• 한국산업융합학회 논문집
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• 제22권5호
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• pp.491-497
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• 2019

Dissimilar friction welding were produced using 15 mm diameter solid bar in superalloy(Alloy718) to chrome molybdenum steel(SCM440) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=60 MPa, UP=120 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 3.5 mm. Acoustic Emission(AE) technique was applied to analyze the dissimilar friction welding of Alloy718 and SCM440. The relationship between the AE parameters and dissimilar friction welding of both material was discussed. In the case of heating time of 6 sec, 10 sec, 14 sec and 20 sec, 5 AE events per 0.5 seconds and energy about $2.7{\times}10^{10}$ were exhibited in heating time. In upsetting time, resulting in various numbers of events per second and very low energy. The frequency range of the signal generated during the heating time was about 200 kHz. However, the upsetting time resulted in a wide range of signals from very low frequency to high frequency of 500 kHz due to rapid plasticity of the material.

• Elastomers and Composites
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• 제54권2호
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• pp.135-141
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• 2019

Polyphenylene sulfide (PPS) was filled with glass fiber (GF), aramid fiber (AF), and solid lubricants to improve the mechanical properties and wear resistance. The addition of GF effectively enhanced the tensile strength, flexural modulus, and impact strength of PPS, while solid lubricants such as polytetrafluoroethylene (PTFE), molybdenum disulfide ($MoS_2$), and tungsten disulfide ($WS_2$) lowered the friction coefficients of the composites to below 0.3. The ball nut and motor pulley of the electric power steering (EPS) were manufactured using the PPS composites, and feasibility was ascertained thereafter by conducting the durability test. The composites filled with GF and AF showed high mechanical strength, but slip occurred at the interface between the pulley and belt while testing above $50^{\circ}C$. When small amounts of lubricants were added, the slip was no longer detected because of the suppression of friction heat. It is realized that the low friction as well as high mechanical properties is important to ensure the reliability of plastic pulleys.

• 농업과학연구
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• 제48권1호
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• pp.179-189
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• 2021

Plants need essential mineral elements to favorably develop and to complete their life cycle. Despite the irreplaceable roles of microelements, they are often ignored due to the relative importance of macroelements with their influence on crop growth and development. We focused on the changes in primary metabolites in the leaves and roots of bell pepper plants under 6 microelements-deficient conditions: Copper (Cu), Zinc (Zn), Iron (Fe), Manganese (Mn), Boron (B) and Molybdenum (Mo). Bell pepper plants were grown in hydroponic containers, and individual elements were adjusted to 1/10-strength of Hoagland nutrient solution. A remarkable perturbation in the abundance of the primary metabolites was observed for the Fe and B and the Mn and B deficiencies in the leaves and roots, respectively. The metabolites with up-accumulation in the Fe-deficient leaves were glucose, fructose, xylose, glutamine, asparagine and serine. In contrast, the Mn deficiency also resulted in a higher accumulation of glucose, fructose, xylose, galactose, serine, glycine, β-alanine, alanine and valine in the roots. The B deficiency noticeably accumulated alanine, valine and phenylalanine in the roots while it showed a substantial decrease in glucose, fructose and xylose. These results show that the primary metabolism could be seriously disturbed due to a microelement deficiency, and the alteration may be either the specific or adaptive responses of bell pepper plants.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.701-708
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• 2022

The mass attenuation coefficients (μ_m) of polyethylene glycol (PEG) of different molecular weights (1000-200,000) were measured using single-beam photon transmission. The X-ray fluorescent (XRF) photons from Zinc (Zn), Zirconium (Zr), Molybdenum (Mo), Silver (Ag) and Cadmium (Cd) targets were used to determine the attenuation of gamma radiation of energy range between 8.67 and 23.19 keV in PEG samples. The results were compared to theoretical values using XCOM and Monte Carlo simulation using Geant4 toolkit which was developed to validate the experiment at those certain energies. The mass attenuation coefficients were then used to compute the effective atomic numbers, electron density and half value layers for the studied samples. The outcomes showed good agreement between experimental and simulated results with those calculated theoretically by XCOM within 5% deviation. The PEG 1000 sample showed slightly higher μ_m value compared with the other samples. The dependence of the photon energy and PEG composition on the values of μ_m and HVL were investigated and discussed. In addition, the values of Z_eff and N_eff for all PEG samples behaved similarly in the given photon energy range, and they decreased as the photon energy increased.

