344 research outputs found
Reconsidering photometric estimation of local star formation environment and its correlation with Type Ia Supernova luminosity
Recent studies on the environmental dependence of Type Ia supernova (SN Ia)
luminosity focus on the local environment where the SN exploded, considering
that this is more directly linked to the SN progenitors. However, there is a
debate about the local environmental, specifically local star formation rate
(SFR), dependence of the SN Ia luminosity. A recent study claims that the
dependence is insignificant ( mag; ), based on the
local SFR measurement by fitting local photometry data. However, we
find that this photometric local SFR measurement is inaccurate. We argue this
based on the theoretical background of SFR measurement and the methodology used
to make that claim with their local photometry data, especially due to
a limited range of extinction parameters used when fitting the data. Therefore,
we re-analyse the same host galaxies with the same fitting code, but with more
physically motivated extinction treatments and global photometry of
host galaxies. We estimate global stellar mass and SFR. Then, local star
formation environments are inferred by using the method which showed that SNe
Ia in globally passive galaxies have locally passive environments, while those
in globally star-forming low-mass galaxies have locally star-forming
environments. We find that there is significant local environmental dependence
of SN Ia luminosities: SNe Ia in locally star-forming environments are
mag () fainter than those in locally passive
environments, even though SN Ia luminosities have been further corrected by the
BBC method that reduces the size of the dependence.Comment: 10 pages, 7 figures, 3 tables and 1 appendix table containing data we
used; accepted for publication in MNRA
Orcc's Compa-Backend demonstration
International audienceThis paper presents the implementation of a video decoding application starting from its dataflow and CAL representations. Our objective is to demonstrate the ability of the Open RVC-CAL Compiler (Orcc) to generate code for embedded systems. For the demonstration, the video application will be an MPEG-4 Part2 decoder. The targeted architecture is a multi-core heterogeneous system deployed onto the Zynq platform from Xilinx
Significant Carrier Extraction Enhancement at the Interface of an InN/p-GaN Heterojunction under Reverse Bias Voltage
In this paper, a superior-quality InN/p-GaN interface grown using pulsed metalorganic vapor-phase epitaxy (MOVPE) is demonstrated. The InN/p-GaN heterojunction interface based on high-quality InN (electron concentration 5.19 × 1018 cm−3 and mobility 980 cm2/(V s)) showed good rectifying behavior. The heterojunction depletion region width was estimated to be 22.8 nm and showed the ability for charge carrier extraction without external electrical field (unbiased). Under reverse bias, the external quantum efficiency (EQE) in the blue spectral region (300⁻550 nm) can be enhanced significantly and exceeds unity. Avalanche and carrier multiplication phenomena were used to interpret the exclusive photoelectric features of the InN/p-GaN heterojunction behavior
Laser module based on monolithically integrated MOPAs at 1.5 ”m for space-borne lidar applications
Space-borne lidar systems require laser transmitters with very good performance in terms of output power, beam quality, conversion efficiency, long term reliability and environmental compatibility. Atmospheric gas sensing additionally requires spectral purity and stability. Solid state lasers are considered the most mature technology for space lidar applications, at expenses of a relatively large size and low conversion efficiency [1]- [3]. Fiber lasers present very high power levels and very good beam quality, but they require specific attention due to their sensitivity to radiation. In this sense, progresses have been made to develop high power fiber amplifiers for different space applications [4]-[6]. Recently, a new generation of high brightness semiconductor lasers based on tapered geometry has demonstrated relatively high average power levels together with a good beam quality [7]-[10]. These devices are emerging candidates for its direct use in space lidar systems
Room-temperature continuous-wave topological Dirac-vortex microcavity lasers on silicon
Robust laser sources are a fundamental building block for contemporary information technologies. Originating from condensed-matter physics, the concept of topology has recently entered the realm of optics, offering fundamentally new design principles for lasers with enhanced robustness. In analogy to the well-known Majorana fermions in topological superconductors, Dirac-vortex states have recently been investigated in passive photonic systems and are now considered as a promising candidate for robust lasers. Here, we experimentally realize the topological Dirac-vortex microcavity lasers in InAs/InGaAs quantum-dot materials monolithically grown on a silicon substrate. We observe room-temperature continuous-wave linearly polarized vertical laser emission at a telecom wavelength. We confirm that the wavelength of the Dirac-vortex laser is topologically robust against variations in the cavity size, and its free spectral range defies the universal inverse scaling law with the cavity size. These lasers will play an important role in CMOS-compatible photonic and optoelectronic systems on a chip
