• Korean Journal of Soil Science and Fertilizer
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• v.31 no.2
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• pp.128-136
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• 1998

Most of total nitrogen in the surface soil exists in organic forms, of which amino acid-N is the major fraction. By-product fertilizers provide soil with humic substances, and humic acid is an essential component of humus. Amino acids(AAs) are easily converted to inorganic-N forms and thus play an important role in N fertility. This experiment was conducted to investigate the contents and distributions of AAs in humic acids which were extracted from the commercial by-product fertilizers of different composting materials. Total contents of AAs in humic acids ranged from 1.2 to 5.6%, of which neutral AAs were the highest with ranges of 0.8~4.5%. AAs contents in fertilizers composted from the plant residues such as leaf litter, sawdust and bark were in an order of neutral>acidic>basic AAs. In contrast, those from animal wastes, such as poultry and pig manures, were in an order of neutral>basic>acidic AAs. Distributions of total, acidic and neutral AAs were in the respective order of leaf litter>sawdust>pig manure>poultry manure>peat, bark>sawdust>leaf litter>peat and leaf litter>sawdust>bark>peat. Distributions of the basic AAs were in the reversed order of the acidic AAs. In bark fertilizer with increasing compost maturity, contents of the acidic AAs were increased in compensation for the decreases in those of neutral and basic AAs. Results demonstrated that distributions of amino acids in humic acid of by-product fertilizers were different from composting raw materials and degrees of humification.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.125-132
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• 2018

In this study, a direct tensile test was planned to identify the tensile performance of UHPC, and the irregularity of cracks, which is a problem of the direct tensile test, was complemented through the introduction of notches at the center of a specimen. In this regard, a number of specimens divided by batch to reduce the deviation of direct tensile test values were fabricated to present reference data with respect to highly reliable direct tensile strength values. In addition, the mechanical properties and reliability of the specimens were examined under the curing conditions of the specified design strength of 120MPa for the steel fiber reinforced concrete with 1.5% fiber volume fraction, which is most suitable for the field application. As a result, the deviation of averages by batch between compressive strength and direct tensile strength did not show a large difference, and all cracks occurred within 20mm in the direct tensile test. At the 95% confidence interval of the direct tensile strength, the range was considerably small in the mean and the standard deviation, and there was no significant difference depending on the curing conditions. The results confirmed that a stable direct tensile test was performed, and highly reliable results were obtained through the fabrication of specimens by batch and test progress.

• Sleep Medicine and Psychophysiology
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• v.5 no.1
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• pp.111-117
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• 1998

Objectives : 'First-night effect' has been a well-known concept since 1960's. It is important because it is one of the major factors to be considered in assessing the reliability of polysomnographic data. However, 'reverse first-night effect' has also been described, resulting in the inconsistency of conceptualization. We attempted to investigate on the first-night effect in adults by having each of them take two nights of polysomnography in a controlled environment. Young healthy adult volunteers were chosen as subjects in order to rule out age- or health-related confounders. Methods : Polysomnography was performed on eight male medical students (mean $age=23.5\;{\pm}\;0.9$) for two nights with Grass model 78 polysomnograph. We scored manually under the standard protocol each epoch of the sleep records. Sleep variables were obtained and compared between the two nights. Results : Sleep period time(SPT) and total sleep time(TST) of the third fraction of night were significantly longer on the first night than on the second night (p<0.05). However, other sleep variables such as percentage of each sleep stage, sleep latency, REM sleep latency, number of waking, and sleep efficiency were not different between the two nights. Conclusion : We could not confirm the existence of first-night effect in this study. In healthy young male adults, it may not happen at all or may happen to a very negligible degree. Young healthy adults may have more adaptability to a new sleep environment. Also, the provision of a reasonably comfortable sleep environment could have helped them with abolition of first-night effect.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.428-433
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• 1999

