• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.239-247
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• 2001

Measured radiative heat fluxes on the furnace exit plane of a heavy duty power boiler of steam output 1650 T/h are discussed. A high-ash pulverized bituminous coal was used. Such measurements are necessary to improve heat fluxes inside a steam boiler furnace was manufactured. An extra small heat radiation sensor was placed in the water cooled head of the probe. The sensor had no direct contact with furnace gases and measured only the radiant energy. There was no exposure to convective heat transfer. With the radiometric probe, one can obtain a spherical indicatrix of radiation intensity as well as hemispherical radiative heat flux incident on any surface passing through a measuring point inside the furnace. Thus, the quantity of radiation energy, passing through the furnace exit plane, to the convective heating surfaces and the quantity of radiation energy going in the opposite direction were measured. A formula for relative radiative heat flux on the furnace exit plane has been proposed.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.81-84
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• 1989

EHZP is a kind of holographic optical element, which is generated by the interference of two divergent spherical waves from point sources on the same axis. It has the spherical aberration that the focal power increases as the radial distance r increases. By using this property, optimal design of EHZP was performed for f-$\theta$ lens. As the result of optimization, the f-$\theta$ condition and the field flattening condition were well satisfied when EHZP has f0=0.803f, faR=4.076f, 1=0.406f. It was assumed for calculation of field flattening condition that the incident wave was a plane wave with the diameter of 1mm.

• Smart Structures and Systems
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• v.19 no.1
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• pp.33-38
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• 2017

This research tries to present a nonlinear thermo-elastic solution for a functionally graded spherical shell subjected to mechanical and thermal loads. Geometric nonlinearity is considered using the Lagrange or finite strain tensor. Non-homogeneous material properties are considered based on a power function. Adomian's decomposition method is used for calculation of nonlinear results. Nonlinear results such as displacement can be evaluated for sphere in terms of different indexes of non-homogeneity. A comprehensive comparison between linear and nonlinear results and evaluation of the percentage of difference between them can be performed in this paper. The obtained results indicate that the improvement of the results due to usage of nonlinear analysis is depending on the non-homogeneous index.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.345-351
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• 2014

Purpose: The accommodative response and the near horizontal phoria were examined with additional spherical power to analyze the stimulus and response AC/A ratios that suggest reference data for the binocular vision. Methods: The open-field autorefractometer (Nvision-K 5001, Shin nippon) and modified thorington method (MIM card; Muscle Imbalance Measure card, Bernell) at 40 cm were utilized to measure the accommodative response and the near horizontal phoria for 81 persons ($20.89{\pm}1.92$ years old) with additional spherical power. The stimulus and the response AC/A ratios were calculated by gradient AC/A method. Results: The exophoria group showed the highest accommodative response ($1.92{\pm}0.26D$) at 40 cm, followed by orthophoria group and esophoria group($1.72{\pm}0.26D$ and $1.62{\pm}0.42D$, respectively) Meanwhile, the esophoria group showed the biggest ocular deviation for the near ($23.24{\Delta}$) followed by the orthophoria group and exophoria group ($19.76{\Delta}$ and $15.14{\Delta}$, respectively). The biggest difference of the stimulus and the response AC/A ratios was $1.72{\Delta}$ for the exophoria group with -2.00 D, while the one was $3.43{\Delta}$ for the esophoria group with +1.00 D. There was a significant difference between AC/A ratios for the exophoria group with -2.00 D, -1.00 D and the esophoria group with +3.00 D, +2.00D, +1.00D and -1.00D. Conclusions: The difference between stimulus and response AC/A was greater when increased minus spherical power for the exophoria group, while it was greater when increased plus spherical power for the esophoria group. Furthermore, the difference for the esophoria group was a greater than the one for the exophoria group.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.323-332
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• 2004

This study researched the visual acuity test object and Auto-refractormeter, visual of near power. The object were composed of middle aged, the old men and women who in habit Daegu. The results were as follows : 1. The subjects consisted of 537 people, 29.98% men, 70.02% women. 2. The emmetropia was 1.12% for myopia, 2.79% for hyperopia, 96.09% for astigmatism. 3. The abnormal refraction was composition for myopic compound astigmatism(16.57%), hyperopia compound astigmatism(45.62%), Mixed astigmatism(33.89%). 4. On the Myopic Spherical Equivalent(S.E) power, the range of -0.50D ${\leq}$ M.S.E < -1.00D was 21.67%, -1.00D ${\leq}$ M.S.E < -2.00D was 48.89%, -2.00D ${\leq}$ M.S.E < -6.00D was 29.44%. 5. On the Hyperopic Spherical Equivalent(S.E) power, the range of +0.50D ${\leq}$ H.S.E < +1.00D was 28.57%, +1.00D ${\leq}$ H.S.E < +2.00D was 49.30%, +2.00D ${\leq}$ H.S.E < +6.00D was 23.13%. 6. The addition power was 1.00D(8.01%), 1.50D(8.57%), 2.00D(13.78%), 2.50D(16.57%), 3.00D(16.95%), 3.50D(17.88%), 4.00D(18.25%).

