Details of a Researcher - Ogawa, Kuniyasu

Papers - Ogawa, Kuniyasu

Division display 1 - 20 of about 68 ／ All the affair displays >>

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: water content distribution in logs measured by magnetic resonance imaging

Ogawa K., Yashima T.

Wood Science and Technology (Wood Science and Technology) 56 ( 1 ) 25 - 62 2022.01

ISSN 00437719

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. To study the enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs, six dried test logs (Quercus serrata, diameter of 38 to 48 mm, length of 110 to 118 mm) were used. Three test logs had shiitake mycelium grown on them, and the remaining three test logs had mold generated on them. Liquid water was supplied to the bottom surface of the test log which had its longitudinal direction along the line of gravity. Water content distribution in the logs was measured in chronological order using magnetic resonance imaging (MRI) with 1 Tesla. The calibration curve for converting the signal intensity of the MR image into the water content in the test log was determined by cutting the test log at 5-mm intervals and measuring the water content distribution using the mass method. Spatial distribution of the water content of the test log without shiitake mycelium depending on the cumulative water supply time was obtained, and the distribution shape was always concave corresponding to the exact solution of an unsteady one-dimensional diffusion equation with one diffusion coefficient. In the case of the test log in which shiitake mycelium grew, within a few hours after liquid water supply the water content increased in the whole region where shiitake mycelium grew, and the shape of the water content distribution in the longitudinal direction became convex. Based on observation of water penetration into logs by MRI and an optical microscope, it is believed that the driving force behind increased rise in liquid water in the longitudinal direction in the test log is the capillary force acting in vessels.

Access to Document (DOI)

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: increase in effective diffusion coefficient based on mass of liquid water uptake

Ogawa K., Yashima T.

Wood Science and Technology (Wood Science and Technology) 55 ( 5 ) 1237 - 1267 2021.09

ISSN 00437719

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. In this study, six test logs (Quercus serrata, diameter of 38–48 mm, length of 110–118 mm) were used, of which some were dried, some had shiitake mycelia grown on them, and some had mold generated on them. Liquid water was supplied to the test logs by placing the longitudinal direction of the test logs along the line of gravity and immersing the bottom of the test logs in water. Water uptake mass of the test logs was measured for 20 h. The effective diffusion coefficient, Deff, was calculated from the change in time of the water uptake mass using Fick's diffusion law. The Deff of test logs in which shiitake mycelium grew were 1.5–3.4 × 10–8 m2/s, and the values were 2.4–4.7 times higher than that for the dried log. On the other hand, the Deff of the moldy logs were 6.7–9.7 × 10–10 m2/s, which was 0.058–0.081 times that of dry test logs. Based on observation of water penetration into logs by magnetic resonance imaging (MRI) and an optical microscope, it is believed that the driving force behind liquid water rising in the longitudinal direction in the test log is the capillary force acting on a three-phase interface consisting of the inner wall surface of the vessel, liquid water and air.

Access to Document (DOI)

MRI visualization of shiitake mycelium growing in logs in order to support shiitake mushroom log cultivation

Ogawa K., Yashima T.

Cellulose (Cellulose) 27 ( 16 ) 9605 - 9621 2020.11

ISSN 09690239

In order to correlate the yield and quality of shiitake mushrooms with the growth process of shiitake mycelium in logs over several years, a non-invasive visualization method using a magnetic resonance imaging (MRI) measurement system was developed. The MRI measurement system had a permanent magnet of 1.0 T magnetic field strength and a 110 mm air gap. The test logs in which grew the shiitake mycelium had a diameter of 43–48 mm, a length of 110–118 mm and a dried mass of 125–135 g. The log was inoculated on one cutting surface after being supplied water, and was placed in a thermostatic chamber (21 °C, about 75% humidity) for 69 days. The test log was observed by MRI, and MR images and T maps of shiitake mycelium growing over time were obtained. It was found that the shiitake mycelium has a T relaxation time constant longer than 150–200 ms, and its signal intensity in the MR images is smaller than that of water penetrated into a log. When making the MRI measurements, it is necessary to dry a log to water content of about 20% or less. In addition, a control log with mold was also observed by MRI. The shiitake mycelium can be distinguished from water penetrated into log and mold occurring in the log by combining the T —signal intensity map and clear recognition of a low-intensity region in MR images acquired at longer echo times. 1 1 1

Access to Document (DOI)

Two-dimensional spatial distributions of the water content of the membrane electrode assembly and the electric current generated in a polymer electrolyte fuel cell measured by 49 nuclear magnetic resonance surface coils: Dependence on gas flow rate and relative humidity of supplied gases

Ogawa K., Sasaki T., Yoneda S., Tsujinaka K., Asai R.

