• Journal of Biosystems Engineering
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• v.26 no.5
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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.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.337-346
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• 2013

It is necessary to consider the median lingual foramen carefully to prevent the bleeding due to the damage of the sublingual artery for implant surgery. This study is to evaluate the frequency, location, diameter and the number of the Mandibular median lingual foramen regarding gender and age in the CBCT. Sixty two images of cone beam computed tomography (CBCT) whose visited the Chonnam National University Dental hospital from Sept. 2010 to Apr. 2011 were evaluated. Frequency, number, location and the diameter of Mandibular median lingual foramen shown in the CBCT image were evaluated. Sixty two patients (100%) had at least one median lingual foramen and fifty six patients (90.32%) had multiple foramens. Forty patients (66.13%) showed the median lingual foramen on the location between Mn. central incisors. The mean vertical position of the genial spine and the median lingual foramen was 24.21 mm and 14.52 mm, respectively. And the relative mean vertical dimension of median lingual foramen was 0.45. The mean diameter of the foramen was 0.93 mm. CBCT demonstrated the frequency, location, diameter and the number of median lingual foramen. It is necessary to take CBCT before implant placement to prevent the bleeding.

• Imaging Science in Dentistry
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• v.34 no.3
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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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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• v.20 no.E2
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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.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.3
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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.

• Journal of the Korean Geographical Society
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• v.32 no.2
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• pp.141-153
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• 1997

In Korea, cable television(CATV) broadcasting has begun in March, 1995. This Paper aims at examining the location of CATV broadcasting station, and demand density(numbers of viewer houshold) of broadcasting area, and at clarifing the factors affecting subscription. The results are as follows: The number of CATV stations is 54 in 1996, and these CATV stations are mainly located in larger cities. The correlation between the number of established or planned CATV station and the number of household is very high. In sphered broadcasting area Permitted in 1997, the location of CATV station is about 73,000 household and 230,000 persons in the minimum values of household and population, and diameter of sphered broadcasting area is 40.6 km in mean. The factors affecting subscription rates of CATV are median age and supply rates of apartment of each dong in Chongju city and each myun in Chongwon county. The correlation between subscription rates of CATV and supply rates of apartment appears higher than correlation between subscription rates and median age other factors based on residual analysis of regression equation are established period of transmission network of CATV and acceptance attitude of dwellers.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.111-125
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• 2018

In this study, we evaluated the uniformity of deposition rate and particle size distributions of the variable rate application technique using the unmanned rotorcraft by measuring the spray pattern according to path location in the range of spraying flight. The coefficient of variation (CV) of the lateral coverage rate for the overlapped distribution with the spray swath of 3.6 m in both guidance and auto-pilot flight modes maintaining constant flight speed was about 30% and the CV of the coverage rate by the flight path location was extremely small. Therefore, it was assessed that the variable rate application technology compensating for the variation of ground speed was superior in terms of spray uniformity. In addition, the droplet size distributions in both volume median diameter(VMD) and number median diameter(NMD) were adequate for aerial application and uniform in terms of lateral distribution. Thereafter, we intend to contribute to a precise application on small-scaled fields using the unmanned agricultural rotorcraft by the variable rate application.

• Journal of Chest Surgery
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• v.57 no.1
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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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• v.14 no.10
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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.