Applied Mechanics and Materials Vols. 217-219

Abstract: In order to find new fault line selection method of single-phase distribution network, First parallel resistance in the neutral point in order to increase the transient component of the fault line, obtained the line energy after the failure through the integral transform , initially selected probable fault lines , on this basis, decompose all the transient zero sequence currents in every line by separation based on nicer separate frequency characteristic of wavelet packets, to accurately determine the greatest fault line by the characteristic that the value of second singular point generated by zero sequence current is maximum and its polarity is opposite to the other normal lines, simulation results show the effectiveness and correctness of the method. So the method for detection of the fault line based on wavelet packets and the compare of energy is new and effective.

Abstract: The characteristics of the high-density circuits are high assembly density of the components and complex functions. It is difficult to detect the electrical defects by the existing optical techniques. The Electromagnetic Scan (EMScan) technology as a new detection method was introduced into the high-density circuit detection. For the new approach, the EMScan process was designed and its key techniques were analyzed. Meanwhile the corresponding recognition algorithm was given toward one of the key techniques determining the anomalous frequencies. The spectrums of the circuit board were transformed into a series of strings. Then according to the string comparison algorithm, the anomalous frequencies were determined. The experimental results show that it is feasible to apply the EMScan into the high-density circuit detection. The recognition algorithm is effective and can determine the anomalous frequencies accurately by this way.

Abstract: Based on the accurate geometrical theory for the extensible elastic beams, an exact mathematical model of post-buckling transverse free vibration of Euler beams subjected to a distributed tangential follower force along the central axis are established. By using shooting method, pre-buckling free vibrations of both simply supported and fixed Euler beam are solved and the responses of small amplitude vibration are obtained. The numerical results show that all the frequencies of unbuckled beams decrease continuously with the increment of the load parameters.

Abstract: This paper studies the effect of damper components on the performance of the impact damper with fine particles as damping agent (IDFPDA). The responses of various damper combinations are obtained from the experiments of a cantilevered beam attached by the IDFPDA with different impactor diameter and particle material. Results show that the average attenuation rate is 72.7~75.4% by changing the particle material in IDFPDA and the average attenuation rate is 72.1~75.9% by changing the diameter of impactors, which are much higher than that without particles or impactors. The conclusions can be drawn that the IDFPDA has more excellent performance than traditional impact damper only with impactors or particles. The impactor diameters and the particle materials have little effect on the damping performance, so both metal and non-metal particles are suitable to IDFPDA.

Abstract: Since working condition of reciprocating compressor is awfully bad and it has bigger risk in operation and higher fault rate，it is of importance to study reciprocating compressor fault. Fault tree has been established in this paper by analyzing factors leading reciprocating compressor fault based on the method of fault tree. 21 minimum cut sets leading to reciprocating compressor fault can be gotten through qualitative analyses on this fault tree，the happening probability of the top event can be calculated and the importance of the basic event s can be analyzed through quantitative analysis. The expert inquiry method combined with fuzzy sets theory is adopted to assess the happening probability of the basic events and top events.

Abstract: The wind speed forecasting accuracy of artificial neural network(ANN) and grey model(GM) is poorly satisfied. Thus, we proposed a new variable weight combined (VWC) model, which was based on the ANN and GM, to improve the wind speed forecasting accuracy. VWC used weighting coefficient of different time to fit the two single models. The forecasting accuracy of VWC is higher than either of the two single models, and is also higher than the unchanged weight combination(UWC) model. Our data show a new method for wind speed forecasting and the reduction of auxiliary service costs of wind farms.

Abstract: This paper analyses the actual applications demand of the real-time PCB production quality management information system for the electronic product manufacturing enterprises, has established functional model for the real-time PCB production and quality management information system, and has used of mathematical statistics and mathematical logic principles, methods to analyzed of PCB production quality information, which was collected in real-time, finally, has established a Quality Information System PCB, this system achieves the various production processes and product quality tracking and retroactively for PCB.

Abstract: To implement high-speed and high-accuracy elliptic interpolation required in high-performance motion control, novel coordinate calculation and end point judgment schemes are proposed. Data Sample method is used for coordinate calculation. High accuracy is guaranteed by avoiding approximation calculation of interpolation points. Exact end point judgment is constructed based on the position relationship of the current interpolation point, the next interpolation point and the end point to avoid incomplete interpolation or over interpolation of elliptic trajectories. The proposed schemes feature fewer amounts of calculation and high accuracy and can produce any elliptic trajectories.

Abstract: Straightness error is the main profile error of guide rail. This paper studies a scanning six-probe system for measuring straightness of two guide rails. The system does not use angle sensors and consists of two probe-units, each having three displacement sensors. The two probe-units are moved by a scanning stage to scan the surface of two guide rails, then they are rotated 180 and scan guide rails again after the first scanning. The zero-differences of two probe-units before and after probe-units being rotated, as well as the straightness of the guide rails, can be accurately evaluated from the outputs of the displacement sensors in two scanning process. The effectiveness of this method is confirmed by computer simulation and experimental results in the case of two probe-units having different zero-differences before and after probe-units being rotated.

Abstract: This article takes the noise control of a cooling tower for a residence area as an example. On the base of measuring data, the noise resource is analyzed and the character of the noise resource is discussed. In the aspects of sound elimination, sound absorption and sound insulation, a set of practical controlling measures are elaborated. The result shows that the effect of noise reduction in this scheme is evident, and in the meantime the wind volume and temperature for the equipment are satisfying as well. Perfect effects of noise reduction can be obtained in the working project.