27,062 research outputs found
Joint Quantization and Diffusion for Compressed Sensing Measurements of Natural Images
Recent research advances have revealed the computational secrecy of the
compressed sensing (CS) paradigm. Perfect secrecy can also be achieved by
normalizing the CS measurement vector. However, these findings are established
on real measurements while digital devices can only store measurements at a
finite precision. Based on the distribution of measurements of natural images
sensed by structurally random ensemble, a joint quantization and diffusion
approach is proposed for these real-valued measurements. In this way, a
nonlinear cryptographic diffusion is intrinsically imposed on the CS process
and the overall security level is thus enhanced. Security analyses show that
the proposed scheme is able to resist known-plaintext attack while the original
CS scheme without quantization cannot. Experimental results demonstrate that
the reconstruction quality of our scheme is comparable to that of the original
one.Comment: 4 pages, 4 figure
Varimax rotation based on gradient projection needs between 10 and more than 500 random start loading matrices for optimal performance
Gradient projection rotation (GPR) is a promising method to rotate factor or
component loadings by different criteria. Since the conditions for optimal
performance of GPR-Varimax are widely unknown, this simulation study
investigates GPR towards the Varimax criterion in principal component analysis.
The conditions of the simulation study comprise two sample sizes (n = 100, n =
300), with orthogonal simple structure population models based on four numbers
of components (3, 6, 9, 12), with- and without Kaiser-normalization, and six
numbers of random start loading matrices for GPR-Varimax rotation (1, 10, 50,
100, 500, 1,000). GPR-Varimax rotation always performed better when at least 10
random matrices were used for start loadings instead of the identity matrix.
GPR-Varimax worked better for a small number of components, larger (n = 300) as
compared to smaller (n = 100) samples, and when loadings were Kaiser-normalized
before rotation. To ensure optimal (stationary) performance of GPR-Varimax in
recovering orthogonal simple structure, we recommend using at least 10
iterations of start loading matrices for the rotation of up to three components
and 50 iterations for up to six components. For up to nine components, rotation
should be based on a sample size of at least 300 cases, Kaiser-normalization,
and more than 50 different start loading matrices. For more than nine
components, GPR-Varimax rotation should be based on at least 300 cases,
Kaiser-normalization, and at least 500 different start loading matrices.Comment: 19 pages, 8 figures, 2 tables, 4 figures in the Supplemen
Non-iterative RGB-D-inertial Odometry
This paper presents a non-iterative solution to RGB-D-inertial odometry
system. Traditional odometry methods resort to iterative algorithms which are
usually computationally expensive or require well-designed initialization. To
overcome this problem, this paper proposes to combine a non-iterative front-end
(odometry) with an iterative back-end (loop closure) for the RGB-D-inertial
SLAM system. The main contribution lies in the novel non-iterative front-end,
which leverages on inertial fusion and kernel cross-correlators (KCC) to match
point clouds in frequency domain. Dominated by the fast Fourier transform
(FFT), our method is only of complexity , where is
the number of points. Map fusion is conducted by element-wise operations, so
that both time and space complexity are further reduced. Extensive experiments
show that, due to the lightweight of the proposed front-end, the framework is
able to run at a much faster speed yet still with comparable accuracy with the
state-of-the-arts
Video Compressive Sensing for Dynamic MRI
We present a video compressive sensing framework, termed kt-CSLDS, to
accelerate the image acquisition process of dynamic magnetic resonance imaging
(MRI). We are inspired by a state-of-the-art model for video compressive
sensing that utilizes a linear dynamical system (LDS) to model the motion
manifold. Given compressive measurements, the state sequence of an LDS can be
first estimated using system identification techniques. We then reconstruct the
observation matrix using a joint structured sparsity assumption. In particular,
we minimize an objective function with a mixture of wavelet sparsity and joint
sparsity within the observation matrix. We derive an efficient convex
optimization algorithm through alternating direction method of multipliers
(ADMM), and provide a theoretical guarantee for global convergence. We
demonstrate the performance of our approach for video compressive sensing, in
terms of reconstruction accuracy. We also investigate the impact of various
sampling strategies. We apply this framework to accelerate the acquisition
process of dynamic MRI and show it achieves the best reconstruction accuracy
with the least computational time compared with existing algorithms in the
literature.Comment: 30 pages, 9 figure
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