• Structural Engineering and Mechanics
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• 제11권4호
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• pp.357-372
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• 2001

In this paper, cantilevered tall structures are treated as cantilever bars with varying cross-section for the analysis of their free longitudinal (or axial) vibrations. Using appropriate transformations, exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived by selecting suitable expressions, such as exponential functions, for the distributions of mass and axial stiffness. The frequency equation of a multi-step bar is established using the approach that combines the transfer matrix procedure or the recurrence formula and the closed-form solutions of one step bars, leading to a single frequency equation for any number of steps. The Ritz method is also applied to determine the natural frequencies and mode shapes in the vertical direction for cantilevered tall structures with variably distributed stiffness and mass. The formulae proposed in this paper are simple and convenient for engineering applications. Numerical example shows that the fundamental longitudinal natural frequency and mode shape of a 27-storey building determined by the proposed methods are in good agreement with the corresponding measured data. It is also shown that the selected expressions are suitable for describing the distributions of axial stiffness and mass of typical tall buildings.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.152-161
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• 2013

This paper presents a control effectiveness analysis of the hawkmoth Manduca sexta. A multibody dynamic model of the insect that considers the time-varying inertia of two flapping wings is established, based on measurement data from the real hawkmoth. A six-degree-of-freedom (6-DOF) multibody flight dynamics simulation environment is used to analyze the effectiveness of the control variables defined in a wing kinematics function. The aerodynamics from complex wing flapping motions is estimated by a blade element approach, including translational and rotational force coefficients derived from relevant experimental studies. Control characteristics of flight dynamics with respect to the changes of three angular degrees of freedom (stroke positional, feathering, and deviation angle) of the wing kinematics are investigated. Results show that the symmetric (asymmetric) wing kinematics change of each wing only affects the longitudinal (lateral) flight forces and moments, which implies that the longitudinal and lateral flight controls are decoupled. However, there are coupling effects within each plane of motion. In the longitudinal plane, pitch and forward/backward motion controls are coupled; in the lateral plane, roll and side-translation motion controls are coupled.

• 가정과삶의질연구
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• 제31권3호
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• pp.81-92
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• 2013

The purpose of this study is to identify difference in motivation of move to senior cohousing communities in Sweden during 10 years between the year of 2001 and 2010 by a longitudinal study. Questionnaire survey was used for the study. 313 data were collected from 12 senior cohousing communities, which were established by residents-initiated process. It includes 8 of Senior g${\aa}$rden cohousings in 2001 and 4 of +40 cohousings in 2010 nationwide in Sweden. The result indicates that there are significant differences in motivation of move to senior cohousing between 2001 and 2010. Comparing motivation of move to senior cohousing during 10 years, respondents of 2010 focus more on social merits than practical merits of cohousing as they move to cohousing communities. They stress more to the reasons as good contacts with neighbors, mutual supports, sharing common activities and getting rid of loneliness rather than burden of housing and garden management, and universal-designed house. The result of this study reveals motivation of move to senior cohousing has been changed during 10 years in Sweden.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.589-592
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• 2011

전력 유도 현상을 평가하는데는 통상 유도 잡음 전압과 종전압 수치를 측정하는데 이 두 잡음은 일반적으로 종전압 수치의 변화에 따라 잡음 진압이 종속적인 관계로 변화한다고 이해되고 있다. 하지만, 실제 전력유도를 평가하기 위한 현장에서 잡음전압이 종전압의 변화에 정확하게 종속적으로 변화되지 않는 현상이 발생하여 혼란을 야기하고 있다. 이에 도시 차폐 효과의 실증 분석을 위해 각각 30개 지역에서 측정된 도시와 시골 개소에서의 종전압 데이터와 잡음전압 데이터를 동기화 프로그램을 통하여 가장 근접한 시간에서 또는 동일한 시간에서 측정된 잡음 수치를 선별하고 이를 비교하여 종전압에 대한 잡음 전압의 변화 관계를 분석해본다.

• Journal of the Korean Data and Information Science Society
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• 제26권3호
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• pp.755-762
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• 2015

One of the main objectives of the U.S. Census Bureau is the proper estimation of median household income for small areas. These estimates have an important role in the formulation of various governmental decisions and policies. Since direct survey estimates are available annually for each state or county, it is desirable to exploit the longitudinal trend in income observations in the estimation procedure. In this study, we consider Fay-Herriot type small area models which include time-specific random effect to accommodate any unspecified time varying income pattern. Analysis is carried out in a hierarchical Bayesian framework using Markov chain Monte Carlo methodology. We have evaluated our estimates by comparing those with the corresponding census estimates of 1999 using some commonly used comparison measures. It turns out that among three types of time-specific random effects the small area model with a time series random walk component provides estimates which are superior to both direct estimates and the Census Bureau estimates.

