Applied Mechanics and Materials Vols. 239-240

Abstract: Acoustic Doppler Velocimeter (ADV)’s applications in measuring velocity profiles of turbulent boundary layers (TBLs) are investigated at a flow Reynolds number of 36000 in a lab-made open channel. The 3D instantaneous velocity signals at different heights of TBLs are obtained, which present very strong abnormal noises in the near wall regions because of the aliasing of Doppler signal spectra. The minimum/maximum threshold filter is adopted for the signal to remove the noises reflected by walls. The mean streamwise velocities and turbulence intensities profiles are then calculated correctly. The measuring results consist with the law of turbulent boundary layer flow. The ADV has a good performance in measurements of TBLs with a simple implementation of filter to the sampled velocity signals. The present research is guidable for applications of ADV in practice.

Abstract: The research is aimed at the development of an image processing system for classification of pathological area for medical images obtained from computed tomography (CT) scans. We proposed a novel semi-supervised image segmentation method based on the curvelet transform and SVM classfication. Firstly, through curvelet transform ultrasound images were decomposed into different directions and scales, the main distribution curvelet coefficients were extracted by cauchy model to reduce the algorithm time complexity, after inverse curvelet transform to obtaine a series of feature vectors from main distribution curvelet coefficients, then training samples and test samples were constructed; Secondly semi-supervised SVM classifier was designed, in order to reducing the weak classifier error rate, iteratively adjustment method was used to modify the SVM parameters, thus SVM strong classifier was constructed; Finally the expert manual tagging map were taken as reference standards, comparison with the existing method, experimental results shows that our algorithm is high anti-interference and has higher accuracy and effectiveness for ultrasound images pathological region segmentation.

Abstract: This paper presents the echo-sounder survey in Dongzhai Bay, Hainan Island, South China to detect the earthquake event in the year of 1605. According the local historical document the earthquake in 1605 caused the subsidence of the coastal plain and the formation of the Dongzhai Bay in north-eastern Hainan Island. In the summer time of 2009, the echo-sounder survey in the Dongzhai Bay was carried out with the StrataboxTM equipments. The geophysical data of the bottom sediment were analysed. This is the first time of the Stratbox TM used in the coastal shallow water in China to detect the sediments and environmental changes.

Abstract: Due to the different PV modules and external conditions, large-scale photovoltaic power plants often show a multi-peak PV characteristics. But the traditional MPPT methods is only for single-peak P-V curve to strike a maximum power point. So we need to improve the conventional MPPT methods. In the MATLAB/Simulink environment, we combined the Hysteresis Comparison Method with Incremental Conductance to build the S-function to create a simulation model obtaining the maximum power point power, voltage and current. In the same simulation system the traditional Incremental Conductance was used to obtain the maximum power, voltage and current which compare with the maximum power, voltage and current which obtained by the proposed method . The results of simulation illustrated the effectiveness of the proposed method .

Abstract: This article proposes a surface reconstruction method by photometric stereovision based on Oren-Nayar’s model. The classical photometric stereovision reconstructs the surface by the exploitation of Lambert’s model. However Lambert’s model does not take into account the complex geometric and radiometric phenomena such as masking, shadowing and inter-reflections between micro-facets on the surface. Thus this article will improve the photometric stereovision by using Oren-Nayar’s model instead of Lambert’s model. The photometric stereovision based on Oren-Nayar’s model will calculate respectively the energies attenuated by the phenomena of masking, shadowing and the energies produced by the phenomenon of inter-reflections. At last, the surface reconstruction experiments show that the result obtained by this method is more precise than the one obtained by classical photometric stereovision.

Abstract: This paper put forward an image fusion algorithm which based on the analysis of the imaging theory fusion, the fusion process is first will have been registration of the original image into several pieces, we calculate the correlation of corresponding piece, as the image contrast evaluation criteria, by selecting two images in the clear image block form fusion image. This paper discusses the principle analysis from optical imaging, the cause of the fusion algorithm, to avoid the use of Gaussian Blur model to explain the image of a fuzzy controversy. The experimental results show that the proposed algorithm is good real-time performance, for registration fusion image can achieve even more than general wavelet decomposition of the fusion algorithm.

Abstract: Proposed and implemented two complete multi-channel spectral reconstruction methods based on basis functions and pseudo-inverse, and using RGB digital camera built up a reconstruction system. A set of algorithms that enable virtually complete digital response value correction were proposed. The root mean square error and color difference as evaluation criteria to compare the reconstruction accuracy of two methods, and experiment show that the accuracy of both methods is basically the same, but the basis function method is more suitable for multi-spectral reconstruction operations.

Abstract: A weak current measurement system is developed. It is mainly used in the accurate measurement of weak current in radiation detection. The principle of the measurement system is introduced. The interference protection measures of current to voltage (I-V) conversion and amplification unit, the technology of ∑-△ ADC and the program design of micro-programmed control unit are described. The system is able to communicate with the computer controlled platform by the USB interface, which has the functions of storage, range selection, data display, data plotting and so on. The measuring range is from 0.1pA to 2.1mA, and the resolution is 5½ bits. The system has been successfully used in the detection of radiation.

Abstract: The precision measurement of horizontal tank volume is one of key problems for the international trade of liquefied petroleum products. According to the technical requirements of international legal metrology recommendations, one volume measurement method for horizontal tank was presented, based on laser scanning principle. Algorithm based on wavelet was studied for noise reduction of data cloud, and one volume calculation model was raised. One comparison experimental system was designed, and 37m3 and 60m3 horizontal tanks were used as test object. It could be concluded from the experimental data that Compared to the volumetric method, the relative errors of both two test tanks were smaller than 0.4% at full range of liquid level, which was satisfied with the regulation of horizontal tank calibration. By using the method discussed, the calibration efficiency of horizontal tank volume can be improved greatly.

Abstract: In order to improve the signal demodulation performance of fiber Bragg grating (FBG) sensing system, a wavelength shift detection method based on cross-correlation analysis is proposed to improve the accuracy of the measurement. The simulation results indicate that the absolute error of the measurement can be between 2 pm - 3 pm within the range of SNR of 14 dB-7 dB. Under the condition with high SNR, the absolute error can be approximately reduced to 0.5 pm. Hence, this demodulation algorithm can reduce the influences of the noises effectively and help to further study the features of the FBG sensor demodulation system.