• Title/Summary/Keyword: regression formulas

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Development of Empirical Formulas for Storage Function Method (저류함수법의 매개변수 산정식 개발)

  • Choi, Jong-Nam;Ahn, Won-Shik;Kim, Tae-Gyun;Chung, Gun-Hui
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.5
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    • pp.125-130
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    • 2009
  • Storage function method which considers the non-linearity of the relationship between rainfall and runoff has been frequently used to predict runoff in a basin and a flood pattern. However, it is time-consuming to estimate appropriate parameters of every basin and rainfall event, which requires the empirical parameter equation applicable in Korea. In this study, multiple regression analysis is used to develop empirical equations to estimate parameters of Storage Function method using basin characteristics. The basin area, maximum stream length, and stream slope are considered as the basin characteristics as the result of the regression analysis. Collinearity is removed and trial-and-error method is used to choose the most descriptive parameters to the dependent variables in Han River basin which is divided into 30 subbasins. The developed equations are validated using the rainfall events in MunMak gauging station and named as 'Han River equation'. The equation could provide the useful information about Storage Function method parameter to calculate runoff from a basin and predict river stage.

Prediction of Scour Depth Using Incorporation of Cluster Analysis into Artificial Neural Networks (인공신경망모형과 군집분석을 이용한 교각 세굴심 예측)

  • Lee, Chang-Hwan;Ahn, Jae-Hyun;Lee, Joo Heon;Kim, Tea-Woong
    • 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.

Prediction of Wave Breaking Using Machine Learning Open Source Platform (머신러닝 오픈소스 플랫폼을 활용한 쇄파 예측)

  • Lee, Kwang-Ho;Kim, Tag-Gyeom;Kim, Do-Sam
    • 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.

A Study on the Characteristics of Concrete mixed with the Converter furnace Slag (전로슬래그를 이용한 콘크리트의 강도에 관한 연구)

  • 곽기주;손순종;김기성
    • Magazine of the Korea Concrete Institute
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    • v.6 no.4
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    • pp.113-122
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    • 1994
  • To examine the applicabilty of the converter furnace slag from iron-works as concrete aggregate respective concrete furnace slag with contents of 20%. 40%, 60%. 80% were mixed with granulated slag, and the strength and stability tests for these specimens were followed. The slump value of the concrete mixed with converter furnace slag was higher than that of the conventional concrete. Furnace slag and granulated slag was increased as the increase of converter furnace content. The strength of the concrete mixed with converter furnace slag and granulate slag increased as an increase of converter furnace content and age. The expansion rate of the concrete mixed with converter furnace slag and granulated slag increased from 0.007% to 0.19% as the converter furnace content changed from 20% to 80%. From the above results in the strength and expansion rate, the concrete with the converter furnace content of 40% was considered to be recommandable for the stable construction of the concrete. Calculated formulas for tensile strength(${\sigma}_t$) and flexural strength(${\sigma}_f$) from the regression a.nalysis of the correlations among these compressive strength (${\sigma}_c$), tensile strength and flexural strength are as follows. ${\sigma}_t$ = 0.16952${\sigma}_c$ - 4.9313 ${\sigma}_f$ = 0.25727${\sigma}_c$ + 6.0528

Load Distribution Factors for Two-Span Continuous I-Girder Bridges (2경간 연속 I-형교의 하중분배계수)

