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Record 229 of
Title:Optical system design and measurement precision analysis of pointing mirror in solar hard x-ray imager
Author(s):Zhao, Jin(1,2); Yang, Jianfeng(1); He, Yinghong(1); Liu, Shengrun(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11341 Issue: DOI: 10.1117/12.2544531 Published: 2019
Abstract:With the development of technology, research on solar flares has been gradually developed, and the corresponding detection band also involves hard X-ray. Due to the particularity of hard X-ray, the collimator is generally used to observe it. When observing the sun, the load is required to point at the sun accurately. This paper mainly introduces an optical system for precise pointing to the sun of the solar hard X-ray imager. By optimizing the design, the measurement requirements are satisfied. In addition, the design results, system ghost images and measurement accuracy are analyzed and evaluated. ? 2019 SPIE.
Accession Number: 20200408063361
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Record 230 of
Title:Athermalization for the supporting structure of space camera primary and secondary mirrors
Author(s):Lin, Shangmin(1); Wang, Hu(1); Liu, Yang(1); Xue, Yaoke(1); Xiang, Binbin(2); Liu, Jie(1); Xie, Yongjie(1); Liu, Meiying(1,3); Wu, Liquan(3)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11052 Issue: DOI: 10.1117/12.2521897 Published: 2019
Abstract:In order to meet the requirements of high-precision alignment of primary and secondary mirrors of space camera in thermal environment, we develop a new supporting structure which can eliminate heat affect between mirrors automatically. Through the simulation analysis, we have verified this structural design is feasible. According to requirements of the optical system, an integrated machining scheme with three-bar supporting structure for the secondary mirror is proposed. The automatic athermalization of the primary and secondary mirrors supporting structure is confirmed by structural analysis and optimization. The displacement between the primary mirror and secondary mirrors in the thermal environment range of-20° ～ +60°C is analyzed by using the PATRAN software, and the results show the position change is within 0.01mm. The structural size of the secondary mirror supporting cylinder is optimized, and the effect of stray light suppression for the multilayer sleeve visor is analyzed and verified by using the TRACEPRO software. The results show that the proposed structural design can achieve the high stability of the primary and secondary mirrors supporting structure and the good effect of stray light suppression. ? 2019 SPIE.
Accession Number: 20190806535050
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Record 231 of
Title:Structural Design of Carbon Fiber-reinforced Plastics Barrel for Space Remote Sensing Camera
Author(s):Ren, Guo-Rui(1,2); Li, Chuang(1); Wang, Wei(1); Xie, Yong-Jie(1); Xu, Liang(1); Wang, Yong-Jie(1); Fan, Xue-Wu(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 48 Issue: 8 DOI: 10.3788/gzxb20194808.0822001 Published: August 1, 2019
Abstract:In this paper, a connecting barrel for space camera of Carbon Fiber-Reinforced Plastics (CFRP) is designed. Based on tolerance distribution in optics and composite lamination theory, the in-plane stiffness and thermal expansion coefficients due to lamination are analyzed, with structure optimized. Position error between primary and secondary mirrors, as well as modal distribution of the connecting barrel under gravity and temperature change are analyzed by finite element software. Finally, molding and fine tooling of the CFRP barrel is carried out, followed by optical inspection of the mirror system and appraisal mechanical test on the assembled camera. The analysis results show that the optical design and structural stability are satisfied by facts of 1) ? 2019, Science Press. All right reserved.
