• Advances in nano research
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• 제7권1호
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• pp.13-24
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• 2019

Well-crystalline $SnO_2$ nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in $SnO_2$ lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of $SnO_2$ lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of $SnO_2$ nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of $SnO_2$ crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped $SnO_2$ nanoparticles occurs through the production of intermediate byproducts such as azure A, azure B, and azure C, direct mineralization of MB takes place for In-doped $SnO_2$ nanoparticles.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.715-719
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• 1999

The incorporation of cobalt into mesoporous molecular sieves MCM-41 and MCM-48 was carried out. Co-PO/MCM41 and Co-PO/MCM48 were prepared using Co(II) acetate solution adjusted to pH = 3.0 with phosphoric acid by the incipient wetness method. Photoacoustic spectroscopy (PAS) was used to study the local environments of Co(II) incorporated into mesopores. The band around 500 nm in PAS of as-prepared Co-PO/MCM41 and Co-PO/MCM48 with Co(II) acetate solution was changed to triplet bands around 600 nm. This could be assigned to the 4 A2(F)-> 4T1(P) transition of Co(II) surrounded tetrahedrally by oxygen ions after calcination. It may be attributable to that the octahedral cobalt species containing phosphate ligands in coordination sphere reacting with framework's silanol groups to be dispersed atomically onto the surface of mesoporous molecular sieves as a tetrahedral species. This is unlike that the Co in Co-Cl/MCM41 and direct-synthesized Co-MCM41 transforms to Co oxide phase upon calcination. Co-PO/MCM41 and Co-PO/MCM48 were stable while treated with water.

• 전기화학회지
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• 제5권4호
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• pp.226-231
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• 2002

Power densities produced by the permeation of methanol through membranes were directly measured by inserting the membrane in front of anode in a membrane-electrode-assembly of a direct methanol fuel cell (DMFC). The power density was closely related to the loss of power in the DMFC and was strongly affected by temperature. As the cell temperature was increased, the power density resulting from methanol crossover was increased. The increase in methanol crossover had be attributed to diffusion caused or affected by temperature. Methanol crossover a major effect on the performance of a DMFC at a relatively low temperature with $26\%\;loss\;at\;30^{\circ}C$. In order to reduce methanol crossover, a conventional Nafion membrane was modified by the incorporation of Pt or Pd. The reduction in methanol crossover was investigated in these modified membranes by our cell performance measurement. Pt and Pd particles incorporated in the Nafion membranes block methanol pathway and prevent methanol transport through the membranes, which was proved by combining with liquid chromatography.

• 한국분말재료학회지
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• 제21권5호
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• pp.389-398
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• 2014

Macroporous ceramics with tailored pore size and shape could be used for well-established and emerging applications, such as molten metal filtration, biomaterial, catalysis, thermal insulation, hot gas filtration and diesel particulate filters. In these applications, unique properties of porous materials were required which could be achieved through the incorporation of macro-pores into ceramics. In this article, we reviewed the main processing techniques which can be used for the fabrication of macroporous ceramics with tailored microstructure. Partial sintering, replica templates, sacrificial fugutives, and direct foaming techniques was described here and compared in terms of microstructures and mechanical properties that could be achieved. The main focus was given to the direct foaming technique which was simple and versatile approach that allowed the fabrication of macro-porous ceramics with tailored features and properties.

• 한국식품영양과학회지
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• 제26권1호
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• pp.130-136
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• 1997

