2023
2023
-
Record 241 of
Title:Towards Handling Sudden Changes in Feature Maps During Depth Estimation
Author(s):Xue, Yao(1); Cao, Yu(2,3,4,5); Feng, Xubin(6); Xie, Meilin(6); Li, Ke(1); Zhang, Xingjun(7); Qian, Xueming(8)Source: IEEE Transactions on Multimedia Volume: 25 Issue: null Article Number: null DOI: 10.1109/TMM.2022.3171400 Published: 2023Abstract:Depth estimation aims to predict depth map from RGB images without high cost equipments. Deep learning based depth estimation methods have shown their effectiveness. However in existing methods, depth information is represented by a per-pixel depth map. Such depth map representation is fragile facing different kinds of depth changes. This paper proposes a Compressive Sensing based Depth Representation (CSDR) scheme, which formulates the problem of depth estimation in pixel space into the task of fixed-length vector regression in representation space. In this way, deep model training errors will not directly interfere depth estimation, and distortions in estimated depth maps can be restrained in the greatest extent. In addition, we improve depth estimation from two other aspects: model structure and loss function. To capture the features in different scales, we propose a Multiscale Encoder & Multiscale Decoder (MEMD) structure as the vector regression model. To further deal with depth change, we also modify the loss function, where the curvature difference between ground truth and estimation is directly incorporated. With the support of CSDR, MEMD and the curvature loss, the proposed approach achieves superior performance on a challenging depth estimation dataset: NYU-Depth-v2. A range of experiments support our claim that regression in CSDR space performs better than traditionally direct depth map estimation in pixel space. ? 2022 IEEE.Accession Number: 20221912092027 -
Record 242 of
Title:Numerical simulation of dual MCP hard x-ray imaging detector on spatial resolution and detection quantum efficiency
Author(s):Liu, Yiheng(1,2,3); Li, Lili(1,2,3); Chen, Ping(1,3); Zhang, Feng(4); Gou, Yongsheng(1); He, Kai(1); Tian, Jinshou(1,3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12595 Issue: null Article Number: 125950D DOI: 10.1117/12.2666993 Published: 2023Abstract:Compton radiography is an important diagnostic tool for inertial confinement fusion (ICF), which provides important parameters about integrity, symmetry and ρR areal density of the dense cold fuel surrounding the hot spot. The dual MCPs (micro-channel plate) configuration detector as a key component for Compton radiography has the ability to detect hard x-rays at energies from 40 to 200 keV with higher detective quantum efficiency (DQE). In this work, a set of simulation methods for calculating the DQE and spatial resolution of dual MCPs are proposed. The photoelectric conversion and secondary electron multiplication processes of 59 KeV X-rays in double MCPs were simulated. The first piece of MCP with 51% lead content absorb x-rays volumetrically to improve the DQE and the second piece of MCP provides a large gain to multiply the secondary electrons. The simulation results indicate that the spatial resolution of the dual MCP detector is 186 μm, and the DQE can reach 6.2%, which will ensure the dual MCP-based framing cameras can obtain imploded capsule images with higher signal-to-noise ratio and spatial resolution. The influence of MCP parameters on DQE and spatial resolution was analyzed, and the simulation method will provide an important reference for further optimization of the detector. ? 2023 SPIE.Accession Number: 20232114124188 -
Record 243 of
Title:Evaluation of grinding characteristics for sapphire ultra-precision grinding using small grit sizes wheels based on AE signals
Author(s):Wang, Sheng(1); Sun, Guoyan(2,3); Zhao, Qingliang(1); Yang, Xiaodong(4)Source: Journal of Manufacturing Processes Volume: 90 Issue: null Article Number: null DOI: 10.1016/j.jmapro.2023.02.009 Published: March 24, 2023Abstract:This paper focused on the grinding characteristics for sapphire ultra-precision grinding with small grit size grinding wheels and acoustic emission signal monitoring of material removal mechanism under the action of multiple abrasive grain. The results show that the use of small grit size grinding wheels allowed for effective removal of sapphire and they facilitated the production of ductile surfaces at the correct parameters. The grinding depth was the most significant effect on the grinding characteristics, the grinding force and subsurface damage scale increased with the grinding depth, and the grinding surface morphology developed from ductile surface to low damage ductile surface and brittle fracture surface. The material removal behavior can be monitored with acoustic emission signals, the original signal, frequency domain and wavelet decomposition features were distinct attributed to the different material removal modes. Besides, low-scale subsurface damage also occurred at the parameters of small size grits and minimal grinding depth. ? 2023 The Society of Manufacturing EngineersAccession Number: 20230713587717 -
