• Tribology and Lubricants
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• v.38 no.3
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• pp.93-100
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• 2022

Micro-light emitting diode (micro-LED) displays offer numerous advantages such as high brightness, fast response, and low power consumption. Hence, they are spotlighted as the next-generation display. However, defective LEDs may be created due to non-uniform contact loads or LED alignment errors. Therefore, a repair process involving the replacement of defective LEDs with favorable ones is necessitated. The general repair process involves the removal of defective micro-LEDs, interconnection material transfer, as well as new micro-LED transfer and bonding. However, micro-LEDs are difficult to repair since their size decreases to a few tens of micron in width and less than 10 ㎛ in thickness. The conventional nozzle-type dispenser for fluxes and the conventional vacuum chuck for LEDs are not applicable to the micro-LED repair process. In this study, transfer conditions are determined using a micro stamp for repairing micro-LEDs. Results show that the aging time should be set to within 60 min, based on measuring the aging time of the flux. Additionally, the micro-LEDs are subjected to a compression test, and the result shows that they should be transferred under 18.4 MPa. Finally, the I-V curves of micro-LEDs processed by the laser and hot plate reflows are measured to compare the electrical properties of the micro-LEDs based on the reflow methods. It was confirmed that the micro-LEDs processed by the laser reflow show similar electrical performance with that processed by the hot plate reflow. The results can provide guidance for the repair of micro-LEDs using micro stamps.

• Computers and Concrete
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• v.29 no.6
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• pp.393-405
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• 2022

Lightweight concrete is a superior material due to its light weight and high strength. There however remain significant lacunae in engineering knowledge with regards to shear failure of lightweight fiber reinforced concrete beams. The main aim of the present study is to investigate the optimum usage of steel fibers in lightweight fiber reinforced concrete (LWFRC). Multi-scale finite element model calibrated with experimental results is developed to study the effect of steel fibers on the mechanical properties of LWFRC beams. To decrease the amount of steel fibers, it is preferred to reinforce only the middle section of the LWFRC beams, where the flexural stresses are higher. For numerical simulation, a multi-scale finite element model was developed. The cement matrix was modeled as homogeneous and uniform material and both steel fibers and lightweight coarse aggregates were randomly distributed within the matrix. Considering more realistic assumptions, the bonding between fibers and cement matrix was considered with the Cohesive Zone Model (CZM) and its parameters were determined using the model update method. Furthermore, conformity of Load-Crack Mouth Opening Displacement (CMOD) curves obtained from numerical modeling and experimental test results of notched beams under center-point loading tests were investigated. Validating the finite element model results with experimental tests, the effects of fibers' volume fraction, and the length of the reinforced middle section, on flexural and residual strengths of LWFRC, were studied. Results indicate that using steel fibers in a specified length of the concrete beam with high flexural stresses, and considerable savings can be achieved in using steel fibers. Reducing the length of the reinforced middle section from 50 to 30 cm in specimens containing 10 kg/m3 of steel fibers, resulting in a considerable decrease of the used steel fibers by four times, whereas only a 7% reduction in bearing capacity was observed. Therefore, determining an appropriate length of the reinforced middle section is an essential parameter in reducing fibers, usage leading to more affordable construction costs.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.54.4-55
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• 2021

