Consideration of Diluents Selection and Input Amounts of the Hunter Process for Tantalum Production

Jae‑Jin Sim,Sang‑Hoon Choi,Yong‑Kwan Lee,Sung Gue Heo,Taek‑Soo Kim,Seok‑Jun Seo,Kyoung‑Tae Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

Tantalum (Ta) is a heavy refractory metal with an atomic weight of 180.95 g/mol, a density of 16.6 g/cm3, and a high meltingpoint of 3017 °C. With its refractory characteristics, it shows excellent chemical and physical stability as well as corrosionand heat resistance at elevated temperatures. The demand for Ta metal and related compounds is increasing with the expansionof the electronics and chemical industries. The Hunter process was proven to be effective in producing Ta powder in1953. Hunter proposed a method in which potassium heptafluorotantalate (K2TaF7) was reduced by sodium (Na). Thus far,this process has been the primary commercial method to produce Ta powder. In this study, quantitative differences wereanalyzed for diluent selection. Additionally, consideration was given to changes in the caloric value depending on the inputamount of diluents. Finally, the optimum material input and the properties of the prepared Ta were analyzed. Stoichiometricratios of K2TaF7(1 mol), NaCl (6.2–6.7 mol), Na (5–7 mol) were weighed, to perform a metallothermic reduction reaction. After the reaction, the tantalum powder was recovered and the flush process was carried out. After that, it was dried in avacuum atmosphere. Physical properties such as oxygen concentration, PSA, ICP-OES, and XRD of powder were conductedto evaluate the characteristics of Ta powder that was finally manufactured.

대아지 숭상을 위한 수문학적 가능성 평가

노재경,이재남 충남대학교 농업과학연구소 2008 농업과학연구 Vol.35 No.2

만경강 수계의 봉동 지점에서 자연사회환경개선의 하천유지유량을 확보하기 위해 상류에위치한 대아저수지를 높이는 방안에 대한 수문학적 타당성을 검토한 결과 다음과 같이 요약된다. 첫째, 동상-대아 직렬 연계에 의해 대아저수지로부터의 용수공급을 분석한 결과 용수공급량/유역면적은 1207.4 mm, 단위유역 용수공급량/강우량 비율은 95.8%, 용수공급량/유입량 비율은 153.1%, 용수공급량/저수량 비율은 236.1%, 유입량/저수량 비율은 200.6%였다. 둘째, 대아-경천 병렬 연계를 고려한 봉동 지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 28.95 ㎥/s, 평수량 2.00 ㎥/s, 저수량 0.95 ㎥/s, 각수량 0.82 ㎥/s로 분석되었으며, 고시유량 1.32 ㎥/s보다 0.50 ㎥/s 적게 나타났다. 셋째, 대아저수지를 lOm 높인 경우 대아저수지로부터의 용수공급을 분석한 결과 용수공급량/유역면적은 1220.7 mm, 단위유역 용수공급량/강우량 비율은 96.8%, 용수공급량/유입량 비율은 154.6%, 용수공급량/저수량 비율은 163.0%, 유입량/저수량 비율은 137.0%였다. 넷째, 대아저수지를 l0m 높인 경우 대아-경천 병렬 연계를 고려한 봉동 지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 28.09 ㎥/s,평수량 1.79㎥/s, 저수량 0.89㎥/s, 갈수량 0.82㎥/S로 분석되어 유량증가 효과는 전혀 나타나지 않았다. 요약하면 대아저수지 용량을 증가시키더라도 용수공급의 증가효과는 전혀 나타나지 않았으며, 봉동지점의 고시유량을 확보하기 위한 대아저수지의 숭상의 수문학적 타당성은 전혀 없는 것으로 분석되었다. The objective of this study is to evaluate the hydrological feasibility of heightening the Dae-ah reservoir in order to save instream flow at the Bong-dong station situated in the Mankyoung river. The results are summarized as follows. Firstly, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1207.4 ㎜, the rate of water supply divided by rainfall of 95.8%, the rate of water supply divided by inflow of 153.1%, the rate of water supply divided by storage capacity of 236.1%, and the rate of inflow divided by storage capacity of 200.6%. Secondly, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 (the 95th high flow) of 28.95 ㎥/s, the Q185 (the 185th high flow) of 2.00㎥/s, the Q275 (the 275th high flow) of 2.00㎥/s, and the Q355 (the 355th high flow) of 0.82㎥/s. Thirdly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1220.7 ㎜, the rate of water supply divided by rainfall of 96.8%, the rate of water supply divided by inflow of 154.6%, the rate of water supply divided by storage capacity of 160.0%, and the rate of inflow divided by storage capacity of 137.0%. Fourthly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 of 28.09㎥/s, the Q185 of 1.79㎥/s, the Q275 of 1.79㎥/s, and the Q355 of 0.82㎥/s. The conclusion appeared not to have the hydrological feasibility of heightening the Dae-ah reservoir from the reason that increased storage capacity does not increase water supply amount any more because of the high rate of the water supply divided by inflow.

