中川 誠司

本研究では,自動車エンジン音に対する聴感印象の客観的評価のための基礎検討として,脳磁界計測による自動車加速時のエンジンの音質評価を試みた.まず,加速音に対する心理的好ましさとアルファ活動との関係を調べた.加速音に対する好ましさを一対比較法により測定し,それらの加速音を提示している間の大脳活動を全頭型脳磁計を用いて計測した.アルファ波帯域の脳磁界の自己相関パラメータと心理尺度の比較を行った結果,好ましくない音を提示した場合に比べて,好ましい音を提示した場合に後頭部付近でのアルファ波の自己相関関数の有効継続時間が長くなる傾向が確認された.さらに,加速音に対する聴覚誘発脳磁界反応とSD法による聴感評価との比較を行った.その結果,周波数の時間変化の違いによる聴感印象の差が,聴覚誘発脳磁界のN1m振幅値に反映されている可能性が示唆された.

骨導超音波刺激下での鼓膜の振動特性を、レーザドップラ振動計を用いた光学的な手法により計測した。まず,計測時に生じる光学系ノイズを効果的に除去し、観測信号のSN比を向上させる手法を提案した。また、骨導超音波知覚の要因を探るため、提案した手法を用いて骨導における非線形歪みの関与、特に可聴な低調波音の発生の可能性について調査した。その結果、鼓膜振動の中に骨導超音波のピッチ感に相当するような可聴な信号を確認することは出来ず、少なくとも非線形なosseotympanic経路の関与は無いことが示唆された。

This paper presents studies on a deterministic annealing algorithm based on<br /> quantum annealing for variational Bayes (QAVB) inference, which can be seen as<br /> an extension of the simulated annealing for variational Bayes (SAVB) inference.<br /> QAVB is as easy as SAVB to implement. Experiments revealed QAVB finds a better<br /> local optimum than SAVB in terms of the variational free energy in latent<br /> Dirichlet allocation (LDA).

Segmental arterial mediolysis（SAM）は腹部内臓動脈瘤の成因の一つとして近年確立された概念である。急性腹症や出血性ショックで発症することが多く，腹部内臓動脈に数珠状の動脈瘤が多発し，冠動脈や頭蓋内に動脈瘤を合併することも報告されている。病理組織学的に確定診断された報告（会議録は除く）は自験例を含み本邦23例と比較的稀な疾患である。症例は83歳の男性。心窩部痛にて他院入院中に，突然の意識障害とショック症状を呈し当院救命救急センターにドクターヘリ搬送となった。搬送中に心肺停止（心静止）となったが急速輸液及び心肺蘇生により 4 分後に心拍再開し当院に到着した。来院時の循環動態は安定していたため，腹部造影CT検査を施行したところ腹腔内に多量の液体貯留を認め，緊急血管造影を行った。下腸間膜動脈造影にて脾彎曲部に造影剤の血管外漏出所見を認め，脾動脈には数珠状の不整な拡張を認めた。以上からSAMを強く疑ったが，腸管虚血を考慮して緊急開腹手術へ移行した。術中所見では中結腸動脈左枝に出血を伴う動脈瘤の形成を認め，動脈瘤切除を施行した。病理組織学的検査にて，動脈瘤壁に島状の中膜残存所見を認めSAMと確定診断した。術後経過は良好で，第33病日に転院となった。術後 2 年に施行した腹部CT検査で未治療の脾動脈・下腸間膜動脈の数珠状変化はほぼ消失しており，現在まで破裂することなく 2 年 4 か月が経過している。原因不明の腹部内臓動脈瘤に対してはSAMを鑑別疾患の一つとして念頭に置く必要があると考えられた。

Rock containing a compliant, fluid-filled fracture can be viewed as one case of heterogeneous poroelastic media. When this fracture is subjected to seismic waves, a strong contrast in the elastic stiffness between the fracture itself and the background can result in enhanced grain-scale local fluid flow. Because this flow—relaxing the pressure building up within the fracture—can increase the dynamic compliance of the fracture and change energy dissipation (attenuation), the scattering of seismic waves can be enhanced. Previously, for a flat, infinite fracture, we derived poroelastic seismic boundary conditions that describe the relationship between a finite jump in the stress and displacement across a fracture, expressed as a function of the stress and displacement at the boundaries. In this paper, we extend these boundary conditions to examine frequency-dependent seismic wave scattering by heterogeneous fractures. Fluid-filled fractures with a range of mechanical and hydraulic properties are examined. From parametric studies, we found that the hydraulic permeability of a fracture fully saturated with water has little impact on seismic wave scattering. In contrast, the seismic response of a partially water-saturated fracture and a heterogeneous fracture filled with compliant liquid (e.g., supercritical CO₂) depended on the fracture permeability.

