• 한국수자원학회논문집
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• 제53권10호
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• pp.871-876
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• 2020

임해발전소의 냉각수 배출구 인근과 준설된 해역을 전파하는 파랑의 특성을 이해하는 것은 임해발전소 건설과 운영에 매우 중요하다. 본 연구에서는 (1) 배출구 주변 외부 흐름과 (2) 준설된 해저지형을 나타내는 함몰지형에 의한 파랑의 반사율을 고유함수전개법을 이용하여 해석하였다. 먼저, 외부흐름을 나타내기 위한 격자수와 소멸파수의 최적값을 수렴 테스트를 통해 산정하였다. 그리고 ¹⁾외부흐름의 속도, ²⁾외부흐름의 폭, ³⁾함몰지형 간 거리, ⁴⁾함몰지형의 개수에 따른 반사율 변화 정도를 분석하였다. 분석결과, 함몰지형 수와 거리에 따른 반사율이 외부흐름의 속도와 폭에 따른 반사율보다 더 민감한 결과를 보였다. 또한, 외부흐름의 영향이 작을지라도 천해와 천해부근 상대수심 (0.01 < kh ≦ 0.70)에서는 외부흐름의 영향을 무시할 수 없다는 것을 확인하였다.

• 한국해안·해양공학회논문집
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• 제22권1호
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• pp.25-33
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• 2010

연직 슬릿 유공벽에서의 정합조건에는 투수 매개변수가 포함되는데, 보통 투수 매개변수는 두 가지 방법으로 계산이 가능하다. 하나는 투수 매개변수를 유공벽에서의 에너지 소산 계수와 제트의 길이로 나타내는 방법으로서, 관련된 모든 변수를 알고 있다는 점에서 장점을 가지고 있으나, 장파의 영역에서 옳지 않은 결과를 초래하는 단점이 있다. 다른 하나는 투수 매개변수를 마찰계수와 관성계수로 나타내는 방법으로서, 단파부터 장파까지 모든 영역에서 올바른 결과를 나타내지만, 반사계수, 투과계수 등에 대한 관측치와 계산치 사이의 최적적합에 기초하여 마찰계수를 결정해야 한다는 단점이 있다. 본 논문에서는 유공벽의 유공율 및 두께, 수심 등 기지의 변수로 마찰계수에 대한 경험식을 제시하였다. 이렇게 함으로써 최적적합 과정을 거치지 않고 마찰계수를 직접 산정할 수 있도록 한다. 경험식을 구하기 위하여 수리실험을 실시하였으며, 다른 연구자들의 결과를 함께 사용하여 경험식을 제시하였다. 제시된 공식을 이용하여 상부는 커튼월이고 하부는 연직 슬릿 유공벽으로 되어 있는 커튼월-파일 방파제의 반사계수 및 투과계수를 계산하였다. 실험치와 계산치가 잘 일치함을 보임으로써 제시한 경험식의 적합성을 검증하였다.

• 한국산업융합학회 논문집
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• 제6권1호
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• pp.65-71
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• 2003

Infrared heating has been traditionally used in industrial applications for processes such as dehydration of food industrial. This heating method involves the application of radiation in the wavelength range of 5~50 micrometers. In this work, simultaneous heat balance equations were developed to simulate the infrared radiation heating of red peppers. The equations assume that moisture diffuses to the outer boundaries of the material in liquid form and evaporation occurs at the surface of the red peppers. Energy for moisture evaporation is supplied by the infrared radiant energy. The equations were validated with experimental data on surface temperature and average moisture content of red peppers. Average deviations of predicted surface red peppers temperature and average red peppers moisture from experimental data were 323~353K and 50~80%, respectively. The spectral extinction coefficients in the wavelength range $1.5<{\lambda}<27$ micrometer at 293K for Red Peppers were determined from results of reflection measurements and the four flux radiative heat transfer calculation. The radiation extinction coefficients were obtained from effective drying factor the temperature 373K.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.720-731
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• 2014

There are many kinds of optical systems to widen a field of view. Fisheye lenses with view angles of 180 degrees and omni-directional systems with the view angles of 360 degrees are recognized as proper systems to widen a field of view. In this study, we proposed a new optical system to overcome drawbacks of conventional omni-directional systems such as a limited field of view in the central area and difficulties in manufacturing. Thus we can eliminate the undesirable reflection components of the omni-directional system and solve the primary drawback of the conventional system. Finally, tolerance analysis using Zernike polynomial coefficients was performed to confirm the productivity of the new optical system. Furthermore, we established a method of optical axis alignment and compensation schemes for the proposed optical system as a result of tolerance analysis. In a sensitivity calculation, we investigated performance degradation due to manufacturing error using Code V(R) macro function. Consequently, we suggested compensation schemes using a lens group decentering. This paper gives a good guidance for the optical design and tolerance analysis including the compensation method in the extremely wide angle system.

