• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.183-190
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• 1996

To design three-mirror telescope system (F/8, 120 inch in focal length) for visible and infra-red band imaging, methods for power configuring and correction of the third order aberrations were studied. In the design of the telescope system, a three-mirror system corrected for spherical aberration, coma, and astigmatism was used for infra-red imaging, and the aberrations were corrected by using conic surfaces. For visible imaging, a singlet corrector lens was appended at the front of the focal plane to correct filed curvature. The telescope system has diffraction limited performance for 10 ${\mu}{\textrm}{m}$ in wavelength within 2.4$^{\circ}$ of field-of-view. In the visible band imaging, the rms spot size of the telescope system is less than 25 ${\mu}{\textrm}{m}$ within 3$^{\circ}$ of field-of-view for monochromatic light, and the telescope system satisfies flat field condition for CCD application.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1187-1194
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• 2011

The hydrogen abstraction reaction of $CF_3CH_2CHO$ + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-$CF_3CH_2CHO$, have been located, and there are four distinct OH hydrogen-abstraction channels from t-$CF_3CH_2CHO$ and two channels from c-$CF_3CH_2CHO$. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

• The Journal of Korean Physical Therapy
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• v.16 no.1
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• pp.60-69
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• 2004

Many methods have been described for the early intervention of adolescent idiopathic scoliosis. Adolescent idiopathic scoliosis is lateral and rotational spinal curvature in absence of associated congenital or neurologic abnormalities, the most common type of scoliosis observed in child and young adults, and refers to curves that develop after the age of $10{\sim}18$. The curves of adolescent idiopathic scoliosis have the potential to progress rapidly during growth. Curves are currently universally measured by the Cobb's method and Ferguson method. Some curves do not remain small, these may be mildly or severely progressive and the ribs on the convex side of the curve separate, and those on the concave side ribs approximate so rib undergoes deformation with rib humping. The latter may make angles that can affect vestibular system, balance, sensory, especially cardipulmonary function. Intervention for adolescent idiopathic scoliosis is based on the patient's age, the angular value of the curve, the maturity of their skeleton, and the topography. The purpose of intervention for adolescent idiopathic scoliosis consists of knowing how to go to the best approach the correction of the lateral curve and rotational deformity holding the achieved for the remainder of spinal growth, preventing significant cosmetic abnormality, pain and cardiopulmonary complication, control the muscle imbalance and proprioceptive postural disturbances, be less need for radical surgery to avoid early surgery.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.240-252
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• 1998

The purpose of this study is to develop a method for predicting the aerodynamic performance of the low speed airfoils in the 2-dimensional, steady and viscous flow. For this study, the airfoil geometry is specified by adopting the longest chord line system and by considering local surface curvature. In case of the inviscid incompressible flow, the analysis is accomplished by the linearly varying strength vortex panel method and the Karman-Tsien correction law is applied for the inviscid compressible flow analysis. The Goradia integral method is adopted for the boundary layer analysis of the laminar and turbulent flows. Viscous and inviscid solutions are converged by the Lockheed iterative calculating method using the equivalent airfoil geometry. The analysis of the separated flow is performed using the Dvorak and Maskew's method as the basic method. The wake effect is also considered by expressing its geometry using the formula of Summey and Smith when no separation occurs. The computational efficiency is verified by comparing the computational results with experimental data and by the shorter execution time.

• Journal of Yeungnam Medical Science
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• v.6 no.1
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• pp.133-140
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• 1989

Augumentation rhinoplasty using autogenous cranial bone graft(outer table)can be used more successfully than other methods. In patients with congenital or posttraumatic severe saddle nose deformity and lateral deviation, cranial bone graft is an excellent method of augumentation. The adventages of cranial bone graft compaired with traditional method of bone graft are summarized as follows ; 1. easy to reach donor site 2. abundance of materal 3. little pain and functional disability 4. shorter hospitalization period 5. unconspicuous donor scar 6. no secondary deformity of donor site 7. appropriate curvature can be obtained by proper selection of donor site. With the above advantages, we conclude that augumentation rhinoplasty using split cranial bone graft is a good method in correction of congenital or posttraumatic deformity of nose.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.707-722
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• 2022

In this study, a new refined hyperbolic shear deformation theory (RHSDT) is developed using an equivalent single-layer shell displacement model for the static bending and free vibration response of cross-ply laminated composite spherical shells. It is based on a new kinematic in which the transverse displacement is approximated as a sum of the bending and shear components, leading to a reduction of the number of unknown functions and governing equations. The proposed theory uses the hyperbolic shape function to account for an appropriate distribution of the transverse shear strains through the thickness and satisfies the boundary conditions on the shell surfaces without requiring any shear correction factors. The shell governing equations for this study are derived in terms of displacement from Hamilton's principle and solved via a Navier-type analytical procedure. The validity and high accuracy of the present theory are ascertained by comparing the obtained numerical results of displacements, stresses, and natural frequencies with their counterparts generated by some higher-order shear deformation theories. Further, a parametric study examines in detail the effect of both geometrical parameters (i.e., side-to-thickness ratio and curvature-radius-to-side ratio), on the bending and free vibration response of simply supported laminated spherical shells, which can be very useful for many modern engineering applications and their optimization design.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.477-490
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• 2022

