• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.323-324
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• 2013

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.300-304
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• 2012

This paper presents a nonlinear observer design method for SOC(state-of-charge) estimation of Lithium polymer battery cell. The dynamic equation of the battery cell is modeled as a simple RC electrical circuit with a nonlinear voltage source and the parameters are obtained via nonlinear optimization. Using the sum of squares decomposition, the observer gain is designed such that the error dynamics is asymptotically stable and the decay rate is below the prescribed value. In order to illustrate the performance of the observer, a computer simulation is performed using the experimental data with the UDDS(urban dynamometer driving schedule) current profile.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.5
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• pp.262-269
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• 2006

The development of eco-friendly low pressure carburizing system with high pressure gas quenching(LPC-GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

• Bulletin of the Korean Chemical Society
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• v.21 no.8
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• pp.823-827
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• 2000

Gas-Phase reactions of methyl and ethyl nitrites with anionic nucleophiles of SH-, F- and OH- are investigated theoretically at the MP2/6-311+G* level. The SN2 processes are all highly exothermic and proceed with a typ-icaI double-weIl reaction coordinate profile. The elimination reactions of methyl nitrite with SH- and F- are double-well energy surface processes,with stabilizedproduct complexes of NO-...H2S and NO-...HF, pro-ceeding by an E1 cb-like E2 mechanism. The $\beta-elimination$ of ethyl nitrite is an E2 type process. The $\alpha-elimi-nation$ reactions of methyl and ethyl nitrites with OH- have triple-well energy profiles of Elcb pathway with an $\alpha-carbanion$ intermediate which is stabilized bythe vicinal $nc\alpha-{\sigma}*o-N$ charge transfer interactions. CompIex-ation ofmethyl carbanion with HF seems to provide a stable intermediate within a triple-well energy profile of El cb channel in the reaction of F- with methyl nitrite.

• Korean Journal of Computational Design and Engineering
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• v.17 no.3
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• pp.156-163
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• 2012

Real-time three-dimensional shape measurement is becoming increasingly important in various fields, including medical sciences, high-technology industry, and microscale measurements. However, there are not so many 3D profile tools specially designed for specifically narrow space, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3D intraoral scanner is proposed for the measurement of tooth profile in the mouth cavity. The proposed system comprises a laser diode beam, a micro charge-coupled device, a graticule, a piezoelectric transducer, a set of optical lenses, and a polhemus device sensor. The phase-shifting technique is used along with an accurate calibration method for the measurement of the tooth profile. Experimental and theoretical inspection of the phase-to-coordinate relation is presented. In addition, a nonlinear system model is developed for collimating illumination that gives the more accurate mathematical representation of the system, thus improves the shape measurement accuracy. Experiment results are presented to verify the feasibility and performance of the developed system. The experimental results indicate that overall measurement error accuracy can be controlled within 0.4 mm with a variability of ${\pm}0.01$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2173-2178
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• 2007

Dynamics of plasma sheath was analyzed using simple ion fluid model with poison equation. Incident ion current, energy, potential distribution and space charge density profile were calculated as a function of time. The effects of initial floating sheath on the evolution of biased sheath were compared with ideal matrix sheath. The effects of finite rising time of pulse bias voltage on the ion current and energy was studied. The influence of surface charging on the evolution of sheath was also investigated

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.304-308
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• 2000

Surface roughness measurement system with capacitance type gap sensor. Tentative result from the calibration measurement showed the potential applicability of the sensor to the processed specimen. In order to test the sensitivity of the measurement system, several parameters including valley depth, width of the specimen have been changed. Effect of the charge area between sensor and specimen surface has been also analyzed.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.511-516
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• 2004

A Li$[Co_{0.17}Li_{0.28}Mn_{0.55}]O_2$ cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as ${\alpha} -NaFeO_2$ structure type with the lattice constants of a = 2.8405(9) ${\AA}$ and c = 14.228(4) ${\AA}$. According to XANES analysis, the oxidation state of Mn and Co ions in the compound were 4+ and 3+, respectively. During the first charge process, the irreversible voltage plateau at around 4.65 V was observed. The similar voltage-plateau was observed in the initial charge profile of other solid solution series between $Li_2MnO_3\;and\;LiMnO_2$ (M=Ni, Cr...). The first discharge capacity was 187 mAh/g and the second discharge capacity increased to 204 mAh/g. As the increase of cycling number, one smooth discharge profile was converted to two distinct sub-plateaus and the discharge capacity was slowly decreased. From the Co and Mn K-edge XANES spectra measured at different cyclic process, it can be concluded that irreversible transformation of phase is occurred during continuous cycling process.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.529-539
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• 1998

The effects of membrane surface charge originated from lipid head groups on ion channels were tested by analyzing the activity of single large conductance $Ca^{2+}-activated\;K^+$ (maxi K) channel from rat skeletal muscle. The conductances and open-state probability ($P_o$) of single maxi K channels were compared in three types of planar lipid bilayers formed from a neutral phosphatidylethanolamine (PE) or two negatively-charged phospholipids, phosphatidylserine (PS) and phosphatidylinositol (PI). Under symmetrical KCl concentrations $(3{\sim}1,000\;mM)$, single channel conductances of maxi K channels in charged membranes were $1.1{\sim}1.7$ times larger than those in PE membranes, and the differences were more pronounced at the lower ionic strength. The average slope conductances at 100 mM KCl were $251{\pm}9.9$, $360{\pm}8.7$ and $356{\pm}12.4$ $(mean{\pm}SEM)$ pS in PE, PS and PI membranes respectively. The potentials at which $P_o$ was 1/2, appeared to have shifted left by 40 mV along voltage axis in the membranes formed with PS or PI. Such shift was consistently seen at pCa 5, 4.5, 4 and 3.5. Estimation of the effect of surface charge from these data indicated that maxi K channels sensed the surface potentials at a distance of $8{\sim}9\;{\AA}$ from the membrane surface. In addition, similar insulation distance ($7{\sim}9\;{\AA}$) of channel mouth from the bilayer surface charge was predicted by a 3-barrier-2-site model of energy profile for the permeation of $K^+$ ions. In conclusion, despite the differences in structure and fluidity of phospholipids in bilayers, the activities of maxi K channels in two charged membranes composed of PS or PI were strikingly similar and larger than those in bilayers of PE. These results suggest that the enhancement of conductance and $P_o$ of maxi channels is mostly due to negative charges in the phospholipid head groups.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.53-61
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• 2004

Characteristics of half cells of graphite/lithium and LiCoO$_2$/lithium, and full cells of graphite/LiCoO$_2$/ were analyzed by the use of GISOC(the gradual increasing of the state of charge). GISOC analyses generated IIE(the initial intercalation efficiency), which represents lithium intercalation property of the electrode material, and IIC$_{s}$(the initial irreversible capacity by the surface), which represents irreversible reaction between the electrode surface and electrolyte. Linear-fit range of graphite and LiCo/O$_2$electrodes were respectively 370 and 150 mAh/g based on material weight. IIE of graphite and LiCo/O$_2$electrodes were respectively 93∼94 % and 94∼95 %, and IICs of graphite and LiCo/O$_2$electrodes were 15∼17 mAH/g and 0.3∼1.7 mAh/g, respectively. IIE of graphite/LiCo/O$_2$full cell for GX25 and DJG311 as graphite showed 89∼90 %, which IIE value was lower than IIE of half cell of the cathode and the anode. Parameters of IIE and IIC$_{s}$ can also be used to represent not only half cell but also full cell. The characteristics of the full cell can be simulated through the correlative interpretation of potential profile, IIE, and IIC$_{s}$ of half cells.cells.