• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.3
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• pp.189-193
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• 2001

Critical cell density (CCD), the maximum cell concentration without mutual shading in algal cultures, can be used as a new operating parameter for high-density algal cultures and for the application of the flashing light effect on illuminated algal cultures. CCD is a function of average cell volume and light illumination area. The CCD is thus proposed as an index of estimation of mutual shading in algal cultures. Where cell densities are below the CCD, all the cells in photobioreactors can undergo photosysnthesis at their maximum rate. At cell densities over CCD, mutual shading will occur and some cells in the illumination chamber cannot grow photoautotrophically. When the cell concentration is higher than the CCD, specific oxygen production rates under flashing light were higher than those under continuous light. The CCD was found to be a useful engineering parameter for the application of flashing light, particularly in high-density algal cultures.

• Journal of Ginseng Research
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• v.15 no.1
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• pp.31-35
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• 1991

In order to know the optimum planting density under shading structures at different light intensity, We investigated the growth status, distribution of ginseng leaf area, correlation between planting density and root weight per plant and yield, correlation between leaf area index and root weight per plant and yield. According to the increase of planting density the leaf area per plant was decreased, but leaf area index (L.A.I) was increased. Ginseng leaf population at different lines under common straw shading were distributed mainly in frost lines but polyethylene net shading at 10fo light intensity were distributed equally in all lines. Optimum planting density in common straw shading at 5% light intensity was 55 plant per tan (90 cmX180 cm) and polyethylene net shading 81 10% light intensity was 60 plant per tan, in consideration of root weight and yield. Optimum leaf area index was 2.4 under common straw shading at 5% light intensity but was 2.7 under polyethylene net shading at 10% light intensity.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.115-124
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• 2002

The optimum design of auto-catalyst needs a good compromise between the pressure drop and flow distribution in the monolith. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. However, there has been no study of evaluating the usefulness of this method on light-off catalyst. We have computationally investigated the effectiveness of variable cell density technique applied to the light-off catalyst using a three-dimensional integrated CFD model. in which transient chemical reacting calculations are involved. Computed results show that variable cell density technique can reduce the accumulated emissions of CO and HC during the early 100sec of FTP cycle by 86.78 and 80.87%, respectively, The effect of air-gap between the monoliths has been also examined. It is found that air-gap has a beneficial effect on reducing pressure drop and cold-start emissions.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.59.2-59.2
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• 2014

Radiative transfer models in a spherical, turbulent interstellar medium (ISM), in which the photon source is situated at the center, are calculated to investigate the correlation between the scattered light and the dust column density. The medium is modeled using fractional Brownian motion structures that are appropriate for turbulent ISM. The correlation plot between the scattered light and optical depth shows substantial scatter and deviation from simple proportionality. It was also found that the overall density contrast is smoothed out in scattered light. In other words, there is an enhancement of the dust-scattered flux in low-density regions, while the scattered flux is suppressed in high-density regions. The correlation becomes less significant as the scattering becomes closer to being isotropic and the medium becomes more turbulent. Therefore, the scattered light observed in near-infrared wavelengths would show much weaker correlation than the observations in optical and ultraviolet wavelengths. We also find that the correlation plot between scattered lights at two different wavelengths shows a tighter correlation than that of the scattered light versus the optical depth.

• Korean Journal of Poultry Science
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• v.46 no.4
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• pp.297-304
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• 2019

This study evaluated the effects of stocking density on performance and behavioral activities of 35-day-old broilers in relation to incandescent white bulb (IB) light and LED yellow and white light. A total of 1,650 day-old chicks were weighed and randomly allocated into six treatment groups in a 2 × 3 factorial arrangement based on stocking density (14 birds m^-2 and 22 birds m^-2) and color of lights (IB; monochromatic LED yellow and white light) with five replicates for each treatment. The results showed that final body weight, weight gain and feed conversion of broilers were improved at a stocking density of 14 birds m^-2 with exposure to LED lights. Similarly, broilers spent more time exhibiting inactive behavior (e.g. standing) and active behaviors (e.g. walking and walking plus pecking) under 14 birds m^-2 with exposure to lights as compared that of other treatment groups. Regarding a stocking density of 22 birds m^-2, broilers performance traits were negatively affected and also activities were less. The performance of broilers was not significantly altered for the main factor of different lights but broilers were less inactive (e.g less time spent sitting plus standing) and more time spent active behavior in walking under IB light than LED light. Thus, we concluded that a stocking density 14 birds m^-2 with exposure to LED light significantly improved broiler performance and behavioral activity and these conditions could therefore improve the overall welfare of farmed chickens.

