• Journal of Korean Ophthalmic Optics Society
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• v.15 no.2
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• pp.123-130
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• 2010

Purpose: The study was conducted to compare the values of auto-refraction, manifest refraction and cycloplegic refraction in school-aged children. Methods: One hundred five myopic school children ranged from 6 to 14 years old (210 eyes, $10.28{\pm}1.59$ years old) were recruited and noncycloplegic auto-refraction (AR) and manifest refraction (MR) were conducted and then underwent cycloplegia and refractive status (CR) again with the auto-refractometer. Results: Refractive powers measured by AR, MR, and CR were highly correlated. However, spherical and cylindrical powers of the subjects measured by AR were measured higher negative power than in CR (p<0.001). From 210 eyes, the discrepancy rate in the spherical and cylindrical powers were 40 eyes (19%) and 19 eyes (9%) of the total subjects, respectively and the differences between noncycloplegic and cycloplegic refractions were higher with the spherical and cylindrical powers increasing. Conclusions: The use of the autorefractometer in children with negative spherical power without cycloplegia may overestimate the actual myopia that subjective refraction is the most important in prescription for the eyeglasses and regression equations would be used to prognose the cycloplegic refraction from the auto-refraction as the basic data for the subjective refraction.

• Structural Engineering and Mechanics
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• v.14 no.6
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• pp.661-677
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• 2002

The subject of this investigation is to study the buckling of cross-ply laminated orthotropic cylindrical thin shells with variable elasticity moduli and densities in the thickness direction, under external pressure, which is a power function of time. The dynamic stability and compatibility equations are obtained first. These equations are subsequently reduced to a system of time dependent differential equations with variable coefficients by using Galerkin's method. Finally, the critical dynamic and static loads, the corresponding wave numbers, the dynamic factors, critical time and critical impulse are found analytically by applying a modified form of the Ritz type variational method. The dynamic behavior of cross-ply laminated cylindrical shells is investigated with: a) lamina that present variations in the elasticity moduli and densities, b) different numbers and ordering of layers, and c) external pressures which vary with different powers of time. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question.

• The Journal of the Acoustical Society of Korea
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• v.25 no.4E
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• pp.159-165
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• 2006

Human, horse and rat bloods in a cylindrical chamber where flow was controlled by a stirring magnet were used for studying red blood cell aggregation. Ultrasound backscattered powers from blood were obtained from the backscattered signals measured by a 5 MHz focused transducer in a pulse-echo setup. The experimental results showed the differences in red blood cell (RBC) aggregation tendency among the three mammalian species with an order of horse > human > rat. The ultrasound backscattered power decreased with stirring speed in human and horse blood, but no variations were observed in rat blood. Sudden flow stoppage led to the slow increase of the backscattered power for human and horse blood. There was no self-aggregation tendency in rat blood. The enveloped echo images showed the spatial and temporal variations of RBC aggregations in the cylindrical chamber. These observations from the different mammalian species may give a better understanding of the mechanism of RBC aggregation.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.321-334
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• 2012

Purpose: In this study, the distribution and differences in refractive powers on trial case lenses were investigated. Methods: We measured refractive powers at optical center and periphery using 4 trial case lens sets. According to international standards, the distribution and uniformity in refractive powers were investigated. Results: The lens shapes were different in different kinds of trial case lenses and some of lenses were out of tolerance according international standards. In some cases, the power differences were found between front and back side as well as between optical center and peripheral regions and also the cylindrical power on spherical lens and spherical power on the cylindrical lens were measured. Conclusions: Trial case lens are used to assess the refractive error, therefore, more precise control of the manufacturing process for trial case lenses and more thorough quality control will be required to offer an accurate vision test. More careful attention in using trial case lens is also required.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.263-276
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• 2015

Purpose: The current study aimed to evaluate the reliability for the combined refractive power when a spherical lens and a cylindrical lens were overlapped in a trial frame. Methods: The refractive powers, central thickness and peripheral thickness of spherical trial lenses and cylindrical lenses with negative power were measured. The combined refractive power of the spherical and cylindrical lenses was measured by auto lens meter. Measurement was repeated by changing the insertion order, and their results were further compared with the calculated combined refractive power. Results: There was no correlation between the variation of central and peripheral thickness in trial lenses and that of the lens power. Among 79 trial lenses, 3 trial lenses wasn't met the international standard. The refractive power calculated by Gullstrand's formula that could compensate vertex distance had smaller difference with the estimated power when compared with that calculated by thin lens formula however, it was significantly different from the estimated power. The refractive powers were generally apparent regardless of the insertion order of a spherical lens and a cylindrical lens: thin lens formula > actual measurements > Gullstrand's formula. The error was only found in cylindrical power calculated by Gullstrand's formula when inserted a spherical lens inside and a cylindrical lens outside however, the error was found in both of cylindrical and spherical powers calculated by Gullstrand's formula when inserted as a opposite order. By comparing actual measurements of equivalent spherical power, the accuracy was higher and the possibility of over-correction was lower when inserted a spherical lens inside and a cylindrical lens outside. Conclusions: From the results, those were revealed that the combined refractive power is influenced by the factors other than the vertex distance and the refractive power varies in accordance with the insertion order of a spherical lens and a cylindrical lens. Thus, it can be suggested that the establishment of standard for these is neccesaty.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.231-237
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• 2014

