• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.175-181
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• 2006

Nursery pig building is imperative to provide environmental conditions favorable to maintenance of piglet health and the efficiency of growth rate. To meet the ultimate goal, it is necessary to apply proper ventilation design and construction to a confinement livestock building. This study was conducted to investigate the performance of a modified ventilation system in terms of devised slot-inlet (modification I) and exhaust fan (modification II) to improve air change rate in a confined nursery pig building, with dimension of 5.9 m(W) ${\times}$ 12.6 m(L) ${\times}$ 2.2 m(H) in an Darby Genetic Station. The experiment was carried out in August, especially when the outdoor peak temperature were above $30^{\circ}C$ and the measured indoor environmental factors were temperature, air velocity, humidity and ammonia concentration which have been known to affect the piglet health and growth. There was no difference in indoor temperature between the original and modified ventilation systems, however the air velocity and ammonia concentration in confined nursery pig building with modified ventilation system were, in most cases, better performance than original ventilation system. Therefore, it was concluded that the slot-inlet system that kept indoor environmental factors pertinent and had an economic advantage, should be considered as a ventilation system for decreasing sensible heat from piglet in confined nursery pig building during extreme summer season.

• Journal of Korean Society of Forest Science
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• v.107 no.1
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• pp.25-34
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• 2018

This study was performed to discover the comparison of the understory species composition and the growth velocity of the regeneration seedlings in Pinus densiflora forests being managed by the seed-tree method from 2008 year. The investigation site located in Bonghwa, Gyeongsangbuk-do province was established by eighteen quadrats such as six control ones, six slope ones and 6 concave ones, in which we carried out the vegetation survey and measured annual height growth of each seedlings. As a result of vegetation analysis, the understory vegetation of the seed-tree forest area was mainly composed of shrub plants such as Lespedeza bicolor, Zanthoxylum schinifolium, Securinega suffruticosa, Lespedeza maximowiczii and Stephanandra incisa, herb plants such as Miscanthus sinensis var. purpurascens, Carex humilis var. nana, Spodiopogon sibiricus and Artemisia keiskeana, and vine plants such as Pueraria lobata, Smilax sieboldii, Dioscorea batatas, Actinidia arguta, Vitis amurensis and Rubus crataegifolius. Especially, the vine plants were relatively more imported to the concave site than the control site and the slope site. As a result of measurement of growth velocity, the seedlings of the Pinus densiflora appeared to be 3,175 trees/ha for the non-suppressed trees and 7,842 trees/ha for the suppressed trees. In cases of the concave site, individuals of seedlings were much lower than those on the slope site, probably due to the competition effects of vine plants. Consideringly, silvicultural practices for clearing the vine plants should be inevitably accompanied. Also, the growth velocity of the suppressed and non-suppressed trees has been constantly increasing, those of the non-suppressed trees much higher than the suppressed trees. This represents that the seedlings grow rapidly after the suppressed period with competition to the surrounding plants. Therefore, specific practices such as blush control and vine clear should be carried out at the beginning stage of regeneration in the seed-tree stand.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.539-543
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• 1992

The continuous growth method was developed for Mn-Zn Ferrite single crystals. It is a new process that the polycrystalline MnχZn1-χFe2O4 raw materials are supplied continuously from the powder feeding system to the crucible heated by R.F. induction and melted in the crucible, and after the single crystals seed is attached to crucible's hole, the crystals are pulled downward with rotation. Growing the crystals by using the growth method different from the conventional Bridgman or Floating Zone method, we defined the factors having effect on the crystal growing through the pre-experiments. They are temperature distribution in the crucible, melt velocity according to its height, wettability between the crucible's bottom and melt. Therefore, Mn-Zn Ferrite single crystals were to be grown by attaining the appropriate melt height in the crucible, powder feeding rate, temperature gradient between the crucible and interface, crystal growing speed, and this method was confirmed to have possibility for single crystal growing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.989-995
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• 2004

This paper presents a semi-empirical model to predict the frost growth formed on the cold cylinder surface. The model is composed of the correlations for frost properties including the various frosting parameters and local heat transfer coefficient. The effects of varying the correlations for local heat transfer coefficient on the frost growth are examined to establish the model. The numerical results are compared with experimental data obtained by the previous researchers. The results agree well with the experimental data within a maximum error of $13\%$. As the results, the frost thickness decreases with changing angular position from front stagnation to separation point. Also, the effects of air velocity on the frost growth are negligible, as compared to the other frosting parameters.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.288-298
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• 1999

In spark ignited engines, the electrical spark not only sets the time for the onset of combustion but also is able to greatly influence the character of the initial flame growth and the subsequent combustion, and thereby can influence engine performance. The relative importance of the ignition energy is particularly high under lean or high residual gas or exhaust gas recirculation (EGR). In this study, a modeling of flame Initiation and its development is proposed. Submodels consist in representing of cylinder pressure and temperature, heat transfer to cylinder wall, and flame kernel heat transfer to ambient air and to spark plug electrodes. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy, and laminar and turbulent flame velocity.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.301-308
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• 2000

