Advances in Science and Technology Vol. 105

Abstract: An iterative polynomial fitting method is proposed for the estimate of the baseline of the X-ray fluorescence spectrum signal. The new method generates automatic thresholds by comparing the X-ray fluorescence spectrum signal with the calculated signal from polynomial fitting in the iterative processes. The signal peaks are cut out consecutively in the iterative processes so the polynomial fitting will finally give a good estimation of the baseline. Simulated data and real data from the soil analysis spectrum are used to demonstrate the feasibility of the proposed method.

Abstract: Poisonous elements such as Cd, Hg, Pb, As, Zn, Cr, Ni, Cu etc. are commonly observed in polluted soil and hard to be removed by soil microbes. It is of significant importance to identify these poisonous elements in-situ and accurately both in qualitative and quantitative sense. In order to determine the Limit of Detection (LOD) for trace elements (e.g. Cadmium) in polluted soil samples based on Energy Dispersion X-ray fluorescence (ED-XRF) spectroscopy, approximately 60 national standard soil samples were collected and measured by an XRF equipment. The authors firstly utilize the Method Detection Limit (MDL) algorithm to calculate the LOD of trace elements, and then develop a new model called Back Propagation Adaboost (BP & Adaboost) classification to determine the LOD based on a presumed tolerance error (e.g. 5%). Furthermore, the Multivariate- Partial Linear Squares Regression (M-PLSR) method is applied to regress the data and validate the LOD values. In this paper, the authors make a detailed comparison between the BP algorithm and the BP & Adaboost classification algorithm under different presumed detection limits, and it is found that the detection results achieved the best qualitative prediction of Cd element (i.e. whether it exists in soil) based on the BP & Adaboost algorithm. The experimental results indicate that the BP & Adaboost algorithm is the most effective method to determine and decrease the LOD of trace element (such as Cd) in soil. The advantages are: It combines the classification effects of several weak classifiers, and determines that the LOD of element Cd is 0.5mg/kg with prediction error rate of 5%. Compared with the traditional methods like MDL, it is proved that the BP & Adaboost algorithm is appropriate to be used in the terms of prediction accuracy. It is recommended that the BP & Adaboost classification method shall be used for material analysis on XRF spectroscopy.

Abstract: X-ray Fluorescence (XRF) analysis technology is used widely to detect and measure elemental compositions of target samples. The MCNP code developed by LANL can be utilized to simulate and generate the XRF spectrum of any sample with various elemental compositions. However, one shortcoming of MCNP code is that it takes quite a lot of time (in hours or longer) to generate one XRF spectrum with reasonable statistical precision; the other shortcoming is that MCNP code cannot produce L shell spectrum accurately. In this paper, a new computation model based on the Sherman equation (i.e., Fundamental Parameters, FP) is proposed to overcome the drawbacks of the MCNP code. The most important feature of this model is to achieve a full and accurate generation of spectral information of each element in a target material very rapidly (in seconds or less), including both K and L shell spectral peaks. Furtherly, it is demonstrated that the simulated data by this new mode match the experimental data very well. It proves that the proposed model can be a better alternative of MCNP code in the application of generation the XRF spectra of many materials, in terms of speed and accuracy. The proposed model can perform the simulation of XRF spectra in situ both fast and accurately, which is essential for real-time calculation of chemical composition by use of X-ray spectrometer, especially for those trace elements in target materials.

Abstract: Surface mechanical attrition treatment is a pre-stressing process that enhances the lifespan of mechanical parts. The experimental evaluation of SMAT parameters is not only very complex but also costly. In this study, the single impact behavior of commercially pure titanium and Ti6Al4V alloys is analyzed using the finite element method. For simulating the single-shot impact process, a rigid sphere on a rectangular component is modeled using ANSYS/AUTODYN explicit dynamic solver. The effects of single-shot impact on the induced compressive residual stress and plastic deformation were investigated. Besides, the change in shot velocity after a single shot was revealed by calculating the restitution coefficient, and its relation to plastic deformation was investigated.

Abstract: Gumbel extreme value distribution is used to predict the maximum depth of decarburization of piston rod. The results show that: 1) The prediction maximum depth of decarburization of piston rod should include four steps: data collection, parameter estimation, distribution test and maximum value prediction. 2) The maximum depth of decarburization of piston rod consistent with Gumbel minimum distribution. 3) When the return period is 1000, the predicted maximum depth of decarburization is (0.12 ± 0.01) mm, (k = 2).

