Applied Mechanics and Materials Vols. 568-570

Abstract: All INT2 sessions from 2002 to 2009 are calculated in this paper, the UT1 corrections calculated by the observations and the periodical change rules of its formal deviation are analyzed with Jurkevich and Fourier methods, and several cases about the corresponding radio source sky-coverage of INT2 sessions are pointed out. According to the results, the atmospheric excitation in summer probably influence the UT1 estimation about 1.5μs, and effective radio source sky-coverage can make up for the defects of few observation scan.

Abstract: The common method to determine Quasi-Geoids is GPS leveling however the Quasi-Geoid of this method determined is a kind of trend surface which not take the physical property of geoid into consideration, and the fitting method is surface fitting which only consider the surveying error, lead to inaccurate fitting result. In allusion to these problems, Remove-restore method is used to remove the long wave information of earth gravity field model to get more smooth residual gravity height anomaly, then compared the influence of different covariance function to the fitting result of least square collocation which take surveying error and model error into account. The results show that Gaussian and resemble Gaussian function can achieve higher fitting precision to the large area with height anomaly value changes significance; the Remove-restore method can effectively improve the fitting precision to least square collocation method which depend on the covariance value of each points.

Abstract: Shear Bond Strength testing is one of the most common used tests for Orthodontics Adhesives. However, the standardizations of such procedures is quite difficult due to a large number of factors. While scientists are designing their studies in order to reduce errors, sometime they may find themselves in front of technical difficulties. A custom device was developed in order to allow a testing procedure that is closer to in vitro conditions. The device, mounted on a material testing machine permits sample inclination to a degree that reduces tensile component to the shear stress, therefore more accurate readings of the values are available and standardization of shear bond testing procedures is more probable.

Abstract: In this paper, knock detection and analysis methods of the gasoline engine are applied to a modified kerosene engine. Two kinds of signals, the cylinder pressure signal and the vibration signal, are acquired by a pressure sensor mounted in a spark plug and an accelerometer mounted on the cylinder block separately. Due to the influence of noise, such as cam shocks, piston up-and-down motion, crank rotation and so on, the vibration signal should be processed to extract knock feature. Firstly, FFT, a frequency analysis approach, is used to determine the characteristic frequency range of knock. Then, combining the sampling frequency, the vibration signal is divided into different frequency sub-bands, and the characteristic sub-band of DWT, a time-frequency analysis method, is determined. After that, DWT is applied to extract knock feature from the vibration signal. At last, the knock energy evaluation index is used to judge knock intensity. The reference knock energy is chosen by the researchers, and it is not absolutely suitable for the engine operating condition, so intuitive cylinder pressure signal is applied to supplement for knock judgment.

Abstract: Measurement systems play important roles in producing consistent, high quality products in manufacturing industries. An important requirement for a measurement system is the consistency or stability of its measurement results. The measurement bias needs to be checked periodically in production to decide whether the measurement system needs to be recalibrated timely to maintain the consistency. A very popular conventional method of statistical bias test recommended by ISO/TS16949 for manufacturing industries has been reviewed. Its flaws and problems are pointed out and illustrated with special examples. A new method of engineering bias test and its equivalent accuracy test have been proposed to correct the problems of the conventional statistical bias test.

Abstract: There are several oxygen concentration measurement methods applied in aircraft fuel tank inerting systems. In this work, an aircraft fuel tank inerting experiment system was built and oxygen concentration of the fuel tank ullage (fuel tank space above the surface of the fuel which is filled with fuel vapor and air) and the dissolved oxygen in the fuel was detected with the methods of light absorption and optical fluorescence. The experiment was conducted through different operating conditions and results has illustrated that the light absorption method as well as the optical fluorescence method has the same accuracy sensing calibration gases, but the suitable condition of the two methods are different. Results have shown that the method of light absorption is more suitable to test oxygen concentration of gas mixture, and the method of optical fluorescence is more suitable to detect the concentration of dissolved oxygen in liquid substance.

Abstract: In order to meet the current needs of complex technical equipment maintenance and support, the paper member with the structural characteristics of Multi-Agent System, which was introduced to the fault diagnosis method based on information fusion, the main research was distributed intelligent monitoring and diagnosis system framework based on information fusion, and analysis of information fusion method for the diagnosis of strategies for the a typical system feature, including the contents of the implementation of the method and research status, and points out its future research directions.

Abstract: A simple model was used to simulate the current pulse induced by charged particles with Si detector. With simulated current shapes of three element groups, H/D/T (6MeV), He-3/He-4 (15MeV) and Li-6/Li-7 (35MeV), three methods of pulse shape analysis (PSA), i.e. the m2-m3 method, the integration method and the second moment method, were compared and analyzed. Their discrimination performance and noise resisting property are investigated. The results show that the charge integration method and the m2-m3 method both have good discrimination performance and noise resisting property. While neither the discrimination performance nor the noise resisting property of the second moment method is satisfactory.

Abstract: In this paper, we study the scale-transformation weak signal detection method based on chaotic Duffing oscillator. Based on this, the frequency characteristics of the weak single-frequency signal with arbitrary frequency and initial phase can be extracted. Furthermore, we propose a signal frequency interception preprocessing method for analyzing weak multi-frequency signal. After combing the preprocessing method with the weak signal detection method based on chaotic Duffing oscillator, we further propose a novel detection method for weak multi-frequency signal. Based on this novel method, we can extract the frequency characteristics and initial phase characteristics of the weak multi-frequency signal. In this research, we also study the automatic detection of unknown multi-frequency signal. According to the numerical simulation, the novel method we propose in this paper is helpful to extract the frequency parameters and initial phase information of each signal component of the weak multi-frequency signal.

Abstract: With the rapid development of the high-speed digital signal processing in radar, spaceflight electronics and communication areas, faster acquisition rate and larger storage capacity in data acquisition and storage system are required. A interleaved sampling architecture is present to improve the acquisition rate, in which the NAND flash is used as the storage medium and pipeline structure is adopted to improve storage capacity and storage rate.