160 research outputs found
Stylizing Face Images via Multiple Exemplars
We address the problem of transferring the style of a headshot photo to face
images. Existing methods using a single exemplar lead to inaccurate results
when the exemplar does not contain sufficient stylized facial components for a
given photo. In this work, we propose an algorithm to stylize face images using
multiple exemplars containing different subjects in the same style. Patch
correspondences between an input photo and multiple exemplars are established
using a Markov Random Field (MRF), which enables accurate local energy transfer
via Laplacian stacks. As image patches from multiple exemplars are used, the
boundaries of facial components on the target image are inevitably
inconsistent. The artifacts are removed by a post-processing step using an
edge-preserving filter. Experimental results show that the proposed algorithm
consistently produces visually pleasing results.Comment: In CVIU 2017. Project Page:
http://www.cs.cityu.edu.hk/~yibisong/cviu17/index.htm
Atomistic Study of the Effect of Magnesium Dopants on the Strength of Nanocrystalline Aluminum
Atomistic simulations have been used to study the deformation mechanisms of nanocrystalline pure Al and Al-Mg binary alloys. Voronoi tessellation was used to fully create a three-dimensional polycrystalline model with a grain size of 10 nm, while hybrid Monte Carlo and molecular dynamic simulations were used to achieve both mechanical and chemical equilibriums in nanocrystalline Al-5 at.%Mg. The results of tensile tests show an improved strength, including the yield strength and ultimate strength, through doping 5 at.%Mg into nanocrystalline aluminum. The results of atomic structures clearly reveal the multiple strengthening mechanisms related to doping in Al-Mg alloys. At the early deformation stage, up to an applied strain of 0.2, the strengthening mechanism of the dopants exhibits as dopant pinning grain boundary (GB) migration. However, at the late deformation stage, which is close to failure of nanocrystalline materials, dopants can prohibit the initiation of intergranular cracks and also impede propagation of existing cracks along the GBs, thus improving the flow stress of Al-Mg alloys
Learning to Hallucinate Face Images via Component Generation and Enhancement
We propose a two-stage method for face hallucination. First, we generate
facial components of the input image using CNNs. These components represent the
basic facial structures. Second, we synthesize fine-grained facial structures
from high resolution training images. The details of these structures are
transferred into facial components for enhancement. Therefore, we generate
facial components to approximate ground truth global appearance in the first
stage and enhance them through recovering details in the second stage. The
experiments demonstrate that our method performs favorably against
state-of-the-art methodsComment: IJCAI 2017. Project page:
http://www.cs.cityu.edu.hk/~yibisong/ijcai17_sr/index.htm
Analysis of a discrete-layout bimorph disk elements piezoelectric deformable mirror
We introduce a discrete-layout bimorph disk elements piezoelectric deformable mirror (DBDEPDM), driven by the circular flexural-mode piezoelectric actuators. We formulated an electromechanical model for analyzing the performance of the new deformable mirror. As a numerical example, a 21-actuators DBDEPDM with an aperture of 165 mm was modeled. The presented results demonstrate that the DBDEPDM has a stroke larger than 10  μm and the resonance frequency is 4.456 kHz. Compared with the conventional piezoelectric deformable mirrors, the DBDEPDM has a larger stroke, higher resonance frequency, and provides higher spatial resolution due to the circular shape of its actuators. Moreover, numerical simulations of influence functions on the model are provided
Role of disordered bipolar complexions on the sulfur embrittlement of nickel general grain boundaries
Minor impurities can cause catastrophic fracture of normally ductile metals. Here, a classic example is represented by the sulfur embrittlement of nickel, whose atomic-level mechanism has puzzled researchers for nearly a century. In this study, coupled aberration-corrected electron microscopy and semi-grand-canonical-ensemble atomistic simulation reveal, unexpectedly, the universal formation of amorphous-like and bilayer-like facets at the same general grain boundaries. Challenging the traditional view, the orientation of the lower-Miller-index grain surface, instead of the misorientation, dictates the interfacial structure. We also find partial bipolar structural orders in both amorphous-like and bilayer-like complexions (a.k.a. thermodynamically two-dimensional interfacial phases), which cause brittle intergranular fracture. Such bipolar, yet largely disordered, complexions can exist in and affect the properties of various other materials. Beyond the embrittlement mechanism, this study provides deeper insight to better understand abnormal grain growth in sulfur-doped Ni, and generally enriches our fundamental understanding of performance-limiting and more disordered interfaces
