• Water Engineering Research
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• v.3 no.1
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• pp.9-22
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• 2002

In general, two dimensionless numbers are used in predicting the front propagation rate of density currents: the densimetric Froude number and the dimensionless front velocity. The former expresses the front speed in terms of the characteristic length and reduced gravitational acceleration. Previous papers report that the range of this dimensionless number is wide. The other is the dimensionless front velocity, which is a function of the buoyancy flux per unit width. This paper presents the state of the art review of the dimensionless numbers for the front propagation rate of density currents. Values of the densimetric Froude number are found to be consistent when the proper characteristic length is used for normalization. Then, the densimetric Froude number and the dimensionless front velocity are compared by using the experimental data of density currents over a horizontal surface.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.1
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• pp.1-7
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• 2023

We studied the changes in growth characteristics of major cultivated rice in low- density transplanting. The culm and spikelet length did not change in low density transplanting conditions. As the distance between hills increased by 10 cm, the number of tillers per hill increased by an average of 4.4 and the number of grains per spikelet increased by 7.5. The cultivar that had more tillers and higher grain number in 80 hills per 3.3 m² tended to have more tillers and grain in low-density transplanting conditions. However, the increase rate of tillers and grain in low-density transplanting was not significanty different from the tiller and grain number in 80 hills per 3.3 m². The total branch number and branch length in spikelets increased in low-density transplanting conditions. The grain number per spikelet was also increased by the in low-density transplanting method.

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.827-832
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• 2001

The excitation temperature and electron number density have been measured for end-on-view ICP discharge. In this work, end-on-view ICP-AES equipped with the newly developed “optical plasma interface (OPI)” was used to eliminate or remove the neg ative effects caused by end-on-plasma source. The axial excitation temperature was measured using analyte (Fe I) emission line data obtained with end-on-view ICP-AES. The axial electron number density was calculated by Saha-Eggert ionization equilibrium theory. In the present study, the effects of forward power, nebulizer gas flow rate and the presence of Na on the excitation temperature and electron number density have been investigated. For sample introduction, two kinds of nebulizers (pneumatic and ultrasonic nebulizer) were utilized.

• Journal of The Korean Society of Grassland and Forage Science
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• v.10 no.1
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• pp.1-9
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• 1990

Tillering of orchardgrass during establishment year was considered as an important factor for ground cover and forage yield. Field experiment was conducted to examine seasonal fluctuation of tiller number in three cultivars of orchardgrass; Potomac, Hall-mark, and Sumas, after transplanting with five planting density. Also, effects of plant density and nitrogen application in cultivar, Potomac were studied on tillering, forage yield and various growth characteristics in pot experiment Tillers per plant decreased with increased density and showed seasonal variations. It increased up to July, decreased during summer months, and increased again from October. Sumas had less tillers than other cultivars, especially at high density. Tillers per unit area kept high during spring. After then, there was stady decrease through summer and remained constant without affecting by planting density. Nitrogen application increased tillers per unit area in Potomac up to 20kg/10a, but decreased its tiller production at 40kg/lOa. Maximum number of tiller was obtained in the combinations of 20kg application of nitrogen with higher density than 324 plant per square meter. Forage yield increased as nitrogen application increased, while it did not respond to plant density. Forage yield had high linear correlation between LAI, leaf number with a peak at 2800 culrns. For high forage yielding, it was suggested to obtain optimum number of tillers per unit area in early season as possible, applying of adequate amount of nitrogen with relative high density depend on cultural condition.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.929-937
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• 2023

Human equivalent phantoms manufactured using 3D printers are cheaper and can be manufactured in a short time than conventional human phantoms. However, many phantoms are manufactured with less than 100 % of Infill Density, one of the 3D printer output setting variables. Therefore, this study compared the Bone Phantom CT number, which differs from the ratio of five Infill Density produced using a 3D printer, to the CT number of the actual human body Bone. In addition, the usefulness of the manufactured phantom was evaluated by producing a 100 % elbow joint phantom with Infill Density and setting the Infill Density to 100 % through CT number comparison for each tissue on computed tomography (CT). As a result, the Bone Phantom printed with 100 % Infill Density did not show the most statistically significant difference from the CT number value of the actual human Bone, and the CT number of each tissue did not show a statistically significant difference from the CT number value of each tissue of the actual human elbow joint.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.125-130
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• 2021

In the AAPM CT performance phantom, there is little data on the CT number of the effective atomic number and physical density corresponding to each peg and water of the CT number calibration insert. Therefore, the necessity of documentation was raised.The purpose of this study is to calculate the effective atomic number for each peg and water of the CT number calibration insert in the AAPM CT performance phantom, and to measure the CT number for the calculated effective atomic number and physical density for comparative analysis.In order to obtain CT number data on the effective atomic number and physical density of each peg and water from the CT number calibration insert of the AAPM CT performance phantom, the effective atomic number for each peg and water was first calculated. Then, CT slices were obtained by scanning the CT number calibration with a CT scanner. CT numbers were measured for each peg and water in the central CT slice. As a result, the CT numbers for the effective atomic number showed a nonlinear pattern of repeating the increase and decrease as the effective atomic number increased. In addition, the CT numbers for physical density showed a nonlinear pattern of repeating the increase and decrease as the physical density increased.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.232-232
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• 2017

