261 research outputs found
Comyco: Quality-Aware Adaptive Video Streaming via Imitation Learning
Learning-based Adaptive Bit Rate~(ABR) method, aiming to learn outstanding
strategies without any presumptions, has become one of the research hotspots
for adaptive streaming. However, it typically suffers from several issues,
i.e., low sample efficiency and lack of awareness of the video quality
information. In this paper, we propose Comyco, a video quality-aware ABR
approach that enormously improves the learning-based methods by tackling the
above issues. Comyco trains the policy via imitating expert trajectories given
by the instant solver, which can not only avoid redundant exploration but also
make better use of the collected samples. Meanwhile, Comyco attempts to pick
the chunk with higher perceptual video qualities rather than video bitrates. To
achieve this, we construct Comyco's neural network architecture, video datasets
and QoE metrics with video quality features. Using trace-driven and real-world
experiments, we demonstrate significant improvements of Comyco's sample
efficiency in comparison to prior work, with 1700x improvements in terms of the
number of samples required and 16x improvements on training time required.
Moreover, results illustrate that Comyco outperforms previously proposed
methods, with the improvements on average QoE of 7.5% - 16.79%. Especially,
Comyco also surpasses state-of-the-art approach Pensieve by 7.37% on average
video quality under the same rebuffering time.Comment: ACM Multimedia 201
Unsupervised Paraphrasing via Deep Reinforcement Learning
Paraphrasing is expressing the meaning of an input sentence in different
wording while maintaining fluency (i.e., grammatical and syntactical
correctness). Most existing work on paraphrasing use supervised models that are
limited to specific domains (e.g., image captions). Such models can neither be
straightforwardly transferred to other domains nor generalize well, and
creating labeled training data for new domains is expensive and laborious. The
need for paraphrasing across different domains and the scarcity of labeled
training data in many such domains call for exploring unsupervised paraphrase
generation methods. We propose Progressive Unsupervised Paraphrasing (PUP): a
novel unsupervised paraphrase generation method based on deep reinforcement
learning (DRL). PUP uses a variational autoencoder (trained using a
non-parallel corpus) to generate a seed paraphrase that warm-starts the DRL
model. Then, PUP progressively tunes the seed paraphrase guided by our novel
reward function which combines semantic adequacy, language fluency, and
expression diversity measures to quantify the quality of the generated
paraphrases in each iteration without needing parallel sentences. Our extensive
experimental evaluation shows that PUP outperforms unsupervised
state-of-the-art paraphrasing techniques in terms of both automatic metrics and
user studies on four real datasets. We also show that PUP outperforms
domain-adapted supervised algorithms on several datasets. Our evaluation also
shows that PUP achieves a great trade-off between semantic similarity and
diversity of expression
Successful Leptogenesis in SO(10) Unification with a Left-Right Symmetric Seesaw Mechanism
We study thermal leptogenesis in a broad class of supersymmetric SO(10)
models with a left-right symmetric seesaw mechanism, taking into account
flavour effects and the contribution of the next-to-lightest right-handed
neutrino supermultiplet. Assuming M_D = M_u and a normal hierarchy of light
neutrino masses, we show that four out of the eight right-handed neutrino mass
spectra reconstructed from low-energy neutrino data can lead to successful
leptogenesis with a reheating temperature in the (10^9 - 10^10) GeV range. In
the remaining four solutions, leptogenesis is dominated by N_2 decays, as in
the type I seesaw case. We find that some of these spectra can generate the
observed baryon asymmetry for reheating temperatures above 10^10 GeV, in
contrast to the type I case. Together with flavour effects, an accurate
description of charged fermion masses turns out to be a crucial ingredient in
the analysis.Comment: 32 pages, 23 figures. v2: 2 comments [below Eq. (53) and at the end
of the conclusions] and 1 reference added, typos corrected. Version to be
published in Nucl. Phys.
