• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Journal of Environmental Impact Assessment
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• v.21 no.5
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• pp.735-743
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• 2012

Since the CBD(Conservation on Biological Diversity)'s 10th Conference of the Parties adopted the protocol on access to genetic resources and benefit sharing in Nagoya 2010, the importance of endangered species studies such as habitat distribution, protection and management have been more emerged. Corylopsis coreana, an endangered species in Korea, was isolated nationally and has been damaged by anthropogenic factors. In this paper, we identified the factors affecting C. coreana habitat at the national scale and regional scale using National Survey of Natural Environment and predicted the distribution of C. coreana. Annual precipitation, precipitation of wettest quarter, temperature seasonality and Digital Elevation Model(DEM) were derived as important factors at the national scale, and precipitation of wettest quarter, DEM and solar radiation on spring were identified as important factors at regional scale. Colylopsis distribution was affected by an effect of climate significantly at the national scale, and by additionally the microclimate and topography at regional scale. These findings will be used as the basis on habitat conservation and restoration plan and climate change.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.331-339
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• 2014

Determination of an ionospheric delay scale factor, which converts ground-based ionospheric delay into low Earth orbit ionospheric delay, using the international reference ionosphere model is proposed. Ionospheric delay from international GNSS service model combined with IRI-derived scale factor is evaluated with NASA GRACE satellite data. At approximately 480km altitude, mean and standard deviation of the scale factor are 0.25 and 0.01 in 2004. The scale factor reaches high in night time and Spring and Fall seasons. Ionospheric delay error by the proposed method has a mean of 3.50 TECU in 2004.

• Journal of Environmental Impact Assessment
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• v.17 no.3
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• pp.167-176
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• 2008

Korea has made the rapid economical development under the condition with the high population density and low available land. In this context, conservation of land environment, connected directly with living quality of human, has mostly ignored. Prior Environment Review System(PERS) is the one to investigate the locational validity, environmental impacts, harmony with surrounding environment, from the early stage of administrative plan or development project. PERS was amended to include SEA(Strategic Environment Assessment) system on June 1, 2006. But, several problems, including the loss of administrative ability, cost, and time, have been appeared, since the system is applied to all administrative plans without any distinction and plans or projects are delayed generally. In this study, the weaknesses of PERS were indicated through the comprehensive analysis including literature survey, study of legal and internet database, and the recently published PERS reports. Based on that, the improvement schemes were suggested to be harmonized with the nature of SEA. This study was mainly focused on a PERS for the designation of conservational area of hot-spring wells, conducted by authors.

• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.197-205
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• 2009

Since large-scale commercial wind turbine generator systems such as MW-class wind turbines are becoming widely operated, the vibration and distortion of the blade are becoming larger and larger. Therefore the soft structure design instead of the solid-design is one of the important concepts to reduce the structural load and the cost of the wind turbine rotors. The objectives of the study are development of the fluid-structure coupled analysis code and evaluation of soft rotor-blade design to reduce the unsteady structural blade load. In this paper, fluid-structure coupled analysis for the HAWT rotor blade is performed by free wake panel method coupled with hinge-spring blade model for the flapwise blade motion. In the model, the continuous deflection of the rotor blade is represented by flapping angle of the hinge with one degree of freedom. The calculation results are evaluated by comparison with the database of the NREL unsteady aerodynamic experiment. In the analysis the unsteady flapwise moments in yawed inflow conditions are compared for the blades with different flapwise eigen frequencies.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.110-122
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• 2008

Pneumatic vibration isolator typically consisting of dual-chamber pneumatic springs and a rigid table are widely employed for proper operation of precision instruments such as optical devices or nano-scale equipments owing to their low stiffness- and high damping-characteristics. As environmental vibration regulations for precision instruments become more stringent, it is required to improve further the isolation performance. In order to facilitate their design optimization or active control, a more accurate mathematical model or complex stiffness is needed. Experimental results we obtained rigorously for a dual-chamber pneumatic spring exhibit significantly amplitude dependent behavior, which cannot be described by linear models in earlier researches. In this paper, an improvement for the complex stiffness model is presented by taking two major considerations. One is to consider the amplitude dependent complex stiffness of diaphragm necessarily employed for prevention of air leakage. The other is to employ a nonlinear model for the air flow in capillary tube connecting the two pneumatic chambers. The proposed amplitude-dependent complex stiffness model which reflects dependency on both frequency and excitation amplitude is shown to be very valid by comparison with the experimental measurements. Such an accurate nonlinear model for the dual-chamber pneumatic springs would contribute to more effective design or control of vibration isolation systems.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.59-66
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• 2006

