• Journal of Adhesion and Interface
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• v.24 no.4
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• pp.136-142
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• 2023

In this study, TEOS was used as a silica source, and a triblock copolymer (P123) was used as a template to produce mesoporous silica with a well-ordered hexagonal mesopore array through a self-assembly method and hydrothermal process under acidic condition. (Surfactant-extracted SBA-15). Surfactant-extracted SBA-15 showed the particle shape of a short rod with a size of approximately 980 nm. The surface area and pore diameter were 730 m²g^-1 and 70.8 Å, respectively. Meanwhile, aminosilane (3-aminopropyltriethoxysilane, APTES) was grafted into the mesopores using a post-synthesis method. Mesoporous silica (APTES-SBA-15) modified with aminosilane had a well-ordered pore structure (p6mm) and well-maintained the particle shape of short rods. The surface area and pore diameter of APTES-SBA-15 decreased to 350 m²g^-1 and 60.7 Å, respectively. APTES-modified mesoporous silica was treated with a solution of rare earth metal ions (Eu³⁺, Tb³⁺) to synthesize a mesoporous silica material in which rare earth metal complexes were introduced into the mesopores. (Eu/APTES-SBA-15, Tb/APTES-SBA-15) These materials exhibited characteristic photoluminescence spectra by λ_ex=250 nm. (⁵D₄→⁷F₅ (543.5 nm), ⁵D₄→⁷F₄ (583.5 nm), ⁵D₄→⁷F₃ (620.2 nm) transitions for Tb/APTES-SBA-15; ⁵D₀→⁷F₀ (577.7 nm), ⁵D₀→⁷F₁ (592.0 nm), ⁵D₀→⁷F₂ (614.9 nm), ⁵D₀→⁷F₃ (650.3 nm) and ⁵D₀→⁷F₄ (698.5 nm) transitions for Eu/APTES-SBA-15)

• Journal of the Korean earth science society
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• v.30 no.7
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• pp.897-908
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• 2009

Inscriptions are integral parts of the current science textbooks, and become medium that makes sense of scientific concepts effectively. This study analyzed the inscriptions from five science textbooks at the secondary level in terms of its type, function, and structures. Analyzing types of inscriptions resulted that the ratio of frequently used photographs and illustrations were much higher than that of graphs and tables used. In case of function analysis, illustrative and complementary functions were dominant in terms of frequency and ratio, whereas explanatory, decorative and inquisitive functions were relatively rare. Inscriptions of single structure was much more than multiple structure. Multiple structure of pair and series were mainly used for representing contrast and sequence, respectively. The proportion of inscriptions in type, function and structure across the textbooks was significantly different. Based on the results, it was suggested that semiotic study about the function and the structure of inscriptions need to be carried out in earth science area to better understand the pedagogical implications of inscriptions in school science.

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.466-473
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• 2008

This study deals with the morphological characteristics and structure of organ fossils of Neocalamites carrerei such as rhizomes, aerial leafy stems, and cones collected in situ from the Amisan Formation of Nampo Group. Judging from the size of some extant Equisetum and paleoclimate of Daedong flora, it is considered that the size of Neocalamites carrerei was probably very large. The cone of Neocalamites takahashii (Kon'no) is closely associated with the leaves of Neocalamites carrerei. It indicates that two organ fossils mentioned above probably belong to the same species. Comparing with very abundant occurrence of aerial leafy stems and rhizomes in the Amisan Formation, cones are very rare. This fact implies that Neocalamites reproduce not only by spore reproduction, but also by asexual reproduction. Neocalamites largely differ in the leaf form and size from Equisetum.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.462-477
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• 2007

The purpose of this study is to determine the petrology of basalt and the volcanic process in the Seondol cinder cone, Seobjikoji area, eastern Jeju Island. The Seondol cinder cone is mainly composed of spatters in the lower part, pyroclastic deposits including reddish brown blocks, ashes with volcanic bombs in the middle part, and dark black scoria deposits in the upper part. The volcanic sequences suggest volcanic processes that progress through Strombolian eruption and end with Hawaiian lava effusion which breached the cinder cone northwestward and extended over northwestward as lava delta and basalt emplaced as a volcanic neck in the central part of crater in the cinder cone. The age of basalt lava flows is about $95\;{\pm}\;3\;ka$. The basalts belong to transitional basalt and show products of fractional crystallization of clinopyroxene and olivine from a parental basalt magma on the basis of variation diagram of major, trace and rare earth elements. Basalts in the region of this study are plotted at the region of within plate basalt.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.431-439
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• 2012

A column chemistry is the most useful tools for isolating the elements of interest in isotope geochemistry. Here we introduce the chemical experimental procedure for Sm, Nd, La and Ce separation such as Teflon powder or Ln-resin method using HDEHP of KIGAM, KBSI, KOPRI and ${\alpha}$-HIBA(${\alpha}$-Hydroxy Isobutyric acid) method of Nagoya University, Japan. This technical report will provide an useful information in selecting the experiment method for rare earth element isotope system study such as Sm-Nd and La-Ce isotope system.

