École Polytechnique de Montréal

About: École Polytechnique de Montréal is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Finite element method & Computer science. The organization has 8015 authors who have published 18390 publications receiving 494372 citations.

Spacetime Metamaterials—Part I: General Concepts

Abstract: This article deals with the general concepts underpinning spacetime metamaterials and related systems. It first introduces spacetime metamaterials as a generalization of (bianisotropic) metamaterials, presented in the holistic perspective of direct and inverse spacetime scattering, where spacetime variance and dispersion offer unprecedented medium diversity despite some limitations related to the uncertainty principle. Then, it describes the fundamental physical phenomena occurring in spacetime systems, such as frequency transitions, nonreciprocity, Fizeau dragging, bianisotropy transformation, and superluminality, allowed when the medium moves perpendicularly to the direction of the wave. Next, it extends some principles and tools of relativity physics, particularly a medium-extended version of the spacetime (or Minkowski) diagrams, elaborates a general strategy to compute the fields scattered by spacetime media, and presents a gallery of possible spacetime media, including the spacetime step discontinuity, which constitutes the building brick of any spacetime metamaterial. Finally, the conclusion section provides a list of 16 items that concisely summarizes the key results and teachings of the overall document. The second part establishes the theory and overviews some current and potential applications of spacetime metamaterials.

IMPACT World+: a globally regionalized life cycle impact assessment method

Abstract: Purpose This paper addresses the need for a globally regionalized method for life cycle impact assessment (LCIA), integrating multiple state-of-the-art developments as well as damages on water and carbon areas of concern within a consistent LCIA framework. This method, named IMPACT World+, is the update of the IMPACT 2002+, LUCAS, and EDIP methods. This paper first presents the IMPACT World+ novelties and results and then analyzes the spatial variability for each regionalized impact category. Methods With IMPACT World+, we propose a midpoint-damage framework with four distinct complementary viewpoints to present an LCIA profile: (1) midpoint impacts, (2) damage impacts, (3) damages on human health, ecosystem quality, and resources & ecosystem service areas of protection, and (4) damages on water and carbon areas of concerns. Most of the regional impact categories have been spatially resolved and all the long-term impact categories have been subdivided between shorter-term damages (over the 100 years after the emission) and long-term damages. The IMPACT World+ method integrates developments in the following categories, all structured according to fate (or competition/scarcity), exposure, exposure response, and severity: (a) Complementary to the global warming potential (GWP100), the IPCC Global Temperature Potentials (GTP100) are used as a proxy for climate change long-term impacts at midpoint. At damage level, shorter-term damages (over the first 100 years after emission) are also differentiated from long-term damages. (b) Marine acidification impact is based on the same fate model as climate change, combined with the H + concentration affecting 50% of the exposed species. (c) For mineral resources depletion Responsible editor: Serenella Sala Electronic supplementary material The online version of this article (https://doi. impact, the material competition scarcity index is applied as a midpoint indicator. (d) Terrestrial and freshwater acidification impact assessment combines, at a resolution of 2°× 2.5°(latitude × longitude), global atmospheric source-deposition relationships with soil and water ecosystems' sensitivity. (e) Freshwater eutrophication impact is spatially assessed at a resolution grid of 0.5°× 0.5°, based on a global hydrological dataset. (f) Ecotoxicity and human toxicity impact are based on the parameterized version of USEtox for continents. We consider indoor emissions and differentiate the impacts of metals and persistent organic pollutants for the first 100 years from longer-term impacts. (g) Impacts on human health related to particulate matter formation are modeled using the USEtox regional archetypes to calculate intake fractions and epidemiologically derived exposure response factors. (h) Water consumption impacts are modeled using the consensus-based scarcity indicator AWARE as a proxy midpoint, whereas damages account for competition and adaptation capacity. (i) Impacts on ecosystem quality from land transformation and occupation are empirically characterized at the biome level. Results and discussion We analyze the magnitude of global potential damages for each impact indicator, based on an estimation of the total annual anthropogenic emissions and extractions at the global scale (i.e., Bdoing the LCA of the world^). Similarly with ReCiPe and IMPACT 2002+, IMPACT World+ finds that (a) climate change and impacts of particulate matter formation have a dominant contribution to global human health impacts whereas ionizing radiation, ozone layer depletion, and photochemical oxidant formation have a low contribution and (b) climate change and land use have a dominant contribution to global ecosystem quality impact. (c) New impact indicators introduced in IMPACT World+ and not considered in ReCiPe or IMPACT 2002+, in particular water consumption impacts on human health and the long-term impacts of marine acidification on ecosystem quality, are significant contributors to the overall global potential damage. According to the areas of concern version of IMPACT World+ applied to the total annual world emissions and extractions, damages on the water area of concern, carbon area of concern, and the remaining damages (not considered in those two areas of concern) are of the same order of magnitude, highlighting the need to consider all the impact categories. The spatial variability of human health impacts related to exposure to toxic substances and particulate matter is well reflected by using outdoor rural, outdoor urban, and indoor environment archetypes. For Bhuman toxicity cancer^impact of substances emitted to continental air, the variability between continents is of two orders of magnitude, which is substantially lower than the 13 orders of magnitude total variability across substances. For impacts of water consumption on human health, the spatial variability across extraction locations is substantially higher than the variations between different water qualities. For regionalized impact categories affecting ecosystem quality (acidification, eutrophication, and land use), the characterization factors of half of the regions (25th to 75th percentiles) are within one to two orders of magnitude and the 95th percentile within three to four orders of magnitude, which is higher than the variability between substances, highlighting the relevance of regionalizing. Conclusions IMPACT World+ provides characterization factors within a consistent impact assessment framework for all region-alized impacts at four complementary resolutions: global default, continental, country, and native (i.e., original and non-aggre-gated) resolutions. IMPACT World+ enables the practitioner to parsimoniously account for spatial variability and to identify the elementary flows to be regionalized in priority to increase the discriminating power of LCA.

