• 분석과학
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• 제11권5호
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• pp.360-365
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• 1998

고상 반응법에 의하여 합성된 $LiMn_2O_4$를 구조적인 특성과 전기적인 충방전 특성과 임피던스 특성에 대하여 연구하였다. X-선 회절 분석 결과에 의하면 4가지 형태의 화합물 모두가 $LiMn_2O_4$의 주요 회절선인(111), (311), (004)와 (400)이 모두 일치하여 나타났다. C1과 C2는 유사하게 (110), (222) 및 (313)의 회절선이 미소하게 나타났음을 알 수 있었다. C4의 경우는 (113)이나 (331)과 같은 새로운 회절선이 나타난 것으로 보아 C1과 C2의 구조에서 C3의 구조를 거쳐서 C4의 구조로 구조변환이 일어나는 과정임을 알 수 있었다. 전기적인 충방전 특성으로 부터 C1의 경우는 충전 방전 특성이 아주 저하된 상태를 나타내었으며, C2와 C3의 경우는 유사하게 나타났으나, 이들은 이론용량에 60-70%의 범위에 미치는데 그쳤다. 그러나 C4의 경우는 이론 용량의 70% 이상을 나타내는 좋은 충전 방전 특성을 나타냄을 알 수 있었다. 전지의 이온이나 전자 전달의 효과를 알아보기 위하여 임피던스의 특성으로부터 실수부의 파장이 높은 부근에서 형성된 C2과 C3의 경우는 비교적 좋은 특성을 보이고 있음을 알 수 있었다.

• 한국전기전자재료학회논문지
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• 제26권9호
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• pp.656-661
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• 2013

In this study, the moisture content, charge discharge current, electrostatic capacity and dielectric loss tangent are measured for the specimen of bisphenol type epoxy resin which is mixed with squared amorphous silica filler and dipped in hot water of $50^{\circ}C$ for 169 days. The results of this study are listed below. The longer of deposition day, the charge and discharge current was increased. It is considered that the reason is because there was water attack through the squared silica surface. The longer of deposition day, the absorption rate of all specimens was increased. It found that the absorption rate reached saturated state after 100 days. The higher frequency and the longer of deposition day, the $tan{\delta}$ was decreased. Also, It found that the $tan{\delta}$ and electrostatic capacity of the specimen which is mixed with squared filler are greater.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.251-256
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• 2006

To design the effective usage of electric double layer capacitors (EDLCs) used for a storage device of dye sensitized solar cell (DSC) energy, we first investigated the accumulation state of electrical charges and the charge behavior in the EDLCs. Based on the results, the voltage characteristics of EDLCs connected to DSC energy were evaluated. The results showed that the charge accumulation region concentrated on the central part of the carbonaceous electrode in EDLCs and the required times for charging and discharging were almost the same.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.86-96
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• 2007

A direct-injection stratified-charge(DISC) engine has been considered as a promising alternative in spite of high unburned hydrocarbon emission levels during light load operation. In this paper investigation is made to characterize formation and combustion processes of stratified mixture charge in a simple constant volume combustion chamber. Both experimental and numerical analyses are performed for fluid and combustion characteristics with 3 different induction types for rich, homogeneous and lean mixture conditions. The commercial code FIRE is applied to the turbulent combustion process in terms of measured and calculated pressure traces and calculated distributions of mean temperature, OH radical and reaction rate. It turns out that the highest combustion rate occurs for the rich state condition at the spark ignition location due to existence of stoichiometric mixture and timing.

• 한국결정성장학회지
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• 제11권1호
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• pp.38-42
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• 2001

Electric and dielectric(Ba,Sr)$TiO_3$[BST] thin films for emtal-Insulator-Semiconductor(MIS) capacitors have been studied. BST thin films wre deposted on p-Si(100) substrates bythe RF magnetron sputtering with tempratue range of 500~$600^{\circ}C$. The dielectric properties of MIS capacitors consisting of Al/BST/$SiO_2$/Si sandwich structure were evaluated ot redcue the leakage current density. The charge state densities of the MIS capacitors were determined by high frequency (1 MHz) C-V measurement. In order to reduce the leakage current in MIS capacitor, high quality $SiO_2$ layer was deposited on bare p-Si substrate. Depending on the oxygen pressure and substrate temperature both positive and negative polarities of effective oxide charge in the MIS capacitors were evaluated. It is considered that the density of electronic states, generated at the BST/$SiO_2$/p-Si interface due to the asymmetric structure within BST/$SiO_2$/Si structure, and the oxygen vacancy content has influence on the behavior of oxide charge.

• 한국광학회:학술대회논문집
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• 한국광학회 1995년도 광학 및 양자전자학 워크샵 논문집
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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.

• 한국연소학회지
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• 제11권2호
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• pp.28-36
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• 2006

A constant volume combustion chamber was used to investigate the combustion characteristics. of homogeneous charge of methane-air mixture under various initial pressure, equivalence ratio and ignition times. The constant volume combustion chamber(CVCC) mostly has been studied by the experiments of visualization until now. So it is needed the numerical analysis of fluid and combustion characteristics in chamber by the more detail simulation. In this paper, the numerical analysis is tried to approach basically the homogeneous charge combustion phenomena under the various conditions, and the combustion phenomena in chamber is numerically analyzed by the commercial FIRE code. As a results, the combustion phenomena which were mean temperature, OH radical and reaction rate in chamber were investigated and it showed that the smallest flame growth occurs for the lean state and the increase of initial charged pressure condition due to the reduced OH radical.

• 전자공학회논문지A
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• 제31A권8호
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• pp.34-45
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• 1994

We studied threshold voltages and I-V characteristics. considering short channel effect of the fully depleted thin film n-channel SOI MOSFET. We presented a charge sharing model when the back surface of short channel shows accumulation depletion and inversion state respectively. A degree of charge sharing can be compared according to each of back-surface conditions. Mobility is not assumed as constant and besides bulk mobility both the mobility defined by acoustic phonon scattering and the mobility by surface roughness scattering are taken into consideration. I-V characteristics is then implemented by the mobility including vertical and parallel electric field. kThe validity of the model is proved with the 2-dimensional device simulation (MEDICI) and experimental results. The threshold voltage and charge sharing region controlled by source or drain reduced with increasing back gate voltage. The mobility is dependent upon scattering effect and electric field. so it has a strong influence on I-V characteristics.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.321-324
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• 2008

This paper presents the battery management system(BMS) for the optimum conditions of the lead-Acid battery in UPS. The proposed system controls the over and under currents of battery for protecting and it was applied algorithm for optimum conditions to estimate the State Of Charge(SOC) in charge or discharge mode. It approved the performance and the algorithm for the estimation of SOC, through the experiments which using the charge and discharge tester and the field tests.

• Current Optics and Photonics
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• 제1권5호
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• pp.544-550
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• 2017

This simulation based study reports a novel tunable, compact, room temperature terahertz (THz) transistor source, operated on the concept of charge plasma oscillation with the capability of radiating within a terahertz gap. A vertical cavity with a quasi-periodic distributed-Bragg-reflector has been attached to a THz plasma wave transistor to achieve a monochromatic coherent surface emission for single as well as multi-color operation. The resonance frequency has been tuned from 0.5 to 1.5 THz with the variable quality factor of the optical cavity from 5 to 290 and slope efficiency maximized to 11. The proposed surface emitting terahertz transistor is able to satisfy the demand for compact solid state terahertz sources in the field of teratronics. The proposed device can be integrated with Si CMOS technology and has opened the way towards the development of silicon photonics.