• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.81-84
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• 1994

A clinically oriented EEG and EP mapping system was developed with user-friendly interface and easy interactive operations. The system was based on the graphical user interface developed with C/C++ and Software Development Kit (SDK) operated under Microsoft Windows 3.1. Continuous acquisition for the EEG signal and burst mode acquisition for EEG signal syncronized to the external stimuli arc implemented with real time display. A neural network based automatic artifact discrimation is developed and implemented with which examination time can be reduced by a factor of 3 or more. Several bands of spectral maps and spectrums arc displayed for EEG diagnosis. Amplitude maps of EP signal at specified times by operator are displayed together with cine mode of EP maps for dynamic study. Source localization and other statistical signal processing are also included.

• Wind and Structures
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• 제21권6호
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• pp.657-675
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• 2015

In this study, the feasibility of vibration-based damage detection methods for the wind turbine tower (WTT) structure is evaluated. First, a frequency-based damage detection (FBDD) is outlined. A damage-localization algorithm is visited to locate damage from changes in natural frequencies. Second, a mode-shape-based damage detection (MBDD) method is outlined. A damage index algorithm is utilized to localize damage from estimating changes in modal strain energies. Third, a finite element (FE) model based on a real WTT is established by using commercial software, Midas FEA. Several damage scenarios are numerically simulated in the FE model of the WTT. Finally, both FBDD and MBDD methods are employed to identify the damage scenarios simulated in the WTT. Damage regions are chosen close to the bolt connection of WTT segments; from there, the stiffness of damage elements are reduced.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.43-58
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• 2002

PSC 보의 비파괴 손상검색을 위한 고유진동수 이용 손상추정법과 모드형상 이용 손상추정법을 제시하였다. 먼저, 고유진동수의 변화를 사용하여 손상의 위치를 예측하는 알고리즘과 고유진동수 1차 섭동 이론에 근거하여 균열크기를 예측하는 알고리즘을 요약하였다 다음으로, 모드형상의 변화로부터 모드민감도의 변화를 감지하고 이를 통해 손상의 위치와 크기를 추정하는 손상지수 알고리즘을 요약하였다. PSC 보의 유한요소모델을 사용하는 수치실험을 통해 고유 진동수 이용 손상추정법과 모드형상 이용 손상추정 법의 정확성을 검증하였다. 분석결과 두 방법 모두 실험 대상 구조에 도입된 균열의 위치를 정확하게 예측하였으며 균열의 크기를 비교적 근사하게 예측하였다.

• 한국통신학회논문지
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• 제29권11C호
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• pp.1573-1580
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• 2004

본 논문은 실제 환경에서 고품질 음성 신호 취득을 위해, 적응 마이크로폰 어레이 시스템을 위한 적응 모드 컨트롤러를 제안한다. 적응 어레이 알고리즘의 올바른 동작을 위하여, 제안된 적응 모드 컨트롤러는 시간 축의 정보뿐만 아니라 공간 축의 정보를 함께 사용한다. 제안된 적응 모드 컨트롤러는 초기화 단계와 수행 단계의 두 단계로 나뉘어 동작되는데, 초기화 단계에서는 음원 위치 추정 기술이 사용되며, 수행 단계는 신호의 상관 관계 특성에 의해 동작한다. 적응 어레이 알고리즘으로는 적응 차단 행렬을 이용한 Generalized Sidelobe Canceller가 사용되었다. 제안한 적응 모드 컨트롤러는 적응 차단 행렬이 수렴되지 않은 경우에도 사용 가능하며, 기존의 전력비 방법에 비해 안정적인 성능을 나타낸다. 본 논문은 제안한 시스템을 실제 환경에서 평가하였으며, 2m 거리에 위치한 화자에 대해 13dB SINR 향상을 얻었다.

• 제어로봇시스템학회논문지
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• 제19권9호
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• pp.813-821
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• 2013

In this paper, we present the development of P-SURO II hybrid AUV (Autonomous Underwater Vehicle) which can be operated in both of AUV and ROV (Remotely Operated Vehicle) modes. In its AUV mode, the vehicle is supposed to carry out some of underwater missions which are difficult to be achieved in ROV mode due to the tether cable. To accomplish its missions such as inspection and maintenance of complex underwater structures in AUV mode, the vehicle is required to have high level of autonomy including environmental recognition, obstacle avoidance, autonomous navigation, and so on. In addition to its systematic development issues, some of algorithmic issues are also discussed in this paper. Various experimental studies are also presented to demonstrate these developed autonomy algorithms.

• 유통과학연구
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• 제10권11호
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• pp.21-30
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• 2012

Purpose - This study aimed to analyze the strategy of late domestic entrants into the Chinese retail market, focusing on the case of Lotte-Mart, given that there are few studies on market entry strategies of domestic retail companies in China. Research Design, data, methodology - The methodology of this paper is a case study approach, focusing on literature reviews and a few interviews. We conducted a survey by disseminating questionnaires and conducting interviews focusing on the Chinese retail market, and analyzed Lotte-Mart's market entry strategy in China. Results - Lotte-Mart chose M&A as the mode of entry, pursuing quick market entry and rapid expansion. It chose small to medium size cities with relatively less competition. Subsequently, Lotte-Mart devoted significant effort towards localization, attempting to organize stores and assorting products to fit the Chinese consumers' preferences. It operated CSR programs to increase its brand awareness and to create a favorable brand image. Conclusions - Lotte-Mart now needs to devise alternative corporate strategies for business expansion and growth. An understanding of the Chinese retail market and the case study analysis of Lotte-Mart's market entry strategy offers significant insights for domestic retail companies looking to expand into China.

