• Journal of the Korean Mathematical Society
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• v.56 no.2
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• pp.475-484
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• 2019

We study the set of critical exponents of discrete groups acting on regular trees. We prove that for every real number ${\delta}$ between 0 and ${\frac{1}{2}}\;{\log}\;q$, there is a discrete subgroup ${\Gamma}$ acting without inversion on a (q+1)-regular tree whose critical exponent is equal to ${\delta}$. Explicit construction of edge-indexed graphs corresponding to a quotient graph of groups are given.

• Journal of Environmental Impact Assessment
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• v.30 no.3
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• pp.155-163
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• 2021

The number of trees to be removed trees (ART) in the environmental impact assessment is an environmental indicator used in various parts such as greenhouse gas emissions and waste of forest trees calculation. Until now, the ART has depended on the forest tree density of the vegetation survey, and the uncertainty of estimating the amount of removed trees has increased due to the sampling bias. A full-scale survey can be offered as an alternative to improve the accuracy of ART, but the reality is that it is impossible. As an alternative, there is an individual tree detection using aerial image (ITD), and in this study, we compared the ARTs estimated by full-scale survey, sample survey, and ITD. According to the research results, compared to the result of full-scale survey, the result of ITD was overestimated by 25. While 58 were overestimated by the sample survey (average). However, as the sample survey is an estimate based on random samples, ART will be overestimated or underestimated depending on the number and size of quadrats.

• Journal of Practical Agriculture & Fisheries Research
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• v.12 no.1
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• pp.3-10
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• 2010

In order to promote the growth of the trees, it is the most important to fertilize efficiently. The organic nutrient "Green-one" which list public notification number 08-organic-3-112" was registered in Rural Development Administration. The "Green-one" is the environment friendly organic nutrient with new concept which is used in planting and maintenance of the trees. The "Green-one" makes the tree grow actively. Also it has a function of the anti germ and sustainable fertilizer effect. In conclusion, "Green-one" promoted the growth of P. thunbergii excellently. Expecially the growth of the root increased. The concentration of "Green-one" dilution was more better 100 times than 300 times in trees grow. This research can apply with the test of fertilizer efficiency in landscape trees.

• Bulletin of the Korean Mathematical Society
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• v.52 no.3
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• pp.955-962
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• 2015

It has been established that the role played by complete graphs in graph theory is similar to the role Dowling group geometries and Projective geometries play in matroid theory. In this paper, we introduce a notion of H-tree, a class of representable matroids which play a similar role to trees in graph theory. Then we give some properties of H-trees such that when q = 0, then the results reduce to the known properties of trees in graph theory. Finally we give explicit expressions of the characteristic polynomials of H-trees, H-cycles, H-fans and H-wheels.

• Communications of the Korean Mathematical Society
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• v.11 no.4
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• pp.1159-1174
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• 1996

The spectrum of the Laplacian matrix of a graph gives an information of the structure of the graph. For example, the product of non-zero eigenvalues of the characteristic polynomial of the Laplacian matrix of a graph with n vertices is n times of the number of spanning trees of that graph. The characteristic polynomial of the Laplacian matrix of a graph tells us the number of spanning trees and the connectivity of given graph. in this paper, we compute the characteristic polynomial of the Laplacian matrix of a graph bundle when its voltage lie in an abelian subgroup of the full automorphism group of the fibre; in particular, the automorphism group of the fibre is abelian. Also we study a relation between the characteristic polynomial of the Laplacian matrix of a graph G and that of the Laplacian matrix of a graph bundle over G. Some applications are also discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.10
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• pp.4007-4024
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• 2020

It is tremendously important to construct decision trees to use as a tool for knowledge representation from a given decision table. However, the usual algorithms may split the decision table based on each value, which is not efficient for numerical attributes. The methodology of this paper is to split the given decision table into binary groups as like the CART algorithm, that uses binary split to work for both categorical and numerical attributes. The difference is that it uses split for each attribute established by the directed acyclic graph in a dynamic programming fashion whereas, the CART uses binary split among all considered attributes in a greedy fashion. The aim of this paper is to study the effect of binary splits in comparison with each value splits when building the decision trees. Such effect can be studied by comparing the number of nodes, local and global misclassification rate among the constructed decision trees based on three proposed algorithms.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.4
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• pp.265-271
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• 2015

This study proposes an algorithm for recognizing apple trees in images and detecting apples to measure the number of apples on the trees. The proposed algorithm explores whether there are apple trees or not based on the number of image block-unit edges, and then it detects apple areas. In order to extract colors appropriate for apple areas, the CIE $L^*a^*b^*$ color space is used. In order to extract apple characteristics strong against illumination changes, modified census transform (MCT) is used. Then, using the AdaBoost learning algorithm, characteristics data on the apples are learned and generated. With the generated data, the detection of apple areas is made. The proposed algorithm has a higher detection rate than existing pixel-based image processing algorithms and minimizes false detection.

• Honam Mathematical Journal
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• v.39 no.4
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• pp.493-501
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• 2017

In this paper, we define and enumerate two tree-like hypergraph structures which we call them (d, k)-trees and d-trees, where $d{\geq}2$ and k > 0 are integers. These new definitions generalize traditional and HP-hypertrees.

• Journal of the Korean Mathematical Society
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• v.54 no.3
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• pp.987-997
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• 2017

A deterministic model for the spread of pine wilt disease with asymptomatic carrier trees in the host pine population is designed and rigorously analyzed. We have taken four different classes for the trees, namely susceptible, exposed, asymptomatic carrier and infected, and two different classes for the vector population, namely susceptible and infected. A complete global analysis of the model is given, which reveals that the global dynamics of the disease is completely determined by the associated basic reproduction number, denoted by $\mathcal{R}_0$. If $\mathcal{R}_0$ is less than one, the disease-free equilibrium is globally asymptotically stable, and in such a case, the endemic equilibrium does not exist. If $\mathcal{R}_0$ is greater than one, the disease persists and the unique endemic equilibrium is globally asymptotically stable.

• Journal of Environmental Impact Assessment
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• v.19 no.3
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• pp.231-245
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• 2010

The the purpose of this study was to analyze of the vegetation structure and phytosociological changes in the area adjacent to GeumJeong Mountain Fortress for fifteen years. The result of this study was as follows; Of the 8 quadrates, site of the North Gate 2 was having a highest in the number of extinct trees, 15 kinds. This is probably due to trampling effect caused by climbers' steps. Site of the West Gate 1 and South gate 1 each had 8 kinds of extinct trees, respectively. The number of newly appeared trees was highest at site of the North Gate 1, (8 kinds) followed by the sites of South gate 1 and South gate 2, respectively (5 kinds). The highest decrease in number of tree species was observed in North Gate 1, therefore, there is a strong relationship between vegetation diversity and the number of users of the available spaces. In order to revitalize the unstable vegetation structure of the Area Adjacent to GeumJeong Mountain Fortress, Robinia pseudo-acacia has to be well maintained in the shrub tree layer, and vines, such as Smilax china, Humulus japonicus, and Pueraria thungergiana, should be removed. To recover natural vegetation, dead leaf layer should be protected, and more shrub trees need to be planted. In the understory and shrub tree layer, multi layer tree planting is highly recommended to recover natural vegetation and increase tree diversity. In order to improve bad soil condition caused by trampling effect of recreational users, special treatments to the soil structure are required, such as mulching and raking soil. Also, depending on its soil damage from users trampling, the areas in the park should be divided into usable areas and user limited areas by the sabbatical year system. To improve the soil acidity due to acidic rain, soil buffering ability should be improved by activating microorganisms in the soil by using lime and organic material.