研究者業績

中川 誠司

Nakagawa Seiji  (Seiji NAKAGAWA)

基本情報

所属
千葉大学 フロンティア医工学センター 教授
(兼任)大学院 工学研究院 教授
(兼任)大学院 融合理工学府 基幹工学専攻 医工学コース 教授,コース長
(兼任)工学部 総合工学科 医工学コース 教授,コース長
(兼任)医学部附属病院 教授
国立研究開発法人 産業技術総合研究所 客員研究員
東京大学 大学院医学系研究科 客員研究員
Univ. of Washington Visiting Scholar
国立研究開発法人 量子科学技術研究開発機構 客員研究員
学位
博士(工学)(1999年3月 東京大学)

連絡先
s-nakagawachiba-u.jp
J-GLOBAL ID
200901063867675418
researchmap会員ID
5000005804

外部リンク

非侵襲的手法による神経生理計測(特に脳機能計測),心理計測,物理計測,さらにはコンピュータ・シミュレーションを駆使して,聴覚を中心とした知覚メカニズムや認知メカニズムの解明を進めています.また,知覚・認知メカニズム研究で得られた成果を利用することで,骨伝導補聴器や骨伝導スマートホンを初めとした福祉機器・医用機器の開発や,室内の視聴覚環境の最適化,騒音の快音化といった応用研究にも取り組んでいます.


