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Aiming at Brushless DC Motor (BLDCM) with a Hall rotor position sensor, this paper presented the design method and implementation of BLDCM control system based on the low cost sine-wave driving method. The period and amplitude of the modulating sine wave were obtained according to the position and velocity information included in the three-phase Hall signals. Then on this basis, the three closed-loop control strategy of position loop, current loop and speed loop was adopted. Furthermore, the hardware and software design were presented in detail. The experiments results show that the proposed control system is available, reasonable and has the better performance and lower cost.

In this study, our objectives was to analyze the molecular characteristics of mutation at embB codon306 in Mycobacterium tuberculosis in Qingdao by pyrosequencing technology, and to assess the value of embB codon306 used as a molecular marker to diagnose multidrug resistant (MDR) TB strains. Pyrosequencing was used to detect mutations at embB codon306 among M. tuberculosis isolates from tuberculosis (TB) patients in Qingdao. The correlation between embB306 mutation and MDR phenotype was evaluated by comparing with conventional drug susceptibility testing results. 60.9% of MDR strains and 15.2% of non-MDR strains carried embB306 mutation, respectively. The percentage of MDR-TB harboring embB306 mutation was significantly higher than that of non- MDR-TB (χ2=15.09, P < 0.01). EmbB306 mutation serving as a marker to diagnose MDR-TB comparing with the traditional susceptibility test, the specificity, sensitivity and accuracy were 85%, 61%, and 77%, respectively. EmbB306 mutation is the main mechanism of TB resistance to multidrug in Qingdao, showing an association with the MDR. Pyrosequencing should be a good diagnostic tool for MDR-TB in Qingdao.

The finite element dynamic model for integrated structures containing distributed piezoelectric sensors and actuators (S/As) is formulated with a new piezoelectric plate bending element in this paper. The problem of active vibration control and suppression of integrated structures is investigated under constant gain negative velocity feedback control law. A general method for active vibration control and suppression of integrated structures is presented. Finally, numerical example is given to illustrate the validity of the method proposed in this paper.

A new time-frequency analysis method of Hilbert-Huang Transform applied in Pipeline leak detection is proposed. Choosing the negative pressure wave signal from dynamic pressure transmitter as research object, the dynamic pressure signal is decomposed by the empirical mode decomposition, and we obtain the proper mode functions that satisfy the condition. The propagation time difference is detected accurately. Then, negative pressure wave signals are processed by Hilbert-Huang transformation method, so as to realize the accurate location of pipeline leak point. The results of experiment show that the new approach can improve the accuracy of detection and location of pipeline leak point.

To suppress interference is a critical technique of online partial discharge monitoring for power equipment insulation. They can be divided into two types: periodical and impulse interference according to their signal characteristic. Different anti-interference techniques can then be chosen to suppress them separately. This paper describes various anti-interference techniques which have been developed recently and their actual effect on online partial discharge monitoring. The above techniques include a combined filter, a digital filter, a differential system and a pulse discrimination system. This paper presents some other anti-interference ideas which are satisfied for online partial discharge monitoring. >

Inductance calculation is essential for internal fault analysis and protective relay of a power transformer. A new model, including several important factors neglected in the previous ones is proposed to calculate the inductance of power transformers. One of the key factors involves the difference between leakage magnetic field distribution under normal operating condition and the one under fault conditions. We have shown that such a difference affects significantly the short circuit reactance or leakage inductance and other parameters of a power transformer. In the proposed model, the inductance of a faulty transformer is firstly calculated by an axially symmetric magnetic field and then modified according to the constraint of the ampere-turn balance. The comparisons between measured impedance and calculated impedance of a faulty transformer model show that our method, while flexible and convenient to use, provides sufficiently precise results in the internal fault analysis of the power transformer.

This paper discusses experiments on the propagation of a partial discharge (PD) pulse between a transformer and other apparatus inside a 500 kV substation. The results could be used to construct a practical PD calibration model and be helpful to design an on-line PD monitoring system for transformers. Some of the frequency characteristics of the external coupling network (the connection lines and neighboring equipment-often referred to as coupling impedance) of the transformer are presented. It is found that with the variation of the monitoring point, the influence of external coupling network on PD monitoring of the transformer varies greatly. When the simulated PD signal is injected through bushing tapping and the monitoring point is at tank grounding, it is sufficient to consider only lines and equipment near the transformer. The external coupling network of the transformer could be represented by a lumped capacitance approximately if the monitoring frequency is below 400 Hz. When the simulated PD signal is injected through the 500 kV terminal of the transformer, the distant lines and equipment of the transformer could not be ignored.