• Journal of Communications and Networks
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• v.11 no.3
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• pp.261-270
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• 2009

We propose a tree-based integration of infrastructure networks and MANETs (TUM) to efficiently extend the scope of mobile Internet protocol to mobile ad hoc networks and devise a tree-based routing protocol (TBRP) that is suitable for the TUM architecture. Infrastructure networks have a number of fixed Internet Gateways that connect two heterogeneous networks. Mobile nodes form a number of small trees named pMANETs, each of them growing from anchor node which can communicate directly with an Internet Gateway. A new node registers with foreign agent and home agent along the tree path without resorting to an inefficient flooding. Furthermore, the TBRP sets up a routing path efficiently by exploiting the tree information without relying on flooding. We show by resorting to simulation that our approach is competitive against the conventional AODV based approach.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.2
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• pp.151-164
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• 2016

In this paper, we deal with a risk analysis for an IPS (Integrated power system) and propose a simulation model combining the fault tree and event tree in order to estimate the system availability and risk level, together. Firstly, the basic information such as operational scenarios, physical structure, safety systems is explained in order to make the fault tree and event tree of the IPS. Next, we propose a discrete-event simulation model using a next-event time advance technique to advance the simulation time. Also the state transition and activity diagrams are explained to represent the relationship between the objects. By numerical examples, the redundancy allocation is considered in order to decrease the risk level of the IPS.

• Journal of Information Technology and Architecture
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• v.9 no.1
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• pp.11-19
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• 2012

Generally, a suffix tree is an efficient data structure since it reveals the detailed internal structures of given sequences within linear time. However, it is difficult to implement a suffix tree for a large number of sequences because of memory size constraints. Therefore, in order to compare multi-mega base genomic sequence sets using suffix trees, there is a need to re-construct the suffix tree algorithms. We introduce a new method for constructing a suffix tree on secondary storage of a large number of sequences. Our algorithm divides three files, in a designated sequence, into parts, storing references to the locations of edges in hash tables. To execute experiments, we used 1,300,000 sequences around 300Mbyte in EST to generate a suffix tree on disk.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.217-219
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• 2001

이동 기기의 발달로 이동 객체의 위치 정보에 대한 연구가 진행되고 있다. 그러나 시공간 데이타베이스에서 요구하는 질의를 효과적으로 처리하기 위한 인덱스 구조는 많지 않다. 사용자는 먼저 범위 질의를 던져 이동 객체를 뽑아낸 후 궤적 질의를 던지게 되는데 이것을 결합 질의라 한다. 기존 방법인 TB-tree는 MBR의 겹침이 심해 성능이 저하된다. 본 논문에서는 결합 질의를 효과적으로 처리할 수 있는 CR-tree 인덱스 구조를 제안한다. CR-tree는 R-tree와 연곁노드로 구성된다. R-tree 부분은 MBR의 겹침을 최소화해 범위 질의를 효과적으로 처리하고 연결 노드 부분은 이동 객체별로 궤적의 부분을 차례로 저장해서 궤적 질의를 빠르게 저리한다. 즉 결합 질의시 R-tree를 이용해 범위에 속하는 이동 객체를 검색하고 연결 노드를 이용해 그 객체의 궤적을 찾는다.

• Journal of Korean Society of Forest Science
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• v.86 no.2
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• pp.158-166
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• 1997

This study presents the method to quantify the stand structure diversity or homogeneity. Gadow's dbh differentiation(Durchmesserdifferenzierung) is introduced which quantifies the horizontal stand structure by the ratio of the dbh between subject tree and neighbour trees. And new stand structure diversity index based on Lorenz curve, which is made by ratio of tree number and basal area or volume by dbh class, is presented. The horizontal stand structure index based on Lorenz curve has a value from 0 to 1 as Gadow's index, and approximates to 1 if the stand structure has high diversity. In the comparative analysis for performance, the new stand structure index based on Lorenz curve is considered to compare with the Gadow's index for describing the stand structure.

• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.924-942
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• 2005

Recently, large-scale directories have been developed for LINUX cluster file systems to store and retrieve huge amount of data. One of them, GFS directory, has attracted much attention because it is based on extendible hashing, one of dynamic hashing techniques, to support fast access to files. One distinctive feature of the GFS directory is the flat structure where all the leaf nodes are located at the same level of the tree. Hut one disadvantage of the mode structure is that the height of the mode tree has to be increased to make the tree flat after a byte is inserted to a full tree which cannot accommodate it. Thus, one byte addition makes the height of the whole mode tree grow, and each data block of the new tree needs one more link access than the old one. Another dynamic hashing technique which can be used for directories is linear hashing and a couple of researches have shown that it can get better performance at file access times than extendible hashing. [n this research, we have designed and implemented an extendible hashing directory and a linear hashing directory for large-scale LINUX cluster file systems and have compared performance between them. We have used the semi-flat structure which is known to have better access performance than the flat structure. According to the results of the performance evaluation, the linear hashing directory has shown slightly better performance at file inserts and accesses in most cases, whereas the extendible hashing directory is somewhat better at space utilization.

