• Resources Recycling
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• v.32 no.3
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• pp.57-67
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• 2023

The treatment of waste plastic has primarily been entrusted to small companies, which has resulted in challenges in obtaining an accurate overview of the current state of affairs and ensuring profitability. Consequently, despite the presence of recycling technology, their practical application has proven to be challenging. In this study, as part of the waste plastic material recycling plan, it is assumed that the PET/OPP laminated waste film is peeled off at the waste film generation site for the second use. The recycling rate of PET/OPP delaminated waste film is assumed to be 2%, 10%, and 30% referring to the figures suggested by "Life-cycle Post Plastic Measures" from the Korean government. In this study, a physical separation method was developed as a recycling approach for waste PET. A result of cost-benefit analysis was conducted to evaluate the economic viability of the recycling process based on changes in the recycling rate. The findings indicated that a recycling rate of waste PET was 30% or higher resulted in a cost-benefit ratio (Benefit-cost ratio, BCR) of 1.32, exceeding the threshold of BCR ≥1, which is considered to meet the minimum requirement for cost-benefit balance. As the government's allocation ratio and unit price are expected to increase in the future, the cost-benefit ratio is expected to increase further. This case is expected to serve as a pilot initiative for waste PET recycling and foster profit creation for businesses in similar industries.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.189-197
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• 2023

Purpose. This study aimed to compare and evaluate the shear bond strength between various temporary prostheses resin blocks fabricated by subtractive and additive manufacturing methods bonded to self-curing reline resin. Materials and methods. The experimental groups were divided into 4 groups according to the manufacturing methods of the resin block specimens and each specimen was fabricated by subtractive manufacturing (SM), additive manufacturing stereolithography apparatus manufacturing (AMS), additive manufacturing digital light processing manufacturing (AMD) and conventional self-curing (CON). To bond the resin block specimens and self-curing resin, the reline resin was injected and polymerized into the same location of each resin block using a silicone mold. The shear bond strength was measured using a universal testing machine, and the surface of the adhesive interface was examined by scanning electron microscopy. To compare between groups, one-way ANOVA was done followed by Tukey post hoc test (α = 0.05). Results. The shear bond strength showed higher values in the order of CON, SM, AMS, and AMD group. There were significant differences between CON and AMS groups, as well as between CON and AMD groups. but there were no significant differences between CON and SM groups (P > .05). There were significant differences between SM and AMD groups, but there were no significant differences between SM and AMS groups. The AMS group was significantly different from the AMD group (P < .001). The most frequent failure mode was mixed failures in CON and AMS groups, and adhesive failures in SM and AMD groups. Conclusion. The shear bond strength of SM group showed lower but not significant bond strength compared to the CON group. The additive manufacturing method groups (AMS and AMD) showed significantly lower bond strength than the CON group, with the AMD group the lowest. There was also a significant difference between the AMD and SM group.

• Journal of Life Science
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• v.33 no.12
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• pp.1015-1024
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• 2023

Antibiotics have greatly contributed to the treatment and prevention of bacterial diseases in humans, animals, and fish. However, antibiotic misuse has led to the emergence and spread of multidrug-resistant bacteria. In addition to antibiotic discovery research, efforts are being made to combat such multidrug-resistant bacteria using antimicrobial agents, antioxidants, host immune enhancement, probiotics, and bacteriophages, as well as various symptomatic therapies. To discover novel bioactive compounds, it is crucial to adopt approaches that incorporate fresh ideas, new targets, innovative techniques, and untapped resources. Halophytes are plants that grow in high-salt soils and are known to adapt to salt-induced stress through unique metabolic processes that produce secondary metabolites. This study aimed to investigate the effects of extracts of halophytes native to Korea on oxidative stress and to determine whether they exert inhibitory activity against biofilms, which are major pathogenic factors of infectious bacteria. The Acinetobacter baumannii strain ATCC 17978, a representative drug-resistant bacterium, was used to measure anti-biofilm activity. The results showed that Aster spathulifolius, Carex kobomugi, Rosa rugosa, and Asparagus cochinchiensis exerted strong antioxidant and anti-biofilm effects without affecting bacterial growth itself. The halophytes used in this study are promising candidates for the development of pharmaceutical agents with antioxidant and antimicrobial properties.

