A reliable and high throughput hybrid routing protocol for vehicular ad-hoc network

Due to highly dynamic topology caused by fast moving nodes the Vehicular ad-hoc network (VANET) results in the existence of transient communication links, which degrade the performance of developed protocols. Established routes frequently become stale, and existing communication flows are interrupted, incurring delay and additional overhead. In this paper we propose a novel hybrid routing protocol, which is the combined between of the table-driven routing and on-demand routing in VANET. It makes fast convergence in routing process, minimal drop links, making more reliable links, and adaptive with changing of VANET topology. With neighbor table is updated instantaneously, and using strong neighbor for routing process makes route discovery process start whenever it received requirement, and through using route mechanism appropriately it reduces significantly route overhead at each node. The simulation results illustrate the outstanding properties of our proposed routing protocol.     

Comparison of Lattice Boltzmann Method and Monte Carlo Method for Modeling Phonon Heat Conduction

In order to investigate the applicability and performance of the Lattice Bohzmann Method （LBM） and the Monte Carlo Method （MCM） to simulate phonon heat transfer, a problem of phonon heat transfer in square geometry structures of silicon dioxide was taken as an example to compare the calculational resuhs and analyze computational efficiency of the two methods. Moreover, this work analyzed the numerical stability for two methods. The results indicate that the MCM takes much more computation time than the LBM in the same condition. In addition, the results of the two methods have a good agreement in diffusive and diffusive-ballistic domain for investigating the phonon heat transfer. So they can be used to verify each other when the experiments of energy transport in these domains faces difficulty. In ballistic domain, duo to the random error, the temperature distribution curve from MCM is fluctuant.     

Using Walsh-m Composite Sequence and LDPC-QPSK Joint Iteration to Reduce ISI in Long-range Underwater Acoustic Systems

To reduce inter-symbol-interference (ISI) in underwater acoustic (UWA) communication systems, a method based on LDPC-QPSK joint iteration and Walsh-m composite sequence is proposed in this paper. The method is intended for use in long-range and low signal-to-noise ratio (SNR) UWA communications. At the transmitter, Walsh-m composite sequence is introduced to resist multipath effect. At the receiver, a soft-input soft-output (SISO) module is implemented in a joint iterative process between QPSK demodulator and LDPC decoder. This method is demonstrated in three types of UWA channel models: positive, negative and invariable sound velocity gradients channels. It is shown that through contrastive simulation experiments, this method is more efficient than conventional methods based on independent decoding and demodulation. After two rounds of joint iteration, the proposed method can obtain 2.5 dB over conventional method at BER of 10-5. Numerical results verify that the proposed method is a good candidate for long-range underwater acoustic communication systems.     

Working Principle and Error Analysis for Hemispherical Resonator Gyro under Force-rebalance Mode

The two control methods, namely the general-control and the quadrature-control modes for HRG under force-rebalance mode were introduced firstly. Then the azimuth of antinode on the hemispherical resonator was deduced. The dynamics equations of resonator under the nonuniformity of density distribution were established by way of Bubonov-Galerkin method which is commonly used for solution of differential equations, and the state equation was established through the dynamics equations. The analytic solutions of the vibration displacement and the velocity were achieved by solving the state equation, and then the ratio of rebalance excitation to primary excitation was derived under the two working modes, thus the estimation of input angular rate of HRG were obtained. By comparing and calculating these two modes, the error caused by resonator’s machining defects can be greatly inhibited under quadrature-control, and the fourth harmonic density error’s tolerance were calculated to ensure the accuracy of HRG under these two modes.     

Experiments in Consensus-based Decentralized Information Feedback Control Strategies on a Real Robotic Fish Platform

A decentralized information feedback mechanism was introduced to a group of mobile robots such that the robots asymptotically converge to a given moving formation. While various distributed cooperative control strategies have been studied in theory, few of them have been systematically validated on experimental platforms. This paper demonstrates the experimental results of consensus-based decentralized information feedback mechanism on a multiple mobile robotic fish platform. In this paper, we firstly introduced a fundamental consensus algorithm for systems model and the cooperative control experimental platform, and then experimentally implemented and validated the formation control algorithm through setting transit point and look- up table method and so on. The experimental results show the effectiveness of the consensus-based decentralized information feedback control strategies.     

