The synthesis of titanium silicides (, , , and TiSi) by mechanical alloying has been investigated. Rapid, self-propagating high-temperature synthesis (SHS) reactions were observed to produce the last three phases during room-temperature high-energy ball milling of elemental powders. Such reactions appeared to be ignited by mechanical impact in an intimate, fine powder mixture formed after a critical milling period. During the high-energy ball milling, the repeated impact at contact points leads to a local concentration of energy which may ignite a self-propagating reaction. From in-situ thermal analysis, each critical milling period for the formation of , and TiSi was observed to be 22, 35.5 and 53.5 min, respectively. and , however, have not been produced even till the milling period of 360 min due to lack of the homogeneity of the powder mixtures. The formation of titanium silicides by mechanical alloying and the relevant reaction rates appeared to depend upon the critical milling period, the homogeneity of the powder mixtures, and the heat of formation of the products involved.

본 연구에서는 경부고속철도의 주요 교량형식인 PSC 박스교량을 3차원 뼈대요소를 사용하여 모형화하였으며, 궤도불규칙성의 형상은 지수 스펙트럴 밀도함수를 사용하여 생성시켰다. 경부고속철도차량(K-TGV)중 동력차는 17자유도의 3차원 주행열차로 모형화하였고, 이러한 교량, 궤도불규칙성 및 차량 모형을 이용하여 교량과 차량의 상호작용을 해석할 수 있는 프로그램을 개발하였다. 동적해석을 위한 교량과 차량의 운동방정식은 Lagrange 방정식을 사용하여 유도하였으며, 운동방정식의 수치해석에는 Newmark-법을 사용하였다. 개발된 프로그램을 이용하여 동력차의 주행에 의한 교량의 시간이력곡선을 구하였으며, 궤도불규칙성의 영향을 분석하였다. 또한 도상의 유무에 따른 교량동적거동의 특성과 함께 열하중의 편심의 영향도 분석하였다.

The aims of this study are to establish a stable isolation method of blastomeres from bovine early embryos and examine their developmental potential in vitro Early embryos were produced by maturation and fertilizaion in vitro of bovine follicular oocytes. Blastomeres were isolated from 2~8-cell embryos in +-, +-free PBS+EDTA after removing the zonae pellucidae Isolated blastomeres were cultured in CZB containing BOEC for upto 240 hpi. Cleavage rates of them were 18.5%(10 /54) in 1 /2 blastomeres, 33.3%(16/48) in 1/4 blastomeres and 34.2%(14 /41) in 1/8 blastomeres, respectively. The rates of blastocystic vesicle formed were 8.7%(4 /46) in 1/2 blastomeres, 26.6% (17/64) in 1/4 blastomeres and 10.3%(8 /78) in 1/8 blastomeres, respectively. Blastomeres developed into various types of blastocystic vesicles and trophoblastic vesicles as evidenced by the Hoechst 33258 staining and morphology. This results suggest that the isolation method used and subsequent culture of isolated blastomeres from bovine early embryos should be useful to obtain extra embryonic cells for various analyses such as PCR and putative ES cell culture.

수정란이식의 주변기술인 초기배의 미세조작및 성 판정은 가축의 경우, 경제 형질의 유전적 개량에 크게 기여하였다. 본 연구는 미세조작 biopsy와 PCR에 의한 체외생산 소 초기배의 급속. 정확한 성 판정 기법을 확립하기 위해 실시하였다. 체외성숙 및 체외수정에 의해 생산된 소수정란은 소 난관상피세포와 공배양을 통해 8-세포부터 배반포시시까지 체외발생시킨 후 미세조작 biopsy에 이용되었다. 미세조작 biopsy 과정중에 약간의 형태적인 손상이 관찰되

The envelope of the rnannnalian oocyte plays crucial roles in sperm-oocyte interactions by providing sperm receptors, inducing acrosome reaction and preventing polyspermy. Understanding of properties of the zona pellucida (ZP) is essential for the artificial control of fertility in mammals. This study was carried out to produce and characterize monoclonal antibodies(MAbs) to porcine ZP proteins. Approximately 8,000 ZPs were obtained from follicular oocytes and dissolved in 40l of double distilled water. Following immunization through foot-pad injections of Balb /c mice with a ZP solution, the popliteal lymph nodes were recovered at 2 weeks after the last injection. Hybridoma cell lines were established by fusing lymph node cells with P3X63 myeloma cells through selection using HAT medium and screening by immunofluorescence(IF) microscopy on the isolated ZP. Secreted MAbs were found to consist k chains and different heavy chains as evidenced by isotyping. Some of the MAbs demonstrated high specificity to the ZP in IF. The Mabs also showed positive cross reactivity with hamster and mouse eggs, while negative with bovine eggs. The results implicate that the MAbs can be used not only for identification of functional regions of the ZP, but also for elucidation of mechanisms involved in fertilization of mammals. The MAbs will provide basic information on biochemical anatomy of the ZP as well as can be candidates for the future contraceptive vaccines.

