The Experts below are selected from a list of 975 Experts worldwide ranked by ideXlab platform
Sung Hyun Kim - One of the best experts on this subject based on the ideXlab platform.
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Composite membranes based on sulfonated poly(ether ether ketone) and SiO_2 for a vanadium redox flow battery
Korean Journal of Chemical Engineering, 2015Co-Authors: Dong Hun Hyeon, Jeong Hwan Chun, Chang Hun Lee, Hyun Chul Jung, Sung Hyun KimAbstract:Organic-inorganic composite membranes were prepared with sulfonated poly(ether ether ketone) (SPEEK) and different amounts of silica to improve chemical stability and vanadium hindrance for a vanadium redox flow battery. The durability of the prepared composite membrane was verified using a self-made Dummy Cell system and fully charged vanadium cathode half-Cell electrolyte, which contained oxidative vanadium ions (VO _2 ^+ ). The prepared composite membranes, with covalent crosslinking between the organic polymer and inorganic particles, resulted in reduced vanadium permeability and enhanced chemical stability. Ion exchange capacity, water uptake, proton conductivity, and vanadium permeability decreased with increasing silica content. Selectivity was defined to consider both permeability and proton conductivity and resulted in a membrane that exhibited both high proton conductivity and low ion permeability simultaneously. The prepared 1 wt% silica composite membrane showed 133-fold higher selectivity compared with that of a Nafion112 membrane. After the stability test, the composite membrane showed little change compared to the membrane before the stability test, which confirmed the commercial prospect of SPEEK/SiO_2 composite membrane for a vanadium redox flow battery.
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Improvement of the mechanical durability of micro porous layer in a proton exchange membrane fuel Cell by elimination of surface cracks
Renewable Energy, 2012Co-Authors: Jeong Hwan Chun, Sang Gon Kim, Sun Hee Park, Chang Hoon Lee, Sung Hyun KimAbstract:In this study, gas diffusion layers (GDLs) for proton exchange membrane fuel Cell (PEMFC) were subjected to accelerated stress tests to investigate the progression of mechanical degradation of micro porous layers (MPLs) over a short period of time, and crack-free MPL was prepared to enhance the mechanical durability of the MPL. A Dummy Cell was designed for the mechanical degradation of MPLs. There was no catalyst layer in the Dummy Cell and only air was supplied into the Dummy Cell to avoid electrochemical degradation of the MPL. In the MPL degradation experiments, several puddle-shape defects were formed only around the cracks in the surface of the MPL, and these defects negatively affected the performance of the PEMFC. The single Cell performance dramatically decreased at a high current density due to the puddle-shape defects. Thus, crack-free MPL was manufactured to reduce mechanical damage on the surface of MPL by adding a water-soluble polymer binder to the MPL slurry. The puddle-shape defects were not detected on the surface of the home-made crack-free MPL, and the decrease in the single Cell performance after mechanical degradation of MPL was insignificant when the home-made crack-free MPL was used in the cathode.
W. Reczek - One of the best experts on this subject based on the ideXlab platform.
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Design concept for radiation hardening of low power and low voltage dynamic memories
IEEE Journal of Solid-State Circuits, 1995Co-Authors: H. Schleifer, T.v.d. Ropp, K. Hoffmann, W. ReczekAbstract:A radiation hard low power, low voltage dynamic memory is obtained by the use of a Dummy Cell concept. Compared to conventional Dummy Cell concepts, this concept applies a fully sized Dummy Cell. By optimizing the Dummy Cell precharge voltage for 5 V and 3 V operation and the timing of the Dummy word-line, the overall soft error rate (SER) of the chip is improved by 2 orders of magnitude. An additional improvement of 1 order of magnitude is possible for 3 V operation by adjusting substrate bias and Cell plate voltage. The results are verified by an accelerated SER measurement with a radium 226 source and an additional field soft error study.