• Journal of Korea Spatial Information System Society
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• v.10 no.3
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• pp.1-18
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• 2008

Because we can usually get many information through analyzing trajectories of moving objects on spatial networks, efficient trajectory index structures are required to achieve good retrieval performance on their trajectories. However, there has been little research on trajectory index structures for spatial networks such as FNR-tree and MON-tree. Also, because FNR-tree and MON-tree store the segment unit of moving objects, they can't support the trajectory of whole moving objects. In this paper, we propose an efficient trajectory index structures based on signatures on a spatial network, named SigMO-Tree. For this, we divide moving object data into spatial and temporal attributes, and design an index structure which supports not only range query but trajectory query by preserving the whole trajectory of moving objects. In addition, we divide user queries into trajectory query based on spatio-temporal area and similar-tralectory query, and propose query processing algorithms to support them. The algorithm uses a signature file in order to retrieve candidate trajectories efficiently Finally, we show from our performance analysis that our trajectory index structure outperforms the existing index structures like FNR-Tree and MON-Tree.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.4
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• pp.15-29
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• 2021

Urban green spaces offer a variety of benefits to living things and humans. However, existing green spaces have been reduced and fragmented due to urbanization, and there is a limit to creating new large green spaces in densely developed cities. Street trees have fewer restrictions on land use, which can be a measure to secure green areas in cities. In Korea, excessive pruning is being done on some street trees for reasons such as blocking of building signboards, contact with electric wires, and restrictions on sidewalk widths. Therefore, it is necessary to quantitatively understand the relationship between the benefits provided by street trees and their structures to come up with an efficient and systematic planning and management plan for urban street trees. In this study, we quantitatively analyzed the relationship between the thermal comfort improvement by the shades of street trees and the vertical structure, planting environment, and types of street trees. To calculate the thermal comfort felt by human body, we calculated UTCI (Universal Thermal Climate Index) of each street tree. For the vertical structure of street trees, we used Terrestrial LiDAR and the point clouds of street tree's crown was sliced vertically at 1m intervals. We conducted a multiple regression analysis on the thermal comfort improvement using the variables we obtained from fields. As a result, in the case of a street tree's vertical structure, the lager the volume of tree's crown located 3-4m (β=0.298, p<.05) and 6-7m (β=0.568, p<.001) above clear length, the better the cooling effect. In addition, the thermal comfort improvement was assessed to decrease as the DBH increased (β=-0.435, p<.001). In general, the crown diameter and DBH are positively correlated, with a cooling effect occurring as crown diameter increases. In this study, the opposite result was obtained due to the small number of trees measured, so additional research is needed by increasing the number of tree samples. In the case of the planting environment, the effect of improving thermal comfort was higher in the shaded area of trees planted to the south (β=-0.541, p<.001). Since unsystematic management of street trees can deteriorate the function of them, quantitative evaluations of the vertical structure of street trees are required, which can provide specific measures for planning and management of urban street trees with thermal comfort effect.

• Journal of KIISE
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• v.41 no.10
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• pp.792-798
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• 2014

In spatial databases, R-tree is one of the most widely used indexing structures and many variants have been proposed for its performance improvement. Among these variants, Hilbert R-tree is a representative method using Hilbert curve to process large amounts of data without high cost split techniques to construct the R-tree. This Hilbert R-tree, however, is hardly applicable to large-scale applications in practice mainly due to high pre-processing costs and slow bulk-load time. To overcome the limitations of Hilbert R-tree, we propose a novel approach for parallelizing Hilbert mapping and thus accelerating bulk-loading of Hilbert R-tree on GPU memory. Hilbert R-tree based on GPU improves bulk-loading performance by applying the inversed-cell method and exploiting parallelism for packing the R-tree structure. Our experimental results show that the proposed scheme is up to 45 times faster compared to the traditional CPU-based bulk-loading schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.18-28
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• 2004

Efficient hardware implementation of address lookup is one of the most important design issues of internet routers. Address lookup significantly impacts router performance since routers need to process tens-to-hundred millions of packets per second in real time. In this paper, we propose a practical IP address lookup structure based on the binary tree of prefixes of different lengths. The proposed structure produces multiple balanced trees, and hence it solve the issues due to the unbalanced binary prefix tree of the existing scheme. The proposed structure is implemented using pipelined binary search combined with a small size TCAM. Performance evaluation results show that the proposed architecture requires a 2000-entry TCAM and total 245 kbyte SRAMs to store about 30,000 prefix samples from MAE-WEST router, and an address lookup is achieved by a single memory access. The proposed scheme scales very well with both of large databases and longer addresses as in IPv6.