2023
2023
-
Record 181 of
Title:Efficient dense attention fusion network with channel correlation loss for road damage detection
Author(s):Liu, Zihan(1); Jing, Kaifeng(1); Yang, Kai(2,3); Zhang, ZhiJun(2); Li, Xijie(2,3,4)Source: IET Intelligent Transport Systems Volume: null Issue: null Article Number: null DOI: 10.1049/itr2.12369 Published: 2023Abstract:Road?damage detection (RDD) is critical to society's safety and the efficient allocation of resources. Most road damage detection methods which directly adopt various object detection models face some significant challenges due to the characteristics of the RDD task. First, the damaged objects in the road images are highly diverse in scales and difficult to differentiate, making it more challenging than other tasks. Second, existing methods neglect the relationship between the feature distribution and model structure, which makes it difficult for optimization. To address these challenges, this study proposes an efficient dense attention fusion network with channel correlation loss for road damage detection. First, the K-Means++ algorithm is applied for data preprocessing to optimize the initial cluster centers and improve the model detection accuracy. Second, a dense attention fusion module is proposed to learn spatial-spectral attention to enhance multi-scale fusion features and improve the ability of the model to detect damage areas at different scales. Third, the channel correlation loss is adopted in the class prediction process to maintain the separability of intra and inter-class. The experimental results on the collected RDDA dataset and RDD2022 dataset show that the proposed method achieves state-of-the-art performance. ? 2023 The Authors. IET Intelligent Transport Systems published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.Accession Number: 20231714009506 -
Record 182 of
Title:Star-8QAM to PAM4 format conversion in highly nonlinear silicon-PTS waveguides
Author(s):Wu, Xiao(1); Li, Xuefeng(2); Ren, Li(1); Liu, Hongjun(3,4)Source: Optical Engineering Volume: 62 Issue: 12 Article Number: 125103 DOI: 10.1117/1.OE.62.12.125103 Published: December 1, 2023Abstract:The optical modulation format conversion scheme of converting star quadrature amplitude modulation signals to four-stage pulse amplitude modulation signals is theoretically realized by combining phase-sensitive amplification in a silicon-p-toluene sulphonate hybrid waveguide. By optimizing the waveguide structure, a phase mismatch bandwidth from 1310 to 1890 nm and an ultra-high nonlinear coefficient of 6.966 × 103 m?1 W?1 are obtained. Constellation plots, error vector magnitude, and bit error rate (BER) are used to evaluate the conversion scheme. Simulation results show that the scheme not only ensures the integrity of the signal information before and after conversion but also achieves nearly 12 dB performance improvement in the converted signal with a BER threshold of 10?3. It is further shown that the scheme has great potential for applications such as long-short distance interconnections and hierarchical modulation of advanced format signals. ? 2023 Society of Photo-Optical Instrumentation Engineers (SPIE)Accession Number: 20240215340045 -
Record 183 of
Title:An Edge Computing Algorithm Based on Multi-Level Star Sensor Cloud
Author(s):Ren, Siyu(1); Qiu, Shi(2); Cheng, Keyang(3)Source: CMES - Computer Modeling in Engineering and Sciences Volume: 136 Issue: 2 Article Number: null DOI: 10.32604/cmes.2023.025248 Published: 2023Abstract:Star sensors are an important means of autonomous navigation and access to space information for satellites. They have been widely deployed in the aerospace field. To satisfy the requirements for high resolution, timeliness, and confidentiality of star images, we propose an edge computing algorithm based on the star sensor cloud. Multiple sensors cooperate with each other to form a sensor cloud, which in turn extends the performance of a single sensor. The research on the data obtained by the star sensor has very important research and application values. First, a star point extraction model is proposed based on the fuzzy set model by analyzing the star image composition, which can reduce the amount of data computation. Then, a mapping model between content and space is constructed to achieve low-rank image representation and efficient computation. Finally, the data collected by the wireless sensor is delivered to the edge server, and a different method is used to achieve privacy protection. Only a small amount of core data is stored in edge servers and local servers, and other data is transmitted to the cloud. Experiments show that the proposed algorithm can effectively reduce the cost of communication and storage, and has strong privacy. ? 2023 Tech Science Press. All rights reserved.Accession Number: 20230813609470 -
Record 184 of
Title:The construction method of space-based digital imaging link mathematical model