• Korean Journal of Heritage: History & Science
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• v.56 no.3
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• pp.138-156
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• 2023

Some of the metal cultural heritage that make up a considerable proportion of Korea's cultural heritage have been installed and displayed outdoors due to their own functions, roles, and scale. Therefore, more diverse and complex damages can occur outdoors than they are in a stable environment. Therefore, it is necessary to combine accurate diagnosis and systematic survey methods in order to utilize basic data obtained from research results as data for the long-term and continuous conservation management as well as to do the research to diagnose the conservation status of outdoor cultural heritage. The clepsydra(hereinafter referred to as Jagyeongnu) of Changgyeonggung Palace, the National Treasure has been installed and displayed outdoors since it was manufactured. Though regular conservation and maintenance of the Jagyeongnu have been carried out, damage still occurred. Therefore, the scientific research on Jagyeongnu to diagnose the state of conservation was conducted prior to the full-scale conservation treatment. First, the state of conservation was investigated with an examination of basic data, macroscopic inspections and past records of repair history according to the purpose of the research. More detailed examinations were also conducted through the 3D scan, surface pattern investigation, and color difference analysis, and the analysis on materials and contaminants were conducted through P-XRF, FT-IR, and Py-GC/MS. The scientific research reveals that squalane and silicone oil have been applied in the past for conservation treatment and directly exposed to outdoor environmental factors, which caused damage to Jagyeongnu and contaminants such as dust adhered thickly to its surface, accelerating severe damage. A greater incidence of damage was found around the part with relatively high exposure effect, which corresponded with the tendency identified by grouping color difference data. As a result of integrating various research methodologies to diagnose the state of conservation and secure basic data, the causes and types of damage were identified. Furthermore, the process of obtaining digital data to be utilized in various ways, and the color difference analysis presenting visible damage as scientific data and identifying the tendency of damage patterns were confirmed to have been effective.

• Information Systems Review
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• v.19 no.2
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• pp.1-19
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• 2017

Original scripts of e-learning lectures for the CEOs of corporation S were analyzed using topic analysis, which is a text mining method. Twenty-two topics were extracted based on the keywords chosen from five-year records that ranged from 2011 to 2015. Research analysis was then conducted on various issues. Promising topics were selected through evaluation and element analysis of the members of each topic. In management and economics, members demonstrated high satisfaction and interest toward topics in marketing strategy, human resource management, and communication. Philosophy, history of war, and history demonstrated high interest and satisfaction in the field of humanities, whereas mind health showed high interest and satisfaction in the field of in lifestyle. Studies were also conducted to identify topics on the proportion of content, but these studies failed to increase member satisfaction. In the field of IT, educational content responds sensitively to change of the times, but it may not increase the interest and satisfaction of members. The present study found that content production for CEOs should draw out deep implications for value innovation through technology application instead of simply ending the technical aspect of information delivery. Previous studies classified contents superficially based on the name of content program when analyzing the status of content operation. However, text mining can derive deep content and subject classification based on the contents of unstructured data script. This approach can examine current shortages and necessary fields if the service contents of the themes are displayed by year. This study was based on data obtained from influential e-learning companies in Korea. Obtaining practical results was difficult because data were not acquired from portal sites or social networking service. The content of e-learning trends of CEOs were analyzed. Data analysis was also conducted on the intellectual interests of CEOs in each field.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.147-160
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• 2015

