Applied Mechanics and Materials Vols. 29-32

Abstract: This paper proposes an optimization method which makes the structural parameters are minimum and the workspace is maximum based on 3-DOF parallel machine tool. By analysis the conditions of boundary, parameters optimization model is built and gives out the explicit solution of dexterous workspace. Analysis the effect of structural parameters on workspace. The results show the workspace is a unsingularity space.

Abstract: Shearlet is a new effective signal representation tool in many image applications. A novel image denoising scheme based on Shearlet transform is proposed in this paper. The original image is first decomposed using shearlet transform, then the shrink threshold of each decomposed subband adopts the different best threshold, producing the preliminary primary denoised image after reconstruction. Experiments show that the proposed scheme can remove the pseudo-Gibbs artifacts and image noise effectively. Besides, it outperforms the existing schemes in regard of both the peak-signal-to-noise-ratio (PSNR) and the edge preservation ability.

Abstract: This note presents the main process of optimization design of foam core/carbon fiber composite sandwich which primarily designed for UAV wing beams. During the actual application, the original design provided excessive structural strength and it has certain capacity to be optimized. So the weight of structure can be reduced under the premise of meet the strength requirement. In order to characterize fully the complex mechanical behavior of such a highly heterogeneous material and find the ultimate strength of this structure, MSC.Patran/Nastran has be applied on analysis of this composite sandwich structure. Base on the result of the numerical simulations, the best combination of composite laminated and the material layer thickness have be determined, and the beams structure of the lightweight has be designed ultimately.

Abstract: RFID has become an important infrastructure technology. However, it does not solve information security problem. An adversary can eavesdrop on the messages exchanged between tag and backend database and track tag’s holder. Many scholars have proposed some lightweight protocols in order to protect user’s privacy and avoid various attacks. In this paper, we analyze some authentication protocols. Especially, we analyze a forward secure RFID privacy protection scheme proposed by Ohkubo et al. Afterwards, we propose an improved protection scheme with two-way authentication. It is lightweight and suitable for low-cost RFID system. Moreover, it not only provides indistinguishability and forward security but also provides two-way authentication.

Abstract: Information security problem has become one of the hottest issues in RFID system. More and more researchers begin to study how to provide security protection in the RFID system. In the paper, we mainly research lightweight authentication protocols in RFID system. Firstly, we analyze some protocols. Secondly, we introduce a serverless authentication protocol for RFID system and analyze its security. We find it does not provide forward security. Thirdly, we propose a revised serverless authentication protocol with forward security. It provides two-way authentication and privacy protection, resists tracking and cloning attack as well as the original protocol. Moreover, it provides forward security protection and resists desynchronization attack. For the efficiency, its computational complexity is at the same level with the protocol proposed by Tan et al.

Abstract: The basic ant colony algorithm is improved by introducing chaos model of Logistic and discrete search in order to improve the global convergence. A program of improved ant colony algorithm has been designed by using Matlab. It can be used for solving optimal design problems with continuous variables, discrete variables or mixed-discrete variables. For an electric circuit, the design problem about the robustness of electric current is discussed and a model of robust optimal design is established. The solution of established model is achieved by using the proposed method and the robustness of the electric circuit has been improved. The example shows that the proposed method is effective in engineering design.

Abstract: As the most important actuator of the attitude control subsystem of the spacecraft, the momentum wheel should be precisely simulated. In this paper, Dual Extended Kalman filter is expressed and used to identify the momentum wheel system. In this way, the identification result can be used in the momentum wheel system simulation. This makes simulations run both fast and precisely. The numerical simulation results show that the algorithm can converge in given error.

Abstract: In auto industry extensive use of traditional IC engines and fossil fuel as power source has lead to serious environmental problems and social issues. Development of hybrid vehicles is a hopeful technology to solve above problems. As a vital part of IC engine-electric hybrid vehicles, power source should generate electricity efficiently. Supported by National High-tech R&D Program (863 Program) a novel Internal Combustion Linear-Generator Integrated Power System (ICLG) is researched in this paper. ICLG mainly consists of four-stroke free-piston engine, linear motor, reversible electrical energy storage device, and control unit and has the potential to convert the chemical energy of fuel to electrical energy efficiently. Achievements for improving efficiency, such as minimizing the energy transmission and conversion link, movement control of piston by adjusting electromagnetic force, optimization of thermodynamic cycle, and sub-cylinder or sub-cylinders mode, are analyzed and validated by testing. Testing results show that the generating efficiency is about 32%, which can be improved by further study. ICLG is hopeful to be the new generation power source of hybrid vehicles which has the character of power saving and environmental protecting.

Abstract: In this paper, laboratory tests on conductor aeolian vibration were designed and carried out, through which the power dissipation characteristics of conductor self-damping and wire dampers(bretelles) were investigated. In addition, the theoretical method was established to estimate the power dissipated by wire damper. The results show that conductor tension and vibration frequency have great influences on its self-damping property; furthermore, the results present that the natural frequency of wire damper is related with its length and the length of wire damper has significant impact on its anti-vibration effect. The theoretical method for calculating the power dissipated by wire damper was verified to be reliable by the test results. These conclusions can provide references for the research and anti-vibration design of transmission line engineering.

Abstract: A novel 5-Degree of Freedom PCMM (parallel coordinate measuring machine) was proposed, and its motion control system was designed. Compared with the other structural PCMMs, the structure feature of proposed PCMM was described. Then its motion control system was designed with the modularized and open architecture. The controlled scheme of hardware, which based on PC, PMAC motion control card and the precision measuring probe, was developed. The software of the motion control system was written by Visual Basic6.0 language. Finally, the process of motion control for 4-UPS-UPU PCMM was proposed. The new method above for design of motion control system is simple and effective, and may be applied to other parallel machine.