684 research outputs found
Existence versus Exploitation: The Opacity of Backbones and Backdoors Under a Weak Assumption
Backdoors and backbones of Boolean formulas are hidden structural properties.
A natural goal, already in part realized, is that solver algorithms seek to
obtain substantially better performance by exploiting these structures.
However, the present paper is not intended to improve the performance of SAT
solvers, but rather is a cautionary paper. In particular, the theme of this
paper is that there is a potential chasm between the existence of such
structures in the Boolean formula and being able to effectively exploit them.
This does not mean that these structures are not useful to solvers. It does
mean that one must be very careful not to assume that it is computationally
easy to go from the existence of a structure to being able to get one's hands
on it and/or being able to exploit the structure.
For example, in this paper we show that, under the assumption that P
NP, there are easily recognizable families of Boolean formulas with strong
backdoors that are easy to find, yet for which it is hard (in fact,
NP-complete) to determine whether the formulas are satisfiable. We also show
that, also under the assumption P NP, there are easily recognizable sets
of Boolean formulas for which it is hard (in fact, NP-complete) to determine
whether they have a large backbone
Fast multipole networks
Two prerequisites for robotic multiagent systems are mobility and
communication. Fast multipole networks (FMNs) enable both ends within a unified
framework. FMNs can be organized very efficiently in a distributed way from
local information and are ideally suited for motion planning using artificial
potentials. We compare FMNs to conventional communication topologies, and find
that FMNs offer competitive communication performance (including higher network
efficiency per edge at marginal energy cost) in addition to advantages for
mobility
RecolorNeRF: Layer Decomposed Radiance Fields for Efficient Color Editing of 3D Scenes
Radiance fields have gradually become a main representation of media.
Although its appearance editing has been studied, how to achieve
view-consistent recoloring in an efficient manner is still under explored. We
present RecolorNeRF, a novel user-friendly color editing approach for the
neural radiance fields. Our key idea is to decompose the scene into a set of
pure-colored layers, forming a palette. By this means, color manipulation can
be conducted by altering the color components of the palette directly. To
support efficient palette-based editing, the color of each layer needs to be as
representative as possible. In the end, the problem is formulated as an
optimization problem, where the layers and their blending weights are jointly
optimized with the NeRF itself. Extensive experiments show that our
jointly-optimized layer decomposition can be used against multiple backbones
and produce photo-realistic recolored novel-view renderings. We demonstrate
that RecolorNeRF outperforms baseline methods both quantitatively and
qualitatively for color editing even in complex real-world scenes.Comment: To appear in ACM Multimedia 2023. Project website is accessible at
https://sites.google.com/view/recolorner
Optimization of antioxidant, mechanical and chemical physical properties of chitosan-sorbitol-gallic acid films by response surface methodology
The interest in the development of biodegradable films is increasing, which is related to the wide availability of resources and methods of synthesis to generate them. For this reason, in this study, the preparation of films containing chitosan, sorbitol and gallic acid this study was proposed. The incorporation of natural antioxidants into films modifies their structure and provides new functionality to them. In order to determine the optimal content of sorbitol and gallic acid in the formulation of the chitosan films to obtain the highest antioxidant capacity and the best mechanical properties, an experimental design based on a two-factor Doehlert model was used. The optimum condition of film synthesis was obtained when a mixture of 1 wt chitosan, 3.62 wt% of sorbitol and 1 wt% of gallic acid was performed. The properties studied were experimentally evaluated at this optimal point and compared with the model predictions, showing good results. It proved to be a promising material to be successfully used as packaging material.Fil: Raspo, Matías Alejandro. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; ArgentinaFil: Gomez, Cesar Gerardo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Andreatta, Alfonsina Ester. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; Argentin
Dust-penetrated morphology in the high-redshift universe: clues from NGC 922
Results from the Hubble Deep Field (HDF) North and South show a large
percentage of high-redshift galaxies whose appearance falls outside traditional
classification systems. The nature of these objects is poorly understood, but
sub-mm observations indicate that at least some of these systems are heavily
obscured (Sanders 2000). This raises the intriguing possibility that a
physically meaningful classification system for high-redshift galaxies might be
more easily devised at rest-frame infrared wavelengths, rather than in the
optical regime. Practical realization of this idea will become possible with
the advent of the Next Generation Space Telescope (NGST). In order to explore
the capability of NGST for undertaking such science, we present NASA-IRTF and
SCUBA observations of NGC 922, a chaotic system in our local Universe which
bears a striking resemblance to objects such as HDF 2-86 (z=0.749) in the HDF
North. If objects such as NGC 922 are common at high-redshifts, then this
galaxy may serve as a local morphological `Rosetta stone' bridging low and
high-redshift populations. In this paper we demonstrate that quantitative
measures of galactic structure are recoverable in the rest-frame infrared for
NGC 922 seen at high redshifts using NGST, by simulating the appearance of this
galaxy at redshifts z=0.7 and z=1.2 in rest-frame K'. Our results suggest that
the capability of efficiently exploring the rest-wavelength IR morphology of
high-z galaxies should probably be a key factor in deciding the final choice of
instruments for the NGST.Comment: 7 pages, 12 Figures. Accepted for publication in A&A. Better version
of the figures can be found at http://www.inaoep.mx/~puerari/ngs
COVID-19 detection and disease progression visualization: Deep learning on chest X-rays for classification and coarse localization
Chest X-rays are playing an important role in the testing and diagnosis of COVID-19 disease in the recent pandemic. However, due to the limited amount of labelled medical images, automated classification of these images for positive and negative cases remains the biggest challenge in their reliable use in diagnosis and disease progression. We implemented a transfer learning pipeline for classifying COVID-19 chest X-ray images from two publicly available chest X-ray datasets1,2. The classifier effectively distinguishes inflammation in lungs due to COVID-19 and Pneumonia from the ones with no infection (normal). We have used multiple pre-trained convolutional backbones as the feature extractor and achieved an overall detection accuracy of 90%, 94.3%, and 96.8% for the VGG16, ResNet50, and EfficientNetB0 backbones respectively. Additionally, we trained a generative adversarial framework (a CycleGAN) to generate and augment the minority COVID-19 class in our approach. For visual explanations and interpretation purposes, we implemented a gradient class activation mapping technique to highlight the regions of the input image that are important for predictions. Additionally, these visualizations can be used to monitor the affected lung regions during disease progression and severity stages
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