• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.419-425
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• 2023

This paper presents the research results of analyzing the high-temperature corrosion characteristics of three currently commercialized heat exchanger tube materials under actual operating conditions of a biomass power plant. In order to precisely analyze the high-temperature corrosion characteristics of these materials, a high-temperature corrosion evaluation device was installed in the power plant equipment, which allows for adjusting the surface temperature of the heat exchanger tubes. Experiments were conducted for approximately 300 hours under various temperature and operating conditions. In this study, the commercialized heat exchanger tube materials used were SA213T12, SA213T22, and SA213T91 alloys. In order to objectively analyze the high-temperature corrosion characteristics of each material, an international standard-based process to remove corrosion products was applied to obtain the weight change of the specimens, and the average thickness loss and corrosion rate were derived. Thus, the high-temperature corrosion results for each condition were quantitatively compared and analyzed. In addition, in order to increase the reliability of the high-temperature corrosion evaluation method introduced in this study, the surface and cross-sectional corrosion of the specimens were confirmed by using scanning electron microscopy and energy-dispersive X-ray analysis. Based on these analysis results, it was found that the corrosion resistance of the commercial heat exchanger materials increases as the content of chrome and nickel in the composition increases. Additionally, it was found that the corrosion phenomenon is rapidly accelerated as the surface temperature increases. Finally, the replacement period (lifetime) of the heat exchanger tubes under each condition could be inferred through this study.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.1-7
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• 2013

The purpose of this study was to provide basic information for breeding cowpeas (Vigna unguiculata L.) by investigating the crop characteristics of 245 accessions of cowpea collected in Korea and abroad. All specimens flowered within 41 to 50 days (51.5%) or 51 to 60 days (43.7%) of sowing and matured 21 to 30 days (53.9%) or 31 to 40 days (23.7%) from flowering. Thus, the total time from sowing to maturity was either 71 to 80 days (26.9%) or 81 to 90 days (23.4%) for all specimens. The accessions were classified into indeterminate type (72.7%), intermediate type (25.7%) and determinate type (1.6%) based on growth; prostrate type (78.8%) and erect type (21.2%) based on plant type; heart shape (98.4%) and lanceolate (1.6%) based on leaflet shape; and purple (85.2%), white (13.6%) and light green (1.2%) based on corolla color. The accessions were classified into brown (54.7%) and yellowish brown (37.6%) based on color at pod maturity; and downward (90.6%), middle (5.7%) and standing upright (3.7%) based on pod setting position. Seed coat color varied as 25.3% were brown, 23.3% were black, and 20.8% were white. Seed shape also varied as 66.9% were egg-shaped, 24.9% were rectangular and 8.2% were kidney-shaped. Pod lengths ranged from 10.1-20.0 cm and from 20.1-30.0 cm in 89.0% and 8.6% of specimens, respectively. There were 12.1-15.0, 9.1-12.0, and 15.1-18.0 seeds per pod in 62.0%, 25.7% and 9.1% of specimens, respectively. The weight of one hundred seeds ranged from 15.1-20.0 g (37.6%) and 10.1-15.0 g (28.6%). Seed yields per plant were 100.1-200.0 g (52.7%), less than 100 g (22.9%), and 200.1-300.0 g (15.9%). The starch content in the seeds of the seven selected resources ranged from 44.1 to 57.0% while the protein content ranged from 23.3 to 27.5% with significant differences. The sucrose content ranged from 1.46 to 2.03%, also with significant differences.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.10
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• pp.1638-1648
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• 2013

