The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Toshitaka Baba - One of the best experts on this subject based on the ideXlab platform.
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near field tsunami amplification factors in the kii peninsula japan for dense oceanfloor network for earthquakes and tsunamis donet
Marine Geophysical Researches, 2014Co-Authors: Toshitaka Baba, Narumi Takahashi, Yoshiyuki KanedaAbstract:We investigated the correlation between coastal and offshore tsunami heights by using data from the Dense Oceanfloor Network for Earthquakes and Tsunamis (DONET) observational array of ocean-bottom Pressure Gauges in the Nankai trough off the Kii Peninsula, Japan. For near-field earthquakes, hydrostatic Pressure changes may not accurately indicate sea surface fluctuations, because ocean-bottom Pressure Gauges are simultaneously displaced by crustal deformation due to faulting. To avoid this problem, we focused on the average waveform of the absolute value of the hydrostatic Pressure changes recorded at all the DONET stations during a tsunami. We conducted a Monte Carlo tsunami simulation that revealed a clear relationship between the average waveforms of DONET and tsunami heights at the coast. This result indicates the possibility of accurate real-time prediction of tsunamis by use of arrays of ocean-bottom Pressure Gauges.
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Dispersive tsunami of the 2010 Chile earthquake recorded by the high‐sampling‐rate ocean‐bottom Pressure Gauges
Geophysical Research Letters, 2010Co-Authors: Tatsuhiko Saito, Takanori Matsuzawa, Kazushige Obara, Toshitaka BabaAbstract:[1] Cabled ocean-bottom Pressure Gauges deployed offshore Japan recorded the Pressure change associated with the 2010 Chile earthquake tsunami over a wider frequency range than that of coastal tide Gauges or hydrophones. Although it was difficult to recognize the dispersive features in the original records, the spectrograms clearly showed wave dispersion. A low-frequency tsunami (∼1 mHz) arrived after an elapsed time of 24 hr from the earthquake origin time, while a high-frequency tsunami (∼9 mHz) arrived after an elapsed time of 48 hr. The arrival times can be explained by assuming a constant water depth of 4 km. However, the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations. Cabled ocean-bottom Pressure Gauges deployed offshore can record broadband tsunami signals reflecting the wide-wavenumber-range spatial spectrum for sea-bottom deformation caused by the earthquake.
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dispersive tsunami of the 2010 chile earthquake recorded by the high sampling rate ocean bottom Pressure Gauges
Geophysical Research Letters, 2010Co-Authors: Tatsuhiko Saito, Takanori Matsuzawa, Kazushige Obara, Toshitaka BabaAbstract:[1] Cabled ocean-bottom Pressure Gauges deployed offshore Japan recorded the Pressure change associated with the 2010 Chile earthquake tsunami over a wider frequency range than that of coastal tide Gauges or hydrophones. Although it was difficult to recognize the dispersive features in the original records, the spectrograms clearly showed wave dispersion. A low-frequency tsunami (∼1 mHz) arrived after an elapsed time of 24 hr from the earthquake origin time, while a high-frequency tsunami (∼9 mHz) arrived after an elapsed time of 48 hr. The arrival times can be explained by assuming a constant water depth of 4 km. However, the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations. Cabled ocean-bottom Pressure Gauges deployed offshore can record broadband tsunami signals reflecting the wide-wavenumber-range spatial spectrum for sea-bottom deformation caused by the earthquake.
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Transient thermal response in ocean bottom Pressure measurement
Geophysical Research Letters, 2006Co-Authors: Kenji Hirata, Toshitaka BabaAbstract:[1] Offshore ocean bottom Pressures usually follow ocean tidal motion but sometimes deviate from it even when no tsunami occurs. Numerous observations suggest that such deviations highly correlate with sudden temperature changes, probably due to irregular deep ocean currents, around the Pressure Gauges regardless of static temperature compensation mechanism. We ascribe this deviation to the transient thermal response of the Pressure Gauges, which produce apparent Pressure fluctuations when temperature change quickly so that temperature equilibrium condition of two quartz transducers is not valid. We put forward an empirical method to estimate the transient thermal response correctly. Such rapid temperature change may have to be corrected for a robust tsunami warning based on offshore tsunami observation with Pressure Gauges.
