• Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.324-330
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• 2009

Cadmium (Cd) accumulation and elimination were assessed in the tissues of the clam R. philippinarum at four experimental concentrations (control, 10, 20, 100, and $200\;{\mu}g/L$) over an exposure period of 2 weeks and an elimination period of 1 week. Cd accumulated in the digestive gland, gill, and residual clam tissues, and accumulation increased with time of exposure and concentration (100 and $200\;{\mu}g/L$). After 2 weeks of Cd exposure, the order of Cd accumulation in tissues was gill > digestive gland > residual tissues. An inverse relationship was observed between concentration factor (CF) and exposure level, but the CF showed an increase with exposure time. During the depuration period, Cd concentrations in the digestive gland, gill, and residual tissues decreased immediately on the cessation of exposure, except in individuals at the $200\;{\mu}g/L$ concentration. The Cd elimination rate from tissues decreased in the order of digestive gland > gill > residual tissues during the depuration period.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.46-60
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• 2023

Climate change causes fluctuations in water quality in the aquatic environment, which can cause changes in water circulation patterns and severe adverse effects on aquatic ecosystems in the future. Therefore, research is needed to predict and respond to water quality changes caused by climate change in advance. In this study, we tried to predict the dissolved oxygen (DO), chlorophyll-a, and turbidity of the Paldang reservoir for about two weeks using long short-term memory (LSTM) and gated recurrent units (GRU), which are deep learning algorithms based on recurrent neural networks. The model was built based on real-time water quality data and meteorological data. The observation period was set from July to September in the summer of 2021 (Period 1) and from March to May in the spring of 2022 (Period 2). We tried to select an algorithm with optimal predictive power for each water quality parameter. In addition, to improve the predictive power of the model, an important variable extraction technique using random forest was used to select only the important variables as input variables. In both Periods 1 and 2, the predictive power after extracting important variables was further improved. Except for DO in Period 2, GRU was selected as the best model in all water quality parameters. This methodology can be useful for preventive water quality management by identifying the variability of water quality in advance and predicting water quality in a short period.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.938-946
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• 2005

We study the firm's strategy to price its products and plan the spare parts manufacturing so as to maximize its profit and at the same time to fulfill its commitment to providing the customers with the key parts continuously over the relevant decision time horizon, i.e., the production plus warrantee period. To examine the research question, we developed and solved a two-stage optimal control theory model. Our analysis suggests that if the cost to produce the spare part during the warrantee period is more expensive than that during the production period, the firm should increase its sales price gradually throughout the production period to control its sales. In addition, during the production period it is optimal for the firm to produce the spare parts more than needed so that the overproduced spare parts can be used to partially meet the demand during the warrantee period. We conducted numerical analysis to investigate the sensitivity dynamics among key variables and parameters such as inventory holding cost, unit spare part production costs, part failure rate, and parameters in the demand function.

• Journal of Korean Port Research
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• v.9 no.2
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• pp.51-64
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• 1995

Generally, it is pointed out that the submerged breakwater with one row can not regulate the long period waves efficiently, because the crown width is very shorter than the wave length of the long period waves. Therefore, the wide crown is needed to raise the controlling efficiency for the long period waves. This study picks up the submerged breakwater with two rows which has smaller construction materials comparing to the one row and discusses the wave controlling function for the long period waves. Judging from the results obtained by using the strict dividing region method, the submerged breakwater with two rows can more regulate the long period waves than one row can, especially, in case that crown width and inner width of its construction come to be wider.

• Journal of Korean Society of Archives and Records Management
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• v.22 no.4
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• pp.175-196
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• 2022

This study aims to determine the research trends in archival preservation through keyword analysis, understand the current research status, and identify the research topics' changes over time. The degree and betweenness centrality analyses were conducted and visualized on 463 "archival preservation studies" articles published from 2000 to 2021 in various academic journals, using NetMiner 4.0. The collected research papers were divided into three time periods according to when they were published: the first period (2000-2007), the second period (2008-2014), and the third period (2015-2021). The subject keywords for the research papers on archival preservation in Korea that have influence and expandability are as follows. Across all periods, these were "electronic records" and "long-term preservation." In addition, if taken separately per period, the "OAIS reference model" and "electronic records" dominated the first and second periods, respectively, while the "records management standard table" and "long-term preservation" both dominated the third period. A conceptual framework and theory-oriented study for archival preservation, such as "digital preservation," "digitalization," and the "OAIS reference model," dominated the first period. During the second period, more research focused on procedures and practical applications related to conservation activities, such as "electronic record," "appraisal," and "DRAMBORA." In contrast, the majority of the research in the third period was on technical implementation according to the changes in the records management environment, such as "data set," "administrative information system," and "social media."

• International Journal of Contents
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• v.11 no.1
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• pp.52-61
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• 2015

In the past decade, East Asian Research has received attention from researchers as well as in South Korea society-at-large. The broad category of East Asian Research includes various disciplinary fields, such as "history, economics, and politics; however, few studies have used quantitative analysis to explore its development. In this paper, we used network analysis to identify the disciplines and active research areas, focusing on productivity, collaboration patterns, and citation networks of East Asian Research in South Korea. For this study, 6,646 journal publications related with East Asian Research and indexed by KCI (Korean Citation Index) during the 10-year period of 2004-2013 were considered. Results show that East Asian Research was led during this period by sole-researchers, rather than interdisciplinary studies. Moreover, a co-institution network represents active institutions with a high degree and collaborative centrality. In terms of journal-journal citation networks, journals belonging to both "history" and "Korean literature" disciplines were dominant.

