• Journal of Korean Society of Transportation
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• v.26 no.4
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• pp.135-147
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• 2008

One of the efforts both to prevent urban sprawling development patterns and to promote use of public transportation is known as Transit-Oriented Development (TOD), including such planning elements as the density and diversity of land use and pedestrian-friendly urban design around a transit center. The aim of this study is thus to conduct impact analyses of TOD planning elements on transit ridership in the Seoul rail station areas. First, the authors investigate and draw out various actual elements of TOD planning by using GIS-based data and Smart Card data. Then the authors analyze impacts of TOD planning elements on transit ridership for the Seoul rail station areas. After condensing 34 variables presumably influencing transit ridership into seven factors by using factor analyses, the study utilizes multiple regression modeling methods to identify their impacts on transit ridership. The analysis results demonstrate that transit ridership tends to increase more in rail station areas where there is a non-residential high density, mixed use of land and narrow and small-size road network patterns. The implementation of TODs should be a useful method in inducing a Transit-Oriented City through redevelopment and new development.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.1-8
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• 2016

Current indoor intrusion detection and location tracking methods have the weakness in seamless operations in tracking the objective because the object must possess a communicating device and the limitation of the single cell size (approximate $100cm{\times}100cm$) exits. Also, the utilization of CCTV technologies show the shortcomings in tracking when the object disappear the area where the CCTV is not installed or illumination is not enough for capturing the scene (e.g. where the context-awarded system is not installed or low illumination presents). Therefore, in this paper we present an improved in-door tracking system based on sensor networks. Such system is built on a simulated scenario and enables us to detect and extend the area of surveillance as well as actively responding the emergency situation. Through simulated studies, we have demonstrated that the proposed system is capable of supplementing the shortcomings of signal cutting, and of estimating the location of the moving object. We expect the study will improve the better analysis of the intruder behavior, the more effective prevention and flexible response to various emergency situations.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.117-128
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• 2002

Virtual LAN (VLAN) is an architecture to enable communication between end stations as if they were on the same LAN regardless of their physical locations. VLAN defines a limited broadcast domain to reduce the bandwidth waste. The Newbridge Inc. developed a layer 3 VLAN product called VIVID, which configures a VLAN based on W subnet addresses. In a VIVID system, a single route server is deployed for address resolution, VLAN configuration, and data broadcasting to a VLAN. If the size of the network, over which the VLANS supported by the VIVID system spans, becomes larger, this single route server could become a bottleneck point of the system performance. One possible approach to cope with this problem is to deploy multiple route servers. We propose two architectures, organic and independent, to expand the original VIVID system to deploy multiple route servers. A course of simulations are done to analyze the performance of each architecture that we propose. The simulation results show that the performances of the proposed architectures depend on the lengths of VLAN broadcasting sessions and the number of broadcast data frames generated by a session. It has also been shown that there are tradeoffs between the scalability of the architecture and their efficiency in data transmissions.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.6
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• pp.683-690
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• 2006

Reducing power consumption to extend network lifetime is one of the most important challenges in designing wireless sensor networks. One promising approach to conserving system energy is to keep only a minimal number of sensors active and put others into low-powered sleep mode, while the active sensors can maintain a connected covet set for the target area. The problem of computing such minimum working sensor set is NP-hard. In this paper, a centralized Voronoi tessellation (CVT) based approximate algorithm is proposed to construct the near optimal cover set. When sensor's communication radius is at least twice of its sensing radius, the covet set is connected at the same time; In case of sensor's communication radius is smaller than twice of its sensing radius, a connection scheme is proposed to calculate the assistant nodes needed for constructing the connectivity of the cover set. Finally, the performance of the proposed algorithm is evaluated through theoretical analysis and extensive numerical experiments. Experimental results show that the proposed algorithm outperforms the greedy algorithm in terms of the runtime and the size of the constructed connected cover set.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.671-676
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• 2014

Based on the data of PSC information management system of MOF(Ministry of oceans and fisheries) and APCIS(Asia-Pacific Computerized Information System) of Tokyo-MOU information system, the result of the evaluation on the reality of PSC was done, and base on 2009, it showed a trend of decrease in every DFR(Deficiency Rate) and DTR(Detention Rate). But for vessels built for more than 30 years, flags of convenience vessels, RO-RO ferry and general cargo vessel, small size vessels with gross tonnage less than 1,000 ton showed a high DFR and DTR. Each harbours is classified by the total harbours' average DFR which was 82.5 % and the average DTR was 5.1 %, excluding the Jeju harbour, showing a hugh deviation for classification of each harbour. Classification of each harbour has to be inspected by PSC and it showed a great unbalance of the number of vessels for each territory for inspection. the biggest problem with our country's PSC, where it was pointed out by the PSCO was lack of workers and independent inspection by just one worker. To strength the substantiality of the inspection of our country is to have concentrated inspection on the high risk cautious vessels, forming a human network each classified by four different sectors of the area, recalculating the amount of assignment of inspection classified by each harbour and securing workforce the PSCO improvements are necessary.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1285-1294
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• 2021

