1,731 research outputs found
Global optimum design of uniform FIR filter bank with magnitude constraints
The optimum design of a uniform finite impulse response filter bank can be formulated as a nonlinear semi-infinite optimization problem. However, this optimization problem is nonconvex with infinitely many inequality constraints. In this paper, we propose a new hybrid approach for solving this highly challenging nonlinear, nonconvex semi-infinite optimization problem. In this approach, a gradient-based method is used in conjunction with a filled function method to determine a global minimum of the problem. This new hybrid approach finds an optimal result independent of the initial guess of the solution. The method is applied to some existing examples. The results obtained are superior to those obtained by other existing methods. © 2008 IEEE
Gravitational Anomaly and Hawking Radiation of Brane World Black Holes
We apply Wilczek and his collaborators' anomaly cancellation approach to the
3-dimensional Schwarzschild- and BTZ-like brane world black holes induced by
the generalized C metrics in the Randall-Sundrum scenario. Based on the fact
that the horizon of brane world black hole will extend into the bulk spacetime,
we do the calculation from the bulk generalized C metrics side and show that
this approach also reproduces the correct Hawking radiation for these brane
world black holes. Besides, since this approach does not involve the dynamical
equation, it also shows that the Hawking radiation is only a kinematic effect.Comment: 11 pages. v2: minor changes and references adde
HDR-ChipQA: No-Reference Quality Assessment on High Dynamic Range Videos
We present a no-reference video quality model and algorithm that delivers
standout performance for High Dynamic Range (HDR) videos, which we call
HDR-ChipQA. HDR videos represent wider ranges of luminances, details, and
colors than Standard Dynamic Range (SDR) videos. The growing adoption of HDR in
massively scaled video networks has driven the need for video quality
assessment (VQA) algorithms that better account for distortions on HDR content.
In particular, standard VQA models may fail to capture conspicuous distortions
at the extreme ends of the dynamic range, because the features that drive them
may be dominated by distortions {that pervade the mid-ranges of the signal}. We
introduce a new approach whereby a local expansive nonlinearity emphasizes
distortions occurring at the higher and lower ends of the {local} luma range,
allowing for the definition of additional quality-aware features that are
computed along a separate path. These features are not HDR-specific, and also
improve VQA on SDR video contents, albeit to a reduced degree. We show that
this preprocessing step significantly boosts the power of distortion-sensitive
natural video statistics (NVS) features when used to predict the quality of HDR
content. In similar manner, we separately compute novel wide-gamut color
features using the same nonlinear processing steps. We have found that our
model significantly outperforms SDR VQA algorithms on the only publicly
available, comprehensive HDR database, while also attaining state-of-the-art
performance on SDR content
Making Video Quality Assessment Models Robust to Bit Depth
We introduce a novel feature set, which we call HDRMAX features, that when
included into Video Quality Assessment (VQA) algorithms designed for Standard
Dynamic Range (SDR) videos, sensitizes them to distortions of High Dynamic
Range (HDR) videos that are inadequately accounted for by these algorithms.
While these features are not specific to HDR, and also augment the equality
prediction performances of VQA models on SDR content, they are especially
effective on HDR. HDRMAX features modify powerful priors drawn from Natural
Video Statistics (NVS) models by enhancing their measurability where they
visually impact the brightest and darkest local portions of videos, thereby
capturing distortions that are often poorly accounted for by existing VQA
models. As a demonstration of the efficacy of our approach, we show that, while
current state-of-the-art VQA models perform poorly on 10-bit HDR databases,
their performances are greatly improved by the inclusion of HDRMAX features
when tested on HDR and 10-bit distorted videos.Comment: Published in IEEE Signal Processing Letters 202
HDR or SDR? A Subjective and Objective Study of Scaled and Compressed Videos
We conducted a large-scale study of human perceptual quality judgments of
High Dynamic Range (HDR) and Standard Dynamic Range (SDR) videos subjected to
scaling and compression levels and viewed on three different display devices.
HDR videos are able to present wider color gamuts, better contrasts, and
brighter whites and darker blacks than SDR videos. While conventional
expectations are that HDR quality is better than SDR quality, we have found
subject preference of HDR versus SDR depends heavily on the display device, as
well as on resolution scaling and bitrate. To study this question, we collected
more than 23,000 quality ratings from 67 volunteers who watched 356 videos on
OLED, QLED, and LCD televisions. Since it is of interest to be able to measure
the quality of videos under these scenarios, e.g. to inform decisions regarding
scaling, compression, and SDR vs HDR, we tested several well-known
full-reference and no-reference video quality models on the new database.
Towards advancing progress on this problem, we also developed a novel
no-reference model called HDRPatchMAX, that uses both classical and bit-depth
sensitive distortion statistics more accurately than existing metrics
Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry
It is shown that the Sigma-Omega model which is widely used in the study of
nuclear relativistic many-body problem can exactly be treated as an Abelian
massive gauge field theory. The quantization of this theory can perfectly be
performed by means of the general methods described in the quantum gauge field
theory. Especially, the local U(1) gauge symmetry of the theory leads to a
series of Ward-Takahashi identities satisfied by Green's functions and proper
vertices. These identities form an uniquely correct basis for the
renormalization of the theory. The renormalization is carried out in the
mass-dependent momentum space subtraction scheme and by the renormalization
group approach. With the aid of the renormalization boundary conditions, the
solutions to the renormalization group equations are given in definite
expressions without any ambiguity and renormalized S-matrix elememts are
exactly formulated in forms as given in a series of tree diagrams provided that
the physical parameters are replaced by the running ones. As an illustration of
the renormalization procedure, the one-loop renormalization is concretely
carried out and the results are given in rigorous forms which are suitable in
the whole energy region. The effect of the one-loop renormalization is examined
by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure
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