• Journal of Animal Reproduction and Biotechnology
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• v.34 no.4
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• pp.300-304
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• 2019

This study was conducted to examine the oocyte recovery efficiency through having an OPU session once and twice a week. Also, the oocyte recovery efficiency was examined by using OPU after two and three months of rest period. Six cows were used for oocytes collection and were randomly divided into two groups. In experiment 1, OPU sessions were conducted once and twice a week to collect oocytes. The collected oocytes between once and twice OPU groups were classified into four groups (grade 1, 2, 3 and 4) according to the quality of cumulus cells and ooplasm. Based on the result, the percentage of collected oocytes per aspirated follicle number was similar between once and twice OPU session groups (65.5 ± 1.9 and 68.7 ± 1.4 vs.). However, the percentage of grade 1 oocytes from the twice OPU session group was significantly high compared with that of the once a week OPU session group (25.3 ± 0.9 and 32.5 ± 1.2% vs. once and twice session group, respectively, p < 0.05). In experiment 2, the group with three months of rest period tended to have a high percentage of collected oocyte compared with the group with two months of rest period (64.6 and 70.9% vs. 2 and 3 months rest group, respectively, p = 0.62). The percentage of grade 4 in the group with three months of rest period was significantly low compared with the group with two months of rest period group (27.3 and 36.5% vs. two and three months rest group, respectively, p = 0.05). In conclusion, twice a week OPU session is suitable for collection of high quality oocytes by using OPU, and three months of rest period is needed for the recovery of oocyte quality of a donor cow.

• Journal of Periodontal and Implant Science
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• v.49 no.1
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• pp.47-57
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• 2019

Purpose: This study was designed to observe the resorption pattern of biphasic calcium phosphate (BCP) used for maxillary sinus augmentation over a 3- to 6-year healing period, and to investigate factors affecting the resorption of BCP. Methods: A total of 47 implants placed in 27 sinuses of 22 patients were investigated. All patients had residual bone height less than 5 mm at baseline. The modified Caldwell-Luc approach was used to elevate the maxillary sinus membrane, and the sinus cavity was filled with BCP (70% hydroxyapatite and 30% ${\beta}$-tricalcium phosphate). Implant placement was done simultaneously or in a staged manner. Serial radiographic analysis was performed up to 6 years postoperatively. Results: During the follow-up period, no implant loss was reported. The mean reduced height of the augmented sinus (RHO) was $0.27{\pm}1.08mm$ at 36 months, and $0.89{\pm}1.39mm$ at 72 months postoperatively. Large amounts of graft material (P=0.021) and a long healing period (P=0.035) significantly influenced the amount of RHO. In particular, there was a significant relationship between a healing period longer than 40 months and RHO. Conclusions: BCP can achieve proper dimensional stability with minimal reduction of the graft height in a 3- to 6-year healing period after maxillary sinus augmentation. The healing period and the amount of graft material influenced the resorption of BCP.

• Journal of Chest Surgery
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• v.55 no.1
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• pp.61-68
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• 2022

Background: While the coronavirus disease 2019 (COVID-19) pandemic has affected all aspects of health care, its impact on cardiac surgical practice and outcomes is yet to be determined. We compared the outcomes of our cardiac surgical practice from the past year during the pandemic to those in a similar pre-pandemic period. Methods: Retrospective data were collected from 307 patients who were involved in all adult cardiac surgical procedures performed between March 2020 and February 2021, which was considered the pandemic period, at Amrita Institute of Medical Sciences, India. These were compared with data from the 1-year period between March 2019 and February 2020. During that earlier period, 491 patients underwent surgery, and the surgical outcomes were assessed. Outpatient visit data were also collected to evaluate the effect of COVID-19 on outpatient follow-up visits. Results: A 37% decrease in surgical case volume was observed during the study period. No difference was found in operative mortality between the 2 time periods (3.3% vs. 2.6%, p=0.383). Overall postoperative complications were less frequent during this period, at 23% compared to 38% the previous year (p<0.001). Conclusion: The COVID-19 pandemic caused a dramatic decrease in surgical volume and outpatient medical follow-up. However, the pandemic and its attendant social restrictions did not yield a significant change in the surgical outcomes of our patients. Hence, it is reasonable to continue cardiac surgical care during global health crises, and this can be done with good results.

• Journal of Mushroom
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• v.20 no.2
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• pp.55-60
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• 2022

This study was conducted to establish an appropriate period of use of sawdust spawn at low temperatures and a nutrient supplement medium for cultivation of Lentinula edodes 'Hwadam'. Of the nutrient supplements, the total yield of rice bran (5%) + corn flour (5%) treatments were 673.3 g, which was higher than rice bran (551.6 g) and wheat bran (546.7 g) treatments, respectively. As shown by the growth of Lentinula edodes 'hwadam' during to the sawdust spawn storage period (at 4℃), the period of spawn running, browning, fruiting body formation, and development was 27 d, 81 d, 5 d, and 11-13 d, respectively, regardless of the length of the storage period at 4 ℃. After 3 months of storage of sawdust spawn, the number of fruiting bodies and yield decreased as the storage period increased. Therefore, the period of use of sawdust spawn (at 4 ℃) for the stable production of fruiting bodies of Lentinula edodes 'Hwadam' was a maximum of 3 months.