  • Back, Sung Yong;Shin, Gi Su
    • Journal of Korean Society of Steel Construction
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    • v.19 no.2
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    • pp.233-245
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    • 2007
  • Previous finite element studies have shown that AASHTO Standard load distribution factor (LDF) equations appear to be conservative for longer spans and larger girder spacing, but too permissible for short spans and girder spacing. AASHTO LRFD specification defines the distribution factor equation for girder spacing, span length, slab thickness, and longitudinal stiffness. However, this equation requires an iterative procedure to correctly determine the LDF value due to an initially unknown longitudinal stiffness parameter. This study presents a simplified LDF equation for interior and exterior girders of two-span continuous I-girder bridges that does not require an iterative design procedure. The finite element method was used to investigate the effect of girder spacing, span length, slab thickness, slab width, and spacing and size of bracing. The computer program, GTSTRUDL, was used to idealize the bridge superstructures as the eccentric beam model, the concrete slab by quadrilateral shell elements, steel girders by space frame members, and the composite action between these elements by rigid links. The distribution factors obtained from these analyses were compared with those from the AASHTO Standard and LRFD methods. It was observed through the parametric studies that girder spacing, span length, and slab thickness were the dominant parameters compared with others. The LRFD distribution factor for the interior girder was found to be conservative in most cases, whereas the factor for the exterior girder to be unconservative in longer spans. Furthermore, a regression analysis was performed to develop simplified LDF formulas. The formulas developed in this study produced LDF values that are always conservative to those from the finite element method and are generally smaller than the LDF values obtained from the AASHTO LRFD specification. The proposed simplified equation will assist bridge engineers in predicting the actual LDF in two-span continuous I-girder bridges.

Development of an Estimation Method for Travel Time (도달시간 산정 방법의 개발)

  • Jeong, Jong-Ho;Keum, Jong-Ho;Yoon, Yong-Nam
    • Journal of Korea Water Resources Association
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    • v.35 no.6
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    • pp.715-727
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    • 2002
  • The travel time of a flood through a river reach can be estimated by dividing the river length by the mean velocity with which the flood passes downstream. It is closely related to storage constant for the watershed routing of a flood. There are so many empirical formulas available for the estimation of travel time but the results computed generally show great different depending on individual formulas. In the present study, the mean velocity data computed in the process of water surface profile computation for a probability flood through more than 100 different river reaches were collected along with the mean river bed slope of each river reach. And then, a regression analysis is made between the mean river bed slope and the mean velocity, which showed a wide scatter along the mean regression curve, which appears to be due to the different in the magnitude of probability rainfall and size of watershed area. Therefore, methods have been developed to remove the effect of these factors and generalized empirical equation is proposed to relate the mean velocity to mean river bed slope of a reach. Hence, if the mean river bed slope of a river reach is estimated from the longitudinal river profile, the mean velocity can be computed by the generalized equation along with the probability rainfall and watershed area of the river reach under consideration, which leads to the estimation of travel time through a river reach.

Analysis of the Correlation between Geological Characteristics and Water Withdrawals in the Laterals of Radial Collector Well (방사형집수정의 수평집수관에서 지질특성과 취수량의 상관관계 분석)

  • Kim, Tae-Hyung;Jeong, Jae-Hoon;Kim, Min;OH, Se-Hyoung;Lee, Jae-Sung
    • The Journal of Engineering Geology
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    • v.24 no.2
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    • pp.201-215
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    • 2014
  • This study was performed to investigate the correlation between hydraulic conductivity and the flow rate of an aquifer, with the flow rate calculated from the laterals of the radial collector well using data obtained by the development project of riverbank filtration (Second Phase) in Changwon City. The hydraulic conductivity was empirically calculated from unconsolidated sediments collected from a sandy gravel layer along the middle-to-downstream sections of the Nakdong River. The Beyer equation produced the most suitable hydraulic conductivity from the various empirical formulas employed. The calculated hydraulic conductivity ranged from 0.083 to 0.264 cm/s, with an average value of 0.159 cm/s, suggesting that the aquifer in the study area possesses a high permeability with a good distribution of sandy gravel. The relationship between the calculated hydraulic conductivity in the aquifer and the entrance velocity into the screen, the flow rate was analyzed through the linear regression analysis. From the result of regression analysis, it showed that the hydraulic conductivity and the entrance velocity into the screen and the flow rate have a linear regression equation having about 72% of the high correlation. The result of verification in the measured data between each variable showed a high suitability from being consistent with the approximately 72% in the linear regression analysis. This study demonstrates that the groundwater flow rate can be estimated within the laterals of the radial collector well using a linear regression equation, if the hydraulic conductivity of the aquifer is known. This methodology could thus be applicable to other aquifers with hydraulic conductivity and permeability parameters similar to those in the present study area.

