• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.381-388
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• 2012

Purpose: In this study, the changes in the shape of silicone hydrogel lenses, dryness of lens and objective/ subjective symptoms that could be induced by repeating dryness of lens and objective/subjective symptoms were investigated. Methods: After drying and rehydrating of silicone hydrogel lenses with different lens material and thickness for 4 times, their overall diameters and base curves were compared. Subjective symptoms, non-invasive tear break-up time (NIBUTs) and blinking rate were evaluated after wearing dehydrated silicone hydrogel lens. Results: Overall diameter and base curve increased in all tested silicone hydrogel lenses by repeating dryness and rehydration. The degree of change in over all diameter and base curve were variable on the material. There were irregular change of lens parameters in thicker lens. When the subjects wore silicone hydrogel lenses after drying and rehydrating, their NIBUTs were decreased and blink rates were increased regardless of lens material or thickness. In addition, repetitive drying of silicone hydrogel lenses affected the lens fitting. Therefore, subjective symptoms such as itching, pain, irritation, foreign body sensation, dryness tended to be increased. Conclusions: The results obtained from the study may suggest to develop durable silicone hydrogel contact lenses against dry environment since the changes in parameters of silicone hydrogel lens and the subjective discomfort were observed after repetitive drying and rehydration.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.389-394
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• 2012

Purpose: The purpose of this study was to examine the corneal topographical changes associated with the wearing of everted silicone hydrogel soft lenses. Methods: The shape and fluorescein pattern of everted silicone hydrogel lenses were investigated. The subject wore the silicone hydrogel everted lenses overnight for 8 hours. Objective refractive error and corneal shape were evaluated at baseline, 1, 2, 3, 5, and 7 days after lens wearing and 1,2,3, and 4 days after discontinuation of lens wear. Results: The Fluorescein pattern of everted silicone hydrogel lenses was similar to the reverse geometry lenses with pressure profile. Objective refractive error(sphere power) and corneal refractive power were decreased and corneal shape had changed during the everted silicone hydrogel lenses wear and recovered during the 4 days of discontinuation. Subject experienced no discomfort associated with the everted silicone hydrogel lenses. Conclusions: It appears that everted silicone hydrogel lenses are capable of inducing significant changes in corneal topography, with overnight wear. Further study must be done to help understand these changes to develop a predictable and effective way of using soft contact lenses for corneal reshaping.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.193-201
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• 2014

This study provided safe sailing speed and appropriate passing time to areas of known strong current water to prevent marine accident of the ships. To the interpretation of these data which target Myeongnyang waterway, AIS data of the ship was collected from $12^{th}$ July to $15^{th}$ July 2010 and site environment was investigated on $4^{th}$ September 2010. On the basis of the collected data, the 'Minimum Navigation Speed' and 'Optimum Navigation Speed' were calculated. It has also considered the 'Spare control force' or allowance and the 'Respond Rudder Angle' for each tidal current speed. Additionally, it suggested the safe passing time to strong current area by analyzing tidal level and tidal current speed. The conclusion of the research are as follows : (1) If the flow rate is greater than 4.4 kn, it is difficult for the model ship to control herself by her own steering power and to cope with tidal current pressure force and yaw moment caused by the tidal current.. (2) The minimum navigation speed should be over 2.3 times the tidal current and the optimum navigation speed should be over 4.0 times the tidal current. (3) When spring tide, the optimum passing time at Myeongnyang waterway is between 30 minutes to 1 hour before the time of high/low water, and at 5 hours after high/low water, passing of ships should be avoided because it is time when the flow rate is over 4 kn.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.821-828
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• 2011

This paper developed the algorithm for improving the performance the auto pilot in the autonomous vehicle system consisting of the Track keeping control, the Automatic steering, and the Automatic mooring control. The automatic steering is the control device that could save the voyage distance and cost of fuel by reducing the unnecessary burden of driving due to the continuous artificial navigation, and avoiding the route deviation. During the step of the ship autonomic navigation control, since the wind power or the tidal force could make the ship deviate from the fixed course, the automatic steering calculates the difference between actual sailing line and the set course to keep the ship sailing in the vicinity of intended course. first, we could get the transfer function for the modeling of ship according to the Nomoto model. Considering the maneuverability, we propose it as linear model with only 4 degree of freedoms to present the heading angle response to the input of rudder angle. In this paper, the model of ship is derived from the simplified Nomoto model. Since the proposed model considers the maximum angle and rudder rate of the ship auto pilot and also designs the Fuzzy controller based on existing PID controller, the performance of the steering machine is well improved.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.87-92
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• 1998