Non-linear behavior of rock under compression can be predicted by a crack model. Crack growth in rock renders rock anisotropic. The degree of anisotropy is explained in terms of elastic moduli as a function of load level. In this study, we calculate the changes of elastic moduli due to crack growth numerically by using a crack model and compare these values with experimental results obtained from the measurement of ultrasonic wave velocities. Image processing technique is used to obtain the initial crack information needed for the numerical calculation of elastic moduli.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.47-55
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• 2000

Non-linear behavior of rock under compression can be predicted by a crack model. Crack growth in rock renders rock anisotropic. The degree of anisotropy is explained in terms of elastic moduli as a function of load level. In this study, we calculate the changes of elastic moduli due to crack growth numerically by using a crack model and compare these values with experimental results obtained from the measurement of ultrasonic wave velocities. Image processing technique is used to obtain the initial crack information needed for the numerical calculation of elastic moduli.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.31-36
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• 1998

By using wind vectors observed by NSCAT and significant wave heights observed by TOPEX/POSEIDON and ERS-2 altimeters, one-dimensional fetch growth of wind waves Is investigated under conditions of strong wind and high waves of the East Asian winter monsoon. The evolution of fetch-limited wind waves can be observed by the altimeters along the ground tracks. The fetch is estimated by using vector wind field observed by NSCAT. The derived growth characteristics of wind waves are compared with empirical relationships between the non-dimensional fetch and significant wave height proposed by previous studies. Good agreement with the empirical fetch graph formula normalized by the friction velocity is discemible, while the formulas normalized by the wind speed at a height of 10 m tend to underestimate the wave height under such severe conditions of high wind and very long fetch.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1540-1545
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• 2004

This paper presents a semi-empirical model to predict the frost growth formed on the cold cylinder surface. The model is composed of the correlations for frost properties including the various frosting parameters and local heat transfer coefficient. The effects of varying the correlations for local heat transfer coefficient on the frost growth are examined to establish the model. The numerical results are compared with experimental data obtained by the previous researchers. The results agree well with the experimental data within a maximum error of 13%. As the results, the frost thickness decreases with changing angular position from front stagnation to separation point. Also the effects of air velocity on the frost growth are negligible, as compared to the other frosting parameters.

• 전기의세계
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• v.28 no.4
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• pp.53-63
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• 1979

Interface recombination velocity in $Al_{x}$G $a_{1-x}$ As-GaAs and $Al_{0.85}$, G $a_{0.15}$ As-GaA $s_{1-y}$S $b_{y}$ heterojunction systems is studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n $Al_{x}$G $a_{1-x}$ As-GaA $s_{1-y}$S $b_{y}$-A $l_{x}$G $a_{1-x}$ As double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAs Sb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates. In the AlGaAs system, elastic lattice deformation with effective Poisson ratios .mu.$_{eff}$ (100=0.312 and .mu.$_{eff}$ (111B) =0.190 was observed. The lattice constant $a_{0}$ (A $l_{x}$G $a_{1-x}$ As)=5.6532+0.0084x.angs. was obtained at 300K which is in good Agreement with Vegard's law. In the GaAsSb system, although elastic lattice deformation was observed in (111) B-oriented crystals, misfit dislocations reduced the Poisson ratio to zero in (100)-oriented samples. When $a_{0}$ (GaSb)=6.0959 .angs. was assumed at 300K, both (100) and (111)B oriented GaAsSb layers deviated only slightly from Vegard's law. Both (100) and (111)B zero-mismatch $Al_{0.85}$ G $a_{0.15}$As-GaA $s_{1-y}$S $b_{y}$ layers were grown from melts with a weight ratio of $W_{sb}$ / $W_{Ga}$ =0.13 and a growth temperature of 840 to 820 .deg.C. The corresponding Sb compositions were y=0.015 and 0.024 on (100) and (111)B orientations, respectively. This occurs because of a fortuitous in the Sb distribution coefficient with orientation. Interface recombination velocity was estimated from the dependence of the effective minority carrier lifetime on double-heterojunction spacing, using either optical phase-shift or electroluminescence timedecay techniques. The recombination velocity at a (100) interface was reduced from (2 to 3)*10$^{4}$ for y=0 to (6 to 7)*10$^{3}$ cm/sec for lattice-matched $Al_{0.85}$G $a_{0.15}$As-GaA $s_{0.985}$S $b_{0.015}$ Although this reduction is slightly less than that expected from the exponential relationship between interface recombination velocity and lattice mismatch as found in the AlGaAs-GaAs system, solar cells constructed from such a combination of materials should have an excellent spectral response to photons with energies over the full range from 1.4 to 2.6 eV. Similar measurements on a (111) B oriented lattice-matched heterojunction produced some-what larger interface recombination velocities.ities.ities.s.