• Smart Structures and Systems
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• v.18 no.1
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• pp.75-92
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• 2016

The design of a semi-active (SA) control system addressed to mitigate wind induced structural demand to high wind turbine towers is discussed herein. Actually, the remarkable growth in height of wind turbines in the last decades, for a higher production of electricity, makes this issue pressing than ever. The main objective is limiting bending moment demand by relaxing the base restraint, without increasing the top displacement, so reducing the incidence of harmful "p-delta" effects. A variable restraint at the base, able to modify in real time its mechanical properties according to the instantaneous response of the tower, is proposed. It is made of a smooth hinge with additional elastic stiffness and variable damping respectively given by springs and SA magnetorheological (MR) dampers installed in parallel. The idea has been physically realized at the Denmark Technical University where a 1/20 scale model of a real, one hundred meters tall wind turbine has been assumed as case study for shaking table tests. A special control algorithm has been purposely designed to drive MR dampers. Starting from the results of preliminary laboratory tests, a finite element model of such structure has been calibrated so as to develop several numerical simulations addressed to calibrate the controller, i.e., to achieve as much as possible different, even conflicting, structural goals. The results are definitely encouraging, since the best configuration of the controller leaded to about 80% of reduction of base stress, as well as to about 30% of reduction of top displacement in respect to the fixed base case.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.3
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• pp.3-9
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• 2016

UAV(unmanned aerial vehicle) can quickly produce orthoimage with high-spatial resolution and DSM(digital surface model) at low cost. However, vertical and horizontal positioning accuracy of orthoimage and DSM, which are obtained by UAV, are influenced by image processing techniques, quality of aerial photo, the number and position of GCPs(ground control points) and overlap in flight plan. In this study, effects of overlap and the number of GCPs are analyzed in orthoimage and DSM. Positioning accuracy are estimated based on RMSE(root mean square error) by using dataset of nine pairs. In the experiments, Overlaps and the number of GCPs have influence on horizontal and vertical accuracy of orthoimage and DSM.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.25-28
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• 2008

Currently, the prefabricated bridge having the effects to reduce the term of works and the cost of construction is often studied and countries such as America have already developed members, the parts of it, and the technique of construction. In addition, they have supplied them to the fields. The study of prefabricated method of steel composite bridge, which has the precast deck - plate and main girder fixed by high tension bolt and can resist horizontal sheer, is being progressed. However, it is difficult to understand the characteristics of the prefabricated bridge's behavior when the superstructure of the prefabricated method is analyzed by applying to the analysis model of existing bridges. Therefore, this study has the purpose of understanding real structural behavior of prefabricated bridge through comparison and analysis between the structural analysis model reflecting the characteristics of the real prefabricated bridge's superstructure and real size experiment.

• Interaction and multiscale mechanics
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• v.3 no.1
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• pp.55-79
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• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.

• International Commerce and Information Review
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• v.13 no.4
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• pp.125-149
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• 2011

The present study made an empirical analysis for investigating the competitiveness of technology trades in Korea. In particular, the study deduced the correlation between technology export and technology import using the variables of Gross Domestic Expenditure on R&D and Per capita industry value added Productivity and employed fixed effect model in panel linear regression model. It is found that the R&D expenditure of OECD countries made a significant effect on the technology import and the value-added labor productivity made a significant result on both technology export and import. Therefore, it showed that the technology trade in Korea made a sensitive response to labor productivity in OECD countries. By panel analysis, machine, construction, ICT, and service industry affect most on technology export in Korea for recent 5 years. For technology import, electric-electron, chemical, service, and construction industry have significant effects. This study contributed to understanding of industrial characteristics affecting technology trades in Korea and empirical analysis to show correlation between the factors affecting technology trade.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.529-535
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• 2017

In this paper the laminate design parameters are researched to maximize the performance index of a composite pressure vessel. The pressure-resistant performance and the light-weight concept with contained internal space are implied in the performance index. To maximize the performance index, the three design variables that the thickness of each of helical and hoop layers and the length of hoop layer are considered under the assumption of fixed internal space. To optimize the variables, the response surface method is introduced for construction of the surrogate model and the ANOVA(analysis of variance) is performed to evaluate the effects of the variables. The optimization problem is formulated to maximize performance index under the burst pressure constraint. To verify the effectiveness of the research, numerical analyses are performed for the optimum model.

