2024

• Record 97 of
  
  Title:Flexible Ge/Cu/ZnSe multilayer photonic structures for triple-band infrared camouflage, visible camouflage, and radiative cooling
  
  Author(s):Huang, Lehong(1,2,3,4); Zhang, Wenbo(1,2,3); Wei, Yuxuan(1,3); Li, Haochuan(1); Li, Xun(1); Ma, Caiwen(1,3,4); Zhang, Chunmin(2)
  Source:Optics Express
  Volume: 32  Issue: 21  DOI: 10.1364/OE.534651  Published: October 7, 2024  
  Abstract:With the rapid advancement of multi-band detection technologies, military and civilian equipment face an increasing risk of being detected, posing significant challenges to traditional single-band camouflage designs. To address this issue, this study presents an innovative multilayer structure using Ge, Cu, and ZnSe materials to achieve triple-band infrared camouflage, visible camouflage, and radiative cooling. The structure exhibits low emissivity in the short-wave infrared (SWIR, 1.2-2.5µm), mid-wave infrared (MWIR, 3-5µm), and long-wave infrared (LWIR, 8-14µm) bands, with values of 0.23, 0.11, and 0.27 respectively, thus realizing effective infrared camouflage. Additionally, it efficiently radiates heat in the non-atmospheric window (Ε¯5−8µm = 0.62). By adjusting the thickness of the top ZnSe layer, the structure can achieve visual camouflage against various backgrounds, significantly enhancing its effectiveness. The total thickness of the multilayer structure is only 1.33µm, and it is deposited on a flexible polyimide substrate via electron beam evaporation, providing remarkable deformation capability to meet camouflage needs in various complex environments. Experimental results show that, under an input power density of 1097 W/m2, the apparent temperature of the structure is reduced by about 10°C compared to the commonly used engineering material titanium alloy (TC4), significantly reducing the detection range and demonstrating excellent infrared camouflage performance. This study also highlights the broad application prospects of this innovative multi-band camouflage material in both military and civilian fields, particularly its ability to flexibly adapt to different environments and conditions. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20244217188319
• Record 98 of
  
  Title:Adaptive sliding mode control by memristor-based neural network and its application
  
  Author(s):Lin, Di(1,2); Wu, Yiming(1,2); Yang, Sen(3); Zhang, Yin(3); Zhao, Mingshu(3)
  Source:Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering
  Volume: 53  Issue: 6  DOI: 10.3788/IRLA20230667  Published: June 2024  
  Abstract:Objective In the optoelectronic pod system, there are various disturbances and unmodeled dynamics. Therefore, it is difficult for conventional control algorithms to adapt to complex situations. The neural network is adopted to realize the adaptive estimation of the unknown dynamics of the model, combined with sliding mode variable structure control, the control accuracy can be effectively improved. However, if the neural network estimation fails to converge to the parameters in the actual model at the initial control stage, chattering phenomenon will arise in the sliding mode control. In order to achieve fast convergence of neural network estimation, suppress the chattering at the initial stage of sliding mode control, and improve control accuracy and stability, the algorithm of adaptive sliding mode control based on memristor-based neural network is proposed herein. Methods An improved memristor-based neural network is adopted to store the weight parameters to approach the unmodeled dynamics, which can reduce network convergence time and improve control accuracy compared to the conventional neural network. In the initial stage of sliding mode variable structure control, a neural network based on memristors is adopted. The adaptive gain is improved to reduce the chattering caused by estimation error of neural network. The improved algorithm in overall significantly reduced the chattering and quickly and accurately estimated unmodeled dynamics, enhancing control accuracy and stability. Under analog simulation conditions, the improved algorithm is compared with conventional sliding mode variable structure method regarding to the sinusoidal position response, and the result shows that the convergence time by the improved algorithm is reduced to half of that of the conventional sliding mode control algorithm (Fig.9). When an actual unmanned aerial vehicle tracking detection is conducted in the outfield, the control accuracy under the improved algorithm is increased by 59.18% compared to the conventional sliding mode control algorithm (Fig.12). Results and Discussions Under analog simulation conditions, compared with conventional sliding mode variable structure method, the convergence accuracy for the sinusoidal position response by adopting the improved algorithm is within 0.0002° while the one by conventional algorithm is within 0.001°, which means the convergence time by the improved algorithm is reduced to half of that of the conventional sliding mode control algorithm (Fig.9). When an unmanned aerial vehicle targets detection is conducted in the outfield, with a maximum speed of maneuvering flight of 15 m/s and a distance of 1 km from the unmanned aerial vehicle to tracking turntable, the stably tracking miss distance (RMS) by the conventional sliding mode control algorithm is 0.009 8°, while the RMS by the improved algorithm is 0.004°, approximately 69.8 μrad, resulting in the increase of accuracy under the improved algorithm by 59.18% compared to the conventional sliding mode control algorithm (Fig.12). Conclusions By adopting the improved algorithm of adaptive sliding mode variable structure control based on the memristor-based neural network, the convergence time of estimation for unknown unmodeled dynamics is reduced, up to half of that of conventional sliding mode control algorithm. In an actual outfield detection experiment, the stably tracking control accuracy by the improved algorithm is increased by 59.18% compared to that by the conventional sliding mode control algorithm. The experimental results show that the use of the improved algorithm of adaptive sliding mode variable structure control based on the memristor-based neural network can not only help the system to realize fast convergence and suppress chattering, but also effectively improve the tracking accuracy and stability of the optoelectronic pod system, which has certain application value in engineering. © 2024 Chinese Society of Astronautics. All rights reserved.
  Accession Number: 20243717021357
• Record 99 of
  
