타타늄의 열처리 조건에 따른 동전위 양극분극특성 및 표면 미세구조 변화

주동현,이용렬,정영화,양홍서,박상원,이도재,송호준,박영준 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.2

The corrosion resistance of metallic implants is essential for successful implant osseointegration. Moreover, the implant surface should have appropriate surface roughness for the attachment of the osteoblast and collagen fibrils. When titanium is exposed to air a thermodynamically very stable oxide film is formed at once. This oxide is very thin and yet it protects the metal from corrosion instantaneously. However, the oxide would not be ideal, and it would be supposed that the state of oxide film would be various by the different conditions when it is formed. The objective of this study was to evaluate the electrochemical properties and surface microstructural changes of titanium after passivation treatment or exposure to high heat (in vacuum or in air). ASTM grade 2 commercially pure titanium (Ti) disks of 10㎜ diameter were wet ground and polished with 240 and 600 grit SiC, and then ultrasonically cleaned with distilled water and ethanol. Cleansed as-received samples (As-R group) were passivated with 30% nitric acid solution at 50℃ for 15 minutes to make the Pas group. The Std-V samples were made by treating the Ti disks in vacuum quartz tube (10^-8 Torr) at 530℃ for 40 min for stress relieving, followed by annealing at 700℃ for 90 min, and then slow cooling to room temperature. The Std-A samples undergo identical procedure as the Std-V group except that it is done in air. For 530℃-V samples, Ti disks were heated at 530℃ for 40 minutes and slow cooled to room temperature. The 1000℃-V samples were produced by heating Std-V specimens again at 1000℃ for 2 hr, followed by cooling to room temperature. 530℃-A and 1000℃-A samples were also prepared. Potentiodynamic anodic polarization measurement, SEM, AFM and XRD analysis were performed to evaluate the effects of the various treatments. The difference in the mean values of E_corr between groups showed statistically significant difference (P<0.05), but that of I_corr did not show significance (P>0.05). When Ti surface was passivated there was a shift of corrosion potential (E_corr) in the noble direction and a lower corrosion current density (I_corr) value. Std-A samples showed most noble E_corr value among the tested groups. 530℃-V samples showed more noble E-corr than other tested groups except Std-A group. 1000℃-V samples showed more noble E-corr than those of Std-V sample. In the case of Std-, 530℃- and 1000℃-groups, -A sub-groups showed better corrosion resistant characteristics than -V sub-groups in regard to E-corr and I_corr values. In the SEM observations, the surfaces of the As-R samples showed only scratch line on smooth surface. In Pas samples, thick oxide layer covered the surface under high magnification observation. 530℃-A samples were covered by oxide granules, and Std-A samples had 25~50 nm-thick acicular oxides. The 1000℃-A samples were covered by coarse oxide crystals with a granule diameter of 0.1~0.6 μm having a gross appearance of milky white color, which was identified by XRD as a rutile. On the other hand, 1000℃-V samples showed an Widmansta¨tten structrue of which the orientation of the lattice is formed along crystallographic planes of the parent crystals. On the AFM observation, 530℃-A samples showed RMS roughness of 79.38 nm which is 5 times rougher than those of the As-R samples. Std-A sample had a roughness of 330.47 nm which is about 20-times rougher than that of the As-R sample. 1000℃-A samples were covered by coarse granular oxides and the roughness were about 0.56 μm. Vacuum sub-group samples showed a more smooth surface than air sub-group samples, and the oxide film was more dense. Due to variability of the surface treatment and heat treatment conditions, the process of the oxide formation seems to be affected thereby making the corrosion properties and surface micro-morphology different. However, more various electrochemical analysis together with surface analysis, and an investigation for the effects of those on the osteoblast cell adhesion and calcium phosphate apposition are needed for the improvement of the osseointegration rates of the titanium implants.

GHA 기반의 홍채 인식 시스템에 관한 연구

주동현,염동훈,고기영,박용기,김두영 동아대학교 정보기술연구소 2001 情報通信硏究所論文誌 Vol.9 No.1

본 논문은 Biometrics분야 중 다른 생체학적 특징보다도 정확도면에서 가장 뛰어난 특징인 안구의 홍채 패턴을 이용하여 사용자를 인증 하는 시스템에 관한 연구이다. 입력된 안구 영상으로부터 전처리 과정을 거쳐 극좌표 변환을 통해 홍채 패턴을 추출한 후 웨이블릿 변환을 이용하여 특징패턴을 압축하였으며, PCA(Principal Component Analysis:주성분 해석)의 한 종류인 GHA(Generalized Hebbian Algorithm)를 사용하여 등록된 사용자의 패턴 DB에서 Basis 배열을 추출하고, 구축된 Basis 배열과 입력 영상 패턴과의 비교 Matching을 통하여 사용자를 인증하는 시스템을 제안한다.

