• 한국주조공학회지
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• 제17권4호
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• pp.402-410
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• 1997

Developing a salt core for squeeze casting process, two different salt cores(pure salt core and mixed salt core) were fabricated and investigated. Pure salt core was composed of 100% NaCl and mixed salt core was made by mixtures of NaCl with MgO(1%), $Na_2B_4O_7$(2%), and talc(1%) as a binder or a strengthening agent. Salt cores were compacted to various theoretical density, heat treated, and then squeeze-cast with molten Al alloy(AC8A). The compression strength of salt cores were measured and the squeeze-cast products were examined for shape retention, infiltration of molten metal into the cores, and microstructures. The shape of salt core compacted at above 75% of the theoretical density was maintained stably. The higher theoretical density of salt cores gave higher compression strength, and the compression strength of mixed salt core was higher than that of pure salt core. Namely at 90% theoretical density, the compression strength of mixed salt core was $6.3 kg/mm^2$, compared to $4.6 kgmm^2$ for pure salt core. At a squeeze casting pressure of $1000 kg/cm^2$, molten Al alloy was infiltrated into pure salt core of under 85% of the theoretical density. At squeeze casting pressure of $1000 kg/cm^2$, only mixed salt core above 90% of the theoretical density were valid, but the shape of the core was altered in the case of pure salt core at 90% of theoretical density. A key factor for developing a salt core for squeeze casting process was estimated as the ultimate compressive strength of salt core.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1166-1172
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• 2018

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.

• 한국지반신소재학회논문집
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• 제5권2호
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• pp.31-37
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• 2006

본 논문에서 고함수비 슬러지와 퇴적물 탈수에 지오텍스타일 튜브의 이용가능성과 이에 영향을 미치는 요인들에 대한 평가를 수행하였다. 네 가지 고함수비물질을 사용하여 두 가지 지오텍스타일에 대해 다른 두 여과압력으로 실험을 실시하였다. 실험결과, 직포지오텍스타일 튜브는 일반적인 토사보유성기준을 만족하지 않지만 상류측의 필터케익 형성에 의해 세립자의 많은 부분을 유지하였고, 필터케익 형성 후, 투수성은 급속하게 감소하였다. 높은 여과압력은 탈수율을 증가시키는 경향이 있지만 여과효율에는 매우 적은 영향을 미치고, 탈수능력은 지오텍스타일에 관계된 여러 요인에 의해 영향을 받는데 슬러지 재료 자체의 특성이 탈수효율에 지배적인 요소로 나타남을 알 수 있었다.

• 상하수도학회지
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• 제10권2호
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• pp.47-54
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• 1996

UASB reactor was operated for treating wastewater containing high sulfate to assess their performance, competition between sulfate-reducing bacteria(SRB) and methane-producing bacteria(MPB), and the change in the characteristics of microbial granules according to change of hydraulic retention time(HRT) in the reactor. The reactor was fed with a synthetic moderate strength wastes(glucose, 2000 mgCOD/l) containing high sulfate($2400mgSO_4{^{2-}}/l$). The organic loading rate(OLR) ranged from 1.5 to 3.0 gCOD/l.d as HRT maintained 15 to 30 hrs in the stage I. The COD removal efficiency was between 80 to 92%. During this period, methane yield rapidly decreased from 0.3 to 0.1 1 $CH_4$/gCODremoved. While sulfide concentration in the effluent increased from 80 to 200 mgS/l. This indicates that SRB becomes dominant over MPB at a relatively long HRT in the excess sulfate. When OLR of reactor maintained from 5 to 8 gCOD/l.d in the stage II, methane yield increased from 0.1 to 0.17 1 $CH_4$/gCODremoved regardless of decrease of COD removal efficiency. This indicates that SRB is more sensitive to the change of a short HRT than MPB. In the competition between SRB and MPB, about 30% of the removed COD was utilized by SRB at HRT of 30 hrs during the start-up period, while about 73% was used by SRB at HRT of 15hrs at the final step of second experimental stage. Whereas after shock exposure of OLR about 62% was utilized by SRB at HRT of 5hrs. It indicates that SRB is strongly suppressed by the wash-out of significant dispersed SRB since a large electron flow is distributed to the MPB. In addition, the granulation in the presence of high sulfate is unfavoured at a long HRT because of substrate transport limitations into MPB like Methanothrix spp. which is an important factor in the composition of the granules. Accordingly, granule sizes in the UASB reactor decreased with time due to weak network frame of granules by the decreased activity of MPB.

