• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.794-798
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• 2016

A polymer-stabilized vertical alignment (PS-VA) mode with fishbone-shaped pixel electrode structure is mainly used in large-sized liquid crystal displays (LCDs) owing to its advantages such as wide viewing angle, good transmittance and fast response time. One drawback of this mode is a main bone electrode, which crosses in the center of a pixel. It causes the transmittance to decrease badly because LCs cannot be reoriented in this region, and thus, it is particularly unfavorable in an ultra-high-definition LCD. Here, we propose an innovative structure with the main bone electrode relocated to the edge area in a pixel, and investigate how this reverse directed fishbone-shaped pixel electrode structure affects electro-optic characteristics. The proposed structure shows enhanced electro-optic performance, such as the higher transmittance and the faster response time than the conventional VA mode with fishbone-shaped pixel electrode structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.111-114
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• 1999

Electroluminescence(EL) devices based on organic thin films have been attracted lots of interests in large-area light-emitting display. In this stuffy, an emissive layer was fabricated using Langmuir-Blodgett(LB) technique in organic light-emitting (OLEDs). This emissive organic material was synthesized and named PECCP[poly(3.6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)] which has a strong electron donor group and an electron acceptor group in main chain repeated unit. This material has good solubility in common organic solvents such as chloroform. THF, etc, and has a good stability in air. The Langmuir-Blodgett(LB) technique has the advantage of precise control of the thickness down to the molecular scale, In particular, by varying the film thickness it is possible to investigate the metal/polymer interface. Optimum conditions for the LB film deposition are usually determined by investigating a relationship between a surface pressure $\pi$ and an effective are A occupied by one molecule on the subphase. The LB films were deposited on an indium-tin-oxide(ITO) glass at a surface pressure of 10 mN/m and dipping speed of 12 mm/min after spreading PECCP solution on distilled water surphase at room temperature, Cell structure was ITO/PECCP LB film/Alq$_3$/Al. We considered PECCP as a hole -transport layer inserted between the emissive layer and ITO. We also used Alq$_3$ as an emissive layer and an electron transport layer. We measured current-voltage(I-V) characteristics, UV/visible absorption, PL spectrum and EL spectrum of the OLEDs.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.371-375
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• 2019

Developing a thin-film transistor with characteristics such as a large area, high mobility, and high reliability are key elements required for the next generation on displays. In this paper, we have investigated the research trends related to improving the reliability of oxide-semiconductor-based thin-film transistors, which are the primary focus of study in the field of optical displays. It has been reported that thermal treatment in a high-pressure oxygen atmosphere reduces the threshold voltage shift from -7.1 V to -1.9 V under NBIS. Additionally, a device with a $SiO_2/Si_3N_4$ dual-structure has a lower threshold voltage (-0.82 V) under NBIS than a single-gate-insulator-based device (-11.6 V). The dual channel structure with different oxygen partial pressures was also confirmed to have a stable threshold voltage under NBIS. These can be considered for further study to improve the NBIS problem.

• 한국전기전자재료학회논문지
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• 제36권5호
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• pp.423-432
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• 2023

With the increasing demand for mobile devices featuring multi-touch operation, extensive research is being conducted on touch screen panel (TSP) Readout ICs (ROICs) that should possess low power consumption, compact chip size, and immunity to external noise. Therefore, this paper discusses capacitive touch sensors and their readout circuits, and it introduces research trends in various circuit designs that are robust against external noise sources. The recent state-of-the-art TSP ROICs have primarily focused on minimizing the impact of parasitic capacitance (Cp) caused by thin panel thickness. The large Cp can be effectively compensated using an area-efficient current compensator and Current Conveyor (CC), while a display noise reduction scheme utilizing a noise-antenna (NA) electrode significantly improves the signal-to-noise ratio (SNR). Based on these achievements, it is expected that future TSP ROICs will be capable of stable operation with thinner and flexible Touch Screen Panels (TSPs).

