• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.171-183
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• 2007

Urban transport demand is derived from activity participation. A variety of individual daily activities based on the decisions on activity participation result in collective spatial behavior. The travel derived from the effort to overcome the spatially distributed locations of adjacent activities represents the detailed structural relationships among activities. An activity-based approach provides an important framework of analyzing contemporary urban daily life in the sense that it studies the interaction between individuals' daily decision making and social practice in time and space, on the one hand, and socio-spatial environment on the other. The current study identifies representative patterns of urban daily activity implementations and analyzes the correlation between representative patterns and individuals' characteristics and contextual characteristics. The study shows that urban daily activity patterns can be grouped in a limited number of representative patterns, which are systematically correlated with socio-spatial characteristics. The results provide related transportation policy implications.

• 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 Digital Convergence
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• v.14 no.2
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• pp.227-233
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• 2016

Typical Web-based learning system is operating the variety of learning contents. However, it is not easy to efficiently select appropriate learning contents. In this paper, we propose a learning content delivery method that can provide the most suitable preferences and feedback to the learner. By analyzing the profile of the learner, it determines the positive feedback and evaluation to be provided to the learner. The result of applying learning techniques were applied to provide the best learning content to adaptively out the form. The proposed method appears as a learning experience and learning outcomes are higher after a study was conducted to suggest that could help in the learning progress of the students themselves. This paper are applied to real learners. And the learners using the system were surveyed by the questionnaire on learning experience and learning outcomes were analyzed.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.6
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• pp.65-76
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• 2007

The P2P file sharing system sends the results to users by searching the files in the shared folders. In the process of it, the problem is that the transferred information includes the pathname and file information and it can be revealed who searches which files. In related to this problem, anonymous file sharing P2P protocol has been an active research area where a number of works have been produced. However, the previous studies still have a few of weakness. Therefore, We propose two anonymous P2P file sharing protocols based on the decentralized and unstructured Random Walk. The first scheme uses the dynamic onion routing where the requester can receive the wanted file without knowing other peers' IDs. The second scheme uses the IP multicast method which lowers the computational overhead. Both of them are more suited for the dynamic P2P system.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.13-24
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• 2006

A site investigation has been performed for bridge abutments constructed on soft ground, which are deformed laterally by backfill. As the result from the evaluation of lateral movement in bridge abutment, the foundation piles were not considered as the passive pile at the design stage and the period for soft ground improvement was not proper. In order to prevent lateral movement of bridge abutment, the pile slab is proposed as a countermeasure. This method can effectively prevent the lateral flow of soft ground, since the overburden surcharge due to backfill on soft ground would be effectively delivered to bedrock through the piles in soft ground. The instrumentation system is designed and installed to investigate the behavior of bridge abutment on soft ground reinforced by pile slab. The instrumentation results show that pile slab effectively resists to the lateral movement of bridge abutment due to backfill. Also, the surcharge loads due to backfill are transmitted to the bedrock through piles. It confirms that the pile slab effectively resists to the lateral movement of bridge abutment due to backfill and the applied design method is reasonable.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.71-81
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• 2008

Wall displacements caused by earth pressure, rainfalls, rise in ground water level, inappropriate deep excavation and structural defects of the wall may produce differential settlements to existing buildings, which often result in damages and/or collapses of the building structures. In this case, measures to protect the walls and nearby structures would be required. One of the recent measures to reduce differential settlements and protecting walls is to reinforce the ground using micro-piles. In this study physical model tests were carried out to evaluate the performance of the micro-pile method. It is revealed that reduction of the settlement was maximized when the length of micro-pile is twice of the foundation width, distance between piles is twice of the pile diameter and the distance to wall is one tenth of the foundation width. Based on the test results some design recommendations were made.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.93-102
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• 2023

Despite recent modifications to building structural standards emphasizing the seismic stability of building foundations, the current design focus remains solely on vertical support, resulting in insufficient consideration of horizontal loads during earthquakes. In this study, we evaluated the dynamic behavior of inclined tripod micropiles (ITMP), which provide additional seismic resistance against horizontal and vertical loads during earthquakes. A comparison of the dynamic characteristics, such as acceleration, displacement, bending moment, and axial force, of ITMP with a 15° installation angle and normal vertical micropiles with a 0° installation angle was performed using dynamic centrifuge model tests. Results show that under moderate seismic loads, the proposed ITMP exhibited lower acceleration responses than the vertical micropiles. However, when subjected to a long-period strong seismic excitation, such as sine (2 Hz), ITMP showed greater responses than the vertical micropiles in terms of acceleration and settlement. These results indicate that the use of ITMP reduces the amplif ication of short-period (high-f requency) contents compared with the use of vertical micropiles. Therefore, ITMP can be used to enhance seismic performance of structures.

• 한국노년학
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• v.40 no.4
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• pp.781-800
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• 2020

This study aims to categorize the daily time use of older adults into different types, examine the factors influencing them and the differences between them by type, and verify the effect of each type on life satisfaction. From the 6th wave of the Korea Retirement and Income Study (KeRIS), analysis was conducted on 3,963 older adults aged 65 (n=3,963). Using Latent Profile Analysis (LPA), three types of daily time use for older adults were identified: basic life maintenance type (16%), free-leisure oriented type (26%), and social activity type (58%). From the results of multinomial logistic regression analysis to identify the factors influencing each type of daily time use, it was found that the main factors influencing free-leisure oriented type, when compared with basic life maintenance type, were the presence of spouse (p<.01) and psychological health status (p<.001). The main factors influencing social activity type, when compared with basic life maintenance type, were age (p<.05), economic activity (p<.001), and chronic disease (p<.001). The life satisfaction seen during free-leisure oriented time and social activity time was higher than that during basic life maintenance time. From these findings, practical and policy proposals were suggested to improve life satisfaction of older adults during basic life maintenance time by pursuing changes in the use of that time.

• Journal of the Society of Disaster Information
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• v.8 no.2
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• pp.138-147
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• 2012

In this paper, the various parametric study of collisions between a offshore wind tower and vessels were performed to estimate the ultimate behaviors of the bucket foundation and the tower. Additionally, the stability of the foundation and the energy dissipation capacities of the tower were analyzed. The results shows that the collision energy of the vessel was mainly dissipated by the plastic deformation energy of the tower and the foundation system shown enough bearing capacity against to this severe loading condition.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.15-25
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• 2008

A soft ground improvement method is used for structures which are constructed on soft ground to decrease settlement and Increase bearing capacity. The Floating Base Plate has been developed for such purposes. In this study, the load-settlement characteristics were investigated by numerical analysis on various Floating Base Plate shapes to select an optimum shape, different from the conventional shape. The selected optimum shape was used to perform plate bearing test and numerical simulations. It was found that the Floating Base Plate is very effective In reducing the settlement and increasing the bearing capacity.