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이동원,이양,정영우,Lee, Dong Won,Lee, Yang,Chung, Young Woo 영남수학회 2014 East Asian mathematical journal Vol.30 No.4
We can easily see the 'cycloid slide' in the many mathematics and science museums. The educational materials, however, do not give us any mathematical principle. For this reason, we, in this thesis, first study the brachistochrone problem in the history of mathematics, and suggest a method of how to teach the principle using 'the dynamic geometry software GSP5' in order to help students understand the idea that the cycloid is the brachistochrone. Secondly, we examine the origin of the calculus of variations and apply it to prove the brachistochrone problem in order to build up the teachers' background knowledge. This allows us to increase the worth of history of mathematics and recognize how useful the learning is which uses technological tools or materials, and we can expect that the learning which makes use of cycloid slide will be meaningful.
이동원,윤중열,신선명,김인수,왕제필,Lee, Dong-Won,Yun, Jung-Yeul,Shin, Shun-Myung,Kim, In-Soo,Wang, Jei-Pil 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.3
The study on the fabrication of iron powder from forging scales using hydrogen gas has been conducted on the effect of hydrogen partial pressure, temperature, and reactive time. The mechanism for the reduction of iron oxides was proposed with various steps, and it was found that reduction pattern might be different depending on temperature. The iron content in the scale and reduction ratio of oxygen were both increased with increasing reactive time at 0.1atm of hydrogen partial pressure. On the other hand, for over 30 minutes at 0.5 atm of hydrogen partial pressure, the values were found to be almost same. In the long run, iron metallic powder was obtained with over 90% of iron content and an average size of its powder was observed to be about $100{\mu}m$.
Spherodization of Granuled Cr<sub>2</sub>O<sub>3</sub> Fine Ceramic Powder by Plasma Spray
이동원,이학성,유지훈,왕제필,Lee, Dong Won,Lee, Hak Sung,Yu, Ji-Hun,Wang, Jei-Pil The Korean Institute of Resources Recycling 2016 資源 리싸이클링 Vol.25 No.6
Spray dried $Cr_2O_3$ powder having an agglomerated structure of particles was twice treated into a plasma flame to increase its apparent density. The powder subjected to the first densification treatment did not show the entirely melted state keeping inner particle hollows, and it was fully melted after the second processing only. The powder size as a result of the second treatment decreased, and the apparent density as well as flowability were increased due to melting and surface smoothing effects. But a part of particles after the second densified treatment showed the hollow structure, especially those which were above $30{\mu}m$ in size. This densification behavior of the powder has been qualitatively discussed in terms of the thermal conductivity and inner gas pressure within aggregates exposed to the plasma flame. Spray dried $Cr_2O_3$ 분말은 겉보기밀도를 향상시키기 위해 plasma flame에 투입하여 실험을 진행 하였다. 첫번째 고밀도화 공정에서의 분말은 입자내부 공간까지 완전히 용해되어지지 않았으며, 두번째 공정 이후 완전히 용해가 되었다. 두번째 공정 결과 분말 입도는 작아졌으며, 용해 및 표면 연화에 의해 겉보기 밀도와 유동도는 향상이 되었다. 두번째 고밀도화 공정이 후 부분적으로 입자들이 $30{\mu}m$ 이상의 hollow structure을 보여주고 있다. 분말의 이러한 고밀도화는 plasma flame에 의해 응집되어진 응집체내의 열전도율 및 내부 가스압의 관점에서 정량적으로 논의 하였다.
마그네슘의 금속염화물 환원에 의한 초미립 TiCN 분말합성
이동원,김진천,김용진,김병기,Lee, Dong-Won,Kim, Jin-Chun,Kim, Yong-Jin,Kim, Byoung-Kee 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.2
The ultrafine titanium carbonitride particles ($TiC_{0.7}N_{0.3}$) below 100nm in mean size were successfully synthesized by Mg-thermal reduction process. The nanostructured sub-stoichiometric titanium carbide ($TiC_{0.7}$) particles were produced by the magnesium reduction at 1123K of gaseous $TiC_{l4}+xC_2Cl_4$ and the heat treatments in vacuum were performed for five hours to remove residual magnesium and magnesium chloride mixed with $TiC_{0.7}$. And final $TiC_{0.7}N_{0.3}$ phase was obtained by nitrification under normal $N_2$ gas at 1373K for 2 hrs. The purity of produced $TiC_{0.7}N_{0.3}$ particles was above 99.3% and the oxygen contents below 0.2 wt%. We investigated in particular the effects of the temperatures in vacuum treatment on the particle refinement of final product.
