• 정보과학회 컴퓨팅의 실제 논문지
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• 제23권2호
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• pp.104-109
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• 2017

본고에서는 다중 웨어러블 센서 데이터로부터 사용자의 일상 생활 행동 패턴을 분석할 수 있는 새로운 기계학습 모델을 제안한다. 제안하는 모델은 다중 웨어러블 센서 데이터를 효과적으로 학습하기 위하여 사람이 다중 센서 정보를 처리하는 방법을 적용한 새로운 신경망 모델이다. 제안하는 Gated multi-modal neural netoworks는 계층적 신경망 구조를 가지고 있으며 Gate 모듈을 통해 각 센서 데이터를 선택적으로 결합하여 처리하는 특징을 가진다. 실험을 위해 다중 웨어러블 장치를 착용하고 일상 생활 중 한 가지인 레스토랑에서의 행동 센서 데이터를 수집하였다. 실험 결과로서, 제시하는 모델을 이용하여 실제 웨어러블 센서 데이터를 분석하였을 때 분류 정확도가 비교적 정확하고 빠르게 처리할 수 있음을 확인하였다. 또한 모델의 중간 계층에서의 노드의 활성화 패턴 분석을 통해 자동으로 일상생활 패턴을 추출할 수 있고 이를 이용하여 지식 스키마를 생성할 수 있음을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.52.3-52
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• 2002

Natural frequencies and mode shapes are two important modal data which specify the system. If the real system and FE model don't have the same local physical parameters, there will be a difference between modal data from real system and FE model. Because there is little difference in displacement mode shapes measured by an accelerometer, displacement modal update based on mode shapes including measurement errors may not be successful. In this research, strain mode shapes are used as modal data because the strain mode shapes measured by strain gauges are more sensitive than the displacement mode shapes with respect to the change of the parameters concerned in FE stiffness matrix...

• 한국공간구조학회논문집
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• 제2권2호
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• pp.59-67
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• 2002

In this study, a method that estimates stiffness and mass matrices of shear building from modal test data is presented. This method applied of building depends on the number of measurement points that are less in number than the total structural degrees of freedom, and on the first two orders of structural mode measured. By means of this method it is possible to use modal data of unmeasurable points to estimate total stiffness and mass matrices of structure. Some examples are studied in this paper, and its result shows that this method is reliable.

• 한국항해항만학회지
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• 제36권2호
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• pp.89-95
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• 2012

Identification of the modal properties of a structural system has received much attention over the years because of its importance in structural model updating, structural health monitoring and structural control. This paper presents experimental modal test results such as natural frequencies and mode shapes of a scale model of floating structure. A modal testing is performed on the structure and modal parameters for the structure are extracted from the measured data. The results are compared to a finite element model and the correlation between the measured and analytical modal parameters is investigated.

• 영어어문교육
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• 제18권1호
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• pp.197-216
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• 2012

This study examines spoken interlanguage of Korean learners of English, focusing on the distribution of modal verbs and devices of epistemic modality. (Semi-) spontaneous speech data were collected from four students participating in a self-organized study group for seven months, which produced a corpus of about 55,000 words. The data analysis reveals the following: 1) The frequency of the modal verbs produced by the learners was lower than that of native speakers; 1.99 vs. 2.32 tokens per 100 words. The range of the modal verbs used by the learners was also very limited, with over-reliance on can (43%). 2) The grammatical categories of the devices marking epistemic modality were in the order of adverbs, lexical verbs, and modal verbs, with a high frequency of a few items in each category. 3) Lexical items conveying certainty and modals of obligation were preferred over markers of weaker commitment, resulting in speech characterized by firmer assertions and a more authoritative tone, a potential cause for pragmatic failure. 4) A weak developmental change was observed in the frequency of modal verbs, but not in their functions over the seven month period of data collection. L1 influence, L2 proficiency, mode of communication, and instruction effects are discussed as possible variables involved in the distribution patterns observed.

