• The KIPS Transactions:PartC
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• v.14C no.6
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• pp.519-524
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• 2007

One of the most important issues on the sensor network with resource limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long lived sensor network is the clustering mechanism which can be further classified into the single hop mode and the multi hop mode. The single hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head(CH) via single hop md, in the multi hop mode, sensor nodes communicate with the CH with the help of other Intermediate nodes. One of the most critical factors that impact on the performance of the existing multi hop clustering mechanism is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non uniformly, the fixed size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic size multi hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed size clustering mechanisms by carrying out numerical analysis and simulations.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.12a
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• pp.121-129
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• 1999

When continuous media are transmitted over the communication networks, asynchrony which can not maintain temporal relationships among packets may occur due to a random transit delay. There exist two types of synchronization schemes ; for guaranteed or non-guaranteed resource networks. The former which applies a resource reservation technique maintains delay characteristics, however, the latter supply a best-effort service. In this paper, I propose a intra-media synchronization scheme to transmit continuous media on general networks not guaranteeing a bounded delay tome. The scheme controls transmission times of the packets by estimating next delay time with the delay distribution. So, the arriving packets may be maintained within a limited delay boundary, and playout will be performed after buffering to smoothen small delay variations. The continually increasing delay due to network overload causes buffer underflow at the receiver. To solve it, the transmitter is required to speed up instantaneously. Too much increase of transmission-rate may cause network congestion. At that time, the transmitter drops the current packet when informed excessive delay from the receiver.

• Journal of Navigation and Port Research
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• v.30 no.1 s.107
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• pp.9-15
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• 2006

At the adjacent sea area of Busan Central Wharf, a variety of vessels, such as middle-large passenger ships, small hugh speed crafts, container ships, cargo ships and working boats as well as small miscellaneous vessels are freely sailing comparatively without special rules and marine traffic control. In this research, we analyzed traffic stream and navigational characteristics cf main traffic route based on statistics and distribution of tracks by ship's type and tonnage cf the passing vessels after conducting marine traffic survey twice using exclusive software. We examined the traffic safety of the passing vessels by classifying the sea area by each function based on the analysis about this traffic situation, and analyzing the effect by designating 'Inner passage'. We also studied the plan for the effective rearrangement cf Central Wharf considering basically the traffic safety of arrival and departure in a point of view of navigators.

• Journal of KIISE:Databases
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• v.37 no.1
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• pp.1-11
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• 2010

Recently, there has been a growing interest in the processing of continuous queries over multiple data streams. When the arrival rates of tuples exceed the memory capacity of the system, a load shedding technique is used to avoid the system becoming overloaded by dropping some subset of input tuples. In this paper, we propose an effective load shedding algorithm for multi-way windowed joins over multiple data streams. Most previous load shedding algorithms estimate the productivity of each tuple, i.e., the number of join output tuples produced by the tuple, based on its "join attribute value" and drop tuples with the lowest productivity. However, the productivity of a tuple cannot be accurately estimated from its join attribute value when the join attribute values are unique and do not repeat, or the distribution of the join attribute values changes over time. For these cases, we estimate the productivity of a tuple based on its "arrival order" on data streams, rather than its join attribute value. The proposed method can effectively estimate the productivity of a tuple even when the productivity of a tuple cannot be accurately estimated from its join attribute value. Through extensive experiments and analysis, we show that our proposed method outperforms the previous methods in terms of effectiveness and efficiency.