An objective of this study is to compare the characteristics of coating layer of plasma sprayed fine $Al_2O_3$ and those of layer by commercial $Al_2O_3$(Metco 105). The microstructure of fine $Al_2O_3$ coating layer was denser compared with commercial $Al_2O_3$ coating layer. The surface roughness$(R_a)$ of the layer by the fine $Al_2$O$_3$ was lower compared with that of commercial $Al_2O_3$. Thickness of splat for fine $Al_2O_3$ was $1.4\mu\textrm{m}$ while the commercial $Al_2O_3$ was $3.53\mu\textrm{m}$. The main phase existing in coating layer was of $\gamma-Al_2O_3$ and the fraction of $\alpha-Al_2O_3$ in fine $Al_2O_3$ coating layer was 8.39% and that of commercial $Al_2O_3$ was 13.79%. Microhardness was no great difference between the fine and commercial $Al_2O_3$ but deviation of the fine $Al_2O_3$ coating layer was relatively large. Accordingly, the strength of splat of the coating was expected that fine $Al_2O_3$was lower than commercial $Al_2O_3$ powder.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.233-247
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• 2012

We have researched the distribution and characteristics of seafloor hydrothermal deposits for the development of economic mineral deposits in the Lau Basin, Tonga since 2009. In this study, we interpreted hydrothermal alteration around TA 26 seamounts of the Tofua volcanic arc using X-ray diffraction analysis for bulk sample and preferred-oriented specimen of clay fraction. We used 2 core samples and several surface samples. Plagioclase and quartz are dominant mineral in the basement rock, whereas kaolin mineral and smectite are superior in marine surface sediments. Especially sulfate and sulfide minerals such as gypsum, barite, sphalerite, and pyrite are predominant in the vent sediments. When we compare the mineral composition between basement rock and sea surface sediments, argillic alteration zone composed of kaolin mineral and smectite could be produced by hydrothermal fluids. Based on the downcore variation of mineral assemblages, most portion of MC08H-06 core could be interpreted as argillic alteration zone composed of kaolin mineral and smectite except top 2 cm area. Various sulfate or sulfide minerals and argillic alteration zone suggest a high probability of massive sulfide deposits in the seafloor of the TA 26 seamount.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.3
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• pp.160-166
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• 2001

The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si (X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both ${\varepsilon}$ and ${\alpha}^{\prime}$martensites are formed in ribbon 1 (15.5wt%Mn), while only ${\varepsilon}$ martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of ${\varepsilon}$ martensite is decreased with increasing Mn contents, and those of ${\varepsilon}$ as well ${\alpha}^{\prime}$martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Ms temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. $M_s$ temperatures of the ribbons 1, 2 and 3 annealed at $300^{\circ}C$ for 3 min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and $600^{\circ}C$ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ${\varepsilon}$ and ${\alpha}^{\prime}$martensites decreased because of the presence of ${\alpha}^{\prime}$martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ${\varepsilon}$ martensite increased with increasing annealing temperature.

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.187-195
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• 2014

In this paper, we report new OSL ages of the marine terrace sediments at Suryum fault site, using single grains of quartz, and briefly discuss their chronological implications on the timing of terrace formation along the southeastern coast of Korea. Of 1200 grains measured, 93 quartz grains were found to have OSL properties suitable for dating, the equivalent dose ($D_e$) values of which varied significantly, ranging from 50 Gy to 610 Gy with the overdispersion of $30{\pm}4%$. Applied to the Central Age Model (CAM) and Minimum Age Model (MAM), these quartz grains showed the OSL ages of $83{\pm}4ka$ and $60^{+3}{_{-7}}ka$, respectively, both of which are stratigraphically inconsistent with the previously reported OSL ages of lower $2^{nd}$ terrace (MIS 5a; ~80 ka). However, Finite Mixture Model (FMM) revealed that a small fraction of the measured quartz grains ($6{\pm}4%$) were of the ages ($194{\pm}24ka$) corresponding to MIS 7. Conclusively, based on single grain OSL ages, it would be prudent not to exclude the possibility that the marine terrace sediments at Suryum fault site have formed during MIS 7. Further, our single grain OSL ages imply that multiple grain(single aliquot) OSL dating methods are not applicable to the marine sediments at Suryum fault site.

