• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.335-335
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• 2014

Over the past several years, transparent conducting oxides have been extensively studied in order to replace indium tin oxide (ITO). Here we report on fluorine doped zinc tin oxide (FZTO) films deposited on glass substrates by radio-frequency (RF) magnetron sputtering using a 30 wt% ZnO with 70 wt% SnO2 ceramic targets. The F-doping was carried out by introducing a mixed gas of pure Ar, CF4, and O2 forming gas into the sputtering chamber while sputtering ZTO target. Annealing temperature affects the structural, electrical and optical properties of FZTO thin films. All the as-deposited FZTO films grown at room temperature are found to be amorphous because of the immiscibility of SnO2 and ZnO. Even after the as-deposited FZTO films were annealed from $300{\sim}500^{\circ}C$, there were no significant changes. However, when the sample is annealed temperature up to $600^{\circ}C$, two distinct diffraction peaks appear in XRD spectra at $2{\Theta}=34.0^{\circ}$ and $52.02^{\circ}$, respectively, which correspond to the (101) and (211) planes of rutile phase SnO2. FZTO thin film annealed at $600^{\circ}C$ resulted in decrease of resistivity $5.47{\times}10^{-3}{\Omega}cm$, carrier concentration ~1019 cm-3, mobility~20 cm2 V-1s-1 and increase of optical band gap from 3.41 to 3.60 eV with increasing the annealing temperatures and well explained by Burstein-Moss effect. Change of work function with the annealing temperature was obtained by ultraviolet photoemission spectroscopy. The increase of annealing temperature leads to increase of work function from ${\phi}=3.80eV$ (as-deposited FZTO) to ${\phi}=4.10eV$ ($600^{\circ}C$ annealed FZTO) which are quite smaller than 4.62 eV for Al-ZnO and 4.74 eV for SnO2. Through X-ray photoelectron spectroscopy, incorporation of F atoms was found at around the binding energy of 684.28 eV in the as-deposited and annealed FZTO up to 400oC, but can't be observed in the annealed FZTO at 500oC. This result indicates that F atoms in FZTO films are loosely bound or probably located in the interstitial sites instead of substitutional sites and thus easily diffused into the vacuum from the films by thermal annealing. The optical transmittance of FZTO films was higher than 80% in all specimens and 2-3% higher than ZTO films. FZTO is a possible potential transparent conducting oxide (TCO) alternative for application in optoelectronics.

• 전기화학회지
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• 제6권4호
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• pp.242-249
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• 2003

아연 전극은 고농도의 KOH전해질 용액의 알카리 전지용 양극재료로 폭넓게 이용되고 있다. 그러나 급속한 전기화학적 반응과 높은 용해도에 의한 수지상의 생성에 의해 사이클 수명이 현저하게 짧아지는 것으로 알려져 있다. 본 연구에서는 용액온도 $25^{\circ}C$의 $40wt.\%$ KOH 전해질에 $Ca(OH)_2$, Citrate, Tartrate 및 Gluconate 등의 첨가제를 첨가하고 그리고 $Pb_3O_4\;5wt\%$를 아연 전극에 혼합하였을 때 아연 전극의 전기화학적 거동에 미치는 Pb,04와 첨가제의 효과를 동전위 분극 곡선, 순환전위전해분석법, 가속수명시험 및 SEM사진 분석을 통하여 고찰하였다. $Pb_3O_4$의 첨가는 아연 전극의 부식 속도를 확실히 감소시키는 효과가 있었으며 그리고 $Pb_3O_4$의 첨가에 의한 아연 전극의 부식 전위는 순수아연 전극에 비하여 다소 높았으나 개로 전압에는 거의 영향이 없었다. 그리고 4가지 종류의 첨가제는 내식성과 가속 수명시험시의 사이클 수명을 향상시키는 데 중요한 역할을 하고 있는 것으로 확인되었다. 더욱이 Tartrate 첨가는 4가지 종류의 첨가제 중에서 상대적으로 충방전 특성을 개선할 뿐 아니라 양호한 내식성 효과가 확인되었다.

