• Title/Summary/Keyword: Mass Properties

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Mesocarbon microbead densified matrix graphite A3-3 for fuel elements in molten salt reactors

  • Wang, Haoran;Xu, Liujun;Zhong, Yajuan;Li, Xiaoyun;Tang, Hui;Zhang, Feng;Yang, Xu;Lin, Jun;Zhu, Zhiyong;You, Yan;Lu, Junqiang;Zhu, Libing
    • Nuclear Engineering and Technology
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    • v.53 no.5
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    • pp.1569-1579
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    • 2021
  • This study aims to provide microstructural characterization for the matrix graphite which molten salt reactors (MSRs) use, and improve resistance to molten salt infiltration of the matrix graphite for fuel elements. Mesocarbon microbeads (MCMB) densified matrix graphite A3-3 (MDG) was prepared by a quasi-isostatic pressure process. After densification by MCMBs with average particle sizes of 2, 10, and 16 ㎛, the pore diameter of A3-3 decreased from 924 nm to 484 nm, 532 nm, and 778 nm, respectively. Through scanning electron microscopy, the cross-section energy spectrum and time-of-flight secondary ion mass spectrometry, resistance levels of the matrix graphite to molten salt infiltration were analyzed. The results demonstrate that adding a certain proportion of MCMB powders can improve the anti-infiltration ability of A3-3. Meanwhile, the closer the particle size of MCMB is to the pore diameter of A3-3, the smaller the average pore diameter of MDG and the greater the densification. As a matrix graphite of fuel elements in MSR was involved, the thermal and mechanical properties of matrix graphite MDG were also studied. When densified by the MCMB matrix graphite, MDGs can meet the molten salt anti-infiltration requirements for MSR operation.

A novel combination of sodium metabisulfite and a chemical mixture based on sodium benzoate, potassium sorbate, and sodium nitrite for aerobic preservation of fruit and vegetable discards and lactic acid fermentation in a total mixed ration for ruminants

  • Ahmadi, Farhad;Lee, Won Hee;Kwak, Wan Sup
    • Animal Bioscience
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    • v.34 no.9
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    • pp.1479-1490
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    • 2021
  • Objective: Our recent findings confirmed the effectiveness of sodium metabisulfite (SMB) in controlling the growth of undesirable microorganisms in fruit and vegetable discards (FVD); however, lactic acid bacteria (LAB) are susceptible to its antibacterial effects. Two series of experiments were conducted to enable the survivability of LAB during silage fermentation of a total mixed ration (TMR) containing SMB-treated FVD. Methods: In Exp. 1, the objective was to isolate a strain of LAB tolerable to the toxic effect of SMB. In Exp. 2, the SMB load was minimized through its partial replacement with a chemical mixture (CM) based on sodium benzoate (57%), potassium sorbate (29%), and sodium nitrite (14%). FVD was treated with SMB + CM (2 g each/kg biomass) and added to the TMR at varying levels (0%, 10%, or 20%), with or without KU18 inoculation. Results: The KU18 was screened as a presumptive LAB strain showing superior tolerance to SMB in broth medium, and was identified at the molecular level using 16S rRNA gene sequence analysis as Lactobacillus plantarum. Inoculation of KU18 in TMR containing SMB was not successful for the LAB development, biomass acidification, and organoleptic properties of the resultant silage. In Exp. 2, based on the effectiveness and economic considerations, an equal proportion of SMB and CM (2 g each/kg FVD) was selected as the optimal loads for the subsequent silage fermentation experiment. Slight differences were determined in LAB development, biomass acidification, and sensorial characteristics among the experimental silages, suggesting the low toxicity of the preservatives on LAB growth. Conclusion: Although KU18 strain was not able to efficiently develop in silage mass containing SMB-treated FVD, the partial substitution of SMB load with the CM effectively alleviated the toxic effect of SMB and allowed LAB development during the fermentation of SMB + CM-treated FVD in TMR.