• Economic and Environmental Geology
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• v.45 no.4
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• pp.377-384
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• 2012

The main field component of the Earth's magnetic field was modeled from the tri-axial magnetometer onboard KOrean MultiPurpose SATellite-II (KOMPSAT-II) for the purpose of satellite attitude control. The model computed by the KOMPSAT-II magnetometer measurement data is compared with the International Geomagnetic Reference Field (IGRF) model of a degree of up to 13 in spherical harmonic coefficients. The previous study with KOMPSAT-I (Kim et al. 2004) indicated a good correlation of power spectrum of spherical harmonic coefficients with respect to the degree up to 5. This study, however, showed an agreement of the degree up to 8-9 of the coefficient power spectrum and a discrepancy between degrees 10 and 13. We have concluded that relevant data selection process, removal of the external field from the data in the high latitude region, an accuracy of the magnetometer all play an important role in finding a coherence with the IGRF model. This study will be extended to the secular variation model of geomagnetism if longer-period data become available.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.669-675
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• 2010

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, $TiCl_4{\cdot}YCl_3$ solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical $TiO_2$ precursor. Then, the $Li_4Ti_5O_{12}$ was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical $TiO_2$ precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which $Li_4Ti_5O_{12}$ spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at $50^{\circ}C$ for 30 minutes and at $850^{\circ}C$ for 6 hours heat treatment time were optimized. $Li_4Ti_5O_{12}$ was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.1
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• pp.55-62
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• 2006

Clinical evaluation of the Closed-view autorefractor and Open-view autorefractor was performed to examine validity and repeatability compared with subjective refraction. Measurements of refractive error were performed on 126 eyes of 65 subjects (aged $26{\pm}7.5$ years) subjectively noncycloplegic. Intersession repeatability of the Closed-view and Open-view were also assessed on all 65 subjects together with Intersession repeatability on 7 to 14 days intervals. Spherical powers and spherical equivalent values of subjective refraction and autorefractions by Closed-view and Open-view were analyzed by paired T-test. The mean spherical powers of subjective refraction, Closed-view and Open-view were determined to be $-2.125{\pm}2.155D$, $-2.146{\pm}1.907D$, $-2.117{\pm}2.121D$, respectively. The mean spherical equivalent values of subjective refraction, Closed-view and Open-view were determined to be $-2.362{\pm}2.204D$, $-2.391{\pm}1.967D$, $-2.366{\pm}2.162D$, respectively. The results showed that the refractive errors as measured by the Closed-view and Open-view were found to be similar to the subjective refraction in all components.

• Journal of Convergence Society for SMB
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• v.6 no.3
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• pp.65-69
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• 2016

We investigated refractive errors and corneal power with 3 factors such as M, $J_0$, and $J_{45}$ as power vector to find out the changes of refractive errors of the before and after cataract surgery in 119 adults aged 45~85 years with cataract. After the surgery, the 3 factors were changed as $-0.29{\pm}2.38D$ to $-0.18{\pm}0.69D$ in spherical equivalent power which is the M factor, $-0.34{\pm}0.68D$ to $-0.05{\pm}0.42D$ in the $J_0$ factor, and $0.11{\pm}0.45$ to $0.02{\pm}0.17$ in the $J_{45}$ factor. Before and after the surgery, corneal mean refractive power, $J_0$, and $J_{45}$ were changed from $44.11{\pm}1.61D$ to $44.20{\pm}1.58D$, $0.01{\pm}0.50D$ to $0.08{\pm}0.49D$, and $0.02{\pm}0.29$ to $0.08{\pm}0.49$, respectively. The results showed that $J_0$ was the highest relativeness in correlation of the pre- and post-surgery for refractive errors, mean corneal power was the highest correlation for corneal power factor, and corneal power factor was the higher correlation much more than refractive error factor.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.2
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• pp.151-154
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• 2010

Purpose: We investigated how the movement of iris and visual axis affects the finite schematic eye Methods: Using the schematic eye with the crystalline lens in the existing forms of the radial GRIN and the spherical GRIN, the iris centre was moved 0.5 mm in nasal direction and visual axis was tilted $5^{\circ}$ in same direction, with the additional degree of 2.5 down to locate the focal point in fovea. This study analyzed performance change of the optical system, designing it same as the real eye. Results: The whole aberration distribution showed a considerable difference in performance in comparison with the real eye; the biggest difference shown at the central field of optical system. The spherical aberration showed the biggest difference, and a peripheral power error and field curvature leaned toward (+) direction in aberration distribution. Conclusions: When designing the schematic eye with the performance similar with that of the real eye by taking into consideration the iris centre and visual axis, the aberration at the center field of optical system in particular should be corrected. Spherical aberration which showed the biggest difference should be corrected in the first place. In addition, a peripheral power error and field curvature that leaned toward (+) direction should be moved toward (-) direction.