• 한국대기환경학회지
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• 제25권6호
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• pp.539-549
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• 2009

The purpose of this study is to estimate hourly Asian dust emission flux in springtime by using the optimized Weather Research Forecasting model (WRF) in order to accurately predict the horizontal flux of Asian dusts. Asian dust emission flux using 5 empirical formulas such as US EPA, Park and Inn, Wang, The Goddard Chemistry Aerosol Radiation and Transport (GOCART) and Dust Entrainment and Deposition (DEAD) were calculated and compared by using classified land-use types and size distribution at various locations in China and Mongolia together with the hourly meteorological elements of the WRF model. As a result, the empirical formula in US EPA among them, which was considered the various conditions such as vegetation, soil type and terrain, was better than the other 4 empirical formulas. However, these formulas were adjusted hourly and vertically in time and space because there was different order and time resolution of dust emissions from original empirical formulas.

• Wind and Structures
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• 제23권5호
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• pp.385-403
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• 2016

The across-wind dynamic loads on L-shaped tall buildings with various geometric dimensions were investigated through a series of wind tunnel testing. The lift coefficients, power spectral densities and vertical correlation coefficients of the across-wind loads were analyzed and discussed in details. Taking the side ratio and terrain category as key variables, empirical formulas for estimating the across-wind dynamic loads on L-shaped tall buildings were proposed on the basis of the wind tunnel testing results. Comparisons between the predictions by the empirical formulas and the wind tunnel test results were made to verify the accuracy and applicability of the proposed formulas. Moreover, a simplified procedure to evaluate the across-wind dynamic loads on L-shaped tall buildings was derived from the proposed formulas. This study aims to provide a simple and reliable way for the estimation of across-wind dynamic loads on L-shaped tall buildings.

• 한국해안·해양공학회논문집
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• 제23권1호
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• pp.109-117
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• 2011

국내 경사식 방파제의 대표적인 피복재인 Tetrapod는 대부분 경험식을 사용하여 중량을 산정한다. 경험식은 수리 실험의 결과를 곡선맞춤(curve-fitting)하여 제안되기 때문에 실험 오차에 따른 불확실성이 내포되어 있다. 이런 불확실성을 최소화하기 위해 인경신경망과 M5' model tree를 사용하여 피복재 안정수를 예측하였다. 각 모형의 불확실성의 정도는 예측된 안정수와 수리실험의 안정수 사이의 일치지수(index of agreement)를 사용하여 평가하였다. 일치지수가 가장 큰 인공신경망은 우수한 예측 능력을 가지고 있지만 일반 설계자들이 쉽게 사용할 수 없는 큰 단점이 있다. 반면에 M5' model tree는 인공신경망보다는 예측 능력이 조금 떨어지지만 기존의 경험식보다는 예측능력이 우수하고 또한 일반 설계자들이 쉽게 사용할 수 있는 공식의 형태로 주어지는 장점이 있다.

• 한국농공학회지
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• 제27권4호
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• pp.42-52
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• 1985

This study was attempted to derivate empirical formulas for the runoff: ratio during ilood. season at three watersheds of Dan Yang, Chung Ju, and Yeo Ju are located at upper, middle, and lower portion of Nam Han river basin, respectively. Obtained formulas for flood runoff ratio can be applied as an element for the estimation, peak discharge for the design of various hydraulics structures which can be concidented with meteorological and topographical condition. The obtained through this study were analyzed as follows. 1.It was found that the magnitude of runoff ratio depends on the amount of rainfall for all studying basins. 2.Empirical formulas 'for the runoff' ratio were derivated as 1- 2,707 Rt0.345, 1-1.691 Rt0.242 and 1-1.807 Rt0.227 at Dan Yang, Chung Ju and Yeo Ju watershed, respectively. 3.The magnitude of runoff ratio was appeared in the order of Dan Yang, Chung Ju, and Yeo Ju are located at upper, middle and lower portion of Nam Han rivet basin, respectively. 4.It was assumed that in general the more it rains, the lesser becomes the ratio of loss rainfall. Especially, the ratio of loss rainfall for Dan Yang, upper portion of river basin was shown as the lowest among three watersheds. Besides, the magnitude of that was appeared in the order of Chung Ju and Yeo Ju watershed located at middle, and lower part of river basin, respectively. 5.Relative and standard errors of runoff ratio calculated by empirical formulas were shown to be within ten percent to the observed runoff ratio in all watersheds. 6.It is urgently essential that the effect of antecedent rainfall have an influence on the next coming flood should be studied in near future.

• 대한토목학회논문집
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• 제5권4호
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• pp.23-30
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• 1985

비점성토 지반에서 말뚝 기초의 지지력을 산정하는 방법으로 동역학적 공식이 있다. 이 공식은 사용이 간편한 반면에 공식에 사용되는 경험적인 계수값들의 타당성과 항타기록의 정확성등이 문제가 된다. 본 논문에서는 현재 널리 사용되는 6 종류의 공식을 선정하여 각 공식이 산출한 계산 허용 지지력을 말뚝 재하 시험으로부터 구한 실측 허용 지지력과 비교 분석하고, 말뚝 재하시험 결과와 동일한 허용 지지력을 산출할 수 있도록 선형 회귀곡선을 이용하여 각 공식을 수정하였다. 수정된 공식중에서 Gates의 공식이 가장 신뢰도가 높은 것으로 나타났으며, 기존의 Olson 수정공식과 비교한 결과 본 논문 제안 공식이 10% 이상 보수적인 결과를 산출하였다.

