2024

• Record 409 of
  
  Title:Detecting the Background-Similar Objects in Complex Transportation Scenes
  
  Author(s):Sun, Bangyong(1); Ma, Ming(1); Yuan, Nianzeng(2); Li, Junhuai(2); Yu, Tao(3)
  Source: IEEE Transactions on Intelligent Transportation Systems  Volume: 25  Issue: 3  DOI: 10.1109/TITS.2023.3268378  Published: March 1, 2024  
  Abstract:With the development of intelligent transportation systems, most human objects can be accurately detected in normal road scenes. However, the detection accuracy usually decreases sharply when the pedestrians are merged into the background with very similar colors or textures. In this paper, a camouflaged object detection method is proposed to detect the pedestrians or vehicles from the highly similar background. Specifically, we design a guide-learning-based multi-scale detection network (GLNet) to distinguish the weak semantic distinction between the pedestrian and its similar background, and output an accurate segmentation map to the autonomous driving system. The proposed GLNet mainly consists of a backbone network for basic feature extraction, a guide-learning module (GLM) to generate the principal prediction map, and a multi-scale feature enhancement module (MFEM) for prediction map refinement. Based on the guide learning and coarse-to-fine strategy, the final prediction map can be obtained with the proposed GLNet which precisely describes the position and contour information of the pedestrians or vehicles. Extensive experiments on four benchmark datasets, e.g., CHAMELEON, CAMO, COD10K, and NC4K, demonstrate the superiority of the proposed GLNet compared with several existing state-of-the-art methods. © 2000-2011 IEEE.
  Accession Number: 20232114129082
• Record 410 of
  
  Title:Multiple marine algae identification based on three-dimensional fluorescence spectroscopy and multi-label convolutional neural network
  
  Author(s):Li, Ruizhuo(1,2); Gao, Limin(1); Wu, Guojun(1,3); Dong, Jing(1,2)
  Source: Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy  Volume: 311  Issue:   DOI: 10.1016/j.saa.2024.123938  Published: April 15, 2024  
  Abstract:Accurate identification of algal populations plays a pivotal role in monitoring seawater quality. Fluorescence-based techniques are effective tools for quickly identifying different algae. However, multiple coexisting algae and their similar photosynthetic pigments can constrain the efficacy of fluorescence methods. This study introduces a multi-label classification model that combines a specific Excitation-Emission matric convolutional neural network (EEM-CNN) with three-dimensional (3D) fluorescence spectroscopy to detect single and mixed algal samples. Spectral data can be input directly into the model without transforming into images. Rectangular convolutional kernels and double convolutional layers are applied to enhance the extraction of balanced and comprehensive spectral features for accurate classification. A dataset comprising 3D fluorescence spectra from eight distinct algae species representing six different algal classes was obtained, preprocessed, and augmented to create input data for the classification model. The classification model was trained and validated using 4448 sets of test samples and 60 sets of test samples, resulting in an accuracy of 0.883 and an F1 score of 0.925. This model exhibited the highest recognition accuracy in both single and mixed algae samples, outperforming comparative methods such as ML-kNN and N-PLS-DA. Furthermore, the classification results were extended to three different algae species and mixed samples of skeletonema costatum to assess the impact of spectral similarity on multi-label classification performance. The developed classification models demonstrated robust performance across samples with varying concentrations and growth stages, highlighting CNN's potential as a promising tool for the precise identification of marine algae. © 2024 Elsevier B.V.
  Accession Number: 20240815614850
• Record 411 of
  
  Title:Compensation control strategy for photoelectric stabilized platform based on disturbance observation
  