Unaided visual acuity was tested by ACP-7 TOPCON chart projector on 376 kindergarteners and objective refraction error was measured by NIDEK ARK-700A auto-refractokeratometer on 554 eyes aged 3 to 5. The results were as follows ; The average unaided visual acuity of children aged 3 was 0.82, aged 4 was 0.90 and aged 5 was 0.92 respectively theerfore children s visual acuity has been gradually developed with their age. The kind of refractive error was 1% for hyperopia, 14% for hyperopic astigmatism, 3% for myopia, 50% for myopic astigmatism, 18% for mixed astigmatism and 14% for emmetropia respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.1
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• pp.53-56
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• 1996

In testing visual acuity of kindergarten's children, single Landolt's ring in chart projector was used under proper intensity of illumination. According to the result of 218 eyes' test, 0.6 V.A. forms 8.5 % at the age of 3, 0.7 V.A. forms 84.7 % at the age of 4, and 1.0 V.A. forms 6.8 % at the age of 5. However, children's visual acuity has been gradually developed with their growth. None of emmetropia can be found through the test. All of the children have ametropic eyes.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.29-34
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• 2004

The aim of this thesis research is to develop equipment measuring refractive state in order to measure the general ocular function using PC-based Foucault Test(Knife Edge Test). The Image of light generated from the reflection of incident light in retina thru Knife Edge Test was photographed using a CCD camera. The resulting image was then analyzed to measure the size of pupil by measuring the diameter of reflected image. The reflection state was judged from the orientation of reflected image and the degree of abnormal reflection was confirmed by measuring the size of second image of reflection. The aberration value was calculated from the magnitude of spherical aberration obtained by comparing the brightness of second reflected image appeared in the opposite direction to the reflected image.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.105-109
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• 2001

The investigate of preschool children at 7-year-old at three kindergartens in Iksan was done by the naked visual acuity, the refractive state and cover-uncover test. Total 246 eyes were examined by the objective and subjective methods. The results were as follows: 1. Among the 246 eyes, the naked visual acuity of below the average 0.7 was 64 eyes(26%). 2. As to the distribution of refractive errors, myopic eyes and hyperopic eyes were 26.55% and 26.55%, respectively. 3. As to the type of astigmatisms, with the rule was 85.8%, against the rule was 8.9% and oblique was 5.3%. 4. The percentage of preschool children who had been tested was 13.8%. 5. In test none of children were the phoria.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.311-316
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• 2004

In order to secure the traffic safety especially in the entrance waterway of harbour, it is important that the breakwater and the port facilities should be designed properly considering ship-handling difficulty and traffic flow. In this study, the lateral force acting on ship hull under the external force(wind, current, wave) is investigated quantitatively for the container ship approaching to the Busan and Gamcheon breakwater. The relation of ship-handling difficulty to the breakwater and the arrangement of ship's routine are examined based on the lateral force under the external force. Some of reviews to secure traffic safety on the design of breakwater are discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.724-727
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• 2007

선박 운항 자동화 시스템은 선내 노동력 감소, 작업 환경 개선, 운항 안전성 확보 및 운항 능률의 향상을 목표로 하며, 궁극적으로는 운항 경제성확보를 위한 승선 인원의 최소화에 그 목적이 있다. 최근에는 적응 제어방법 등을 응용하여 선박의 비선형성을 보상하여 선박의 회두각 유지제어(Course Keeping Control), 항로 추적제어(Track Keeping Control), 롤-타각제어(Roll-Rudder Stabilization), 선박 위치제어(Dynamic Ship Positioning), 선박자동 접이안(Automatic Mooring Control) 등에 관한 연구를 수행하고 있으며 실제의 선박으로 대상으로 응용연구가 진행 중이다. 선박은 Steering Machine에 의해 조정되는 Rudder angle과 선박의 회두각의 관계는 비선형적이며, 선박의 Load Condition은 선박의 Parameter에 영향을 주는 비선형적인 요소로서 작용한다. 또한 외란요소인 파도의 유속(流速)과 방향, 풍속과 풍량 등이 비선형적인 형태로 작용하므로 선박의 운항을 힘들게 하는 요인이 된다. 따라서 선박의 운항시스템에는 비선형성을 극복할 수 있는 강인한 제어 알고리즘을 요구한다. 본 논문에서는 퍼지 알고리즘을 이용하여 선박의 비선형적인 요인 및 외란을 극복할 수 있는 선박의 자율운항 시스템을 설계하고 시뮬레이션을 통해 그 결과를 살펴보았다.