• Journal of Korean Society of Forest Science
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• v.89 no.5
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• pp.634-644
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• 2000

Sterba's theory that stem number maintaining maximum basal area per ha is maximum stem number of a stand, had been applied to data from 103 temporary plots in even-aged Pinus densiflora stands in Kangwon province, Korea and a maximum stem number and mortality model was prepared. DBH growth model which estimates dbh with the independent variables of stem number per ha and dominant height shows the good statistical performance, and explains well differences in dbh growth that would be caused by stem number per ha and dominant height. Basal area model derived from dbh growth model also explains well differences in basal area according to stem number per ha and dominant height. The maximum stem number curve, which is derived from stem number per ha at maximum basal area for dominant height and dbh, represents well the upper range of stem number per ha observed. And maximum stand density index derived from the maximum stem number model for dbh could be used for the index of maximum potential density of a stand. The maximum stem number model and maximum stand density index in this study were not based on stand data with maximum density but based on the temporary data from stands with various density. This maximum stem number model can be applied to the estimation of mortality and maximum potential volume.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.28.2-28.2
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• 2015

High redshift quasars (z > 5) hold keys to understanding the evolution of the universe in its early stage. Yet, the number of high redshift quasars uncovered from previous studies is relatively small (70 or so), and are concentrated mostly in a limited redshift range (z ~ 6). To understand the early mass growth of supermassive black holes and the final stage of the cosmic reionization, it is important to find a statistically meaningful sample of quasars with various physical properties. Here we present a survey for high redshift quasars at 5 < z < 7. Through color selection techniques using multi-wavelength data, we found quasar candidates and carried out imaging follow-up observations to reduce contaminants. After optical spectroscopy, we discovered eight new quasars. We obtained near-infrared spectra for 3 of these 8 quasars, measured their physical properties such as black hole masses and Eddington ratios, and found that the high redshift quasars we discovered are growing via accretion more vigorous than those of their lower redshift counterparts. We estimated the quasar number densities from our discoveries and compared them to those expected from the quasar luminosity functions in literature. In contrast to the observed number density of quasars at z ~ 5, which agrees with literature, the observed number density at z ~ 7 shows values lower than what is expected, even after considering an extrapolated number density evolution. We conclude that the quasar number density at z ~ 7 declines toward higher redshift, more steeply than the empirically expected evolution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.788-794
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• 1985

A study on the number density in a dual beam LDV is carried out with moving particles of various irregular arrangements. Ratious of the particle diameter to the particle to the fringe Spacing are D/.delta. = 0.3, 0.5, 1.0 and 1.5. In the case of the small number of moving particles(N<10), the visibility is influenced much by the difference of the phase of particles for one side fringe and the change in visibility is shown remarkable. In the case of the larger number of particles, the decreasing rate for visibility on the graph is smooth because the effect of the phase difference of particles is decreased by more unitorm distribution of particles over fringes. And the formula of the number density on the basis of probability is fairly compared with experimental values.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.250.1-250.1
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• 2014

A multicusp ion source has been used widely in negative hydrogen cyclotrons mainly for radioisotope productions. The ion source is designed to have cusp geometries of magnetic field inside plasma chamber, where ions are confining and their mean lifetimes increase. The magnetic confinement produced a number of permanent magnetic poles helps to increase beam currents and reduce the emittance. Therefore optimizing the number of magnets confining more ions and increasing their mean lifetime in plasma has to be investigated in order to improve the performance of the ion source. In this work a numerical simulation of the magnetic flux density from a number of permanent magnets is carried to optimize the cusp geometries producing the highest plasma density, which is clearly indicated along the full-line cusp geometry. The effect of magnetic fields and a number of poles on the plasma structure are investigated by a computing tool. The electron confinement effect becomes stronger and the density increases with increasing the number of poles. On the contrary, the escape of electrons from the loss cone becomes more frequent as the pole number increases [1]. To understand above observation the electron and ion's trajectories along with different cusp geometries are simulated. The simulation has been shown that the optimized numbers of magnets can improve the ion density and uniformity.

• Plant Resources
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• v.8 no.2
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• pp.91-95
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• 2005

In spring, to determine the optimal planting date and plant density of rapeseed in southern areas of Korea. $Taiwan^{\#1}$ variety for spring sowing, the highest yielding variety was grown under five different planting date and plant density. Yield components such as plant height, ear length, number of seedling stand per $m^2$, number of per ear and seed set percentage were highest at the plots with Mar. 5 of planting date and 50/20cm drilling of plant density. Yield of seed, oil, gas and 1,000 grains weight and erucic acid content were highest at the Mar. 5 of planting date and 50/20cm drilling of plant density. Judging from the results reported above, at optimum planting date and plant density of rapeseed seemed too be Mar. 5 of planting date and 50/20cm plant density in spring sowing.