The Seoul National University AGN Monitoring Project (SAMP) is a welldesigned long-term AGN reverberation mapping project. SAMP focuses on the luminous AGNs out to z~0.5 with relative long time lags between AGN continuum and broad emission lines and aims to probe the high-end of the AGN broad line region (BLR) size-luminosity (R-L) relation. The pilot observations started in October 2015 for 100 AGNs to confirm the variability and the H and [O III] emission line strengths. Based on the initial variability test, 48 quasars has been continued spectroscopic monitoring since Feb. 2016 with Lick 3m and MDM 2.4m telescopes with a cadence of ~20 days. Supporting photometric monitoring in B and V band was conducted at multiple facilities including the MDM 1.3m, LOAO, and DOAO telescopes with a cadence of ~10 days. By the time of Feb. 2021, we have obtained five years spectroscopic and photometric data. More than 30 AGNs shows significant variability in five-year baseline and 16 of them show well detected lags between B-band and H. Here, we report some examples of SAMP light curves and lag detections using the first five-year data as well as the location of our 16 targets in the AGN BLR R-L relation. These measurements are consistent with the existing R-L relation and located at the high-end. With the coming data, SAMP are hopefully to report more AGNs with well detected lags. Our results demonstrate the general feasibility and potential of long-term reverberation project with medium cadence for luminous AGNs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.2-5
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• 2022

Human organs in the body have a complex structure, and in particular, the small intestine is about 7m long, so endoscopy is not easy and the risk of endoscopy is high. Currently, the test is performed with a capsule endoscope, and the test time is very long. The doctor connects the removed storage device to the computer to store the patient's capsule endoscope image and reads it using a program, but the capsule endoscope test results in a long image length, which takes a lot of time to read. In addition, in the case of the small intestine, there are many curves due to villi, so the occlusion area or light and shade of the image are clearly visible during the examination, and there may be cases where lesions and abnormal signs are missed during the examination. In this paper, we provide a method of assisting small intestine capsule endoscopic lesion examination using artificial neural networks to shorten the doctor's image reading time and improve diagnostic reliability.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.3
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• pp.486-493
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• 2008

Safflower red colorants extracted by two solvents including the traditional ash solution and $K_{2}CO_{3}$ solution was used for dyeing cotton, ramie, viscose rayon, silk, wool, and nylon fabrics. The effects of extraction solvents on the reflectance, K/S value, and color properties of the dyed fabrics were investigated. Wash/dry cleaning and light colorfastness were evaluated. Reflectance curves of cotton, ramie, viscose rayon, and silk fabrics dyed with red colorants extracted by $K_{2}CO_{3}$ solution were similar, showing the maximum absorption at 520nm, to that of the dyed fabrics with red colorants extracted by ash solution. The reflectance curves of wool and nylon fabrics were different, showing the maximum absorption at 400nm. K/S values of dyed fabrics with red colorants extracted by $K_{2}CO_{3}$ solution were higher than that by ash solution with the exception of nylon. $L^{*},\;a^{*},\;b^{*}$, and $C^{*}$ of the dyed fabrics with red colorants extracted by $K_{2}CO_{3}$ solution were higher than that by ash solution except for $L^{*}$ of nylon and $b^{*}$ of viscose rayon. Color difference(${{\Delta}E}^*$) of the dyed fabrics between ash solution and $K_{2}CO_{3}$ solution increased in the order named as cotton, silk, ramie, viscose rayon, wool, and nylon. Regardless of extraction solvents, safflower red colorants produced RP color on cotton, ramie, and nylon, R color on viscose rayon and silk, and YR color on wool. Wash/dry cleaning fastness of the dyed fabrics was high above 3/4 rating but light fastness was very poor. It is considered that the use of $K_{2}CO_{3}$ solution instead of the traditional ash solution would be more effective in terms of color reproducibility and extraction process.

• Radiation Oncology Journal
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• v.16 no.4
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• pp.505-515
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• 1998

