• 한국정보과학회논문지:데이타베이스
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• 제31권2호
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• pp.132-139
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• 2004

범위 상위-$\kappa$ 질의는 질의 범위 내의 다차원 데이타 중 값 애트리뷰트를 기준으로 상위 k개의 레코드를 반환하는 질의로 공간 데이타베이스와 데이타 웨어하우스에서 분석을 위해 많이 사용되는 유용한 질의 형태이다. 이 논문에서는 계층 최대 R-트리의 선택적인 탐색을 통해 범위 상위-k 질의를 효과적으로 수행하는 기법을 제시한다. 이 기법은 단말 노드의 일부만을 접근하여 질의를 수행할 수 있으며, 질의 범위의 크기에 관계없이 거의 일정한 성능을 보인다. 또한 이 기법은 우선순위 큐를 효율적으로 관리함으로써 큐의 유지비용을 최소화하며, 기존 R-트리와 같은 팬아웃을 보장할 수 있다.

• 한국정보과학회논문지:데이타베이스
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• 제34권5호
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• pp.465-472
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• 2007

XML과 같은 준구조적 데이타가 많이 사용됨에 따라 이를 효과적으로 저장하고 관리하는 것이 중요해지고 있다. XML 데이타는 트리 형태로 모델링이 가능하며, 기본적으로 질의 처리는 트리를 탐색하는 방식으로 이루어진다. 본 논문에서는 XML 데이타를 디스크 블록에 저장하는 알고리즘을 제안한다. 제안하는 알고리즘은 트리의 각 노드마다 아래쪽에서 위쪽으로 숫자를 할당하며 그 숫자를 이용하여 디스크 블록에 노드들을 매핑한다. 제안하는 알고리즘은 접근 패턴 정보를 필요로 하지 않으며 어떠한 접근 패턴에 대해서도 좋은 성능을 보인다. 제안하는 방법의 몇가지 특성을 증명하고, 실험을 통해서 성능을 평가한다.

• 한국빅데이터학회지
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• 제3권1호
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• pp.83-94
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• 2018

본 연구의 목적은 플랫폼 비즈니스 모델의 초기 활성화 문제점인 Chicken & Egg Problem 이슈를 짚어보고자 한다. 이를 위해 인터뷰 기반의 탐색적 연구를 수행하여 UGC 플랫폼의 초기 활성화 방안에 대해 각 요인들의 인과관계와 영향을 분석하였다. 본연구의 결과를 통해 전략적 시행착오의 오류를 최소화하는데 기여하고자하며 또한, 투자자 측면의 UGC 스타트업에 투자함에 있어 피투자기업의 마일스톤상 현재 위치를 알 수 있도록 해 객관적인 투자의사 결정을 할 수 있는데 실무적 시사점을 제공할 수 있을 것으로 기대한다.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권9호
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• pp.547-555
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• 2005

A fault-tolerant gait of multi-legged robots with static walking is a gait which can maintain gait stability and continue its walking against an occurrence of a leg failure. This paper proposes fault-tolerant gait planning of a quadruped robot walking over a rough planar terrain. The considered fault is a locked joint failure, which prevents a joint of a leg from moving and makes it locked in a known position. In this Paper, two-phase discontinuous gaits are presented as a new fault-tolerant gait for quadruped robots suffering from a locked joint failure. By comparing with previously developed one-phase discontinuous gaits, it is shown that the proposed gait has great advantages in gait performance such as the stride length and terrain adaptability. Based on the two-phase discontinuous gait, quasi follow-the-leader(FTL) gaits are constructed which enable a quadruped robot to traverse two-dimensional rough terrain after an occurrence of a locked joint failure. During walking, two front legs undergo the foot adjustment procedure for avoiding stepping on forbidden areas. The Proposed wait planning is verified by using computer graphics simulations.

• 한국컴퓨터정보학회논문지
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• 제7권1호
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• pp.68-73
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• 2002

최근 인터넷 네트워크 공격자들이 익명성을 얻기 위하여 가장 보편적으로 사용하는 방법이 이른바 징검다리를 이용한 공격이다. 징검다리 방법은 공격자가 그들 고유의 컴퓨터가 아닌 이미 사전에 계정을 획득하였거나 침입에 성공한 호스트를 통하여 공격을 하는 방법으로 그 공격의 근원지를 찾기가 무척 힘들다. 따라서 본 논문에서는 이 같은 공격들을 인터넷에 접근 가능한 사이트를 모니터링 함으로서 찾아낼 수 있는 효과적인 탐지 알고리즘을 개발하고자 한다. 본 알고리즘은 네트워크 플로우의 패킷 사이즈와 전송 타이밍을 이용하여 탐지하기 때문에 네트워크 플로우의 컨텐츠들이 암호화되어 있어도 적용이 가능하다. 또한 DoS공격에 사용될 수 있는 사이트들을 탐지해 내고 그 위험 순위를 매김으로서 DoS공격에 효과적인 대응책이 될 수 있는 탐지 알고리즘을 소개한다.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1407-1423
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• 2020

A graph is a data structure consisting of nodes and edges between these nodes. Graph embedding is to generate a low dimensional vector for a given graph that best represents the characteristics of the graph. Recently, there have been studies on graph embedding, especially using deep learning techniques. However, until now, most deep learning-based graph embedding techniques have focused on unweighted graphs. Therefore, in this paper, we propose a graph embedding technique for weighted graphs based on long short-term memory (LSTM) autoencoders. Given weighted graphs, we traverse each graph to extract node-weight sequences from the graph. Each node-weight sequence represents a path in the graph consisting of nodes and the weights between these nodes. We then train an LSTM autoencoder on the extracted node-weight sequences and encode each nodeweight sequence into a fixed-length vector using the trained LSTM autoencoder. Finally, for each graph, we collect the encoding vectors obtained from the graph and combine them to generate the final embedding vector for the graph. These embedding vectors can be used to classify weighted graphs or to search for similar weighted graphs. The experiments on synthetic and real datasets show that the proposed method is effective in measuring the similarity between weighted graphs.

