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1

The relationship between changes in joint kinematics parameters and mechanomyographic signals during non-isometric contraction in human skeletal muscle

Ohta Y.

Acta of Bioengineering and Biomechanics

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2013

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Vol. 15, no. 2

97--104

EN

The present study determines the effects of summation of contraction on joint kinematics in human ankle and mechanomyography (MMG) signals during non-isometric contraction. The excursion and angular velocity of dorsiflexion and eversion were measured during several summation profiles during non-isometric contractions. The joint kinematics parameters and MMG responses to 1–8 pulses at a constant interval of 10 ms were recorded to investigate the effects of different numbers of stimuli. In an examination of two-pulse trains with different inter-pulse intervals, the joint kinematics parameters and MMG responses to inter-pulse intervals of 10–100 ms were recorded from the tibialis anterior muscle. The main finding was that facilitating effects of subsequent stimulation were limited to angular velocity of eversion during the contribution of a second stimulus, suggesting that facilitating effects of second stimulus reflect angular velocity but not joint angle excursion. A comparison with MMG signals clarified that MMG signals poorly correlate with changes in the joint kinematics parameters (excursion and angular velocity) when the inter-pulse intervals or numbers of stimuli are increased. These findings will provide useful information for assessing the muscle contractile properties with evoked MMG signals during non-isometric contraction.

2

Effects of tendinous tissue properties on force output evoked by 2-pulse trains at different inter-pulse intervals in the human tibialis anterior muscle

Ohta Y.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 4

45-52

EN

The aim of this study was to clarify the effects of tendinous tissue properties on origin of greater force output at short inter-pulse intervals in the 2-pulse trains compared to those at longer inter-pulse intervals. Thus, this study investigated the contributions of the second stimulus (C2) in 2-pulse trains with different inter-pulse intervals on the torque response and tendinous tissue properties of human skeletal muscle in vivo. The torque response and tendinous tissue elongation following single pulses and 2-pulse trains at different inter-pulse intervals (5, 10, 20, 30, 40, 50, 80, 100, 150, and 200 ms) were recorded in the tibialis anterior muscle using real-time ultrasonography. C2 with inter-pulse intervals of 5-100 ms invoked significantly greater torque responses than single pulses. In contrast, the elongation and compliance of tendinous tissue for C2 with inter-pulse intervals from 5-80 ms were significantly lower than those of the single-pulse response. A significant negative relationship between torque response and tendinous tissue compliance was observed in C2 with different inter-pulse intervals. The torque response as a result of C2 is greater at short inter-pulse intervals in which the force summation due to second stimulus coincides with the period of decreased tendinous tissue compliance due to the first stimulus.

3

Low-temperature ignition phenomena and control for the internal combustion engine applications

Ohta Y.

Journal of KONES

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2006

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Vol. 13, No. 2

479-479

EN

Autoignition timing of the premixed cylinder charge is still in the God's will, however, it should be controlled to be the optimum artificially in the real engines. Basic studies on physico-chemical characteristics of low-temperature flames: cool and blue flames, using a rapid-compression machine, a motored engine, shock tubes and a flat-flame Powling burner have been of great assistance to understand the in-cylinder ignition phenomena and to develop the ignition-control procedures in engines. In the first half, the properties of low-temperature flames will be shown, and then some examples of application will be presented. The following is an example. We proposed two kinds of ignition-timing control procedures. The first one: the high/ low-octane two-fuel premixed compression-ignition would make it easy to achieve the best ignition timing. By changing the ratio of fuel amount between high- and low-octane fuels in intake charge, both output torque and ignition timing can be controlled, as well as achieving a high thermal efficiency and clean exhaust. The role of the low-octane fuels is a promoter for the high-octane main fuel ignition. The second one: a small amount of formaldehyde is supplied, not as a fuel but as an additive, into the premixed intake charge of fuel and air. The formaldehyde addition would show a strong promoting effect for the mixture ignition of natural gas. A certain amount of formaldehyde to be added into the intake fuel/air mixture can be chosen for the adequate ignition occurrence near the top dead center depending on the mixture strength. The reasons of low-NOx / high-HC emission characteristics were also explored and explained. • The amount of formaldehyde added to the fuel/air mixture becomes a sole controlling factor to the ignition timing. The effect of formaldehyde addition is inhibitory for the mixtures with advanced hot-flame ignition timings as contrasted with a promoting effect to the mixtures with retarded ignition timings. • The day-by-day ignition-characteristic fluctuation of the fuel gases can be eliminated by using a small amount of formaldehyde. Formaldehyde is efficacious as an ignition controlling medium for the hydrocarbon/air mixtures in engine cylinders. The effect leading to the ignition would be an inhibitory event for the cool-flame generating constituent and a promoting event of the preflame reaction of the non-cool-flame generating constituent in the fuel gases. Neither secondary fuel nor additives, i.e. the in-cylinder transformation of the charge to be ready for autoignition would be the near-future subjects for the engines of all kinds, especially for the premixed compression-ignition engines.

