• 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.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.75-75
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• 2003

All published and newly observed times of minimum light of the massive, early-type eclipsing binary star AH Cep were analyzed. After subtracting the light time effect due to the well-known third body from the residuals of the observed times of minimum light, it was found that the second-order Ο-C residuals varied in a cyclical way. It was assumed that the secondary oscillations were produced by a light time effect due to a fourth body so all the times of minimum light were reanalyzed with a differential least-squares scheme in order to obtain the light time orbits due to both the third and fourth bodies. The periods, eccentricities, semi-amplitudes of the light time orbits for the third and fourth-bodies were derived as : P$\_$3/=68.$\^$y/3 and P$\_$4/=9.$\^$y/3, e$_3$=0.53 and e$_4$=0.83, K$_3$=0.$\^$d/0585 and K$_4$=0.$\^$d/0045, respectively. The analysis of the radial velocities of AH Cep published so far, do not conflict with the hypothesis of the multiplicity of the system but their accuracies are not high enough to be useful to support the interpretation. Other properties of the distant bodies are discussed for assorted possible inclinations of their orbits.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.4
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• pp.316-326
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• 2011

In this study, the entrapped number is investigated on the UV light with different illuminance to fluorescent bait cage for swimming crab in order to find the appropriate illuminance which has the best attraction effect of fluorescent bait cage for pots. In addition, preference to the light, arrival time and residence time at light area are compared and analyzed to fluorescent bait cage and non-fluorescent bait cage for American lobster at the UV light and ordinary light according to the illuminance condition. Pot with red non-fluorescent bait cage at the no lighting (<0.01lux), pot with blue fluorescent bait cage at the 20W UV lighting (0.16lux) and pot with blue fluorescent bait cage at the 30W UV lighting (0.22lux) were soaked for 6 hours and the entrapped number of swimming crab was examined. The mean entrapped number of swimming crab in pot with red non-fluorescent bait cage at the no lighting (<0.01lux) was 1.0, but the mean entrapped number of swimming crab in pot with blue fluorescent bait cages at the 20W UV lighting (0.16lux) and 30W UV lighting (0.22lux) were 1.4 and 0.4, respectively (P<0.05). The rate of preference to the blue fluorescent bait cage at the UV lighting shows 1.6-4.8 times higher than that of preference to the red non-fluorescent bait cage at the ordinary lighting. In addition, The rate of preference to the blue fluorescent bait cage at the UV lighting is higher when the illuminance of ordinary light is same as or is lower than that of UV light (P<0.05). However, the preference to the light depending on gender shows no significant difference (P>0.05). The arrival time to UV light area of lobster is shown as 1.2-2.4 times faster than that to ordinary light area. Generally, it is shown that arrival time to UV light area is faster than the arrival time to ordinary light area when the illuminance of ordinary light is the same as or lower than that of UV light (P<0.05). However, arrival time to the light area depending on gender shows no significant difference (P>0.05). The residence time at UV light area of lobster is 1.2-1.7 times longer than that at ordinary light area. The residence time depending on different illuminance of ordinary light and genders showed no significant difference (P>0.05).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.190-197
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• 2019

This study investigated the luring effect of the sardine bait, which is used to catch octopus with pot, as the preliminary study for the development of alternative bait for octopus pot. The soaking time for bait was divided into "5 days or less" and "11 days or longer" The number of times octopus entered the pot with bait and the empty pot was investigated under dark adaptation and light adaptation processes and the distribution of tank section was investigated under light adaptation process. The case of "11 days or longer" sardine soaking time showed higher rate of distribution in the section of pot with bait compared to the case of "5 days or less" In the case of "5 days or less" soaking time, the number of times the octopus entered the pot with bait was similar to that it entered the pot without it even during dark adaptation and light adaptation. However, in the case of "11 days or longer", the octopus entered the pot with bait more quickly than the pot without bait and more frequently during dark adaptation hours. There were cases where the octopus did not enter any pot. In the case of "5 days or less", with less decomposition of baits, the octopus entered the empty pot more during light adaptation process, and it appeared that the pot was used as a hideout.