  Author(s):Chang, Sansan(1,2,5); Cao, Jianzhong(1,5); Pang, Ji(3); Zhou, Feihang(3); Chen, Weining(1,4,5)
  Source: Aerospace Science and Technology  Volume: 145  Issue:   DOI: 10.1016/j.ast.2024.108909  Published: February 2024  
  Abstract:The accuracy and stability of the photoelectric stabilized platform will be inevitably affected by the friction disturbance and the base platform disturbance in the actual operation. To improve the disturbance rejection performance, two kinds of the disturbance observers are employed and compared in this paper, including the adaptive proportion-integrator observer and the robust sliding mode observer. The disturbances of the friction torque and the moving base are observed, then these observed values are compensated to the voltage loop by the feedback and feedforward, respectively. While the disturbances of the friction torque and the shaking base are compensated, the parameters of the speed stability loop are also tuned to improve the performance of this photoelectric stabilized platform. Finally, the effectiveness of the proposed method is verified by both simulations and experiments. The results show that the proposed disturbance compensation control method based on the sliding mode observer has strong robustness and can effectively reduce the impact of system disturbances. © 2024
  Accession Number: 20240615508203
• Record 412 of
  
  Title:Design, Simulation, and Characterization of a Partial Negative Curvature Antiresonant Hollow-Core Fiber for Low Loss Terahertz Wave Transmission
  
  Author(s):Mu, Qiyuan(1); Zhu, Yuanfeng(2); Kong, Depeng(1); He, Zhengquan(1); Liu, Hongjun(1); Wang, Lili(1)
  Source: IEEE Transactions on Terahertz Science and Technology  Volume:   Issue:   DOI: 10.1109/TTHZ.2024.3393609  Published: 2024  
  Abstract:The present paper demonstrates a novel partial negative curvature hollow-core fiber for low-loss terahertz transmission. In the optimized fiber structure, the tubes in the vertical direction are replaced by plate-like dielectric sheets, thereby achieving low loss and low blocked risk of 3D printing, while retaining a small fiber hollow core and fiber diameter. The 3D printed fiber is characterized by a terahertz time-domain spectroscopy (THz-TDS) system. The obtained transmission spectrum demonstrates the mode beating phenomenon and its peak position varies periodically with fiber length at short distances. The thin antiresonant walls endow the fiber with two broad low-loss windows of 0.2–0.4 THz and 0.55–0.85 THz. Besides, the x-polarization and y-polarization waves achieve minimum losses of 16.2 dB/m@0.28 THz and 16.0 dB/m@0.29 THz, respectively. Furthermore, our fiber has low experimental dispersions, namely −0.18±1.1 ps/THz/cm (x-pol) and 0.67±0.77 ps/THz/cm (y-pol). The experimental losses and dispersions match well with the simulation results. Additionally, the simulation results reveal that the fiber has the potential to attain a high birefringence of 10−3. IEEE
  Accession Number: 20241816022823
• Record 413 of
  
  Title:Optical Design of High-compression Ratio and Low-wavefront Error Gravitational Wave Detection Telescope
  