High concentration of chlorophyll a occurred around the Ulleung Warm Eddy off Ulleung Island in the East Sea of Korea in spring season. The abnormal distributions of chlorophyll a were captured by satellite remote sensing and measured field data. The temporal and spatial scale of the abnormal distributions were around 20days and 50km diameter off Ullung Island. The anomalies were quantified b)'estimated chlorophyll a derived from OCM and SeaWiFS ocean color data from 2000 to 2004. The origin of abnormal hish concentrations was estimated by this study. It was that suspended material discharged from the Nakdong River and the coastal water located in the southeastern part of Korean Peninsula moved to northeastern coast, and then moved to off Ullung island, The high chlorophyll a concentrations including inorganic materials were accumulated by anticyclonic eddy such as the Ullung Warm Eddy around Ullung island in the East Sea of Korea in spring season.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.4
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• pp.452-459
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• 1994

Fabric hand was assessed for 14 women's spring-fall dress fabrics based on the subjective hand evaluation scale developed in the part 1 of this study. The effects of fabric type, seam and dress style on the subjective hand evaluation of 470 Korean consumers (205 textile experts and 265 non-experts) were investigated. Mechanical properties obtained from KES-FB system were compared with the each dimension of subjective hand expression. The type of fiber and construction were considered to be important factors in affecting hand assessment of Korean consumers, however, the presence and type of seam were not considered to be important. There were certain characteristics of subjective hand attributes for each dress style. Surface properties of fabrics, even though it is not strictly mechanical properties, appeared to be the most effective dimension in the developement of new products which appeal to Korean conssumers.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.386-392
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• 2008

The purpose of this study is to clarify playground types by characteristics of playground environment in child care facilities, to analyze the needs and estimation of users according to playground types. The subjects of this study were care-givers, who assist outdoor play activities of children and manage safety in playground, to estimate adequateness of playground's environment to children's outdoor plays and to report needs. The data were collected by field measurement survey for clarification playground environments in 21 child care facilities and structured-questionnaire for estimation and needs of 181 care-givers in them. The major results showed the following. 1) The playgrounds were clarified to five type according to number of child and size of playground. The five types include A-type as large-scale facility/small-size playground, B-type as small-scale facility/large-size playground, C-type as small-scale facility/small-size playground, D-type as middle-scale facility/large-size playground, and E-type as large-scale facility/large-size playground. 2) The adequateness of playground environment of D-type were estimate higher than others. C-type were estimated lower than other types in size and outdoor play areas organization of playground. 3) The care-givers in D-type and E-type wanted to install various play equipments, but the care-giver in C-type didn't wanted to install play equipment. 4) The various outdoor play areas were needed in D-type.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2002.11a
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• pp.295-300
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• 2002

Since the contents of large-scale repair of a condominium were various, a plan document was not prepared. The owners association of the condominium has given priority to decision-making of price priority over quality. Examination is not performed about the contents of the construction supervision business, which checks whether suitable construction is performed, either. On the other hand, the know-how for builders, such as decision of the process plan under which the repair work lessens influence to the safety and life as much as possible since the place where the resident is living turns into a construction site, and selection of a method of construction, is just going to ask. It is an important subject how the structure of the construction contractor selection, which considered quality, is built. Then, this research focuses on large-scale repair construction of the condominium, and arranges the actual condition of a series of processes from plan document creation to construction supervision. The method of research collects the construction documents of the condominium that carried out Barge-scale repair construction. Next, collection arrangement of the data of construction builder selection is carried out. The method of the construction builder selection of those other than a construction price is examined. The method of quality control of large-scale repair construction is examined.