• Journal of the Korea Convergence Society
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• v.12 no.1
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• pp.205-210
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• 2021

In this study, I studied how to generate input values to achieve the same value as the target value. The general procedures are explained to regenerate the excitation input, which is made by using the frequency response function between input-output. In this study, a mount model connected by a bushing was used as a numerical model. The response value for the excitation input was compared with the target value. The excitation input was corrected to obtain the same response as the target value. Through the iterative process, the reconstructed input value was obtained to have the same response as the test.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.419-421
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• 2022

어선은 어획물로 인한 무게 변화 및 어구 사용에 의한 외력으로 GM이 변화한다. 하지만 실시간으로 변화하는 GM을 추정하는 것은 어려우며, 현재 적용되는 추정식은 어선에 대입하기에 정확성이 떨어진다. 이에 본 논문은 어선의 GM 추정식 개발에 기여하기 위해 어선의 Roll 운동응답을 분석하고, 실험과 시뮬레이션의 GM과 파경사 관계를 밝히고자 한다. 7톤 급의 실제 운항 중인 어선의 모델선 GM을 변화시키면서 파경사별 Roll 운동응답 데이터를 수집한다. GM 변화의 경우 선박 무게중심부에 높이 방향으로 추를 조절할 수 있도록 했으며, 파경사는 동일 주기 4가지 파경사를 선정하였다. GM과 파경사가 커질수록 Roll 응답이 증가하는 경향을 보이며, GM과 파경사가 커짐에 따라 기울기가 비선형성을 보이며 증가하는 것을 확인하였다. 본 연구를 통해서 어선의 GM과 파경사의 관계를 파악하고, GM추정에 사용할 수 있느 보정 계수를 도출할 수 있다. 추후에 본 연구 내용을 활용하여 운항 중인 어선의 실시간 GM 추정시스템 개발에 기여가 가능할 것으로 생각한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.71-80
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• 2013

According to design specifications for structural safety, a bridge in initial design step has been modelled to have larger self-weight, external loads and less stiffness than those of real one in service. Thereby measured buffeting responses of existing bridge show different distributions from those of the design model in design step. In order to obtain accurate buffeting responses of the in-site bridge, the analysis model needs to be modified by considering the measured natural frequencies. Until now, a Manual Tuning Method (MTM) has been widely used to obtain the Measurement-based Model(MBM) that has equal natural frequencies to the real bridge. However, since state variables can be selected randomly and its result is not apt to converge exact rapidly, MTM takes a lot of effort and elapsed time. This study presents Buffeting Response Correction Method (BRCM) to obtain more exact buffeting response above MTM. The BRCM is based on the idea the commonly used frequency domain buffeting analysis does not need all structural properties except mode shapes, natural frequencies and damping ratio. BRCM is used to improve each modal buffeting responses of the design model by substituting measured natural frequencies. The measured natural frequencies are determined from acceleration time-history in ordinary vibration of the real bridge. As illustrated examples, simple beam is applied to compare the results of BRCM with those of a assumed MBM by numerical simulation. Buffeting responses of BRCM are shown to be appropriate for those of in-site bridge and the difference is less than 3% between the responses of BRCM and MTM. Therefore, BRCM can calculate easily and conveniently the buffeting responses and improve effectively maintenance and management of in-site bridge than MTM.

• The Korean Journal of Applied Statistics
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• v.34 no.6
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• pp.923-936
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• 2021

A large number of non-responses are occurring in the sample survey, and various methods have been developed to deal with them appropriately. In particular, the bias caused by non-ignorable non-response greatly reduces the accuracy of estimation and makes non-response processing difficult. Recently, Chung and Shin (2017, 2020) proposed an estimator that improves the accuracy of estimation using parametric super-population model and response rate model. In this study, we suggested a bias corrected non-response mean estimator using a nonparametric function generalizing the form of a parametric super-population model. We confirmed the superiority of the proposed estimator through simulation studies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.35-43
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• 2012

In general, load carrying capacity, one of the load & resistance capacities in bridges, has more margins than the load carrying capacity evaluated with theoretical methods, unless there are severe damages, defects or material deterioration phenomena that can have a great impact on the behavior of bridges. However, errors have been already included in the current processes of loading tests and structural analysis for measuring load carrying capacity, thus devaluing the reliability of response adjustment factor. Therefore, this study found out the problems of existing electric resistance strain and displacement sensors in sensor suite to solve the problems with sensors and the errors in the appropriateness of structural analysis model, thereby leading to the changes into an optical fiber smart sensor with excellent performance. Besides, the study attempted to ensure the accuracy of response adjustment factor by selecting the optimal models through the interpretation of various structural analysis models.

