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排序方式: 共有335条查询结果,搜索用时 15 毫秒
1.
Sang Pyo Kim 《Gravitation and Cosmology》2014,20(3):193-196
Particle production in de Sitter space provides an interesting model for understanding the curvature effect on Schwinger pair production by a constant electric field or the Schwinger mechanism on de Sitter radiation. For that purpose, we employ the recently introduced complex analysis method in which the quantum evolution in complex time explains pair production via the geometric transition amplitude and gives the pair-production rate as a contour integral. We compare the result from the contour integral with that of the phase-integral method. 相似文献
2.
Solid extraction of caffeine and theophylline from green tea by molecular imprinted polymers 总被引:1,自引:0,他引:1
Dexian?Wang Seung?Pyo?Hong Kyung?Ho?RowEmail author 《Korean Journal of Chemical Engineering》2004,21(4):853-857
This paper involves a feasibility study on using molecular imprinted polymers as the sorbent materials in solid phase extraction
for caffeine and theophylline from green tea. Two kinds of MIPs, with caffeine-theophylline mixture and pentoxifylline-theophylline
mixture as the templates respectively, MAA as the monomer, EDMA as the crosslinker and ATBN as the initiator, were applied
to this purpose. Mixture solution of caffeine and theophylline (1 Μg/ ml in acetonitrile) was applied to the solid extraction
cartridges following a load, wash and elute procedure with acetonitrile, methanol, methanol-acetic acid (90/10, v/v) as the
solvents, respectively. This solid phase extraction protocol was applied for extraction of caffeine and theophylline from
green tea. Comparison between the results obtained with the MIPs cartridges and a traditional C18 reversed-phase cartridge was made. It showed that the MIP-based sorbent on the solid phase extraction was comparable with
that of C18 material. HPLC analysis using a C18 column (5 Μm, 250× 4.6 mm from Rstech corporation), methanol: water (60 :40, v/v) as the mobile phase at a flow rate of 0.6
ml/min was applied for the quantitative determination. 相似文献
3.
The effect of Pd on the growth rate of metal-induced lateral crystallization (MILC) from Ni seed and the electrical properties of thin-film transistors (TFTs) fabricated on the films crystallized by MILC were investigated. When the Pd metal is placed on the amorphous-silicon/Ni-seed layer, the MILC growth rate is two to three times faster than that of conventional Ni-MILC, without any degradation of TFTs. These results were explained by a stress that is generated by the formation of Pd2Si 相似文献
4.
Seong Sik Hwang Hong Pyo Kim Joung Soo Kim Kenneth E. Kasza Jangyul Park William J. Shack 《Nuclear Engineering and Design》2005,235(23):1060011-2484
A forced outage due to a steam generator tube leak in a Korean nuclear power plant has been reported [Kim, J.S., Hwang, S.S., et al., 1999. KAERI Internal Report (Korean). Destructive analysis on pulled tubes from Ulchin unit 1. Korea Atomic Energy Research Institute]. Primary water stress corrosion cracking has occurred in many tubes in the plant, and they were repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to understand the leak behavior of the tubes containing stress corrosion cracks. Cracked specimens were prepared using a room temperature cracking technique, and the leak rates and burst pressures of the degraded tubes were determined both at room temperature and at a high temperature. Some tubes with 100% through wall cracks did not show a leakage at 10.8 MPa, which is the typical pressure difference of the pressurized water reactors (PWRs) during a normal operation. In some tests, the leak rates of the tubes increased with time at a constant pressure. In a high temperature pressure test at 282 °C one specimen showed a very small leakage at 18.6 MPa, which stopped after a small increase in the test pressure. Because stress corrosion cracks can develop at relatively low stresses, even 100% through wall cracks can be so tight that they will not leak at a normal operating pressure. 相似文献
5.