Purpose : This study is intended to understand the sensitometric characteristics and the emulsion properties of the commercially available CEA TVS film in comparison with the Kodak X-Omat V film. Materials and Methods : For this purpose, we have formulated an analytic expression of the characteristic curves for x-ray film exposed to mixed radiation of electrons, photons, and visible light. This mathematical expression was developed based on reaction-rate and target-hit theories. Unlike previous expressions. it relates optical density to emulsion properties such as grain size and silver bromide content We have also developed a quantity which characterizes the film response to visible light relative to that to photons and electrons. This quantity could be expressed as a function of grain area. Thus, we have developed mathematical expressions and quantities with which the emulsion properties of the films can be revealed based on the sensitometric characteristics. Demonstrating the use of this analytical study, we exposed CEA and Kodak verification films to the mixed radiation of electrons, photons, and visible light, and interpreted the experimental results accordingly. Results : We have demonstrated that: (1) the saturation density increases as the silver bromide content increases, (2) the time required to reach the threshold dose (to which the film begins to respond) when films are exposed to visible light decreases as the grain size increases, and (3) the CEA film contains more silver bromide. whereas the Kodak film contains larger grains. These findings were supported by the data provided by the manufacturers afterward. Conclusion : This study presented an analytical and experimental basis for understanding the response of X-ray film with respect to the emulsion properties.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.2
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• pp.93-101
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• 2007

In order for bioremediate the benthic layer in polluted inner Bay, the effects of irradiance and wave-length irradiated from light emission diode (LED) on the growth of benthic diatom Nitzschia sp. (Hakozaki Bay strain of Japan) were investigated. The Nitzschia sp. was cultured under blue LED (450 nm), yellow LED (590 nm), red LED (650 nm) and fluorescent lamp (mixed wavelengths). At $25^{\circ}C$ and 30 psu, the growth of Nitzschia sp. showed its peak at $20\;{\mu}mol\;m^{-2}\;s^{-1}$ (blue LED) and $40\;{\mu}mol\;m^{-2}\;s^{-1}$ (fluorescent lamp), and was inhibited at the irradiance higher than that irradiance. Nitzschia sp. in yellow LED and red LED is fitted by a rectangular hyperbolic curve because no photoinhibition was observed under maximum irradiance used in this study. The irradiance-growth curves were described as ${\mu}=-0.46{\exp}(1-I/6.32)+0.46-0.00043I,\;(r^2=0.98)$ under blue LED, ${\mu}=0.42(I+7.87)/(I+58.9),\;(r^2=0.99)$ under yellow LED, ${\mu}=0.39(I+3.39)/(I+21.6),\;(r^2=0.94)$ under red LED, ${\mu}=-0.38{\exp}(1-I/7.23)+0.38-0.00016I,\;(r^2=0.96)$ under fluorescent lamp. Maximum specific growth rate of blue LED, yellow LED, red LED and fluorescent lamp was $0.44\;day^{-1},\;0.42\;day^{-1},\;0.39\;day^{-1}$ and $0.37\;day^{-1}$, respectively. The absorption coefficient ($a_{ph}$) of Nitzschia sp. was similar under all the wavelengths (400 nm-700 nm), although maximum $a_{ph}$ was $0.0224\;m^2\;mg\;chi.\;{\alpha}^{-1}$ in 472 nm and $0.0179\;m^2\;mg\;chi.\;{\alpha}^{-1}$) in 663 nm. The results may indicate the possibility of environmental improvement around the benthic layer in polluted coastal area because microphytobenthos growth is stimulated by means of irradiated blue LED at the benthic boundary layer during both autumn and winter, and yellow LED, which might have been suppressed growth of harmful algae, at the layer during both spring and summer.

• Journal of Korean Society of Forest Science
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• v.13 no.1
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• pp.1-24
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• 1971