論文

 321
  • Seiji Nakagawa
    REVIEW OF SCIENTIFIC INSTRUMENTS 82(4) 044901-044901 2011年4月  査読有り
    Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver-the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 degrees C, and concurrently with x-ray CT imaging. The described split Hopkinson resonant bar test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples, and a natural rock sample. (C) 2011 American Institute of Physics. [doi:10.1063/1.3579501]
  • Masashi Nakayama, Shunsuke Ishimitsu, Seiji Nakagawa
    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING 6(2) 144-150 2011年3月  
    An existing problem for speech recognition is that the recognition rate tends to decrease because of the noise. Body-conducted speech offers a robust signal extraction method to extract speech signals from noisy environments, particularly because body-conducted speech is a propagated sound and not easily influenced by noise. However, when body-conducted speech is extracted with an accelerator, the typical frequency component of 2 kHz or more decreases in comparison with normal speech. Therefore, much research has been carried out investigating the techniques for improving the sound quality of body-conducted speech. Particularly, conventional methods require normal speech to estimate clear speech. Here, we propose a technique that combines differential acceleration and noise reduction to estimate a clear signal using only body-conducted speech. By comparing spectrogram differences with each method, we found that the Wiener filtering method was suitable for eliminating noise with differential acceleration. Thereafter, improvements in recognition rates were obtained using retrieval signals although the decoder has an acoustic model made by speech parameters. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
  • Yosuke Okamoto, Seiji Nakagawa
    NEUROSCIENCE LETTERS 487(2) 207-210 2011年1月  査読有り
    For a flickering light with two or more frequency components, the temporal envelope of the flickering light is perceived, although there is no frequency component at the frequency of the envelope. To address the processing of the temporal envelope, we compared cortical responses to the envelope of amplitude-modulated (AM) flickering lights with responses to sinusoidal flickering lights. We measured magnetoencephalographic (MEG) responses to AM and sinusoidal flickering lights while changing the frequency of the temporal envelope of AM flickering light and the stimulus frequency of sinusoidal flickering light. The result showed that the strength of the MEG response to sinusoidal flickering light increased with stimulus frequency in the low frequency range. This probably resulted from the band-pass filtering in the visual system. However, such an increase in the low frequency range was not observed for the envelope of AM flickering light. The absence of the increase in MEG responses suggests that the envelope of AM flickering light is not subject to band-pass filtering in the visual system. It is therefore possible that the envelope is represented after the band-pass filtering stage. (C) 2010 Elsevier Ireland Ltd. All rights reserved.
  • Ayumi Nasu, Kentaro Kotani, Takafumi Asao, Seiji Nakagawa
    Human Interface and the Management of Information. Interacting with Information - Symposium on Human Interface 2011, Held as Part of HCI International 2011, Orlando, FL, USA, July 9-14, 2011, Proceedings, Part I 6771 478-487 2011年  査読有り
  • Takayuki Kagomiya, Seiji Nakagawa
    17th International Congress of Phonetic Sciences, ICPhS 2011, Hong Kong, China, August 17-21, 2011 998-1001 2011年  査読有り
  • Takayuki Kagomiya, Seiji Nakagawa
    12TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION 2011 (INTERSPEECH 2011), VOLS 1-5 2220-2223 2011年  査読有り
    Human listeners can perceive speech signals in a voice-modulated ultrasonic carrier from a bone-conduction stimulator, even if the listeners are patients with sensorineural hearing loss. Considering this fact, we have been developing a bone-conducted ultrasonic hearing aid (BCUHA). The purpose of this study is to evaluate the usability of BCUHA regarding transmission of speaker discrimination information. For this purpose, a prototype of speaker discrimination test was developed. The test consists of 120 pairs of 10 words spoken by 10 speakers, and examinee is requested to judge the speakers of each pair are "same" or "different". The usability of BCUHA was assessed by using the speaker discrimination test. The test was also conduced to air-conduction (AC) and cochlear implant simulator (CIsim) condition. The results show that BCUHA can transmit speaker information speaker as well as CIsim.
  • Nakayama M, Ishimitsu S, Nakagawa S
    Speech Technologies, Intech 343-360 2011年  査読有り
  • Soeta Y, Nakagawa S
    Advances in Sound Localization, Intech 387-406 2011年  査読有り
