• Journal of The Korean Association For Science Education
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• v.16 no.1
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• pp.51-60
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• 1996

The purpose of this study is to develope and analyze a test for the assessment of physics inquiry experiment. To do this, three experiments about 'analysis of motion', 'the relation of force and acceleration', and 'free fall motion' in high school physics textbooks were chosen, and 5 scientific inquiry domains and 16 science process skills have been specified. For each experiments, test sheet of $29{\sim}44$ questions for assessing students' ability about physics inquiry experiment were developed on the basis of the scientific inquiry processes developed earlier. After instruction about 3 experiments mentioned above, a test was administered to the students who took experiment. After the adminstration of a test, the ratio of correct answers, discrimination index, and reliability were analyzed. Using the ratio of correct answers, we can determine item difficulty. Through the D.I(discrimination index), we can find which items can discriminate the students who took experiment well from those who took experiment badly, and we can also find the stability of a test result by the reliability analysis. The test developed in this study were also administered to the students who did not take experiments, and the results were compared with the those of the students who took experiments. With the comparison by chi-square method, we could find which items can discriminate the students who took experiments from those who did not take experiments.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.105-110
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• 2011

Some research work on CFD computation of ship motions and added resistance in waves for a high speed trimaran is carried out in this paper. The governing equations, Reynolds Averaged Navier-Stokes and continuity equations are discretized by finite volume method. Volume of fluid method is adopted to deal with the nonlinear free surface. The incident waves are generated from the inflow boundary by prescribing a velocity profile resembling flexible flap wavemaker motions, and the outgoing waves are dissipated inside an artificial damping zone located at the rear part of the wave tank. In this paper, the computed results of ship motion and added resistance for a high speed trimaran are presented. The results of seakeeping experiment for the high speed trimaran carried out in CSSRC towing tank are also presented in this paper. Rather good agreements are shown between the computational and experimental results. The work in this paper provides a numerical tool for the study of seakeeping performance of high speed trimarans.

• Journal of the Ergonomics Society of Korea
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• v.21 no.1
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• pp.81-93
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• 2002

This study aims to provide joint angles of comfort for females, based on the psychophysical scaling method. Ten female subjects participated in the experiment for measuring perceived discomfort for varying joint motions. The subjects were instructed to maintain given joint motions for a minute, and to rate their perceived discomfort for the motions during a minute's rest by using the free modulus method of the magnitude estimation. Joint angles of comfort were calculated from the regression equations based on the experimental results, in which levels of joint motions were used as independent variables and perceived discomforts as dependent variables. The results showed that joint angles of comfort for the joint motions investigated were much smaller than full range of motions for corresponding joint motions. The ratios of joint angle of comfort to its range motion for the hip were found to be smallest of all joint motions dealt with in this study, and those for the neck were the largest. In addition, comfortable joint angles for females were much smaller than those for males. It is recommended that when designing or evaluating workplaces ergonomically, different comfortable joint angles should be applied according to workers' or population's gender.

• Transactions on Electrical and Electronic Materials
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• v.8 no.4
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• pp.166-169
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• 2007

In applying LCD to TV application, one of the most significant factors to be improved is image sticking on the moving picture. LCD is different from CRT in the sense that it's continuous passive device, which holds images in entire frame period, while impulse type device generate image in very short time. To reduce image sticking problem related to hold type display mode, we made an experiment to drive TN-LCD like CRT. We made articulate images by turn on-off backlight, and we realized the ratio of Back Light on-off time by counting between on time and off time for video signal input during 1 frame (16.7 ms). Conventional CCFL (cold cathode fluorescent lamp) cannot follow fast on-off speed, so we evaluated new fluorescent substances of light source to improve residual light characteristic of CCFL. We realized articulate image generation similar to CRT by CCFL blinking drive and TN-LCD overdriving. As a result, reduced image sticking phenomenon was validated by naked eye and response time measurement.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.164-169
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• 2001

The active magnetic bearing has many advantages - an active positioning, no contact and lubrication free motion - and is widely used in high precision motion stages. But, the conventional magnetic bearings composed of electromagnets only are power consuming due to their bias current and have the excessive heat generation, which can make the repeatability of the positioning system worse. To overcome this drawback, we developed a novel permanent magnet (PM) biased linear magnetic bearing for a high precision magnetically levitated stage. The permanent magnets provide a bias flux and generate a bias force, and the electromagnet increases or reduces a flux of the permanent magnets and gives a levitation force. This paper presents a theoretical magnetic circuit analysis, FEM analysis and experimental data from the 1-DOF tests, and compares the theoretical power consumption of the electromagnetic bearings and the PM biased linear magnetic bearings. The PM biased linear magnetic bearing presented in this paper gives better load capacity but lower power consumption than a conventional electromagnetic bearing and will be adopted in our 6-DOF high precision linear positioning maglev stage.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.295-306
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• 2007

