• 한국정밀공학회지
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• 제33권3호
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• pp.235-242
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• 2016

The purpose of this study is an attempt to improve the functionality of a conventional Fused Deposition Modeling (FDM) process using the Automatic Tool Changer (ATC) to perform multimaterial production and post-processing. Hybrid-FDM means a fusion of an Additive Manufacturing process and grinding process using the ATC system. In order to enhance the potentiality of production capacity for multi-material fabrication and surface roughness improvement, two extrusion tools and one grinding tool system are suggested. A pneumatic chuck is attached on a moving platform in the XY axes plane and an extrusion head and grinding head are placed in a docking station, allowing for a quick changeover with each other. Therefore, the manufacturing lead time can be reduced efficiently for the fabrication of a product.

• International Journal of Contents
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• 제10권3호
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• pp.17-25
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• 2014

In this paper, we describe an adaptive Markov chain Monte Carlo-based particle filter that effectively addresses real-time multi-face tracking on mobile platforms. Because traditional approaches based on a particle filter require an enormous number of particles, the processing time is high. This is a serious issue, especially on low performance devices such as mobile phones. To resolve this problem, we developed a tracker that includes a more sophisticated likelihood model to reduce the number of particles and maintain the identity of the tracked faces. In our proposed tracker, the number of particles is adjusted during the sampling process using an adaptive sampling scheme. The adaptive sampling scheme is designed based on the average acceptance ratio of sampled particles of each face. Moreover, a likelihood model based on color information is combined with corner features to improve the accuracy of the sample measurement. The proposed tracker applied on various videos confirmed a significant decrease in processing time compared to traditional approaches.

• Journal of Power Electronics
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• 제15권6호
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• pp.1654-1663
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• 2015

Compared to LC resonance, LCL resonance has distinct advantages such as a large resonant capability, low voltage and current stresses of the power device, constant voltage or current output characteristics, and fault-tolerance capability. Thus, LCL resonant compensation is employed for a movable Inductive Contactless Power Transfer (ICPT) system with a multi-load in this paper, which achieves constant current output characteristics. Peculiarly, the primary side adopts a much larger compensation inductor than the primary leakage inductor to lower the reactive power, reduce the input current ripple, generate a large current in the primary side, and realize soft-switching. Furthermore, this paper proposes an approximate resonant point for large inductor-ratio LCL resonant compensation through fundamental wave analysis. In addition, the PWM control strategy is used for this system to achieve constant current output characteristics. Finally, an experimental platform is built, whose secondary E-Type coils can ride and move on a primary rail. Simulations and experiments are conducted to verify the effectiveness and accuracy of both the theory and the design method.

• 한국통신학회논문지
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• 제33권8B호
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• pp.699-706
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• 2008

본 논문에서는 다양한 망 환경에서 SCTP 및 TCP 프로토콜의 전송처리율(throughput) 성능을 비교 분석한다. 실험을 위해 리눅스 테스트베드를 구축하고 성능측정 변수로써 MSS(Maximum Segment Size), 전송지연, 패킷 손실률을 고려하였다. 또한, SCTP 세션의 스트림(stream) 수가 성능에 미치는 영향을 분석하였다. 실험 결과, 동일한 망 환경에서 SCTP는 TCP에 비해 $20%{\sim}50%$ 정도의 높은 처리율을 제공하는데 이는 SCTP의 고유특성인 청크번들링(chunk bundling), 2 MTU로 시작하는 혼잡윈도우, SACK 기반 오류제어 등에서 기인한다. 한편, 패킷 손실이 존재하는 망에서 SCTP는 멀티스트리밍(multi-streaming) 전송을 통해 HoLB(Head-of-Line Blocking) 현상을 효과적으로 방지할 수 있음을 확인하였다.

• 한국정보시스템학회지:정보시스템연구
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• 제27권1호
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• pp.89-110
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• 2018

Purpose There is much information in customer reviews, but finding key information in many texts is not easy. Business decision makers need a model to solve this problem. In this study we propose a multi-topic sentiment analysis approach using Latent Dirichlet Allocation (LDA) for user-generated contents (UGC). Design/methodology/approach In this paper, we collected a total of 104,039 hotel reviews in seven of the world's top tourist destinations from TripAdvisor (www.tripadvisor.com) and extracted 30 topics related to the hotel from all customer reviews using the LDA model. Six major dimensions (value, cleanliness, rooms, service, location, and sleep quality) were selected from the 30 extracted topics. To analyze data, we employed R language. Findings This study contributes to propose a lexicon-based sentiment analysis approach for the keywords-embedded sentences related to the six dimensions within a review. The performance of the proposed model was evaluated by comparing the sentiment analysis results of each topic with the real attribute ratings provided by the platform. The results show its outperformance, with a high ratio of accuracy and recall. Through our proposed model, it is expected to analyze the customers' sentiments over different topics for those reviews with an absence of the detailed attribute ratings.

