Takao Murakami

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Anil K. Jain23
George Theodorakopoulos20
Reza Shokri20
Rafal Zdunek20
Jean-Pierre Hubaux20
16Kenta Takahashi
14Nobuaki Minematsu
13Keikichi Hirose
10Satoshi Asakawa
5Yan Sui

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Japanese Vowel Recognition Using External Structure of Speech
Speech acoustics is inevitably distorted by non-linguistic features such as vocal tract length, gender, age, microphone, room, line, hearing characteristics, and so on. Recently, a novel acoustic representation of speech was proposed, called the acoustic universal structure[1, 2]. It discards all the absolute properties of speech events and captures only… (More)
Towards optimal countermeasures against wolves and lambs in biometrics
Claimants and enrollees who have high similarity scores against many others are referred to as wolves and lambs, respectively. These animals can cause false accepts against many others and compromise the security of the system. The aim of this paper is to develop a fusion algorithm which has security against both of them while minimizing the number of query… (More)
Stability of autotrophic nitrogen removal system under four non-steady operations.
Stable nitrogen removal from the digester supernatant for sludge via the nitritation-anammox process under steady operations of ammonium concentration and flow rate has been often reported. In this study, the effects of four non-steady operations, intentional fluctuations of influent concentration from 890 to 650 mg-N/L and hydraulic load of the 10%… (More)
Novel autotrophic nitrogen removal system using gel entrapment technology.
A pilot plant involving a nitritation-anammox process was operated for treating digester supernatant. In the preceding nitritation process, ammonium-oxidizing bacteria were immobilized in gel carriers, and the growth of nitrite-oxidizing bacteria was suppressed by heat-shock treatment. For the following anammox process, in order to maintain the anammox… (More)
Accuracy improvement with high convenience in biometric identification using multihypothesis sequential probability ratio test
Biometric identification has lately attracted attention because of its high convenience; it does not require a user to enter a user ID. The identification accuracy, however, degrades as the number of the enrollees increases. Although many multimodal biometric techniques have been proposed to improve the identification accuracy, it requires the user to input… (More)
Japanese vowel recognition based on structural representation of speech
Speech acoustics varies from speaker to speaker, microphone to microphone, room to room, line to line, etc. Physically speaking, every speech sample is distorted. Socially speaking, however, speech is the easiest communication media for humans. In order to cope with the inevitable distortions, speech engineers have built HMMs with speech data of hundreds or… (More)
Fast and accurate biometric identification using score level indexing and fusion
Biometric identification provides a very convenient way to authenticate a user because it does not require the user to claim an identity. However, both the identification error rates and the response time increase almost in proportion to the number of enrollees. A technique which decreases both of them using only scores has the advantage that it can be… (More)
Location prediction attacks using tensor factorization and optimal defenses
Recent studies have proposed various attacks against location privacy using a Markov Chain transition matrix trained for each user. However, when a user has disclosed only a small amount of location information in the past, the training data can be extremely sparse. In this paper, we show how the attacker can solve this sparse data problem, and how the… (More)
Information-theoretic performance evaluation of likelihood-ratio based biometric score fusion under modality selection attacks
Likelihood-ratio based biometric score fusion is gaining much attention, since it maximizes accuracy if a log-likelihood ratio (LLR) is correctly estimated. It can also handle some missing query samples due to adverse physical conditions (e.g. injuries, illness) by setting the corresponding LLRs to 0. In this paper, we refer to the mode that allows missing… (More)