• Structural Engineering and Mechanics
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• 제77권4호
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• pp.495-508
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• 2021

This study devises a novel approach, namely quadruple 1D convolutional neural network, for detecting connection stiffness reduction in steel truss bridge structure using experimental and numerical modal data. The method is developed based on expertise in two domains: firstly, in Structural Health Monitoring, the mode shapes and its high-order derivatives, including second, third, and fourth derivatives, are accurate indicators in assessing damages. Secondly, in the Machine Learning literature, the deep convolutional neural networks are able to extract relevant features from input data, then perform classification tasks with high accuracy and reduced time complexity. The efficacy and effectiveness of the present method are supported through an extensive case study with the railway Nam O bridge. It delivers highly accurate results in assessing damage localization and damage severity for single as well as multiple damage scenarios. In addition, the robustness of this method is tested with the presence of white noise reflecting unavoidable uncertainties in signal processing and modeling in reality. The proposed approach is able to provide stable results with data corrupted by noise up to 10%.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.691-709
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• 2012

This paper provides a variety of viewpoints to illustrate the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges. Based on the smooth and convergent bridge shapes obtained by the initial shape analysis, the one-element cable system (OECS) and multi-element cable system (MECS) models of the Kao Ping Hsi Bridge in Taiwan are developed to verify the applicability of the analytical model and numerical formulation from the field observations in the authors' previous work. For this purpose, the modal analysis of the two finite element models are conducted to calculate the natural frequency and normalized mode shape of the individual modes of the bridge. The modal coupling assessment is also performed to obtain the generalized mass ratios among the structural components for each mode of the bridge. The findings indicate that the coupled modes are attributed to the frequency loci veering and mode localization when the "pure" deck-tower frequency and the "pure" stay cable frequency approach one another, implying that the mode shapes of such coupled modes are simply different from those of the deck-tower system or stay cables alone. The distribution of the generalized mass ratios between the deck-tower system and stay cables are useful indices for quantitatively assessing the degree of coupling for each mode. These results are demonstrated to fully understand the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges.

• 한국의학물리학회지:의학물리
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• 제21권4호
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• pp.360-366
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• 2010

최근 정밀한 암 치료를 위해 방사선 치료기술이 강도변도 방사선치료, 영상유도 방사선치료 등의 눈부신 발전을 이루어 왔다. 2000년 이후로는 치료실에서 환자의 실제 치료위치를 정확히 파악하여 정밀한 치료를 가능하게 하는 영상 유도방사선 치료기술이 사용되고 있으며 가장 중요한 기술 중 하나가 방사선 치료 전에 다양한 방법의 의료 영상을 이용하여 환자의 치료 위치를 보정하는 것으로 가장 최근의 기술로는 선형가속기에 장착된 2차원 평면검출기를 이용한 콘빔CT (Cone Beam CT: CBCT)가 사용되고 있다. 본 연구에서는 기존의 CBCT의 "half fan" 조건에서 획득된 projection영상을 이용하여 360도 회전한 모든 영상이 아닌 제한된 각도에서 획득한 투사영상을 이용하여 환자의 해부학적 정보를 볼 수 있는 디지털 영상합성영상(Digital Tomosynthesis) 기술을 구현하였고 실제 위치교정을 위해 촬영된 환자 데이터를 이용하여 방사선 치료 환자 위치 교정을 위한 효용성을 검증하였다. 그 결과 동일 단층상에서의 해부학적 정보 표현에서 CBCT 영상과 비교하였을 때 유사성을 보였고 선량적인 측면에서 우월성을 나타냈다. 이러한 DTS의 장점을 극대화 하고 최적화가 이루어진다면 방사선 치료 위치 보정용으로 CBCT를 대체 할 수 있는 기술이 될 수 있을 것이라 기대한다.

• 로봇학회논문지
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• 제10권3호
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• pp.139-145
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• 2015

This paper proposed a method of cooperative control of three mobile robots for carrying an object placed on a floor together. Each robot moves to the object independently from its location to a pre-designated location for grasping the object stably. After grasping the common object, the coordination among the robots has been achieved by a master-slave mode. That is, a trajectory planning has been done for the master robot and the distances form the master robot to the two slave robots have been kept constant during the carrying operation. The localization for mobile robots has been implemented using the encoder data and inverse kinematics since the whole system does not have the slippage as much as a single mobile robot. Before the carrying operation, the lifting operations are implemented using the manipulators attached on the top of the mobile robots cooperatively. The real cooperative lifting and carrying operations are implanted to show the feasibility of the master-slave mode control based on the kinematics using the mobile manipulators developed for this research.