• 한국지구과학회지
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• 제25권8호
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• pp.663-673
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• 2004

본 연구에서는 ‘달의 운동’ 단원에 대한 상호작용형 WBI 학습 프로그램을 개발하였다. 개발된 프로그램은 중학교 과학교사 20명에게 의뢰하여 의견을 들었으며, 중학생 49명에게 3개월 동안 투입하여 그 질적 수준을 조사하였다. 그 결과 흥미유발, 궁금증 해결, 탐구능력 신장, 학습 참여도, 난이도 등의 면에서 응답자의 85%이상이 긍정적이라고 응답하였다. 그리고 과학에 대한 부정적인 인식을 갖고 있는 학습자들의 반응은 본 WBI 프로그램 학습 후 통계적으로 유의수준 .05에서 유의미한 차이를 나타내었다(p<.05). 또한 본 WBI 프로그램 투입 전후 학습자들의 개념 수준을 비교한 결과, ‘달의 운동’과 관련된 개념을 갖고 있지 않은 경우가 부분적인 개념을 갖고 있는 경우보다 개념 향상 정도가 더 높았다.

• 한국융합학회논문지
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• 제10권3호
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• pp.135-140
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• 2019

본 연구는 가상환경 기반 VR(가상환경)과 실사 환경 기반 VR 중심으로 콘텐츠의 환경에서 사이버 멀미 요인을 분석하는 데 목적이 있다. 1차로 문헌연구를 통해 사이버 멀미의 원인을 규명하기 위해 3D 애니메이션과 다큐멘터리에 관한 이론을 정리하였다. 멀미 정도에 대한 측정 도구로써는 표준화된 SSQ(Simulator Sickness Questionnaire) 설문지를 활용하여 증상 값을 측정하였다. 측정 후에는 SSQ 설문지를 바탕으로 심층 인터뷰를 진행하였다. 연구 결과는 첫째, 가상환경 기반 VR보다는 실사 환경 기반 VR의 콘텐츠가 사이버 멀미를 유발한다, 둘째, VR 콘텐츠는 강한 채도 값이 사이버 멀미를 유발한다. 본 연구는 VR 초기 콘텐츠를 구성하는데 디자인 가이드라인으로 활용할 수 있으며, 사이버 멀미 연구에 활용할 수 있을 것으로 기대한다.

• 한국정밀공학회지
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• 제26권2호
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• pp.109-117
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• 2009

This paper presents a linear air bearing stage with compensated motion errors by active control of preloads generated by magnetic actuators with combination of permanent and electromagnets. A 1-axis linear stage motorized with a linear motor with 240mm of travel range is built for verifying this design concept and tested its performances. The three motions of the table are controlled with four magnetic actuators driven by current amplifiers and a DSP based digital controller. Three motion errors were measured combined method with laser interferometer and two-probe method with $0.085{\mu}m$ of repeatability for straightness error. The measured motion errors were modeled as functions of the stage position, and compensation were carried out with feedforward control because the characteristics of the motion control with magnetic actuators are linear and independent for each degree-of-freedoms. As the results, the errors were reduced from $1.09{\mu}m$ to $0.11{\mu}m$ for the vertical motion, from 9.42 sec to 0.18 sec for the pitch motion and from 2.42 sec to 0.18 sec for roll motion.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.213-216
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• 1996

This paper studies a class of in-parallel manipulators with special geometry where the forward displacement analysis problem can be solved easier than the fully parallel manipulators. Three horizontal links of this mechanism provide 3DOFs(Degrees of Freedom), which are one degree of orientational freedom and two degrees of translatory freedom. Three vertical links of this mechanism provide 3DOFs, which are two degrees of orientational freedom and one degree of translatory freedom. The main advantages of this manipulator, compared with the Stewart platform type, are the capability to produce pure rotation and to predict the motion of the moving platform easily. Since this manipulator has simple kinematic characteristics compared with the Stewart platform, controlling in real-time is possible due to less computational burden. The purpose of this investigation is to develope an analytical method and systematic method to analyze the basic kinematics of the manipulator. The basic kinematic equations of the manipulator are derived and simulation is carried out to show the performance of the mechanism.

• Wind and Structures
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• 제5권2_3_4호
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• pp.379-392
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• 2002

Numerical flow computations around an aeroelastic 3D square cylinder immersed in the turbulent boundary layer are shown. Present computational code can be characterized by three numerical aspects which are 1) the method of artificial compressibility is adopted for the incompressible flow computations, 2) the domain decomposition technique is used to get better grid point distributions, and 3) to achieve the conservation law both in time and space when the flow is computed a with moving and transformed grid, the time derivatives of metrics are evaluated using the time-and-space volume. To provide time-dependant inflow boundary conditions satisfying prescribed time-averaged velocity profiles, a convenient way for generating inflow turbulence is proposed. The square cylinder is modeled as a 4-lumped-mass system and it vibrates with two-degree of freedom of heaving motion. Those blocks which surround the cylinder are deformed according to the cylinder's motion. Vigorous oscillations occur as the vortex shedding frequency approaches cylinder's natural frequencies.