• Journal of Periodontal and Implant Science
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• 제26권1호
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• pp.143-160
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• 1996

The purpose of this study was to evaluate the response in aspect of attachment and growth rate of osteoblasts and growth rate of osteoblasts and human gingival fibroblasts to the commercially pure titanium(CP titanium)and titanium alloy(Ti-6AI-4V) that are used widely as implant materials, and to obtain the basic information to ideal implant materials. In the studly, commercially pure titanium in first test group, titanium alloy(Ti-6AI-4V) in second test group, cobalt-chrome-molybdenum alloy(Co-Cr-Mo alloy) in positive control group, and tissue culture polystyrene plate in negative control group were used. The results of this study were as follows. 1. Bone marrow cells cultured on CP titanium and Ti-6Al-4V showed significantly greater attachment and growth rate(p(0.05) compared to Co-Cr-Mo alloy in each time. 2. There were no significant differences(p>0.05) in attachment and growth rate of bone marrow cells cultured on CP titanium and Ti-6AI-4V or tissue culture plate. 3. Most bone marrow cells cultured on CP titanium, Ti-6Al-4V and tissue culture plate were attached well to each substratum in first 2days, and then, grew at higher growth rate. On the other hand, some cells cultured on Co-Cr-Mo alloy failed to attach in first 2 days, and then, attached cells grew at lower growth rate than other groups. 4. Attachment and growth rates of gingival fibroblasts cultured on CP titanium and Ti-6Al-4V showed no significant differences(p>0.05) compared to Co-Cr-Mo alloy in 2 days, but significantly greater increase(p<0.05) in 5 and 9 days. 5. There were no significantly differences(p>0.05) between growth rates on gingival fibroblasts cultured on CP titanium, Ti-6Al-4V and tissue culture plate in 2 and 5days, but a significant lower growth rate(p<0.05) on CP titanium and Ti-6Al-4V versus tissue culture plate. 6. Some gingival fibroblasts cultured on all specimen groups failed to attach, but attached cells grew well, especially on CP titanium, Ti-GAl-4V and tissue culture plate. 7. There were no significant differences(P>0.05) between growth rates of both bone marrow cells and gingival fibroblasts cultured on CP titanium and Ti-6AI-4V. As a result of this study, both commercially pure titanium and Ti-6AI-4V showed excellent biocompatibility and there was no significant difference in the cellular response to the both metals. Bone marrow cells cultured on each substratum showed significantly greater growth rate and responded sensitively to cytotoxic effects of metal surfaces compared to gingival fibroblasts. Considering cell response to the substrate, it was likely that the composition itself of titanium metals have no significant effect on the biocompatibility. Further study need to be done to evaluate the influence of surface characteristics on cellular responses.

• 대한화학회지
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• 제36권1호
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• pp.3-15
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• 1992

크롬이움, 몰리브덴늄, 텅그스텐의 carbene 착물인 $(CO)_5Cr=CCHCH_2(XCH_3)\;,\;(CO)_5Mo=CCHCH_2(XCH_3)\;,\;(CO)_5W=CCHCH_2(XCH_3)$에 대해서 확장된 Huckel 방법으로 계산하여 이들의 전자구조와 반응성 등을 고찰하였다. fragment들의 궤도함수 상관도로부터 M=Ccarb 이중결합의 특성을 알 수 있다. M=Ccarb 이중결합의 ${\sigma}$결합은 carbene의 HOMO로부터 $(CO)_5M$의 LUMO로 전자가 이동하므로 형성되고 ${\pi}$결합은 전이금속의 축퇴된 d${\pi}$ 궤도함수로부터 carbene의 LUMO로 전자가 역이동하므로서 형성된다. M=Ccarb 결합에서 전하분극은 Mo, W-착물에 대해서 M쪽이 더욱 양으로 계산되었다. 화학적 또는 물리적 성질은 carbene 탄소원자의 양전하에 의하여 결정되며 carbene 탄소원자의 친전자적 반응성은 전하에 의해서가 아니라 frontier orbital의 LUMO에 의해서 지배받는다.

