450 research outputs found

    Magnetic and mechanical effects of Mn substitutions in AlFe2B2

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    The mechanical and magnetic properties of the newly discovered MAB-phase class of materials based upon AlFe2B2 were investigated. The samples were synthesised from stoichiometric amounts of all constituent elements. X-ray diffraction shows that the main phase is orthorhombic with an elongated b-axis, similar to AlFe2B2. The low hardness and visual inspection of the samples after deformation indicate that these compounds are deformed via a delamination process. When substituting iron in AlFe2B2 with manganese, the magnetism in the system goes from being ferro- to antiferromagnetic via a disordered ferrimagnetic phase exhibited by AlFeMnB2. Density functional theory calculations indicate a weakening of the magnetic interactions among the transitions metal ions as iron is substituted by manganese in AlFe2B2. The Mn-Mn exchange interactions in AlMn2 B2 are found to be very small

    Temperature stability of intersubband transitions in AlN/GaN quantum wells

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    Temperature dependence of intersubband transitions in AlN/GaN multiple quantum wells grown with molecular beam epitaxy is investigated both by absorption studies at different temperatures and modeling of conduction-band electrons. For the absorption study, the sample is heated in increments up to 400∘400^\circC. The self-consistent Schr\"odinger-Poisson modeling includes temperature effects of the band-gap and the influence of thermal expansion on the piezoelectric field. We find that the intersubband absorption energy decreases only by ∼6\sim 6 meV at 400∘400^\circC relative to its room temperature value

    1.6 GHz Low-Power Cross-Correlator System Enabling Geostationary Earth Orbit Aperture Synthesis

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    We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 x 136 mm(2) and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit

    Co‑creating coastal sustainability goals and indicators

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    Indicators can be powerful tools to measure progress towards achieving societal goals, and many indicators have been developed for sustainability goals nationally and internationally. When indicators are developed solely through top-down approaches without engaging local knowledge, they often fall short of capturing local perceptions and concerns relevant to decision-making. The aim of this project was to co-create a Coastal Barometer and its component indicators, together with local knowledge-holders and communities, using the Ocean Health Index as a framework. As a frst step, local knowledgeholders from six communities dispersed across Northern Norway were invited to articulate local sustainability goals and the required knowledge for eight broad topics pertaining to global OHI goals: small-scale fsheries, food production, sense of place, tourism, food production, clean waters, carbon storage and economy and livelihoods. In this paper, our main focus is the co-design phase of the Coastal Barometer, namely eliciting sustainability goals. We thus, present locally desired sustainability goals and sub-goals and the process of eliciting these goals. We also include suggestions from local knowledge-holders on how to reach these goals (i.e. proposed management measures), along with researchers’ assessment of data availability (part of the co-production process) for developing indicators to measure progress towards these goals. Finally, we discuss the benefts and challenges of co-developing sustainability goals and indicators with local knowledge-holders. We conclude that co-design can increase the quality of sustainability assessments by enriching the view of coastal sustainability. This knowledge can subsequently be used to align indicators with local sustainability goals as well as to the local context where the indicators will be applied. Blue growth · Ecosystem services · Public participation · Sustainability indicators · Sustainable development goals · Ocean health indexpublishedVersio
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