随着现代科技不断发展以及社会的进步,越来越多的研究人员开始更多地关注无线宽带数字通信系统的发展。制约这个系统的传输性能和信息速率的主要因素之一,则是无线信道时延扩展引起的符号间干扰。因此,消除符号间干扰,以及由无线信道时...随着现代科技不断发展以及社会的进步,越来越多的研究人员开始更多地关注无线宽带数字通信系统的发展。制约这个系统的传输性能和信息速率的主要因素之一,则是无线信道时延扩展引起的符号间干扰。因此,消除符号间干扰,以及由无线信道时延扩展引起的频率选择性衰减,成为无线宽带通信系统中必须要解决的问题,在研究过程中正交频分复用(Orthogonal Frequency Division Multiplexing OFDM)技术显现出了其明显的优势。因此OFDM成为下一代宽带移动通信系统的候选方案。展开更多
Based on polymer microstructured optical fibers (PMOF) and selective liquid crystal injection technology, a novel tem- perature control tunable attenuator is designed theoretically in this paper. In our experiments, P...Based on polymer microstructured optical fibers (PMOF) and selective liquid crystal injection technology, a novel tem- perature control tunable attenuator is designed theoretically in this paper. In our experiments, PMMA microstructured optical fibers with high performance are drawn successfully and the selective injection of liquid crystal 5CB into micro- holes is realized. The tunable attenuator is fabricated with an extinction ratio of over 60dB, which agrees well with the design.展开更多
Based on guided wave theory and considering the grouted rock bolt as waveguide medium, we have constructed a three dimensional model of grouted rock bolt with the dynamics of finite difference numerical simulation sof...Based on guided wave theory and considering the grouted rock bolt as waveguide medium, we have constructed a three dimensional model of grouted rock bolt with the dynamics of finite difference numerical simulation software FLAC3D4.0, and simulated the propagation behavior of the guided wave in the full grouted rock bolt. The simulated waveform and wave velocity matched well with the experimental results. We have made a more in-depth and comprehensive study of the wave velocity, wave component and attenuation characteristics of the guided wave propagating in rock bolt, and found some new characteristics and phenomena. In addition, some phenomena that haven’t been explained in the previous researches have also been discussed in this paper. The result showed that when guided wave propagates in grouted rock bolt, after the body wave decays, there is still the interface wave-Stoneley wave that does not decay in the axial direction of the bolt. The findings can provide some reference for rock bolt testing and the selection of the optimal excitation wave of testing.展开更多
文摘随着现代科技不断发展以及社会的进步,越来越多的研究人员开始更多地关注无线宽带数字通信系统的发展。制约这个系统的传输性能和信息速率的主要因素之一,则是无线信道时延扩展引起的符号间干扰。因此,消除符号间干扰,以及由无线信道时延扩展引起的频率选择性衰减,成为无线宽带通信系统中必须要解决的问题,在研究过程中正交频分复用(Orthogonal Frequency Division Multiplexing OFDM)技术显现出了其明显的优势。因此OFDM成为下一代宽带移动通信系统的候选方案。
基金the National Basic Research Program ofChina (973 Program) (2003CB314907), Tsinghua National Labo-ratory for Information Science and Technology (TNList), and Na-tional Natural Science Foundation of China.
文摘Based on polymer microstructured optical fibers (PMOF) and selective liquid crystal injection technology, a novel tem- perature control tunable attenuator is designed theoretically in this paper. In our experiments, PMMA microstructured optical fibers with high performance are drawn successfully and the selective injection of liquid crystal 5CB into micro- holes is realized. The tunable attenuator is fabricated with an extinction ratio of over 60dB, which agrees well with the design.
基金supported by the Specialized Research Fund for the Doc-toral Program of Higher Education (Grant No. 20090211110016)the Gansu Provincial Natural Science Foundation of China (Grant No. 096RJZA048)
文摘Based on guided wave theory and considering the grouted rock bolt as waveguide medium, we have constructed a three dimensional model of grouted rock bolt with the dynamics of finite difference numerical simulation software FLAC3D4.0, and simulated the propagation behavior of the guided wave in the full grouted rock bolt. The simulated waveform and wave velocity matched well with the experimental results. We have made a more in-depth and comprehensive study of the wave velocity, wave component and attenuation characteristics of the guided wave propagating in rock bolt, and found some new characteristics and phenomena. In addition, some phenomena that haven’t been explained in the previous researches have also been discussed in this paper. The result showed that when guided wave propagates in grouted rock bolt, after the body wave decays, there is still the interface wave-Stoneley wave that does not decay in the axial direction of the bolt. The findings can provide some reference for rock bolt testing and the selection of the optimal excitation wave of testing.
