Among efforts to improve techniques for the chemical vapor deposition of large-area and high-quality graphene films on transition metal substrates, being able to reliably transfer these atomistic membranes onto the desired substrate is a critical step for various practical uses, such as graphene-based electronic and photonic devices. However, the most used approach, the wet etching transfer process based on the complete etching of metal substrates, remains a great challenge. This is mainly due to the inevitable damage to the graphene, unintentional contamination of the graphene layer, and increased production cost and time. Here, we report the systematic study of an H2 bubbling-assisted transfer technique for graphene films grown on Cu foils, which is nondestructive not only to the graphene film but also to the Cu substrate. Also, we demonstrate the origin of the graphene film tearing phenomenon induced by this H2 bubbling-assisted transfer process. This study reveals that inherent features are produced by rolling Cu foil, which cause a saw-like corrugation in the poly(methyl methacrylate) (PMMA)/graphene stack when it is transferred onto the target substrate after the Cu foil is dissolved. During the PMMA removal stage, the graphene tearing mainly appears at the apexes of the corrugated PMMA/graphene stack, due to weak adhesion to the target substrate. To address this, we have developed a modified heat-press-assisted transfer technique that has much better control of both tearing and the formation of residues in the transferred graphene films.

Graphene has attracted the interest of many researchers due to various its advantages such as high mobility, high transparency, and strong mechanical strength. However, large-area graphene is grown at high temperatures of about 1,000 °C and must be transferred to various substrates for various applications. As a result, transferred graphene shows many defects such as wrinkles/ripples and cracks that happen during the transfer process. In this study, we address transfer-free, large-scale, and high-quality monolayer graphene. Monolayer graphene was grown at low temperatures on Ti (10nm)-buffered Si (001) and PET substrates via plasma-assisted thermal chemical vapor deposition (PATCVD). The graphene area is small at low mTorr range of operating pressure, while 4 × 4 cm2 scale graphene is grown at high working pressures from 1.5 to 1.8 Torr. Four-inch wafer scale graphene growth is achieved at growth conditions of 1.8 Torr working pressure and 150 °C growth temperature. The monolayer graphene that is grown directly on the Ti-buffer layer reveals a transparency of 97.4 % at a wavelength of 550 nm, a carrier mobility of about 7,000 cm2/V×s, and a sheet resistance of 98 W/□. Transfer-free, large-scale, high-quality monolayer graphene can be applied to flexible and stretchable electronic devices.

The heat transfer of Jet impingement is a very effective technique for exchanging high heat fluxs between a heated plate and a fluid. The purpose of current investigation is to carry out the experiment in order to study heat transfer characteristics between a vertical round water jet and a horizontal surface for different flow rates and geometric conditions. The effect of flow rates on heat transfer were investigated. The data obtained in this study are represented in terms of Nusselt number as a function of Reynolds and Peclet numbers. The correlation for the Nusselts number in terms of the Peclet number and  was obtained. The proposed correlation predicts the current data of heat transfer very well.

As a simple and economical method for in vitro produced embryos, we have used BSA instead of serum for the production and embryo transfer of Hanwoo in vitro fertilized (IVF) embryos and obtained the following results: 1) When using serum (FBS; fetal bovine serum) or BSA-containing culture media as the initial culture media for immature oocytes, it is regarded as inappropriate to add only BSA to the culture solutions from maturation of the immature oocytes to development stage culture, but serum still needs be added though there is no significant difference in the concentration, with a change from 5% to 10%. 2) The results of culturing IVF embryos after development (4 cell stage) in the Medium199 solutions containing BSA instead of serum (FBS) showed that 0.3% BSA concentration is not optimal and 0.5% or higher BSA concentration has no significant difference among 0.5%, 0.7%, 1% and 2% (p > 0.05). 3) The post-freezing survival ratio after development in 5% FBS-Medium199 showed that 1% BSA concentration of the culture solution is the most suitable in the BSA concentrations of 0.3% (51%), 0.5% (67%), 0.7% (69%), 1% (77%) and 2% (75%). 4) The pregnancy rates of the transplanted fresh(not frozen) blastocyst had no significant concentration dependency (p > 0.5), and the average pregnancy rate was 63.8%. 14% of overweight calves were found among the calves given birth to by the transfer of IVF blastocysts cultured in the serum-added culture solution, but none was found in the experimental groups in which BSA was added instead of serum.

