• The Korean Journal of Applied Statistics
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• v.33 no.2
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• pp.203-213
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• 2020

The self-controlled case series (SCCS) study measures the relative risk of exposure to exposure period by setting the non-exposure period of the patient as the control period without a separate control group. This method minimizes the bias that occurs when selecting a control group and is often used to measure the risk of adverse events after taking a drug. This study used SCCS to examine the increased risk of side effects when two or more drugs are used in combination. A conditional Poisson model is assumed and analyzed for drug interaction between the narcotic analgesic, tramadol and multi-frequency combination drugs. Bayesian inference is used to solve the overfitting problem of MLE and the normal or Laplace prior distributions are used to measure the sensitivity of the prior distribution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.20-33
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• 1999

The evolution of deep-sea waves is driven by energy input from wind, nonlinear energy transfer between wave components, and dissipation through whitecaps. A comparative study was implemented by the use of two wave models in which only the computation methods of nonlinear wave-wave interactions are different from each other. It was reaffirmed that the nonlinear interaction plays a central role in such phenomena that occurred during the spectral growth of wind-seas as down-shift of the spectral peak frequency, overshoot, undershoot, and formation of self-similar spectrum. Specifically, the directional distribution at high frequencies develops into bimodal form, which is attributed to the nonlinear interactions. As saturation stage is reached, spectral density at high frequencies becomes proportional to negative 4 power to the frequency. Perturbations introduced into the spectrum quickly vanished through the actions of the self-similar mechanism. Thus, the nonlinear transfer has important contribution to the stability of numerical ocean wave models.

• Archives of design research
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• v.13 no.3
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• pp.261-270
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• 2000

In general, sign is the way of communication directing human beings with their daily activities particularly in urban circumstances. And sign planning is designing and installing signboards systematically in urban environment. Generally, the range of application in space sign is pretty wide, and it may safely be say that the attractiveness of the city image is considerably decided upon the sign system. The subject of this study investigates the meaning and the role of sign system applying on human environment, and disirable design direction cope with the constant change of city space. The present study doesn't specifically deals with the basic function of signboards only, but with the problems and solution corresponding with sign system as structual element in city environment.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.443-446
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• 2004

추진기에 의한 소음은 선형 특성에 의한 반류 분포, 추진기 재질 및 유체 연동 등 다양한 주변 인자들에 의해 발생하여, 민수용 선박의 경우는 과도한 추진기 수중 방사 소음으로 해양 생태계 교란 및 선박 거주구역 내 과대 소음 형성의 주 요인이 된다. 더구나, 군사용 함정의 경우에는 추진기 유기 소음은 수중 방사소음의 형태로 전파되어 함정/무기 자체에 탑재된 음향센서의 기능을 저하시키는 영향을 줄 뿐 아니라, 원거리까지 전파되는 수중소음으로 인해 치명적인 자기 노출이 되어 적 함정에 의한 피탐 거리 증대라는 전술적 취약점을 초래하는 중요한 요소이다. 본 발표는 삼성 공동수조(SCAT)에서 이루어지는 추진기 유기 소음 측정에 대한 기술적 사항과 모형선-추진기 수조 시험을 통해 구해진 추진기 유기음향과 이론 및 경험식을 토대로 계산된 추진기 소음의 정량/정성적 비교를 통해, 추진기 설계 단계에서 소음수준 예측 도구로의 활용 가능성을 제시하였다.

• Korea journal of population studies
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• v.31 no.1
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• pp.99-125
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• 2008

This article aimed to clear that the systematic bias according to the length of work time exists between estimated work time by self-reported questions used mainly in measuring and calculating the length of work time because of strong points of easy in measuring and so on and diary work time by time-diary method used because of the strong point that can measure more accurate lifetime by recording various activities of respondents during 24 hours in the stream. As the result that analyze the data from Lifetime Use Survey in 2004, the result like the contradiction came that the tendency of overstating work time is rising according as estimated work time increases via estimated work time, whereas the tendency of understating work time is rising according as diary work time increases via diary work time. The reason that the opposite results come despite the data from the same survey is that random errors act in the opposite directions by regression to the mean. Therefore, we cannot emphasize that a man working long hours tends to exaggerate his work hours by the result via estimated work time. That is, the fact that the systematic bias by the increase of work time does not exist is confirmed, and therefore, it is also impossible to raise questions about the accuracy of the data through estimated work time by self-reported questions from the evidence of the existence of that bias.

• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.787-806
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• 2016

Mixed-mode (MM) designs in which data are collected by different modes in one design have become increasingly popular. An MM data collection has several advantages such as reductions of coverage error, non-response and cost. However, MM designs may introduce mode effects that are confounded by selection effects and measurement effects, which can make MM data quality poor. In order to investigate mode effects, SRI implemented a concurrent mixed-mode experiment in 2014 where respondents could choose between a self-administrated Web survey and a self-administrated paper survey. This paper separately estimates selection effects and measurement effects. We found that measurement effects on some items are large.