4

Ionization of in-cylinder charge during preflame period in compression ignition of mixtures

Furutani M., Sato M., Shichi H., Ohta Y.

Journal of KONES

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2004

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Vol. 11, No. 1-2

157-164

EN

Ion formation has been detected in cool and blue flames that appear during the preflame period of mixture ignition caused in a rapid compression machine. An ionization gap was installed in the combustion chamber. Ion current level is much lower than that of normally observed in propagation flames, but highly reproducible. Ions arise at the time the cool flame degenerates, and again in the blue-flame induction time T2. Breakdown of electric non-conductance during the preflame period has been investigated recently using a motored premixed-compression ignition engine. An electrode gap was installed in the combustion chamber. Between the electrodes a high static voltage of 2 200 V was given, charged in a small capacitor. It has been found that the timing of discharge or break down during the preflame period was the time in which the cool flame began to appear. Several attempts have been made to detect ionization of low-temperature flames produced by piston compression or on a flat burner, and to obtain advanced knowledge on the role the low-temperature reactions, which perform for the onset of final hot-flame ignition.

5

Glow-plug assisted cold start of premixed compression-ignition natural-gas engines

Yamaya Y., Takemoto T., Furutani M., Ohta Y.

Journal of KONES

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2003

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Vol. 10, No. 1-2

303-309

EN

A glow-plug assisted procedure is examined herewith to try to establish easy start and warm-up processes of the premixed-compression-ignition (i.e. homogeneous charge compression ignition, HCCI) natural-gas engines easy. A confirmation experiment is shown using a single cylinder engine and the natural gas/air mixture with an equivalence ratio of 0.6. The wall temperature of the combustion chamber was an important controlling factor to obtain the heat release of hot-flame explosion for the engine starting and warming, even though the glow plug would assist the ignition process of the mixture. It is necessary to get blue-flame dominant charge temperature, 850 K, near the top dead center by the piston compression of the mixture to establish self-sustaining engine operations. A glow plug installation will raise the local mixture temperature, which will result in the higher local temperature of compressed mixture. The formaldehyde addition into the charge makes it easy to obtain the hot-flame ignition during the starting and warming.

6

Formaldehyde for the premixed compression-ignition engine - an additive for ignition-timing control -

Yamaya Y, Furutani M., Ohta Y.

Journal of KONES

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2002

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Vol. 9, No. 1-2

291-297

EN

Lean fuel/air mixtures with various fuel/fuel ratios between methane and n-butane were supplied to a premixed compression-ignition engine (i.e. homogeneous charge compression ignition engine, HCCI) with or without supplementary gaseous formaldehyde induction as an ignition controlling additive. In the no additive case the methane and butane function as the two fuels in the high/low-octane two-fuel premixed compression-ignition operation we proposed previously as another ignition control procedure. The formaldehyde addition to the methane/ butane/air mixtures has given the engine desired and stable ignition timings controllable by the amount of formaldehyde to be added, almost independent on the fuel/fuel ratios between methane and butane. The efficacy of formaldehyde has been confirmed as an ignition controlling medium for the piston-compression ignition of hydrocarbon/air mixtures.

7

A key to achieve ignition carbon monoxide generation/consumption in blue-flame period during hydrocarbon compression ignition

Furutani M., Ohta Y., Nose M.

Journal of KONES

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2001

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Vol. 8, No. 1-2

1-8

EN

A criterion between success and failure of marginal fuel/air compression ignition was searched for using a rapid compression machine. A barely achieved ignition process was compared to a case no ignition was established due to a slightly insufficient compression pressure level. The differential on the chemical species histories during the induction periods between both cases was examined by continual different-timing gas samplings. A distinguished difference could be found only on the carbon-monoxide/carbon-dioxide ratio between the flammable and nonflammable critical conditions. The ratio increased continuously in the ignition success cases. There were no differences in other species concentration, such as gaseous water, hydrogen, formaldehyde and ethylene . At the time just before the final hot-flame onset the carbon-monoxide concentration came up to around 7 000 ppm, independent of the mixture strength. A steady carbon-monoxide/carbon-dioxide ratio was observed in the case no hot-flame onset was established. Continuous growing of carbon monoxide during the blue-flame period would be an indication for the transfer to the final hot-flame ignition.