1,162 research outputs found
Experimental results obtained on a new circuit topology of a broadband and low spurious frequency doubler
A CRLH (Composite Right-/Left-Handed) based distributed frequency multiplier circuit topology is proposed. It is demonstrated that using fully-distributed CRLH based unit cells, low spurious output spectrum and flat output power level may be obtained for a large frequency bandwidth. To validate the proposed frequency multiplier, a frequency doubler is designed and fabricated. The experimental results have shown that the conversion losses on the output second harmonic is less than 9 dB and 7 dB, for input power level of -1 dBm and 5 dBm, respectively, within an input frequency bandwidth from 4 GHz to 6 GHz. In the same frequency bandwidth, due to the CRLH based circuit topology, the first and third output harmonics are well filtered
Broadband and small-size 3-DB ring coupler
A topology for a 3-dB broadband and small-size ring coupler is proposed. It consists of fully distributed Composite Right-/Left-Handed phase shifters and a Lange coupler. For the fabricated coupler, the frequency bandwidth is one octave, centered on 1.5 GHz, while the footprint area is 25% compared to the conventional ring coupler topology. The experimental results are in good agreement with the expected ones, obtained by electromagnetic simulation
Snow cover monitoring by machine processing of multitemporal LANDSAT MSS data
LANDSAT frames were geometrically corrected and data sets from six different dates were overlaid to produce a 24 channel (six dates and four wavelength bands) data tape. Changes in the extent of the snowpack could be accurately and easily determined using a change detection technique on data which had previously been classified by the LARSYS software system. A second phase of the analysis involved determination of the relationship between spatial resolution or data sampling frequency and accuracy of measuring the area of the snowpack
An improved geometric inequality via vanishing moments, with applications to singular Liouville equations
We consider a class of singular Liouville equations on compact surfaces
motivated by the study of Electroweak and Self-Dual Chern-Simons theories, the
Gaussian curvature prescription with conical singularities and Onsager's
description of turbulence. We analyse the problem of existence variationally,
and show how the angular distribution of the conformal volume near the
singularities may lead to improvements in the Moser-Trudinger inequality, and
in turn to lower bounds on the Euler-Lagrange functional. We then discuss
existence and non-existence results.Comment: some references adde
How distant? An experimental analysis of students’ COVID-19 exposure and physical distancing in university buildings
University buildings are significant closed built environments for COVID-19
spreading. As universities prepare to re-start in-class activities, students'
adherence to physical distancing requirements is a priority topic. While
physical distancing in classrooms can be easily managed, the movement of
students inside common spaces can pose higher risks due to individuals'
proximity. This paper provides an experimental analysis of unidirectional
student flow inside a case-study university building, by investigating
students' movements and grouping behaviour according to physical distancing
requirements. Results show general adherence with the minimum required physical
distancing guidance, but some spaces, such as corridors, pose higher exposure
than doorways. Their width, in combination with group behaviour, affects the
students' capacity to keep the recommended distance. Furthermore, students
report higher perceived vulnerability while moving along corridors.
Evidence-based results can support decision-makers in understanding
individuals' exposure in universities and researchers in developing behavioural
models in preparation of future outbreaks and pandemics.Comment: 22 pages, 5 figures, 1 table. Currently submitted to "International
Journal of Disaster Risk Reduction
New improved Moser-Trudinger inequalities and singular Liouville equations on compact surfaces
We consider a singular Liouville equation on a compact surface, arising from
the study of Chern-Simons vortices in a self dual regime. Using new improved
versions of the Moser-Trudinger inequalities (whose main feature is to be
scaling invariant) and a variational scheme, we prove new existence results.Comment: to appear in GAF
How distant? An experimental analysis of students’ COVID-19 exposure and physical distancing in university buildings
Closed university buildings proved to be one of the main hot spots for virus transmission during pandemics. As shown during the COVID-19 pandemic, physical distancing is one of the most effective measures to limit such transmission. As universities prepare to manage in-class activities, students’ adherence to physical distancing requirements is a priority topic. Unfortunately, while physical distancing in classrooms can be easily managed, the movement of students inside common spaces can pose high risk of close proximity. This paper provides an experimental analysis of unidirectional student movement inside a case-study university building to investigate how physical distancing requirements impact student movement and grouping behaviour. Results show general adherence with the minimum required physical distancing guidance, but spaces such as corridors pose higher risk of exposure than doorways. Doorway width, in combination with group behaviour, affect the students' capacity to keep the recommended physical distance. Furthermore, questionnaire results show that students report higher perceived vulnerability while moving along corridors. Evidence-based results can support decision-makers in understanding individuals’ exposure to COVID-19 in universities and researchers in developing behavioural models in preparation of future outbreaks and pandemics
Microwave broadband characterization of aging of SU-8 polymer as CPW substrate
In this paper we present the methodology and the
numerical results related to the analysis of aging of the SU-
8 polymer when used as a primary layer for the realization
of Coplanar Waveguide (CPW) structures. As test devices,
we used a set of transmission lines with different lengths and
T-shaped open stubs shunt resonators; by using these
geometries, we are able to acquire the data in a broadband
range, in principle between 1 GHz and 40 GHz. We conduct
the analysis by comparing two different technology run: the
first wafer with a deposited layer by a 12-year-old SU-8 and
the second wafer, with the same photolithographed metallic
geometries, with a brand-new processed SU-8 photoresist
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