Advanced Materials Research Vol. 740

Abstract: The spine, which is throughout the trunk, is of great importance to the skeleton structure of human beings. For spine is vulnerable, the rate of spine incident trauma injury is relatively high. In the contemporary technology, the internal fixation prosthetics with implanting pedicle screws is the most efficient way in clinical treatment. However spine internal fixation surgery has many disadvantages like complex in the operation, the high penetration rate and inability to be used in the field battle. As a result, according to the magnetic property difference of different vertebra tissues, an eddy current detection method which is used in localization and recognition of different vertebra tissues to realize the navigation of spine internal fixation surgery is proposed in this paper. A set of improved series-reverse-three coils eddy current sensor is used to test the NaCl solution which electrical conductivity matches that of biological tissue. And the result of several experiments indicates this method can detect the biological tissue with the electrical conductivity no less than 0.5 S/m, which lays a solid foundation to further study of recognition different vertebra tissues.

Abstract: In Location Based Services, some queries from mobile clients to databases on server can be transformed into queries from mobile clients to theirs local databases by data preprocessing and sending ahead so as to reduce the time wasted on waiting. At the same time the strategy of intelligent learning is used to improve the hit rate for service information which makes our service more suitable to users requirements. The experiments show that the technology of data preprocessing can improve the query efficiency and reduce the dependence on instability of wireless network with less data errors and data resending.

Abstract: The design and implementation of video-decoding system are analyzed. And then, the video decoding and data processing scheme based on the FPGA and video-decoding chip ADV7181B is proposed. The I²C interface, used to configurate the register parameters of video-decoding chip ADV7181B, and the decoder of ITU-656, the storage of YCrCb, conversion between YCrCb and RGB and the display of VGA are implemented using FPGA. The all sub modules were described using Verilog HDL in the design, and merged in a module after they were emulated successfully. The module was come through and verified. The experiments results show that the system designed in this paper performed well.

Abstract: In the paper, parallel mechanism is applied to Marine stable platform field. The integrated model,which consists of mechanical system, hydraulic driving system and control system, is established by the software of dynamic analysis of mechanical system (Adams) and Matlab/Simulink. The simulation result shows the decent capability of hydraulic cylinders length tracking, however further improvement can be made. This research provides valuable and fundamental knowledge for the system design and optimization.

Abstract: With the growth of hard disk storage, it would be difficult to meet the specification of the high track density with conventional single actuator. Therefore the next generation of high speed hard disk drive uses the concept of dual-stage actuated hard disk drive where a secondary actuator is mounted onto the VCM actuator. This helps to achieve higher servo bandwidth and, therefore, more precise tracking. Improved tracking error allows higher track density and hence higher storage capacity. Piezoelectric actuator has been a popular choice as the secondary stage. However, the piezoelectric actuators exhibit an unavoidablecharacteristic of hysteresis which causes inaccuracies and oscillations in the system responses.In this paper, the hysteresis behaviour is investigated for asuspension based PZT actuator which is used as the secondary actuator of HDD available in the market. The Generalized Prandtl-Ishlinskii (GPI) hysteresis model which is a phenomenological based model is obtained usingnon-linear least square curve-fitting. In the secondexperiment, a second order linear dynamics model of the PZT actuator is obtained using frequency response identificationmethod. High frequency resonance modes of the PZT actuator are eliminated using a notch filter. By integrating the obtained GPI hysteresis model with this second-order lineardynamics, a nonlinear dynamic model and an inverse feedforward controller are developed.Preliminary simulation results demonstrate that inverse feedforward controller can be appliedfor precise tracking of triangular and multiple frequency sinusoidal trajectories.

Abstract: This paper proposes a prevention mechanism for resource exhaustion attack in Wireless Sensor Networks (WSN). WSNs are widely used in science, medical, and military applications. However, WSN has problems of small memory, weak processors, and the limited battery power. On the other hands, public key techniques provide powerful security, but they need high energy, memory, computation cost than the symmetric cryptography. Therefore, we propose a more efficient protocol than the existing protocols in WSN, which analyze RSA algorithm and simulate ECC algorithm in CC2420 which is a true single-chip 2.4Ghz IEEE 802.15.4 compliant RF transceiver designed for low-power and low voltage wireless application. We also compared our proposed protocol and other public key-based protocols.

Abstract: The maximum power point tracking (MPPT) control implements an effective utilization of solar energy. On the basis of the equivalent mathematical model of the photovoltaic (PV) array, presents the fixed step size perturbation and observation method, which has considerable power loss and poor adaptability. Because the existing variable step size control is complex, a fuzzy algorithm controller was designed according to the power variation and the previous step of the duty cycle, which could adjust the duty cycle of PWM dynamically, to make the PV system impedance matching and obtain the maximum power rapidly and steadily. The simulation shows that the self-optimizing fuzzy control can achieve good adaptability and good robustness when the parameters change.

Abstract: This paper takes the spindle of inner cavity shaping machine tool as the research object, analyzes the spindle structure of the machine tool and establishes the equations of motion, analyzes the influence that the spindle speed and tool deflection speed have on the tool rotary speed using Matlab and ADAMS, determines the allowed deflection range of the tool, sets up the transfer function of the servo motor current loop and analyzes the stability of spindle servo motor current loop .

Abstract: A wavelet transformation based estimating algorithm for the symbol rate of BPSK signals is adopted . This method extracts baseband signal from the generated BPSK modulated signal by means of different ways, utilizing the modulus of wavelet transformation coefficients of this baseband signal to construct a singular pulse sequence consistent with the code rate of original modulated signal. Theoretical analysis on the power spectrum of this singular pulse sequence indicates that there exist discrete spectral lines in the integral multiples of baseband signal symbol rate, thus detecting these discrete spectral lines can achieve the estimation of signal symbol rate. Our proposed algorithm can estimate the signal symbol rate under the low SNR condition.

Abstract: For automated fiber placement machine, tensioner is one of the important modules, which precisely generates and controls the tension of fibers.This paper performs a system analysis and synthesis of the key technologies of tensioner in recent years by summing up the development course of the tensioner. A new type of tensioner specially designed for fiber placment technology is presented. Experiments results prove the feasibility of the proposed mechanism and control algorithm. In addition, this paper also aims at giving a perspective in such area in the future.