• Title/Summary/Keyword: NI-01

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Study on deposition condition of epitaxial $Y_2O_3$ buffer layer deposited on textured metal substrates for $YBa_2Cu_3O_7$ coated conductors (YBCO Coated Conductor를 위한 texture된 금속 기판위의 epitaxial $Y_2O_3$ 완충층 증착 조건에 관한 연구)

  • Shin, K.C.;Ko, R.K.;Park, Y.M.;Chung, J.K.;Shi, Dongqi;Choi, S.J.;Song, K.J.;Park, C.;Son, Y.G.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07a
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    • pp.565-568
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    • 2003
  • 2세대 초전도 선재로 알려져 있는 $YBa_2Cu_3O_{7-\delta}$ coated conductor는 금속모재/완충층/초전도층/보호층의 구조를 가진다. 2개 이상의 산화물 다층 박막으로 이루어진 완충층은 금속기판의 집합조직을 초전도층까지 전달하는 역할, 금속기판의 금속이 초전도층으로 확산되어 초전도층의 전기적 특성을 열화시키는 것을 막아주는 확산장벽으로의 역할 등을 수행한다. 1차 완충층은 금속기판의 집합조직을 유지하여야하며, 금속기판의 산화를 방지하면서 증착 되어야 한다. coated conductor 제조를 위한 첫 단계로 Pulsed Laser Deposition법을 이용하여 cube texture된 Ni 기판 위에 $Y_2O_3$ 박막을 증착 하였다. 최적의 증착 조건을 찾기 위해 증착 챔버의 산소 및 $H_2/Ar$ 혼합가스 분압과 기판온도를 변화시키면서 증착 하였다. $Y_2O_3$층의 (100) 집합조직은 기판온도 $600{\sim}700^{\circ}C$와 산소 분압 $0.01{\sim}0.1mTorr$에서 증착된 Y2O3 박막에서 금속기판과 유사한 집합조직을 얻을 수 있었다. 최적의 증착 조건에서 $Y_2O_3$ (222) ${\Phi}-scan$의 full width at half maximum (fwhm)이 $11^{\circ}$이고 (400) ${\omega}-scan$ fwhm은 $6^{\circ}$이었다.

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Mineralogy and Geochemistry of Green-colored Cr-bearing Sericite from Hydrothermal Alteration Zone of the Narim Gold Deposit, Korea (나림 금광상의 열수변질대에서 산출되는 녹색크롬-견운모의 광물학적 및 지구화학적 특징)

  • Lee, Hyun Koo;Lee, Chan Hee
    • Economic and Environmental Geology
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    • v.30 no.4
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    • pp.279-289
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    • 1997
  • Dark to pale green-colored, Cr-bearing sericites from hydrothermal alteration zone of the Narim gold deposit were investigated mineralogically and geochemically. The alteration zone is composed mineralogically of quartz, carbonate minerals and green sericite with minor amounts of chlorite, barite and sulfide minerals (pyrite, sphalerite, galena). The zone is enriched in As (967 to 1520 ppm), Cu (31 to 289 ppm), Ni (1027 to 1205 ppm), Pb (0.20 to 1.24 wt.%) and Zn (1.03 to 1.07 wt. %) compared with fresh rocks such as granitic gneiss, porphyritic biotite granite and basic dyke. The Cr, probably the chromophore element, is highly enriched in the alteration zone (1140 to 1500 ppm), host granitic gneiss (1200 ppm) and porphyritic biotite granite (1200 ppm). Occurrence and grain size of sericite are diverse, but most of the Cr-bearing sericites (150 to $200{\mu}m$ long and 20 to $30{\mu}m$ wide) occur along the boundaries between ore veins and host rocks (especially basic dyke and granitic gneiss). X-ray diffraction data of the sericite show its monoclinic form with unit-cell parameters of $a=5.202{\AA}$, $b=8.994{\AA}$, $c=20.103{\AA}$, ${\beta}=95.746^{\circ}$ and $V=935.83{\AA}^3$, which are similar with the normal 2M1-type muscovite. Representative chemical formula of the sericite is ($K_{1.54}Ca_{0.03}Na_{0.01}$)($Al_{3.42}Mg_{0.38}Cr_{0.14}Fe_{0.06}V_{0.02}$)($Si_{6.69}Al_{1.31}$)$O_{20}(OH)_4$. The Cr content increases with decrease of the octahedral Al content, and ranges from 0.36 to 2.58 wt.%. DTA and TG curves of the sericite show endothermic peaks at $342^{\circ}$ to $510^{\circ}$, $716^{\circ}$ to $853^{\circ}$ and $1021^{\circ}C$, which are due to the expulsion of hydroxyl group. The total weight loss by heating is measured to be about 8.8 wt. %, especially at $730^{\circ}C$. Infrared absorption experiments of the sericite show broad absorption band due to the O-H bond stretching vibration near the $3625cm^{-1}$, coupled with the 825 and $750cm^{-1}$ doublet. The vibration bands related with the H-O-Al and Si-O-Al bonds occur at $1030cm^{-1}$ and 500 to $700cm^{-1}$, respectively. Based on paragonite content of the sericite, the formation temperature of the Narim gold deposit is calculated to be $220{\pm}10^{\circ}C$.