  Title:PDE Standardization Analysis and Solution of Typical Mechanics Problems
  
  Author(s):Wang, Ningjie(1); Wang, Yihao(1); Pei, Yongle(2); Li, Luxian(1)
  Source:CMES - Computer Modeling in Engineering and Sciences
  Volume: 141  Issue: 1  DOI: 10.32604/cmes.2024.053520  Published: 2024  
  Abstract:A numerical approach is an effective means of solving boundary value problems (BVPs). This study focuses on physical problems with general partial differential equations (PDEs). It investigates the solution approach through the standard forms of the PDE module in COMSOL. Two typical mechanics problems are exemplified: The deflection of a thin plate, which can be addressed with the dedicated finite element module, and the stress of a pure bending beam that cannot be tackled. The procedure for the two problems regarding the three standard forms required by the PDE module is detailed. The results were in good agreement with the literature, indicating that the PDE module provides a promising means to solve complex PDEs, especially for those a dedicated finite element module has yet to be developed. Copyright © 2024 The Authors. Published by Tech Science Press.
  Accession Number: 20243516928022
• Record 100 of
  
  Title:Global pixel-value-ordering framework with dynamic sequence partition for reversible data hiding
  
  Author(s):Fan, Guojun(1); Wang, Ping(1); Li, Zijing(1); Zhou, Quan(2); Pan, Zhibin(1,3)
  Source:Knowledge-Based Systems
  Volume: 297  Issue:   DOI: 10.1016/j.knosys.2024.111930  Published: August 3, 2024  
  Abstract:Recently, pixel-value-ordering (PVO) based reversible data hiding (RDH) methods have become hotspots in spatial domain RDH research. In PVO-based methods, the pixel value correlation within a local region is exploited for data embedding. To embed secret data, the cover images are partitioned into non-overlapped rectangle blocks to be sorted locally, and a lower embedding distortion is thus obtained. However, their embedding capacities are often limited by the fixed local blocks from which pixels are sorted. To maintain the advantages and overcome disadvantages of the PVO-based methods, a new global pixel-value-ordering (GPVO) framework is proposed in this paper. By applying our GPVO framework, a PVO-based method can utilize pixels from any position in the cover image rather than from local pixel blocks. Then, through the dynamic sequence partition realized by the GPVO framework for the first time, the embedding capacity of PVO-based methods can be greatly improved while reducing embedding distortion further reduced. Finally, we propose a two-stage pairwise embedding scheme to be applied to the sequences, aiming to achieve an advanced embedding performance. Experimental results illustrate that the proposed GPVO works better than other related state-of-the-art RDH methods. © 2024 Elsevier B.V.
  Accession Number: 20242216182135
• Record 101 of
  
  Title:A Dual-FSM GI LiDAR Imaging Control Method Based on Two-Dimensional Flexible Turntable Composite Axis Tracking
  
