• Current Optics and Photonics
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• v.7 no.5
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• pp.496-503
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• 2023

We present a detailed analysis of the light extraction efficiency (LEE) of a core-shell nanorod light emitting diode (LED) using finite-difference time-domain (FDTD) simulations. We found that the LEE has a deep dependence on source positions and polarization directions based on the calculated LEE results for every x and z position inside the core-shell nanorod structure. The LEEs are different for the upper part (pyramid) and the lower part (sidewall) of the core-shell nanorod owing to total internal reflection (TIR) and the generated optical modes in the structure. As a result, the LEE of sidewall is much larger than that of pyramid. The averaged LEE of the core-shell nanorod LED is also investigated with variable p-GaN thickness, n-GaN thickness, and height for the design guidelines for the optimized LEE of core-shell nanorod LEDs.

• The Journal of Internal Korean Medicine
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• v.30 no.1
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• pp.173-180
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• 2009

Objectives : The aim of this study was to investigate the evaluation of gastrointestinal parasympathetic nerve activity by comparing between HRV and bowel sound parameters in patients with functional dyspepsia. Methods : 62 patients (male 22, female 40) were enrolled. HRV was measured in all patients. and TP (total power), LF (low frequency density: 0.04$\sim$0.15Hz), HF (high frequency density: 0.15$\sim$0.4Hz). and LF/HF ratio were analyzed. HF band is a reflection of parasympathetic activity. and the LF-to-HF ratio is considered a marker of sympathovagal balance. Bowel sounds were recorded at the day after, and postprandial %BS was used to indicate the gastric vagal activity after eating. HRV and bowel sound parameters were compared. and correlation between them was analyzed. Results : There was no difference in LF/HF ratio between patient group and healthy group of other report. According to values of %BS, each patient was classified into a normal (>6 %BS) or hypoactivity (<6 %BS) of gastric vagus nerve group. HF component of the hypoactivity group was not significantly higher than that of the normal group. There was no correlation between HRV and bowel sound parameters. Conclusions : Because no correlation was found between HRV and bowel sound parameters in patients with functional dyspepsia, we concluded that it is not proper to evaluate gastric vagus nerve activity by HRV measurement.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.1-12
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• 2011

Large-sized multi-touch screen is usually made using infrared rays. That is because it has technical constraints or cost problems to make the screen with the other ways using such as existing resistive overlays, capacitive overlay, or acoustic wave. Using infrared rays to make multi-touch screen is easy, but is likely to have technical limits to be implemented. To make up for these technical problems, two other methods were suggested through Surface project, which is a next generation user-interface concept of Microsoft. One is Frustrated Total Internal Reflection (FTIR) which uses infrared cameras, the other is Diffuse Illumination (DI). FTIR and DI are easy to be implemented in large screens and are not influenced by the number of touch points. Although FTIR method has an advantage in detecting touch-points, it also has lots of disadvantages such as screen size limit, quality of the materials, the module for infrared LED arrays, and high consuming power. On the other hand, DI method has difficulty in detecting touch-points because of it's structural problems but makes it possible to solve the problem of FTIR. In this thesis, we study the algorithms for effectively correcting the distort phenomenon of optical lens, and image processing algorithms in order to solve the touch detecting problem of the original DI method. Moreover, we suggest calibration algorithms for improving the accuracy of multi-touch, and a new tracking technique for accurate movement and gesture of the touch device. To verify our approaches, we implemented a table-based multi touch screen.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.1
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• pp.13-18
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• 2010

Most of the research in the multi-touch area is based on the FTIR(Frustrated Total Internal Re리ection), which is just implemented by using the previous approach. Moreover, there are not the software solutions to improve a performance in the multi touch-blobs detection or the user gesture recognition. Therefore, we implement a multi-touch table-top display that is based on the DI(Diffused Illumination), the improved touch-points detection and user gesture recognition. The proposed method supports a simultaneous transformation multi-touch command for objects in the running application. Also, the system latency time is reduced by the proposed ore-testing method in the multi touch-blobs detection processing. Implemented device is simulated by programming the Flash AS3 application in the TUIO(Tangible User Interface Object) environment that is based on the OSC(Open Sound Control) protocol. As a result, Our system shows the 37% system latency reduction, and is successful in the multi-touch gestures recognition.

• Journal of The Korean Association For Science Education
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• v.41 no.6
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• pp.533-542
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• 2021

This study aims to develop an instrument for measuring high school students' action competence on climate change (ACoCC). The instrument is defined as the construct comprised of seven factors and thirty-five items and takes approximately 15 minutes to fill out. A panel of experts and students' content validation were undertaken to modify the items. Five hundred and twenty-eight first and second graders in Korean high schools participated in the instrument survey. To assess the reliability and validity of ACoCC instrument, item analysis (mean, skewness, kurtosis, item-total correlation), internal consistency estimate, and confirmatory factor analysis were used. It was appropriate to use the 7-dimensional ACoCC instrument (knowledge about climate change, climate change sensibility, reflection, communication, integrated thinking, willingness, decision making), with 35 items for high school students. The following instrument was self-report given in the 5-point Likert scale (1=strongly disagree, 2=disagree, 3=neutral, 4=agree, 5=strongly agree). The internal consistency coefficient was shown as a whole was shown as 0.953, and the subscale's internal consistency coefficient ranged from 0.786 to 0.862.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.80-83
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• 2009