• 핵의학기술
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• 제17권2호
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• pp.48-52
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• 2013

본 연구의 목적은 한국원자력연구원에서 개발되고 있는 $(n,{\gamma})^{99}Mo/^{99m}Tc$발생기의 성능을 평가하고 개선방안을 연구함으로써 의학적 유효성을 확보하는 것이다. 이를 위해 본 연구에서는 한국원자력연구원에서 제조된 $(n,{\gamma})^{99}Mo/^{99m}Tc$발생기를 이용하여 $^{99m}Tc$ 용출 방사능량 시험, $^{99m}Tc$정도평가, $^{99m}Tc-DPD$, $^{99m}Tc-tetrafomin$ 표지수율 및 동물영상 평가를 진행하였다. 용출 방사능양은 상용 제품에 동일 용량에 비해 다소 적었으나, 발열성 물질 검사를 제외한 전영역의 $^{9m}Tc$정 도평가 실험에서 정상범위를 나타냈다. 표지 수율도 90% 이상 높은 수율을 관찰할 수 있었다. $^{99m}Tc-HDP$와 $^{99m}Tc-DPD$를 주입한 쥐 영상에서 한국 원자력 연구원 발생기는 모두 간과 비장의 집적을 관찰할 수 있었고 간과 비장은 상용발생기 일부에서도 관찰되었다. 이에 원자력 연구원 발생기는 발열성 물질을 제거한다면 비상시 훌륭한 대체 발생기 역할을 수행할 수 있을거라 생각한다.

• 핵의학기술
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• 제14권2호
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• pp.83-86
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• 2010

$^{99}Mo$-$^{99m}Tc$ 발생기의 원료물질인 몰리브덴은 원자로에서 생산되고 있으나 현재 의료용 방사성 동위원소를 공급하는 두 원자로인 캐나다 온타리오주의 초크리버(Chalk River)와 네덜란드 페튼(Petten) 원자로의 노후화로 인한 유지 보수로 가동이 정지된 이후세계적인 몰리브덴 품귀 현상은 발생기 공급차질로 이어 지고있다. 이에 저자들은 발생기의 효율적인 운용 방법을 찾아 $^{99m}Tc$ 생산량을 증가 시키고 그 결과로 얻은$^{99m}Tc$의 안전성을 실험을 통해 확인하였다. 교정일자가 동일한 두 대의 발생기(Malinckrodt Medical, Dutch), 40.5 GBq (1500 mCi)를 이용하여 월요일부터 금요일까지 5일 동안 1회/일(24시간 주기, 오전8시 용출) 총 5회 용출한 $^{99m}Tc$의 방사능과, 5일 동안 2회/일(오전8시와 오후1시 용출) 총 10회 용출한 $^{99m}Tc$의 방사능을 비교 분석 하였다. 용출된 $^{99m}Tc$의 안정성을 $^{99}Mo$-$^{99m}Tc$ 발생기 정도 관리 항목 중 성상 검사, pH 검사, 발열성 물질 검사(LAL test), 무균 검사, 발생기의 화학 순도 검사, 방사화학적 순도 검사, 방사성 핵종의 순도 검사를 통해 확인해 보았다. 24시간 주기로 주 5회 용출한 $^{99m}Tc$의 총 방사능은 평균 168.2 GBq (4545 mCi)였고, 24시간 주기 용출 방법에 오후1시 추가 용출을 실시하여 주 10회 용출한 $^{99m}Tc$의 총 방사능은 평균 230.5 GBq (6230 mCi)로 24시간 주기의 주 5회 용출한 방사능보다 총 62.3 GBq (1685 mCi), 일 평균 12.46 GBq (337 mCi)로 전체 용출 방사능이 27.04% 증가 하였으며 각 시간 별로 얻어진 $^{99m}Tc$의 정도 관리는 정상 범위 내에 있었다. 이번 실험을 통하여 2회/일 용출방법이 1회/일 용출방법보다 62.3 GBq (1685 mCi)의 더 많은 방사능의 $^{99m}Tc$을 생산 할 수 있었으며 각 시간 별로 얻어진 $^{99m}Tc$의 정도 관리는 정상 범위 내에 있었다. 이에 따라 각 시간 별로 용출된 $^{99m}Tc$을 방사성 표지 화합물과 결합시켜 검사를 시행하여도 무관할 것으로 생각된다.

