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Si W.,Harbin Engineering University | Wan L.,Harbin Engineering University | Liu L.,Harbin Engineering University | Tian Z.,Science and Technology on Underwater Test and Control Laboratory
Progress in Electromagnetics Research | Year: 2013

The pattern of each element in conformal array has a different direction for the curvature of conformal carrier, which results in polarization diversity of conformal array antenna. Polarization parameters of incident signals are considered in snapshot data model in order to describe the polarization diversity of conformal array antenna. It is required that the polarization parameters and direction of arrival (DOA) of incident signals are estimated together. An integrated frequency and DOA estimation method is proposed in this paper for cylindrical conformal array antenna. The frequency estimation of signal source is obtained by constructing state-space matrix. Through well-designed configuration of elements on cylindrical carriers along with estimation of signal parameters via propagator method (PM), the decoupling scheme for DOA and polarization parameters is implemented. A novel parameter pairing method for frequency and DOA of multiple sources utilizing the interpolation technique is given, based on which the fast frequency-DOA estimation algorithm is developed. Effectiveness of the proposed method is demonstrated by simulation experimental results. Source


Tian Z.X.,Science and Technology on Underwater Test and Control Laboratory
Applied Mechanics and Materials | Year: 2013

To resolve the problems of short working life and narrow operating voltage range of the spark gap with one-offin gas filling structure, a spark gap with repeatable gas filling structure was designed. The spark gap was composed of three electrodes and two gaps as well as gas filling devices. Electrodes structures adopted the form of field aberration three-electrode gas spark switch forming two discharge gaps between three electrodes of anode, cathode and triggering electrode. Gas filling devices were composed of fast connector, gas pipe, barometer and air valve, by which the gaps could be repeatedly charged and deflated from a hole at the center of anode. Working life is lengthened by exchanging gas, and operating voltage range is widened by changing gas pressure in a certain range. The spark gap was manufactured and applied successfully in a TEA CO2 laser with pulse energy 170J. The results prove the designs feasible. © (2013) Trans Tech Publications, Switzerland. Source


Wan L.,Harbin Engineering University | Si W.,Harbin Engineering University | Liu L.,Harbin Engineering University | Tian Z.,Science and Technology on Underwater Test and Control Laboratory | Feng N.,Xiamen University
International Journal of Antennas and Propagation | Year: 2014

Due to the polarization diversity (PD) of element patterns caused by the varying curvature of the conformal carrier, the conventional direction-of-arrival (DOA) estimation algorithms could not be applied to the conformal array. In order to describe the PD of conformal array, the polarization parameter is considered in the snapshot data model. The paramount difficulty for DOA estimation is the coupling between the angle information and polarization parameter. Based on the characteristic of the cylindrical conformal array, the decoupling between the polarization parameter and DOA can be realized with a specially designed array structure. 2D-DOA estimation of the cylindrical conformal array is accomplished via parallel factor analysis (PARAFAC) theory. To avoid parameter pairing problem, the algorithm forms a PARAFAC model of the covariance matrices in the covariance domain. The proposed algorithm can also be generalized to other conformal array structures and nonuniform noise scenario. Cramer-Rao bound (CRB) is derived and simulation results with the cylindrical conformal array are presented to verify the performance of the proposed algorithm. © 2014 Liangtian Wan et al. Source


Zhang Y.,Dalian University of Technology | Zhou Z.,Science and Technology on Underwater Test and Control Laboratory | Wang J.,Dalian University of Technology | Li X.,Dalian University
Materials and Manufacturing Processes | Year: 2013

As a hard-to-machine material, titanium alloy has a combination of superior heat resistance, corrosion resistance, and mechanical properties, and this leads to poor machinability. High cutting forces and cutting temperature greatly accelerate tool wear during the cutting of titanium alloy frequently. In this article, the ultrasonic vibration turning method was adopted to reduce the wear of diamond tool in the turning of TC4 titanium alloy. Ultrasonic vibration turning tests were carried out in a variety of cutting parameters. The experimental results indicated that the wear of diamond tool was significantly reduced during the turning of TC4 using the ultrasonic vibration turning. In the ultrasonic vibration machining tests, the tool vibration amplitude and frequency are the primary and most influential factors on tool wear, followed by the feed rate and then the cutting depth. © 2013 Copyright Taylor and Francis Group, LLC. Source


Liu Y.L.,Science and Technology on Underwater Test and Control Laboratory
Applied Mechanics and Materials | Year: 2014

Virtual Instrument as the fifth-generation instrument has been a new technology with its unique advantages and got applying and developing more and more widely. From the view of composition and characteristics of the virtual instrument, the paper expounds the designing and developing process of electric field sensor calibration system based on the Ethernet and GPIB communication protocols. The table of the electric field sensor calibration system developed in the paper with a friendly interface improves the work efficiency of the electric field sensor calibration greatly, and the method and process of developing the electric field sensor calibration system could be a reference for the development of other relevant virtual instruments. © (2014) Trans Tech Publications, Switzerland. Source

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