  Author(s):Cao, Yu(1,2,3,4); Xie, Meilin(1,2,3); Wang, Haitao(1,2); Hao, Wei(1,2,3); Guo, Min(1,2,3); Jiang, Kai(1,2); Wang, Lei(1,2); Guo, Shan(1,2); Wang, Fan(1,2)
  Source:Remote Sensing
  Volume: 16  Issue: 10  DOI: 10.3390/rs16101679  Published: May 2024  
  Abstract:In this study, a tracking and pointing control system with a dual-FSM (fast steering mirror) two-dimensional flexible turntable composite axis is proposed. It is applied to the target-tracking accuracy control in a GI LiDAR (ghost imaging LiDAR) system. Ghost imaging is a multi-measurement imaging method; the dual-FSM GI LiDAR tracking and pointing imaging control system proposed in this study mainly solves the problems of the high-resolution remote sensing imaging of high-speed moving targets and various nonlinear disturbances when this technology is transformed into practical applications. Addressing the detrimental effects of nonlinear disturbances originating from internal flexible mechanisms and assorted external environmental factors on motion control’s velocity, stability, and tracking accuracy, a nonlinear active disturbance rejection control (NLADRC) method based on artificial neural networks is advanced. Additionally, to overcome the limitations imposed by receiving aperture constraints in GI LiDAR systems, a novel optical path design for the dual-FSM GI LiDAR tracking and imaging system is put forth. The implementation of the described methodologies culminated in the development of a dual-FSM GI LiDAR tracking and imaging system, which, upon thorough experimental validation, demonstrated significant improvements. Notably, it achieved an improvement in the coarse tracking accuracy from 193.29 μrad (3σ) to 87.21 μrad (3σ) and enhanced the tracking accuracy from 10.1 μrad (σ) to 1.5 μrad (σ) under specified operational parameters. Furthermore, the method notably diminished the overshoot during the target capture process from 28.85% to 12.8%, concurrently facilitating clear recognition of the target contour. This research contributes significantly to the advancement of GI LiDAR technology for practical application, showcasing the potential of the proposed control and design strategies in enhancing system performance in the face of complex disturbances. © 2024 by the authors.
  Accession Number: 20242216171109
• Record 102 of
  
  Title:Noncollinear phase matching and effective nonlinear coefficient calculations for biaxial crystal out of the principal plane
  
  Author(s):Xing, Dingding(1,2); Yi, Dongchi(1); Yuan, Suochao(3); Chen, Xiaoyi(1); Da, Zhengshang(1)
  Source:Applied Physics B: Lasers and Optics
  Volume: 130  Issue: 6  DOI: 10.1007/s00340-024-08247-4  Published: June 2024  
  Abstract:The essential factor in laser frequency conversion involves phase matching within nonlinear optical crystals. To our knowledge, few studies have investigated the noncollinear phase matching calculation for biaxial crystal out of the principal plane. In this paper, we propose an arbitrary direction phase matching model and a computational method based on gradient descent (GD) algorithm, which can be applied to noncollinear in the principal plane, collinear and noncollinear out of the principal plane. In the case of 1053 nm third harmonic generation (THG) in LiB3O5 (LBO) crystal, the phase matching conditions are converted into a system of nonlinear equations with six variables and six equations, which can be solved by iterative optimization search with the GD algorithm and includes type-I (ss-f) and type-II (fs-f). We reveal the relationship of phase matching angles and effective nonlinear coefficients (deff) for various structures. Our method uncovers the existence of many solutions in the non-principal plane with γ > 8° and the deff close to the maximum value 0.66834 pm/V at θ = 90°, φ = 141.84° and γ = 0. The resolution of the arbitrary direction phase matching problem holds significant importance, as it expands the possibilities for laser frequency conversion, especially for noncollinear structures. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
  Accession Number: 20242316215773
• Record 103 of
  
  Title:A frequency-response-optimized Shack-Hartmann zonal wavefront reconstructor based on Fan's model
  
  Author(s):Fan, Yao(1,2,3,4); Duan, Yaxuan(1,3,4); Da, Zhengshang(1,3,4); Yue, Yang(2)
  Source:Review of Scientific Instruments
  Volume: 95  Issue: 5  DOI: 10.1063/5.0197071  Published: May 1, 2024  
  Abstract:This paper introduces an optimized method for zonal wavefront reconstruction utilizing Fan’s model, specifically tailored to enhance the frequency response. Analysis of the system frequency response demonstrates a 27% increase in bandwidth compared to the Southwell model. Examination of reconstruction errors at various frequency points reveals consistently smaller values when compared to the Southwell model. Validation through numerical simulations and real experiments underscores the superior performance of the proposed reconstructor, particularly noticeable at higher response levels within the mid- and high-frequency domains. © 2024 Author(s).
  Accession Number: 20242116106971
• Record 104 of
  
  Title:Development current status and trends analysis of deep space laser communication (cover paper·invited)
  
