2023

• Record 133 of
  
  Title:Design method of freeform off-axis three-mirror reflective imaging systems
  
  Author(s):Zhao, Huaixue(1,2); Gao, Limin(2); Mao, Xianglong(2); Duan, Yaxuan(2); Xue, Xun(2)
  Source: Applied Optics  Volume: 62  Issue: 29  Article Number: null  DOI: 10.1364/AO.498270  Published: October 10, 2023  
  Abstract:In this paper, a novel, to the best of our knowledge, method is proposed to design a freeform off-axis three-mirror reflective imaging system. A special algorithm is demonstrated to calculate the data points on the unknown freeform surface using the rays from the pupil of the center field. Then the three-dimensional shape of the freeform surface is solved by these characteristic points, which serves as a good starting point for further optimization. The benefit of this design method is demonstrated by designing a freeform off-axis three mirror imaging system with high performance. The final system operates at F/2 with an entrance pupil diameter of 400 mm and a field of view of 2.4◦ × 2.4◦. The modulation transfer function (MTF) value of the system reaches 0.6 at 100 lp/mm or higher at all fields of view. © 2023 Optica Publishing Group.
  Accession Number: 20234515011460
• Record 134 of
  
  Title:Design and stray light analysis of a high NA night vision zoom optical system
  
  Author(s):Xie, Bingqing(1); Chang, Jun(1); Li, Yiting(1); Li, Xuyang(2); Huang, Yi(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12617  Issue: null  Article Number: 126177I  DOI: 10.1117/12.2666850  Published: 2023  
  Abstract:In order to solve the problems of limited clear viewing range and small field angle of the existing night vision equipment, a large numerical aperture zoom night vision objective is designed combined with the zoom optical imaging technology. The night vision zoom objective designed uses a lens with large curvature on the first surface to achieve large field of view detection. The aspheric surface is added to improve the imaging quality of the system and reduce the weight of the system, so that users can have a better user experience when using the objective lens. The operating band of the objective lens is 436nm-656nm, the focus range is 4.5mm-40mm, and the maximum field angle can reach 74 °. Finally, through simulation analysis, the MTF (Modulation Transfer Function, MTF) of the system at Nyquist frequency under different focal lengths is greater than 0.3, and the imaging quality is good. Through stray light analysis, it is found that the designed system is less affected by stray light in the central field of view and the half field of view, while the edge field of view is more affected by stray light. © 2023 SPIE.
  Accession Number: 20232114130669
• Record 135 of
  
  Title:Optimal design of middle-wavelength infrared dual field-of-view optical system
  
  Author(s):Peipei, Yan(1); Huaili, Zhang(2); Kai, Liu(1); Kai, Jiang(1); Jing, Duan(1); Qiusha, Shan(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12921  Issue: null  Article Number: 129211N  DOI: 10.1117/12.2688535  Published: 2023  
  Abstract:A middle infrared dual field-of-view(FOV) optical system with staring focal plane array and reimaging optics is presented for cool 640×512 detector. Based on zoom system principle and optical design software, the Modulation Transfer Function (MTF)curve, spot diagram, and the encircled energy are investigated.The design results show that this system can realize 300mm/600mm dual field-of-view at the spectrum region of 3.7～4.8um and the F number of 4, which can obtain the cold shield efficiency of 100% and the MTF more than 0.2 at the spatial frequency of 33lp/mm.The optical system is analyzed in two modes of long focal length and short focal length, results show that it has the advantages of simple structure, high image quality, low price and easy to adjustment. © 2023 SPIE.
  Accession Number: 20234815132575
• Record 136 of
  
  Title:Medium- and Long-Term Prediction of Polar Motion Using Weighted Least Squares Extrapolation and Vector Autoregressive Modeling
  