• Molecules and Cells
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• 제37권1호
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• pp.81-87
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• 2014

Chronic pressure-overload cardiac hypertrophy is associated with an increased risk of morbidity/mortality, largely due to maladaptive remodeling and dilatation that progresses to dilated cardiomyopathy. Alternative splicing is an important biological mechanism that generates proteomic complexity and diversity. The recent development of next-generation RNA sequencing has improved our understanding of the qualitative signatures associated with alternative splicing in various biological conditions. However, the role of alternative splicing in cardiac hypertrophy is yet unknown. The present study employed RNA-Seq and a bioinformatic approach to detect the RNA splicing regulatory elements involved in alternative splicing during pressure-overload cardiac hypertrophy. We found GC-rich exonic motifs that regulate intron retention in 5' UTRs and AT-rich exonic motifs that are involved in exclusion of the AT-rich elements that cause mRNA instability in 3' UTRs. We also identified motifs in the intronic regions involved in exon exclusion and inclusion, which predicted splicing factors that bind to these motifs. We found, through Western blotting, that the expression levels of three splicing factors, ESRP1, PTB and SF2/ASF, were significantly altered during cardiac hypertrophy. Collectively, the present results suggest that chronic pressure-overload hypertrophy is closely associated with distinct alternative splicing due to altered expression of splicing factors.

• 정보관리연구
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• 제35권4호
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• pp.35-56
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• 2004

인터넷을 통한 웹 콘텐츠가 증가하면서 도서관 장서구성에서 전자자원의 비중이 점차 확대되고 있다. 장서의 선정, 유지, 구독중단을 위한 평가기준은 여러 가지가 있으나, 전자저널의 경우에는 이 용량에 근거한 평가가 중요한 비중을 차지하고 있다. 이에 본고에서는 전자저널 이용통계의 역할과 문제점 등에 대해 살펴본 후 ICOLC, COUNTER의 지침을 중심으로 전자저널 이용통계 요소를 추출하여 전자저널 출판사별 통계서비스에 대해 평가해 보았다. 그 결과 COUNTER 실행코드 채택이후 전자저널 이용통계서비스가 많이 개선되었으나, 장서평가에 활용되기에는 여전히 미흡한 부분이 존재하고 있었다. 전자저널 이용통계가 도서관 장서평가에 활용되기 위해서는 도서관, 관련 단체, 출판사 등의 협력을 통해 좀더 구체적이고 표준화된 이용통계 요소가 개발되어야 하고, 전자저널 출판사, 대행사들은 이를 적극적으로 수용해야 할 것이다.

• 국제지역연구
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• 제15권2호
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• pp.225-245
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• 2011

본 연구는 중국의 북경, 청도, 상해 등에 거주하는 대학생과 일반인을 대상으로 중국 소비자들의 공정성 차원 즉 분배 공정성, 절차 공정성, 상호작용 공정성과 부정적 감정, 회복 만족 및 행동의도(재구매 의도, 구전의도) 간의 상호 관련성을 연구하고자 하는 것이다. 또한 공정성 차원과 회복 만족 간의 관계에서 부정적 감정의 매개효과를 조사하는 것이다. 본 연구의 결과에 의하면, 공정성 차원 즉 분배 공정성, 절차 공정성 및 상호작용 공정성은 부정적 감정에 부의 영향을, 회복만족에 정의 영향을 미치는 것으로 나타났다. 둘째, 부정적 감정은 회복만족에 부의 영향을 미치는 것으로 나타났다. 셋째, 본 연구의 결과, 서비스 실패에 따른 회복 만족은 행동의도 즉 재구매 의도와 긍정적 구전의도에 정의 영향을 미치는 것으로 나타났다. 마지막으로 지각된 공정성 차원이 회복만족에 미치는 영향에 있어 부정적 감정의 매개효과를 검증한 결과, 부정적 감정은 공정성 차원 즉 분배 공정성, 절차 공정성 및 상호작용 공정성은 부정적 감정의 매개를 통해서 뿐만 아니라 직접적으로 회복만족에 미치는 것으로 나타났다. 본 논문은 서비스 실패에 따른 회복 과정에서 중국 소비자들의 구매행동을 이해하고, 이에 따른 할인점의 수익성 및 고객 유지 관리를 위한 전략 수립에 필요한 지식을 제공하고 있다.

