• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.505-513
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• 2017

In this study, we collected 200,578,703 geo-tweets and removed the twitter bots. Using the concept of activity radius, Twitter users are classified. Users are also divided first into domestic and overseas, and again domestic ones are divided into locals and non-locals. Statistical characteristics of activity strength and active area of Twitter users are described according to activity radius and home region, and the geographical distribution is presented visually. Through a case study of Las Vegas, we have identified the difference in activity strength and active area by the user's home residence. We expect to derive theories about human mobility by analyzing various cities with the method proposed in this study.

• Journal of the Korean Geographical Society
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• v.48 no.6
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• pp.897-913
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• 2013

The main purpose of the paper is to examine the spatial characteristics of school choice through residential mobility by conducting a correlation analysis on the relationships between the middle schools' entrance rates to special high schools and the elementary schools' net transfer rates. Analyses are done at both the individual school level and the school catchment area level. Prior to the calculation, the two variables involved in the correlation analysis are transformed via a standardization equation, and the standardized scores are mapped and explored. Both the global and local correlation analyses are done for the standardized variables. Main findings are twofold. First, the global correlation analysis reports that there exists a statistically significant correlation between the two variables at both the analytical levels. Second, albeit the prominent positive correlation at the global level, the local analysis reveals the existence of a considerable level of spatial heterogeneity in terms of bivariate association. While several school catchment areas with very high local correlation coefficients (the HH association type) are popped up, other areas with various types of bivariate association including ones even opposite to the global trend are also observed.

• Journal of the Economic Geographical Society of Korea
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• v.19 no.4
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• pp.729-742
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• 2016

Socio-economic polarization in Korea partly due to recent globalization and industrial restructuring could reduce social mobility significantly through passing down educational achievement to one's children. Under the notion that residential segregation is geographical frame for the reproduction of educational inequality, this research investigates residential segregation by educational attainment and neighborhood disparity with a case study of Seoul. The statistical analyses employed local segregation measures such as Location Quotient and Local Moran's I and a variety of variables that reflect neighborhood characteristics. As a result, it found that there are sharp and clear contracts between low- and high-educational group concentrations/clusters particularly in terms of housing characteristics and educational facilities. This results provide some evidences that support the arguments about the causes of residential segregation by class in Korean Cities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.781-785
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• 2004

Mobile IP maintains Internet connectivity while Mobile Hosts moving from one Internet attachment point to another. However, Mobile If is not appropriate for seamless mobility. Some micromobility protocols were proposed to complement Mobile IP by offering fast and seamless handoff control in limited geographical areas. In this paper, a new scheme, based on path prediction and resource reservation, is proposed to reduce the handoff latency by trying to eliminate the link setup time for fast handoff in all-IP wireless networks. Analytical results show that the proposed scheme offers shorter handoff delay and can improve the handoff efficiency.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1529-1532
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• 2004

A Mobile Ad Hoc NETwork (MANET) is a collection of wireless mobile nodes that forms a temporary network without the need for any existing network infrastructure or centralized administration. Therefore, such a network is designed to operate in a highly dynamic environment due to node mobility. In mobile ad hoc network, frequent topological changes cause routing a challenging problem and without the complete view of the network topology, establishing the shortest path from the source node to the destination node is difficult. In this paper, we suggest a routing approach which utilizes location information to setup the shortest possible path between the source node and the destination node. Location information is obtained through Global Positioning System (GPS) and this geographical coordinate information of the destination node is used by the source node and intermediate nodes receiving route request messages to determine the shortest path to the destination from current node.

• Journal of KIISE:Databases
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• v.27 no.1
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• pp.53-63
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• 2000

The mobile computing service market is increasing rapidly due to the development of low-cost wireless network technology and the high-performance mobile computing devices. In recent years, several methods have been proposed to effectively deal with restrictions of the mobile computing environment such as limited bandwidth, frequent disconnection and short-lived batteries. Amongst those methods, much study is being done on the caching method - among the data transmitted from a mobile support station, it selects those that are likely to be accessed in the near future and stores them in the local cache of a mobile host. Existing cache replacement methods have some limitations in efficiency because they do not take into consideration the characteristics of user mobility and spatial attributes of geographical data. In this paper, we show that the value and the semantic of the data, which are stored in the cache of a mobile host, changes according to the movement of the mobile host. We argue it is because data that are geographically near are better suited to provide an answer to a users query in the mobile environment. Also, we define spatial location of geographical data has effect on, using the spatial attributes of data. Finally, we propose two new cache replacement methods that efficiently support user mobility and spatial attributes of data. One is based on the location of data and the other on the meaningful region of data. From the comparative analysis of the previous methods and that they improve the cache hit ratio. Also we show that performance varies according to data density using this, we argue different cache replacement methods are required for regions with varying density of data.