Effect of Air Pressure on Hardened Layer of U75V 60 kg/m Heavy Rail after Heat Treatment

The samples cut from U75V 60 kg/m heavy rail are heated to 900 ℃ in resistance furnace and then put into air spraying channel to be cooled for 80 s, and change air pressure from 0.16 MPa to 0.33 MPa, and observe the effect of air pressure on hardened layer. The thickness and hardness of hardened layer increases with the increase of air pressure, and the thickness is more than 24 mm at the center and top fillets of rail head, and more than 15 mm at the blow fillets of rail head when air pressure is more than 0.26 MPa. During the tempering after heat treatment, tempering temperature of rail head is more than 570 ℃ when air pressure is separately 0.16 MPa, 0.20 MPa and 0.23 MPa, which is higher than finishing temperature of pearlite transformation at the cooling rate of 3 ℃/s according to CCT curve of U75V steel. When air pressure is separately 0.26, 0.30 and 0.33 MPa, the tempering temperature is 529 ℃ lower than finishing temperature of pearlite transformation at the cooling rate of 3 ℃/s. Under this condition, pearlite transformation is finished totally, so in order to reduce air consumption and control the cost, proper air pressure for U75V 60 kg/m heavy rail heat treating should be 0.26 MPa; the cooling rate increases with the increase of air pressure, and the average cooling rate on the surface of rail head is more than 3.21 ℃/s when air pressure is more than 0.26 MPa, and the largest cooling rate occurs at the top fillets of rail head.     

Research of Velocity Compensation Method Based on Range Profile Feature

In this paper, based on the feature of high resolution one-dimensional range profile, two effective motion compensation methods are presented. Firstly, the processing method of stepped-frequency and the response of target moving to range profile are analyzed. Secondly, the function of range profile entropy and range profile contrast are presented for velocity compensation, and then the theory analysis, math model, and solution method are analyzed in detail. Finally, several simulation experiments are designed to prove the accuracy and effectiveness of these two methods. From the final theory analysis and simulation experiments, the conclusion can be drawn that these two methods are effective, which can get much higher velocity estimation accuracy, well real-time and easy to be used in project application. After motion compens-ation, the high resolution one-dimensional range profile will be much better than that used to be, and is used for the detection, recognition and ranging of moving targets.     

Research on Social Tags Recommendation Techniques Based on Content

With the rapid development of the Internet, more and more people begin to pay attention to social tagging which is a flexible and efficient method for classification. How to retrieve tags from the huge tag library becomes a hot topic to research. Firstly, the existing systems of social tags and its recommendation principles used in Web 2.0 are introduced in this paper. Secondly, the existing techniques about tag recommendation are summarized, and their merits and demerits are analysed. In most techniques for tag recommendation only two dimensions “resource-user” are considered. But there are three dimensions “resource-user-tag” in recommendation system based on social tags. A new method of social tag recommendation based on content-Feature Vote Tagging (FVT) is proposed in this paper. Finally, several kinds of evaluation methods are used to assess the return results of methods. The experiment results show that the method proposed in this paper can satisfy the expectation of the user for the recommendation results.     

Prediction of Aircraft Engine Health Condition Parameters Based on Ensemble ELM

In view of aircraft engine health condition parameters prediction, an ensemble ELM based prediction approach is proposed in this paper. In the approach, the AdaBoost.RT algorithm is improved to adjust its threshold adaptively, and is utilized as the basic framework to establish the ensemble learning model using ELM as weak learners. The proposed approach is evaluated through the prediction of the actual engine fuel flow deviation time series, and the results demonstrate that this approach is feasible for the prediction of aircraft engine health condition parameters. The performance of the proposed approach is compared with single ELM, single process neural network (PNN), and a similar ensemble ELM based approach using AdaBoost.RT as basic framework. The results show that, the proposed approach is more accurate than single ELM and single PNN, and no worse than the ensemble prediction approach for contrast, furthermore, the given approach is more convenient for practical application. Therefore, the proposed approach is better suited to the prediction of aircraft engine health parameters.     

大规模地形快速渲染算法的研究

探讨了如何有效地进行大规模地形的快速绘制，并详细介绍了一个基于mip-map技术的地形渲染算法的原理及其实现过程。