• Communications for Statistical Applications and Methods
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• 제7권1호
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• pp.327-336
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• 2000

We are mainly interested in hazard rate changes which are usually occur in survival times of manufactured products or patients. We may expect early failures with one hazard rate and next another hazard rate. For this type of data we apply a hazard rate change-point model and estimate the unkown time point to improve the model adequacy. We introduce change-point logistic model to the discrete time hazard rates. The MLEs are obtained routinely and we also explain the suggested model through a dataset of survival times.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.131-141
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• 2021

Simulation is a widely used functional verification method for FBD programs of PLC-based digital I&C system in nuclear power plants. It is difficult, however, to estimate the thoroughness (i.e., effectiveness or quality) of a simulation in the absence of any clear measure for the estimation. This paper proposes two sets of structural coverage adequacy criteria for the FBD simulation, toggle coverage and modified condition/decision coverage, which can estimate the thoroughness of simulation scenarios for FBD programs, as recommended by international standards for functional safety. We developed two supporting tools to generate numerous simulation scenarios and to measure automatically the coverages of the scenarios. The results of our experiment on five FBD programs demonstrated that the measures and tools can help software engineers estimate the thoroughness and improve the simulation scenarios quantitatively.

• 복합신소재구조학회 논문집
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• 제1권2호
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• pp.29-35
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• 2010

탄성계수와 함께 포아송비는 구조의 거동을 결정하는 중요 구조인수중의 하나이다. 따라서 구조응답의 불확실성에 미치는 포아송비의 독립적 영향에 대한 평가가 필요하다. 본 연구에서는 포아송비의 불확실성이 복합적층판의 거동에 미치는 영향을 산정하기 위한 정식화를 제안한다. 포아송비의 영향은 동일 차수인 임의인수의 영향을 포함하는 부행렬을 통하여 얻을 수 있으며, 이는 대상 인수의 평균을 중심으로 한 Taylor전개를 통하여 구할 수 있다. 제안방법의 검증을 위하여 예제 평판을 해석하였고, 그 결과를 몬테카를로 해석에 의한 결과와 비교하였다. 두 방법을 통하여 얻은 결과는 상화 잘 일치하는 결과를 나타내어, 제안한 방법이 적절함을 제시하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.69-70
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• 2013

This is an foundational study to adequacy the non-destruction testing for the estimation of compressive strength of high strength concrete The results are as follows, In high strength concrete, H type is NR type rebound number rather than higher. The relation between rebound number and compressive strength of high strength concrete have lower coefficient. when compressive strength estimation of high strength concrete, it consider that rebound hardness test is not applied and should be consider to combined method or addition method.

• Structural Engineering and Mechanics
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• 제83권2호
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• pp.229-244
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• 2022

This paper investigates the seismic performance of buildings designed using DDBD (Direct Displacement based Design) and FBD (Force based Design) approaches from the probabilistic viewpoint. It aims to estimate the collapse capacity of structures and assess the adequacy of seismic design codes. In this regard, (i) IDA (Incremental Dynamic Analysis) curves, (ii) interstory drift demand distribution curves, (iii) fragility curves, and (iv) the methodology provided by FEMA P-695 are applied to examine two groups of RC moment resistant frame buildings: 8-story structures with different plans, to study the effect of different span arrangements; and 3-, 7- and 12-story structures with a fixed plan, to study the dynamic behavior of the buildings. Structural modeling is performed in OpenSees software and validated using the results of an experimental model. It is concluded that increasing the building height would not significantly affect the response estimation of IDA and fragility curves of DDBD-designed structures, while the change in span arrangements is effective in estimating responses. In the investigation of the code adequacy, unlike the FBD approach, the DDBD can satisfy the performance criteria presented in FEMA P-695 and hence provide excellent performance.

• 대한간호학회지
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• 제31권2호
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• pp.221-231
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• 2001

This study was conducted by analyzing all 33 articles based on the LISREL, published from January 1991 to March 1999 in Korea. The analyses consisted of the publication date of articles, principal dependent variables, subjects of the research, adequacy of sampling, adequacy of research purposes and results, accordance between theoretical model and hypothetical model, fit measures, theoretical base of model modification, and adequacy of conclusion. The results were as follows : . The thesis of 33 articles in total were outnumbered as 25 (75.8%) to 8 (24.2%) research articles. As for a sex classification of the subjects, 45.5% of the research were conducted around a female group of subjects, while 54.5% were done for both sex, The range of the sample size was 105 to 803, and the average was 259 subjects. . A single theoretical variable was measured for each measurement variable, any difference between variables was hardly found in 8 articles (24.2%), and 19 articles (57.6%) did not consider any measurement error. To analyze if the representative has been articles (21.2%) were seen with a sign of a representative. Questionnaires were used in a majority (31 articles) of the data collecting process. Only 2 articles (6.1%) were measured with a physiologic index simultaneously. . 14 articles (42.2%) were centered on theory development, 10 articles on theory synthesis, and 9 articles on theory test. The research purposes and results were consistent in 25 articles (75.5%) and 8 articles (24.2%) were inconsistent. The quality of life and health promotion behavior were the concepts most frequently studied as a dependent variable, and 7 articles centered on them. In applied theories a health promotion model was used on 4 articles (12.1%), while role theory and stress-coping models were in 3 articles respectively. . The articles were analyzed to see if the hypothetical model was elaborated and tested by the theoretical model. Twenty-five articles proved to be rationale for the inconsistencies. Also, 56.5% proposed hypotheses were supported among the subject articles, and 30 articles (90.0%) suggested a revised model. Path coefficient (17 articles) and theoretical adequacy (17 articles) were the standards mostly used. In conclusion, the principal factors were obtained from the research are to be considered as the principes of LISREL application. First, a model has to be established on a theoretical base rather than empirical results dependent on the data. The results are also required to be globally interpreted. Secondly, at least 200 samples are necessary to satisfy the need. Third, more than 3 measurement variables are to be adjusted to a single theoretical variable; the measurement errors must be suggested as well. Finally, normal distribution characteristics of the data and the estimation method need to be reported. Based on the research result, the follows are suggested; . Systematic criteria on the LISREL application and procedure need to be developed . Agreement form is required to report the results of research using the LISREL