Tatsuhiko Saito - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Seismic Centroid Moment Tensor Using Ocean Bottom Pressure Gauges as Seismometers
Geophysical Research Letters, 2017Co-Authors: Tatsuya Kubota, Tatsuhiko Saito, Wataru Suzuki, Ryota HinoAbstract:We examined the dynamic Pressure change at the seafloor to estimate the centroid moment tensor solutions of the largest and second largest foreshocks (Mw 7.2 and 6.5) of the 2011 Tohoku-Oki earthquake. Combination of onshore broadband seismograms and high-frequency (~20–200 s) seafloor Pressure records provided the resolution of the horizontal locations of the centroids, consistent with the results of tsunami inversion using the long-period (> ~10 min) seafloor Pressure records although the depth was not constrained well, whereas the source locations were poorly constrained by the onshore seismic data alone. Also, the waveforms synthesized from the estimated CMT solution demonstrated the validity of the theoretical relationship between Pressure change and vertical acceleration at the seafloor. The results of this study suggest that offshore Pressure records can be utilized as offshore seismograms, which would be greatly useful for revealing the source process of offshore earthquakes.
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Dispersive tsunami of the 2010 Chile earthquake recorded by the high‐sampling‐rate ocean‐bottom Pressure Gauges
Geophysical Research Letters, 2010Co-Authors: Tatsuhiko Saito, Takanori Matsuzawa, Kazushige Obara, Toshitaka BabaAbstract:[1] Cabled ocean-bottom Pressure Gauges deployed offshore Japan recorded the Pressure change associated with the 2010 Chile earthquake tsunami over a wider frequency range than that of coastal tide Gauges or hydrophones. Although it was difficult to recognize the dispersive features in the original records, the spectrograms clearly showed wave dispersion. A low-frequency tsunami (∼1 mHz) arrived after an elapsed time of 24 hr from the earthquake origin time, while a high-frequency tsunami (∼9 mHz) arrived after an elapsed time of 48 hr. The arrival times can be explained by assuming a constant water depth of 4 km. However, the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations. Cabled ocean-bottom Pressure Gauges deployed offshore can record broadband tsunami signals reflecting the wide-wavenumber-range spatial spectrum for sea-bottom deformation caused by the earthquake.
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dispersive tsunami of the 2010 chile earthquake recorded by the high sampling rate ocean bottom Pressure Gauges
Geophysical Research Letters, 2010Co-Authors: Tatsuhiko Saito, Takanori Matsuzawa, Kazushige Obara, Toshitaka BabaAbstract:[1] Cabled ocean-bottom Pressure Gauges deployed offshore Japan recorded the Pressure change associated with the 2010 Chile earthquake tsunami over a wider frequency range than that of coastal tide Gauges or hydrophones. Although it was difficult to recognize the dispersive features in the original records, the spectrograms clearly showed wave dispersion. A low-frequency tsunami (∼1 mHz) arrived after an elapsed time of 24 hr from the earthquake origin time, while a high-frequency tsunami (∼9 mHz) arrived after an elapsed time of 48 hr. The arrival times can be explained by assuming a constant water depth of 4 km. However, the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations. Cabled ocean-bottom Pressure Gauges deployed offshore can record broadband tsunami signals reflecting the wide-wavenumber-range spatial spectrum for sea-bottom deformation caused by the earthquake.
Hidehiko Nonaka - One of the best experts on this subject based on the ideXlab platform.
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Measurement of a wide range of hydrogen concentration with rapid response using dual Pressure Gauges
International Journal of Hydrogen Energy, 2008Co-Authors: A. Suzuki, Hidehiko NonakaAbstract:Abstract We investigated the dependence of hydrogen sensing on the hydrogen density at 0.1–100 vol% in air atmosphere by commercially available diaphragm and quartz friction Pressure Gauges (D- and Q-Gauges). It was demonstrated that the Q-gauge Pressure reading depends on the hydrogen concentration for concentrations up to 100 vol% and can be used to measure the hydrogen concentration in air. The response times using the dual Pressure Gauges were shown to be below one second for hydrogen concentrations of 0.1–100 vol% in air atmosphere, indicating that our hydrogen-sensing method has a rapid response in the above range of hydrogen concentrations. In conclusion, hydrogen sensing with dual Pressure Gauges can be used to measure a wide range of hydrogen concentrations with a fast response; thus, this method is particularly practical for ensuring a safe hydrogen-based economy.