• Journal of the Korean earth science society
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• v.42 no.6
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• pp.623-631
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• 2021

The increased transport of marine hazardous and noxious substances (HNS) has resulted in frequent HNS spill accidents domestically and internationally. There are about 6,000 species of HNS internationally, and most of them have toxic properties. When an accidental HNS spill occurs, it can destroys the marine ecosystem and can damage life and property due to explosion and fire. Constructing a spectral library of HNS according to wavelength and developing a detection algorithm would help prepare for accidents. In this study, a ground HNS spill experiment was conducted in France. The toluene spectrum was determined through hyperspectral sensor measurements. HNS present in the hyperspectral images were detected by applying the spectral mixture algorithm. Preprocessing principal component analysis (PCA) removed noise and performed dimensional compression. The endmember spectra of toluene and seawater were extracted through the N-FINDR technique. By calculating the abundance fraction of toluene and seawater based on the spectrum, the detection accuracy of HNS in all pixels was presented as a probability. The probability was compared with radiance images at a wavelength of 418.15 nm to select abundance fractions with maximum detection accuracy. The accuracy exceeded 99% at a ratio of approximately 42%. Response to marine spills of HNS are presently impeded by the restricted access to the site because of high risk of exposure to toxic compounds. The present experimental and detection results could help estimate the area of contamination with HNS based on hyperspectral remote sensing.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1239-1247
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• 2020

Sedum kamtschaticum Fisch., a native plant of Korea, has been used in Korean traditional medicine in the form of water extract for its capacity to improve blood circulation and for its antioxidant and anti-inflammatory effects. Since previous research suggests that S. kamtschaticum Fisch. has excellent antioxidant and mushroom tyrosinase inhibition activities, in this study, the root and stem parts of S. kamtschaticum Fisch. are extracted in 70% ethanol (SKS, SKR), fractionated with and in order of n-hexane (SSH), ethyl acetate (SSE, SRE), chloroform (SSC, SRC) and water (SSW, SRW) according to the polarity of each solvent, and tested for its applicability as a cosmetic material. According to the total polyphenol, flavonoid contents and DPPH radical scavenging activity of each fraction, the contents and scavenging activity of the root extractions (SKR) were higher than those of the stem extractions (SKS), ethyl acetate fractions (SSE, SRE) being the most effective. In addition, ethyl acetate fractions had the highest tyrosinase inhibition activity and melanin synthesis inhibition activity used on B16F10 melanoma cells, at the concentration of 10 ㎍/mL. HPLC analysis detected a variety of polyphenols including gallic acid and quercetin. This study suggests the potential role of S. kamtschaticum Fisch. as a natural cosmeceutical material.

• Animal Bioscience
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• v.35 no.7
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• pp.999-1009
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• 2022

Objective: To improve the feeding value of rice straw (RS), this study evaluated the potential of rice straw fermented with Pleurotus sajor-caju (FRS) as dairy goat feed. Methods: Spent Pleurotus sajor-caju mushroom substrate was used as fungi inoculum to break the lignocellulose linkage of rice straw, which was solid-fermented at 25℃ to 30℃ for 8 weeks. The ruminal degradation of pangolagrass hay (PG), FRS, and RS were measured in situ for 96 hours in three dry Holstein cows, respectively. Effect of fungi fermented RS on milking performance was studied in feeding trials. A total of 21 Alpine goats a trial were divided into 3 groups: a control group in which PG accounted for 15% of the diet dry matter, and FRS or RS was used to replace the PG in the control group. Goats were fed twice a day under two 28-day trial in individual pens. Meanwhile, a 3×3 Latin square trial (14 days/period) was conducted to study the rumen digestion of three diets by using three fistulated dry goats. Rumen contents were collected for metabolite analyses every one to three hours on the last two days. Results: In situ study showed that fermentation could elevate the rumen degradable fraction and effective degradability of RS (p<0.05). Effective degradability of FRS dry matter was significantly increased from 29.5% of RS to 41.7%. Lactating trial results showed that dry matter intake and milk yield in the PG group and FRS group were similar and higher than those in RS group (p<0.05). The concentration of propionic acid and total volatile fatty acid in the RS group tended to be lower than those in PG group (p<0.10). There were no differences in rumen pH value and ammonia nitrogen level among the groups tested. Conclusion: Fermentation of rice straw by spent Pleurotus sajor-caju mushroom substrate could substantially enhance its feeding value to be equivalent to PG as an effective fiber source for dairy goat. The fermented rice straw is recommended to account for 15% in diet dry matter.