• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.4
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• pp.79-88
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• 1986

A nonlinear cumulative damage theory, which can model the effects of the magnitude and sequence of variable amplitude fatigue loadings, is proposed. The concrete beam specimens are prepared and tested in four-point flexural loading conditions. The variable-amplitude fatigue loadings in two and three stages are considered. The present experimental study indicates that the fatigue failure of concrete is greatly influenced by the magnitude and sequence of applied, variable-amplitude fatigue loadings. It is seen that the linear damage theory proposed by Palmgren and Miner is not directly applicable to the concrete under such loading cases. The sum of the cumulative damage is found to be greater than 1 when the magnitude of fatigue loading is gradually increased and less than 1 when the magnitude of fatigue loading is gradually decreased. The proposed nonlinear damage theory, which includes the effects of the magnitude and sequence of applied fatigue loadings, allows more realistic fatigue analysis of concrete structures.

• The Korean Journal of Applied Statistics
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• v.15 no.2
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• pp.297-310
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• 2002

Liang and Zeger proposed generalized estimating equations(GEE) for analyzing repeated data which is discrete or continuous. GEE model can be extended to model for repeated categorical data and its estimator has asymptotic multivariate normal distribution in large sample sizes. But GEE is based on large sample asymptotic theory. In this paper, we study the properties of GEE estimators for repeated ordinal data in small sample sizes. We generate ordinal repeated measurements for two groups using two methods. Through Monte Carlo simulation studies we investigate the empirical type 1 error rates, powers, relative efficiencies of the GEE estimators, the effect of unequal sample size of two groups, and the performance of variance estimators for polytomous ordinal response variables, especially in small sample sizes.

• The Korean Journal of Applied Statistics
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• v.19 no.1
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• pp.149-161
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• 2006

The most important component in decision tree algorithm is the rule for split variable selection. Many earlier algorithms such as CART and C4.5 use greedy search algorithm for variable selection. Recently, many methods were developed to cope with the weakness of greedy search algorithm. Most algorithms have different selection criteria depending on the type of variables: continuous or nominal. However, ordinal type variables are usually treated as continuous ones. This approach did not cause any trouble for the methods using greedy search algorithm. However, it may cause problems for the newer algorithms because they use statistical methods valid for continuous or nominal types only. In this paper, we propose a ordinal variable selection method that uses Cramer-von Mises testing procedure. We performed comparisons among CART, C4.5, QUEST, CRUISE, and the new method. It was shown that the new method has a good variable selection power for ordinal type variables.

• 한국노년학
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• v.40 no.3
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• pp.389-411
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• 2020

The purpose of this study was to identify the needs and characteristics of Korean senior consumers. To this end, the factors of Maslow's seven-levels of needs hierarchy were re-established and applied to suit the actual situation in Korea. For analysis, an online survey was conducted on 440 adults (50-75 years old), who are considered active seniors living in Korea, on the factors of 7-levels of needs and demographic characteristics. The study found that the 7-levels needs of Korean senior consumers were derived in a different order from Maslow's. Other diverse theoretical and practical implications were also presented.

• Environmental and Resource Economics Review
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• v.12 no.4
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• pp.687-708
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• 2003

The purpose of this paper is to introduce time-series causality analysis by combining time-series technique with graph theory. Vector autoregressive (VAR) models can provide reasonable interpretation only when the contemporaneous variables stand in a well-defined causal order. We show that how graph theory can be applied to search for the causal structure In VAR analysis. Using Maryland crop cash prices and CBOT futures price data, we estimate a VAR model with directed acyclic graph analysis. This expands our understanding the degree of interconnectivity between the employed time-series variables.

• The Journal of Korean Academic Society of Nursing Education
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• v.5 no.2
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• pp.332-346
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• 1999