• Korean Journal of Culture and Social Issue
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• v.20 no.2
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• pp.133-154
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• 2014

The purpose of this study was to investigate psychological processes based on the Korean college students' development of social justice interest and commitment. For this study, we replicated Miller and colleagues'(2009) study, which explained the development of social justice interest and commitment by social-cognitive career theory(SCCT). Social desirability was controlled, and then self-reports data from 343 college students were analyzed using Structural Estimate Modeling(SEM). As a result, the final research model that social justice self-efficacy and outcome expectations affect social justice interest and commitment was proven valid for Korean college students. Also, in comparison with the direct effects model(social supports and barriers affect directly on commitment), the indirect effects model(social supports and barriers affect indirectly on commitment through self-efficacy) was supported. As an unique path of social-justice domain, the indirect effect by social support on commitment through outcome expectation was proved, as well. This study covers measurement limitations, future directions for research, and some lessons points with regards to how Korean college students to have social justice interest and commitment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.389-398
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• 2006

The present study compositely applied the self-organizing map (SOM), which is a kind of artificial neural networks (ANNs), and the back propagation algorithm (BPA) for the rainfall-runoff prediction model taking account of the irregular variation of the spatiotemporal distribution of rainfall. To solve the problems from the previous studies on ANNs, such as the overestimation of low flow during the dry season, the underestimation of runoff during the flood season and the persistence phenomenon, in which the predicted values continuously represent the preceding runoffs, we introduced SOM theory for the preprocessing in the prediction model. The theory is known that it has the pattern classification ability. The method proposed in the present research initially includes the classification of the rainfall-runoff relationship using SOM and the construction of the respective models according to the classification by SOM. The individually constructed models used the data corresponding to the respectively classified patterns for the runoff prediction. Consequently, the method proposed in the present study resulted in the better prediction ability of runoff than that of the past research using the usual application of ANNs and, in addition, there were no such problems of the under/over-estimation of runoff and the persistence.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.331-335
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• 2011

흔히 진흙으로 불리는 점착성 유사는 모래 등의 비점착성 유사와는 다른 특성을 보인다. 가장 큰 특징은 점착력에 의해 서로 엉겨 붙어 큰 덩어리(플럭)를 형성하고 다시 큰 플럭이 파괴되는 과정인 응집현상(Flocculation Process)을 보인다는 것이다. 이 응집현상의 과정을 통해 플럭은 크기 및 밀도를 지속적으로 변화시킨다. 크기 및 밀도의 변화는 플럭의 침강속도를 변화시켜 점착성 유사의 부유, 퇴적, 이송, 확산의 과정에 직접적인 영향을 미친다. 응집현상은 플럭의 침강속도 뿐 아니라 부피농도와 질량농도 사이의 비선형적 관계를 야기하여 흐름 운동량 방정식 유도, 난류의 모형화 등에서도 비점착성 유사와 다른 방향으로 진행된다. 점착성 유사가 우세한 지역의 또 다른 특성은 자기하중에 의한 압밀현상에 따라 발생하는 가변적인 한계소류력이다. 따라서 점착성 유사의 이동을 모형화 하는 과정에서는 가변적인 침식율의 가정 등을 통해 이에 대한 고려가 반드시 이루어져야 한다. 흐름의 운동량 방정식 및 난류 모형에서는 플럭의 부피 농도와 질량농도가 각 항의 물리적 의미에 부합하도록 개별적으로 선택 및 적용되어야 질량보존의 문제 등으로 발생할 수 있는 계산상의 오류를 배제할 수 있다. 적용 결과, 점착성 유사가 우세한 지역에서 나타나는 높은 부유 및 흐름정체기에서의 부유사 존재 등의 특성이 점착성 유사 이동을 위한 모형에서 보다 합리적으로 계산된다는 사실이 확인되었다. 그리고 비점착성 유사에 적합한 이동 모형이 점착성이 우세한 지역에 적용될 경우, 상황에 따라 유사량을 과대 및 과소 산정할 수 있다는 결론이 도출되었다. 조류의 영향이 존재하는 하구부의 경우에는 조류의 형태와 비대칭성에 따라 유사량의 차이가 큰 것으로 나타났다. 조류의 형태는 주로 하구부의 지형에 의해 결정되므로 준설, 매립, 확폭 등과 같은 하구부에서의 사업이 진행되는 경우, 유사량 변화에 대한 고려가 반드시 이루어져야 할 것으로 판단된다.

• The Journal of the Korea Contents Association
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• v.17 no.10
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• pp.65-71
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• 2017

It is true that there is a possibility of distortion in the statistical surveys or actual surveys depending on which investigator, what purpose, and how research method. Even statistical results are more likely to be 'lying', and statistics on crime or delinquent are sometimes referred to as 'whopper'. There are many reasons for not trusting statistics on crime or delinquent, but one of the main causes is the existence of a hidden crime or an unreported crime. In order to overcome these hidden crime problems, victim surveys or self-report surveys are being used. However, this method also has the problem of underreporting or overreporting depending on the type of crime. Because investigations into crime, delinquency, and deviant behavior are very sensitive, the subjects have a psychological burden. A randomized response model has been developed and used in the field of statistics as a way to induce a true answer to the sensitive content which is burdensome to reveal the experiences of the survey subjects. This technique is a very useful way to solve the problems of victim surveys or self-report surveys. Nevertheless, there are very few cases in the field of criminology in Korea. Therefore, in order to examine the applicability of the randomized response model in the field of criminology, this study used the randomized response model to actually measure the content of prostitution for college students and the effectiveness of the randomized response model was confirmed.