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Behavior of piston rings passing over cylinder ports in two-stroke cycle engines
Kohei Nakashima,Yuki Nakano,Soichi Ishihara,Yoshio Murakami,Masago Yamamoto 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
In two-stroke cycle engines, the piston and piston ring slide over not only the cylinder wall but also the cylinder ports. This study investigates whether piston rings project and get caught in the cylinder ports. We installed strain gauges, on the bottom sides of piston rings,over the intake and exhaust ports, and plotted the variation of strain per cycle, while running the engine. By examining the variation in strain on the bottom of the piston ring, we clarified that our piston ring indeed became momentarily caught in the cylinder ports.
Computer Simulation of Enhancement of Coerciviy in Nd-Fe-B/(Nd,Dy)-Fe-B Composite Magnets
Kohei Kawasaki,Takeshi Yanai,Masaki Nakano,Hirotoshi Fukunaga 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
The coercivity Hc of Nd₂Fe₁₄B magnets and Nd₂Fe₁₄B/(Nd0.7Dy0.3)₂Fe₁₄B composite magnets were calculated by computer simulation based on the micromagnetic theory under assumptions that Nd₂Fe₁₄B and (Nd0.7Dy0.3)₂Fe₁₄B grains have magnetically deteriorated layers on their surfaces and diffusion of Dy from (Nd0.7Dy0.3)₂Fe₁₄B grains to Nd₂Fe₁₄B ones through the contacting boundaries recovers the magnetic anisotropy of the deteriorated layers of Nd₂Fe₁₄B grains. Hc of Nd₂Fe₁₄B/(Nd0.7Dy0.3)₂Fe₁₄B composite magnets increased by the diffusion of Dy from (Nd0.7Dy0.3)₂Fe₁₄B grains to Nd₂Fe₁₄B ones and the resultant recovery of the anisotropy field of deteriorated layers of Nd₂Fe₁₄B grains. The Hc vs fraction of (Nd0.7Dy0.3)₂Fe₁₄B grains curve were convex for the magnets with the degree of alignment between 0.94 and 0.99, which suggests that the above composite magnets have larger Hc values than the alloy-magnets with the same Dy content, and that we can save the consumption of Dy by using these composite magnets.
Zikrilla Bobamuratovich Alimov,Hyunwoo Youn,Ayumi Iwata,Kohei Nakano,Takuma Okamoto,Ayaha Sasaki,Takuya Katori,Tomoaki Okuda 한국대기환경학회 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.3
Cyclone sampling devices have been helpful in assessing the toxic effects of fine particulate matter (PM2.5). The particle collection efficiency of sampling devices is critical. This study investigated the effect of cyclone size on particle size, chemical composition, and particle toxicity. Three cyclones with different inner diameters (12-68 mm) were tested for penetration using an aerodynamic particle sizer, fluorescent polystyrene latex, and a differential mobility analyzer. The elemental and water-soluble ion compositions of the particles collected by different cyclones were compared. An evaluation of the particles’ toxicity was conducted by comparing the results of dithiothreitol (DTT), limulus amebocyte lysate (LAL), and cell exposure assays. The experimental evaluation showed a 50% cut-size of the cyclones between 0.17-0.28, 0.34-0.36, and 0.70 μm for the small, medium, and large cyclones, respectively. To collect PM2.5 and evaluate separation performance in the real environment, the small and large cyclones were selected according to the particle penetration and flow rate. A comparison of chemical composition and enrichment factor values found that the particles in the small cyclone samples contained smaller and more anthropogenic sources than those in the large cyclone samples. The oxidative potential (OP) measured by the DTT assay of the samples collected using the small and large cyclones differed across sampling periods and associated with the transition metals. The viability of human epithelial A549 cells after exposure to the collected particles using the cyclones was different across sampling periods and associated with OP. The endotoxin concentrations measured in the LAL assay were found only in the large cyclone samples; they affected the estimated level of cytokine based on IL(interleukin)-6 release from human leukemia monocytic (THP-1) cells derived macrophage- like cells. Regardless of the size, the cyclone techniques used in this study to collect aerosol particles would be a powerful tool for a detailed evaluation of particle toxicity.
