• 소성∙가공
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• 제25권1호
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• pp.5-11
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• 2016

The control of the roll velocities is essential in maintaining stability during ring rolling, but such control is difficult. The determination of the best roll velocities can be helped with the use of FE simulations and processing maps, which give the useful information such as power dissipation and flow instability for hot metal forming processes. In the current study, the workability of 7050 aluminum alloy is evaluated by using processing map. With the developed information, the stability of the ring rolling condition, called the Constant Growth Velocity Condition (CGVC), is evaluated.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 춘계학술발표대회
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• pp.45-48
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• 2013

In this paper, we proposed an Indexing Structure System (ISS) based on Apache Hadoop in Wireless Sensor Network (WSN). Nowadays sensors data continuously keep growing that need to control. Data constantly update in order to provide the newest information to users. While data keep growing, data retrieving and storing are face some challenges. So by using the ISS, we can maximize processing quality and minimize data retrieving time. In order to design ISS, Indexing Types have to be defined depend on each sensor type. After identifying, each sensor goes through the Indexing Structure Processing (ISP) in order to be indexed. After ISP, indexed data are streaming and storing in Hadoop Distributed File System (HDFS) across a number of separate machines. Indexed data are split and run by MapReduce tasks. Data are sorted and grouped depend on sensor data object categories. Thus, while users send the requests, all the queries will be filter from sensor data object and managing the task by MapReduce processing framework.

• 소성∙가공
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• 제21권7호
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• pp.412-419
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• 2012

The ingot-breakdown scheme of a tower flange material (low-alloy steel) for offshore wind turbine was investigated using finite element (FE) simulations and experimental analyses. Based on compression test results of the low-alloy steel, a deformation processing map was generated using the superposition approach between the dynamic materials model (DMM) and Ziegler's instability criterion. The deformation processing map allowed determination of the optimum process conditions for the tower flange material. Within the FE simulations of the ingot breakdown process, the Cockcroft-Latham criterion, which considers ductile fracture, was used to predict the possibility of forming defects during the hot working process. In general, the critical value for the ductile fracture of steel is 0.74. During the ingot-breakdown under optimum process conditions, the actual tower flange forgings exhibited a relatively uniform shape without any forming defects.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제22권2호
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• pp.89-94
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• 2016

최근 클라우드 컴퓨팅 시장의 클러스터 환경이 일반 클러스터 환경에서 가상화 클러스터 환경으로 변화하고 있다. 이러한 클러스터 환경의 변화는 대용량 분산처리 성능에 영향을 끼치고 있으며, 국내외의 많은 IT관련 기업에서 경쟁적으로 연구와 서비스에 집중 투자하고 있다. 본 논문에서는 대용량 데이터 분산 처리 성능에 하이퍼바이저가 미치는 영향을 비교하기 위한 목적으로 하이퍼바이저를 사용하는 Xen과 컨테이너 기반의 Docker를 사용하여 가상 클러스터 환경을 만들고, MapReduce의 성능을 측정하는 실험을 하였다. 이 결과 하이퍼바이저를 사용하지 않은 Docker 성능이 약 1.44배 - 2.92배 더 좋은 것을 검증하였다.

• 한국정보통신학회논문지
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• 제18권3호
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• pp.576-585
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• 2014

대량의 개인정보가 수집되어 활용됨에 따라 개인정보 유출 등의 보안 문제가 발생하고 있다. 이에 최근에는 수집된 개인정보를 암호화 하여 저장하고 활용하는 방법이 사용되고 있다. 본 논문에서는 기존에 수집된 대량의 개인정보를 단시간에 암호화하기 위한 방법으로 맵리듀스 기반의 분산 암호화 처리 방법을 제안하고, 시스템을 설계하고 구현하였다. 또한 맵리듀스 기반의 분산 암호화 처리 방법의 성능을 검증을 위해 테스트 환경을 구축하여 비교 실험을 진행하였다. 실험 결과 토큰 서버의 암호화 처리 시간이 순차처리 대비 평균 시간 효율이 약 15.3% 정도 향상 하였으며, 병렬처리대비 약 3.13%정도 향상되는 것을 확인 하였다.