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The Effect of indoor illuminance depends on direction of the side windows lighting (측창채광의 방향에 따른 실내조도의 영향)

  • Cho, Shee-Man;Kim, Won-Joong;Jang, Woo-Jin
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.05a
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    • pp.253-260
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    • 2004
  • 실내의 조명은 자연채광방식과 인공조명으로 나누어지는데 자연형 채광방식에서도 측창채광과 천창채광, 정 측창채광 그리고 반사 채광방식이 있다. 측창채광은 벽면에 대하여 일반적으로 연직인 창에 의한 채광을 말한다. 측창채광의 방향에 따라 실내조도는 영향을 많이 받는다. 따라서 본 연구는 측창채광의 동서남북의 방향에 따라 봄, 여름, 가을, 겨울의 계절에 따라 아침, 점심, 저녁시간대에 따라 변화되는 실내조도를 알아보았다. 실험방법은, 조명시뮬레이션 프로그램인 Lightscape V3.2를 사용하여 교실공간의 치수와 작업면의 높이를 가로 5.8[m], 세로 10.8[m], 높이 3[m], 작업면의 높이 0.75[m]로 정하였고, 각 시설물의 반사율[p]은 벽 80%, 창문 12%, 출입문 13%, 바닥 20%, 천장 85%로 지정하였으며 창문의 투과율은 88%로 설정하였다. 본 연구에서 측정하고자 하는 변수 값은 계절은 여름을 6월20일, 겨울은 1월20일 기준으로 하고 시간대는 09시, 13시, 18시로 하였으며 창측방위는 동, 서, 남, 북으로 정하였으며 계절과 시간은 가장 차이가 많이 나는 값을 선택하였다. 결론으로 창이 남쪽일 때 평균조도가 9,100[lx]로 가장 높았고, 시간별로는 점심에 19,590[lx]로 조도가 가장 높은 것을 알 수 있었고 조도 균제도는 창이 동쪽일 때 겨울에 가장 높았다. 창이 북쪽일 때는 여름이 겨울보다 평균조도가 약간 높았고, 시간별로는 아침에 조도가 약간 높은 것을 알 수 있었고 전체적으로 북쪽 창에서 실내조도가 현저하게 떨어지는 것을 알 수 있었다. 이와 같은 결과로 측창의 브라인드를 현재 사용하고 있는 수직 브라인드 대신에 수평 브라인드를 사용하여 주광의 범위를 넓게 조절하여 사용하게 하고, 점등제어를 현재 측창면과 수직으로 되어있는 배열을 수평으로 한다면 자연채광의 효과를 배가 할 수 있으리라고 사료된다. 미백 전, 미백후, 재광화 후 미세경도 변화 양상이 미백을 하지 않은 대조군과 차이를 보이지 않았으며 (p > 0.05) 미백 전과 미백 후의 미세경도의 차이 미백후와 재광화 후의 미세경도의 차이도 유의할 만한 차이가 없었다 (p > 0.05). 따라서 시중에 판매되고 있는 whitening strip과 미백 젤은 14일 동안의 통상적인 미백과정 동안 법랑질의 미세경도에 영향을 미치지 않는 것으로 사료된다.able pitch와 helical angle보다는 근본적으로 radial land가 screw-in effect의 예방에 더 큰 역할을 하는 것으로 추정될 수 있다 따라서 NiTi file의 사용 경험이 없는 초심자의 경우 근단부 폭경의 유지능력이 좋은 ProFile$^{(R)}$의 사용이 추천된다.)되었다.였으나 강남콩군 외에는 단백질의 소화 흡수율 및 효율은 크게 향상되지 않아 단백질의 소화 흡수율을 떨어뜨리는 요인에 관한 연구가 집중적 으로 이루어져야 하리라고 생각된다.면 바로 위 지점의 풍속을 측정하였다. 각 Seeding 물질에 대해 팬을 켜지 않았을 때, 즉 바람의 영향이 없을 때 측정한 표면유속을 바람의 세기가 변한 경우의 기준 표면유속으로 이용하였다. 본 연구의 결과 비중이 0.01 내외인 Ecofoam과 white polystyrene에 비해 비중이 0.92인 black polypropylene은 대부분이 물속에 잠겨 있어 흐름과 거의 일치하여 움직임을 알 수 있었다. 또한 흐름의 평균유속이 0.165 m/s의 저유속에서 바람이 tracers에 미치는 영향이 평균유속 0.558m/s인 경우보다 커서, 바람의 세기의 증가에 따라 표면유속 측정값이 급속히 감소되었다. 흐름의 평균유속이 큰 경우에는 바람이 tracer에 마치는 영향이 현격히 줄어듬을 보이고 있다. 결론적으로 유속이 증가함에 따라 바람의 영향은 감소하나, 바

