• 한국수자원학회논문집
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• 제44권6호
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• pp.449-459
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• 2011

사석 입자의 운동을 시작하는 한계평균유속은 사석의 평균입경, 수심에 대한 사석의 평균입경 비, Froude수 및 한계평균유속에 대한 난류전단속도 비에 따라 증가함을 실험을 통해 확인하였고, 이 값을 사석의 수리적 안정성을 지배하는 변수로 채택하여 회귀분석을 통한 사석의 안정성 실험식을 개발하였다. 개발된 사석 안정성 식은 기존 실험의 유속범위인 0.36~0.73 m/s에서 0~5.0 m/s까지 확장시켜 실제 하천에 적용 가능성을 검토하였다. 큰 값의 Reynolds수의 확장에 따른 한계평균유속을 포함한 매개변수간의 유용한 상관성을 제시하였다. 실험값으로부터 확장된 큰 값의 Reynolds의 범위에서의 사석 안정성에 대한 평균입경의 산정은 0~3.0 m/s에서는 미국 토목학회 공식과 미개척국에서 제시한 안정성식과 적합함을 보였으며, 3.0~5.0 m/s에서는 미국 토목학회 공식과 잘 일치하였다. 개발된 사석평균입경 결정공식은 일반적으로 미국 토목학회 공식과 잘 일치하였고, 기존 안정성식과 비교한 결과 대부분 잘 일치하는 것으로 확인되었다. 따라서 개발된 사석평균입경 산정식은 높은 사용성을 가지고 있음을 확인하였다.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.913-922
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• 2012

환경 및 화학공업에서 액-액 교반조내의 특성을 파악하는 일은 매우 중요하다. 액적 부근의 물질이동용량계수 $k_La$와 Sauter 평균경 $d_{32}$은 에스테르의 알칼리 가수분해반응을 이용하여 임펠러 부착위치나 액높이를 변화시켜 측정하였다. 그 결과 아래와 같은 이들의 양호한 상관식을 얻었다. $$d_{32}=0.270\(\frac{{\sigma}^{0.6}}{{\rho}^{0.2}P^{0.4}_{Vi}}\)k_La=0.49\(\frac{6{\phi}D_A}{d^2_{32}}\)\(\frac{P_Vd^4_{32}}{{\rho}v^3}\)^{0.193}Sc^{1/3}$$.

• 대한기계학회논문집
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• 제12권2호
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• pp.319-327
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• 1988

본 논문에서는 비증발 디이젤 분무의 고속도음영사진을 화상해석 함으로서, 분무선단지달거리와 분무용 이외에 어떤 연문의 분무속 전체 액적군의 평균입자경(sauter mean diameter)과 분무내 연료농도분포를 동시에 측정할 수 있는 새로운 측정법을 제시한다.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.42-50
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• 2000

Drop size distribution of an air-assisted fuel injector(AAFI) was investigated. Influence of parameters such as ambient air density supply pressure and air-liquid mass ratio(ALR) was examined through both measurement and analysis. The Sauter mean diameter$D_{32}$ varied from 9 to 25$\mu$m throughout all experimental conditions. An empirical correlation for droplet size was obtained. Analytical correlations for predicting $D_{32}$ with respect to operating conditions were also derived through energy consideration and introduction of a simplified model of the from the empirical fitting was adapted to the original equation the proposed correlation in this study matched more closely with measured results. The current correlation exhibited a favorable study matched more closely with measured results. The current correlation exhibited a favorable prediction for $D_{32}$ compared to that by the empirical correlation at selected experimental conditions so that it may be used to predict atomization performance of the AAFI at operating conditions which was not covered in the measurements. After validation the analytical equation was applied to survey the feasible operating conditions for gasoline direct injection application.

• 한국분무공학회지
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• 제1권3호
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• pp.51-59
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• 1996

An experiment was carried out on the structure of twin spray from pressurize-swirl nozzles, in order to investigate the effect of different size of spray nozzles on the characteristics of the overlap of two single sprays, for example, mean diameter, number density, and spatial distribution of flow rate. Using image processing method, the distributions of size and velocity of droplets of a single spray and twin spray were measured and compared to investigate the overlapping effect of two identical sprays. Comparing experimental results from a twin-spray with those from two-single sprays shows that the flow rate distribution of the twin-spray was concentrated around the midst of the overlapping region of two sprays. In this region, Sauter mean diameter (SMD) did not change much in the twin spray from 6032 nozzles, but it was smaller by 10 micrometers in the twin-spray than two-single sprays from 60063 nozzles. In spite of large difference in Weber numbers of the colliding sprays between the 60063 and 6032 nozzles, the phenomena did not have a big change in the overlapping region of twin spray. This shows that in the collision between droplets from two single spray in the overlapping region to cause the disruption of droplets, the size distribution of spray droplets was also important as well as Weber number.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.125-128
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• 2008

