6,201 research outputs found
A new ADMM algorithm for the Euclidean median and its application to robust patch regression
The Euclidean Median (EM) of a set of points in an Euclidean space
is the point x minimizing the (weighted) sum of the Euclidean distances of x to
the points in . While there exits no closed-form expression for the EM,
it can nevertheless be computed using iterative methods such as the Wieszfeld
algorithm. The EM has classically been used as a robust estimator of centrality
for multivariate data. It was recently demonstrated that the EM can be used to
perform robust patch-based denoising of images by generalizing the popular
Non-Local Means algorithm. In this paper, we propose a novel algorithm for
computing the EM (and its box-constrained counterpart) using variable splitting
and the method of augmented Lagrangian. The attractive feature of this approach
is that the subproblems involved in the ADMM-based optimization of the
augmented Lagrangian can be resolved using simple closed-form projections. The
proposed ADMM solver is used for robust patch-based image denoising and is
shown to exhibit faster convergence compared to an existing solver.Comment: 5 pages, 3 figures, 1 table. To appear in Proc. IEEE International
Conference on Acoustics, Speech, and Signal Processing, April 19-24, 201
Internames: a name-to-name principle for the future Internet
We propose Internames, an architectural framework in which names are used to
identify all entities involved in communication: contents, users, devices,
logical as well as physical points involved in the communication, and services.
By not having a static binding between the name of a communication entity and
its current location, we allow entities to be mobile, enable them to be reached
by any of a number of basic communication primitives, enable communication to
span networks with different technologies and allow for disconnected operation.
Furthermore, with the ability to communicate between names, the communication
path can be dynamically bound to any of a number of end-points, and the
end-points themselves could change as needed. A key benefit of our architecture
is its ability to accommodate gradual migration from the current IP
infrastructure to a future that may be a ubiquitous Information Centric
Network. Basic building blocks of Internames are: i) a name-based Application
Programming Interface; ii) a separation of identifiers (names) and locators;
iii) a powerful Name Resolution Service (NRS) that dynamically maps names to
locators, as a function of time/location/context/service; iv) a built-in
capacity of evolution, allowing a transparent migration from current networks
and the ability to include as particular cases current specific architectures.
To achieve this vision, shared by many other researchers, we exploit and expand
on Information Centric Networking principles, extending ICN functionality
beyond content retrieval, easing send-to-name and push services, and allowing
to use names also to route data in the return path. A key role in this
architecture is played by the NRS, which allows for the co-existence of
multiple network "realms", including current IP and non-IP networks, glued
together by a name-to-name overarching communication primitive.Comment: 6 page
alpha -Lactalbumin (LA) Stimulates Milk beta-1,4-Galactosyltransferase I (beta 4Gal-T1) to Transfer Glucose from UDP-glucose to N-Acetylglucosamine: CRYSTAL STRUCTURE OF beta 4Gal-T1·LA COMPLEX WITH UDP-Glc*
beta-1,4-Galactosyltransferase 1 (Gal-T1) transfers galactose (Gal) from UDP-Gal to N-acetylglucosamine (GlcNAc), which constitutes its normal galactosyltransferase (Gal-T) activity. In the presence of alpha -lactalbumin (LA), it transfers Gal to Glc, which is its lactose synthase (LS) activity. It also transfers glucose (Glc) from UDP-Glc to GlcNAc, constituting the glucosyltransferase (Glc-T) activity, albeit at an efficiency of only 0.3-0.4% of Gal-T activity. In the present study, we show that LA increases this activity almost 30-fold. It also enhances the Glc-T activity toward various N-acyl substituted glucosamine acceptors. Steady state kinetic studies of Glc-T reaction show that the Km for the donor and acceptor substrates are high in the absence of LA. In the presence of LA, the Km for the acceptor substrate is reduced 30-fold, whereas for UDP-Glc it is reduced only 5-fold. In order to understand this property, we have determined the crystal structures of the Gal-T1·LA complex with UDP-Glc·Mn2+ and with N-butanoyl-glucosamine (N-butanoyl-GlcN), a preferred sugar acceptor in the Glc-T activity. The crystal structures reveal that although the binding of UDP-Glc is quite similar to UDP-Gal, there are few significant differences observed in the hydrogen bonding interactions between UDP-Glc and Gal-T1. Based on the present kinetic and crystal structural studies, a possible explanation for the role of LA in the Glc-T activity has been proposed
CoMaL Tracking: Tracking Points at the Object Boundaries
Traditional point tracking algorithms such as the KLT use local 2D
information aggregation for feature detection and tracking, due to which their
performance degrades at the object boundaries that separate multiple objects.
Recently, CoMaL Features have been proposed that handle such a case. However,
they proposed a simple tracking framework where the points are re-detected in
each frame and matched. This is inefficient and may also lose many points that
are not re-detected in the next frame. We propose a novel tracking algorithm to
accurately and efficiently track CoMaL points. For this, the level line segment
associated with the CoMaL points is matched to MSER segments in the next frame
using shape-based matching and the matches are further filtered using
texture-based matching. Experiments show improvements over a simple
re-detect-and-match framework as well as KLT in terms of speed/accuracy on
different real-world applications, especially at the object boundaries.Comment: 10 pages, 10 figures, to appear in 1st Joint BMTT-PETS Workshop on
Tracking and Surveillance, CVPR 201
Is Explicit Congestion Notification usable with UDP?
We present initial measurements to determine if ECN is usable with
UDP traffic in the public Internet. This is interesting because ECN
is part of current IETF proposals for congestion control of UDPbased
interactive multimedia, and due to the increasing use of UDP
as a substrate on which new transport protocols can be deployed.
Using measurements from the author’s homes, their workplace,
and cloud servers in each of the nine EC2 regions worldwide, we
test reachability of 2500 servers from the public NTP server pool,
using ECT(0) and not-ECT marked UDP packets. We show that
an average of 98.97% of the NTP servers that are reachable using
not-ECT marked packets are also reachable using ECT(0) marked
UDP packets, and that ~98% of network hops pass ECT(0) marked
packets without clearing the ECT bits. We compare reachability of
the same hosts using ECN with TCP, finding that 82.0% of those
reachable with TCP can successfully negotiate and use ECN. Our
findings suggest that ECN is broadly usable with UDP traffic, and
that support for use of ECN with TCP has increased
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