  Author(s):Liang, Rong(1,2); Zhou, Xiaojun(1); Zou, Chunbo(3); Xu, Huangrong(1); Li, Chenxi(1); Yu, Tao(1,2); Yu, Weixing(1,2)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 1  DOI: 10.3788/gzxb20245301.0122002  Published: January 2024  
  Abstract:Since the first detection of gravitational wave，gravitational wave astronomy has advanced swiftly. As a crucial component of the detection system，the gravitational wave telescope is obviously crucial. The highly stable laser telescope with a low wavefront error and a high suppression ratio of stray light is a crucial medium for the detection of gravitational waves，as it must not only transmit energy in the order of watt to distant spacecraft，but also receive weak laser signals in the order of picowatt from other satellite base station located millions of kilometers away. Therefore，the backward stray light of the local telescope is required to reach 10−10 orders of the incident laser power. Considering the requirements of small size，light weight，and high compactness，it is clear that the benefits of a reflective system cannot be compared to those of a transmission design. In general，the coaxial Cassegrain structure and off-axis multi-mirror structure are utilized. The off-axis design is preferred over the coaxial design for gravitational wave telescopes due to advantages such as the ability to optimize multiple parameters，the absence of a central obstruction，and the high energy collection capacity. In this paper，based on the design of off-axis four-mirror and the theory of coaxial reflection system，we designed and optimized the telescope combined with the characteristics of high magnification，low wavefront error and high suppression ratio of stray light. In the capture field of view of ±200 µrad，we realized the compression ratio of 100 of telescope，and the entrance pupil diameter of the principle system is 300 mm，whose design result of wavefront error is less than of λ/80 because the actual outgoing wavefront error must be less than λ/40. The system distortion of the edge field is less than 0.056 9%. In order to verify the processing and alignment of the principle system as well as the ability of stray light suppression of it，a 0.5 times scale system is established beneath the system with a wavefront error less than λ/175. Internal stray light is suppressed by increasing the light turning angle between the tertiary mirror and quaternary mirror on the condition of low wavefront error of λ/80. The optimized deflection angle of the tertiary mirror is 5.5 degrees，and the tertiary mirror is the plane surface，which can significantly reduce the difficulty of processing and alignment. A simulation of stray light is applied to analyze the stray light of our designed telescope. The steps of stray light analysis consist of the following steps：1）selection and optimization of the optical structure；2）model setting of the corresponding reflection，scattering，and absorption surfaces；3）stray light analysis of the entire system；4）iterative optimization design；5）fulfillment of the system's requirements. Therefore，we investigated the optical paths and power of the backscattered stray light. After positioning the field stop in the middle image plane between the secondary mirror and the tertiary mirror，the proportion of the stray light caused by the secondary mirror is the smallest. The stray light energy caused by the tertiary mirror and the quaternary mirror is the largest，which can reach more than 90%. The tolerance of the optical design is also analyzed，and the results of the analysis indicate that the tolerance of the parabolic primary mirror has the strongest impact on the wavefront error of the system. The principle system has a 90% cumulative probability wavefront error less than λ/40，which can satisfy the design requirement of gravitational wave detection and have the potential to play a significant role in future missions aimed at low wavefront error，high magnification and a high suppression ratio of stray light in the telescope while detecting gravitational waves. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815579474
• Record 414 of
  
  Title:Design of an Integrated Optical System for Detection and Imaging of Large Aperture and Long Focal Length Based on Continuous Zoom
  
  Author(s):Wei, Jinyang(2); Li, Xuyang(1,2); Tan, Longyu(2,3); Yuan, Hao(1); Ren, Zhiguang(1,2); Zhao, Jiawen(1,2); Yao, Kaizhong(1,2)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 1  DOI: 10.3788/gzxb20245301.0122001  Published: January 2024  
  Abstract:In space target observation missions,there is a need for highly sensitive target detection and high-quality imaging. However,there is a significant disparity in the field of view between detection and imaging,and currently,two primary solutions are predominantly employed. One approach involves the design of two independent subsystems,while the other method utilizes a shared-aperture dual-channel design to integrate the functions of detection and imaging into a single system. However,designing two independent systems necessitates a substantial amount of space to accommodate these two subsystems, often exceeding the carrying capacity of most existing space optical payloads. On the other hand,adopting the shared-aperture dual-channel system requires additional electronic components and structural elements,with challenges during the assembly and calibration processes. This may potentially lead to uneven energy distribution issues. In order to achieve high sensitivity detection and precise identification of space targets,this paper introduces the design of an optical system based on a continuous zoom structure that balances a large aperture with a long focal length. This system aims to achieve short focal length and wide-field target detection,as well as long focal length and narrow-field target imaging. In terms of the design methodology,the inherent complexity of the system makes it challenging to obtain an ideal structure during the optimization process. Consequently,this system combines the structures of reflective mirrors and corrective lenses with a zoom structure through optical pupil matching. It employs two reflective mirrors to compress the optical path. During the zooming process,both the zooming components and compensating components move together to maintain the position of the image plane. At the intermediate zoom position,image quality is excellent,allowing for continuous target tracking. To address the issue of uneven energy distribution within the system,this optical system utilizes a shared-aperture detection and imaging integration structure. Furthermore,with an aperture size of 280 mm,the system can detect targets as faint as magnitude 14,effectively resolving the challenges associated with detecting faint and weak targets. The system operates within the spectral range of 450 nm to 850 nm and focal lengths ranging from 700 mm to 3 500 mm. At the detection end,the focal length is 700 mm,with an F-number of 2.5 and a field of view angle of 0.5°×0.5°. At the imaging end,the focal length varies from 1 400 mm to 3 500 mm, with F-numbers ranging from 5 to 12.5 and a field of view angle of 0.18° ×0.18° . At the detection end, 80% of the optical spot's encircled energy is concentrated within 17.4 μm. At the imaging end,the edge field MTF is 0.36,approaching the diffraction limit,while at the intermediate zoom position,MTF values range from 0.31 to 0.36,ensuring consistent image quality during the zooming process. This system integrates the detection and imaging systems into a single unit,achieving shared-aperture functionality. After conducting tolerance analysis on the system,it was observed that under relatively loose tolerances, MTF degradation in both the sagittal and tangential directions is minimal. Moreover, at an 80% probability,the optical spot diameter is smaller than 18.4 μm for each field of view,indicating that the system maintains excellent detection and imaging performance even under these relaxed tolerance conditions. The zoom cam curve is a critical design parameter for zoom systems,and in this system,the cam curves for both the zoom and compensator groups have an apex angle of less than 30°,meeting the design requirements. This system offers strong detection capabilities,excellent image quality,a compact overall length,and a minimal zoom cam curve apex angle. In terms of structure and design objectives,it provides valuable insights for the future development of continuous tracking integrated optical systems for the detection and imaging of targets. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815570755
• Record 415 of
  
