7 results on '"Li, Fang-Li"'
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2. Holographic Einstein rings of a black hole with a global monopole
- Author
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Xiao-Xiong Zeng, Li-Fang Li, and Peng Xu
- Subjects
Astrophysics ,QB460-466 ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Abstract The global monopole solutions which give rise to quite unusual physical phenomena have captured considerable attention. In this paper, we study the Einstein ring of the spherically symmetric AdS black hole solution with a global monopole based on the AdS/CFT correspondence. With the help of the given response function of the QFT on the boundary, we construct the holographic images of the black hole in the bulk. Our results exhibit the absolute amplitude of total response function $$|\langle \mathcal {O}\rangle |$$ | ⟨ O ⟩ | increases with the decrease of the monopole parameter b and the temperature T. And the frequency $$\omega $$ ω of the Gaussian source will also increase the absolute amplitude. These parameters also affects the Einstein ring. With the change of the observation position, this ring will change from the concentric stripe to a luminosity-deformed ring, or light points. And the monopole parameter has an effect on the brightness and the position of Einstein ring. All these results imply that the holographic images can be used as an effective tool to distinguish different types of black holes for fixed wave source and optical system. These theoretical proposal opens a door to gravitational phenomena on strongly correlated material. Therefore, the holographic Einstein ring is of great theoretical and experimental significance for our research. In theory, it provides us a new way to find a necessary condition for the existence of the dual black hole. And experimentally speaking, if we can realize suitable targets for observing AdS black holes successfully, we would be able to observe Einstein rings by tabletop experiments when we apply localized sources on such materials and measure their responses.
- Published
- 2024
- Full Text
- View/download PDF
3. Holographic Einstein rings of non-commutative black holes
- Author
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Xin-Yun Hu, Xiao-Xiong Zeng, Li-Fang Li, and Peng Xu
- Subjects
Astrophysics ,QB460-466 ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Abstract With the help of AdS/CFT correspondence, we derive the desired response function of QFT on the boundary of the non-commutative black hole. Using the virtual optical system with a convex lens, we obtain the Einstein rings of the black hole from the response function. All the results show that the holographic ring always appears with the concentric stripe when the observer located at the north pole. With the change of the observation position, the ring changes into a luminosity-deformed ring, or bright spot. We also investigate the effect of the non-commutative parameter on the ring and find the ring radius becomes larger as the parameter increases. The effect of the temperature on the ring radius is also investigated, it is found that the higher the temperature, the smaller the ring radius. In addition, we also obtain the ingoing angle of the photon via geometric optics, as expected, this angle is consistent well with the angle of the Einstein ring obtained via holography.
- Published
- 2024
- Full Text
- View/download PDF
4. Holographic study on Einstein ring for a charged black hole in conformal gravity
- Author
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Xin-Yun Hu, Xiao-Xiong Zeng, Li-Fang Li, and Peng Xu
- Subjects
AdS/CFT correspondence ,Holographic dual ,Holographic Einstein ring ,Physics ,QC1-999 - Abstract
Under the help of AdS/CFT correspondence, the Einstein ring of a charged black hole in conformal gravity has been studied. As an alternative to standard Einstein’s theory, the conformal gravity is both renormalizable and unitary. And such conformal theory can naturally solve some troublesome problems in physics, such as the quantum gravity problem, the dark matter problem and so on. Considering the conformal gravity has many advantages, therefore in this paper, we study Einstein ring and the effect of gravity-related parameters c0, temperature T and chemical potential u on such Einstein ring in the conformal gravity through the holographic method. Explicitly, imposing an oscillating Gauss source on one side of the AdS boundary which propagates in the bulk, the response functions are derived on the other side of the boundary. Given the proposed wave optics system, the Einstein rings are observed as expected. All these results reveal that when the observer locates at the north pole, there always exists the Einstein ring and surrounding concentric stripes. And such ring becomes into a luminosity-deformed ring or light spot while the observer departs away from the north pole. We also investigate the effect of temperature T, chemical potential u and gravity-related parameters c0 on the ring radius. We find the ring radius increases with the decrease of the temperature, increase of the chemical potential, and increase of the gravity-related parameters respectively. And more, in conformal gravity, because the charge does not appear in the metric but is given by the constraint relation, the chemical potential affects the radius of the ring differently compared with that in Einstein’s gravity. To check the results in the framework of holography, we investigate the ingoing angle of photon at the photon ring via geometric optics and find it is consistent with the angle of Einstein ring obtained via holography.
