Published papers

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.

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.

吸着式酸素濃縮器の加圧・減圧過程をモデル化し、酸素・窒素の質量保存式、拡張Langmuirの吸着式、吸着時の発熱・吸熱を含むゼオライトのエネルギー方程式、流動仕事を含むガスのエネルギー方程式、ガスの流速の式を立てた。これらを連立させ、加減圧過程でのゼオライト充填層内の酸素・窒素濃度およびガス温度、ゼオライト温度を解析した。

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

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

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.

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.

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。

固体高分子形燃料電池（PEFC）の電解質膜の含水量と発電電流の空間分布を計測するために128個のRFコイルを用いてNMR信号を0.5秒間隔で計測できる装置を開発した。この計測装置を用いて、98個のRFコイルを挿入した燃料電池を計測した。これにより、高分子膜の含水量とガス流路内の水の空間分布の時間変化が計測できた。

ゼオライト充てん層内の微量の水分量をMRIで計測する手法を開発した。破過前であってもガス中の水分の150分の１が細いゼオライト充てん層を透過して太い充てん層に付着することを見出した。小型酸素濃縮機のゼオライト充てん層の酸素排出側に付着した水はゼオライト充てん層を透過して酸素排出側に達した水であることが分かった．

吸着式酸素濃縮器のゼオライト充てん層の空気吸入側に水分が吸着する。この水分が装置停止時に拡散して、ゼオライトの吸着能力を低下させる。ゼオライト充てん層内に付着した水分の時系列変化をMRIで定量的に計測た。この結果を基に、水分の見かけの拡散係数を解析と付き合わせることで算出した。

吸着式酸素濃縮器のゼオライト充てん層には水分が吸着し、ゼオライトの吸着能力を低下させる。ゼオライト充てん層内に付着した水分の時系列変化をMRIで計測し、水分が時間的に拡散していく様子を見かけの拡散係数として整理した。

小型NMRセンサーを用いて固体高分子形燃料電池内の電流分布を計測した際に、周波数シフト量の空間勾配から電流の空間分布を求めるためのアルゴリズムを開発し、実際の計測結果に適用した。

固体高分子形燃料電池（PEFC）内に小型表面コイルを挿入し、取得したNMR信号の周波数シフト量から電流の空間分布を逆解析する手法を開発した。

固体高分子形燃料電池で用いられる高分子膜の表面の水移動抵抗を計測した。触媒が塗布された高分子膜では乾燥と加湿で水の移動抵抗が異なった。

燃料電池の含水量と電流分布を計測するための計測装置を開発し、同軸ケーブルを使った共振回路を提案した。燃料電池の発電電流分布を計測し、その時系列変化を示した。

核磁気共鳴法を用いた小型表面コイルによる燃料電池内電流密度および固体高分子膜内含水量の空間分布と時間変化を計測した。第二報として、PEFCに供給する燃料ガスの相対湿度と利用率が電流密度分布に及ぼす影響を調べた。

核磁気共鳴法を用いた小型表面コイルによる燃料電池内電流密度および固体高分子膜内含水量の空間分布と時間変化を計測した。第一報として、PEFCに供給する燃料ガスの相対湿度と利用率を変えた時のPEM内含水量に及ぼす影響を計測した。

燃料電池用の固体高分子膜内に水素ガスが溶解する量をNMRにより計測した。水素ガスの圧力と溶解量との関係をまとめた。

固体高分子形燃料電池（PEFC）に小型NMRコイルを挿入し、NMR信号の周波数のシフト量からPEFC内の発電電流の空間分布を計測する方法を開発した。発電時のPEFC内の発電電流の空間分布を示した。