• Journal of Biosystems Engineering
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• 제26권5호
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• pp.431-440
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• 2001

Generated agri-chemical droplets by orchard sprayers are evaporated regenerated and transported along wind streams. The droplets are deposited to targets after changing their sizes, affecting the retention of droplets. An orchard sprayer, designed for spraying grapevines was studied on the spatial distribution of droplet size. The experimental variables were spray direction (0, 22.5, 45, 67.5 and 90˚), distance(2.5, 3.0 and 3.5 m) and fan speed (2,075 and 3,031 rpm). Droplet sizes were converted and analyzed from spray stains, sampled using water sensitive papers. The number median diameter (NMD) increased with an increase of the distance due to disappeared fine droplets (<50 ㎛): however, the volume median diameter (VMD) decreased due to shrunken large droplets (>100 ㎛). Fast fan speed delivered large droplets to 3.5 m, but the spatial distributions of NMD and VMD were not uniform. Slower fan speed decreased the possibility of evaporation and drift; therefore, plenty of droplets were maintained up to 3.0 m. The upward blasting distance was limited within 3 m, but the limit to the ground level was extended to 3.5 m. Concentrated wind and droplets to the ground level should be redistributed to upper canopy direction, leading more uniform deposits. High speed wind and system pressure should be avoided because of generating fine droplets, which would be disappeared and drifted away.

• 구강회복응용과학지
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• 제29권4호
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• pp.337-346
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• 2013

정중설공은 하악 전치부에 존재하는 해부학적 구조물로서, 구강저의 혈행을 담당하는 설하 동맥이 통과한다. 임플란트 시술 시 설하 동맥의 손상으로 인한 대량 출혈을 예방하기 위해서는 CBCT를 통한 정중설공의 주의 깊은 관찰이 필요하다. 본 연구의 목적은 하악 정중설공의 해부학적 특성인 출현빈도, 위치, 직경과 그 수를 성별과 나이에 따라 CBCT 이미지를 이용하여 평가하기 위함이다. 2008년 11월부터 2011년 5월까지 전남대학교 치과병원을 내원한 62명의 CBCT 이미지(남성 41명, 여성 21명; 평균 연령 43세; 연령 분포 9~85세)를 평가하였다. 하악 전치부 CBCT에서 관찰되는 정중설공의 출현빈도, 수, 위치, 수직적 거리와 직경을 계측하였다. 62명의 환자(100%) 모두에서 설극 상방에 1개 이상의 정중설공을 관찰할 수 있었고, 56명(90.32%)은 다수의 정중설공을 가지고 있었다(2개 64.52%, 3개 25.8%). 42명(66.13%)의 환자에서 하악 양 중절치 사이의 정중설공을 관찰할 수 있었다. 치조정에서 설극까지의 평균 높이는 24.21 mm 였고, 하악골 하연에서 정중설공까지의 평균높이는 14.53 mm, 하악골에서의 상대적인 높이는 0.45였다. 설공의 평균 직경은 0.93 mm였다. CBCT를 통해 정중설공의 출현빈도, 위치, 직경과 그 수를 쉽게 확인할 수 있다. 전치부 임플란트 시술 시 대량 출혈의 합병증을 예방하기 위해서는 임플란트 식립 전 CBCT를 촬영하여 개개인의 정중설공의 해부학적 평가하는 것이 필요할 것이다.

• Imaging Science in Dentistry
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• 제34권3호
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• pp.129-136
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• 2004

Purpose: To evaluate whether cone beam computed tomography can depict the distribution, position, frequency, relative vertical dimension, and the diameter of the lingual foramen and direction of lingual bone canal. Materials and Methods : Cone beam computed tomography of mandible was performed on 25 males and 25 females with no history of any orthodontic treatments or any other dental surgeries. A statistical comparison was done on the mean values of males and females. Results: In the location and distribution of lingual foramina, median lingual foramen was found in all subjects and lateral lingual foramen in 58%. In the lateral lingual foramen, bilateral type was found in 28% and unilateral type in 30%. In the number of lingual foramina, median lingual foramen had two foramina and lateral lingual foramen had one foramen, mostly. In the relative mean vertical dimension of lingual foramina, median lingual foramen was 0.03±0.08, and both lateral lingual foramina was 0.20±0.04. The mean diameter of lingual foramina, median lingual foramen was 0.9mm±0.28, right lateral lingual foramen was 0.92mm±0.23, and left lateral lingual foramen was 0.88mm±0.27. The most frequent direction of the lingual bone canals, median lingual bone canal proceeded in anteroinferior direction and lateral lingual bone canal in anterosuperolateral direction. Conclusion : Cone beam computed tomography can be helpful for surgery and implantation on the mandibular area. Radiologist should be aware of this anatomical feature and its possible implications.

