Applied Mechanics and Materials Vols. 511-512

Abstract: Liquefied natural gas (LNG) is obtained by reducing the gas temperature to-162 degree, Fault of the inside steel cans, the insulation layer or the concrete outer tank of the LNG storage tank can lead to changes of the temperature field, local temperature decreases, and the outer concrete tank safety is threatened. Infrared thermal imagers are used to monitor the temperature of the LNG storage tank, get the overall temperature distribution image of the outside concrete tank, establish the communication between the thermal imagers and the computer, and analyze the heat image of tank by the compute, find out the failure structure of the LNG storage tank according to the temperature field changes. Multi-point temperature monitoring system for the LNG storage tank can provide powerful guarantee for the safe storage of the liquefied natural gas.

Abstract: CNC machine tools are widely used in precision machining and automation production. The on-line detection technology provides an efficient testing method for quality control in CNC machining process. And the CNC servo dynamic characteristic is an important factor affecting the accuracy of on-line detection. In order to study the effects of servo dynamic characteristic, CNC servo system mathematical model was set up, probe system error model was established based on probe measuring time sequence and on-line detection error model was built. The cylindrical feature measurement example shows that on-line detection accuracy is improved through the secondary trigger measurement method and the probe path planning.

Abstract: This paper describes the content and process of comprehensive testing the TOPCON NET-G3A GNSS receivers, which includes five parts, such as general performance testing and internal noise level testing of receiver, stability testing of Antenna phase center, TEQC testing and repetition rate testing of long baseline of receivers. Meanwhile, data of GNSS receiver testing is calculated and analyzed. The testing results show that TOPCON NET-G3A receiver is a high-precision GNSS receiver and fully meets the requirements for the GNSS precision measurement.

Abstract: Base on the virtual instrument technology, a micro signal measurement system was established and applied to the electronic teaching experiment. It is composed of PC, oscilloscope, signal generator, ac constant current source, low noise preamplifier and tested operational amplifier, etc. it can complete the measurement of uV weak voltage, uA weak current measure, wires and printing plate conductor resistance and inductance, amplifier open-loop amplitude frequency and phase frequency characteristics, and so on many aspects of modern electronic measurement experiment content. The system not only has the characteristics of functional diversity, measurement accuracy, and good graphic interface, simple operation and overcomes the shortcomings in the course of electronic technology experiment teaching, and play an important role on improving the experimental conditions,reducing the cost of experiments, raising the level of classroom teaching and practice of teaching.

Abstract: The core component of profilometer is a stylus displacement measuring system, whose resolution reaches nanoscale. Since the stylus tip is very small, a variation on probing force has a great impact on the results of high-precision displacement measurements. In this paper, a special flat rectangular voice coil motor is designed to realize a constant probing force for the stylus displacement measuring system. Experimental results show the probing force can be adjusted from 5mg to 1000mg and the resolution can reach 5mg.

Abstract: This paper proposes a new method of getting sound velocity by measuring the sound pressure at three positions in a tube. By using LabVIEW software as a platform and building the measurement system, sound velocity at different frequencies in current media is measured. Compared the experimental results with theoretical calculation ones, the correctness of the method discussed in this paper and the reliability of the system are validated.

Abstract: In the paper the measurement program of transformer winding temperature was proposed by using the fluorescence lifetime. We produced a probe to measure the temperature of the oil immersed transformer winding and used high temperature fiber to transfer fluorescence. Three methods were used to calculate the fluorescent life. By comparing advantages and disadvantages of three methods, the Prony algorithm was selected .Because it can fit multi-exponential and improve the accuracy of temperature measurement which is suitable for the fluorescence curve. At the same time, the calibration experiments of the measured temperature were carried out to achieve a real-time measurement of oil temperature.

Abstract: Aiming at the problem of traditional thickness measurement methods, the paper proposes a design and realization scheme of non-contact high-precision online thickness gauge. Double sensors are used to realize the differential measurement which can effectively reduce errors caused by the vibration of the tested object. TMS320F2812 is chosen as the main control chip to realize data collection, equipment control and signal processing. Finally algorithms of signal filtering and curve fitting are designed to improve the precision. Practical application shows that the system has easy operation, high resolution, stability and reliability.

Abstract: Aiming at the present status of the groundwater monitoring in HeiHe river basin, the groundwater auto detecting system was designed based on the internet of things, this system has several features such as high integration, low power consumption, minitype, computerization. The hardware and software of the monitoring device were introduced in the paper and several measures were taken to reduce the power consumption and improve reliability. The system mainly solved several key technologies including monitoring data collection, transmission, management and remote control. Through one-year field experiment, it is found that the system run well. Finally the successful designed system would make a contribution to the groundwater monitoring for our country.

Abstract: The Duffing equation has been widely used to detect weak periodic signals. The transition threshold is the key to detect. Unfortunately, there is no effective method to determine the critical threshold. To solve this problem, a new method based on the QR decomposition to calculate Lyapunov exponent is presented. The accuracy of the algorithm will gradually improve with the sampling time increasing or the sampling period decreasing. The experimental results show that the method can determine the interval which contains the threshold, and detect the mutation acts of chaotic systems.