• 한국지반공학회논문집
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• 제17권6호
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• pp.149-162
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• 2001

삼랑진에 위치한 삼랑진양수발전 상.하부댐의 댐마루에 시공 후 종방향 균열이 발생하였다. 이 댐들은 전력을 생산하기 위한 양수발전댐으로 상부댐과 하부댐으로 구성되어 있으며, 매일 10m이상의 수위변화를 받아왔다. 본 논문은 이들 댐중 상부댐에 발생한 종방향 균열의 원인을 찾는데 있다. 균열의 주요 원인은 수위변동으로 인한 것으로 판단되었으며, 이를 검토하기 위해 hyperbolic model을 이용한 수치해석을 수행하였다. 수치해석을 위한 입력자료를 얻기 위해 심벽재료와 사석재료에 대해 일련의 삼축압축시험을 수행하였다. 또한 수위변동으로 인한 주기적인 응력변화를 검토하기 위한 입력자료를 얻기 위해 진동삼축압축시험을 수행하였다. 수치해석결과 반복하중이 작용했을 경우 댐마루에서 깊이 4m까지 구속압력이 음이 되는 것으로 나타났으며, 이로 인해 종방향균열이 발생한 것으로 판단되었다. 이 종방향균열의 깊이는 댐 마루에서 수행한 시험굴에서 확인하였으며, 현장 조사결과와 잘 부합하였다.

• 보건교육건강증진학회지
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• 제26권3호
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• pp.25-34
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• 2009

Objectives: This study has longitudinally analyzed male smokers in order to find out the trend rate of re-smoking after smoking cessation. Methods: The study was conducted with 800 male smokers who were provided with smoking cessation services for 3 years at public health centers from July 16, 2005 to July 15, 2008. Results: The results can be summarized as follows: First, the success rate of smoking cessation for at least 6 months during 3-year period was 54.4%. The failure rate of smoking cessation at the second year was 47.5% and the third 27.2%, which indicates that the failure rate diminishes as the period of smoking cessation extends. Second, the success rate of smoking cessation at the first trial was 35.0%, the second 24.3%, and the third 16.4%. The success rate diminished as the number of trial increased. Third, the continuation rate of smoking cessation for a year was 18.3%, for 2 years 13.4%. For the success group, the continuation rate of smoking cessation for a year was 52.5%, for 2 years 38.2%. For the failure group, the rate for a year was 21.5%. Fourth, in this longitudinal analysis, the most crucial variables that affect the success rate of smoking cessation are total number of consultation and the past experience of successful smoking cessation. Conclusion: This study shows that success of smoking cessation and the continuance of smoking cessation are both difficult, and that the past experience of smoking cessation plays an important role determining the present success of smoking cessation and continuance of smoking cessation. Thus, it is necessary to divide people into success group and failure group based on the results of the past experience of smoking cessation when they consult at smoking cessation clinics at public health centers. Further, in order to increase the continuation rate of smoking cessation, this study suggests that we need to consider ways to take care of those who successfully abstained from smoking for 6 months.

• Asia pacific journal of information systems
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• 제18권3호
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• pp.147-165
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• 2008