Record 244 of
Title:Monitoring of ductile–brittle transition mechanisms in sapphire ultra-precision grinding used small grit size grinding wheel through force and acoustic emission signals
Author(s):Wang, Sheng(1); Sun, Guoyan(2,3); Zhao, Qingliang(1); Yang, Xiaodong(4)Source: Measurement: Journal of the International Measurement Confederation Volume: 210 Issue: null Article Number: 112557 DOI: 10.1016/j.measurement.2023.112557 Published: March 31, 2023Abstract:Progressive ultra-precision grinding experiments used small grit size grinding wheels were performed to investigate the ductile–brittle transition process of sapphire, force and AE signals were employed to monitor the material removal behavior. Precision dressing and measurement of circular arc grinding wheels were performed to meet the minimum grinding depth for ultra-precision grinding. A grinding force model was proposed to interpret the grinding forces in different materials removal modes. A continuous complete ductile–brittle transition process was observed and monitored, the progressive grinding was divided into three stages: ductile dominant, ductile–brittle transition and brittle eruption. The grinding force, surface profile, micro morphology and brittle fracture percentage were discussed. Brittle fracture will not entirely occur, but rather brittle fracture and ductile grooves were coexisted on the surface in the brittle eruption stage, which was attributed to the grinding characteristics of small grit wheels. In addition, raw AE signals and multiple transformation forms were utilized to monitor the material removal behavior and their respective roles were analyzed. The Fourier transform, discrete wavelet, continuous wavelet and wavelet coefficients in different stages can all establish a mapping relationship with material removal modes. ? 2023Accession Number: 20230613555334 -
Record 245 of
Title:Optical design and fabrication of a common-aperture multispectral imaging system for integrated deep space navigation and detection
Author(s):Cao, Jiajing(1); Chang, Jun(1); Huang, Yi(1); Wu, Yunan(1); Ji, Zhongye(1); Lai, Xiaoxiao(1); Wang, Junya(1); Li, Yiting(1); Zhu, Weihong(2); Li, Xuyang(3)Source: Optics and Lasers in Engineering Volume: 167 Issue: null Article Number: 107619 DOI: 10.1016/j.optlaseng.2023.107619 Published: August 2023Abstract:Multispectral imaging systems enable the simultaneous acquisition of spatial and multispectral information about a target, thereby improving the capability of all-weather autonomous spacecraft operations for sensing measurements and condition identification. This paper reports designing and constructing a common-aperture multispectral imaging system (CAMIS) that can simultaneously obtain ultraviolet, visible, mid-wave, and long-wave infrared wavebands. Such a system can simultaneously realize distant stars' navigation and multispectral detection. An experimental setup was constructed to verify the basic principles of the device. The device is used to image an optical-resolution target and a pinhole. The results indicated that the system could perform celestial navigation in the visible waveband and image objects well in multiple wavebands, thereby realizing the integration of deep-space navigation and detection. ? 2023 Elsevier LtdAccession Number: 20231714005636 -
Record 246 of
Title:Timing fluctuation correction for the front end of a 100-PW laser
Author(s):Li, Hongyang(1,2,3); Liu, Keyang(3,4); Wang, Xinliang(2,3); Liu, Xingyan(2,3); Meng, Xianze(2,3); Liu, Yanqi(2,3); Song, Liwei(2,3); Leng, Yuxin(2,3); Li, Ruxin(2,3)Source: High Power Laser Science and Engineering Volume: 11 Issue: null Article Number: e52 DOI: 10.1017/hpl.2023.41 Published: June 13, 2023Abstract:The development of high-intensity ultrafast laser facilities provides the possibility to create novel physical phenomena and matter states. The timing fluctuation of the laser pulses is crucial for pump-probe experiments, which is one of the vital means to observe the ultrafast dynamics driven by intense laser pulses. In this paper, we demonstrate the timing fluctuation characterization and control of the front end of a 100-PW laser that is composed of a high-contrast optical parametric amplifier (seed) and a 200-TW optical parametric chirped pulse amplifier (preamplifier). By combining the timing jitter measurement with a feedback system, the laser seed and preamplifier are synchronized to the reference with timing fluctuations of 1.82 and 4.48 fs, respectively. The timing system will be a key prerequisite for the stable operation of 100-PW laser facilities and provide the basis for potential pump-probe experiments performed on the laser. ? The Author(s), 2023. Published by Cambridge University Press in association with Chinese Laser Press.Accession Number: 20232514277985 -
