• Current Optics and Photonics
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• 제1권6호
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• pp.626-630
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• 2017

GaN-based green light-emitting diode (LED) structures suffer from low internal quantum efficiency (IQE), known as the "green gap" problem. The IQE of LED structures is expected to be improved to some extent by exploiting the Purcell effect. In this study, the Purcell effect on the IQE of green LED structures is investigated numerically using a finite-difference time-domain simulation. The Purcell factor of flip-chip LED structures is found to be more than three times as high as that of epi-up LED structures, which is attributed to the high-reflectance mirror near the active region in the flip-chip LED structures. When the unmodified IQE is 20%, the relative enhancement of IQE can be greater than 50%, without utilizing the surface-plasmon coupling effect. Based on the simulation results, the "green gap" problem of GaN-based green LEDs is expected to be mitigated significantly by optimizing flip-chip LED structures to maximize the Purcell effect.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.50-51
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• 2000

가속된 전자빔을 금속회절격자의 위로 통과시킬 때 결맞은 복사광(coherent radiation)이 발생하는데 이를 Smith- Purcell 효과라고 한다. 이때 발생하는 전자기파의 파장은 회절격자의 주기, 전자빔의 속도 및 복사광의 방출각도에 관계된다$^{(1)}$ . 그리고 방출된 복사광의 출력세기는 전자빔의 군집을 고려하지 않는 경우, 회절이론(diffraction theory)에 의해 얻을 수 있는데, 그 세기는 입사시킨 전자빔의 전류세기에 선형적으로 비례한다$^{(2)}$ . (중략)

• 인포메이션 디스플레이
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• 제20권5호
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• pp.3-6
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• 2019

• 대한물리치료과학회지
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• 제25권1호
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• pp.11-19
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• 2018

Purpose : The purpose of this study was to examine the effects of ankle kinesio taping on postural control function during exercise in university students. Method : Thirty subjects were randomly allocated to three groups: Y taping group (n=20), I taping group (n=20) and Non-taping group (n=20). All groups underwent the same exercise program including stretching for 30 minutes. The exercise program proceeded in the following order: five minutes of stretching, a 20-minutes exercise program, and additional five 5 minutes of stretching. Of the eight exercise methods suggested by Purcell et al, seven were chosen (lateral shuffle, forward & backward running, agility ladder, figure-of-8, forward jogging while jumping over cones, wall jumps and zigzags); $90^{\circ}$ cuts with lateral shuffle were omitted. The postural control functions was measured participants's perceptions of stability, confidence, and reassurance using methods suggested by Purcell et al,. Result : The confidence was significant difference in I taping group compared to Non taping group. The reassurance was significant difference in Y taping group and I taping group compared to Non taping group. Conclusion : The Kinesio taping increased confidence, and reassurance during exercise in university students. Additional research on Kinesio taping for improving range of motion and agility is need.

• Physical Therapy Rehabilitation Science
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• 제3권1호
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• pp.63-68
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• 2014

Objective: The purpose of this study was to examine the effects of ankle Kinesio taping on range of motion and agility during exercise in university students. Design: Cross-sectional study. Methods: Thirty subjects were randomly allocated to two groups: taping group (n=15) and non-taping group (n=15). All groups underwent the same exercise program including stretching for 30 minutes. The exercise program proceeded in the following order: five minutes of stretching, a 20-minutes exercise program, and additional five minutes of stretching. Of the eight exercise methods suggested by Purcell et al, seven were chosen (lateral shuffle, forward and backward running, agility ladder, figure-of-8, forward jogging while jumping over cones, wall jumps and zigzags); $90^{\circ}$ cuts with lateral shuffle were omitted. The range of motion of ankle dorsiflexion and plantarflexion was measured using the goniometer. Agility was measured using the side hop test. Results: For ankle range of motion, the taping group showed significant differences in dorsiflexion and plantarflexion on both sides (p<0.05). The non-taping group showed significant differences only in left plantarflexion (p<0.05). There was a significant difference in dorsiflexion on both sides between the taping group and the non-taping group (p<0.05). All groups showed significant differences in agility on the left and right ankle (p<0.05). There was a significant difference in left ankles between the taping group and the non-taping group (p<0.05). Conclusions: Kinesio taping increased range of motion and agility during exercise in university students. Additional research on Kinesio taping for improving range of motion and agility is needed.

• Investigative Magnetic Resonance Imaging
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• 제5권1호
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• pp.33-37
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• 2001