• Journal of Global Scholars of Marketing Science
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• v.8
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• pp.61-87
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• 2001

Internet, which has been developed as a new exchange revolution, forms a huge virtual exchange market, and the innovative electronic commerce has completely broken off the way of existing goods distribution. This study begins with an awareness of the importance of customer retention to keep winning over the competition in internet shopping mall. In order to explain of the customer retention between individual and internet shopping mall, the study introduces first a satisfaction on shopping followed by an awareness of the importance of customer retention, and looks into a formation process of trust, satisfaction, and relationship orientation occurred by the offer of valuable convenience to customers. The study also explores the influence on shopping value by the characteristics with which internet shopping mall can bear, unfold by a cause and effect relationship the degree of shopping satisfaction, trust, and relationship orientation, and inquires a question to find out how to fuse the characteristics for internet retention. Therefore, this study has the following purposes: After examining prior research for the characteristics of internet shopping mall, it presents a possibility to connect shopping value with customer retention in light of theoretical system on characteristic elements derived from emotional and utilitarian perspectives. In order to achieve the purposes, the characteristics of internet retailing shop included site design, virtual reality, web awareness, customer concern, merchandise search, information supply, product value, and transaction system. Hypotheses were set up for the relationship with these characteristics and substantially analyzed. To prove this research, we analyzed collected data in which customers had experienced in shopping at internet shopping mall and discussed strategic current issues about its analytic results.

• Korean Journal of Health Education and Promotion
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• v.16 no.1
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• pp.149-166
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• 1999

Self-care and the performance of their own role might be important for the prevention of complications and improvement of quality of life in hemodialysis patients with chronic renal failure(CRF). To improve well-being and quality of life for the patients, the author estimated the level of self-care and associating factors through a questionnaire. The information was composed of the knowledge for hemodialysis and renal disease, the level of self-care, health belief, supports from the family, disease-related stresses, personal characteristics, medical history, relationships with medical personnel, etc. The data was gathered from 126 hemodialysis patients who were undergoing hemodialysis in one university hospital and five hospitals in Kyungsangnam-Do area from December 1997 to January 1998, and was analyzed by PC SAS program(version 6.12) with the level of significance($\alpha$=0.05). The mean age of subjects was 47.0$\pm$13.5years with no significant difference in gender distribution. The mean duration of hemodialysis was 39.0 months, and their frequencies of hemodialysis were more than three times per week(77.0%). Only 21.4% had the specific education on hemodialysis and CRF. In the level which was expressed as the score out of 100, the mean of knowledge was 90.7$\pm$9.1 and the mean of self-care was 73.9$\pm$12.7, that means, they only partially carried their knowledge into practice. They showed a significant correlation between knowledge and health belief($\gamma$=0.282); self-care and health belief($\gamma$=0.357), family supports and knowledge($\gamma$=0.221), self-care($\gamma$=0.402), health belief($\gamma$=0.431); and health belief and stress($\gamma$=-0.361). Age, religion, marrital status, education, and relationships with medical personnel showed positive correlations, and smoking showed negative correlation with self-care. In the multiple regression with the level of self-care as dependent variable, and each of the characeristics as independent variables, supports from the family($\beta$=6.615=0.158), the experience of disease specific education($\beta$=4.959), relationships with medical personnel($\beta$=6.615), current smoking($\beta$=-6.986), and current drinking ($\beta$=-7.095) were detected as significant factors. The value of R-square was 34%. In summary, to promote the level self-care and to improve the well beings and Quality of life for the hemodialysis patients, it would be emphasized that they terminate smoking and drinking, and it would be recommended that the education programs and supports from the family be strengthened. And, because there was a considerable difference between the level of knowledge and self-care, it would also be emphasized to propose the education programs which focused on execution. In addition to that, there is a need to improve relationships between the patients and medical personnel through positive changes in the attitudes of the medical personnel.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.5
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• pp.423-432
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• 2004