Author(s):Li, Yaru(1,2); Zhou, Liang(1); Liu, Zhaohui(1); She, Wenji(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 52 Issue: 12 Article Number: 20230351 DOI: 10.3788/IRLA20230351 Published: December 2023Abstract:Objective With the proposal of digital equipment construction, it is imperative to build space-based digital equipment that can simulate situational awareness capabilities. As one of the core equipment for space-based situational information acquisition, the optical imaging system is inevitably an integral part of the construction of space-based digital equipment systems. Establishing a scientifically and reasonably accurate model of space target imaging link is crucial for constructing a space-based digital imaging system. Additionally, due to the involvement of various scientific and technological fields, the construction of a space target imaging system is characterized by a large-scale system and a long development cycle. Traditional research methods are unable to meet the needs of key technology verification for space-based systems. Therefore, it is also necessary to construct this digital model. By using simulation and comprehensive integration, critical technologies of imaging systems can be validated. Additionally, it provides a demonstration environment for research on space target imaging technology and serves as an auxiliary tool for the design of space-based observation platforms. Methods Based on Kepler's three laws and visibility analysis (Tab.2), this paper constructs a visible model for camera and target optical observations. Based on the uniform smoothing algorithm and advanced wavefront algorithm, the triangulated mesh division technique and the five-parameter bidirectional reflectance distribution function (BRDF) (Tab.3) are used to construct the geometric and optical characteristic model of the target. By employing path tracing and importance sampling of light rays, a global illumination algorithm (Fig.5) is used to construct the imaging radiative transfer model. Finally, the target radiance image undergoes optical-electric energy conversion and imaging modulation (Fig.7) to become the final output image of the sensor. This paper simulates target images satisfying visibility conditions using the Hubble Space Telescope as the imaging object, based on the given orbital parameters of imaging platform and space target. Results and Discussions By comparing the visibility simulation results within 15 days of the two-body orbit model in Satellite Tool Kit (STK) (Fig.9), the correctness of the imaging visible model proposed in this paper is validated. The close-range imaging results of the target (Fig.11) demonstrate the accuracy of the global illumination algorithm in a multi-light source space-based imaging scenario. The quality degradation simulation results (Fig.14) indicate that the convolution of the frequency domain transfer function and the accumulation of temporal noise can simulate different levels of image quality degradation in on-orbit imaging. Under the conditions of a time interval of 3 seconds and a distance range of 70 to 200 km, imaging simulations were performed on the target with a Earth-oriented attitude. The imaging results (Fig.10) demonstrate that the imaging chain model can effectively generate target sequence images that satisfy the requirements of orbit monitoring conditions. Conclusions This paper starts from the camera and target's orbital parameters and calculates the observable time periods of the target under the condition of orbital flight using the camera and target visible model. Using the target geometry and optical characteristic model, the reflection of light source energy by targets with different materials and geometric shapes is described. The target radiance image is obtained by performing a rapid calculation of the visible parts of the target using the imaging radiative transfer model. Finally, the final sensor output image is generated through the process of photoelectric energy conversion and imaging modulation model. The imaging chain mathematical model constructed in this paper allows for the research of digital imaging technology in specific imaging scenarios without relying on other orbit and imaging software such as STK and OpenGL. It provides references and foundations for the design of physical cameras, detector selection, and the construction of core modules in the digital twin system for space-based imaging. ? 2023 Chinese Society of Astronautics. All rights reserved.Accession Number: 20241115748296 -
Record 185 of
Title:High Quality Bessel Beam Array Generation Method Based on Computer Generated Holography
Author(s):Zhang, Ruidi(1,2); Duan, Yaxuan(1,3); Da, Zhengshang(1,3)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 52 Issue: 9 Article Number: 0909001 DOI: 10.3788/gzxb20235209.0909001 Published: September 2023Abstract:Bessel beam array has been widely used in femtosecond laser processing， particle capture， optical microscopy， optical communication， and other fields. Especially in the field of industrial processing， the Bessel beam plays an important role in the process of pore structures with the ratio of height to depth due to its long focal depth characteristics. For the preparation of large-area periodic pore micro-nano structures， the parallel processing method of the Bessel beam array can significantly improve the machining efficiency. The machining quality of materials is closely related to the quality of the light field of the Bessel beam array， so it is significant to study the generation method of Bessel beam array with high quality. The traditional Bessel beam array generation methods include： multi-axicon phase serial superposition method， Dammann grating， and axicon phase superposition method， which can generate parallel and divergent Bessel beam array， respectively. However， the generated Bessel beam array has problems of poor uniformity and low diffraction efficiency. Therefore， two computational holography methods are proposed in this paper， which