  Title:Fabricating S-scheme Sb2S3@CdSexS1–x quasi-one-dimensional heterojunction photoanodes by in-situ growth strategy towards photoelectrochemical water splitting
  
  Author(s):Liu, Dekang(1); Zhang, Dekai(1); Wang, Yishan(2); Liu, Enzhou(3); Miao, Hui(1)
  Source: Journal of Materials Science and Technology  Volume: 201  Issue:   DOI: 10.1016/j.jmst.2024.02.049  Published: December 1, 2024  
  Abstract:Nowadays, energy and environmental problems are becoming increasingly prominent in society, the development of clean and environmentally friendly energy is in line with the construction of ecological civilization and energy, which have attracted the attention of many researchers over the past decades. Narrow band gap semiconductor Sb2S3 is widely used in the area of solar cells because of its high light absorption coefficient and suitable bandgap width. However, numerous deep-level defects provide plentiful photogenerated carrier recombination sites, which restricts the improvement of photoelectrochemical properties seriously. In this work, S-scheme Sb2S3@CdSexS1–x core-shell quasi-one-dimensional heterojunction photoanodes were prepared on the FTO substrate by a two-step vapor transport deposition (VTD) method, chemical bath deposition (CBD) and in-situ selenization method. The results showed that CdSexS1–x nanoparticles (NPs) were tightly coated on the Sb2S3 nanorods (NRs). The photocurrent density of the Sb2S3@CdSexS1–x photoanodes was 1.61 mA cm–2 under 1.23 VRHE. Compared with the Sb2S3 photoanodes (0.61 mA cm–2), Sb2S3@CdSexS1–x photoanodes obtained a 2.64-fold improvement, and the dark current was effectively reduced. It showed excellent stability and fast photocurrent response in a 600 s optical stability test. It was concluded that: (1) The charge transfer mechanism of the S-scheme can avoid the problem of high recombination rate of photogenerated charge carriers due to the defects of Sb2S3 effectively, and realized spatial separation of photogenerated carriers. (2) The [hk1] oriented Sb2S3 NRs and the formed quasi-one-dimensional heterostructures promote efficient carrier transport. (3) The introduction of Se effectively regulated the band structure of CdS, slowed down the photocorrosion of S, and improved the stability of the photoelectrodes significantly. © 2024
  Accession Number: 20241916035918
• Record 416 of
  