Journal of Power Sources (Journal of Power Sources) 444 2019.12

ISSN 03787753

A PEFC (polymer electrolyte fuel cell) with a large power generation area of 140 mm × 160 mm has spatial distributions of the water content of the MEA (membrane electrode assembly) and the electric current produced that depend on the flow rate and relative humidity of the supplied gas. When 49 NMR (nuclear magnetic resonance) surface coils arranged in 7 rows × 7 columns were inserted into the PEFC, two-dimensional spatial distributions of the water content of the MEA and the electric current could be measured from the acquired NMR signals. The water content of the MEA was calculated from the intensity of the NMR signal, and the electric current distribution was determined by an inverse analysis that reproduces the spatial distribution of the resonance frequency of the NMR signals. The PEFC, which was supplied with hydrogen and oxygen at a high humidity of 80 %RH, generated electric power at 130 A over the whole area of the MEA. On the other hand, under a low humidity of 40 %RH and low flow rate conditions, the water content of the MEA became high in the midstream and downstream regions, and a high electric current was generated in these regions.

Access to Document (DOI)

MRI visualization of shiitake mycelium growing in woodchip blocks used for shiitake mushroom cultivation

Ogawa K., Yashima T.

Magnetic Resonance Imaging (Magnetic Resonance Imaging) 58 90 - 96 2019.05

ISSN 0730725X

In order to eliminate woodchip blocks where unwanted fungi have grown and select only blocks where shiitake mycelium are growing well, there is a need to develop a visualization technique for shiitake mycelium growing in woodchip blocks, and MRI is an obvious candidate technique. From the results of measurements of the woodchip bed in a small bottle (26 mm inside diameter) where shiitake mycelium was growing, the T relaxation time constant immediately after inoculation was 77.9 ± 5.5 ms, and the value after about 10 to 20 days increased to 135.0 ± 9.8 ms (the increase rate was 73%). The T maps of the wood-chip block (130 mm length, 75 mm height and 55 mm thickness) in which shiitake mycelium grew were calculated from T weighted images measured by changing TR from 28 to 400 ms. From the T maps of time series, it was found that the shiitake mycelium extended from the right-hand side to the left-hand side of the woodchip block in a planar manner. Furthermore, in a woodchip block in which penicillium was generated, since the T relaxation time constant of only the shiitake mycelium became longer, it was possible to visualize the shiitake mycelium distinctly from penicillium. 1 1 1 1 1

Access to Document (DOI)

Numerical analysis of O2 concentration, gas - zeolite temperatures in two zeolite columns for an oxygen concentrator

OGAWA KUNIYASU

International Journal of Heat and Mass Transfer (Elsevier) 129 238 - 254 2019.01

Research paper (scientific journal), Joint Work, Accepted, ISSN 00179310

Access to Document (DOI)

Two dimensional distribution measurement of electric current generated in a polymer electrolyte fuel cell using 49 NMR surface coils

Ogawa K., Sasaki T., Yoneda S., Tsujinaka K., Asai R.

Magnetic Resonance Imaging (Magnetic Resonance Imaging) 51 163 - 172 2018.09

ISSN 0730725X

In order to increase the current density generated in a PEFC (polymer electrolyte fuel cell), a method for measuring the spatial distribution of both the current and the water content of the MEA (membrane electrode assembly) is necessary. Based on the frequency shifts of NMR (nuclear magnetic resonance) signals acquired from the water contained in the MEA using 49 NMR coils in a 7 × 7 arrangement inserted in the PEFC, a method for measuring the two-dimensional spatial distribution of electric current generated in a unit cell with a power generation area of 140 mm × 160 mm was devised. We also developed an inverse analysis method to determine the two-dimensional electric current distribution that can be applied to actual PEFC connections. Two analytical techniques, namely coarse graining of segments and stepwise search, were used to shorten the calculation time required for inverse analysis of the electric current map. Using this method and techniques, spatial distributions of electric current and water content in the MEA were obtained when the PEFC generated electric power at 100 A.

