• Proceedings of the Optical Society of Korea Conference
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• 1995.06a
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• pp.161-168
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• 1995

Nonlinear optical absorption in solid films of poly(3-octyl thiophene) (P3OT) sensitized with methanofullerene was inverstigated for wacelengths from 620 to 960nm. The nonlinear absorption is ehnanced over that in either of the component materials by more than two orders orders of magitude at 760nm. The large nonlinearity results from effient photoinduced interm olecular charge transfer from P3OT to methanofullerene, followed by absorption in the charge separated excited state. P3OT/fullerene films are promising as reverse saturable absorbers and the optical limiting performance is demonstrated at 760nm.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.54.1-54.1
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• 2012

Recent significant development of organic electronics is worthy of notice for its practical application as well as fundamental understandings. Complementary-like logic circuit is a key factor to realize actual operating organic electronic devices since its advantages of low power dissipation, good noise margin and stable operations. In this reason, studies on ambipolar properties of organic materials which can act as either n-type or p-type are getting more attentions. Performances of ambipolar transistors vary a lot along its molecular structures and film properties. When properly fabricated, balanced hole and electron mobilities over 1 cm2/Vs were observed recently. Study of charge transport in ambipolar organic transistors to understand this high performance was carried out through charge modulation spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4063-4068
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• 2012

Oxide substrates in semiconductor-sensitized solar cells (SSSCs) have a great impact on their performance. $TiO_2$ has long been utilized as an oxide substrate, and other alternatives such as ZnO and $SnO_2$ have also been explored due to their superior physical properties over $TiO_2$. In the development of high-performance SSSCs, it is of significant importance to understand the effect of oxides on the electron injection and charge recombination as these two are major factors in dictating solar cell performance. In addition, elucidating the relationship between these two critical processes and solar cell performance in each oxide is critical in building up the basic foundation of SSSCs. In this study, ultrafast pump-probe laser spectroscopy and open-circuit decay analysis were conducted to examine the characteristics of three representative oxides ($TiO_2$, ZnO, and $SnO_2$) in terms of electron injection kinetics and charge recombination, and the implication of results is discussed.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.241-243
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• 2007

Two-stage charge equalization scheme for HEV lithium-ion battery string is proposed with the optimal power rating design rule in this paper, where in the first stage the over charged energy of higher voltage cells is drawn out to the single common output capacitor and then, that discharged energy is recovered into the overall battery stack in the second stage. To achieve charge equalization of sort, the conventional flyback DC/DC converters of low power and minimized size are employed. The industrial sample employing both the proposed two-stage cell balancing scheme and the optimal power rating design rule shows good cell balancing performance with reduced size as well as low voltage stresses of the electronic devices.

• Journal of Power Electronics
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• v.18 no.1
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• pp.129-136
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• 2018

An accurate state-of-charge (SOC) estimation ensures the reliable and efficient operation of a lithium-ion battery management system. On the basis of a combined electrochemical model, this study adopts the forgetting factor least squares algorithm to identify battery parameters and eliminate the influence of test conditions. Then, it implements online SOC estimation with high accuracy and low run time by utilizing the low computational complexity of the unscented Kalman filter (UKF) and the rapid convergence of a particle filter (PF). The PF algorithm is adopted to decrease convergence time when the initial error is large; otherwise, the UKF algorithm is used to approximate the actual SOC with low computational complexity. The effect of the number of sampling particles in the PF is also evaluated. Finally, experimental results are used to verify the superiority of the combined method over other individual algorithms.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.71-75
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• 2021

Recently, transition-metal-based hydroxide materials have attracted significant attention in various electrochemical applications owing to their low cost, high stability, and versatility in composition and morphology. Among these applications, transition-metal-based hydroxides have exhibited significant potential in supercapacitors owing to their multiple redox states that can considerably enhance the supercapacitance performance. In this study, nanostructured Ni-Mn double hydroxide is directly grown on a conductive substrate using an electrodeposition method. Ni-Mn double hydroxide exhibits excellent electrochemical charge-storage properties in a 1 M KOH electrolyte, such as a specific capacitance of 1364 Fg-1 at a current density of 1 mAcm-2 and a capacitance retention of 94% over 3000 charge-discharge cycles at a current density of 10 mAcm-2. The present work demonstrates a scalable, time-saving, and cost-effective approach for the preparation of Ni-Mn double hydroxide with potential application in high-charge-storage kinetics, which can also be extended for other transition-metal-based double hydroxides.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.640-648
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• 2004