• Ocean and Polar Research
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• 제32권4호
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• pp.337-350
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• 2010

This study conducted sedimentological and geophysical surveys for 3 years (2006-2008) in southern Gyeonggi Bay, Korea to elucidate temporal changes in subaqueous dune morphology on a sand ridge trending northeast to southwest that has been excavated by marine sand mining. The sand ridge (~20 m in height, ~2 km in width and 3~4 km in length) has a steep slope on the NW side and a gentle slope on the SE side, creating an asymmetric profile. Large (10~100 m in length) and very large (>100 m in length) dunes occurring on the SE side of the ridge show a northeastward asymmetrical shape, whereas dunes on the NW side destroyed by marine sand mining display a southwestward asymmetry. The comparison between Flemming (1988)'s correlation and the height-length correlation of this study indicates that tidal current and availability of sand sediment are major controlling factors to the development and maintenance of dunes. Depth and sedimentary characteristics (grain size) are not likely to be major controlling factors, but indirectly influence dune growth by hydrological and sedimentary processes. The length and the height of dunes decrease toward the southeastern trough away from the crest of the ridge. These features result from the decrease of tidal current and sediment availability. The length and the height of dunes on the southeast side decrease gradually over time. This is a result of the interaction between tidal current and the decrease in sediment availability due to sediment extraction by marine sand mining. Marine sand mining has destroyed the dunes directly, causing irregular shapes of shorter length and lower height. The coarse fraction of suspended sediments is transported and deposited very close to the sand pit. By contrast, relatively fine sediments are transported by the tidal current and deposited over a wide range by the settling-lag effect, resulting in a decrease of sediment grain size in the area where suspended sediments are deposited. In addition, marine sand mining, decreases the height of dunes. Therefore, morphological and sedimentological characteristics of dunes around the sand pits will be significantly changed by future sand mining activities.

• 한국융합학회논문지
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• 제10권3호
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• pp.39-47
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• 2019

본 논문에서는 실시간으로 보행자를 추적할 때 배경 제거를 이용하여 변형된 HOG(Histogram of Oriented Gradients) 특징 추출을 제안하였다. 기존의 HOG 특징 추출은 연산량이 많아 추적 속도가 느린 문제가 있다. 배경 제거를 통해 연산량 감소와 추적률을 향상시키기 위해 연구하였다. 불필요한 영역에서의 특징 추출을 감소시키기 위해 HSV 색공간에서 S 채널과 V 채널을 이용하여 영역 제거를 진행하였다. 영상의 평균 S 채널과 V 채널로 배경 제거 후 입력 영상이 전체적으로 어두워 객체 추적에 실패하는 경우가 있다. 이러한 경우를 방지하기 위해 히스토그램 평활화를 하였다. 제거된 영역에서 추출되는 HOG 특징이 감소되고, 객체에서는 명확한 HOG 특징이 추출되어 객체 추적 속도와 추적률이 향상되었다. 본 실험에서는 다수의 보행자나 한명의 보행자가 존재하는 영상, 배경이 복잡한 영상, 흔들림이 심한 영상을 가지고 실험하였다. 제안하는 방법은 기존의 HOG-SVM 방법과 비교하여 처리 속도는 약 41.84% 향상되었으며 오 추적률은 약 52.29% 감소되어 개선된 추적률을 보였다.

• 대한치과보철학회지
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• 제49권4호
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• pp.316-323
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• 2011

연구 목적: 본 연구의 목적은 치과용 임플란트 나사산 디자인이 변연골 응력에 미치는 영향에 정량적인 분석을 하고자 한다. 연구 재료 및 방법: 외경 4.1 mm (경부직경 3.5 mm), 매식부 길이 10 m인 표준형 ITI 임플란트 시스템(ITI Dental Implant System; Straumann AG, Waldenburg, Switzerland)을 기본모델(대조모델)로 채택하고, 그 몸체의 나사산은 다른 임플란트 시스템에 채택되고 있는 삼각형, 사각형, buttres형 디자인을 가지는 가상의 해석모델을 4종 만들었다. 해석모델은 나사산 형태와 크기에 따라 (1) 모델 A (작은 삼각형 나사산), (2) 모델 B (큰 삼각형 나사산), (3) 모델 C (buttres형 나사산), 및 (4) 모델 D (사각형 나사산)로 구분하였다. 유한요소 모델링과 해석에는 NISA II/DISPLAY III (Engineering Mechanics Research Corporation, Troy, MI, USA) 프로그램을 사용하였다. Mesh 구성에는 NKTP type 34형 solid 요소(4각형 축대칭 요소, 요소당 절점수 8개)를 사용하여 임플란트 장축과 평행한 축대칭 하중은 물론 장축과 경사각을 갖는 비축대칭 하중조건을 모두 해석할 수 있도록 하였다. 임플란트의 표면으로부터 각각 0.2, 0.4, 0.6, 0.8, 1.0 mm 떨어진 위치에 5개의 응력관찰점(stress monitoring point)을 설정 하여 기록된 응력 값으로부터 회귀분석을 통하여 변연골 응력 최대값(peak stress)을 정량화하였다. 해석에 사용한 하중 조건은 2가지로, 임플란트 축에 평행한 수직하중 100 N과 임플란트 축과 $30^{\circ}$를 이루는 경사력 100 N 조건이었다. 결과: 임플란트 경부와 접하고 있는 인접 변연골에 응력집중현상이 보이고 있었으며, 그 양상은 임플란트 나사산 디자인과 무관하게 거의 유사하게 관찰되었다. 수직력 100 N 조건에서 산출된 변연골 최대응력값은 대조모델과 실험모델 A, B, C, D에서 7.84, 6.45, 5.96, 6.85, 5.39 MPa이었고, 경사력 조건에서는 각각 29.18, 26.45, 25.12, 27.37, 23.58 MPa이었다. 결론: 임플란트 나사산의 디자인은 변연골의 응력에 영향을 미치는 중요한 요소이다.

