http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
전동식 니켈 티타늄 파일의 표면 결함 및 단면 형태가 반복응력 하에서 피로 파절에 미치는 영향
신유미,김의성,김광만,금기연 大韓齒科保存學會 2004 Restorative Dentistry & Endodontics Vol.29 No.3
The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files (K3^(TM), ProFile®, and HERO 642®) with #30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups: control (no surface defects) and experimental group (artificial surface defects). A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the K3^(TM) (p〈0.05). There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.
Ⅷ족 전이금속 촉매를 이용한 메탄에 의한 이산화탄소의 개질반응
조영복,유의연,선우창신 全南大學校 觸媒硏究所 1997 觸媒硏究 論文集 Vol.19 No.-
Carbone dioxide reforming by methane was studied using a fixed bed reactor under an atmosphere. Transition metal catalysts and noble metals supported on α - AI₂O₃were compared. The order of activity was Ni> Pd> Co. The effects of metal additives on Ni/α - AI₂O₃were investigated for activated catalysts. The order of activity was Co > Cu > Fe. The catalyst performance depend on the CO₂/CH₄ratio and the reaction temperature.
Ni/Ti0₂ 촉매상에서 CO₂ 개질 반응에 있어서 조촉매 및 Ni 담지량의 영향
서호준,유의연 全南大學校 觸媒硏究所 1996 觸媒硏究 論文集 Vol.18 No.-
The effect of Ni loading andition of promoters such as KCI, NaCl, CaO and MgO was studied on the CO₂reforming over Ni/TiO₂catalysts in a fixed bed flow reactor at atmospheric pressure. 10wt% Ni loaded catalyst showed optimum activity. The effect of promoters on the catalytic activity was Ca>Mg>K>Na in order. Adding promoter could be suggested that the reverse Boudouard reaction occur.
개시제를 이용한 폴리에틸렌 왁스상에 MAH그라프팅 반응
강웅일,선우창신,유의연 全南大學校 觸媒硏究所 1998 觸媒硏究 論文集 Vol.20 No.-
Polyethylene wax was grafted with maleic anhydride using DCPO, DTBP, BPO, AIBN as an initiators and xylene as a solvent, The effect of reaction parameters such as MAH and initiator concentration, reaction temperature on percent grafting were studied. The maximum MAH extent of grafting achieved was 4.5%. The occurrence of a grafting reaction was analyzed by FT-IR spectrum of the polymeric reaction product of strong carbonyl streching absorbtions at ?? band. The efficiency of the radical initiators in reaction of polyethylene was with maleic anhydride was in the following order : DCPO ≒ DTBP〉BPO, ≒ AIBN
메탄에 의한 이산화탄소 개질반응에서 니켈 촉매의 반응특성
조영복,김상채,유의연 전남대학교 촉매연구소 2000 觸媒硏究 論文集 Vol.22 No.-
A study on the reaction characteristics of nickel catalysts for carbon dioxide reforming of methane was performed. The experiments were carried out at atmospheric pressure using a fixed bed flow reactor. Effects of reaction parameters on catalytic activity and carbon deposition were investigated. The carbon deposition on the catalysts was affected by reaction conditions such as temperature, molar ratio (CO2/CH4). While the formation of coke was increased as the reaction temperature increase, it was reduced above 700℃ by reverse Boudouard reaction, which is known to cause the vaporization of carbon.
조영복,선우창신,유의연 全南大學校 觸媒硏究所 2003 觸媒硏究 論文集 Vol.24 No.-
A study on the carbon deposition of nickel catalysts for carbon dioxide reforming by methane was performed. The experiments were carried out at atmospheric pressure using a fixed bed flow reactor. The nickel catalysts for the carbon dioxide reforming were compared concerning the influence of promoter on catalytic activity and carbon deposition. The coke deposition on the promoted nickel catalysts was remarkably diminished with the addition of promoters such as K, Mn and Sm. The activitie of the promoted nickel catalysts decreased in the order Ni-Li> Ni-Mg > Ni-Ca > Ni > Ni-K > Ni-Na> Ni-Cs. The carbon deposition of the promoted nickel nickel catalysts decreased in the order Ni-Mg> Ni-Li> Ni> Ni-Ne> Ni-K> Ni-Cs. In the Ni-K/α-Al_2O_3, its activity was maintained over 70 hours at 700℃ without deactivation.
