• Geomechanics and Engineering
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• 제32권1호
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• pp.49-68
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• 2023

The three-dimensional failure criterion is essential for maintaining wellbore stability and sand production problem. The convenient factor for a stable wellbore is mud weight and borehole orientation, i.e., mud window design and selection of borehole trajectory. This study proposes a new three-dimensional failure criterion with linear relation of three in-situ principal stresses. The number of failure criteria executed to understand the phenomenon of rock failure under in-situ stresses is the Mohr-Coulomb criterion, Hoek-Brown criterion, Mogi-Coulomb criterion, and many more. A new failure criterion is the extended Mohr-Coulomb failure criterion with the influence of intermediate principal stress (σ₂). The influence of intermediate principal stress is considered as a weighting of (σ₂) on the mean effective stress. The triaxial compression test data for eleven rock types are taken from the literature for calibration of material constant and validation of failure prediction. The predictions on rock samples using new criteria are the best fit with the triaxial compression test data points. Here, Drucker-Prager and the Mogi-Coulomb criterion are also implemented to predict the failure for eleven different rock types. It has been observed that the Drucker-Prager criterion gave over prediction of rock failure. On the contrary, the Mogi-Coulomb criterion gave an equally good prediction of rock failure as our proposed new 3D failure criterion. Based on the yield surface of a new 3D linear criterion it gave the safest prediction for the failure of the rock. A new linear failure criterion is recommended for the unique solution as a linear relation of the principal stresses rather than the dual solution by the Mogi-Coulomb criterion.

• 한국환경보건학회지
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• 제48권5호
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• pp.266-271
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• 2022

Background: The selection of distributions of input parameters is an important component in probabilistic exposure assessment. Goodness-of-fit (GOF) methods are used to determine the distribution of exposure factors. However, there are no clear guidelines for choosing an appropriate GOF method. Objectives: The outcomes of probabilistic consumer exposure assessment were compared by using five different GOF methods for the selection of input distributions: chi-squared test, Kolmogorov-Smirnov test (K-S), Anderson-Darling test (A-D), Akaike information criterion (AIC) and Bayesian information criterion (BIC). Methods: Individual exposures were estimated based on product usage factor combinations from 10,000 respondents. The distribution of individual exposure was considered as the true value of population exposures. Results: Among the five GOF methods, probabilistic exposure distributions using the A-D and K-S methods were similar to individual exposure estimations. Comparing the 95th percentiles of the probabilistic distributions and the individual estimations for 10 CPs, there were 0.73 to 1.92 times differences for the A-D method, and 0.73 to 1.60 times differences (excluding tire-shine spray) for the K-S method. Conclusions: There were significant differences in exposure assessment results among the selection of the GOF methods. Therefore, the GOF methods for probabilistic consumer exposure assessment should be carefully selected.

• 응용통계연구
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• 제29권5호
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• pp.849-858
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• 2016

관측 자료를 이용한 인과연구에서 관심 있는 처리변수의 효과가 다른 공변량의 효과와 중첩되지 않도록 조건화할 공변량을 선택하는 것이 중요하다. 인과연구에서의 공변량선택 문제는 공분산분석 모형에서의 변수선택 문제와 다르다는 것을 예를 들어 설명하였다. 그리고 모든 변수들 사이의 인과관계를 파악하지 않고도 적용할 수 있는 실용적인 공변량선택기준에 대해 살펴보았다. VanderWeele과 Shpitser (2011)가 새로운 기준을 제안하면서 새로운 기준이 다른 두 기준보다 나은 성능을 보인다고 주장하였는데, 이 기준에도 한계와 단점이 있음을 예증하였다. 새로운 기준이 완전한 기준은 아니지만 조건을 조금 수정하면 다른 두 기준과 달리 중첩을 제거할 수 있다는 점에서 좀 더 나은 기준이라고 할 수 있다.

• 한국농촌건축학회논문집
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• 제19권4호
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• pp.1-8
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• 2017

The purpose of this study is to deduce dwelling selection criterion and to consider change of values and consciousness of dwelling on people who return to farming & going to village. For that, questionnaire of evaluation of housing choice is conducted by people who return to farming & going to village in Jellanam-do by the AHP. The results are as follows. First, four factors as the primary hierarchy structure and 12 factors as the secondary hierarchy structure of dwelling selection criterion are deduced. The primary hierarchy are "education environment", "economic & Convenience in life", "residence safety and image", and "economic value". Second, weight value deduced from the primary hierarchy structure is showed that "economic & convenience in life(0.345)" is the highest and next is "education environment(0.262)". "Residence safety and image(0.237)", and e "economic value(0.157)" is relatively low(C.I. 0.213). Third, for the secondary hierarchy structure, the case of life convenience is showed that economic condition(0.403) is the highest, the case of educational condition is showed that education facilities(0.479), the case of residence safety and image is showed that residence area(0.490) is the highest, and the case of economic importance is showed that financial technology(0.470) is the highest.