  Title:Environmentally stable all-fiber femtosecond laser for industrial application based on a SESAM mode-locked ytterbium-doped laser
  
  Author(s):Cao, Xue(1,2,3); Li, Feng(1); Song, Dongdong(1); Wang, Yishan(1); Li, Qianglong(1,2,3); Zhao, Hualong(1); Zhao, Wei(1); Wen, Wenlong(1); Si, Jinhai(2)
  Source: Microwave and Optical Technology Letters  Volume: 66  Issue: 4  DOI: 10.1002/mop.34119  Published: April 2024  
  Abstract:We demonstrate an environmentally stable femtosecond laser for industrial application based on all polarization-maintaining Yb-doped laser and experimentally explore the effect of the net cavity dispersion (NCD) on output characteristics. The oscillator emits pulses with 5.1 ps and a 23 nm spectral bandwidth, then the pulse is compressed to 88 fs. The instabilities over 120 h gives 0.32% relative root mean square noise, indicating high stability of the pulse laser. With effective regulation of NCD, we obtained the maximum spectral bandwidth of 27 nm. Such broadband oscillator with compact all-fiber configurations provide extremely high stability should be very attractive for long-term industrial application. © 2024 Wiley Periodicals LLC.
  Accession Number: 20241315798070
• Record 417 of
  
  Title:Study on Stray Light Testing and Suppression Techniques for Large-Field of View Multispectral Space Optical Systems
  
  Author(s):Lu, Yi(1); Xu, Xiping(1); Zhang, Ning(1); Lv, Yaowen(1); Xu, Liang(2)
  Source: IEEE Access  Volume: 12  Issue:   DOI: 10.1109/ACCESS.2024.3369471  Published: 2024  
  Abstract:To evaluate the ability of space optical systems to suppress off-axis stray light, this paper proposes a stray light testing method for large-field of view, multispectral spatial optical systems based on point source transmittance (PST). And a stray light testing platform was developed using a high-brightness simulated light source, large-aperture off-axis reflective collimator, high-precision positioning mechanism and a double column tank to evaluate the stray light PST index of spatial optical system. On the basis of theoretical analyses, a set of calibration lenses and stray light elimination structures such as hoods, baffle and stop are designed for the accuracy calibration of stray light testing systems. The theoretical PST values of the calibration lens at different off-axis angles are analyzed by Trace Pro software simulation and compared with the measured values to calibrate the accuracy of the system. The testing results show that the PST measurement range of the system reaches 10-3 ~10-10 when the off-axis angles of the calibration lens are in the range of ±5? ~ ±60?. The stray light test system has the advantages of wide working band, high automation and large dynamic range, and its test results can be used in the correction of lens hood and other applications. © 2013 IEEE.
  Accession Number: 20240915654572
• Record 418 of
  
  Title:Effective correction of dissolved organic carbon interference in nitrate detection using ultraviolet spectroscopy combined with the equivalent concentration offset method
  
