In vitro maturation (IVM) systems have become indispensable for the production of large numbers of competent oocytes in domestic species. The quality of in vitro matured oocyte is one of the important factors determining the success of assisted reproductive technologies (ARTs) including intracytoplasmic sperm injection (ICSI), in vitro fertilization (IVF), and somatic cell nuclear transfer (SCNT) in human and livestock. Incomplete cytoplasmic maturation of oocytes can lead not only to a failure of fertilization but also to a developmental arrest after ARTs. Thus, establishment of a stable IVM system to produce a large number of high quality oocytes, especially in domestic animals, is essential for improvement of ARTs efficiency by producing high quality embryos. The morphological characteristics are commonly used to predict the developmental potential of oocytes and embryos. Usually, normal oocytes shrink when exposed to a hypertonic medium, and recover their morphology when returned to an isotonic medium. During this process, oocytes show various morphologic changes, such as shrinkage in spherical (SSP) or irregular shapes (SIR). In the first study, we investigated whether the shrinkage pattern of oocytes that was observed after hyperosmotic treatment could be used as a morphologic characteristic to predict the quality of IVM oocytes in pigs. We found that SSP oocytes showed improved developmental competence after PA and SCNT. This improved embryonic development was most likely because of the more advanced nuclear and cytoplasmic maturation in SSP oocytes compared with SIR oocytes. Pig oocytes shows a wide variation in the size of perivitelline space (PVS) after IVM. Based on this finding, we examined in the second study whether or not there was any correlation between the PVS size of IVM oocytes and their developmental competence after PA and SCNT. Our results demonstrated that in vitro developmental competence to the blastocyst stage positively correlated with the size of the PVS of oocytes after IVM. In addition, we observed that mature oocytes with a larger PVS showed higher levels of intracellular GSH content and transcription factor expression. Furthermore, enlargement of the PVS by culturing in reduced NaCl medium improves the embryonic development after PA and SCNT. In the third study, we investigated the effects of a hypotonic medium with reduced NaCl (61.6 mM) compared with an isotonic medium (108.0 mM NaCl) on oocyte maturation and embryonic development after PA and SCNT. In addition, we attempted to optimize our IVM system using a hypotonic maturation medium by examining the effects of hypotonic medium during various stages of IVM on oocyte maturation and subsequent embryonic development. Our results demonstrated that maturation of pig oocytes in hypotonic medium with reduced NaCl during the last 11 hr of IVM increased the developmental competence of oocytes after PA and SCNT. These beneficial effects was also shown in a commercial medium (a minimum essential medium; aMEM) in which the NaCl concentration was reduced to 61.6 mM. In addition, IVM of oocytes in medium with reduced NaCl increases the proportion of SSP oocytes in pigs. In summary, our results demonstrate that IVM of pig oocytes in a hypotonic medium with low-NaCl is better able to support embryonic development after PA and SCNT, most likely by improving the cytoplasmic maturation via increased intraoocyte GSH content and widened PVS. Based on these results, the newly developed IVM system using a hypotonic medium with reduced NaCl can produce high quality oocytes and be considered a new strategy for improving ARTs efficiency in pigs.

Lanthanum zirconate, La2Zr2O7, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a La2Zr2O7-4YSZ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.

In order to improve indoor air quality of apartment, indoor ventilation system had to be installed in each unit, from 2006 in Korea. However, a duct which is connecting each room in ventilation system became a flanking path of sound. Sound which is generated in one room can easily transmitted into the adjacent room by the duct and speech privacy in apartment room can be seriously degraded. In this study, low noise duct system consisted of noise diffuser and multi drop chamber was developed and noise reduction performance was measured in mock-up system. Noise reduction performance of low noise duct system was compared with conventional duct system. From the result of measurement, it was found that noise diffuser reduce more than 10 dB in the range of 200 Hz and higher frequency band, also multi drop chamber was effective in 2000 HZ and higher frequency band. Noise reduction performance of low noise duct system is effective in the frequency range (from 300 Hz to 4000 Hz bands) of speech conversation.