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Interview Survey of Elementary School Students' Nutrition Education and Practice (면접조사를 통한 초등학생의 영양교육 실태 및 실천도 조사)

  • Oh, Yu-Jin;Lee, Young-Mee;Kim, Jung-Hyun;Ahn, Hong-Seok;Kim, Jeong-Weon;Park, Hae-Ryun;Seo, Jung-Sook;Kim, Kyung-Won;Kwon, O-Ran;Park, Hye-Kyoung;Lee, Eun-Ju;Sung, Huy-Ni
    • Korean Journal of Community Nutrition
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    • v.13 no.4
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    • pp.499-509
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    • 2008
  • This study investigated the experience and practice of elementary school students on nutrition education. The data were collected from 217 male and female students attending 5-6th grade elementary schools in Seoul and Kyunggi-Do from March to June 2007, interviewing face to face by a nutrition teacher and 3 interns of a nutrition teacher. The results were as follows: 86.5% of the subjects learned about 'Table etiquette', 'Reasons for eating fruits and vegetables'(78.7%), 'Food waste and environment'(72.3%), 'Healthy snacks'(55.7%), 'Food sanitation'(52.3%), 'Food culture of foreign countries'(48.1%). Nutrition education experience was significantly different by gender. A total of 43.5% boys responded that they never learned about 'basic food preperation'(p<0.01). They had learned 'Nutrients for body' and 'Food waste and environment' in school, 'Healthy weight loss', 'Food culture of foreign countries', 'Food circulation' on television, Most content('Table etiquette', 'Simple cooking', 'Food sanitation', 'Eating behaviors for health', 'Reasons for eating fruits and vegetables', 'Healthy snacks') was learned from parents. The practice after nutrition education was higher in 'Table etiquette'(2.14), 'Eating fruits and vegetables'(2.07) than others compared with education experience. The most reason of non-practice on nutrition information was 'Troublesome'. In 'Nutrients for body', a boy answered 'Difficult for practice' 20.0%, a girl answered 'Difficult to understand' 32.6%, showing a significant difference between the gender groups(p<0.001). They remembered the 'Nutrients for body'(49.6%), 'Food sanitation'(44.5%) because of 'important content', 'Basic food preparation'(40.6%), 'Food culture of foreign countries'(36.3%) because of 'interesting content', 'Healthy weight loss'(52.0%), 'Eating behavior for health'(44.5%) and 'Healthy snacks'(33.7%) because of 'need for my health'.

