• 방송공학회논문지
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• 제27권1호
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• pp.133-145
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• 2022

국내에서 지속적으로 증가하는 반려견 인구 및 산업 규모에 비해 이와 관련한 데이터의 체계적인 분석이나 품종 분류 방법 연구 등은 매우 부족한 실정이다. 본 논문에서는 국내에서 양육되는 반려견의 주요 14개 품종에 대해 딥러닝 기술을 이용한 자동 품종 분류 방법을 수행하였다. 이를 위해 먼저 딥러닝 학습을 위한 반려견 이미지를 수집하고 데이터셋을 구축하였으며, VGG-16 및 Resnet-34를 백본 네트워크로 사용하는 전이학습을 각각 수행하여 품종 분류 알고리즘을 만들었다. 반려견 이미지에 대한 두 모델의 전이학습 효과를 확인하기 위해, Pre-trained 가중치를 사용한 것과 가중치를 업데이트하는 실험을 수행하여 비교하였으며, VGG-16 기반으로 fine tuning을 수행했을 때, 최종 모델에서 Top 1 정확도는 약 89%, Top 3 정확도는 약 94%의 정확도 성능을 각각 얻을수 있었다. 본 논문에서 제안하는 국내의 주요 반려견 품종 분류 방법 및 데이터 구축은 동물보호센터에서의 유기·유실견 품종 구분이나 사료 산업체에서의 활용 등 여러가지 응용 목적으로도 활용될 수 있는 가능성을 가지고 있다.

• 해양환경안전학회지
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• 제23권3호
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• pp.258-265
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• 2017

This paper validates a system identification method using mathematical optimization using sea trial measurement data as a benchmark. A fast time simulation tool, SIMOPT, and a Rheinmetall Defence mathematical model have been adopted to conduct initial hydrodynamic coefficient estimation and simulate ship modelling. Calibration for the environmental effect of sea trial measurement and sensitivity analysis have been carried out to enable a simple and efficient optimization process. The optimization process consists of three steps, and each step controls different coefficients according to the corresponding manoeuvre. Optimization result of Step 1, an optimization for coefficient on x-axis, was similar compared to values applying an empirical regression formulae by Clarke and Norrbin, which is used for SIMOPT. Results of Steps 2 and 3, which are for linear coefficients and nonlinear coefficients, respectively, was differ from the calculation results of the method by Clarke and Norrbin. A comparison for ship trajectory of simulation results from the benchmark and optimization results indicated that the suggested stepwise optimization method enables a coefficient tuning in a mathematical way.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1508-1517
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• 2015

Optimal Power dispatch is the short-term decision of the optimal output of a number of power generation facilities, to meet the system demand, with the objective of Power dispatching at the lowest possible cost, subject to transmission lines power loss and operational constraints. The operational constraint includes power balance constraint, generator limit constraint, and emission dispatch constraint and valve point effects. In this paper, Opposition based Differential Evolution Algorithm (ODEA) has been proposed to handle the objective function and the operational constraints simultaneously. Furthermore, the valve point loading effects and transmission lines power loss are also considered for the efficient and effective Power dispatch. The ODEA has unique features such as self tuning of its control parameters, self acceleration and migration for searching. As a result, it requires very minimum executions compared with other searching strategies. The effectiveness of the algorithm has been validated through four standard test cases and compared with previous studies. The proposed method out performs the previous methods.

• 한국정밀공학회지
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• 제29권4호
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• pp.417-425
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• 2012

This paper presents reference ZMP trajectory generation and implementation for a biped robot via linear inverted dumbbell model (LIDM), which can consider the effect of external momentum on the center of mass (COM) of robot. Based on a reference ZMP trajectory derived by using LIDM, a base trajectory is proposed not only to make the locomotion of robot similar to that of human but also to facilitate its implementation and tuning. In order to realize a dynamic walking using the proposed trajectory, compliance, impedance and ZMP tracking controllers are adopted together. Extensive experiments show that the proposed locomotion of a biped robot is stable and also, similar to that of human. Further researches on balance recovery of a biped robot will be carried out to guarantee its robust locomotion in combination with the proposed trajectory.