How to Design Membrane Chromatography for Bioseparations: A Short Review (바이오분야 분리용 막크로마토그래피 설계 방안)

  • Park, Inho;Yoo, Seung Yeon;Park, Ho Bum
    • Membrane Journal
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    • v.31 no.2
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    • pp.145-152
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    • 2021
  • While there are increasing demands on biomolecules separation, resin chromatography lacks in terms of throughput and membrane chromatography is an alternative with high binding capacity and enhanced mass transfer properties. Unlike typical membrane processing, where the performance can only be empirically assessed, understanding how mechanisms work in membrane chromatography is decisive to design biospecific processing. This short review covers three separation mechanisms, including affinity interaction modes for selectively capturing bulk molecules using biospecific sites, ion exchange modes for binding biomolecules using net charges and hydrophobic interaction modes for binding targeted, hydrophobic species. The parameters in designing membrane chromatography that should be considered operation-wise or material-wise, are also further detailed in this paper.

Structural Adjustment of In-Situ Surface-Modified Silica Matting Agent and Its Effect on Coating Performance

  • Xu, Qingna;Ji, Tongchao;Tian, Qingfeng;Su, Yuhang;Niu, Liyong;Li, Xiaohong;Zhang, Zhijun
    • Nano
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    • v.13 no.12
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    • pp.1850137.1-1850137.9
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    • 2018
  • A series of silica surface-capped with hexamethyldisilazane (denoted as $H-SiO_2$) were prepared by liquid-phase in-situ surface-modification method. The as-obtained $H-SiO_2$ was incorporated into acrylic amino (AA) baking paint to obtain AA/$H-SiO_2$ composite extinction paints and/or coatings. $N_2$ adsorption-desorption tests were conducted to determine the specific surface area as well as pore size and pore volume of $H-SiO_2$. Moreover, the effects of $H-SiO_2$ matting agents on the physical properties of AA paint as well as the gloss and transmittance of AA-based composite extinction coatings were investigated. Results show that $H-SiO_2$ matting agents possess a large specific surface area and pore volume than previously reported silica obtained by liquid-phase method. Besides, they have better dispersibility in AA baking paint than the unmodified silica. Particularly, $H-SiO_2$ with a silica particle size of $6.7{\mu}m$ and the dosage of 4% (mass fraction) provides an extinction rate of 95.2% and a transmittance of 79.3% for the AA-based composite extinction coating, showing advantages over OK520, a conventional silica matting agent. Along with the increase in the silica particle size, $H-SiO_2$ matting agents cause a certain degree of increase in the viscosity of AA paint as well as a noticeable decrease in the gloss of the AA-based composite extinction coating, but they have insignificant effects on the hardness and adhesion to substrate of the AA-based composite coatings. This means that $H-SiO_2$ matting agents could be well applicable to preparing low-viscosity and low-gloss AA-based matte coatings.

Characterization of the Bacteriocin from Enterococcus faecium CJNU 2008 (Enterococcus faecium CJNU 2008 균주 생산 박테리오신의 특성 규명)

  • Seo, Souk-Jin;Yang, Jung-Mo;Moon, Gi-Seong
    • Journal of Food Hygiene and Safety
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    • v.33 no.6
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    • pp.516-520
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    • 2018
  • Bacteriocin is a proteinaceous compound produced by microorganisms showing antimicrobial activities. In this study, the physicochemical properties of the bacteriocin produced by Enterococcus faecium CJNU 2008 strain were characterized. Partially purified bacteriocin showed stabilities against heat treatments at $100^{\circ}C$ for 30 min and $121^{\circ}C$ for 15 min and against solvents treatments such as methanol, ethanol, acetone, acetonitrile and chloroform. The bacteriocin also exhibited stabilities against lipase and ${\alpha}-amylase$ treatments but the stability was abolished at protease treatment, indicating that the antimicrobial agent from E. faecium CJNU 2008 was a proteinaceous bacteriocin. The bacteriocin also showed bactericidal mode of action against Listeria monocytogenes. The molecular mass of the bacteriocin was estimated to be under 6.5 kDa by a tricine-SDS-PAGE analysis. The bacteriocin was purified by HPLC. Further studies toward biochemical analysis of the bacteriocin are needed in near future.

