36 research outputs found

    Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

    Get PDF
    This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

    Dual-band self-diplexed modulated metasurface antennas

    No full text
    International audienceThis paper presents a simple and effective technique to design dual-band modulated metasurface (MTS) antennas. In MTS apertures, an equivalent surface inductance supports the propagation of a transverse magnetic (TM) surface wave (SW). The SW power can be gradually radiated at one frequency by periodically modulating the surface reactance. Indeed, one can choose the period of the modulation so its interaction with the SW results in the (-1) indexed Floquet mode entering the visible region. Therefore, in order to achieve dual-band operation with a single aperture, one has to tailor a modulation able to radiate the SW power in the desired directions at both frequencies. The proposed approach consists in superimposing two modulations with different periods on the antenna aperture. One modulation produces beam #1 at frequency f1, whereas the other one generates beam #2 at frequency f2. The resulting inductive surface is then synthesized by means of sub-wavelength patches printed on a grounded dielectric slab. Moreover, it is possible to define a different position for the source of each modulation, which allows one to self-diplex the signals at f1 and f2. After providing basic design guidelines, we present numerical results for a design case consisting of an antenna with broadside pencil beams in the K and Ka bands. © Institution of Engineering and Technology.All Rights Reserved

    Transformation optics for anisotropic metasurfaces

    No full text
    In this paper, Transformation Optics is exploited to design anisotropic modulated metasurfaces able to control the wavefront and Poynting vector distribution of surface waves. This methodology can be applied to design a large number of planar devices. As an example, a beam shifting device has been implemented using a metasurface consisting of dipoles printed on a grounded slab. The capability of the device to laterally shift a surface wave has been verified through full wave simulations

    Flat lens antenna using gap waveguide technology at millimeter waves

    No full text
    In this paper, a flat lens antenna using Gap Waveguide (GW) technology working in the millimeter waves band was designed. The metamaterial lens is fed using a Groove Gap Waveguide (GGW) horn antenna in order to achieve a plane wavefront at broadside. Both devices, metalens and GGW antenna achieve excellent radiation results when combined together. Due to metallic composition, the structure presents more robustness, low loss, and adaptability to a flat surface, able to be used in millimeter wave application.This research was funded by Spanish Ministerio de Ciencia, InnovaciĂłn y Universidades, Project RTI2018-094475-B-I00 (MCIU/AEI/FEDER,UE)

    Metasurface leaky-wave antennas: A comparison between slot and patch implementation

    No full text
    This paper is devoted to the analysis and design of a high-gain circularly polarized antenna with low profile for deep space communications in the X-band. In this context, the low-mass and high efficiency requirements can be addressed at the same time by properly designing a layer of patches (slots) printed (etched) on a grounded dielectric substrate. The interaction between this layer and the surface wave launched by a simple and compact feeder leads to leaky-wave radiation. The overall structure is very light and low profile; in particular, for the slot-based solution the dielectric slab is extremely thin (0.15 mm) and characterized by a low permittivity. The design procedure is summarized, and the patch and slot layouts are shown along with their respective directivity patterns

    Antennas for space instruments from GHz to THz

    No full text
    International audienceIn this paper we present an overview of different antenna technologies for space-based instruments. We show that some of the designs that work well at gigahertz frequencies are difficult to implement at terahertz frequencies due to tight tolerance and rms surface finish requirements. We also show that antenna designs are dictated not only by the frequency of operations but also by the space platform of choice. In this paper, we also present ideas for low-profile terahertz antennas for implementation on SmallSat and CubeSat platforms. © Institution of Engineering and Technology.All Rights Reserved
    corecore