• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.75-93
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• 2022

Machine learning (ML) data-driven meta-model is proposed as a surrogate model to reduce the excessive computational cost of the physics-based model and facilitate the real-time prediction of a nuclear power plant's transient response. To forecast the transient response three machine learning (ML) meta-models based on recurrent neural networks (RNNs); specifically, Long Short Term Memory (LSTM), Gated Recurrent Unit (GRU), and a sequence combination of Convolutional Neural Network (CNN) and LSTM are developed. The chosen accident scenario is a control element assembly withdrawal at power concurrent with the Loss Of Offsite Power (LOOP). The transient response was obtained using the best estimate thermal hydraulics code, MARS-KS, and cross-validated against the Design and control document (DCD). DAKOTA software is loosely coupled with MARS-KS code via a python interface to perform the Best Estimate Plus Uncertainty Quantification (BEPU) analysis and generate a time series database of the system response to train, test and validate the ML meta-models. Key uncertain parameters identified as required by the CASU methodology were propagated using the non-parametric Monte-Carlo (MC) random propagation and Latin Hypercube Sampling technique until a statistically significant database (181 samples) as required by Wilk's fifth order is achieved with 95% probability and 95% confidence level. The three ML RNN models were built and optimized with the help of the Talos tool and demonstrated excellent performance in forecasting the most probable NPP transient response. This research was guided by the Systems Engineering (SE) approach for the systematic and efficient planning and execution of the research.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.320-320
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• 2022

Coriander(Coriandrum sativum L.) belongs to the family Umbelliferae/Apiaceae. It is cultivated as a spice and medicinal herb around the world, including its leaves and seeds. Coriander leaves have soft and fragrant, so they can be used in cuisines such as China, Mexico, and, Southeast Asia. Coriander leaves contain a high amount of vitamin C, carotene, and multiple polyphenols. Coriander essential oils and extracts have various chemical components and are known to have antioxidant, antibacterial, and antifungal activities. This study was carried out for resource discovery, propagation, and DB construction of aromatic plants. In order to evaluate the genetic characteristics, 30 kinds of Coriander seeds were supplied from the Center for Genetic Resources. The evaluation of characteristics of the basal part leaf number, leaf shape, and plant height was investigated. Also, Essential oils extract from various parts of plants including the leaves, flowers, and steam isolated by simultaneous distillation extraction(SDE) apparatus. In the results, heights showed growing to 70 cm over and basal part leaf number 0 to7. The leaves are variable, they are measured according to leaves incisions, and most of the included incision. The qualitative analysis of EOs was performed using gas chromatography-mass spectrometry. EOs had various chemical compositions. Major compounds were trans-2-Decenal, linalool, decanal, 2-Dodecenal, 13-Tetradecanal, 2-Undecenal.

• Journal of Surface Science and Engineering
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• v.56 no.6
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• pp.401-411
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• 2023

This study investigates the synthesis, characterization, and application of zinc oxide (ZnO) nanoparticles for corrosion resistance and stress corrosion cracking (SCC) mitigation in high-temperature and high-pressure environments. The ZnO nanoparticles are synthesized using plasma discharge in water, resulting in rod-shaped particles with a hexagonal crystal structure. The ZnO nanoparticles are applied to Alloy 600 tubes in simulated nuclear power plant atmospheres to evaluate their effectiveness. X-ray diffraction and X-ray photoelectron spectroscopy analysis reveals the formation of thermodynamically stable ZnCr₂O₄and ZnFe₂O₄ spinel phases with a depth of approximately 35 nm on the surface after 240 hours of treatment. Stress corrosion cracking (SCC) mitigation experiments reveal that ZnO treatment enhances thermal and mechanical stability. The ZnO-treated specimens exhibit increased maximum temperature tolerance up to 310 ℃ and higher-pressure resistance up to 60 bar compared to non-treated ZnO samples. Measurements of crack length indicate reduced crack propagation in ZnO-treated specimens. The formation of thermodynamically stable Zn spinel structures on the surface of Alloy 600 and the subsequent improvements in surface properties contribute to the enhanced durability and performance of the material in challenging high-temperature and high-pressure environments. These findings have significant implications for the development of corrosion-resistant materials and the mitigation of stress corrosion cracking in various industries.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3717-3729
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• 2024