• Computers and Concrete
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• 제32권1호
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• pp.27-44
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• 2023

The current study targets to apply the adaptive neuro-fuzzy inference system (ANFIS) for the estimation of the shear resistance offered by the externally bonded fiber-reinforced polymer (EB-FRP) U-jackets. A total of 202 groups of data cumulated from previous investigations, were employed for the development and evaluation of the ANFIS model. A relative appraisal between the ANFIS predictions and the results of experiments has shown that the assessments by current ANFIS model are in good concurrence with the latter. In addition, assessment of the accuracy of the ANFIS model was done by relating the ANFIS predictions with the forecasts of eight extensively used design guidelines. Based on the examination of various performance measures, it has been derived that the adequacy of the ANFIS model is better than the available guidelines. A parametric investigation has additionally been done to reconnoiter the influence of individual parameters as well as their combined effects on the shear contribution of EB-FRP. Based on the observations made from the parametric study, it has been witnessed that the ANFIS model has incorporated the effect of different parameters more competently than the considered design guidelines.

• 한국정보처리학회논문지
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• 제5권9호
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• pp.2345-2352
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• 1998

최근에 개발되어 성공적으로 적용되고 있는 초기하분포 소프트웨어 신뢰성 성장 모델의 모수는 최우추정법으로 추정하기가 쉽지 않으므로주로 최소자승법으로 추정하고 있다. 본 논문에서는 먼저 기존의 최소자승법에서 사용된 최소화 기준을 비교한 다음, 새로 발견되는 결함수의 분산이 일정하지 않음을 고려한 가중최소자승법을 제안한다. 그리고 두 개의 실제 자료를 분석하여 가중최소자승법이 적합함을 보인다. 마지막으로 임의의 테스팅 시점에서 추가 시험에 의해 발견된 새로운 결함수를 예측하는 방법을 제안한다. 이 예측 방법은 테스팅을 중단하는 시점을 결정할 때 이용될 수 있을 것이다.

• 자원ㆍ환경경제연구
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• 제25권1호
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• pp.1-25
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• 2016

본 연구는 조기사망 위험 감소를 위한 지불의사금액에 대한 양분선택형 조건부가치측정(CV) 자료를 이용하여, 자의적인 모수적 분포(즉, 정규분포, 로지스틱분포, 로그정규분포, 지수분포)를 가정하여 도출하는 지불의사금액 대푯값(즉, 평균 내지 중앙값)의 변동성을 비교 검토하였다. 이를 위해 특정 모수적 분포라는 제약을 갖지 않는 Turnbull 비모수적 추정방법(nonparametric estimation method)에 의한 결과를 함께 비교 검토하면, 정책의사결정에서는 인정되기 어려운 수준의 WTP 대푯값들의 변동성이 확인되었다. 한편 Turnbull 비모수적 추정방법에 의한 WTP의 대푯값은 기본적으로 자의적 모수적 분포 가정에 의한 일종의 오지정 편의를 회피할 수 있다. 또한 Turnbull 비모수적 추정방법으로는 단일양분선택형 CV 자료이든 이중양분선택형 CV 자료이든 거의 유사한 추정치를 도출하고, 모수적 분포를 가정한 추정방법으로는 통계적으로 유의한 추정치를 얻지 못하는 상황에서도 통계적으로 유의한 추정치를 얻을 수 있는 강건성(robustness)을 보여주었다. 그러므로 양분선택형 CV 자료에서 특정 모수적 분포의 적합성을 판단하기 어려운 상황에서 자의적 모수적 분포의 가정에서 도출한 WTP의 대푯값들이 상당한 변동성을 보인다면, Turnbull 비모수적 추정방법에 의한 WTP의 평균 추정치가 정책의사결정에서 논란의 여지를 회피할 수 있는 비자의적이고 강건한 추정치가 될 수 있음을 확인할 수 있다.

• 대한간호학회지
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• 제29권5호
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• pp.1030-1041
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• 1999

This study examined those problems noticed under the Asymptotically Generalized Least Squares estimator in evaluating a structural model of physical health. The problems were highly correlated parameter estimates and high standard errors of some parameter estimates. Separate analyses of the endogenous part of the model and of the metric of a latent factor revealed a highly skewed and kurtotic measurement indicator as the focal point of the manifested problems. Since the sample sizes are far below that needed to produce adequate AGLS estimates in the given modeling conditions, the adequacy of the Maximum Likelihood estimator is further examined with the robust statistics and the bootstrap method. These methods demonstrated that the ML methods were unbiased and statistical decisions based upon the ML standard errors remained almost the same. Suggestions are made for future studies adopting structural equation modeling technique in terms of selecting of a reference indicator and adopting those statistics corrected for nonormality.