• 한국항공우주학회지
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• 제34권11호
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• pp.18-25
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• 2006

비정상 공기력 측정이 두 쌍의 날개를 갖는 잠자리 유형 모델의 위상차에 따른 효과를 조사하기 위하여 수행되었다. 잠자리 유형 모델의 플런징 운동에 의하여 발생된 공기역학적인 힘을 측정하기 위하여 로드셀을 사용하였다. 본 잠자리 유형 모델은 실제 잠자리와 동역학적으로 상사하며, 앞뒤날개는 각각 0°의 10°의 붙임각(incidence angle)을 가지고 있다. 다른 실험 조건은 다음과 같다. 자유류의 속도는 1.6 m/sec이고, 이와 관련된 시위 레이놀즈수 2.88×103이며, 앞뒤날개의 위상차는 각각 0°, 90°, 180°, 그리고 270°이다. 잠자리 유형 날개의 한 주기 동안 공기역학적 계수의 변화가 제시되었다. 연구 결과는 잠자리 유형 모델의 양력은 앞뒤날개가 downstroke 운동을 수행할 때 발생되며, 뒷날개가 downstroke 운동과정을 수행하면 양력 발생과 함께 항력도 발생한다는 것을 보여준다.

• Journal of Korean Neurosurgical Society
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• 제55권6호
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• pp.331-336
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• 2014

Objective : The purpose of this study was to evaluate the differences in sagittal spinopelvic alignment between lumbar degenerative spondylolisthesis (DSPL) and degenerative spinal stenosis (DSS). Methods : Seventy patients with DSPL and 72 patients with DSS who were treated with lumbar interbody fusion surgery were included in this study. The following spinopelvic parameters were measured on whole spine lateral radiographs in a standing position : pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis angle (LL), L4-S1 segmental lumbar angle (SLL), thoracic kyphosis (TK), and sagittal vertical axis from the C7 plumb line (SVA). Two groups were subdivided by SVA value, respectively. Normal SVA subgroup and positive SVA subgroup were divided as SVA value (<50 mm and ${\geq}50mm$). Spinopelvic parameters/PI ratios were assessed and compared between the groups. Results : The PI of DSPL was significantly greater than that of DSS (p=0.000). The SVA of DSPL was significantly greater than that of DSS (p=0.001). In sub-group analysis between the positive (34.3%) and normal SVA (65.7%), there were significant differences in LL/PI and SLL/PI (p<0.05) in the DSPL group. In sub-group analysis between the positive (12.5%) and normal SVA (87.5%), there were significant differences in PT/PI, SS/PI, LL/PI and SLL/PI ratios (p<0.05) in the DSS group. Conclusion : Patients with lumbar degenerative spondylolisthesis have the propensity for sagittal imbalance and higher pelvic incidence compared with those with degenerative spinal stenosis. Sagittal imbalance in patients with DSPL is significantly correlated with the loss of lumbar lordosis, especially loss of segmental lumbar lordosis.

• Journal of Radiation Protection and Research
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• 제19권3호
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• pp.189-198
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• 1994

Teledyne 9150 판독장치에서 사용되는 PB-3 열형광선량계의 방향의존성에 관한 실험을 실시하였고 ANSI N13.11-1992에 의거하여 성능실험을 실시하였다. 조사선원은 $^{137}Cs$과 X선이었다. Teledyne 9150 선량판독장치는 $0^{\circ}$에서는 모든 경우에 방향의존성에 대한 성능시험범주를 만족하였다. 그러나 저에너지 X선의 경우, ${\pm}60^{\circ}$에서는 방향의존성에 대한 성능시험범주를 만족할 수 없었으며 $^{137}Cs$은 모든 경우에 방향의존성에 대한 성능시험범주를 만족하였다.

• 한국전자파학회논문지
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• 제27권6호
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• pp.512-520
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• 2016

본 논문에서는 평면 위에 소형화된 단위구조의 반복 배열을 통해 입사파의 편파 및 입사각에 대하여 안정적인 주파수 특성을 갖는 대역 저지 동작 주파수 선택적 표면구조(FSS: Frequency Selective Surface)를 설계하였다. 제안된 소형화 FSS 구조는 삼각형의 루프가 반복되는 육각 형태 구조로 2.5 GHz 동작주파수에서 $0.081{\lambda}{\times}0.081{\lambda}$의 단위셀 크기를 가지며, 매우 안정적인 입사각 및 편파 주파수 응답 특성을 갖는다. 또한, 제안구조는 기존 소형화 기법의 단점인 높은 설계 복잡도를 개선하고, 단일 설계 변수의 조정을 통해 2~8 GHz 광대역에서 안정적인 주파수 응답 특성을 갖는 FSS 구조 설계가 가능함을 확인하였다. 제안된 구조의 검증을 위해 2.5 GHz, 5 GHz, 8.2 GHz 대역에서 동작하는 FSS 구조를 각각 설계 및 제작하였고, 측정 결과로부터 계산된 결과와 잘 일치함을 확인하였으며, 넓은 대역에 걸쳐 입사파의 편파와 입사각에 대하여 안정적인 성능을 가짐을 확인하였다.

