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  • 2020 Volume 37 Issue 2
    Published: 25 April 2020
      
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  • Research on Fault Feature Extraction Technology of Acoustic Emission Signal of Inter-shaft Bearing Based on Multi-scale Quantum Entropy
    2020, 37(2): 1-9.
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    Aiming at the non-stationary, non-linear and weak characteristics of acoustic emission fault signals of Inter-shaft bearings, a multi-scale quantum entropy based fault feature extraction method for Inter-shaft bearings is proposed, which combines information entropy theory with quantum theory. Firstly, the multi-qubit system of AE signal is established, and the calculation method of quantum information entropy is constructed. Then, the AE signals of Inter-shaft bearings under four different working conditions are collected. Finally, the fault signals are decomposed at multi-scale to extract the quantum entropy values of coarse-grained vectors at different scales. The results show that the fault features extracted can accurately characterize the fault state of Inter-shaft bearings and have good stability.
  • Study on thermal stability of anisotropic modified coupled stressed Mindlin laminates by finite element method
    2020, 37(2): 10-20.
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    According to the anisotropic new modified couple stress theory, the thermal stability model of composite Mindlin laminates is established. A triangular plate element is proposed, which satisfies the C0 continuous and C1 weak continuous conditions. By giving examples of different boundary conditions, the use of limited The thermal stability of the composite Mindlin laminate was analyzed by the meta-method. The results show that the finite element solution and the analytical solution of the critical load are not much different when considering the temperature load, which proves the accuracy of the used unit. The size effect of the Mindlin laminate under temperature load is one. At the timing, the critical load of the instability increases with the increase of the scale parameter. When the scale parameter is constant, the critical load of the instability increases with the increase of the temperature change, indicating that the influence of the temperature change on the critical load of the instability cannot be ignored.
  • Static stress analysis of composite laminated plates based on Reddy-type global-local higher-order theory
    2020, 37(2): 21-27.
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    A Reddy-type global-local high-order theory (RGLHT) is presented in terms of the global-local superposition technique. The global displacement components are taken from the Reddy theory, while the local displacements are constructed by using third-order local functions. The present theory satisfies the free surface conditions and the displacement and stress continuity conditions at interfaces, and only seven displacement variables are contained in proposed model. By using the principle of virtual displacements，the equilibrium equations of laminated composite plates subjected to double sinusoidal loads have been presented, and analytical solutions of composite plates with simply- supported boundaries are also given in this paper. By means of the proposed model, static behaviors of laminated composite plates have been analyzed, and the present results were compared with available results in the literature. Numerical results illustrate that the RGLHT is capable to accurately calculate displacement and stress.
  • Health monitoring of composite materials based on buckypaper sensors under air thermal cycle
    2020, 37(2): 28-34.
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    In this article, a composite test specimen formed by co-curing buckypaper sensor with glass fiber prepreg is subjected to air thermal cycling to demonstrate that the sensor still exhibits good monitoring performance under special circumstances. After an air thermal cycle treatment at 20 C to 150 ° C, the composite test piece was subjected to a static tensile test and 1500 cycles pull-pull fatigue test. Under the static tensile test, after different times of air thermal cycle treatment, the resistance change rate and strain of the damage decrease with the increase of the number of thermal cycles, but the sensor can still monitor the damage of the composite. In addition, under the pull-pull fatigue test, the sensor exhibits excellent durability. And we can see that after 150 cycles of air thermal cycling, the residual resistance of the sensor has only a slight change. It further proves that the buckypaper sensor has excellent service performance under special circumstances.
  • Influence of Sc on corrosion behavior of Al-3Cu-1Li alloy under acidic condition
    2020, 37(2): 35-42.
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    Abstract：Al-3Cu-1Li-xSc (x=0, 0.1, 0.3 and 0.5, wt%) alloys were prepared by flux protection method. The composition and microstructure of these four alloys were measured and obeserved by atomic emission spectrometry, x-ray diffraction (XRD) and optical mictroscopy. Sulfuric acid solution with pH=2 were used to the experimental solution. Influence of Sc on the alloy corrosion behavior was investigated by the electrochemical testing methods. The composition and defect of corrosion product film formed on the alloy surface were tested by x-ray photoelectron spectroscopy (XPS) and Mott-Schottky curve. The results show that the corrosion mechanism and n-type semiconductor characteristic of Al-3Cu-1Li alloy can not be changed by Sc addtion. With the increasing of Sc, corrosion current density increase and anti-corrosion property of the alloy decrease. The ration of Al3+/(Al3++Al) decreasing and oxygen vacancy concentration increasing in the corrosion product film of the alloy led to decrease anti-corrosion property.
  • Infrared Spectral Emissity Calculating Method Based on Support Vector Machine
    2020, 37(2): 43-48.
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    Spectral emissivity has important research significance and application value in the field of national defense and medicine. Establishment of a target infrared radiance model based on Support Vector Machine Neural Network (SVM), this model is used for network training of test samples,infrared radiance models of 3-5mm and 8-12mm bands are established,then calculate the spectral emissivity of the target under different wavelength. Verification by comparison of standard blackbody, the spectral emissivity of the SVM network model is compared with the actual spectral emissivity of blackbody, the maximum relative error is less than 1.1%, and this method is applied to the calculation of spectral emissivity of stealth coated steel plate for aircraft.