It is well known that mathematical solutions for multi-agent planning problems are very difficult to obtain due to the complexity of mutual interactions among multi-agents. Most of the past research results are thus based on the probabilistic completeness. However, the practicality and effectiveness of the solution from the probabilistic completeness is significantly reduced by heavy computational burden. In this paper, we propose a practically applicable solution technique for multi-agent planning problems, which assures a reasonable computation time and a real world application for more than 3 multi-agents, for the case of general shaped paths in agent movement. First, to reduce the computation time, an extended collision map is developed and utilized for detecting potential collisions and obtaining collision-free solutions for multi-agents. Second, a priority for multi-agents is considered for successive and interactive modifications of the agent movements with lower priority. Various solutions using speed reduction and time delay of the relevant agents are investigated and compared in terms of the computation time. A practical implementation is finally provided for three different types of agents to emphasize the effectiveness of the proposed interactive approach to multi-agent planning problems.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.32-39
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• 1998

A numerical analysis for large amplitude motions of submerged circular cylinder is presented. The method is based on potential theory and two-dimensional motions in regular harmonic waves are tented as an initial value problem. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed an assumed common boundary to a linear solution in outer domain. Calculations of the large amplitude motion of a submerged circular cylinder are directly simulated in time domain. It is shown that relative motion between the body and fluid particle gives a significant effect on the lift and drift motions.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.693-710
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• 2015

This paper presents a nonlocal shear deformation beam theory for bending, buckling, and vibration of functionally graded (FG) nanobeams using the nonlocal differential constitutive relations of Eringen. The developed theory account for higher-order variation of transverse shear strain through the depth of the nanobeam, and satisfy the stress-free boundary conditions on the top and bottom surfaces of the nanobeam. A shear correction factor, therefore, is not required. In addition, this nonlocal nanobeam model incorporates the length scale parameter which can capture the small scale effect and it has strong similarities with Euler-Bernoulli beam model in some aspects such as equations of motion, boundary conditions, and stress resultant expressions. The material properties of the FG nanobeam are assumed to vary in the thickness direction. The equations of motion are derived from Hamilton's principle. Analytical solutions are presented for a simply supported FG nanobeam, and the obtained results compare well with those predicted by the nonlocal Timoshenko beam theory.

• Journal of the Korea Computer Industry Society
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• v.3 no.3
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• pp.283-294
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• 2002

Now is the time for web-based video e-mail system because of world wide use of internet. But video data is so large, then data compression is much needed for transmission by web. In this paper, my colleagues and I implement full motion video e-mail system using MPEG-4, the international standards for audio-visual data. This video e-mail system is made of web-based active-X control, so easily accessible by web, and applies real-time audio-video compression. It's possible for everyone to send video e-mail for free to everywhere in the world if this system is used. The main application areas of this system are multimedia mailing service, web-based video advertisement, remote education, remote medical service and shopping mall construction, etc.

• Journal of Yeungnam Medical Science
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• v.35 no.1
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• pp.63-69
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• 2018

Background: Kinovea software that tracking semi-automatically the motion in video screen has been used to study motion-related tasks in several studies. However, the validation of this software in open field test to assess locomotor activity have not been studied yet. Therefore, this study aimed to examine the reliability and validity of this software in analyzing locomotor activities. Methods: Thirty male Institute Cancer Research mice were subjected in this study. The results examined by this software and the classical method were compared. Test-retest reliability and inter-rater reliability were analyzed with Pearson's correlation coefficient and intraclass correlation coefficient (ICC). The validity of this software was analyzed with Pearson's correlation coefficient. Results: This software showed good test-retest reliability (ICC=0.997, 95% confidence interval [CI]=0.975-0.994, p<0.001). This software also showed good inter-rater reliability (ICC=0.987, 95% CI=0.973-0.994, p<0.001). Furthermore, in three analyses for the validity of this software, there were significant correlations between two methods (Pearson's correlation coefficient=0.928-0.972, p<0.001). In addition, this software showed good reliability and validity in the analysis locomotor activity according to time interval. Conclusion: This study showed that this software in analyzing drug-induced locomotor activity has good reliability and validity. This software can be effectively used in animal study using the analysis of locomotor activity.