• 소성∙가공
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• 제11권6호
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• pp.529-537
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• 2002

A series of load-relaxation tests and tensile tests were conducted to study the high temperature deformation mechanism of fine duplex gamma TiAl alloy at temperatures ranging from 800 to 105$0^{\circ}C$. Results of load relaxation test showed that deformation behavior at a small imposed strain ($\varepsilon$≒0.05) was dominated by dislocation glide and dislocation climb. To investigate the deformation behavior at a large amount of strain, the processing map was constructed using a dynamic materials model. Two domains were characterized in the processing map obtained at a strain level of 0.6. One domain was found at the region of 98$0^{\circ}C$ and $10^{-3}/sec$ with a peak efficiency of 48%, which was identified as a domain of dynamic recrystallization from the microstructural observation. The order was observed at the region of 125$0^{\circ}C$ and $10^{-4}/sec$ with a peak efficiency of 64%. The strain rate sensitivity measured indicates that the material was deformed by the superplasticity in the region.

• 정보처리학회논문지D
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• 제18D권2호
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• pp.81-88
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• 2011

시퀀스(sequence) 데이터가 주어졌을 때 그 중에서 빈번(frequent)한 순차 패턴을 찾는 순차 패턴 마이닝(sequential pattern mining)은 여러 어플리케이션(application)에 사용되는 중요한 데이터마이닝 문제이다. 순차 패턴 마이닝은 웹 접속 패턴, 고객 구매 패턴, 특정 질병의 DNA 시퀀스를 찾는 등 광범위한 분야에서 사용된다. 본 논문에서는 맵리듀스(MapReduce) 프레임웍 상에서 맵리듀스 함수 호출을 최적화하는 순차 패턴 마이닝 알고리즘을 개발하였다. 이 알고리즘은 여러 대의 기계에 데이터들을 분산시켜 병렬적으로 빈번한 순차 패턴을 찾는다. 실험적으로 다양한 데이터를 이용하여 파라미터 값을 변화시켜가며 제안된 알고리즘의 성능을 종합적으로 확인하였다. 그리고 실험 결과를 통해 제안된 알고리즘은 기계 수에 대해 선형적인 속도 개선을 보인다는 것을 확인하였다.

• Spatial Information Research
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• 제15권2호
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• pp.95-109
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• 2007

최근 도로네트워크 환경에서 위치기반 서비스를 제공하는데 있어서 2차원 공간 데이터를 기반으로 하고 있다. 3차원 데이터는 사용자에게 2차원 보다 친근감을 주는 중요한 매체가 되지만, 데이터의 크기가 커지기 때문에 이동단말기의 메모리 공간의 한계로 모든 데이터를 저장할 수 없게 되는 문제점이 발생한다. 본 논문에서는 도로네트워크에서 이동객체에게 3차원 데이터를 제공할 수 있는 연속원근질의를 정의하고 이를 처리하는 방법론을 제안하였다.

• 대한공간정보학회지
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• 제24권2호
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• pp.37-46
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• 2016

The difference between definition time of GPS (Global Positioning System) position data and actual display time of car positions on a map could reduce the accuracy of car positions displayed in PND (Portable Navigation Device)-type CNS (Car Navigation System). Due to the time difference, the position of the car displayed on the map is not its current position, so an improved method to fix these problems is required. It is expected that a method that uses predicted future positionsto compensate for the delay caused by processing and display of the received GPS signals could mitigate these problems. Therefore, in this study an analysis was conducted to correct late processing problems of map positions by mapmatching using a Kalman filter with only GPS position data and a RRF (Road Reduction Filter) technique in a light-weight CNS. The effects on routing services are examined by analyzing differences that are decomposed into along and across the road elements relative to the direction of advancing car. The results indicate that it is possible to improve the positional accuracy in the along-the-road direction of a light-weight CNS device that uses only GPS position data, by applying a Kalman filter and RRF.

• ETRI Journal
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• 제41권6호
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• pp.797-810
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• 2019

Image saliency detection is the basis of perceptual image processing, which is significant to subsequent image processing methods. Most saliency detection methods can detect only a single object with a high-contrast background, but they have no effect on the extraction of a salient object from images with complex low-contrast backgrounds. With the prior knowledge, this paper proposes a method for detecting salient objects by combining the boundary contrast map and the geodesics-like maps. This method can highlight the foreground uniformly and extract the salient objects efficiently in images with low-contrast backgrounds. The classical receiver operating characteristics (ROC) curve, which compares the salient map with the ground truth map, does not reflect the human perception. An ROC curve with distance (distance receiver operating characteristic, DROC) is proposed in this paper, which takes the ROC curve closer to the human subjective perception. Experiments on three benchmark datasets and three low-contrast image datasets, with four evaluation methods including DROC, show that on comparing the eight state-of-the-art approaches, the proposed approach performs well.