Rice yields are determined by the number of spikes per unit area, the number of rice per grain, the rate of ripening, and the weight of brown rice gravel. Among these yield components, the most important factor that reflects the characteristics of rice is the number of rice per grain and the number of rice per grain. The characteristics of rice panicle are influenced by genetic factors rather than environmental factors and revealed that it had different genetic characteristics in each of Japonica, Indica and Japonica ${\times}$ Indica type. In general, the number of rice per grain is affected by number of secondary rachis branches and generated spikelets number of secondary rachis branches. This study conducted to investigate the characteristics of the grain according to the planting density of two varieties of Jap. ${\times}$ Ind. type. Number of primary rachis branches and number of primary rachis branches of Palbangmi variety were 9.9 ~ 10.6 and 53.4 ~ 58.5, respectively. Number of secondary rachis branches and number of secondary rachis branches were 25.8 ~ 29.6, 85.8 ~ 101.4, Number of tertiary rachis branch and number of tertiary rachis branches were 1.0 ~ 2.4 and 2.0 ~ 6.1, respectively. Number of primary rachis branches and number of primary rachis branches of Semimyeon variety were 8.6 ~ 9.5 and 43.1 ~ 47.8, respectively. Number of secondary rachis branches and number of secondary rachis branches were 21.0 ~ 24.9, 66.2 ~ 77.9, Number of tertiary rachis branch and number of tertiary rachis branches were 1.6 ~ 2.6 and 3.8 ~ 6.3, respectively. The ratio of the spikelets of primary, secondary and tertiary rachis branches of Palbangmi variety were 37.7 ~ 39.4, 58.0 ~ 60.5 and 1.2 ~ 3.1%, respectively, and those of Semimyeon were 40.1 ~ 42.6 55.0 ~ 56.4 and 2.5 ~ 3.4% respectively. Number of primary and secondary rachis branches of Palbangmi variety showed no difference among the planting density. However, generated spikelets number of secondary rachis branches and ripening rate were higher with lower planting density. The number of secondary rachis branches and generated spikelets number of secondary rachis branches per acre decreased as the planting density increased in the Semimyeon variety

• Asian Journal of Turfgrass Science
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• v.3 no.1
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• pp.5-12
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• 1989

Tiller numbers per Unit area were increased as plant density heightened followed by little difference in tiller number in 110 days after transplanting(ll0DAT), this being caused by the immediate increment of tiller since' 90DAT During the growth period, the greatest number of green leaves per unit area was attained in 90DAT of both 160-density and 200-density plots, and in l00DAT of 40-, 80-, and I 20-density plots. Thus, the period to reach the maximum green leaf number with the high plant density was earlier than with the' low plant density. The increment of plant density increased the DM weight of ahoveground part and, with 40-densitytreatment. DNI weight was increased 6.1 times as much up to 110DAT as up to 7ODAT but 2 to 2.9 times with other ehe'nsity treatments. The' rate of increase in stolon length was greatest at the period between 80 and 90DAT when DM weight of stolon showed a large increment. Meanwhile, the average number of stolon was 1.7 at 70DAT but was increased up to 10 at 110DAT probably due to accelerative appeance of Ist stolon branch since 8.0DAT. DM weight of stolon was found to exceeded that of root after 90DAT Thus it was concluded that, when turfs is estahlished from sprig. it may be desirable for first mowing practice to be made at least within l00 days after planting.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.6
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• pp.825-832
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• 2009

A series of laboratory experiments has been performed to investigate the flow characteristics of 2-dimensional density currents induced by selective withdrawal, which is commonly suggested as a measure for removal of high turbid water from reservoirs. Saltwater has been used to simulate the density stratification over depth and PIV(Particel Image Velocimetry) for observing the velocity structure. Experimental conditions have been established according to Richardson number, which is the dimensionless number that expresses the ratio of potential to kinetic energy. From the experiments, the patterns of longitudinal decay of centerline axial velocity induced by the withdrawal have been distinguished from other experimental cases. The rate of longitudinal decay increase as the Richardson number increases. The variations of volumetric and momentum flux along the longitudinal axis have also shown to be dependent on Richardson number.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.3
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• pp.378-386
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• 2009

The effect of fuel mixing on soot structure with methane, ethane, and propane to ethylene-base counterflow diffusion flames has been investigated by measuring the volume fraction, number density, and particle size of soot by adopting the light extinction/scattering techniques. The experimental result showed that the mixing of ethane and propane in ethylene diffusion flame increased soot volume fraction while the mixing of methane decreased. As compare to the ethylene-base flame, the diameters of soot particles for mixture flames are slightly smaller. While the soot number densities for the mixture flames are much higher. Thus, the increase in the soot volume fraction can be attributed to the appreciably increased soot number density by the fuel mixing.