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A possible hydrogen sensing method with dual Pressure Gauges
Sensors and Actuators A: Physical, 2006Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:Abstract In this work, we present a novel method for hydrogen sensing, based on partial Pressure measurements with a diaphragm and a quartz friction Pressure gauge (D- and Q-Gauges, respectively). The D-gauge measures absolute Pressure, whereas Q-gauge readings are affected by viscosity changes occurring when hydrogen is mixed with air, thus enabling H 2 detection. The new method is safe and sensitive and has a quick-response to hydrogen leakage. The measured minimum detection limit for hydrogen is 0.05 vol.% in air, and the response time to hydrogen introduction is less than 1 s; these characteristics are practically sufficient for hydrogen sensing.
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Hydrogen Gas Sensing using Two Type of Pressure Gauges
Journal of The Vacuum Society of Japan, 2005Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:For safety hydrogen sensing, the Pressure measurement with a capacitance manometer and a quartz friction Pressure gauge (Q-gauge) were investigated. Q-gauge Pressure reading decreases when hydrogen gas is introduced into air supplied from atmosphere without any change of Pressure measured by a capacitance manometer. This result indicates that the present Pressure measurement using two Pressure Gauges is possible to detect the hydrogen leakage into air. In addition, a decrease of Q-gauge Pressure reading correlates with a flow rate of the hydrogen gas, and increases with hydrogen concentration in air. Then it was shown that the low detection limit of hydrogen concentration is below 1%. Response time for hydrogen introduction is faster than 30 seconds, which meets the requirements for the hydrogen gas leak sensor. As above, the present safe Pressure measurement using a capacitance manometer and a Q-gauge is satisfactorily useful for the hydrogen gas leak sensing.
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Influence of Temperature and Humidity on Partial Pressure Measurement using Dual Pressure Gauges
Shinku, 2005Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:Taking into account the utilization of partial Pressure measurement under various temperatures and humidity, their influence on this measurement with a capacitance manometer and a quartz friction Pressure gauge (Q-gauge) is studied. With increasing humidity, a Q-gauge Pressure reading, calibrated by air gas, decreases as well as when the hydrogen leakage is detected. To avoid this error by humidity for the hydrogen sensing, we tried to compensate influence of humidity using a humidity coefficient which is calculated from the humidity dependence of the Q-gauge Pressure reading at constant temperature, and suppressed to one-fifth of the fluctuation of the Q-gauge Pressure reading background due to humidity change. Regarding to influence of temperature on the Q-gauge Pressure reading, it is calibrated by the temperature dependence at low humidity. Finally, influences of temperature and humidity on the hydrogen sensing can be reduced by the calculation below the reading by 0.6 at.% of hydrogen gas.
Tokihiko Kobata - One of the best experts on this subject based on the ideXlab platform.
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evaluation and correction for long term drift of hydraulic Pressure Gauges monitoring stable and constant Pressures
Measurement, 2019Co-Authors: Hiroaki Kajikawa, Tokihiko KobataAbstract:Abstract We have evaluated a long-term drift of hydraulic Pressure Gauges which are kept under constant Pressure application. Three Pressure Gauges were pressurized and kept at 100 MPa, and the variations in calibration results at 100 MPa have been traced for 800 days. The calibration results significantly varied immediately after the Pressure application, and the variation rate became small and almost constant as the Pressure was continuously applied. The observed drift trend was different from the drift which is observed when the Gauges are always kept at atmospheric Pressure. In addition, during the Pressure application, the Pressure was intermittently released to atmospheric Pressure for a short time, and outputs at atmospheric Pressure were obtained. The calibration results at 100 MPa and atmospheric Pressure showed a similar drift trend, showing that most part of the drift under Pressure can be corrected by zero offset. Several methods are proposed to appropriately evaluate and correct the long-term drift of Pressure Gauges during use under constant Pressure application.