To promote the utilization of wild edible plants, this study examined blanching, drying, and fermentation as methods for enhancing the functionality of Hemerocallis coreana Nakai. Specimens fermented for 24 hours at a fermentation temperature of $50^{\circ}C$, with a relative humidity of 65%, contained the highest amount of organic acid (18,109.82 mg/100 g). For the blanched; specimens, total organic acid content decreased about 30% compared with the freeze-dried specimens. The main organic acid of Hemerocallis coreana Nakai was confirmed as succinic acid. After fermentation, free sugars decreased; in particular, specimens fermented at a relative humidity of 80% showed a 32~75% reduction in free sugar compared with the freeze-dried specimens. In terms of amino acid content, Hemerocallis coreana Nakai was mainly composed of valine, isoleucine, and phenylalanine. In fermented specimens the total amino acid content was highest in a moderately fermented (17 hr) specimen, (1,010.71 mg/100 g fresh wt.), but decreased in the maximally fermented (24 hr) specimen. The longer the fermentation, the higher the decrease in non-essential amino acids content, while the content of more essential amino acids consistently increased. In conclusion, since seasoned Hemerocallis coreana Nakai contains a considerable amount of glutamine and asparagine, it has a fresh sour and sweet taste; thus, it will likely be a highly preferred wild edible plant. Also, with an increase of essential amino acids after fermentation, Hemerocallis coreana Nakai is excellent in terms of nutrition. Thus, it may be possible to utilize fermented Hemerocallis coreana Nakai in the development of diverse products.

• Journal of Conservation Science
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• v.26 no.1
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• pp.95-107
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• 2010

Biochemical research was carried out on 4 human skeletal remains from historical lime-layered tombs assigned to the Joseon Dynasty in Oknam-ri, Seocheon. The preservation of femur was evaluated by stereoscopic microscopy and scanning electron microscopy. Most of specimens showed good histological preservation. The histological results proved to be a good potentiality for biochemical analysis using bio-molecules. The amelogenin gene and mitochondrial DNA (mtDNA) analyses revealed that three specimens perhaps have maternal consanguinity due to sharing with mtDNA haplogroup D4b1, and two specimens buried in the same tomb were a couple in Gatjaegol site. Carbon and nitrogen stable isotope analysis indicated that four deads diet were built around C3 plant as rice, barley, wheat and bean. In this study we characterized genetic and diet features from the social stratum who could make lime-layered tombs during period of the Joseon Dynasty. The results suggest that biochemical research using the human skeletal remains from the Joseon Dynasty has the great potential and reasonable value for archaeology, anthropology, and population genetics.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.81-89
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• 1996

It is very important for ultrasonic test method to evaluate the integrity of the class I components in nuclear power plants. However, as the rltrasonic test is affected by internal structures and configurations of test materials, backscattering, that is, time invariant noise is generated in large grain size materials. Due to the above reason, the received signal results in low signal to noise(S/N) ratio. Split spectrum processing(SSP) technique is effective to suppress the grain noise. The conventional SSP technique. however, has been applied to unique algorithm. This paper shows that MPO(minimization and polarity threshold) algorithm which two algorithms are applied simulatancously, was utilized, the signal processing time was shorten by using the new constant-Q SSP with the FIR filter which frequency to bandwidth ratio is constant and the optimum parameters were analysed for the signal processing to longitudinal wave and shear wave with the same requirements of inspection on nuclear power plant site. Moreover, the new ultrasonic test instrument, the reference block of the same product form and material specification, stainless stell test specimens and copper test specimens block of the same fabricated for the application of new SSP technique. As the result of experimental test with new ultrasonic test instrument and test specimens, the signal to noise ratio was improved by appying the new SSP technique.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.276-284
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• 2022

In this study, performance evaluation and rheological characteristics were analyzed for recycling the fine powder of nuclear power plant dismantled waste concrete as a solidifying agent for radioactive waste disposal. The radioactive concrete fine powder was used to prepare a simulated sample, and the test specimen was prepared using Di-water, CoCl₂, and 1 mol CsCl aqueous solution as mixing water. Regardless of the aggregate mixing ratio and the type of mixing water, it satisfies the performance standard of 3.45 MPa for compressive strength at 28 days of age. All specimens satisfied the criteria for submersion strength, and the thermal cycle compressive strength satisfies the criteria for all specimens except Plain-50. As a result of evaluating the rheological properties of the solidifying agent, it was found that the increase in the aggregate mixing rate decreased the yield stress and plastic viscosity. The leaching index for cobalt and cesium of all specimens was 6 or higher, which satisfies the standard. In order to secure the stable performance of the solidifying agent, it is considered effective to use 40 % or less of the aggregate component in the solidifying agent.