• Wind and Structures
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• 제11권1호
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• pp.35-50
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• 2008

Wind and temperature have been shown to be the critical sources causing changes in the modal properties of large-scale bridges. While the individual effects of wind and temperature on modal variability have been widely studied, the investigation about the effects of multiple environmental factors on structural modal properties was scarcely reported. This paper addresses the modeling of the simultaneous effects of wind and temperature on the modal frequencies of an instrumented cable-stayed bridge. Making use of the long-term monitoring data from anemometers, temperature sensors and accelerometers, a neural network model is formulated to correlate the modal frequency of each vibration mode with wind speed and temperature simultaneously. Research efforts have been made on enhancing the prediction capability of the neural network model through optimal selection of the number of hidden nodes and an analysis of relative strength of effect (RSE) for input reconstruction. The generalization performance of the formulated model is verified with a set of new testing data that have not been used in formulating the model. It is shown that using the significant components of wind speeds and temperatures rather than the whole measurement components as input to neural network can enhance the prediction capability. For the fundamental mode of the bridge investigated, wind and temperature together apply an overall negative action on the modal frequency, and the change in wind condition contributes less to the modal variability than the change in temperature.

• 항공우주기술
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• 제6권1호
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• pp.114-119
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• 2007

본 연구는 KSLV-I 페이로드 페어링을 제외한 2단 구조부에 대한 모드시험 결과를 기술하고 있다. 2단부는 크게 위성 분리부, 탑재부, 킥모터 지지부, 킥모터로 구성되어 있다. 번지코드를 이용하여 자유경계단 조건을 모사하였고 가진은 대형 가진 망치를 사용하였다. 이러한 모드시험 결과를 통하여 모드변수를 추출할 수 있고, 2단부 구조체의 동특성을 파악할 수 있다. 시험 결과는 TDAS를 사용하여 분석하였고, 100Hz 이하의 모드변수 및 모드형상을 추출하였다.

• 한국멀티미디어학회논문지
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• 제7권3호
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• pp.427-437
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• 2004

3차원 모델간의 형상을 비교하는 것은 형상을 기반으로 하는 인식, 검색, 분류 등을 위해 매우 중요하다. 본 논문에서는 모델의 이동, 회전, 스케일 변화에 영향받지 않고, 모델을 구성하는 정점들이 비균일 하고 불완전한 경우에도 강인한 3차원 형상 비교 방법을 제안한다. 먼저 입력 데이터로부터 고유 모드를 이용한 모달 모델을 구성하고 모달 스트레인 에너지를 이용하여 형상 간의 유사성을 비교한다. 제안된 방법은 고유 진동수에 따라 고유 모드들을 순서화 함으로써 형태 변형을 전역적인 것에서부터 지역적인 것으로 체계화한다. 이렇게 체계화된 형상 표현과 모달 스트레인 에너지를 이용함으로써 국부적인 형태에 치우치지 않고 전체적인 형태의 유사성을 평가하였다.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.1-18
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• 2015

Traditionally, it is not easy to carry out tests to identify modal parameters from existing railway bridges because of the testing conditions and complicated nature of civil structures. A six year (2007-2012) research program was conducted to monitor a group of 25 railway bridges. One of the tasks was to devise guidelines for identifying their modal parameters. This paper presents the experience acquired from such identification. The modal analysis of four representative bridges of this group is reported, which include B5, B15, B20 and B58A, crossing the Caraj$\acute{a}$s railway in northern Brazil using three different excitations sources: drop weight, free vibration after train passage, and ambient conditions. To extract the dynamic parameters from the recorded data, Stochastic Subspace Identification and Frequency Domain Decomposition methods were used. Finite-element models were constructed to facilitate the dynamic measurements. The results show good agreement between the measured and computed natural frequencies and mode shapes. The findings provide some guidelines on methods of excitation, record length of time, methods of modal analysis including the use of projected channel and harmonic detection, helping researchers and maintenance teams obtain good dynamic characteristics from measurement data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1718-1723
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• 2003

This paper presents a computational method for deformation modes of a flexible body in multibody system from the experimental modal analysis and an efficient method for flexible multibody dynamic analysis by use of the modes. It is difficult to directly use experimental modal parameters in flexible multibody dynamic analysis. The major reasons are that there are many inconsistencies between experimental and analytical modal data and experimental noises are inherent in the experimental data. So two methods, such as, a method for ortho-normalization of experimental modes and the other one for mode expansion, are suggested to gain deformation modes of a flexible body from the experimental modal parameters. Using the virtual work principle, the equation of motion of a flexible body is derived. The effectiveness of the proposed method will be verified in the numerical example of cab vibration of a truck by comparing analysis and test results.