• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.451-457
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• 2011

Purple non-sulfur (PNS) bacterium $Rhodobacter$ $sphaeroides$ KD131 was studied with the aim of achieving maximum hydrogen production using various carbon and nitrogen sources at different pH conditions. Cells grew well and produced hydrogen using $(NH_4){_2}SO_4$ or glutamate as a nitrogen source in combination with a carbon substrate, succinate or malate. During 48h of photo-heterotrophic fermentation under 110$W/m^2$ illumination using a halogen lamp at $30^{\circ}C$, 67% of 30mM succinate added was degraded and the hydrogen yield was estimated as 3.29mol $H^2$/mol-succinate. However, less than 30% of formate was consumed and hydrogen was not produced due to a lack of genes coding for the formate-hydrogen lyase complex of strain KD131. Initial cell concentrations of more than 0.6g dry cell weight/L-culture broth were not favorable for hydrogen evolution by cell aggregation, thus leading to substrate and light unavailability. In a modified Sistrom's medium containing 30mM succinate with a carbon to nitrogen ratio of 12.85 (w/w), glutamate produced 1.40-fold more hydrogen compared to ammonium sulfate during the first 48h. However, ammonium sulfate was 1.78-fold more effective for extended cultivation of 96h. An initial pH range from 6.0 to 9.0 influenced cell growth and hydrogen production, and maintenance of pH 7.5 during photofermentation led to the increased hydrogen yield.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.145-145
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• 2011

Light-emitting diodes (LEDs) based on III-nitrides compound semiconductors have achieved a high performance device available for display and illumination sector. However, the conventional c-plane oriented LED structures are still showing several problems given by the quantum confined Stark effect (QCSE) due to the effects of strong piezoelectric and spontaneous polarizations. The QCSE results in spatial separation of electron and hole wavefunctions in quantum wells, thereby decreasing the internal quantum efficiency and red-shifting the emission wavelength. Due to demands for improvement of device performance, nonpolar structure has been attracting attentions, since the quantum wells grown on nonpolar templates are free from the QCSE. However, current device performance for nonpolar LEDs is still lower than those for conventional LEDs. In this study, we discuss the potential possibilities of nonpolar LEDs for commercialization. In this study, we characterized current-light output power relation of the a-plane InGaN/GaN LEDs structures with the variation of quantum well structures. On-wafer electroluminescence measurements were performed with short pulse (10 us) and low duty factor (1 %) conditions applied for eliminating thermal effects. The well and barrier widths, and indium compositions in quantum well structures were changed to analyze the efficiency droop phenomenon.

• Korean Journal of Materials Research
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• v.20 no.1
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• pp.31-36
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• 2010

Methylene blue (MB) was degraded by $TiO_2$ and ZnO deposited on an activated carbon fiber (ACF) surface under UV light. The ACF/$TiO_2$ and ACF/ZnO composites were characterized by BET, SEM, XRD, and EDX. The BET surface area was related to the adsorption capacity for composites. The SEM results showed that titanium dioxide and zinc oxide are distributed on the ACF surface. The XRD results showed that the ACF/$TiO_2$ and ACF/ZnO composites contained a unique anatase structure for $TiO_2$ and a typical hexagonal phase for ZnO respectively. These EDX spectra showed the presence of peaks of Ti element on ACF/$TiO_2$ composite and peaks of Zn element on the ACF/ZnO composite. The blank experiments for either illuminating the MB solution or the suspension containing ACF/$TiO_2$ or ACF/ZnO in the dark showed that both illumination and the catalyst were necessary for the mineralization of organic dye. Additionally, the ACF/$TiO_2$ composites proved to be efficient photocatalysts due to degradation of MB at higher reaction rates. The addition of an oxidant $([NH_4]_2S_2O_8)$ led to an increase of the degradation rate of MB for ACF/$TiO_2$ and ACF/ZnO composites.