• Asian Journal of Turfgrass Science
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• v.10 no.3
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• pp.213-230
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• 1996

A study of occurrence and distribution of cellular slime molds(CSMs) in forest soils of central areas of Korea was carried out. Samples for CSMs isolation were collected from 4 study sites; Mt.Kyeryong, Mt. Taebaek, Mt. Sobaek and Mt. Sokri. In Mt. Kyeryong, six species were found. These were Dictyostelium fasciculatum, D.firmibasis, D. mucoroides, D. minutum, D. brefeldianum and Polysphondylium pallidum. The average number of species isolated at one site was 0.75, and average density(clones /g soil) was 292. The results of soil sample analyses were that the concentration of Pb was higher than any other areas. In Mt. Taebaek, seven species were found; D. fasciculatum, D.firmibasis, D. mucoroides, D. miuutum, P.pallidum. P. violaceum, P. candidum. The average number of species isolated at one site was 2.3,and average density was 1,108. Based on importance values calculated from study sites within each of three elevation ranges, several of the more widely distributed and abundant species have distribution patterns that show a response to elevation. In Mt. Sobaek, eleven species were found. These were D. fasciculatum. D.firmibasis, D. mucoroides, D. miuutum, D. brefeldianum, D. crassicaule,D. deminutivum, D. implicatum, P. pallidum. P. violaceum and P. candidum. The average number of species isolated at one site was 3, and average density was 793. Species diversity appeared to be the highest in this area. In Mt. Sokri, six species were found. These were D. fasciculatum. D. mucoroides, D. minutum, D. purpureum, P. pallidum. and P. violaceum. The average number of species isolated at one site was 2.4 and average density was 858. It was noticeable that D.purpureum were much more comrnonly found in this pinus evergreen forest. Key words: Cellular slime molds(CSMs), Importance value, Elevation, Average number of species, Average density.

• Korean Journal of Medicinal Crop Science
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• v.22 no.6
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• pp.469-474
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• 2014

This study was performed to investigate the effects of sowing density and number of seeds sown on the emergence rate and growth characters of Panax ginseng C. A. Meyer under direct sowing cultivation in a blue plastic greenhouse. Ginseng seedlings, derived from seeds sown directly at different densities (90, 108, 135, and 162 seeds per $162m^2$), were cultivated in sandy loam soil within a blue plastic greenhouse. In contrast to the emergence rate, which decreased with an increase of sowing density, number of survival plant showed an increasing trend. Interestingly, the emergence and number of survival plant were significantly enhanced when 2 or 3 seeds were sown per hole compared with when one seed was sown per hole. Growth of the aerial parts of ginseng were not markedly influenced by sowing density or the number of seeds sown. However, chlorophyll content (SPAD values) increased with an increase in sowing density. Root parameters, such as root length, diameter, and weight, and the number of lateral roots decreased with an increase in sowing density, but were not noticeably influenced by the number of seeds sown. Total saponin content was the highest in the treatment plot containing 135 seeds. Similarly, the content of each ginsenoside was also tended to be higher in this treatment than in other treatment plots. On the basis of the results obtained in this study, it was possible to determine the optimal sowing density and seed number for the direct sowing cultivation of ginseng in blue plastic greenhouse.

• Journal of Welding and Joining
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• v.23 no.5
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• pp.49-54
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• 2005

The effective charge number and the critical current density of electromigration in eutetic SnPb and Pb Free $(SnAg_{3.8}Cu_{0.7)$ flip chip solder bumps are studied. The effective charge number of electromigration in eutectic SnPb solder is obtained as 34 and the critical current density is $j=0.169{\times}({\delta}_{\sigma}/{\delta}_x})\;A/cm^2,\;where\;({\delta}_{\sigma}/{\delta}_x})$ is the electromigration-induced compressive stress gradient along the length of the line. While the effect of electromigration in Pb free solder is much smaller than that in eutectic SnPb, the product of diffusivity and effective charge number $DZ^{\ast}$ has been assumed as $6.62{\times}10^{-11}$. The critical length for electromigration are also discussed.

• Journal of Forest and Environmental Science
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• v.34 no.1
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• pp.61-65
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• 2018

To know if small changes in rearing water temperature and density affect the number of bacterial and fungal colonies in metamorphosed frogs, Dybowski's frog tadpoles were reared from Gosner 25-26 stages at either low ($1^{\circ}C$ low to ambient water temperature), ambient, or high ($1^{\circ}C$ high) water temperature (each 15 tadpoles in 20 L water) condition and at either low (10 tadpoles/20 L water), medium (20 tadpoles), or high (30 tadpoles) density condition. Immediately after metamorphosis, we sampled bacteria and fungi from skin, liver, and heart of six metamorphosed frogs, randomly selected for each treatment group. After separate incubation of bacteria and fungi on 3M Petrifilm plates, we counted the number of bacterial and fungal colonies appeared on the plates and compared the numbers among the temperature and density treatment groups. For temperature treatment, high-temperature group had fewer bacterial colonies, while low-temperature group had more fungal colonies than the other two groups. For density treatment, low-density group had fewer bacterial colonies than the other two groups, but the number of fungal colonies were not different among the groups. Our results suggest that small increased rearing water temperature and lowered rearing density could potentially reduce pathogens in farming frogs.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.2
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• pp.57-63
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• 1979

This study has been carried out to find out the optimum plant density and number of seedling per hill in the late season culture of rice at Chung Buk. P.O.R.D. Up to the level of 33 hills per m2 and 6 number of seedling per hill, rice yield was increased as the number of seedling per hill and plant density per unit areas increased. However it is recommendable to have a plant density of 28~33 hills per m$^2$ with 4~6 number of seedling per hill for the late season culture.