Applied Mechanics and Materials Vols. 128-129

Abstract: The paper proposes a novel method for online measuring the open-circuit loss (OCL) and the short-circuit loss (SCL) of distribution transformer DT, based on the consideration of the drawbacks of the offline measuring method, which is regarded as the mainly and traditionally used methods for measuring the OCL and the SCL of DT. The novel method avoids the drawbacks of the offline method which is not cost-effective and is not good for the reliability of the power supply. Firstly, the relation expression of the short-circuit impedance with respect to the voltage and current of the primary and secondary side is developed from the analysis of the equivalent circuit model of DT, and the relations between the SCL and OCL and the short-circuit impedance are also deduced according to power balance. Then, the online short-circuit impedance is computed by using linear regression technique and the value of online voltage and current of DT. Furthermore, according to the developed relations, the online OCL and the SCL of DT can be acquired by using the obtained short-circuit impedance. Numerical simulations have been carried out on Matlab/smulink and results verified feasibility and effectiveness of the novel method for online measuring the OCL and the SCL of DT.

Abstract: To improve the accuracy of strain, the design method and technology based on the theory of double-channel parametric measurement is proposed. At last, the measuring circuit with linear conversion function is designed. Based on the theory, a measuring system is developed. The practical experimentation indicates that the theory and technology are right, and the accuracy, stability, anti-interference and reliability are excellent.

Abstract: This paper proposes a new skin image detection method. First, skin pixel histogram in RGB color space is analyzed. Then Gaussian Mixture Model is used to constructed distribution of skin pixels. Second, a Gaussian parameter combination and selection procedure is implemented with Genetic Algorithms, and the optimal Gaussian Mixture Model can be obtained. Experimental results on public database show that our proposed method outperforms the traditional method with ROC test.

Abstract: A side-coupled optical-fiber liquid level sensor is proposed to realize intrinsically safe measurement to liquid level in flammable environments. The sensor consists of two parallel side-polished fibers is based on the different coupling coefficient between the fibers in different media according to the Fresnel equation. One of the fibers is for emitting and the other is for receiving, and a reflector is attached to the end of the fibers to enhance the power of light. The power of the light from the top of receiving fiber is measured by the signal processing circuit which is mainly organized by an instrumentation amplifier and a correlator. This sensor is fabricated in the laboratory and the results of the experiments show good performance. It is demonstrated that the sensor is safe and sensitive, but there is still a lot of work to do before its commercial usage.

Abstract: A cascaded modular structure is proposed to implement the blind MVDR detector. In each module of the structure, a vector filter is introduced for adaptive interference cancellation. The weight vector is determined based on a maximum magnitude cross correlation criterion which maximizes the magnitude of the cross correlation between the output of the nonadaptive filter and that of the weight vector filter. The performance of the proposed receiver has been evaluated via computer simulation and shown to be comparable to that of the optimum method under asymptotic condition. When the number of received vectors is non-ideal, the proposed method outperform the optimum method.

Abstract: The automatic identification of 2D (two dimensional) bar code PDF417 is very sensitive to skew angle, but, the common skew angle detection methods have shortcomings such as weak performance in time complexity. In this paper, based on the properties of PDF417 character code and the extraction of feature points, we get skew angle of PDF417 bar code image using the least square method. Experiments show that this algorithm has virtue of less computation and high accuracy.

Abstract: In this paper an adaptive method of shrinkage of the wavelet coefficients is presented. In the method, the wavelet coefficients are divided into two classes by a threshold. One class of them with the smaller absolute values at a scale is transformed with a proportional relation，another class with the larger absolute values at the same scale is transformed with a linear function. The threshold and the coefficient in the proportional relation or in the linear function are determined by the principle of minimizing the Stein’s unbiased risk estimate. In the paper, the method of estimation of the threshold and the coefficient is given and the adaptive method of shrinkage of the wavelet coefficients is applied to image denoising. Examples in the paper show that the presented method has an advantage over SureShrink from the point of view of both the Stein’s unbiased risk estimate and the signal-to-noise ratio. In addition, the method takes almost the same computing time as the SureShrink in image denoising.

Abstract: In this paper, a singing evaluation approach based on pitch and rhythm accuracy is proposed. A comparative study was first carried out between speech and singing voice, which demonstrated the characteristic of consonant and vowel in singing voice. A phoneme boundary detector was adopted to perform note segmentation in a high time resolution by using characteristics of consonant and vowel. As for singing skill evaluation, relative pitch interval between reference score and actual sung pitch was adopted to estimate pitch deviation while difference between absolute position and expected position of beats served as rhythm consistency measure. Experiments on a solfege corpus demonstrated a noticeable improvement in the performance of onset detection. A detailed subjective evaluation showed great consistency between the proposed evaluation approach and experts’ judgment.

Abstract: Of all current methods for measuring spacecraft attitude, the use of star sensors produces the most accurate measurements. Conventional star sensors repeat these processes with Lost-In-Space case. To advance the methods available to solve these problems, this paper presents an autonomous predictive centroiding algorithm for the star sensor. The star sensor works in the star predictive centroiding case while few recognized stars within the FOV (Field of View). The ideal locations of unrecognized stars and recognized stars in star image are predicted at first. Then the corresponding real locations of recognized stars and unrecognized stars are obtained in the threshold scan window of predictive centroiding. It enables only several hundred pixels to be scanned. The speed and the accuracy of this algorithm are successfully demonstrated in comparison with the ordinary centroiding algorithms which don't use the previous image data. Finally the autonomous predictive centroiding algorithm was successfully demonstrated with real sky experiment in 2008 and on-orbit in 2010.

Abstract: Wireless Sensor Networks have many limited capacities such as battery power, computation and communication bandwidth, how to balance the energy dissipation and prolong the network lifetime is a key problem. Based on the extensive analysis of LEACH algorithm, EBCP algorithm is proposed. It considers the nodes’ energy when clustering, and takes the nodes’ energy as a factor of the cluster head election: Increasing the probability to be cluster head of the higher-level energy nodes, and decreasing the probability to be cluster head of the lower-level energy nodes, so the nodes can adjust their probability to be cluster head as to their energy. Simulation results show that the modified algorithm can balance the energy distribution of the network and achieve better performance than LEACH in terms of the network lifetime.