• Electrical & Electronic Materials
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• v.6 no.3
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• pp.255-260
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• 1993

본 논문은 과도고전압 측정시스템의 단위계단응답으로부터 구한 보정계수를 사용하여 수치계산에 의해 출력값을 보정하는 방법에 대하여 기술하였다. 또한 실규모 용량성분압기의 분압비와 상승시간을 갖는 모의등가회로를 구성하여 측정한 바, 본 연구에서 제안된 보정방법은 급준파 및 차단파 등의 어떠한 입력에도 유용하게 사용할 수 있다.

• Survey Research
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• v.10 no.1
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• pp.169-186
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• 2009

The propensity score method is used to minimize the bias level in social survey, which comes from nonresponse. The theoretical concept and the background of the propensity score method is discussed first. The propensity score method was first applied in the epidemiology observational study. I have summarized the process of the three propensity score methods that were used to reduce estimation bias in this study. Matching by propensity score is applied to the relatively large control group. Subclassification has the advantage of using whole control group data and regression adjustment is applied to multiple covariates as well as propensity score of each unit is computable and usable. Lastly, the application procedures of propensity score method to reduce the nonresponse bias is suggested and its applicability to real situation is reviewed with the existing data.

• The Korean Journal of Applied Statistics
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• v.33 no.1
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• pp.11-23
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• 2020

Sampling design should provide statistics to meet a given accuracy while saving cost and time. However, a large number of non-responses are occurring due to the deterioration of survey circumstances, which significantly reduces the accuracy of the survey results. Non-responses occur for a variety of reasons. Chung and Shin (2017, 2019) and Min and Shin (2018) found that the accuracy of estimation is improved by removing the bias caused by non-response when the response rate is an exponential or linear function of variable of interests. For that case they assumed that the error of the super population model follows normal distribution. In this study, we proposed a non-response bias adjusted estimator in the case where the error of a super population model follows the gamma distribution or the log-normal distribution in a business survey. We confirmed the superiority of the proposed estimator through simulation studies.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.27-33
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• 2003

본 논문에서는 측정된 가속도신호만을 사용하여 변위응답을 추정하는 시간영역과 주파수영역에서의 동적 응답변환 알고리즘을 제시하였다. 본 알고리즘에서 사용되는 변환변위응답은 속도와 변위성분의 초기조건에 대한 정보 없이 측정된 가속도신호의 적분에 의하여 계산되며 실제 변위응답과 상관관계를 갖는다. 이에 측정된 구조물의 동적응답이 무재하부분과 자유진동부분을 포함하고 있을 때 변환응답을 보정하여 초기치 문제를 해결할 수 방법을 제시함으로써 가속도신호만을 사용하여 실제 변위응답을 추정할 수 있도록 하였다. 제시된 응답변환 알고리즘의 타당성을 평가하기위해 실교량에 대한 현장시험자료를 적용하여 변위응답을 추정하고 실측된 동적 변위와 비교하였다. 또한, 주파수영역에서의 응답변환에서 적분구간을 상이하게 사용함으로써 동적성분과 정적성분으로 분리된 추정응답을 평가할 수 있었으며 이에 따른 충격계수의 계산은 신뢰성 있는 평가방법임을 확인하였다.

• The Korean Journal of Applied Statistics
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• v.32 no.3
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• pp.375-389
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• 2019

Sample attrition according to a long-term tracking reduces the representativeness of the sample data in a panel study. Most panel surveys in South Korea and other countries have prepared response adjustment weights in order to solve problems regarding representativeness due to sample attrition. In this paper, we divided the panel data into continuous response group and non-continuous response group according to response patterns and considered a weighting adjustment method to reduce the bias of the non-continuous response group. A simulation indicated that the proposed composite estimation type weighting method, which reflected the characteristics of non-continuous response groups, could be more efficient than other weighting methods in terms of reducing non-response bias. As a case study, the proposed methods are applied to the Korean Longitudinal Study of Ageing (KLoSA) data of the Korea Employment Information Service.