• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.10
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• pp.46-53
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• 2011

This paper presents an equalizer reducing CCI(cell-to-cell interference) in MLC NAND flash memory. The CCI is a critical factor which affects occurring data errors in a cell, when surrounding cells are programed. We derived a characteristic equation for CCI considering write procedure of data that is similar with signal equalizing. The model considers the floating gate capacitance coupling effect, the direct field effect, and programming methods of the MLC NAND flash memory. We verify the proposed equalizer comparing with the measured data of 1-block MLC NAND flash memory. As the simulation result, the equalizer shows an error correction ratio about 60% under 20nm NAND process.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.291-295
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• 2007

The oxidation treatment of needle cokes with 70 wt% of nitric acid and sodium chlorate ($NaClO_3$) was attempted to achieve an electrochemically active material with a large capacitance. The structure of needle cokes was changed to graphite oxide after oxidation treatment of needle cokes with acidic solution having the composition ratio, $NaClO_3$/needle cokes, of 7.5, and the inter-layer distance of the oxidized needle cokes was extended to $6.9{\AA}$with increasing oxygen content. On the other hand, the electrochemical performance of oxidized needle cokes as a polarized electrode for an Electric Double Layer Capacitor (EDLC) was examined with an electrolyte of 1.2 M $TEABF_4$ (tetraethylammonium tetrafluoroborate) and $TEABF_4$ (triethylmethylammonium tetrafluoroborate) in acetonitrile. The capacitor cell using 1.2 M $TEABF_4$/acetonitrile has exhibited smaller electric resistance of $0.05{\Omega}$, and larger capacitance per weight and volume of 32.0 F/g and 25.5 F/mL at the two-electrode system in the potential range 0~2.5 V than that of the capacitor cell using $TEABF_4$. The observed electrochemical performance was discussed with the correlation between the inter-layer distance in graphite oxide structure and the anionic size of electrolyte.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.21-26
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• 2002

A supercapacitor was developed using an amorphous ruthenium oxide material. The electrode of supercapacitor was prepared using an amorphous ruthenium oxide, which was synthesized from ruthenium trichloide hydrate$(RuCl_3{\cdo5}xH_2O)$. Thin film of tantalum was used as a current collector because it had wide. potential window characteristics than titanium and 575304 materials. A supercapacitor was assembled with ruthenium oxide as an electrode active material and 4.8M sulfuric acid solution as an electrolyte. The specific capacitance of the electrode was tested by a cyclic voltammetry using a half cell. The maximum differential specific capacitances during the oxidative and the reductive scans were 710 and $645\;F/g-RuO_2{\cdot}nH_2O$, respectively. The average specific capacitance was $521\;F/g-RuO_2{\cdot}nH_2O$. The assembled supercapacitor was protonated to the potential level of 0.5V vs. SCE. Super-capacitor, which was adjusted to the appropriate protonation level, had the specific capacitance of $151\;F/g-RuO_2{\cdot}nH_2O$ based on the concept of full cell.

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.113-117
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• 2001

Specific capacitance and charge-discharge rate of EDLC using activated carbon electrode were affected by the compositions of electrolytes, the conditions of charge-discharge and physical properties of activated carbon materials. The activated carbon electrode was prepared by dip coating method. Charge-discharge test and electrochemical experiments were carried out for various kinds of organic electrolytes. Effects of charge and discharge current density on the specific capacitance were studied. Characteristics of leakage current, self-discharge and time-voltage curves in optimum conditions of organic electrolytes were compared with conventional $1M-Et_4NBF_4/PC$ electrolyte. The EDLC using MSP-20(specific surface area: $2000m^2/g$) electrode and $1M-LiPF_6/PC-DEC(1:1)$ was exhibited th highest specific capacitance of 130F/g and low polarization resistances. The EDLC using MSP-20 electrode at $1M-LiPF_6/PC-DEC(1:1)$ was small leak current of 0.0004A for 15min, long voltage retention of 0.8V after 100h and linear time-voltage curves with small IR-drop.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.353-354
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• 2006

This work describes the effect of binders, such as carboxymethylcellulose (CMC), CMC+Polytetrafluoroethylene (PTFE) and PTFE, on the electrochemical and mechanical properties of activated carbon-electrode for electric double layer capacitor. The cell capacitors using the electrode bound with binary binder composed of CMC and PTFE, especially m composition CMC ; PTFE = 60 : 40 wt %, has exhibited the better rate capability and the lower internal resistance than those of the cell capacitor with CMC. On the other hand, the sheet type electrode kneaded with PTFE was bonded with conductive adhesive on Al foil. This cell capacitor using the electrode with PTFE exhibited the best mechanical properties and rate capability compared to the CMC and CMC+PTFE one These behaviors could be explained by the well-developed network structure of PTFE fibrils during the kneading process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1167-1171
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• 2006