In 2014, on 31 August and 1 September, the emissions of $CH_4$, $CO_2$, and $O_2$ gases were measured six times using the closed chamber method from exposed tidal flat sediments in the same position relative to the low point of the tidal cycle in the Eoeun-ri, Taean-gun, on the Mid-western Coast of Korea. The concentrations of $CH_4$ in the air sample collected in the chamber were measured using gas chromatography with an EG analyzer, model GS-23, within 6 hours of collection, and the other gases were measured in real time using a multi-gas monitor. The gas emission fluxes (source (+), and sink (-)) were calculated from a simple linear regression analysis of the changes in the concentrations over time. In order to see the surrounding parameters (water content, temperature, total organic carbon, average mean size of sediments, and the temperature of the inner chamber) were measured at the study site. On the first day, across three measurements during 5 hours 20 minutes, the observed $CO_2$ flux absorption was -137.00 to $-81.73mg/m^2/hr$, and the $O_2$ absorption, measured simultaneously, was -0.03 to $0.00mg/m^2/hr$. On the second day using an identical number of measurements, the $CO_2$ absorption was -20.43 to $-2.11mg/m^2/hr$, and the $O_2$ absorption -0.18 to $-0.14mg/m^2/hr$. The $CH_4$ absorption before low tide was $-0.02mg/m^2/hr$ (first day, Pearson correlation coefficient using the SPSS statistical analysis is -0.555(n=5, p=0.332, pronounced negative linear relationship)), and $-0.15mg/m^2/hr$ (second day, -0.915(n=5, p=0.030, strong negative linear relationship)) on both measurement days. The emitted flux after low tide on both measurement days reached a minimum of $+0.00mg/m^2/hr$ (+0.713(n=5, p=0.176, linear relationship which can be almost ignored)), and a maximum of $+0.03mg/m^2/hr$ (+0.194(n=5, p=0.754, weak positive linear relationship)) after low tide. However, the absolute values of the $CH_4$ fluxes were analyzed at different times. These results suggest that rate for $CH_4$ fluxes, even the same time and area, were influenced by changes in the tidal cycle characteristics of surface sediments for understanding their correlation with these gas emissions, and surrounding parameters such as physiochemical sediments conditions.

• Journal of Korean Society of Forest Science
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• v.45 no.1
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• pp.26-36
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• 1979

Through several trials that has done for making the fertilizing-counter plan on the soil improving species, some results have been got as follows; 1. In the non-phosphorus dressing plots soil improving species have very poor survial ratio and show us to be died step by step. It may be resons that root can not make the nodule in case of non-phosphorus dressing and so tree could not absorb the nitrogen nutrient fixed by the nodule. And root competition with the weedy speces for utilizing the nutrient and oxygen in the soil could be reasons when planting in the heavy weedy rooting site. 2. Triple super phosphate, Fused Mg Phosphate and Fused super phosphate have showed the remarkable effects on the growth of soil improving species within 3rd year after planting. But Koreaan tablet fertilizer(9-12-4) for forest purpose have reacted considerably lower effect in comparision with the above powder and grain type phosphorous fertilizer. 3. In case of tablet type fertilizer tree root will have very little phosphorus absorbing surface because phosphorus can be utilized only from the tablet surface and root can not penetrate into the tablet. This my be reson to show the poor dressing reaction of tablet fertilizer but tablet fertilizer has a possibility to be utilized during long years as a sympton in photo 6. So tablet fertilizer can have a recommendation to dress much fertilizer at p]anting year and then tree root can get much more chance for absorbing the phosphorus that could keep the high survival and for utilizing it during many years without after dressing. 4. The granurar and powder type phosphate can develop the dense root mat like photo 8 because of giving the large surface for absorbing the phosphorus and weedy root can approch to the nodule for taking the nitrogen element. So this type seems to present better effect than tablet type to control the soil movement, stem weight as 200g per meter(l meter long${\times}$0.1m width). When added the lime any effect could not be found and rather give the negative effect. So Lespedeza seed sowing and phosphorus dressing system seems us to be very reasonable method for covering the raw material of basket making, fodder and fuel wood supply. 7. Fused Mg phosphate and Fused super phosphate are good fertilizer to the soil improving species and dressing more than 30g per seedling can be recommendable amount. 5. In the unproductive and dry soil with phosphorus fertilizer Robinia pseudoacacia and Alnus firnui can grow more than 2.3m in height at 3rd year and Alnus inokumae have the rapid height growth that is more than 1.8m at 2nd year. Depending on the growth situation like the above example minirotated management has possibilities and rapid covering of erosed land can be done with the soil improving species and phosphorus fertilizer. 6. In the Lespedeza sowing plot with 40g Fused Mg phosphate dressing per meter in the eroded and unproductive forest soil Lespedeza have completely covered this poor land and produced the green.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.227-237
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• 2008