• 경영과학
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• 제32권2호
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• pp.111-124
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• 2015

In the management literature, it has been widely accepted among both researchers and practitioners that the level of team creativity is significantly related to the organizational performance. Besides, researchers posited with confidence that team diversity and task difficulty would affect team creativity through team members' activities of exploration and exploitation. However, empirical approaches to proving this belief suffered from lack of real data and proper methods as well. To tackle the research void like this, we propose a multi-agent simulation (MAS) mechanism. By adopting a set of parameters which validity were proven in the related literature, we conducted a series of experiments in the environment of the MAS platform named NetLogo. There sults suggest that managers can differentiate team diversity strategies according to task difficulty. In the case of a difficult task, managers need to increase team diversity so that their teams can maximize team creativity through rigorous exploration and exploitation. It is desirable to maintain an average level of team diversity when performing an easy task.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.670-686
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• 2017

MapReduce (MRV1), a popular programming model, proposed by Google, has been well used to process large datasets in Hadoop, an open source cloud platform. Its new version MapReduce 2.0 (MRV2) developed along with the emerging of Yarn has achieved obvious improvement over MRV1. However, MRV2 suffers from long finishing time on certain types of jobs. Speculative Execution (SE) has been presented as an approach to the problem above by backing up those delayed jobs from low-performance machines to higher ones. In this paper, an adaptive SE strategy (ASE) is presented in Hadoop-2.6.0. Experiment results have depicted that the ASE duplicates tasks according to real-time resources usage among work nodes in a cloud. In addition, the performance of MRV2 is largely improved using the ASE strategy on job execution time and resource consumption, whether in a multi-job environment.

• 한국컴퓨터정보학회논문지
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• 제16권6호
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• pp.11-20
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• 2011

본 논문에서는 DVFS 기능을 제공하는 멀티코어 프로세서 상에서 실시간 비디오 태스크의 에너지 소모량을 최소화하는 최적 스케쥴링 기법을 제안한다. 제안된 스케쥴링 기법은 멀티코어의 병렬처리 기법을 활용하도록 적절한 수의 멀티코어들을 태스크의 수행에 할당하고, 사용되지 않는 코어들의 전원을 끄며, 실시간 태스크의 데드라인을 만족하는 최저 클락 주파수를 배정한다. 단일 코어에서 태스크를 실행하는 기존 방법과 그리고 모든 코어들에서 태스크를 실행하는 기존 방법을 제안된 스케쥴링 기법과 비교하는 실험 결과에서, 제안된 스케쥴링 기법이 기존 방법들의 에너지 소모량을 각각 최대 67%, 89% 감소시킴을 확인하였다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 가을 학술발표논문집 Vol.32 No.2 (2)
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• pp.625-627
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• 2005

사용자가 시간과 장소에 구애 받지 않고 컴퓨터를 자연스럽고 효율성 있게 사용할 수 있는 환경을 의미하는 유비쿼터스 컴퓨팅은 네트워크와 센서(Sensor), smart devices, 무선 통신과 smart middleware(UPnP(Universal Plug and Play), Jini, HAVi(Home Audio Video Interoperability) IEEE 1394, PLC (Power Line Communication) 등) 등을 기반으로 Smart Space를 만들 수 있다. 그러나 여러 종류의 가전제품들이 늘어나고 수많은 사용자들의 요구를 충족시키기엔 smart middleware의 단일 제어로는 처리가 불가능하여 본 논문에서는 이기종간의 미들웨어간의 상호작용을 위해 개발된 OSGi(Open Service Gateway Initiative) Spec. 3에서 제공하는 서비스 플랫폼(Service Platform)을 기반으로 사용자/디바이스 관리 및 분산 시스템 등의 취약점들을 보완하여 Smart Space상에서 효율적인 서비스 번들을 관리하기 위해 MASBM(Multi-Agent Service Bundle Manager)을 제안하였다.

• 제어로봇시스템학회논문지
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• 제19권10호
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• pp.915-920
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• 2013

Payload capacity and transition ability are essential for climbing robots to apply the robots to various applications such as inspection and exploration. This paper presents a new climbing robotic platform with multi-link structure of track-wheel modules to enhance payload capacity and transition ability, and its tracking controller design and experimental results. The compliances between track-wheel modules achieve stable internal and external transitions while the large adhesion area of the track-wheel module enhances the payload capacity of the robot. Kinematic model-based tracking controller is designed and implemented for autonomous internal transition, and the gains of the controller are optimized by experimental design. Experiments on the automatic internal transitions are performed and the results guarantee autonomous internal transition with little tracking error.