• 미술이론과 현장
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• 제15호
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• pp.31-49
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• 2013

This paper delves into the recent 'paintings' of African-American artist David Hammons, which combine rubbish-like plastic wraps with the abstract-expressionist style paintings. In straddling between rubbish and art object, his works tend to blur the boundary drawn between two opposite categories in value, art and garbage, provoking the sophisticated taste of Upper-East-side white community in Manhattan, New York. Choosing the venue of his exhibition at a commercial gallery, Hammons's creative efforts is also a critique of what can be seen as the dominance of abstract expressionism and white elitism in American art history. The artist is known for his use of unconventional materials in art making such as black hair, barbecue bones, and elephant droppings, ones that are often associated with African-American experiences in all different levels. Since his debut in the art scene in the 1970s, Hammons has pursued the view of art-making as a medium for provoking contentious issues of racial relations in the States. On the other hand, the reception of Hammons's work as African-American art can be potentially quite limiting, overlooking as it does multi-faceted meanings of his art practice. His unconventional approach to art often took him outside art galleries and museums, where he was seen using a variety of common materials for site-specific installations and performances. Staged in different parts of Manhattan, these acts of art making traverse seemingly opposite communities and cultures, often blurring their boundaries. Hammons's artistic practice can label him what Abdul Jan Mohamed calls "specular border intellectual", revealing as it does the symbiosis of binary oppositions that is basic to the experience of communnal living.

• Korean Journal of Geomatics
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• 제3권1호
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• pp.73-79
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• 2003

To manage national territory and cadastral data efficiently, accuracy and cost-efficiency in cadastral boundary surveying is inevitable. The efficient management of cadastral data is a very important element in national land management. Survey techniques are being introduced. Recently, improvements in survey techniques have been made with the development of satellite surveying, Allowing accurate and fast surveys. If we can calculate the output accurately in real-time in survey fields, it will open a new method in cadastral detail surveying. According to the classification on Law of cadastral surveying, Cadastral surveying can be divided into cadastral control point surveying and cadastral detail surveying. The control point survey can be divided into cadastral triangulation surveying and cadastral traverse surveying. The detailed survey is usually perform by plane surveying. Among these, cadastral detail surveying will be reviewed in this study. In this study, the combination of the satellites, such as US managed GPS and Russian managed GLONASS was used. In the satellite survey in downtown, data interruption symptoms arose(according to the mask angle of the satellite). Therefore; we combined the satellites to get date more accurately. A block of Haewoondae New City in Busan, Korea, which has Numerical Cadastral Law was selected as the sample area for this study. Block II and III are surrounded by high rise apartments. One side of Block I and IV is level ground and the other side is full of high rise apartments. Especially, Block II is surrounded by high rise apartment houses with 20 meters width. In the results of the study Block II did not satisfy the allowable precision, while Block I, II and IV satisfied the allowable precision of the enforcement regulations of Cadastral Law. Therefore, it is judged that the traditionally used Total Station method should be used for supplementary survey on Block II, in stead.

• Tribology and Lubricants
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• 제34권2호
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• pp.55-59
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• 2018

This paper proposes a new type of electro-mechanical wedge brake for commercial vehicles. The brake operates on a novel mechanism for self-boosting braking friction forces using eccentric shafts, and involves wedges that are inserted between the rampbridge and traverse; this self-boosting mechanism is explained herein. A dynamic analysis using ADAMS was conducted, and the findings are reported. The constraint and contact conditions are explained to verify the precision of the dynamic analysis. The dynamic analysis shows that in the proposed mechanism, the self-boosting effect occurs as desired. However, it is also noted that the system has a limitation in terms of the production of unlimited braking forces that can jam the roller inside the wedges. After demonstrating the self-boosting effect, dynamic analyses are performed for several values of the wedge angles and friction coefficients between the brake pads and disks. Conventionally, a lower wedge angle has been suggested owing to its provision of a larger clamping force for given friction coefficients. However, it is noted that lower wedge angles can lead to a higher probability of occurrence of undesirable high braking forces, which can jam the roller into the wedge; thus, a larger wedge angle is preferable for avoiding the undesirable jamming phenomena. These analysis results are presented and discussed herein.

• 한국컴퓨터정보학회논문지
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• 제29권8호
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• pp.59-65
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• 2024

본 논문에서는 삼각형 메쉬 기반 옷감 시뮬레이션에서 계산이 큰 자기충돌(Self-collision) 처리를 GPU 기반으로 가속화하는 방법을 소개한다. CUDA(Compute Unified Device Architecture) 기반 병렬 최적화를 위해, 본 논문에서는 1) GPU에서 BVH(Bounding Volume Hierarchy) 트리를 효율적으로 구축, 업데이트 및 순회하는 방법을 제안하고, 2) 삼각형 메쉬 기반에서는 R-Triangle(Representative-Triangle) 기법을 GPU에서 최적화하여 프리미티브 충돌 검사를 최소화한다. 결과적으로, 제안된 방법은 GPU 환경에서 옷감 시뮬레이션의 자기충돌과 객체 충돌을 CPU기반 알고리즘에 비해 빠르고 효율적으로 처리할 수 있으며, 다양한 장면에서 실험한 결과 5배~10배정도 빠른 시뮬레이션 결과를 얻을 수 있다. 본 논문에서 제안하는 방법은 BVH를 GPU에서 최적화했기 때문에 BVH를 기반으로 활용하는 다양한 알고리즘과 분야에 쉽게 통합이 가능하다.