• Korean Journal of Plant Resources
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• v.30 no.4
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• pp.410-426
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• 2017

To identify the flora of the vascular plants in the Anmyeon Island, field surveys were conducted from June, 2015 to August, 2016. Based on the collected specimens, the vascular plants of the Anmyeon Island were summarized as 717 taxa: 119 families, 400 genera, 632 species, 5 subspecies, 73 varieties and 7 formas. Among the 717 identified taxa, 17 rare plants designated by the Koren Forest Service according to the IUCN valuation species were described: 3 taxa of critically endangered species (CR), 1 taxa of endangered species (EN), 6 taxa of least concerned species (LC), 7 taxa of vulnerable species (VU). 99 taxa of floristic regional indicator plants specially designated by Ministry of Environment also were identified. In addition, 6 Korean endemic species such as Forsythia koreana Nakai and Hemerocallis taeanensis S.S.Kang & M.G.Chung, and 91 naturalized plants such as Rumex acetocella L., Amaranthus lividus L. and Diodia teres Walter etc. were described.

• Korean journal of applied entomology
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• v.60 no.3
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• pp.323-329
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• 2021

This study investigated the seasonal distribution of ticks in Boeun, Chungbuk, South Korea, from 2016 to 2020. Over the five-year period, ticks were collected annually from four different sites. A total of 17,704 ticks belonging to three tick species (Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis) were collected. H. longicornis was the dominant species across all four sites with the highest density of 68.40% of the total collected specimens, followed by H. flava (3.53%) and I. nipponensis (0.06%). The larvae of unidentified species were also collected: 11.81 T.I. (28.01%). The H. longicornis population peaked during the spring season (May-June), whereas the larval population peaked during August and September. H. longicornis was collected the most from four sites (coniferous forest, broad-leaf forest, mountain path, and copse), with the exception of the larvae, which was collected the most in grassland and grave. H. flava was collected from all sites, but in a small proportion. The SFTS virus was not found in any of the 828 pools of ticks during 2016-2020. Based on the results of this study, the continuous surveillance of the tick population is recommended to mitigate the spread of diseases by these vectors.

• Journal of Microbiology and Biotechnology
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• v.30 no.3
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• pp.404-416
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• 2020

Bacteria that are resistant to high temperatures and alkaline environments are essential for the biological repair of damaged concrete. Alkaliphilic and halotolerant Bacillus sp. AK13 was isolated from the rhizosphere of Miscanthus sacchariflorus. Unlike other tested Bacillus species, the AK13 strain grows at pH 13 and withstands 11% (w/v) NaCl. Growth of the AK13 strain at elevated pH without urea promoted calcium carbonate (CaCO₃) formation. Irregular vaterite-like CaCO₃ minerals that were tightly attached to cells were observed using field-emission scanning electron microscopy. Energy-dispersive X-ray spectrometry, confocal laser scanning microscopy, and X-ray diffraction analyses confirmed the presence of CaCO₃ around the cell. Isotope ration mass spectrometry analysis confirmed that the majority of CO₃^2- ions in the CaCO₃ were produced by cellular respiration rather than being derived from atmospheric carbon dioxide. The minerals produced from calcium acetate-added growth medium formed smaller crystals than those formed in calcium lactate-added medium. Strain AK13 appears to heal cracks on mortar specimens when applied as a pelletized spore powder. Alkaliphilic Bacillus sp. AK13 is a promising candidate for self-healing agents in concrete.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.158-162
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• 2004

Reliability of welded structures in power plant facilities is very important, and their reliability evaluation requires exact materials properties. But, the conventional PQR (Procedure Qualification Record) can hardly reflect the real material properties in the field because the test is only done on specimens with simulated welding. Therefore, a continuous indentation technique is proposed in this study for simple and non-destructive testing of in-field structures. This test measures the indentation load-depth curve during indentation and analyzes the mechanical properties such as the yield strength, tensile strength and work hardening index. This technique has been applied to evaluate the tensile properties of the weldment in the main steam pipe and hot reheater pipe in power plants under construction and in operation.