This article investigates the nonlinear behavior of two-directional functionally graded materials (TDFGM) doubly curved panels with porosities for the first time. An improved and effectual approach is established based on the improved first-order shear deformation shell theory (IFSDST) and von Karman's type nonlinearity. The IFSDST considers the effects of shear deformation without the need for a shear correction factor. The composition of TDFGM constitutes four different materials, and the modified power-law function is employed to vary the material properties continuously in both thickness and longitudinal directions. A nonlinear finite element method in conjunction with Hamilton's principle is used to obtain the governing equations. Then, the direct iterative method is incorporated to accomplish the numerical results using the frequency-amplitude, nonlinear central deflection relations. Finally, the influence of volume fraction grading indices, porosity distributions, porosity volume, curvature ratio, thickness ratio, and aspect ratio provides a thorough insight into the linear and nonlinear responses of the porous curved panels. Meanwhile, this study emphasizes the influence of the volume fraction gradation profiles in conjunction with the various material and geometrical parameters on the linear frequency, nonlinear frequency, and deflection of the TDFGM porous shells. The numerical analysis reveals that the frequencies and nonlinear deformations can be significantly regulated by changing the volume fraction gradation profiles in a specified direction with an appropriate combination of materials. Hence, TDFGM panels can overcome the drawbacks of the functionally graded materials with a gradation of properties in a single direction.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.153-160
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• 2010

We modified the optical system of 500 mm wide-field telescope of which point spread function showed an irregularity. The telescope has been operated for Near Earth Space Survey (NESS) located at Siding Spring Observatory (SSO) in Australia, and the optical system was brought back to Korea in January 2008. After performing a numerical simulation with the tested value of surface figure error of the primary mirror using optical design program, we found that the surface figure error of the mirror should be fabricated less than root mean square (RMS) $\lambda$/10 in order to obtain a stellar full width at half maximum (FWHM) below $28\;{\mu}m$. However, we started to figure the mirror for the target value of RMS $\lambda$/20, because system surface figure error would be increased by the error induced by the optical axis adjustment, mirror cell installation, and others. The radius of curvature of the primary mirror was 1,946 mm after the correction. Its measured surface figure error was less than RMS $\lambda$/20 on the table of polishing machine, and RMS $\lambda$/15 after installation in the primary mirror cell. A test observation performed at Daeduk Observatory at Korea Astronomy and Space Science Institute by utilizing the exiting mount, and resulted in $39.8\;{\mu}m$ of stellar FWHM. It was larger than the value from numerical simulation, and showed wing-shaped stellar image. It turned out that the measured-curvature of the secondary mirror, 1,820 mm, was not the same as the designed one, 1,795.977 mm. We fabricated the secondary mirror to the designed value, and finally obtained a stellar FWHM of $27\;{\mu}m$ after re-installation of the optical system into SSO NESS Observatory in Australia.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.2
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• pp.195-199
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• 2010

Purpose: This study was to investigate the relevance between refractive and anatomical changes temporarily on the eyes after alcohol ingestion. Methods: Eight subjects (16 eyes) which were $24.5{\pm}1.5$ aged males drunk the alcohol of 0.42 g per kg of body weight within 30 minutes. Refractive errors, the radius of corneal curvature, corneal thickness, pupillary size, intraocular pressure, and the length of the ocular axis at 1 h, 4 h, and 24 h after alcohol ingestion were compared with them of non-alcoholic state. Results: At 1 h after alcohol ingestion, breath alcohol concentration was the highest (p<0.001), more negative spherical power was needed (p<0.05) for correction, pupillary diameter was decreased (p<0.05), intraocular pressure was decreased (p<0.001), and the length of the ocular axis was increased compared with each one of non-alcoholic state. At 4 h after alcohol ingestion, all anatomical changes were the same tendency as at 1 h after alcohol ingestion. But at 24 h after alcohol ingestion, both refractive changes and anatomical changes were not significant compared with them of non-alcoholic state. Conclusions: Temporary changes of refractive error after alcohol ingestion may be related with decrease of intraocular pressure and increase of the length of ocular axis.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.129-137
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• 2013

A force calibration of a nanoindenter and a 3D morphology observation of indenters were carried out in this study. A microbalance calibrated with standard weights was used for measuring the loads generated by a nanoindenter. The indentation load could be calibrated from the ratio of measured and generated loads and the first contact load also could be detected from the microbalance data. By analyzing atomic force microscopy images of two indenters, curvature radii of apexes were determined by $19.71{\pm}3.03$ and $1043.94{\pm}50.91$ nm, respectively, for the nearly new indenter A and the severly worn indenter B. Corresponding bluntness depths were estimated by 1.22 and 64.56 nm for the both indenters by overlapping their profiles on the perfect pyramidal shape. In addition, nanoindentation curves obtained from a fused silica reference material with the both indenters showed a depth difference corresponding to the bluntness depth difference along the indentation depth axis. By shifting amounts of the bluntness depths along the horizontal axis, whole nanoindentation curves overlapped on themselves and resulted in nanohardness values consistent within 1.11 % without considering the complex indenter area function of each indenter.