• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.2
• /
• pp.1-10
• /
• 2002

Hull-propeller-rudder interactions are studied by the iterative computational procedures. Hull effects on the propeller are reflected through the effective velocities computed by the vortex ring method which used the measured nominal wake as input data. A potential based panel method has been developed to solve the propeller-rudder interactions using the obtained effective velocities. Steady flow characteristics around the rudder surface can be obtained by computing the induced velocities on the rudder by the propeller and vice versa are computed by the iterative manner until the converged solutions are obtained. Flow characteristics around the propeller and the rudder are measured by Laser Doppler Velocimetry(L.D.V.) in large cavitation tunnel at Samsung Heavy industries. The gap flow model is adopted to solve the characteristics of the horn rudder. Numerical results are compared with the experimental values and the computed velocity fields and pressure distributions with rudder angle on the horn rudder surface show good agreement with measured ones in large cavitation tunnel.

• Journal of Korean Ophthalmic Optics Society
• /
• v.8 no.1
• /
• pp.41-45
• /
• 2003

The researchers have studied on the effect of three main morphological types(nuclear, cortical, and subcapsular cataract) of age related cataract on refractive error. We also identified that spherical and cylinderical shift in each type of morphological cataract accoding to their locations and effect of intraocular pressure before and after cataract surgery. Nuclear cataract showed myopic shift while cortical cataract showed hyperopic shift, and subcapsular cataract showed not significant changes on both direction. Age related cataract subjects(120 eyes) only were recruited from sun-cheon area. We use optic section of slit lamp biomicroscope to identify the anatomical location of cataract, and optimal refractive correction determined by objective(retinoscope) and subjective refraction then spherical changes were calculated from the spherical eqivalent value. Intra-ocular pressure were measured by auto-tonometer before and 7 days after cataract has been replaced by IOL. The change in cylindrical power, usually A-P diameter decreased according to increases of age, A-P diameter increased because intra-ocular pressure rises by progression of cataract and this convertion with the rule astigmatism to against the rule astigmatism and this increases more by intra-ocular pressure.

• Journal of Korean Ophthalmic Optics Society
• /
• v.20 no.4
• /
• pp.527-536
• /
• 2015

Purpose: In this paper, we have dealt with problems and improvement of korean optician system. Methods: Using the relevant material of korean optician system and international optometrist system, provides the theoretical basis of the need for regulatory changes optician. Results: The people with refractive errors are increasing, 67% of refractive error test is made from optical shop and korean optician are sufficient trained, many opticians are in charge of the refractive error test at the ophthalmic hospital. We have confirmed that current law does not reflect adequately the nature of optician's work. Conclusions: Since current capacity of the Korean opticians and education system ready to provide health services for people, therefore an korean optician must redefine the law to fit the reality.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.10a
• /
• pp.801-804
• /
• 2003

The autopilot system of vessel is proposed to take service safety sorority, to elevate service efficiency, to decrease labor and to improve working environment. Ultimate purpose of it is to minimize the number of crew by guaranteeing economical efficiency of shipping service. Recently, the research is being achieving to compensate various nonlinear parameters of vessel and apply it is course keeping control, track keeping control, roll-rudder stabilization, dynamic ship positioning and automatic mooring control etc. using optimizing control technique. Relation between rudder angle controlled by steering machine of vessel and ship-heading angle, and load condition of ship are nonlinear, which affect various parameters of shipping service. The speed and direction of waves, velocity and quantity of wind, which also cause the non-linearity of it. Therefore the autopilot system of ship requires the robust control algorithm can overcome various non-linearity. On this paper, we design the autopilot system of ship, which overcome nonlinear parameters and disturbance of it using Fuzzy Algorithm, evaluate the proposed algorithm and its excellence through simulation

• Journal of Navigation and Port Research
• /
• v.29 no.1 s.97
• /
• pp.1-7
• /
• 2005

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.

