• Journal of Ecology and Environment
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• 제30권2호
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• pp.127-133
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• 2007

The effects of water flow rate and phytoplankton concentration on the growth of the sandy shore clam Gafrarium tumidum was investigated in a laboratory flume study using a $3{\times}3$ factorial design. After 60 days, shell length, shell weight and tissue dry weight increased significantly with phytoplankton concentration. For the effect of flow rate, growth was faster when flow rate increased from low to medium level; further increases in flow rate, however, either did not sustain faster growth or resulted in a reduction in growth. The condition index (CI) of a standard-sized clam was significantly higher at low flow rate than at medium and high flow rates and was negatively correlated with phytoplankton concentration. The uncoupled growth of shell and tissue in response to flow rate and phytoplankton concentration may be adaptations to low food environments, so that energy can either be stored to sustain life or reserved for gametogenesis during the reproductive period.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.858-863
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• 2001

In this paper, the test and result of flow and combustion for 21AFR lean fuel models are described. The necessity to develop the low emission combustor has been issued from the concern on the increase of green house and the destruction of ozone layer. To evaluate the flow and combustion performance of new designed 21AFR lean modules, the hydraulic tests in stereo lithographic airflows models, the low pressure combustion tests in three injectors model for weak extinction and ignition and the high pressure combustion tests in single sector for NOx, SAE and efficiency are performed. The low pressure tests reveal that the governing parameters in weak extinction and ignition at atmospheric condition are prefilmer length, swirl flow rotation direction, secondary swirl angle and flow split. As a results of combustion test at high pressure, the efficiency and smoke level are satisfied with performance targets, but EINOx of 17.8 is higher than target value of 13.1. The high pressure tests show that the main parameters influenced on NOx are primary swirl angle, swirl flow rotation direction, heatshield exit angle and liner mixing hole location.

• 대한지하수환경학회지
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• 제7권1호
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• pp.8-14
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• 2000

오늘날 급격한 산업화, 도시화, 인구증가 등으로 용수수요 급증, 수질오염 수자원 개발의 한계, 용수공급의 안정성 등으로 인하여 갈수량에 관한 관심이 증대하고 있다. 물리적 토대를 둔 유로-대수층 모형을 이용하여 영산강 유역에 위치하고 있는 주요하천의 지역 갈수 유출모형의 개발을 모색하였다. 이를 위하여 영산강 유역의 주요하천에서 23개의 대상 소유역을 선정하였으며, 여기서 갈수량을 측정하여 본 연구의 모형개발에 이용하였다. 그리고 최종적으로 영산강 유역의 미계측 지점에서 갈수량을 추정하기 위한 지역갈수 유출 모형을 제안하였다.

• Spatial Information Research
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• 제17권2호
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• pp.223-239
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• 2009

우리나라 중소규모의 대부분 하천의 경우 유량 자료의 부족 또는 미계측 지역으로 인하여 효율적인 저수유량 산정이 어려운 실정이다. 따라서 본 연구의 목적은 수계별 환경용량을 고려한 허용부하량 산정을 위해 면적함수 관계식을 이용한 저수유량의 산정방안을 제시하는 것이다. 이를 위해 남한강 상류 지역의 유역면적 $606km^2$인 주천강 유역과 미계측 유역면적 $4,551km^2$인 옥동천 합류 후인 한강 유역을 시험하천으로 선정하였다. 적용결과, 주천 하류부의 저수 유량은 $1.9m^3/s$로, 미계측 유역인 옥동천과 한강의 합류 후의 저수유량은 $20.7m^3/s$로 계산되었다. 이를 영월군에서 고려하고 있는 BOD목표치 1.0-1.2mg/l로 계획하면 허용부하량은 각각 164-197kg/day 및 1,788-2,146kg/day로 추정되었다. 본 연구에서 제시한 허용부하량 산정방법은 자료가 충분하지 않은 유역이나 미계측 유역에 대해 유용하게 이용될 것으로 기대한다.