• Journal of Bio-Environment Control
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• v.22 no.3
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• pp.214-219
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• 2013

This study was conducted to examine the effect of LED light quality and treatment time on the growth and flowering in potted plants of Impatiens (Impatiens hawkerihybrid). Plant height of Impatiens was enhanced under Blue light, regardless of treatment time. Root length and stem diameter of Impatiens were enhanced by Red light or Blue light. The number of internodes was not influenced by LED light quality. The number of branches of Impatiens was increased under Blue light, but treatment time did not result in statistically significant differences. Leaf area was increased by all LED lights in Impatiens. The number of flower buds and open flowers was decreased by LED light, but days to flowering were reduced by Red light in Impatiens. Chlorophyll and anthocyanin content were not significantly affected by LED light, but anthocyanin content tended to increase by Blue light for 4 h after sunset. Fresh and dry weights were enhanced by Blue light in Impatiens.

• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.67-73
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• 2015

We present a novel method to implement time-delayed propagation of radiation fields in cosmological radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative transfer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.19-24
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• 2019

In this study, the Ag nano-dots structure was applied to the textured wafer surface to improve the light trapping effect of crystalline silicon solar cell. The Ag nano-dots structure was formed by the annealing of Ag thin film. Ag thin film deposition was performed using a thermal evaporator. The effect of light trapping was compared and analyzed through light reflectance measurements. The optimization process of the Ag nano-dots structure was made by varying the thickness of Ag thin film, the annealing temperature and time. The thickness of Ag thin films was in the range of 5 ~ 20 nm. The annealing temperature was in the range of 450~650℃ and the annealing time was in the range of 30 ~ 60 minutes. As a result, the light reflectance of 10 nm Ag thin film annealed at 650℃ for 30 minutes showed the lowest value of about 9.67%. This is a value that is about 3.37% lower than the light reflectance of the sample that has undergone only the texturing process. Finally, the change of the light reflectance by the HF treatment of the sample on which the Ag nano-dots structure was formed was investigated. The HF treatment time was in the range of 0 ~ 120 seconds. As a result, the light reflectance decreased by about 0.41% due to the HF treatment for 75 seconds.

• KIEAE Journal
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• v.13 no.4
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• pp.3-10
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• 2013

This study aims to identify convenient surrounding of the hospital room to be improved by specifically focusing on light environment and to examine a change of inflow of the daylight in the hospital room by using blind and light shelf device as base data of preliminary research for comprehending the relationship between healing environment and natural day light. Simulation analysis on previous facilities and the installation of horizontal light shelf that derives the inflow of day light has been specifically referred by using ECOTECT2011 program. In case of C-facility that mostly adjoined to exterior spaces, it was shown to be closer to a proper uniformity factor when an angle was controlled on the light shelf with blind installed at the same time. However, it was not overall appropriate because of visual displeasure occurred from inflow of much day light. In conclusion, it is the form of flat surface such as H-facility that provides an effect after installing the device to derive day light. Especially, it was shown that interior day light environment was improved when installing blind and controlling the angle at the same time.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.325-336
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• 1997

The purpose of this study was to evaluate the compensation effect of exposure duration increase to decreased light intensity of visible-light curing unit. The specimen with 2mm thickness was made of Restorative $Z-100^{TM}$ (A2 shade, 3M Dental Products, U.S.A.) and cured with $Optilux^{TM}$ (Demetron Research Co. U.S.A.). The light intensity was controlled to 420 $mW/cm^2$, 540 $mW/cm^2$, 630 $mW/cm^2$ and curing time, also, controlled to 40, 60, 80 seconds. Cured specimen was stored in a light-proof container for 24 hours to post-irradation was completed. Microhardness of top and bottom surface of specimen were measured to evaluate the depth of cure. The obtained results were as follows: 1. The microhardness of top and bottom surface of the composite resin specimen was increased significantly as light intensity and exposure time was increased (P<0.01). 2. Light intensity was more correlated with bottom microhardness(${\gamma}{\geq}$0.438) than top microhardness(${\gamma}{\geq}$0.213), and exposure time was more correlated with top microhardness (${\gamma}{\geq}$0.424) than bottom microhardness(${\gamma}{\geq}$0.335). 3. The regressive equation was obtained in this study as follows : $H=0.07{\times}D+0.012{\times}I+76$ (H : Microhardness(KHN), D : Exposure time, I : Light intensity)

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.314-316
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• 2005

Light flicker is a notorious phenomenon influencing light quality. The flicker of the light flux outputs from the light sources perceived by human eyes depends upon the lamp brightness fluctuations for projector display. This paper describes a ballast ignition control system, which makes the lamp strike frequency phase lock the blanking time period to minimize the flicker effect