Arsenic has recently become of the most serious environmental concerns, and the worldwide regulation of arsenic fur drinking water has been reinforced. Arsenic contaminated groundwater and soil have been frequently revealed as well, and arsenic contamination and its treatment and measures have been domestically raised as one of the most important environmental issues. Arsenic behavior in geo-environment is principally affected by oxides and clay minerals, and particularly iron (oxy)hydroxides have been well known to be most effective in controlling arsenic. Among a number of iron (oxy)hydroxides, for this reason, 2-line ferrihydrite was selected in this study to investigate its effect on arsenic behavior. Adsorption of 2-line ferrihydrite was characterized and compared between As(III) and As(V) which are known to be the most ubiquitous species among arsenic forms in natural environment. Two-line ferrihydrite synthesized in the lab as the adsorbent of arsenic had $10\sim200$ nm for diameter, $247m^{2}/g$ for specific surface area, and 8.2 for pH of zero charge, and those representative properties of 2-line ferrihydrite appeared to be greatly suitable to be used as adsorbent of arsenic. The experimental results on equilibrium adsorption indicate that As(III) showed much stronger adsorption affinity onto 2-line ferrihydrite than As(V). In addition, the maximum adsorptions of As(III) and As(V) were observed at pH 7.0 and 2.0, respectively. In particular, the adsorption of As(III) did not show any difference between pH conditions, except for pH 12.2. On the contrary, the As(V) adsorption was remarkably decreased with increase in pH. The results obtained from the detailed experiments investigating pH effect on arsenic adsorption show that As(III) adsorption increased up to pH 8.0 and dramatically decreased above pH 9.2. In case of As(V), its adsorption steadily decreased with increase in pH. The reason the adsorption characteristics became totally different depending on arsenic species is attributed to the fact that chemical speciation of arsenic and surface charge of 2-line ferrihydrite are significantly affected by pH, and it is speculated that those composite phenomena cause the difference in adsorption between As(III) and As(V). From the view point of adsorption kinetics, adsorption of arsenic species onto 2-line ferrihydrite was investigated to be mostly completed within the duration of 2 hours. Among the kinetic models proposed so for, power function and elovich model were evaluated to be the most suitable ones which can simulate adsorption kinetics of two kinds of arsenic species onto 2-line ferrihydrite.

• Korean Journal of Soil Science and Fertilizer
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• v.23 no.2
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• pp.87-93
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• 1990