THE COMPARISON OF CANAL SHAPING ABILITY BY ENGINE-DRIVEN NICKEL-TITANIUM FILE AND ENDOSONIC FILE IN CURVED CANAL (만곡 근관에서 엔진 구동용 Ni-Ti File과 초음파 기구에 의한 근관성형 능력의 비교)

  • Kim, Hyun-Ju;Oh, Won-Mann;Yang, Kyuo-Ho
    • Restorative Dentistry and Endodontics
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    • v.20 no.2
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    • pp.758-767
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    • 1995
  • The purpose of this study was to evaluate canal shaping ability after canal preparation by using engine-driven nickel-titanium file and endosonic file in curved canals. 30 mesiobuccal canals of molars extracted within recent 3 months were divided into 3 groups. Group I and group II were prepared by using engine-driven nickel-titanium Gates-Glidden drill type and the engine-driven nickel-titanium file type. Group III prepared by using en do sonic file. The image of preinstrumented canals was taken by X-ray. The image of postinstrumented canal was taken by X-ray in the same condition of preinstrumentation. A magnified X-ray image on magnifier screen was traced and then compared the preinstrumentated canal image with the postinstrumentated canal image by superimposing method. The following results were obtained : 1. In the change of canal curvature, the engine-driven nickel-titanium Gates-Glidden drill type showed the least change and the ultrasonically filing showed the greatest change. 2. In the percentage of canal enlargement, the engine-driven nickel-titanium file type was greatest at all level(p<0.05), the apex of all group was the greatest, the difference of ultrasonically filing group showed greater between apex and cervix. 3. The percentage of canal enlargement on convex side was greater than that of on concave side in apex of each group(p<0.05). In the ultrasonically filing group, both sides of canal enlargement showed sharply difference(p<0.01). 4. The percentage of canal enlargement on convex side was greater than that of on concave side in the third of cervix of the engine-driven nickel-titanium file type and the ultrasonically filling. The percentage of canal enlargement of convex and concave side in the third of middle of the engine-driven nickel-titanium Gates-Glidden drill type show a similar canal enlargement between convex side and concave side. As above result, the engine-driven nickel-titanium file type was greater in canal enlargement than the other instruments. The engine-driven nickel-titanium Gates-Glidden dirll type was efficient endodontic instrument for curved canal preparation because it was least change in canal curvature.

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Geochemistry and Water Quality in the Tidal Flat of Saemangum Area, West Sea of Korea in Summer (하계 새만금 갯벌의 수질 분포 및 지화학적 특성에 관한 연구)

  • Park, Gyung Soo;Park, Soung Yun;Lee, Sam Geun;Lee, Yoon
    • Journal of Wetlands Research
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    • v.6 no.1
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    • pp.133-147
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    • 2004
  • Environmental quality(water and sediment) was analyzed in the tidal flat of Saemangum of Jeonbuk Province, the west coast of Korea, using the 101 sediment samples and 69 water samples collected in September 4~13, 2001. Major water quality parameters with the means of 69 surface water samples are as follows; $25.51{\pm}0.68^{\circ}C$ for water temperature, $29.88{\pm}5.01$ for salinity, $1.40{\pm}0.78mg/L$ for COD, $0.352{\pm}0.417mg/L$ for DIN, and $0.027{\pm}0.023mg/L$ for phosphate, respectively. Higher values were found at the subestuary of Dongjin and Mangyung River, and lower values at the Saemangum embayment and Gomso Bay. There was a significant negative correlation between salinity and the other water quality parameters(p<0.0001) such as COD, nutrients, SS and N/P. This correlation suggested that the major pollution sources be from terrestrial inputs through tributaries in this area. Principal component analysis clearly revealed a spatial variation of water quality; stations with higher values of nutrients and COD located subestuary of tributaries. 14 sediment quality parameters including 8 trace metals were measured using the 101 surface sediment samples. Average values for the parameters are as follows; Al $2.28{\pm}0.92%$, Cd $0.61{\pm}0.27ppm$, Cu $8.95{\pm}4.06ppm$, Fe $1.19{\pm}0.37%$, Mn $182.31{\pm}77.45ppm$, Ni $10.83{\pm}4.97ppm$, Pb $15.20{\pm}4.35ppm$, Zn $41.34{\pm}34.62ppm$, COD $2.68{\pm}1.85mg/g\;dry$, AVS $0.04{\pm}0.08mg/g\;dry$, IL $1.29{\pm}1.08%$, water content $24.11{\pm}4.49%$, TN $0.02{\pm}0.02%$, TC $0.22{\pm}0.30%$. Spatial variations of sediment quality were not clear as water quality. Some higher values were found at the subestuary of Gum River and lower values at the other area. There was a significant positive correlation between the heavy metal concentrations and organic materials within the sediment(p<0.05). Enrichment factors showed the ranges of 1~2 for most of the metals in the sediment except zinc(1~6), indicating no serious exogenous input of heavy metals in the study area. Also, the heavy metal concentrations in the sediment were within the ranges found at the natural marine environments.

