分类： 天文学 >> 天文仪器与技术 提交时间： 2024-01-22 合作期刊: 《天文技术与仪器（英文）》
摘要：An extreme ultraviolet solar corona multispectral imager can allow direct observation of high temperature coronal plasma, which is related to solar flares, coronal mass ejections and other significant coronal activities. This manuscript proposes a novel end-to-end computational design method for an extreme ultraviolet (EUV) solar corona multispectral imager operating at wavelengths near 100 nm, including a stray light suppression design and computational image recovery. To suppress the strong stray light from the solar disk, an outer opto-mechanical structure is designed to protect the imaging component of the system. Considering the low reflectivity (less than 70%) and strong-scattering (roughness) of existing extreme ultraviolet optical elements, the imaging component comprises only a primary mirror and a curved grating. A Lyot aperture is used to further suppress any residual stray light. Finally, a deep learning computational imaging method is used to correct the individual multi-wavelength images from the original recorded multi-slit data. In results and data, this can achieve a far-field angular resolution below 7", and spectral resolution below 0.05 nm. The field of view is ±3 R☉ along the multi-slit moving direction, where R☉ represents the radius of the solar disk. The ratio of the corona's stray light intensity to the solar center's irradiation intensity is less than 10−6 at the circle of 1.3 R☉.
分类： 计算机科学 >> 计算机科学技术其他学科 提交时间： 2023-03-22
摘要： To address the challenges of long-tailed classification, researchers have proposed several approaches to reduce model bias, most of which assume that classes with few samples are weak classes. However, recent studies have shown that tail classes are not always hard to learn, and model bias has been observed on sample-balanced datasets, suggesting the existence of other factors that affect model bias. In this work, we systematically propose a series of geometric measurements for perceptual manifolds in deep neural networks, and then explore the effect of the geometric characteristics of perceptual manifolds on classification difficulty and how learning shapes the geometric characteristics of perceptual manifolds. An unanticipated finding is that the correlation between the class accuracy and the separation degree of perceptual manifolds gradually decreases during training, while the negative correlation with the curvature gradually increases, implying that curvature imbalance leads to model bias. Therefore, we propose curvature regularization to facilitate the model to learn curvature-balanced and flatter perceptual manifolds. Evaluations on multiple long-tailed and non-longtailed datasets show the excellent performance and exciting generality of our approach, especially in achieving significant performance improvements based on current state-ofthe-art techniques. Our work opens up a geometric analysis perspective on model bias and reminds researchers to pay attention to model bias on non-long-tailed and even samplebalanced datasets. The code and model will be made public.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We report a novel method to generate arbitrary optical focus arrays (OFAs). Our approach rapidly produces computer-generated holograms (CGHs) to precisely control the positions and the intensities of the foci. This is achieved by replacing the fast Fourier transform (FFT) operation in the conventional iterative Fourier-transform algorithm (IFTA) with a linear algebra one, identifying/removing zero elements from the matrices, and employing a generalized weighting strategy. On the premise of accelerating the calculation speed by >70 times, we demonstrate OFA with 99% intensity precision in the experiment. Our method proves effective and is applicable for the systems in which real-time OFA generation is essential.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Mingwei Tang
Yubing Han
Dehao Ye
Qianwei Zhang
Chenlei Pang
Xiaowei Liu
Weidong Shen
Yaoguang Ma
Clemens F. Kaminski
Xu Liu
Qing Yang
摘要： Developing a chip-based super-resolution imaging technique with large field-of-view (FOV), deep subwavelength resolution, and compatibility for both fluorescent and non-fluorescent samples is desired for material science, biomedicine, and life researches, etc. Previous on-chip super-resolution methods focus on either fluorescent or non-fluorescent imaging, putting an urgent requirement on the general imaging technique compatible with both of them. Here, we introduce a universal super-resolution imaging method based on tunable virtual-wavevector spatial frequency shift (TVSFS), realizing both labeled and label-free super-resolution imaging on a single delicately fabricated scalable photonic chip. Theoretically, with TVSFS, the diffraction limit of a linear optical system can be overcome, and the resolution can be improved more than three times, which is the limitation for most super-resolution imaging based on spatial frequency engineering. Diffractive units were fabricated on the chip's surface to provide a wavevector-variable evanescent wave illumination and induce tunable deep SFS in the samples' Fourier space. A resolution of {\lambda}/4.7 for the label-free sample and {\lambda}/7.1 for the labeled sample with a large FOV could be achieved with a CMOS-compatible process on a GaP chip. The large FOV, high-compatibility, and high-integration TVSFS chip may advance the fields like cell engineering, precision inspection in the industry, chemical research, etc.