Accession Number: 20194207534433
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Record 232 of
Title:Surface Modification and Corrosion Behavior of Anode Material for Magnesium Battery
Author(s):Wang, Xiao-Cong(1); Zhu, Li-Xia(1); Zhang, Hong(2)
Source: Jingxi Huagong/Fine Chemicals Volume: 36 Issue: 10 DOI: 10.13550/j.jxhg.20190040 Published: October 15, 2019
Abstract:Anode materials for magnesium batteries were surface modified by dip-coating method using a nano-powder emulsion (EMT) with a small molecule water magnetization. XRD and SEM were used to characterize the microstructure and surface morphology of the samples. The corrosion resistance of the magnesium anodes were investigated by means of immersion test at 25℃ in an electrolyte solution with 3.5% NaCl solution. EIS and Tafel plots were used to study the effect of dip-coating times on the corrosion resistance of magnesium anodes. The results showed that the corrosion current densities of the magnesium anodes coated for 3, 6 and 9 times were 106.8, 90.7 and 89.0 μA/cm2, respectively, which were lower than that of the uncoated sample (283.8 μA/cm2). The SEI film formed on the surface of the material by EMT could effectively inhibit the corrosion behavior of the magnesium anodes without affecting the phase structure of the materials. The corrosion resistance of the sample increased with the increase of dip-coating times. ? 2019, Editorial Office of FINE CHEMICALS. All right reserved.
Accession Number: 20194807741379
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Record 233 of
Title:Sequential Combination of Femtosecond Laser Ablation and Induced Micro/Nano Structures for Marking Units with High-Recognition-Rate
Author(s):Sun, Xiaoyun(1,2); Wang, Wenjun(1,2); Mei, Xuesong(1,2); Pan, Aifei(1,2); Zhang, Ju(1,2); Li, Ming(3); Li, Xun(3)
Source: Advanced Engineering Materials Volume: 21 Issue: 8 DOI: 10.1002/adem.201900350 Published: August 2019
Abstract:This study reported the sequential combination of femtosecond laser ablation and induced micro/nano structures on the titanium alloy and nickel-based alloy for laser marking. The preliminary optimization of processing parameters of laser ablation for the marking units is first carried out. The repetition frequency of 50 kHz, the pulse energy of 150 μJ, the scanning speed from 60 to 80 mm s?1, and the groove spacing from 10 to 20 μm are selected as the best processing parameters. Laser-induced micro/nano structures with anti-reflective properties are formed in the primary laser marking zone, which resulted in further improvement in the recognition rate of the markings. For the two alloys, the recognition rate of combined markings is higher than that of primary markings, because the reflectance of the combined markings is lower than that of the primary markings in the spectrum ranging from 380 to 1000 nm. X-ray diffraction analysis showed that the phase constitution of the processed surface is basically consistent with that of the substrate. Moreover, the cracks and re-cast are not observed under metallographic analysis. Therefore, the sequential combination of femtosecond laser ablation and induced micro/nano structures provides a new marking technology with high recognition rate and quality. ? 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Accession Number: 20192507073185
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Record 234 of
Title:High-speed light focusing through multimode fiber for spot-scanning imaging
Author(s):Chen, Hui(1,3); Geng, Yi(1,3); Xu, Chengfang(1,3); Zhuang, Bin(1,3); Ren, Liyong(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11209 Issue: DOI: 10.1117/12.2548288 Published: 2019
Abstract:The image distortions caused by the inherent mode dispersion and coupling of the multimode fiber (MMF) lead its output light field to be scattered and prevent it from applicating in endoscopy. Although various wavefront shaping methods have been proposed to overcome these image distortions and form the focused spots through the MMF, they are usually time-consuming due to the multiple iterations and tedious calculation. In this paper, based on the phase-only modulation of the spatial light modulator (SLM) and the parallel algorithm, we experimentally demonstrate the highspeed focusing through the MMF without the iteration process. Our parallel algorithm, including the online speckle recording process and the offline compensated phase calculation process, allows it possible to calculate the compensated phase masks for generating several focused spots at different predefined positions at one time, which is quite timesaving. Experiment shows that a series of focused spots at arbitrary target positions at the MMF output facet are efficiently generated by just one-loop accessing the SLM and the speckle capturing-device and one-time phase retrieval. Besides, focusing at different depths along the output light axis of the MMF is demonstrated by modifying the compensated phase masks. We predict the high-speed focusing method through the MMF might have the potential application for fast spotscanning imaging. ? 2019 SPIE.
