2024

• Record 421 of
  
  Title:Fractional Fourier-Based Frequency-Spatial-Spectral Prototype Network for Agricultural Hyperspectral Image Open-Set Classification
  
  Author(s):Chen, Maoyang(1,2); Feng, Shou(1,2,3); Zhao, Chunhui(1); Qu, Bo(2,4,5); Su, Nan(1); Li, Wei(3); Tao, Ran(3)
  Source: IEEE Transactions on Geoscience and Remote Sensing  Volume: 62  Issue:   DOI: 10.1109/TGRS.2024.3386566  Published: 2024  
  Abstract:At present, hyperspectral image classification (HSIC) technology has been warmly concerned in all walks of life, especially in agriculture. However, existing classification methods operate under the closed-set assumption, which deviates from the real world with open properties. At the same time, there are more serious phenomena of different crops with similar spectrums and the same crops with different spectrum in agricultural hyperspectral data, which is also a great challenge to existing methods. In this work, a fractional Fourier-based frequency-spatial-spectral prototype network (FrFSSPN) is proposed to address the challenges of open-set HSIC in agricultural scenarios. First, fractional Fourier transform (FrFT) is introduced into the network to combine the information in the frequency domain with the spatial-spectral information, so as to expand the difference between different classes on the premise of ensuring the similarity between classes. Then, the prototype learning strategy is introduced into the network to improve the feature recognition capability of the network through prototype loss. Finally, in order to break the stubbornly closed-set property of the closed-set classification (CSC) method, the open-set recognition module is proposed. The difference between the prototype vector and the feature vector is used to judge the unknown class. Experiments on three agricultural hyperspectral datasets show that this method can effectively identify unknown classes without sacrificing the classification accuracy of closed-set, and has satisfactory classification performance. © 1980-2012 IEEE.
  Accession Number: 20241615917288
• Record 422 of
  
  Title:Luminescence properties of ZnSxO1-x:Ce3+ phosphors with tunable short fluorescence lifetime
  
  Author(s):Xing, Xue(1,2,3); Cao, Weiwei(1,3,4); Wu, Zhaoxin(2); Bai, Xiaohong(1); Gao, Jiarui(1); Liang, Xiaozhen(1); Wang, Bo(1); Wang, Chao(1); Shi, Dalian(1); Lv, Linwei(1); Bai, Yonglin(1)
  Source: Materials Letters  Volume: 355  Issue:   DOI: 10.1016/j.matlet.2023.135472  Published: January 15, 2024  
  Abstract:Fluorescence lifetime of phosphors is a critical index in the field of high energy physics and astrophysical detection. A series of ZnSxO1-x:0.05Ce3+ phosphors with tunable short fluorescence lifetime were prepared by performing high temperature solid state reaction method. The phosphors exhibited two mixed phases consisting of the hexagonal phase ZnO and the hexagonal phase ZnS. They are spherical and the average particle size is 2.24 μm. As the component content of the ZnS in ZnSxO1-x:0.05Ce3+ phosphors varies, the emission wavelength can be tuned from 448 nm to 495 nm, the short fluorescence lifetime can be tuned within the range of 6 μs–200 μs. By performing exponential fitting, we obtained the equation for the variation of fluorescence lifetime of ZnSxO1-x:0.05Ce3+ phosphors with ZnS fraction. © 2023 Elsevier B.V.
  Accession Number: 20234414987304
• Record 423 of
  
  Title:Design of multi-channel sequential front light imaging system for transient condition
  
