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81.
82.
Youbao Wan Junhao Chu Shaoling Guo Lingxian Bo Tianyan Yu Bingkun Yu 《International Journal of Infrared and Millimeter Waves》2001,22(1):197-205
The potassium lithium niobate crystals have been grown up. The shapes of solid-melt interfaces which maintaining the steady growth of the potassium lithium niobate crystals have been described. The optical transmission spectrum of the crystal has been surveyed. The perfected crystals showed good Second Harmonic Generation properties. 相似文献
83.
ADAPTIVE NONLINEAR FEEDBACK CONTROL OF CHAOTIC SYSTEMS BASED ON REDUCED PARAMETER QUADRATIC PREDICTORS 总被引:1,自引:0,他引:1 下载免费PDF全文
An adaptive nonlinear feedback-control method is proposed to control continuous-time chaotic dynamical systems, where the adaptive nonlinear controller acts on only one-dimensional error signal between the desired state and the observed chaotic state of a system. The reduced parameter adaptive quadratic predictor used in adaptive feedback cancellation of the nonlinear terms can control the system to any desired state. Computer simulation results on the Lorenz system are shown to demonstrate the effectiveness of this feedback-control method. 相似文献
84.
在KT-5C托卡马克上,采用多块组合的可偏压限制器控制等离子体边缘电场.进行了改善等离子体的边缘参数及其机制的研究.实验显示,限制器的正、负偏压都能改变等离子体电位,但正偏压更有效,能有效地建立边缘电场,进而抑制边缘扰动改善等离子体约束.利用可移动静电探针,测得正偏压期间边缘电子温度T_e(r)、电子密度n_e(r)、空间电位V_p(r)分布变陡,与计算得到的边缘粒子通量Г(a_(?))减少,整体粒子约束时间τ_p增加结果是一致的. 相似文献
85.
0.9Pb(Zn1/3Nb2/3)–0.1BaTiO3 (0.9PZN–0.1BT) of perovskite structure has been successfully prepared by mechanically activating mixed oxides of PbO, ZnO, Nb2O5, BaO and TiO2. The novel mechanochemical technique skips the phase-forming calcination step at an intermediate temperature that is always required in both the conventional solid state reaction and chemistry-based precursor routes. Ultrafine 0.9PZN–0.1BT particles of perovskite structure were formed when the constituent oxides were mechanically activated for more than 10 h. The powder was sintered to a density of 96% theoretical density at 1100°C for 1 h. The sintered 0.9PZN–0.1BT exhibits perovskite structure and a peak dielectric constant of 8800 at the Curie temperature of 60°C when measured at a frequency of 100 Hz. 相似文献
86.
Xiangming He Weihua Pu Jianguo Ren Li Wang Jiulin Wang Changyin Jiang Chunrong Wan 《Ionics》2008,14(4):335-337
The charge/discharge characteristics of the sulfur composite cathodes were investigated at different temperatures and different
current densities. The composite presented the discharge capacities of 854 and 632 mAh g−1 at 60 and −20 °C, respectively, while it had the discharge capacities of 792 mAh g−1 at 25 °C. The composite presented the discharge capacities of 792 and 604 mAh g−1 at 55.6 and 667 mA g−1, respectively, at room temperature. The results showed that the sulfur composite cathodes presented good charge/discharge
characteristics between 60 and −20 °C and at a high c-rate up to 667 mA g−1. 相似文献
87.
A Novel UWB Antenna with Small Side-Leakage 总被引:2,自引:0,他引:2
Wang Xianghui Jiang Yangsheng Wan Wenbing 《International Journal of Infrared and Millimeter Waves》2004,25(9):1325-1335
A successful design for a UWB (ultra-wideband antennas) antenna based on NRD-guide (nonradiative dielectric waveguide) with small side-leakage is presented. The rule of the theoretical selection of its parameters, if NRD-guide is used as the UWB antennas, is studied firstly, then the temporal propagation characteristics of the NRD-guide and the radiation characteristics for an tapered open-ended NRD-guide are calculated by FDTD (finite-difference time-domain) method. 相似文献
88.
Da-ping Wan Hong-bin Liu Yu-ming Wang De-jin Hu Zhen-xing Gui 《Optics & Laser Technology》2008,40(2):309-314
Laser texturing is a novel technique that may be used to texture a cold roller in the process of manufacturing high quality steel sheets. With the aim of improving the quality of the textured roller by using a CO2 laser, a new laser beam modulating device is proposed. An optical beam expander with a fast rotating chopper system is designed. The laser pulse is split into two parts by the chopper blades; one is the preheating pulse that is reflected onto optical loop mirrors; the other is the directly transmitted pulse that creates the craters at the preheated spots. The preheating beam focus spot size and position can be adjusted. The focusing characteristics and optical parameter compensation for the flying optics are investigated. The heat transfer and melt process of laser texturing are numerically simulated. The effects of the double pulses on the texturing are analyzed. The effect of preheating the sample ahead of the laser texturing pulse is examined. The surface profile and bump hardness show improvements by using this approach. 相似文献
89.
Wireless Networks - Secure localization in the presence of cheating anchors is a critical issue in wireless sensor networks, where compromised anchors attempt to falsify the measured distances in... 相似文献
90.
Video transmission over IEEE 802.11e wireless networks still shows poor performance for large bandwidth demand and frequently changed environments. Thus, several enhancements of IEEE 802.11e were proposed. On the other hand, big frames and simultaneous sending of adjacent frames always cause packet dropping for buffer overflow. In the past, we proposed an IEEE 802.11e enhancement named DFAA and a content aware mechanism to solve the above problems. The motivation of this paper is to find a proper way to integrate these two mechanisms. A DFAA enhancement (DFAA-E) is proposed to make up the insufficiency of content aware mechanism. Experiments results show that the combination of DFAA-E and content aware mechanism improves the video decoded quality greatly. And its performance can be further enhanced by selecting the suitable settings of certain parameters. 相似文献