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Optimization of Cookie Preparation by Addition of Yam Powder (마분말 첨가 쿠키 제조조건 최적화)

  • Joo, Na-Mi;Lee, Sun-Mee;Jung, Hee-Sun;Park, Sang-Hyun;Song, Yun-Hee;Shin, Ji-Hun;Jung, Hyeon-A
    • Food Science and Preservation
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    • v.15 no.1
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    • pp.49-57
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    • 2008
  • This study was conducted to develop an optimal composite recipe for a cookie including yam powder that would be attractive to all age groups. Wheat flour was partially substituted by yam powder to reduce the content of wheat flour. This study has produced the sensory optimal composite recipe by making cookies, respectively with each 5 level of yam powder $(X_1)$, Sugar$(X_2)$, butter$(X_3)$, by C.C.D (Central Composite Design) and conducting sensory evaluation and instrumental analysis by means of RSM (Response Surface Methodology). Sensory items showed very significant values in color, softness, overall quality (p<0.01), flavor (p<0.05) and those of instrumental analysis showed significant values in lightness, redness (p<0.05), spread ratio, hardness (p<0.01). Also sensory optimal ratio of yam cookie was calculated at yam powder 37.35 g, sugar 50.75 g, butter 78.40 g and it was revealed that the factors of influencing yam cookie aptitude were in older of yam powder, butter, sugar.

A Study on the Heavy Metals Concentrations in the Air of the Dental Laboratories, in the Blood and Urine of Dental Laboratory Technicians (치과기공실 공기중 및 치과기공사의 혈액, 요중 중금속 함량에 관한 연구)

  • Cha, Sung-Soo
    • Journal of Technologic Dentistry
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    • v.10 no.1
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    • pp.11-24
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    • 1988
  • The purpose of this study was to determine the concentration of cadmium, nickel and chromium in the air of the work-place, blood of and urine of workers and compare the level of those heavy metals by the duration of work, work-place, process of work, smoking and other factors. In this study, 48 male dental laboratory technicans and 72 office workers as the control group were subjected. The concentration of cadmium, nickel and chromium in their blood sand urine, and that of heavy metals in the air of their work-rooms were examined and analyzed from June I 1987 to September 30, 1987. The results were as follows : 1. The concentration of cadmium in the air was the highest in the porcelain part, $0.0087{\pm}0.0016mg/m^3$, that of nickel was the highest in the crown bridge part, $0.4253{\pm}0.0052mg/m^3$, and that of chrnmium was highest in the partial denture part, $0.1063{\pm}0.0024mg/m^3$. 2. cadmium, nickel and chromium concentrations in the blood and urine of dental laboratory techincians were higher that in the office workers'. Especially the concentration of cadmium in the blood($1.92{\pm}1.23{\mu}g$/100ml) of th dental laboratory techician was about two times as high as that in the office workers'($0.90{\pm}0.73{\mu}g$/100ml), and the concentration of nickel in the urine($48.53{\pm}38.83{\mu}g$/e) of the dental laboratory thchnician was about two times as high as that in the office worker's($20.24{\pm}15.35{\mu}g$/e). 3. there was no difference in the concentration of cadmium, nickel and chromium in the blood and urine with a longer duration of work. 4. The concentration of cadmium and chromium in the blood and urine differed significantly depending upon the place of work. The concentration of cadmium was the highest in the blood of dental laboratory technicians working kin the poreclain part marking at $2.53{\pm}1.08{\mu}g$/100ml. The chromium level was the heighest in the blood of partial denture park workers with a concentration of $3.60{\pm}1.02{\mu}g$/100ml. Concerning the level of cadmium in urine, it was the highest in the porcelain part workers with a concentration of $3.41{\pm}3.15{\mu}g$/e. 5. The concentration of cadmium in the urine of metal trimming and polishing group($2.64{\pm}2.41{\mu}g$/e) was higher than that of non-metal trimming and polishing group($1.39{\pm}1.18{\mu}g$/e). 6. The concentration of chromium in the blood of smoking group($2.46{\pm}1.54{\mu}g$/100ml)was higher than that lf non-smoking group($1.54{\pm}1.25{\mu}g$/100ml). 7. The height positive correlation coefficient was shown between the concentration of nickel and chromium in the blood among the all correlations between 3metals(Cd, Ni, Cr) in the blood and those in urine. The correlation coefficient was relatively high(r=0.605,,p<0.01). In general, the higher the concentration of heavy metals in the air of work places the higher the concention lf them in the blood and urine of workers, mere attention should be paid to the working environment of dental laboratory workers, Furthermore, continuous biological monitoring and further research are required for an efficient health management for dental laboratory workers.