• Wind and Structures
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• 제30권2호
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• pp.181-198
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• 2020

In the traditional buffeting response analysis method, the spanwise incomplete correlation of buffeting forces is always assumed to be same as that of the incident wind turbulence and the action of the signature turbulence is ignored. In this paper, three typical bridge decks usually adopted in the real bridge engineering, a single flat box deck, a central slotted box deck and a two-separated paralleled box deck, were employed as the investigated objects. The wind induced pressure on these bridge decks were measured via a series of wind tunnel pressure tests of the sectional models. The influences of the wind speed in the tests, the angle of attack, the turbulence intensity and the characteristic distance were taken into account and discussed. The spanwise root coherence of buffeting forces was also compared with that of the incidence turbulence. The signature turbulence effect on the spanwise root coherence function was decomposed and explained by a new empirical method with a double-variable model. Finally, the formula of a sum of rational fractions that accounted for the signature turbulence effect was proposed in order to fit the results of the spanwise root coherence function. The results show that, the spanwise root coherence of the drag force agrees with that of incidence turbulence in some range of the reduced frequency but disagree in the mostly reduced frequency. The spanwise root coherence of the lift force and the torsional moment is much larger than that of the incidence turbulence. The influences of the wind speed and the angle of attack are slight, and they can be ignored in the wind tunnel test. The spanwise coherence function often involves several narrow peaks due to the signature turbulence effect in the high reduced frequency zone. The spanwise coherence function is related to the spanwise separation distance and the spanwise integral length scales, and the signature turbulence effect is related to the deck-width-related reduced frequency.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.566-574
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• 2015

We report for the first time highly efficient trans-reflective color filters capable of demonstrating coloration in both transmission and reflection modes by taking advantage of a multilayer stack consisting of MgF₂ and TiO₂ used respectively as the low and high index materials. In order to enable such trans-reflective performance, securing an optimal stop band assuming an appropriate bandwidth within the visible regime is pivotal, which was realized by tailoring the thicknesses and the numbers of TiO₂-MgF₂ bi-layers. Three devices were designed through rigorous simulations and developed via e-beam evaporation to demonstrate vivid blue, green, and red colors in the reflection mode, and yellow, magenta, and cyan colors in the transmission mode, featuring an enhanced efficiency exceeding 90% under normal incidence. The color performance of the filters was examined by referring to the chromaticity coordinates of the transmission and reflection spectra, alongside photographed color images. The dependence of the performance on the angle of incidence was explored with respect to incident polarization, indicating that a transmission surpassing 60% could be stably maintained up to an angle of 75°. Polarization independent transfer characteristics were especially achieved for the normal incidence. The proposed devices may be readily extended to other spectral regimes by adjusting the thicknesses of the films.

• 한방재활의학과학회지
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• 제20권3호
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• pp.93-107
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• 2010

Objectives : The purpose of this study was to assess the efficacy of Chuna and taping treatment in patients with genu varum. Methods : Twenty-seven patients(male:10, female:17) with genu varum were recruited in this study. Chuna treatment at pelvic, and taping treatment at both legs were applied to whole participants. Outcomes were assessed using Q-angle(Quadriceps angle, QA), tibiofemoral angle(TFA), width and length of lesser trochanter(LT), pelvic incidence(PI), pelvic(PT), sacral slope(SS), lumber lordosis angle(LLA), meridian-electromyography(MEMG), Korean western ontario and McMaster universities osteoarthritis index(KWOMAC), and distance of femoral intercondylar distance(ICD). Results : 1. QA, LT width and LT length in radiograph were significantly increased. 2. PI, SS, PT and TFA in radiograph were significantly decreased. 3. The left vastus medialis portion contraction of female was significantly decreased after treatment. 4. The left rectus femoris portion fatigue was significantly decreased after treatment in male subjects. 5. The vastus medialis portion fatigue was significantly decreased after treatment in female subjects. 6. The distance of femoral ICD was significantly decreased. Conclusions : This study showed that Chuna and taping treatment could be used as an effective method for the treatment of genu varum.