본 논문에서는 AR 보드 게임을 위한 FTIR 방식의 멀티 터치 스크린 시스템을 제안한다. 기존 보드 게임은 카드의 정보나 위치등 다양한 정보를 보여주면서 사용자와의 상호작용에 있어서 버튼과 같은 단순한 형태의 입력을 요구한다. 이러한 낮은 상호작용을 보완하기 위해서 다양한 형태의 패턴 등을 입력할 수 있는 멀티 터치 스크린 시스템을 적용한 텐저블 사용자 인터페이스를 제공하여 사용자로 하여금 더 많은 상호작용과 높은 몰입감을 제공하고자 한다. 본 논문에서 제안하는 시스템은 다음과 같이 구성된다. 먼저, 텐저블 사용자 인터페이스를 위해서 Jefferson Y. Han이 제안한 시스템과 유사한 형태의 FTIR 방식의 멀티 터치 스크린을 테이블 탑 형태로 제작한다. 또한, 스크린 위의 카드를 인식하기 위해서 특정한 모양의 패턴을 적용한 적외선 반사지를 카드에 입힌 후, DI 방식을 사용하여 카드의 고유한 정보를 인식할 수 있도록 하였다. 마지막으로 사용자에게 인터페이스의 확장뿐만 아니라 시각적으로 높은 몰입감을 제공하기 위해 Bimber가 제안한 Virtual Showcase를 적용하였다. 이러한 시스템을 통해 사용자는 이전의 단조로운 형태의 게임에서 벗어나 훨씬 다양하고 높은 몰입감을 즐길 수 있게 되었다.

• BMB Reports
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• v.50 no.2
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• pp.55-57
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• 2017

Toll-like receptor 4 (TLR4) together with MD2, one of the key pattern recognition receptors for a pathogen-associated molecular pattern, activates innate immunity by recognizing lipopolysaccharide (LPS) of Gram-negative bacteria. Although LBP and CD14 catalyze LPS transfer to the TLR4/MD2 complex, the detail mechanisms underlying this dynamic LPS transfer remain elusive. Using negative-stain electron microscopy, we visualized the dynamic intermediate complexes during LPS transfer-LBP/LPS micelles and ternary CD14/LBP/LPS micelle complexes. We also reconstituted the entire cascade of LPS transfer to TLR4/MD2 in a total internal reflection fluorescence (TIRF) microscope for a single molecule fluorescence analysis. These analyses reveal longitudinal LBP binding to the surface of LPS micelles and multi-round binding/unbinding of CD14 to single LBP/LPS micelles via key charged residues on LBP and CD14. Finally, we reveal that a single LPS molecule bound to CD14 is transferred to TLR4/MD2 in a TLR4-dependent manner. These discoveries, which clarify the molecular mechanism of dynamic LPS transfer to TLR4/MD2 via LBP and CD14, provide novel insights into the initiation of innate immune responses.

• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.53-56
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• 2012

We have developed a slab-type Nd:YAG gain module based on the techniques of conduction cooling and end pumping. The Nd:YAG slab is end-capped on both ends by undoped pure YAG and is pumped through the end-caps by stacked arrays of laser diode bars. The slab's surfaces of total internal reflection are in contact on both sides with microchannel cooling blocks which are cooled by water circulation. The power oscillator based on the gain module generates more than 400 W at 1-kW pumping with a slope efficiency of 55%. The small-signal gain of the gain module is 10 in a single zig-zag pass, and the amplified beam shows a near diffraction-limited beam quality.

• Journal of the Optical Society of Korea
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• v.17 no.3
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• pp.269-274
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• 2013

The effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light-emitting diodes (OLEDs) was studied by optical simulation based on the point-dipole model. The diffusing substrate included Mie scatterers by which the condition of total internal reflection could be broken. The finite-difference time-domain method was used to obtain the intensity distribution on the transparent electrode of an OLED, which was used as a light source to carry out a ray-tracing simulation of the OLED and the diffusing substrate. It was found that the outcoupling efficiency of the OLED was sensitive to the thickness of organic layers and could be increased by 21.0% by adopting a diffusing substrate in which Mie scatterers whose radius was $2.0{\mu}m$ were included at the density of $10^7mm^{-3}$ and by 65.5% by forming one pillow lens with the radius of 2 mm on the front surface of the glass substrate. This study revealed that the outcoupling efficiency could be improved by adopting diffusing substrate and pillow lenses along with the optimization of the thickness of each layer in the OLED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.150-150
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• 2008

고효율 LED를 얻기 위해서는 LED의 내부 양자효율과 외부 양자효율이 높아야 한다. 현재 GaN-Based LED의 내부 양자효율은 결정의 질의 개선 및 이중이종접합 또는 다중양자우물 구조와 같이 활성층의 캐리어 농도를 높이는 접합구조로 설계되어 거의 100%에 가까워졌다. 그러나 외부 양자효율은 반도체 재료의 높은 굴절률로 인하여 외부로 탈출하지 못하고 내부로 전반사 되어 반도체 내부에 갇히게 되는데 이처럼 갇힌 빛은 반도체와 중간 Interface에 TIR(total internal reflection) 또는 반사판에 의해 계속적으로 반사 된다. 그러므로 이를 해결하기 위한 플립칩 구조, 포토닉 크리스탈 등의 여러 가지 방법들이 제시되고 있지만 아직도 더 높은 외부 양자 효율의 개선을 요구하고 있다. 본 연구에서는 새로운 형태의 반사판(Al) 즉 p-GaN과 반사판 사이의 interlayer로 반사판과의 오믹 접촉을 고려한 Embo type의 NiO를 구현하여 반사된 빛의 방향을 내부반사를 줄일 수 있는 방향으로 변화시킴으로써 광 추출 효율의 향상을 기대할 수 있게 되었다.