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Conventional energy-integration black-white X-ray imaging lacks spectral information of X-ray photons. Although X-ray spectra (energy) can be distinguished by photon-counting technique typically with CdZnTe detectors, it is very challenging to be applied to large-area flat-panel X-ray imaging (FPXI). Herein, we design multi-layer stacked scintillators of different X-ray absorption capabilities and scintillation spectrums, in this scenario, the X-ray energy can be discriminated by detecting the emission spectra of each scintillator, therefore the multispectral X-ray imaging can be easily obtained by color or multispectral visible-light camera in one single shot of X-ray. To verify this idea, stacked multilayer scintillators based on several emerging metal halides were fabricated in the cost-effective and scalable solution process, and proof-of-concept multi-energy FPXI were experimentally demonstrated. The dual-energy X-ray image of a bone-muscle model clearly showed the details that were invisible in conventional energy-integration FPXI. By stacking four layers of specifically designed multilayer scintillators with appropriate thicknesses, a prototype FPXI with four energy channels was realized, proving its extendibility to multispectral or even hyperspectral X-ray imaging. This study provides a facile and effective strategy to realize energy-resolved flat-panel X-ray imaging.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Soliton molecules have been a striking research area, which is significant for the exploration of physical mechanism in various nonlinear systems, the analog to the molecule of matter, and the potential applications in multilevel encoding of optical communications. Here, we demonstrate a novel dichromatic soliton-molecular compound (SMC) that is a hybrid bound states of multiple pulses with two different frequencies connected by two different binding mechanisms. It exhibits unique temporal and spectral profiles that can be described as the bounded temporal and dichromatic soliton molecules. The vibrating SMCs are generated experimentally and numerically to demonstrate the intrinsic solution in the dissipative nonlinear system, which is characterized with the vibration both in time and frequency dimensions and dual-peak evolution trajectory induced by the time-frequency coupling. These results enrich the concept of soliton molecules and further promote the analogy to matter molecules.
分类： 计算机科学 >> 计算机科学的集成理论 提交时间： 2023-02-16
摘要： Model bias triggered by long-tailed data has been widely studied. However, measure based on the number of samples cannot explicate three phenomena simultaneously: (1) Given enough data, the classification performance gain is marginal with additional samples. (2) Classification performance decays precipitously as the number of training samples decreases when there is insufficient data. (3) Model trained on sample-balanced datasets still has different biases for different classes. In this work, we define and quantify the semantic scale of classes, which is used to measure the feature diversity of classes. It is exciting to find experimentally that there is a marginal effect of semantic scale, which perfectly describes the first two phenomena. Further, the quantitative measurement of semantic scale imbalance is proposed, which can accurately reflect model bias on multiple datasets, even on sample-balanced data, revealing a novel perspective for the study of class imbalance. Due to the prevalence of semantic scale imbalance, we propose semantic-scale-balanced learning, including a general loss improvement scheme and a dynamic re-weighting training framework that overcomes the challenge of calculating semantic scales in real-time during iterations. Comprehensive experiments show that dynamic semantic-scale-balanced learning consistently enables the model to perform superiorly on large-scale long-tailed and non-long-tailed natural and medical datasets, which is a good starting point for mitigating the prevalent but unnoticed model bias. In addition, we look ahead to future challenges.
分类： 生物学 >> 植物学 >> 植物生理学 提交时间： 2016-05-03
Lichao Zhang
Guoxiang Liu
Jizeng Jia
Guangyao Zhao
Chuan Xia
Lina Zhang
Fu Li
Qiang Zhang
Chunhao Dong
Shuangcheng Gao
Longzhi Han
Xiuping Guo
Xin Zhang
Jinxia Wu
Xu Liu
Xiuying Kong
摘要： >Through large-scale transformation analyses, TaMYB72 was identified as a flowering time regulator in wheat. TaMYB72 is a MYB family transcription factor localized to the nucleus. Three TaMYB72 homologs, TaMYB72-A, TaMYB72-B and TaMYB72-D, cloned from hexaploid wheat were mapped to the short arm of the group 6 chromosomes. Under the long-day conditions, over-expression of the TaMYB72 in rice shortened the flowering time by approximately 12d. Expression analyses suggest that TaMYB72 may function through up-regulation of florigen genes Hd3a and RFT1.
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