• 한국토양비료학회지
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• 제39권6호
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• pp.339-344
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• 2006

유기성 폐자원을 퇴비원료로서 재활용하는데 대한 규정에는 현재 유기물과 8종의 중금속 함량에 대한 기준만 있기 때문에 미량원소(붕소, 코발트, 몰리브덴 및 셀레늄) 및 유해 유기화합물(PAHs) 함량을 기준 항목으로 추가하기 위하여 전국 6 2개소에서 채취한 16종에 대한 성분분석을 실시한 결과는 다음과 같다. 붕소의 경우 피혁오니가 $154.2mg\;kg^{-1}$, 식품오니가 $57.1mg\;kg^{-1}$로 가장 높았고, 코발트는 공단지역 하수오니에서 $95.2mg\;kg^{-1}$, 대도시 하수오니에서 $22.9mg\;kg^{-1}$, 몰리브덴은 식품오니에서 $16.8mg\;kg^{-1}$, 대도시 하수오니에서 $40.1mg\;kg^{-1}$, 셀레늄은 섬유오니에서 $28.1mg\;kg^{-1}$, 피혁오니에서 $16.9mg\;kg^{-1}$ 그리고 식품오니에서 $15.9mg\;kg^{-1}$으로 가장 높았다. 유해 유기화합물 중 총 PAHs는 제지오니에서 $3,462ug\;kg^{-1}$로 가장 높았고, PAHs의 성분별 비교해 보면, naphthalene, phenanthrene, pyrene, fluoroanthene, anthracene 및 acenaphthene의 함량이 다른 화합물보다 현저히 높은 것으로 나타났다. 따라서 현재 우리나라에서 유기성자원의 퇴비원료로 활용에 대한 기준은 유기물함량과 중금속(8성분: Zn, Cu, Cr, Pb, Ni, Cd, As, Hg)으로 규제하고 있으나, 미량원소(B, Co, Mo, Se), 유해 유기화합물(PAHs)에 대한 보완연구를 통해 퇴비원료기준에 규제기준을 추가하여 선별체계를 확립한다면, 유기성 폐기물도 자원으로써 농업적인 재활용이 가능하다고 생각된다.

• 대한예방한의학회지
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• 제4권2호
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• pp.25-56
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• 2000

Trace element are involved in enzymatic activities, immunological reactions. physiological mechanisms. Deficiency in some trace elements, such as iron and iodine. is still an important health problem, The role of trace elements deficiency is suspected in various clinical situations and is now confirmed by well designed supplementation studies. However, the importance of trace elements as chinese herbal constituents is not sufficiently appreciated by the oriental medical profession, although in recent years a significant increase of new finding on their essential character in chinese herbal medicine occurred. It is well known that herbal medicine contains a variety of trace elements which would show therapeutic effects with active components in herbal medicine . In china, recent work showed some positive correlation between trace element and traditional chinese medicine (TCM) in terms of therapeutic effects even if their role in therapeutic effects is still obscure. In korea, not much attention has been on the therapeutic importance of trace element contained in herbal medicine Here, the therapeutic effects of trace element in TCM were reviewed and summarized. 1. Iron, copper, zinc and manganese are mainly contained in TCM. In addtion, chromium, magnesium, molybdenum, nickel, alminium, cobalt, arsenic and selenium has been studied for their therapeutic effects 2. Zinc, is decreased in patients who have deficiency of kindney(腎虛) and chronic disease. Fe is decreased in patients who have deficiency of blood(血虛). However copper is increased in patients who have chronic disease and hepatic disease.3 Iron concentration is high in herbs used for tonifying and nourishing yin or blood(補陰補血藥) Zinc concentration is high also in herb used for tonifying kidiney and vital essence(補腎補精藥). In addition. copper concentration Is high in herb used for replenishing qi(補氣藥) 4 In herbal drugs, the therapeutic substances in TCM are not only organic but also inorganic. It seems that trace elements would be one of components in herb for its therapeutic effects. This indicates that therapeutic effects of TCM should be extended not only to herb itself, bur also to trace elements contained in herb.