• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.72-78
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• 2009

We propose the separation algorithm to simultaneously measure two-dimensional refractive index distribution and thickness profile of transparent samples using three wavelengths. The optical system was based on the Mach-zehnder interferometer with LD (Laser Diode)-based multi-wavelength sources. A LCR (Liquid Crystal Retarder) was used to obtain interference images at four phase states and then the optical phase of the object is calculated by four-bucket algorithm. Experimental results with a glass rod are provided at the different wavelengths of 635nm, 660nm and 675nm. The refractive indices of the sample are distributed with accuracy of less than 0.0005 and the thickness profile of sample was cylindrical type. This result demonstrates that it is possible to separate refractive index distribution and thickness profile of samples in two dimensions using the proposed algorithm.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.61-64
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• 2003

Optical resolution of a-amino acid (tryptophan and tyrosine) optical isomers was achieved by a pressure driven membrane separation process, using self-supporting crosslinked membranes base on polysaccharide with different swelling indices that ranged from 100 to 70%. The membranes prepared by casting and drying the polymer solution containing 5wt% acetic acid on an acryl plate followed by crosslinking with glutaraldehyde were characterized using such analytical methods as FTIR and swelling index measurements. On the way of separating the optical isomers, several experimental factors such as the concentration of the feed solutions, operating pressure and temperature, and degree of crosslinking of the membranes have been studied. When the chitosan membranes with 70% of swelling index were used , almost complete optical resolution was obtained; 97.92% of enantiomeric excess (ee %) and 2.26 g/$m^2$ㆍh of flux. The operating pressure and the concentration of feed solutions were respectively 1.0 kgf/$\textrm{cm}^2$ and 0.49 mmol/L.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.757-759
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• 1996

This paper proposes an application of artificial neural networks to the bus-bar separation in a substation for radial network operation. For the effective bus-bar operation, the insecurity index of transmission line load is introduced. For the radial network operation. the constraints of bus-bar switch is formulated in the performance function with the insecurity index. The determination of bus-bar switching is to find the states of 0 or 1 in the circuit breakers. In this paper, it is tested that the bus-bar separation of binary optimization problem can be solved by Hopfield networks with adequate manipulations.

• International Journal of Contents
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• v.15 no.3
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• pp.1-6
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• 2019

The purpose of this study was to identify the psychometric properties of the vocational ability scale used in the 8th Panel Survey of Employment for the Disabled in Korea by using the Rasch model. The sample data was collected from 398 individuals with intellectual disabilities. Item fitness, item difficulty, the appropriateness of the rating scale, and the separation index of the vocational ability scale were evaluated. All 15 items show an appropriate fitness level. The analysis of item difficulty indicate that modifications are required. Specifically, the need for the addition of less difficult question items is identified. The use of a 5-point rating scale is shown to decrease the test difficulty in terms of clarity and readability when appropriate and a 4-point modification is also determined as appropriate. With respect to the outcomes of the analysis, the person separation reliability value and separation index are high, and the reliability of the items is also high.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.145-150
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• 2004

In this study the numerical analysis on staging flow with forward ejector is conducted. The forward ejector plays a vital role in staging, which jets out from aftbody. This staging environment needs careful flow analysis for securing staging safety Present study investigates the steady inviscid staging flow phenomena with variation of separation distance. The performance index is forebody base pressure coefficients. The three dominant flow phenomena are observed according to separation distance which could be told as impinging stage, cavity vortex dominancy stage, and pure base flow characteristics stage. Impinging stage shows high thrust for forebody as one might think. However, important point is that cavity vortex dominancy stage can be more favorable for separation than impinging stage as one simply think in certain separation distance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.53-62
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• 2006

Two-dimensional steady flowfields generated by transverse injection jets into a supersonic mainstream are numerically simulated. Fine-scale turbulence effects are represented by a k-${\omega}$ SST two-equation closure model which includes $y^+$ effects on the turbulence model. Solution convergence is evaluated by using Grid Convergence Index(GCI), a measure of uncertainty of the grid convergence. Comparison is made with experimental data and other turbulence models in term of surface static pressure distributions, the length of the upstream separation region, and the penetration height. Results indicate that the k-${\omega}$ SST model correctly predicts the mean surface pressure distribution and the upstream separation length for low static pressure ratios. However, the numerical predictions become less consistent with experimental results as the static pressure ratio increases. All these results are taken within 1% error band of grid convergence.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.287-292
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• 2005

