• Ocean Science Journal
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• v.42 no.4
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• pp.211-222
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• 2007

We compare insolation results calculated from two well-known empirical formulas (Socket and Beaudry's SB73 formula and the original Smithsonian (SMS) formula) and a radiative transfer model using input data predicted from meteorological weather-forecast models, and review the accuracy of each method. Comparison of annual mean daily irradiance values for clear-sky conditions between the two formulas shows that, relative to the SMS, the SB73 underestimates spring values by 9 W $m^{-2}$ in the northern Adriatic Sea, although overall there is a good agreement between the annual results calculated with the two formulas. We also elucidate the effect on SMS of changing the 'Sun-Earth distance factor (f)', a parameter which is commonly assumed to be constant in the oceanographic context. Results show that the mean daily solar radiation for clear-sky conditions in the northern Adriatic Sea can be reduced as much as 12 W $m^{-2}$ during summer due to a decrease in the f value. Lastly, surface irradiance values calculated from a simple radiative transfer model (GM02) for clear-sky conditions are compared to those from SB73 and SMS. Comparison with iu situ data in the northern Adriatic Sea shows that the GM02 estimate gives more realistic surface irradiance values than SMS, particularly during summer. Additionally, irradiance values calculated by GM02 using the buoy meteorological fields and ECMWF (The European Centre for Medium Range Weather Forecasts) meteorological data show the suitability of the ECMWF data usage. Through tests of GM02 sensitivity to key regional meteorological factors, we explore the main factors contributing significantly to a reduction in summertime solar irradiance in the Adriatic Sea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.3
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• pp.186-189
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• 2003

Various empirical formulas have been developed to describe the stability of breakwater armor stones. The Hudson formula is known to have needs to be refined in many ways. but it is most widely used because of its simplicity. The van der Meer formula is sometimes used for the cross-check, but it is not very popularly used due to its complexity and the uncertainty of the relevant parameters. Recently, on the other hand, Yoo(2003) proposed a formula of a simple form using a new non-dimensional number which is called 'action slope' (abbreviated as Yoo formula hereinafter). In this study, in order to provide coastal engineers with some idea of the use of these formulas, their accuracies were estimated by comparing with the experimental data reported by van der Meer in 1987 and 1988. It was found that the van der Meer formula showed the highest accuracy, while the Hudson formula of very low accuracy needed considered judgment on its use. On the other hand, the Yoo formula of slightly lower accuracy but simpler expression than the van der Meer formula seems to be able to be used in engineering practice if a slightly higher safety factor is taken.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.3
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• pp.69-78
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• 1986

This studies were established to find out the characteristics of frequency distributiom for the number of occurrence and magnitude, probable flood flows according to the return periods, design floods, and design frequency factors for the studying basins in relation to the risk levels which can be correlated with design return period and the life of structure in the non-annual exceedance series. Eight watersheds along Han, Geum, Nak Dong and Seom Jin river basin were selected as studying basins. The results were analyzed and summarized as follows. 1. Poisson distribution and Exponential distribution were tested as a good fitted distributions for the number of occurrence and magnitude for exceedance event, respectively,at selected watersheds along Han, Geum, Nak Dong and Seom Jin river basin. 2.Formulas for the probable flood flows and probable flood flows according to the return periods were derivated for the exponential distribution at the selected watersheds along Han, Geum, Nak Dong, and Seom Jin river basin. 3.Analysis for the risk of failure was connected return period with design life of structure in the non-annual exceedance series. 4.Empirical formulas for the design frequency factors were derivated from under the condition of the return periods identify with the life of structure in relation to the different risk levels in the non-annual exceedance series. 5.Design freguency factors were appeared to be increased in proportion to the return periods while those are in inverse proportion to the levels of the risk of failure. Numerical values for the design frequency factors for the non-annual exceedance series ware appeared generally higher than those of annual maximum series already published by the first report. 6. Design floods according to the different risk levels could be derivated by using of formulas of the design frequency factors for all studying watersheds in the nor-annual exceedance series.

• Herbal Formula Science
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• v.10 no.2
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• pp.1-4
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• 2002

The development of Korean Oriental medicine is based upon the accumulation of experience and knowledge gathered over the centuries. The approaches taken are holistic and empirical. There is a need to understand their actions at molecular levels with more rational, objective and scientific studies. Today it appears that Chronic and age-associated diceases may be multifactorial and hence more complex. A different approach may be required. One claimed usage of Korean Oriental medicine is for the treatment and prevention of chronic and age-associated illnesses. Some of the botanical formulas used for this purpose were discovered thousands of years ago and continue to be used today. There are indications that these formulas may indeed be helpful in the treatment or prevention of chronic diseases. This multi-component medicine could not only be very useful meeting the unmet clinical needs but for defining a more synergistic therapy that supports and maintains the bodies natural curative abilities. The potential usefulness of Korean Oriental medicine embodies the belief of maintaining healthy homeostasis of the body through the proper balance of a mixture of chemical at different organs or tissues. This concept is different from western medicine and implies that multiple compounds may act on multiple mechanisms of action to maintain the balance of the complex web of biology. This is very important in view of sciences current direction to integrate fragmented information to develop future medicines. The western and eastern approaches to human health and disease are complementary to each other. The best approach in developing future medicines is to integrate both approaches.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.543-560
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• 2010

