Water Vapor Exchange Flow Channels to Enhance the Performance of Polymer Electrolyte Fuel Cells Without Cathode Humidification

The membrane hydration of the polymer electrolyte fuel cell (PEFC) is required to maintain the efficient and stable operation. In general, the inlet gases are humidified for this purpose. However, from the viewpoint of the total efficiency of a PEFC system and the cost, the humidifier should be omitted. In particular, the cathode side is feasible due to the product water. We have thus developed a flow field design having flow channels for water exchange between the cathode and anode to circulate the product water in a cell. The anode GDL used at the active area was a commercial carbon paper (SGL SIGRACET® 24BA) without the MPL, which was treated by 5 wt% polytetrafluoroethylene (PTFE) loading to impart hydrophobicity. The cathode GDL used at the active area was a 24BA GDL coated with a hydrophobic MPL. The GDLs used at the water vapor exchange part were a 24BA GDL, a hydrophobic MPL coated GDL and a hydrophilic MPL coated GDL. The hydrophilic MPL consisting of polyvinyl alcohol (PVA) and carbon black was coated on the 24BA GDL with a PVA content of 20 wt%. This result indicates that the water vapor exchange part with the hydrophilic MPL coated GDL at the cathode is effective for the recovery of the water contained in the cathode downstream gas, which promotes water transport from the cathode to the anode dry gas in the upstream. This is effective to prevent the membrane dehydration, which reduces the ohmic loss, enhancing PEFC performance, as shown in Acknowledgments This work was supported by Grant-in-Aid for Scientific Research (S) 23226015 from Japan Society for the Promotion of Science (JSPS). References 1. T. Kitahara, H. Nakajima, and K. Mori, Journal of Power Sources, 199, 29 (2012). Abstract #1623, 224th ECS Meeting

Comparison of Humidified Hydrogen and Partly Pre-Reformed Natural Gas as Fuel for Solid Oxide Fuel Cells applying Computational Fluid Dynamics

A three-dimensional computational fluid dynamics (CFD) approach based on the finite element method (FEM) is used to investigate a solid oxide fuel cell (SOFC). Governing equations for heat, gas-phase species, electron, ion and momentum transport are implemented and coupled to kinetics describing electrochemical as well as internal reforming reactions. The model cell design is based on a cell from Ningbo Institute of Material Technology and Engineering in China and the electrochemical area-to-volume ratios are based on experimental work performed at Kyushu University in Japan. A parameter study is performed focusing on the inlet fuel composition, where humidified hydrogen, 30 % pre-reformed natural gas (as defined by IEA) and 50 % pre-reformed natural gas (as defined by Kyushu University) are compared. It is found that when 30 % pre-reformed natural gas is supplied as fuel the air mass flow rate is halved, compared to the case with humidified hydrogen, keeping the inlet and outlet temperatures constant. The current density is decreased but the fuel utilization is kept at 80 %. It is found that the cathode support layer has a significant oxygen gas-phase resistance in the direction normal to the cathode/electrolyte interface (at positions under the interconnect ribs), as well as an electron resistance inside the cathode (at positions under the air channel) in the same direction. The methane steam reforming reaction is shown, both according to the experiments and to the models, to proceed along the main flow direction throughout the cell

Vestibular Compensation after Vestibular Dysfunction Induced by Arsanilic Acid in Mice

When vestibular function is lost, vestibular compensation works for the reacquisition of body balance. For the study of vestibular dysfunction and vestibular compensation, surgical or chemical labyrinthectomy has been performed in various animal species. In the present study, we performed chemical labyrinthectomy using arsanilic acid in mice and investigated the time course of vestibular compensation through behavioral observations and histological studies. The surgical procedures required only paracentesis and storage of 50 μL of p-arsanilic acid sodium salt solution in the tympanic cavity for 5 min. From behavioral observations, vestibular functions were worst at 2 days and recovered by 7 days after surgery. Spontaneous nystagmus appeared at 1 day after surgery with arsanilic acid and disappeared by 2 days. Histological studies revealed specific damage to the vestibular endorgans. In the ipsilateral spinal vestibular nucleus, the medial vestibular nucleus, and the contralateral prepositus hypoglossal nucleus, a substantial number of c-Fos-immunoreactive cells appeared by 1 day after surgery with arsanilic acid, with a maximum increase in number by 2 days and complete disappearance by 7 days. Taken together, these findings indicate that chemical labyrinthectomy with arsanilic acid and the subsequent observation of vestibular compensation is a useful strategy for elucidation of the molecular mechanisms underlying vestibular pathophysiologies

