• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.5-6
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• 2011

최근 환경 문제와 에너지 자원 고갈 등의 이유로 전력 사용에 있어서 효율이 매우 중요시 되고 있다. 이와 맞물려 기존의 교류배전에 비해 직류배전이 가지는 효율적 이점이 주목받으면서 직류 배전에 대한 연구가 활발히 이루어 지고 있다. 본 연구에서는 직류배전 적용시 이용 가능한 양방향 AC/DC 전력 변환기의 경부하 효율 향상을 위해 새로운 skip-cycle mode를 개발하고 이를 디지털 제어를 이용하여 구현하였다. 풀브릿지 타입의 3.3kW 양방향 전력변환기를 이용하였다.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.343-347
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• 2001

Advanced Pressurized Reactor 1400(APR-1400), which is a standard evolutionary advanced light water reactor(ALWR), has been developed from 1992 as one of long-term Government Project(G-7). The APR-1400 is designed to operate at the rated output of 4000MWt to produce an electric power output of around 1450MWe. The balance of plant (BOP) for the secondary system consists of main steam, feedwater, condensate, turbine generator and auxiliary system. In this paper, we describe the major design features of secondary component, balance of plant configuration, and then the turbine cycle thermal performance evaluation using PEPSE code.

• Development and Reproduction
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• v.17 no.2
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• pp.87-97
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• 2013

The seminiferous epithelium cycle and developmental stages of spermatids in Clethrionomys rufocanus were observed under a light microscope. The seminiferous epithelium cycle was divided into 8 stages. Type Ad spermatogonia appeared through all stages. Type Ap, In, and B spermatogonia appeared in stages I, II, III, and IV. In the first meiosis prophase, the leptotene spermatocytes appeared from stage V, the zygotene spermatocytes in stages I, VI, VII, VIII, the pachytene spermatocytes from stages II to VI, the diplotene spermatocytes in stage VII. The meiotic figures and interkinesis spermatocytes were observed in stage VIII. Developing spermatids were subdivided into 10 steps, based on the morphological characteristics such as the acrosome formation changes in spermatozoa, nucleus, cytoplasm, and spermiation changes. The C. rufocanus spermatocytogenesis and spermiogenesis results displayed similar results with Apodemus agrarius coreae and A. speciosus peninsulae. Considering all the results, the spermatogenesis may be useful information to analyze the differentiation of spermatogenic cells and the breeding season.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.E
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• pp.364-372
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• 1993

The purpose of this study is to analyze traffic patterns by use of TRANSYT-7F Model, and to choose the optimum traffic-light cycle length and cycle splite to improve traffic flow and air quality at Samsung Intersection in Seoul. Emission rates of air pollutants are calculated for three time segments 0700-0900, 0900-1800 and 1800-2000. The traffic volume correlated reasonably well with air pollutants emitted ; however, the phasing and timing of traffic signals was found to equally be important. The results of performance with optimal setting indicate that the best cycle length were 80sec(0700-0900), 95sec(0900-1800) and 90sec(1800-2000), res-pectively. As expected the highest emissions of air pollutants were observed during the evening rush hours (1800-2000). A properly designed signalized intersection can help reduce traffic delay, driver discomfort, fuel consumption, and air pollution by efficiently the capacity of existing intersection.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1123-1125
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• 2006

As Kyoto protocol has been effective in 2005, the reduction of $CO_2$ emission is a global urgent problem. In Korea, the $CO_2$ emission of transportation increases continuously, which can be solved partially by the use of railroad. Therefore, it is necessary to calculate exactly the $CO_2$ emission of railroad through life cycle approach. In this study, the $CO_2$ emission of electric motor unit (EMU) was evaluated with its carboy material using life cycle inventory analysis (LCIA). Among the life cycles of EMU, $CO_2$ emission was the highest in the running phase. As the total weight of EMU was lowered, $CO_2$ emission was reduced. In conclusion, the light-weighting of EMU can reduce $CO_2$ emission efficiently.

• Nuclear Engineering and Technology
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• v.12 no.3
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• pp.194-213
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• 1980

The paper describes and quantifies the wastes arising in the nuclear fuel cycle for Light Water Reactors, Heavy Water Reactors and Fast Breeder Reactors. The management and disposal technologies are indicated, together with their environmental impacts. Both once-through and uranium-plutonium recycle systems are evaluated, and comparisons are made on the basis of tingle reference technologies for waste management, and for one gigawatt/year of electricity generation. Environmental impacts are assessed, particularly that of health and safety, and a reference costing system is applied purely as a basis for comparing the fuel cycles. From this study it call be concluded generally that the relative differences of the impacts of waste management and disposal between the selected fuel cycles are not decisive factors in choosing a fuel cycle. Employing the technologies assumed, the radioactive wastes from any of the fuel cycles studied can be managed and disposed of with a high degree of safety and without undue risk to man or the environment. The cost of waste management and disposal is only a few percent of the value of the electricity generated and does not vary greatly between fuel cycles.