• Composites Research
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• 제20권1호
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• pp.15-22
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• 2007

이 논문에서는 섬유강화 복합재료에서의 초음파의 거동에 대해 파동의 모드, 방향, 자유표면에서의 반사파의 반사계수 등을 예측하는 해석적인 방법을 소개한다. 이 논문은 또한 복합재료의 자유표면에서 반사가 일어날 때의 특이한 현상을 새로이 고찰하였는데, 이는 완도면(slowness surface)만을 고려하면 존재할 것으로 예상되지만 실제로는 존재하지 않는 반사파에 대한 것이다. 이는 입사파가 유사횡파일 경우, 입사각이 이 논문에서 새로 정의된 제3임계각을 넘어설 경우 나타나는 현상이다. 본 논문의 내용은 초음파검사와 같은 해당 분야에 종사하는 연구자들에게 유용한 가이드라인을 제시할 것으로 기대된다.

• 대한방사선기술학회지:방사선기술과학
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• 제30권2호
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• pp.105-111
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• 2007

상악동은 연령이 증가함에 따라 크기와 형태가 변화하고, 추체부와의 해부학적 상관관계도 변화된다. 유 소아의 연령대별 상악동과 추체부의 상관관계 변화에 따른 촬영 기준 각도(OML과 IP가 이루는 각도)를 산출함으로서 PNS Water's 영상의 이상적 구현을 위한 촬영 기준 각도를 제시하고자 한다. 본원 내원 환자 50명을 대상으로 두개부에 납볼을 붙이고, PNS Water's 촬영 자세에서 X-선 발생장치와 디지털카메라를 동시에 이용하여 PNS Water's 및 Skull trans-Lat.의 X-선 촬영을 실시하고 PNS Water's 촬영 자세에서 일반사진 측면상을 촬영한 후, 방사선 영상을 이용 중심선속의 입사 경로와 OML과 상악동 하연에서 추체부를 연결하는 선의 각도(Angle A)를 산출하여 $90^{\circ}-Angle A의 그래프를 얻고, 일반사진 측면상에서는 이상적인 Water's 영상으로 평가된 환자의 OML과 Image Plate(IP)가 이루는 각도(Angle B)를 산출하여 연령에 따른 그래프를 작성한 후, 두 개의 그래프를 비교 분석하였다. 분석 결과 OML과 Image Plate(IP)가 이루는 각도(Angle B)는 4세 소아에서는 평균 $43^{\circ}로 마호니가 제시한 기준각도인 $37^{\circ} 보다 크게 나타났으며, 연령이 증가함에 따라 각도가 감소하여, 만 30세 부터는 $37^{\circ}에 근접하는 결과를 얻을 수 있었다. PNS Water's 검사에서 상악동의 성장을 고려하여 연령별 OML과 Image Plate(IP)가 이루는 각도에 변화를 주어 촬영한다면, 유 소아 발생하기 쉬운 상악동의 왜곡을 최소화하여 보다 정확한 검사가 가능할 것으로 사료된다.

• Journal of Korean Neurosurgical Society
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• 제52권4호
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• pp.365-371
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• 2012

Objective : To document lumbar lordosis (LL) of the spine and its change during surgeries with the different height but the same angle setting of the anterior cage. Additionally, we attempted to determine if sufficient LL is achieved at different cage heights and to quantify the change in LL during multi-level anterior lumbar interbody fusion (ALIF). Methods : The medical records and radiographs of 42 patients who underwent more than 2 level ALIFs between 2008 and 2009 were retrospectively reviewed. We evaluated 3 parameters seen on lateral whole spine radiographs : LL, pelvic incidence (PI), and sagittal vertical axis (SVA). The mean follow-up time was 28.1 months and the final follow-up radiographs of all patients were reviewed at least 2 years after surgery. Statistical analysis was performed using the paired t-tests. Results : Lumbar lordosis had changed up to 30 degrees immediately and 2 years after surgery (preoperative mean LL, SVA : 22.45 degrees, 112.31 mm; immediate postoperative mean LL, SVA : 54.45 degrees, 37.36 mm; final follow-up mean LL, SVA : 49.56 degrees, 26.95 mm). Our goal of LL is to obtain as much PI as possible, preoperative mean PI value was $55.38{\pm}3.35$. The pre-operative and two year post-surgery follow-up mean of the Japanese Orthopedic Association score were $9.2{\pm}0.6$ and $13.2{\pm}0.6$ (favorable outcome rate : 95%), respectively. In addition, we were able to obtain good clinical outcomes and sagittal balance with a subsidence rate of 22.7%. Conclusion : We were able to achieve sufficient LL, such that it was similar to the PI, utilizing multi-level ALIF with the use of a tall cage with the same angle setting of the cage. We have found out that achieving sufficient lumbar lordosis and sagittal balance require an anterior lumbar cage with high angle and height.