250g내외의 횐쥐에게 Thiry-Vella fistula를 만든 후 수술과 비경구 영양 효과로 인하여 위축되는 소장의 누공에 각각 nucleosides/nucleotide혼합용액 (Nuc군)이나 glutamine(Gln군), glycine(Gly군)등을 투여하여 소장 점막의 위축 방지나 재생효과가 있는지를 알아보고 자 실험하여 다음과 같은 결과를 얻었다. Thiry-Vella fistula 시술 후 9일 동안 2일에 한 번씩 총 4회 소장 누공으로 주입한 이미노산들과 nucleosides/nucleotide 혼합물의 효과는 누공의 소장 점막에 미치는 직접적인 효과와 비누공 부분에 대한 간접적인 효과로 나누어 볼 수 있다. Nucleosides/nucleotide 혼합물은 소장 누공으로 주입되어 직접 접촉되는 부분의 소장 DNA함량을 유의적으로 증가 시켰으며 단백질 함량도 높은 수치를 보여 주었고 조직 검사 결과 소장 융모의 길이와 표면적을 증가시킨 것으로 나타났다. 그러나 ［$^3$H］ thymidine incorporation의 결과는 대조군과 유의적인 차이를 보이지 않았다. Glycine은 소장 단백질과 DNA에 있어서 대조군보다는 높고 Nuc군보다는 낮은 경향을 보여 주었으나 ［$^3$H］-thymidine incorporation은 누공과 비누공부분에서 모두 가장 높게 나타났으며 특히 비누공부분에서는 유의적으로 증가되어 있었다. Glutamine의 효과는 glycine 투여 효과와 비슷하거나 오히려 떨어지는 것으로 나타났다.

• 한국콘텐츠학회논문지
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• 제20권12호
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• pp.166-179
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• 2020

이 연구의 목적은 서울대 내부 구성원의 인식과 경험을 중심으로 법인화 이후 서울대가 무엇이 변화되었는지를 탐색적으로 분석하는 것이다. 이를 위해 서울대 내부 구성원인, 교수, 직원, 학생을 대상으로 반구조화된 면담을 실시하였다. 면담결과는 서울대 법인화에 대한 전반적 평가, 법인화에 따른 긍정적 및 부정적 변화, 교육, 연구, 사회공헌, 그리고 운영체제 측면에서 변화로 구분하여 제시하였다. 전반적으로 볼 때, 법인화 이후의 변화에 대해 서울대 내부 구성원들은 변화를 체감하기 어렵거나 변화가 별로 없다는 공통적인 인식을 보였다. 긍정적 변화로는 대학 재정의 확대와 운영의 자율성 확대, 환경변화에 대한 대응력 향상을, 부정적 변화로는 서울대의 법적 지위 모호, 대학 외부로부터의 직접적이고 공격적인 영향력의 과도한 증가를 언급하였다. 마지막 부분에서는 주요 결과를 정리하면서, 그 의미와 시사점에 관해 논의하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2008년도 제34회 동계학술대회 초록집
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• pp.346-346
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• 2008

• KCI Concrete Journal
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• 제12권2호
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• pp.85-93
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• 2000

Potentially significant mechanical improvements in tension can be achieved by the incorporation of randomly distributed, short discrete fibers in concrete. The improvements due to the incorporation fibers significantly influence the composite stress - strain ($\sigma$-$\varepsilon$) characteristics. In general incorporating fibers in a plain concrete has relatively small effect on its precracking behavior. It, however, alters its post-cracking behavior quite significantly, resulting in greatly improved ductility, crack controls, and energy absorption capacity (or toughness). Therefore, a thorough understanding the complete tensile stress - strain ($\sigma$-$\varepsilon$) response of fiber reinforced concrete is necessary for proper analysis while using structural components made with fiber reinforced concrete. Direct tensile stress applied to a specimen is in principle the simplest configuration for determining the tensile response of concrete. However, problems associated with testing brittle materials in tension include (i) the problem related to gripping of the specimen and (ii) the problem of ensuring centric loading. Routinely, indirect tension tests for plain concrete, flexural and split-cylinder tests, have been used as simpler alternatives to direct uniaxial tension test. They are assumed to suitable for fiber reinforced concrete since typically such composites comprise 98% by volume of plain concrete. Clearly since the post-cracking characteristics are significantly influenced by the reinforcing parameters and interface characteristics, it would be fundamentally incorrect to use indirect tensile tests for determining the tensile properties of fiber reinforced concrete. The present investigation represents a systematic look at the failure and toughening mechanisms and macroscopic stress - strain ($\sigma$-$\varepsilon$) characteristics of fiber reinforced concrete in the uniaxial tension test. Results from an experimental parametric study involving used fiber quantity, type, and mechanical properties in the uniaxial tension test are presented and discussed.