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Radiation hardening of dynamic memories by the use of a new Dummy Cell concept
Proceedings of IEEE International Workshop on Memory Technology Design and Test, 1994Co-Authors: H. Schleifer, V.d. T. Ropp, W. ReczekAbstract:The soft error rate (SER) of DRAMs with advanced structures can be reduced significantly by the use of a new Dummy Cell concept. Compared to conventional Dummy Cell concepts, this concept applies a fully sized Dummy Cell. By optimising the Dummy Cell precharge voltage and the timing for activation of the Dummy word line, the overall SER of the chip is reduced by two orders of magnitude. This is because the SER sensitivity for a physical "1" is matched to the SER sensitivity for a physical "0". The results are verified by an accelerated SER measurement with a radium 226 source and an additional field soft error study.
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Design Concept for Radiation Hardening of Low Power and Low Voltage Dynamic Memories
ESSCIRC '94: Twientieth European Solid-State Circuits Conference, 1994Co-Authors: H. Schleifer, T.v.d. Ropp, K. Hoffmann, W. ReczekAbstract:A radiation hard low power, low voltage dynamic memory is obtained by the use of an advanced Dummy Cell concept. Compared to conventional Dummy Cell concepts, this concept applies a fully sized Dummy Cell. By optimizing the Dummy Cell precharge voltage for 5V and 3V operation and the timing of the Dummy wordline, the overall soft error rate (SER) of the chip is improved by 2 orders of magnitude. This is because the SER sensitivity for a physical "1" is matched to the SER sensitivity for a physical "0". An additional improvement of 1 order of magnitude is possible for 3V operation by adjusting substrate bias and Cell plate voltage. The results are verified by an accelerated SER measurement with a radium 226 source and an additional field soft error study.
Shawn M. Clapham - One of the best experts on this subject based on the ideXlab platform.
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In-situ membrane hydration measurement of proton exchange membrane fuel Cells
Journal of Power Sources, 2015Co-Authors: Yeh-hung Lai, Gerald W Fly, Shawn M. ClaphamAbstract:Abstract Achieving proper membrane hydration control is one of the most critical aspects of PEM fuel Cell development. This article describes the development and application of a novel 50 cm 2 fuel Cell device to study the in-situ membrane hydration by measuring the through-thickness membrane swelling via an array of linear variable differential transducers. Using this setup either as an air/air (Dummy) Cell or as a hydrogen/air (operating) Cell, we performed a series of hydration and dehydration experiments by cycling the RH of the inlet gas streams at 80 °C. From the linear relationship between the under-the-land swelling and the over-the-channel water content, the mechanical constraint within the fuel Cell assembly can suppress the membrane water uptake by 11%–18%. The results from the air/air humidity cycling test show that the membrane can equilibrate within 120 s for all RH conditions and that membrane can reach full hydration at a RH higher than 140% in spite of the use of a liquid water impermeable Carbel MP30Z microporous layer. This result confirms that the U.S. DOE's humidity cycling mechanical durability protocol induces sufficient humidity swings to maximize hygrothermal mechanical stresses. This study shows that the novel experimental technique can provide a robust and accurate means to study the in-situ hydration of thin membranes subject to a wide range of fuel Cell conditions.
T. Higashi - One of the best experts on this subject based on the ideXlab platform.
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Generation of Accurate Reference Current for Data Sensing in High-Density Memories by Averaging Multiple Pairs of Dummy Cells
IEEE Journal of Solid-State Circuits, 2011Co-Authors: Takashi Ohsawa, Katsuyuki Fujita, Kosuke Hatsuda, Fumiyoshi Matsuoka, T. HigashiAbstract:Methods to generate an accurate reference current by averaging multi-pair Dummy Cells' currents for distinguishing the data in sense amplifiers (S/As) of a large scale memory with resistance change Cell is presented and analyzed. The predicted characteristics are confirmed by comparing them with measurement results of the functionalities and the retention time distributions in a floating body random access memory (FBRAM). The methods are found to be especially effective in situations where signals are seriously degraded such as in sensing the signals of tail bit Cells in retention time distributions, making the retention time performance of the FBRAM improved drastically. The sense amplifiers which can accommodate the Dummy Cell averaging methods are identified to find a necessary condition for a S/A to afford the methods.