• 대한토목학회논문집
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• 제37권6호
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• pp.989-999
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• 2017

본 연구에서는 분기수로에서 발생되는 에너지손실을 계산하기 위한 손실계수의 경험식을 산정하기 위해 수리모형실험을 수행했다. 수리모형은 유입수로와 90도의 각도를 갖는 두 유출수로로 구성되어 있으며, 유입수로과 유출수로에서 압력수두와 속도수두를 측정하여 분기수로에서 발생되는 에너지손실을 분석했다. 각 측선에서 동수경사선의 변화를 비교한 결과, 수로의 분기점에서 동수경사선이 급격히 하강하여 에너지손실이 분기점에서 발생되었으며, 유량비의 증가에 따라 속도수두의 감소폭이 증가했다. 유량비와 Froude수가 증가함에 따라 유출량이 더 큰 수로에서 수두손실량이 지수적으로 증가하는 결과를 보였으며, 손실계수 또한 증가했다. 반면에, 유출량이 작은 수로에서는 유량비와 Froude수의 증가에 따라 손실계수가 감소하는 결과가 나타났다. 손실계수 계산결과를 이용하여 두 유출수로에서 손실계수 경험식을 제안하였으며, 경험식의 계산오차가 각각 3.91%, 5.19%로 나타났다. 그리고 두 경험식을 이용하여 계산한 총 손실계수를 실험결과와 비교하여 3.62%의 오차가 발생했다.

• 동의생리병리학회지
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• 제22권5호
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• pp.1078-1105
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• 2008

An empirical formula that has been empirically shown to be effective for a particular condition can be said to add medicinal materials to an existing formula or to make a new prescription by the Korean medical doctors' empirical clinic. This dissertation aims to study the prescriptions according to A Confidential Document of A Distinguished Medical Family written by the writer's ancestor and to contribute to the development of Korean medicine. A Confidential Document of A Distinguished Medical Family is a medicinal recipe that is an heirloom of the Gyeongju Kim family for the eighth generation. And the date and the writer of the book are unknown. The contents of the book consist of 18 parts and are made up of about 300 medical recipes. Of these, 158 formulas and indications of cold damage, wind, urination, stool, jaundice, and internal injury are found in the book. From among these, 61 formulas was directly quoted out of The Precious Mirror of Oriental Medicine, 97 formulas are adjusted in proportion or combined. By the parity of reasoning of the above, I think that this book was published after The Precious Mirror of Oriental Medicine. I will continue to study other formulas except the formulas above mentioned.

• Steel and Composite Structures
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• 제25권5호
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• pp.617-624
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• 2017

In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity ($M_u$) and moment demand ($M_d$) to plastic moment capacity ($M_p$) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min $[(M_u-M_d)/M_p]$ of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.

• 한국항공우주학회지
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• 제47권11호
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• pp.768-778
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• 2019

고속으로 비행하는 항공기의 구성품에 관한 적절한 설계를 위해서는 공기역학적 가열과 표면 온도를 계산하는 능력이 필수적이다. 본 연구에서는 항공기의 공력가열을 효율적으로 계산하기 위한 다양한 경험식들을 분석한 다음, 경험식에 기초한 전산코드를 개발하였다. 계산된 결과는 Navier-Stokes-Fourier 방정식 기반의 ANSYS FLUENT와 경험식에 기초한 ThermoAnalytics사의 MUSES 코드의 결과와 비교하였다. FLUENT의 계산결과와는 벽면 및 정체점 온도에 대해 매우 일치하였다. MUSES 코드와도 온도와 열유속에서 각각 1%, 5%의 차이를 보여주어 매우 근접한 결과를 보여 주었다.

• 한국해양공학회지
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• 제25권5호
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• pp.69-75
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• 2011

The purpose of this study was to develop a buckling analysis technique for a windpower system structure under environmental loadings (hydrostatic pressure) using FEM. We analyzed an isotropic material and composite material and made a comparison using buckling pressure formulas. First, finite element analyses for an isotropic material (SC410) were performed to obtain the variation of buckling pressure for the number of elements and boundary conditions in a pressure-shell model, and the numerical results were compared with those of existing empirical formulas. Then, additional finite element analyses based on the results of the isotropic material (SC410) were performed to determine the optimum lamination angle and pattern for a composite material (URN300). The results of the FE analyses for the composite material were also compared with those of existing empirical formulas. The ply orientations (lamination angles) used in the FE analyses were $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and. The lamination patterns in the FE analyses were and. The lamination pattern was assumed to be the equivalent model of. The results of the FE analyses for the isotropic material (SC410) indicated that the optimal values for the number of elements and the boundary conditions were 6000 and both simply supported, respectively. The results of the FE analyses for the composite material (URN300) showed that the optimal ply orientation was $60^{\circ}{\sim}75^{\circ}$.