- Published
- 2024
- Full Text
- View/download PDF
5. A segmentation model to detect cevical lesions based on machine learning of colposcopic images
- Author
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Zhen Li, Chu-Mei Zeng, Yan-Gang Dong, Ying Cao, Li-Yao Yu, Hui-Ying Liu, Xun Tian, Rui Tian, Chao-Yue Zhong, Ting-Ting Zhao, Jia-Shuo Liu, Ye Chen, Li-Fang Li, Zhe-Ying Huang, Yu-Yan Wang, Zheng Hu, Jingjing Zhang, Jiu-Xing Liang, Ping Zhou, and Yi-Qin Lu
- Subjects
HSIL ,Colposcopy ,Diagnosis ,Segmentation ,Artificial intelligence ,Science (General) ,Q1-390 ,Social sciences (General) ,H1-99 - Abstract
Background: Semantic segmentation is crucial in medical image diagnosis. Traditional deep convolutional neural networks excel in image classification and object detection but fall short in segmentation tasks. Enhancing the accuracy and efficiency of detecting high-level cervical lesions and invasive cancer poses a primary challenge in segmentation model development. Methods: Between 2018 and 2022, we retrospectively studied a total of 777 patients, comprising 339 patients with high-level cervical lesions and 313 patients with microinvasive or invasive cervical cancer. Overall, 1554 colposcopic images were put into the DeepLabv3+ model for learning. Accuracy, Precision, Specificity, and mIoU were employed to evaluate the performance of the model in the prediction of cervical high-level lesions and cancer. Results: Experiments showed that our segmentation model had better diagnosis efficiency than colposcopic experts and other artificial intelligence models, and reached Accuracy of 93.29 %, Precision of 87.2 %, Specificity of 90.1 %, and mIoU of 80.27 %, respectively. Conclution: The DeepLabv3+ model had good performance in the segmentation of cervical lesions in colposcopic post-acetic-acid images and can better assist colposcopists in improving the diagnosis.
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- 2023
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6. Efficacy of the feedback teaching method on the compliance of tumor patients in preventing falls
- Author
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Li-Fang Li, Xiao-Yan Zhao, Yue-Jie Chen, and Mei Ji
- Subjects
Surgery ,RD1-811 - Published
- 2022
- Full Text
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7. LAMOST medium-resolution spectroscopic survey of binarity and exotic star (LAMOST-MRS-B): Observation strategy and target selection
- Author
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Jiao Li, Jiang-Dan Li, Yan-Jun Guo, Zhan-Wen Han, Xue-Fei Chen, Chao Liu, Hong-Wei Ge, Deng-Kai Jiang, Li-Fang Li, Bo Zhang, Jia-Ming Liu, Hao Tian, Hao-Tong Zhang, Hai-Long Yuan, Wen-Yuan Cui, Juan-Juan Ren, Jing-Hao Cai, and Jian-Rong Shi
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,General Physics and Astronomy ,FOS: Physical sciences ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
LAMOST-MRS-B is one of the sub-surveys of LAMOST medium-resolution (R ∼ 7500) spectroscopic survey. It aims at studying the statistical properties (e.g., binary fraction, orbital period distribution, mass ratio distribution) of binary stars and exotic stars. We intend to observe about 30000 stars (10 mag ≤ G < 14.5 mag) with at least 10 visits in five years. We first planned to observe 25 plates around the galactic plane in 2018. Then the plates were reduced to 12 in 2019 because of the limitation of observation. At the same time, two new plates located at the high galactic latitude were added to explore binary properties influenced by the different environments. In this survey project, we set the identified exotic and low-metallicity stars with the highest observation priorities. For the rest of the selected stars, we gave the higher priority to the relatively brighter stars in order to obtain high quality spectra as many as possible. Spectra of 49129 stars have been obtained in LAMOST-MRS-B field and released in DR8, of which 28828 and 3375 stars have been visited more than twice and ten times with SNR ≥ 10, respectively. Most of the sources are B-, A-, and F-type stars with –0.6 < [Fe/H] < 0.4 dex. We also obtain 347 identified variable and exotic stars and about 250 stars with [Fe/H] < –1 dex. We measure radial velocities (RVs) by using 892233 spectra of the stars. The uncertainties of RV achieve about 1 km ⋅ s−1 and 10 km ⋅ s−1 for 95% of late- and early-type stars, respectively. The datasets presented in this paper are available at http://www.doi.org/10.57760/sciencedb.j00113.00035.
- Published
- 2022
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