Digital HDTV: A technical challenge

Author(s):  
Arun N. Netravali
Keyword(s):  
2015 ◽  
Vol 63 (S 01) ◽  
Author(s):  
M. Shrestha ◽  
H. Krüger ◽  
E. Beckmann ◽  
F. Fleissner ◽  
T. Kaufeld ◽  
...  

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 655-665
Author(s):  
Stephanie C. Malek ◽  
Adam C. Overvig ◽  
Sajan Shrestha ◽  
Nanfang Yu

AbstractActively tunable and reconfigurable wavefront shaping by optical metasurfaces poses a significant technical challenge often requiring unconventional materials engineering and nanofabrication. Most wavefront-shaping metasurfaces can be considered “local” in that their operation depends on the responses of individual meta-units. In contrast, “nonlocal” metasurfaces function based on the modes supported by many adjacent meta-units, resulting in sharp spectral features but typically no spatial control of the outgoing wavefront. Recently, nonlocal metasurfaces based on quasi-bound states in the continuum have been shown to produce designer wavefronts only across the narrow bandwidth of the supported Fano resonance. Here, we leverage the enhanced light-matter interactions associated with sharp Fano resonances to explore the active modulation of optical spectra and wavefronts by refractive-index tuning and mechanical stretching. We experimentally demonstrate proof-of-principle thermo-optically tuned nonlocal metasurfaces made of silicon and numerically demonstrate nonlocal metasurfaces that thermo-optically switch between distinct wavefront shapes. This meta-optics platform for thermally reconfigurable wavefront shaping requires neither unusual materials and fabrication nor active control of individual meta-units.


2020 ◽  
Author(s):  
Martin Biermann ◽  
Salim Kanoun ◽  
Trond Davidsen ◽  
Robert Gray

Abstract Aims Since 2017, medical students at the University of Bergen were taught PET/CT “hands-on” by viewing PET/CT cases in native format on diagnostic workstations in the hospital. Due to the COVID-19 pandemic, students were barred access. This prompted us to launch and evaluate a new freeware PET/CT viewing system hosted in the university network. Methods We asked our students to install the multiplatform Fiji viewer with Beth Israel PET/CT plugin (http://petctviewer.org) on their personal computers and connect to a central image database in the university network based on the public domain orthanc server (https://orthanc-server.com). At the end of course, we conducted an anonymous student survey. Results The new system was online within eight days, including regulatory approval. All 76 students (100 %) in the fifth year completed their course work, reading five anonymized PET/CT cases as planned. 41 (53 %) students answered the survey. Fiji was challenging to install with a mean score of 1.8 on a 5-point Likert scale (5 = easy, 1 = difficult). Fiji was more difficult to use (score 3.0) than the previously used diagnostic workstations in the hospital (score 4.1; p < 0.001, paired t-test). Despite the technical challenge, 47 % of students reported having learnt much (scores 4 and 5); only 11 % were negative (scores 1 and 2). 51 % found the PET/CT tasks engaging (scores 4 and 5) while 20 % and 5 % returned scores 2 and 1, respectively. Conclusion Despite the initial technical challenge, “hands-on” learning of PET/CT based on the freeware Fiji/orthanc PET/CT-viewer was associated with a high degree of student satisfaction. We plan to continue running the system to give students permanent access to PET/CT cases in native format regardless of time or location.


2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Kanato Goto ◽  
Thomas Hartman ◽  
Amirhossein Tajdini

Abstract Quantum extremal islands reproduce the unitary Page curve of an evaporating black hole. This has been derived by including replica wormholes in the gravitational path integral, but for the transient, evaporating black holes most relevant to Hawking’s paradox, these wormholes have not been analyzed in any detail. In this paper we study replica wormholes for black holes formed by gravitational collapse in Jackiw-Teitelboim gravity, and confirm that they lead to the island rule for the entropy. The main technical challenge is that replica wormholes rely on a Euclidean path integral, while the quantum extremal islands of an evaporating black hole exist only in Lorentzian signature. Furthermore, the Euclidean equations for the Schwarzian mode are non-local, so it is unclear how to connect to the local, Lorentzian dynamics of an evaporating black hole. We address these issues with Schwinger-Keldysh techniques and show how the non-local equations reduce to the local ‘boundary particle’ description in special cases.


2017 ◽  
Vol 99 (7) ◽  
pp. e213-e215
Author(s):  
S Anwer ◽  
R Egan ◽  
N Cross ◽  
S Guru Naidu ◽  
K Somasekar

Common bile duct stones in patients with a previous gastrectomy can be a technical challenge because of the altered anatomy. This paper presents the successful management of two such patients using non-traditional techniques as conventional endoscopic retrograde cholangiopancreatography was not possible.


2021 ◽  
Vol 26 (1-2) ◽  
pp. 187-188
Author(s):  
Michael Joel Bartelle
Keyword(s):  

2021 ◽  
Author(s):  
Ajmir Khan ◽  
Muhammad Naveed ◽  
Muhammad Rabnawaz

The melt-reprocessing of thermosets such as polyurethanes (PUs) and epoxy network materials has been a constant technical challenge. Here we report, for the first time, melt-reprocessing of mixed PUs made...


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