• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.939-951
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• 1996

The previous study of virtual path design for one traffic class with ATM DCS only should be generalized to that for the multiple traffic class cases of being given neither virtual path candidate set nor end nodes o each virtual path. In this paper, a design model of virtual paths for the general case with multiple traffic classes is suggested. The model is represented as an optimization rpoblem with a special structure. It is solved by SQA algorithm, which is developed by authors in [3, 4]. The model and the algorithm are applied to a numerical example, and results are shown.

• The Journal of Korea Robotics Society
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• v.10 no.2
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• pp.112-118
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• 2015

This paper proposes a pose-graph based SLAM method using an upward-looking camera and artificial landmarks for AGVs in factory environments. The proposed method provides a way to acquire the camera extrinsic matrix and improves the accuracy of feature observation using a low-cost camera. SLAM is conducted by optimizing AGV's explored path using the artificial landmarks installed on the ceiling at various locations. As the AGV explores, the pose nodes are added based on the certain distance from odometry and the landmark nodes are registered when AGV recognizes the fiducial marks. As a result of the proposed scheme, a graph network is created and optimized through a G2O optimization tool so that the accumulated error due to the slip is minimized. The experiment shows that the proposed method is robust for SLAM in real factory environments.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.231-234
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• 2001

The torque of SRM depends on phase current and the derivative of inductance. But the inductance of SRM is nonlinearly changed according to rotor position angle and phase current because of saturation in magnetic circuit. Therefore this has a concern in torque ripple and speed variation, and it is difficult to control the desired torque The torque of SRM depends on phase current and the derivative of inductance. But the inductance of SRM is nonlinearly changed according to rotor position angle and phase current because of saturation in magnetic circuit, and it is difficult to control the desired torque. This paper proposes an optimization control scheme by adjusting both the turn-on and turn-off angle according to high efficiency points which are simulated by GA-Neural Network, which is used to simulate the reasonable switching angle which is nonlinearly varied with rotor speed and load.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.151-156
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• 2012

The current study presents a zero-one integer programming approach to determine the minimum break point set for the coordination of directional relays. First, the network is reduced if there are any parallel lines or three-end nodes. Second, all the directed loops are enumerated to reduce the iteration. Finally, the problem is formulated as a set-covering problem, and the break point set is determined using the zero-one integer programming technique. Arbitrary starting relay locations and the arbitrary consideration of relay sequence to set and coordinate relays result in navigating the loops many times and futile attempts to achieve system-wide relay coordination. These algorithms are compared with the existing methods, and the results are presented. The problem is formulated as a setcovering problem solved by the zero-one integer programming approach using LINGO 12, an optimization modeling software.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.454-458
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• 2008

This article describes an interference reduction scheme for Mobile WiMAX in an indoor environment. The feasibility of user deployed femtocells in the same frequency channel as an existing macro cell network is investigated. One of the important requirements for co-channel operation of femtocells such as auto-configuration and self optimization are discussed. In femtocell deployments, leakage of the pilot signal to the outside of a house can result of the higher number of mobility events caused by passing user of macrocell. This interference effect can be minimized by reducing the pilot power using proper scheme. This paper introduces existing auto-configuration method of power control and proposed interference reduction scheme using power control for Mobile WiMAX in an indoor environment.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.292-295
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• 2008

We propose a PON repeater system which transports multiple PON channels at the same time over the physical limit of the standard E-PON reach. To increase the physical reach up to 60km, we used the O-E-O (optic-electric-optic) signal regeneration on an active remote terminal which is placed between a central office and passive remote nodes. Also, by incorporating the well-established WDM technology to aggregate multiple E-PON channels, we successfully increased the split ratio (the number of subscribers per fiber core) to over 256.

• Annual Conference of KIPS
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• 2018.10a
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• pp.699-701
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• 2018

본 연구는 인공 신경망 '추론'과정에서 연산량을 줄이는 아이디어를 고안했고, 이를 구현하여 기존 알고리즘과 성능을 비교 분석하였다. 특정 데이터 셋에 대한 실험을 통해 ReLU(Rectified Linear Unit) 함수의 결과를 분석했고, 그 결과를 통해 ReLU 함수의 결과가 예측가능함을 확인했다. 또한 인공 신경망 알고리즘에 ReLU 함수의 결과 예측 기법을 적용하여 인공 신경망 추론과정을 최적화했다. 이 아이디어를 기반으로 구현된 인공 신경망은 기존 아이디어로 구현된 인공 신경망에 비해 약 3배 빠른 성능을 보였다.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.429-438
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• 1996

An incremental learning algorithm is presented that constructs a multilayer perceptron whose size is optimal for solving a given problem. Unlike conventional algorithms in which a fixed size training set is processed repeat-edly, the method uses an increasing number of critical examples to find a necessary and sufficient number of hidden units for learning the entire data. Experimental results in hand- writtern digit recognition shows that the network size optimization combined with incremental pattern selection generalizes significantly better and converges faster than conventional methods.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.325-326
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• 2007

SAW filter was designed by optimization technique using impulse sampling. To carry out characteristics of SAW filter the uniform IDT was adapted. And SAW filter was fabricated on $LiNbO_3$ substrates to evaluate frequency response. To apply properties of photolithography, lift off method was used. Lift off method was superior to etch method in fabrication process, frequency response property was measured by network analyzer. From a measurement of acoustic property, SAW propagation velocity was 2663.5m/sec.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.188-189
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• 2006

차세대 반도체 공정을 위한 많은 노력 중 미세가공의 중요성이 날로 증가함에 따라 reactive ion etching (RIE)에 대한 연구 또한 그 중요성이 커지고 있다. 본 논문에서는 RIE 과정에서 etch rate과 uniformity에 영향을 줄 수 있는 요인 4가지 즉, $CHF_3$, $O_2$, chamber pressure, RF power의 변화에 대한 실험 계획법(DOE)을 통해 계획하고, 실험한 후 neural network를 통해 학습함으로서 RIE 공정상의 최적화를 모색하였다.