In coastal area of Inchon, dredging and the disposal of dredged material for sea-wall construction and reclamation have increased in recent years. These activities may impact the benthic environment and result in changes in benthic communities, but little information is available on the extent and direction of these changes. We investigated whether there have been changes in the dominant macrobenthic species and benthic community over the last decade, and explored the relationship between environmental variables and spatial patterns of macrobenthic community structure. We sampled macrobenthos and recorded environmental variables in the coastal habitats of Inchon in March and June 2004. In total, 212 macrobenthic species were recorded during this study, predominately crustaceans $(34{\%})$, mollusks $(32{\%})$ and polychaetes $(21{\%})$. The mean density of macrobenthos was $1,393\;ind./m^{2}$.The most abundant species was Amphioplus japonicus $(20.5{\%})$, followed by Heteromastus filiformis $(14.4{\%})$, Theora fragilis $(8.2{\%})$ and Ampharete sp. $(4.0{\%})$. Over the past decade the dominant macrobenthic species in this area shifted. Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among three regions: the middle part of the sampling area (B), site 8 (C) and other sites (A). Mean density varied significantly among the three regions, but no differences in the number of species and diversity (H') were observed. The distribution of the macrobenthic community was affected by environmental variables such as percentage sand content and sediment kurtosis. Species that were important in different areas included A. japonicus in region A, Raeta puchella in region B and T. fragilis in region C. The important species in regions B and C were filter-feeding bivalves, and the abundance of these species may be related to the increase in percentage sand content. We suggest that the sediment composition (percentage sand content) may be an important factor in determining the dominant species and structure of the macrobenthic communities in coastal Inchon. Long-term monitoring programs are necessary to understand ongoing changes in the benthic communities of this area.

• Journal of the Korea Convergence Society
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• v.6 no.4
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• pp.139-146
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• 2015

WSN has been utilized in various directions from basic infrastructure of environment composition to business models including corporate inventory, production and distribution management. However, as energy organizations' private information, which should be protected safely, has been integrated with ICT such as WSN to be informatization, it is placed at potential risk of leaking out with ease. Accordingly, it is time to need secure sensor node deployment strategies for stable enterprise business. Establishment of fragmentary security enhancement strategies without considering energy organizations' security status has a great effect on energy organizations' business sustainability in the event of a security accident. However, most of the existing security level evaluation models for diagnosing energy organizations' security use technology-centered measurement methods, and there are very insufficient studies on managerial and environmental factors. Therefore, this study would like to diagnose energy organizations' security and to look into how to accordingly establish strategies for planning secure sensor node deployment strategies.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.5
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• pp.67-79
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• 2020

Plans to mitigate overheating in urban areas requires the identification of the characteristics of the thermal environment of the city. The key information is the distribution of higher and lower temperatures (referred to as "hotspot" or "coldspot", respectively) in the city. This study aims to identify the areas within Jeonju City that are suffering from increasing land surface temperatures (LST) and the factors linked to such this phenomenon. To identify the hot and cold spots, Local Moran's I and Getis-Ord Gi^* were calculated for the LST based on 2017 images taken using the thermal band of the Landsat 8 satellite. Hotspot analysis revealed that hotspot regions, (the areas with a high concentration of Land Surface Temperature) are located in the old town area and in industrial districts. To figure out the factors linked to the hotspots, a correlation analysis, and a regression analysis taking into account environmental covariates including Normalized Difference Vegetation Index (NDVI) and land cover. The values of NDVI showed that it had the strongest effect on the lowering LSTs. The results of this study are expected to provide directions for urban thermal environment designing and policy development to mitigate the urban heat island effect in the future.

• The KIPS Transactions:PartD
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• v.9D no.5
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• pp.755-768
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• 2002

We investigate the effect of the data skew of join attributes on the performance of a pipelined multi-way hash join method, and propose two new hash join methods with load balancing capabilities. The first proposed method allocates buckets statically by round-robin fashion, and the second one allocates buckets adaptively via a frequency distribution. Using hash-based joins, multiple joins can be pipelined so that the early results from a join, before the whole join is completed, are sent to the next join processing without staying on disks. Unless the pipelining execution of multiple hash joins includes some load balancing mechanisms, the skew effect can severely deteriorate system performance. In this paper, we derive an execution model of the pipeline segment and a cost model, and develop a simulator for the study. As shown by our simulation with a wide range of parameters, join selectivities and sizes of relations deteriorate the system performance as the degree of data skew is larger. But the proposed method using a large number of buckets and a tuning technique can offer substantial robustness against a wide range of skew conditions.