  • Yoshiharu Soeta, Seiji Nakagawa
    NeuroReport 21(18) 1157-1161 2010年12月  査読有り
  • Takuya Hotehama, Seiji Nakagawa
    The Journal of the Acoustical Society of America 128(5) 3011-3018 2010年11月  査読有り
    <jats:p>Ultrasonic vibration generates a sensation of sound via bone-conduction. This phenomenon is called bone-conducted ultrasonic (BCU) hearing. Complex sounds can also be perceived by amplitude-modulating a BCU stimulus (AM-BCU). The influence of the modulation frequency on the sensitivity to detecting amplitude modulation of sinusoidal carriers of 10, 20, and 30 kHz was examined to clarify the characteristics of the perception of amplitude modulation over the sonic or audio-frequency range and the ultrasonic range. In addition, the detection sensitivity for single-sideband modulation for a 20 kHz carrier was measured. Temporal modulation transfer functions (TMTFs) obtained at each carrier frequency suggest that the auditory system has the ability to process timing information in the envelopes of AM-BCUs at lower modulation frequencies, as is the case with audio-frequency sounds. The possible influence of peripheral filtering on the shape of the TMTF at higher frequencies was examined.</jats:p>
  • Michael B. Kowalsky, Seiji Nakagawa, George J. Moridis
    SPE JOURNAL 15(3) 634-645 2010年9月  査読有り
    Many studies involving the application of geophysical methods in the field of gas hydrates have focused on determining rock-physics relationships for hydrate-bearing sediments, with the goal being to delineate the boundaries of gas-hydrate accumulations and to estimate the quantities of gas hydrate that such accumulations contain using remote-sensing techniques. However, the potential for using time-lapse geophysical methods to monitor the evolution of hydrate accumulations during production and, thus, to manage production has not been investigated. In this work, we begin to examine the feasibility of using time-lapse seismic methods specifically, the vertical-seismic-profiling (VSP) method for monitoring changes in hydrate accumulations that are predicted to occur during production of natural gas. A feasibility study of this nature is made possible through the coupled simulation of large-scale production in hydrate accumulations and time-lapse geophysical (seismic) surveys. We consider a hydrate accumulation in the Gulf of Mexico that may represent a promising target for production. Although the current study focuses on one seismic method (VSP), this approach can be extended easily to other geophysical methods, including other seismic methods (e.g., surface seismic or crosshole measurements) and electromagnetic surveys. In addition to examining the sensitivity of seismic attributes and parameters to the changing conditions in hydrate accumulations, our long-term goals in this work are to determine optimal sampling strategies (e.g., source frequency, time interval for data acquisition) and measurement configurations (e.g., source and receiver spacing for VSP), while taking into account uncertainties in rock-physics relationships. The numerical-modeling strategy demonstrated in this study may be used in the future to help design cost-effective geophysical surveys to track the evolution of hydrate properties. Here, we describe the modeling procedure and present some preliminary results.
  • James G. Berryman, Seiji Nakagawa
    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 127(2) 720-729 2010年2月  査読有り
    Poroelastic analysis has traditionally focused on the relationship between dry and drained constants, which are assumed known, and the saturated or undrained constants, which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the effects of the fluids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore fluid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.
  • S. Ishimitsu, K. Takami, S. Nakagawa, Y. Soeta
    The Proceedings of the AES International Conference 38 211-219 2010年  査読有り
  • Kagomiya T, Nakagawa S
    Proc.Int'l Conf. Acoust. 2010 2010年  査読有り
  • Kagomiya T, Nakagawa S
    Proceedings of Speech Prosody 2010 2915-2918 2010年  査読有り
  • Kazuhito Ito, Seiji Nakagawa
    Japanese Journal of Applied Physics 49(7) 07HF31-1-07HF31-7 2010年  査読有り
    <jats:p> Acoustic fields/vibrations in the external auditory meatus (ear canal) and tympanic membrane (TM) under bone-conducted ultrasonic stimulation were measured to elucidate the contributions of the osseotympanic and inertial routes to bone-conducted ultrasonic (BCU) perception. Evidence showing nonlinear distortions, especially the generation of audible subharmonics in the outer and middle ear, was examined. In the results, we did not find any audible signals corresponding to the subjective pitch of a BCU tone in the acoustic fields for the auditory meatus and TM vibrations. This suggests that nonlinear distortions in the osseotympanic and inertial routes do not contribute to bone-conducted ultrasonic perception. Specific properties of perception may be related to mechanisms in the cochlea or afferent neural pathway. </jats:p>