• Korean Journal of Environmental Agriculture
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• v.30 no.4
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• pp.402-408
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• 2011

BACKGROUND: Effect of various light wavelength and plant defense molecules were evaluated on the hardness and the contents of free amino acid including ${\gamma}$-aminobutyric acid (GABA) in soybean sprouts. METHODS AND RESULTS: Germinating soybean seeds were treated with various single wavelength of light (380, 440, 470, and 660 nm) or without light at $25^{\circ}C$ for six days. Soybean seeds were also treated with stress-signaling molecule ethephon or $H_2O_2$ at the same time. Soybean sprouts treated with 470 nm substantially raised the hardness almost two times than the control. The free amino acid contents were higher in 470 nm and $H_2O_2$ treated soybean seeds than the control. Nutritionally beneficial GABA contents were increased by the treatments of 470 nm, 440 nm, ethephon, and $H_2O_2$. CONCLUSION: These results suggest that the hardness and the contents of amino acids can be regulated by stimuli, which stimuli could be composed of various wavelength and plant defense molecules. Especially, single wavelength 470 nm illumination has the effect of increasing GABA contents with increased hardness.

• International journal of advanced smart convergence
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• v.7 no.4
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• pp.50-56
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• 2018

The Internet of Things (IoT) and Visible Light Communication (VLC) is opening up new services in lighting industry by integrating sensory network features in addition to standard illumination functionality. In this progressive developments, the next generation lighting devices for smart homes are capable to sense the environmental conditions and transfer the captured data through lights to gateway controller to access remotely. The smart home environmental sensor information's are few kbps only so VLC systems need to built-in with low rate light connectivity to transfer data to the gateway. To provide error free communication, the quality of a received light signal is important to be considered when designing an VLC receiver. Therefore, this paper proposes the design of robust low rate IoL receiver design using NCP302 voltage detector for micro controller to adapt the IoT/IoL front end module for system integration. To evaluate the proposed system performance, the Arduino UNO based IoT/IoL controller designed with lighting, sensors and lights connectivity interfaces. The experimental result shows that the robust interference rejection is feasible on proposed VOL receiver and possible to have an error-free communication up to 10 kbps at a low SNR using OOK modulation.

• ALGAE
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• v.37 no.2
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• pp.163-174
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• 2022

Light-emitting-diodes (LEDs) are a lighting source useful for the precise evaluation of light quality effect on biological systems. Despite the importance of light spectra on the regeneration of land plant protoplasts ("naked cells"), this factor has not been tested yet on protoplasts from multicellular algae. This study reports on the effects of pure primary colors (red, blue, and green), dichromatic (red plus blue, RB, 1 : 2) and white LEDs on protoplast regeneration from male and female Undaria pinnatifida gametophytes. We also evaluated the effect of different light spectra on pigment composition (chlorophyll a, chlorophyll c, and fucoxanthine), and the light intensities under the best condition on the regeneration process. In the early stages, blue or RB LEDs increased the percentage of dividing female protoplasts, whereas red, blue, and RB LEDs enhanced that of dividing male protoplasts. In the later stages, RB LEDs showed a positive effect only on the percentage of multiple rhizoid-like protrusions (male gametophyte). They also increased the final area of both regenerated gametophytes. The LEDs did not affect pigment composition in female gametophytes. In male gametophytes, in contrast, they reduced chlorophyll c, while blue, RB, and green LEDs decreased fucoxanthin. Under RB LEDs, the optimal light intensity was 80 µmol photons m^-2 s^-1 for female gametophytes and 40 to 60 µmol photons m^-2 s^-1 for male gametophytes. Our results suggest that dichromatic LED illumination (red-blue) improves regeneration of U. pinnatifida gametophyte-isolated protoplasts. Thus, dichromatic LEDs might a suitable light source for enhancing protoplast regeneration in brown seaweeds.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.587-597
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• 2004