can generate high-quality parallel and divergent Bessel beam arrays respectively. Firstly， the computational hologram model of the proposed method is established， and the multi-axicon phase parallel splicing method is proposed， which effectively reduce the background noise of the optical field by improving the "aperture utilization ratio" of the window； The multi-lens and axicon phase superposition method is proposed， the multi-lens phase superposition method is used to generate multiple focus distributions on the observation plane， and then the beams of each focus are modulated into Bessel beams by superimposing axicon phase， thus forming Bessel beam array，the key of this method is the multi-lens phase superposition to generate multi-focus distributions with controllable position. Secondly， holograms of a 3×3 Bessel beam array are generated by the proposed method and the traditional method， and then simulated respectively， the transverse optical field distribution and diffraction pattern of the Bessel beam array in free space are obtained， the uniformity and diffraction efficiency of the Bessel beam array generated by the proposed method and the traditional method are compared and analyzed. The simulation results show that the uniformity and diffraction efficiency of the parallel Bessel beam array generated by the proposed method are 98.94% and 78.12%， respectively； the uniformity and diffraction efficiency of the diverging Bessel beam array generated by the proposed method are 97.95% and 79.23%， respectively. Finally， the images of 120 mm， 130 mm and 140 mm along the transmission direction of Bessel beam array are collected through experiments， which are highly consistent with the simulation results. Compared with traditional methods， the uniformity of parallel and divergent Bessel beam arrays produced by the proposed method is increased by 2.97% and 4.70%， respectively， and the diffraction efficiency is increased by 48.22% and 54.75%. The method proposed in this paper provides a technical approach to the generation of high quality Bessel beam arrays and has certain engineering application value. ? 2023 Chinese Optical Society. All rights reserved.Accession Number: 20234014824843 -
Record 186 of
Title:Ultrafast observation of air plasma induced by femtosecond laser micromachining
Author(s):Wang, Qianhao(1,2); Yang, Xiaojun(1); Wen, Wenlong(1); Zhao, Hualong(1); Li, Yi(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 52 Issue: 11 Article Number: 20230158 DOI: 10.3788/IRLA20230158 Published: November 2023Abstract:Objective Femtosecond laser micromachining application scenarios commonly occur in atmospheric environments. When the femtosecond laser is focused and interacts with air, it ionizes to produce air plasma, which has a direct impact on the whole machining process. Among other things, the interaction of Kerr self-focusing with plasma scattering leads to filamentation, which changes the light field distribution, and air ionization can significantly affect the laser energy acting on the material. Studying the interaction between femtosecond laser and air, especially the process of ionization of air by laser pulses, is the key to leapfrogging to enhanced applications. To deeply understand the laser micromachining process in atmospheric environment, the transient evolution characteristics of air plasma generated by focused femtosecond laser pulses are studied by building a femtosecond time-resolved pump-probe shadow imaging system, and the temporal characteristics of air plasma under different focusing conditions are numerically simulated. Methods A high time-resolved pump-probe shadow imaging system was built. The laser beam is focused in the air by a microscopic objective and imaged by another laser beam for detection(Fig.1). A 20× microscope objective was used for high-resolution imaging of the plasma to record the time-space evolution of the air plasma. The optical range difference between the pump light and the detection light is adjusted to determine the detection time interval, and the spatial morphology of the air plasma is characterized by the shadow image on the CCD. In the numerical simulation, the ionization model in atmospheric environment is established to obtain the complete process of plasma generation and dissipation in light calling ionization. Results and Discussions Under the microscope focusing conditions at 20×, the plasma is growing and moving rapidly from 0 fs to 59 fs; After 64 fs, it enters a slow evolutionary stage, with the shadow moving speed and propagation distance slowly decreasing; And at 135 fs, the plasma enters a saturation stage and the shadow signal intensity stops growing (Fig.3). The wave front velocity of its ionization keeps decreasing with time and is overall less than the speed of light (Fig.4). From the computational model, it is obtained that the transition times between multiphoton ionization and tunneling ionization are ?1.158τ and ?1.26τ for 20-fold and 40-fold focusing conditions, and the times of complete dissipation of free electrons are 23.2 ps and 13.1 ps, respectively. Conclusions A laser pulse with a pulse width of 290 fs, a single pulse energy of 160 μJ, and a central wavelength of 1 026 nm was used as the pump light pulse, and the time-space process of the focused femtosecond pulse transport ionization in air was investigated by building a femtosecond time-resolved pump-probe shadow imaging experiment. The time course of air plasma generation and