This work describes the effect of binders, such as carboxymethylcellulose (CMC), CMC+ Polytetrafluoroethylene (PTFE) and PTFE, on the electrochemical and mechanical properties of activated carbon-electrode for electric double layer capacitor. The cell capacitors using the electrode bound with binary binder composed of CMC and PTFE, especially in composition CMC PTFE = 60 : 40 wt.%, has better rate capability and the lower internal resistance than those of the cell capacitor with CMC. On the other hand, the sheet type electrode kneaded with PTFE was bonded with conductive adhesive on Al foil. This cell capacitor using the electrode with PTFE exhibited the best mechanical properties and rate capability compared to the CMC and CMC+PTFE one. These behaviors could be explained by the well-developed network structure of PTFE fibrils doting the kneading process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1248-1253
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• 2004

This work describes the effect of electrode binder on the characteristics of electric double layer capacitor Among carboxymethylcellulose (CMC), Polyvinylpyrrolidone (PVP), Polyvinyl Alcohol (PVA), and Polyvinylidene Fluoride (PVDF), the unit cell using CMC showed good rate capability between $2.5mA/cm^2{\sim}100mA/cm^2$ current density. However, CMC as a binder is incongruent, because the electrode bound with CMC is rigid and easy to crack during a press and winding process for fabrication of capacitor. The unit cell capacitor using the electrode bound with binary binder composed of CMC and Polytetrafluoroethylene (PTFE), especially in composition CMC : PTFE : 60 : 40 wt.%, has exhibited the better mechanical properties than those of the unit cell with CMC. On the other hand, it was also noted that the mechanical properties of CMC+PTFE electrode, coated on underlayer composed of CMC and carbon black, were much improved the binding force.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1079-1084
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• 2004

This work describes the effect of electrode binder on the characteristics of electric double layer capacitor. Among carboxymethylcellulose (CMC), Polyvinylpyrrolidone (PVP), Polyvinyl Alcohol (PVA), and Polyvinylidene Fluoride (PVDF), the unit cell using CMC showed good rate capability at current densities between 2.5 mA/$\textrm{cm}^2$～100 mA/$\textrm{cm}^2$. However, CMC as a binder is incongruent, because the electrode bound with CMC is rigid and easy to crack during a press and winding process for fabrication of capacitor. The unit cell capacitor using the electrode bound with binary binder composed of CMC and Polytetrafluoroethylene (PTFE), especially in composition CMC : PTFE =60 : 40 wt.%, has exhibited the better mechanical properties than those of the unit cell with CMC. On the other hand, the mechanical properties of CMC+PTFE electrode, coated on underlayer composed of CMC and carbon black, were much improved.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.407-412
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• 2008

As an activation procedure, in this study, the oxidation treatment of needle cokes with a dilute nitric acid and sodium chlorate $(NaClO_3)$, combined with heat treatment, was attempted. The structures of acid-treated and pyrolyzed coke were examined with XRD, FESEM, elemental analyzer, BET, and Raman spectroscopy. The behavior of double layer capacitance was investigated with the analysis of charge and discharge. The structure of needle coke treated with acid was revealed to a single phase of (001) diffraction peak after 24 h. On the other hand, thecoke oxidized by heat treatment was reduced to a graphite structure of (002) at $300^{\circ}C$. The distorted graphene layer structure, derived from the process of oxidation and reduction of the inter-layer, makes the pores by the electric field activation at the first charge, and generates the double layer capacitance from the second charge. The cell using pyrolyzed coke with 24 h acid treatment and $300^{\circ}C$ heat treatment exhibited the maximum capacitance per weight and volume of 33 F/g and 30 F/mL at the two-electrode system in the potential range of 0~2.5 V.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.6
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• pp.529-543
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• 2020

In contrast to ventricular myocytes, the structural and functional importance of atrial transverse tubules (T-tubules) is not fully understood. Therefore, we investigated the ultrastructure of T-tubules of living rat atrial myocytes in comparison with ventricular myocytes. Nanoscale cell surface imaging by scanning ion conductance microscopy (SICM) was accompanied by confocal imaging of intracellular T-tubule network, and the effect of removal of T-tubules on atrial excitation-contraction coupling (EC-coupling) was observed. By SICM imaging, we classified atrial cell surface into 4 subtypes. About 38% of atrial myocytes had smooth cell surface with no clear T-tubule openings and intracellular T-tubules (smooth-type). In 33% of cells, we found a novel membrane nanostructure running in the direction of cell length and named it 'longitudinal fissures' (LFs-type). Interestingly, T-tubule openings were often found inside the LFs. About 17% of atrial cells resembled ventricular myocytes, but they had smaller T-tubule openings and a lower Z-groove ratio than the ventricle (ventricular-type). The remaining 12% of cells showed a mixed structure of each subtype (mixed-type). The LFs-, ventricular-, and mixed-type had an appreciable amount of reticular form of intracellular T-tubules. Formamide-induced detubulation effectively removed atrial T-tubules, which was confirmed by both confocal images and decreased cell capacitance. However, the LFs remained intact after detubulation. Detubulation reduced action potential duration and L-type Ca²⁺ channel (LTCC) density, and prolonged relaxation time of the myocytes. Taken together, we observed heterogeneity of rat atrial T-tubules and membranous ultrastructure, and the alteration of atrial EC-coupling by disruption of T-tubules.