Applied Mechanics and Materials Vols. 475-476

Abstract: Range accuracy is one of the key parameters for 3D laser imaging systems. A gain-modulated 3D imaging system employing multi-pulse accumulation method is proposed to improve the range accuracy performance. Experiments results show that the range error decreases exponentially with the number of accumulated laser echoes.

Abstract: For soft threshold function are likely to cause a constant deviation with the original signal, hard threshold function can not fully remove noise and the selection of semi threshold function parameters is complex, we presented a critical threshold function, and analyzed the parameter selection for the new threshold. The simulation experiments prove that the denoising of critical threshold method is much better, and it also can make up for the deficiencies of traditional threshold.

Abstract: An acquisition and analysis system for indicator diagram (ID) of piston engine is developed for monitoring the cylinder pressure in engine development. The hardware component of the data acquisition system is introduced. The method of the determination of the TDC, the method of filtering the interference signal of ID and the method of implementation with Visual C++ are presented. The system can provide ID online through the experiment on Honda 125 engine. It can directly and conveniently display the information about combustion. Therefore it has a high potential value in engineering applications.

Abstract: Multi-resolution optical flow is the main trends of the current optical flow calculation. Wavelet transform and Gaussian filter are widely used to build multi-resolution structure of the image. In this paper, LK optical flow method mixed with pyramid was used to study the optical flow field. The different effects of wavelet transform and Gaussian filter in the flow distribution was also discussed. Experimental results show that the selected image decomposition method has a significant role in optical flow field calculation.

Abstract: Is EM algorithm parameter estimation under Rayleigh distribution sensitive to missing data and if it is, what extent is it By designing computer simulation methods, contrast and analyze the results of maximum likelihood estimation and EM algorithm estimation under different missing rate. It shows that the results were almost identical when the missing rate is below 0.30, but the efficiency of EM algorithm gradually deteriorates as the missing rate increases. Meanwhile the results also show that the EM algorithm is sensitive to sample size and the selection of initial value.

Abstract: In order to deal with the contradiction between suppressing speckle noise and reserving details in laser active imaging recognition system, a denoising method based on contour curvature is proposed. Due to the contour curvature, the pixels in the image are divided into different classes, which contain different amount of information. The filter parameters are different for each class. Firstly, the origin image is smoothed using wavelet soft thresholding, then the contours are extracted by Morphological edge detection operator. Due to the difference of contour curvature, the pixels are labeled with point of strong signal, point of weak signal or point of no signal. Pixels with different labels are filtered by Lee filter of different step width. Experiment result indicates that compared with classical Lee filter, the proposed method performs better in filtering and keeping edge information.

Abstract: TEQC is a tool which can be commonly used in GNSS data translation, editing, and quality checking, it's widely used in GNSS data preprocessing. This paper has introduced the common syntax and instruction of TEQC when it used in GNSS data processing, also introduced the testing examples of GNSS receiver under three environments: 220KV UHV transmission line environment, 500KV UHV transmission line environment and standard GNSS calibration field, then using TEQC to preprocess and analysis the data. The results showed that: a)The GNSS observation data Efficiency is not effected from radio interference generated by EHV transmission lines; b)Within 25 meters ranges GNSS observation data under EHV transmission line, the multi-path effects (mp1 and mp2 value) significantly exceeded the normal range, and the voltage higher, the multi-path value larger. c)Apart from 50 meters outside EHV transmission line, there is almost no effect about multi-path affects in the high-precision GNSS observation data.

Abstract: In this paper, a new method for blind source separation of the noisy mixed speech signals is introduced. Firstly, the adaptive spectral subtraction is adopted to eliminate noise of noisy mixed speech signals. Secondly, the FASTICA algorithm is used to separate denoised mixed speech signals .Finally, wavelet transform is applied to remove the residual noise, and then the estimation of each speech source signal can be got.

Abstract: As is known to us, conventional photogrammetry uses the double phase stereopair for forward intersection, but this paper proposed a new method for 3D coordinates acquisition based on single camera. Under the defined relationship of the object relative position, three-dimensional coordinates can be obtained by space resection through single photo. The principle of this method is simple but practical, especially suitable for measuring the overall mobile objects. Experiments show that within1500mm, plane normal direction is better than 0.02°in the measurement accuracy , and can replace stereopair measurement in certain conditions for its higher measurement accuracy.

Abstract: Aiming at the problem that uncertainty risk loss is lacking of considering in testability demonstration test, a method for testability demonstration test based on cost optimization is proposed. In the method cost of fault injection, risk cost of producer and consumer is synthetically considered, and a model based on test cost is established. On the basis of binomial distribution theory, the calculation method of producers risk and consumers risk is provided, and the variation tendency of producers risk and consumers risk changing along with the test plan is analyzed. On this basis, optimization solving method of test cost model is presented under the principle of minimize the posterior expected cost. At last, an example is given to show the validity of the proposed method.