  • Shunsuke Ishimitsu, Masashi Nakayama, Seiji Nakagawa
    International Journal of Advanced Mechatronic Systems 2(4) 246-253 2010年  査読有り
    Speech recognition tends to be influenced by noise in the air. Body-conducted speech offers a robust signal extraction method from noisy environments, particularly because body-conducted speech is a propagated sound and not easily influenced by noise. However, when body-conducted speech is extracted with an accelerator, the typical frequency component of 2 kHz or more decreases compared with normal speech. Thus, we investigated a technique combining differential acceleration and noise reduction to estimate a clear signal using only body-conducted speech from a noisy room. The recognition rate confirmed about 3-4% is improved with proposed method. © 2010 Inderscience Enterprises Ltd.
  • Seiji Nakagawa
    17TH INTERNATIONAL CONFERENCE ON BIOMAGNETISM ADVANCES IN BIOMAGNETISM - BIOMAG2010 28 274-277 2010年  査読有り
    Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. We have been developing a novel hearing-aid using BCU perception, which transmits a 30-kHz bone-conducted carrier that is amplitude-modulated by speech. The fundamental capabilities of the BCU hearing-aid (BCUHA) were objectively assessed by magnetoencephalography. Frequency- and temporal-resolution were assessed by measuring mismatch fields (MMFs). As well, the capability to discriminate two-channel BCUs presented to the left and right mastoids was verified by the laterality of auditory evoked magnetic field N1m. In the frequency-discrimination tests, amplitude-modulated BCU (AM-BCU) and air-conducted sound (AC) showed almost the same MMF-magnitudes when frequency/modulation-frequency of the standard-stimuli were 1.0 kHz, even though MMF-magnitudes for BCU were smaller than those of AC at 0.125 kHz. In the temporal-discrimination tests, MMFs for changes of stimulus-duration were measured. MMF-magnitudes for AM-BCUs reached more than 80% of those for air-conducted sounds (ACs). In addition, in the laterality-discrimination tests, N1m evoked by contralateral stimuli were larger in amplitude and shorter in latency than those evoked by ipsilateral stimuli for both AM-BCUs and ACs. This result agrees with earlier reports of AC auditions, and suggests that two-BCU channels presented to the left and right mastoid were separately localized. These findings objectively indicate that the BCUHA has practical frequency- and temporal resolution, and give a rationale for the development of a multi-channel (at least two) BCUHA.
  • Yosuke Okamoto, Seiji Nakagawa
    17TH INTERNATIONAL CONFERENCE ON BIOMAGNETISM ADVANCES IN BIOMAGNETISM - BIOMAG2010 28 294-+ 2010年  査読有り
    For a sinusoidal flickering light amplitude-modulated (AM) sinusoidally, flicker with a periodicity of a temporal envelope (modulation-frequency) of the light is perceived even though there is no such frequency component. However, the mechanisms underlying the perception are still unclear. In human visual system, it is known that there are two temporal channels with a lower and a higher peak frequency. Therefore, we investigated whether the two temporal channels affected the perception of the envelope of the AM flickering light. Visual sensitivity and magnetoenceplialographic (MEG) responses to the envelope periodicity were measured when the sensitivity of each of the temporal channel was reduced by adaptation. Sinusoidal flickering lights with a low (2 Hz) and a high (16 Hz) temporal frequency were used as adapting stimuli. The sinusoidal flickering lights of 2 and 16 Hz and an AM flickering light with a modulation-frequency of 2 Hz and a carrier-frequency of 16 Hz were presented as test stimuli. The results showed that the sensitivity and MEG responses to the sinusoidal flickering light decreased more when the sensitivity of the temporal channel tuned for the test stimulus frequency was reduced than when that of the other temporal channel was reduced. On the other hand, the sensitivity and MEG responses to the envelope periodicity decreased more when the sensitivity to the frequency corresponding to the envelope periodicity was reduced than when that to the carrier frequency was reduced, even though a frequency component corresponding to the envelope periodicity did not exist in the stimulus. The results indicated that the envelope component of AM flickering light was affected by the low-frequency channel and suggest the possibility that the envelope component arises before or while the AM flickering signal passes the low-frequency channel.
