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Multilayer Dry Film Photoresist Fabrication of a Robust >100 GHz Gap Waveguide Slot Array Antenna
Full text linkThis article presents the first use of a multilayer dry film photoresist to fabricate a slot array antenna by micromachining. The proposed fabrication process demonstrates a straightforward and fast method of realizing antenna structures and delicate features with very high accuracy above 100 GHz. The slot array antenna design is based on gap waveguide technology. The designed antenna consists of two layers: a slot layer and a feed layer with a transition to measuring waveguide. The antenna contains structures that require a multiple level dry film fabrication process with thicknesses ranging from 80 μm to 400 μm with \ub1 10 μm tolerance. The fabricated antenna shows good accuracy. To make the fabricated antenna layers conductive, the fabricated polymer antenna was coated with Ti and Au. The input reflection coefficient was measured to be below – 11 dB over a 10% bandwidth from 136-148 GHz, and the antenna gain was measured to be 11.4 dBi at 142 GHz, both of which are in fair agreement with simulations. A thermal cycling test has been conducted on the fabricated antenna and the results show insignificant degradation at least up to 300 cycles in the temperature range –50 \ub0C to 135 \ub0C which is the typical temperature gradient range for many practical outdoor wireless applications
Is There a Need for Critical Robotics Research?
No full textWhat research questions and approaches are currently missing in the field of human-robot interaction research? We discuss humanistic and critical dimensions of critical robotics - an initiative created to investigate a possible paradigm shift in the field of robotics research. Robotic solutions are increasingly presented as a potentially desirable and emerging technologies in different social domains and institutions. At the same time, both this vision and the reality of robots in society pose a great deal of challenges. We provide some background to the critical robotics movement and present examples of research that takes a critical robotics perspective
A New Proposal for Power Sharing in LVDC Energy Community Microgrids
No full textIn recent years the development of LVDC distribution networks is under consideration. DC electrical distributions offer several advantages compared to AC ones in many applications, in particular in the presence of energy storage systems and distributed generation like high efficacy, flexibility and simple integration of renewables. The DC distribution allows to integrate in a more efficient “microgrid” different sources with DC/DC converters. The paper proposes an innovative model of microgrid configuration for aggregations of end-users able to share the power produced by common generators and energy services named by the authors Power Sharing Model (PSM) using a DC bus that connects in a one way approach, the common generators to the end-users. The paper investigates on the different suggested configurations of the PSM, with the converter characteristics and controls. A simplified case study is analyzed to test the performance of the sharing model and the stability of the control in different scenarios. The paper compares the PSM based on a LVDC grid with existing approaches of virtual aggregations, and it highlights the main differences between the currently existing methods and our new LVDC microgrid approach. The suggested PSM appears more efficient, convenient and flexible than the existing virtual models, because users physically self-consume and share the energy locally generated
Techno-economics of 5G transport deployments
Full text linkNetwork densification is a crucial enabler for 5G, requiring the installation of a large number of devices and/or cables for the 5G transport network. This invited paper provides a techno-economic study focusing on adopting microwave and fiber equipment for 5G transport network deployments. Different architectures for low layer split supporting latency critical services are considered
Vacuum misalignment in presence of four-Fermi operators
Full text linkWe consider the issue of vacuum misalignment induced by four-Fermi couplings in a generic strongly coupled four-dimensional gauge theory. After briefly reviewing the general formalism, we focus on the case of partial compositenesslike operators at leading order, which is relevant in applications to phenomenology. We show that the interactions between an elementary fermion and composite spin-1/2 operators in various representations contribute to the effective potential with relative sign differences. Thus the correct sign required to misalign the vacuum is guaranteed to occur for some representations but not all of them. The overall sign dictating the specific representations responsible for misalignment can in principle be determined on the lattice. We also comment on the likely sign for some simple cases