간호학에서 간호업무를 이끌어갈 간호이론이(지식체) 필요하다는 생각은 20세기가 되면서부터 시작되었다. 하지만 아직도 간호학은 간호학 특유의 지식체가 부족하다는 지적을 받고 있다. 주된 이유는 간호 업무가 재대로 확인되지 않았고 간호업무를 이끌어갈 간호학 특유의 간호이론이 확실히 정립되지 않았기 때문이다. 따라서 간호가 독자적 학문으로서 인정받고 발전하기 위해서는 간호업무에 적용이 쉽고, 간호 업무에 바탕을 둔 간호이론의 개발이 필수적이다. 왜냐하면 간호 이론이 간호업무에 쉽게 적용됨으로서 간호학의 지식체가 발전할 뿐 아니라 환자 간호도 더욱 증진 될 수 있기 때문이다. 이 논문에서는 간호지식의 발전 단계를 시대적 순서와 배경을 덧붙여 고찰하였고 간호학에서 간호 분류체계가 발전하게 된 동기, 그리고 간호 분류체계가 환자 간호와 간호학의 이론개발과 발전에 어떻게 활용되는 가에 대해 서술하였다. 그리고 간호분류체계가 가지는 특성으로는 먼저 간호실무를 체계적으로 명명하고 분류함으로서 간호학에서 필요한 연구영역을 확인하게 하게 하고 간호학 고유의 지식체의 발전에 공헌하는 것 뿐 아니라 간호정보화 시스템의 개발, 다른 의료전문가들과의 효과적인 커뮤니케이션 수단 제공, 간호의 지속성을 유지, 그리고 간호의 효과성 연구에의 활용 등이 있다.

• Journal of Power System Engineering
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• v.4 no.2
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• pp.17-24
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• 2000

직경비가 0.26, 0.39, 그리고 0.56인 경우 거칠기를 내벽면에, 외벽면에, 그리고 양벽면에 각각 설치한 동심환형관에서 완전히 발달된 난류유동에 대한 거칠기 효과를 실험과 이론으로 해석하였다. 그리고 거칠기 효과를 정량적으로 파악하기 위해 양벽면 모두 매끈한 환형관의 경우도 포함하였다. 실험에서 마찰계수를 구하는데 필요한 속도분포와 전단응력들은 피토튜브와 X-형 열선풍속계를 사용하였다. 이론 해석은 수정대수 난류모델을 사용하였고 그 결과를 이론값과 비교하여 아래의 결론을 얻었다. 1) 무디다이어그램 (Moody diagram)은 거칠기가 설치된 이중관에는 적용할 수 없음을 보였다. 2) 경우(c) 와 (d)에서는 반경비가 클수록 반드시 마찰계수가 증가하지 않았다. 3) 4개의 경우중 거칠기로 인해 마찰계수가 증가하는 크기의 순서는 경우(d)가 가장 컸고 경우(a)가 가장 작았다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.10a
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• pp.63-65
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• 1993

전통적 의사결정 이론에 입각한 기존의 다기준 의사결정 모형은 명확하게 정의된 문제에 대해서 실함수로 표현된 사전의 선호정보에 의하여 모호함이 없이 확실한 선호의 판별을 산출하는 true-criterion 모형이다. 그러나 현실적인 의사결정 환경하에서 선호정보가 사전에 명확하게 하나의 실함수로 얻어지기는 매우 어렵다. 이는 곧 선호의 불확실성(fuzziness)이나 선호판별을 할 수 없는 비교불가능성(incomparability)등이 있을 수 있음을 의미한다. 1980년대 이후의 다기준의사결정 이론에 대한 연구는 불명확한 문제의 정형화나 선호의 불확실성을 인정하고, 이를 fuzzy 이론을 이용하여 모형의 설정에 반영하고 있다. 심지어는 선호관계의 비추이성(intransitivity)이나 비교불가능성까지도 인정하는 등 모형의 강건성(robustness)을 고려하는 연구가 활발하게 이루어지고 있다.

• Journal of the Korean Society for information Management
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• v.18 no.4
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• pp.201-215
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• 2001

The purpose of this study is to identify how to construct an internet shopping mall classification system used on the library classification theories. To aid in identifying classification system, this study focused on the Ranganathan’s classification canons; canons for characteristics, canons for terms. The study shows six priniciples for an internet shopping mall classification system construct: products’characteristics, inclusiveness, various access points, category sequence and term consistency, term currency and obviousness, no term duplication. For future research, product’s search patterns and relationship to interface are suggested.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.579-584
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• 1996

The HOMO-LUMO gap, and static and dynamic third-order polarizabilities for the polyenes are evaluated by means of the time-dependent Hartree Fock(TDHF) semiempirical PM3, AM1, MNDO, and MINDO/3 calculations. All calculations have performed on the series $C_2H_4$ to $C_{32}H_{34}$. The HOMO-LUMO gap increases in the order: MINDO/3> MNDO> PM3> AM1 levels. THG, DC-EFISHG, IDRI, and OKE for the various calculations show the order: AM1 > MNDO > PM3 levels. The various third-order effects for the polyenes have the following order: THG> DC-EFISHG> IDRI> OKE.