In order to elucidate the feasibility to identify the plant species through the photographic tone this study was made. In this study the author made photographs of Juniperus chinensis L., and Populus glandulosa Uyeki, with the panchromatic film using either yellow filter or red filter in different seasons respectively. The author analyzed the value of tone variation at the level of stereoscopic view of the same photographs by using tone scale and Automatic Micro-Photo-Densitometer. The results obtained are summarized as follows: A. Tone scale reading 1. The tone of Populus glandulosa Uyeki was darker than that of Juniperus chinensis L. in a photograph. 2. Regardless of the tree species, tone of photographs obtained with yellow filter was darker than that with red filter. 3. Along the progresses of seasons, the photographic tone was changed. That is, from the spring to the summer it showed darker and than, from the summer to winter it changed lighter. 4. During winter and spring the discrimination between the both species of trees can be easily made by stereoscopic view whether there are leaves on the tree or not rather than by tone observation. 5. Regardless of tree species, variation of tone due to the age was noticed. The older trees have darker tone than the younger one. 6. It is recognized that the yearly difference depends on insolation quantities. 7. The highest reflex light-waves were in between $600m{\mu}$ and $660m{\mu}$ for both species of trees. B. Density reading 1. For the density reading, there was the same tendency as in tone scale reading. 2. The changes of peaks of the scanning curves with Populus glandulosa Uyeki is smoother and takes place in lower position than with Juniperus chinensis L. 3. The scanning curves on the 20th May was smoothest, and change of peaks increased gradually according to the season progresses. 4. In relation to the types of filter the photographs with yellow filter showed less changes of peaks then that with red filter.

• The Korean Journal of Malacology
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• v.25 no.2
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• pp.161-171
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• 2009

The present study was performed to describe the influence of water temperature and salinity on filtration rates of the venus clam, Gomphina veneriformis, a suspension-feeding (filter-feeding) bivalve species. The calmswere collected from the eastern coastal area of Sokcho, Gangneung and Jumunjin at Kangwon-do, Korea, during December 2006 and May 2007. Isochrysis galbana (KMCC H-002) cells as food organisms were indoor-cultured by f/2 medium, and were used to measure the filtration rate of clam. Filtration rates of clam were measured by indirect method. Cell concentration of food organisms were determined by direct counting cells used the hemacytometer under the light microscope. The filtration rates of clams by water temperature sharply increased with temperatures up to $15^{\circ}C$ as optimum temperature and above this temperature, the filtration rates decreased exponentially. Venus clams showed very low filtration rates at low salinity (10-15 psu) and maximum values at high salinity (30-35 psu). Regardless of water temperature and salt change, 2-year class clams showed high filtration rates, but low in 4-year-class. Polynomial regression curves with water temperature were shifted to the left in low temperature region. Thermal coefficient $Q_{10}$ values showed much higher values at low temperature range than at high temperature range, too. These results indicate that the venus clam is more sensitive in cold water. Polynomial regression curves with salinity were shifted to the right in high saline region. According to this study, the venus clam Gomphina veneriformis, subtidal filter-feeding bivalve, was the stenothermal organism, inhabited mainly in low temperature and the stenohaline, in high saline waters.

• Korean Journal of Environmental Biology
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• v.32 no.2
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• pp.112-117
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• 2014

Predation efficiency and preference of the hydrophilid water beetle, Hydrochara affinis (Coleoptera: Hydrophilidae), larvae on two mosquito species, Culex pipiens molestus and Ochlerotatus togoi, were tested under laboratory conditions. Experiments were conducted in a transparent cylindrical plastic container (diameter, 100 mm; height, 40 mm; water level, 15 mm) for 24 hours (16 h, light; 8 h, dark) at $25^{\circ}C$. The predation efficiency of H. affinis on mosquito larvae was investigated under various prey conditions (1, 2, 4, 8, 16, 32, 64, and 128 larvae) with five replicates. Further, in order to investigate the prey preference on two mosquito species, each 32 larvae of C. pipiens molestus and O. togoi were provided simultaneously for the first instar larva of H. affinis with 5 replicates. As a result, the predation curves of H. affinis on two mosquito species were logarithmic; and the number of consumed prey increased as the number of predator instars were increased. As predicted from the predation curves, the estimated maximum number of C. pipiens molestus and O. togoi consumed by a third instar larva of H. affinis per a day was 926 and 304 larvae, respectively. As predicted from the Holling's disk equation, the differences in consumed prey number between predator instars and prey species were caused by handling time rather than attack rate. Handling time decreased rapidly as the predator larvae grew, and that of O. togoi was twice longer than that of C. pipiens molestus.