• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.127-138
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• 1994

The application of fault tree technique to the analysis of compressor failure is considered. The techniques involve the decomposition of the system into a form of fault tree where certain basic events lead to a specified top event which signifies the total failure of the system. In this paper, fault trees are made by using fault train of screw type air compressor failure. The fault trees are used to obtain minimal cut sets from the modes of system failure and, hence the system failure rate for the top event can be calculated. The method of constructing fault trees and the subsequent estimation of reliability of the system is illustrated through compressor failure. It is proved that FTA is efficient to investigate the compressor failure modes and diagnose system.

• Journal of Information Processing Systems
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• v.17 no.1
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• pp.37-50
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• 2021

Query applications based on nested data, the most commonly used form of data representation on the web, especially precise query, is becoming more extensively used. MapReduce, a distributed architecture with parallel computing power, provides a good solution for big data processing. However, in practical application, query requests are usually concurrent, which causes bottlenecks in server processing. To solve this problem, this paper first combines a column storage structure and an inverted index to build index for nested data on MapReduce. On this basis, this paper puts forward an optimization strategy which combines query execution service tree and frequent sub-query trajectory to reduce the response time of frequent queries and further improve the efficiency of multi-user concurrent queries on large scale nested data. Experiments show that this method greatly improves the efficiency of nested data query.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.210-211
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• 2022

Pruning is the most important work for the growth and aesthetics of street trees. It is also the most actively conducted maintenance work. However, the specifications, application methods, and cost criteria for pruning have not been systematically established. This has recently caused a lot of confusion in the practice of street tree pruning, such as indiscriminate pruning and lack of construction costs. Therefore, this study clarified the contents of work according to the form of pruning. It added 'aesthetic pruning,' which takes into account design. In addition, It revised equipment not in conformity with the law and excluded personnel necessary for on-site traffic control so that they could be reflected separately. As a result, this study is expected to contribute a lot to securing appropriate construction costs for maintaining street trees.

• Journal of IKEEE
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• v.24 no.2
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• pp.372-377
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• 2020

This paper is based on the triangular inset patch antenna as the basic structure, and the array structure is the twin tree form to improve the antenna's main lobe gain and reduce the side lobe gain. A twin tree structure was implemented by placing two identical trees of 2-4-6 arrays of triangular inset patches side by side. The parametric analysis confirmed that the gap between tree structures arranged side by side is most effective for impedance matching. The fabricated antenna has a gain of 16.74 dBi at 24.15 GHz, and the beam width of the main lobe is 22° in the E-plane and 6° in the H-plane. The antenna size was 125 mm × 50 mm, and a Taconic TLC substrate with a dielectric constant of 3.2 was used. Although the main lobe gain is improved over the twin tree structure, The directivity in the beam pattern due to the mutual interference of the two tree array structure can be improved.

• Journal of KIISE:Software and Applications
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• v.32 no.12
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• pp.1178-1191
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• 2005

In this paper, we propose a synthesis method of software fault tree from software requirements specification written in NuSCR formal specification language. The software fault tree, proposed in this paper, reflects requirements on both structure and behavior and it is an integrated form. The software fault tree can be used for analyzing safety in the view of structure and behavior. We propose templates for each components in NuSCR specification language and a synthesis method of software fault tree using the templates. The research was applied into the main trip logic of the reactor protection system of ARP1400, the Korean next generation nuclear reactor system, developed by KNICS. And we evaluate feasibility of our approach through this case study.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.119-130
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• 2012

In this paper, we propose ubiquitous tree management system based on GIS and smart-phone using the object-oriented design modeling to maximize the efficiency of tree management. For this, proposed system is implemented in the form of client/server (C/S). The spot tree management system as the client is based on the mobile(PDA, Smart-Phone), whereas the tree management system based on PC as the server makes use of GIS. Also, Web service method instead of CDMA used in exist studies is used for tree data communication among C/S. And problems of existing studies, that is excessive maintenance costs, accessibility shortage of variety users, connectivity shortage of geographic information system will be settled through the convergence of the proposed system development methods, GIS system, smart devices. Therefore, we verify proposed system by using the systemic unit test and qualitative assessment respectively and prove to be more excellent than the existing system based on the mobile, in terms of systemic effectiveness and extendability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.24-35
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• 2008

We propose a tree-based integrated network of infrastructure network and mobile ad hoc network to effectively support Mobile IP for mobile ad hoc networks and also proposed a network management protocol for formation and management of the integrated network and a tree-based routing protocol suitable for the integrated network. The integrated network has fixed gateways(IGs) that connect two hybrid networks and the mobile nodes in the network form a small sized trees based on the mobile nodes that are in the communication distance with a IG. A new node joins an arbitrary tree and is registered with its HA and FA along tree path. In addition, the proposed protocol establishes a route efficiently by using the tree information managed in every node. We examined the effectiveness of the tree-based integrated network for some possible network deployment scenarios and compared our routing protocol against the Mobile IP supported AODV protocol.

