86 research outputs found
Consensus Message Passing for Layered Graphical Models
Generative models provide a powerful framework for probabilistic reasoning.
However, in many domains their use has been hampered by the practical
difficulties of inference. This is particularly the case in computer vision,
where models of the imaging process tend to be large, loopy and layered. For
this reason bottom-up conditional models have traditionally dominated in such
domains. We find that widely-used, general-purpose message passing inference
algorithms such as Expectation Propagation (EP) and Variational Message Passing
(VMP) fail on the simplest of vision models. With these models in mind, we
introduce a modification to message passing that learns to exploit their
layered structure by passing 'consensus' messages that guide inference towards
good solutions. Experiments on a variety of problems show that the proposed
technique leads to significantly more accurate inference results, not only when
compared to standard EP and VMP, but also when compared to competitive
bottom-up conditional models.Comment: Appearing in Proceedings of the 18th International Conference on
Artificial Intelligence and Statistics (AISTATS) 201
Simultaneous Orthogonal Planarity
We introduce and study the problem: Given planar
graphs each with maximum degree 4 and the same vertex set, do they admit an
OrthoSEFE, that is, is there an assignment of the vertices to grid points and
of the edges to paths on the grid such that the same edges in distinct graphs
are assigned the same path and such that the assignment induces a planar
orthogonal drawing of each of the graphs?
We show that the problem is NP-complete for even if the shared
graph is a Hamiltonian cycle and has sunflower intersection and for
even if the shared graph consists of a cycle and of isolated vertices. Whereas
the problem is polynomial-time solvable for when the union graph has
maximum degree five and the shared graph is biconnected. Further, when the
shared graph is biconnected and has sunflower intersection, we show that every
positive instance has an OrthoSEFE with at most three bends per edge.Comment: Appears in the Proceedings of the 24th International Symposium on
Graph Drawing and Network Visualization (GD 2016
ShapeClipper: Scalable 3D Shape Learning from Single-View Images via Geometric and CLIP-based Consistency
We present ShapeClipper, a novel method that reconstructs 3D object shapes
from real-world single-view RGB images. Instead of relying on laborious 3D,
multi-view or camera pose annotation, ShapeClipper learns shape reconstruction
from a set of single-view segmented images. The key idea is to facilitate shape
learning via CLIP-based shape consistency, where we encourage objects with
similar CLIP encodings to share similar shapes. We also leverage off-the-shelf
normals as an additional geometric constraint so the model can learn better
bottom-up reasoning of detailed surface geometry. These two novel consistency
constraints, when used to regularize our model, improve its ability to learn
both global shape structure and local geometric details. We evaluate our method
over three challenging real-world datasets, Pix3D, Pascal3D+, and OpenImages,
where we achieve superior performance over state-of-the-art methods.Comment: Accepted to CVPR 2023, project website at
https://zixuanh.com/projects/shapeclipper.htm
Inner Space Preserving Generative Pose Machine
Image-based generative methods, such as generative adversarial networks
(GANs) have already been able to generate realistic images with much context
control, specially when they are conditioned. However, most successful
frameworks share a common procedure which performs an image-to-image
translation with pose of figures in the image untouched. When the objective is
reposing a figure in an image while preserving the rest of the image, the
state-of-the-art mainly assumes a single rigid body with simple background and
limited pose shift, which can hardly be extended to the images under normal
settings. In this paper, we introduce an image "inner space" preserving model
that assigns an interpretable low-dimensional pose descriptor (LDPD) to an
articulated figure in the image. Figure reposing is then generated by passing
the LDPD and the original image through multi-stage augmented hourglass
networks in a conditional GAN structure, called inner space preserving
generative pose machine (ISP-GPM). We evaluated ISP-GPM on reposing human
figures, which are highly articulated with versatile variations. Test of a
state-of-the-art pose estimator on our reposed dataset gave an accuracy over
80% on PCK0.5 metric. The results also elucidated that our ISP-GPM is able to
preserve the background with high accuracy while reasonably recovering the area
blocked by the figure to be reposed.Comment: http://www.northeastern.edu/ostadabbas/2018/07/23/inner-space-preserving-generative-pose-machine
Liquid crystal elastomer shell actuators with negative order parameter
Liquid crystals (LCs) are nonsolids with long-range orientational order, described by a scalar order parameter ⟨P2⟩=1/2⟨3cos2β−1⟩. Despite the vast set of existing LC materials, one-third of the order parameter value range, −1/2< 〈P2〉 < 0, has until now been inaccessible. Here, we present the first material with negative LC order parameter in its ground state, in the form of elastomeric shells. The optical and actuation characteristics are opposite to those of conventional LC elastomers (LCEs). This novel class of anti-ordered elastomers gives access to the previously secluded range of liquid crystallinity with 〈P2〉 < 0, providing new challenges for soft matter physics and adding a complementary type of LCE actuator that is attractive for applications in, e.g., soft robotic
A Closest Point Proposal for MCMC-based Probabilistic Surface Registration
We propose to view non-rigid surface registration as a probabilistic
inference problem. Given a target surface, we estimate the posterior
distribution of surface registrations. We demonstrate how the posterior
distribution can be used to build shape models that generalize better and show
how to visualize the uncertainty in the established correspondence.
Furthermore, in a reconstruction task, we show how to estimate the posterior
distribution of missing data without assuming a fixed point-to-point
correspondence.
We introduce the closest-point proposal for the Metropolis-Hastings
algorithm. Our proposal overcomes the limitation of slow convergence compared
to a random-walk strategy. As the algorithm decouples inference from modeling
the posterior using a propose-and-verify scheme, we show how to choose
different distance measures for the likelihood model.
All presented results are fully reproducible using publicly available data
and our open-source implementation of the registration framework
Process integration for purification and concentration of red cabbage (Brassica oleracea L.) anthocyanins
Multistage aqueous two phase extraction was carried out using polyethylene glycol (PEG) 4000/magnesium sulfate (14.8/10.3%, w/w) system. The phase forming polymer (PEG 4000) was successfully separated from anthocyanins employing organic–aqueous extraction. Different processes employed for the purification and concentration of anthocyanins were compared with one another. The highest concentration of anthocyanins (3123.45 mg/L and 43 °Brix) was obtained in case of integration of aqueous two phase extraction with forward osmosis. Non-enzymatic browning index (0.11) and degradation constant (0.21) were found to be lowest in case of the integrated process involving aqueous two phase extraction followed by forward osmosis when compared to other processes. Color density was found to increase from 0.6 to 14.56 and stability of anthocyanins (with respect to pH and temperature) was found to be more in case of integrated process (aqueous two phase extraction followed by forward osmosis)
- …