In recent years, as rainfall is concentrated and rainfall intensity increases worldwide due to climate change, the scale of flood damage is increasing. Rainfall of a previously unobserved magnitude falls, and the rainy season lasts for a long time on record. In particular, these damages are concentrated in ASEAN countries, and at least 20 million people among ASEAN countries are affected by frequent flooding due to recent sea level rise, typhoons and torrential rain. Korea supports the domestic flood warning system to ASEAN countries through various ODA projects, but the communication network is unstable, so there is a limit to the central control method alone. Therefore, in this study, an artificial intelligence-based flood prediction model was developed to develop an observation station that can observe water level and rainfall, and even predict and warn floods at once at one observation station. Training, validation and testing were carried out for 0.5, 1, 2, 3, and 6 hours of lead time using the rainfall and water level observation data in 10-minute units from 2009 to 2020 at Junjukbi-bridge station of Seolma stream. LSTM was applied to artificial intelligence algorithm. As a result of the study, it showed excellent results in model fit and error for all lead time. In the case of a short arrival time due to a small watershed and a large watershed slope such as Seolma stream, a lead time of 1 hour will show very good prediction results. In addition, it is expected that a longer lead time is possible depending on the size and slope of the watershed.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.7
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• pp.191-198
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• 2021

Since the size of training dataset become large and the model is getting deeper to achieve high accuracy in deep learning, the deep neural network training requires a lot of computation and it takes too much time with a single node. Therefore, distributed deep learning is proposed to reduce the training time by distributing computation across multiple nodes. In this study, we propose hybrid allreduce strategy that considers the characteristics of each layer and communication and computational overlapping technique for synchronization of distributed deep learning. Since the convolution layer has fewer parameters than the fully-connected layer as well as it is located at the upper, only short overlapping time is allowed. Thus, butterfly allreduce is used to synchronize the convolution layer. On the other hand, fully-connecter layer is synchronized using ring all-reduce. The empirical experiment results on PyTorch with our proposed scheme shows that the proposed method reduced the training time by up to 33% compared to the baseline PyTorch.

• International Area Studies Review
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• v.18 no.3
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• pp.47-66
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• 2014

A noticeable aspect of Korean firms' outward sequential FDIs to China is that they occur sequentially, which means that they implement the outward FDIs to China with a long-term perspective. To analyze the strategic advantages of sequential investment, we introduce Cournot type quantity competition model. According to the model, three important implications are derived. First, sequential FDIs enhances the Korean parents' production capabilities. Second, the parents are more likely to establish new Chinese subsidiaries as they stay longer in China. Third, the production effect of sequential investments incurs more sequential investments. Some regression models are tested for verifying the predictions. According to empirical results, three important results are found. First, initial entry mode affects the size expansion of the Korean parents. Second, the longer the duration of intial subsidiary in China, the more the sequential investment will be. Third, sequential investments are positively associated with the productivity of the Korean parents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.551-563
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• 2019

This study examined the characteristics of a district through the concept of a block system in the physical aspect of the four land readjustment project districts of Cheongju City in the 1970s. The results of this study are as follows. First, the local road system for accessing the main road network and blocks was well established compared with the current urban development standards. On the other hand, since the access roads to the individual lots in the block were not equipped properly, it was difficult to improve a house. Second, according to the characteristics of the block, the Aspect Ratio of blocks was 1: 2 on average and most of those directions was east-west. The area of block from the 1st to 3rd districts was increasing, but districts 4 were decreasing. This also was changed to the shape of a contemporary block system. The larger the size of the block area, the lower the Jeobdoyul. Third, in terms of the characteristics of the lot array, blocks with a multi-row system of $4{\times}4$ or more were lots up to the 1st to 3rd district, but 4th district was improved greatly. Because blocks close a square shape have become excessively poor with Jeobdoyul, it was judged that it is difficult to improve the residential environment. Moreover, as the type of the residential development by the land readjustment project is standardized considerably and this type of land area is extensive, it can be an alternative to control the urban sprawl of suburbs if it finds the way to improve this type of the residential area considering this characteristic.

• Journal of Internet Computing and Services
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• v.20 no.3
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• pp.43-59
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• 2019

Today, with the spread of smartphones and the development of social networking services, structured and unstructured big data have stored exponentially. If we analyze them well, we will get useful information to be able to predict data for the future. Large amounts of data need to be collected first in order to analyze big data. The web is repository where these data are most stored. However, because the data size is large, there are also many data that have information that is not needed as much as there are data that have useful information. This has made it important to collect data efficiently, where data with unnecessary information is filtered and only collected data with useful information. Web crawlers cannot download all pages due to some constraints such as network bandwidth, operational time, and data storage. This is why we should avoid visiting many pages that are not relevant to what we want and download only important pages as soon as possible. This paper seeks to help resolve the above issues. First, We introduce basic web-crawling algorithms. For each algorithm, the time-complexity and pros and cons are described, and compared and analyzed. Next, we introduce the state-of-the-art web crawling algorithms that have improved the shortcomings of the basic web crawling algorithms. In addition, recent research trends show that the web crawling algorithms with special purposes such as collecting sentiment words are actively studied. We will one of the introduce Sentiment-aware web crawling techniques that is a proactive web crawling technique as a study of web crawling algorithms with special purpose. The result showed that the larger the data are, the higher the performance is and the more space is saved.