490 research outputs found
RIDI: Robust IMU Double Integration
This paper proposes a novel data-driven approach for inertial navigation,
which learns to estimate trajectories of natural human motions just from an
inertial measurement unit (IMU) in every smartphone. The key observation is
that human motions are repetitive and consist of a few major modes (e.g.,
standing, walking, or turning). Our algorithm regresses a velocity vector from
the history of linear accelerations and angular velocities, then corrects
low-frequency bias in the linear accelerations, which are integrated twice to
estimate positions. We have acquired training data with ground-truth motions
across multiple human subjects and multiple phone placements (e.g., in a bag or
a hand). The qualitatively and quantitatively evaluations have demonstrated
that our algorithm has surprisingly shown comparable results to full Visual
Inertial navigation. To our knowledge, this paper is the first to integrate
sophisticated machine learning techniques with inertial navigation, potentially
opening up a new line of research in the domain of data-driven inertial
navigation. We will publicly share our code and data to facilitate further
research
A framework for space-efficient string kernels
String kernels are typically used to compare genome-scale sequences whose
length makes alignment impractical, yet their computation is based on data
structures that are either space-inefficient, or incur large slowdowns. We show
that a number of exact string kernels, like the -mer kernel, the substrings
kernels, a number of length-weighted kernels, the minimal absent words kernel,
and kernels with Markovian corrections, can all be computed in time and
in bits of space in addition to the input, using just a
data structure on the Burrows-Wheeler transform of the
input strings, which takes time per element in its output. The same
bounds hold for a number of measures of compositional complexity based on
multiple value of , like the -mer profile and the -th order empirical
entropy, and for calibrating the value of using the data
Pre-endoscopy SARS-CoV-2 testing strategy during COVID-19 pandemic: the care must go on
Background: In response to the COVID-19 pandemic, endoscopic societies initially recommended reduction of
endoscopic procedures. In particular non-urgent endoscopies should be postponed. However, this might lead to
unnecessary delay in diagnosing gastrointestinal conditions.
Methods: Retrospectively we analysed the gastrointestinal endoscopies performed at the Central Endoscopy Unit
of Saarland University Medical Center during seven weeks from 23 March to 10 May 2020 and present our real-world
single-centre experience with an individualized rtPCR-based pre-endoscopy SARS-CoV-2 testing strategy. We also
present our experience with this strategy in 2021.
Results: Altogether 359 gastrointestinal endoscopies were performed in the initial period. The testing strategy enabled us to conservatively handle endoscopy programme reduction (44% reduction as compared 2019) during the frst
wave of the COVID-19 pandemic. The results of COVID-19 rtPCR from nasopharyngeal swabs were available in 89%
of patients prior to endoscopies. Apart from six patients with known COVID-19, all other tested patients were negative. The frequencies of endoscopic therapies and clinically signifcant fndings did not difer between patients with
or without SARS-CoV-2 tests. In 2021 we were able to unrestrictedly perform all requested endoscopic procedures
(>5000 procedures) by applying the rtPCR-based pre-endoscopy SARS-CoV-2 testing strategy, regardless of next
waves of COVID-19. Only two out-patients (1893 out-patient procedures) were tested positive in the year 2021.
Conclusion: A structured pre-endoscopy SARS-CoV-2 testing strategy is feasible in the clinical routine of an endoscopy unit. rtPCR-based pre-endoscopy SARS-CoV-2 testing safely allowed unrestricted continuation of endoscopic
procedures even in the presence of high incidence rates of COVID-19. Given the low frequency of positive tests, the
absolute efect of pre-endoscopy testing on viral transmission may be low when FFP-2 masks are regularly used
Statistical Mechanical Development of a Sparse Bayesian Classifier
The demand for extracting rules from high dimensional real world data is
increasing in various fields. However, the possible redundancy of such data
sometimes makes it difficult to obtain a good generalization ability for novel
samples. To resolve this problem, we provide a scheme that reduces the
effective dimensions of data by pruning redundant components for bicategorical
classification based on the Bayesian framework. First, the potential of the
proposed method is confirmed in ideal situations using the replica method.
Unfortunately, performing the scheme exactly is computationally difficult. So,
we next develop a tractable approximation algorithm, which turns out to offer
nearly optimal performance in ideal cases when the system size is large.
Finally, the efficacy of the developed classifier is experimentally examined
for a real world problem of colon cancer classification, which shows that the
developed method can be practically useful.Comment: 13 pages, 6 figure
Angular sensitivity of blowfly photoreceptors: intracellular measurements and wave-optical predictions
The angular sensitivity of blowfly photoreceptors was measured in detail at wavelengths λ = 355, 494 and 588 nm.
The measured curves often showed numerous sidebands, indicating the importance of diffraction by the facet lens.
The shape of the angular sensitivity profile is dependent on wavelength. The main peak of the angular sensitivities at the shorter wavelengths was flattened. This phenomenon as well as the overall shape of the main peak can be quantitatively described by a wave-optical theory using realistic values for the optical parameters of the lens-photoreceptor system.
At a constant response level of 6 mV (almost dark adapted), the visual acuity of the peripheral cells R1-6 is at longer wavelengths mainly diffraction limited, while at shorter wavelengths the visual acuity is limited by the waveguide properties of the rhabdomere.
Closure of the pupil narrows the angular sensitivity profile at the shorter wavelengths. This effect can be fully described by assuming that the intracellular pupil progressively absorbs light from the higher order modes.
In light-adapted cells R1-6 the visual acuity is mainly diffraction limited at all wavelengths.
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