• 전기화학회지
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• 제11권1호
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• pp.42-46
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• 2008

연료전지는 수소를 직접 사용하는 것이 가장 효율이 높지만 가정이나 사무실에서는 수소 저장탱크를 사용하기보다는 도시가스(메탄가스)를 연료 source로 하여 수소를 생산하는 것이 유리하다. 연료전지에 사용하는 수소는 천연가스나 바이오가스, 탄화수소계열의 연료를 개질하여 생산하며 개질반응과정에서 필연적으로 여러 성분의 불순물이 포함되어 있다. CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$등의 불순물이 포함된 수소연료가 PEM fuel cell에 공급되면 연료전지 성능에 영향을 준다고 보고되어 있다. 이러한 영향에는 전극 촉매의 피독에 의한 kinetic losses, 전해질막과 촉매이온층의 양이온 전도성 감소에 의한 ohmic losses 그리고 촉매층의 구조나 소수성 감소에 의한 mass transport losses가 있다. 개질기에서 생산된 수소연료는 약 73%의 $H_2$와 20% 이하의 $CO_2$, 5.8% 이하의 $N_2$, 2% 이하의 $CH_4$, 10ppm 이하의 CO로 최종 공급된다. 본 연구에서는 연료 중에 $CO_2$가 고분자전해질 연료전지 anode측 성능에 미치는 영향을 조사하였다. 실험은 연료전지에 공급되는 연료중에 $CO_2$농도를 10%, 20%, 30%로 전류와 전압의 성능곡선과 장시간(10시간)실험 그리고 임피던스를 측정하였다. 또한 가스크로마토그래피를 이용하여 순수한 수소와 $CO_2$가 함유된 수소의 혼합을 통해 나온 연료전지 inlet에서의 불순물의 농도를 검증하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제47권2호
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• pp.197-219
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• 2008

Unlike ordinary situations, deifinitions play a very important role in mathematics education in schools. Mathematical concepts have been mainly acquired by given definitions. However, according to didactical intentions, mathematics education in schools has employed mathematical concepts and definitions with less strict forms than those in pure mathematics. This research mainly discusses definitions used in geometry (promising) course in primary schools to cope with possibilities of creating misconception due to this didactical transformation. After analyzing problems with potential misconceptions, a survey was conducted $\underline{with}$ 80 primary school teachers in Jeju to investigate their recognitions in meaning of mathematical concepts in geometry and attitudes toward teaching. Most of the respondents answered they taught their students while they knew well about mathematical definitions in geometry but the respondents sometimes confused mathematical concepts of polygons and circles. Also, they were aware of problems in current mathematics textbooks which have explained figures in small topics (classes). Here, several suggestions are proposed as follows from analyzing teachers' recognitions and researches in mathematical viewpoints of definitions (promising) in geometric figures which have been adopted by current mathematics textbooks in primary schools from the seventh educational curriculum. First, when primary school students in their detailed operational stage studying figures, they tend to experience $\underline{a}$ collision between concept images acquired from activities to find out promising and concept images formed through promising. Therefore, a teaching method is required to lessen possibility of misconceptions. That is, there should be a communication method between defining conceptual definitions and Images. Second, we need to consider how geometric figures and their elements in primary school textbooks are connected with fundamental terminologies laying the foundation for geometrical definitions and more logical approaches should be adopted. Third, the consistency with studying geometric figures should be considered. Fourth, sorting activities about problems in coined words related to figures and way and time of their introductions should be emphasized. In primary schools mathematics curriculum, geometry has played a crucial role in increasing mathematical ways of thoughts. Hence, being introduced by parts from viewpoints of relational understanding should be emphasized more in textbooks and teachers should teach students after restructuring this. Mathematics teachers should help their students not only learn conceptual definitions of geometric figures in their courses well but also advance to rigid mathematical definitions. Therefore, that's why mathematics teachers should know meanings of concepts clearly and accurately.