• 한국융합학회논문지
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• 제9권2호
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• pp.171-176
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• 2018

본 연구는 스마트 사이니지를 실제 일정한 공간에 설치하여 상호작용성 수준(고 vs. 저)과 플로우 수준(고 vs. 저)에 따라 미디어 인게이지먼트와 광고 인게이지먼트 뿐 아니라 어떠한 정보를 기억하는지와 관련한 기억 효과까지 실증적으로 분석하였다. 48인치 스마트 사이니지를 실제 대학 구내에 설치하여 실험 연구로 진행하였다. 연구 결과 상호작용성과 인게이지먼트 수준이 모두 높은 경우 모두 낮은 경우보다 광고 인게이지먼트는 높게 나타났다. 또한 상호작용성 수준이 낮고 플로우 수준이 높은 경우 미디어 인게이지먼트가 높게 나타났다. 마지막으로 상호작용성 수준이 낮고 플로우 수준이 높으면 비평가적인 속성 정보를 종합적인 평가 정보에 비해 많이 기억하여 회상하였으며, 스마트 사이니지의 상호작용성이 높고 사용자의 플로우가 낮으면 태도적인 평가적 회상 정보를 더 많이 회상하는 것으로 나타났다. 향후 스마트 사이니지 전략에 있어 상호작용성을 무조건 높이는 전략보다는 사용자 플로우를 높이기 위한 세부적인 전략이 필요할 것이다.

• 물과 미래
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• 제14권1호
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• pp.31-37
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• 1981

금강수계의 미계획지점에 대한 갈수량빈도곡선의 합성은 하천형태학적 인자인 유역면적, 유역의 기복량, 하천의 연장 및 미국연방주환경국의 하천수질기준인 10년 7월 평균 갈수량을 이용한 상관관계를 분석함으로서 가능하였다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.356-361
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• 1997

To investigate parametric effect on CHF and to get CHF data, experimental study has been performed with vertical round tubes under the condition of low pressure and low flow (LPLF). Test sections are made of Inconel-625 tube and have the geometry of 8 and 10 mm in diameter, and 0.5 and 1.0 m in heated length. All experiments have been conducted at the pressure of under 9 bar, the mass flux of under 250 kg/$m^2$ and the inlet subcooling of 350 and 450 kJ/kg, for stable upward flow with water as a coolant. Flow regime analysis has been performed for obtained CHF data with Mishima's flow regime map, which reveals that most of the CHF occur in the annular-mist flow regime. General parametric trends of the collected CHF data are consistent with those of previous studies. However, for the pressure effect on CHF, two different are observed; For relatively high mass flux, CHF increases with pressure and far lower mass flux, CHF decrease with pressure. Using modern data regression tool, ACE algorithm, two new CHF correlations for LPLF condition are developed based on local condition and inlet condition, respectively. The developed CHF correlations show better prediction accuracy compared with existing CHF prediction methods.

• 한국유체기계학회 논문집
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• 제16권2호
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• pp.48-53
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• 2013

This paper presents a numerical investigation of the influence of the blade back sweep angle on the performance and flow characteristics in a centrifugal compressor with a vaneless diffuser. Five impellers with different back sweep angles were tested in the flow simulations. It was found that a low back sweep angle could improve the total-to-total pressure ratio and the work coefficient over whole operating ranges. However, the flow field in an impeller with a low back sweep angle produced a more non-uniform velocity distribution at the impeller exit because the wake region was significantly increased. As a consequence, the impeller with a low back sweep angle caused a low diffuser performance.

• 대한기계학회논문집
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• 제18권7호
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• pp.1840-1850
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• 1994

Enhancement of numerical algorithms for low speed compressible flow will be considered. Contemporary time-marching algorithm has been widely accepted and applied as the method of choice for transonic, supersonic and hypersonic flows. In the low Mach number regime, time-marching algorithms do not fare as well. When the velocity is small, eigenvalues of the system of compressible equations differ widely so that the system becomes very stiff and the convergence becomes very slow. This characteristic can lead to difficulties in computations of many practical engineering problems. In the present approach, the time-derivative preconditioning method will be used to control the eigenvalue stiffness and to extend computational capabilities over a wide range of flow conditions (from very low Mach number to supersonic flow). Computational capabilities of the above algorithm will be demonstrated through computation of a variety of practical engineering problems.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1449-1459
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• 2005

This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.