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71.
In the reaction of paraoxon with alkali metal ethoxides, ion-paired EtO-M+ species are more reactive than the dissociated EtO- with the reactivity order EtO-Li+ EtO-Na+ > EtO-K+ > EtO-, while in the reaction of parathion, the reactivity follows the order EtO-K+ > EtO- > EtO-Na+ > EtO-Li+. 相似文献
72.
73.
Gun Sang Jeon Chia-Chen Chang Jainendra K. Jain 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):271-282
We review and extend the composite fermion theory for semiconductor quantum dots in high magnetic fields. The mean-field model
of composite fermions is unsatisfactory for the qualitative physics at high angular momenta.
Extensive numerical calculations demonstrate that the microscopic CF theory,
which incorporates interactions between composite fermions, provides an excellent qualitative and quantitative account
of the quantum dot ground state down to the largest angular momenta studied,
and allows systematic improvements by inclusion of mixing between composite
fermion Landau levels (called Λ levels). 相似文献
74.
Kyung Ah Jeon Hyo Jeong Son Chang Eun Kim Jong Hoon Kim Sang Yeol Lee 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):222
ZnO nanowires were fabricated on c-plane (0 0 0 1), a-plane (1 1 2¯ 0) sapphire, and boron doped p-type (1 0 0) Si substrates in vacuum furnace by simple physical vapor deposition. Room temperature photoluminescence spectra of the nanowires show the near band-edge emission and the deep-level green light emission. The ZnO nanowires formed on sapphire (1 1 2¯ 0) substrates exhibited enhancement on optical properties and better crystalline structures than those of nanowires grown on other substrates. The formation mechanism and the effect of substrate direction on structural and optical properties of the nanowires are discussed. 相似文献
75.
Hyun Sik Yoon Chung Ho Jeon Jae Hwan Jung Bonguk Koo Changyoung Choi Sung Chul Shin 《国际流体数值方法杂志》2013,73(3):250-265
In the present paper, a direct forcing/fictitious domain (DF/FD)–level set method is proposed to simulate the twophase flow–body interaction. The DF/FD does not sacrifice accuracy and robustness by employing a discrete δ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, the easy implementation and the utilization of original governing equation without modification. The main idea is to combine DF/FD method with the level set method in the Cartesian coordinates. We present the results of a number of test cases to illustrate the effectiveness of the proposed method for single‐phase flow–body interaction problem and the two‐phase flows with a stationary body. Eventually, the simulations of various water entry problems have been conducted to validate the capability and the accuracy of the present method on solving the twophase flow–body interaction. Consequently, the present results are found to be in good agreement with those of previous studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
76.
Young-Kwon Park Hyung Won Lee Jong-Ki Jeon Seung-Soo Kim Changkook Ryu Ji Man Kim Ho-Jeong Chae Kwang-Eun Jeong 《Research on Chemical Intermediates》2011,37(9):1283-1291
The catalytic cracking of oil fractions separated from summer food waste leachate was investigated over BEA zeolite and Al-SBA-15 catalysts. In this study, a mixture of food waste oil fractions and catalyst was directly introduced to pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), with the resulting vapor phase products being simultaneously analyzed. Various acid compounds, including oleic acid, produced by the non-catalytic pyrolysis of food waste leachate were reformed into valuable compounds, such as oxygenates, hydrocarbons, and aromatics. The BEA zeolite catalyst showed higher selectivity for hydrocarbon compounds, especially aromatics, within the gasoline range due to its superior cracking ability originating from its highly acidic sites. Conversely, the cracking performance of the Al-SBA-15 catalyst, possessing mild acidic sites, was lower than that of the BEA zeolite. Increasing the amount of Al-SBA-15 catalyst enhanced the cracking activity and resulted in higher selectivity for hydrocarbons. 相似文献
77.