• 한국발생생물학회:학술대회논문집
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• 한국발생생물학회 2009년도 특별 Symposium
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• pp.49-57
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• 2009

The cloning of canids was succeeded in 2005, several years after the birth of Dolly the sheep and also after the cloning of numerous other laboratory and farm animal species. The delay of successful somatic cell nuclear transfer (SCNT)was due to the unique reproductive characteristics of the female dogin comparison to other domestic mammals, such as ovulation of immature canine oocyte and a requirement of 25 days for the completion of meiosis within the oviduct (Holst & Phemister, 1971). When the technology for the recovery of in vivo matured oocyte was established, the application of cloning also became possible and cloned dog offspring were obtained. This report summarizes the progress of technical procedures that are required for cloning canids and the application of this technique. The first cloned dog, Snuppy, was achieved using an in vivo-matured oocyte which was enucleated and transferred with an adult skin cell of male Afghan hound. After establishment of a criterion of well-matured oocyte for the improvement of SCNT efficiency, we obtained three cloned female Afghan hound and a toy poodle cloned from 14 year-old aged Poodle using SCNT through this factor. To date, cloned dogs appeared to be normal and those that have reached puberty have been confirmed to be fertile. Through application of canine SCNT technique, first, we demonstrated that SNCT is useful for conserving the breed of endangered animal from extinction through cloning of endangered gray wolves using inter-species SCNT and keeping the pure pedigree through the cloning of Sapsaree, a Korean natural monument. Secondly, we showed possibility of human disease model cloned dog and transgenic cloned dog production through cloning of red fluorescent protein expressing dog. Finally, SCNT can be used for the propagation of valuable genotypes for making elite seed stock and pet dog. In summary, dog cloning is a reproducible technique that offers the opportunity to preserve valuable genetics and a potential step towards the production of gene targeted transgenic cloned dogs for the study of human diseases.

• 생명과학회지
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• 제26권1호
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• pp.123-128
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• 2016

본 연구의 최종 목표는 한방제제인 심적환과 심혈관계 양방 치료제인 cilostazol과 병용 투여 효과에 대한 포괄적이고 통합의학 측면에서 정확한 정보를 얻는 것이다. Cilostazol은 말초 동맥질환 치료제로 개발 된 항 혈소판 및 혈관확장제이다. 사이클릭 AMP protein kinase A를 활성 시켜 세포내 사이클릭 AMP (cAMP) 증가를 통하여 내피세포의 NO생산을 활성화 시킨다. 심적환을 단 회 또는 반복 투여 후 cilostazol의 약물 동태학적 효과를 평가하기 위하여 순수한 증류수 단회 용량과 증류수에 심적환 콜로이드 현탁액을 각각 대조군과 시험군에 투여 하여 30분 후, 두 그룹에 cilostazol를 투여하였다. 혈청은 cilostazol 약물 투여 30분 전에 수집 하였으며, cilostazol 약물 처리 후 0.25, 0.5, 0.45 및 1, 2, 4, 6, 8, 24시간 후에 각각 수집 하였다. 그 다음 실험군과 및 테스트 그룹 사이에 실로 스타 졸에서 관찰 된 약동학 적 변화를 평가 하였다. 통계적으로 유의 한 차이는 심적관 단독 투여와 반복투여군 그룹의 약물 동태 학에서 관찰되지 않았다. 이러한 연구 결과는 만성 질환 환자에서 한약제인 심적환의 투여는 cilostazol의 약동학에 영향을 미치지 않았음을 보여 주었다. 본 연구에서 얻어진 결과는 만성 혈관질환 환자에서 심적환과 cilostazol의 병용 투여를 제안하며 두 약물간의 잠재적 인 약물 상호 작용에 대한 cilostazol의 생체 이용률에 영향을 미치지 않을 것이라 판단된다.