마그네슘환원에 의한 C/N 조성제어 초미립 TiC<sub>x</sub>N<sub>y</sub> 분말 합성
이동원,김병기,윤중열,유지훈,김용진,Lee, Dong-Won,Kim, Byoung-Kee,Yun, Jung-Yeul,Yu, Ji-Hoon,Kim, Yong-Jin 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
The ultrafine titanium carbonitride ($TiC_xN_y$) particles below 100 nm in mean size, including various carbon and nitrogen contents (x=0.55~0.9, y=0.1~0.5), were successfully synthesized by new Mg-thermal reduction process. Nanostructured sub-stoichiometric titanium carbide ($TiC_x$) particles were initially produced by the magnesium reduction of gaseous $TiCl_4+x/2C_2Cl_4$ at $890^{\circ}C$ and post heat treatments in vacuum were performed for 2 hrs to remove residual magnesium and magnesium chloride mixed with $TiC_x$. Finally, well C/N-controled $TiC_xN_y$ phases were successfully produced by nitrification heat treatment under normal $N_2$ gas atmosphere at $1150^{\circ}C$ for 2 hrs. The values of purity, mean particle size and oxygen content of produced particles were about 99.3%, 100 nm and 0.2 wt.%, respectively.
이동원,김여향,현명철,권태찬,이상범,Lee, Dong-Won,Kim, Yeo-Hyang,Hyun, Myung-Chul,Kwon, Tae-Chan,Lee, Sang-Bum 대한소아청소년과학회 2010 Clinical and Experimental Pediatrics (CEP) Vol.53 No.4
목 적: 지속적인 발열과 3개 이하의 가와사끼병 진단 기준을 만족하는 환자군에서 불완전 가와사끼병을 감별하는데 있어 NT-proBNP가 가지는 진단적 의미를 살펴보고자 하였다. 방 법: 2008년 1월부터 2009년 6월까지 가와사끼병으로 진단 및 치료 받은 환자 96명을 대상으로 하였다. 진단은 입원 당일 열을 포함한 가와사끼병의 고전적인 진단 기준에 따랐고, 진단 기준의 만족 정도에 따라서 완전 가와사끼병 환자군과 불완전 가와사끼병 환자군으로 구분하였으며, NT-proBNP를 포함한 혈액검사를 시행하였다. 지속되는 열과 함께 3개 미만의 진단 기준을 만족하였지만 임상 경과와 여러 검사들을 통해 환자 19명을 대조군으로 하여 분석하였다. 결 과: 96명의 가와사끼병 환자 중 고전적인 진단 기준을 3가지 이하로 만족한 불완전 가와사끼병 환자는 33명으로 전체 가와사끼병 환자의 34% 였다. 임상 양상으로 구강 점막의 변화와 안검 충혈이 가장 많았는데 완전 가와사끼병에 비해 발생 빈도는 적었다(76% vs 98%, 76% vs 90%). 불완전 가와사끼병 환자의 NT-proBNP는 대조군에 비해 유의하게 높았으며($1407.7{\pm}1633.5pg/mL$ vs $126.2{\pm}135.5pg/mL$, $P$<0.001), cutoff value를 158 pg/mL으로 하였을 때 민감도 81%, 특이도 74% 로 C 반응성 단백 ${\geq}3mg/dL$의 민감도 74%, 특이도 68% 보다 높았지만, 적혈구 침강 속도 ${\geq}40mm/hr$의 민감도 70%, 특이도 84%로 특이도에서 적혈구 침강 속도보다 낮았다. 결 론: 지속되는 열, 안검 충혈, 구강 점막의 변화가 있어 불완전 가와사끼병으로 의심해야 하는 환자에서 NT-proBNP 검사를 시행하고 진단에 이용하는 것이 가와사끼병의 빠른 진단과 치료에 도움이 될 것이다. Purpose : To determine the efficacy of the N-terminal fragment of B-type natriuretic peptide (NT-proBNP) as a useful diagnostic method in children with incomplete Kawasaki disease (KD). Methods : Ninety-six patients who were diagnosed as having KD between January 2008 and June 2009 were enrolled in the study. American Heart Association recommendations for diagnosis were used, and patients were divided into the complete KD and incomplete KD groups. Blood tests including NT-proBNP were performed on admission day. Nineteen patients who had other febrile diseases other than KD were enrolled as control. Results : Thirty-three patients (34%) had incomplete KD. Change in the lips and oral cavity and conjunctivitis were the most common clinical features, but their frequency was lower than complete KD (76% vs 98%, 76% vs 90%). Patients with incomplete KD exhibited significantly higher NT-proBNP level