• 한국정밀공학회지
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• 제14권7호
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• pp.49-58
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• 1997

In process planning for pocket machining, the selection of tool size, tool path, overlap distance, and the calculation of machining time are very important factors to obtain the optimal process planning result. Among those factors, the tool size is the most important one because the others depend on tool size. And also, it is not easy to determine the optimal tool size even though the shape of pocket is simple. Therefore, the optimal selection of tool size is the most essential task in process planning for machining a pocket. This paper presents a method for selecting optimal toos in pocket machining. The branch and bound method is applied to select the optimal tools which minimize the machining time by using the range of feasible tools and the breadth-first search.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2023년도 춘계학술발표대회
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• pp.427-429
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• 2023

인공지능 기술의 발전에 따라 유체 시뮬레이션 분야에서는 복잡한 액체의 흐름을 모사하기 위해 기계학습 기술이 많이 활용되고 있다. 이러한 시뮬레이션에서 성능 향상의 가장 중요한 요소는 학습 데이터다. 이 논문에서는 기계학습 기반 유체 시뮬레이션의 학습 데이터 생성 단계 중 기존의 방법보다 효율적으로 비말(splash) 탐색하는 방법을 제안한다. 기존 방법에서는 CPU 환경에서 큐(queue)를 이용하는 너비우선탐색(breadth first search) 기법을 사용하기 때문에 처리속도가 느리다. 반면에 제안하는 기법에서는 배열로 되어 있는 해시 테이블(hash table)을 이용해 충돌 문제를 해결해 GPU 환경에서 비말을 신속하게 검출하도록 하기 때문에 빠른 학습 데이터 생성이 가능하도록 했다. 이 알고리즘의 유효성을 확인하기 위하여 정확성과 수행시간을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권6호
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• pp.612-627
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• 2009

The high-level contribution of this paper is to illustrate the effectiveness of using graph theory tree traversal algorithms (pre-order, in-order and post-order traversals) to generate the chain of sensor nodes in the classical Power Efficient-Gathering in Sensor Information Systems (PEGASIS) data aggregation protocol for wireless sensor networks. We first construct an undirected minimum-weight spanning tree (ud-MST) on a complete sensor network graph, wherein the weight of each edge is the Euclidean distance between the constituent nodes of the edge. A Breadth-First-Search of the ud-MST, starting with the node located closest to the center of the network, is now conducted to iteratively construct a rooted directed minimum-weight spanning tree (rd-MST). The three tree traversal algorithms are then executed on the rd-MST and the node sequence resulting from each of the traversals is used as the chain of nodes for the PEGASIS protocol. Simulation studies on PEGASIS conducted for both TDMA and CDMA systems illustrate that using the chain of nodes generated from the tree traversal algorithms, the node lifetime can improve as large as by 19%-30% and at the same time, the energy loss per node can be 19%-35% lower than that obtained with the currently used distance-based greedy heuristic.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1643-1660
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• 2016

Connectivity and trust in social networks have been exploited to propose applications on top of these networks, including routing, Sybil defenses, and anonymous communication systems. In these networks, and for such applications, connectivity ensures good performance of applications while trust is assumed to always hold, so as collaboration and good behavior are always guaranteed. In this paper, we study the impact of differential behavior of users on performance in typical social network-enabled routing applications. We classify users into either collaborative or rational (probabilistically collaborative) and study the impact of this classification and the associated behavior of users on the performance of such applications, including random walk-based routing, shortest path based routing, breadth-first-search based routing, and Dijkstra routing. By experimenting with real-world social network traces, we make several interesting observations. First, we show that some of the existing social graphs have high routing costs, demonstrating poor structure that prevents their use in such applications. Second, we study the factors that make probabilistically collaborative nodes important for the performance of the routing protocol within the entire network and demonstrate that the importance of these nodes stems from their topological features rather than their percentage of all the nodes within the network.

• Journal of Information Processing Systems
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• 제16권1호
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• pp.201-209
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• 2020

The graph data structure is popular because it can intuitively represent real-world knowledge. Graph databases have attracted attention in academia and industry because they can be used to maintain graph data and allow users to mine knowledge. Mining reachability relationships between two nodes in a graph, termed reachability query processing, is an important functionality of graph databases. Online traversals, such as the breadth-first and depth-first search, are inefficient in processing reachability queries when dealing with large-scale graphs. Labeling schemes have been proposed to overcome these disadvantages. The state-of-the-art is the 2-hop labeling scheme: each node has in and out labels containing reachable node IDs as integers. Unfortunately, existing 2-hop labeling schemes generate huge 2-hop label sizes because they only consider local features, such as degrees. In this paper, we propose a more efficient 2-hop label size reduction approach. We consider the topological sort index, which is a global feature. A linear combination is suggested for utilizing both local and global features. We conduct experiments over real-world and synthetic directed acyclic graph datasets and show that the proposed approach generates smaller labels than existing approaches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권7호
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• pp.3393-3412
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• 2017

As a main challenge in network virtualization, virtual network embedding problem is increasingly important and heuristic algorithms are of great interest. Aiming at the problems of poor correlation in node embedding and link embedding, long distance between adjacent virtual nodes and imbalance resource consumption of network components during embedding, we herein propose a two-stage virtual network embedding algorithm NA-PVNM. In node embedding stage, resource requirement and breadth first search algorithm are introduced to sort virtual nodes, and a node fitness function is developed to find the best substrate node. In link embedding stage, a path fitness function is developed to find the best path in which available bandwidth, CPU and path length are considered. Simulation results showed that the proposed algorithm could shorten link embedding distance, increase the acceptance ratio and revenue to cost ratio compared to previously reported algorithms. We also analyzed the impact of position constraint and substrate network attribute on algorithm performance, as well as the utilization of the substrate network resources during embedding via simulation. The results showed that, under the constraint of substrate resource distribution and virtual network requests, the critical factor of improving success ratio is to reduce resource consumption during embedding.