  Author(s):Lei, Yu(1); Zhao, Danning(2); Guo, Min(3)
  Source: Artificial Satellites  Volume: 58  Issue: 2  Article Number: null  DOI: 10.2478/arsa-2023-0004  Published: June 1, 2023  
  Abstract:This article presents the application of weighted least squares (WLS) extrapolation and vector autoregressive (VAR) modeling in polar motion prediction. A piecewise weighting function is developed for the least squares (LS) adjustment in consideration of the effect of intervals between observation and prediction epochs on WLS extrapolation. Furthermore, the VAR technique is used to simultaneously model and predict the residuals of xp, yp pole coordinates for WLS misfit. The simultaneous predictions of xp, yp pole coordinates are subsequently computed by the combination of WLS extrapolation of harmonic models for the linear trend, Chandler and annual wobbles, and VAR stochastic prediction of the residuals (WLS+VAR). The 365-day-ahead xp, yp predictions are compared with those generated by LS extrapolation+univariate AR prediction and LS extrapolation+VAR modeling. It is shown that the xp, yp predictions based on WLS+VAR taking into consideration both the interval effect and correlation between xp and yp outperform those generated by two others. The accuracies of the xp predictions are 13.97 mas, 18.47 mas, and 20.52 mas, respectively for the 150-, 270-, and 365-day horizon in terms of the mean absolute error statistics, 36%, 24.8%, and 33.5% higher than LS+AR, respectively. For the yp predictions, the 150-, 270-, and 365-day accuracies are 15.41 mas, 21.17 mas, and 21.82 mas respectively, 27.4%, 11.9%, and 21.8% higher than LS+AR respectively. Moreover, the absolute differences of the WLS+VAR predictions and observations are smaller than the differences from LS+VAR and LS+AR, which is practically important to practical and scientific users, although the improvement in accuracies is no more than 10% relative to LS+VAR. The further comparison with the predictions submitted to the 1st Earth Orientation Parameters Prediction Comparison Campaign (1st EOP PCC) shows that while the accuracy of the predictions within 30 days is comparable with that by the most accurate prediction techniques including neural networks and LS+AR participating in the campaign for xp, yp pole coordinates, the accuracy of the predictions up to 365 days into the future are better than accuracies by the other techniques except best LS+AR used in the EOP PCC. It is therefore concluded that the medium- and long-term prediction accuracy of polar motion can be improved by modeling xp, yp pole coordinates together. © 2023 Yu Lei et al., published by Sciendo.
  Accession Number: 20233114473410
• Record 137 of
  
  Title:A signal separation method based on the subarray beam synthesis
  
  Author(s):Liu, Chengzhou(1); Wang, Jianhui(1); Cui, Weijia(1); Xu, Haiyun(1); Yang, Bingqing(2)
  Source: IET Radar, Sonar and Navigation  Volume: 17  Issue: 2  Article Number: null  DOI: 10.1049/rsn2.12332  Published: February 2023  
  Abstract:Large-scale arrays are widely used due to their advantages of high gain, high resolution, and strong beam control capability. The large number of antennas leads to a sharp increase in computational complexity, and thus, it is necessary to reduce the complexity of signal processing. A signal separation method is proposed based on subarray beam synthesis. This method can improve signal reception and separation performance through zero-forcing calculation and realise system gain and phase error corrections in the front end of an antenna. Compared with back-end processing, it has the advantage of low implementation difficulty. The feasibility and performance of the method are verified by simulations. © 2022 The Authors. IET Radar, Sonar & Navigation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
  Accession Number: 20224012838341
• Record 138 of
  
  Title:Parallel Multistage Wide Neural Network
  
  Author(s):Xi, Jiangbo(1); Ersoy, Okan K.(2); Fang, Jianwu(3); Wu, Tianjun(4); Wei, Xin(5); Zhao, Chaoying(1)
  Source: IEEE Transactions on Neural Networks and Learning Systems  Volume: 34  Issue: 8  Article Number: null  DOI: 10.1109/TNNLS.2021.3120331  Published: August 1, 2023  
  Abstract:Deep learning networks have achieved great success in many areas, such as in large-scale image processing. They usually need large computing resources and time and process easy and hard samples inefficiently in the same way. Another undesirable problem is that the network generally needs to be retrained to learn new incoming data. Efforts have been made to reduce the computing resources and realize incremental learning by adjusting architectures, such as scalable effort classifiers, multi-grained cascade forest (gcForest), conditional deep learning (CDL), tree CNN, decision tree structure with knowledge transfer (ERDK), forest of decision trees with radial basis function (RBF) networks, and knowledge transfer (FDRK). In this article, a parallel multistage wide neural network (PMWNN) is presented. It is composed of multiple stages to classify different parts of data. First, a wide radial basis function (WRBF) network is designed to learn features efficiently in the wide direction. It can work on both vector and image instances and can be trained in one epoch using subsampling and least squares (LS). Second, successive stages of WRBF networks are combined to make up the PMWNN. Each stage focuses on the misclassified samples of the previous stage. It can stop growing at an early stage, and a stage can be added incrementally when new training data are acquired. Finally, the stages of the PMWNN can be tested in parallel, thus speeding up the testing process. To sum up, the proposed PMWNN network has the advantages of: 1) optimized computing resources; 2) incremental learning; and 3) parallel testing with stages. The experimental results with the MNIST data, a number of large hyperspectral remote sensing data, and different types of data in different application areas, including many image and nonimage datasets, show that the WRBF and PMWNN can work well on both image and nonimage data and have very competitive accuracy compared to learning models, such as stacked autoencoders, deep belief nets, support vector machine (SVM), multilayer perceptron (MLP), LeNet-5, RBF network, recently proposed CDL, broad learning, gcForest, ERDK, and FDRK. © 2012 IEEE.
  Accession Number: 20214511130588
• Record 139 of
  