than that of control ($1,407.7{\pm}1633.5pg/mL$ vs $126.2{\pm}135.5pg/mL$, $P$<0.001). An NT-proBNP cutoff value of 158 pg/mL provided a sensitivity of 81% and a specificity of 74% for diagnosis of incomplete KD. Conclusion : NT-proBNP assay can be clinically useful for the diagnosis of incomplete KD, if the patient has persistent fever, change in the lips and oral cavity, and conjunctivitis, and if the patient with those symptoms is suspected to have incomplete KD.
화학기상응축법으로 제조된 철 나노분말의 산화저항에 관한 연구
이동원,유지훈,배정현,장태석,김병기,Lee Dong-Won,Yu Ji-Hun,Bae Jeoung-Hyun,Jang Tae-Suk,Kim Byoung-Kee 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.3
In order to prevent the oxide formation on the surface of nano-size iron particles and thereby to improve the oxidation resistance, iron nanoparticles synthesized by a chemical vapor condensation method were directly soaked in hexadecanethiol solution to coat them with a polymer layer. Oxygen content in the polymer-coated iron nanoparticles was significantly lower than that in air-passivated particles possessing iron-core/oxide-shell structure. Accordingly, oxidation resistance of the polymer-coated particles at an elevated temperature below $130^{\circ}C$ in air was $10\~40$ times higher than that of the air- passivated particles.
이동원,박근태,임태수,이혜문,유지훈,Lee, Dong-Won,Park, Geun-Tae,Lim, Tae-Soo,Lee, Hye-Moon,Yu, Ji-Hun 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.4
Zr-Ti alloy powders were successfully synthesized by magnesium thermal reduction of metal chlorides. The evaporated and mixed gasses of $ZrCl_4+TiCl_4$ were injected to liquid magnesium and the chloride components were reduced by magnesium leading to the formation of $MgCl_2$. The released Zr and Ti atoms were then condensed to particle forms inside the mixture of liquid magnesium and magnesium chloride, which could be dissolved fully in post process by 1~5% HCl solution at room temperature. By the fraction-control of individually injected $ZrCl_4$ and $TiCl_4$ gasses, the final compositions of produced alloy powders were changed in the ranges of Zr-0 wt.%~20 wt.%Ti and their purity and particle size were about 99.4% and the level of several micrometers, respectively.
화학기상응축공정에 의한 WS<sub>2</sub> 나노입자의 합성 및 특성평가
이동원,김주형,올레그토로츠코,윤중열,김병기,Lee, Dong-Won,Kim, Ju-Hyeong,Tolochko, O.,Yun, Jung-Yeul,Kim, Byung-Kee 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.4
Nano-sized tungsten disulfide ($WS_2$) powders were synthesized by chemical vapor condensation (CVC) process using tungsten carbonyl ($W(CO)_6$) as precursor and vaporized pure sulfur. Prior to the synthesis of tungsten disulfide nanoparticles, the pure tungsten nanoparticles were produced by same route to define the optimum synthesis parameters, which were then successfully applied to synthesize tungsten disulfide. The influence of experimental parameters on the phase and chemical composition as well as mean size of the particles for the produced pure tungsten and tungsten disulfide nanoparticles, were investigated.