• Industrial Engineering and Management Systems
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• v.12 no.4
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• pp.330-335
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• 2013

A surface mount device (SMD) assembles electronic components on printed circuit boards (PCB). Since a component assembly process is a bottleneck process in a PCB assembly line, making an efficient SMD plan is critical in increasing the PCB assembly line productivity. Feeder assignment is an important part of the SMD plan optimization. In this paper, we propose a feeder re-assign improvement algorithm for a specific type of SMD machine with a piano type multi-head gantry. Computational results on some real-world benchmark data sets show the effectiveness of our proposed algorithm.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.209-219
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• 2015

A robust multi-fidelity optimization methodology has been developed, focusing on efficiently handling industrial runner design of hydraulic Francis turbines. The computational task is split between low- and high-fidelity phases in order to properly balance the CFD cost and required accuracy in different design stages. In the low-fidelity phase, a physics-based surrogate optimization loop manages a large number of iterative optimization evaluations. Two derivative-free optimization methods use an inviscid flow solver as a physics-based surrogate to obtain the main characteristics of a good design in a relatively fast iterative process. The case study of a runner design for a low-head Francis turbine indicates advantages of integrating two derivative-free optimization algorithms with different local- and global search capabilities.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.253-255
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• 2016

본 논문에서는 다중 지역 이진 패턴(Multi-scale Bock LBP, MB-LBP) 특징과 랜덤 포레스트에 기반한 새로운 기법의 머리 방향 분류 기법을 제안한다. 제안 기법에서는 occlusion 과 조명의 변화에 강인한 분류 정확도를 얻기 위해서 랜덤화된 트리를 학습하는 것을 목표로 한다. 우선, 얼굴 이미지로부터 많은 MB-LBP 특징을 추출하고, 얼굴 영상들을 랜덤하게 입력하고 MB-LBP 크기 파라미터와 같은 랜덤 특징과 블록 좌표들을 사용하여 트리를 생성한다. 게다가 각 노드에서 정보 이득을 최대화 하는 트리의 내부 노드를 생성하기 위해서 uniform LBP 의 특성을 고려한 분할 함수를 개발한다. 랜덤화된 트리는 랜덤 포레스트에 포함되어 있으며 마지막 결정단계에서 Maximum-A-Posteriori criterion 으로 최종 결정을 한다. 실험 결과는 제안 기법이 다양한 조명, 자세, 표현, occlusion 상황에서 기존의 방법보다 개선된 성능으로 머리 방향을 분류 할 수 있음을 보여준다.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.287-289
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• 2009

무선 메쉬 네트워크(WMN, Wireless Mesh Network)에서의 전체적인 성능은 채널의 간섭을 최소화함으로써 개선될 수 있다. 본 논문은 3개의 멀티 채널을 지원하는 IEEE 802.11b/g 기반 WMNs를 위해 제안된 클러스터 기반 채널 할당 기법인 CB-CA(Cluster-Based Channel Assignment)[3] 알고리즘을 멀티 라디오 멀티 채널 WMN 환경에 적합하게 개선시키고자 한다. CB-CA 알고리즘에서는 메쉬 라우터들중에 선택된 클러스터 헤드(CH, Cluster Head) 노드들과 클러스터들 간의 에지 게이트웨이(EG, Edge Gateway) 노드들 간에는 모두 동일 채널을 사용함으로써 채널 스캐닝과 채널 스위칭을 수행하지 않는다. 그러나 이러한 모든 CH들과 EG들 간의 동일 채널의 사용은 많은 노드들에서 채널 간섭을 발생 시키는 문제점이 발생한다. 본 논문에서는 이를 해결하기 위하여 송수신 인터페이스를 구분하고 각 인터페이스에서의 채널을 랜덤하게 설정하고 이를 통신 범위 내에 인접한 이웃 클러스터들에게 알림으로써 서로 간섭이 발생하지 않는 채널들이 설정되도록 한다. 이로써 각 클러스터 간의 채널 간섭을 최소화 할 수 있음과 동시에 다중 인터페이스와 다중 채널을 모두 활용할 수 있어서 QoS를 향상시킬 수있다.