• 한국컴퓨터정보학회논문지
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• 제11권1호
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• pp.63-69
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• 2006

언제 어디서나 네트워크에 연결되어 있는 유비쿼터스 환경에서의 무선 단말기의 컨텐츠에 대한 연구가 활성화되고 있다. 본 논문에서는 일반 컴퓨터의 인터넷 컨텐츠를 무선 단말기를 이용하여 얻을 수 있도록 하는 프레임워크를 제안하고자 한다. 프레임워크의 컨텐츠를 관리하는 서버의 성능 향상을 위해서 다수의 리소스 중에서 위한 중요 이미지를 선정하고, 선정된 이미지만을 단말기에서 재생 가능한 이미지로 변환하는 것이 본 논문의 목표이다. 이를 위해 웹 문서의 이미지 관련 정보 중 화면 표시율(DPR)과 이미지의 분포 영역을 고려하여 다수의 변환 요구 이미지 중에서 중요 이미지를 선별한 후 모바일 이미지로 변환 서비스하여 서버의 모바일 이미지로의 변환 시간 및 자원을 축소 시켜 서버의 성능을 향상시키고자 한다.

• 한국정보과학회논문지:시스템및이론
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• 제31권5_6호
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• pp.321-327
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• 2004

SPIHT는 수행속도가 빠르고 효율적인 웨이블릿 기반의 이미지 압축 알고리즘으로 잘 알려져 있다. 그러나, SPIHT는 알고리즘을 수행하는 과정에서 발생하는 제로트리 및 계수의 상태를 저장하기 위하여 리스트 구조를 사용하고 있어 추가 메모리를 요구하며, 비트율의 증가에 따라 메모리 요구량이 증가하는 단점을 가진다. 본 논문에서는 SPIHT 알고리즘을 수행하는데 있어 추가 메모리를 요구하지 않는 MZC-BFS 알고리즘을 제안한다. 제안된 기법은 peano 코드를 이용하여 완벽한 너비우선 순서에 따라 공간트리를 탐색하며, 부호화 과정에서 이전상태 중요계수 테스트 및 복원과정에서 계수의 LSB를 이용함으로써 SPIHT에서 리스트 문제를 제거한다. MZC-BFS는 SPIHT에 비하여 리스트를 사용하지 않기 때문에 하드웨어 구현이 간단하고 수행속도가 빠를 뿐 아니라 추가 메모리를 요구하지 않기 때문에 하드웨어 제작비용을 절감할 수 있다.

• 한국정보과학회논문지:데이타베이스
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• 제28권4호
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• pp.606-619
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• 2001

본 논문에서는 SGML/XML 문서의 구 버전과 신 버전간의 타이를 계산할 수 있는 효율적인 알고리즘을 제안한다. 타이는 구 버전의 문서를 신 버전으로 변환하는데 소요되는 편집 스크립트로 간주할 수 있다. 제안된 알고리즘은 상향식과 하향식의 복합적인 접근 방식을 적용한다. 먼저 두 버전을 구성하는 노드간의 대응관계를 상향식으로 생성하며 하향시 너비 우선 탐색을 적용하여 편집 스크립트를 계산한다. 제안된 알고리즘은 모든 노드간의 대응 여부를 모두 조사할 필요가 없기 때문에 대응관계를 보다 빠르게 생성할 수 있다. 또한 삽입, 삭제, 그리고 갱신의 단순한 변화는 물론이고 부트리 이동과 복사의 구조적으로 보다 의미 있는 변화를 탐지할 수 있다.

• 대한전기학회논문지:전력기술부문A
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• 제53권11호
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• pp.596-603
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• 2004

This paper proposes an expert system based on the pattern recognition method which can enhance the accuracy and effectiveness of real-time bus reconfiguration strategy for the transfer of faulted load when a main transformer fault occurs in the automated substation. The minimum distance classification method is adopted as the pattern recognition method of expert system. The training pattern set is designed MTr by MTr to minimize the searching time for target load pattern which is similar to the real-time load pattern. But the control pattern set, which is required to determine the corresponding bus reconfiguration strategy to these trained load pattern set is designed as one table by considering the efficiency of knowledge base design because its size is small. The training load pattern generator based on load level and the training load pattern generator based on load profile are designed, which are can reduce the size of each training pattern set from max L/sup (m+f)/ to the size of effective level. Here, L is the number of load level, m and f are the number of main transformers and the number of feeders. The one reduces the number of trained load pattern by setting the sawmiller patterns to a same pattern, the other reduces by considering only load pattern while the given period. And control pattern generator based on exhaustive search method with breadth-limit is designed, which generates the corresponding bus reconfiguration strategy to these trained load pattern set. The inference engine of the expert system and the substation database and knowledge base is implemented in MFC function of Visual C++ Finally, the performance and effectiveness of the proposed expert system is verified by comparing the best-first search solution and pattern recognition solution based on diversity event simulations for typical distribution substation.