• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.1-5
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• 2018

In this work, we study the ion conductivity by analyzing the impedance to the high current density range that the PEMFC (Proton Exchange Membrane Fuel Cell) is actually operated. The effect of GDL (Gas Diffusion Layer)presence on impedance was investigated indirectly by measuring hydrogen permeability. When the RH (Relative Humidity)was higher than 60% in the low current range (< $80mA/cm^2$), the moisture content of the polymer membrane was sufficient and the ion conductivity of the membrane was not influenced by the current change. However, when RH was low, ion conductivity increased due to water production as current density increased. The ion conductivity of the membrane obtained by HFR (High Frequency Resistance) in the high current region ($100{\sim}800mA/cm^2$)was compared with the measured value and simulated value. At RH 100%, both experimental and simulated values showed constant ion conductivity without being influenced by current change. At 30~70% of RH, the ionic conductivity increased with increasing current density and tended to be constant.

• Journal of the Semiconductor & Display Technology
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• v.2 no.3
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• pp.19-23
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• 2003

Extended unbalanced magnetron sputtering system based on the cylindrical magnetron with a rotating cathode was developed. The unbalanced configuration of magnetic field was realized by means of additional lines of permanent magnets, placed along both sides of a 89 mm outer diameter and 600 mm long cylindrical cathode. The performance of the unbalanced magnetron was assessed in terms of the ion current density and the ion-to-atom ratio incident at the substrate. Furthermore, the paper presents the comparison of the internal plasma parameters, such as the electron temperature, electron density, plasma and floating potentials, measured by a Langmuir probe in various positions from the cathode, for conventional and unbalanced constructions of the cylindrical magnetron. The plasma density and ion current density are about 3-5 times higher than those of conventional one, in the unbalanced magnetron in a 0.24 Pa Ar atmosphere with a DC cathode power of 3 kW.

• Journal of Electrochemical Science and Technology
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• v.6 no.1
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• pp.1-6
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• 2015

With increasing interest in flexible electronic devices and wearable appliances, flexible lithium ion batteries are the most attractive candidates for flexible energy sources. During the last decade, many different kinds of flexible batteries have been reported. Although research of flexible lithium ion batteries is in its earlier stages, we have found that developing components that satisfy performance conditions under external deformation stress is a critical key to the success of flexible energy sources. Among the major components of the lithium ion battery, electrodes, which are connected to the current collectors, are gaining the most attention owing to their rigid and brittle character. In this mini review, we discuss candidate materials for current collectors and the previous strategies implemented for flexible electrode fabrication.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.44.1-44.1
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• 2009

Identification of wave characteristics during current disruption events in the near-Earth geomagnetic tail region (~ 10 RE) is important to understand the substorm onset mechanism. In this paper, linear stability analysis in the ion-cyclotron grequency range, considering temperature anisotropy and cross-field flow is presented. It is found that the ion-cyclotron drift waves propagating in a quasi-perpendicular direction with respect to the ambient magnetic field are characterized by low frequencies ($\omega$ < $0.5{\Omega}ci$), while quasi-parallel waves have frequencies close to the ion-cyclotron frequency ($\omega{\sim}{\Omega}ci$). This finding is consistent with the observation by THEMIS spacecraft of a current disruption event in which a similar high- and low-frequency band structure is also present [A. T. Y. Lui, et al., J. Geophys. Res. 113, A00C06 (2008)]. It is also found that the quasi-perpendicular mode is excited by the ion cross-field flow.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.538-542
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• 1995

The etching characteristics of magnetic thin films of permalloy and Fe-based alloys are investigated. The thin films are fabricated by rf magnetron sputtering and the substrates used are silicon and glass. Etching is done by ion beam technique and the main process parameters investigated are beam voltage, beam current and accelerating voltage. The etch rate of the magnetic films is proportional to the beam current, but it is not directly related to the accelerating voltage and beam voltage. The dependence of etch rate on the process parameters can be explained by ion current density. It is found that the ion beam etching is effective in obtaining well-developed micro-patterns on the permalloy and Fe- based magnetic thin films.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.400-406
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• 2015

This study researched the structure of the source of an ion milling machine used to fabricate a scanning electron microscope (SEM) sample. An ion source is used to mill out samples of over 1 mm dimension using a broad ion beam to generate plasma between the anode and cathode using a permanent magnet. To mill the sample in the vacuum chamber, the ion source should be greater than 6 kV for a positive ion current over $200{\mu}A$. To discover the optimum operating conditions for the ion miller, the diameter of the extractor, anode shape, and strength of the permanent magnet were varied in the experiments. A silicon wafer was used as the sample. The sputter yield was measured on the milled surface, which was analyzed using the SEM. The wafer was milled by injecting 1 sccm of argon gas into the 0.5 mTorr vacuum chamber.