disappearance was obtained by solving the free electron rate equation for different injection energies and focusing conditions numerically. The experimental results show that the ionized air plasma is shuttle-shaped, and the transient electron number density increases and then decreases as the delay time increases, while the extension velocity of the plasma gradually decreases from 2.9×108 m/s to 0. Solving the free electron rate equation shows that the transient electron number density of the air plasma ionized by the femtosecond laser is higher under the focusing conditions of the high-NA objective, and the tunneling ionization contributes to a higher electron number density in the whole ionization process. The number of electrons contributing to the whole ionization process is higher; And considering the diffusion and compounding of ions, the decay of plasma density is faster under high NA focusing conditions, and the ionization and diffusion processes present a high degree of temporal asymmetry. The process optimization parameters in femtosecond laser micromachining are numerous and extensive, and often require a lot of labor and resources for experimental exploration. The existing micromachining computational models are unable to reproduce the actual processing results due to the lack of key physical parameters such as transient electron eigenvalues in the simulation model. Femtosecond time-resolved pumping probe technology can provide an important tool for transient measurement of physical feature parameters and improve the simulation model, thus increasing the accuracy of simulation results. Overall, femtosecond time-resolved pump-probe shadow imaging can provide a means to observe transient physical processes in different processing environments and is expected to become a powerful tool for online monitoring of high-end femtosecond processing equipment. ? 2023 Chinese Society of Astronautics. All rights reserved.Accession Number: 20241115747963 -
Record 187 of
Title:Equivalent Modeling Method for Screw Joints Based on Stiffness Calculation
Author(s):Li, Xiangyu(1,2,3); Ruan, Ping(1,2); Hao, Wei(1,2); Xie, Meilin(1,2); Song, Wei(1,2,3)Source: Journal of Physics: Conference Series Volume: 2557 Issue: 1 Article Number: 012016 DOI: 10.1088/1742-6596/2557/1/012016 Published: 2023Abstract:Accurate assessment of the mechanical properties of an assembly with screw joints has to rely on the equivalent modeling of the screw joint and accurate kinetic properties analysis. In this paper, an equivalent modeling method for screw joints based on stiffness calculation is proposed. With the solid model of the screw-coupled member, the equivalent virtual material parameters that can characterize the mechanical properties of the joint surface of the coupled member are obtained by calculating the joint surface stiffness, and then the accurate parametric modeling of the screw joints is realized. In addition, the vibration modal test platform for screw joints is built. By comparing the frequency response function obtained from the experiment with that obtained from the equivalent model simulation, it is found that the errors of the 1st-order and 2nd-order bending natural frequencies of the cantilever beam are 3.96% and 5.5%, respectively, and the simulation analysis results are of high accuracy. Furthermore, by comparing the first 6th-order of natural frequencies of the cantilever beam, the maximum frequency deviation between the simulation analysis results and the test results is ≤ 7%, and the average frequency deviation is 4.67%, which can better reflect the mechanical properties of the screw joint. ? Published under licence by IOP Publishing Ltd.Accession Number: 20233614673299 -
Record 188 of
Title:Infrared Small Target Detection Method Based on Frequency Domain Clutter Suppression and Spatial Feature Extraction
Author(s):Duan, Chengpeng(1,2); Hu, Bingliang(1,2); Liu, Wei(3); Ma, Tianlei(4); Ma, Qi(4); Wang, Hao(4)Source: IEEE Access Volume: 11 Issue: null Article Number: null DOI: 10.1109/ACCESS.2023.3303486 Published: 2023Abstract:With the continuous development of infrared technology, the application of infrared imagery is increasingly widespread. Nonetheless, infrared imagery suffers from low contrast and high noise characteristics, making it challenging to detect and recognize infrared small targets. Frequently, existing deep learning-based infrared target detection methods solely employ spatial information, neglecting frequency domain information, thereby creating susceptibility to background clutter interference and low detection accuracy in complex scenes. Here, a deep learning-based method is proposed that combines frequency domain clutter suppression and spatial feature extraction to detect infrared small targets. Firstly, the spatial domain infrared image is transformed into the frequency domain using block discrete cosine transform (DCT). Secondly, the frequency domain information is filtered using an attention mechanism to adaptively enhance the targets and suppress the background clutter. Finally, the compressed attention map is transformed back to the spatial domain and inputted into a lightweight neural network for spatial feature extraction and fusion to obtain detection results. This approach enhances detection accuracy, and reduces computational complexity and storage space, thereby making it practical and deployable. Experimental outcomes demonstrate strong detection capabilities on public datasets, and significant advantages over traditional and existing deep learning methods. ? 2013 IEEE.Accession Number: 20233314569538 -