  Author(s):Zhang, Zhanfei(1); Huang, Jie(2); Song, Qiang(2); Feng, Fei(1); Ding, Jianwen(2)
  Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering  Volume: 32  Issue: 4  DOI: 10.37188/OPE.20243204.0478  Published: February 2024  
  Abstract:In order to obtain stable and high-quality sequential images under transient condition and different object distances, a four-channel sequential front light high-speed imaging system was designed. The system used image space parallel light splitting, taking the imaging principle as the starting point to analyze the key design elements of system. Based on the theoretical calculation parameters, the sub-lens groups (objective lens group, field mirror and collimating lens group, converging lens group) was designed and aberrations were independently corrected. Adding field mirror to reduce the size and weight of system and improve light energy utilization. The transmission effect of beam was improved by accurate connection of field of view and pupil. On this basis, the sub lens groups were integrated and optimized, and beam splitters were added to form the final four-channel sequential front light imaging system. The object distance adjustable optical path was designed, and the image quality of system at the object distance of 0.5 m~∞ was guaranteed by adjusting the handwheel of objective lens group in use, while keeping the position of primary image plane unchanged, enhancing the stability of system performance stability and reducing the difficulty of installation and adjustment. The receiving part of system can be replaced according to actual needs, and the system can be expanded to eight-channel system after adding splitters in the beam splitting region. The installed and adjusted sequential front-light imaging system is used for laboratory testing and field tests, and main optical performance is good. the resolution of each channel can reach 72 lp/mm, and imaging consistency is greater than 98%. Field test results show that the optical system can meet the requirements for shooting sequence images under transient condition. © 2024 Chinese Academy of Sciences. All rights reserved.
  Accession Number: 20241115748899
• Record 424 of
  
  Title:Scintillation Index and Bit Error Rate of Double Laguerre-Gaussian Vortex Beams under Ocean Turbulence
  
  Author(s):Diao, Luxin(1); Wang, Mingjun(1,2,3); Huang, Chaojun(3); Wu, Xiaohu(4); Wang, Wei(5)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 2  DOI: 10.3788/gzxb20245302.0201002  Published: February 2024  
  Abstract:The oceans have a large amount of unexplored resources，so the exploration area of human beings is moving towards the unknown ocean as land resources are getting scarce. Underwater wireless optical communication technology with higher rates and better security has become the key to underwater environmental monitoring，wireless sensor networks，offshore exploration and communication between submarines. Vortex beams are a class of beams with helical phase wavefront carrying Orbital Angular Momentum（OAM），which have been widely used in the fields of optical communication，remote sensing and super-resolution imaging due to their specific helical phase structure and dark hollow ring light intensity distribution. The transmission of vortex beams in seawater environments is interfered by ocean turbulence，which results in light intensity scintillation，phase undulation and spot drift，which can degrade the communication quality. However，as human activities extend from free space to the marine environment，the demand for the communication capacity of underwater optical communication systems is increasing，so it is of great significance to study the coded communication of underwater vortex beams and their superposition states，and to further explore methods to suppress the effect of ocean turbulence on the transmission of the beams，for the underwater vortex optical communication systems. In this paper，power spectrum inversion method are used to establish a phase screen model of ocean turbulence，simulate real ocean turbulence，and study the light intensity and phase characteristics of Double Laguerre-Gaussian Vortex Beam （DLGVB） generated by coaxial superposition during transmission in ocean turbulence. The scintillation index of DLVGB beam under different ocean turbulence parameters and topological charge difference is simulated and analyzed. According to the scintillation index，the bit error rate of the underwater optical communication system based on On-off Keying（OOK）modulation under different ocean turbulence parameters is further calculated， and the bit error rate of the optical communication system under different topological charge difference is simulated and analyzed. The results show that the scintillation index of Double Laguerre-Gaussian Vortex Beam（DLGVB）increases with the decrease of turbulent kinetic energy dissipation rate，the increase of transmission distance，salinity temperature fluctuation equilibrium parameter and temperature variance dissipation rate. The main reason is that the intensity of ocean turbulence will gradually increase with the decrease of turbulent kinetic energy dissipation rate and the increase of salinity temperature fluctuation equilibrium parameter and temperature variance dissipation rate. Compared with the traditional Laguerre Gaussian vortex beam，the DLGVB beam with lower topological charge difference（v © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240715561741
• Record 425 of
  