Accession Number: 20200508093018
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Record 235 of
Title:Controllable dot-matrix marking on titanium alloy with anti-reflective micro-structures using defocused femtosecond laser
Author(s):Sun, Xiaoyun(1,2); Wang, Wenjun(1,2); Mei, Xuesong(1,2); Pan, Aifei(1,2); Liu, Bin(1,2); Li, Ming(3)
Source: Optics and Laser Technology Volume: 115 Issue: DOI: 10.1016/j.optlastec.2019.02.022 Published: July 2019
Abstract:This paper reports on the fabrication of marking units of controllable size ranging from 300 to 500 μm equipped with anti-reflective micro-structures using defocused femtosecond laser on titanium alloy TC4. The results show that the range of diameters of marking units (laser ablation-based craters) goes through three stages with the increase of the pulse number. The craters are too shallow for the first stage and too deep for the third stage to meet the criterion of depth, so the second stage turns out to be the optimal stage of parameter selection, where the diameter and depth of marking units are within a desired range with modification of laser energy and defocusing amount. Besides meeting the marking requirements of the size and morphology, the anti-reflective micro-structures with great color difference are formed on the surface of marking units, which contributes to the high recognition rate. Compared with the conventional marking methods, this method has a great recognition rate without recast layer and micro-cracks. Therefore, the femtosecond laser-based processing would provide a new marking technology with high efficiency and quality. ? 2019 Elsevier Ltd
Accession Number: 20190906548623
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Record 236 of
Title:Camouflage target detection based on short-wave infrared hyperspectral images
Author(s):Yan, Qiangqiang(1); Li, Haiwei(1); Wu, Yinhua(1); Zhang, Xiaorong(1); Wang, Shuang(1); Zhang, Qiang(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11023 Issue: DOI: 10.1117/12.2521361 Published: 2019
Abstract:After years of development, military camouflage has formed a set of theoretical and technical systems represented by color camouflage. At present, a large number of camouflage technology research has been carried out for multispectral reconnaissance of visible and near-infrared. In order to better detect and identify the camouflage target, it is necessary to expand the new reconnaissance band and improve the spectral resolution of the reconnaissance instrument. In this paper, the research on camouflage target recognition technology is carried out through short-wave infrared hyperspectral imaging technology, and the camouflage target is identified by SAM, ACM and CEM algorithms respectively, and the characteristics of three methods in short-wave infrared camouflage target recognition are verified. This research can improve the ability to detect and identify camouflage targets and provide a new means for modern battlefield reconnaissance. ? 2019 SPIE.
Accession Number: 20191506748662
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Record 237 of
Title:Discrete Spectral Hashing for Efficient Similarity Retrieval
Author(s):Hu, Di(1); Nie, Feiping(1); Li, Xuelong(2)
Source: IEEE Transactions on Image Processing Volume: 28 Issue: 3 DOI: 10.1109/TIP.2018.2875312 Published: March 2019
Abstract:To meet the required huge data analysis, organization, and storage demand, the hashing technique has got a lot of attention as it aims to learn an efficient binary representation from the original high-dimensional data. In this paper, we focus on the unsupervised spectral hashing due to its effective manifold embedding. Existing spectral hashing methods mainly suffer from two problems, i.e., the inefficient spectral candidate and intractable binary constraint for spectral analysis. To overcome these two problems, we propose to employ spectral rotation to seek a better spectral solution and adopt the alternating projection algorithm to settle the complex code constraints, which are therefore named as Spectral Hashing with Spectral Rotation and Alternating Discrete Spectral Hashing, respectively. To enjoy the merits of both methods, the spectral rotation technique is finally combined with the original spectral objective, which aims to simultaneously learn better spectral solution and more efficient discrete codes and is called as Discrete Spectral Hashing. Furthermore, the efficient optimization algorithms are also provided, which just take comparable time complexity to existing hashing methods. To evaluate the proposed three methods, extensive comparison experiments and studies are conducted on four large-scale data sets for the image retrieval task, and the noticeable performance beats several state-of-the-art spectral hashing methods on different evaluation metrics. ? 1992-2012 IEEE.