  Author(s):Dong, Jing(1,2); Tang, Junwu(1,3); Wu, Guojun(1,3); Xin, Yu(4); Li, Ruizhuo(1,2); Li, Yahui(3)
  Source: RSC Advances  Volume: 14  Issue: 8  DOI: 10.1039/d3ra08000e  Published: February 12, 2024  
  Abstract:Nitrate contamination in water sources poses a substantial environmental and health risk. However, accurate detection of nitrate in water, particularly in the presence of dissolved organic carbon (DOC) interference, remains a significant analytical challenge. This study investigates a novel approach for the reliable detection of nitrate in water samples with varying levels of DOC interference based on the equivalent concentration offset method. The characteristic wavelengths of DOC were determined based on the first-order derivatives, and a nitrate concentration prediction model based on partial least squares (PLS) was established using the absorption spectra of nitrate solutions. Subsequently, the absorption spectra of the nitrate solutions were subtracted from that of the nitrate-DOC mixed solutions to obtain the difference spectra. These difference spectra were introduced into the nitrate prediction model to calculate the equivalent concentration offset values caused by DOC. Finally, a DOC interference correction model was established based on a binary linear regression between the absorbances at the DOC characteristic wavelengths and the DOC-induced equivalent concentration offset values of nitrate. Additionally, a modeling wavelength selection algorithm based on a sliding window was proposed to ensure the accuracy of the nitrate concentration prediction model and the equivalent concentration offset model. The experimental results demonstrated that by correcting the DOC-induced offsets, the relative error of nitrate prediction was reduced from 94.44% to 3.36%, and the root mean square error of prediction was reduced from 1.6108 mg L−1 to 0.1037 mg L−1, which is a significant correction effect. The proposed method applied to predict nitrate concentrations in samples from two different water sources shows a certain degree of comparability with the standard method. It proves that this method can effectively correct the deviations in nitrate measurements caused by DOC and improve the accuracy of nitrate measurement. © 2024 The Royal Society of Chemistry.
  Accession Number: 20240815567105
• Record 419 of
  
  Title:A semi-supervised cross-modal memory bank for cross-modal retrieval
  
  Author(s):Huang, Yingying(1,2,3); Hu, Bingliang(3); Zhang, Yipeng(1,2,3); Gao, Chi(1,2,3); Wang, Quan(1,3)
  Source: Neurocomputing  Volume: 579  Issue:   DOI: 10.1016/j.neucom.2024.127430  Published: April 28, 2024  
  Abstract:The core of semi-supervised cross-modal retrieval tasks lies in leveraging limited supervised information to measure the similarity between cross-modal data. Current approaches assume an association between unlabelled data and pre-defined k-nearest neighbour data, relying on classifier performance for this selection. With diminishing labelled data, classifier performance weakens, resulting in erroneous associations among unlabelled instances. Moreover, the lack of interpretability in class probabilities of unlabelled data hinders classifier learning. Thus, this paper focuses on learning pseudo-labels for unlabelled data, providing pseudo-supervision to aid classifier learning. Specifically, a cross-modal memory bank is proposed, dynamically storing feature representations in a common space and class probability representations in a label space for each cross-modal data. Pseudo-labels are derived by computing feature representation similarity and adjusting class probabilities. During this process, imposing constraints on the classification loss between labelled data and contrastive losses between paired cross-modal data is a prerequisite for the successful learning of pseudo-labels. This procedure significantly contributes to enhancing the credibility of these pseudo-labels. Empirical findings demonstrate that using only 10% labelled data, compared to prevailing semi-supervised techniques, this method achieves improvements of 2.6%, 1.8%, and 4.9% in MAP@50 on the Wikipedia, NUS-WIDE, and MS-COCO datasets, respectively. © 2024
  Accession Number: 20241015679996
• Record 420 of
  
  Title:Satellite Pose Measurement Using an Improving SIFT Algorithm
  
  Author(s):Zhang, Renhao(1,2); Zhou, Zuofeng(1,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 13063  Issue:   DOI: 10.1117/12.3021301  Published: 2024  
  Abstract:Due to the strong reflective properties of the spacecraft surface coatings, there are significant challenges in processing images from outer space. Furthermore, the volume of data for image feature processing and matching is immense, and existing algorithms are insufficient for aerospace system applications. Therefore, this paper proposes a three-dimensional pose measurement algorithm based on binocular vision. The binocular vision-based three-dimensional pose measurement system consists of four main components: camera calibration, camera rectification, stereo matching, and pose determination. Traditional image processing algorithms are employed for satellite image processing. Camera calibration is performed using M software, and the calibration results are further optimized. Due to real-time requirements, an improved SIFT algorithm is used to detect local features in the images, extract feature points, and perform feature point matching under epipolar constraints. Experimental results demonstrate that this algorithm can achieve accurate and fast three-dimensional pose measurement. © 2024 SPIE.
  Accession Number: 20241115744309