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Evaluation of Possibility of Water Plant Wastes in Composting for Agricultural Recycling (수생식물 고사체의 농업적 재활용을 위한 퇴비화 가능성 평가)

  • Choi, Ik-Won;Seo, Dong-Cheol;Kang, Se-Won;Seo, Young-Jin;Lee, Sang-Gyu;Kang, Seog-Jin;Lim, Byung-Jin;Lee, Jun-Bae;Heo, Jong-Soo;Cho, Ju-Sik
    • Korean Journal of Soil Science and Fertilizer
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    • v.45 no.2
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    • pp.248-252
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    • 2012
  • To evaluate the possibility of water plant wastes in composting for agricultural recycling, Phragmites communis (PHRCO), Typha orientalis (TYHOR) and Zizania latifolia (ZIZLA) were used as a compost materials. In composting basin, cumulative oxygen consumptions of the compost used by water plant wastes were rapidly increased at the early stage and slightly decreased in around 15 days. Cumulative oxygen consumptions under different water plant wastes were higher in the order of TYHOR > ZIZLA > PHRCO. Temperature changes during composting process were rapidly increased at the early stage and then slowly decreased to $30{\sim}40^{\circ}C$. The maximum temperatures were higher in the order of ZIZLA ($72.2^{\circ}C$ at 11 days after starting composting) > TYHOR ($70.2^{\circ}C$ at 10 days after starting composting) > PHRCO ($66.5^{\circ}C$ at 7 days after starting composting). Oxygen consumptions at maximum temperature were higher in the order of TYHOR ($12,485mg\;O_2\;kg^{-1}$) > ZIZLA ($12,400mg\;O_2\;kg^{-1}$) > PHRCO ($9,340mg\;O_2\;kg^{-1}$). Organic matter contents, moisture contents and OM/N rates in the compost ranged 39.5~44.8%, 29.6~35.6% and 27.9~32.9, respectively. Considering that water plant waste can supply some of the nutrient requirements of crops and is a valuable fertilizer.

THREE DIMENTIONAL FORCE ANALYSIS OF FORCE SYSTEM IN CONTINUOUS ARCHWIRE BY FINITE ELEMENT METHOD (CONTINUOUS ARCHWIRE의 FORCE SYSTEM에 대한 3차원 유한 요소법적 연구)

  • Row, Joon;Ryu, Young-Kyu
    • The korean journal of orthodontics
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    • v.26 no.1 s.54
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    • pp.17-32
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    • 1996
  • It is important to understand the operating mechanism and force system of fixed appliance that most effective for individual tooth movement in various orthodontic appliances. The archwire system of fixed appliance is devided into 3 types, which is continuous arch, segmented arch and sectional arch. The last two types have longer interbracket distance and simple force operating points, so it is easy to control force system by operator. But the continuous arch has shorter interbracket distance and various bracket geometry, so it is hard to control and anaylze the force system. The purpose of this study was three dimentional force and moment analysis of continuous arch system by finite element method, which is similar situation to three dimentional elastic beam in structural engineering. Several sample form of various bracket geometry and artificial lower crowding typodont made by author were constructed, analyzed and compared each other. The results were as follows : 1. The force magnitude is linear proportional to the degree of displacement or tilting of the bracket. 2. The force magnitude is inversely non-linear proportional to the interbracket distance. 3. In three dimensional typodont model, while the force can be compared with that of the sample form in the area where adjacent bracket geometry is simple, the force is much more than the expected value in the area where adjacent bracket geometry is complex.

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