13,470 research outputs found
Mechanism for bipolar resistive switching in transition metal oxides
We introduce a model that accounts for the bipolar resistive switching
phenomenom observed in transition metal oxides. It qualitatively describes the
electric field-enhanced migration of oxygen vacancies at the nano-scale. The
numerical study of the model predicts that strong electric fields develop in
the highly resistive dielectric-electrode interfaces, leading to a spatially
inhomogeneous oxygen vacancies distribution and a concomitant resistive
switching effect. The theoretical results qualitatively reproduce non-trivial
resistance hysteresis experiments that we also report, providing key validation
to our model.Comment: Accepted for publication in Physical Review B, 6 twocolumn pages, 5
figure
Hybrid flexible (HyFlex) seminar delivery – A technical overview of the implementation
This paper investigates a new technology for Hybrid flexible delivery (known as HyFlex), as implemented at King's College London. The relatively novel character of HyFlex, of mixing synchronously on-line and in-room teaching, and the recent changes due to the COVID-19 pandemic mean this use of the technology and teaching model is largely new to the UK. This research evaluated audio quality in the context of a HyFlex technical environment. The paper provides a high-level overview of the process of designing a HyFlex solution and presents a detailed evaluation of the impact of reverberation in relation to the accuracy of automatically generated subtitles and the influence of microphone selection. The paper shows that there was a significant relationship between the reverberation, the audio quality, and the subtitling system, which is important as past studies highlighted audio quality is key for the students' experience. It presents a viable and simple methodology to estimate the audio quality on installed HyFlex systems to improve the students experience in a hybrid teaching environment
Preliminary optical design of PANIC, a wide-field infrared camera for CAHA
In this paper, we present the preliminary optical design of PANIC (PAnoramic
Near Infrared camera for Calar Alto), a wide-field infrared imager for the
Calar Alto 2.2 m telescope. The camera optical design is a folded single
optical train that images the sky onto the focal plane with a plate scale of
0.45 arcsec per 18 micron pixel. A mosaic of four Hawaii 2RG of 2k x 2k made by
Teledyne is used as detector and will give a field of view of 31.9 arcmin x
31.9 arcmin. This cryogenic instrument has been optimized for the Y, J, H and K
bands. Special care has been taken in the selection of the standard IR
materials used for the optics in order to maximize the instrument throughput
and to include the z band. The main challenges of this design are: to produce a
well defined internal pupil which allows reducing the thermal background by a
cryogenic pupil stop; the correction of off-axis aberrations due to the large
field available; the correction of chromatic aberration because of the wide
spectral coverage; and the capability of introduction of narrow band filters
(~1%) in the system minimizing the degradation in the filter passband without a
collimated stage in the camera. We show the optomechanical error budget and
compensation strategy that allows our as built design to met the performances
from an optical point of view. Finally, we demonstrate the flexibility of the
design showing the performances of PANIC at the CAHA 3.5m telescope.Comment: This paper has been presented in the SPIE of Astronomical Telescopes
and Instrumentation 2008 in Marseille (France
Improving graph-based detection of singular events for photochemical smog agents
Recently, a set of graph-based tools have been introduced for the
identification of singular events of O3, NO2 and temperature time series, as
well as description of their dynamics. These are based on the use of the
Visibility Graphs (VG). In this work, an improvement of the original approach
is proposed, being called Upside-Down Visibility Graph (UDVG). It adds the
possibility of investigating the singular lowest episodes, instead of the
highest. Results confirm the applicability of the new method for describing the
multifractal nature of the underlying O3, NO2, and temperature. Asymmetries in
the NO2 degree distribution are observed, possibly due to the interaction with
different chemicals. Furthermore, a comparison of VG and UDVG has been
performed and the outcomes show that they describe opposite subsets of the time
series (low and high values) as expected. The combination of the results from
the two networks is proposed and evaluated, with the aim of obtaining all the
information at once. It turns out to be a more complete tool for singularity
detection in photochemical time series, which could be a valuable asset for
future research.Comment: 35 pages, 7 figure
The Effects of Different Intensities on Eccentric Cycling Blood Flow Patterns at a Concentric Cycling Workload Match
Decrease of blood flow to tissues, due to plaque built by atherosclerosis, increases mortality and morbidity. Homeostatic balance in the vascular system depends directly on endothelial cells, and blood flow, better known as endothelial sheer stress (ESS). Different types of blood flow patterns have been established measured by Reynolds number (Re), and turbulent flow has been associated with the decrease of ESS. Eccentric exercise (ECC) has gained attention as a novel exercise modality that increases muscle performance without increasing metabolic demands; however, little is known about ESS during ECC. PURPOSE: To determine the effects of ECC cycling in blood flow patterns in young, apparently healthy individuals. METHODS: 18 apparently healthy participants, were recruited for two laboratory visits. First visit served to obtain maximum oxygen consumption and peak power (PP), to determine workload intensities, followed by a 5-min familiarization on eccentric ergometer. Second visit on eccentric ergometer assessed blood flow patterns (i.e. ESS and Re measured via imaging ultrasound and Doppler) during a 3-workload steady exercise test at low, moderate, and high intensities. RESULTS: There was an interaction of exercise intensity on antegrade ESS (F(3,53.7)=26.90, p\u3c0.001), but not Sex (p\u3e0.05), and a random effect of participant (p\u3c0.001) and Re anterograde (F(3,53.6)=25.03, p\u3c0.001), but not Sex or random effect of participant (p\u3e0.05). There was an interaction of condition on retrograde ESS (F(3,53.4)=11.21, p\u3c0.001), but not Sex (p\u3e0.05), and a random effect of participant (p\u3c0.001). and Re retrograde (F(3,54.3)=12.34, p\u3c0.001), Sex (F(1,18.5)=4.41, p=0.05), and random effect of participant (p\u3e0.05). CONCLUSION: Eccentric cycling exercise produces exercise-induced blood flow patterns that are intensity-dependent in males and females and these patterns are similar to traditional concentric cycling
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