Record 247 of
Title:Difference-Enhancement Triplet Network for Change Detection in Multispectral Images
Author(s):Zhang, Wuxia(1); Zhang, Yuhang(1); Su, Liangxu(2); Mei, Chao(3); Lu, Xiaoqiang(4)Source: IEEE Geoscience and Remote Sensing Letters Volume: 20 Issue: null Article Number: 5002505 DOI: 10.1109/LGRS.2023.3312734 Published: 2023Abstract:Change detection is the process of detecting and evaluating differences from bitemporal remote sensing images. Deep-learning-based change detection methods have become the mainstream approaches due to their discriminative features and good change detection performance. However, most of the existing deep-learning-based change detection methods did not perform well in detecting subtle changes and did not fully explore the underlying information of features learned by deep neural networks. To address the above-mentioned problems, we propose an end-to-end deep neural network for multispectral change detection, named difference-enhancement triplet network (DETNet). DETNet mainly includes two modules: the triplet feature extraction module and the difference feature learning module. First, the triplet feature extraction module uses the triple CNN as the backbone to extract representative spatial-spectral features. Second, the difference feature learning module mines the underlying information of difference representations of learned spatial-spectral features to detect subtle changes. Finally, the model uses a compound loss function, which includes triplet loss, contrastive loss, and cross-entropy loss, to guide DETNet toward learning more discriminative features. Extensive experimental results of the proposed DETNet and other state-of-the-art methods on four datasets demonstrate its superiority. ? 2004-2012 IEEE.Accession Number: 20233814764298 -
Record 248 of
Title:Efficient electrocatalytic CO2 reduction to ethanol through the proton coupled electron transfer process of PVnMo(12-n) (n = 1, 2, 3) over indium electrode
Author(s):Sun, Wencong(1); Yao, Dong(2); Tai, Yuehua(1); Zhou, Li(1); Tian, Wenxue(1); Yang, Min(3); Li, Chunxiang(1)Source: Journal of Colloid and Interface Science Volume: 650 Issue: null Article Number: null DOI: 10.1016/j.jcis.2023.06.167 Published: November 15, 2023Abstract:The multistep proton-coupled electron transfer (PCET) processes are beneficial for products distribution and selectivity of the electrocatalytic CO2 reduction reaction (CO2RR), which are affected by the nature of the catalyst and electrolyte at electrode–electrolyte interface. Polyoxometalates (POMs) are electron regulators of PCET processes, which can catalyze CO2RR effectively. Accordingly, the commercial indium electrodes are combined in this work with a series of Keggin-type POMs (PVnMo(12-n)O40)(n+3)?, n = 1, 2, 3) to process CO2RR with Faradaic efficiency toward ethanol reaching 93.4% at ?0.3 V (vs. RHE). The cyclic voltammetry and X-ray photoelectron spectroscopy results reveal the activation of CO2 molecules by the first PCET process of the VⅤ/Ⅳ in POM. Subsequently, the PCET process of MoⅥ/Ⅴ results the oxidation of the electrode, causing the loss of In0 active sites. Electrochemical in-situ infrared spectroscopy confirms the weak adsorption of *CO at the later stage of electrolysis due to the oxidation of the In0 active sites. The indium electrode in PV3Mo9 system retains more In0 active sites owing to the highest V-substitution ratio, thereby ensuring a high adsorption ratio of *CO and C–C coupling. In sum, the regulation of the interface microenvironment by POM electrolyte additives can be used to boost the performance of CO2RR. ? 2023 Elsevier Inc.Accession Number: 20232714353089 -
Record 249 of
Title:Energy-Efficient Design for a NOMA Assisted STAR-RIS Network With Deep Reinforcement Learning
Author(s):Guo, Yi(1,2,3); Fang, Fang(4); Cai, Donghong(5); Ding, Zhiguo(6)Source: IEEE Transactions on Vehicular Technology Volume: 72 Issue: 4 Article Number: null DOI: 10.1109/TVT.2022.3224926 Published: April 1, 2023Abstract:Simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) have been considered promising auxiliary devices to enhance the performance of the wireless network, where users located at different sides of the surfaces can be simultaneously served by the transmitting or reflecting signals. In this article, an energy efficiency (EE) optimization problem for non-orthogonal multiple access (NOMA) assisted STAR-RIS downlink network is investigated. Due to the fractional form of the objective function, it is challenging to solve the EE optimization problem using traditional convex optimization solutions. This article proposes a deep deterministic policy gradient (DDPG)-based algorithm to maximize the EE by jointly optimizing the transmission beamforming vectors at the base station and the coefficients matrices at the STAR-RIS. Simulation results demonstrate that the proposed algorithm can effectively maximize the system EE considering the time-varying channels. ? 1967-2012 IEEE.Accession Number: 20225113273729 -
