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43 results on '"Noguchi, Yasuaki"'

1. Linear bipolar OTAs based on a triple-tail cell employing exponential circuits

Author

Matsumoto, Fujihiko and Noguchi, Yasuaki

Subjects
Integrated circuits -- Research, Semiconductor chips -- Research, Standard IC, Business, Computers and office automation industries, Electronics, Electronics and electrical industries
Abstract

Two types of new operational transconductance amplifiers (OTAs), which are composed of exponential circuits and a triple-tail cell, are presented. The linear input voltage ranges of the proposed OTAs are wider than that of the triple-tail cell and have lower current consumption. The improvement of the signal-to-noise ratio is confirmed. The results of SPICE simulation show that the OTAs have good frequency responses. Monte Carlo simulation shows that the transconductance deviation of the proposed OTAs due to process variation is comparatively similar to that of the triple-tail cell. Index Terms--Exponential circuit, hyperbolic circuit, linear circuit, operational transconductance amplifier (OTA), triple-tail cell.

Published
2004

16. Time-Frequency Analysis of a Noisy Ultrasound Doppler Signal With a 2nd Figure Eight Kernel

Author

NATIONAL DEFENSE ACADEMY YOKOSUKA (JAPAN), Noguchi, Yasuaki, Kashiwagi, Eiichi, Watanabe, Kohtaro, Matsumoto, Fujihiko, Sugimoto, Suguru, NATIONAL DEFENSE ACADEMY YOKOSUKA (JAPAN), Noguchi, Yasuaki, Kashiwagi, Eiichi, Watanabe, Kohtaro, Matsumoto, Fujihiko, and Sugimoto, Suguru

Abstract

Nonstationary ultrasound Doppler signals, those are changing with time and frequency simultaneously, are widely observed in biological and speech signals. A Cohen's class time-frequency (TF) analysis can analyze nonstationary signals with high resolution in time and frequency at a same time. A time-frequency distribution (TFD) is largely affected by a kernel function. Thus, there is sometimes a case where auto-terms (those are signal components) are covered by cross-terms (those are spurious components). In order to apply TFDs to a nonstationary and nonlinear Doppler ultrasound signals, experimental data were obtained by moving a steel ball to and fro by continuously irradiating it with ultrasound in olive oil. The movement of the steel ball was controlled by various functions. To analyze these signals, four kernels were used: (1) a Wigner kernel, (2) a Choi-Williams kernel, (3) a figure eight kernel, and (4) a 2nd figure eight kernel. Using our 2nd figure eight kernel, the demodulation accuracy was improved even with noise., Presented at Annual International Conference of the IEEE Engineering in Medicine and Biology Society (23rd) held in Istanbul, Turkey on 25-28 Oct 2001. See also ADM001351 for entire conference on CD-ROM.

Published
2001

37. Central Computerized Automatic Fetal Heart Rate Diagnosis with a Rapid and Direct Alarm System

Author

Maeda, Kazuo, Utsu, Masaji, Noguchi, Yasuaki, Matsumoto, Fujihiko, and Nagasawa, Takashi

Abstract

Aims: This study aimed to simplify fetal monitoring, reduce inter-observer differences and false-positive diagnosis and monitor a large number of births simultaneously. Methods: Fetal signals from several births were transmitted to a central computer via local area network (LAN) or telemetry and analyzed using a multichannel timesharing system. Fetal heart rate (FHR) abnormalities were detected by using three programs: the experts' knowledge system, power spectral analysis and artificial neural network. Abnormal results were automatically communicated directly to the attending doctor. Instead of an FHR chart recorder, the original fetal signals were stored on the computer and re-processed on demand. Results: a maximal FHR score in the first stage of labor indicated a low Apgar score, and correlated with umbilical blood pH. The fetal distress index derived from the FHR score was three or more in cases of fetal acidosis. The neural network yielded probabilities of fetal outcome that coincided with the FHR score, and the neural index derived from these probabilities predicted fetal outcome. Pathological sinusoidal FHR and severe loss of FHR variability were automatically diagnosed by power spectral analysis. Perinatal mortality was 1.1 in 1.000 births, which was significantly lower using this central computerized system than the previous system, and no cases of cerebral palsy were reported 2 months after delivery. Conclusion: The central computerized automated fetal monitoring system improved fetal outcomes even in institutions dealing with a large number of births.

Published
2012

38. 1/f Frequency Fluctuations of a Quartz Oscillator and Temperature Fluctuations.

Author

Noguchi, Yasuaki, Teramachi, Yasuaki, and Musha, Toshimitsu

Subjects
*CRYSTAL oscillators, *RADIO frequency, *TEMPERATURE, *ELECTRIC oscillators, *FLUCTUATIONS (Physics), *STOCHASTIC processes
Abstract

We have investigated correlations between an ambient temperature and a frequency of a 5-MHz, 5th overtone IC-cut plano-convex quartz oscillator. We found that the spectral density of frequency fluctuations is composed of three parts over a fluctuation frequency from 10-6 to 10-2 Hz; in the lowest frequency part it is proportional to 1/f2, which continues to 1/f and eventually to F0. The 1/f2 and f0 spectra are caused by ambient temperature fluctuations. Thus we have found that the 1/f spectrum has nothing to fo with temperature fluctuations, which, therefore, provides a limit for frequency stability of a quartz oscillator. [ABSTRACT FROM AUTHOR]

Published
1984
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