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자기유변유체를 이용한 Fused silica glass의 미세연마공정특성에 관한 연구
이정원,김동우,신영재,장호수,조명우 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-
A new, commercially available polishing process called magnetorheological fluid polishing is used to fabrication optical glass and bio-chip. This polishing process guarantees high polishing quality by controlling the fluid density electrically. The applied material in experiments is fused silica glass. Fused silica glass is widely used in the optical and biochip field because of high degree of purity. For MR polishing experiments, MR fluid was composed with DI-water, carbonyl iron and nano slurry ceria. The wheel speed and electric current were chosen as the variables for analyzing the characteristics of MR polishing process. In results, the surface roughness according to the variation of wheel speed and electric current was analyzed.
인산용액의 농도 및 적용시간 차이에 따른 상아질 표면의 형태적 변화
김명수,온영석,이광원,손호현 大韓齒科保存學會 1998 Restorative Dentistry & Endodontics Vol.23 No.1
The depth and patterns of demineralization according to the difference in concentration and application time of phosphoric acid were observed through the transmission electron microscope, and shear bond strengths to the acid-conditioned dentin were then measured and compared with the TEM results. To investigate the influence of polymer addition into the phosphoric acid and the effect of difference in concentration and application time of the acid, the specimens were randomly divided into 9 groups. Among the specimens, the exposed dentin surfaces were acid-conditioned with 10% polymer-thickened phosphoric acid(All Bond 2, Bisco, U.S.A.) and aqueous 10%, 20%, 30%, 40% phosphoric acid for 20 seconds, The rest of the specimens were acid-conditioned with 10% phosphoric acid for 15s, 30s, 60s, 120s respectively. The specimens were immersed in 4% glutaraldehyde in 0.1M sodium cacodylate buffer and postfixed with 1% osmium tetroxide without decalcification and then observed under a JEOL Transmission Electron Microscope(JEM 1200 EXⅡ,Japan). After the specimens were acid-conditioned as the above, primer and adhesive resin were applied to blot-dried dentin and shear bond strengths were then measured and analysed. The results were as follows : 1. The intertubular demineralization depth of 4.0-5.0㎛ in 10% polymer-thickened phosphoric acid gels was similar or slightly deeper than that of 4.0-4.5㎛ in aqueous 10% phosphoric acid solution. 2. The intertubular demineralization depth of aqueous 20%, 30% and 40% phosphoric acid solution was 6.5-7.0㎛, 6.5-7.5㎛ and 9.0-15.0㎛ respectively. It showed that the depth of dentin demineralization is partly related to the concentration of phosphoric acid solution. 3. The intertubular demineralization depth of aqueous 10% phosphoric acid solution in application time for 15s, 30s, 60s and 120s was 2.5-3.0㎛, 4.0-6.0㎛, 6.5-7.0㎛ and 8.5-14.0㎛ respectively. It showed that the depth of dentin demineralization is directly related tothe application time of phosphoric acid solution. 4. The partially demineralized dentin layer between demineralized collagen layer and unaffected dentin was showed to a width of 0.5-1.0㎛ in lower concentration groups treated with aqueous 10% phosphoric acid for 20s, 60s, 120s and 20% phosphoric acid for 20s. 5. The demineralization effect at the border of intertubular-peritubular junction was less evident than that in the peritubular and intertubular dentin. The collagen fibers in the intertubular dentin had a random orientation, whereas those that lined the tubules were circumferentially aligned. The cross-linkage of dentinal collagen in demineralized collagen layer was clearly seen. 6. A statistically significant difference of bond strengths according to the difference in phosphoric acid concentration did not exist among the groups treated with 10%, 20%, 30% and 40% acid solution (P>0.05). However, bond strengths to the treated dentin with 10% phosphoric acid solution for 30s were significantly higher than that for 120s (P<0.05).