• 대한기계학회논문집B
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• 제25권4호
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• pp.475-484
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• 2001

The purpose of this study is to investigate the heat transfer augmentation using the perforated plate placed in front of a target plate in an axisymmetric impinging air jet system. The new liquid crystal technique using neural networks with median filtering is used to determine the Nusselt number distributions on the target surface. The experiments were made for the jet Reynolds number (Re) 23,000. The effects of the pitch-to-diameter (p/d1) from 1.5 to 2.5 in the perforated plate, the hole diameter on perforated plate (d1) from 4㎜ to 12㎜, the perforated plate to target surface distance (z/d1) from 1 to 3, and the nozzle-to-target surface distance (L/d) from 2 to 10 on the heat transfer characteristics were experimentally investigated. It was found that when the perforated plate was located between the nozzle exit and the target plate, the average heat transfer rate at the stagnation region corresponding to r/d$\leq$1.0 was increased up to the maximum 2.3 times compared to the case without the perforated plate.

• Journal of Korean Society for Atmospheric Environment
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• 제20권E2호
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• pp.61-68
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• 2004

Aerosol losses in a 100L Tedlar$^{(R)}$ bag were investigated for the aerosols with number median diameter of 0.05 ${\mu}{\textrm}{m}$ and number concentration of 6.4 ${\times}$ 10$^4$ cm$^{-3}$ . Over a 1 hr period, loss of particles in the bag is apparent, and the volume decrease with time is significant. The number concentration, surface area, and volume concentration of the aerosols decreased to 34, 50, and 52% of the initial value in 30 min, respectively. This indicates that deposition to the walls was the main loss process for aerosols in the Tedlar$^{(R)}$ bag. Theoretical calculations showed that coagulations and deposition by diffusion and gravitational sedimentation would not change aerosol characteristics significantly, and the electrical force was the dominant loss process for particles in the Tedlar$^{(R)}$ bag over a 1 hr period.eriod.

• 한국산업보건학회지
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• 제22권3호
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• pp.184-190
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• 2012

Objectives: This study aimed to characterize the nanoparticles produced by welding and grinding processes. Methods: The number concentrations of particles were mapped to determine the distribution of welding fumes in a workplace atmosphere using a hand-held condensation particle counter. An electrical low-pressure impactor was used for measuring the number concentration and particle size distribution. Results: High number concentrations were found around arc cutting and welding (grinding) processes. In the worker's breathing zone, the mean number concentration was 655,000 particles/cm3 and the count median diameter (CMD) was 84 nm with several multi peak distributions (~20, 70, 300 nm). However, at a distance of 3 m from the welding position, the number concentration decreased to 153,000 particles/cm3 with a 70 nm single peak size distribution. During a grinding process, peaks with high concentrations of nanoparticles were temporarily observed. The mean number concentration was 1,520,000 particles/cm3, and the CMD was 30 nm. Nanoparticles (<100 nm) made up 58% and 92% of the aerosols produced by welding and grinding processes, respectively.

• 대한지리학회지
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• 제32권2호
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• pp.141-153
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• 1997

1996년 현재 케이블TV 방송국수는 전국에 54개로, 인구규모가 큰 도시에 방송국이 많이 입지하고 있다. 그리고 방송국의 분포는 각 시ㆍ도의 수요규모가 가장 큰 도청 소재지나 제2의 도시에 입지하는 특징을 나타내고 있다. 각 시ㆍ도의 설립예정 방송국수와 가구수와의 상관관계는 매우 높다는 것이 밝혀졌다. 광역화 방송구역의 가구수와 인구수를 보면, 평균 가구수는 약 181,000가구이고, 인구수는 약 585.000명이고, 케이블 TV방송국이 입지하기 위하여 최소의 필요 시장규모는 가구수가 약 73.000가구, 인구수는 약 230,000명이다. 광역화 방송구역과 1차 허가 전국 방송구역의 가구수와 인구수를 비교해 보면, 광역화 방송구역의 표준편차 값이 커져 시장규모 크기의 분산도가 커졌다는 것을 알 수 있다. 청주시.청원군 방송구역의 동ㆍ면별 케이블TV 가입률에 영향을 미치는 요인은 평균연령, 아파트 보급률이나, 이 중 아파트 보급률이 더 영향을 미치고 있다.