An active suspension system has an external energy source, from which energy is constantly supplied to the system for continuous control of the vehicle's motion. There are some control strategies. In the study, the reduced-order active suspension control strategy via the singular perturbation technique is applied to the half car model which has 4 DOF. The performance of the hydraulic active suspension system utilizing this control strategy is investigated and compared with those of the systems with the full-order state feedback control and the sky-hook damping control. Their performances are compared through the computer simulation in the time and the frequency responses, respectively. In the transient response analysis, the C-language program is used, and Matlab program tool is used in the frequency response analysis. It is shown that the reduced-order control strategy yields almost the same performance as that of the full-order state feedback control, and gives better performance than that of the sky-hook damping control, especially in ride quality.

잘 구축된 축소시스템은 동하중을 받는 구조물의 거동을 정확하게 계산할 수 있으며, 유한요소 기반 동적해석에서 문제가 될 수 있는 계산시간과 전산자원의 문제를 해결할 수 있다. 본 연구에서는 축소모델 기반 동적해석 알고리즘을 개발하였고, 동적 축소모델의 구축을 위한 주자유도 선정방법을 제안하였다. 이 과정에서 기존 연구에서 신뢰성이 검증된 2단계 축소기법을 사용하여 중요 자유도를 선정하고, IRS 방법에 의해 최종 축소모델을 구축하였다. 이를 임의의 동하중을 받는 수치예제에 적용하고 전체시스템의 동적해석 결과와 비교하여 제안 방법의 신뢰성을 검증하였다.

The purpose of this research is to develop a joint system for two concrete pipes with reduced wall thickness by a carbon fiber reinforced polymer (CFRP) fabric. As compared to conventional concrete pipe, the concrete pipe with the reduced wall thickness has more flexibility. However, the reduced wall thickness makes the conventional joint system not feasible. As an alternative joint, externally wrapping system with the CFRP fabric was proposed. The two CFRP widths (75mm and 150mm) were accounted for as a variable under joint shear test from ASTM C497M specification. The externally wrapping system showed 81.07% higher shear strength, as compared to the required shear strength by ASTM C497M.

본 논문에서는 시소 시스템에 Pl형의 상태 피드백 제어기와 축소차수 관측기를 결합한 제어시스템을 적용하여 시소 시스템의 안정화 문제를 다루었다. LQ 이론에 근간을 두는 Pl형의 상태 피드백 제어기는 계단상의 외란이나 잡음에 대해 양호한 성능을 가지도록 오차에 대한 새로운 상태변수를 고려한 제어기이다. 축소차수 관측기는 상태변수의 계측이 어려운 경우나 경제적인 이유로 센서의 부착이 어려운 경우에 종종 사용되는데 본 논문에서는 시소 시스템의 각도와 대차의 위치로부터 시소의 각속도와 대차의 속도를 추정하기 위해 사용된다. 여러 초기조건과 외란이 인가되는 환경 하에서 실시한 시뮬레이션을 통해 본 논문에서 목적으로 하는 시소 시스템의 안정화가 가능함을 보인다.

N fertilizer required by rice could be reduced greatly in the rice-barley double cropping system than in the rice single cropping system. This study was conducted to investigate how much of the N fertilizer during the early stage of rice in the rice-barley double cropping system, could be saved compared to that in the rice single cropping system. This experiment was carried out at the paddy field of the National Crop Experiment Station in Suwon, Korea during three years from 1999 to 2001. Amounts of soil mineral nitrogen (SMN) and SPAD values of rice leaf during rice growing season in the rice-barley double cropping system were higher than those in the rice single cropping system under the same amount of N application during two years. Yield and N uptakes of rice at harvesting time were also higher in the rice-barley double cropping system than in the rice single cropping system during two years. Yield and N uptake of rice in the rice single cropping system were decreased when basal N fertilizer was omitted, but those reductions were not found by either omitting basal N fertilizer or omitting N fertilizer at tillering stage in the rice-barley double cropping system during 2000 and 2001. But yield and N uptakes of rice were decreased by 70 kg/10a and 2kgN/10a by the omission of both N application at basal and tillering stages in the rice-barley double cropping system in 2002. It was concluded that N fertilizer as much as tillering N fertilizer could be saved in the rice-barley double cropping system.