  • Dongbing Shao, Bidan Zhang, Sajan Marokkey, Todd C. Bailey, Derren N. Dunn, Emily E. Gallagher, Yea-Sen Lin, Takashi Murakami, Seiji Nakagawa, Chandrasekhar Sarma, Mohamed Talbi
    PHOTOMASK TECHNOLOGY 2010 7823(Pt.1) 1-78230 2010年  査読有り
    To reduce cost, implant levels usually use masks fabricated with older generation mask tools, such as laser writers, which are known to introduce significant mask errors. In fact, for the same implant photolithography process, Optical Proximity Correction (OPC) models have to be developed separately for the negative and positive mask tones to account for the resulting differences from the mask making process. However, in order to calibrate a physical resist model, it is ideal to use single resist model to predict the resist performance under the two mask polarities. In this study, we show our attempt to de-convolute mask error from the Correct Positive (CP) and Correct Negative (CN) tone CD data collected from bare Si wafer and derive a single resist model. Moreover, we also present the predictability of this resist model over a patterned substrate by comparing simulated CD/profiles against wafer data of various features.
  • 伊藤 一仁, 中川 誠司
    生体医工学 47(6) 588-594 2009年12月  
    骨導超音波刺激下での生体鼓膜振動をレーザードップラ振動計により計測し、骨導による超音波知覚が外耳や中耳系での非線形歪みに起因する可聴音の発生によるものか検証した。計測時に生じた光学系ノイズを効果的に除去し、観測信号のS/N比の向上を図る信号処理手法を構築した。30kHzの骨導超音波刺激下で、ノイズの重畳していない場合の代表的な鼓膜振動の時間波形と周波数特性の計測状況は良好で、目立った光学系ノイズが発生しなかった。次に、同じく30kHzの骨導超音波刺激下で、ノイズが重畳した場合、周波数全域に渡ってノイズが乗り、30kHzの刺激信号はこのノイズの中に埋もれた。これに対して、この時間波形にノイズ除去処理を施した後の周波数特性はノイズフロアが全体的に低下し、30kHzの刺激信号の存在が明確になり、良好な計測状況で得られた信号の周波数特性と遜色ないS/N比が得られた。
  • 伊藤 一仁, 中川 誠司
    生体医工学 47(6) 588-594 2009年12月  
  • Yosuke Okamoto, Seiji Nakagawa, Kenji Fujii, Takashi Yano
    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 26(11) 2346-2352 2009年11月  査読有り
    To investigate the perception of a temporal envelope of flickering light is important for understanding nonlinear temporal processing in the visual system. The influence of the frequency components of a flickering light on the perception of the envelope remains unclear, with few studies having investigated the cortical activities for the envelope. We investigated the detection thresholds, brightness, and magnetoencephalographic responses related to amplitude-modulated (AM) flickering lights. The results showed that the sensitivity to flicker at the envelope periodicity of the AM flickering light was lower for a high-frequency carrier (40 Hz) than for a lower-frequency one (10, 20, or 30 Hz). Also, the primary visual cortex responded at the frequency corresponding to the envelope periodicity of the AM flickering light, and the strength of the cortical response reflected the brightness of the flicker at the envelope periodicity. (C) 2009 Optical Society of America
  • Tadashi Nishimura, Seiji Nakagawa, Akinori Yamashita, Takefumi Sakaguchi, Hiroshi Hosoi
    Acta oto-laryngologica. Supplementum (562) 28-33 2009年6月  査読有り
    CONCLUSION: N1m growth indicates the differences in central auditory processing between bone-conducted ultrasound and air-conducted audible sound. OBJECTIVES: Bone conduction enables ultrasound to be heard by the human ear. Despite many studies, the perceptual mechanism of bone-conducted ultrasound has not yet been clarified completely. Therefore, this study investigated the ultrasonic perception of humans, especially as regards the effects of stimulus intensity or loudness. SUBJECTS AND METHODS: The effect of the stimulus level on N1m amplitude was measured over the psycho-acoustical dynamic range. RESULTS: The dynamic range for 30 kHz bone-conducted ultrasound (18.2 +/- 3.3 dB) was found to be significantly narrower than that for 1 kHz air-conducted sound (85.9 +/- 11.9 dB). As the stimulus level increased, the N1m amplitude in response to bone-conducted ultrasound grew faster than that to air-conducted sound. Although the growth of the N1m amplitude for air-conducted sound saturated below the uncomfortable loudness level (UCL), that for bone-conducted ultrasound continued to grow above the UCL.
  • Yoshiharu Soeta, Seiji Nakagawa
    NEUROREPORT 20(6) 548-552 2009年4月  査読有り
    The aim of this study was to determine whether the amplitude and/or latency of the N1m deflection of auditory-evoked magnetic fields are influenced by the level and frequency of sound. The results indicated that the amplitude of the N1m increased with sound level. The growth in amplitude with increasing sound level was almost constant with low frequencies (250-1000 Hz); however, this growth decreased with high frequencies (> 2000 Hz). The behavior of the amplitude may reflect a difference in the increase in the activation of the peripheral and/or central auditory systems. NeuroReport 20:548-552 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.
  • 中川 誠司
    日本音響学会誌 65(1) 46-51 2009年  査読有り
  • Nakagawa S
