Advanced Materials Research Vols. 301-303

Abstract: Aim to the low measuring precision of non-cylinder pin hole using the coordinate measuring machine(CMM)and pneumatic measuring instrument, a new solution is proposed which use the high-precision digital lever probe to detect the contours of pin hole with a single clamping situation. The measuring principal of non-cylinder pin hole of piston is introduced and the functions and measuring processes of the measurement system are also presented. The software modules are given and the probe centering error and the parallelism movement error are discussed detailedly. A measuring example is given in the end. The measuring results show that the measurement system has the ability to detect the contours of pin hole with high-precision and efficiently.

Abstract: Laser-generated surface acoustic waves (LSAWs) technique is a feasible method to determine the Young’s modulus of thin films. The raw surface acoustic wave (SAW) signals detected from the experimental system are often contaminated by external noises. A novel de-noising method is proposed in this paper with wavelet and FIR filter. The wavelet threshold de-noising is essential to reduce the high frequency noise components in the raw SAW signals, while FIR filter can remove the useless low frequency noises. The useful bandwidth of the detected signal ranges from 50 to 190 MHz. Young’s modulus of the detected samples can be obtained by matching the experimental dispersive curves with the theoretical calculated ones via an improved least square fitting method. The Young’s moduli of four low dielectric constant (low-k) samples detected in the measurement are 7.1, 6.8, 1.1 and 1.0 GPa, respectively.

Abstract: The aim of this paper is to validate the modal parameters used in coupled structural finite element and acoustic boundary element algorithm to analysis the structure subjected to diffuse acoustic field. The theoretical deduction of non-symmetric coupled vibro-acoustical modal analysis was introduced firstly. In order to verify the modal truncation frequency how to affect the simulation results, based on the reciprocity theorem used in coupled FE-BE model, three different truncation frequency conditions were performed. The contrastive results show that twice the upper calculation frequency as the truncated modal frequency can make the simulation effectively and efficiently.

Abstract: This paper describes the quantitative analysis of the shape, boundary, and depth of subsurface defects by ultrasound lock-in thermography. The phase difference between defective areas and non-defective areas illustrates the qualitative analysis of the shape and the boundary of the subsurface defect. In order to accurately estimate the shape, boundary and depth of the defects, the optimal threshold value method is proposed to identify the shape and boundary of the subsurface defects based on the canny operator of image processing. A self–adaption artificial neural network (ANN) with Takagi-Sugeno modeling is proposed to determine the depth of the subsurface defect. Experimental results for a steel plate with artificial subsurface defects show good agreement with actual values.

Abstract: Land subsidence in urban area is becoming a severe geological hazard disturbing the urban construction and development. Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique has demonstrated a good capability of monitoring the large scale land deformation. High resolution and short wave radar data can help to improve the precision of deformation detection based on PSInSAR. In this paper, 15 scenes of TerraSAR-X SAR data are used to derive the estimation of the subsidence rate in the Wuqing district, Tianjin city in China. The combination of TIN and nearest-connection method (NCM) are first used to establish the differential network model. The results show that high resolution TX image can dramatically increase the valid PSs and improve investigation reliability, especially in linear man-made constructs.

Abstract: In order to solve the problem of low accuracy and high power consumption, A new ultrasonic flow measurement method was proposed in this paper. With this method, the influence of the delay-time in the circuit was eliminated,the temperature of fluid was compensated automaticly and the accuracy of the flow measurement was improved. The ultrasonic flow-meter was designed with the micro-power timing chips TDC-GP2 and MSP430F435, which reduced the power consumption effectively. The experimental results showed that the accuracy of the ultrasonic flow-meter was 1.5% and the average operating current was lower than 35uA.

Abstract: A time domain technique based on numerical inversion of Laplace transform is extended and applied to transient analysis of pulses reflected from a Lorentz half space both for TE and TM cases. Its correctness and effectiveness are validated by comparing our results with those published in the literature. With this technique, the TM case when the incident angle is equal to 45⁰ does not need to be processed separately and can be treated as a general case for any incident angle. This technique brings good accuracy in both late and early time, a simple algorithm, short calculation time, small required memory size and readily controlled error.

Abstract: According to the particularity of relational databases, a new watermarking relational database based on image is proposed combined with the existing digital watermarking technique. Watermark image is scrambled using Arnold transform first, and then numeric attributes satisfying the requirement of the effective bits in relational database are partitioned using the K-Means algorithm, at last the binary 3-bit-set sequences of watermark image are embedded into the clusters. Experiment indicates that the algorithm possesses better robustness and invisibility and better practical value.

Abstract: Induction-type coil target is a common used zone-block device for measuring projectile’s velocity. The magnetized projectile is simplified as the point magnetic dipole, and then the physical model of magnetized projectile passing through the coil target is established, based on these the mathematic model of inductive electromotive force when the magnetized projectile flying through the coil target in a certain speed is deduced with the electromagnetic theory; According to the model, the characteristic parameters such as the zero-crossing point, the slope of zero-crossing point and the extreme value point are discussed, finally the principle and the influence factors of velocity measurement by single-coil target and paired- coil targets are described. All these above provide some foundation and advices for designing and using induction-type coil target.

Abstract: Computational fluid dynamics and wind tunnel test are two main technical means to examine the aerodynamic performance of airfoil and two-dimensional(2-D) configuration. Two dimensional wind tunnel tests use commonly wake flow field measurement to integrate for drag of airfoil or two-dimensional configuration, but the integral formulas are based on certain assumptions and of certain bounds of application. In this paper, based on Navier-Stokes equations numerical simulation and two dimensional wind tunnel testing, the drag measuring technique for high lift configuration in low speed wind tunnel is researched. Navier-Stokes equations is solved for the flow around a multi-element airfoil, the wake flow characteristics behind the multi-element airfoil and the assumptions for conventional drag measuring method are analyzed, then a new more precise drag formula for two dimensional wind tunnel test is put forward; Based on the simulation results of multi-element airfoil flow, it’s aerodynamic performance is obtained respectively by integrating the surface pressure and friction drag, and computing with the information of wake flow according to conventional and newly proposed drag calculation formulas, and the three results are compared to verify the accuracy of the new drag formula; The wind tunnel test is carried out to ascertain the accuracy of the new drag formula. It is shown from the results that in the high-lift case the conventional drag formula with the wake information is of many limitations and must be improved, and the new drag formula presented in this paper is more accurate because of consideration of the wake flow characteristics of airfoil or two-dimensional configuration.