• Journal of Korean Society of Rural Planning
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• v.26 no.4
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• pp.41-52
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• 2020

The purpose of this study is to identify the conflict between residents and governments in partnership arising from the designation of National Important Agricultural Heritage for Damyang Samdari village and to suggest directions for improvement. To this end, residents of Samdari Village in Damyang, designated as an important national agricultural heritage, were interviewed. Interviews were analyzed through grounded theory, categorized into open coding, axial coding, and selective coding, and a paradigm model was constructed. Through this, the central phenomena of resident participation patterns currently appearing in the village were identified, and causal, contextual, and intervening conditions were analyzed. Causal conditions were analyzed as one-sided administrative treatment, assortment matching project, one-time plan, excessive dependence of residents and economic damages of residents at the beginning of the designation of national important agricultural heritage. As a result, conflict between residents and local governments occurred as a central phenomenon, and contextual conditions such as decline in the competitive of bamboo resources and frequent change in managers were also affecting the central phenomenon. As intervening conditions to alleviate the central phenomenon, there are local government's purchase of bamboo fields and fragmentary business effects. The action taken by the residents and officials in response to a fixed conflict is called an action-interaction strategy. Residents refused to change and settled in reality, and local governments avoided conflict. From the beginning of the designation to the present, the villagers gradually lost interest in the National Important Agricultural Heritage due to problems and conflicts that occurred in the process of forming a partnership in the National Important Agricultural Heritage project. Based on the analyzed model, a plan to build the partnership standards on Damyang bamboo field to secure the sustainability of the field and increase the practicality of resident participation, that is partnership, was suggested.

• International Area Studies Review
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• v.18 no.3
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• pp.293-316
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• 2014

This paper examined a comparative study on the domestic violence of general families and multicultural families using meta analysis. Based on the analysis of one twenty studies of domestic violence as seven studies of social welfare, seven studies of education, and six studies of counseling and psychology, the following results were found. First, domestic violence, effective sample size, have a significantly difference on domestic families and multicultural families. Second, fixed effect model, compared to random effect model, have a significantly difference on the domestic violence of domestic families and multicultural families. Third, domestic violence, relative and cumulative effects, have a significantly difference on domestic families and multicultural families.

• Journal of Preventive Medicine and Public Health
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• v.52 no.1
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• pp.51-59
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• 2019

Objectives: The purpose of this study was to estimate the mediating effect of subjective unmet healthcare needs on poor health. The mediating effect of unmet needs on health outcomes was estimated. Methods: Cross-sectional research method was used to analyze Korea Health Panel data from 2011 to 2015, investigating the mediating effect for each annual dataset and lagged dependent variables. Results: The magnitude of the effect of low income on poor health and the mediating effect of unmet needs were estimated using age, sex, education level, employment status, healthcare insurance status, disability, and chronic disease as control variables and self-rated health as the dependent variable. The mediating effect of unmet needs due to financial reasons was between 14.7% to 32.9% of the total marginal effect, and 7.2% to 18.7% in lagged model. Conclusions: The fixed-effect logit model demonstrated that the existence of unmet needs raised the likelihood of poor self-rated health. However, only a small proportion of the effects of low income on health was mediated by unmet needs, and the results varied annually. Further studies are necessary to search for ways to explain the varying results in the Korea Health Panel data, as well as to consider a time series analysis of the mediating effect. The results of this study present the clear implication that even though it is crucial to address the unmet needs, but it is not enough to tackle the income related health inequalities.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.3
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• pp.334-340
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• 2019

Objective: The objective of this study was to investigate the genetic components of daily milk yield and to re-rank bulls in South Korea by estimated breeding value (EBV) under heat stress using the temperature-humidity index (THI). Methods: This study was conducted using 125,312 monthly test-day records, collected from January 2000 to February 2017 for 19,889 Holstein cows from 647 farms in South Korea. Milk production data were collected from two agencies, the Dairy Cattle Genetic Improvement Center and the Korea Animal Improvement Association, and meteorological data were obtained from 41 regional weather stations using the Automated Surface Observing System (ASOS) installed throughout South Korea. A random regression model using the THI was applied to estimate genetic parameters of heat tolerance based on the test-day records. The model included herd-year-season, calving age, and days-in-milk as fixed effects, as well as heat tolerance as an additive genetic effect, permanent environmental effect, and direct additive and permanent environmental effect. Results: Below the THI threshold (${\leq}72$; no heat stress), the variance in heat tolerance was zero. However, the heat tolerance variance began to increase as THI exceeded the threshold. The covariance between the genetic additive effect and the heat tolerance effect was -0.33. Heritability estimates of milk yield ranged from 0.111 to 0.176 (average: 0.128). Heritability decreased slightly as THI increased, and began to increase at a THI of 79. The predicted bull EBV ranking varied with THI. Conclusion: We conclude that genetic evaluation using the THI function could be useful for selecting bulls for heat tolerance in South Korea.