• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.34.3-34.3
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• 2020

Faint z ~ 5 quasars with M1450 ~ -23 mag are known to be the potentially important contributors to the ultraviolet ionizing background in the post-reionization era. However, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (IGM). In this work, we present the updated results of our z ~ 5 quasar survey using the Infrared Medium-deep Survey (IMS), a near-infrared imaging survey covering an area of 85 square degrees. From our spectroscopic observations with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8 m Telescope, we discovered eight new quasars at z ~ 5 with -26.1 ≤ M1450 ≤ -23.3. Combining our IMS faint quasars with the brighter Sloan Digital Sky Survey (SDSS) quasars, we derive, for the first time, the z ~ 5 quasar luminosity function (QLF) without any fixed parameters down to the magnitude limit of M1450 = -23 mag. We find that the faint-end slope of the QLF is very flat (-1.2) with a characteristic luminosity of -25.7 mag. The number density of z ~ 5 quasars from the QLF gives lower ionizing emissivity and ionizing photon density than those in previous works. These results imply that quasars are responsible for only 10-20% of the photons required to completely ionize the IGM at z ~ 5, disfavoring the idea that quasars alone could have ionized the IGM at z ~ 5.

• Analytical Science and Technology
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• v.22 no.6
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• pp.488-497
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• 2009

In this study, analytical methodology for several organic fatty acids (OFA: propionic acid (PA), butyric acid (BA), isovaleric acid (IA), and valeric acid (VA)) designated as new offensive odorants in Korea (as of year 2010) was investigated along with some odorous VOCs (styrene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, and isobutyl alcohol). For this purpose, working standards (WS) containing all of these 13 compounds were loaded into adsorption tube filled with Tenax TA, and analyzed by gas chromatography (GC) system thermal desorber interfaced with. The analytical sensitivities of organic fatty acids expressed in terms of detection limit (both in absolute mass (ng) and concentration (ppb)) were lower by 1.5-2 times than other compounds (PA: 0.24 ng (0.16 ppb), BA: 0.19 ng (0.11 ppb), IA: 0.15 ng (0.07 ppb), and VA: 0.28 ng (0.13 ppb)). The precision of BA, IA, and VA, if assessed in terms of relative standard error (RSE), maintained above 5%, while the precison of other compounds were below 5%. The reproducibility of analysis improved with the aid of internal standard calibration (PA: $1.1{\pm}0.4%$, BA: $10{\pm}0.46$, IA; $12{\pm}0.3%$, VA: $4{\pm}0.1%$), respectively. The results of this study showed that organic fatty acid can be analyzed using adsorption tube and thermal desorber in a more reliable way to replace alkali absorption method introduced in the odor prevention law of the Korea Ministry of Environment (KMOE).

• Journal of Food Hygiene and Safety
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• v.38 no.3
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• pp.131-139
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• 2023

In this study, we investigated pesticide residue levels in 535 domestically distributed agricultural products in South Korea using multi-residue analysis. Agricultural products from 13 regions, including Seoul, were pretreated using QuEChERS and d-SPE, and subsequently analyzed using LC-MS/MS and GC-MS/MS. Residual pesticides were detected in 288 (53.8%) out of the 535 samples, including 40 of apples, 40 of peppers, 33 of mandarins, 31 of peaches, and 144 other commodities. Furthermore, one sample of Korean cabbage exceeded the permitted maximum residue limit (MRL), diniconazole (0.18 mg/kg), detected at about twice the MRL. In total, 91 types of residual pesticides were detected, including fungicides (42), insecticides (48), and a nematicide. The most frequently detected pesticides were dinotefuran (91), carbendazim (75), tebuconazole (61), and pyraclostrobin (59). Our results showed that continuous monitoring of agricultural products is necessary.

• Journal of Food Hygiene and Safety
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• v.38 no.3
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• pp.112-122
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• 2023

We assessed the pesticide residues in the medicinal agricultural products distributed in Korea. Pesticide residues in 72 samples were analyzed using the QuECheRS method for 339 pesticides, using GC-MS/MS and LC-MS/MS. The pesticide residues were below the maximum residues limit (MRL) in 42 samples (58.3%); however, they exceeded the MRL in 5 samples (6.9%). These included 43 types of pesticides; 20 fungicides and 23 insecticides were detected 75 times and 58 times, respectively. Tebuconazole and carbendazim were the most detected fungicides, each 11 times. The levels of acetamiprid, cadusafos, chlorpyrifos, flubendiamide, fluopyram, and triazophos exceeded the MRL in Gogi berry, Omija, and Reishi mushroom. All of them were positive list system (PLS) items that lacked pesticide residue standards. Therefore, authorities should monitor the distributed medicinal agricultural products.

