4,702 research outputs found
Exact multi-parameter persistent homology of time-series data: one-dimensional reduction of multi-parameter persistence theory
In various applications of data classification and clustering problems,
multi-parameter analysis is effective and crucial because data are usually
defined in multi-parametric space. Multi-parameter persistent homology, an
extension of persistent homology of one-parameter data analysis, has been
developed for topological data analysis (TDA). Although it is conceptually
attractive, multi-parameter persistent homology still has challenges in theory
and practical applications. In this study, we consider time-series data and its
classification and clustering problems using multi-parameter persistent
homology. We develop a multi-parameter filtration method based on Fourier
decomposition and provide an exact formula and its interpretation of
one-dimensional reduction of multi-parameter persistent homology. The exact
formula implies that the one-dimensional reduction of multi-parameter
persistent homology of the given time-series data is equivalent to choosing
diagonal ray (standard ray) in the multi-parameter filtration space. For this,
we first consider the continuousization of time-series data based on Fourier
decomposition towards the construction of the exact persistent barcode formula
for the Vietoris-Rips complex of the point cloud generated by sliding window
embedding. The proposed method is highly efficient even if the sliding window
embedding dimension and the length of time-series data are large because the
method precomputes the exact barcode and the computational complexity is as low
as the fast Fourier transformation of . Further the proposed
method provides a way of finding different topological inferences by trying
different rays in the filtration space in no time.Comment: 29 page
Supervised low-rank semi-nonnegative matrix factorization with frequency regularization for forecasting spatio-temporal data
We propose a novel methodology for forecasting spatio-temporal data using
supervised semi-nonnegative matrix factorization (SSNMF) with frequency
regularization. Matrix factorization is employed to decompose spatio-temporal
data into spatial and temporal components. To improve clarity in the temporal
patterns, we introduce a nonnegativity constraint on the time domain along with
regularization in the frequency domain. Specifically, regularization in the
frequency domain involves selecting features in the frequency space, making an
interpretation in the frequency domain more convenient. We propose two methods
in the frequency domain: soft and hard regularizations, and provide convergence
guarantees to first-order stationary points of the corresponding constrained
optimization problem. While our primary motivation stems from geophysical data
analysis based on GRACE (Gravity Recovery and Climate Experiment) data, our
methodology has the potential for wider application. Consequently, when
applying our methodology to GRACE data, we find that the results with the
proposed methodology are comparable to previous research in the field of
geophysical sciences but offer clearer interpretability.Comment: 34 page
Rotting infinitely many-armed bandits
We consider the infinitely many-armed bandit problem with rotting rewards, where the mean reward of an arm decreases at each pull of the arm according to an arbitrary trend with maximum rotting rate ϱ=o(1). We show that this learning problem has an Ω(max{ϱ1/3T,T−−√}) worst-case regret lower bound where T is the time horizon. We show that a matching upper bound O~(max{ϱ1/3T,T−−√}), up to a poly-logarithmic factor, can be achieved by an algorithm that uses a UCB index for each arm and a threshold value to decide whether to continue pulling an arm or remove the arm from further consideration, when the algorithm knows the value of the maximum rotting rate ϱ. We also show that an O~(max{ϱ1/3T,T3/4}) regret upper bound can be achieved by an algorithm that does not know the value of ϱ, by using an adaptive UCB index along with an adaptive threshold value
Contextual Linear Bandits under Noisy Features: Towards Bayesian Oracles
We study contextual linear bandit problems under uncertainty on features;
they are noisy with missing entries. To address the challenges from the noise,
we analyze Bayesian oracles given observed noisy features. Our Bayesian
analysis finds that the optimal hypothesis can be far from the underlying
realizability function, depending on noise characteristics, which is highly
non-intuitive and does not occur for classical noiseless setups. This implies
that classical approaches cannot guarantee a non-trivial regret bound. We thus
propose an algorithm aiming at the Bayesian oracle from observed information
under this model, achieving regret bound with respect to
feature dimension and time horizon . We demonstrate the proposed
algorithm using synthetic and real-world datasets.Comment: 30 page
Are Histrionic Personality Traits Associated with Irritability during Conscious Sedation Endoscopy?
Aim. We aimed to evaluate whether histrionic personality traits are associated with irritability during conscious sedation endoscopy (CSE). Materials and Methods. A prospective cross-sectional study was planned. Irritability during CSE was classified into five grades: 0, no response; I, minimal movement; II, moderate movement; III, severe movement; IV, fighting against procedure. Patients in grades III and IV were defined as the irritable group. Participants were required to complete questionnaire sheet assessing the extent of histrionic personality traits, extraversion-introversion, and current psychological status. The present authors also collected basic sociodemographic data including alcohol use history. Results. A total of 32 irritable patients and 32 stable patients were analyzed. The histrionic personality trait score of the irritable group was higher than that of the stable group (9.5 ± 3.1 versus 6.9 ± 2.9; P = 0.001), as was the anxiety score (52.8 ± 8.6 versus 46.1 ± 9.6; P = 0.004). Heavy alcohol use was more frequently observed in the irritable group (65.6% versus 28.1%; P = 0.003). In multivariate analysis, all these three factors were independently correlated with irritability during CSE. Conclusion. This study revealed that histrionic personality traits, anxiety, and heavy alcohol use can affect irritability during CSE
Primary Candida guilliermondii Infection of the Knee in a Patient without Predisposing Factors
Isolated primary candidal infection of joint is extremely rare, with only a few reported cases. It occurs as a result of accidental implantations of fungus during traumatic procedures, such as surgery, and is usually reported in patients with predisposing factors such as immunosuppression, malignancy, and drug abuse. If left untreated, irreversible deformity and pain with severe osteoarticular destruction occur. Thus, early diagnosis and treatment are important. This paper presents a case of 72-year-old man with primary C. guilliermondii infection of knee joint without predisposing factors and previous traumatic procedures, who was misdiagnosed with advanced degenerative osteoarthritis. Our case is the second case of primary C. guilliermondii arthritis of knee to be reported in the English-language literature and the first to be successfully treated with total knee arthroplasty following IV amphotericin B and oral fluconazole. Primary candidal infection of joint is generally asymptomatic or involves only mild pain and swelling in the affected knee. Thus, although the majority of knee joint infections are of a pyogenic or tuberculous origin, if a patient complains of mild pain and swelling in the knee and has mild signs of infection, the possibility of fungal infection should be considered
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