Access to Document (DOI)

Two dimensional distribution measurement of electric current generated in a polymer electrolyte fuel cell using 49 NMR coils

OGAWA KUNIYASU

Magnetic Resonance Imaging 51 163 - 172 2018

Research paper (scientific journal), Joint Work, Accepted

100Aで発電している固体高分子形燃料電池（PEFC）から49個のRFコイルでNMR信号を取得し、周波数シフト量の時系列空間分布計測を行った。得られた周波数シフト量を基にして逆解析により電流密度分布を算出した。この論文では逆解析を短時間化する手法として、粗視化法と段階的電流収束法を提案した。これにより、一つの電流分布が10時間で計算できるようになった。

NMR measurement system with 128 rf coils for in-situ water monitoring in a polymer electrolyte fuel cell

OGAWA KUNIYASU

Review of Scientific Instruments (AIP) 88 014701 2017.01

Research paper (scientific journal), Joint Work, Accepted

Access to Document (DOI)

破過前のゼオライト充てん層を通過する微量な水分質量のMRI計測

OGAWA KUNIYASU

日本機械学会論文集B編 (日本機械学会) 82 ( 844 ) 1 - 12 2016.12

Research paper (scientific journal), Joint Work, Accepted

Access to Document (DOI)

The apparent counter diffusion coefficient of water absorbing on zeolite particles packed in a column after stopping the PSA operation

OGAWA KUNIYASU

11th Asian Thermophysical Properties Conference, ATPC2016 2016.10

Research paper (international conference proceedings), Joint Work, Accepted

The apparent counter diffusion coefficient of water absorbing on　zeolite particles in the case of the water moving through macro-size　pores in a column packed with zeolite particles

OGAWA KUNIYASU

Chemical Engineering Journal (Elsevier) 306 889 - 896 2016.08

Research paper (scientific journal), Joint Work, Accepted

METHOD TO ANALYZE THE SPATIAL CURRENT DISTRIBUTION IN AN OPERATING PEFC BASED ON NMR MEASUREMENT USING SMALL PLANAR SURFACE COILS

Kuniyasu Ogawa, Yasuo Yokouchi, Tomoyuki Haishi, Kohei Ito

Proceedings of the 15th International Heat Transfer Conference, IHTC-15 (IHTC-15) IHTC15-8725 2014.08

Research paper (international conference proceedings), Joint Work, Accepted

核磁気共鳴を利用した小型表面コイルによるPEFC 内の電流分布計測法の開発（第３報：PEFC 積層方向に流れる電流分布の逆解析法）

OGAWA KUNIYASU

日本機械学会論文集B編 (日本機械学会) 80 ( 812 ) 1 - 12 2014.04

Research paper (scientific journal), Joint Work, Accepted

Access to Document (DOI)

Differences in Drying/WettingWater Transfer Resistance Through a Platinum Catalyst Layer of a PEMFC Electrode Membrane

OGAWA KUNIYASU

Journal of The Electrochemical Society (ECS) 161 ( 3 ) F239 - F245 2014.01

Research paper (scientific journal), Joint Work, Accepted

Development of an eight-channel NMR system using RF detection coils for measuring spatial distributions of current density and water content in the PEM of a PEFC

Kuniyasu Ogawa,Yasuo Yokouchi,Tomoyuki Haishi and Kohei Ito

Journal of Magnetic Resonance (Elsevier) 234 147 - 153 2013.08

Research paper (scientific journal), Joint Work, Accepted

Measurement of time-dependent changes and spatial distributions of current density in PEFC and water-content of PEM using a planer-surface coil as an NMR signal detector (Second report: Effect of relative humidity and utilization ratio of fuel gas)

Yasuo YOKOUCHI, Kuniyasu OGAWA Tomoyuki HAISHI and Kohei ITO

日本機械学会論文集B編 (日本機械学会) 78 ( 788 ) 928 - 938 2012.04

Research paper (scientific journal), Joint Work, Accepted

Measurement of time-dependent changes and spatial distributions of current density in PEFC and water-content of PEM using a planer-surface coil as an NMR signal detector (Effect of relative humidity and ratio of utilization of fuel gas)

Yasuo YOKOUCHI, Kuniyasu OGAWA Tomoyuki HAISHI and Kohei ITO

日本機械学会論文集B編 (日本機械学会) 78 ( 788 ) 917 - 927 2012.04

Research paper (scientific journal), Joint Work, Accepted

Measurement of Hydrogen-gas Solubility and Diffusivity in Polymer Electrolyte Membrane by NMR Method

Ryosuke Nagahisa, Daiki Kuriya, Kuniyasu Ogawa, Yasuyuki Takata and Kohei Ito

220th ECS Meeting (The Electrochemical Society) 2011.10

Research paper (international conference proceedings), Joint Work

Measurement of current-density in PEFC with NMR sensors

Kuniyasu Ogawa, Yasuo Yokouchi, Tomoyuki Haishi and Kohei Ito

Proceedings of the ASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC2011 (AJTEC2011) AJTEC2011-44370 2011.03

Research paper (international conference proceedings), Joint Work, Accepted

　 Previous page - Next page 　