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A 128Mb Floating Body RAM(FBRAM) on SOI with Multi-Averaging Scheme of Dummy Cell
2006 Symposium on VLSI Circuits 2006. Digest of Technical Papers., 1Co-Authors: Takashi Ohsawa, T. Higashi, Katsuyuki Fujita, Kosuke Hatsuda, Nobuyuki Ikumi, Tomoaki Shino, Hiroomi Nakajima, Yoshihiro Minami, Naoki Kusunoki, Atsushi SakamotoAbstract:A 128Mbit FBRAM using the floating body Cell (FBC) the size of 0.17mum2 (6.24F2 with F=0.165mum) was successfully fabricated and a high bit yield (~99.999%) was obtained
Jeong Hwan Chun - One of the best experts on this subject based on the ideXlab platform.
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Composite membranes based on sulfonated poly(ether ether ketone) and SiO_2 for a vanadium redox flow battery
Korean Journal of Chemical Engineering, 2015Co-Authors: Dong Hun Hyeon, Jeong Hwan Chun, Chang Hun Lee, Hyun Chul Jung, Sung Hyun KimAbstract:Organic-inorganic composite membranes were prepared with sulfonated poly(ether ether ketone) (SPEEK) and different amounts of silica to improve chemical stability and vanadium hindrance for a vanadium redox flow battery. The durability of the prepared composite membrane was verified using a self-made Dummy Cell system and fully charged vanadium cathode half-Cell electrolyte, which contained oxidative vanadium ions (VO _2 ^+ ). The prepared composite membranes, with covalent crosslinking between the organic polymer and inorganic particles, resulted in reduced vanadium permeability and enhanced chemical stability. Ion exchange capacity, water uptake, proton conductivity, and vanadium permeability decreased with increasing silica content. Selectivity was defined to consider both permeability and proton conductivity and resulted in a membrane that exhibited both high proton conductivity and low ion permeability simultaneously. The prepared 1 wt% silica composite membrane showed 133-fold higher selectivity compared with that of a Nafion112 membrane. After the stability test, the composite membrane showed little change compared to the membrane before the stability test, which confirmed the commercial prospect of SPEEK/SiO_2 composite membrane for a vanadium redox flow battery.
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Improvement of the mechanical durability of micro porous layer in a proton exchange membrane fuel Cell by elimination of surface cracks
Renewable Energy, 2012Co-Authors: Jeong Hwan Chun, Sang Gon Kim, Sun Hee Park, Chang Hoon Lee, Sung Hyun KimAbstract:In this study, gas diffusion layers (GDLs) for proton exchange membrane fuel Cell (PEMFC) were subjected to accelerated stress tests to investigate the progression of mechanical degradation of micro porous layers (MPLs) over a short period of time, and crack-free MPL was prepared to enhance the mechanical durability of the MPL. A Dummy Cell was designed for the mechanical degradation of MPLs. There was no catalyst layer in the Dummy Cell and only air was supplied into the Dummy Cell to avoid electrochemical degradation of the MPL. In the MPL degradation experiments, several puddle-shape defects were formed only around the cracks in the surface of the MPL, and these defects negatively affected the performance of the PEMFC. The single Cell performance dramatically decreased at a high current density due to the puddle-shape defects. Thus, crack-free MPL was manufactured to reduce mechanical damage on the surface of MPL by adding a water-soluble polymer binder to the MPL slurry. The puddle-shape defects were not detected on the surface of the home-made crack-free MPL, and the decrease in the single Cell performance after mechanical degradation of MPL was insignificant when the home-made crack-free MPL was used in the cathode.
