• 한국항해항만학회지
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• 제38권1호
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• pp.65-71
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• 2014

국내 경부고속도로와 남해고속도로는 부산항을 각각 남북방향과 동서방향으로 연계하며 20%이상의 중대형화물트럭 혼재율과 특정시간대 통행량이 집중되는 핵심 간선도로로 시간교통량계수(K-factor)에 대해 연구의 필요성을 깨닫게 되었다. 그리하여 본 연구에서는 경부고속도로와 남해고속도로의 기본구간에서 단기간동안 수집된 차량검지시스템(vehicle detection system, VDS)자료를 이용하여 고속도로의 K-factor와 K-factor추정치(estimate)사이의 상관분석을 통해서 고속도로의 K-factor추정모형 구축을 목적으로 연구하였다. 결과적으로 7일 VDS자료의 K-factor추정치(estimate)와 함께 파워(POW)모형이 K-factor를 추정에 높은 설명력과 신뢰성이 있음을 확인할 수 있었다.

• 응용통계연구
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• 제25권4호
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• pp.553-561
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• 2012

Various statistical models to Estimate GDP (measured as a nation's economic situation) have been developed. In this paper an autoregressive distributed lag model, factor model, and a Bayesian VAR model estimate quarterly GDP as a single model; the combined estimates were evaluated to compare a single model. Subsequently, we suggest that some combined models are better than a single model to estimate quarterly GDP.

• 대한수학회지
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• 제32권1호
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• pp.7-15
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• 1995

Multigrid method has been used widely to solve elliptic problems because of its applicability to many class of problems and fast convergence ([1], [3], [9], [10], [11], [12]). The estimate of convergence rate of multigrid is one of the main objectives of the multigrid analysis ([1], [2], [5], [6], [7], [8]). In many problems, the convergence rate depends on the regularity of the solutions([5], [6], [8]). In this paper, we present an improved estimate of reduction factor of multigrid iteration based on the proof in [6].

• Structural Engineering and Mechanics
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• 제23권2호
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• pp.195-207
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• 2006

An efficient and accurate algorithm is proposed to estimate cable safety factor of suspension bridges satisfying prescribed reliability levels. Uncertainties in the structure and load parameters are incorporated. The proposed algorithm integrates the concepts of the inverse reliability method and deterministic method for assessing cable safety factors of suspension bridges. The unique feature of the proposed method is that it offers a tool for cable safety assessment of suspension bridges, when the reliability level is specified as a target to be satisfied by the designer. After the accuracy and efficiency of the method are demonstrated through two numerical examples, the method is used to estimate cable safety factors of suspension bridges with span length ranging from 2000 to 5000 m. The results show that the deterministic method overestimates cable safety factor of suspension bridges because of neglecting the parameter uncertainty effects. The actual cable safety factor of suspension bridges should be estimated based on the proposed method.

• 지반과기술
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• 제3권3호
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• pp.15-22
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• 2006

The optimum blasting pattern to excavate a quarry efficiently and economically can be determined based on the minimum production cost, which is generally estimated according to rock fragmentation. Therefore, it is a critical problem to predict fragment size distribution of blasted rocks over an entire quarry. By comparing various prediction models, it can be ascertained that the result obtained from Kuz-Ram model relatively coincides with that of field measurements. Kuz-Ram model uses the concept of rock factor to signify conditions of rock mass such as block size, rock jointing, strength and others. For the evaluation of total production cost, it is imperative to estimate 3-D spatial distribution of rock factor for the entire quarry. In this study, a sequential indicator simulation technique is adopted for estimation of spatial distribution of rock factor due to its higher reproducibility of spatial variability and distribution models than Kriging methods. Further, this can reduce the uncertainty of predictor using distribution information of sample data. The entire quarry is classified into three types of rock mass and optimum blasting pattern is proposed for each type based on 3-D spatial distribution of rock factor. In addition, plane maps of rock factor distribution for each ground level are provided to estimate production costs for each process and to make a plan for an optimum blasting pattern.