  Title:Feasible spindle speed interval identification method for large aeronautical component robotic milling system
  
  Author(s):Wang, Zhanxi(1); Zhang, Banghai(1); Gao, Wei(2); Qin, Xiansheng(1); Zhang, Yicha(3); Zheng, Chen(1)
  Source: Mechatronics  Volume: 99  Issue:   DOI: 10.1016/j.mechatronics.2024.103143  Published: May 2024  
  Abstract:Robotic machining systems have been widely implemented in the assembly sites of large components of aircraft, such as wings, aircraft engine rooms, and wing boxes. Milling is the first step in aircraft assembly. It is considered one of the most significant processes because the quality of the subsequent drilling, broaching, and riveting steps depend strongly on the milling accuracy. However, the chatter phenomenon may occur during the milling process because of the low rigidity of the components of the robotic milling system (i.e., robots, shape-preserving holders, and rod parts). This may result in milling failure or even fracture of the robotic milling system. This paper presents a feasible spindle speed interval identification method for large aeronautical component milling systems to eliminate the chatter phenomenon. It is based on the chatter stability model and the analysis results of natural frequency and harmonic response. Firstly, the natural frequencies and harmonics of the main components of the robot milling system are analyzed, and the spindle speed that the milling system needs to avoid is obtained. Then, a flutter stability model considering the instantaneous cutting thickness is established, from which the critical cutting depth corresponding to the spindle speed can be obtained. Finally, the spindle speed interval of the robotic milling system could be optimized based on the results obtained from the chatter stability model and the analysis result of the natural frequency and harmonic response of the milling system. The effectiveness of the proposed spindle speed interval identification method is validated through time-domain simulation and experimental results of the large aeronautical component milling system. © 2024 Elsevier Ltd
  Accession Number: 20240715537558
• Record 426 of
  
  Title:Influencing mechanisms of hot isostatic pressing on surface properties of additively manufactured AlSi10Mg alloy
  
  Author(s):Sun, Lijun(1,2); Yang, Yulei(3); Li, Siyuan(2); Chen, Wencong(2); Wang, Yichun(2); Yan, Peng(2); Zhu, Yueqi(2); Wu, Weichao(1); Hu, Bingliang(2)
  Source: Journal of Materials Processing Technology  Volume: 329  Issue:   DOI: 10.1016/j.jmatprotec.2024.118426  Published: August 2024  
  Abstract:Additively manufactured AlSi10Mg alloys have received considerable attention due to the prospectives in light-weight structural applications. Hot isostatic pressing (HIP) is widely utilized to minimize internal pores and enhance mechanical properties in terms of fatigue strength and ductility. Whereas the influence and mechanisms of HIP on surface properties, which is of crucial importance for aerospace optical components, remain to be further clarified. In the present study, systematic surface and subsurface analysis were conducted to unveil the underlying mechanisms of HIP on the surface qualities of an additively manufactured AlSi10Mg alloy. Three-dimensional white-light interfering profilometer, high-resolution X-ray micro computed tomography, X-ray diffraction, scanning electron microscope and transmission electron microscope were exploited to characterize the surface and subsurface alterations induced by HIP. The results demonstrate that, although remarkable reduction in the amount and size of internal pores can be achieved, sharp increase in the surface defects and roughness occurred for the precisely machined surface of the HIP treated alloy. Surface and subsurface analysis reveal that the deterioration in surface properties results from the establishment of micron Si particles and the reduction in nanohardness induced by HIP treatment. © 2024 Elsevier B.V.
  Accession Number: 20241916054071
• Record 427 of
  
  Title:Secure FSO communication based on optical frequency-hopping technology using delay interferometers
  