The MeerKAT Absorption Line Survey: Homogeneous continuum catalogues towards a measurement of the cosmic radio dipole
Full text linkThe number counts of homogeneous samples of radio sources are a tried and true method of probing the large-scale structure of the Universe, as most radio sources outside the Galactic plane are at cosmological distances. As such, they are expected to trace the cosmic radio dipole, an anisotropy analogous to the dipole seen in the cosmic microwave background (CMB). Results have shown that although the cosmic radio dipole matches the direction of the CMB dipole, it has a significantly larger amplitude. This unexplained result challenges our assumption of the Universe being isotropic, which can have large repercussions for the current cosmological paradigm. Though significant measurements have been made, sensitivity to the radio dipole is generally hampered by systematic effects that can cause large biases in the measurement. Here we assess these systematics with data from the MeerKAT Absorption Line Survey (MALS), a blind search for absorption lines with pointings centred on bright radio sources. With the sensitivity and field of view of MeerKAT, thousands of sources are observed in each pointing, allowing for the possibility of measuring the cosmic radio dipole given enough pointings. We present the analysis of ten MALS pointings, focusing on systematic effects that could lead to an inhomogeneous catalogue. We describe the calibration and creation of full band continuum images and catalogues, producing a combined catalogue containing 16 307 sources and covering 37.5 square degrees of sky down to a sensitivity of 10 μJy beam-1. We measure the completeness, purity, and flux recovery statistics for these catalogues using simulated data. We investigate different source populations in the catalogues by looking at flux densities and spectral indices and how they might influence source counts. Using the noise characteristics of the pointings, we find global measures that can be used to correct for the incompleteness of the catalogue, producing corrected number counts down to 100-200 μJy. We show that we can homogenise the catalogues and properly account for systematic effects. We determine that we can measure the dipole to 3significance with 100 MALS pointings
Modulating the Formation of Coke to Improve the Production of Light Olefins from CO2 Hydrogenation over In2O3 and SSZ-13 Catalysts
Full text linkModerately acidic aluminophosphates (SAPOs) are often integrated with methanol synthesis catalysts for the hydrogenation of CO2 to olefins, but they suffer from hydrothermal decomposition. Here, an alternative SSZ-13 zeolite with high hydrothermal stability is synthesized and coupled with an In2O3 catalyst in a hybrid system. Its performance regarding selectivity for olefins and coke formation was investigated for CO2 hydrogenation under varying temperatures and pressures. Various reactions occur, producing mainly CO and different hydrocarbons. The results indicate that the hydrogenation of hydrocarbons are dominant at high temperatures (around 400 \ub0C) over SSZ-13 zeolite with a high acid density and that the coke deposition rate is slow. Polymethylbenzenes are the main coke species, but the selectivity for light olefins is low among hydrocarbons at high temperatures. However, at low temperatures (around 325 \ub0C), and especially under high pressure (40 bar), methanol disproportionation becomes significant. This results in an increased selectivity for light olefins; however, it also leads to a rapid coke deposition, which gives inactive adamantanes as the main coke species that block the pores and cause rapid deactivation. However, after coking at 325 \ub0C and regeneration at 400 \ub0C under the reaction atmosphere, the accumulated adamantanes can be decomposed into smaller coke species, which reopens the channel structure and generates modulated active sites within the zeolite, resulting in a higher yield of olefins without deactivation. The performances of acidic SSZ-13 zeolites, with varying ratios of Si/Al in transient experiments, further verified that a dynamic balance exists between the formation and degradation of coke within the SSZ-13 zeolite during a long-term CO2 hydrogenation reaction. This balance can be achieved by optimizing the reaction conditions to match the acid density of the catalyst. Using the conditions of 20 bar and 375 \ub0C, with a H2 to CO2 mole ratio of 3, the results obtained for the precoked hybrid catalysts of In2O3 and SSZ-13 (Si/Al = 25) exhibited very stable activity, with the selectivity for light olefins (based on hydrocarbons formed) of max. 70% after 100 h time-on-stream. This work provides new insights into the design of stable hybrid catalysts, especially the influence of a precoking process for SSZ-13 zeolite in the production of light olefins
