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941.
Moon Jeon-Yeol Miura Takatsugu Imae Ichiro Park Dae-Won Kawakami Yusuke 《Silicon Chemistry》2002,1(2):139-143
Disiloxane-arylene polymers having phenylene, biphenylene, and fluorenylene groups as arylene units were synthesized by dehydrocoupling polymerization of corresponding bis(silane) derivatives with water. The reactivity of Si-H was not affected by the structure of aromatic groups in the reaction. The polymers containing biphenylene and fluorenylene units are amorphous and show higher glass transition temperatures than the polymer from 1,4-bis(dimethylsilyl)benzene. 相似文献
942.
O. Yavas P. Leiderer H. K. Park C. P. Grigoropoulos C. C. Poon W. P. Leung N. Do A. C. Tam 《Applied Physics A: Materials Science & Processing》1994,58(4):407-415
The dynamics of liquid-vapor phase-change in the nanosecond time-scale induced by pulsed-laser heating of a liquid on a solid sample is studied by means of optical reflectance and scattering measurements, and the piezoelectric detection technique. The liquids studied include water, ethanol, methanol, IsoproPropyl Alcohol (IPA), and mixtures of water and IPA. The threshold fluence for nucleation is determined with high accuracy using the optical and acoustic signals. Heat diffusion calculations performed for the threshold fluences indicate that the liquids are sufficiently superheated before nucleation sets on. The transient optical reflectance signal is analyzed by an effective-medium theory to provide bubble-growth kinetics, so that the bubble-growth velocity for the test liquids could be estimated. In addition, it is observed that, following the thermally induced nucleation, repetitive acoustic cavitation at the surface of the solid sample occurs, with a time interval related to the speed of sound in the liquid. 相似文献
943.
Nanosized ZnGa2O4:Cr3+ powder is synthesized through hydrothermal method. The average particle size is 20 nm and they are spherical in shape. The excitation band from the charge transfer between Cr3+-O2− shows a blueshift behavior due to quantum confinement effect. X-ray diffraction pattern, Fourier transform-infrared spectrum, and electron paramagnetic resonance signal indicate that nanosized ZnGa2O4:Cr3+ phosphor shows many defect-related energy states and heavy lattice distortion in comparison with bulk ZnGa2O4:Cr3+ phosphor. Many defect states result in more nonradiative loss and shorter decay time. 相似文献
944.
945.
Jong Dae Lee Dong-Hwal Lee No-Kuk Park Si Ok Ryu Tae Jin Lee 《Current Applied Physics》2006,6(6):1040
The reduction–carburization of tungsten trioxide (WO3) under carbon monoxide flow was studied in the temperature range of 300–750 °C. The reduction–carburization of WO3 was improved by mechanically mixing with zeolite-HX, -NaX and -KX. The interaction between cation in zeolite-X and oxygen in WO3 affected the improvement of the reduction–carburization of WO3 to WC. Moreover, the improved reduction–carburization of WO3 could lead to the decrease of reaction temperature. Because the particle size of WC is in contact with a reaction temperature, the nanophase WC can be prepared at low temperature. In particular, the particle size of WC was controlled by reaction temperature. The particle sizes of produced WC at 550, 650 and 700 °C were 25, 50 and 100 nm respectively. 相似文献
946.
Y.M. Park Y.J. Park K.M. Kim J.I. Lee K.H. Yoo 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):647-653
We have investigated the optical properties of InAs self-assembled quantum dots (SAQDs) with the Si-doped GaAs barrier layer. Two types of samples are fabricated according to the position of the Si-doped GaAs layer. For type A samples the Si-doped GaAs layer is grown below the QDs, whereas for type B samples the Si-doped GaAs layer is grown above the QDs. For both types of samples the excited-state emissions caused by state filling are observed in photoluminescence (PL) spectra at high excitation power densities. The bandgap renormalization of QDs can be found from the shift of the PL peak energy. Particularly, for type A samples the Si atoms act as nucleation centers during the growth of InAs QDs on the Si-doped GaAs layer and affect the density and the size of the QDs. The Si-doped GaAs layer in type A samples has more effects on the properties of QDs, such as state filling and bandgap renormalization than those of type B samples. 相似文献
947.
Ultrafast laser ablation of indium tin oxide thin films for organic light-emitting diode application
Mira Park Byong Hyok Chon Hyun Sun Kim Sae Chae Jeoung Dongho Kim Jeoung-Ik Lee Hye Yong Chu Hyeong Rae Kim 《Optics and Lasers in Engineering》2006,44(2):138-146
Ultrafast laser ablation of ITO thin film coated on the glass has been investigated as a function of laser fluence as well as the number of laser pulses. The ablation threshold of ITO thin film was found to be 0.07 J/cm2 that is much lower than that of glass substrate (about 1.2–1.6 J/cm2), which leads to a selective ablation of ITO film without damage on glass substrate. The changes in the electrical resistance and morphology of ablated trench of ITO electrode were found to be strongly dependent on the processing conditions. We present the performance of organic light-emitting diodes (OLED) fabricated with ITO electrode patterned by ultrafast laser ablation. 相似文献
948.
Polycrystalline Zn1−xCoxO (x=0, 0.02, 0.05, 0.10 and 0.15) oxides have been synthesized by solid state reaction via sintering ZnO and Co powders in open air. X-ray diffraction analyses using Rietveld refinement indicate that a stoichiometric single phase with a wurtzite-like structure was found in Zn1−xCoxO samples with x up to 0.10. The elemental mapping using energy dispersive X-ray spectroscopic analyses presents a uniform distribution of Co. Optical transmittance measurements show that several extra absorption bands appear in the Co-doped ZnO, which is due to the transitions between the crystal-field-split 3d levels of tetrahedral Co2+ substituting Zn2+ ions. Raman measurements show that limited host lattice defects are induced by Co doping. Magnetization measurements reveal that the Co-doped ZnO samples are paramagnetic due to the absence of free carriers and in low temperature the dominant magnetic interaction is nearest-neighbor antiferromagnetic. 相似文献
949.
Ki Mann Jee Dong Chul Park 《International Journal of Infrared and Millimeter Waves》2003,24(12):2105-2117
A spurious-suppressed transversal filter using the multiple-coupled line is proposed. The frequency characteristics of the multiple-coupled line are analyzed in detail. In order to compare the performances, the novel spurious-suppressed transversal filter using triple-coupled half-wavelength directional couplers is designed at 30 GHz. The spurious-suppression characteristics of the proposed transversal filter are verified by the full wave analysis and the measurement. The spurious response of the fabricated filter is effectively suppressed and the large attenuation is obtained in the stopband. 相似文献
950.
An efficient procedure for preparation of the simple alkaloids, 2,3-polymethylene-4(3H)-quinazolinones, luotonin A, tryptanthrin, and rutaecarpine has been established by the reaction of lactam-HCl salts with POCl3 followed by cyclization with methyl anthranilate. 相似文献