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91.
Ming Chang Wang Gun-Sik Park Jae Koo Lee 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(4):797-809
An electron beam source based on pseudospark discharge was successful in operation at the beam voltage of 200keV and beam current of 2kA. The detailed design of a compact free electron laser using an electron beam by a pseudospark discharge is described. The compact free electron laser consists of a smaller Marx generator with 6 capacitors and switches, a water capacitance of 6nF and a beam source with a high brightness of 3×1011 A/(m rad)2. The computer simulation shows that an output power of 101MW is expected at a frequency of 38GHz with a beam energy of 300keV, a current of 2kA and a beam emittance of 48mm mraa. 相似文献
92.
Nanzhe Jiang Jeong-Boon Koo Sang-Cheol Han Sang-Eon Park 《Research on Chemical Intermediates》2008,34(5-7):507-517
Metal incorporation into nanoporous materials could give Lewis acid sites through the framework substitution of silica matrix, which are supposed to be in tetrahedral substitution of silica. In this work, Zr- and Sn-incorporated SBA-16 were directly synthesized by the microwave synthesis method. These microwave synthesized Zr- and Sn-incorporated mesoporous silica materials were applied in activation of ketones by Lewis acid sites to catalyze Meerwein-Ponndorf-Verly reduction of cyclohexanone and Baeyer-Villiger oxidation of adamantanone, respectively. Optimum incorporated Zr- and Sn-species gave almost 100% selectivity with high activity onto corresponding alcohol and lactone, respectively. 相似文献
93.
Danh Tran Kee Koo Sang Sheem 《Quantum Electronics, IEEE Journal of》1981,17(6):988-991
Rugged single-mode fiber couplers have been fabricated by two different techniques: 1) twist-etch RTV potting, and 2) twist-etch gel glass potting. The performances, in terms of optical stability, mechanical ruggedness, and lifetime, are compared between the couplers made by these two techniques, and also with those of the original twist-etched (bottle) coupler reported earlier. 相似文献
94.
Jae Koo Lee Sang June Hahn 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(1):52-54
For beam-plasma instability in the absence of a magnetic field, hybrid simulations produce almost identical results to those of particle simulations (both agree with linear and nonlinear analyses), but with much reduced computing cost and noise level. With the verification by simulations, it is shown that the saturation level is very strongly influenced by the discrete wave number spectrum, sometimes giving different, by an order of magnitude, results by choosing slightly different off-peak (in growth rate curve) parameters, which must be considered in most simulations (whether hybrid or particle or whether magnetized or unmagnetized) 相似文献
95.
Effect of external perturbations on fiber-optic magnetic sensors 总被引:1,自引:0,他引:1
The effects of external nonmagnetic perturbations on a fiber-optic magnetic sensor are analyzed theoretically. It is shown that the deleterious effects of these perturbations can be controlled by maintaining the DC magnetic field at prescribed levels. Experiments have been performed with externally applied stresses and accelerations (vibrations) that validate the theory and yield values for the stress and acceleration responsivities of the sensors studied in this investigation. The analysis and techniques given apply equally well to any interferometric sensor using nonlinear transduction mechanisms 相似文献
96.
This article reviews the current status of high-density capacitor for volatile memory devices. The dielectric properties for both the Ta2O5 film and the (Ba, Sr)TiO3 (BST) dielectric materials using either the metal organic chemical vapor deposition (MOCVD) or the atomic layer deposition (ALD) are reviewed briefly. New challenges of dielectric material for the next generation, and serious problems emerged during integration to date using Ta2O5 and BST. The material characteristics of many electrode materials for the high dielectric materials are introduced. We present the basic properties and integration issued for MOCVD-ruthenium (Ru). The second part of this review summarized the failure mechanisms from barrier properties of previously reported diffusion barriers and emphasizes new design concepts of diffusion barrier for high-density memory devices. Finally, the future direction for a diffusion barrier to advance high-density memory capacitors is suggested. 相似文献
97.
The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent SnO2 thin-film prepared by ion beam-assisted deposition (IBAD) was investigated. After encapsulation process, our organic thin-film transistors (OTFTs) showed somewhat degraded field-effect mobility of 0.5 cm2/(V s) that was initially 0.62 cm2/(V s), when a buffer layer of thermally evaporated 100 nm SnO2 film had been deposited prior to IBAD process. However, the mobility was surprisingly sustained up to 1 month and then gradually degraded down to 0.35 cm2/(V s) which was still three times higher than that of the OTFT without any encapsulation layer after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over 105 to that of the unprotected devices (∼104) which was reduced from ∼106 before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of H2O and O2 into the devices by the IBAD SnO2 thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices. 相似文献
98.
99.
W. M. Koo 《Journal of statistical physics》1995,81(3-4):561-578
Based on transfer matrix techniques and finite-size scaling, we study the oriented polymer (self-avoiding walk) with nearest neighbor interaction. In the repulsive regime, various critical exponents are computed and compared with exact values predicted recently. The polymer is also found to undergo a spiral transition for sufficiently strong attractive interaction. The fractal dimension of the polymer is computed in the repulsive and attractive regimes and at the spiral transition point. The later is found to be different from that at the collapse transition of the ordinary self-avoiding walk. 相似文献
100.
A simple extension to the technique of “pre-lase” Q-switching ensures that a TEM00 mode, Q-switched NdYAG laser produces single longitudinal mode oscillation on every shot. 相似文献