• Applied Microscopy
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• v.36 no.3
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• pp.227-234
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• 2006

To investigate the comparative effect of spherical and aspherical RGP lens were worn during 3 weeks on rabbit's cornea. Four white rabbits were worn right eyes with spherical lens and 4 white rabbits were worn right eyes with aspherical RGP lens. Left eyes were served as control. The rabbits were sacrificed at 3 weeks after fitting and observed morphological changes by scanning electron microscopy and also investigate proliferation rate of the corneal epithelium with RGP wearing. After spherical RGP lens wearing, the epithet layer damaged compared to aspherical lens. The superficial cell layer strip off seriously, cell size significantly changed abnormal. Both spherical and aspherical RGP lens fitting group showed so many bacteria and back surface of lens was found like a fern shape. The aspherical RGP lens original material type was some formal than spherical lens. We thought that these pattern was significantly altered with spherical lens by prohibited transmitter oxygen from atmosphere therefore the epithelium shape was changed. This suggested wearing the aspherical lens might be less physiologic than shperical lens fitting.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.794-795
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• 2006

Metal powder for dust core application was developed. The powder can be produced improved high-pressure water atomization process. The process has produced powder of spherical shape and lower coercivity. The dust core obta ined shows lower core loss.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.205-214
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• 1991

Calcium carbonate fine powders were synthesized by blowing CO2 gas in CaO or Ca(OH)2 suspension, and the shapes of powders obtained were examined for each synthetic condition. When water was used as a solvent, ultrafine calcite powders with the average size of∼0.03$\mu\textrm{m}$ were obtained. When synthesized using methanol as a solvent, amorphous phase and spherical vaterite phase were obtained by suction filtering and non-filtering, respectively. Reaction did not occured in ethanol medium, but spherical vaterite phase was obtained by adding ethylene glycol in ethanol.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1491-1495
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• 2004

In this paper, resonant ultrasound spectroscopy(RUS) was used to determine the natural frequency of a spherical and a aspherical lens. The objective of the paper is to evaluate defect and shape error by using nondestructive evaluation method with Resonant Ultrasound Spectroscopy(RUS). The principle of RUS is that the mechanical resonant frequency of the materials depends on density, and the coefficient of elasticity. We evaluated existence of flaws through comparison with resonant frequency of a spherical and a aspherical lens. The spherical glass lenses were made of BK-7 glass, one's diameter in 2mm and 5mm. The polished spherical glass lenses had no deflection or a deflection below 2.0${\mu}{\textrm}{m}$. Also, The aspherical lens were made of same material and ones diameter in 7mm and thickness in 3.4mm. In the experiment, we were performed to investigate relationship between frequency measuring parameter($\beta$) and mass of each specimens. The difference between resonant frequency and mode of aspherical glass lens which has no defect was distinguished from aspherical glass lens which has some defects.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.568-573
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• 2009

In this study, we used coal based activated carbons as starting material and phenolic resin (PR) as a bonding agent to prepare spherical shaped activated carbons. The textural properties of SAC were characterized by BET surface area, XRD, SEM, iodine adsorption, strength intensity and pressure drop. According to the results, the spherical activated carbon prepared with activated carbon and PR at a ratio of 60:40 was found to have the best formation of spherical shape, which was found in sample SAC40. After activation, SAC40 has high BET surface area, iodine adsorption capability and strength value, and lowest pressure drop.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1495-1496
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• 2008

The Ceramic Metal Halide lamp is different from optical characteristic on shapes of arc-tube and driving method of ballast. In this paper, we measured optical characteristics of the Ceramic Metal Halide lamp that uses arc tubes which are spherical and cylindrical shapes, and analyzed the Ceramic Metal Halide lamp connecting ballast that is electronic and magnetic types through the lamp measurement system that is given for stabilization period of fifteen minutes. In result, the arc-tube of spherical shape is more improvement in the optical properties than the arc tube of cylindrical shape, moreover, the electronic ballast is more efficient than the optical properties of the magnetic ballast.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.752-757
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• 2001

To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The ranked bidirectional evolutionary structural optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.806-811
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• 2003

Ultrafine TaC powders were synthesised by spray drying using tantalum oxalate solution. The spray dried powders were spherical shape and less than 30 $\mu\textrm{m}$ in size. The powders calcined at 500 and X$700^{\circ}C$ showed amorphous structures and $Ta_2$$O_{5}$ phase was obtained by calcining at $700^{\circ}C$. The particle size and shape remains constant after calcination. The calcined spherical powders were composed of an agglomerate of primary particles under 50 nm in size. The complete formation of TaC could be achieved by heat treatment at $1050^{\circ}C$ for 6 hrs. The observed size of TaC powders by TEM was less than 200 nm.

• Journal of Korea Foundry Society
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• v.23 no.3
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• pp.130-136
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• 2003

Rheocasting of AZ91D magnesium alloys yielded the microstructure consisted of the spherical primary particles in the matrix which is different from conventional casting. Rheocast ingots were produced under various processing conditions using batch type rheocaster. Morphology of primary particles was changed from rosette-shape to spherical shape with increasing stirring rate$(V_s)$ and decreasing isothermal stirring temperature$(T_s)$. With increasing $V_s$, more effective shearing between the particles occurred rather than the agglomeration and clustering, so the primary particle size decreased. But with decreasing $T_s$, primary particle size increased mainly due to sintering and partially Ostwald ripening. The sphericity of primary particles increased with increasing $V_s$ and decreasing $T_s$ due to enhanced abrasion among the primary particles. The uniformity of primary particle size increased with increasing Vs and $T_s$.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.959-961
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• 2001

Nanosized CeO$_2$Powders were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Spherical shape of CeO$_2$powder was obtained at 175$^{\circ}C$ for 6h. TEM and X-ray diffraction patterns showed that the synthesized particle was crystalline. The average size and size distribution of the synthesized particles were below 30 nm and narrow, respectively. In addition, the effects of synthesis parameters under hydrothermal process are discussed.