1,504 research outputs found
Manipulating Highly Deformable Materials Using a Visual Feedback Dictionary
The complex physical properties of highly deformable materials such as
clothes pose significant challenges fanipulation systems. We present a novel
visual feedback dictionary-based method for manipulating defoor autonomous
robotic mrmable objects towards a desired configuration. Our approach is based
on visual servoing and we use an efficient technique to extract key features
from the RGB sensor stream in the form of a histogram of deformable model
features. These histogram features serve as high-level representations of the
state of the deformable material. Next, we collect manipulation data and use a
visual feedback dictionary that maps the velocity in the high-dimensional
feature space to the velocity of the robotic end-effectors for manipulation. We
have evaluated our approach on a set of complex manipulation tasks and
human-robot manipulation tasks on different cloth pieces with varying material
characteristics.Comment: The video is available at goo.gl/mDSC4
Molecular Mechanics Studies of Protein Signaling and Conformation Change
Physiology signals can be passed by proteins. Many protein signaling starts from ligand binding and undergoes conformation change of the receptors. Many cellular surface receptor proteins contain a Von Willebrand factor (vWF), which is a large multimeric glycoprotein present in blood plasma. This dissertation employed molecular dynamics (MD) simulation to investigate the binding and signaling process of several vWF type A proteins. Chapter 2 discussed the potential errors modeling and MD sampling methods, and evaluated the accuracy and precision of free energy calculation. An optimized sampling strategy was established to obtain the best computational efficiency. The strategy can be applied to a wide range of protein binding research. The following chapters investigated the binding and signaling process of anthrax receptors and integrins, which are vWF type A proteins. Binding mechanism, possibility of conformational change, and the role of metal ion in binding process, were analyzed and compared for two structurally highly similar anthrax receptor proteins, tumor endothelial marker 8 (TEM8) and capillary morphogenesis gene 2 (CMG2). The two highly similar proteins are the drug target for distinct diseases. The differences in these two processes were found can guide the further development of drug specifically targeting one of the proteins. A conformation change between open and closed conformation is known to exist in most vWF type A proteins, but has not been experimentally observed in the anthrax receptors. Chapter 5 investigated the binding and conformation change process of integrins using targeted molecular dynamics simulation, and compared with anthrax receptors. The key residues and correlated motions in conformation change process were revealed, which can serve as a reference to the development in small molecule inhibitors of the signaling process. Results further confirmed the difficulties of observing conformation change in anthrax receptors
A Covert Data Transport Protocol
Both enterprise and national firewalls filter network connections. For data
forensics and botnet removal applications, it is important to establish the
information source. In this paper, we describe a data transport layer which
allows a client to transfer encrypted data that provides no discernible
information regarding the data source. We use a domain generation algorithm
(DGA) to encode AES encrypted data into domain names that current tools are
unable to reliably differentiate from valid domain names. The domain names are
registered using (free) dynamic DNS services. The data transmission format is
not vulnerable to Deep Packet Inspection (DPI).Comment: 8 pages, 10 figures, conferenc
Fine-grained Discriminative Localization via Saliency-guided Faster R-CNN
Discriminative localization is essential for fine-grained image
classification task, which devotes to recognizing hundreds of subcategories in
the same basic-level category. Reflecting on discriminative regions of objects,
key differences among different subcategories are subtle and local. Existing
methods generally adopt a two-stage learning framework: The first stage is to
localize the discriminative regions of objects, and the second is to encode the
discriminative features for training classifiers. However, these methods
generally have two limitations: (1) Separation of the two-stage learning is
time-consuming. (2) Dependence on object and parts annotations for
discriminative localization learning leads to heavily labor-consuming labeling.
It is highly challenging to address these two important limitations
simultaneously. Existing methods only focus on one of them. Therefore, this
paper proposes the discriminative localization approach via saliency-guided
Faster R-CNN to address the above two limitations at the same time, and our
main novelties and advantages are: (1) End-to-end network based on Faster R-CNN
is designed to simultaneously localize discriminative regions and encode
discriminative features, which accelerates classification speed. (2)
Saliency-guided localization learning is proposed to localize the
discriminative region automatically, avoiding labor-consuming labeling. Both
are jointly employed to simultaneously accelerate classification speed and
eliminate dependence on object and parts annotations. Comparing with the
state-of-the-art methods on the widely-used CUB-200-2011 dataset, our approach
achieves both the best classification accuracy and efficiency.Comment: 9 pages, to appear in ACM MM 201
Quantum Interactions in Topological R166 Kagome Magnet
Kagome magnet has been found to be a fertile ground for the search of exotic
quantum states in condensed matter. Arising from the unusual geometry, the
quantum interactions in the kagome lattice give rise to various quantum states,
including the Chern-gapped Dirac fermion, Weyl fermion, flat band and van Hove
singularity. Here we review recent advances in the study of the R166 kagome
magnet (RT6E6, R = rare earths; T = transition metals; and E = Sn, Ge, etc.)
whose crystal structure highlights the transition-metal-based kagome lattice
and rare-earth sublattice. Compared with other kagome magnets, the R166 family
owns the particularly strong interplays between the d electrons on the kagome
site and the localized f electrons on the rare-earth site. In the form of
spin-orbital coupling, exchange interaction and many-body effect, the quantum
interactions play an essential role in the Berry curvature field in both the
reciprocal and real spaces of R166 family. We discuss the spectroscopic and
transport visualization of the topological electrons hosted in the Mn kagome
layer of RMn6Sn6 and the various topological effects due to the quantum
interactions, including the Chern-gap opening, the exchange-biased effect, the
topological Hall effect and the emergent inductance. We hope this work serves
as a guide for future explorations of quantum magnets.Comment: Submitted versio
Multifault Models of the 2019 Ridgecrest Sequence Highlight Complementary Slip and Fault Junction Instability
The 2019 Ridgecrest M_w 6.4 and M_w 7.1 earthquakes ruptured a complex fault system, posing challenges in understanding their physical processes. Modeling of the ruptures relies on fault geometries at depth, which are usually assumed based on surface traces and aftershocks. Here we use seismic and geodetic data to jointly constrain the fault geometries and slip distributions. We first represent the first‐order rupture processes with a series of subevents, then conduct slip inversions with subevent‐guided fault geometries. We find that the foreshock sequentially ruptured the NW and SW striking faults starting from their junction. The mainshock initiated at a complex three‐fault junction along the extension of the foreshock NW rupture, with major slip first occurring bilaterally near the hypocenter and then minor unilateral slip later to the southeast end. The slip distributions of the foreshock and mainshock are complementary to each other on the overlapping fault section
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