• Computers and Concrete
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• 제17권4호
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• pp.489-498
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• 2016

In this paper, the flexural strength ($f_{fs}$) and splitting tensile strength ($f_{sts}$) of concrete containing different proportions of fly ash have been modeled by using gene expression programming (GEP). Two GEP models called GEP-I and GEP-II are constituted to predict the $f_{fs}$ and $f_{sts}$ values, respectively. In these models, the age of specimen, cement, water, sand, aggregate, superplasticizer and fly ash are used as independent input parameters. GEP-I model is constructed by 292 experimental data and trisected into 170, 86 and 36 data for training, testing and validating sets, respectively. Similarly, GEP-II model is constructed by 278 experimental data and trisected into 142, 70 and 66 data for training, testing and validating sets, respectively. The experimental data used in the validating set of these models are independent from the training and testing sets. The results of the statistical parameters obtained from the models indicate that the proposed empirical models have good prediction and generalization capability.

• 한국환경과학회지
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• 제23권9호
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• pp.1537-1549
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• 2014

The objectives of this study were to analyze reservoir trophic state, based on Trophic State Index (TSI), spatial variation patterns of three zones (riverine, transition, and lacustrine zone), and empirical models through 20-years long-term data analysis. Trophic variables of TP and CHL-a were highest during the summer monsoon, and decreased along the main axis from the riverine to lacustrine zone. In the mean time, TN did not show the trend. Ratios of N:P and Secchi disc transparency (SD) increased from the riverine to lacustrine zone. The analysis of trophic state index (TSI) showed that mean TSI (TP) and TSI (CHL-a) were 62 and 57, respectively, and these values were highest in the transition zone during the summer. This zone should be managed well due to highest lake water pollution. The analysis of Trophic State Index Deviation (TSID) showed that algal growth was primarily limited by light penetration, and this was most pronounced in the monsoon season. The analysis of empirical models showed that the value of $R^2$, based on CHL-SD model, was 0.30 (p < 0.0001) in the transition zone and the $R^2$, based on TP-SD model, was 0.41 (p < 0.0001) in the transition zone.

• Journal of Ship and Ocean Technology
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• 제11권1호
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• pp.11-24
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• 2007

Better prediction of a ship's manouevrabilty in initial design stage is becoming more, important as IMO manoeuvring criteria has been activated in the year of 2004. In the present study, in order to obtain more exact and reliable results for ship manoeuvrability in the initial design stage, numerical simulation is carried out by use of RANS equation based calculation of hydrodynamic forces exerted upon the ship hull. Other forces such as rudder force and propeller force are estimated by one of the empirical models recommended by MMG Group. Calculated hydrodynamic force coefficients are compared with those obtained by empirical models. Standard manoeuvring simulations such as turning circle and zig-zag are also carried out for a medium size Product Carrier and the results are compared with those of pure empirical models and manoeuvring sea trial. Generally good qualitative agreement is obtained in hydrodynamic forces due to steady oblique motion and steady turning motion between the results of CFD calculation and those of MMG model, which is based on empirical formulas. The results of standard manoeuvring simulation also show good agreement with sea trial results.

• 천문학논총
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• 제30권2호
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• pp.489-490
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• 2015

We present population synthesis models for the calcium II triplet (CaT), currently the most popular metallicity indicator, based on high-resolution empirical spectral energy distributions (SEDs). Our new CaT models, based on empirical SEDs, show a linear correlation below [Fe/H] ~ -0.5, but the linear relation breaks down in the metal-rich regime by converging to the same equivalent width. This relation shows good agreement with the observed CaT of globular clusters (GCs) in NGC 1407 and the Milky Way. However, a model based on theoretical SEDs does not show this feature of the CaT and fails to reproduce observed GCs in the metal-rich regime. This linear relation may cause inaccurate metallicity determination for metal-rich stellar populations. We have also confirmed that the effect of horizontal-branch stars on the CaT is almost negligible in models based on both empirical and theoretical SEDs. Our new empirical model may explain the difference between the color distributions and CaT distributions of GCs in various early-type galaxies. Based on our model, we claim that the CaT is not a good metallicity indicator for simple stellar populations in the metal-rich regime.

• 기술혁신학회지
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• 제5권2호
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• pp.129-140
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• 2002

This study is try to do the empirical tests on the relationship among innovation cycle, investment cycle, and business cycle suggested in recent economic growth models. We apply co-spectra analysis to estimate dynamic correlations in the extraction HP filtered variables and first difference filtered variables in our data set. Our empirical results are; (i) an existing asynchronization between innovation cycle and investment cycle, (ii) in the long frequency, an existing positive correlation between innovation cycle and business cycle, (iii) in the short frequency, however, a finding the high negative correlation between the two cycle. Our empirical findings support the recent growth through cycle models and suggest some economic policy implementations for economic stabilization during a severe business cycle.

