Co-Cr계 합금의 기계적 성질 및 내부식성에 미치는 B 첨가의 영향

白勝男,鄭宗鉉 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.1

This paper aims to investigate the effect of B on the mechanical properties. microstructure and corrosion resistance of Co-Cr base alloy. Five groups of alloy ingot with various contents of B were remelted by a high frequency induction furnace and cast into tensile specimen of A.D.A. Specification No.14. Tensile and hardness test were carried out by Amsler and Rockwell hardness tester (R-30N). respectively. The microstructures of specimen were observed by SEM. The results obtained are summarized as follows: 1. As B content is increased. tensile strength. yield strength and hardness are also increased significantly. while the elongation is decreased significantly. 2. As B content is increased. corrosion resistance is decreased and is at best with 1.5% B content. 3. As B content is increased. precipitates are increased in number at grain boundaries. 4. Co rich-Or alloy is present through matrix whereas Cr base precipitates are primarily formed at the grain boundaries.

입력역률을 개선한 단상 PWM 스위칭 컨버터

백종현 대구산업정보대학 2000 논문집 Vol.14 No.2

In this paper, single-phase PWM AC to AC converter that operates with unit power factor and sinusidal input line currents is presented. The current control of this converter is based on the predicted current control method with fixed switching frequency and the line currents track to reference currents within one sampling time interval. By using this control method low lipples in the output current and the voltage as well as fast dynamic response are achieved with small dc link capacitance employed.

함수량이 다른 오염지반의 지지력 결정

안종필,박경호,백현 朝鮮大學校 建設技術硏究所 1999 建設技術硏究 Vol.19 No.1

This study, investigates the existing theoretical backgrounds in order to examine the behavior of lateral flow owing to the plasticity of soils when unsymmetrical surcharge is worked on polluted soils by the increase of water content, compares and analyzes the results measured through model tests. Unsymmetrical surcharge is increased at regular intervals to soil tank made up the polluted soils and then the amounts of settlement, lateral displacement and upheaval are observed. Critical surcharge was decided q_(cr)=3.42 C_(u) similar to those had proposed Terzaghi and JHI, and the value of ultimate capacity was decided q_(ult)=7.71 C_(u) similar to that of Tschebotarioff and JHI

비페닐 구조를 가지는 액정폴리머의 합성과 특성

이종백,이광현,강병철 동의대학교 산업기술개발연구소 2005 産業技術硏究誌 Vol.19 No.-

A series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, and hexamethylene diisocyanate with 4,4'-Bis(9-hydroxynonoxy)biphenyl (BP9). Structures of the monomer and the corresponding polymers were identified using FT-IR and ^(1)H-NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry and optical polarizing microscopy. 4,4'-bis(9-hydroxynonoxy)biphenyl exhibited a smectic type mesophase. Mesophase was found for all synthesized liquid crystalline polyurethanes except 1,4-PDI/BP9 based polyurethane.

금은화 추출물의 세포독성에 관한 연구

한종현,백승화,김일광,한두석 圓光大學校 韓醫學硏究所 1993 원광한의학 Vol.3 No.1

In order to investigate the cytotoxicity of Lonicerae Flos extract, their extracts were dissolved in distilled water and methanol. All material diluted from 10^-3to 10^-7(㎎/㎖) with distilled water putted in each well of 24 multidish cultured rat fibroblast for 48hours. The cell number was calculated at 2 days and cell shape takes photographed by inverted microscope at same day. The results were as follows: 1. The rate of cell multiplication was the lowest in water extract from 10^-3 to 10^-7(㎎/㎖) concentration and the highest in ether and hexane extract at 10^-7(㎎/㎖) concentration. 2. Index of cytotoxicity was the highest with 3 score in water extract at 10^-3(㎎/㎖) concentration and the lowest with 1 score in ether, ethyl acetate or hexane extract at same concentration. 3. The degeneration of cell shape and number was the severest in water extract of 10&-4(㎎/㎖) concentration, but ether and hexane extracts in same concentration were weaker than water extract. These results indicate that the cytotoxicity of extracts by ether and hexane from same Lonicerae Flos was weaker then water extract.

생체분해성 망막압정을 이용한 망막고정에 대한 실험적 연구

김용백,민병무,김창식,박근성,김승영,길숙종,조항진,이성복,노승무,송규상,강대영,조준식,양준묵,정경수,최선웅,이진호,김학용,인현빈 충남대학교 의과대학 지역사회의학연구소 1998 충남의대잡지 Vol.25 No.1