대나무 섬유소를 이용한 섬유보강 콘크리트의 역학적 특성

류현기,권용주,신상용 忠州大學校 2009 한국교통대학교 논문집 Vol.44 No.-

This study is a experiment on the mechanical properties of concrete according to the fiber additional quantity of bamboo. The experiment and analysis results are as the following. The slump as a quality of the concrete not to harden showed to decrease more remarkably for a slump value than the plain according to the increment of cellulose additional rate. Air quantity showed to increase only in 0.2% fiber additional rate and to get out of KS allowable error of bad air content in 0.4% and 0.6%, and capacity mass by unit showed a reverse tendency against air quantity according to the change of cellulose additional quantity. Compression intensity as a quality of hardening concrete showed collectively a tendency to decrease in the remnant past days except only 0.6% at the standard past day 愀8 and the initial 3 days. Pulling intensity showed to increase more than the plain in all past days according to the change of fiber additional quantity of bamboo, and bending intensity also showed to be higher revelation intensity than the plain in the measurement result at the standard past day 28. In the result of length change rate, we can find the bigger the cellulose additional rate as a special quality increased, the more it decreased according to the pass of the past day.

사회적 자본이 방문판매사업의 성과에 미치는 영향

최용주, 이동현, 성재열 가톨릭대학교 사회과학연구소 2010 社會科學硏究 Vol.26 No.-

전문비서란 무엇인가? : Its Concept and Function

김주연,용주현,신동희,유민,최정윤 이화여자대학교 법정대학 비서학과 1995 비서학연구 Vol.- No.15

광섬유 편광간섭계를 이용한 광파장 측정

이현우,이영주,김용평 경희대학교 산학협력기술연구원 1999 산학협력기술연구논문집 Vol.5 No.-

A simple and accurate wavemeter for measuring the wavelength of monochromatic light for WDM (Wavelength Division Multiplexing) is theoretically described The device uses the wavelength-dependent phase lag between principal polarization states of a length of birefringent material (retarder) as the basis for the measurement of the optical wavelength We used the PM(Polarization Maintaining) fiber for birefringent material at implementations of the device with fiber-optic. This device offers the advantage for increased resolution through the choice of the retarder length.

PZN-BT-PT계 복합 세라믹스의 유전특성

류주현,이용우 世明大學校 1998 世明論叢 Vol.7 No.-

(1-X)LTC-XHTC composites were manufactured with the variation of X in the range of 0.3<X<0.6 and its dielectric properties were investigated. Here, LTC and HTC are PZN-BT-PT-based ceramics with qurie temperature(Tc) of 100℃, -30℃,respectively. 0.6HTC-0.4LTC composite ceramics show excellent values of △εγ/ε[%] which were -7.1% at -20℃ and -12% at 50℃, respectively. It is thought that composite ceramics with above result can be applied to electrostrictive actuator, high voltage ceramic capacitor etc.