• 대한방사성의약품학회지
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• 제4권2호
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• pp.57-64
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• 2018

${\omega}-[^{18}F]$-Fluorohexadecanoic acid (FHA) has been used for imaging of fatty acid metabolism of myocardium. To increase retention of radiolabeled fatty acid by blocking ${\beta}$-oxidation, methyl branched analogues have been used. In this experiment, we tried to synthesize 18F-labeled ${\alpha}-$, ${\beta}-$ and ${\omega}-FHA$ for imaging of the myocardial fatty acid metabolism. We synthesized ${\alpha}-$, ${\beta}-$ and ${\omega}$-mesylated methyl hexadecanoates and labeled with $^{18}F$ by reacting with $[^{18}F]$TBAF in acetonitrile at $80^{\circ}C$ for 10 min. Methyl ester group was removed by 1 M NaOH at $80^{\circ}C$ for 5 min. The yields of ${\alpha}-[^{18}F]$ and ${\omega}-[^{18}F]FHA$ were 25.5 and 45.5%, respectively [EOS]. However, ${\beta}-[^{18}F]FHA$ was not labeled at all due to a fast elimination reaction. The biodistribution study in ICR-mice showed that ${\omega}-[^{18}F]FHA$ has higher myocardial uptake and lower liver uptake than ${\alpha}-[^{18}F]FHA$. The electron-withdrawing effect of fluorine at ${\alpha}-$ position is believed to be the major factor affecting the biodistribution.

• 한국약용작물학회지
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• 제27권2호
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• pp.143-150
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• 2019

Background: Skin is an organ that protects the human body from various environmental stimuli that can induce immune system activation. Skin aging can be largely divided into two categories: physiological aging, which is caused by the a decreased physiological function of the skin and structural changes with aging, and photoaging, which is caused by the chemical stress induced by external stimuli such as ultraviolet (UV) radiation. Methods and Results: The objective of this study was to investigate the anti-wrinkle and UV protective effect of catechin-rich green tea extract (CGTE) in activated keratinocyte (HaCaT cells) and UV-induced skin damage in hairless mice. The results showed that CGTE inhibits the tumor necrosis factor-alpha interferon-gamma ($TNF-{\alpha}+IFN-{\gamma}$)-induced expression of matrix metalloproteinase (MMP)-1 in HaCaT cells. In addition, the CGTE treatment significantly reduced wrinkle formation, epidermal thickness, collagen deposition, and transepidermal water loss in dorsal skin irradiated with UVB. However, the ${\beta}$-glucosidase activity was significantly increased. The CGTE treatment inhibits mRNA expression and enzyme activity of MMP-2 and MMP-9 in the dorsal skin irradiated with UVB. Conclusions: It is expected that CGTE can be effectively used as a functional food and cosmetic ingredient to improve skin moisture retention and reduce wrinkle formation.

• Fisheries and Aquatic Sciences
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• 제24권6호
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• pp.219-227
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• 2021

The effects of various feeding ratios on the growth, body composition, and blood chemistry of the juvenile mandarin fish Siniperca scherzeri (initial body weight 9.6 g) were examined in recirculating freshwater system equipped with 21, 300 L tanks at 20 fish per tank. The triplicate groups of seven feeding ratios treatments were prepared: 100% (control), 95%, 90%, 85%, 80%, 75%, and 70% of satiation. The feed amount of control group was determined by supplying with apparent satiation and then the feed amounts of the other six feeding groups were determined based on the feed amount of the control group. Fish were hand-fed with test diet (55.4% crude protein) for 10 weeks. Weight gain (WG) and specific growth rate of fish fed to 100% satiation were not significantly (p > 0.05) different from those of fish fed to ≥ 80% satiation but were significantly higher than those of fish fed to 75% and 70% satiation. Feed efficiency, protein efficiency ratio, and protein retention of 100% satiation were not significantly different from those of 95% and 90% satiation but were significantly (p <0.05) lower than ≤ 85% satiation. Condition factor, hepatosomatic index, and coefficient variation were not significantly (p > 0.05) affected by feeding ratio. Whole body composition and contents of hematocrit, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, glucose, total protein, and high-density lipoprotein cholesterol in blood serum were not significantly (p > 0.05) affected by the feeding ratio; however, content of total cholesterol tended to decrease as the feeding ratio decreased. Using broken-line analysis of WG, it was suggested that the optimum feeding ratio of juvenile mandarin fish, ranging from 9.0 g to 37.0 g, appeared to be 87.7% of satiation without growth inhibition.