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Effects of setting attitude of high gas Pressure gauge on calibrated values
2017 56th Annual Conference of the Society of Instrument and Control Engineers of Japan (SICE), 2017Co-Authors: Hideaki Iizumi, Hiroaki Kajikawa, Tokihiko KobataAbstract:For high gas Pressure measurements, a quartz Bourdon-type Pressure gauge is one of the highest precision Pressure Gauges. Setting attitude of the Pressure Gauges differ according to measurement application. In this paper, the effects of the setting attitude on calibrated values were evaluated. The maximum difference of calibration values by the setting attitude was about 10 kPa, relatively 0.01 % at 100 MPa. The reason for the effect of setting attitude was related to the gravitational force generated by the weight of Pressure medium inside a sensing element. The Pressure gauge was also calibrated by using nitrogen and helium at different attitudes. From those evaluations, the effect on the calibrated values is evaluated as function of the setting attitude and Pressure medium. It is recommended that the Pressure Gauges are used with the same fixed setting attitude as they were calibrated.
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reproducibility of calibration results by 0 a 0 pressurization procedures for hydraulic Pressure transducers
Measurement Science and Technology, 2014Co-Authors: Hiroaki Kajikawa, Tokihiko KobataAbstract:This paper focuses on 0-A-0 pressurization for the calibration of electromechanical Pressure Gauges in order to obtain reproducible results by various procedures. In 0-A-0 pressurization, Pressure is released to atmospheric Pressure after finishing each measurement at each calibration Pressure, and the output reading at atmospheric Pressure is used for offset correction. Pressure Gauges are calibrated under various Pressure sequence and time interval conditions in the Pressure range of 10 MPa to 100 MPa using a fully automated calibration system that uses a Pressure balance as the standard device. Results for a quartz Bourdon-type Pressure transducer are mainly reported. The hysteresis obtained by 0-A-0 pressurization is found to be nearly one-tenth of that obtained by stepwise pressurization. The effect of the previously applied Pressure is less than 10 parts per million even for a random Pressure sequence. Key points for calibration procedures are proposed from the calibration results for different time intervals. When the appropriate procedure is used, 0-A-0 pressurization largely reduces the effect of pressurization history, thus yielding highly reproducible calibration results.
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effects of pressurization procedures on calibration results for precise Pressure transducers
Measurement Science and Technology, 2010Co-Authors: Hiroaki Kajikawa, Tokihiko KobataAbstract:The output of electromechanical Pressure Gauges depends on not only the currently applied Pressure, but also the pressurization history. Thus, the calibration results of Gauges are affected by the pressurization procedure. In this paper, among several important factors influencing the results, we report the effects of the interval between the calibration cycles and the effects of the preliminary pressurizations. In order to quantitatively evaluate these effects, we developed a fully automated system that uses a Pressure balance to calibrate Pressure Gauges. Subsequently, Gauges containing quartz Bourdon-type Pressure transducers were calibrated in a stepwise manner for Pressures between 10 MPa and 100 MPa. The typical standard deviation of the data over three cycles was reduced to a few parts per million (ppm). The interval between the calibration cycles, which ranges from zero to more than 12 h, exerts a strong influence on the results in the process of increasing the Pressure, where at 10 MPa the maximum difference between the results was approximately 40 ppm. The preliminary pressurization immediately before the calibration cycle reduces the effects of the interval on the results in certain cases. However, in turn, the influence of the waiting time between the preliminary pressurization and the main calibration cycle becomes strong. In the present paper, we outline several possible measures for obtaining calibration results with high reproducibility.
Shingo Ichimura - One of the best experts on this subject based on the ideXlab platform.
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A possible hydrogen sensing method with dual Pressure Gauges
Sensors and Actuators A: Physical, 2006Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:Abstract In this work, we present a novel method for hydrogen sensing, based on partial Pressure measurements with a diaphragm and a quartz friction Pressure gauge (D- and Q-Gauges, respectively). The D-gauge measures absolute Pressure, whereas Q-gauge readings are affected by viscosity changes occurring when hydrogen is mixed with air, thus enabling H 2 detection. The new method is safe and sensitive and has a quick-response to hydrogen leakage. The measured minimum detection limit for hydrogen is 0.05 vol.% in air, and the response time to hydrogen introduction is less than 1 s; these characteristics are practically sufficient for hydrogen sensing.
