• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.2
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• pp.1-10
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• 2016

In this paper, we present a new way to derive the mean cycle time of the G/G/m failure prone queue when the loading of the system approaches to zero. The loading is the relative ratio of the arrival rate to the service rate multiplied by the number of servers. The system with low loading means the busy fraction of the system is low. The queueing system with low loading can be found in the semiconductor manufacturing process. Cluster tools in semiconductor manufacturing need a setup whenever the types of two successive lots are different. To setup a cluster tool, all wafers of preceding lot should be removed. Then, the waiting time of the next lot is zero excluding the setup time. This kind of situation can be regarded as the system with low loading. By employing absorbing Markov chain model and renewal theory, we propose a new way to derive the exact mean cycle time. In addition, using the proposed method, we present the cycle times of other types of queueing systems. For a queueing model with phase type service time distribution, we can obtain a two dimensional Markov chain model, which leads us to calculate the exact cycle time. The results also can be applied to a queueing model with batch arrivals. Our results can be employed to test the accuracy of existing or newly developed approximation methods. Furthermore, we provide intuitive interpretations to the results regarding the expected waiting time. The intuitive interpretations can be used to understand logically the characteristics of systems with low loading.

• Horticultural Science & Technology
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• v.35 no.2
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• pp.220-231
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• 2017

Grafting using a pumpkin (Cucurbita sp.) rootstock is an effective way to improve cucumber (Cucumis sativus) resistance to a combination of chilling and salinity stresses. We evaluated the tolerance of 15 pumpkin cultivars to chilling, salinity, and combined stresses at the germination and seedling stages. Selected plant characteristics, including germination rate, germination potential, germination index, plant height, stem thickness, fresh weight, and dry weight, were analyzed. We used the unweighted pair group method with arithmetic mean for cluster analyses to determine the stress tolerance levels of the pumpkin cultivars. The 15 cultivars were divided into three clusters: tolerant, moderately tolerant, and susceptible to stress treatments. The stress tolerances of all cultivars were variable in the germination and seedling stages, and most cultivars were not tolerant to individual treatments of chilling or salinity stresses at both stages. These results suggest that identifying suitable cultivars for use as rootstock during cucumber grafting should involve the evaluation of stress tolerance during different growth stages. Additionally, cultivars tolerant to chilling stress may not be tolerant to salinity stress; therefore, the choice of pumpkin rootstock should depend on where the grafted plant will be grown. Cultivars tolerant to a combination of chilling and salinity stresses may be useful as rootstock for cucumber grafting. Our findings may serve as reference material for choosing appropriate pumpkin rootstocks for cucumber grafting.

• Convergence Security Journal
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• v.13 no.3
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• pp.33-38
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• 2013

Security between mobile nodes and efficient communication is one of the most important parts of the MANET. In particular, the wireless network is significantly higher for the attack threats because of collaborative structure for open communication media and communication. However, application of existing security mechanisms and intrusion detection system is not easy due to the characteristics of MANET. It is because collection and integration of adult data by the dynamic topology due to the mobility of nodes and many network sensors is difficult. In this study, we propose cooperative security system technique that can improve the reliability based on authentication assessing confidence about the whole nodes which joins to network and detect effectively this when intrusion occurs. Cluster head which manages the cluster performs CA role for the certificate issue and the gateway node performs role of intrusion detection system. Intrusion detection is performed by cooperating with neighboring nodes when attack is not detected in one intrusion detection node. The performance of the proposed method was confirmed through experiments comparing with the SRP technique.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.368-374
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• 2015

On the basis of vegetation data by point quarter sampling method, the natural forest of Jirisan(Mt.) was classified into eight forest types by cluster analysis. They were Quercus mogolica forest type, Fraxinus mandshurica - Betula costata forest type, Mixed mesophytic forest type, Abies koreana forest type, Carpinus laxiflora forest type, Quercus serrata forest type, Pinus densiflora forest type, and Quercus variabilis forest type. Then, succession index was estimated for each forest type so as to evaluate succession process comparatively among forest types. The results showed that Carpinus laxiflora forest type had highest succession index of 219.7, followed by Mixed mesophytic forest type with little difference of the index of 218.3. Pinus densiflora forest type had lowest index. Succession indices were hardly correlated with species diversity indices of forest types. We presumed that the higher value of succession index a forest type had, the closer toward the climax forest. However, the estimated index was not supposed to be absolute level of successional stage, but it could play a role of comparative assessment in the position of the seral stage among forest types.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.405-420
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• 2006

This study was conducted to understand the change of spatial environmental factors including populations, air pollution source and land-use in Busan, during the period of 1995 and 2004. Firstly, the grids (5 km $\times$ 5 km) were divided using the TM coordinates of Busan and the statistical data of populations and land-use were marked on each grid during studying period. Secondly, the SO$_2$, NO$_2$ and O$_3$ concentrations of areas where air quality monitoring station was not established were estimated on the basis of these air pollutants measured at close air quality monitoring station by kriging method. In order to understand spatial change of air pollution and to investigate duplication and reduction of existing stations, semivariogram, correlation and cluster analysis were carried out. This study showed that the population increased in 2004 only on 8 grids compared to in 1995. The spatial change of SO$_2$, NO$_2$ and O$_3$ was investigated by semivariogram in Busan area. As the results of semivariogram, the spatial change of 502 become smaller and simpler, while that of NO2,03 become larger and more complex in 2004 than in 1995, According to the result of correlation and cluster analysis, the reduction of measurement item or the relocation of air quality monitoring station can be needed in the high dense grid area.