• 농업생명과학연구
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• 제52권6호
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• pp.111-125
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• 2018

본 연구에서는 변량방제기술을 적용한 농용 회전익기를 이용하여 살포한 입자의 구간비행 상태에서의 거리별 살포 패턴을 측정함으로써 무인 항공방제의 농약 부착률과 입자경의 분포 균일도를 평가하였다. 비행을 등속으로 유지하는 안내비행과 자동비행 모드에서 유효살포폭 3.6m로 인접비행 구간과 살포폭이 일부 중첩된 피복률에 대한 가로방향 분포의 변이계수는 30% 정도를 보였고, 비행방향 진로위치에 대한 피복률의 변이계수는 10% 미만으로 매우 균등한 것으로 평가되었다. 따라서 살포작업시 기체의 지면속도(ground speed)의 변이를 보상하는 변량살포기술은 균일도 측면에서 우수한 것으로 판명되었으며, 또한 입자경의 분포에 있어서 체적중위직경(VMD)과 개체중위직경(NMD) 모두 항공방제에 적절한 크기와 균일한 분포를 보였다. 따라서 농용 회전익기를 이용하여 소필지의 항공방제작업을 무인화 하는데 있어, 변량방제장치를 적용함으로써 소규모 필지의 균일 정밀방제를 도모하고자 하였다.

• Journal of Chest Surgery
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• 제57권1호
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• pp.70-78
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• 2024

Background: This study investigated the outcomes of biventricular repair using right ventricle to pulmonary artery (RV-PA) conduit placement in patients aged <1 year. Methods: Patients aged <1 year who underwent biventricular repair using an RV-PA conduit between 2011 and 2020 were included in this study. The outcomes of interest were death from any cause, conduit reintervention, and conduit dysfunction (peak velocity of ≥3.5 m/sec or moderate or severe regurgitation). Results: In total, 141 patients were enrolled. The median age at initial conduit implantation was 6 months. The median conduit diameter z-score was 1.3. The overall 5-year survival rate was 89.6%. In the multivariable analysis, younger age (p=0.006) and longer cardiopulmonary bypass time (p=0.001) were risk factors for overall mortality. During follow-up, 61 patients required conduit reintervention, and conduit dysfunction occurred in 68 patients. The 5-year freedom from conduit reintervention and dysfunction rates were 52.9% and 45.9%, respectively. In the multivariable analysis, a smaller conduit z-score (p<0.001) was a shared risk factor for both conduit reintervention and dysfunction. Analysis of variance demonstrated a nonlinear relationship between the conduit z-score and conduit reintervention or dysfunction. The hazard ratio was lowest in patients with a conduit z-score of 1.3 for reintervention and a conduit z-score of 1.4 for dysfunction. Conclusion: RV-PA conduit placement can be safely performed in infants. A significant number of patients required conduit reintervention and had conduit dysfunction. A slightly oversized conduit with a z-score of 1.3 may reduce the risk of conduit reintervention or dysfunction.

• Journal of Mechanical Science and Technology
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• 제14권10호
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• pp.1159-1167
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• 2000

Particles in liquid-solid suspension flow might enhance or suppress the rate of heat transfer and turbulence depending on their size and concentration. The heat transfer characteristics of liquid-solid suspension in turbulent flow are not well understood due to the complexibility of interaction between solid particles and turbulence of the carrier fluid. In this study, the heat transfer coefficients of liquid-solid mixtures are investigated using a double pipe heat exchanger with suspension flows in the inner pipe. Experiments are carried out using spherical fly ash particles with mass median diameter ranging from 4 to $78{\mu}m$. The volume concentration of solids in the slurry ranged from 0 to 50% and Reynolds number ranged from 4,000 to 11,000. The heat transfer coefficient of liquid-solid suspension to water flow is found to increase with decreasing particle diameter. The heat transfer coefficient increases with particle volume concentration exhibiting the highest heat transfer enhancement at the 3% solid volume concentration and then gradually decreases. A correlation for heat transfer to liquid-solid flows in a horizontal pipe is presented.