• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.44-51
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• 2008

In this paper, the optimal tuning of a cross-coupled controller linked with the feedforward controller is studied to reduce contouring and tracking errors of a bi-axial servomechanisms by using the previously developed integrated tuning method. The CCC system for an arbitrary curve, which is combined with the feedforward controller, is formulated by a state-space based on a series of linear motion trajectories. An optimal tuning problem is formulated as a nonlinear constrained optimization problem including relevant controller parameters of the servo. To verify the effectiveness of the proposed optimal tuning procedure, linear and circular motion experiments are performed on the xy-table. Experimental results confirm that both tracking and contouring errors are significantly reduced by applying the proposed control and tuning system.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.1
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• pp.37-40
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• 1975

Heave and pitch amplitude and phase lag, relative vertical displacement, velocity and acceralation at bow as bow motion and wave exciting force and moment of a DWT 260,000 ton class tanker in the regular head wave have been calculated. All the calculations have been made by the computer program SD08 of Seoul National University. As the results it is cleared heave amplitude and acceralation have large value in the ballast condition and low Froude-number than full load condition and higher Froude numer as for as the $\frac{\lambda}{L}$ is lower than near around 1.0, however they have quite large values as $\frac{\lambda}{L}$ goes up.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.5-10
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• 2003

This paper is mainly concerned with the assessment of safe navigation between ships moving each other in restricted waterways. The manoeuvring simulation was conducted parametrically to propose an appropriate sage speed and distance, which is required to avoid sea accident under the different conditions, such as ship-velocity ratios, ship-length ratios, separation and stagger between ships. The manoeuvring characteristics based on this investigation will be very useful for keeping the safety of navigation from the practical point of ships design and traffic control in confined water.

• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.44-48
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• 2016

물 속에서 고속으로 유영하는 상당수의 어류는 긴 부리 모양의 주둥이를 가진다. 대표적으로 지구상 가장 빠른 물고기인 돛새치가 있다. 이러한 사실은 이 독특한 형상과 고속운동의 상관관계에 대해 학구적 호기심을 자아냈고 그에 따라 본 연구를 수행하였다. 본 연구에서는 돛새치, 청새치들의 2차원 형상을 가지고 부리의 존재 유무가 항력에 미치는 영향을 분석하고 더 나아가 미사일의 spike가 항력에 미치는 영향을 분석하였다. 또한 부리가 방향전환 시 기동성 증진에도 기여하는지를 알아보았다. 해석을 위해 Kflow Edison_13와 2D_Comp_P 해석자를 활용하여 동일 유동조건에서 항력계수를 비교하였다. 그리고 돛새치가 방향 전환할 때 발생하는 모멘트계수를 얻기 위해 2D_Incomp_P 해석자를 활용하였다.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.52-60
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• 1997

This paper proposes the effective method of the software based motion control by using lenear, exponential and bell type discrete filters for acceleration and deceleration of servo motors. Recursive filters are designed in discrete time domain which can reduce computation time and vibration of motors due to load disturbance. Also it deals with the method which decides the time constants of filters when a machine tool is driven at rapid, cutting and jog feedrate. Validity of the proposed method is verified by corner cutting experiments.

• Journal of the Korean Society of Radiology
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• v.82 no.4
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• pp.988-993
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• 2021

Cardiac papillary fibroelastoma (CPF) is the second or third most common primary cardiac tumor. Although histologically benign, it can cause serious symptoms depending on its location of occurrence, size, and motility. Herein, we report CPF in the left ventricular trabeculation as a potential cause of cerebral infarction.

• Journal of the Korean Chemical Society
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• v.60 no.6
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• pp.436-451
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• 2016

This study analyzed activities in chemistry chapters of middle school science textbooks for the 2009 revised curriculum using 8 science practices. All the activities that students could experience inquiry were analyzed in this study. There were the most activities in 'Molecular motion and change of state' and the least activities in 'Heat and our life' of three textbooks. There were the most science practices in 'Features of substance' in two textbooks, but there were the least science practice in 'Heat and our life' of three textbooks. 'Investigation planning and performing', 'data analyzing and interpreting', and 'explanation composition and problem solution designing' were frequently included, but 'asking questions and defining issues' was not included at all. For 'Investigation planning and performing', 'data analyzing and interpreting', and 'explanation composition and problem solution designing', a variety of achievement goals were targeted while a few goals were frequently targeted. Two to four kinds of science practices were frequently included in an inquiry activity. There were few activity that includes over 5 different kinds of science practice.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.226-233
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• 2002

