Simulation and Analysis of Indoor Visible Light Propagation Characteristics Based on the Method of SBR/Image

The indoor visible light propagation characteristics are simulated and analyzed using the method of SBR/Image (shooting and bounding ray tracing/Image). A good agreement is achieved between the results simulated and the results given in published literature. So the correctness of the method has been validated. Some propagation parameters are obtained in the simulation, such as the indoor received power distribution, statistical distribution of phase angle of received power, RMS (root mean square) delay spread, direction of arrival, and Doppler shift. The foundation for the wireless network coverage of indoor visible light communication system is provided by the analysis of the above results

Total Nuclear Reaction Cross Section Induced by Halo Nuclei and Stable Nuclei

We develop the method for the calculation of the total reaction cross sections induced by the halo nuclei and stable nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energy. It is extended for nuclear reactions at low energy and intermediate energy by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with the 30 experimental data within 10 percent accuracy.The comparison between the numerical results and the 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies the quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root mean square radii of these nuclei can be extracted from above comparison based on the improved Glauber model, which indicate clearly the halo structures of these nuclei. Especially, it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very weak binding and the very extended density distribution.Comment: 15 pages,2 figures. Communucations in Theoretical Physics, (2003) in pres

Study of double-potential-well leaf spring system’s chaotic vibration

Chaotic vibration has become increasingly popular in the study of acoustic and vibration engineering. Many engineering designs have taken advantage of the special characteristics of chaos, and deliberately introduced it into the system to improve efficiency. As an important component, leaf springs have long been used in the suspension system of wheeled vehicles. Recent development is considering chaotic vibration in the design of leaf springs to improve the system’s reliability. However, little experimental research has been carried out to investigate the chaos characteristics of leaf springs. Meanwhile, a preliminary study showed that some of the conventional signal processing methods may not be able to successfully identify the chaos features from a leaf spring test rig due to the complexity of the practical signal. Therefore, in this paper, a leaf spring system’s chaotic vibration and relevant signal processing strategy were investigated in theory and experiment. Firstly, the relationship between the amplitude and frequency of the double potential well system is derived with averaging method. The stability is analyzed on the Vander pol plane and the global bifurcation diagram and Lyapunov exponent spectrum are applied to determine the chaotic regime accurately. Numerical simulation was conducted using a finite element method to give an idea of the leaf spring’s natural frequencies where chaotic vibration can be potentially generated. The experimental rig was then designed based on double potential well theory to generate stable and repeatable chaotic vibration, and an experimental study was carried out to investigate the system’s response characteristics under different excitation strengths and frequencies. An improved signal processing method, Wavelet-SG-EEMD (Wavelet, Savitzky-Golay (SG) and Ensemble Empirical Mode Decomposition (EEMD)), was used to reduce noise and beneficial to identify chaotic features of the vibration signal generated by the system. The nonlinear vibration response features of the system were carefully analyzed. Sub-harmonic phenomena, periodic modes and chaotic behavior were discovered during the experiment

Machining-path mapping from free-state to clamped-state for thin-walled parts

Thin-walled parts with curved surface are widely used in industrial applications and the high-quality machining is still a major problem because of the low stiffness. By using the machining-path obtained from the design model of thin-walled parts with curved surface, the machining accuracy requirement may easily not be met due to the springback of clamping deformation when the machining process is finished. It is a novel idea that when the machining-path mapping from free-state to clamped-state is realized based on the clamping deformation, the final machining-path of thin-walled parts can be re-designed to directly ensure the machining accuracy requirement after the fixture is released. Based on the concomitant thought of curved surface and the elastic deformation theory of thin shell in this study, the mathematical model for the machining-path mapping from free-state to clamped-state is established for the thin-walled parts with curved surface. Then, the corresponding relationship of cutter contact (CC) points is calculated by grid mapping. Finally, the machining-path for the thin-walled parts with curved surface is re-designed under the clamped-state. Taking a thin-walled cylinder workpiece as an example, the experiment results show that the proposed method can achieve the avoiding purpose for the machining error caused by clamping deformation. These research achievements are of vital importance for realizing high-quality machining of the thin-walled parts with curved surface