• Structural Engineering and Mechanics
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• 제26권5호
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• pp.517-544
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• 2007

This study shows a fuzzy tuning scheme to fuzzy sliding mode controller (FSMC) for seismic isolation of earthquake-excited structures. The sliding surface can rotate in the phase plane in such a direction that the seismic isolation can be improved. Since ideal sliding mode control requires very fast switch on the input, which can not be provided by real actuators, some modifications to the conventional sliding-mode controller have been proposed based on fuzzy logic. A superior control performance has been obtained with FSMC to deal with problems of uncertainty, imprecision and time delay. Furthermore, using the fuzzy moving sliding surface, the excellent system response is obtained if comparing with the conventional sliding mode controller (SMC), as well as reducing chattering effect. For simulation validation of the proposed seismic response control, 16-floor tall building has been considered. Simulations for six different seismic events, Elcentro (1940), Hyogoken (1995), Northridge (1994), Takochi-oki (1968), the east-west acceleration component of D$\ddot{u}$zce and Bolu records of 1999 D$\ddot{u}$zce-Bolu earthquake in Turkey, have been performed for assessing the effectiveness of the proposed control approach. Then, the simulations have been presented with figures and tables. As a result, the performance of the proposed controller has been quite remarkable, compared with that of conventional SMC.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.407-410
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• 2005

고성능 액체 로켓엔진에서 일반적으로 사용되는 기체-액체형 분사기가 장착된 연소실의 음향장을 수치적으로 해석하였다. 해당 분사기는 반파장 공명기의 역할을 할 수 있다. 다수의 공명기가 장착된 경우 연소실과 분사기간의 음향학적인 연계성으로 특이한 음향학적 특성이 관측되었다. 분사기 길이가 반파장 공명기 길이에 도달함에 따라 분사기와 연계된 새로운 음향 모드가 나타났으며, 그 음향 모드의 감쇠인자는 상당히 작았다. 따라서, 분사기의 음향감쇠 효과를 최적화 하려면 본래의 반파장 길이보다 약간 작은 길이를 갖도록 해야함을 알았다.

• Wind and Structures
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• 제7권4호
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• pp.251-264
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• 2004

The effects of a class of nonlinear Tuned Mass Dampers on the aeroelastic behavior of SDOF systems are investigated. Unlike classical linear TMDs, nonlinear constitutive laws of the internal damping acting between the primary oscillator and the TMD are considered, while the elastic properties are keept linear. The perturbative Multiple Scale Method is applied to derive a set of bifurcation equations in the amplitude and phase and a parametric analysis is performed to describe the postcritical scenario of the system. Both cubic- and van der Pol-type dampings are considered and the dependence of the limit-cycle amplitudes on the system parameters is studied. These new results, compared with the previously obtained bifurcation scenario of a SDOF aeroelastic oscillator equipped with a linear TMD, show a detrimental effect on the maximum limit-cycle amplitude reduction of the nonlinear TMD. However, the analyses evidence that in the parameter region away from the perfect tuning condition the nonlinear connection can be used to tune the system with an enhancement of the limit-cycle amplitude reduction.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1097-1100
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• 2008

We demonstrate that the performance of amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFT) can be optimized by controlling the interfaces between IGZO and sandwiching insulators and by proper deposition of IGZO layer. Specifically, contact and channel resistances are decreased by reducing IGZO bulk resistance and optimizing dry-etch process, respectively. Field-effect mobility ($\mu_{FE}$) and subthreshold gate swing (S) are further enhanced by fine-tuning IGZO deposition condition.

• 한국전산구조공학회논문집
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• 제22권5호
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• pp.429-437
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• 2009

본 연구에서는 수평관과 수직관의 단면이 다른 액체기둥흡진기(LCVA)의 제진효과를 극대화하기 위한 최적형상을 수치 해석에 의한 변수연구를 통해 찾았다. 특정 진동수에 동조되고, 동일한 총질량을 가지면서 치수 및 수위와 관련된 구속조건을 만족하는 다양한 형상의 LCVA를 설계하고, 이 가운데 가장 큰 등가감쇠비를 획득하는 형상을 찾았다. 그 결과 LCVA 형상의 설계에서 수위변동폭이 최적형상을 결정하는 중요한 구속조건 역할을 한다는 것을 확인하였다. 유체가 운동하는 평면과 직교하는 방향의 LCVA 수평폭을 증가시킬수록 등가감쇠비가 증가하였으며, 증가율은 점차 둔화되는 것으로 나타나 적정 수평폭의 결정이 중요한 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.412-422
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• 1999

Scale defects generated on the strip surface in a tandem finishing mill line are collected from the strip trapped among the production mills by freezing the growing scale on the strip by the melt glass coating and shutting down the line simultaneously. The samples observed of its cross sectional figure showed the process of scale defect formation where the defects are formed at the base metal surface by thicker oxidized scale during each rolling passes. The properties of the oxidized layer growth both at rolling and inter-rolling are detected down sized rolling test simulating carefully the rolling condition of the production line. The thickness of the oxidized layer at each rolling pass are simulated numerically. The critical scale thickness to avoid the defect formation is determined through the expression of mutual relation between oxidized layer thickness and the lanks of the strip called quality for the scale defects. The scale growth of scale less than the critical thickness and also to keep the bulk temperature tuning the water flow rate and cooling time appropriately. Two units of Inerstand Cooler are designed and settled among the first three stands in the production line. Two units of scale defect is counted from the recoiled strip and the results showed distinct decrease of the defects comparing to the conventionaly rolled products.