Room-temperature continuous-wave Dirac-vortex topological lasers on silicon
Robust laser sources are a fundamental building block for contemporary
information technologies. Originating from condensed-matter physics, the
concept of topology has recently entered the realm of optics, offering
fundamentally new design principles for lasers with enhanced robustness. In
analogy to the well-known Majorana fermions in topological superconductors,
Dirac-vortex states have recently been investigated in passive photonic systems
and are now considered as a promising candidate for single-mode large-area
lasers. Here, we experimentally realize the first Dirac-vortex topological
lasers in InAs/InGaAs quantum-dot materials monolithically grown on a silicon
substrate. We observe room-temperature continuous-wave single-mode linearly
polarized vertical laser emission at a telecom wavelength. Most importantly, we
confirm that the wavelength of the Dirac-vortex laser is topologically robust
against variations in the cavity size, and its free spectral range defies the
universal inverse scaling law with the cavity size. These lasers will play an
important role in CMOS-compatible photonic and optoelectronic systems on a
chip
GaAs Compounds Heteroepitaxy on Silicon for Opto and Nano Electronic Applications
III-V semiconductors present interesting properties and are already used in electronics, lightening and photonic devices. Integration of III-V devices onto a Si CMOS platform is already in production using III-V devices transfer. A promising way consists in using hetero-epitaxy processes to grow the III-V materials directly on Si and at the right place. To reach this objective, some challenges still needed to be overcome. In this contribution, we will show how to overcome the different challenges associated to the heteroepitaxy and integration of III-As onto a silicon platform. We present solutions to get rid of antiphase domains for GaAs grown on exact Si(100). To reduce the threading dislocations density, efficient ways based on either insertion of InGaAs/GaAs multilayers defect filter layers or selective epitaxy in cavities are implemented. All these solutions allows fabricating electrically pumped laser structures based on InAs quantum dots active region, required for photonic and sensing applications
ATCO2 corpus: A Large-Scale Dataset for Research on Automatic Speech Recognition and Natural Language Understanding of Air Traffic Control Communications
Personal assistants, automatic speech recognizers and dialogue understanding
systems are becoming more critical in our interconnected digital world. A clear
example is air traffic control (ATC) communications. ATC aims at guiding
aircraft and controlling the airspace in a safe and optimal manner. These
voice-based dialogues are carried between an air traffic controller (ATCO) and
pilots via very-high frequency radio channels. In order to incorporate these
novel technologies into ATC (low-resource domain), large-scale annotated
datasets are required to develop the data-driven AI systems. Two examples are
automatic speech recognition (ASR) and natural language understanding (NLU). In
this paper, we introduce the ATCO2 corpus, a dataset that aims at fostering
research on the challenging ATC field, which has lagged behind due to lack of
annotated data. The ATCO2 corpus covers 1) data collection and pre-processing,
2) pseudo-annotations of speech data, and 3) extraction of ATC-related named
entities. The ATCO2 corpus is split into three subsets. 1) ATCO2-test-set
corpus contains 4 hours of ATC speech with manual transcripts and a subset with
gold annotations for named-entity recognition (callsign, command, value). 2)
The ATCO2-PL-set corpus consists of 5281 hours of unlabeled ATC data enriched
with automatic transcripts from an in-domain speech recognizer, contextual
information, speaker turn information, signal-to-noise ratio estimate and
English language detection score per sample. Both available for purchase
through ELDA at http://catalog.elra.info/en-us/repository/browse/ELRA-S0484. 3)
The ATCO2-test-set-1h corpus is a one-hour subset from the original test set
corpus, that we are offering for free at https://www.atco2.org/data. We expect
the ATCO2 corpus will foster research on robust ASR and NLU not only in the
field of ATC communications but also in the general research community.Comment: Manuscript under review; The code will be available at
https://github.com/idiap/atco2-corpu
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