Hiroshi Sawada

ORCID: 0000-0002-4831-9286
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About
Contact & Profiles
Research Areas
  • Speech and Audio Processing
  • Blind Source Separation Techniques
  • Advanced Adaptive Filtering Techniques
  • Fluid Dynamics Simulations and Interactions
  • Ship Hydrodynamics and Maneuverability
  • Music and Audio Processing
  • Formal Methods in Verification
  • Spectroscopy and Chemometric Analyses
  • Neural Networks and Applications
  • Advanced Condensed Matter Physics
  • Optical Network Technologies
  • Ocean Waves and Remote Sensing
  • Photonic and Optical Devices
  • Human Mobility and Location-Based Analysis
  • Speech Recognition and Synthesis
  • Neural Networks and Reservoir Computing
  • Embedded Systems Design Techniques
  • Data Management and Algorithms
  • VLSI and Analog Circuit Testing
  • Electronic and Structural Properties of Oxides
  • Face and Expression Recognition
  • Structural Integrity and Reliability Analysis
  • Transportation Planning and Optimization
  • Machine Learning in Materials Science
  • Complex Network Analysis Techniques

NTT (Japan)
2015-2024

Yamagata University Hospital
2024

Miyagi Prefectural Hospital Organization
2024

National Agriculture and Food Research Organization
2023

National Institute of Animal Health
2023

National Maritime Research Institute
2003-2022

Kyoto Seika University
2004-2022

Showa Denko (Japan)
2002-2015

JEOL (Japan)
2002-2015

Nara Institute of Science and Technology
2009-2010

Blind source separation (BSS) for convolutive mixtures can be solved efficiently in the frequency domain, where independent component analysis (ICA) is performed separately each bin. However, frequency-domain BSS involves a permutation problem: ambiguity of ICA bin should aligned so that separated signal time-domain contains components same signal. This paper presents robust and precise method solving problem. It based on two approaches: direction arrival (DOA) estimation sources...

10.1109/tsa.2004.832994 article EN IEEE Transactions on Speech and Audio Processing 2004-08-16

This paper presents a blind source separation method for convolutive mixtures of speech/audio sources. The can even be applied to an underdetermined case where there are fewer microphones than operation is performed in the frequency domain and consists two stages. In first stage, frequency-domain mixture samples clustered into each by expectation-maximization (EM) algorithm. Since clustering bin-wise manner, permutation ambiguities should aligned. solved second stage using probability on how...

10.1109/tasl.2010.2051355 article EN IEEE Transactions on Audio Speech and Language Processing 2010-06-03

This paper addresses the determined blind source separation problem and proposes a new effective method unifying independent vector analysis (IVA) nonnegative matrix factorization (NMF). IVA is state-of-the-art technique that utilizes statistical independence between sources in mixture signal, an efficient optimization scheme has been proposed for IVA. However, since model based on spherical multivariate distribution, cannot utilize specific spectral structures such as harmonic of pitched...

10.1109/taslp.2016.2577880 article EN IEEE/ACM Transactions on Audio Speech and Language Processing 2016-06-07

This paper presents new formulations and algorithms for multichannel extensions of non-negative matrix factorization (NMF). The employ Hermitian positive semidefinite matrices to represent a version elements. Multichannel Euclidean distance Itakura-Saito (IS) divergence are defined based on appropriate statistical models utilizing multivariate complex Gaussian distributions. To minimize this distance/divergence, efficient optimization in the form multiplicative updates derived by using...

10.1109/tasl.2013.2239990 article EN IEEE Transactions on Audio Speech and Language Processing 2013-01-14

The authors present a novel exact algorithm and gradual improvement methods for minimizing binary decision diagrams (BDDs). In the minimization algorithm, optimum order is searched by exchanges of variables BDDs based on framework S.J. Friedman K.J. Supowit (1990). use BDD representation given function intermediate functions makes it possible to produce pruning into method, which drastically reduces computation cost. succeeded in 17-variable introduction pruning. They also propose greedy...

10.1109/iccad.1991.185307 article EN 2002-12-10

We propose a new framework for joint multichannel speech source separation and acoustic noise reduction. In this framework, we start by formulating the minimum-mean-square error (MMSE)-based solution in context of multiple simultaneous speakers background noise, outline importance estimation activities speakers. The latter is accurately achieved introducing latent variable that takes N+1 possible discrete states mixture N signals plus additive noise. Each state characterizes dominance one...

10.1109/tasl.2013.2263137 article EN IEEE Transactions on Audio Speech and Language Processing 2013-05-14

Abstract Magnetic Weyl semimetals have novel transport phenomena related to pairs of nodes in the band structure. Although existence fermions is expected various oxides, evidence oxide materials remains elusive. Here we show direct quantum an epitaxial 4 d ferromagnetic SrRuO 3 . We employ machine-learning-assisted molecular beam epitaxy synthesize films whose quality sufficiently high probe their intrinsic properties. Experimental observation five signatures fermions—the linear positive...