Safety-related concrete structures in a nuclear power plant must be protected against the impact of flying objects, referred to in the profession as missiles. In practice, the structural verification is usually carried out by means of empirical formulas, which relate the velocity of the impinging missile to the wall thickness needed to prevent scabbing or perforation. The purpose of this study is to reevaluate the predictability of the local effect prediction formulas for the penetration and scabbing depths and perforation thickness. Therefore, available formulas for predicting the penetration depth, scabbing thickness, and perforation thickness of concrete structures impacted by solid missiles are summarized, reviewed, and compared. A series of impact analyses is performed to predict the local effects of the projectile at impact velocities varing from 95 to 215 m/s. The results obtained from the numerical simulations have been compared with tests that were carried out at Kojima to validate numerical modelling. The simulation results show reasonable agreement with the Kojima test results for the overall impact response of the RC slabs. From these results, it seems that the Degen equation give a very good estimate of perforation thickness against a tornado projectile for test data. Finally, the results obtained from the impact analysis have been compared with Degen formula to determine the perforation thickness of the RC slab.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.111-120
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• 2009

A local scour around a bridge pier is known as one of important factors of bridge collapse. Two approaches are usually used in estimating a scour depth in practice. One is to use empirical formulas, and the other is to use computational methods. But the use of empirical formulas is limited to predict a scour depth under similar conditions to which the formulas were derived. Computational methods are currently too expensive to be applied to practical engineering problems. This study presented the application of artificial neural networks (ANN) to the prediction of a scour depth around a bridge pier at an equilibrium state. This study also investigated various ANN algorithms for estimating a scour depth, such as Backpropagation Network, Radial Basis Function Network, and Generalized Regression Network. Preliminary study showed that ANN models resulted in very wide range of errors in predicting a scour depth. To solve this problem this study incorporated cluster analysis into ANN. The incorporation of cluster analysis provided better estimations of scour depth up to 42% compared with other approaches.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.5
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• pp.277-283
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• 2016

Tetrapod is one of the most widely used concrete armor units for rubble mound breakwaters. The calculation of the stability number of Tetrapods is necessary to determine the optimal weight of Tetrapods. Many empirical formulas have been developed to calculate the stability number of Tetrapods, from the Hudson formula in 1950s to the recent one developed by Suh and Kang. They were developed by using the regression analysis to determine the coefficients of an assumed formula using the experimental data. Recently, software engineering (or machine learning) methods are introduced as a large amount of experimental data becomes available, e.g. artificial neural network (ANN) models for rock armors. However, these methods are seldom used probably because they did not significantly improve the accuracy compared with the empirical formula and/or the engineers are not familiar with them. In this study, we propose an explicit method to calculate the stability number of Tetrapods using the weights and biases of an ANN model. This method can be used by an engineer who has basic knowledge of matrix operation without requiring knowledge of ANN, and it is more accurate than previous empirical formulas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.262-272
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• 2020

A large number of studies on wave breaking have been carried out, and many experimental data have been documented. Moreover, on the basis of various experimental data set, many empirical or semi-empirical formulas based primarily on regression analysis have been proposed to quantitatively estimate wave breaking for engineering applications. However, wave breaking has an inherent variability, which imply that a linear statistical approach such as linear regression analysis might be inadequate. This study presents an alternative nonlinear method using an neural network, one of the machine learning methods, to estimate breaking wave height and breaking depth. The neural network is modeled using Tensorflow, a machine learning open source platform distributed by Google. The neural network is trained by randomly selecting the collected experimental data, and the trained neural network is evaluated using data not used for learning process. The results for wave breaking height and depth predicted by fully trained neural network are more accurate than those obtained by existing empirical formulas. These results show that neural network is an useful tool for the prediction of wave breaking.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.384-395
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• 2020

Breaking waves generated by wave shoaling in coastal areas have a close relationship with various physical phenomena in coastal regions, such as sediment transport, longshore currents, and shock wave pressure. Therefore, it is crucial to accurately predict breaker index such as breaking wave height and breaking depth, when designing coastal structures. Numerous scientific efforts have been made in the past by many researchers to identify and predict the breaking phenomenon. Representative studies on wave breaking provide many empirical formulas for the prediction of breaking index, mainly through hydraulic model experiments. However, the existing empirical formulas for breaking index determine the coefficients of the assumed equation through statistical analysis of data under the assumption of a specific equation. In this paper, we applied a representative linear-based supervised machine learning algorithms that show high predictive performance in various research fields related to regression or classification problems. Based on the used machine learning methods, a model for prediction of the breaking index is developed from previously published experimental data on the breaking wave, and a new linear equation for prediction of breaker index is presented from the trained model. The newly proposed breaker index formula showed similar predictive performance compared to the existing empirical formula, although it was a simple linear equation.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.117-124
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• 2003

Wind-induced motions, like acceleration for instance, often influence designs for high-rise buildings. As a consequence, correct assessment of natural frequency becomes important. The empirical expressions used to quantify this parameter at the design phase tend to yield values that are significantly different from each other. This paper is concerned with the natural periods of steel buildings. It describes the vibration measurement methods that were employed for testing buildings. This paper will also present reliable methods of assessing the natural period from ambient vibration tests. Data from measurements on 21 buildings in Seoul were provided while 21 buildings were tested by ambient vibration measurements to obtain the natural periods. While regression formulas of natural periods for steel-frarried tall buildings were suggested,the obtained formula was compared with the empirical expressions of structural standards and the Eigen-value analysis.