This paper describes a new magnetization method for non-destructive testing with magneto-optical sensor (denoted as MO sensor) which have the following characteristic : high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as multiple cracks. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B$\_$Z/, is almost uniform over the no-crack area (denoted as B$\_$Z,BASE/), while the magnetic flux density is smaller in the surroundings of the crack(denoted as B$\_$Z,CRACK/) If B$\_$Z, BASE/ is a bit larger than the saturated magnetic flux density of the MO sensor (B$\_$s/) , then small magnetic domains occur over the crack area and a large domain over the non-crack area because B$\_$Z,CRACK/ is smaller than B$\_$s/.

• Journal of Astronomy and Space Sciences
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• v.21 no.3
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• pp.201-208
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• 2004

In this paper we have examined the effect of dust charge density on nonlinear ion acoustic solitary wave which propagates obliquely with respect to the external magnetic field in a dusty plasma. For the dusty charge density below a critical value, the Sagdeev potential $\Psi1(n)$ has a singular point in the region n < 1, where n is the ion number density divided by its equilibrium number density. If there exists a dust charge density over the critical value, the Sagdeev potential becomes a finite function in the region n < 1, which means that there may exist the rarefactive ion acoustic solitary wave. By expanding the Sagdeev potential in the small amplitude limit up to on4 near n=1, we find the solution of ion acoustic solitary wave. Therefore we suggest that the dust charge density plays an important role in generating the rarefactive solitary wave.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.725-733
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• 2002

In this study, the heat transport limitations of a two-phase closed thermosyphon were investigated. For the test, a two-phase closed thermosyphon ($L_t/: 600 mm,\;L_e:105mm,\;L_a:75mm,\;L_c:420mm,\;D_o:22.2mm,$ container: copper (inner grooved surface), working fluid: PFC ($C_6F_14$) was fabricated with a reservoir that can change the fill charge ratio. The following was imposed as the factors on the heat transport limitations of a two-phase closed thermosyphon. 1) Fill charge ratio of the working fluid. 2) Tilt angle of the longitudinal axis. From tile experimental data, some results were obtained as follows. When the fill charge ratio was relatively small ($\psi$20%), the heat transport limitation occurred about 100W by dry-out limitation. However over 40%, it shelved nearly constant value (500 W) by flooding limitation. The heat transport limitation according to the tilt angle increased smoothly until the tilt angle was $60^{\circ}$,/TEX>, after then decreased slowly.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2002.11a
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• pp.89-95
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• 2002

The purpose of this study is to assess the residential satisfaction of no-charge welfare facility for the elderly, and to examine the effect of the integration with pay-training institute on residential satisfaction. The data were collected from staffs and fifty one residents of welfare facility by interview and questionnaire. The statistical analysis was conducted to identify the residential satisfaction. A half of the elderly were aged over seventy five years old, eighty four percents of them were female, and seventy seven percents of them were non-educated. Forty two percents of the elderly considered themselves to be unhealthy, but the ADL data reveals that they are relatively healthy. The most of residents are highly satisfied with whole welfare facility. But, the level of satisfaction on the bathroom, the storing space, the cooking table and the benches were relatively low. These dissatisfactions can be solved by the expanding of the storing space, setting up of a common washing room and electric cooking stove, and the increasing of the number of benches. Also, it was recommended for the elderly to set up the Ondol-style rest room with the western style rest room. The level of satisfaction on the attached training institute with no-charge welfare facility for the elderly were high. This has positive effect on residential satisfaction of the elderly. Therefore, the community integrated welfare facility can be the alternative plan for the enhancement of residential satisfaction and quality of elderly life.