프로그램화 된 신체운동이 ADHD 아동의 주의산만행동과 과잉행동에 미치는 효과

최재원(Jae Won Choi),강경두(Kyoung Doo Kang),정혜연(Hye Yeon Jung) 한국사회체육학회 2012 한국사회체육학회지 Vol.0 No.47

The purpose of this study is to deeply analyze a change of the programmed physical exercise in attentiondeficient behavior and hyperactivity of children with ADHD, through the single-subject research design method. The research subjects were 4 elementary school students who are under being cured due to being judged to be ADHD at Child Psychiatric Clinic for C University Hospital where is located in Seoul at that time of beginning experiment in order to be conformed with the objective of research. For visual observation, the attention-deficient behavior was used the frequency-typed case sampling method(Shin So-yeon, Park Jaeguk, Kim Yeong-mi, Lee Hwa-eun, 2007). Observation of hyperactivity was used the contents, which Carlson and Hotfield(1991) defined, by referring to the contents by Mun Jae-gyeong(1998). The following are the results that were elicited through the research procedure of this study. First, the programmed physical exercise was indicated to reduce attention-deficient behavior in children with ADHD. Second, the programmed physical exercise was indicated to reduce hyperactivity in children with ADHD.

양측성 관상동정맥루 1예

최용원,오석규,이재훈,이상재,권경희,최은경,김남호,정진원 圓光大學校 醫科學硏究所 2002 圓光醫科學 Vol.17 No.1

저자들은 호흡곤란, 흉부불쾌감, 심계항진 등을 주소로 내원한 환자에서 경흉부 및 경식도 심초음파 검사상 주폐동맥에서 이완기에 전행하는 지속적인 혈류의 흐름을 관찰하고, 관상동맥 조영술을 통해 좌전하행지 중간부위와 우관상동맥 근위부에서 각각 기시하여 공통경로를 이루면서 주폐동맥으로 유입되는 양측성 관상동정맥루를 보이는 드문 1예를 경험하였기에 문헌 고찰과 함께 보고하는 바이다. A coronary arteriovenous fistula is infrequently encountered vascular communication between a coronary artery and a cardiac chamber, a great artery or the vena cava. It is the most common congenital anomaly that can affect coronary perfusion. Bilateral involvement of coronary fistula constitutes an uncommon subgroup of coronary arteriovenous fistulas. A 69 year-old female patient presented with chest discomfort, palpitation, and dyspnea. In the echocardiography, doppler color flow imaging visualized abnormal flow signals with mosaic appearance in the main pulmonary artery during diastolic phase. Coronary angiography revealed arteriovenous fistula arising from the left anterior descending artery and the right coronary artery. Both coronary arteriovenous fistulas drained into the main pulmonary artery. We report a case of bilateral coronary arteriovenous fistula that was confirmed by echocariography and coronary angiography.

신장에 발생한 섬유육종 1례

이재규,손경민,권동득,오봉렬,류수방,박양일,최찬 大韓泌尿器科學會 2001 Korean Journal of Urology Vol.42 No.7

조직공학적 연골생성에 있어서 연골막의 필요성

오경석,김해진,이동준,정재호,최준혁 大韓成形外科學會 2001 Archives of Plastic Surgery Vol.28 No.4

유한요소법과 경계요소법을 이용한 광도파로 내에서의 산란특성 해석

吳炅姬,朴宰弘 東亞大學校 大學院 1995 大學院論文集 Vol.20 No.-

Scattering from arbitrary discontinuities in an optical wave guide can be analyzed by combining finite element method and the modal expansion technique. By introducing the boundary element method far the semi-infinite region, however, the number of nodal points can be reduceded considerably. In this paper, a numerical algorithm is developed, which utilizes FEM, BEM and the modal expansion method. The algorithm can be applied to arbitrary discontinuty problems. The validity of the algorithm is tested for the well-known step-discontinuity problem.

유아언어교육의 총체적 접근

제경숙 慶南大學校 人文科學硏究所 2002 人文論叢 Vol.15 No.-

초기 유방암 환자에서 피하 유방 절제술후 즉시 유방 재건술에 대한 고찰

오경석,김해진,정재호,설정현 大韓成形外科學會 2001 Archives of Plastic Surgery Vol.28 No.5

등척성 운동 시 요추의 각도에 따른 중앙주파수와 토크의 특성

박경희,권오윤,장근,강성재,김영호 한국전문물리치료학회 2001 한국전문물리치료학회지 Vol.8 No.2

Fatigue is the decline in force produced as a result of prolonged muscle activity. Localized muscle fatigue can be identified by a shift toward low in the frequency components of the EMG signal, typically represented by a fall in the median frequency. Previous studies show that a shortened muscle developes a higher fatigue than elongated muscles. The purpose of this study was to investigate the time-related change of median frequency and torque during maximal isometric back extension exercises at different exercise angles (0˚, 12˚, 36˚, 72˚). Twenty healthy subjects (mean age = 24.35 ± 2.70) were evaluated in this study. Median frequency was extracted from the EMG signals by fast Fourier transform (FFT). Initial median frequency and the slope of median frequency change over time were computed from linear regression analysis. Pearson's product moment correlation was used to quantify the relationship between scope of median frequency and torque. The results were as follows: 1) Significant differences in y-intercepts of torque regression equation with respect to exercise angle were shown. However, there were no differences in the slopes of the median frequency and torque, and y intercept of the median frequency among exercise angles. 2) There was no significant correlation between slope of median frequency and torque. 3) But there was moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slope of median frequency and torque. But results showed that median frequency and torque shift were highly correlated in all subjects.