• 대한토목학회논문집
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• 제34권4호
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• pp.1139-1150
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• 2014

본 연구에서는 M-PRISM 모형을 이용하여 $1km{\times}1km$ 공간해상도 일강수량 추정에 대한 적용성을 검토하였다. 또한 회귀모형을 이용하여 M-PRISM 모형 매개변수를 추정하였으며, 잭나이프 방법을 이용하여 모형을 검증하였다. 기상청 385개 강수 관측지점에 대하여 M-PRISM을 이용하여 일강수량을 추정하고 PRISM 모형과 비교하였다. 비교결과, 강수의 정량적 크기를 추정에서는 두 모형에서 뚜렷한 차이를 찾아볼 수 없었으나, 강수의 발생빈도 추정에 있어서는 M-PRISM 모형이 더 우수한 결과를 나타내었다. 따라서 본 연구에서 제안한 M-PRISM 모형은 고해상도의 일강수량을 추정함에 있어서 매우 유용하게 사용될 수 있을 것으로 판단된다.

• Journal of Information Display
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• 제7권4호
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• pp.1-4
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• 2006

The optical performances of rounded prism films were investigated using a ray tracing technique. The angular distribution of the luminous intensity was obtained as functions of the prism pitch and the curvature of rounded apex and valley of prism arrays. The gain of the on-axis luminance decreased with decreasing curvature (increasing diameter) and pitch. The existence of the curved area on the prism film decreased the recycling efficiency of the prism film, i.e., the rays which would otherwise have been recycled through total internal reflections via the prism surfaces were refracted on the curved regions and redirected toward directions other than the on-axis direction. Quantitative correlation between the luminance gain and the curvature in addition to the prism pitch was obtained, which might serve as basic data for the optimization of prism films and the manufacturing processes.

• 대기
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• 제17권3호
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• pp.255-268
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• 2007

This study generated and evaluated the high resolution (5 km) gridded data of monthly mean, maximum and minimum temperature from 2002 to 2005 over South Korea using a modified PRISM(Parameter-elevation Regressions on Independent Slopes Model: K-PRISM) developed by Daly et al. (2003). The performance of K-PRISM was evaluated by qualitative and quantitative ways using the observations and gridded data derived by inverse distance weighting (IDW) and hypsometric methods (HYPS). For the generation of high resolution gridded data, geographic informations over South Korea, such as the digital elevation, topographic facet and coastal proximity, are derived from the 1 km digital elevation data. The spatial patterns of temperature derived by K-PRISM were more closely linked to topography and coastal proximity than those by IDW. The K-PRISM performed much better than IDW for all months and temperatures, but it was equal to or slightly better than the HYPS. And the performances of K-PRISM were better in the minimum and mean temperature (winter) than the in maximum temperature (summer).

• 한국융합학회논문지
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• 제8권12호
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• pp.299-305
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• 2017

본 논문은 아베-코닉 프리즘의 설계 데이터 산출 및 평가 프로그램에 관한 것이다. 우선 아베-코닉 프리즘의 설계 변수를 설정하였고, 이들 사이의 관계식을 유도하였다. 이 식들에 의해 우리는 face-length, 유효 수속 입사빔의 입사각 및 프리즘의 굴절률이 주어질 때 아베-코닉 프리즘의 설계를 위한 수치 데이터 및 아베-코닉 프리즘 분석을 위한 3가지 평가 데이타들이 출력되는 프로그램을 개발하였다. 실제 이 프로그램을 상용 사이즈가 아닌 프리즘에 적용한 결과 아주 빠른 설계 데이타를 산출할 수 있었고, 3가지 평가 데이타에 의해 설계되어진 아베-코닉 프리즘의 광학적 구조를 쉽게 이해할 수 있었다. 이는 제품 개발에 필요로 하는 아베-코닉 프리즘의 구조적인 데이터를 신속하게 확보할 수 있다는 것을 의미한다.

• Wind and Structures
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• 제17권3호
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• pp.245-262
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• 2013

The flow interaction between two identical neighboring twin square prisms in a staggered arrangement in an open terrain was investigated experimentally. The downwind prism was mounted on a rigid-aeroelastic setup in an open-terrain boundary layer flow to measure its acrosswind root-mean-square responses and aerodynamic damping ratios. By varying the relative location of the upwind prism and the Scruton number associated with the downwind prism, the acrosswind aeroelastic behavior of the downwind prism was analyzed and compared to that of an isolated one. Results showed that the acrosswind root-mean-square response of the downwind prism could be either suppressed or enhanced by the wake flow produced by the neighboring upwind prism. Besides the assessment of the wake effect of the downwind prism, finally, regressed relationships were presented to describe the variation of the aerodynamic damping ratio so as to predict its acrosswind fluctuating response numerically.