Jinkeun Oh W. C. Lee Sung Gyu Pyo Woojin Park Sunghak Lee Nack J. Kim 《Metallurgical and Materials Transactions A》2002,33(12):3649-3659
This study is concerned with the microstructural analysis of multilayered or bulk Ti aluminide sheets fabricated by the self-propagating
high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. Multilayered Ti/Al sheets were prepared by
stacking thin Ti and Al sheets alternately, and a good Ti/Al interfacial bonding was achieved after rolling at 500 °C. When
these sheets were held at 1000 °C, spheroidal TiAl3 phases were formed by the SHS reaction at Ti/Al interfaces and inside Al layers. Microstructural analysis on the hot-rolled,
multilayered Ti/TiAl3 sheets revealed that intermetallic phases such as TiAl2, TiAl, and Ti3Al were formed at Ti/TiAl3 interfaces due to interaction between Ti and TiAl3 and that pores formed in the TiAl3 layer were significantly reduced during hot rolling. When multilayered Ti/Ti aluminide sheets were heat treated at 1000 °C,
Ti3Al, TiAl, and TiAl2 were grown as Ti and TiAl3 were consumed. As the heat treatment proceeded, TiAl grew further, eventually leading to the fabrication of multilayered
sheets composed of Ti3Al and TiAl. Bulk Ti aluminide sheets, having a lamellar structure of Ti3Al and TiAl, instead of multilayered sheets, were also fabricated successfully by heat treatment at 1400 °C. This fabrication
method of the bulk sheets had several advantages over the method by hot forging or rolling of conventional cast Ti aluminides.
From these findings, an idea to fabricate multilayered or bulk Ti aluminide sheets by hot rolling and heat treatment is suggested
as an economical and continuous fabrication method, and the formation and growth mechanisms of interfacial phases are elucidated
in this study. 相似文献
6.
Moumita Mukherjee Biswanath Mukherjee Youngill Choi Kyoseung Sim Junghwan Do Seungmoon Pyo 《Synthetic Metals》2010,160(5-6):504-509
We report a copper hexadecafluorophthalocyanine (F16CuPc) based n-type organic field-effect transistor (OFET) with polymeric gate dielectrics with different physical/electrical properties. The gate dielectrics are four types of cross-linked poly(4-vinylphenol) and newly prepared poly(4-phenoxy methyl styrene) and those are characterized based on surface tension, leakage current and capacitance. The performance of F16CuPc OFETs with those gate dielectrics was compared. We found that the composition of the gate dielectrics and the interfacial interaction of F16CuPc with the gate dielectric play a decisive role in the performance of OFETs. The effect of physical/electrical properties, composition and processing condition of the gate dielectrics on the device performance was investigated. 相似文献
7.
8.
Food Science and Biotechnology - MV was reported to have beneficial effects in ameliorating insulin resistance in db/db mice, but the intrinsic mechanisms for glucose homeostasis are unclear. This... 相似文献
9.
A new chelating fabrics are synthesized by radiation induced grafting of acrylonitrile (AN) onto polypropylene nonwoven fabrics (PP fabrics) and subsequent conversion of cyano to an imine by reaction with ethylene diimine (EDA). Influence of various parameters such as initial concentration, pH and adsorption time on the adsorption amount for palladium ions was investigated. It was found that adsorbent achieved excellent adsorption performance in palladium ion removal in the pH range of 1.88–5.70. The adsorption amount of ions increased with shaking time and initial concentration of palladium ions. The grafted and aminated fabrics were characterized by FT‐IR, TGA and SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
10.
Piezoelectric and dielectric properties of (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3–PVDF composites
Jeong-Hyeon Seol Jae Shin Lee Han-Na Ji Yun-Po Ok Gyoung Pyo Kong Ki-Soo Kim Chang Yoon Kim Weon-Pil Tai 《Ceramics International》2012
(Li, Ta, Sb) modified sodium potassium niobate/poly(vinylidene fluoride) [(K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3–PVDF] 0-3 composites were prepared by a cold press technique, and their piezoelectric and dielectric properties were characterized. All composites exhibited good dispersion of ceramic particles in the polymer matrix. The piezoelectric and dielectric constants were found to be enhanced as the concentration of sodium potassium niobate increases. Even though the process is simple, the composite prepared in this study showed better piezoelectric and dielectric properties than PZT–polymer composites. At room temperature, a (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3–PVDF (7:3) composite revealed a relative dielectric constant, ?r = 166, piezoelectric constant, d33 = 33 pC/N and coercive field, Ec = 5 kV/cm. 相似文献