  Author(s):Gao, Duorui(1,2,3); Sun, Mingyang(1,2,3); He, Mingze(1,2,3); Jia, Shuaiwei(1,2,3); Xie, Zhuang(1,2,3); Yao, Bin(1,2,3); Wang, Wei(1,2)
  Source:Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering
  Volume: 53  Issue: 7  DOI: 10.3788/IRLA20240247  Published: July 2024  
  Abstract:Significance Deep space exploration is the cornerstone of humanity to explore and understand the universe, and it is one of the frontier fields of scientific research. Deep space communication serves as the information bridge that establishes contact between deep space detectors and Earth, acting as a spatial link to ensure the successful completion of deep space exploration missions. The communication system that uses lasers as carrier, characterized by high communication rates, small size, and light weight, has become the main direction for the future development of deep space communication and has also become an international research hotspot in recent years. Progress The article summarizes the characteristics of deep space optical communication technology. Deep space laser communication has the following features: long link distance, significant space loss, extended transmission delay, non-cooperative pointing acquisition and tracking, high relative velocity, large point ahead angle, substantial Doppler frequency shift, and long mission duration. Using examples such as LLCD, DSOC, O2O, LunaNet, OPTEL-D, and DOCS, the article provides a detailed overview of the development trends, latest research progress, and future plans in deep space laser communication technology across the United States, Europe, and China. In the future, deep space laser communication will continue to evolve towards longer communication distances, network integration, terminal miniaturization, integration and type serialization. Key areas of focus include ultra-long-distance PAT, high photon utilization modulation and coding, high-power optical emission, terrestrial large-aperture optical antenna, and ultra-sensitive single-photon reception. The article concludes with a summary and prospects, offering valuable insights for the development of deep space laser communication and interstellar laser communication networks in China. Conclusions and Prospects Both the United States and Europe have been pioneers in deep space laser communication technology research. They have conducted in-orbit technology verification for lunar-to-Earth laser communication and achieved breakthroughs in several key technologies related to deep space laser communication. In contrast, domestic deep space laser communication in China is still in its early stages. Laser communication is an inevitable choice for the future development of deep space communication and is a crucial component of space exploration activities. The moon is the closest celestial body to the earth, carrying out the moon - earth laser communication will provide a more efficient means of data transmission for lunar exploration. Additionally, this effort contributes to building a solid technological foundation for more distant deep space laser communication, marking the first step in China’s research on deep space laser communication technology. Simultaneously, China has initiated planetary exploration projects, and future plans include launching missions to more distant targets such as asteroids and Mars sample return missions. To ensure the successful completion of these long-distance exploration tasks, establishing a matching deep space communication capability is of paramount importance. As laser communication technology continues to evolve, deep space laser communication will become a critical component of the interstellar internet. It will play essential roles in interstellar backbone networks, extension networks, and planetary networks. Furthermore, the development of deep space laser communication complements space optical communication network technologies, mutually reinforcing each other. Ultimately, this progress will lead to the establishment of a near-Earth laser communication network based on ground stations and near-Earth orbit satellites, which will serve as the foundation for an interstellar laser communication network. © 2024 Chinese Society of Astronautics. All rights reserved.
  Accession Number: 20243717021107
• Record 105 of
  
  Title:Research on the Effect of Vibrational Micro-Displacement of an Astronomical Camera on Detector Imaging
  
  Author(s):Liu, Bin(1); Guan, Shouxin(1); Wang, Feicheng(1); Zhang, Xiaoming(2); Yu, Tao(1); Wei, Ruyi(3,4,5)
  Source:Sensors
  Volume: 24  Issue: 3  DOI: 10.3390/s24031025  Published: February 2024  
  Abstract:Scientific-grade cameras are frequently employed in industries such as spectral imaging technology, aircraft, medical detection, and astronomy, and are characterized by high precision, high quality, fast speed, and high sensitivity. Especially in the field of astronomy, obtaining information about faint light often requires long exposure with high-resolution cameras, which means that any external factors can cause the camera to become unstable and result in increased errors in the detection results. This paper aims to investigate the effect of displacement introduced by various vibration factors on the imaging of an astronomical camera during long exposure. The sources of vibration are divided into external vibration and internal vibration. External vibration mainly includes environmental vibration and resonance effects, while internal vibration mainly refers to the vibration caused by the force generated by the refrigeration module inside the camera during the working process of the camera. The cooling module is divided into water-cooled and air-cooled modes. Through the displacement and vibration experiments conducted on the camera, it is proven that the air-cooled mode will cause the camera to produce greater displacement changes relative to the water-cooled mode, leading to blurring of the imaging results and lowering the accuracy of astronomical detection. This paper compares the effects of displacement produced by two methods, fan cooling and water-circulation cooling, and proposes improvements to minimize the displacement variations in the camera and improve the imaging quality. This study provides a reference basis for the design of astronomical detection instruments and for determining the vibration source of cameras, which helps to promote the further development of astronomical detection. © 2024 by the authors.
  Accession Number: 20240715548318
• Record 106 of
  