  Title:Improved edge gradient image clarity evaluation algorithm
  
  Author(s):Shen, Xiangquan(1); Xiao, Maosen(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12918  Issue: null  Article Number: 1291805  DOI: 10.1117/12.3009367  Published: 2023  
  Abstract:A sharpness evaluation method based on image edge detection is proposed for the problems of poor real-time, weak anti-interference ability and low sensitivity of the traditional gradient evaluation algorithm in the auto-focusing process of digital image processing. The edge pixel points are extracted from the image using an improved adaptive double-threshold Canny operator based on the idea of variance minimization within the OSTU class, and then the extracted image edge pixel points are evaluated. The evaluation function is based on the characteristics of human visual system, and the adaptability and sensitivity of the evaluation function to multiple direction edges are enhanced by improving the evaluation weights of the SMD function for horizontal and vertical direction edges and combining the advantages of the Roberts function for the evaluation of ±45°direction edges. The experimental results show that the improved edge gradient image sharpness evaluation algorithm proposed in this paper has the advantages of good real-time performance, strong anti-noise capability and high sensitivity. © 2023 SPIE.
  Accession Number: 20234615045807
• Record 140 of
  
  Title:Ground test bench for X-ray pulsar navigation dynamic simulation
  
  Author(s):Sheng, Lizhi(1); Zheng, Wei(2); Su, Tong(1); Zhang, Dapeng(2); Wang, Yidi(2); Yang, Xianghui(1); Xu, Neng(1); Li, Zhize(2)
  Source: Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica  Volume: 44  Issue: 3  Article Number: 526656  DOI: 10.7527/S1000-6893.2022.26656  Published: February 15, 2023  
  Abstract:Theoretical and preliminary experimental studies of X-ray pulsar-based navigation have been carried out at home and abroad，but there are still some defects such as lack of credible experimental verification and imperfect theo⁃ retical model. In this paper，a method for simulation of X-ray pulsar dynamic signals is proposed，which can be used to generate the pulsar dynamic signal based on X-ray pulsar properties and the spacecraft orbit model. An X-ray pulsar simulation source and the whole ground test bench are developed. Static and dynamic ground simulation tests are per⁃ formed. Based on the parameters of the pulsars PSR B0531+21 and PSR B1937+21，the pulse profile similarity ob⁃ tained with the static simulation test is 99. 5% and 99. 1%，respectively. Dynamic simulation tests of the two pulsars at the circular orbit height of 200 km are performed. Deviation of the test results and the theory results of the pulse period is 38 451 ps and 350 ps and the pulse profile similarity is 99. 8% and 99. 9% when the timing coordinate transfer to SSB，for PSR B0531+21 and PSR B1937+21，respectively. The test bench system can realize orbit maneuver simu⁃ lation based on the Hofmann model. The ground experiment system has stable performance and can meet the needs of different types of simulation experiments. © 2023 AAAS Press of Chinese Society of Aeronautics and Astronautics. All rights reserved.
  Accession Number: 20232314186037
• Record 141 of
  
  Title:Electrical treeing failure in silicone gel insulation for encapsulation under high frequency bipolar square-wave voltage
  
  Author(s):Zhang, Chuang(1); Wang, Shihang(1); Chen, Zhen(2); Zhang, Haoran(1); Zha, Xiaopeng(1); Zhou, Fusheng(1); Li, Jianying(1); Li, Shengtao(1)
  Source: Engineering Failure Analysis  Volume: 148  Issue: null  Article Number: 107092  DOI: 10.1016/j.engfailanal.2023.107092  Published: June 2023  
  Abstract:Silicone gel insulation has been widely used in power electronic devices, serving as the encapsulation material. Its dielectric strength under high-frequency voltage determines the reliable operation of the devices. Electrical tree is a typical failure of solid insulating materials, and the electrical tree propagation in silicone gel under bipolar square-wave voltage are investigated in this paper. The results show that electrical trees are pearl-line like, bush-like and bubble-like under varied voltage conditions. After the rapid growth period, the electrical trees stagnate under frequency lower than 20 kHz while develop steadily when the voltage frequency is higher than 25 kHz. The number of tree branch, fractal dimension and accumulated damage increase with the voltage frequency. In comparison, the electrical trees propagate slowly under sinusoidal-wave voltage. The partial discharge and photo-degradation corresponding to the fluorescence are found in main tree channel, which are related to voltage waveform and lead to different electrical tree behavior. The injection and transportation of space charge accelerates the electrical tree propagation, especially at the rising/falling edge of bipolar square-wave field due to polarity reversal. Besides, the amorphous carbon deposited near the needle tip and the bubbles in tree channels filled with hydrogen and carbon monoxide are all related with the electrical tree propagation. © 2023 Elsevier Ltd
  Accession Number: 20231213750733
• Record 142 of
  