• ALGAE
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• v.35 no.3
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• pp.263-275
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• 2020

Water temperature is known to affect the growth and feeding of marine dinoflagellates. Each dinoflagellate species grows well at a certain optimal temperature but dies at very cold and hot temperatures. Thus, changes in water temperatures driven by global warming and extremely high or low temperatures can affect the distribution of dinoflagellates. Yihiella yeosuensis is a mixotrophic dinoflagellate that can feed on only the cryptophyte Teleaulax amphioxeia and the chlorophyte Pyramimonas sp. Furthermore, it grows fast mixotrophically but rarely grows photosynthetically. We explored the direct and indirect effects of water temperature on the growth and ingestion rates of Y. yeosuensis feeding on T. amphioxeia and the growth rates of T. amphioxeia and Pyramimonas sp. under 7 different water temperatures (5-35℃). Both the autotrophic and mixotrophic growth rates of Y. yeosuensis on T. amphioxeia were significantly affected by temperature. Under the mixotrophic and autotrophic conditions, Y. yeosuensis survived at 10-25℃, but died at 5℃ and ≥30℃. The maximum mixotrophic growth rate of Y. yeosuensis on T. amphioxeia (1.16 d^-1) was achieved at 25℃, whereas the maximum autotrophic growth rate (0.16 d^-1) was achieved at 15℃. The maximum ingestion rate of Y. yeosuensis on T. amphioxeia (0.24 ng C predator^-1 d^-1) was achieved at 25℃. The cells of T. amphioxeia survived at 10-25℃, but died at 5 and ≥30℃. The cells of Pyramimonas sp. survived at 5-25℃, but died at 30℃. The maximum growth rate of T. amphioxeia (0.72 d^-1) and Pyramimonas sp. (0.75 d^-1) was achieved at 25℃. The abundance of Y. yeosuensis is expected to be high at 25℃, at which its two prey species have their highest growth rates, whereas Y. yeosuensis is expected to be rare or absent at 5℃ or ≥30℃ at which its two prey species do not survive or grow. Therefore, temperature can directly or indirectly affect the population dynamics and distribution of Y. yeosuensis.

• The Journal of the Petrological Society of Korea
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• v.24 no.2
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• pp.141-147
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• 2015

Using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), we evaluated the reliability of trace element abundance data measured from the silicate rock references of JR-3, JG-3, JGb-1 and JB-1b using glass discs made by alkali fusion. For 28 elements including rare earth elements, relative standard deviations (RSD) are better than 7% in case when the concentrations of the elements in the rock samples are greater than 10 ppm. However, RSD shows somewhat increased values for the concentrations less than 10 ppm, but never exceeds 25%. Compared with previously reported averages of the compiled abundance data, our data display satisfactory results for the most cases with differences less than 10%. We suggest that LA-ICP-MS analysis using fused glass beads is a reliable, precise and time-saving method of trace element analysis for the silicate rocks spanning from mafic to felsic compositions.

• Journal of Magnetics
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• v.21 no.3
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• pp.315-321
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• 2016

M-Zn (M = Sb, V, Nb) substituted M-type strontium hexaferrites were prepared by a ceramic method. The phase composition, morphology and magnetic properties were studied by x-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry. Saturation magnetization increases with a substitution up to 75.0 emu/g (2.5 % higher compared to unsubstituted hexaferrite) and then decreases with a further substitution. A coercive field of substituted hexaferrite powders with highest saturation magnetization is more than 3 kOe. Substituted strontium hexaferrite powders prepared in this work are a rare example of high $M_S$ compositions without doping rare-earth elements and would be a promising candidate for a permanent magnet application.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.375-378
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• 1999

In tho XRD study of $56ZrF_4 \cdot34BaF_2 \cdot4AIF_3 \cdot(6-x)LaF_3 \cdotxLnF_3$ glassdLn=Ce, Nd, Gd, Th), halo pattern charactarktic fo an amorphous sample appeared. When the halo peak angle ($\theta_p$) was converted into a wavenumber with $Qp=4\pi sinG\pi/\lambda(\lambda$ is the wavolongth of the radialion used), it was found that the Qp values varied almost liuearly with the concentration 01 $LnF_3$. The emissiou spect1.a of $Ce^{3-}$-containing fluoride glasses nnder 273 nm excitation had a peak maximum at ea. 300 nm $(Ce^{3+}$ 5d-4f- transition). The maximal intensity of the fluorescence was observed when the $CeF_3$, content was extremely low (ca. 1 mol%j. DTA measurement revealed tbat these fluoride glasses had two crystallization temperatures. In $56ZrF_4. 34BaF_2. 4NF_3. (6-x)LaF_3 .xNdF_3$ glasses, the actmation energies of crystallization obtained from a Kssinger plot were 1.7 and 5.0 eV for the glass with x=2, and 1.9 and 5.6 eV for the glass with x=4.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.811-815
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• 1995

회토류계 영구자석은 종래의 Ferrite계나 Alnico계와 비교해서 대단히 강하여, 전기전자부품의 소형화에 크게 기여하고 있다. 최근에는, 전자기기산업 이외의 분야에 있어서도 그의 응용이 확대되어가고 있는 추세로 자성재료의 생산액은 매년 증가하고 있다. 회토류계 영구자석재료의 연구는 1960년대에 시작되어 Sm $Co_{5}$, Sm$_{2}$ $Co_{17}$ 화합물의 등장을 거쳐 현재는 1982년데 Sagawa 및 Croat가 독자적으로 발견한 Nd$_{2}$ Fe$_{14}$B 자석이 주류로 되고 있다. 그렇지만 이 화합물에는 다른 영구자석에 비하여 큐리온도가 낮은 결점이 있어서, 아직도 새로운 화합물의 탐색이 계속되고 있다. 그 중에서도, 1990년대에 Coey에 의해서 최초로 학회지에 보고되어진 Sm$_{2}$Fe$_{17}$N$_{x}$는, Nd$_{2}$Fe$_{14}$B와 같은 정도의 이론 최대에너지급, Sm $Co_{5}$에 대등한 거대한 이방성자장, 750K에 달하는 큐리온도등의 우수한 성질을 갖고 있어 Nd$_{2}$Fe$_{14}$B를 극복하는 자성재료로서 큰 기대가 되어진다. 되어진다.진다.