• 한국전문물리치료학회지
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• 제25권3호
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• pp.12-18
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• 2018

Background: Passive straight leg raising (PSLR) is the common clinical test to measure of hamstring muscle length. Hip flexion angle contributes to change the lumbopelvic rotation during PSLR. Pressure biofeedback unit (PBU) is commonly used to detect lumbopelvic movement during lower limb movements. Thus, there may be the relationship between pressure of PBU and lumbopelvic motion during PSLR. Objects: The objective of this study was to determine the relationship between pressure of PBU and lumbopelvic motion during PSLR. Methods: Thirty two subjects participated in this study. A three-dimensional motion analysis system were used to measure the lumbopelvic angle during PSLR, while recording the pressure of PBU according to angle of PSLR by 10 degree increments. Pearson product moment correlations and linear regression analysis were used to describe the relationship between variables. Results: The results showed that there was a significant relationship between the lumbopelvic and angle of PSLR (Pearson's r=.83, p<.05), between the pressure of PBU and angle of PSLR (Pearson's r=.75, p<.05), and between lumbopelvic motion and pressure of PUB (Pearson's r=.83, p<.05). Linear regression equation using lumbopevic angle as an independent factor was as follows: Pressure of PBU = 47.35 + (2.55 ${\times}$ angle of lumbopelvic motion) ($R^2=.69$, p<.05). Conclusion: Results of the present study indicate that pressure of PBU can be used to indirectly detect the amounts of lumbobevic motion during muscle length test or stretching of hamstring.

• International Journal of Ocean System Engineering
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• 제3권1호
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• pp.10-15
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• 2013

A ship cruising in the ocean oscillates continuously due to wave action. In order to reduce the ship's roll, we developed a fin stabilizer as an anti-rolling device for a 500-ton-class high-speed marine vessel. During the development phase, it was necessary to set up control gains for the motion and hydraulic systems and assess the effectiveness of the anti-rolling performance on the ground. For this reason, a Target Simulator, which simulated the ship's motion, was given operator inputs such as the engine telegraph and waterjet deflection angle, and generated roll using a one-degree-of-freedom motion base. Hardware-In-the-Loop Simulation (HILS) was performed using the Target Simulator in order to confirm the various logics of the developed fin stabilizer, select initial control gains, and estimate the anti-rolling performance. In conclusion, it was confirmed that HILS was very helpful to develop the fin stabilizer because it could reduce the number of sea trial tests that were needed and could find many malfunctions in the factory a priori.

• Earthquakes and Structures
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• 제9권5호
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• pp.1091-1114
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• 2015

The adequacy of a number of advanced earthquake Intensity Measures (IMs) to predict the structural damage of earthquake resistant 3D R/C buildings is investigated in the present paper. To achieve this purpose three symmetric in plan and three asymmetric 5-storey R/C buildings are analyzed by nonlinear time history analysis using 74 bidirectional earthquake records. The two horizontal accelerograms of each ground motion are applied along the structural axes of the buildings and the structural damage is expressed in terms of the maximum and average interstorey drift as well as the overall structural damage index. For each individual pair of accelerograms the values of the aforementioned seismic damage measures are determined. Then, they are correlated with several strong motion scalar IMs that take into account both earthquake and structural characteristics. The research identified certain IMs which exhibit strong correlation with the seismic damage measures of the studied buildings. However, the degree of correlation between IMs and the seismic damage depends on the damage measure adopted. Furthermore, it is confirmed that the widely used spectral acceleration at the fundamental period of the structure is a relatively good IM for medium rise R/C buildings that possess small structural eccentricity.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.1999-2010
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• 2023

Undesirable flapping motion of discs can cause the failure of swing check valves in nuclear passive safety systems. Time-resolved particle image velocimetry (PIV) was employed to investigate the flow characteristics around a free-to-rotate plate and the motion response, with the Reynolds numbers, based on the hydraulic diameter of the channel, from 1.32 × 10⁴ to 3.95 × 10⁴. Appreciable flapping motion (±3.52°) appeared at the Reynolds number of 2.6 × 10⁴ with the frequency of 5.08 Hz. In the low-Reynolds-number case, the plate showed negligible flapping. In the high-Reynolds-number case, the deflection angle increased with reduced flapping amplitude. The torque from the fluid determined the flapping amplitude. In the low-Reynolds-number case, Karman vortices were absent. With increasing Reynolds numbers, Karman vortices developed behind the plate with larger deflection angles. Strong interaction between the wake flow from the leading and trailing edge of the plate was observed. Based on power spectrum density (PSD) analysis, the vortex shedding frequency coincided with the flapping frequency, and the amplitude was positively correlated to the strength of the vortices. Proper orthogonal decomposition (POD) modes evince that, in the case of appreciable motion, coherent structures exhibited a larger spatial scale, enhancing the magnitude of the external torque on the plate.

• 패션비즈니스
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• 제24권4호
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• pp.63-84
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• 2020

It is essential to consider the heavy industrial working environment factors which are regarded as harmful to workers' health and safety and suitable work motion factors for the workers' motion while developing the work clothes for painting workers in the machinery and shipbuilding industries. This study suggests the use of 3D virtual clothing simulations as a solution to protect the human body from hazardous working conditions accompanying the development of painting work clothes and assessing the work motion performance associated with the comfort while workers wear them during the work clothes. The initial aim of the study is to examine a male avatar to run work motions simultaneously within a 3D virtual clothing simulator, secondly, to present the simulation images of coverall type men's painting work clothes with the application of two experimental painting work motions and one control motion to the avatar, and finally, to present the distance analysis images of the painting work clothes and the avatar body and air gap rates through the analysis of cross-sections of the avatar body while wearing the coverall work clothes according to the work motions. The results showed that the distance degree of painting work clothes to the avatar body for each part of the human body when performing painting work motions. Moreover, 3D virtual clothing simulations enabled the creation of a male model avatar to run painting work motions together and the painting work clothes developed were found to be suitable for the painting work motions.