Absorption properties and size distribution of aerosol particles during the fall season at an urban site of Gwangju, Korea

  • Park, Seungshik;Yu, Geun-Hye
    • Environmental Engineering Research
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    • v.24 no.1
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    • pp.159-172
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    • 2019
  • To investigate the influence of pollution events on the chemical composition and formation processes of aerosol particles, 24-h integrated size-segregated particulate matter (PM) was collected during the fall season at an urban site of Gwangju, Korea and was used to determine the concentrations of mass, water-soluble organic carbon (WSOC) and ionic species. Furthermore, black carbon (BC) concentrations were observed with an aethalometer. The entire sampling period was classified into four periods, i.e., typical, pollution event I, pollution event II, and an Asian dust event. Stable meteorological conditions (e.g., low wind speed, high surface pressure, and high relative humidity) observed during the two pollution events led to accumulation of aerosol particles and increased formation of secondary organic and inorganic aerosol species, thus causing $PM_{2.5}$ increase. Furthermore, these stable conditions resulted in the predominant condensation or droplet mode size distributions of PM, WSOC, $NO_3{^-}$, and $SO{_4}^{2-}$. However, difference in the accumulation mode size distributions of secondary water-soluble species between pollution events I and II could be attributed to the difference in transport pathways of air masses from high-pollution regions and the formation processes for the secondary chemical species. The average absorption ${\AA}ngstr{\ddot{o}}m$ exponent ($AAE_{370-950}$) for 370-950 nm wavelengths > 1.0 indicates that the BC particles from traffic emissions were likely mixed with light absorbing brown carbon (BrC) from biomass burning (BB) emissions. It was found that light absorption by BrC in the near UV range was affected by both secondary organic aerosol and BB emissions. Overall, the pollution events observed during fall at the study site can be due to the synergy of unfavorable meteorological conditions, enhanced secondary formation, local emissions, and long-range transportation of air masses from upwind polluted areas.

Development of Uniaxial Tensile Test Method to Evaluate Material Property of Tungsten Carbide-Cobalt Alloys for Cold Forging Dies (냉간단조 금형 WC-Co합금의 인장시험방법 개발 및 물성평가)

  • Kwon, I.W.;Seo, Y.H.;Jung, K.H.
    • Transactions of Materials Processing
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    • v.27 no.6
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    • pp.370-378
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    • 2018
  • Cold forging, carried out at room temperature, leads to high dimensional accuracy and excellent surface integrity as compared to other forging methods such as warm and hot forgings. In the cold forging process, WC-Co (Tungsten Carbide-Cobalt) alloy is the mainly used material as a core dies because of its superior hardness and strength as compared to other structural materials. For cold forging, die life is the most significant factor because it is directly related to the manufacturing cost due to periodic die replacement in mass production. To investigate die life of WC-Co alloy for cold forging, mechanical properties such as strength and fatigue are essentially necessary. Generally, uniaxial tensile test and fatigue test are the most efficient and simplest testing method. However, uniaxial tension is not efficiently application to WC-Co alloy because of its sensitivity to alignment of the specimen due to its brittleness and difficulty in thread machining. In this study, shape of specimen, tools, and testing methods, which are appropriate for uniaxial tensile test for WC-Co alloy, are proposed. The test results such as Young's modulus, tensile strength and stress-strain curves are compared to those in previous literature to validate the proposed testing methods. Based on the validation of test results it was concluded that the newly developed testing method is applicable to other cemented carbides like Titanium carbides with high strength and brittleness, and also can be utilized to carry out fatigue tests for further investigation on die life of cold forging.

Seed Germination Rate and Growth Characteristics according to Ripening Stages in Angelica acutiloba Kitagawa (일당귀의 등숙에 따른 종자 발아 및 생육 특성)

  • Lee, Eun Song;An, Tae Jin;Kim, Yong Il;Park, Woo Tae;Lee, Jeong Hoon;Kim, Young Guk;Chang, Jae Ki;Oh, Myung Min
    • Korean Journal of Medicinal Crop Science
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    • v.27 no.3
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    • pp.167-172
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    • 2019
  • Background: Angelica acutiloba Kitagawa belongs to the flowering plant family Apiaceae. Its young leaves are consumed as a vegetable, and its roots have medicinal properties. This study was conducted to analyze the seed germination characteristics of A. acutiloba according to its ripening stages. Methods and Results: The seeds were harvested from a research farm managed by the Department of Herbal Crop Research, Rural Development Administration in 2018 and were divided into six groups according to their specific gravities. In particular, we studied the effect of harvesting periods and umbel orders on seed characteristics. The results showed that the rates of germination, emergence, and early growth improved as the specific gravity of the seeds increased. In addition, the germination rates of the seeds harvested in mid July and early August were significantly higher than those harvested in the other seasons, and the seeds obtained from the first floret had the greatest mass and weight. Conclusions: In this study, we demonstrated that it is possible to improve the germination rate by appropriate selection of seeds and harvesting period both of which are closely related to seed maturity.