• Management Science and Financial Engineering
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• 제1권1호
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• pp.67-90
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• 1995

In planning an assembly system, choosing the proper assembly sequence is one of the most important decisions because it significantly affects the costs associated with the assembly process. This paper deals with the selection of assembly sequences in flexible assembly systems. The selection criterion is the minimization of makespan to complete all assembly products. This problem is formulated as a "modified FAS scheduling problem" (MFASSP) and its scheduling procedure is described. The experimental results show that the procedure is very efficient for both quality of solution and computation time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1371-1374
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• 1987

This paper presents a new automatic multithreshold selection method which is based on the threshold selection method proposed by Otsu. This method can overcome some of limitations of the Otsu's method. An optimal threshold is selected by the new criterion so as to maximize the separability in all subregions. To get multiple thresholds, the procedure may be recursively applied to the resultant classes which are determined by the proposed evaluation measure.

• Communications for Statistical Applications and Methods
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• 제10권3호
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• pp.627-635
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• 2003

In this short communication we discuss the bias problem of C4.5 in split variable selection and suggest a method to reduce the variable selection bias among categorical predictor variables. A penalty proportional to the number of categories is applied to the splitting criterion gain of C4.5. The results of empirical comparisons show that the proposed modification of C4.5 reduces the size of classification trees.

• 한국통신학회논문지
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• 제32권10C호
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• pp.965-974
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• 2007

본 논문에서는 내용 기반 음악 범주 분류 시스템에서 다중 범주를 위한 특징벡터 선택 알고리즘을 제안한다. 제안된 특징벡터 선택 알고리즘은 분리 성능을 측정할 때 가우시안 혼합 모델(Gaussian Mixture Model: GMM)을 기반으로 GMM separation score을 측정함으로써 확률분포 및 분리 성능 추정의 정확도를 높였고, sequential forward selection 방법을 개선하여 이전까지 선택된 특징벡터들이 분리를 잘 하지 못하는 범주들을 기준으로 다음 특징벡터를 선택하는 알고리즘을 제안하여 다중 범주 분류의 성능을 높였다. 제안된 알고리즘의 성능 검증을 위해 음색, 리듬, 피치 등 오디오 신호의 특징을 나타내는 다양한 파라미터를 오디오 신호로부터 추출하여 제안된 특징벡터 선택 알고리즘과 기존의 알고리즘으로 특징벡터를 선택한 후 GMM classifier와 k-NN classifier를 이용하여 분류 성능을 평가하였다. 제안된 특징벡터 선택 알고리즘은 기존 알고리즘에 비하여 3%에서 8% 정도의 분류 성능이 향상된 것을 확인할 수 있었고 특히 낮은 차원의 특징벡터의 분류 실험에서는 분류 정확도 측면에서 5%에서 10% 향상된 좋은 성능을 보였다.

• 응용통계연구
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• 제29권4호
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• pp.643-656
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• 2016

고차원 자료(high dimensional data)는 변수의 수가 표본의 수보다 많은 자료로 다양한 분야에서 관측 또는 생성되고 있다. 일반적으로, 고차원 자료에 대한 회귀 모형에서는 모수의 추정과 과적합을 피하기 위하여 변수 선택이 이루어진다. 벌점화 회귀 모형(penalized regression model)은 변수 선택과 회귀 계수의 추정을 동시에 수행하는 장점으로 인하여 고차원 자료에 빈번하게 적용되고 있다. 하지만, 벌점화 회귀 모형에서도 여전히 조율 모수 선택(tuning parameter selection)을 통한 최적의 모형 선택이 요구된다. 본 논문에서는 벌점화 회귀 모형 중에서 대표적인 LASSO 회귀 모형을 기반으로 모형 선택의 기준들에 대한 LASSO 회귀 추정량의 편의가 어떠한 영향을 미치는지 모의실험을 통하여 수치적으로 연구하였고 편의의 보정의 필요성에 대하여 나타내었다. 실제 자료 분석에서의 영향을 나타내기 위하여, 폐암 환자의 유전자 발현량(gene expression) 자료를 기반으로 바이오마커 식별(biomarker identification) 문제에 적용하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.122-124
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• 1987

This paper presents a new algorithm in formulating a performance index for contingency selection method considering voltage security. Security limits defined-in terms of real power line flows and voltage magnitudes are considered in normalized subspaces where in critical contingencies are identified by a filtering algorithm using the infinite norm. Two types of limits, warning limit and emergency limit, are introduced for voltage and line flow. Usually performance indices have been constructed for real power line flows and voltages with each different criterion. This paper, however, presents a method that constructs them with the same criterion in use of the norm properties, so that we can assess security considering both of them. Rapid contingency simulation is performed using one iteration of fast decoupled load flows with LMML(Inverse Matrix Modification Lemma).