1,139 research outputs found
Generalized Projective Representations for sl(n+1)
It is well known that -dimensional projective group gives rise to a
non-homogenous representation of the Lie algebra on the polynomial
functions of the projective space. Using Shen's mixed product for Witt algebras
(also known as Larsson functor), we generalize the above representation of
to a non-homogenous representation on the tensor space of any
finite-dimensional irreducible -module with the polynomial space.
Moreover, the structure of such a representation is completely determined by
employing projection operator techniques and well-known Kostant's
characteristic identities for certain matrices with entries in the universal
enveloping algebra. In particular, we obtain a new one parameter family of
infinite-dimensional irreducible -modules, which are in general not
highest-weight type, for any given finite-dimensional irreducible
-module. The results could also be used to study the quantum field
theory with the projective group as the symmetry.Comment: 24page
An Approach for Chinese-Japanese Named Entity Equivalents Extraction Using Inductive Learning and Hanzi-Kanji Mapping Table
Named Entity Translation Equivalents extraction plays a critical role in machine translation (MT) and cross language information retrieval (CLIR). Traditional methods are often based on large-scale parallel or comparable corpora. However, the applicability of these studies is constrained, mainly because of the scarcity of parallel corpora of the required scale, especially for language pairs of Chinese and Japanese. In this paper, we propose a method considering the characteristics of Chinese and Japanese to automatically extract the Chinese-Japanese Named Entity (NE) translation equivalents based on inductive learning (IL) from monolingual corpora. The method adopts the Chinese Hanzi and Japanese Kanji Mapping Table (HKMT) to calculate the similarity of the NE instances between Japanese and Chinese. Then, we use IL to obtain partial translation rules for NEs by extracting the different parts from high similarity NE instances in Chinese and Japanese. In the end, the feedback processing updates the Chinese and Japanese NE entity similarity and rule sets. Experimental results show that our simple, efficient method, which overcomes the insufficiency of the traditional methods, which are severely dependent on bilingual resource. Compared with other methods, our method combines the language features of Chinese and Japanese with IL for automatically extracting NE pairs. Our use of a weak correlation bilingual text sets and minimal additional knowledge to extract NE pairs effectively reduces the cost of building the corpus and the need for additional knowledge. Our method may help to build a large-scale Chinese-Japanese NE translation dictionary using mono-lingual corpora
Noise and Speckle Reduction in Doppler Blood Flow Spectrograms Using an Adaptive Pulse-Coupled Neural Network
A novel method, called adaptive pulse coupled neural network (AD-PCNN) using a two-stage denoising strategy, is proposed to reduce noise and speckle in the spectrograms of Doppler blood flow signals. AD-PCNN contains an adaptive thresholding PCNN and a threshold decaying PCNN. Firstly, PCNN pulses based on the adaptive threshold filter a part of background noise in the spectrogram while isolating the remained noise and speckles. Subsequently, the speckles and noise of the denoised spectrogram are detected by the pulses generated through the threshold decaying PCNN and then are iteratively removed by the intensity variation to speckle or noise neurons. The relative root mean square (RRMS) error of the maximum frequency extracted from the AD-PCNN spectrogram of the simulated Doppler blood flow signals is decreased 25.2% on average compared to that extracted from the MPWD (matching pursuit with Wigner Distribution) spectrogram, and the RRMS error of the AD-PCNN spectrogram is decreased 10.8% on average compared to MPWD spectrogram. Experimental results of synthetic and clinical signals show that the proposed method is better than the MPWD in improving the accuracy of the spectrograms and their maximum frequency curves
Unified gas-kinetic wave-particle methods VII: diatomic gas with rotational and vibrational nonequilibrium
Hypersonic flow around a vehicle in near space flight is associated with
multiscale non-equilibrium physics at a large variation of local Knudsen number
from the leading edge highly compressible flow to the trailing edge particle
free transport. To accurately capture the solution in all flow regimes from the
continuum Navier-Stokes solution to the rarefied gas dynamics in a single
computation requires genuinely multiscale method. The unified gas-kinetic
wave-particle (UGKWP) method targets on the simulation of such a multicale
transport. Due to the wave-particle decomposition, the dynamics in the
Navier-Stokes wave and kinetic particle transport has been unified
systematically and efficiently under the unified gas-kinetic scheme (UGKS)
framework. In this study, the UGKWP method with the non-equilibrium among
translation, rotation and vibration modes, is developed based on a multiple
temperature relaxation model. The real gas effect for high speed flow in
different flow regimes has been properly captured. Numerical tests, including
Sod tube, normal shock structure, hypersonic flow around two-dimensional
cylinder and three-dimensional flow around a sphere and space vehicle, have
been conducted to validate the UGKWP method. In comparison with the discrete
velocity method (DVM)-based Boltzmann solver and particle-based direct
simulation Monte Carlo (DSMC) method, the UGKWP method shows remarkable
advantages in terms of computational efficiency, memory reduction, and
automatic recovering of multiscale solution
Contextual Modeling for 3D Dense Captioning on Point Clouds
3D dense captioning, as an emerging vision-language task, aims to identify
and locate each object from a set of point clouds and generate a distinctive
natural language sentence for describing each located object. However, the
existing methods mainly focus on mining inter-object relationship, while
ignoring contextual information, especially the non-object details and
background environment within the point clouds, thus leading to low-quality
descriptions, such as inaccurate relative position information. In this paper,
we make the first attempt to utilize the point clouds clustering features as
the contextual information to supply the non-object details and background
environment of the point clouds and incorporate them into the 3D dense
captioning task. We propose two separate modules, namely the Global Context
Modeling (GCM) and Local Context Modeling (LCM), in a coarse-to-fine manner to
perform the contextual modeling of the point clouds. Specifically, the GCM
module captures the inter-object relationship among all objects with global
contextual information to obtain more complete scene information of the whole
point clouds. The LCM module exploits the influence of the neighboring objects
of the target object and local contextual information to enrich the object
representations. With such global and local contextual modeling strategies, our
proposed model can effectively characterize the object representations and
contextual information and thereby generate comprehensive and detailed
descriptions of the located objects. Extensive experiments on the ScanRefer and
Nr3D datasets demonstrate that our proposed method sets a new record on the 3D
dense captioning task, and verify the effectiveness of our raised contextual
modeling of point clouds
Less Emphasis on Difficult Layer Regions: Curriculum Learning for Singularly Perturbed Convection-Diffusion-Reaction Problems
Although Physics-Informed Neural Networks (PINNs) have been successfully
applied in a wide variety of science and engineering fields, they can fail to
accurately predict the underlying solution in slightly challenging
convection-diffusion-reaction problems. In this paper, we investigate the
reason of this failure from a domain distribution perspective, and identify
that learning multi-scale fields simultaneously makes the network unable to
advance its training and easily get stuck in poor local minima. We show that
the widespread experience of sampling more collocation points in high-loss
layer regions hardly help optimize and may even worsen the results. These
findings motivate the development of a novel curriculum learning method that
encourages neural networks to prioritize learning on easier non-layer regions
while downplaying learning on harder layer regions. The proposed method helps
PINNs automatically adjust the learning emphasis and thereby facilitate the
optimization procedure. Numerical results on typical benchmark equations show
that the proposed curriculum learning approach mitigates the failure modes of
PINNs and can produce accurate results for very sharp boundary and interior
layers. Our work reveals that for equations whose solutions have large scale
differences, paying less attention to high-loss regions can be an effective
strategy for learning them accurately.Comment: 22 page
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