  Author(s):Wang, Jian(1,2); Jin, Ya(1,2); Xie, Zhuang(3); Chen, Yinfang(1); Liu, Yu(1,2); Zhu, Ninghua(1,2)
  Source: Optics Communications  Volume: 550  Issue:   DOI: 10.1016/j.optcom.2023.129939  Published: January 1, 2024  
  Abstract:—A novel optical frequency-hopping (OFH) scheme using optical delay interferometers (DI) is proposed and demonstrated for secure transmission in free space. By performing carrier suppression modulation on the light wave emitted by the laser and connecting the phase modulator (PM) and DI in series, the conversion of the light wave modulated by the Mach-Zehnder modulator (MZM) from phase modulation to intensity modulation can be realized, and finally output the desired optical frequency-shift-keying (OFSK) carrier signal. Meanwhile, by controlling the positions of the frequencies of the positive and negative first-order sideband light waves on the DI frequency response curve, the OFSK signals output by the two ports of the DI can be complemented in the time domain. For the proposed OFH scheme, we carried out simulation experiments of 5 km free-space link transmission and back-to-back transmission with a communication rate of 10 Gbps, and the simulation results proved the feasibility of the scheme. Additionally, we also analyze the security performance of the proposed scheme and give the security space based on the eavesdropping probability. © 2023 Elsevier B.V.
  Accession Number: 20233914793103
• Record 428 of
  
  Title:Fast and Robust Restoration of Single Photon 3D Data Using Parameterized Kernel
  
  Author(s):Chen, Songmao(1,3); Su, Xiuqin(1,3); Zhang, Zhenyang(1,2,3); Xu, Weihao(1,2); Wang, Jie(1,2,3); Hao, Wei(1,3)
  Source: IEEE Journal of Selected Topics in Quantum Electronics  Volume: 30  Issue: 1  DOI: 10.1109/JSTQE.2023.3269747  Published: January 1, 2024  
  Abstract:Single photon 3D imaging is an emerging topic for optronic sensing under extreme scenarios (e.g. spaceborne altimeter, long range imaging). However, such technique suffers from low photon counts and strong noise, which is due to either strong attenuation from the environment or reduced acquisition time. Although state-of-the-art algorithms have been proposed to achieve high resolution results from corrupted single photon 3D data, the trade-off between the restoration performance and computational complexity remains challenging. This paper presents a fast and robust restoration approach for single photon 3D data, which adaptively smooth the sparse and noisy histogram by applying a parameterized kernel and finally reconstruct the 3D image using matched filter. The implementation can be fast as the core step of the processing is generalized as a 3D convolution that can be solved by Fast Fourier Transform (FFT). The method is validated on various conditions and scenarios from Middbury dataset and real data, where the proposed method showed robust results as the competing state-of-the-art algorithms with fast implementation. © 1995-2012 IEEE.
  Accession Number: 20232114129221
• Record 429 of
  
  Title:Alternating projection combined with fast gradient projection (FGP-AP) method for intensity-only measurement optical diffraction tomography in LED array microscopy
  
  Author(s):Yang, Zewen(1); Zhang, Lu(1,2); Liu, Tong(1); Wang, Huijun(1); Tang, Zhiyuan(3); Zhao, Hong(1,2); Yuan, Li(4); Zhang, Zhenxi(5); Liu, Xiaolong(6)
  Source: Biomedical Optics Express  Volume: 15  Issue: 4  DOI: 10.1364/BOE.518955  Published: April 1, 2024  
  Abstract:Optical diffraction tomography (ODT) is a powerful label-free measurement tool that can quantitatively image the three-dimensional (3D) refractive index (RI) distribution of samples. However, the inherent "missing cone problem,"limited illumination angles, and dependence on intensity-only measurements in a simplified imaging setup can all lead to insufficient information mapping in the Fourier domain, affecting 3D reconstruction results. In this paper, we propose the alternating projection combined with the fast gradient projection (FGP-AP) method to compensate for the above problem, which effectively reconstructs the 3D RI distribution of samples using intensity-only images captured from LED array microscopy. The FGP-AP method employs the alternating projection (AP) algorithm for gradient descent and the fast gradient projection (FGP) algorithm for regularization constraints. This approach is equivalent to incorporating prior knowledge of sample non-negativity and smoothness into the 3D reconstruction process. Simulations demonstrate that the FGP-AP method improves reconstruction quality compared to the original AP method, particularly in the presence of noise. Experimental results, obtained from mouse kidney cells and label-free blood cells, further affirm the superior 3D imaging efficacy of the FGP-AP method. © 2024 Optica Publishing Group.
  Accession Number: 20241815995654
• Record 430 of
  
