• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.688-695
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• 2012

The present study represents the effects of boundary condition on the performance of a centrifugal blower at the interference plane between rotational and stationary domains using three dimensional compressible Navier-Stocks equations. Two boundary conditions, frozen-rotor and stage, are compared to analyze the blower performance. Installation angle between the cutoff of a volute casing and a impeller blade is also introduced to evaluate the blower performance and to understand the internal flow inside the blower. Throughout numerical simulation, it is found that the frozen rotor interface method at the interference plane represents well the variations of flow field inside the blower compared to stage interface method. However, pressure has maximum two percent error according to the installation angles while pressure is almost constant for the stage interface method. And stage interface method can relatively well predict the blower performance. Detailed internal flows of the centrifugal blower are compared and analyzed by numerical simulation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.45-48
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• 2007

In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the midplane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.141-142
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• 2006

This paper describes estimation method for 2D position error of planar XY stage from measured profiles of guide-ways. The XY stage usually moves along its guide ways. The motion error of each stage has effect on 2D position errors of XY stages and affected mainly by profiles of guide-ways. To estimate 2D position error and flatness of stages, the profiles of guide-ways were measured and used in motion error estimation.

• 한국전산유체공학회지
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• 제12권4호
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• pp.85-89
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• 2007

In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the mid-plane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

• 전기학회논문지
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• 제57권9호
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• pp.1491-1499
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• 2008

This paper presents a study on reliability evaluation of a power system considering wind turbine generators (WTG) with multi-state. Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Wind energy is one of the most successful sources of renewable energy for the production of electrical energy. But, reliability evaluation of generating system with wind energy resources is a complex process. While the wind turbine generators can not modelled as two-state model as like as conventional generators, they should be modelled as multi-state model due to wind speed random variation. The methodology for obtaining reliability evaluation index of wind turbine generators is different from it of the conventional generators. A method for making outage capacity probability table of WTG for reliability is proposed in this paper. The detail process is presented using case study of simple system.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1320-1327
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• 2006

Parallel procedure and performance of two-step Eulerian code have not been reported sufficiently yet even though it was developed and utilized widely in the impact simulation. In this study, parallel strategy of two-step Eulerian code was proposed and described in detail. The performance was evaluated in the self-made linux cluster computer. Compared with commercial code, a relatively good performance is achieved. Through the performance evaluation of each computation stage, remap is turned out to be the most time consuming part among the other part such as FE processing, communication, time marching etc.

• 환경영향평가
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• 제5권2호
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• pp.33-47
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• 1996

To select the criteria, literature review was made in the quantitative case of conservation biology, foreign country's EIA and domestic ecology. Among them, a few factors was extracted. To applicate the criteria to domestic forest ecosystem, expert opinion survey was executed to the ecologist. The results were summarized as follows; 1. Classification of sites was made of land use system which is related to forest ecosystem or forest conservation. Sites are divided into 3 categories which are nature preservation area, seminature preservation area and urbanized area. Evaluation criteria is consisted of rarity and naturalness. 2. Each area had different criteria composition according to the site characteristics. Criteria of nature preservation area is rarity in the broad sense (distribution pattern of vegetation), vegetation size, successional stage and depth of organic matters. Those of seminature preservation area are rarity in the broad sense (distribution area of vegetation), vegetation size, successional stage, diameter at breath height and depth of organic matters. And those of urbanized area are vegetation distribution in area, successional stage, age of forest and diameter of breath height. The basic data of criterion was gathered by field survey. 3. Evaluation index and total naturalness index was obtained by adding the each criterion. It is made up of two categories-rarity and naturalness. TNi is divided into 3 grades. Grade I is more than 70% for TNi, grade IT is 50~70%, and grade III is below 50%. According to the each grade, permitted action and facilities were suggested.. This research just focuses on the evaluation of vegetation quality and the assessment results do not directly judge conservation or development. To make better evaluation criteria, various fields of forest ecosystem-geological or physical nature environment and fauna ecosystem etc. -will be added wholly to this research.

• 한국ITS학회 논문지
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• 제15권3호
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• pp.1-11
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• 2016

본 연구는 철도역의 환적저항요인을 평가하고 시사점을 도출하고자 수행하였다. 모형추정을 위한 자료는 RP자료와 SP자료이다. 모형 형태는 본송단계와 환적단계, 셔틀단계를 합친 통합모형과 이를 개별적으로 적용한 분리모형으로 추정하였다. 모형추정 결과 벌크화물 화주는 본송단계에 주안점을 두지만 환적단계 역시 중요하게 인식하는 것으로 나타났다. 특히 환적단계가 셔틀단계보다 더 중요하게 인식되는 점은 주목할 사항이다. 따라서 향후 벌크화물의 철도운송 정책에서 본송단계의 경쟁력을 확보하는 것도 중요하지만 철도역을 중심으로 하는 환적단계에 대한 개선 노력도 요구된다.

• ETRI Journal
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• 제38권2호
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• pp.366-375
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• 2016

This paper describes an algorithm to suppress composite noise in a two-microphone speech enhancement system for robust hands-free speech communication. The proposed algorithm has four stages. The first stage estimates the power spectral density of the residual stationary noise, which is based on the detection of nonstationary signal-dominant time-frequency bins (TFBs) at the generalized sidelobe canceller output. Second, speech-dominant TFBs are identified among the previously detected nonstationary signal-dominant TFBs, and power spectral densities of speech and residual nonstationary noise are estimated. In the final stage, the bin-wise output signal-to-noise ratio is obtained with these power estimates and a Wiener post-filter is constructed to attenuate the residual noise. Compared to the conventional beamforming and post-filter algorithms, the proposed speech enhancement algorithm shows significant performance improvement in terms of perceptual evaluation of speech quality.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.