• 지질공학
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• 제24권4호
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• pp.463-471
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• 2014

This paper considers the effect of rainfall on non-point source (NPS) pollutant loads. The impact of runoff on the occurrence of NPS pollutants was found to be influenced by rainfall amount, rainfall intensity, and the number of antecedent dry days (ADD), both independently and in combination. The close correlation ($R^2$ = 0.9920) between rainfall and runoff amounts was demonstrated at the study site (a flower farm) over the period between January 2011 and December 2013. The relationships among pollutant levels, runoff, and rainfall was not satisfactory results except for the Biochemical Oxygen Demand ($BOD_5$). The correlation coefficients between $BOD_5$, and both runoff and rainfall, were greater than 0.92. However, the relationships of other pollutants, such as Suspended Solid (SS), Chemical Oxygen Demand ($COD_{Mn}$), Total Nitrogen (TN), and Total Phosphorus (TP), with runoff and rainfall had correlation coefficients of less than 0.70. The roles of rainfall was different from rainfall categories on the occurrence of runoff. Instantaneous rainfall intensity was a principle factor on the occurrence of runoff following light rainfall events (total ${\leq}30mm$). For rainfall of intermediate intensity (total precipitation 31-50 mm), the combined effect of both average rainfall intensity and ADD was found to influence runoff generation. We conclude that the control of NPS pollutants with the reflection of the climate change that makes the remarkable effect of amounts and forms on the rainfall and runoff.

• 한국해양공학회지
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• 제18권4호
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• pp.23-32
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• 2004

Specially shaped concrete blocks are used for the armor layer of rubble structure for breakers, seawalls, or other shore protection work. In this study, the hydraulic characteristics of the Modified-Tribar(MTB), which addresses the shortcomings of the Arch-Tribar, and the most widely used Tetrapod(TTP) in Korea are examined through hydraulic model tests. The MTB are much more stable than the TTP, as shown through the stability model tests under non-breaking and non-overtopping condition. The value of the stability coefficient(KD) was obtained at around 30. The model tests show that the TTP random two layers and MTB uniform 1.5 layers have similar effects, but the MTB one layer shows slightly low effects in dissipating wave energy. The TTP random two layer model is the most effective in reducing wave overtopping rate, under overtopping condition, while the MTB uniform one layer and the MTB uniform 1.5 layer models follow respectively.

• 대한원격탐사학회지
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• 제27권6호
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• pp.677-692
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• 2011

Suspended sediment is an important oceanic variable for monitoring changes in coastal environment related to physical and biogeochemical processes. In order to estimate suspended sediment concentration (SSC) from satellite data, we derived SSC coefficients by fitting satellite remote sensing reflectances to in-situ suspended sediment measurements. To collect in-situ suspended sediment, we conducted ship cruises at 16 different locations three times for the periods of Sep.-November 2009 and Jul. 2010 at the passing time of Landsat $ETM_+$. Satellite data and in-situ data measured by spectroradiometers were converted to remote sensing reflectances ($R_{rs}$). Statistical approaches proved that the exponential formula using a single band of $R_{rs}$(565) was the most appropriate equation for the estimation of SSC in this study. Satellite suspended sediment using the newly-derived coefficients showed a good agreement with insitu suspended sediment with an Root Mean Square (RMS) error of 1-3 g/$m^3$. Satellite-observed SSCs tended to be overestimated at shallow depths due to bottom reflection presumably. This implies that the satellite-based SSCs should be carefully understood at the shallow coastal regions. Nevertheless, the satellite-derived SSCs based on the derived SSC coefficients, for the most cases, reasonably coincided with the pattern of in-situ suspended sediment measurements in the study region.

• Journal of electromagnetic engineering and science
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• 제5권3호
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• pp.122-125
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• 2005

This paper describes a design of a miniature patch antenna and its 4-channle array for 5.25 GHz wireless LAN band. Each patch element is designed for the low mutual coupling between each element and for the small size of the array antenna. The size of the each element is $7 mm{\times}14.5 mm{\times}5.6 mm$ and it satisfy IEEE 802.11a frequency band. It is arrayed for independent 4-channel operation. The total size of the array antenna is $35.6 mm{\times}52.5 mm{\times}5.6 mm$. The measured reflection coefficients and the radiation patterns of the fabricated antennas show the reasonable agreements with prediction.

• ETRI Journal
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• 제26권3호
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• pp.262-264
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• 2004

We investigate the characteristics of a wideband and high-gain cavity-backed slot antenna in terms of the reflection coefficients, radiation patterns, and gain. A cavity-backed slot antenna structure includes baffles, reflectors, and thick ground planes. The measured gain and bandwidth of a 10-dB return loss in a cavity-backed $2{\times}2$ array slot antenna with $h_1=2 $mm, d=2 mm are 15.5 dBi and nearly 27%, respectively, at 42 GHz. Baffles and reflectors are used to increase antenna gain, thus reducing the coupling among the slots on the thick ground plane.

• Journal of electromagnetic engineering and science
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• 제14권1호
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• pp.43-45
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• 2014

We propose a printed circuit board (PCB)-embedded antenna for millimeter-wave chip-to-chip communication. The antenna is 0.18 mm in height which is 1/20 wavelength at 80 GHz. In order to realize such a low profile, a zeroth-order resonator antenna with a periodic array of four unit cells is employed, and its geometry is optimized to cover an 8-GHz bandwidth from 76 to 84 GHz. With this;the antenna is capable of radiating in a direction parallel to the board length despite the short distance between the ground and the radiator. Simulation and measurement results show that the optimized design has low reflection coefficients and consistent radiation patterns throughout the target bandwidth.