메탄에 의한 이산화탄소 개질반응의 탄소침적에 관한 연구
조영복,김상채,유의연 全南大學校 觸媒硏究所 2002 觸媒硏究 論文集 Vol.23 No.-
A study on the carbon deposion of nickel catalysts for carbon dioxide reforming by methane was performed. The experiments were carried out at atmospheric pressure using a fixed bed flow reactor. The results of TEM/EDS showed that the forms of the deposited carbons were filamentous carbon and encapsulated carbon. The deposited carbon on Ni/TiO_2 revealed only encapsulated carbon. The deactivation of Ni/TiO_2 catalyst was mainly resulted from the encapsulated carbon. Encapsulated and filamentous carbon were found on Ni/α-Al_2O_3, compared to the Ni/TiO_2. The deposited carbon on Ni/La_2O_3 revealed mainly filamentous carbon. In spite of the large amount of coke formation on Ni/La_2O_3, filament carbon did not deactivate the catalyst. Using TPH results, two types of coke have been identified. One was more reactive carbidic carbon at lower temperature peak, the other was less reactive graphite one at higher temperature peak.
니켈 담지촉매상에서 메탄의 이산화탄소 개질반응 : 담체 및 조촉매에 의한 탄소침적
조영복,김상채,유의연 전남대학교 촉매연구소 2000 觸媒硏究 論文集 Vol.21 No.-
The reforming of methane by carbon dioxide is studied over nickel based catalysts, which compared the influence of the support and promoter on catalyst activity and carbon deposition. The experiments were carried out at atmospheric pressure using a fixed bed flow reactor. The carbon deposition was observed in all nickel based catalysts. The results of TEM/EDS showed that the forms of the deposited carbon revealed filamentous carbon and encapsulated carbon. In the Ni-K/Al2O3, its activity was maintaned over 72 hours at 700℃ without deactivation. Any type of the coke deposition was not observed on Ni-K/ Al2O3 catalyst.
열분해반응을 통한 폴리에틸렌-폴리프로필렌 혼합물의 오일회수 특성
정도성,김상채,유의연 全南大學校 觸媒硏究所 1998 觸媒硏究 論文集 Vol.20 No.-
The thermal degradation of polyethylene, polypropylene alone an their mixture into oil and gas products has been carried out at different reaction conditions. The effect of various parameters such as temperatures, space velocity, mixing ratio on the yield and composition of the oil recovery for these polymers at different reaction temperature. In polyethylene-polypropylene mixtures, the more polypropylene is added, the more rate of degradation of PE and conversion of PE/PP mixture increase at a lower temperature than that of PE alone. It is proposed that this enhancement is due to the free radical from polypropylene, in which can form free radical from polyethylene a lower temperature.
정도성,김상채,선우창신,유의연 全南大學校 觸媒硏究所 2003 觸媒硏究 論文集 Vol.24 No.-
Thermogravimetric analysis and pyrolysis experiment were used as studying the effent of conversional level on the thermal degradation of HDPE. The wide conversional range in this work encompassed a change in the degradation mechanism. To accommodate this mechanism change, the data were treated as a pseudo first-order reaction. It was observed that the data conformed to a first-order fit at conversional range of 0.05∼0.98 with an activation energy of 376 kJ/mol. The lower activation energy occurring at lower conversion (0.01∼0.05) is attributed to scission of 'weak links' in macromolecles. The higher activation energy was similar to the carbon-carbon bond dissociation energy and is associated with random scission throughout backbone chain. The lower the conversional level, the more abundant the paraffinic hydrocarbon in product. To what extent this finding are influenced by limitation of terminate reaction of radicals.