• Journal of Ethics
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• no.80
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• pp.51-77
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• 2011

This study aims to explore how to establish any foundation of the value of the unification of the Korean Peninsula in multicultural society of Korea. Its main issue is related to Korean identity of a nation and its shared value among the mulitcultural members, in particular, of North Koreans including defectors, foreign workers, and immigrants of international marriage and their children. For this study, I would utilize a given research of the application of two concepts of culture to multicultural levels by criticizing its limit; as an alternative, furthermore, I would pay attention to the possibility of the concept of emotion in multicultural members. A short feature in a given study of two conceptions of culture in a multicultural society is as follows: the first is to regard it as the patterns of meanings and symbols, which is very useful to understand others or other culture; secondly, to see it as the lasting process of perfection in human life, which makes us recognize ourselves as a member, so to speak, identity. In application it to Korean muliticultural members, however, there are crucial and complicated problems according to the cases of their lives. For North Koreans, firstly, they tend to get the conception of Korean identity in terms of ideological policies and education of North Korean government. This means that they have a strong hatred towards the word multiculture, in the level of recognizing the self-culture. Secondly, North Korean defectors also have the recognition of the self-culture, but their serious problem is discriminative treatments by South Korean in terms of socio-economics, in the process of their settlement. Thirdly, parents and their children in multicultural family can have their identity as Korean. In parents, however, the level is double that they can have both identities of Korean as well as of their countries. The foundation, therefore, of the value of the unification in the Korean Peninsula is closely related to the issue of identity as Korean. To recognize it, it is possible only to consider and reflect all members' lives by applying the dual conceptions of culture to their multicultural lives. That is not of outer system, but of inner, relational and cultural emotion, which enables them to share their common value of unification.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.11
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• pp.471-480
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• 2023

The Korean construction order volume in South Korea grew significantly from 91.3 trillion won in public orders in 2013 to a total of 212 trillion won in 2021, particularly in the private sector. As the size of the domestic and overseas markets grew, the scale and complexity of EPC (Engineering, Procurement, Construction) projects increased, and risk management of project management and ITB (Invitation to Bid) documents became a critical issue. The time granted to actual construction companies in the bidding process following the EPC project award is not only limited, but also extremely challenging to review all the risk terms in the ITB document due to manpower and cost issues. Previous research attempted to categorize the risk terms in EPC contract documents and detect them based on AI, but there were limitations to practical use due to problems related to data, such as the limit of labeled data utilization and class imbalance. Therefore, this study aims to develop an AI model that can categorize the contract terms based on the FIDIC Yellow 2017(Federation Internationale Des Ingenieurs-Conseils Contract terms) standard in detail, rather than defining and classifying risk terms like previous research. A multi-text classification function is necessary because the contract terms that need to be reviewed in detail may vary depending on the scale and type of the project. To enhance the performance of the multi-text classification model, we developed the ELECTRA PLM (Pre-trained Language Model) capable of efficiently learning the context of text data from the pre-training stage, and conducted a four-step experiment to validate the performance of the model. As a result, the ensemble version of the self-developed ITB-ELECTRA model and Legal-BERT achieved the best performance with a weighted average F1-Score of 76% in the classification of 57 contract terms.

• Korean Journal of Heritage: History & Science
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• v.56 no.3
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• pp.62-74
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• 2023

Much attention has been focused on the Baekpoman area due to the archaeological achievements of the past, but studies on prehistoric times when villages began to form is insufficient, and the Bronze Age village landscape was examined in order to supplement this. In the area of Baekpo Bay, the natural geographical limit connected to the inland was culturally confirmed by the distribution density of dolmens, and the generality of the Bronze Age settlement was confirmed with the Hwangsan-ri settlement. Bunto Village in Hwangsan-ri represents a farming-based village in the Baekpo Bay area, and the residential group and the tomb group are located on the same hill, and it is composed of three individual residential groups, and the village landscape had attached buildings used as warehouses and storage facilities. In the area of Baekpo Bay, it spread in the Tamjin River basin and the Yeongsan River basin where Songgukri culture and dolmen culture were integrated, and the density distribution of the villages was considered to correspond to the distribution density of dolmens. In order to examine the landscape of village distribution, the classification of Sochon-Jungchon-Daechon was applied, and it was classified as Sochon, a sub-unit constituting the village, in that the number of settlements constituting the village in the Bronze Age was mostly less than five. There are numerical differences between Jungchon and Daechon, and the distribution pattern does not necessarily coincide with the hierarchy. The three individual residential groups of Bunto Village in Hwangsan-ri are Jungchon composed of complex communities of blood relatives with each family community, and a stabilized village landscape was created in the Gusancheon area. In the area of Baekpo Bay, Bronze Age villages formed a landscape in which small villages were scattered around the rivers and formed a single-layered relationship. Dolmens (tombs) were formed between the villages and villages, and seem to have coexisted. Sochondeul is a family community based on agriculture, and it is believed that self-sufficient stabilized rural villages that live by acquiring various wild resources in rivers, mountains, and the sea formed a landscape.