• Fire Science and Engineering
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• v.27 no.2
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• pp.75-79
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• 2013

The present study measured the light transmission to quantify the smoke density(smoke mass concentration) through the doorway in a compartment fire and performed the uncertainty analysis to evaluate the reliability of the measurement technique. The optical light extinction method based on Bourguer's law was applied to estimate the smoke density of doorway exhausting smoke flow in upper layer of a compartment for methane gas fires. The measurement uncertainty of the light extinction measurement was evaluated for the light transmittance, path length, and specific mass extinction coefficient and the expanded uncertainty was estimated about 20% with confidence level of 95%. The mean smoke density through the doorway for the methane fire was calculated for quasi-steady fire and the smoke density linearly increased as the GER increased.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.817-822
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• 2000

A proper flashing light is expected to enhance microalgal biomass productivity and photosynthetic efficiency. The effect of flashing light on high-density Chlorella kessleri (UTEX 398) cultures was studied using light-emitting diodes. A frequency modulator was designed to flash LEDs, and the device successfully provided wide range of frequencies and various duty cycles of flashing. A relatively high frequencies of 10, 20 and 50 kHz were used in this study. These frequencies have very short flashing time ($2-50{\mu}s$), which corresponded to the time constant of the light reaction of photosynthesis. The specific oxygen production rates of photosynthesis under flashing light were compared with those under an equivalent continuous light in specially designed illumination cuvette. The specific oxygen production rates under flashing light were 5-25% higher than those under the continuous light. A range of cell concentration was discovered, where the benefit of flashing light was maximized. The photosynthetic efficiency was also higher under flashing light with frequencies of over 1 kHz, which was a clear indication of flashing light effect and the degree of mutual shading could by overcome by flashing lights, particularly at high-density algal cultures.

• Biotechnology and Bioprocess Engineering:BBE
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• v.4 no.1
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• pp.78-81
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• 1999

Light penetration depth in high-density Chlorella cultures can be successfully estimated by Beer-Lambert's law. The efficiency of light energy absorption algal cultures was so high that algal cells near the illuminating surface shade the cells deep in the culture. To exploit the potential of high-density algal cultures, this mutual shading should be eliminated or minimized. However, providing more light energy will not ease the situation and it will simply drop the overall light utilization efficiency.

• ALGAE
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• v.38 no.4
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• pp.283-294
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• 2023

Previous research indicated that free-living sporangial filament keep hollow morph under high-culture density and form bipartite cells under low-culture density, while the following conchospore release was inhibited by high light. Here, we further explored the molecular bases of these affects caused by light and culture density using a transcriptome analysis. Many differentially expressed genes (DEGs) related to carbon dioxide concentration and fixation, photosynthesis, chlorophyll synthesis and nitrogen absorption were upregulated under high-light conditions compared with low-light conditions, indicating the molecular basis of rapid vegetative growth under the former. The stress response- and ion transport-related DEGs, as well as the gene encoding the vacuole formation-brefeldin A-inhibited guanine nucleotide exchange protein (BIG, py05721), were highly expressed under high-density conditions, indicating the molecular basis of the hollow morph of free-living sporangial filaments under high-culture density conditions. Additionally, the brefeldin A treatment indicated that the hollow morph was directly influenced by vacuole formation-related vesicle traffic. Others DEGs related to cell wall components, zinc-finger proteins, ASPO1527, cell cycle and cytoskeleton were highly expressed in the low density with low-light group, which might be related to the formation and release of conchospores. These results provide a deeper understanding of sporangial filaments in Neopyropia yezoensis and related species.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.81-86
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• 1998

The light aggregates were fabricated by sintering green bodies made form the fly ash-clay alip. The content of fly ashes in the slip could be increased up to 70wt.% due to controlled rheological behavior of the slip, and the green body of uniform microstructure could be obtained by DCC(Direct Coagulation Casting)method. The apparent density, microstructure and compressive strength for sintered bodies fired at 1100∼1200$^{\circ}C$ were evaluated. The properties of light aggregates fabricated depend on slip density, particle behavior in the slip and sintering conditions. The sintered body prepared by firing a green body made from slip of density 1.60 at 1150$^{\circ}C$/2hr satisfied conditions of a light aggregate as apparent density of 1.49${\pm}$0.02 and compressive strength of 584${\pm}$62kg/$\textrm{cm}^2$.