• IE interfaces
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• v.10 no.1
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• pp.155-167
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• 1997

The purpose of this study is to develop the program for efficient operation of a multi-functional surface mounting device(SMD) which mount various components on a printed circuit board(PCB). These components are provided by diverse types of feeders such as cassette, stick and tray feeders. The SMD has one or two heads. In the SMD, the positions of PCB and feeders and fixed, and the head moves to pick up a component from a feeder and to mount it on the PCB. The number of lanes occupied by each feeder and the nozzle used for each component can be different. We develop an off-line program to minimize the cycle-time of the SMD by studying the optimal assignment of feeders and the optimal mounting sequence of components. Graphical User Interface(GUI) is also developed. Additionally, we consider the line balancing problem which appears when two SMDs are used sequentially.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.142-147
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• 2008

In wireless sensor networks, one of the most important issue is improvement of network lifetime with an efficient energy consumption. we repose effective multi-hop routing algorithm which increases the number of nodes alive at any time. In our algorithm we use the dynamic selection of cluster head and short distance transmission method. We simulated the proposed algorithm by using Network Simulator 2 and compared its performance with LEACH. The experimental result shows that the number of the nodes alive is increased up to 39.71[%] during the simulation time.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.3
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• pp.119-129
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• 2016

This paper presents an integrated navigation system for accurate navigation solution-based safety and convenience services in the vehicular augmented reality (AR)-head up display (HUD) system. For lane-level guidance service, especially, an accurate navigation system is essential. To achieve this, an inertial navigation system (INS)/global positioning system (GPS)/vision/digital map (IGVM) integrated navigation system has been developing. In this paper, the concept of the integrated navigation system is introduced and is implemented based on a multi-model switching filter and vehicle status decided by using the GPS data and inertial measurement unit (IMU) measurements. The performance of the implemented navigation system is verified experimentally.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.526-533
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• 2005

Reliability problem in inkjet printhead, one of MEMS devices, is also very important. To eject an ink drop, the temperature of heater must be high so that ink contacting with surface reaches above $280^{o}C$ on the instant. Its heater is embedded in the thin multi-layer in which several materials are deposited. MEMS processes are the main sources of residual stresses development. Residual stress is one of the factors reducing the reliability of MEMS devices. We measured residual stresses of single layers that consist of multilayer. FE analysis is performed using design of experiment(DOE). Transient analysis for heat transfer is performed to get a temperature distribution. And then static analysis is performed with the temperature distribution obtained by heat transfer analysis and the measured residual stresses to get a stress distribution in the structure. Although the residual stress is bigger than thermal stress, thermal stress is more influential on fatigue life.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.781-786
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• 2015

Recently, studies of 3D printing methods have been working in various applications. For example, the powder base method laminates the prints by using a binding or laser sintering method. However, the draw back of this method is that the post process is time consuming and does not allow for parts to be rapidly manufactured. The binding method requires the post process while the time required for the post process is longer than the manufacturing time. This paper proposes a UV curing binding method with an integrated piezo printing head system. The optimization of an arbitrary waveform generation for the control of a UV curable resin droplet was researched, in addition to developed optimized UV curing processes in multi nozzle ink jet heads.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.154-155
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• 2014

본 논문에서는 TV 시청환경에서의 실내소음의 스트레스 평가를 위한 소음 데이터베이스(database, DB) 설계 방법을 제안한다. 제안된 DB 는 TV 시청공간을 포함하는 실제 주거환경 내에서 binaural recording을 위한 1 개의 dummy head 와 multi-channel recording 을 위한 2 개의 다채널 마이크 배열을 활용하여 TV 콘텐츠 및 실내소음의 음향 정보를 취득한다. 설계된 DB는 TV 시청자의 청각정보에 해당하는 binaural recording 신호와 실내소음의 위치 및 종류 추정을 위한 multi-channel recording 신호를 모두 포함하기 때문에 TV 시청환경에서 실내소음이 시청자에게 유발하는 스트레스의 분석 및 평가 관련 연구에 적합하게 설계되었다. 본 DB 는 5 가지 종류의 TV 콘텐츠 10 시간 분량, 30 가지 종류의 실내소음 2 시간 분량으로 구성되었다.