• 대한소아치과학회지
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• 제26권2호
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• pp.218-231
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• 1999

마취된 흰쥐를 사용하여 해마의 CA영역에 위치한 피라밋세포들의 세포막 특성을 in vivo의 세포내 기록법에 의해서 관찰한 후 2.5% neurobiotin을 세포내 기록용 미세전극에 채워 세포내로 충진시킨후 충진전과 동일한 실험순서로 반응을 다시 관찰하고 ABC kit를 이용하여 면역조직염색을 행하여 형태학적인 관찰을 하였다. 피라밋세포의 세포내 반응 특성은 높은 휴지막 세포막전위, 낮은 input resistance 그리고 큰 활동전위를 가졌다. neurobiotin 충진 전 후에 따른 세포막 특성의 변화는 sustained AHP의 duration과 amplitude, input resistance, 그리고 세포외 및 세포내 자극에 따른 AP 수에서 유의한 차이를 보였고(P<0.05), 세포외 자극에 의한 억제는 주로 전반부에 나타났으며 CA3 영역에 위치한 이 세포의 형태학적 관찰 결과 세포체는 피라밋층에서 분명한 피라미드 형태를 띄고 있었고 기저 및 선단 가지가 각각 백색판층 및 섬유방-분자층까지 뻗어 있었으며 축삭은 겉질을 향해 기저가지돌기면에서 수직으로 뻗어 있었다. 해마의 주세포인 피라밋세포의 세포막 특성과 세포내 염색지시체(marker)로 주로 쓰이는 neurobiotin에 의해 세포막 특성중 일부가 변화됨을 알 수 있었고, 뇌내의 신경세포연결망이 완전히 보존되어 세포들 사이의 시냅스관계를 추측할 수 있는 in vivo 실험 모델이 응용될 수 있음을 제시하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.199-199
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• 2016

Commercially pure titanium (cp-Ti) and Ti alloys (typically Ti-6Al-4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally. Ti and its alloys are not bioactive. Therefore, they do not chemically bond to the bone, whereas they physically bond with bone tissue. The electrochemical deposition process provides an effective surface for biocompatibility because large surface area can be served to cell proliferation. Electrochemical deposition method is an attractive technique for the deposition of hydroxyapatite (HAp). However, the adhesions of these coatings to the Ti surface needs to be improved for clinical used. Plasma electrolyte oxidation (PEO) enables control in the chemical com position, porous structure, and thickness of the $TiO_2$ layer on Ti surface. In addition, previous studies h ave concluded that the presence of $Ca^{+2}$ and ${PO_4}^{3-}$ ion coating on porous $TiO_2$ surface induced adhesion strength between HAp and Ti surface during electrochemical deposition. Silicon (Si) in particular has been found to be essential for normal bone and cartilage growth and development. Zinc (Zn) plays very important roles in bone formation and immune system regulation, and is also the most abundant trace element in bone. The objective of this work was to study electrochemical characteristcs of Zn and Si coating on Ti-6Al-4V by PEO treatment. The coating process involves two steps: 1) formation of porous $TiO_2$ on Ti-6Al-4V at high potential. A pulsed DC power supply was employed. 2) Electrochemical tests were carried out using potentiodynamic and AC impedance methoeds. The morphology, the chemical composition, and the micro-structure an alysis of the sample were examined using FE-SEM, EDS, and XRD. The enhancements of the HAp forming ability arise from $Si/Zn-TiO_2$ surface, which has formed the reduction of the Si/Zn ions. The promising results successfully demonstrate the immense potential of $Si/Zn-TiO_2$ coatings in dental and biomaterials applications.