  Title:Simulation Analysis of Key Parameters for CH4 Gas Point Source Detection Based on F-P Interferometer
  
  Author(s):Zhang, Qiang(1,2); Bai, Caixun(3); Fu, Di(1); Li, Juan(2); Chang, Chenguang(1); Zhao, Hengxiang(1); Wang, Sufeng(1); Feng, Yutao(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 1  DOI: 10.3788/gzxb20245301.0130001  Published: January 2024  
  Abstract:The increase in greenhouse gases carbon dioxide and methane can directly lead to changes in the global climate and cause a significant impact on the economies of countries and human life. Methane，as the second-largest greenhouse gas on Earth，has a global warming potential 30 times higher than CO2 over a 100-year period，and its lifespan is approximately 9.1 years. At present，anthropogenic CH4 emissions primarily originate from numerous point sources. Implementing measures to reduce CH4 emissions can help decrease the rate of global warming. Therefore，it is crucial to conduct research on monitoring technologies for CH4 and investigate key carbon emission sources. Hyperspectral satellite remote sensing for detecting greenhouse gases has become a candidate technology for point source detection. It has advantages such as high viewpoint，wide field of view，the ability to achieve dynamic monitoring，obtain more precise and demand-driven information data. Utilizing remote sensing methods to monitor and provide feedback on point source emissions of greenhouse gases like methane plays a crucial role in effectively addressing climate change. Existing payload technologies in China are geared towards large satellite platforms，enabling wide-area coverage with low spatial resolution monitoring. However，traditional methods such as grating spectrometry，Michelson interferometry，and spatial heterodyne are unable to meet the efficient and high-precision monitoring requirements for small-scale anthropogenic emission sources. They struggle to achieve point source detection. Therefore，it is necessary to conduct research on satellite remote sensing carbon monitoring technologies that offer high accuracy and high spatial resolution. The Fabry-Pérot interferometry technique possesses extremely high spectral resolution，capable of discerning minute wavelength differences in the spectrum. The theoretical basis of this technique is the multi-beam equal-inclination interferometry. By using an interference ring，it is possible to directly obtain the spectral information of target light at different incident angles. By collecting the spectral information corresponding to different wavelengths of the target at different positions from multiple consecutive shots，the target spectral curve is obtained. This technique establishes a relationship between CH4 gas concentration and the depth of spectral curve notches，offering advantages in point source detection with high spectral resolution and high spatial resolution. In CH4 gas detection，the parameters of the Fabry-Pérot interferometer and the optical filter have a significant impact on detection sensitivity. Properly configuring these parameters is crucial for improving detection accuracy. This paper presents a study on a high spatial resolution method for detecting point sources of methane gas based on the principle of multi-beam interferometric spectral imaging. Firstly，the working principle and detection scheme of the methane gas detector are introduced. The system parameters of the Fabry-Pérot interferometer are designed， and a forward model for methane gas detection is established. Subsequently，the correspondence between interference signals and methane concentration，as well as the influence of instrument parameters on detection sensitivity，are analyzed. In the end，iterative optimization is performed to obtain the optimal values of various optical structural parameters. The results indicate that within the methane detection wavelength range of 1 630~1 675 nm，with a free spectral range of 12.5 nm and a spectral resolution of 0.1 nm，the optimal parameters for the Fabry-Pérot interferometer are a cavity length of 0.08 mm and an intra-cavity reflectance of 97.5%. By using a cutoff filter with a range of（1 630±4）nm ~ （1 675±4）nm，the relative change in interference signal corresponding to a 25% concentration variation of the detection source falls within the range of［0.65%，4.30%］，indicating a good detection sensitivity. The research results of this study provide a theoretical basis and technical support for high-precision. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815582116
• Record 431 of
  