A statistical model to predict soil temperature from the ambient meteorological factors including mean, maximum and minimum air temperatures, precipitation, wind speed and snow depth combined with Fourier time series expansion was developed with the data measured at the Suwon Meteorolical Service from 1979 to 1988. The stepwise elimination technique was used for statistical analysis. For the yearly oscillation model for soil temperature with 8 terms of Fourier expansion, the mean square error was decreased with soil depth showing 2.30 for the surface temperature, and 1.34-0.42 for 5 to 500-cm soil temperatures. The $r^2$ ranged from 0.913 to 0.988. The number of lag days of air temperature by remainder analysis was 0 day for the soil surface temperature, -1 day for 5 to 30-cm soil temperature, and -2 days for 50-cm soil temperature. The number of lag days for precipitaion, snow depth and wind speed was -1 day for the 0 to 10-cm soil temperatures, and -2 to -3 days for the 30 to 50-cm soil teperatures. For the statistical soil temperature prediction model combined with the yearly oscillation terms and meteorological factors as remainder terms considering the lag days obtained above, the mean square error was 1.64 for the soil surfac temperature, and ranged 1.34-0.42 for 5 to 500cm soil temperatures. The model test with 1978 data independent to model development resulted in good agreement with $r^2$ ranged 0.976 to 0.996. The magnitudes of coeffcicients implied that the soil depth where daily meteorological variables night affect soil temperature was 30 to 50 cm. In the models, solar radiation was not included as a independent variable ; however, in a seperated analysis on relationship between the difference(${\Delta}Tmxs$) of the maximum soil temperature and the maximum air temperature and solar radiation(Rs ; $J\;m^{-2}$) under a corn canopy showed linear relationship as $${\Delta}Tmxs=0.902+1.924{\times}10^{-3}$$ Rs for leaf area index lower than 2 $${\Delta}Tmxs=0.274+8.881{\times}10^{-4}$$ Rs for leaf area index higher than 2.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.230-236
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• 2010

Jeju Island is a volanic island which is located about 96 km south of Korean Peninsula. Volcanic ejecta, and volcaniclastic materials are widespread as soil parent materials throughout the island. Soils on the island have the characteristics of typical volcanic ash soils. This study was conducted to reclassify Jeju series based on the second edition of Soil Taxonomy and to discuss the formation of Jeju series in Jeju Island. Morphological properties of typifying pedon of Jeju series were investigated, and physico-chemical properties were analyzed according to Soil survey laboratory methods manual. The typifying pedon has dark brown (10YR 3/3) silt clay loam A horizon (0~22 cm), strong brown (7.5YR 4/6) silty clay BAt horizon (22~43 cm), brown (7.5YR 4/4) silty clay Bt1 horizon (43~80 cm), brown (7.5YR 4/6) silty clay loamBt2 horizon (80~105 cm), and brown (10YR 5/4) silty clay loam Bt3 horizon (105~150 cm). It is developed in elevated lava plain, and are derived from basalt, and pyroclastic materials. The typifying pedon contains 1.3~2.1% oxalate extractable (Al + 1/2 Fe), less than 85%phosphate retention, and higher bulk density than 0.90 Mg $m^{-3}$. That can not be classified as Andisol. But it has an argillic horizon from a depth of 22 to 150 cm, and a base saturation (sum of cations) of less than 35% at 125 cm below the upper boundary of the argillic horizon. That can be classified as Ultisol, not as Andisol. Its has 0.9% or more organic carbon in the upper 15 cm of the argillic horizon, and can be classified as Humult. It dose not have fragipan, kandic horizon, sombric horizon, plinthite, etc. in the given depths, and key out as Haplohumult. A hoizon (0~22 cm) has a fine-earth fraction with both a bulk density of 1.0 Mg $cm^{-3}$ or less, and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Thus, it keys out as Andic Haplohumult. It has 35% or more clay at the particle-size control section, and has thermic soil temperature regime. Jeju series can be classified as fine, mixed, themic family of Andic Haplohumults, not as ashy, thermic family of Typic Hapludands. In the western, and northern coastal areas which have a relatively dry climate in Jeju Island, non Andisols are widely distributed. Mean annual precipitation increase 110 mm, and mean annual temperature decrease $0.8^{\circ}C$ with increasing elevation of 100m. In the western, and northern mid-mountaineous areas Andisols, and non Andisols are distributed simultaneously. Jeju series distributed mainly in the western and northern mid-mountaineous areas are developed as Ultisols with Andic subgroup.