• Journal of Korean Society of Forest Science
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• v.96 no.2
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• pp.160-169
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• 2007

The data used to develop distance-independent individual models for natural mixed forests were collected from 712 remeasured permanent sample plots (25,526 trees) of 10-year periodic from 1990 to 2000 in Baihe Forest Bureau of Changbai Mountains, northeast China. Based on analyzing relationship between diameter increment of individual trees with tree size, competitive status, and site condition, the diameter growth models for individual trees of 15 species growing in mixed-species uneven-aged forest stands, that have simple form, good predicting precision, and easily applicable, were developed using stepwise regression method. The main variables influencing on diameter increment of individual trees were tree size and competition, however, the site conditions were not significantly related with diameter increment. The tree size variables (lnDBH and $DBH^2$) were the most significant and important predictors of diameter growth existing in all 15 growth models. The diameter increment was directly proportional to tree diameter for each species. For the competitive factors in growth model, the relative diameter (RD), canopy closure (P), and the ratio of diameter of subject tree with maximum diameter (DDM) were contributed to the diameter increment at a certain extent. Other measures of stand density, such as basal area of stand (G) and stand density index (SDI), were not significantly influenced on diameter increment. Site factors, such as site index, slope and aspect were not important to diameter increment and excluded in the final models. The total variance explained by the final models of squared diameter increment ($R^2$) for all 15 species ranged from 35% to 72% and these results compared quit closely with those of Wykoff (1990) for mixed conifer stands. Using independent data set, validation measures were evaluated for predicting models of diameter increment developed in this study. The result indicated that the estimated precision was all greater than 94% and the models were suitable to describe diameter increment.

• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.49-60
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• 2021

This study presents a methodology to estimate two distinct fractal dimensions of natural river basin by using fractal tree concept. To this end, an analysis is performed on fractal features of a complete drainage network which consists of all possible drainage paths within a river basin based on the growth process of fractal tree. The growth process of fractal tree would occur only within the limited drainage paths possessing stream flow features in a river basin. In the case of small river basin, the bifurcation process of network is more sensitive to the growth step of fractal tree than the meandering process of stream segment, so that various bifurcation structures could be generated in a single network. Therefore, fractal dimension of network structure for small river basin should be estimated in the form of a range not a single figure. Furthermore, the network structures with fractal tree from this study might be more useful information than stream networks from a topographic or digital map for analysis of drainage structure on small river basin.

• Journal of Korean Society of Forest Science
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• v.70 no.1
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• pp.28-37
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• 1985

In order to estimate breast-height form factors of Pinus thunbergii and Cryptomeria japonica, 8 models based on tree age, diameter at breast height and tree height were suggested and evaluated. It was the following equations that turned out to be most fit for estimating them; for Pinus thunbergii, $F=0.553-4.567\;1/A+71.409\;1/A^2$ ($R^2=0.928$), based on tree age, ($6.727^{**}$) ($14.100^{**}$) $F=0.356+1.774\;1/D-0.770\;1/D^2$ ($R^2=0.944$), based on diameter at breast height, ($15.102^{**}$) ($2.908^{**}$) $F=0.316+1.546\;1/H+0.397\;1/H^2$ ($R^2=0.941$), based on tree height, ($8.380^{**}$) ($3.896^{**}$) for Cryptomeria japonica, $F=0.400+2.348\;1/A+17.053\;1/A^2$ ($R^2=0.889$), based on tree age, ($3.501^{**}$) ($3.298^{**}$) $F=0.353+2.118\;1/D-1.462\;1/D^2$ ($R^2=0.923$), based on diameter at breast height, ($14.873^{**}$) ($3.545^{**}$) $F=0.403+0.427\;1/H+2.843\;1/H^2$ ($R^2=0.887$), based on tree height. ($3.254^{**}$) ($5.742^{**}$) The above estimated breast-height form factors proved to be overestimated for young trees and small diameter trees, and to be underestimated for old trees and large diameter trees, in comparison to generally accepted figure in Korea, that is, the form factor of 0.45.