The Relationship between Anthropometric Parameters of the Foot and Kinetic Variables during Running (달리기 시 발의 인체측정학적 변인과 운동역학적 변인의 관계)

  • Lee, Young Seong;Ryu, Jiseon
    • Korean Journal of Applied Biomechanics
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    • v.29 no.3
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    • pp.173-183
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    • 2019
  • Objective: The aim of this study was to investigate the correlation coefficients between anthropometric parameters of the foot and kinetic variables during running. Method: This study was conducted on 21 healthy young adults (age: $24.8{\pm}2.1yes$, height: $177.2{\pm}5.8cm$, body mass: $73.3{\pm}7.3kg$, foot length: $256.5{\pm}12.3mm$) with normal foot type and heel strike running. To measure the anthropometric parameters, radiographs were taken on the frontal and sagittal planes, and determined the length and width of each segment and the navicular height. Barefoot running was performed at a preferred velocity ($3.0{\pm}0.2m/s$) and a fixed velocity (4.0 m/s) on treadmill (Bertec, USA) in order to measure the kinetic variables. The vertical impact peak force, the vertical active peak force, the braking peak force, the propulsion peak force, the vertical force at mid-stance (vertical ground reaction when the foot is fully landed in mid-stance or at the point where the weight was uniformly distributed on the foot) and the impact loading rate were calculated. Pearson's correlation coefficient was used to investigate the relationship between anthropometric variables and kinetical variables. The significance level was set to ${\alpha}=.05$. Results: At the preferred velocity running, the runner with longer forefoot had lower active force (r=-.448, p=.041) than the runner with short forefoot. At the fixed velocity, as the navicular height increases, the vertical force at full landing moment increases (r= .671, p= .001) and as the rearfoot length increases, the impact loading rate decreases (r=- .469, p= .032). Conclusion: There was a statistically significant difference in the length of fore-foot and rearfoot, and navicular height. Therefore it was conclude that anthropometric properties need to be considered in the foot study. It was expected that the relationship between anthropometric parameters and kinetical variables of foot during running can be used as scientific criteria and data in various fields including performance, injury and equipment development.

Stability analysis of an unsaturated expansive soil slope subjected to rainfall infiltration

  • Qi, Shunchao;Vanapalli, Sai K.;Yang, Xing-guo;Zhou, Jia-wen;Lu, Gong-da
    • Geomechanics and Engineering
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    • v.19 no.1
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    • pp.1-9
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    • 2019
  • Shallow failures occur frequently in both engineered and natural slopes in expansive soils. Rainfall infiltration is the most predominant triggering factor that contributes to slope failures in both expansive soils and clayey soils. However, slope failures in expansive soils have some distinct characteristics in comparison to slopes in conventional clayey soils. They typically undergo shallow failures with gentle sliding retrogression characteristics. The shallow sliding mass near the slope surface is typically in a state of unsaturated condition and will exhibit significant volume changes with increasing water content during rainfall periods. Many other properties or characteristics change such as the shear strength, matric suction including stress distribution change with respect to depth and time. All these parameters have a significant contribution to the expansive soil slopes instability and are difficult to take into consideration in slope stability analysis using traditional slope stability analysis methods based on principles of saturated soil mechanics. In this paper, commercial software VADOSE/W that can account for climatic factors is used to predict variation of matric suction with respect to time for an expansive soil cut slope in China, which is reported in the literature. The variation of factor of safety with respect to time for this slope is computed using SLOPE/W by taking account of shear strength reduction associated with loss of matric suction extending state-of-the art understanding of the mechanics of unsaturated soils.