First-Order Interfacial Transformations with a Critical Point: Breaking the Symmetry at a Symmetric Tilt Grain Boundary
First-order interfacial phaselike transformations that break the mirror symmetry of the symmetric ∑5(210) tilt grain boundary (GB) are discovered by combining a modified genetic algorithm with hybrid Monte Carlo and molecular dynamics simulations. Density functional theory calculations confirm this prediction. This first-order coupled structural and adsorption transformation, which produces two variants of asymmetric bilayers, vanishes at an interfacial critical point. A GB complexion (phase) diagram is constructed via semigrand canonical ensemble atomistic simulations for the first time
Joint Face Hallucination and Deblurring via Structure Generation and Detail Enhancement
We address the problem of restoring a high-resolution face image from a
blurry low-resolution input. This problem is difficult as super-resolution and
deblurring need to be tackled simultaneously. Moreover, existing algorithms
cannot handle face images well as low-resolution face images do not have much
texture which is especially critical for deblurring. In this paper, we propose
an effective algorithm by utilizing the domain-specific knowledge of human
faces to recover high-quality faces. We first propose a facial component guided
deep Convolutional Neural Network (CNN) to restore a coarse face image, which
is denoted as the base image where the facial component is automatically
generated from the input face image. However, the CNN based method cannot
handle image details well. We further develop a novel exemplar-based detail
enhancement algorithm via facial component matching. Extensive experiments show
that the proposed method outperforms the state-of-the-art algorithms both
quantitatively and qualitatively.Comment: In IJCV 201
Ballistic-diffusive phonon heat transport across grain boundaries
The propagation of a heat pulse in a single crystal and across grain boundaries (GBs) is simulated using a concurrent atomistic-continuum method furnished with a coherent phonon pulse model. With a heat pulse constructed based on a Bose-Einstein distribution of phonons, this work has reproduced the phenomenon of phonon focusing in single and polycrystalline materials. Simulation results provide visual evidence that the propagation of a heat pulse in crystalline solids with or without GBs is partially ballistic and partially diffusive, i.e., there is a co-existence of ballistic and diffusive thermal transport, with the long-wavelength phonons traveling ballistically while the short-wavelength phonons scatter with each other and travel diffusively. To gain a quantitative understanding of GB thermal resistance, the kinetic energy transmitted across GBs is monitored on the fly and the time-dependent energy transmission for each specimen is measured; the contributions of coherent and incoherent phonon transport to the energy transmission are estimated. Simulation results reveal that the presence of GBs modifies the nature of thermal transport, with the coherent long-wavelength phonons dominating the heat conduction in materials with GBs. In addition, it is found that phonon-GB interactions can result in reconstruction of GBs
One-for-All: Towards Universal Domain Translation with a Single StyleGAN
In this paper, we propose a novel translation model, UniTranslator, for
transforming representations between visually distinct domains under conditions
of limited training data and significant visual differences. The main idea
behind our approach is leveraging the domain-neutral capabilities of CLIP as a
bridging mechanism, while utilizing a separate module to extract abstract,
domain-agnostic semantics from the embeddings of both the source and target
realms. Fusing these abstract semantics with target-specific semantics results
in a transformed embedding within the CLIP space. To bridge the gap between the
disparate worlds of CLIP and StyleGAN, we introduce a new non-linear mapper,
the CLIP2P mapper. Utilizing CLIP embeddings, this module is tailored to
approximate the latent distribution in the P space, effectively acting as a
connector between these two spaces. The proposed UniTranslator is versatile and
capable of performing various tasks, including style mixing, stylization, and
translations, even in visually challenging scenarios across different visual
domains. Notably, UniTranslator generates high-quality translations that
showcase domain relevance, diversity, and improved image quality. UniTranslator
surpasses the performance of existing general-purpose models and performs well
against specialized models in representative tasks. The source code and trained
models will be released to the public
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