Over the past 20 years, great strides have been made in research regarding the mechanisms involved in the progression of carious lesions, but new equipment and research tools need to be developed to continue these advancements in caries research. Various methods have been applied to reduce the incidence of carious lesions, which have led to a significant decrease in the number of occlusal caries, but a concurrent increase in the proportion of proximal carious lesions. New diagnostic equipment has been developed to detect early stage carious lesions, and these have demonstrated excellent laboratory results and show promise in clinical applications. The research presented here examines the efficacy of the newly developed $DIFOTI^{TM}$ system in detecting proximal carious lesions compared to traditional intraoral exam and bitewing radiography, possible problems or deficiencies of using the system in clinic, possible improvements that can be made to the system, and the efficacy of detecting early, reversible carious lesions that can be remineralized by preventative fluoride applications. The subject pool consisted of 23 grammer school age patients just prior to entering the mixed dentition phase. Each patient was given a thorough oral examination, radiographic examination consisting of bitewing radiographs of the posterior teeth, and $DIFOTI^{TM}$ examination of the anterior and posterior teeth. Each examination was carried out two times by two examiners, and the data were statistically analyzed. The results are as follows: 1. The mean alpha value of reliability test of the visual oral examination was as follows; occlusal surface was 0.8470. mesial surface was 0.6430, distal surface was 0.5727. lingual surface was 0.2807 and distal surface was 0.2339. When the examination was limited to posterior teeth, the mean alpha value was as follows; occlusal surface was 0.8577, distal surface was 0.8211, lingual surface was 0.7728, buccal surface was 0.7152 and mesial surface was 0.6782. 2. The alpha value of reliability test of the radiographic analysis of carious lesions of the occlusal, mesial, and distal surfaces was 0.8500. 3. The alpha value of reliability test of the $DIFOTI^{TM}$ diagnostic analysis of carious lesions of the occlusal, buccal, lingual, mesial, and distal surfaces was determined to be 0.7917. 4. The $DIFOTI^{TM}$ diagnostic system was found to be the most accurate means of detecting occlusal, buccal, and lingual surface carious lesions (p<0.05), while mesial and distal proximal carious lesions were most accurately assessed using bitewing radiography (p<0.05).

• Education of Primary School Mathematics
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• v.12 no.1
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• pp.1-20
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• 2009

The purposes of this study are to analyze elementary school student's intuitive thinking in the process of mathematical problem solving and to analyze elementary school student's errors of intuitive thinking in the process of mathematical problem solving. According to these purposes, the research questions can be set up as followings. (1) How is the state of illumination of the elementary school student's intuitive thinking in the process of mathematical problem solving? (2) What are origins of errors by elementary school student's intuitive thinking in the process of mathematical problem solving? In this study, Bogdan & Biklen's qualitative research method were used. The subjects in this study were 4 students who were attending the elementary school. The data in this study were 'Intuitine Thinking Test', records of observation and interview. In the interview, the discourses were recorded by sound and video recording. These were later transcribed and analyzed in detail. The findings of this study were as follows: First, If Elementary school student Knows the algorithm of problem, they rely on solving by algorithm rather than solving by intuitive thinking. Second, their problem solving ability by intuitive model are low. What is more they solve the problem by Intuitive model, their Self- Evidence is low. Third, in the process of solving the problem, intuitive thinking can complement logical thinking. Last, in the concept of probability and problem of probability, they are led into cognitive conflict cause of subjective interpretation.

• The Korean Journal of Archival Studies
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• no.68
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• pp.5-39
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• 2021

In this study, the origin of the record continuum theory was analyzed in conjunction with the record management situation in Australia after the mid-20th century and record lifecycle model. For an in-depth understanding of the record continuum theory, it is necessary to consider the background and process of its formation, and to analyze the lifecycle model itself in terms of a theoretical system built with reflections on the lifecycle model. To this end, first of all, with the aim of analyzing the historical background of the formation of the record continuum theory, the background and process that led to intensive illumination of the US lifecycle model in the process of seeking an independent public records management system in Australia in the 1950s were reviewed. Then, the meaning and limitations of the lifecycle model were considered along with the background of the formation. In order to examine the main contents, significance, and limitations of the lifecycle model, it is necessary to analyze the circumstances under which it was formed. Based on this analysis, finally, the problems associated with the application of the lifecycle model in Australia's new record creation environment, as well as the factors that were the origin of the newly born record continuum theory were examined.