• The Korean Journal of Physiology and Pharmacology
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• 제2권4호
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• pp.493-501
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• 1998

The most significant direct role of estrogen in vivo is its ability to elicit receptor-mediated cellular proliferation in mammalian target tissues. However, the mechanism by which exogenously added estrogen causes the neoplastic transformation of renal cortical cells is yet to be uncovered. The present study was designed to evaluate interaction of $17{\beta}-estradiol\;(E_2)$ with epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on proliferation and $P_i$ uptake in primary cultured rabbit renal proximal tubular cells in phenol red-free, hormonally defined-medium. $[^3H]-thymidine$ incorporation increased markedly by about 133% and 141% more in the presence of $10^{-9}\;and\;10^{-6}\;M\;E_2$, respectively, than that of control. Cell count was 162% and 143% greater in the presence of $10^{-9}\;and\;10^{-6}\;M\;E_2$ , respectively, compared with control. Among all time points examined, there was an increase in $[^3H]-thymidine$ incorporation in the presence of $10^{-9}\;M\;E_2$ at day 9 or 13, respectively. However, $E_2$ ($10^{-9}\;M$) significantly drove up cell count to 160% of that of control at day 13, while it had a slight but statistically insignificant effect at day 9. $E_2-induced$ stimulation of $[^3H]-thymidine$ incorporation was completely reversed by $E_2$ antagonists (progesterone or tamoxifen). $E_2$ ($10^{-9}\;M$) or EGF ($10^{-8}\;M$) significantly stimulated $[^3H]-thymidine$ incorporation by 144% and 154% of control. $E_2$ plus EGF was synergistic on $[^3H]-thymidine$ incorporation (204% of control), while $E_2$ plus IGF-I showed a slight but no significant synergistic effect. Cell number also displayed similar pattern. $E_2$ ($10^{-9}\;M$) significantly stimulated $P_i$ uptake to 134% of control. $E_2$-induced stimulation of $P_i$ uptake was partially reversed by $E_2$ antagonists. EGF or IGF-I ($10^{-8}\;M$) significantly also increased $P_i$ uptake to 132% or 129% of control. $E_2$ plus EGF had synergistic effect on $P_i$ uptake, while $E_2$ plus IGF-I did not. In conclusion, $E_2$ may act not only directly interaction with its receptors but also indirectly as a modulator of EGF in proliferation and $P_i$ uptake of primary cultured rabbit renal proximal tubular cells.

• 한국분말재료학회지
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• 제30권4호
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• pp.318-323
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• 2023

The thermoelectric effect, which converts waste heat into electricity, holds promise as a renewable energy technology. Recently, bismuth telluride (Bi2Te3)-based alloys are being recognized as important materials for practical applications in the temperature range from room temperature to 500 K. However, conventional sintering processes impose limitations on shape-changeable and tailorable Bi₂Te₃ materials. To overcome these issues, three-dimensional (3D) printing (additive manufacturing) is being adopted. Although some research results have been reported, relatively few studies on 3D printed thermoelectric materials are being carried out. In this study, we utilize extrusion 3D printing to manufacture n-type Bi_1.7Sb_0.3Te₃ (N-BST). The ink is produced without using organic binders, which could negatively influence its thermoelectric properties. Furthermore, we introduce graphene oxide (GO) at the crystal interface to enhance the electrical properties. The formed N-BST composites exhibit significantly improved electrical conductivity and a higher Seebeck coefficient as the GO content increases. Therefore, we propose that the combination of the extrusion 3D printing process (Direct Ink Writing, DIW) and the incorporation of GO into N-BST offers a convenient and effective approach for achieving higher thermoelectric efficiency.