• 대한기계학회논문집B
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• 제25권3호
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• pp.315-321
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• 2001

Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.

• Structural Engineering and Mechanics
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• 제5권1호
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• pp.1-19
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• 1997

A numerical procedure for dynamic analysis of structures including lateral-torsional coupling, axial force effect and soil-structure interaction is presented in this study. A simple soil-structure system model has been designed for microcomputer applications capable of reflecting both kinematic and inertial soil-foundation interaction as well as the effect of this interaction on the superstructure response. A parametric study focusing on inertial soil-structure interaction is carried out through a simplified nine-degree of freedom building model with different foundation conditions. The inertial soil-structure interaction and axial force effects on a 20-storey building excited by an Australian earthquake is analysed through its top floor displacement time history and envelope values of structural maximum displacement and shear force.

• 제어로봇시스템학회논문지
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• 제13권7호
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• pp.637-648
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• 2007

This paper presents a sensor fusion method based on indirect Kalman filter(IKF) for error compensation of low-cost inertial sensors and its application to the determination of attitude and position of small flying robots. First, the analysis of the measurement error characteristics to zero input is performed, focusing on the bias due to the temperature variation, to derive a simple nonlinear bias model of low-cost inertial sensors. Moreover, from the experimental results that the coefficients of this bias model possess non-deterministic (stochastic) uncertainties, the bias of low-cost inertial sensors is characterized as consisting of both deterministic and stochastic bias terms. Then, IKF is derived to improve long term stability dominated by the stochastic bias error, fusing low-cost inertial sensor measurements compensated by the deterministic bias model with non-inertial sensor measurement. In addition, in case of using intermittent non-inertial sensor measurements due to the unreliable data link, the upper and lower bounds of the state estimation error covariance matrix of discrete-time IKF are analyzed by solving stochastic algebraic Riccati equation and it is shown that they are dependant on the throughput of the data link and sampling period. To evaluate the performance of proposed method, experimental results of IKF for the attitude determination of a small flying robot are presented in comparison with that of extended Kaman filter which compensates only deterministic bias error model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.744-749
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• 2005

In this paper, a lens actuator for mobile devices is proposed using stack type piezoelectric materials. In general, the deformation of PZT actuators is not enough for lens motion when the allowed voltage is applied. The small stroke problem can be solved by accumulating a lot of small displacements in high frequency. In this paper, a new inch-worm type model for focusing actuator is suggested based on the interaction of inertial and frictional forces. Theoretical analysis and simulation using ANSYS are performed to verify the feasibility of the inch-worm PZT actuator model. Various types of clamps are considered to determine the effect of frictional force on the motion, and appropriate clamp-actuator models are proposed. The proposed models are experimentally verified and the experimental results show high correspondence with theoretical and simulated values. The inch-worm type focusing actuator enable a large stroke with 7.79 mm/sec with 10kHz and 10V.

• 설비공학논문집
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• 제30권2호
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• pp.92-99
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• 2018

A numerical analysis of a compressor dehumidifier has been conducted focusing on the air side heat transfer, which is a part of a series research on the dehumidifier. The moving reference frame was applied to the fan modeling, and the porous model was used for the evaporator and condenser modeling. Curve fitting obtained the inertial and viscous resistances parameters to the results of the physical model of the unit cell with actual shape of a fin tube. The porous model was validated within a reasonable computation time for the range of practical inlet velocity of a dehumidifier. A parametric study has been conducted for fin number, fan speed (i.e., air flow rate), and evaporator/condenser tube arrangement. ANOVA analysis showed the dependency of each parameter on the velocity and temperature uniformity, which are desirable for high performance of the dehumidifier.

• 한국수산과학회지
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• 제53권4호
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• pp.637-649
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• 2020

An ideal 3D primitive equation model is implemented to investigate upper ocean response to typhoons, focusing on rightward bias (RWB) which means an appearance of an intensified sea surface cooling to the right side of the typhoon track. The model has 26-stratified levels and a flat bottom (1000 m), covering a rectangular domain of about 3,060 km×3,300 km with four open boundaries. The sea water is forced by an atmospheric pressure and a gradient wind of the typhoon. The model well reproduces the RWB in previous observations and theoretical analyses. For the fast moving typhoon (FMT) (-8m/sec), the model shows that in the mixed layer (ML), the RWB in the SST noticeably appears clearly illustrating the coupling between inertial motion and wind stress, but in the subsurface layer (-100m), the RWB does not emerge since a cyclonic current field (CCF) caused by wind stress curl is primarily dominant. For the slowly moving typhoon (SMT) (-3m/sec), however, the RWB does not emerge because the coupling is weakened and the CCF is rather predominant even in the ML. In the model, we conclude that the RWB noticeably emerges in the FMT but does not emerge in the SMT related to predominance of CCF.

• 한국전문물리치료학회지
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• 제29권2호
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• pp.87-93
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• 2022

To solve the pathological problems of the musculoskeletal system based on evidence, a sophisticated analysis of human motion is required. Traditional optical motion capture systems with high validity and reliability have been utilized in clinical practice for a long time. However, expensive equipment and professional technicians are required to construct optical motion capture systems, hence they are used at a limited capacity in clinical settings despite their advantages. The development of information technology has overcome the existing limit and paved the way for constructing a motion capture system that can be operated at a low cost. Recently, with the development of computer vision-based technology and optical markerless tracking technology, webcam-based 3D human motion analysis has become possible, in which the intuitive interface increases the user-friendliness to non-specialists. In addition, unlike conventional optical motion capture, with this approach, it is possible to analyze motions of multiple people at simultaneously. In a non-optical motion capture system, an inertial measurement unit is typically used, which is not significantly different from a conventional optical motion capture system in terms of its validity and reliability. With the development of markerless technology and advent of non-optical motion capture systems, it is a great advantage that human motion analysis is no longer limited to laboratories.

• Ocean and Polar Research
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• 제39권3호
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• pp.169-179
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• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• 한국재난정보학회 논문집
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• 제18권3호
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• pp.433-443
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• 2022

연구목적: 본 논문에서는 스마트 디바이스의 높은 보급률을 활용하여 근감소증을 추정 및 예측하는 딥러닝 알고리즘을 제안과 연구를 수행한다. 연구방법: 딥러닝 학습을 위해 스마트 디바이스에 내장된 관성센서를 활용하여 실험 데이터를 수집하였다. 데이터를 수집하는 테스트용 어플리케이션 구현하여 '정상'과 '비정상'걸음과 '달리기', '낙상', '스쿼트' 자세의 5 가지 상태를 구분하여 데이터를 수집하였다. 연구결과: LSTM, CNN, RNN model 사용 시 예측 정확도를 분석했고 CNN-LSTM 융합형 모델을 활용하여 이진분류 정확도 99.87%, 다중 분류 92.30%의 정확도를 보였다. 결론: 근감소증이 있는 사람의 경우 걸음걸이의 이상이 생긴다는 점에 착안하여 스마트 디바이스를 활용한 연구를 진행하였다. 본 연구를 활용하여 근감소증으로 인해 생기는 재난안전을 강화 할 수 있을 것이다.