Abstract: The effect of non-rigid motion on creep analysis for cylinders have been investigated. inner surface of the cylinder is exposed to a uniform heat flux and for cooling the outer surface of the cylinder an air steam is applied to it. The cylinder is subjected to a body force. That produced by rotating cylinder about its own axis. It is assumed the cylinder is not rigid. Therefore, using equations of equilibrium, stress–strain and kinematic equation, governed equation which includes redial displacement and creep strains, is obtained. The material creep constitutive model is defined by the Bailey-Norton time-dependent creep law. From a solution consisting of analytical solution and iteration method has been used to obtain history of stresses and deformations during creep evolution of rotating cylinders. Therefore, Prandtle-Ruess equation substituted in equilibrium equation in the rate form, the radial displacement rate is obtained for plane strain condition. To investigate the effect of non-rigidity, the non-rigidity parameter (ζ) is defined and its effect on the creep behavior of the structure is investigated. It was revealed that Considering the structure as rigid does neglect the amount of stresses and radial displacement. History of stresses and displacement during 20 years are studied and it is observed that the changes have not accrued in recent years. The effect of velocity is another parameter that is investigated its effect on structural behavior during the time. it was revealed that, velocity has significant effect on structural behavior which cause trend of variation behavior change from linear to polynomial curve.

Abstract: Wavelet Transform (WT) and Wavelet Packet Transform (WPT) approaches have shown great promise in the field of signal analysis in recent decades. The main merit of these methods is their capability in localization of each signal in distinct time or space interval. However, the frequency resolution of such transformation is relatively poor in high frequency regions. The WPT, which is an extended form of the WT, provides a complete level-by-level signal decomposition. Therefore, a frequency analysis creates an arbitrary time. In this study, dynamic transient analysis is performed employing a finite element software (ANSYS) on a beam and acceleration time history of various points is investigated. Then, the captured signals are decomposed to the wavelet packet components using MATLAB and energy rate index is calculated for each component utilizing a wavelet packet rate index (WPERI). The results indicate that not only are the obtained index values sensitive, but they also are precise for the crack identification.

Abstract: The existing high-density distributed distribution network single-phase earth fault interval location method has the disadvantage of long positioning time. Hence, a single-phase earth fault interval positioning method for high-density distributed distribution network is proposed to solve this problem. In order to accurately locate the single-phase earth fault interval of distribution network, zero-order equivalent model of distribution network is built at first. Next the clustering algorithm is used to extract the single-phase earth fault characteristics, while the single-phase earth fault phase current increment is calculated by using the analysis method to obtain the single-phase earth fault phase current increment law. Then a fault-maximum interval T-shaped structure is built to divide the potential fault interval. Finally, the S-transformation is applied to accurately locate the single-phase earth fault interval, and the localization of the single-phase earth fault interval of the high-density distributed distribution network is achieved. The experimental results show that comparing with the existing high-density distributed distribution network single-phase earth fault interval positioning method, the proposed high-density distributed distribution network single-phase earth fault interval positioning method dramatically reduces the positioning time. It is fully explained that the proposed method in this article has a better positioning effect.

Abstract: In this work, adjustable second-order digital frequency-dependent components that are used in robotic systems are considered. The obtained approximations of the PFR dependence on the ripple level allow us to find the digital filter transfer function denominator coefficients' values that result contributes to a more rapid rearrangement of their responses in robotic systems.

Abstract: Wireless anti-jamming data link was widely applied in modern electronic warfare environment recently. Anti-jamming function of wireless data link was realized by constantly changing the signal carrier frequency according to a specific pseudo-random sequence. Frequency switching time and bandwidth were the main factors of frequency hopping anti-jamming performance. With the development DDS technology, frequency switching time and bandwidth had been improved significantly. The hardware of anti-jamming data link node in this paper was composed of frequency synthesizer module and FPGA control module taking advantage of both DDS technology and FPGA. Frequency synthesizer module was under the control of FPGA to output appropriate frequency carrier signal. FPGA control module is designed in Quartus II software development platform environment. The frequency tuning and control of frequency synthesizer module output signal were operated through serial or parallel I/O ports. Two kinds of configuration mode were designed in FPGA control module: serial configuration mode and parallel configuration mode. Digital signal data process in serial configuration logic and parallel configuration logic of FPGA control module were studied especially. The main function of serial configuration logic and parallel configuration logic were realized to process the digital signal data under appropriate time sequence correctly. By the correct time sequence of reading and writing function, frequency synthesizer module worked well with FPGA control module. Simulation and experiment results showed that anti-jamming data link node outputted stable frequency carrier signals by the excellent processing of digital signal data transferred between FPGA control module and frequency synthesizer module.