Biodegradable retinal fixation devices obtain mechnical fixation of the retina with desirable chorioretinal scarring and with the potential for local, sustained release of antimetabolites and steroids to inhibit proliferative vitreoretinopathy. We manufactured a biodegradable retinal tack with barb that was designed in order to prevent intrusion from implantation of retinal tacks. This study was carried to evaluate the efficacy for retinal fixation and the capability for sustained release of drugs with a newly designed biodegradable retinal tack Biodegradable retinal tacks were made of polymers of glycolic acids and were designed with barbs in a shape to prevent the disinsertion. Biodegradale retinal tacks are divided into 3 parts, a conical portion that is inserted into the sclera, a cylinder portion that remains in the vitreous, and a neck portion between the pin and the cylinder. The tapered conical end was manufactured to allow easy insertion through the retina and choroid into the sclera. A cylinder portion was manufactured with a tapered angle that fixes firmly into the orifice of 19 gauge spinal needle. A neck portion, 0.4 mm in diameter, was designed to prevent disinsertion from following implantation of retinal tack. The applicator was a 19 gauge spinal needle and its orifice was prepared to 15°angle to accept the tapered cylinder portion of the retinal tack. The retinal tacks, secured in the needles, were passed through the formed vitreous and inserted into the retina, choroid, and sclera and were released by pushing the internal needle, usually within 2-3mm of the medullary ray of the posterior rabbit retina A retinal tack was placed in each of 8 pigmented rabbit eyes. Slit-lamp biomicroscopy, indirect ophthalmoscopy and fundus photography were performed periodically from 1 day to 8 weeks after surgery. Eight eyes were enucleated and studied by light microscopy at 8 weeks. Biomicroscopic evaluation of the animals revealed edemas adjacent to the retinal surfaces immediately after insertion of the biodegradable retinal tacks in all the animals. These edemas disappeared after 1 week. The first noticeable change in the size of retinal tacks was shown after 2weeks. The size of the retinal tacks gradually got smaller, decreasing to about one-half at 4 weeks and about one-third at 8 weeks. All retinal tacks remained in inserted places without any movement for an 8 week period. On light microscopy, epiretinal proliferations were seen to extend into the vitreous cavity. Cellular capsules that lined the inner aspect of the scleral defect caused by tack insertion were found. However the adjacent retina had a normal cytologic appearance and architecture in all specimens. We manufactured a biodegradable retinal tack that is designed to prevent intrusion from implantation of retinal tacks. All biodegradable retinal tacks reduce in size with time, but no retinal tacks extruded from the inserted place. The newly designed biodegradable retinal tack can be used for retinal fixation and may be used as a vehicle for the introduction of pharmacologic agents to prevent the cellular events that promote proliferative vitreoretinopathy.

생체용 Ti합금의 양극분극특성에 미치는 Zr 및 Pd의 영향

정종현,이길홍,최칠남,노학,백승남,이상열 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.2

The corrosion resistance of Ti-Zr-Pd-Cr alloys were investigated in order to reveal their possible use for new biomedical implant materials. Titanium alloys consisting of 10∼20%Zr, 0.0∼0.4%Pd and 0.15%Cr were prepared by vacuum arc-melting as alloying elements instead of using hardness Al and V in response to recent concerns about the long term safety of Ti-6%Al-4%V ELI alloys. The Ti-Zr-Pd-Cr alloys were heat-treated at 1000℃ for 2hrs under a vacuum atmosphere. The effect of Zr and Pd Ti alloys on the corrosion resistance for biomedical implant was investigating the anodic polarization curve at 37℃ in 5%HCI solution deaerated by high-purity N₂gas bubbling. The critical current density for passivation(I ) of Ti-Zr-Pd-Cr alloys didn't reveal markedly. Passive current density(I ) at 1.0V vs. SCE of this alloys decreased with increasing Zr in the contents from 10 to 20% and decreased with containing Pd in the range from 0.2 to 0.4%. Potential(E ) at 0.1A * m-² of this alloys increased with increasing Zr in the contents from 10 to 20% and increased with containing Pd in the range from 0.2 to 0.4%. For the Co-30%Cr-6%Mo alloy, passivity zone is narrow, and rapid increase of current density result from the low potential in comparison with Ti and Ti alloys. The corrosion resistance by the anodic polarization of Ti-20%Zr-0.2%Pd-0.15%Cr alloy was found to be superior to those of the Ti, Ti-6%Al-4%V alloy and Co-30%Cr-6%Mo alloy. The passive films formed on the Ti-20%Zr-0.2%Pd-0.15%Cr and Ti-6%Al-4%V alloys in the anodic polarization test consist mainly of TiO₂, Ti compound, ZrO₂, Al₂O₃and V₂O₃.