10.1038/s41467-020-18646-8 article EN cc-by Nature Communications 2020-10-09

Materials informatics exploiting machine learning techniques, e.g., Bayesian optimization (BO), have the potential to reduce number of thin-film growth runs for conditions through incremental updates models in accordance with newly measured data. Here, we demonstrated BO-based molecular beam epitaxy (MBE) SrRuO3, one most intensively studied materials research field oxide electronics, mainly owing its unique nature as a ferromagnetic metal. To simplify intricate search space entangled...

10.1063/1.5123019 article EN cc-by APL Materials 2019-10-01

This paper presents a new method for grouping bin-wise separated signals individual sources, i.e., solving the permutation problem, in process of frequency-domain blind source separation. Conventionally, correlation coefficient signal envelopes is calculated to judge whether or not originate from same source. In this paper, we propose measure that represents dominance mixtures, and use it calculating coefficient, instead envelope. Such measures exhibit dependence/independence more clearly...

10.1109/iscas.2007.378164 article EN 2022 IEEE International Symposium on Circuits and Systems (ISCAS) 2007-05-01

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes a new formulation and optimization procedure for grouping frequency components in frequency-domain blind source separation (BSS). We adopt two techniques, independent component analysis (ICA) time–frequency (T–F) masking, the BSS. With ICA, corresponds to aligning permutation ambiguity of ICA solution each bin. T–F classifying sensor observations domain individual sources. The...

10.1109/tasl.2007.899218 article EN IEEE Transactions on Audio Speech and Language Processing 2007-06-20

Fashion magazines contain a number of photographs fashion models, and their clothing coordinates serve as useful references. In this paper, we propose recommender system for using full-body from magazines. The task is that, given photograph item (e.g. tops) query, to recommend other items bottoms) that appropriate the query. With proposed method, use probabilistic topic model learning information about visual features in each region. We demonstrate effectiveness method real magazine two...

10.5591/978-1-57735-516-8/ijcai11-377 article EN International Joint Conference on Artificial Intelligence 2011-07-16

Understanding the impacts and patterns of network events such as link flaps or hardware errors is crucial for diagnosing anomalies. In large production networks, analyzing log messages that record has become a challenging task due to following two reasons. First, are composed unstructured text generated by vendor-specific rules. Second, equipment routers, switches, RADIUS severs generate various induced span across several geographical locations, layers, protocols, services. this paper, we...

10.1109/infocom.2014.6847986 article EN IEEE INFOCOM 2022 - IEEE Conference on Computer Communications 2014-04-01

We address the problem of underdetermined BSS. While most previous approaches are designed for instantaneous mixtures, we propose a time-frequency-domain algorithm convolutive mixtures. adopt two-step method based on general maximum posteriori (MAP) approach. In first step, estimate mixing matrix hierarchical clustering, assuming that source signals sufficiently sparse. The works directly complex-valued data in time-frequency domain and shows better convergence than algorithms...

10.1155/2007/24717 article EN cc-by EURASIP Journal on Advances in Signal Processing 2006-09-05

This paper presents a method for enhancing target sources of interest and suppressing other interference sources. The are assumed to be close sensors, have dominant powers at these non-Gaussianity. enhancement is performed blindly, i.e., without knowing the position active time each source. We consider general case where total number larger than neither nor known. based on two-stage process independent component analysis (ICA) first employed in frequency bin then time-frequency masking used...

10.1109/tasl.2006.872599 article EN IEEE Transactions on Audio Speech and Language Processing 2006-10-18

This paper derives two spatio-temporal extensions of the well-known FastICA algorithm Hyvarinen and Oja that are applicable to convolutive blind source separation task. Our time-domain algorithms combine multichannel prewhitening via multistage least-squares linear prediction with novel adaptive procedures impose paraunitary constraints on filter. The techniques converge quickly a solution without any step size selection or divergence difficulties, unlike other methods, ours do not require...

10.1109/tasl.2007.899176 article EN IEEE Transactions on Audio Speech and Language Processing 2007-06-20

Natural gradient adaptation is an especially convenient method for adapting the coefficients of a linear system in inverse filtering tasks such as convolutive blind source separation and multichannel deconvolution. When developing practical implementations methods, however, it not clear how best to window signals truncate filter impulse responses within filtered updates. We show inadequate use truncation signal windowing well-known natural algorithm deconvolution can introduce bias into its...

10.1109/tsa.2004.838538 article EN IEEE Transactions on Speech and Audio Processing 2004-12-20

A model test was conducted for models with two kinds of bow flare form in both regular and irregular waves order to obtain information on effects the deck wetness asymmetry vertical wave bending moment. The made synthetic resins so as simulate rigidity a full scale ship. measured results are analysed give intensity impact pressure bow, frequency green sea Discussions given effectiveness against estimation method nonlinearity

10.2534/jjasnaoe1968.1989.166_259 article EN Journal of the Society of Naval Architects of Japan 1989-01-01

This paper proposes a two-stage method for the blind separation of convolutively mixed sources. We employ time-frequency masking, which can be applied even to an underdetermined case where number sensors is insufficient In first stage method, frequency bin-wise mixtures are classified based on Gaussian mixture model fitting. second stage, permutation ambiguities signals aligned by clustering posterior probability sequences calculated in stage. Experimental results separating four speeches...

10.1109/aspaa.2007.4393012 article EN 2007-10-01
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