    Brain topography and multimodal imaging 95-98 2009年  査読有り
  • Tadashi Nishimura, Seiji Nakagawa, Akinori Yamashita, Takefumi Sakaguchi, Hiroshi Hosoi
    ACTA OTO-LARYNGOLOGICA 129(SUPPL. 562) 28-33 2009年  査読有り
    Conclusion: N1m growth indicates the differences in central auditory processing between bone-conducted ultrasound and air-conducted audible sound. Objectives: Bone conduction enables ultrasound to be heard by the human ear. Despite many studies, the perceptual mechanism of bone-conducted ultrasound has not yet been clarified completely. Therefore, this study investigated the ultrasonic perception of humans, especially as regards the effects of stimulus intensity or loudness. Subjects and methods: The effect of the stimulus level on N1m amplitude was measured over the psycho-acoustical dynamic range. Results: The dynamic range for 30 kHz bone-conducted ultrasound (18.2 +/- 3.3 dB) was found to be significantly narrower than that for 1 kHz air-conducted sound (85.9 +/- 11.9 dB). As the stimulus level increased, the N1m amplitude in response to bone-conducted ultrasound grew faster than that to air-conducted sound. Although the growth of the N1m amplitude for air-conducted sound saturated below the uncomfortable loudness level (UCL), that for bone-conducted ultrasound continued to grow above the UCL.
  • Takayuki Kagomiya, Seiji Nakagawa
    INTERSPEECH 2009: 10TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION 2009, VOLS 1-5 2887-2890 2009年  査読有り
    Human listeners can perceive speech signals from a voice-modulated ultrasonic carrier which is presented through a bone-conduction stimulator, even if they are sensorineural hearing loss patients. As an application of this phenomenon, we have been developing a bone-conducted ultrasonic hearing aid (BCUHA). This research examined whether formant space and F(0) can be cues of speaker discrimination in BCU hearing as well as via air-conduction (AC) hearing. A series of speaker discrimination experiments revealed that both formant space and F(0) can act as cues for speaker discrimination even via BCUHA. However, sensitivity to formant space in BCU hearing is less than in AC hearing.
  • Seiji Nagahara, Kazuhiro Takahata, Seiji Nakagawa, Takashi Murakami, Kazuhiro Takeda, Shinpei Nakamura, Makoto Ueki, Masaki Satake, Tatsuhiko Ema, Hiroharu Fujise, Hiroki Yonemitsu, Yuriko Seino, Shinichiro Nakagawa, Masafumi Asano, Yosuke Kitamura, Takayuki Uchiyama, Shoji Mimotogi, Makoto Tominaga
    ADVANCES IN RESIST MATERIALS AND PROCESSING TECHNOLOGY XXVI 7273(Pt.2) 1-72733 2009年  査読有り
    Resist process challenges for 32-nm node and beyond are discussed in this paper. For line and space (L/S) logic patterns, we examine ways to balance the requirements of resolution-enhancement techniques (RETs). In 32-nm node logic patterning, two-dimensional (2D) layout pattern deformation becomes more severe with stronger RET (e.g., narrow angle CQUAD illumination). Also pattern collapse more frequently happens in 2D-pattern layouts when stronger RET is used. In contrast, milder RET (annular illumination) does not induce the severe pattern collapse in 2D-pattern layout. For 2D-pattern layouts, stronger RET seems to worsen image contrast and results in high background-light in the resist pattern, which induces more pattern collapse. For the minimum-pitch L/S pattern in 32-nm node logic, annular illumination is acceptable for patterning with NA1.35 scanner when high contrast resist is used. For contact/via patterns, it is necessary to expand the overlapping CD process window. Better process margin is realized through the combination of hole-shrink technique and precise acid-diffusion control in an ArF chemically amplified resist.
  • Seiji Nakagawa, Aya Nakagawa
    2009 ICME INTERNATIONAL CONFERENCE ON COMPLEX MEDICAL ENGINEERING 145-+ 2009年  査読有り
    Several studies have reported that bone-conducted ultrasound (BCU) is even perceived by the profoundly sensorineural deaf; however, the mechanisms involved remain unclear. We previously reported some unique characteristics of BCU perception that suggest unique neurophisiological mechanisms. For example: (1) the pitch of BCU is 10-odd kHz and is independent of its frequency; (2) no beats occur between BCU and 10-odd-kHz air-conducted sinusoids; (3) BCU masks 10-14 kHz air-conducted sounds; and (4) the dynamic range of loudness for BCU is less than 20 dB. In the present study, several electrophysiological measurements were carried out to clarify the neural pathway involved in BCU perception. Specifically, auditory brainstem responses (ABRs), middle latency responses (MLRs), and cortical magnetic activities evoked by BCU were measured in humans. Substantial ABRs (wave I-V) and MLRs were evoked by BCU as well as air-conducted audible sound. In terms of cortical activities, clear N1m responses were elicited by BCU, with their sources being localized in the auditory cortices. However, BCU showed later, smaller, more posterior, and more lateral sources than audible-frequency sounds, and therefore did not appear to follow a tonotopic organization at the cortical level. These results indicate that: (1) the cochlea substantially contributes to BCU perception; (2) BCU goes through the normal auditory pathway and there is no special organ for BCU perception; and (3) some differences in the inner ear mechanisms may exist between audible sounds and BCU.