Hypoxia Tolerance Evaluation of Red Leaf Lettuce by Expression Analysis of LsADH Gene
( Mana Kumazawa ),( Manasikan Thammawong ),( Hushna Ara Naznin ),( Kohei Nakano ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
The aim of this study was to evaluate the hypoxia tolerance of fresh produce by gene expression analysis. An alcohol dehydrogenase-encoding gene (ADH), which is a key factor determining anaerobic metabolism, was analyzed in red leaf lettuce stored at 25 ºC under various O<sub>2</sub> conditions. LsADH expression of samples stored under 15%, 10% and 3.5% O<sub>2</sub> condition was detected about 6 times higher than the control (20.9%), and it was remarkably increased by 12 times when stored under 2% O<sub>2</sub>. On the other hand, the respiratory quotient breakpoint (RQB) was determined as 0.3% because RQ was mostly stable at around 1.1 under the O<sub>2</sub> level ranged from 20.9% to 0.3%, and notably increased at below 0.3%. The fermentation threshold (FT) was found as 1% because ethanol and acetaldehyde were remarkably accumulated at below 1%O<sub>2</sub>. In this study, 2% O<sub>2</sub> at which the relative gene expression level of LsADH increased markedly was considered as the gene expression breakpoint (GEB). From this fact, the ‘low O<sub>2</sub> limit’, estimated based on GEB is relatively higher and more sensitive compared to RQB and FT methods. GEB is thought to be a useful indicator in determining the appropriate O<sub>2</sub> concentration for storing fresh produce.
Change of Phospholipid Species in Japanese Mustard Spinach Leaves during Senescence
( Daichi Nagaya ),( Daimon Syukri ),( Manasikan Thammawong ),( Kohei Nakano ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
In this study, a wide target analysis of phospholipid species in Japanese mustard spinach leaves stored for different durations was conducted by mass spectrometry, and phospholipid class distribution and fatty acid composition were compared for the purpose of identifying the freshness maker metabolites. Self-cultivated Japanese mustard spinach (Brassica rapa var. perviridis) leaves were harvested and stored for 4 and 7days at 20°C. Lipid in the leaves was extracted by a MTBE method and brought to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The multiple reaction monitoring (MRM) program for a total 141 phospholipids was prepared and used for a highly sensitive detection. Peak area of MRM chromatogram for each phospholipid molecule were calculated and compared using t-statistics. The highest number of phospholipids (43) were detected on day 7 whereas 41 was found on day 0. Almost all the phosphatidylcolines (PC) and phosphatidylinositols (PI) increased during senescence, but the other phospholipid classes were found unchanged. Especially, PI (14:1/16:1) and PC (32:1) increased significantly and were suggested to be a potential freshness marker metabolite. Further study is needed to confirm these findings through the quantitative determination.
( Nana Takahara ),( Manasikan Thammawong ),( Hushna Ara Naznin ),( Kohei Nakano ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
The aim of this study was to explore the optimum temperature treatments for prolonged storage of vegetables avoiding chilling stress. Electrolyte leakage, antioxidant gene expressions and ascorbic acid (AsA) were analyzed in cucumber fruits, stored at different temperature conditions to reveal the relationship between the reversibility of chilling injury (CI) and antioxidant activity. Results showed that electrolyte leakage from cucumber fruit was increased during storage at 2°C, however, it decreased when storage temperature was changed from 2°C to 15°C on 3rd and 6th day of storage, that is, CI was reduced. On the other hand, electrolyte leakage continued to increase, even storage temperature was changed on 9th day of storage; CI was progressed. In addition, the expressions of CsAPX and CsSOD1 were always found increased when the storage temperature was changed at any storage length. Meanwhile, the expression of CsCAT was found increased only when storage temperature was changed on 3rd day of storage and it was reduced in spite of changing of the store temperature on 6th and 9th day of storage. From these observations, antioxidant activity might be accelerated when fruits were moved from low temperature to over the critical temperature for chilling stress, as a result, accumulation of reactive oxygen species (ROS) was decreased to recover the membrane function leading to the reversibility of chilling injury by 6 days of storage. In addition, expression of CsCAT was reduced when storage temperature was changed after 6th day of storage. However, excessive accumulation of ROS at 9 days caused by long storage at 2°C, the decreasing of CsCAT gene expression and lower production of AsA lead to the irreversibility of chilling injury.