• Journal of the Korean Geographical Society
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• v.44 no.6
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• pp.813-832
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• 2009

As accessibility to health-care service in less populated rural areas is geographically limited and demand for public health-care by the aging is increasing, a new approach for health-care service such as a home care service is becoming more popular. For a home care service, health-care personnels directly visit to location of health-care clients. Such changes in provision of health services require developing innovative and scientific approaches for efficient allocation of health resources and managing services by public health-care organizations. The purpose of this study is to formulate a location model for visiting health-care districting for the rural elderly and to develop an Automated Zoning Procedure (AZP) to solve this model. Mobility, workload balance and contiguity criteria are considered in the model. Three different objective functions are evaluated; 1) minimizing the sum of network distance between the unit areas in a district, 2) maximizing spatial interaction between the unit areas in a district, and 3) minimizing tour distance that visits each unit area exactly once in a district. The AZP for solving the model is developed and applied to a rural area. The application results demonstrate that the AZP can generate different districting systems for each objective functions.

• Tunnel and Underground Space
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• v.34 no.1
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• pp.1-14
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• 2024

An image-reconstruction technology, involving the deployment of an unmanned mobility equipped with high-speed LiDAR (Light Detection And Ranging) has been proposed to reconstruct the shape of abandoned mine. Unmanned mobility operation is remarkably useful in abandoned mines fraught with operational difficulties including, but not limited to, obstacles, sludge, underwater and narrow tunnel with the diameter of 1.5 m or more. For cases of real abandoned mines, quadruped robots, quadcopter drones and underwater drones are respectively deployed on land, air, and water-filled sites. In addition to the advantage of scanning the abandoned mines with 2D solid-state lidar sensors, rotation of radiation at an inclination angle offers an increased efficiency for simultaneous reconstruction of mineshaft shapes and detecting obstacles. Sensor and robot posture were used for computing rotation matrices that helped compute geographical coordinates of the solid-state lidar data. Next, the quadruped robot scanned the actual site to reconstruct tunnel shape. Lastly, the optimal elements necessary to increase utility in actual fields were found and proposed.

• Journal of the Economic Geographical Society of Korea
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• v.6 no.1
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• pp.145-170
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• 2003

Since 1980's, the opportunities of higher education have increased absolutely to the extent worrying of over-education. The over-education means that job-seekers having a bachelor degree flow into job market much more than necessary and the problem of unemployment and under-employment becomes more serious. These changes in the labor market can affect the university selection behaviors of high school graduates. This study aims to reveal the impacts of over-education in Chungbuk, a periphery region, Korea. As expected, many of college graduates flow down into jobs asking school years less than higher education. On the other hand, high school graduates have an tendency of choosing a college, especially a college in center region, other than universities in Chungbuk, to expect more stable and rewarding job in income and upward mobility after the graduation of higher education. As the result of this, a regional university district, which means most of students in the region enter college within region limit, is getting broken into more smaller districts, a kind of local district. It can be thought as a sign that the dominance of regional center is weakening and more cities in the region receive a direct affects from center region, not through regional center.

• Journal of the Korean Geographical Society
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• v.32 no.2
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• pp.245-263
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• 1997

Housing market is segmented through 1) housing supply classified by housing characteristics and 2) housing demand classified by different housing opportunity of household. Moreover, neighborhood plays a role in intensifying housing market segmentation as a factor affecting on decision making relevant to housing supply and demand. while segmented housing markets have different mechanism, existing studies on residential differentiation and housing market have overlooked the characteristic differences among housing submarkets as the studies presume metropolitan housing market to be a single housing market. while the concept of 'residential differentiation' pays much attention on spatial pattern after the ecological approach appeared, the concept of ‘housing submarkets' is explanatory of the process of urban space structure formation. Analysis on housing submarkets makes up for the weak points of the behavioral approach inquiring into socio-economic constraint and different housing opportunity of household.