Advanced Materials Research Vols. 912-914

Abstract: The leakage protection system usually trends to make a misjudgment and tripping in normal operation after applying the converter in the coal mine power system. This seriously affects the safety in coal production. Based on the research of the structure and working principle of the converter, it has obtained the definite reason for the converter interfere the leakage protection system. It is the higher harmonics and pulses that generate the zero sequence current through the ground capacitance. Combined with the actual situation in coal mine, it has proposed two corresponding solutions: one is adding the isolation transformer in the output lines of the converter; another is modifying criterion of the leakage protection system. Both methods have their own characteristics, and have verified the feasibility of the methods through the MATLAB simulation.

Abstract: An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

Abstract: The Quickly changed Doppler frequency offset is calculated and researched under low SNR during mobile satellite communications receiver carrier capture process. Firstly, current carrier frequency offset calculation technology is introduced, and the influence of the Doppler shift caused by the carrier capture is analyzed; Secondly, carrier frequency offset acquisition affected by changing rate of Doppler frequency offset is analyzed. Its mainly considered that first order changing rate and second order changing rate affect carrier acquisition. The changing rate would seriously reduces non-coherent accumulation number during carrier frequency offset estimation at low SNR; Finally, carrier frequency offset caused by the rate of change of the first order and second-order Doppler shift is analyzed and researched. It is demonstrated that platform effort caused by Doppler frequency offset can be improved, and the efficiency of the carrier capture increased through sampling points N reasonable by MATLAB simulation.

Abstract: BIM technology is used throughout the whole course of engineering project by establishing a set of digital BIM parameter model. This paper introduces various applications of BIM technology in engineering project and application in specific conditions.

Abstract: Water gate is one of important equipments for arbitrating water supply and maintaining safety of dam. Water gate is made of high tensile strength of steel plate, this kind of steel plate used as constructional material of water gate is weighed for the economical consideration. Steel plate must be cut, welded and rivet to manufacture water gate. Thus, there are some crevices, induced by the defects of material, bad construction, seismic excitation and errors of size, on water gate. This phenomena causes stress concentration, induced high crack increase rate, affect the safety and usage of water gate. In this research, digital image correlation method is developed to measure the mechanics behavior of single steel plate and bi-steel plate with crevices under tension force according to the characteristics of water gate filed test. The test and analysis results of laboratory test reveal that this digital image correlation method can easily indentify the corrosion point on the steel plate. Otherwise, the crack variation of crack tip of steel plate-single steel plate and bi-material steel plate under loadings can be easily identified by the laboratory test.

Abstract: The 3Bs Teaching Method has turned out to be successful in the English teaching in Junior Middle Schools in China. To testify its efficacy on the foreign language acquisition for the university English majors in China, an empirical study was made. The experiment reveals that the 3Bs Teaching Method is more effective than the traditional teaching methods. The 3Bs Teaching Method is indeed a desirable approach to the quality education for the university English majors. Key words: constructivism, 3BsTeaching Method, quality-education, efficiency

Abstract: Proposed on the basis of nondestructive testing technology, such as ultrasonic testing and X-ray detecting, image processing of hull welding based on MATLAB is a simple detecting method to detect the quality of welding. By image processing, physical dimensions, such as circumferences and shapes, as well as the intensity and texture features of welds can be concluded. Then, through numerical analysis, quality problems, including porosities, slags, undercuts, overlaps, welding defects and others, if exist, can be determined. This method decreases the cost and reduces the harm to people’s health. Experimental results showed that the detecting system can calculate and determine the major features of the welds effectively and accurately, and possesses good practical value.

Abstract: In combination with the practical application of heat pump units, designed a heat pump PLC remote monitoring system based on SMS communication with GSM. The system can be monitored through the heat pump running, reduce equipment unsupervised time, to provide users with effective operational management and maintenance; While also providing an effective means of operating data and the real-time observation of optimizing the fault diagnosis of the pump and so on.

Abstract: The principles and apparatus of measuring low frequency internal friction are described in this paper. The low frequency internal friction apparatus have been evidently improved in automation and functions since the Ke^,s pendulum was invented in 1947. The degree of automation of the internal friction apparatus is elevated and the functions of the apparatus are increased/ strengthened. The resolution of internal friction is increased. The accuracy of strain and frequency is also enhanced. The scope of measuring parameters such as temperature, strain, frequency and so on is enlarged.

Abstract: Individual soldier plays a more and more important role in the complex environment of battlefield electromagnetism, and its combat ability should be improved rapidly. A situation awareness system based on individual soldier radio surveillance equipment is presented. The probable equipment adapts mini size and low power hardware and intelligent signal processing technology. In this system, every soldier acts as a reconnaissance sensor, and also he can be a node among the battlefield situation awareness network. The system can improve the ability of battlefield situation awareness and the combat ability in the future information battlefield.