• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.587-596
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• 2014

A new ${\pi}$-stacked donor-acceptor (D-A) system, [Ru(1-([2,2'-bipyridine]-6-yl-methyl)-3-(2-cyclohexa-2',5'-diene-1,4-dionyl)-1H-imidazole)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (ImQ_T), has been synthesized and characterized. Similar to its precedent, [Ru(6-(2-cyclohexa-2',5'-diene-1,4-dione)-2,2':6',2"-terpyridine)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (TQ_T), this system has a cofacial alignment of terpyridine (tpy) ligand and quinonyl (Q) group, which facilitates an electron transfer through ${\pi}$-stacked manifold. Despite the presence of lowest-energy charge transfer transition from the Ru-based-HOMO-to-Q-based-LUMO (MQCT) predicted by theoretical calculations by using time-dependent density functional theory (TD-DFT), the experimental steady-state absorption spectrum does not exhibit such a band. The selective excitation to the Ru-based occupied orbitals-to-tpy-based virtual orbital MLCT state was thus possible, from which charge separation (CS) reaction occurred. The photo-induced CS and thermal charge recombination (CR) reactions were probed by using ultrafast visible-pump/mid-IR-probe (TrIR) spectroscopic method. Analysis of decay kinetics of Q and $Q^-$ state CO stretching modes as well as aromatic C=C stretching mode of tpy ligand gave time constants of <1 ps for CS, 1-3 ps for CR, and 10-20 ps for vibrational cooling processes. The electron transfer pathway was revealed to be Ru-tpy-Q rather than Ru-bpy-imidazol-Q.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.218-219
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• 2011

In this paper Li-polyer batteries, which are in use of EV recently, are used. The Li-polymer batteries have high density of energy and invulnerability of the fluids and explosion. It is confirmed that the DC-bias pulse mode/cc mode characteristics on charge by designing Fast-charging system designed in three phase PWM and full-bridge converter.

• Korean Journal of Materials Research
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• v.27 no.5
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• pp.248-254
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• 2017

In the present work, graphene powder was synthesized by laser scribing method. The resultant flexible light-scribed graphene is very appropriate for use in micro-supercapacitors. The effect of the laser scribing process in reducing graphene oxide (GO) was investigated. GO was synthesized using a chemical mixture of GO solution; then, it was coated onto a LightScribe DVD disk and laser scribed to reduce GO and create laser-scribed graphene (LSG). The CV curves of pristine rGO at various scan rates showed that the ultimate product possesses the ability to store energy at the supercapacitor level. Charge-discharge curves of pristine rGO at two different current densities indicated that the specific capacitance ($C_m$) increases due to the reduction of the discharge current density. Finally, the long-term charge-discharge stability of the LSG was plotted and indicates that the specific capacitance decreases very slightly from its primary capacitance of ${\sim}10F\;cm^{-3}$ and that the cyclic stability is favorable over 1000 cycles.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.288-292
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• 2010

Recently, in energy storage system, the EDLC is paid attention as a new environmentally friendly energy storage element. This capacitor has higher energy density than the electrolytic capacitor. Also, this capacitor has a lot of advantage such as no maintenance, longer life cycle and faster charge-discharge time than the battery system. But the EDLC must have a each charge-discharge controller to effectively control, an energy design method circuit to use effectively energy, and several compensation techniques to control a optimal operating. In this respect, this study suggests major parameters to effectively represent the characteristics of EDLC, the measurement methods of those parameters have been investigated with experiments, and the interpretation about the buck/boost DC/DC converter for the operation of EDLC.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.461-461
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• 2000

We have investigated electronic structuresof antiferromagnetic YBaCo_2O_5 using the local spin-density approximation (LSDA) + U method. The charge and orbital ordered insulating ground state is correctly obtained with the strong on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the high spin (HS) and intermediate spin (IS) state, respectively. The tetragonal to orthorhombic structural transition is responsible for the ordering phenomena and the spin states of Co ions. The large contribution of the orbital moment to the total magnetic moment indicates that the effect of the spin-orbit coupling is very important in YBaCo_2O_5.

• YAKHAK HOEJI
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• v.33 no.2
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• pp.87-100
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• 1989

Salicylic acids as anti-inflammatory agents were analyzed by ab initio, quantum chemical methods to study the possible modes of binding to the receptor. As the result of multiple regression analysis of reactivity indices and interpretation of normalized frontier orbital charges of drugs, potency seems to be related to energy of HOMO and LUMO at the 5 position of benzene ring, and in the 5-phenyl substituted case, the para position of substituting ring is important. The binding occurs first at the positive site of its receptor. The charge density exhibited by the frontier orbitals suggests that charge moves from receptor site to carboxyl group. The electrostatic orientation effect makes an important contribution to the binding of the active molecules to their receptors. Also the electrostatic potential model may be able to rationalize the source of activity or inactivity of the drugs under investigation.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.274-277
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• 1995

Recent environmental pollutions have intensified the need to develop zero emission vehicles. The most effect method of such solutions is EV. EV is high energy efficiency, easy to maintain, repair and is possible to make high performance control. However, because energy density of batteries is constrained and the distance covered one charge is short range. Also because EV has disadvantage of poor accelation ability, development of high performance battery is required for large scale use of EV. EV charger analogous to gas apparatus must also be developed immediately. Charger is discriminate between on-vehicle type and off-vehicle type. As off-vehicle type is able to charge fast and safe, inductive charging is considered. This paper aims to develope off-vehicle inductive charging system. Therefore, it achieved power factor correction converter, high frequency DC/AC inverter control algorithm development which gives proof validity through simulation and formulated the basic concept of high frequency transformer design for inductive charging.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.94-95
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• 2007

In this paper, the dependence of electrical characteristics of Silicon-$Al_2O_3$-Nitride-Oxide-Silicon (SANOS) memory cell transistors and program speed, reliability of memory device on interface trap between Si substrate and tunneling oxide was investigated. The devices were fabricated by the identical processing in a single lot except the deposition method of the charge trapping layer, nitride. In the case of P/E speed, it was shown that P/E speed is slower in the SONOS cell transistors with larger interface trap density by charge blocking effect, which is confirmed by simulation results. However, the data retention characteristics show much less dependence on interface trap. Therefore, to improve SANOS memory characteristic, it is very important to optimize the interface trap and charge trapping layer.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.593-596
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• 1998

Effects of current re-stress after anneal on leakage current and trapped charges in oxides are investigated. Current stress on 6 nm thick oxide has generated mostly positive traps within the oxide resulting in leakage currents. The interface states generated are several orders of magnitude smaller, determined by C-V and charge pumping method. Annealing has eliminated only the charged traps not the neutral traps, thus the leakage current and trap density are increased when the oxides are re-stressed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.252-252
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• 2010

Carbon nanotubes(CNTs) have excellent electrical, mechanical and chemical properties. In this paper, the variation of charge density and resistivity in MWCNT gas sensor were defined by three Dimensional Finite element method, and an accurate description of equivalent circuit of MWCNT gas sensor was investigated.