  • Masashi Nakayama, Shunsuke Ishimitsu, Seiji Nakagawa
    2009 IEEE INTERNATIONAL CONFERENCE ON NETWORKING, SENSING AND CONTROL, VOLS 1 AND 2 848-+ 2009年  査読有り
    Speech-recognition rates decrease in noisy environments. The body-conducted speech, conducted in solids such as body and skins, has a noise-robust characteristics and can be served for recognition systems even in 98 -dBSPL (20 dBSNR) noise environments. However, the body-conduction can not capture high frequency sounds. Conventional methods to improve sound quality of body-conducted speeches need both speeches themselves and body-conducted speeches. In this paper, a new body-conducted speech retrieval technique in sound quality without a speech signal itself is proposed. First, high-frequency components in the body-conducted speech were emphasized using differential acceleration. Second, a conventional noise reduction method was adopted to make a clear body-conducted speech from a retrieval speech which contains constant noise. The recognition experiments using the proposed method showed that it improved recognition rate in all speakers.
  • Keisuke Ehara, Tatsuhiko Ema, Toshinari Yamasaki, Seiji Nakagawa, Seiji Ishitani, Akihiko Morita, Jeonghun Kim, Masashi Kanaoka, Shuichi Yasuda, Masaya Asai
    ADVANCES IN RESIST MATERIALS AND PROCESSING TECHNOLOGY XXVI 7273(Pt.1) 1-727322 2009年  査読有り
    The intention of this study is to develop an immersion lithography process using advanced track solutions to achieve world class critical dimension (CD) and defectivity performance in a state of the art manufacturing facility. This study looks at three important topics for immersion lithography: defectivity, CD control, and wafer backside contamination. The topic of defectivity is addressed through optimization of coat, develop, and rinse processes as well as implementation of soak steps and bevel cleaning as part of a comprehensive defect solution. Develop and rinse processing techniques are especially important in the effort to achieve a zero defect solution. Improved CD control is achieved using a biased hot plate (BHP) equipped with an electrostatic chuck. This electrostatic chuck BHP (eBHP) is not only able to operate at a very uniform temperature, but it also allows the user to bias the post exposure bake (PEB) temperature profile to compensate for systematic within-wafer (WiW) CD non-uniformities. Optimized CD results, pre and post etch, are presented for production wafers. Wafer backside particles can cause focus spots on an individual wafer or migrate to the exposure tool's wafer stage and cause problems for a multitude of wafers. A basic evaluation of the cleaning efficiency of a backside scrubber unit located on the track was performed as a precursor to a future study examining the impact of wafer backside condition on scanner focus errors as well as defectivity in an immersion scanner.
  • Yoshiharu Soeta, Ryota Shimokura, Seiji Nakagawa
    NEUROREPORT 19(17) 1709-1713 2008年11月  査読有り
    Effects of center frequency on the binaural auditory filter in the human auditory cortex were examined using auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli. Eight normal-hearing participants took part in the study. The amplitudes of the N1m components of auditory-evoked magnetic fields were approximately constant when the frequency separation was less than 10-20% of the center frequency; however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 10-20% of the center frequency. This indicates that binaural auditory filter bandwidth is approximately 10-20% of the center frequency. NeuroReport 19:1709-1713 (C) 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins.
  • Yoshiharu Soeta, Seiji Nakagawa
    JOURNAL OF SOUND AND VIBRATION 314(3-5) 453-456 2008年7月  査読有り
    The effects of the bandwidth of high-frequency sounds oil loudness are investigated. Loudness matches are obtained using a two-interval, adaptive forced-choice procedure converging on the point of subjective equality by following a simple 1-up, 1-down rule. Loudness increases significantly when the sound has a 1/3 octave band compared with smaller bandwidth sounds, confirming the effect of bandwidth of high-frequency sounds. (C) 2008 Elsevier Ltd. All rights reserved.