Design-based Properties of Least Square Estimators in Panel Regression Model (패널회귀모형에서 회귀계수 추정량의 설계기반 성질)

  • Kim, Kyu-Seong
    • Survey Research
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    • v.12 no.3
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    • pp.49-62
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    • 2011
  • In this paper we investigate design-based properties of both the ordinary least square estimator and the weighted least square estimator for regression coefficients in panel regression model. We derive formulas of approximate bias, variance and mean square error for the ordinary least square estimator and approximate variance for the weighted least square estimator after linearization of least square estimators. Also we compare their magnitudes each other numerically through a simulation study. We consider a three years data of Korean Welfare Panel Study as a finite population and take household income as a dependent variable and choose 7 exploratory variables related household as independent variables in panel regression model. Then we calculate approximate bias, variance, mean square error for the ordinary least square estimator and approximate variance for the weighted least square estimator based on several sample sizes from 50 to 1,000 by 50. Through the simulation study we found some tendencies as follows. First, the mean square error of the ordinary least square estimator is getting larger than the variance of the weighted least square estimator as sample sizes increase. Next, the magnitude of mean square error of the ordinary least square estimator is depending on the magnitude of the bias of the estimator, which is large when the bias is large. Finally, with regard to approximate variance, variances of the ordinary least square estimator are smaller than those of the weighted least square estimator in many cases in the simulation.

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Development of the Pants Patterns for Muscular Men (근육형 남성용 팬츠 원형 개발)

  • Jeong, Hye-Jin;Kim, So-Ra
    • Journal of Fashion Business
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    • v.14 no.2
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    • pp.1-13
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    • 2010
  • Recently, young men have become more muscular, as they have become increasingly more interested in health and their physical appearances. The trend these days is to wear slim suits to accentuate their figures. Men's pants are the one of the most general clothes which men wears. While pants are an ordinary item of clothing, most muscular men have fitting problems with ready-made pants. In view of this, this study aimed at developing a prototype pants pattern for muscular men. In this study, five muscular men were selected for wearing tests. The regression formulas, in which muscular men's body measurements were adopted, were applied to unsuitable body parts, especially the body parts determined inappropriate based on the results of the existing pants pattern wearing tests. After going through the first and second pants pattern wearing tests, the final pants patterns were developed that were suitable for muscular men. The results of the study were as follows: In order to solve the problem of the insufficient of ease due to the development of the hip muscles, the crotch length was made longer, (0.08${\times}$hip circumference+17.648)+1.5cm and front crotch width and back crotch width were made wider, 1.0cm each than those of the existing pants prototype patterns. The ease of 0.5cm was added to the hip circumference/4+2.5cm because of the development of the hip and thigh muscles.

Ultimate Resisting Capacity of Axially Loaded Circular Concrete-Filled Steel Tube Columns (축력이 재하된 원형 콘크리트 충전강관 기둥의 최대 저항능력)

  • Kwak, Hyo-Gyoung;Kwak, Ji-Hyun
    • Journal of the Korea Concrete Institute
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    • v.24 no.4
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    • pp.423-433
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    • 2012
  • The axial load on the concrete-filled steel tube (CFT) column produces confinement stress, which enhances strength of the core concrete. The amount of strength increase in concrete depends on the magnitude of produced confinement stress. From nonlinear analyses, the ultimate resisting capacity of the CFT columns subjected to axial loads was calculated. Nonlinear material properties such as Poisson's ratio and stress-strain relation were considered in the suggested model, and the maximum confining stress was obtained by multi axial yield criteria of the steel tube. This proposed model was verified by comparing the analytical results with experimental results. Then, regression analyses were conducted to predict the maximum confining stress according to D/t ratio and material properties without rigorous structural analysis. To ensure the validity of the suggested regression formula, various empirical formulas and Eurocode4 design code were compared.