난자의 체외성숙 및 체외배양에는 일반적으로 동물의 혈청을 사용하고 있다. 그러나, 채취한 소의 상태에 따라서 혈청의 질에 차이가 있어 실험데이터가 일정하지 않을 수 있고, 그것으로부터 바이러스, 세균, 마이코플라즈마 등에 오염될 가능성이 있다. 따라서, 본 실험에서는 완전 무 혈청 배양액에서 난자의 성숙, 배 발생율, 세포 수, 동결성을 검토하였다. 다음으로, 근래 혈청배지로 생산한 체외 배양 수정란은 과체중의 산자 생산, 초기 산자 사망률, caesa

The purpose of this study was to investigate the development of bovine nuclear transfer (NT) embryos cultured in serum-free conditions. Bovine NT embryos cultured in various culture conditions were compared blastocyst development, total cell number and apoptosis using TUNEL assay. In experiment 1, blastocyst rates of NT embryos were significantly higher (P<0.01) in FBS (22.0％) and BSA (26.6％) groups than in PVA (6.3％) group. Total cell number was significantly higher in FBS (78.4±19.4) and BSA (90.9±29.1) groups than in PVA group (46.0±0.0). Apoptotic cell number was significantly fewer in FBS (3.1±1.4) and BSA (1.7±1.4) groups than in PVA group (7.0±20.0) However, all of results were not different between the FBS and BSA group. In experiment 2, blastocyst rates of NT embryos were significantly higher (P<0.05) in fatty acid free-BSA (FAF-BSA) group (26.8％) than in fraction V-BSA group (11.2％). Total cell number were somewhat higher in FAF-BSA group (89.8±30.7) than in fraction V-BSA group (88.1±19.3). Apoptotic cell number were somewhat fewer in FAF-BSA (1.7±1.5) group than in fraction V-BSA group (4.2±2.9). These findings suggest that serum free condition were effective for the in vitro development of bovine NT embryos. Therefore, we concluded that fatty acid free-BSA has beneficial effect in development bovine NT embryos and can be use as a serum substitute.

In vitro embryo culture techniques provide significant contributions not only for a basic research of fertilization and early embryogenesis, but also for a low cost mass production of bovine embryos for transfer, embryo diagnosis, nuclear cloning and the production of transgenic cows. This presentation introduces newly developed serum-free media (IVD101 and IVMD101) that are effective far high yields of transferable embryos of excellent quality from in vitro-matured and fertilized oocytes. Both serum-free media are superior to a conventional serum-containing medium on the increased rates of blastocyst formation, post-thaw embryo viability, and pregnancy after transfer. Furthermore, reduced risks of calf mortality and large calf syndrome are also observed for the serum-free-derived embryos. Serum-derived embryos contain a large number of lipid droplets and immature mitochondria in their cytoplasm that may account for the lower production of transferable embryos and poor embryo quality.

본 연구에서는 전달영향계수법의 개념을 사각형 평판의 자유진동해석에 적용하여, 그 계산결과들을 전달매트릭스법 및 엄밀해 또는 Leissa 방법의 결과와 비교하여 그 유용성을 확인하였다. 전달영향계수법은 전달매트릭스법으로는 구하기 곤란한 고차의 고유진동수에 대해서도 정도좋게 구할 수 있으며, 계산속도의 면에서도 전달매트릭스법보다 우수함을 알 수 있었다. 또한, 전달영향계수법은 모든 경계조건 및 중간 경탄성 지지조건도 전단 및 회전 스프링정수 값의 조절만으로 간편하게 대응시킬수 있었다

직선상 2층 구조물의 임의의 절점에 변위벡터가 불연속인 죠인트 요소를 갖는 경우, 면내 굽힘 자유진동을 해석하기 위한 알고리즘을 전달영향계수법에 의해 정식화하고, 간단한 모델에 의해 수치실험을 행한 결과, 다음과 같이 요약할 수 있다. (1) 전달영향계수법은 종래의 전달매트릭스법에 비해 계산정도 및 계산속도 양면에서 우수함을 확인할 수 있다. (2) 구조물의 임의의 중간 절점에서 상태벡터량(횡변위, 각변위, 전단력 및 모멘트 등) 중 일부의 물리량이 불연속성을 갖더라도, 알고리즘 자체를 변화시켜야 하는 전달매트릭스법과는 달리, 스프링전수 값의 조절만으로 간단히 처리할 수 있어, 알고리즘의 일반화 및 프로그램의 범용화가 가능하다. (3) 전달영향계수법에서는, 구조물의 중간에 반고정지지와 같은 단단한 탄성지지부가 다수 존재하는 경우에도, 기본적인 알고리즘을 변경할 필요 없이 전단 및 회전 스프링정수에 적당한 값을 대입하는 것만으로 중간조건에 대응시킬 수 있고, 모든 경계조건도 마찬가지로 처리할 수 있다.