Air-Filled Substrate Integrated Waveguide for Low-Loss and High Power-Handling Millimeter-Wave Substrate Integrated Circuits

Abstract: An air-filled substrate integrated waveguide (SIW) made of a multilayer printed circuit board process is proposed in this paper. It is of particular interest for millimeter-wave applications that generally require low cost and low-loss performance and excellent power-handling capability. This three-layered air-filled SIW allows for substantial loss reduction and power-handling capability enhancement. The top and bottom layers may make use of a low-cost standard substrate such as FR-4 on which baseband or digital circuits can be implemented so to obtain a very compact, high-performance, low-cost, and self-packaged millimeter-wave integrated system. Over Ka-band (U-band), it is shown that the air-filled SIW compared to its dielectric-filled counterparts based on Rogers substrates RT/Duroid 5880 and also 6002 reduces losses by a mean value of 0.068 dB/cm (0.098 dB/cm) and 0.104 dB/cm (0.152 dB/cm), increases average power-handling capability by 8 dB (6 dB) and 7.5 dB (5.7 dB), and quality factor by 2.7 (2.8) and 3.6 (3.8) times, respectively. The peak power-handling capability of the proposed structure is also studied. A wideband transition is presented to facilitate interconnects of the proposed air-filled SIW with dielectric-filled SIW. Design steps of this transition are detailed and its bandwidth limitation due to fabrication tolerances is theoretically examined and established. For validation purposes, a back-to-back transition operating over the Ka-band is fabricated. It achieves a return loss of better than 15 dB and an insertion loss of ${\hbox{0.6}} \pm {\hbox{0.2 dB}}$ ( ${\hbox{0.3}} \pm {\hbox{0.1}}~{\hbox{dB}}$ for the transition) from 27 to 40 GHz. Finally, two elementary circuits, namely, the T-junction and 90 $^{\circ}$ hybrid coupler based on the air-filled SIW, are also demonstrated.

New planar dual-mode filter using cross-slotted patch resonator for simultaneous size and loss reduction

Abstract: A class of new planar dual-mode filters are proposed and developed for hybrid and monolithic microwave and millimeter-wave integrated-circuit design. The novelty of the proposed structure is to use a pair of unequal crossed slots that are formed on a square patch resonator such that its radiation loss and structure size can be significantly reduced simultaneously. The physical background of the crossed slots on the patch resonator is explained. Our simulation results show that the proposed filter presents a number of attractive features for practical applications. It is found that the resonant frequency of a filter is reduced, e.g., by 36%, while its unloaded Q/sub 0/ is improved from 180 to 310 as the crossed slot length increases. The coupling characteristics of two degenerate modes backed by a resonator are studied with respect to unequal length of the crossed slots. A dual-mode filter is designed and fabricated with 1.6% bandwidth operating at 1.6 GHz to showcase our proposal. Measured results validate the design predictions well.