관상동맥질환의 중증도와 혈중지질치 및 아포지단백과의 상관관계

임현주,황종현,류재근,정병천,조용근,채성철,전재은,박의현 慶北大學校 醫科大學 1997 慶北醫大誌 Vol.38 No.1

목적 : 관상동맥질환의 위험인자로서 혈청지질 및 혈장 지단백에 대한 관심이 높아지고 있고 또 아포지단백이 관상동맥 질환을 일으키는데 다른 지질보다 더 중요하다는 연구가 많이 발표되고 있으나 우리나라에서는 아포지단백에 대한 연구가 그리 많지 않은 편이다. 이에 저자등은 혈중지질치와 새로운 위험인자로 알려지고 있는 아포지단백치를 측정하고 이들과 관상동맥질환 중증도와의 상관 관계를 알아보았다. 대상 및 방법 : 관상동맥질환이 의심되어 관상동맥조영술을 실시한 69명의 환자를 대상으로 하였으며 12시간 이상 공복후 혈청을 채취하여 총콜레스테롤, 중성지방, HDL-콜레스테롤, 아포지단백 AI (ape AI), 아포지단백 B (ape B)를 측정하였다. 관상동맥조영상 50%이상의 협착이 있는 혈관의 수 (lesion number), 최대협착을 합한 값 (lesion score), 각 분절의 최대협착을 합한 값 (total score), 가장 심한 협착 값 (peak stenosis) 등으로 관상동맥 중증도를 알아본 다음 이들과 혈청지질치, 아포지단백과의 상관 관계를 비교해 보았다. 상관 관계는 Spearman's correlation coefficient를 구하였다. 결과 : 관상동맥질환의 중증도와 각 지질치 간의 상관 관계를 비교해 보았을때 lesion number와 관계있는 것은 연령 (r=0.2789), 중성지방치 (r=0.2829)이며 lesion score와 관계있는 것은 연령(r=0.2911), 중성지방치0 (r=0.3316), 총콜레스테롤과 HDL-콜레스테롤의 비 (r=0.2361), apo B 치(r=0.2759), apo AI과 apo B의 비 (-0.3154)로 나타났다. Total score는 연령 (r=0.3100), 총콜레스테롤치 (r=0.2452), 중성지방치 (r=0.3022), 총콜레스테롤과 HDL-콜레스테롤의 비 (r=0.2770), apo B치 (r=0.2927), apo AI과 apo B의 비 (r=-0.3408)와 연관이 있었고 peak stenosis는 중성지방 치(r=0.3305), ape B 치 (r=0.2968), apo AI과 apo B의 비 (r=-0.3977)와 관계가 있었다. 연령으로 조정하여 partial correlation을 좌면, 관상동맥조영술상 중증도는 중성지방치 (r=0.3408), apo B 치(r=0.2877), apo AI과 apo B의 비 (r=-0.3460)와 유의한 상관 관계가 있었다. 이중 ape AI과 ape B의 비는 lesion score (r=-0.2640), total score (r=-0.3057), peak stenosis (r=-0.3460)와 유의한 상관관계를 보였다. 결론 : 이상의 결과로 보아 apo B치 그리고 apo AI과 apo B의 비가 관상동맥 중증도의 예견인자로 다른 혈중 지질 치보다 더 유용하다는 것을 알 수 있었다. Objectives : Recently, it was reported that the measurements of apolipoprotein levels may be valuable in the clinical assessment of coronary artery disease severity. However there are a few reports regarding to the relationship between coronary artery disease severity and apolipoprotein levels in Korea. Thus, we measured serum lipid and apolipoprotein levels and studied the relationship between coronary artery disease severity and serum lipids and apolipoproteins levels. Subjects and Methods : The 69 patients who underwent coronary angiography to evaluate chest pain were subjected to this study. We measured the levels of serum cholesterol, triglycerides, HDL cholesterol, apolipoprotein AI(apo AI) and apolipoprotein B(Apo B) and measured the severity of coronary artery disease by lesion number, lesion score, total score and peak stenosis. Then, we studied the relationship between coronary artery disease severity and apolipoproteins and calculated the correlation coefficient. Results : The results were as follows. There are significant correlation(r=0.3) between age, triglycerides, apo B levels, apo AI/B ratio and coronary artery disease severity. In controlling for age, tyiglycerides, apo B levels and apo AI/B ratio shows significant correlation(r=0.3) with coronary artery disease severity. Especially, apo AI/B ratio shows significant correlation(r=0.3) with lesion number, total score and peak stenosis. Conclusion : These results suggest that the apo B levels and the ratio of apo AI/B can be used as significant independent predictor for coronary artery disease severity rather than other serum lipid levels.

치주조직 재생을 위한 칼슘 포스페이트 글라스 분말이 백서 두개골 결손부의 골조직 재생에 미치는 영향

이용근,문현주,이상배,김광만,김경남,최성호 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.2

The treatment of the tone defects resulting from trauma, neoplasm, surgery, or infection is one of the major concern in dentistry. The major goal is the functional, esthetical regeneration of supporting structures already destructed by disease. Transplantation technique have been used to provide a scaffold for bone regeneration, to augment bony defects resulting from trauma or surgery, to restore bone loss caused by dental disease, to prevent the collapse the alveolar ridge in recent extraction sites, to replace bone loss by periodontal disease, to augment the alveolar ridge in implant surgery. There are autogeneous, allogenic, xenogenic and alloplastic bone-grafts in transplantation. Among the alloplastic bone-graft materials, calcium phosphates have been received the most attention. In this study, the critical size defects were surgically produced in the calvarial bone of Sprague-Dawley rats using the 8 ㎜ trephine bur. Calcium phosphate glass powders with mean diameter 400 ㎛ transplanted onto the produced detects in the experimental group, while sutured without grafting anything in the control group. Histomorphometric as well as radiodensitometric analyses were performed after sacrifice at 2, 4 and 8 weeks following operation. The prepared calcium phosphate glass powder with average size 400 ㎛ in CaO-CaF_2-P_2O_5-MgO-Al_2O_3 promoted new bone formation in the calvarial defects in the Sprague-Dawley rats. New bone was formed in the upper side of the detects as well as the defect margin and dura mater. Experimental group always exhibited higher values in the length, area and density of the newly formed bone than that of the control group. There were significant differences between the experimental and the control groups, except the density after 4 weeks (p<0.05).

전문가 시스템에서 지식의 그룹화와 추론 메타니즘

강현석,황용주,김용화 전북대학교 전자산업개발연구소 1990 전자산업연구 Vol.1 No.-

Most expert systems infer typically by using knowledges i.e.. rules and facts. If we grouped knowledges of the expert system effectively, it is very easy to maintain them. And we also can infer new knowledges from them efficiently because the inference is done only on a set of the finite grouped knowledges. In this paper, we propose a method in which some common attributed knowledges or some related knowledges are grouping efficiently. To show in we describe and algorithm which groups the rules of the expert system. and also we present a method which infers new knowledges by using the grouped knowledges.