Accession Number: 20184205949164
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Record 238 of
Title:Improved Multi-exposure Image Pyramid Fusion Method
Author(s):Liu, Xin-Long(1,2); Yi, Hong-Wei(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 48 Issue: 8 DOI: 10.3788/gzxb20194808.0810002 Published: August 1, 2019
Abstract:Aiming at the partial overexposure and the loss of shadow detail in the multi-exposure Laplacian pyramid fusion algorithm, to replace the contrast function in the fusion coefficient of the original algorithm by using the phase congruency filter function was proposed. The algorithm can ignore the illumination and contrast when extracting the edge. The effect of the change on the image makes the fusion result more natural and richer in detail. The advantages of the algorithm were verified by multiple sets of sequence images, and compared with the original algorithm. The results show that in terms of subjective evaluation the fusion result of improved algorithm is natural, and it can better preserve the details of the dark part under the strong light background and reduce the halo at the light source. In terms of objective evaluation, the variance and histogram results of the high dynamic range image fused by the algorithm are obviously better than the original algorithm, and more information is retained than the original algorithm. ? 2019, Science Press. All right reserved.
Accession Number: 20194207534499
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Record 239 of
Title:Generalized Uncorrelated Regression with Adaptive Graph for Unsupervised Feature Selection
Author(s):Li, Xuelong(1); Zhang, Han(2,3); Zhang, Rui(4,5); Liu, Yun(6); Nie, Feiping(2,3)
Source: IEEE Transactions on Neural Networks and Learning Systems Volume: 30 Issue: 5 DOI: 10.1109/TNNLS.2018.2868847 Published: May 2019
Abstract:Unsupervised feature selection always occupies a key position as a preprocessing in the tasks of classification or clustering due to the existence of extra essential features within high-dimensional data. Although lots of efforts have been made, the existing methods neglect to consider the redundancy of features, and thus select redundant features. In this brief, by virtue of a generalized uncorrelated constraint, we present an improved sparse regression model [generalized uncorrelated regression model (GURM)] for seeking the uncorrelated yet discriminative features. Benefited from this, the structure of data is kept in the Stiefel manifold, which avoids the potential trivial solution triggered by a conventional ridge regression model. Besides that, the uncorrelated constraint equips the model with the closed-form solution. In addition, we also incorporate a graph regularization term based on the principle of maximum entropy into the GURM model (URAFS), so as to embed the local geometric structure of data into the manifold learning. An efficient algorithm is designed to perform URAFS by virtue of the existing generalized powered iteration method. Extensive experiments on eight benchmark data sets among seven state-of-the-art methods on the task of clustering are conducted to verify the effectiveness and superiority of the proposed method. ? 2012 IEEE.
Accession Number: 20184105917298
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Record 240 of
Title:Multi-source Integrated Navigation Algorithm for Iterated Maximum Posteriori Estimation Based on Sliding-window Factor Graph
Author(s):Xu, Haowei(1); Lian, Baowang(1); Liu, Shangbo(1,2)
Source: Binggong Xuebao/Acta Armamentarii Volume: 40 Issue: 4 DOI: 10.3969/j.issn.1000-1093.2019.04.016 Published: April 1, 2019
Abstract:In the process of data fusion in multi-source integrated navigation using factor graph, the time-varying characteristics of the subsystem's observed noise have a great influence on the estimation accuracy of navigation state. In order to solve the problem, a Gaussian model-based method to estimate the mean vector and covariance matrix of sub-system observation is proposed. In the proposed method, the observed-measurement residuals for each iterative cycle in the process of factor graph optimization are utilized to update the maximum posteriori estimated values of mean vectors and covariance matrices. A more accurate estimated value of navigation state can be obtained by estimating the sub-system noise state. The influence of the new algorithm on the convergence of optimization process was also deduced. Both the simulated and experimental results show that, compared with the existing algorithms as factor graph, maximum likelihood estimation based factor graph and maximum posteriori based factor graph, the proposed factor graph method based on iterative maximum posteriori estimation can effectively improve the accuracy of navigation estimation when the subsystem observing state varies. ? 2019, Editorial Board of Acta Armamentarii. All right reserved.
Accession Number: 20193107246130