생체용 Ti₁-x-Zrx합금의 기계적 성질과 내부식성

정종현,백승남,노학,고영무 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.1

While titanium and its alloys has been well studied for a long time, new interest in these materials and their properties has arisen in recent years with respect to their application as biomedical metallic materials. For practical purposes, the following performances are essential for biomaterials. (1) low specific gravity (2) high corrosion resistance (3) good biostability and biocompatibility (4) sufficient mechanical properties (5) non-toxicity To develop biomedical implant materials having all the properties mentioned above, new titanium-zirconium alloys were prepared in this study. Mechanical properties and corrosion resistance were then investigated for as-cast and as-homogeneized Ti₁_x-Zrx alloys in order to reveal their possible use for biomaterials. From the experiments, the following results are obtained: 1. No martensite structure are observed in the specimens made of pure Ti and Zr. In contrast them, Ti-Zr alloys containing 18wt%Zr, 24wt%Zr and 48wt%Zr show a kind of martensite structure regardless heat treatment. 2. Fineness of structures for as-cast-alloys seems to vary with alloy composition. Ti-Zr alloy containing 48wt%Zr shows the finest microstructure. 3. Hardness of Ti-Zr alloys shows continuous change through the system and the alloys containing 48 to 60wt%Zr indicate higher hardness compared with those of pure Ti and other alloys. It is well known that hardness is usually changed with substitutional atoms, and effect of solute atom on hardness is greatest with an equi-atomic composition. The greatest hardness which was obtained in Ti-Zr alloys containing 48 to 60wt%Zr is therefore reasonable. Also, enhanced hardness can be explained on elastic interaction between dislocation and substitutional solute atoms in crystal structure and on fineness of structure. 4. Pure Ti and Zr alloys containing 6wt%Zr, 12wt%Zr, 18wt%Zr, 36wt%Zr show better corrosion resistance compared with those of pure Zr, stainless steel(SUS 316L) and the Ti-Zr alloy containing 48wt%Zr. 5. Comparing hardness, microstructure and corrosion of Ti₁_x-Zrx alloys, no large differences between as-cast and as-homogenized alloys are seen.

중금속[Cu(Ⅱ), Zn(Ⅱ)]의 분리 및 농축을 위한 역삼투 판틀형 모듈의 적용

이광현,강병철,이종백,김종팔 한국물환경학회 2004 한국물환경학회지 Vol.20 No.4

This study was focused on experiment for the separation and concentration process of Cu(Ⅱ), Zn(Ⅱ) solution with the variation of applied pressure and concentration using reverse osmosis plate and frame modules. Rejection coefficient and degree of concentration for Cu(Ⅱ) component using single and multi-stage reverse osmosis process were showed 96.3 ~ 97.8%, 0.044 ~ 0.191(in single-stage), 96.3 ~ 98.4%, 0.400 ~ 2.264(in multi-stage) within the range of experimental condition, respectively. Those of Zn(Ⅱ) were 93.3 ~ 97.1%, 0.019 ~ 0.395(in single-stage), 96.3 ~ 98.2%, 0.365 ~ 1.454(in multi-stage), respectively. Degree of concentration of multi-stage were higher than those of single-stage. Heavy metal[Cu(Ⅱ), Zn(Ⅱ)] separation was very efficient in using reverse osmosis plate and frame type modules. Separation efficiency for a mixed solution Cu(Ⅱ) and Zn(Ⅱ) was higher than those of each one of Cu(Ⅱ) and Zn(Ⅱ).

나프탈렌기를 갖는 새로운 액정폴리우레탄의 합성 및 특성

이종백,이광현 한국고무학회 2005 엘라스토머 및 콤포지트 Vol.40 No.1

새로운 형태의 액정성 폴리우레탄을 2,6-bis(ω-hydroxyalkoxy)naphthalene (BHNm; m= 5, 6, 8, 11)과 2,5-tolylene diisocyanate 또는 1,4-phenylene diisocyanate의 중부가 반응에 의해 합성하였다. 폴리우레탄의 고유 점성도는 0.28-0.43 dL/g 였다. 열적 성질은 DSC 및 편광현미경에 의해 측정되었다. 단량체 BHNm과 메틸치환기를 가진 2,5-tolylene diisocyanate에 의해 합성된 폴리우레탄은 모두 단방성 액정성을 나타내었다. 그러나 BHNm와 1,4-phenylene diisocyanate를 합성한 폴리우레탄에서는 DSC와 편광현미경으로 조사 결과 전혀 액정성을 나타내지 않았다. Novel polyurethanes containing no mesogenic unit were synthesized by the polyaddition reaction of para-type diisocyanates such as 2,5-tolylene diisocyanate (2,5-TDI) or 1,4-phenylene diisocyanate (1,4-PDI) with 2,6-bis(ω-hydroxyalkoxy)naphthalene (BHNm; m= 5, 6, 8, 11). Intrinsic viscosities of the polymers were in the range of 0.28-0.43 dL/g. The thermal properties of these polymers were studied by differential scanning calorimetry and polarizing microscopy. Polyurethanes prepared from BHNm and 2,5-TDI having methyl sub stituent on the phenylene unit exhibited monotropic liquid crystallinity. However, in the series of polyurethanes prepared from 1,4-PDI and BHNm, no explicit mesomorphic behavior was observed by differential scanning calorimetry and polarizing microscopy.