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.

To clarify mechanisms of the bone-conducted ultrasonic (BCU) perception, tympanic membrane (TM) vibrations under BCU stimuli were measured in a human subject using a laser Doppler vibrometer (LDV). We presented a signal processing algorithm to increase the SNRs (signal-to-noise ratios) of measured LDV signals by removing only optical noise components from the wave signals. Further, we analyzed the TM vibrations using the presented method to investigate the contribution of nonlinear distortion in the BCU perception, i. e. the possibility of generating the audible subharmonics. As a result, we did not find any audible signals corresponding to the subjective pitch of BCU in the TM vibrations. This suggests that there is no evidence for nonlinear distortion in the outer and middle ear.

We present a distance measurement for the semiregular variable S Crateris (S Crt) based on its annual parallax. With the unique dual beam system of the VLBI Exploration for Radio Astrometry (VERA) telescopes, we measured the absolute proper motion of a water maser spot associated with S Crt, referred to the quasar J1147-0724 located at an angular separation of 1.degrees 23. In observations spanning nearly two years, we detected the maser spot at an LSR velocity of 34.7 km s(-1), for which we measured an annual parallax of 2.33 +/- 0.13 mas, corresponding to a distance of 430(-23)(+25) pc. This measurement has an accuracy one order of magnitude better than the parallax measurements of HIPPARCOS. The angular distribution and three-dimensional velocity fieI6 of maser spots indicate a bipolar outflow with the flow axis along the northeast-south west direction. Using the distance and photospheric temperature, we estimated the stellar radius of S Crt and compared it with those of Mira variables.

We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H2O masers associated with a young stellar object (YSO) IRAS22198+6336 in a dark cloud, L 1204 G. Based on phase-referencing VLBI astrometry, we derived an annual parallax of IRAS 22198+6336 to be 1.309 +/- 0.047 mas, corresponding to the distance of 764 27 pc from the Sun. Although the most principal error source of our astrometry is attributed to the internal structure of the maser spots, we successfully reduced the errors in the derived annual parallax by employing position measurements for all of the 26 detected maser spots. Based on this result, we reanalyzed the spectral energy distribution of IRAS 22198+6336 and found that the bolometric luminosity and total mass of IRAS 22198+6336 are 450 L-circle dot and 7 M-circle dot, respectively. These values are consistent with an intermediate-mass YSO deeply embedded in the dense dust core, which has been proposed to be an intermediate-mass counterpart of a low-mass Class 0 source. In addition, we obtained absolute proper motions of the H2O masers for the most blue-shifted components. We propose that the collimated jets aligned along the east-west direction are the most plausible explanation for the origin of the detected maser features.

We report on astrometric observations of H2O masers around the red supergiant VY Canis Majoris carried out with VLBI Exploration of Radio Astrometry (VERA). Based on astrometric monitoring for 13 months, we successfully measured a trigonometric parallax of 0.88 +/- 0.08 mas, corresponding to a distance of 1.14(-0.09)(+0.11) kpc. This is the most accurate determined distance to VY CMa and the first one based on an annual parallax measurement. The luminosity of VY CMa has been overestimated due to a previously accepted distance. With our result, we re-estimated the luminosity of VY CMa to be (3 +/- 0.5) x 10(5) L-circle dot using the bolometric flux integrated over optical and IR wavelengths. This improved luminosity value makes the location of VY CMa on the Hertzsprung-Russell (HR) diagram much closer to the theoretically allowable zone (i.e. the left side of the Hayashi track) than previous ones, though the uncertainty in the effective temperature of the stellar surface still does not permit us to make a final conclusion.

We have used the Japanese VLBI array VERA to perform high-precision astrometry of an H2O maser source in the Galactic star-forming region NGC 281 West, which has been considered to be part of a 300-pc superbubble. We successfully detected a trigonometric parallax of 0.355 +/- 0.030 mas, corresponding to a source distance of 2.82 +/- 0.24 kpc. Our direct distance determination of NGC 281 has resolved a large distance discrepancy between previous photometric and kinematic studies; likely NGC 281 is in the far side of the Perseus spiral arm. The source distance as well as the absolute proper motions were used to demonstrate the 3D structure and expansion of the NGC 281, superbubble, similar to 650pc in size parallel to the Galactic disk and with a shape slightly elongated along the disk or spherical, but not vertically elongated, indicating that the superbubble expansion may be confined to the disk. We estimate the expansion velocity of the superbubble as being similar to 20 km s(-1), both perpendicular to and parallel to the Galactic disk with a consistent timescale of similar to 20 Myr.