Purpose: This study is research of the conditions which causes difference between the refractive power of the measurement of autorefractometer and the prescription using phoropter. Methods: Autorefractometer (SR-7000) and phoroptor (AV-9000) were used to measure 60 eyes of 30 participants who had no eye diseases and wore the corrective lens due to Ametropia. To prevent the dependence of the prescription value of the refractive power on the testers, two testers measured the refractive power of the eyes of the participants at the same measuring conditions. Results: Statistically, the prescribed values of the refractive power by two testers were not significantly different. Most of the prescribed values of the refractive power were smaller than the refractive power by autorefractometer In case of myopic eyes, the difference between refractive powers by the measurement of autorefractometer and the prescription using phoropter showed the trend of increase as the spherical refractive power became larger. The result was analyzed by the range of the different cylindrical refractive power for the myopic astigmatic eyes. In this case, the difference between refractive powers showed the trend of decrease as the cylindrical refractive power became larger. Conclusions: No difference between the prescribed value by two testers was observed. In case of myopic or myopic astigmatic eyes, the difference between refractive powers by autorefractometer and the prescription were measured to be approximately proportional to the refractive powers of ametropic eyes. As the this difference become larger for the participant who needs the lens of larger refractive power, additional caution is needed in the prescription of the refractive power of the corrective lens.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.1
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• pp.63-69
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• 2006

Clinical evaluation by Astigmatic Components of autorefractors was performed to examine validity and accuracy compared with subjective refraction. The mean cylindrical powers of Astigmatic Components of Subjective Refraction, Closed-view and Open-view were found to be $-0.689{\pm}0.516D$, $-0.691{\pm}0.530D$, $-0.470{\pm}0.507D$, respectively. The Difference of cylindrical Components between Subjective Refraction and Closed, Open-view were found to be $0.002{\pm}0.191D$, $0.015{\pm}0.137D$, respectively. Approximately 85% of Closed-view and Open-view autorefractor measurements were within ${\pm}20^{\circ}$ range of the difference of cylindrical axis with subjective refraction. The mean $J_0$ Components of Astigmatic Components of subjective refraction, Closed-view and Open-view were found to be $-0.155{\pm}0.332D$, $-0.004{\pm}0.178D$, $-0.001{\pm}0.156D$, respectively. The mean $J_{45}$ Components of Astigmatic Components, Closed-view and Open-view were found to be $-0.023{\pm}0.227D$, $-0.026{\pm}0.172D$, $-0.014{\pm}0.182D$, respectively. Both of the Closed-view and Open-view refractor showed available accuracy in measuring astigmatic components.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.103-107
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• 2008

Purpose: This research measured the near addition powers of presbyopia in wearing the near spectacle for the first time. Methods: We evaluated age, sex, working group, spherical power and cylindrical power and measured the power of refractive error performed the both eyes (310 eyes) of 155 subjects subjectively noncycloplegic and power of addition using the cross cylinder method. Results: There were measured the near addition powers in the range of +0.75D ~ +1.75D. In case of the average addition, they were measured with +1.06D in subjects under 43 years of age, +1.08D in 44 to 46 years, +1.23D in 47 to 49 years and +1.46D in over 50 years of age. The average age in subjects was 47.6 years old and 74 male, 81 female, 71 near sighted working group and 83 far sighted working group. Conclusions: Near addition was correlated with age, working group and cylindrical power (P<0.05, P<0.05, P<0.05).

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.340-355
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• 2018

The methods and performance of a fast reactor multigroup cross section (XS) generation code EXUS-F are described that is capable of directly processing Evaluated Nuclear Data File format nuclear data files. RECONR of NJOY is used to generate pointwise XS data, and Doppler broadening is incorporated by the Gauss-Hermite quadrature method. The self-shielding effect is incorporated in the ultrafine group XSs in the resolved and unresolved resonance ranges. Functions to generate scattering transfer matrices and fission spectrum matrices are realized. The extended transport approximation is used in zero-dimensional calculations, whereas the collision probability method and the method of characteristics are used for one-dimensional cylindrical geometry and two-dimensional hexagonal geometry problems, respectively. Verification calculations are performed first for various homogeneous mixtures and cylindrical problems. It is confirmed that the spectrum calculations and the corresponding multigroup XS generations are performed adequately in that the reactivity errors are less than 50 pcm with the McCARD Monte Carlo solutions. The nTRACER core calculations are performed with the EXUS-F-generated 47 group XSs for the two-dimensional Advanced Burner Reactor 1000 benchmark problem. The reactivity error of 160 pcm and the root mean square error of the pin powers of 0.7% indicate that EXUF-F generates properly the broad-group XSs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.412-420
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• 2005

This article proposes analytical solutions for sound radiation from radial vibration modes of a thick annular disk. Structural eigensolutions are calculated using the transfer matrix method. The far-field sound pressure distribution is obtained using two alternate methods. In the first method, pressure is calculated using the Rayleigh integral technique. The second method treats sound radiating radial surfaces as cylindrical radiators of finite length. The Sinc function approach is employed for calculations. Acoustic powers and radiation efficiencies of radial modes are also determined from the far-field sound pressure calculations. Analytical predictions match well with measured data as well as computational results from a finite element code in terms of structural eigensolutions and from a boundary element code in terms of sound pressure, directivity etc.