• 대기
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• 제24권1호
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• pp.101-110
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• 2014

This study estimates and evaluates the daily January temperature from 2003 to 2012 with 30 m-resolution over South Korea, using a modified Parameter-elevation Regression on Independent Slopes Model (K-PRISM). Several factors in K-PRISM are also adjusted to 30 m grid spacing and daily time scales. The performance of K-PRISM is validated in terms of bias, root mean square error (RMSE), and correlation coefficient (Corr), and is then compared with that of inverse distance weighting (IDW) and hypsometric methods (HYPS). In estimating the temperature over Jeju island, K-PRISM has the lowest bias (-0.85) and RMSE (1.22), and the highest Corr (0.79) among the three methods. It captures the daily variation of observation, but tends to underestimate due to a high-discrepancy in mean altitudes between the observation stations and grid points of the 30 m topography. The temperature over South Korea derived from K-PRISM represents a detailed spatial pattern of the observed temperature, but generally tends to underestimate with a mean bias of -0.45. In bias terms, the estimation ability of K-PRISM differs between grid points, implying that care should be taken when dealing with poor skill area. The study results demonstrate that K-PRISM can reasonably estimate 30 m-resolution temperature over South Korea, and reflect topographically diverse signals with detailed structure features.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.799-806
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• 2016

We present a polarization-dependent prism array film for controlling the viewing angle distribution of liquid crystal (LC) display panels without loss of light efficiency. On a directional backlight unit, our polarization-dependent prism array film, made into a stacked bilayer with a well-aligned liquid crystalline reactive mesogen (RM) layer on the UV-imprinted prism structure, can continuously control the light refraction function of the prism array by electrically switching incident polarization states of a polarization-controlling layer prepared by a twisted nematic LC mode. The viewing angle control properties of the polarization-dependent prism array film are analyzed under different prism angle and refractive index conditions of the RM layer. A simple analytic model is also presented to describe the intermediate viewing angle distributions with continuously varying applied voltages and incident polarization states.

• 대한기계학회논문집B
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• 제22권5호
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• pp.708-715
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• 1998

The shelter effect of a porous wind fence on a triangular prism was experimentally investigated in a circulating water channel. A porous fence of porosity .epsilon.=38.5% was installed in front of the prism model. The fence and prism model were embedded in a turbulent boundary layer. The instantaneous velocity fields around the fence and prism model were measured by using the instantaneous velocity fields around the fence and prism model were measured by using the 2-frame PTV(Particle Tracking Velocimetry) system. By installing the fence in front of the prism, the recirculation flow region decreases compared with that of no fence case. The porous fence also decreases the mean velocity, turbulent intensity and turbulent kinetic energy around the prism. Especially, at the top of the prism, the turbulent kinetic energy is about half of that without the fence.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.205-209
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• 2016

본 연구는 상류측에 작은 삼각주를 가진 정방형주의 유동장 특성을 정방형주 한 변의 길이에 대한 삼각주의 폭비 및 정방형주 전면에서부터 삼각주 후면까지의 간격을 변수로 하여 PIV를 이용한 가시화실험으로 파악한 것이다. 그 결과를 요약하면 다음과 같다. 정방형주 후류측 스트로할 수는 항력감소율과 같은 특성을 나타내었는데, 간격비가 증가할수록 증가한 후 감소하는 특성을 보였다. 삼각주를 설치한 경우 정방형주 상류측과 하류측에 정체영역이 나타났으며, 그 정체영역의 크기는 정방형주의 상류측은 삼각주의 폭비가 클수록 증가하는데 비해, 하류측은 오히려 감소했다.

• 센서학회지
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• 제26권2호
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• pp.91-95
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• 2017

Recently, infrared (IR) spectrometers have been required in various fields such as environment, safety, mobile, automotive, and military. This IR dispersive sensor detection method of substances is widely used. In this study, we fabricated a silicon (Si) prism-based near infrared (NIR) spectrometer utilizing micro electro mechanical system (MEMS) technology. Si prism-based NIR spectrometer utilizing MEMS technology consists of upper, middle, and lower substrates. The upper substrate passes through the incident IR ray selectively. The middle substrate, acting as a prism, disperses and separates the incident IR beam. The lower substrate has an amorphous Si (a-Si)-based bolometer array to detect the IR spectrum. The fabricated Si prism-based NIR spectrometer utilizing MEMS technology has the advantage of a simple structure, easy fabrication steps, and a wide NIR region operating range.