• Journal of Korean Ophthalmic Optics Society
• /
• v.6 no.1
• /
• pp.65-69
• /
• 2001

To investigate the visual acuity of the primary school children. This study was researched visual acuity test using objective and subjective methods. 1. The eye types were 90.3% positive for myopia, 3.1% for emmetropia, 4.9% hyperopia, 1.7% for mired astigmatism. 2. The abnormal refraction eyes were 58.6% positive for simple myopia, 29.9% for myopic compound astigmatism, 5.1% for my optic simple astigmatism and 1.9% for simple hyperopia, 1.9% for hyperopic compound astigmatism, 1.3% for hyperopic simple astigmatism, 1.3% for mixed astigmatism. 3. The axis of astigmatism were 85.7% for astigmatism with-the-rule, 9.3% for astigmatism against-the-rule, 5.0% for astigmatism oblique. 4. On total myopic spheric power. the -0.50

• Journal of Korean Ophthalmic Optics Society
• /
• v.6 no.1
• /
• pp.71-76
• /
• 2001

In this study, the variation of astigmatism axis according to the age was studied 4227 eyes of healthy eyes. The refractive errors were measured by objective and subjective refraction. The astigmatism among the total eyes was 76.5%. With-the-rule, against-the-rule and oblique astigmatism were 51.4%, 31.7% and 16.9%, respectively. The frequency of with-the-rule was the highest and against-the-rule was the lowest of all the astigmatism in the refractive error. In relation to the age and astigmatism, the with-the-rule was 68.3% in the 10's age group which was the highest among the astigmatism and the against-the-rule was 10.3% in the 50's age group and upward which was the lowest among the astigmatism. The difference in the with-the-rule and against-the-rule ratio was a little in the 30's age group. As they aged, the tendency of the with-the-rule was increased between 10's and 20's age group continually. And the tendency of the against-the rule was increased between 30's and 50's age group and upward. There was a decrease in with-the-rule and an increase in against-the-rule, with the age increase. The oblique astigmatism relationship to age could not be determined.

• Journal of Korean Ophthalmic Optics Society
• /
• v.10 no.1
• /
• pp.47-52
• /
• 2005

The purpose of this study was to provide the accurate information on improvement of visual life by examining old age's eye refraction state and investigating distribution of ametropia in old age. The test was performed the visual acuity test by object and subject methods to over 60 years of age. The results were as follows: 1. As the result to investigate the inconvenience degree of visual life, the subjects appealed 81% for very inconvenience and 14% for a little inconvenience. 5% of them didn't feel any inconvenience in visual life. 2. The eye types were 1.7% for emmetropia, 10% for myopia, 74.7% for hyperopia, and 13.6% mixed astigmatism, respectively. 3. The axis of astigmatisms were 65% positive for indirect astigmatism, 8% for direct astigmatism, and 27% for oblique astigmatism, respectively.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.4
• /
• pp.60-65
• /
• 1996

Mathematical model of maneuvering motion for a single-screw single-rudder ship established and versatile applications to the special situations of maneuvering are attempted. While, the mathematical model for twin-screw twin-rudder ship is not presented so much, because that type of ship is not popular. Lee et al. have examined the characteristics of such ship by captive model tests in 1988. This paper treats new mathematical models for propeller effective wake ($1-w_p$) and effective neutral rudder angle ${\delta}_R$ in the case of twin-screw twin-rudder ship. And some maneuvering motions are calculated with proposed models and compared with exact simulations.

• Journal of Korean Ophthalmic Optics Society
• /
• v.11 no.2
• /
• pp.151-157
• /
• 2006

We researched distant & near horizontal heterophoria of myope using von graefe method on full correction condition for young people 49 subjects(98eyes) with myopia after testing the objective refraction. Among the whole subjects, we got the results as Orthophoria 51.00%, Exophoria 38.75%, Esophoria 10.25% and Heterophoria 49.00% at a long distant. At a short distant, they showed Orthophoria 22.45%, Exophoria 67.35, Esophoria 10.20%, and Heterophoria 77.55%, Orthophoria 22.45. At a long distant they showed Orthophoria 4.08%, Exophoria 8.16%, Esophoria 0% on high myopia, Orthophoria 18.37%, Exophoria 12.25%, Esophoria 0% on middle myopia and Orthophoria 28.57%, Exophoria 18.37%, Esophoria 10.20% on low myopia.