이중모드 위상도플러속도계(Dual-mode Phase Doppler Anemometry, DPDA)를 이용하여 소형 액체 로켓엔진 인젝터 분무의 미립화 특성을 고찰하였다. 분무액적의 반경방향 이동에 따른 속도, 크기, 수밀도, 부피플럭스 등을 다양한 분사압력에서 측정하여 인젝터 분무의 공간분포 특성을 규명한다. 분사 압력이 증가함에 따라 분무액적의 속도, 난류강도, 수밀도, 그리고 부피플럭스는 증가하지만, 산술평균 직경($D_{10}$)과 분무액적의 증발율에 대한 척도인 Sauter Mean Diameter($D_{32}$)로 표현되는 액적의 크기는 감소하였다. 또, 속도와 부피플럭스는 Sauter 평균직경(Sauter mean diameter, SMD)에 비례하는 것을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.113-116
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• 2008

액체추력기 인젝터로부터 발생하는 분무의 분열과 확산거동을 파악하기 위해 이중모드 위상도플러속도계(DPDA)를 사용하여 분무액적의 준3차원적 공간분포를 계측하고 도시한다. 분무는 27.6 bar의 분사압력 조건에서 길이-직경비가 1.67인 노즐 오리피스로부터 지면에 수직으로 분사된다. 분무액적의 수직 및 수평방향 평균속도, AMD, SMD, 그리고 부피플럭스는 분무의 상류/중심에서 하류/외곽으로 이동함에 따라 분무분열에 의해 그 크기가 감소한다.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.572-579
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• 2002

The experimental measurements were carried out to examine turbulent disintegration characteristics ejecting from a counter-flowing internal mixing pneumatic nozzle under variable conditions of swirl angles and air pressures. The air injection pressure was varied from 60 kPa to 180 kPa and four counter-flowing internal mixing nozzles with axi-symmetric tangential-drilled holes at swirl angle of 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, and 60$^{\circ}$to the central axis have been specially designed. The experimental results were quantitatively analyzed, focusing mainly on the comparison of turbulent atomization characteristics issuing from an internal mixing swirl nozzle. To illustrate the swirl phenomena, the distributions of mean velocities, turbulence intensities, volume flux, and SMD (Sauter Mean Diameter, or D$\sub$32/) were comparatively analyzed.

• 한국임상수의학회지
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• 제3권1호
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• pp.265-276
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• 1986

Pathological study was made of 173 gallbladders among 652 slaughter pigs. The size and the pH of the bile juice were made of 50 among 173 gallbladders with lesions and 50 normal gallbladders as control. The results are summerized as follows : 1. The histological lesions were shown hyperemia and congestion(83.2%), Iymphocytic infiltration(37.5%), Iympoid hyperplasia(27%), epithelial downgrowth(27%), erosion and ulcer(22%), papillary hyperplasia (20.2%), pericholecystic edema(19.5%), hemorrhage(11%), and leukemic cell infiltration(0.6%). 2. In the gallbladders with lesions mean size was 4.26${\times}$7.88cm in diameter and mean pH is 7.2. In the control means size and mean pH were 4.57${\times}$8.13cm in diameter and 7.1. The difference of size between gallbladders with lesions and these as control was not statistically significant. The pH of bile juice between two showed also no statistically significant difference.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권6호
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• pp.432-439
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• 2012

Purpose: The aim of this study was to investigate the blood supply to the maxillary sinus in Koreans using computed tomography of the lateral wall of the sinus, and to analyze the data according to demographic data, and to compare our results with previously published research. Methods: One hundred and three patients (males 51, females 52) who visited the dental clinic were evaluated. We investigated the canals with cone-beam computed tomography, and measured the diameter and length from the bony notch of the vascular canal at the lateral wall of the sinus to each of the reference planes. Results: Most types of vascular canal were type I & II (total 72.2%) which were driving through inside the sinus wall. Type IV, V were frequently investigated in 1st premolar and 2nd molar. Mean height; from anterior nasal spine-posterior nasal spine plane to vascular canal was 5.56 mm in 1st premolar, 2.11 mm in 2nd premolar, 0.98 mm in 1st molar, 4.32 mm in 2nd molar; from the basal layer of the sinus was 4.93 mm in 1st premolar, 5.00 mm in 2nd premolar, 6.05 mm in 1st molar, 7.91 mm in 2nd molar; and from alveolar crest, 20.80 mm in 1st premolar, 16.57 mm in 2nd premolar, 14.01 mm in 1st molar, 16.17 mm in 2nd molar. The mean height of the vascular canal of each reference plane showed no significant difference between sex, site (left or right) and age. The mean diameters of the canals were 1.76 mm in male, and 1.50 mm in female. Diameter decreased with age, and tooth site (from 1st premolar to 2nd molar). Conclusion: These results show that the mean diameter of the vascular canal of the maxillary sinus varies according to age, sex, and tooth site, but that the mean height of canal had no significant difference based on these three factors.