• Analytical Science and Technology
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• v.36 no.6
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• pp.291-299
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• 2023

The benzo[a]pyrene in edible oils is extracted using methods such as Liquid-liquid, soxhlet and ultrasound-assisted extraction. However these extraction methods have significant drawbacks, such as long extraction time and large amount of solvent usage. To overcome these drawbacks, this study attempted to improve the current complex benzo[a]pyrene analysis method by applying the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method that can be analyzed in a simple and short time. The QuEChERS method applied in this study includes extraction of benzo[a]pyrene into n-hexane saturated acetonitrile and n-hexane. After extraction and distribution using magnesium sulfate and sodium chloride, benzo[a]pyrene is analyzed by liquid chromatography with fluorescence detector (LC/FLR). As a result of method validation of the new method, the limit of detection (LOD) and quantification (LOQ) were 0.02 ㎍/kg and 0.05 ㎍/kg, respectively. The calibration curves were constructed using five levels (0.1~10 ㎍/kg) and coefficient (R²) was above 0.99. Mean recovery ratio was ranged from 74.5 to 79.3 % with a relative standard deviation (RSD) between 0.52 to 1.58 %. The accuracy and precision were 72.6~79.4 % and 0.14~7.20 %, respectively. All results satisfied the criteria ranges requested in the Food Safety Evaluation Department guidelines (2016) and AOAC official method of analysis (2023). Therefore, the analysis method presented in this study was a relatively simple pretreatment method compared to the existing analysis method, which reduced the analysis time and solvent use to 92 % and 96 %, respectively.

• Journal of Korean Society of Forest Science
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• v.112 no.4
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• pp.502-514
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• 2023

This study was conducted to understand the long-term changes in soil physiochemical properties and seedling growth in Larix kaempferi (larch) stands planted in clear-cut larch and Pinus rigida (pine) forest soils over an 11-year period after reforestation. Two-year-old bare-root larch seedlings were planted in 2009-2010 at a density of 3,000 seedlings ha^-1 in clear-cut areas that harvested larch (Chuncheon and Gimcheon) and pine (Wonju and Gapyeong) stands. We analyzed the physiochemical properties of the mineral soils sampled at 0-20 cm soil depths in the planting year, and the 3^rd, 7^thand 11^th years after planting, and we measured seedling height and root collar diameter in those years. We found significant differences in soil silt and clay content, total carbon and nitrogen concentration, available phosphorus, and cation exchangeable capacity between the two stands; however, seedling growth did not differ. The mineral soil was more fertile in Gimcheon than in the other plantations, while early seedling growth was greatest in Gapyeong. The seedling height and diameter at 11 years after planting were largest in Wonju (1,028 tree ha^-1) and Chuncheon (1,359 tree ha^-1) due to decreases in stand density after tending the young trees. The soil properties in all plantations were similar 11 years after larch planting. In particular, the high sand content and high available phosphorus levels (caused by soil disturbance during clear-cutting and planting) showed marked decreases, potentially due to soil organic matter input and nutrient uptake, respectively. Thus, early reforestation after clear-cutting could limit nutrient leaching and contribute to soil stabilization. These results provide useful information for nutrient management of larch plantations.

• Korean Journal of Remote Sensing
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• v.39 no.6_2
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• pp.1651-1669
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• 2023

Sea ice currently covers approximately 7% of the world's ocean area, primarily concentrated in polar and high-altitude regions, subject to seasonal and annual variations. It is very important to analyze the area and type classification of sea ice through time series monitoring because sea ice is formed in various types on a large spatial scale, and oil and gas exploration and other marine activities are rapidly increasing. Currently, research on the type and area of sea ice is being conducted based on high-resolution satellite images and field measurement data, but there is a limit to sea ice monitoring by acquiring field measurement data. High-resolution optical satellite images can visually detect and identify types of sea ice in a wide range and can compensate for gaps in sea ice monitoring using Geostationary Ocean Color Imager-II (GOCI-II), an ocean satellite with short time resolution. This study tried to find out the possibility of utilizing sea ice monitoring by training a rule-based machine learning model based on learning data produced using high-resolution optical satellite images and performing detection on GOCI-II images. Learning materials were extracted from Liaodong Bay in the Bohai Sea from 2021 to 2022, and a Random Forest (RF) model using GOCI-II was constructed to compare qualitative and quantitative with sea ice areas obtained from existing normalized difference snow index (NDSI) based and high-resolution satellite images. Unlike NDSI index-based results, which underestimated the sea ice area, this study detected relatively detailed sea ice areas and confirmed that sea ice can be classified by type, enabling sea ice monitoring. If the accuracy of the detection model is improved through the construction of continuous learning materials and influencing factors on sea ice formation in the future, it is expected that it can be used in the field of sea ice monitoring in high-altitude ocean areas.