정명아,서유승,양진수,박준섭,윤진훈,이중건,이준승,이영규,김동희,조성범,주종은 대한신장학회 2002 Kidney Research and Clinical Practice Vol.21 No.2
Pelvic actinomycosis is a chronic granulomatous suppurative disease caused by an anaerobic grampositive organism Actinomyces israelii. It is com-monly associated with an intrauterine device(IUD) and can mimick pelvic or intra-abdominal malignant neoplasm. Ureteral obstruction leading to hydronephrosis is a rare complication of tubo-ovarian abscess. We experienced a case of hydronephrosis as a complication of pelvic actinomycotic abscess. The patient was a 46-year-old women presenting with fever and right flank pain. Leukocytosis and pyuria were present and a hydronephrosis was diagnosed by intravenous pyelography. Ultrasonography and a computerised tomography revealed a mass in right adnexum compressing the right ureter. Removal of retroperitoneal abscess and salphingo-oophorectomy were done and the diagnosis of actinomycosis was made by pathologic finding of resected mass. Postoperatively, the patient was treated with second-generation cephalosporin successfully. (Korean J Nephrol 2002;21(2):337-340)
가연성물질의 인화점에 관한 연구 : 용액론에 의한 3성분계의 인화점 예측을 중심으로
하동명,이수경 한국화재소방학회 2001 한국화재소방학회논문지 Vol.15 No.3
인화점은 가연성물질의 화재 및 폭발의 잠재위험성를 결정하는 데 가장 중요한 기초적인 특성치 가운데 하나이다. 인화점의 구분은 혼합용제를 구성하는 가연성액체를 안전하게 취급하기 위해서 매우 중요하다. 모든 인화점 거동의 기초는 증기압과 폭발한계이다. 가연성혼합용제의 인화점은 라울의 법칙, 달톤의 법칙, 르샤틀리에 법칙 그리고 활동도계수 모델을 사용함으로서 계산할 수 있다. 본 연구에서는 가연성 3성분계의 하부인화점의 문헌값을 라울의 법칙과 MRSM모델을 의해 계산된 값과 비교하였다. 3성분계의 하부인화점의 자료는 라울의 법칙과 MRSM모델에 의해 예측된 값과 거의 일치하였다. 제시한 방법론에 의해 가연성혼합용제의 인화점 실험자료의 신뢰도를 평가하는 것이 가능하다. The flash points are one of the most important fundamental properties used to determine the potential for fire and explosion hazards of flammable substances. A classification of the flash points is important for the safe handling of flammable liquids which constitute the solvent mixtures. Basic to all flash points behavior are vapor pressure and explosive limits(lower explosive limit and upper explosive limit). The flash points of flammable solvent mixtures can be calculated with the appropriate use of the fundamental laws of Raoult, Dalton, Le Chatelier and activity coefficient models. In this study, the reference values of lower flash points were compared with the calculated values by using Raoult's law and MRSM(modified response surface methodology) model. The lower flash points were in agreement with the predicted by Raoult's law and MRSM model. By means of this methodology, it is possible to evaluate reliability of experimental data of the flash points of the flammable mixtures. Keywords : Flash point, Flammables mixtures, Vapor pressure, Explosive limit, Le Chatelier
Fe-Ni에 Si와 Cr을 첨가한 박막의 자기적 특성에 관한 연구
금채,이명섭,전관수 충남대학교 자연과학연구소 1989 忠南科學硏究誌 Vol.16 No.1
Alloy thinfilms-Fe_50 Ni_59, Fe_47.5Ni47.5 Si47.5, Fe_47.5Ni_47.5 Cr_47.5- have been made by DC sputtering method. The electric and magnetic properties of alloy thinfilms have been measured between 100K and 300K. The temperature coefficients of resistivity of Fe_50Ni_50 was 0.7053 10^-6/K, that of Fe_47.5 Ni_47.5 Si_47.5 was 0.693 10^-6/K, that of Fe_47.5Ni_47.5 Cr_47.5 was 1.8363 10^-6/K. The magnetic properties of Fe-Ni compound containing Si have been better and Fe-Ni compounds containing Cr have had low electric resistance and high coercivity.
유능수,남윤수,이정완,이명재 강원대학교 산업기술연구소 2005 産業技術硏究 Vol.25 No.B
Two methods, the bin averaging method and least square method, are often used in calibrating wind turbine test sites. The objective of this work was to determine a better method to predict the wind speed at wind turbine installing point. The calibration was done at the test site on a complex terrain located in Daegwallyeong, Korea. It was performed for two different cases based on the IEC 61400-12 power performance measurement standard. The wind speeds averaged for 10 minutes ranged between 4 m/s and 16 m/s. The wind-direction bins of each meteorological mast were 10 degrees apart, and only the bins having data measured for more than 24 hours were employed for the test site calibration. For both cases, the two methods were found to yield almost same results which estimated real wind speed very closely.