The UV Luminosity Function of Star-forming Galaxies via Dropout Selection at Redshifts z ~ 7 and 8 from the 2012 Ultra Deep Field Campaign
We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z â 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe ~0.65 (0.25) mag fainter in absolute UV magnitude, at z ~ 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z ~ 7 and 27 at z ~ 8. Incorporating brighter archival and ground-based samples, we measure the z â 7 UV luminosity function to an absolute magnitude limit of M_(UV) = â17 and find a faint end Schechter slope of É =-1.87^(+0.18)_(-0.17). Using a similar color-color selection at z â 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z â 8, É =-1.94^(+0.21)_(-0.24). We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique
CO2âHydroquinone Clathrate: Synthesis, Purification, Characterization and Crystal Structure
Organic clathrate compounds, particularly those formed between hydroquinone (HQ) and gases, are supramolecular entities recently highlighted as promising alternatives for applications such as gas storage and separation processes. This study provides new insights into CO2âHQ clathrate, which is a key structure in some of the proposed future applications of these compounds. We present a novel synthesis and purification of CO2âHQ clathrate monocrystals. Clathrate crystals obtained from a single synthesis and native HQ are characterized and compared using Raman/Fourier transform infrared/NMR spectroscopies, optical microscopy, and thermogravimetric analysis coupled to mass spectrometry. The molecular structure of the clathrate has been resolved by X-ray diffraction analysis, and detailed crystallographic information is presented for the first time
Soft Water Level Sensors for Characterizing the Hydrological Behaviour of Agricultural Catchments
An innovative soft water level sensor is proposed to characterize the hydrological behaviour of agricultural catchments by measuring rainfall and stream flows. This sensor works as a capacitor coupled with a capacitance to frequency converter and measures water level at an adjustable time step acquisition. It was designed to be handy, minimally invasive and optimized in terms of energy consumption and low-cost fabrication so as to multiply its use on several catchments under natural conditions. It was used as a stage recorder to measure water level dynamics in a channel during a runoff event and as a rain gauge to measure rainfall amount and intensity. Based on the Manning equation, a method allowed estimation of water discharge with a given uncertainty and hence runoff volume at an event or annual scale. The sensor was tested under controlled conditions in the laboratory and under real conditions in the field. Comparisons of the sensor to reference devices (tipping bucket rain gauge, hydrostatic pressure transmitter limnimeter, Venturi channelsâŠ) showed accurate results: rainfall intensities and dynamic responses were accurately reproduced and discharges were estimated with an uncertainty usually acceptable in hydrology. Hence, it was used to monitor eleven small agricultural catchments located in the Mediterranean region. Both catchment reactivity and water budget have been calculated. Dynamic response of the catchments has been studied at the event scale through the rising time determination and at the annual scale by calculating the frequency of occurrence of runoff events. It provided significant insight into catchment hydrological behaviour which could be useful for agricultural management perspectives involving pollutant transport, flooding event and global water balance
Probing the in vitro mechanism of action of cationic lipid/DNA lipoplexes at a nanometric scale
Cationic lipids are used for delivering nucleic acids (lipoplexes) into cells for both therapeutic and biological applications. A better understanding of the identified key-steps, including endocytosis, endosomal escape and nuclear delivery is required for further developments to improve their efficacy. Here, we developed a labelling protocol using aminated nanoparticles as markers for plasmid DNA to examine the intracellular route of lipoplexes in cell lines using transmission electron microscopy. Morphological changes of lipoplexes, membrane reorganizations and endosomal membrane ruptures were observed allowing the understanding of the lipoplex mechanism until the endosomal escape mediated by cationic lipids. The study carried out on two cationic lipids, bis(guanidinium)-tris(2-aminoethyl)amine-cholesterol (BGTC) and dioleyl succinyl paramomycin (DOSP), showed two pathways of endosomal escape that could explain their different transfection efficiencies. For BGTC, a partial or complete dissociation of DNA from cationic lipids occurred before endosomal escape while for DOSP, lipoplexes remained visible within ruptured vesicles suggesting a more direct pathway for DNA release and endosome escape. In addition, the formation of new multilamellar lipid assemblies was noted, which could result from the interaction between cationic lipids and cellular compounds. These results provide new insights into DNA transfer pathways and possible implications of cationic lipids in lipid metabolism
Interpreting Deep Learning-Based Networking Systems
While many deep learning (DL)-based networking systems have demonstrated
superior performance, the underlying Deep Neural Networks (DNNs) remain
blackboxes and stay uninterpretable for network operators. The lack of
interpretability makes DL-based networking systems prohibitive to deploy in
practice. In this paper, we propose Metis, a framework that provides
interpretability for two general categories of networking problems spanning
local and global control. Accordingly, Metis introduces two different
interpretation methods based on decision tree and hypergraph, where it converts
DNN policies to interpretable rule-based controllers and highlight critical
components based on analysis over hypergraph. We evaluate Metis over several
state-of-the-art DL-based networking systems and show that Metis provides
human-readable interpretations while preserving nearly no degradation in
performance. We further present four concrete use cases of Metis, showcasing
how Metis helps network operators to design, debug, deploy, and ad-hoc adjust
DL-based networking systems.Comment: To appear at ACM SIGCOMM 202
- âŠ