  • Akinori Yamashita, Tadashi Nishimura, Seiji Nakagawa, Takefumi Sakaguchi, Hiroshi Hosoi
    NEUROSCIENCE LETTERS 438(2) 260-262 2008年6月  査読有り
    According to previous studies, ultrasound can be perceived through bone conduction and ultrasound amplitude modulated by different speech sounds can be discriminated by some profoundly deaf subjects as well as the normal-hearing. These findings suggest the usefulness of development of a bone-conducted ultrasonic hearing aid (BCUHA) for profoundly deaf subjects. In this study, with a view to developing a frequency modulation system in a BCUHA, the capability to discriminate the frequency of sinusoidal bone-conducted ultrasound (BCU) was evaluated by measuring mismatch fields (MMF). We compared MMFs between BCU (standard stimuli were 30 kHz, and deviant stimuli were 27 and 33 kHz) and air-conducted audible sound (ACAS; standard stimuli were 1 kHz, and deviant stimuli were 900 and 1100 Hz). MMFs were observed in all subjects for ACAS, however, not observed in a few subjects for BCU. Further, the mean peak amplitudes of MMF for BCU were significantly less than those for ACAS. These findings indicate that the discrimination capability of frequency of sinusoidal BCU is inferior to that of ACAS. It was also demonstrated that normal hearing could to some extent discriminate differences in frequency in sinusoidal BCU. The results indicate a possibility of transmission system for language information making use of frequency discrimination. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
  • Yoshiharu Soeta, Seiji Nakagawa
    NEUROREPORT 19(7) 783-787 2008年5月  査読有り
    The aim of this paper was to determine whether the latency and/or amplitude of the NIm deflection of the auditory-evoked magnetic fields are influenced by the delay and number of iterations of iterated rippled noise, which are related to pitch and pitch strength, respectively. The results indicate that the NIm amplitude decreased sharply for delays between 16 and 32 ms, suggesting that the NIm amplitude reflects the lower limit of the audible pitch range. The NIm latency increases with increasing delay of up to 8-16 ms and then decreases again for delays longer than 16 ms. The behavior of the latency may reflect the balance between the pitch-related component of the NIm and a specific pitch-unrelated component.
  • Masayuki Hirabayashi, Katsuhiro Narasaki, Shoji Tsunematsu, Yoshiyuki Kimura, Seiji Yoshida, Hiroshi Murakami, Takao Nakagawa, Akira Ohnishi, Toshio Matsumoto, Hidehiro Kaneda, Keigo Enya, Masahide Murakami
    CRYOGENICS 48(5-6) 189-197 2008年5月  査読有り
    The AKARI satellite (formerly known as ASTRO-F) is Japan's first infrared astronomical satellite. AKARI is equipped with the infrared camera (IRC) and the far-infrared surveyor (FIS), which are cooled below 7 K. The AKARI's 68.5 cm telescope, which is made of SiC, is also cooled below 7 K. A unique feature of the AKARI cryostat is that it uses both cryogen and mechanical coolers. Using mechanical coolers, the helium lifetime can be greater than one year with 170 L of liquid helium. AKARI was launched on February 21, 2006 (UT), from the Uchinoura Space Center (USC). It has been performing successfully in orbit. (C) 2008 Elsevier Ltd. All rights reserved.
  • Nakagawa S, Nakagawa A
    Proceedings of International Symosiumu on Complex Medical Engineering 2008年  査読有り
  • Takami K, Ishimitsu S, Nakagwa S, Asami T
    Proceedings of Acoustics'08 4749-4754 2008年  査読有り
  • Nakayama H, Ishimitsu S, Nakagwa S
    Proceedings of Acoustics'08 1407-1412 2008年  査読有り
  • Soeta Y, Nakagawa S
    Biomagnetism: Transdisciplinary Res. and Exploration 95-97 2008年  査読有り
  • Soeta Y, Nakagawa S
    Journal of Temporal Design in Architecture and the Environment 8(1) 1-7 2008年  査読有り
  • Nakagawa S
    Biomagnetism: Interdisciplinary Research and Exploration 98-100 2008年  査読有り
  • 中川誠司, 藤崎恵美子, 岡本洋輔
    情報科学技術フォーラム講演論文集 7(3) 51-53 2008年  査読有り
  • Mareki Honma, Takeshi Bushimata, Yoon Kyung Choi, Tomoya Hirota, Hiroshi Imai, Kenzaburo Iwadate, Takaaki Jike, Osamu Kameya, Ryuichi Kamohara, Yukitoshi Kan-Ya, Noriyuki Kawaguchi, Masachika Kijima, Hideyuki Kobayashi, Seisuke Kuji, Tomoharu Kurayama, Seiji Manabe, Takeshi Miyaji, Takumi Nagayama, Akiharu Nakagawa, Chung Sik Oh, Toshihiro Omodaka, Tomoaki Oyama, Satoshi Sakai, Katsuhisa Sato, Tetsuo Sasao, Katsunori M. Shibata, Motonobu Shintani, Hiroshi Suda, Yoshiaki Tamura, Miyuki Tsushima, Kazuyoshi Yamashita
    MAPPING THE GALAXY AND NEARBY GALAXIES 27-+ 2008年  査読有り
    In this paper we review the current status of VERA (VLBI Exploration of Radio Astrometry) project. First, we present an overview of VERA, and then we report on recent results from VERA, particularly the parallax measurement of Galactic star forming region S269 at the distance of 5.3 kpc.

MISC

 1016

書籍等出版物

 8

担当経験のある科目(授業)

 28

共同研究・競争的資金等の研究課題

 27