  Title:Accurate two-step random phase retrieval approach without pre-filtering based on hyper ellipse fitting
  
  Author(s):Li, Ziwen(1); Du, Hubing(1); Feng, Leijie(1); Gu, Feifei(2); Li, Yanjie(1); Zhu, Qian(1); Wei, Pengfei(1); Zhang, Gaopeng(3)
  Source:Optics Express
  Volume: 32  Issue: 18  DOI: 10.1364/OE.533121  Published: August 26, 2024  
  Abstract:In this work, we propose a hyper ellipse fitting-based high-precision random two-frame phase shifting algorithm to improve the accuracy of phase retrieval. This method includes a process of Gram-Schmidt orthonormalization, followed by a hyper ellipse fitting procedure. The Gram-Schmidt orthonormalization algorithm constructs a quadrature fringe pattern relative to the original fringe pattern. These two quadrature fringe patterns are then fed into the hyper ellipse fitting procedure, which reconstructs the phase map and refines the background light to produce the final accurate phase of interest. Due to the hyper ellipse fitting procedure, the demodulation results are significantly improved in many cases. This method allows us to design a two-shot phase reconstruction algorithm without the need for least squares iteration or pre-filtering, effectively mitigating residual background to the greatest extent. It combines the advantages of both the Gram-Schmidt orthonormalization method and the Lissajous ellipse fitting method, making our hyper ellipse fitting approach a simple, flexible, and accurate phase retrieval algorithm. Experiments show that by using the weighted least squares method and adjusting the weights, this method can prioritize data points with more significant information or higher reliability, ensuring more accurate estimation of the ellipse parameters. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20243616971492
• Record 107 of
  
  Title:Real-Time Registration of Unmanned Aerial Vehicle Hyperspectral Remote Sensing Images Using an Acousto-Optic Tunable Filter Spectrometer
  
  Author(s):Liu, Hong(1,2,3,4); Hu, Bingliang(1,3,4); Hou, Xingsong(2); Yu, Tao(1,3,4); Zhang, Zhoufeng(1,3); Liu, Xiao(1,3); Liu, Jiacheng(1,3,4); Wang, Xueji(1,3)
  Source:Drones
  Volume: 8  Issue: 7  DOI: 10.3390/drones8070329  Published: July 2024  
  Abstract:Differences in field of view may occur during unmanned aerial remote sensing imaging applications with acousto-optic tunable filter (AOTF) spectral imagers using zoom lenses. These differences may stem from image size deformation caused by the zoom lens, image drift caused by AOTF wavelength switching, and drone platform jitter. However, they can be addressed using hyperspectral image registration. This article proposes a new coarse-to-fine remote sensing image registration framework based on feature and optical flow theory, comparing its performance with that of existing registration algorithms using the same dataset. The proposed method increases the structure similarity index by 5.2 times, reduces the root mean square error by 3.1 times, and increases the mutual information by 1.9 times. To meet the real-time processing requirements of the AOTF spectrometer in remote sensing, a development environment using VS2023+CUDA+OPENCV was established to improve the demons registration algorithm. The registration algorithm for the central processing unit+graphics processing unit (CPU+GPU) achieved an acceleration ratio of ~30 times compared to that of a CPU alone. Finally, the real-time registration effect of spectral data during flight was verified. The proposed method demonstrates that AOTF hyperspectral imagers can be used in real-time remote sensing applications on unmanned aerial vehicles. © 2024 by the authors.
  Accession Number: 20243116775992
• Record 108 of
  
  Title:Electron vortices generation of photoelectron of H 2 + by counter-rotating circularly polarized attosecond pulses
  
  Author(s):Yang, Haojing(1); Liu, Xiaoyu(1); Zhu, Fengzheng(2); Jiao, Liguang(3,4); Liu, Aihua(1,5)
  Source:Chinese Physics B
  Volume: 33  Issue: 1  DOI: 10.1088/1674-1056/ad011a  Published: January 1, 2024  
  Abstract:Molecular-frame photoelectron momentum distributions (MF-PMDs) of an H 2 + molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrödinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counter-rotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distance-dependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs. © 2024 Chinese Physical Society and IOP Publishing Ltd
  Accession Number: 20240515465957