The effects of adding A–B diblock copolymer to a polymer blend (A/B) on phase‐separation kinetics and morphology have been investigated in a fixed shallow‐quench condition (ΔT = 1.5 °C) by in situ time‐resolved light scattering and phase‐contrast optical microscopy. A shear‐quench technique was used in this study instead of a conventional temperature‐quench method. Mixtures of nearly monodisperse low relative‐molecular masses of polybutadiene (Mw = 2.8 kg/mol), polystyrene (Mw = 2.6 kg/mol), and a near‐symmetric butadiene–styrene diblock copolymer (Mw = 6.3 kg/mol) as an interfacial modifier were studied. We observed that the addition of the diblock copolymer could either retard or accelerate the phase‐separation kinetics depending on the concentration of the diblock copolymer in the homopolymer blends. In contrast to the conventional temperature quench, we observed complex phase‐separation kinetics in the intermediate and late stages of phase separation by the shear‐quench technique. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 819–830, 2001 相似文献
78.
Passivation treatment on indium-doped Hg0.8Cd0.2Te epitaxial layers grown on p-Cd0.96Zn0.04Te substrates by molecular beam epitaxy has been performed in order to improve the surface stability of the Hg0.8Cd0.2Te layers. Room-temperature capacitance–voltage measurements clearly revealed metal-insulator–semiconductor (MIS) behavior for the Al/ZnS/passivated Hg0.8Cd0.2Te layer/Cd0.96Zn0.04Te diodes. The fast state density and the fixed charge density of the Al/ZnS/passivated Hg0.8Cd0.2Te/Cd0.96Zn0.04Te diode with a sulfur-treated Hg0.8Cd0.2Te layer were smaller than those with a chemically oxidized Hg0.8Cd0.2Te layer. The interface state density at the ZnS/sulfur-treated Hg0.8Cd0.2Te interface were low at 1011 eV−1 cm−2 at the middle of the Hg0.8Cd0.2Te energy gap. These results indicate that the Hg0.8Cd0.2Te epilayer is significantly passivated by sulfur treatment and that the passivated Hg0.8Cd0.2Te layers can be used for Hg1−xCdxTe-based MIS diodes and MIS field-effect transistors. 相似文献
79.
Soon Moon Park Seung Ho Jeon Taikyue Ree 《Journal of polymer science. Part A, Polymer chemistry》1989,27(12):4109-4117
Interpolymer complex formation between poly(L -proline) (PLP) with helical structure and poly(methacrylic acid) (PMAA) with random-coil structure through hydrogen bonding in aqueous medium has been studied by several experimental techniques, e.g., viscometry, turbidimetry, potentiometry, conductometry, scanning electron microscopy, and x-ray diffraction methods. The decreases in reduced viscosity of the solution on addition of an increasing quantity of PLP to a constant amount of PMAA reveals the formation of a complex between PLP and PMAA. The minimum in reduced viscosity at a unit-mole ratio [PLP]/[PMAA] = 1.0 suggests a 1 : 1 complex formation. A distinct change in the curves for turbidity, pH, and conductance versus [PLP]/[PMAA] supports this conclusion. A scanning electron micrograph for the 1 : 1 PLP–PMAA complexes shows that the PLP/PMAA complex has the shape of entangled long fibers. An x-ray diffraction pattern for the PLP/PMAA complexes gives no diffraction patterns which appear in pure PLP, indicating the destruction of the helical structure of PLP due to the interpolymer complexation. Mixtures of PMAA with poly(γ-hydroxy-L -proline) (PHLP) which has a similar conformation as PLP, but involves intra- or intermolecular hydrogen bonds, has also been investigated by vicometry measurements. The reduced viscosity of a solution of the mixed polymers increases with increasing [PHLP], indicating no complex formation. All the results reveal that the magnitude and the nature of the forces acting in the polymers play an important role in interpolymer complexation. 相似文献
80.
Sul Lee Sunho Jeong Dongjo Kim Sookhyun Hwang Minhyon Jeon Jooho Moon 《Superlattices and Microstructures》2008
Nanocrystalline zinc oxide (ZnO) particles with controlled shapes and sizes were prepared at 180 °C by a simple polyol method. The amount of water and the method of addition played an important role in determining the characteristics of the synthesized particles. Rod-shaped ZnO particles with major axis lengths of ∼114 nm were obtained by heating the precursor solution, while equiaxial particles with average diameters of ∼24 nm were prepared by injecting water into hot precursor solution. Increasing the amount of water added to the precursor solution enlarged the aspect ratio of the rod-shaped particles and increased the particle size of the equiaxial particles due to enhanced hydrolysis and condensation of the Zn ion complex. 相似文献