• Korean Journal of Materials Research
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• v.27 no.5
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• pp.276-280
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• 2017

This study was carried out to evaluate the developed microstructures and mechanical properties of friction welded A6063 alloy. For this work, specimens were prepared at a size of 12 mm ${\O}{\times}80mm$, and friction welding was carried out at a rotation speed of 2,000 RPM, friction pressure of $12kgf/cm^2$ and upset pressure of $25kgf/cm^2$. To perform an analysis of the grain boundary characteristic distributions, such as the grain size, orientation and misorientation angle distributions, the electron back-scattering diffraction method was used. In addition, in order to identify the dispersed intermetallic compounds of the base and welded materials, transmission electron microscopy was used. The experimental results found that the application of friction welding on A6063 led to significant grain refinement of the welded zone relative to that of the base material. Besides this, intermetallic compounds such as AlMnSi and $Al_2Cu$ were found to be dispersed with more refined size relative to that of the base material. This formation retains the mechanical properties of the welds, which results in the fracture aspect at the base material zone. Therefore, based on the developed microstructures and mechanical properties, the application of friction welding on A6063 could be used to obtain a sound weld zone.

• Korean Journal of Medicinal Crop Science
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• v.19 no.1
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• pp.24-30
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• 2011

This text was analyzed and investigated the vegetation and floristic composition by cluster analysis and classification of phytosociological method, to evaluate the species composition, habitat environment and community structure of Liriope platyphylla and Liriope spicata group in Korea. The southeast slope gradient of the habitat of L. platyphylla and L. spicata was 6.7 to 8.4%, and the habitat altitude of L. platyphylla (41.0 m), L. spicata (114.9 m) was different. Habitat distribution of L. spicata was broader than L. platyphylla. Appearing plants of L. platyphylla and L. spicata group was 58 taxa, 99 taxa, respectively, and Coverage of tree layer was 87.5%, 92.5% respectively. In genus Liriope group, the highest appearing frequency of plant grow in the moist valley as Quercus serrata. Thus, plants of genus Liriope growth was better in moist shade. The vegetation of L. platyphylla group was classified into Quercus serrata community, Castanopsis sieboldii community, Pinus densiflora community and Pinus thunbergii community, and the Liriope spicata group was classified into Quercus serrata community, Quercus alien community, Quercus acutissima community, Prunus verecunda community, Robinia pseudoacacia community, Pinus densiflora community and Pinus thunbergii community. In genus Liriope group, Quercus serrata and Pinus densiflora communities was the closest the similarities.

• Journal of the Korean Institute of Landscape Architecture
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• v.25 no.4
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• pp.1-17
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• 1998

Most of the tourist resort facilities in our country cannot be used in the winter season, and only a few spa resorts and sky resorts are available in the winter. To ameliorate this problem, various types of winter resort facilities have been constructed since 1970s and the massive development of winter resort facilities changed the resort market from a seller's market to a buyer's market. There has been however,few researches on marketing strategies for winter resorts, and there is a growing need for a rational method to maximize tourists' satisfaction and developers'profit at the same time. This research aims to develop a positining strategy to engance the marketability of winter resorts by classifying the resort market with the self-image types of users, and by analyzing the structure of the market, users' preferences, and locational factors. A survey was conducted with cases of Yong-Pyung resort, Mu-Ju resort, Alps resort, Bears resort, Back-Am spa resort, Su-An-Bo spa resort, and I-Chon spa resort. A list of questions in five categories -- similarity, characteristics, preferences, self-image, and personal characteristics of the respondents -- was constructed and tested. Among the 750 copies of questionnaire distributed, 700 were returned by only 378 were analyzed after screening missing or reckless answers. The statistical analysis of the data were conducted using techniques of correlation analysis, frequency analysis, factor analysis. Factor analysis and cluster analysis were used to group the cluster of self-image and a discriminant analysis were used to confirm this classification. The demographical characteristics were identified by frequency analysis, and resorts attributes were analyzed by oneway ANOVA analysis. Multidimensional scaling methods such as KYST, PROFIT, and PREFMAP were used for the positioning strategy.

• Journal of KIISE
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• v.45 no.3
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• pp.224-233
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• 2018

Recently, there are many of studies on SWRL reasoning engine based on user-defined rules in a distributed environment using a large-scale ontology. Unlike the schema based axiom rules, efficient inference orders cannot be defined in SWRL rules. There is also a large volumet of network shuffled data produced by unnecessary iterative processes. To solve these problems, in this study, we propose a method that uses Map-Reduce algorithm and distributed in-memory framework to deduce multiple rules simultaneously and minimizes the volume data shuffling occurring between distributed machines in the cluster. For the experiment, we use WiseKB ontology composed of 200 million triples and 36 user-defined rules. We found that the proposed reasoner makes inferences in 16 minutes and is 2.7 times faster than previous reasoning systems that used LUBM benchmark dataset.

• Journal of Korean Society for Geospatial Information Science
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• v.4 no.2 s.8
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• pp.181-193
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• 1996

A new technique for land cover classification which applies digital image pre-classified by unsupervised classification technique, clustering, to Canonical Correlation Analysis(CCA) was proposed in this paper. Compared with maximum likelihood classification, the proposed technique had a good flexibility in selecting training areas. This implies that any selected position of training areas has few effects on classification results. Land cover of each cluster designated by CCA after clustering is able to be used as prior information for maximum likelihood classification. In case that the same training areas are used, accuracy of classification using Canonical Correlation Analysis after cluster analysis is better than that of maximum likelihood classification. Therefore, a new technique proposed in this study will be able to be put to practical use. Moreover this will play an important role in the construction of GIS database