• Journal of the Korean earth science society
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• v.37 no.7
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• pp.389-397
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• 2016

In order to investigate the light curve difference in visual and infrared wavelength of ${\delta}$ Scuti variable Bo Lyn, observations were performed using BOAO 1.8m reflecting telescope and an infrared detector, KASINICS, with J, H, and Ks filters. Infrared light curves of total 7 nights were obtained between March and April in 2011, and those were compared to the V-filter light curve to examine the differences in period, time of maximum light, amplitude, and shape. From the periodic analysis of infrared light curve, a single frequency of $f_1=10.712cycle/day$, $P=0.09335{\pm}0.00002days$ was obtained, and there was no difference in the period along different wavelengths. In the infrared light curve, a frequency of $2f_1$ was detected. This frequency well explains the asymmetric shape of light curve, one of the characteristics of high-amplitude ${\delta}$ Scuti variables. We compared the locations of the measured infrared maxima and the predicted maxima of V-filter, finding that the times of maxima were delayed about 0.3 phase at infrared wavelengths. Amplitude ratios were adopted to be ${\Delta}J/{\Delta}V=0.328$, ${\Delta}H/{\Delta}V=0.216$, and ${\Delta}Ks/{\Delta}V=0.211$, with the range of variation being smaller at longer wavelengths. It seems that the differences in the times of maxima and amplitude occurred because the changes in brightness of a pulsating variable star are mainly caused by the change in temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.304-311
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• 2020

The purpose of this study is to change plant growth according to the light quantity of LED light source and to standardize plant factories technology according to the optimal LED light range. Growth was relatively stable at the 1,400 lx and 1,600 lx intensities, and growth continued with increasing light intensity, but growth slowed down with growth without leaves (Ed- I don't understand). The growth characteristics at 400 lx to 800 lx were sustained to some extent during the experimental period, but the growth of the larvae was maintained until the 7th day and the growth of leaves was not developed. From 1,000 lx to 1,400 lx, brightness, leaf growth and daily growth increased, and the growth cycle exhibited a repeating cycle of growth and slowdown. In addition, 1,600 lx and 1,800 lx showed similar growth to that at 1,400 lx, but leaf growth was high. However, at 1,800 lx, the growth was slightly higher than at 1,400lx and it slowed down over time. In addition, the stronger the light, the higher the temperature around the plant and the greater the dryness of the leaves due to the heat emitted from the light source.

• Journal of Photoscience
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• v.12 no.1
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• pp.33-39
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• 2005

Plants possess the ability to dissipate the excitation energy for the protection of photosynthetic apparatus from absorbed excess light. Heat dissipation is regulated by xanthophyll cycle in thylakoid membranes of chloroplasts. We investigated the mechanistic aspects of xanthophyll cycle-dependent photoprotection against low-temperature photoinhibition in plants. Using barley and rice as chilling-resistant species and sensitive ones, respectively, chilling-induced chlorophyll fluorescence quenching, composition of xanthophyll cycle pigments and mRNA expression of the zeaxanthin epoxidase were examined. Chilled barley plants exhibited little changes in chlorophyll fluorescence quenching either of photochemical or non-photochemical nature and in the photosynthetic electron transport, indicating low reduction state of PS II primary electron acceptor. In contrast to the barley, chilled rice showed a marked decline in those parameters mentioned above, indicating the increased reduction state of PS II primary electron acceptor. In addition, barley plants were shown to have a higher capacity to elevate the pool size of xanthophyll cycle pigments in response to cold stress compared to rice plants. Such species-dependent regulation of xanthophyll cycle activity was correlated with the gene expression level of cold-induced zeaxanthin epoxidase. Chilled rice plants depressed the gene expression of zeaxanthin epoxidase, whereas barley increased its expression in response to cold stress. We suggest that chilling-induced alterations in the pool size of xanthophyll cycle pigments related to its capacity would play an important role in regulating plant's sensitivity to chilling stress.

• Tribology and Lubricants
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• v.21 no.6
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• pp.268-271
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• 2005

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15N contact force in a reciprocal sliding motion of sliding distance of 10mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji II LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.