In the field of research of sea keeping quality, much development has been made in recent years using the method of calculation based on the strip theory. It is very important to investigate the hull response of a fishing vessel in waves to ensure the safe navigation and fishing operation in rough seas by preserving excellent sea keeping qualities. For this purpose, the author measured various responses of three fishing vessels in waves using real sea experimental measuring system and analyzed the experimental data The results obtained can be summarized as follow. 1. The amplitudes of pitching motion in the experiments appeared low values with more than one peak occasionally in following sea and quartering sea, and the band width of those was found to be wide relatively. 2. The amplitudes of rolling motion in the experiments appeared high values with only one peak in following sea and quartering sea regardless of ship's tonnage, and the band width of those was found to be narrow relatively. 3. The comparisions of theoretical results with those of experiments for the pitching motions and rolling motion in following sea and quartering sea show that the theoretical values are higher slightly than those of experiments in both directions and the period at which the peak appears in the calculations and the experiments has good agreement approximately 4. The calculated responses of two vessels under a assumed wave of 2.2m height and 5.0sec period showed that the response of pitching motion of ship-A are 2.2 times bigger than those of ship-C in following sea and quartering sea, and the response of rolling motion of ship-A is 4.2 times bigger than that of ship-C in quartering sea.

• Journal of Korean Elementary Science Education
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• v.42 no.1
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• pp.93-108
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• 2023

This study aims to analyze the types and roles of visualization materials presented in the third- and fourth-grade national and authorized science textbooks based on the 2015 revised curriculum. Using the type and role framework, 17 chapters were analyzed. The analysis revealed, first, that the national and authorized textbooks had different total amounts of visualization data and total amounts of simple illustrations. However, no difference in the amounts of simple illustrations and infographics used in the units was evident. The units that used the most infographics were Life, Earth and Universe, in that order, in both the national and the authorized textbooks. Second, simple illustrations were observed to have role differences according to the type of visualization data, but infographics had no such differences. Specifically, the motivational role in a simple illustration increased in all the authorized textbooks. Third, looking at the frequencies of the infographic subtypes, the Process, Structure, Comparative Analysis, and Timeline types accounted for 86% of the total, but the proportions of those subtypes varied in the national and authorized textbooks. Based on the results of this study, I suggest that to achieve differentiation in the types or roles of visualization materials, changes in the types, processes, and skills of inquiry must first occur, as must changes in the structure of chapters or lessons. Continuous research and discussion on the standards and methods for authorized textbooks are also needed.

• Journal of Chest Surgery
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• v.39 no.9 s.266
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• pp.674-680
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• 2006

Background: Acute myocardial infarction (MI) is a life-threatening disease and surgical revascularization plays a major role in selected cases. The purpose of this study is to evaluate the left ventricular contractility improvement by examining the wall motion score index (WMSI) and left ventricular ejection fraction (LVEF) in patients who under-went surgical revascularization under diagnosis of acute MI. Material and Method: From January, 2001 to December, 2004, 149 patients who underwent coronary artery bypass surgery within 2 weeks of acute MI were included. We evaluated pre- and postoperative left ventricular contractility by measuring WMSI and LVEF and examined the associating factors. Result: WMSI decreased from $1.54{\pm}4.30\;to\;1.43{\pm}0.40$ (p<0.001) and LVEF increased from $48.1{\pm}12.2%\;to\;49.7{\pm}12.3%$ after surgery (p=0.009). Off-pump technique, non-Q wave, anterior MI, and surgery within 7 days after MI were favorable factors for LVEF improvement (p=0.046, p=0.006, p=0.003, p=0.005, respectively). Conversely, aforementioned factors were irrelevant with WMSI improvement. For triple vessel disease, complete revascularization was favorable factor for WMSI improvement (p<0.001). Conclusion: Coronary artery by-pass surgery can improve WMSI and LVEF in patients with acute MI. In case of anterior MI with non-Q wave, early surgical revascularization within 7 days may be most beneficial in LVEF improvement. Regarding WMSI, complete revascularization may be essential.