• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.672-677
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• 2001

This study has been conducted to design the high efficiency centrifugal compressor for a HFC-134a. The 2-stage centrifugal compressor consists of inlet guide vanes, two impellers with splitters, a deswirler, a vaneless diffuser and a volute casing. We have designed the high efficiency centrifugal compressor by applying the repeated design procedure including a meanline design, a 3D geometry generation of 1st and 2nd impellers etc. Also, a fluid dynamic calculation of impellers and deswirler have been conducting using a commercial code STAR-CD.

• 한국광학회지
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• 제13권1호
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• pp.27-31
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• 2002

본 논문에서는 광자 크리스탈로 구성된 1$\times$4 광 분배기를 설계하여 특성을 Finite-Difference Time-Domain 방법을 사용하여 고찰하였다. Simulation한 결과 bend에서의 4가지 광자 크리스탈 배열 구조와 입사파의 주파수에 따라 투과 특성이 변하는 것을 관찰하였다. 투과 특성이 가장 좋은 bend구조로 1$\times$4광 분배기를 설계하고 특정 주파수를 입사시킨 결과, 입사파의 파워가 4개로 균등히 나누어 짐과 전체 전송 효율이 약 93%임을 관찰하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1395-1400
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• 2004

A centrifugal compressor for geothermal heat pump system using R134a as working fluid has been developed. The centrifugal compressor consists of an impeller with splitters, two vaneless diffuser, a low solidity vaned diffuser and a volute. In this compressor, diffuser blade angles are controlled to satisfy both heating and cooling conditions. A aerodynamic design was done by applying the repeating design procedure including a meanline design, a 3D geometry generation and fluid dynamic calculation. In this paper, design and performance prediction results of the compressor are presented.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1992년도 수공학연구발표회논문집
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• pp.133-141
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• 1992

A three water-intake structure designed to built along the right bank of the Missouri River near Chesterfield, Missouri was model-tested at an undistorted scale of 1:5. Although the discharge capacity of each of six pumps to be installed is only 21,000 gpm, the model indicated strong flow circuation and unstable free-surface conditions as flow entered the two-pump bay through a narrow sluice opening at an angle. Strong free-surface vartices were also observed in the model. The sump modifications developed in the study included an array of baffle bars, a perforated plate, floor splitters, and floor-corner fillets. The solutions developed in this study could be applied to other pump sumps with multiple pump units.

• 한국경영과학회지
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• 제36권2호
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• pp.1-14
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• 2011

In this paper, we deal with an access network design problem of fiber-to-the-home passive optical network (FTTH-PON). The FTTH-PON network design problem seeks to minimize the total cost of optical splitters and cables that provide optical connectivity between central office and subscribers. We develop a flow-based mixed integer programming (MIP) model with nonlinear link cost. By developing valid inequalities and preprocessing rules, we enhance the strength of the proposed MIP model in generating tight lower bounds for the problem. We develop an effective Tabu Search (TS) heuristic algorithm that provides good quality feasible solutions to the problem. Computational results demonstrate that the valid inequalities and preprocessing rules are effective for improving the LP-relaxation lower bound and TS algorithm finds good quality solutions within reasonable time bounds.

• Current Optics and Photonics
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• 제2권1호
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• pp.47-52
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• 2018

We systematically investigated the negative-refraction effect for both TE and TM polarizations in annular photonic crystals. Since two polarization waves are excited in different bands, they result in different refractive angles, and so polarization beam splitters can be made of annular photonic crystals. It was found that, in comparison to normal square-lattice air-hole photonic crystals, annular photonic crystals have a much wider common frequency band between TE-1 and TM-2, which is quite beneficial to finding the overlap between the negative-refraction regions belonging to TE-1 and TM-2 respectively. Further analyses of equifrequency surfaces and the electric-field distribution of annular photonic crystals with different parameters have not only demonstrated how the filling factor of annular cells affects the formation of the common negative-refraction region between TE-1 and TM-2, but also revealed some ways to improve the performance of a polarization beam splitter based on the negative-refraction effect in an annular photonic crystal.

• 한국유체기계학회 논문집
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• 제3권4호
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• pp.44-51
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• 2000

The present study has been conducted to design the high efficiency centrifugal compressor for a R134a turbo-chiller. The centrifugal compressor consists of an impeller with splitters, two vaneless diffusers, a low-solidity vaned diffuser and a volute. A cycle analysis program for a turbo-chiller was developed to obtain compressor design parameters and requirements. We have designed the high efficiency centrifugal compressor by applying the repeated design procedure including a meanline design, a 3D geometry generation and fluid dynamic loading calculations.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.484-485
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• 2003

We report on the optimization of the fabrication process of hybrid sol-gel thin film deposition to produce low cost $1 {\times} 16$ splitters for optical communications. We learn that sol-gel film thickness is dependent upon the spinning speeds and viscosity of the sol-gel solutions and refractive index upon the dopant concentrations of Al and Zr in the sol solutions. We could find the optimized physical conditions to achieve the desired thickness of core and cladding layers. We will further carry out the fabrication and measurements of insertion loss, polarization dependent loss (PDL), etc. for the performance of fabricated splitter devices.

• 한국전산유체공학회지
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• 제21권3호
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• pp.77-88
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• 2016

A parametric study on a fluidic oscillator was performed numerically in this work. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations were solved to analyze the flow in the fluidic oscillator. As turbulence closure, $k-{\varepsilon}$ model was employed. Validation of the numerical results was performed by comparing numerical results with experimental data for frequency of the oscillation. The parametric study was performed using five geometric parameters. Performance of the fluidic oscillator was evaluated in terms of velocity ratio and pressure drop. The results show that the inlet channel width and the distance between splitters are important factors in determining the performance of the fludic oscillator.

• 한국정밀공학회지
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• 제23권2호
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• pp.122-128
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• 2006

This study focuses on a performance improvement of the vent silencer using acoustic analysis. Since the vent silencer is generally used for a high level shock noise, it should be designed to reduce a wide frequency band noise. In the designing stage of the vent silencer, structural shapes of diffuser and splitter are the most significant design parameters. Effects of modifying the original structure of the diffuser and the splitter are analyzed and evaluated. From the results, It is found that the diffuser with two pipes and double-step structure more effectively reduces a wide frequency band noise but the increment of the number of splitters is not desirable.