented for electromagnetic (EM) shielding applications. Passive EM shields lack reconfigurability which severely limits their application. Moreover, active EM shields involving PIN diodes and other active elements consume power all the time. This paper incorporates a novel adaptive approach with frequency selective surface (FSS) to create a smart environment. The unit cell of the designed FSS has the shape of an octagon loop; each loop includes a pin diode at 180° intervals. An envelope detector has been used to trigger the microcontroller whenever an incident RF signal has been detected. The PIN diodes are switched ON or OFF automatically based on the requirements using a microcontroller to save power. When the PIN diodes are OFF, the FSS is in the shielding mode and when they are ON it is in the transmission mode. A prototype has been built for measurements. A good agreement between theory and experiment has been observed. The proposed AFSS can also be programmed as a time-based event and remote-controlled for on-demand EM wave shielding applications.

This article presents how to design multiband energy selective surface (ESS), which has a nonlinear transmission response to the power of incidence in multiple frequency band. It is demonstrated that ESSs with an arbitrary number of operating bands could be obtained with both parallel and serial LC resonance circuits and each single operating band could be modulated from a passband with low insertion loss (IL) to a stopband with high shielding effectiveness (SE). Furthermore, a dual-band ESS is designed to verify the proposed methods, in which two rectangular resonance rings mounted with Sckotty diodes are used. A 0.5 IL and 30 dB SE are observed at the central frequency of both operating bands with ECM and full-wave simulations. Prototypes are fabricated and measured with a waveguide set-up. There is a good agreement between the simulations and measurements under low-power incidence. However, some differences are observed under high-power incidence. The reason behind is discussed in detail and some measures for improvement are also proposed. The proposed approach provides general guidelines for multiband ESS design and is supposed to obtain wide use in adaptive shielding for high power microwave (HPM). [ABSTRACT FROM AUTHOR]

Purpose: Current, clinically applicable intracavitary brachytherapy applicators that utilize shielded ovoids contain a pair of tungsten-alloy shields which serve to reduce dose delivered to the rectum and bladder during source afterloading. After applicator insertion, these fixed shields are not necessarily positioned to provide optimal shielding of these critical structures due to variations in patient anatomies. The authors present a dosimetric evaluation of a novel prototype intracavitary brachytherapy ovoid [anatomically adaptive applicator (A3)], featuring a single shield whose position can be adjusted with two degrees of freedom: Rotation about and translation along the long axis of the ovoid. Methods: The dosimetry of the device for a HDR 192Ir was characterized using radiochromic film measurements for various shield orientations. A MCNPX Monte Carlo model was developed of the prototype ovoid and integrated with a previously validated model of a v2 mHDR 192Ir source (Nucletron Co.). The model was validated for three distinct shield orientations using film measurements. Results: For the most complex case, 91% of the absolute simulated and measured dose points agreed within 2% or 2 mm and 96% agreed within 10% or 2 mm. Conclusions: Validation of the Monte Carlo model facilitates future investigations into any dosimetric advantages the use of the A3 may have over the current state of art with respect to optimization and customization of dose delivery as a function of patient anatomical geometries. [ABSTRACT FROM AUTHOR]