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Reconfigurable metasurface aperture for integrated compressive electromagnetic sensing and imaging
No full textIn this paper, a reconfigurable metasurface aperture (RMA) is proposed for integrated compressive electromagnetic sensing and imaging (ISAI) applications. The proposed RMA consists of randomly distributed switchable meta-atoms with two orthogonal orientations to enable dual-polarized radiation. The meta-atoms are loaded with PIN diodes, and by reconfiguring their operating states, the meta-atoms are selectively deactivated or activated. This dynamic mechanism is used to reconfigure the aperture state of metasurface and generate spatially lowcorrelated radiation patterns. These patterns serve as measurement modes for ISAI implementation. The performance of RMA is characterized using the reflection coefficient (S11) to assess the antenna behavior, and the correlation coefficient (CC) and the singular value (SV) spectrum to evaluate the spatial orthogonality of its measurement modes. An RMA-based ISAI study is conducted to validate the proposed design, in which the incident angles of far-field sources are accurately estimated and both the image and orientation of a target are successfully retrieved, confirming the effectiveness of the approach.<br/
Negotiating peace with pro-government militias?: human rights violations, international pressure, and the case of the Self Defense Forces of Colombia (AUC)
No full textThis article theorizes when and why governments negotiate peace with pro-government militias (PGMs) or “pro-state” paramilitary groups. I argue that governments are more likely to negotiate with PGMs when PGMs conduct mass human rights violations and when the government faces domestic and international pressure to account for PGM violence. While governments support (even if tacitly) PGMs for short-term advantages in counterinsurgency, PGMs often pursue their own agendas and can end up harming state interests resulting in a shift from support to curtailing PGM activity. I build this argument drawing on examples from around the world and providing initial evidence from the Colombian government’s negotiated agreements with the Autodefensas Unidas de Colombia (AUC) in Santa Fe de Ralito in 2003-2005
Embodied AI and the future of accessible music-making: a review of developments in AI-ADMIs post-Frid
No full textThis paper examines the evolution of Accessible Digital Musical Instruments (ADMIs) since 2019, a period marked by the increasing integration of Artificial Intelligence (AI). We refer to these emerging instruments as AI-ADMIs. Emma Frid's 2019 systematic review [1] identified key design priorities for ADMIs, including adaptability, user-specific customisation, multisensory feedback, and participatory design. However, Frid's study notably lacked discussion of AI or machine learning, reflecting the limited adoption of these technologies at the time.Since then, AI-ADMIs have rapidly expanded, incorporating camera-based gesture recognition, interactive machine learning, and adaptive deep learning systems. This paper provides an overview of these post-2019 innovations and critically assesses how they build upon or diverge from Frid’s foundational concerns. Drawing on the primary author’s doctoral research into an AI-driven, gesture-controlled instrument, we explore current challenges such as algorithmic bias, normative assumptions in datasets, and the absence of user-specific training data.In response, we propose an Embodied AI Design Principles framework to guide the creation of inclusive, disability-led AI musical interfaces. We argue that an embodied approach, one that foregrounds the lived experiences of disabled musicians and the physicality of musical interaction, is essential for developing equitable and accessible AI-ADMIs. We conclude by reflecting on future directions for the field
Properties of circularly polarised spherical retrodirective array
No full textIn this paper we provide the first ever discussion of the characteristics of a spherical retrodirective array. The array is populated with planar circularly polarised (CP) microstrip patch antennas. The proposed retrodirective array offers significant potential to realise orientation-agnostic, continuous, self-steering coverage in both hemispheres. In this work we use numerical full-wave simulations to determine for the first time the main radiation characteristics, far-field and axial ratio, of a spherical CP retrodirective array operating at 2.45 GHz and describe their dependence on both orientation and aperture cross section. Beampatterns with main lobe directivity of 16−16.6 dBi, comparable indirectivity to a planar array of the same aperture, that preservethe handedness of the pilot signal, are presente in all cardinal direction