アルサニル酸を用いたマウス内耳破壊後の前庭代償過程

When vestibular function is lost, vestibular compensation works for the reacquisition of body balance. For the study of vestibular dysfunction and vestibular compensation, surgical or chemical labyrinthectomy has been performed in various animal species. In the present study, we performed chemical labyrinthectomy using arsanilic acid in mice and investigated the time course of vestibular compensation through behavioral observations and histological studies. The surgical procedures required only paracentesis and storage of 50 µL of p-arsanilic acid sodium salt solution in the tympanic cavity for 5 min. From behavioral observations, vestibular functions were worst at 2 days and recovered by 7 days after surgery. Spontaneous nystagmus appeared at 1 day after surgery with arsanilic acid and disappeared by 2 days. Histological studies revealed specific damage to the vestibular endorgans. In the ipsilateral spinal vestibular nucleus, the medial vestibular nucleus, and the contralateral prepositus hypoglossal nucleus, a substantial number of c-Fos-immunoreactive cells appeared by 1 day after surgery with arsanilic acid, with a maximum increase in number by 2 days and complete disappearance by 7 days. Taken together, these findings indicate that chemical labyrinthectomy with arsanilic acid and the subsequent observation of vestibular compensation is a useful strategy for elucidation of the molecular mechanisms underlying vestibular pathophysiologies.博士（医学）・甲第742号・令和2年3月16日© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

Cold start cycling durability of fuel cell stacks for commercial automotive applications

System durability is crucial for the successful commercialization of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs). Besides conventional electrochemical cycling durability during long-term operation, the effect of operation in cold climates must also be considered. Ice formation during start up in sub-zero conditions may result in damage to the electrocatalyst layer and the polymer electrolyte membrane (PEM). Here, we conduct accelerated cold start cycling tests on prototype fuel cell stacks intended for incorporation into commercial FCEVs. The effect of this on the stack performance is evaluated, the resulting mechanical damage is investigated, and degradation mechanisms are proposed. Overall, only a small voltage drop is observed after the durability tests, only minor damage occurs in the electrocatalyst layer, and no increase in gas crossover is observed. This indicates that these prototype fuel cell stacks successfully meet the cold start durability targets for automotive applications in FCEVs

Accelerated durability testing of fuel cell stacks for commercial automotive applications : a case study

System durability is crucially important for the successful commercialization of fuel cell electric vehicles (FCEVs). Conventional accelerated durability testing protocols employ relatively high voltage to hasten carbon corrosion and/or platinum catalyst degradation. However, high voltages are strictly avoided in commercialized FCEVs such as the Toyota MIRAI to minimize these degradation modes. As such, conventional durability tests are not representative of real-world FCEV driving conditions. Here, modified start-stop and load cycle durability tests are conducted on prototype fuel cell stacks intended for incorporation into commercial FCEVs. Polarization curves are evaluated at beginning of test (BOT) and end of test (EOT), and the degradation mechanisms are elucidated by separating the overvoltages at both 0.2 and 2.2 A cm-2. Using our modified durability protocols with a maximum cell voltage of 0.9 V, the prototype fuel cell stacks easily meet durability targets for automotive applications, corresponding to 15-year operation and 200,000 km driving range. These findings have been applied successfully in the development of new fuel cell systems for FCEVs, in particular the second-generation Toyota MIRAI

Management of retained products of conception with marked vascularity.

Cases of retained products of conception (RPOC) with marked vascularity present a clinical challenge because simple dilation and curettage (D&C) can lead to life-threatening hemorrhage. We describe here two cases of hypervascular RPOC that were successfully managed with two different approaches. Case 1: A 26-year-old woman with history of 3 D&Cs was transported to the emergency room for heavy vaginal bleeding 45 days after a spontaneous abortion. Diagnosis of RPOC with aneurysm-like structure was considered and uterine artery embolization was performed. Four days after the uterine artery embolization, reduction of the vascularity of RPOC was confirmed on color Doppler ultrasonography and D&C was successfully carried out. Case 2: A 37-year-old woman with history of one cesarean section became pregnant after the regular menses. She underwent D&C for missed abortion at 8 weeks' gestation. Seven days after the D&C, sonographically heterogenous mass emerged in the vicinity of the previous cesarean scar. Thereafter, the mass gradually grew larger and diagnosis of hypervascular placental polyp was considered. As the amount of vaginal bleeding was small, expectant management was instituted. Sixty-one days after the first D&C, reduction of the vascularity of RPOC was confirmed on color Doppler ultrasonography and D&C was successfully completed

Analytical Study on Involvement of Temperature in Friction and Scuffing for Engine Tribo-Components

Regarding the solution for various issues on engine tribology, in order to understand the involvement of temperature in the friction and scuffing under the mixed and/or boundary lubrication regime, the two cases of piston ring & cylinder liner and cam & tappet were analytically studied. The friction between sliding interfaces is composed of four shear stresses from the viscous oil-films, the adsorbed oil molecules, the tribofilms due to oil additives, and the true metal contacts on surface asperities. Since all the shear stress have exponential temperature dependences, the relationship between the frictional shear stress and temperature is assumed to be expressed by the Arrhenius equation. Through analyzing friction data measured in laboratory tests conducted under the same temperature and sliding conditions as during the break-in of engines, various levels of temperature involvement were clarified