To investigate the phase transformation behaviors of mechanically alloyed Nb-25 at%Al powders, the mixed Nb-25 at%Al powders were mechanically alloyed in SPEX 8000 Mixer/Mill. Mechanical alloying(MA) time was varied between 0.5 hour and 72 hours. The phase formation behaviors of these mechanically alloyed powders were examined using X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential thermal analysis(DTA). Appreciable amorphization started from 6 hours of MA. The powders mechanically alloyed for 10 hours were in almost amorphous phase. DTA results showed that the powders mechanically alloyed for 12 hours had a strong exothermic peak about, whereas the powders mechanically alloyed for 6 hours had two exothermic peaks. The first peak was found to be due to the stress relief effect and the second one due to the formation ofphases by crystallization.

기계적 합금화(mechanical alloying:MA) 방법에 의해 원소 Nb와 Al의 혼합분말로부터 금속간 화합물 NbA1₃와 비정질상을 얻었다. 혼합분말의 조성은 Nb-45wt%Al(75at%Al)으로 하였으며, 기계적 합금화는 고에너지 SPEX8000 mixer/mill을 사용하여 72시간까지 행하였다. 얻어진 분말은 XRD, DTA, SEM 및 TEM으로 분석했다. 기계적 합금화 초기 단계의 분말은 층상 구조를 나타냈고, 정상상태에 도달하였을 때는 분말 내에서 원소 Nb와 Al이 균일하게 분포되어 있었다. 4시간 기계적 합금화를 하였을 때 금속간 화합물 NbA1₃가 형성되었다. 기계적 합금화된 분말들은 안정한 NbA1₃형성 및 응력 완화에 해당되는 600℃ 근처에서 큰 발열 peak을 나타냈다.

비압축성 물체률 위한 일반적인 유한요소 공식화는 혼히 사용되는 사각형요소에서조차 압력해의 진동화 (oscillations ) 또는 pressure ~es 현상융 나타낸다. 압력해의 안정화률 위한 규준은 소위 BabuSka-Brezzi 안정조건이며， 위의 요소들은 이 조건율 만족시키지 못한다. 본 연구에서는 선형변위해와 상수값의 압력해률 갖는 사각형요소 사용시 압력해률 안정화시키기 위해 요소의 변에서 발생하는 불연속압에 근거한 압력연속여 분치률 사용한다. 이 압력여분치률 비압축성 탄성론으로부터 유도되는 QIPO요소에 적용하며 매개변수의 변 화에 따른 수치혜의 안정화의 정도률 연구한다. 압력해는 압력 여분치 사용시 안정화될 수 있으며， 혜의 안정 화는매개변수에 민감성을나타내었다.

단조증가하중을 받는 평면골조의 비탄성해석을 위하여 개발된 기존의 직접해석법을 확장하여 반복하중에 적용하였다. 직접해석법을 위한 골조요소로서 비탄성 트러스와 비탄성 보요소의 두 가지 요소가 개발되었다. 제안된 방법의 정확성과 신뢰성을 기존의 Step-by-step 해석과 비교하여 검증하였다. 기존의 Step-by-step 해석은 하중증분의 크기에 따른 해의 불안정성, 단계별 오차의 누적, 하중증분의 세분에 따른 과다한 계산 등의 문제를 가지는데 비하여 직접해석법은 하중증분의 크기에 무관하게 해의 신뢰성이 보장되고 증분평형식을 사용하지 않으므로 단계별 오차의 누적이 없고 하중증분을 세분하지 않아도 되므로 해석비용이 적게 드는 이점이 있다.

This study was experimented that developmental effects of bovine in vitro fertilized embryos by coculture system and supplementation of energy materials into simple media. With the ovaries from slaughter house in vitro maturation by 24h, in vitro fertilization was performed with sperms collected by Percoll gradient method. Fertilized embryos were cocultured in 15% FCS+CZB medium with BOEC(bovine oviductal epithelial cell), GCM (granulosa cell monolayer) and MEFC(mouse embryonic fihrohlast cell). And also in this study, there was trying to improve the early developmental rate of embryos by addition of concentration-controlled Na-pyruvate, D-glucose which were used as energy sources into CZB medium. In vitro developmental rate was confirmed by the cleavage rate of 48h post-IVF and the embryo development rate at 240h culture. In the coculture system BOEC had 20.0% of blastocysts rate, which was higher than that of other coculture systems. To determine the optimum concentration for early embryo developmental rate rapidly, through the gradient of concentrations of Na-pyruvate and D-glucose, we focused on the cleavage rate at 48h and blastocysts rate at 240h. In case of Na-pyruvate, cleavage rate and developmental rate over 3-cell were lower at the concentration of 1.OOrnM than the other treatment concentrations, otherwise the blastocysts rate was higher as 23.2% than the others. That result showed that as like reported group which had higher develop-mental rate over 3-cell was also higher to the blastocysts rate. In case of D-glucose, there was no effects through the concentration changes. It was the result of this study for which the use of BOEC coculture system and 1.OOmM Na-pyruvate as an energy source had an effect upon embryo development.