Accurately predicting evacuation time in a ventilated main control room (MCR) during fire emergencies is crucial for ensuring the safety of personnel at nuclear power plants. This study proposes to use neural networks alongside consolidated fire and smoke transport (CFAST) simulations to serve as a surrogate model for physics-based simulation tools. Our neural networks can promptly predict the evacuation time in MCRs, proving to be a valuable asset in fire emergencies and eliminating the need for time-consuming rollouts of the CFAST simulations. The CFAST model simulates fire and evacuation scenarios in a ventilated MCR with variations in input parameters such as door conditions, ventilation flow rate, leakage area, and fire propagation time. Target output parameters, such as hot gas layer temperature (HGLT), heat flux (HF), and optical density (OD), are used alongside standardized evacuation variables to train a machine learning model for predicting evacuation time. The findings suggest that high ventilation flow rates help to dilute smoke and discharge hot gas, leading to lower target output parameters and quicker evacuation. Standardized evacuation variables exceed the required abandonment criteria for all door conditions, indicating the importance of proper evacuation procedures. The results show that neural networks can generate evacuation times close to those obtained from CFAST simulations.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.483-487
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• 2001

This study was carried out to investigate the role of attached leaflet on rooting and growth by one nodal cutting in tomato. As cutting sources 4 to 6 nodes could be obtained from one nursery seedling. Medium for cutting was a mixture with perlite plus peat moss (1 : 1, v/v), and each plug capacity was 30mL in the 72 cells-plug tray. Plant height and the number of leaves were significantly increased by attached leaflet cutting in 'Pepe' and 'Coco' cherry tomato. Dry weights of top and root were increased as much as 3 to 15 times in the cutting attached leaflet. Rooting percentage was 93.5% in one node cutting and 86% in the cutting with hypocotyl node part. At 20 to 24 days after nodal cutting, healthy nursery plant could be produced to transplant in field. The nursery plants by nodal cutting (NPNC) showed more fibrous roots and less tap roots than that of seedling. In terms of rooting pattern, NPNC rooted at the whole ground stem part, while rooting of seedling occurred at basal part of hypocotyl.

• Korean Journal of Environment and Ecology
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• v.16 no.1
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• pp.87-93
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• 2002

The tree of heaven naturalized plant grows in the various habitats of the city. The principal reason is that it is reproduced not only through sexual reproduction but through asexual reproduction. By the spreading of sucker and a bud appearance of the seed it forms a group easily inside the city habitat. The distribution of seed and spreading of the seedlings of the tree of heaven were investigated like the followings. As the result of the sexual reproduction by the seed and hangs in cluster farm, 350 individuals are germinated at the Namsan the best environment, and 50 individuals at Toegyewon Rotary These seeds are dispersed by the effect of wind and geographical factor. Because the northwest wind is blowing mainly from late autumn to early spring, it is dispersed in the south. In Toegyewon Rotary, a slant site, is dispersed mainly by down the site. Compared with width of crown, the seedling of a seed germination are distributed outside more than inside the crown and the seed is spreaded until the maximum 7.5 times of crown width at the investigated area. 1 year seedlings appeared as a group at the place of 2-4 times of the crown (in 20m from the crown, 75% distribution). Considering the distribution by the seed scattering of the tree of heaven, there is a possibility of sudden individual increase even in the deteriorated city environment. So this possibility shows that we need to consider the protection of the city soil, and the species variety decrease resulted from the successful competition to the other species.

• Korean Journal of Agricultural Science
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• v.30 no.2
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• pp.128-138
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• 2003

The bacterial density of partially processed horticultural crops in the commercial market was relatively high probably due to improper handing or processing. Between crops, the bacterial density was low in peeled garlic and ranged above $10^8cfu{\cdot}g^{-1}fw$ in other crops. Especially in brake fern, the bacterial density was the highest and non food materials such as packing strips were found. There was difference in the effects of ozone-treated water washing treatment between crops. In root crops such as burdock and lotus root, ozone showed positive effect on preventing discoloration as well as lowing bacterial density resulting in the increase of marketing period. Any positive effect was not found when sliced crops were treated over 5 min at $0.3mg{\cdot}L^{-1}$ of dissolved ozone. In lettuce slices, leaf tissues were severely discolored and rapidly soften at $0.3mg{\cdot}L^{-1}$ for 2 min dipping. Ozone was highly effective on inhibiting bacterium propagation and off-flavor. This effect was more stronger in Fischer ligulariata than brake fern, probably due to the difference of tissue thickness. Results indicated that ozone-treated water washing had a strong potential to improve the market quality of partially processed horticultural crops including dried wild greens and sliced root crops.

