420 research outputs found
Randomized Group-Greedy Method for Large-Scale Sensor Selection Problems
The randomized group-greedy method and its customized method for large-scale
sensor selection problems are proposed. The randomized greedy sensor selection
algorithm is applied straightforwardly to the group-greedy method, and a
customized method is also considered. In the customized method, a part of the
compressed sensor candidates is selected using the common greedy method or
other low-cost methods. This strategy compensates for the deterioration of the
solution due to compressed sensor candidates. The proposed methods are
implemented based on the D- and E-optimal design of experiments, and numerical
experiments are conducted using randomly generated sensor candidate matrices
with potential sensor locations of 10,000--1,000,000. The proposed method can
provide better optimization results than those obtained by the original
group-greedy method when a similar computational cost is spent as for the
original group-greedy method. This is because the group size for the
group-greedy method can be increased as a result of the compressed sensor
candidates by the randomized algorithm. Similar results were also obtained in
the real dataset. The proposed method is effective for the E-optimality
criterion, in which the objective function that the optimization by the common
greedy method is difficult due to the absence of submodularity of the objective
function. The idea of the present method can improve the performance of all
optimizations using a greedy algorithm
The Diagnosis and Treatment of Early-Stage Colorectal Cancer
The introduction of colorectal endoscopic submucosal dissection (ESD) has expanded the applications for endoscopic treatment; as a result, lesions with low metastatic potential can be treated endoscopically regardless of the lesion size. The most attractive feature of ESD is the achievement of en bloc resection with a lower local recurrence rate in comparison to that of endoscopic piecemeal mucosal resection. However, in case of gastric cancers, ESD is not as widely applied to the treatment of colorectal neoplasms because of its technical difficulty, longer procedural time, and increased perforation risk. In the movement toward diversified endoscopic treatment strategies for superficial colorectal neoplasms, endoscopists who begin to perform ESD need to recognize the indications of ESD, as well as the technical issues and associated complications of this procedure
Fast Data-driven Greedy Sensor Selection for Ridge Regression
We propose a data-driven sensor-selection algorithm for accurate estimation
of the target variables from the selected measurements. The target variables
are assumed to be estimated by a ridge-regression estimator which is trained
based on the data. The proposed algorithm greedily selects sensors for
minimization of the cost function of the estimator. Sensor selection which
prevents the overfitting of the resulting estimator can be realized by setting
a positive regularization parameter. The greedy solution is computed in quite a
short time by using some recurrent relations that we derive. Furthermore, we
show that sensor selection can be accelerated by dimensionality reduction of
the target variables without large deterioration of the estimation performance.
The effectiveness of the proposed algorithm is verified for two real-world
datasets. The first dataset is a dataset of sea surface temperature for sensor
selection for reconstructing large data, and the second is a dataset of surface
pressure distribution and yaw angle of a ground vehicle for sensor selection
for estimation. The experiments reveal that the proposed algorithm outperforms
some data-drive selection algorithms including the orthogonal matching pursuit
Measurement of positron lifetime to probe the mixed molecular states of liquid water
Positron lifetime spectra were measured in liquid water at temperatures
between 0c and 50c. The long lifetime of ortho-positronium atoms (o-Ps)
determined by electron pick-off in molecular substances decreases smoothly by
10% as the temperature is raised. This lifetime temperature dependence can be
explained by combining the Ps-bubble model and the mixture state model of
liquid water.Comment: 11 pages, 6 page
Data-Driven Sensor Selection Method Based on Proximal Optimization for High-Dimensional Data With Correlated Measurement Noise
The present paper proposes a data-driven sensor selection method for a
high-dimensional nondynamical system with strongly correlated measurement
noise. The proposed method is based on proximal optimization and determines
sensor locations by minimizing the trace of the inverse of the Fisher
information matrix under a block-sparsity hard constraint. The proposed method
can avoid the difficulty of sensor selection with strongly correlated
measurement noise, in which the possible sensor locations must be known in
advance for calculating the precision matrix for selecting sensor locations.
The problem can be efficiently solved by the alternating direction method of
multipliers, and the computational complexity of the proposed method is
proportional to the number of potential sensor locations when it is used in
combination with a low-rank expression of the measurement noise model. The
advantage of the proposed method over existing sensor selection methods is
demonstrated through experiments using artificial and real datasets
Detectability of Colon Polyp Using Computed Virtual Chromoendoscopy with Flexible Spectral Imaging Color Enhancement
The aim of this pilot study was to assess the feasibility of using computed virtual chromoendoscopy with the flexible spectral imaging color enhancement (FICE) for colon neoplasia screening. A modified back-to-back colonoscopy using FICE and white light in the right-sided colon was conducted prospectively for the consecutive patients attending for the postoperative (sigmoidectomy or anterior resection) follow-up colonoscopy. Histopathology of detected lesions was confirmed by evaluation of endoscopic resection or biopsy specimens. One-hundred and two patients were enrolled, and 100 patients (61 males and mean age 63 years) were finally analyzed. The total number of polyps detected by FICE and white light colonoscopy was 65 and 45, respectively. The miss rate for all polyps with FICE (24%) was significantly less than that with white light (46%) (P = 0.03). Colonoscopy using FICE could beneficially enhance the detection of neoplastic lesions in the right-sided colon compared to white light colonoscopy
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