631 research outputs found
Blind Demixing for Low-Latency Communication
In the next generation wireless networks, lowlatency communication is
critical to support emerging diversified applications, e.g., Tactile Internet
and Virtual Reality. In this paper, a novel blind demixing approach is
developed to reduce the channel signaling overhead, thereby supporting
low-latency communication. Specifically, we develop a low-rank approach to
recover the original information only based on a single observed vector without
any channel estimation. Unfortunately, this problem turns out to be a highly
intractable non-convex optimization problem due to the multiple non-convex
rankone constraints. To address the unique challenges, the quotient manifold
geometry of product of complex asymmetric rankone matrices is exploited by
equivalently reformulating original complex asymmetric matrices to the
Hermitian positive semidefinite matrices. We further generalize the geometric
concepts of the complex product manifolds via element-wise extension of the
geometric concepts of the individual manifolds. A scalable Riemannian
trust-region algorithm is then developed to solve the blind demixing problem
efficiently with fast convergence rates and low iteration cost. Numerical
results will demonstrate the algorithmic advantages and admirable performance
of the proposed algorithm compared with the state-of-art methods.Comment: 14 pages, accepted by IEEE Transaction on Wireless Communicatio
Pair density wave, unconventional superconductivity, and non-Fermi liquid quantum critical phase in frustrated Kondo lattice
Motivated by the recent discovery of an intermediate quantum critical phase
between the antiferromagnetic order and the Fermi liquid in the frustrated
Kondo lattice CePdAl, we study here a Kondo-Heisenberg chain with frustrated
- XXZ interactions among local spins using the density matrix
renormalization group method. Our simulations reveal a global phase diagram
with rich ground states including the antiferromagnetic order, the
valence-bond-solid and bond-order-wave orders, the pair density wave state, the
uniform superconducting state, and the Luttinger liquid state. We show that
both the pair density wave and uniform superconductivity belong to the family
of Luther-Emery liquids and may arise from pair instability of an intermediate
quantum critical phase with medium Fermi volume in the presence of strong
quantum fluctuations, while the Luttinger liquid has a large Fermi volume. This
suggests a deep connection between the pair density wave, the unconventional
superconductivity, and the non-Fermi liquid quantum critical phase.Comment: 10 pages, 9 figure
Dual-Branch Temperature Scaling Calibration for Long-Tailed Recognition
The calibration for deep neural networks is currently receiving widespread
attention and research. Miscalibration usually leads to overconfidence of the
model. While, under the condition of long-tailed distribution of data, the
problem of miscalibration is more prominent due to the different confidence
levels of samples in minority and majority categories, and it will result in
more serious overconfidence. To address this problem, some current research
have designed diverse temperature coefficients for different categories based
on temperature scaling (TS) method. However, in the case of rare samples in
minority classes, the temperature coefficient is not generalizable, and there
is a large difference between the temperature coefficients of the training set
and the validation set. To solve this challenge, this paper proposes a
dual-branch temperature scaling calibration model (Dual-TS), which considers
the diversities in temperature parameters of different categories and the
non-generalizability of temperature parameters for rare samples in minority
classes simultaneously. Moreover, we noticed that the traditional calibration
evaluation metric, Excepted Calibration Error (ECE), gives a higher weight to
low-confidence samples in the minority classes, which leads to inaccurate
evaluation of model calibration. Therefore, we also propose Equal Sample Bin
Excepted Calibration Error (Esbin-ECE) as a new calibration evaluation metric.
Through experiments, we demonstrate that our model yields state-of-the-art in
both traditional ECE and Esbin-ECE metrics
Querying a Matrix Through Matrix-Vector Products
We consider algorithms with access to an unknown matrix M in F^{n x d} via matrix-vector products, namely, the algorithm chooses vectors v^1, ..., v^q, and observes Mv^1, ..., Mv^q. Here the v^i can be randomized as well as chosen adaptively as a function of Mv^1, ..., Mv^{i-1}. Motivated by applications of sketching in distributed computation, linear algebra, and streaming models, as well as connections to areas such as communication complexity and property testing, we initiate the study of the number q of queries needed to solve various fundamental problems. We study problems in three broad categories, including linear algebra, statistics problems, and graph problems. For example, we consider the number of queries required to approximate the rank, trace, maximum eigenvalue, and norms of a matrix M; to compute the AND/OR/Parity of each column or row of M, to decide whether there are identical columns or rows in M or whether M is symmetric, diagonal, or unitary; or to compute whether a graph defined by M is connected or triangle-free. We also show separations for algorithms that are allowed to obtain matrix-vector products only by querying vectors on the right, versus algorithms that can query vectors on both the left and the right. We also show separations depending on the underlying field the matrix-vector product occurs in. For graph problems, we show separations depending on the form of the matrix (bipartite adjacency versus signed edge-vertex incidence matrix) to represent the graph.
Surprisingly, this fundamental model does not appear to have been studied on its own, and we believe a thorough investigation of problems in this model would be beneficial to a number of different application areas
COMPARISON OF MARKER AND MARKERLESS MOTION CAPTURE SYSTEM FOR GAIT KINEMATICS
The purpose of this study was to compare gait kinematics measured with a markerless motion capture system against data measured with a marker-based motion capture system. A sample of 14 over-ground walking trials were captured simultaneously with two camcorders (60Hz) and an 8-camera marker system. The markerless data was further processed to landmarks using markerless human movement automatic capture system (FastMove). Body landmarks data of X and Z coordinates were highly consistent between the two systems, while data of Y coordinate showed low consistency. The Bland-Altman plots’ results showed low agreement between individual measurements of the maximum and minimum of knee and ankle flexion angles from both systems against the average of the measurement
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