Frozen storage of the oocytes has been used in a few mammalian species including mouse, hamster, human and cattle. However, frozen4hawed oocvtes show different sperm penetration on the levels of the zona pellucida and the plasma memhrane when compared with fresh oocytes. To elucidate biological changes occurring during freezing and thawing, we examined the kinetics of sperm penetration into frozen-thawed hamster oocytes. Oocytes obtained from superovulated female golden hamsters were frozen-thawed in an autofreezer according to an established method. Fresh and frozen4hawed oocytes were fertilized in vitro with capacitated hamster spermatozoa after removing the zona pellucida. The oocytes were examined at 1, 2, 3 and 6 h postinsemination. Sperm penetration found to be 1 h delayed in frozen-thawed oocytes. Other parameters such as degree of polyspermy and decondensing sperm heads were not affected by freezing and thawing. The results suggest that freezing and thawing may cause changes in the egg membrane surface and subsequently which leads to delay in the sperm-egg fusion.

This study was performed to establish the condition and the methods for the techniques of insertion the isolated blastomere cells into cytoplasm, in order to research the develop-mental ability of bovine embryo blastomere cells in vitro produced. After 24h in vitro ovary maturation with the ovaries from a slaughter house, in vitro fertilization was performed to the vital sperms which their mobility were decided by percoll gradient method, with 2~8 cell stage embryos, the blastomeres were isolated in +. +-free PBS, and following that embedded into agar and alginate solution, respectively. The rates of in vitro develop-ment are as follows ; in agar embedded 11 among 120(9.2%) 1 /2~1 /3 blastomers cleaved and 6 among 93(6.5%) 1 /4~1 /8 blastomeres cleaved. In sodium alginate-embedded 14 among 84(16.7%) 1 /2~1 /3 blastomeres cleaved and 6 among 85(7.1%) 1 /4~1 /8 blastomeres cleaved. In case of Na-alginate, the rate of the cells were better than those of agar. The results suggest that the techniques for embeeding the isolated blastomeres into gel may help cloning of bovine early embryo without nuclear transplantation.

In the experiment I for maas production of bovine early embryos, 18~20hpi fertilized eggs (756 eggs) and parthenogenic eggs (618 eggs) which were treated by 10% ethanol were cultured in both TGM and CZB. In the experiment II, suppiment effects each in CZB and CRlaa were tested by matured and fertilized oocytes which were after 18~20hpi. In the case of experiment I after 48hr, the cleavage rates of normally fertilized eggs were 66.6% in TCM treatment and 77.7% in CZB treatment, and after 240h the blastocysts were 7.5% in TCM and 14.1% in CZB. In the parthenogenic eggs, the deavage rates at 48hr were 39.6% in TCM and 57.5% in CZB, and at 240h, the blastocysts were 0.9% in TCM and 4.4% in CZB. These results showed that the effects of CZB on developmental ability to parthenogenic eggs as well as nomally fertilized eggs are relatively high. In experiment W, the effect of exposing the cleaved embryos to CZB for 30h on the blastocyst formation was examined. Similar rates of blastocyst formation were obtained both in TCM and CZB, suggesting that CZB exposure. during ealry development is critical. In experiments III ~ V, the effects of supplements were examined. The cleavage rates of CZB treatments at 48h were 83.8% in control, 78.1% in BSA+A.A+SIT, 75% in 5% FCS+A. A+SIT, 88.6% in BSA+A.A+SIT and not co-cultured BSA+A.A+SIT had 85.7% and in the case of 240h blastocysts showed 22.6, 0.0, fl.1, 6.5 and 0%, respectively. As a result, this study showed that CZB was effective culture system for in vitro development, and that CZB and CRaa had no significant differences and effects between them. It may be concluded that in the simple media containing supplements could replace the co-culture systems of bovine early embryo development.

초기배의 성판정은 대상가축의 성을 선발하는 수단으로써 가축의 육종 및 번식에 있어 가치가 매우 높다. 체세포, 체외수정 또는 처녀발생 초기배의 성을 결정하기 위해 capillary polymerase chain reaction (PCR)을 이용하였으며 성판정에 이용되는 상실배 또는 배반포는 체외수정과 그 후의 난관상피세포와의 공배양에 의해 생산되었다. 초기배의 genomic DNA는 0.2g/L proteinase K를 함유하고 있는 PCR lysis