  Title:Design and optimization research of Φ 1.6m space mirror and its supporting structure
  
  Author(s):Wei, De Jing(1,2); Wang, Wei(1); Hu, Bin(1); Lin, Shang Min(1); Cheng, Peng Fei(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12557  Issue: null  Article Number: 1255730  DOI: 10.1117/12.2651768  Published: 2023  
  Abstract:This article aiming at the high performance requirements of the space camera mirror assembly, and in order to ensure that the space camera main mirror has good surface shape accuracy and high first-order natural frequency, the mirror and flexible support structure are studied and designed. First, according to the selection principle of the mirror material, SiC is selected as the mirror blank material of the mirror. According to the empirical formula, the three-point support scheme on the back of the mirror and the structural size parameters of the mirror body are determined. And a flexible support structure with multi-axis flexible hinge and dual-axis flexible hinge in series is designed for the mirror. Finally, the parameter optimization method is used to optimize the position radius of the mirror back support hole and the key dimensions of the flexible structure。The static analysis and modal analysis of the mirror assembly were carried out using the finite element method。The results show that the surface shape accuracy of the mirror is 0.015λ nm, the first-order natural frequency of the mirror is 145.57Hz, the weight is 135.35Kg, and the lightweight rate is 87.57%. © 2023 SPIE.
  Accession Number: 20230813600571
• Record 143 of
  
  Title:Construction, Spectral Modeling, Parameter Inversion-Based Calibration, and Application of an Echelle Spectrometer
  
  Author(s):Wang, Yuming(1,2); Qu, Youshan(1); Zhao, Hui(1); Fan, Xuewu(1)
  Source: Sensors  Volume: 23  Issue: 14  Article Number: 6630  DOI: 10.3390/s23146630  Published: July 2023  
  Abstract:We have developed a compact, asymmetric three-channel echelle spectrometer with remarkable high-spectral resolution capabilities. In order to achieve the desired spectral resolution, we initially establish a theoretical spectral model based on the two-dimensional coordinates of spot positions corresponding to each wavelength. Next, we present an innovative and refined method for precisely calibrating echelle spectrometers through parameter inversion. Our analysis delves into the complexities of the nonlinear two-dimensional echelle spectrogram. We employ a variety of optimization techniques, such as grid exploration, simulated annealing, genetic algorithms, and genetic simulated annealing (GSA) algorithms, to accurately invert spectrogram parameters. Our proposed GSA algorithm synergistically integrates the strengths of global and local searches, thereby enhancing calibration accuracy. Compared to the conventional grid exploration method, GSA reduces the error function by 22.8%, convergence time by 2.16 times, and calibration accuracy by 7.05 times. Experimental validation involves calibrating a low-pressure mercury lamp, resulting in an average spectral accuracy error of 0.0257 nm after performing crucial parameter inversion. Furthermore, the echelle spectrometer undergoes a laser-induced breakdown spectroscopy experiment, demonstrating exceptional spectral resolution and sub-10 ns time-resolved capability. Overall, our research offers a comprehensive and efficient solution for constructing, modeling, calibrating, and applying echelle spectrometers, significantly enhancing calibration accuracy and efficiency. This work contributes to the advancement of spectrometry and opens up new possibilities for high-resolution spectral analysis across various research and industry domains. © 2023 by the authors.
  Accession Number: 20233114470375
• Record 144 of
  
  Title:Construction of Vehicle Driving Cycle Based on Markov Model
  
  Author(s):Liu, Panxiong(1); Yang, Kai(2,3); Li, Xijie(3)
  Source: Proceedings - 2023 3rd Asia-Pacific Conference on Communications Technology and Computer Science, ACCTCS 2023  Volume: null  Issue: null  Article Number: null  DOI: 10.1109/ACCTCS58815.2023.00049  Published: 2023  
  Abstract:With the continuous development of China's economy, the sales volume of automobiles across the country continues to grow. The vehicle driving cycle describes the vehicle speed time curve, which is used to determine vehicle pollutant emissions, fuel consumption, new model development and evaluation. It is a key basic technology in the automotive industry. Therefore, it is of great significance to carry out research on the driving cycle of vehicles on urban roads in China. Markov model is used to model the vehicle driving cycle in a given city. The average speed, average driving speed, average acceleration, average deceleration, idling time ratio, acceleration time ratio, deceleration time ratio, standard deviation of speed, standard deviation of acceleration and other index values are extracted for each kinematics segment, and these index values are input into the Markov chain to obtain the corresponding vehicle driving condition data. At the same time, the comprehensive evaluation system is constructed based on the calculated index values. We use the entropy weight method combined with the gray evaluation model to evaluate the vehicle driving cycle model. The evaluation results show that the Markov model of vehicle driving cycle proposed by us has a good effect. © 2023 IEEE.
  Accession Number: 20232714347104