Advanced Materials Research Vols. 631-632

Abstract: Cloud is one of the most common noises of remote sensing monitoring in Yellow River. It is one of the important tasks to remove or weaken the effect of thin cloud. Based on the imaging model and characteristics of thin cloud, some technologic methods to remove cloudy are introduced, such as the method of filtering in space domain, the method of filtering in frequency domain and the method of band ratio. This paper analyzed the characteristics, application method and work flow of those methods, and evaluated the application effect of remote sensing monitoring using these methods in Yellow River. Thin cloud removal method improves the using-efficiency of remote sensing data, and ensures the reliability of remote sensing results.

Abstract: Swing cams are important components of main-compensating constant spring hangers, therefore the design of cam curve is the key of constant spring hangers. The working principle of the constant hangers is studied .Based on the mechanical analysis of the constant spring hanger, the mathematical model of cam curve is established by means of coordinate transformation. Meanwhile, the cam curve model is programmed in the MATLAB programming environment, and then IBL document that consistent with the PRO/E is generated, after that the model is imported into PRO/E to achieve three-dimensional modeling of the cam. The method in this paper effectively and accurately solve the swing cam problems.

Abstract: Since the equipment early fault signal is very weak and unstable, it is very difficult to judge the fault type and fault degree through the traditional method of fault diagnosis .For this reason, this paper presents an effective method. Firstly, the fault signal is decomposed into a number of intrinsic mode functions (IMF) by Empirical Mode Decomposition (EMD) method, then the IMF’s energy entropy is calculated, the AR model is established, and the auto-regressive parameters are extracted. At the same time, the residual variance of the model is taken as the fault feature vector, which can be used as input parameters of SVM classifier to distinguish working state and fault types of the equipment. Finally, the validity of the proposed method is verified by taking the rolling bearing fault diagnosis as an example.

Abstract: The result of null testing is usually used as the criterion in the fabricating process of aspheric mirrors. To ensure the accuracy of paraxial radius of curvature and conic constant is important when the null compensator emerges a problem. From the equation of conic aspheric mirror, we derive a set of algorithm from which the paraxial radius of curvature R and conic constant k can be obtained by using Singular Value Decomposition (SVD) method. The simulating result of an aspheric mirror with an aperture of 1229mm is presented and the solving precision reaches △R=0.1% and △k=0.14%. Thus the supplement to null testing of aspheric mirror is achieved effectively.

Abstract: The differences of instantaneous frequency (IF) characteristics between the defect echo and the noise can be used to detect defect and suppress noise for ultrasonic testing signal. Therefore, the IF is one of the important instantaneous parameters of ultrasonic testing signal. To estimate the IF of ultrasonic testing signals more effectively, the peak of time-frequency representation (TFR) from matching pursuits (MP) decomposition is proposed. The performances of IF estimators are compared on the simulated signals at different signal-to-noise ratio (SNR) and the real ultrasonic testing signal. The simulation results present that the proposed method can estimate accurate IF at different SNR.

Abstract: To resolve the problem of Gabor transform window width and order selection for Time-Frequency Distribution Series (TFDS), a parameters selection method for TFDS based on normalized entropy has been proposed, especially the adaptive selection method of order. The normalized entropy is used to measure the concentration and cross-terms of TFDS firstly, and then the relation between the order and width of Gabor transform window function and the concentration and cross-terms of TFDS is used to realize adaptive selection of window width and order parameter, which overcomes the subjective selection problem of the order. The simulation results show that the proposed method can effectively select optimal TFDS parameters for simulated and experimental ultrasonic tesing signal, and can get TFDS with good concentration and high resolution.

Abstract: Since the birth of mankind, thousands of tools have been invented where computer is the greatest one. All inventions are the expansion and extension of various organs of the human, so the invention of the computer is the expansion and extension of the human’s brain. It enables the human to be smarter and more intelligent, so it is the superlative intelligence tool. Nowadays, we have stepped into the computer age, and the impact and influence of the computer technology on the arts and art design has emerged and seems to be overwhelming.

Abstract: Criminals often destructed or hided evidence after making crime by computer, they hindered computer forensics by anti-forensics technology. A new approach of computer forensics based on steganalysis is proposed. The common anti-forensics technologies, such as steganography, data encryption delete evidence and make forensics invalid. In order to enhance the evidence efficiency, steganalysis is applied in the computer forensics to collect and transfer evidence. Simulation results show that steganography based on least significant bit (LSB) by java program embeds the text files into the BMP image files, which sizes are nearly invariable. Steganalysis restores the hidden information and provides convenient method for computer forensics.

Abstract: Current information security risk assessment models usually focus on the security problems of information system and its environment, however they ignore data changes and the accompanying risks in the whole production process. Aiming at the problems above, the paper analyzes the risks of oil and gas production management system during the different stages of data generation, transmission, processing, storage and demonstration, then proposes a set of data risk assessment model and method focusing on data security. The data risk assessment model provides a new way to prevent intrusion, protect data and safeguard information system’s integrity, availability and security.

Abstract: In this paper, fast algorithms for computing composite-number-less-than-20-point DFT is developed, it is based on the matrix operation, makes as much use of the characteristics of twiddle factor, repeatedly transforms the twiddle factor matrix, finally, the core matrixs for computing N-point DFT is obtained. This paper provides the core matrix, calculation process and the amount of computation of less-than-20-point DFT. The algorithm is easy to be understood and applied.