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Hydrogen Gas Sensing using Two Type of Pressure Gauges
Journal of The Vacuum Society of Japan, 2005Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:For safety hydrogen sensing, the Pressure measurement with a capacitance manometer and a quartz friction Pressure gauge (Q-gauge) were investigated. Q-gauge Pressure reading decreases when hydrogen gas is introduced into air supplied from atmosphere without any change of Pressure measured by a capacitance manometer. This result indicates that the present Pressure measurement using two Pressure Gauges is possible to detect the hydrogen leakage into air. In addition, a decrease of Q-gauge Pressure reading correlates with a flow rate of the hydrogen gas, and increases with hydrogen concentration in air. Then it was shown that the low detection limit of hydrogen concentration is below 1%. Response time for hydrogen introduction is faster than 30 seconds, which meets the requirements for the hydrogen gas leak sensor. As above, the present safe Pressure measurement using a capacitance manometer and a Q-gauge is satisfactorily useful for the hydrogen gas leak sensing.
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Influence of Temperature and Humidity on Partial Pressure Measurement using Dual Pressure Gauges
Shinku, 2005Co-Authors: Atsushi Suzuki, Akira Kurokawa, Hidehiko Nonaka, Shingo IchimuraAbstract:Taking into account the utilization of partial Pressure measurement under various temperatures and humidity, their influence on this measurement with a capacitance manometer and a quartz friction Pressure gauge (Q-gauge) is studied. With increasing humidity, a Q-gauge Pressure reading, calibrated by air gas, decreases as well as when the hydrogen leakage is detected. To avoid this error by humidity for the hydrogen sensing, we tried to compensate influence of humidity using a humidity coefficient which is calculated from the humidity dependence of the Q-gauge Pressure reading at constant temperature, and suppressed to one-fifth of the fluctuation of the Q-gauge Pressure reading background due to humidity change. Regarding to influence of temperature on the Q-gauge Pressure reading, it is calibrated by the temperature dependence at low humidity. Finally, influences of temperature and humidity on the hydrogen sensing can be reduced by the calculation below the reading by 0.6 at.% of hydrogen gas.
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Ozone Concentration Measurement of O2-O3 Binary Gas with Two Types of Pressure Gauges
Shinku, 2004Co-Authors: Akira Kurokawa, Sonoko Tsukahara, Hisao Hojyo, Takichi Kobayashi, Shingo IchimuraAbstract:A concentration measuring method for a binary gas system, which was based on the viscosity measurement, was investigated. The method utilizes two types of Pressure Gauges, a capacitance manometer which depends just on Pressure and a quartz friction Pressure gauge which depends on both viscosity and Pressure of a binary gas. The concentration of the binary gas can be estimated from the viscosity because the viscosity is given as a function of concentration of the binary gas. Firstly we applied the Pressures-observing system to evaluate concentration of ozone in an O3/O2gas mixture. The results indicated that this method allows a concentration measurement of ozone with an accuracy ofΔ Cozone = 0.2 vol%, near atmospheric Pressure. Secondly, we used an impedance measurement system of a quartz oscillator and we estimated the accuracy at Δ Cozone=0.05 vol%.
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Partial-Pressure measurement of atmospheric-Pressure binary gas using two Pressure Gauges
Vacuum, 2004Co-Authors: Akira Kurokawa, Kenji Odaka, Shingo IchimuraAbstract:Abstract We investigated a new method to measure the partial Pressure of a binary gas system at near-atmospheric Pressure conditions. The method utilizes two types of vacuum Gauges, a capacitance manometer and a quartz friction Pressure gauge. The partial Pressure of the binary gas can be estimated by measuring the impedance change with a quartz friction Pressure gauge, which depends on both viscosity and total Pressure of a binary gas, and considering the total Pressure change as measured by a capacitance manometer. We applied this method to measure the partial Pressure of ozone in an ozone–oxygen gas mixture. The results suggested that the new method allows a partial-Pressure measurement of ozone with an accuracy of Δ p =0.2 kPa , close to atmospheric Pressure. The advantages of the new method include compact size, high safety standards when measuring highly reactive gases, and the allowance for in-line monitoring.