• Journal of Plant Biotechnology
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• v.35 no.3
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• pp.229-234
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• 2008

An efficient micropropagation was established by using axillary bud explants from two-year-old tree(Echinosphorea koreensis Nakai), which has been known as a rare and endangered species. Among various basal media tested, DKW medium was shown to be the best for axillary shoot elongation. The addition of both BA and TDZ to the medium induced 6 to 10 shoots per explant during eight weeks of culture, without showing any abnormal morphology at the shoot proliferation stage. However, high concentration of TDZ(>0.05 mg/L) appeared to cause hyperhydration on either leaf or shoot at the later developmental stage. Approximately 20% of shoots produced roots by the addition of 1.0 mg/L NAA but not by IBA($0.2{\sim}1.0$ mg/L). Ex vitro micro-cuttings were better source for root induction; up to 58.6% of the micro-cuttings rooted when 100 mg/L IBA was applied to the soil(vermiculite). More than 90% of plantlets with roots were successfully acclimatized and grew normally in the field. Therefore, we suggest that this endangered tree species can be effectively micropropagated by axillary bud culture system developed in this study.

• Korean Journal of Plant Resources
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• v.14 no.2
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• pp.175-181
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• 2001

Dormancy of intact zoysiagrass seeds hinders its seed propagation in which presowing seed treatment must be done to overcome it. The study was done to remodel the presowing treatments of zoysiagrass seeds by determining the treatment effects of seedcoat softening, prechilling, drying and combined light treatment with them or during germination stage. Seedcoat softening with different chemicals (NaOH 20%, KOH 20%, $H_2SO_4\;8M, acetone 20%) and periods (10, 30, 60 min.), prechilling with different periods at 3$^{\circ}C$, and drying with 4 hours at 35$^{\circ}C$ was done. Light sources were also applied with 660 nm red LED light, commercial fluorescent and incandescent light and darkness. Germination test was done in alternative day and night temperature of 35 and 2$0^{\circ}C$ to check the daily germination rates. With seeds treated with NaOH 20% for 30 minutes, red and incandescent light showing similar responses inclined their germination rates compared to dark conditions. Drying resulted in its higher rate than non-drying but fluorescent light treatment forced during drying more enhanced the rate than red light. While mean germination rate considering all the seedcoat softening treatment periods was the greatest in $H_2SO_4$ in comparison with NaOH, KOH and acetone, NaOH treatment for 30 minutes showed the best rate among the all the treatment levels. In the conditions of sowing them to no-mulching field, presowing treatment procedure of zoysiagrass seeds was remodeled: the seedcoat softening treatment with NaOH 20% for 30 minutes was done, washed, and chilled at 3$^{\circ}C$ for 2 weeks before dried under 4 hour fluorescent light illumination at 35$^{\circ}C$.

• Korean Journal of Plant Tissue Culture
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• v.25 no.1
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• pp.33-36
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• 1998

Guzmania was propagated through in vitro culture of lateral shoots. When new shoots grown in greenhouse were cut and cultured in vitro, contamination rate was very high at about 80% in the first stage of in vitro culture. Among cytokinin treatments for agar medium, 2.0 mg/L BA was most effective for shoot multiplication, and those with 0.5 mg/L kinetin and 0.5~1.0 mg/L BA were favorable for shoot multiplication. BA was more effective for shoot multiplication than kinetin, and shoot multiplication was more enhanced when 2.0 mg/L BA was combined with 0.1~0.5 mg/L IAA than 2.0 mg/L BA alone. The medium with 2.0 mg/L BA and 0.1 mg/L IAA showed the highest rate of shoot multiplication with about 8.7 in shoot number, and those with 2.0 mg/L BA and 0.5~1.0 mg/L IAA also resulted in high multiplication of shoots. Shoots were multiplicated more in liquid rotation culture(80 rpm) with the medium containing 0.5 mg/L BA and 0.1 mg/L IAA than liquid stagnating and solid cultures. Regenerated shoots formed roots very favorably in the medium supplemented with 2.0 mg/L IBA.