IT education can be summarized as persuading the educatee to accept IT. The persuasion is made by delivering the messages for how-to-use and where-to-use to the educatee, which leads formulation of a belief structure for using IT. Therefore, message based persuasion theory, as well as IT acceptance theories such as technology acceptance model(TAM), would play a very important role for explaining IT education. According to elaboration likelihood model(ELM) that has been considered as one of the most influential persuasion theories, people change attitude or perception by two routes, central route and peripheral route. In central route, people would think critically about issue-related arguments in an informational message. In peripheral route, subjects rely on cues regarding the target behavior with less cognitive efforts. Moreover, such persuasion process is not a one-shot program but continuous repetition with feedbacks, which leads to changing a belief structure for using IT. An educatee would get more knowledge and experiences of using IT as following an education program, and be more dependent on a central route than a peripheral route. Such change would reformulate a belief structure which is different from the intial one. The objectives of this study are the following two: First, an identification of the relationship between ELM and belief structures for using IT. Especially, we analyze the effects of message interpretation through both of central and peripheral routes on perceived usefulness which is an important explaining variable in TAM and perceived use control which have perceived ease of use and perceived controllability as sub-dimensions. Second, a longitudinal analysis of the above effects. In other words, change of the relationship between interpretation of message delivered by IT education and beliefs of IT using is analyzed longitudinally. For achievement of our objectives, we suggest a research model, which is constructed as three-layered. While first layer has a dependent variable, use intention, second one has perceived usefulness and perceived use control that has two sub-concepts, perceived ease of use and perceived controllability. Finally, third one is related with two routes in ELM, source credibility and argument quality which are operationalization of peripheral route and central route respectively. By these variables, we suggest five hypotheses. In addition to relationship among variables, we suggest two additional hypotheses, moderation effects of time in the relationships between perceived usefulness and two routes. That is, source credibility's influence on perceived usefulness is decreased as time flows, and argument quality's influence is increased. For validation of it, our research model is tested empirically. With measurements which have been validated in the other studies, we survey students in an Excel class two times for longitudinal analysis. Data Analysis is done by partial least square(PLS), which is known as an appropriate approach for multi-group comparison analysis with a small sized sample as like this study. In result. all hypotheses are statistically supported. One of theoretical contributions in this study is an analysis of IT education based on ELM and TAM which are considered as important theories in psychology and IS theories respectively. A longitudinal analysis by comparison between two surveys based on PLS is also considered as a methodological contribution. In practice, finding the importance of peripheral route in early stage of IT education should be notable.

• 한국산업융합학회 논문집
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• 제27권4_2호
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• pp.961-972
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• 2024

As the global elderly population rapidly increases, the mental health of the elderly, particularly depression, has emerged as a significant social issue. This study analyzes the various factors influencing depression in the elderly based on the ICF model. Utilizing data from the Korea Welfare Panel Study, the study identifies the types of changes in depression among individuals aged 65 and older and examines the factors influencing these changes. This longitudinal secondary data analysis research uses the most recent three years of data (2021-2023) from the Korea Welfare Panel. The study sample consisted of 965 elderly individuals, and a latent class growth model was applied to identify the types of depression changes, while a multinomial logistic regression analysis was conducted to analyze the influencing factors. The analysis revealed that elderly depression could be categorized into four types: high-level decrease, high-level maintenance, low-level increase, and low-level maintenance. Main influencing factors included gender, age, education, poverty, social trust, social relationships, participation in economic activities, participation in religious activities, and health status. Particularly, social relationships and health status were significant factors affecting the types of depression changes. To mitigate depression in the elderly, a multifaceted approach considering both individual characteristics and social relationships and health status is required. The study suggests the development of community-based programs and trust-building activities at the community level to maintain and strengthen the social relationships of the elderly. These findings can serve as important foundational data for policies and practices aimed at improving the mental health of the elderly.

• 한국콘텐츠학회논문지
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• 제19권7호
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• pp.138-148
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• 2019

사회적관계 요인이 노인의 우울 수준과 밀접한 관련이 있다는 것은 선행연구를 통해 확인되고 있으나, 우울 수준 궤적에 영향을 미치는 사회적관계 하위요인에 대한 구체적인 연구는 이루어지지 않고 있다. 이러한 한계를 고려한 본 연구는 노인의 사회적관계 하위요인이 노인의 우울 궤적에 미치는 영향요인을 분석하는데 연구 목적이 있다. 연구를 위해 한국고용정보원이 제공하고 있는 고령화연구패널자료(Korean Longitudinal Survey of Ageing: KLoSA)의 3, 4, 5, 6차 자료를 활용 했으며, 65세 이상 4차시 모두 설문에 응답한 2,484명을 최종 분석대상으로 활용하였다. 65세 이상 노인의 우울 수준에 대한 종단적 연구에서 시간이 지날수록 개인별 우울 수준이 낮아지고 있어 긍정적 변화가 있음을 확인했고, 잠재성장모형의 조건부 모형을 통해 노인의 우울 궤적에 미치는 구체적인 사회적관계 요인을 분석하였다. 분석 결과, 배우자유무, 가구원수, 친한 사람과의 만남, 경제활동 유무, 종교 유무 등이 노인의 우울 수준 초기값에 영향을 미치는 요인으로 나타났으며, 가구원수, 친한 사람과의 만남, 삶에 대한 기대감 등이 노인의 우울 수준 궤적에 영향을 미치는 요인으로 나타났다. 연구결과를 통해 노인의 우울수준을 지속적으로 낮출 수 있는 구체적인 프로그램 및 지원의 필요함 등을 제언하였다.