• 한국세라믹학회지
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• 제45권11호
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• pp.701-706
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• 2008

High frequency dielectric ceramics have potential for applications in mobile and satellite communications systems at frequencies higher than 10GHz. The Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics are known to have a high quality factor, a small temperature coefficient of the resonance frequency and a high dielectric constant. On the other hands, sintering at high temperature for extended time is required to obtain the ordered structure for high quality factor. In this study, the microwave dielectric properties of $ZrO_2$ and NiO-added Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics prepared by solid-state reaction have been investigated. Adding $ZrO_2$ and NiO could effectively promote the densification even the case of decreasing the sintering time. At the surface of samples, secondary phase of Ba-Ta compounds was formed possibly due to the evaporation of ZnO, however, the interior of the samples remained as pure Ba$(Zn_{1/3}Ta_{2/3})O_3$. The samples sintered at $1600^{\circ}C$ for 2h exhibited 1:2 ordering of Zn and Ta cations. Excellent microwave dielectric properties of $Q{\cdot}f$(>96,000 GHz) and ${\varepsilon}_r$=30 has been obtained.

• Journal of Ginseng Research
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• 제38권1호
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• pp.1-7
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• 2014

Background: Although ginsenosides such as Rg1, Rb1 and Rg3 have shown promise as potential nutraceuticals for cognitive impairment, their use has been limited due to high production cost and low potency. In particular, the process of extracting pure Rg3 from ginseng is laborious and expensive. Methods: We described the methods in preparing ginseol k-g3, an Rg3-enriched fraction, and evaluated its effects on scopolamine-induced memory impairment in mice. Results: Ginseol k-g3 (25-200 mg/kg) significantly reversed scopolamine-induced cognitive impairment in the passive avoidance, but not in Y-maze testing. Ginseol k-g3 (50 and 200 mg/kg) improved escape latency in training trials and increased swimming times within the target zone of the Morris water maze. The effect of ginseol k-g3 on the water maze task was more potent than that of Rg3 or Red ginseng. Acute or subchronic (6 d) treatment of ginseol k-g3 did not alter normal locomotor activity of mice in an open field. Ginseol k-g3 did not inhibit acetylcholinesterase activity, unlike donezepil, an acetylcholinesterase inhibitor. Rg3 enrichment through the ginseol k-g3 fraction enhanced the efficacy of Rg3 in scopolamine-induced memory impairment in mice as demonstrated in the Morris water maze task. Conclusion: The effects of ginseol k-g3 in ameliorating scopolamine-induced memory impairment in the passive avoidance and Morris water maze tests indicate its specific influence on reference or long-term memory. The mechanism underlying the reversal of scopolamine-induced amnesia by ginseol k-g3 is not yet known, but is not related to anticholinesterase-like activity.

• 청정기술
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• 제21권4호
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• pp.241-247
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• 2015

굴 패각은 한국 남쪽의 해안의 바다 양식 폐기물로써 처리문제로 대두되고 있다. 폐기물인 굴 패각을 실용화하기 위해서, 현지 회사에서 구입한 소성된 굴 패각(COS)에 AITC (allyl isothiocyanate)를 흡착시킨 후 식품 감염 질병을 일으키는 박테리아에 대해 성장억제능력을 시험하였다. COS 분말은 Escherichia coli, Staphylococcus aureus, Salmonella thyphimurium 균에 대해 1% 정도의 농도에서 세균 발육 억제 효과를 3에서 5 log 10 CFU/mL로 나타냄으로써 세균 발육 억제 효과를 보였으며, 순수 AITC의 MIC 결과는 Escherichia coli, Staphylococcus aureus, Salmonella thyphimurium에 대해 각각 1 mg/mL, 0.8 mg/mL 0.7 mg/mL을 나타내었다. 소성된 굴 패각은 소성과정에서 기공이 생성되어 225 mg/g의 AITC를 흡착하였고, FTIR 결과로 COS에 AITC가 흡착이 되었음을 확인하였다. 입자의 특성은 매우 미세한 입자 크기 및 높은 선상 표면을 나타내었다. AITC가 흡착된 소성된 굴 패각(ACOS)은 1% 농도에서 완전히 세균 세포를 억제함에 따라, ACOS는 COS보다 더 나은 항균활성을 나타냄을 확인하였으며, 이는 박테리아에 대해 AITC와 소성된 굴 패각의 상승효과가 있음을 나타내었다.

• Corrosion Science and Technology
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• 제8권4호
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• pp.162-169
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• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.