SPLITTING SCHEMES FOR FITZHUGH-NAGUMO STOCHASTIC PARTIAL DIFFERENTIAL EQUATIONS
No full text. We design and study splitting integrators for the temporal discretization of the stochastic FitzHugh-Nagumo system. This system is a model for signal propagation in nerve cells where the voltage variable is the solution of a one-dimensional parabolic PDE with a cubic nonlinearity driven by additive space-time white noise. We first show that the numerical solutions have finite moments. We then prove that the splitting schemes have, at least, the strong rate of convergence 1/4. Finally, numerical experiments illustrating the performance of the splitting schemes are provided
The supply and demand balance of recyclable textiles in the Nordic countries
Full text linkThe textile industry is on its early steps towards circular economy. Being a highly resource-intensive and waste-generating industry, it is essential to embrace fiber-to-fiber recycling in addressing the increasing textile waste problem. Several innovative initiatives are happening within this area, not least in the Nordic countries, where automated sorting and fiber-to-fiber recycling technologies and capacities are developing. These large investments require economy of scale; however, this is challenged by the fractioned supply due to the specific fiber requirements of the recycling facilities. To ensure economy of scale and support strategic planning, it is important to investigate the balance of the demand of those capacities with the supply of recyclables generated in the region. Local and regional perspectives are needed in order to avoid unnecessary transportation of low value materials. Based on a synthetises of existing textile flow studies and interviews with relevant actors in four Nordic countries, this study investigates the balance between the supply of recyclable textiles and the sorting and recycling capacity. This is accomplished by estimating the volumes of recyclables and their fiber composition (based on developed weighting average method) and comparing these with the current and upcoming capacities in each country and in the Nordics as a whole. The findings indicate that the upcoming automatic sorting and recycling capacity will be sufficient to deal with the total recyclable fraction in the Nordic region, except for some of the synthetic fibers. However, there are imbalances between supply and demand within individual countries, highlighting opportunities for collaboration
The Role of the PAA1 Gene on Melatonin Biosynthesis in Saccharomyces cerevisiae: A Search of New Arylalkylamine N-Acetyltransferases
Full text linkRecently, the presence of melatonin in fermented beverages has been correlated with yeast metabolism during alcoholic fermentation. Melatonin, originally considered a unique product of the pineal gland of vertebrates, has been also identified in a wide range of invertebrates, plants, bacteria, and fungi in the last two decades. These findings bring the challenge of studying the function of melatonin in yeasts and the mechanisms underlying its synthesis. However, the necessary information to improve the selection and production of this interesting molecule in fermented beverages is to disclose the genes involved in the metabolic pathway. So far, only one gene has been proposed as involved in melatonin production in Saccharomyces cerevisiae, PAA1, a polyamine acetyltransferase, a homolog of the vertebrate’s aralkylamine N-acetyltransferase (AANAT). In this study, we assessed the in vivo function of PAA1 by evaluating the bioconversion of the different possible substrates, such as 5-methoxytryptamine, tryptamine, and serotonin, using different protein expression platforms. Moreover, we expanded the search for new N-acetyltransferase candidates by combining a global transcriptome analysis and the use of powerful bioinformatic tools to predict similar domains to AANAT in S. cerevisiae. The AANAT activity of the candidate genes was validated by their overexpression in E. coli because, curiously, this system evidenced higher differences than the overexpression in their own host S. cerevisiae. Our results confirm that PAA1 possesses the ability to acetylate different aralkylamines, but AANAT activity does not seem to be the main acetylation activity. Moreover, we also prove that Paa1p is not the only enzyme with this AANAT activity. Our search of new genes detected HPA2 as a new arylalkylamine N-acetyltransferase in S. cerevisiae. This is the first report that clearly proves the involvement of this enzyme in AANAT activity