Showing papers by "David S. Smith published in 2023"

“Monogamy? In this Economy?”: Stigma and Resilience in Consensual Non-Monogamous Relationships

Abstract: Abstract Monogamous marriage, sometimes called “the bedrock of society,” still carries an apparent “halo” of moral superiority as a relationship structure. In contrast, consensual non-monogamous (CNM) configurations are stigmatized. Research indicates a connection between stigma, stress, and negative health outcomes, despite CNM comparing favorably with monogamy. The present study uses interviews to explore minority stress and resilience among individuals in CNM relationships. Participants experienced structural stigma as erasure, and interpersonal stigma as erasure and educational/emotional work. They also describe complex enmeshment between their relationship minority status and other aspects of their sexual and gender identities. Strategic disclosure and concealment were important management tools. Furthermore, managing individual (internalized) stigma was described as unlearning mononormative bias and surrounding oneself with supportive peers/allies. The strongest motivator for perseverance was the steadfast conviction that the advantages of CNM outweighed the challenges.

Experimental Characterization of a Waveguide-Fed Varactor-Tuned Metamaterial Element Using the Coupled Dipole Framework

Abstract: We confirm experimentally that the essential electromagnetic properties of a single, waveguide-fed, tunable metamaterial radiator can be described within a coupled dipole framework, providing a foundation for metasurface array antenna design. The metamaterial element considered here is an electrically small aperture consisting of a complementary electric-LC resonator with its resonance frequency controlled by a pair of varactor diodes. Using the dipole framework, we reduce the detailed properties of the tunable element—which is a complex composite of electrically small resonant opening and bias circuitry—to a combination of effective magnetic and electric polarizabilities, with the magnetic response modeled by a Lorentzian resonance with a dc component. Experiments reveal that the designed element scatters the excitation fields into the waveguide and free space predominantly as a polarizable magnetic dipole, with a polarizability matching that is predicted from a simulation-based polarizability retrieval. This experimental analysis validates the dipole framework, unlocking the potential for improved holographic beamforming approaches for the design and analysis of reconfigurable metasurface antennas.

Study of neck formation and densification in porous hydroxyapatite ceramics using thermal conductivity measurements

Abstract: Neck formation and densification during sintering have strong effects on the thermal conductivity of a porous ceramic body. This has been described by an analytical model using grain conductivity, grain size, pore fraction and particle – particle contact area as input parameters. It has been tested on hydroxyapatite ceramics sintered with conventional, microwave and spark plasma techniques. The green bodies containing at least 40% porosity yield conductivity values in the range 0.24–0.29 Wm−1K−1. Neck formation in the initial stage of sintering increases the values to above 0.5 Wm−1K−1. Further increase is achieved by densification, well described by Landauer's relation as part of the model with close agreement to experiment for hydroxyapatite ceramics containing 40 to 5% porosity. An evaluation of thermal conductivity for 100% dense hydroxyapatite gives a value of 1.5 Wm−1K−1 which is almost constant between room temperature and 900 °C.

Sub-6-GHz Uplink Massive MIMO System Using Holographic Beamforming Metasurfaces: A Conceptual Development

Abstract: We propose an uplink massive MIMO system using an array of holographic metasurfaces as a sector antenna operating at 3.5 GHz. The antenna consists of a set of rectangular waveguide-fed metasurfaces combined along the elevation direction into a planar aperture, each with subwavelength-sized metamaterial elements as radiators. The metamaterial radiators are designed such that the waveguide-fed metasurface implements a holographic solution for the guided (or reference) mode, generating a directional beam towards a prescribed direction, thereby forming a multibeam antenna system. We demonstrate that a narrowband uplink massive MIMO system using the metasurfaces can achieve the sum capacity close to that offered by the Rayleigh channel. We show that metasurfaces supporting multiple beams can achieve high spatial resolution in the azimuth directions in sub-6 GHz channels, and thereby form uncorrelated MIMO channels between the base station and users. Also, the proposed metasurface antenna is structurally simple, low-cost, and efficient, and thus is suitable to alleviate RF hardware issues common to massive MIMO systems equipped with a large antenna system.

Computation of Input Impedance of Rectangular Waveguide-backed Metasurface Arrays with Feed Networks using Coupled Dipole Framework

Abstract: We present a method for computing the input impedance of a rectangular waveguide-backed metasurface array excited by a common feed network. The metasurface array consists of rectangular waveguides loaded with subwavelength metamaterial radiators fed by the guided modes, excited with the feed. Thus, computation of the impedance at the input feed requires considering the electromagnetic interaction of the metasurfaces with its feed. Recently, semi-analytical models of metasurfaces using a coupled dipole framework have been proposed as efficient analysis tools. However, the models assume ideal waveguide ports for excitation and do not incorporate the response of feed networks, thus creating a gap in analyzing the overall response of the antenna. This paper addresses this gap by presenting a method using the coupled dipole framework and segmentation technique, which utilizes the impedance matrices for cascading multiport networks representing the metasurfaces and feed. The proposed method is verified via full-wave simulations.