318 research outputs found
PEA265: Perceptual Assessment of Video Compression Artifacts
The most widely used video encoders share a common hybrid coding framework
that includes block-based motion estimation/compensation and block-based
transform coding. Despite their high coding efficiency, the encoded videos
often exhibit visually annoying artifacts, denoted as Perceivable Encoding
Artifacts (PEAs), which significantly degrade the visual Qualityof- Experience
(QoE) of end users. To monitor and improve visual QoE, it is crucial to develop
subjective and objective measures that can identify and quantify various types
of PEAs. In this work, we make the first attempt to build a large-scale
subjectlabelled database composed of H.265/HEVC compressed videos containing
various PEAs. The database, namely the PEA265 database, includes 4 types of
spatial PEAs (i.e. blurring, blocking, ringing and color bleeding) and 2 types
of temporal PEAs (i.e. flickering and floating). Each containing at least
60,000 image or video patches with positive and negative labels. To objectively
identify these PEAs, we train Convolutional Neural Networks (CNNs) using the
PEA265 database. It appears that state-of-theart ResNeXt is capable of
identifying each type of PEAs with high accuracy. Furthermore, we define PEA
pattern and PEA intensity measures to quantify PEA levels of compressed video
sequence. We believe that the PEA265 database and our findings will benefit the
future development of video quality assessment methods and perceptually
motivated video encoders.Comment: 10 pages,15 figures,4 table
Capacity Constrained Influence Maximization in Social Networks
Influence maximization (IM) aims to identify a small number of influential
individuals to maximize the information spread and finds applications in
various fields. It was first introduced in the context of viral marketing,
where a company pays a few influencers to promote the product. However, apart
from the cost factor, the capacity of individuals to consume content poses
challenges for implementing IM in real-world scenarios. For example, players on
online gaming platforms can only interact with a limited number of friends. In
addition, we observe that in these scenarios, (i) the initial adopters of
promotion are likely to be the friends of influencers rather than the
influencers themselves, and (ii) existing IM solutions produce sub-par results
with high computational demands. Motivated by these observations, we propose a
new IM variant called capacity constrained influence maximization (CIM), which
aims to select a limited number of influential friends for each initial adopter
such that the promotion can reach more users. To solve CIM effectively, we
design two greedy algorithms, MG-Greedy and RR-Greedy, ensuring the
-approximation ratio. To improve the efficiency, we devise the scalable
implementation named RR-OPIM+ with -approximation and
near-linear running time. We extensively evaluate the performance of 9
approaches on 6 real-world networks, and our solutions outperform all
competitors in terms of result quality and running time. Additionally, we
deploy RR-OPIM+ to online game scenarios, which improves the baseline
considerably.Comment: The technical report of the paper entitled 'Capacity Constrained
Influence Maximization in Social Networks' in SIGKDD'2
Experimental determination of the Weiss temperature of Mn-ac and Mn-ac-MeOH
We report measurements of the susceptibility in the temperature range from
K to K of a series of Mn-ac and Mn-ac-MeOH samples in
the shape of rectangular prisms of length and square cross-section of
side . The susceptibility obeys a Curie-Weiss Law, ,
where varies systematically with sample aspect ratio. Using published
demagnetization factors, we obtain for an infinitely long sample
corresponding to intrinsic ordering temperatures K and
K for Mn-ac and Mn-ac-MeOH, respectively. The
difference in for two materials that have nearly identical unit cell
volumes and lattice constant ratios suggests that, in addition to dipolar
interactions, there is a non-dipolar (exchange) contribution to the Weiss
temperature that differs in the two materials because of the difference in
ligand molecules.Comment: 4.5 page
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