• 한국농공학회논문집
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• 제58권6호
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• pp.55-69
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• 2016

RUSLE (Revised Universal Soil Loss Equation) is the empirical formular widely used to estimate rates of soil erosion caused by rainfall and associated overland flow. Among the factors considered in RUSLE, rainfall erosivity factor (R factor) is the major one derived by rainfall intensity and characteristics of rainfall event. There has been developed various methods to estimate R factor, such as energy based methods considering physical schemes of soil erosion and simple methods using the empirical relationship between soil erosion and annual total rainfall. This study is aimed to quantitatively evaluate the variation among the R factors estimated using different methods for South Korea. Station based observation (minutely rainfall data) were collected for 72 stations to investigate the characteristics of rainfall events over the country and similarity and differentness of R factors calculated by each method were compared in various ways. As results use of simple methods generally provided greater R factors comparing to those for energy based methods by 76 % on average and also overestimated the range of factors using different equations. The variation coefficient of annual R factors was calculated as 0.27 on average and the results significantly varied by the stations. Additionally the study demonstrated the rank of methods that would provide exclusive results comparing to others for each station. As it is difficult to find universal way to estimate R factors for specific regions, the efforts to validate and integrate various methods are required to improve the applicability and accuracy of soil erosion estimation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.677-686
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• 2005

The allowable bearing capacity of a pile, the most important factor in stability estimation, is determined by applying safety factor to the ultimate load or yield load. There are several but contradictory methods available in current design codes to estimate the allowable bearing capacity and the safety factor. This paper analyzes load-settlement curves obtained from 19 static load tests measured from 11 sites. At all tests, the load is applied until apparent failure is observed. The validity of the ultimate and yield load estimation method and load caculated from the settlement criterion is investigated through comparison with the measured data. In addition, a new procedure to estimate allowable load and safety factor is proposed. Additional data from field static load tests, such as those incorporated in this study, are needed to more reliably apply the proposed method in design practice.

• 품질경영학회지
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• 제18권2호
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• pp.127-133
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• 1990

In this article, several problems inherent in histogram estimate of unknown probability density function are discussed. Those include so called sharp comers and bin edge effect. A resolution for these problems occurred with histogram is discussed. The resulting estimate is called kernel density estimate which is most widely used by data analysts. One of the most recent and reliable data-based choices of scale factor (bandwidth) of the estimate, which has been known to be most crucial, is also discussed.

• Structural Engineering and Mechanics
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• 제39권6호
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• pp.767-793
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• 2011

An efficient edge-based smoothed finite element method (ES-FEM) has been recently developed for solving solid mechanics problems. The ES-FEM uses triangular elements that can be generated easily for complicated domains. In this paper, the complexity study of the ES-FEM based on triangular elements is conducted in detail, which confirms the ES-FEM produces higher computational efficiency compared to the FEM. Therefore, the ES-FEM offers an excellent platform for adaptive analysis, and this paper presents an efficient adaptive procedure based on the ES-FEM. A smoothing domain based energy (SDE) error estimate is first devised making use of the features of the ES-FEM. The present error estimate differs from the conventional approaches and evaluates error based on smoothing domains used in the ES-FEM. A local refinement technique based on the Delaunay algorithm is then implemented to achieve high efficiency in the mesh refinement. In this refinement technique, each node is assigned a scaling factor to control the local nodal density, and refinement of the neighborhood of a node is accomplished simply by adjusting its scaling factor. Intensive numerical studies, including an actual engineering problem of an automobile part, show that the proposed adaptive procedure is effective and efficient in producing solutions of desired accuracy.

• 한국환경농학회지
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• 제32권4호
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• pp.359-365
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• 2013

BACKGROUND: Methane ($CH_4$) emission is calculated using the default $CH_4$ emission factor as recommended by the International Panel on Climate Change(IPCC guidelines). However, the default emission factor has been derived using including the data from other countries having different soil and environmental conditions and may not reflect the real $CH_4$ emission rates in Korea. The objective of this study was to estimate the baseline emission factor of $CH_4$ in Korean paddy soils during rice cultivation. METHODS AND RESULTS: Methane emission patterns were characterized in four different paddy soils across country for a consecutive 3 years during the rice cultivation period. Rice plants were cultivated under continuous flooding and fertilized using the recommended chemical fertilization in Korea ($N-P_2O_5-K_2O$=90-45-57kg/ha). The mean $CH_4$ emission rate was 2.32 kg $CH_4$/ha/day and the uncertainty of the investigated data was 21.7%, with a valuable error range at 1.82-2.82 kg $CH_4$/ha/day with a 95% confidence interval. CONCLUSION(S): Conclusively, the Korean paddy soils' baseline emission factor of $CH_4$ is approximately 2.32 kg $CH_4$/ha/day and can be used to estimate the $CH_4$ emissions more exactly.