Record 189 of
Title:Modeling 3D sliding electrical contact considering fully coupled thermal-mechanical-electrical effects
Author(s):Sui, Yijin(1); Wang, Wenzhong(1); Zhang, Haibo(1); Xie, Youjin(2,3)Source: Tribology International Volume: 184 Issue: null Article Number: 108491 DOI: 10.1016/j.triboint.2023.108491 Published: June 2023Abstract:The 3D sliding electrical contact model considering thermal-mechanical-electrical coupling is presented in this paper. The semi-analytical method (SAM) is used to solve this complex multi-physical contact model. Firstly, the frequency response functions (FRFs) for thermal-mechanical-electrical fields are derived. Then, with discrete convolution and fast Fourier transform (DC-FFT) speeding calculation, a solving procedure, including the conjugate gradient method for force balance and algorithms for electrical potential equilibrium and heat flux partition, is proposed for the first time to solve the fully coupled electrical contact problem. Last, the effects of multiple loadings including the current, normal force, and sliding velocity on electrical contact behaviors are systematically investigated. ? 2023Accession Number: 20231513877180 -
Record 190 of
Title:Visual aiming and positioning system based on diffraction effect
Author(s):Li, Fu-Sheng(1,2); Xie, Zheng-Mao(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12964 Issue: null Article Number: 1296402 DOI: 10.1117/12.2692331 Published: 2023Abstract:In order to overcome the shortcomings of the aiming system in inertial confinement fusion device, such as small field of view, long preparation time and large manual interpretation error, a vision aiming system based on diffraction effect is designed. After the diffraction of the reflected light of the target, the starlight detection device is used to detect the center of the target automatically, which reduces the manual interpretation error. The system uses forward illumination to improve imaging integrity, uses quarter-wave plate and polarization splitter to improve system energy utilization, uses diffraction effect and starlight detector to improve aiming accuracy up to 9.52μm, which reduces preparation time. The quality of illumination system and diffraction system is evaluated by using spot diagram in Zemax, and the simulation of the system is carried out. The results meet the engineering requirements. ? 2023 SPIE.Accession Number: 20240315394906 -
Record 191 of
Title:Stability research of fore-Telescope system with mechanical passive athermalization design
Author(s):Sun, Jian(1,2); Wang, Wei(1); Hu, Bing-Liang(1); Li, Si-Yuan(1); Zou, Chun-Bo(1); Feng, Yu-Tao(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12558 Issue: null Article Number: 125580F DOI: 10.1117/12.2651530 Published: 2023Abstract:With the improvement of spatial resolution, the focal length of space cameras and spectral imagers become longer. The thermal stability of image stability is more sensitive, with the temperature, especially in VNIR (visible and near-infrared). To solve the thermal stability of R-C(Ritchey-Chrétien) long focal length fore-Telescope system, the relevant factors are discussed, on the basis of the LASIS(Large Aperture Static Imaging Spectrometer), and the change in the spacing between primary mirror and secondary mirror with temperature is proposed. Base on the calculation in theory, the method of mechanical passive athermalization design is developed. Mechanical test results indicate that the first natural frequency is 195Hz, above the 100 Hz. The thermal experiments show that the stability of primary mirror and secondary mirror spacing is 0.5μm-1, consisting with the FEA(Finite Element Analysis) value ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Accession Number: 20230713574401 -
Record 192 of
Title:Recent advances of lanthanide nanomaterials in Tumor NIR fluorescence detection and treatment
Author(s):Fan, Qi(1,2); Sun, Chao(1,2); Hu, Bingliang(1); Wang, Quan(1,2)Source: Materials Today Bio Volume: 20 Issue: null Article Number: 100646 DOI: 10.1016/j.mtbio.2023.100646 Published: June 2023Abstract:Lanthanide nanomaterials have garnered significant attention from researchers among the main near-infrared (NIR) fluorescent nanomaterials due to their excellent chemical and fluorescence stability, narrow emission band, adjustable luminescence color, and long lifetime. In recent years, with the preparation, functional modification, and fluorescence improvement of lanthanide materials, great progress has been made in their application in the biomedical field. This review focuses on the latest progress of lanthanide nanomaterials in tumor diagnosis and treatment, as well as the interaction mechanism between fluorescence and biological tissues. We introduce a set of efficient strategies for improving the fluorescence properties of lanthanide nanomaterials and discuss some representative in-depth research work in detail, showcasing their superiority in early detection of ultra-small tumors, phototherapy, and real-time guidance for surgical resection. However, lanthanide nanomaterials have only realized a portion of their potential in tumor applications so far. Therefore, we discuss promising methods for further improving the performance of lanthanide nanomaterials and their future development directions. ? 2023 The AuthorsAccession Number: 20231914055642