  • Object detection algorithm for high resolution remote image based on FT visual salient region detection
    2020, 37(2): 49-55.
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    In this paper, a high resolution remote image target detection method based on FT visual salient region extraction is proposed. Firstly, the high resolution remote image is preprocessed for smoothing and denoising. Secondly, FT salient region extraction algorithm is used to extract significant target regions in high resolution remote images. Then, Otsu threshold segmentation algorithm is used to segment the image, and the salient area of the map area is segmented, and the salient area is connected by mathematical morphological processing. Finally, realize the positioning of salient target in the remote image. The experimental results on multiple high resolution remote images verify the effectiveness of the proposed method.
  • Design of Interactive Demo System with Video Hand Gesture Recognition
    2020, 37(2): 56-62.
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    The interactive demonstration system currently in common use mostly uses specialized hardware, which is insufficient in application scenarios and the selling price is expensive.The most common projection presentation systems often do not have interactive features that influenced the result of presentation.Based on the projection demonstration system, this paper adds video-based hand gesture recognition technology to make the projection system have interactive functions. The interaction system function is composed of three modules: interaction area detection, gesture detection and recognition, tracking and interaction. The preprocessing module is mainly responsible for detecting and locating the interaction area. The gesture detection and recognition module are used to detect and identify specific gestures that occur within the interaction area. The tracking and interaction module implement tracking of the user's gesture through Kalman filtering, and operates the virtual hardware according to the gesture recognition result to realize human-computer interaction. The system has been extensively tested in complex environments, it shows robustness to lighting variations and complex backgrounds with an average accuracy of 85.2%. In addition, with CPU-GPU parallel computing, the average processing speed reaches 15 frames per second, which has better real-time processing capability. The proposed system only introduces a webcam based on the original projection system. The whole system is simple in structure and does not depend on specialized hardware. The software uses open source image and video processing tools with Python language to achieve high portability.

  • Airport Runway Detection Based on Improved LSD Algorithm
    2020, 37(2): 63-69.
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    Abstract：This paper proposes an improved LSD line extraction method for airport runway detection. Based on the traditional method line extraction, the line connection method and parallel line pair detection are improved. For the edge information extraction part, a new Frost filter is used to suppress the speckle and accelerate. The extraction speed of the line segment is improved, and the verification method is improved. The false line segment is removed to obtain more accurate runway information. The experiment is carried out on Zhuzhou Airport. After comparison, the detection time is reduced compared with the traditional LSD algorithm, and the detection efficiency of the algorithm is high. The detected useless line segments are less, and the airport runway extraction effect is more accurate than the traditional LSD algorithm. The runway in the detected image rarely has missed detection and false detection, and has good engineering application value.
  • Research status of thermal dissolution technology and its factors
    2020, 37(2): 70-77.
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    Thermal dissolution technology (TD) provides a way for producing coal-based alternative fuel of aviation jet. This paper introduced the development of thermal dissolution technology of coal, and analyzed the effects of main factors such as coal type, pretreatment of coal sample, TD mode, TD temperature and TD solvent on the process of TD. The molecular bond energy of low-rank coal is low and can be broken under milder condition. Pretreatment of coal changes the hydrogen bond distribution and improves the hydroliquefaction activity of coal. Intermittent TD is easy for operation of TD process and separation between solid and liquid. Continuous TD can avoid the secondary reaction between soluble portions (SPs) and solvent. The yield of SPs increases rapidly and then slowly or even decreases slightly with the increase of TD temperature, which is caused by pyrolysis and polycondensation of coal. TD temperature corresponding to maximum of the yields of SPs is related to softening temperature of coal itself. The selective attack of polar or non-polar solvents on the macromolecular network framework of coal can promote the formation of solutes with small molecular. Further researches are needed, i.e. improvement of TD devices, behavior of TD under the condition of low boiling point and cheap solvents, and directional TD of soluble portion.
  • The Research of Restricted Stock Incentive’s Long-term Stock Price Effect based on PSM
    2020, 37(2): 87-96.
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    This paper bases on propensity score matching method (PSM) and takes the Chinese listed companies in 2007~2017 as research samples, to finish the empirical research of the restricted stock incentives’ long-term stock price effect. The result shows that：for the full sample, the companies that implement have higher buy and hold abnormal return (BHAR) in the five years (0-60months). The companies that implement restricted stock incentives have long-run abnormal stock returns. The distribution shows an inverted "U" pattern with the peak skewed to the right in the intervals of 0-24months and 24-60months. It is found that the effect of incentive-based type on long-term stock price effect is significantly better than that of welfare -based type motivation. The empirical results prove the effectiveness of restricted stock incentive in China from the market perspective, and the incentive-based type motivation plays a positive role in the effect of stock incentive.