Record 250 of
Title:Optical design and implementation of a compact and long focal length imaging system
Author(s):Zhong, Yue(1); Chang, Jun(1); Zhao, Xuehui(1); Du, Shan(1); Mu, Yu(1); Jiang, Huilin(1,2); Li, Xuyang(3)Source: Optics and Lasers in Engineering Volume: 163 Issue: null Article Number: 107467 DOI: 10.1016/j.optlaseng.2022.107467 Published: April 2023Abstract:In this paper, we demonstrate a compact and long focal length imaging system for building detection. This system is an all-spherical system. In order to avoid the use of aspheres, the system relies on two groups of correction elements to correct aberrations. This allows for short manufacturing cycles and simplified adjustments. The system works in the visible band from 460 nm to 750 nm. The focal length is 900 mm, and the optical length is only 280 mm. The designed modulation transfer function (MTF) is consistent with the diffraction limit. The MTF curve is 0.63 at the Nyquist frequency of 78 lp/mm. The optomechanical structure is developed based on the analysis consequence of tolerance and stray light, and a device is fabricated. We also propose a simplified method for measuring the space between the primary mirror and the secondary mirror in a compact coaxial optical system. According to the experimentation, the device is proven to meet the application requirement. Detailed descriptions of the design and implementation are provided. ? 2022 Elsevier LtdAccession Number: 20230313385584 -
Record 251 of
Title:Deep learning methods for medical image fusion: A review
Author(s):Zhou, Tao(1,4); Cheng, QianRu(1,4); Lu, HuiLing(2); Li, Qi(1,4); Zhang, XiangXiang(1,4); Qiu, Shi(3)Source: Computers in Biology and Medicine Volume: 160 Issue: null Article Number: 106959 DOI: 10.1016/j.compbiomed.2023.106959 Published: June 2023Abstract:The image fusion methods based on deep learning has become a research hotspot in the field of computer vision in recent years. This paper reviews these methods from five aspects: Firstly, the principle and advantages of image fusion methods based on deep learning are expounded; Secondly, the image fusion methods are summarized in two aspects: End-to-End and Non-End-to-End, according to the different tasks of deep learning in the feature processing stage, the non-end-to-end image fusion methods are divided into two categories: deep learning for decision mapping and deep learning for feature extraction. According to the different types of the networks, the end-to-end image fusion methods are divided into three categories: image fusion methods based on Convolutional Neural Network, Generative Adversarial Network, and Encoder-Decoder Network; Thirdly, the application of the image fusion methods based on deep learning in medical image field is summarized from two aspects: method and data set; Fourthly, evaluation metrics commonly used in the field of medical image fusion are sorted out from 14 aspects; Fifthly, the main challenges faced by the medical image fusion are discussed from two aspects: data sets and fusion methods. And the future development direction is prospected. This paper systematically summarizes the image fusion methods based on the deep learning, which has a positive guiding significance for the in-depth study of multi modal medical images. ? 2023Accession Number: 20231814038467 -
Record 252 of
Title:Monte Carlo Modeling Method for Surface Light Source
Author(s):Tang, Haisong(1,2); Mao, Xianglong(3); Feng, Zexin(1,2); Li, Haoran(1,2)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 43 Issue: 21 Article Number: 2122001 DOI: 10.3788/AOS230880 Published: November 2023Abstract:Objective Monte Carlo simulations are widely applied in the fields such as imaging evaluations, graphical rendering, scattering analysis, and illumination design. Light source modeling, which directly determines the accuracy of the simulation results, is crucial in Monte Carlo simulation. However, light source modeling, especially surface light source modeling, is difficult and rarely discussed publicly. Surface light sources including extended filaments and curved fluorescent tubes are still commonly employed in general and special lighting. Additionally, the external radiation of the non-transparent components of the mechanical structure can also be considered as surface light sources in stray light analysis of far-infrared