목적 : 자성 자기공명조명제의 효율을 결정하는데는 상자성물질의 물분자 결합위치에 구속되어 있는 물분자와 자유 물분자사이의 물분자 교환율이 매우 중요한 역할을 담당한다. 따라서 본 연구에서는 $^{17}O-NMR$기법을 사용하여 현재 상용화 되어 있는 Gd 자기공명조영제 및 최근 간특이성 자기공명조영제로 제안되고 있는 Gd-EOB-DTPA의 물분자 교율을 측정하고자 하였다. 대상 및 방법 본 연구에 사용된 조영제는 Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA 이며 여기에 Isotech 사의 5% $^{17}O$로 치환된 증류수를 혼합하여 사용하였다. 결과적인 시료의 pH는 buffer용액을 사용하여 pH=7로 고정하였으며 다양한 온도에서 Bruker-600 (14.1 T, 81.3 MHz)모델의 NMR장비를 사용하여 측정하였다. 에코열 24개의 Carr-Purcell-Meiboom-Gill (CPMG) 펄스 시권스를 사용하여 $^{17}O$의 스핀-스핀 이완시간(T2)을 측정하고 이렇게 얻어진 T2 데이터는 최소자승법을 이용하여 Solomon-Bloembergen방정식에 fitting시켜서 최종적으로 각 조명제의 물분자 교환율을 계산하였다. 결과 : 측정된 각 조영제의 물분자 교환시간은 300k의 온도에서는 Gd-DTPA의 경우 0.427, Gd-DTPA-BMA의 경우 $1.99{\;}{\mu}s$, Gd-DOTA의 경우 $0.27{\;}{\mu}s$, Gd-EOB-DTPA의 경우 $0.11{\;}{\mu}s$로 나타났으며 이러한 물분자 교환시간은 온도에 따라 변화함을 알았다. 물분자 교환시간의 온도 의존성은 모든 조영제에서 지수함수의 형태로 나타났으나 조영제에 따라 온도가 올라감에 따라 물분자 교환시간이 감소하는 감소율에서는 차이를 나타내었다. 결론 : 상자성 조영제의 relaxation enhancement 기전을 이해하는데는 물분자 교환율에 대한 정보가 매우 중요하며 이러한 물분자 교환율을 정확히 측정하는데는 $^{17}O-NMR$기법이 매우 유용함을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.184-184
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• 2012

Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.308-308
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• 2017

The low and unstable yield of soybean has been a major problem in Japan. Excess soil moisture conditions are one of the major factors to restrict soybean productivity. More than 80 % of soybean crops are cultivated in converted paddy fields which often have poor drainage. In central and eastern regions of Japan, the early vegetative growth of soybean tends to be restricted by the flooding damage because the early growth period is overlapped with the rainy season. Field observation shows that induced excess water stress in early vegetative stage reduces dry matter production by decreasing intercepted radiation by leaf and radiation use efficiency (RUE) (Bajgain et al., 2015). Therefore, it is necessary to evaluate the responses of soybean growth for excess water conditions to assess these effects on soybean productions. In this study, we aim to modify the soybean crop model (Sinclair et al., 2003) by adding the components of the restriction of leaf area development and RUE for adaptable to excess water conditions. This model was consist of five components, phenological model, leaf area development model, dry matter production model, plant nitrogen model and soil water balance model. The model structures and parameters were estimated from the data obtained from the field experiment in Tsukuba. The excess water effects on the leaf area development were modeled with consideration of decrease of blanch emergence and individual leaf expansion as a function of temperature and ground water level from pot experiments. The nitrogen fixation and nitrogen absorption from soil were assumed to be inhibited by excess water stress and the RUE was assumed to be decreasing according to the decline of leaf nitrogen concentration. The results of the modified model were better agreement with the field observations of the induced excess water stress in paddy field. By coupling the crop model and the ground water level model, it may be possible to assess the impact of excess water conditions for soybean production quantitatively.

• Investigative Magnetic Resonance Imaging
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• 제10권1호
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• pp.20-25
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• 2006

목적 : 새로 개발한 상자성 복합체의 자기이완 특성을 조사해 보고자 하였다. 대상 및 방법 : DMF(15 mL)와 DTPA-bis-anhydride(0.71g, 2 mmol)의 서스펜션 용액에 4-aminomethylcyclohexane carboxylic acid(0.63g, 4 mmol)를 넣어 리간드를 합성한 후 Gd2O3(0.18g, 0.5 mmol)을 넣어 최종적인 Gd 착화물을 합성하였다. 상자성 복합체의 자기이완율을 측정하기 위해 상자성 복합체를 3차 증류수를 사용하여 1 mM로 희석시켰으며 1.5T(64 MHz)에서 자기이완 시간을 측정하였다. T1 자기이완시간을 측정하기 위하여 반전 회복(inversion-recovery) 펄스열을 사용하였으며 T2 자기이완시간은 CPMG(Carr-Purcell-Meiboon-Gill) 펄스열을 사용하였다. 자기이완 시간 및 자기이완율을 영상으로 표현한 T1 자기이완 지도, R1 지도, T2 자기이완 지도 및 R2 지도를 구현 하였다. 결과 : 현재 시판중인 상자성 조영제인 Omniscan(Gadodiamide)의 $R1=4.9mM^{-1}sec^{-1},\;R2=4.8mM^{-1}sec^{-1}$에 비해 R1의 경우 SUK090(Gd-C32H74N5O24)는 $12.46mM^{-1}sec^{-1}$, SUK091(Gd-C34H78N5O24)는 $12.77mM^{-1}sec^{-1}$의 값을 나타낸 반면 SUK092(Gd-C30H56N5O17)는 $2.09mM^{-1}sec^{-1}$로 자기이완율이 감소하였다. R2의 경우 SUK090(Gd-C32H74N5O24)는 $8.76mM^{-1}sec^{-1}$, SUK091(Gd-C34H78N5O24)는 $7.60mM^{-1}sec^{-1}$의 값을 나타낸 반면 SUK092(Gd-C30H56N5O17)는 $1.82mM^{-1}sec^{-1}$로 감소 하였다. 결론 : 본 연구에서 합성한 상자성 복합체중 SUK090(Gd-C32H74N5O24)와 SUK091(Gd-C34H78N5O24)는 기존의 상자성 조영제에 비해 T1, T2 자기이완율이 크고 결과적으로 T1/T2 조영증강 효과가 클 것으로 예상된다.