• Communications for Statistical Applications and Methods
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• 제30권4호
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• pp.355-368
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• 2023

This article introduces the R package ELCIC (https://cran.r-project.org/web/packages/ELCIC/index.html), which provides an empirical likelihood-based information criterion (ELCIC) for model selection that includes, but is not limited to, variable selection. The empirical likelihood is a semi-parametric approach to draw statistical inference that does not require distribution assumptions for data generation. Therefore, ELCIC is more robust and versatile in the context of model selection compared to the currently existing information criteria. This paper illustrates several applications of ELCIC, including its use in generalized linear models, generalized estimating equations (GEE) for longitudinal data, and weighted GEE (WGEE) for missing longitudinal data under the mechanisms of missing at random and dropout.

• 한국정보전자통신기술학회논문지
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• 제15권6호
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• pp.433-439
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• 2022

최대근지구력시간(MET, maximum endurance time)을 예측하기 위한 근피로모델은 실험적으로 측정한 MET를 이용하여 구축한 실증적 모델과 생리학적 과정을 수학적으로 표현한 이론적 모델로 나뉜다. 본 연구에서는 전완의 등척성 수축시 MET을 예측하기 위한 이론적 모델인 동적 근피로모델의 예측성 평가를 위하여 실증적 모델과 비교 및 평가하고자 한다. 실험에 참여한 피검자는 40명(남성 20, 여성 20)이며 실증적 모델인 지수모델과 거듭제곱모델 및 이론적 모델인 동적 근피로모델을 이용하여 비교하였다. 평가를 위하여 평균절대치편차(MAD, mean absolute deviation), 상관계수 및 급내상관계수를 구한 결과 동적 근피로모델과 실증적 모델들 사이에 MAD는 3.5%p 이하였으며, 상관계수는 0.93, 급내상관계수는 0.87 이상으로 전완의 등척성 수축시 MET을 예측하기 위한 이론적 모델인 동적 근피로모델이 적합함을 확인하였다.

• 한국정보전자통신기술학회논문지
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• 제16권5호
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• pp.338-346
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• 2023

등척성 팔굽 굽힘시 전완길이(florearm length)는 전완에 가해진 힘의 방향이 직각일 때 관절토크 뿐만 아니라 최대근지구력시간(maximum endurance time: MET)을 결정하는 중요한 요소이다. 본 연구의 목표는 전완의 등척성 수축시 MET의 대표적인 두 가지 실증적 모델인 지수모델과 거듭제곱모델에 전완길이를 추가요소로 적용했을 때 미치는 영향을 검토하는 것이다. 30명의 자원자가 실험에 참여하였으며, 요소변수로 사용할 참여자의 상완 및 전완의 둘레 및 길이들과 최대자율수축강도의 백분율(percent of maximum voluntary contraction intensity: %MVC)에 따른 MET를 측정하였다. 실험과정에서 ln(MET)의 다중선형회귀모델에서 유의확률을 산츨한 결과 %MVC와 전완길이가 유의한 독립변수임을 확인하였다 (P<0.05). 또한, 측정 MET와 기존의 두 가지 실증적 모델들 사이의 평균절대편차는 19.4초 였으나 전완길이를 적용한 모델을 이용한 경우 16.2초로 감소하였으며, 상관계수과 급내상관계수는 모두 평균 0.87 이었으나 전완길이를 적용했을 때 평균 0.91로 모두 증가하였다. 실험결과로부터 전완의 길이가 실증적 모델에 유의한 추가 요소임을 확인하였다.

• 한국식품위생안전성학회지
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• 제19권1호
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• pp.19-24
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• 2004

미생물 위해성 평가의 용량-반응 모델은 생물학적 모델과 경험적 모델로 나눌 수 있다. 생물학적 모델은 미생물의 분포형태, 미생물에 대한 숙주의 감수성, 감염을 일으킬 수 있는 미생물 수에 대한 가정을 바탕으로 성립된 모델로서, 대표적으로 Exponential model과 $\beta$-Poisson model이 있다. 경험적 모델은 주로 화학물질의 독성을 나타내는데 이용되어 온 모델로, Weibull-Gamma model등이 있다. 여러 용량-반응 모델 중에서 실험 데이터에 적합한 모델을 걱정하는 데에는 deviance function(Y)을 이용하며, 현재 일부 식중독균에 대해서는 사람과 실험동물에서의 용량-반응 모델이 연구되어 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.659-664
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• 1999

The majority of published conclusions about structural configuration effects of bond strength were based on the observed performance of test specimens and their interpretations are mostly empirical and statistical. The empirical and statistical interpretation on bond strength have to be replaced by rational models based on simple, sound and verifiable mechanical principles. It is likely that such models also represent the key to a deeper understanding of some existing experimental data on bond strength. The presented truss model is capable of explaining failure modes involving bond slip that cannot be explained by current truss model.