The flowfields generated by gaseous slot injection into a supersonic flow at a Mach number of 3.75 and a Reynolds number of $2.07{\times}10^7$ are simulated numerically. Fine-scale turbulence effects are represented by a two-equation(k-w SST model) closure model which includes $y^+$ effects on the turbulence model. Grid convergence index(GCI) is also considered to provide a measure of uncertainty of the grid convergence. Comparison is made with experimental data and other turbulence model in term of surface static pressure distributions, the length of the upstream separation region, and the penetration height. Results indicate that the k-w SST model correctly predicts mean surface pressure distribution and upstream separation length. However, it is also observed that the numerical simulation over predicts the pressure spike and penetration height compared with experimental data. All these results are taken within $1\%$ error band of grid convergence.

• Physical Therapy Korea
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• v.24 no.4
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• pp.20-28
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• 2017

Background: Rasch analysis has the advantage of placing both the items and the person along a single ratio scale and calibrates person ability and item difficulty onto an interval scale by logits. Therefore, Rasch analysis has been recommended as a better method for evaluating functional outcome questionnaires than traditional analyses. Objects: The aim of current study was to investigate item fit, item difficulty, rating scale, and separation index of the Korean version of the Fullerton Advanced Balance (KFAB) scale using Rasch analysis. Methods: In total, 93 patients with stroke (male=58, female=35) participated in this study. To investigate the item fit, difficulty, rating scale, and separation index of the KFAB scale, Rasch analysis was completed by the Winsteps software program. Results: In this study, all items of the KFAB scale were included in the Rasch model. The most difficult item was 'standing with feet together and eyes closed', and the easiest item was 'two-footed jump'. The rating scale was a 4-point scale instead of the original 5-point scale. Person and item separation indices showed high values that can identify a person with a wide range of balance ability. Conclusion: The KFAB scale appears to be a reliable and valid tool to assess balance function in patients with stroke. Furthermore, the scale was found to discriminate among stroke patients of varying balance abilities.

• Current Optics and Photonics
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• v.8 no.1
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• pp.30-37
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• 2024

Implemented at the Geochang Observatory in South Korea, our slope detection and ranging (SLO-DAR) system features a 508 mm Cassegrain telescope (f /7.8), incorporating two Shack-Hartmann wave-front sensors (WFS) for precise measurements of atmospheric phase distortions, particularly from nearby binary or double stars, utilizing an 8 × 8 grid of sampling points. With an ability to reconstruct eight-layer vertical atmospheric profiles, the system quantifies the refractive index structure function (C_n²) through the crossed-beam method. Adaptable in vertical profiling altitude, ranging from a few hundred meters to several kilometers, contingent on the separation angle of binary stars, the system operates in both wide (2.5 to 12.5 arcminute separation angle) and narrow modes (11 to 15 arcsecond separation angle), covering altitudes from 122.3 to 611.5 meters and 6.1 to 8.3 kilometers, respectively. Initial measurements at the Geochang Observatory indicated C_n² values up to 181.7 meters with a Fried parameter (r₀) of 8.4 centimeters in wide mode and up to 7.8 kilometers with an r₀ of 8.0 centimeters in narrow mode, suggesting similar seeing conditions to the Bohyun Observatory and aligning with a comparable 2014-2015 seeing profiling campaign in South Korea.

• Journal of the Korean institute of surface engineering
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• v.34 no.3
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• pp.240-246
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• 2001

The possibility of using a glass block with the composition of sodium borosilicate as starting materials for GRIN glass was examined from the view points of the phase separation of the matrix glass, the effects of leaching and the heating conditions for a porous structure, and the change in the refractive index. Glass specimens with similar compositions were prepared in the form of porous glass using a phase-separation technique. An examination of the heating and leaching conditions and the microstructure dependence of these conditions was made.; Specimens with porous structure were obtained when the heat treatment and leaching conditions were fixed at $540^{\circ}C$ for 30hrs and in a 0.3N$ H_2$$SO_4$ solution at $100^{\circ}C$, respectively. The resultant specimens had some important features on the GRIN glass.; the depth of the gradient and the change in refractive index (Δn) were 4mm and 0.015~0.02, respectively.