  Title:Domain Adaptation of Anchor-Free object detection for urban traffic
  
  Author(s):Yu, Xiaoyong(1,2); Lu, Xiaoqiang(3)
  Source: Neurocomputing  Volume: 582  Issue:   DOI: 10.1016/j.neucom.2024.127477  Published: May 14, 2024  
  Abstract:Modern detectors are mostly trained under single and limited conditions. However, object detection faces various complex and open situations in autonomous driving, especially in urban street scenes with dense objects and complex backgrounds. Due to the shift in data distribution, modern detectors cannot perform well in actual urban environments. Using domain adaptation to improve detection performance is one of the key methods to extend object detection from limited situations to open situations. To this end, this article proposes a Domain Adaptation of Anchor-Free object detection (DAAF) for urban traffic. DAAF is a cross-domain object detection method that performs feature alignment including two aspects. On the one hand, we designed a fully convolutional adversarial training method for global feature alignment at the image level. Meanwhile, images can generally be decomposed into structural information and texture information. In urban street scenes, the structural information of images is generally similar. The main difference between the source domain and the target domain is texture information. Therefore, during global feature alignment, this paper proposes a method called texture information limitation (TIL). On the other hand, in order to solve the problem of variable aspect ratios of objects in urban street scenes, this article uses an anchor-free detector as the baseline detector. Since the anchor-free object detector can obtain neither explicit nor implicit instance-level features, we adopt Pixel-Level Adaptation (PLA) to align local features instead of instance-level alignment for local features. The size of the object has the greatest impact on the final detection effect, and the object scale in urban scenes is relatively rich. Guided by the differentiation of attention mechanisms, a multi-level adversarial network is designed to perform feature alignment of the output space at different feature levels called Scale Information Limitation (SIL). We conducted cross-domain detection experiments by using various urban streetscape autonomous driving object detection datasets, including adverse weather conditions, synthetic data to real data, and cross-camera adaptation. The experimental results indicate that the method proposed in this article is effective. © 2024 Elsevier B.V.
  Accession Number: 20241215767931
• Record 432 of
  
  Title:Flexible fiberbotic laser scalpels: Material and fabrication challenges
  
  Author(s):Zou, Yuqi(1,2); Ren, Zhihe(1,2); Xiang, Yuanzhuo(1,2); Liu, Chao(1,2); Gao, Anzhu(3,4); Huang, Shaoping(4); Yang, Lvyun(1); Hou, Chong(5); Guo, Haitao(6); Yang, Guang-Zhong(4); Tao, Guangming(1,2,4)
  Source: Matter  Volume: 7  Issue: 3  DOI: 10.1016/j.matt.2024.01.007  Published: March 6, 2024  
  Abstract:Rapidly developed fiber lasers have shown great potential in interventional urology, inspiring the use of advanced laser delivery to meet the demand for manipulation in other complex surgical scenarios. While medical robots are enhancing precision in the field of minimally invasive surgery, laser ablation has been demonstrated as a promising candidate compared to traditional mechanical cutting tools in interventions. Nevertheless, based on their ablation mechanisms, the advantages of lasers are still not fully leveraged. In this Perspective, we outline how fiber-shaped robots combined with laser scalpels are primed to emerge as the next generation of medical robots to achieve minimally invasive surgery. We review the mechanisms involved, analyze their applications, and discuss several prospects for future applications. © 2024 Elsevier Inc.
  Accession Number: 20240915657499