• Korean Journal of Acupuncture
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• v.18 no.1
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• pp.143-156
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• 2001

Modulatory effect of cAMP-PKA system on inhibitory- and excitatory herbs-induced ion currents were investigated by nystatin-perforated patch clamp method under voltage-clamp condition. Ion currents induced by Bupleuri radix and Coptidis rhizoma were not affected by cAMP-PKA system. Ion current induced by Ecliptae herba was partially inhibited by cAMP-PKA system. Ion currents induced by Aconiti tuber and Boshniakiae herba were inhibitory modulated and ion current induced by Zingiberis rhizoma was excitatory modulated by cAMP-PKA system. Modulation of cAMP-PKA system on ion currents induced by Ginseng radix was fluctuated. In this results, it can be seen generally that excitatory herbs-induced ion currents were modulated by cAMP-PKA system while cAMP-PKA system did not affect inhibitory herbs-induced ion currents.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.6
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• pp.337-342
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• 2008

Human bone marrow mesenchymal stem cells (hBM-MSCs) represent a potentially valuable cell type for clinical therapeutic applications. The present study was designed to evaluate the effect of long-term culturing (up to $10^{th}$ passages) of hBM-MSCs from eight individual amyotrophic lateral sclerosis (ALS) patients, focusing on functional ion channels. All hBM-MSCs contain several MSCs markers with no significant differences, whereas the distribution of functional ion channels was shown to be different between cells. Four types of $K^+$ currents, including noise-like $Ca^{+2}$-activated $K^+$ current ($IK_{Ca}$), a transient outward $K^+$ current ($I_{to}$), a delayed rectifier $K^+$ current ($IK_{DR}$), and an inward-rectifier $K^+$ current ($K_{ir}$) were heterogeneously present in these cells, and a TTX-sensitive $Na^+$ current ($I_{Na,TTX}$) was also recorded. In the RT-PCR analysis, Kv1.1,, heag1, Kv4.2, Kir2.1, MaxiK, and hNE-Na were detected. In particular, ($I_{Na,TTX}$) showed a significant passage-dependent increase. This is the first report showing that functional ion channel profiling depend on the cellular passage of hBM-MSCs.

• Membrane and Water Treatment
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• v.1 no.1
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• pp.13-37
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• 2010

The performance of an electrodialyzer for concentrating seawater is predicted by means of a computer simulation, which includes the following five steps; Step 1 mass transport; Step 2 current density distribution; Step 3 cell voltage; Step 4 NaCl concentration in a concentrated solution and energy consumption; Step 5 limiting current density. The program is developed on the basis of the following assumption; (1) Solution leakage and electric current leakage in an electrodialyzer are negligible. (2) Direct current electric resistance of a membrane includes the electric resistance of a boundary layer formed on the desalting surface of the membrane due to concentration polarization. (3) Frequency distribution of solution velocity ratio in desalting cells is equated by the normal distribution. (4) Current density i at x distant from the inlets of desalting cells is approximated by the quadratic equation. (5) Voltage difference between the electrodes at the entrance of desalting cells is equal to the value at the exits. (6) Limiting current density of an electrodialyzer is defined as average current density applied to an electrodialyzer when current density reaches the limit of an ion exchange membrane at the outlet of a desalting cell in which linear velocity and electrolyte concentration are the least. (7) Concentrated solutions are extracted from concentrating cells to the outside of the process. The validity of the computer simulation model is demonstrated by comparing the computed results with the performance of electrodialyzers operating in salt-manufacturing plants. The model makes it possible to discuss optimum specifications and operating conditions of a practical-scale electrodialyzer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.539-540
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• 2010