optical systems. We provide a Monte Carlo modeling method for surface light sources. In this method, we introduce a statistical model of the surface light source and two ray sampling strategies. Results show that the proposed modeling method has high precision. The influence of different sampling strategies and different random numbers on the modeling accuracy and speed is also discussed to guide balancing the modeling accuracy and speed. Methods Based on the homogeneity assumption, we analyze the spatial and orientational properties of the surface light source separately. We clarify the stochastic ray parameters including the starting point coordinates, direction vectors, energy weights, and their physical implications in the Monte Carlo modeling. Based on the radiation properties of the source, the desired probability density functions for different parameters of the ray are derived. In addition, we describe how to sample the parameters following an arbitrary two-dimensional probability density function based on inverse transform sampling. We introduce two ray sampling strategies of uniform sampling with equal weights and uniform sampling in parameter space. The former strategy samples the rays strictly according to the probability density functions, with equal energy weights. The latter strategy assigns the corresponding weights to the rays and ensures that the weights are proportional to the desired probability density functions, which can considerably improve the computational speed by avoiding numerical integration and interpolation operations. The proposed method can model light sources with arbitrary surfaces, with strong versatility. To verify the accuracy of the modeling results, the integral formula of the irradiance distribution formed by the surface light source on the receiver is derived as the theoretical illuminance distribution (Fig. 1). The accuracy of the modeling method is measured by comparing the relative deviation of the simulated irradiance distribution of the sampled rays from the theoretical value. Results and Discussions Monte Carlo modeling results and precision analysis are implemented for two different surface light sources, which are expressed by XY-polynomial (Fig. 2) and non-uniform rational B-spline (NURBS) (Fig. 6) respectively. The sampled starting points, ray directions, and rays (Figs. 3 and 7) are provided respectively to show the differences between the two sampling strategies. The calculated theoretical irradiance distributions formed by the two surface light sources at the specified receiver have an extremely high spatial resolution, which can be regarded as continuous (Figs. 4 and 8). The maximum relative deviation between the simulated value and the theoretical value is within 1% for 224 (≈ 1. 6 × 107 ) sampling rays, demonstrating a high modeling accuracy (Figs. 5 and 9). The uniform sampling strategy with equal weights leads to slightly higher modeling accuracy than that of uniform sampling in parameter space. For the NURBS surface light source, we analyze the differences in modeling accuracy and speed between the two sampling strategies under different numbers of rays and the influence of different random numbers on modeling accuracy (Fig. 10). This shows that the average modeling error gradually decreases while the modeling time increases with the rising number of rays. In contrast to pseudorandom numbers, the utilization of quasi-random numbers can improve the modeling accuracy. The strategy of uniform sampling in parameter space is faster than that of uniform sampling with equal weights since the latter employs the computationally expensive inverse transform sampling. Conclusions We propose a Monte Carlo modeling method for surface light sources. Based on the homogeneity assumption, the spatial and orientational radiation characteristics are analyzed separately. Probability density functions and sampling strategies are presented for different parameters of the rays, and a way to verify the accuracy of the modeling results is also proposed. For the two modeling examples of surface light sources, the maximum relative deviation of the simulated irradiance distribution from the theoretical value at the specified receiver is less than 1% when the number of sampled rays is at the order of 107, demonstrating high modeling accuracy. In addition, the effect of different sampling strategies on modeling accuracy and speed is analyzed under different numbers of rays. The uniform sampling strategy with equal weights leads to higher modeling accuracy. In contrast, the uniform sampling strategy in parameter space is considerably faster. Comparisons through different random numbers show that quasi-random numbers can improve modeling accuracy. ? 2023 Chinese Optical Society. All rights reserved.Accession Number: 20234915183485