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167 results on '"Wei, Jingbo"'

19. Despeckling SAR Images With Log-Yeo–Johnson Transformation and Conditional Diffusion Models

Author

Ma, Yaobin, Ke, Peng, Aghababaei, Hossein, Chang, Ling, and Wei, Jingbo

Abstract

Satellite images of synthetic aperture radar (SAR) sensors are contaminated by speckles from the coherent imaging mechanism. Although removing or mitigating speckle has been a critical issue for SAR applications, effective reduction continues to be a significant challenge for existing methods when preserving the intricate structures within SAR images. To address this issue, this work proposes a novel conditional diffusion model for SAR despeckling (DiffusionSAR). The new method explicitly learns data distributions by forward diffusion toward multiplicative gamma noise. The logarithmic and Yeo–Johnson (log-Yeo–Johnson) transformation are harnessed in preprocessing for fine-tuning or hybrid training. A prolonging steps technique is suggested in fine-tuning to match the preprocessing. A new synthetic dataset is designed for satellite SAR despeckling. The proposed method is compared with eight state-of-the-art methods using both synthetic and real-world SAR satellite images. The qualitative and quantitative evaluations confirm the effectiveness of the proposed method in structural preservation as well as noise reduction. A fine-tuning experiment using stacked multitemporal data shows the necessity of tine-tuning training in bridging the domain gap when trained with synthetic data and tested with real-world SAR data.

Published
2024
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29. Analytical Modeling of Air Gap Magnetic Fields and Bearing Force of a Novel Hybrid Magnetic Thrust Bearing

Author

Wei Jingbo, Hongjing Hu, Kun Liu, and Haoze Wang

Subjects
Physics, Bearing (mechanical), Magnetic domain, Mechanics, Magnetic flux, Electronic, Optical and Magnetic Materials, law.invention, Magnetic field, Thrust bearing, law, Magnet, Electrical and Electronic Engineering, Air gap (plumbing), Magnetic levitation
Abstract

In this article, an analytical method is presented for modeling the complex air gap field distribution and the magnetic force of a novel permanent magnet (PM) bias hybrid magnetic thrust bearing (HMTB). This bearing has a very compact structure and is proposed to replace the traditional magnetic thrust bearings (MTBs) for high-speed rotor systems. The proposed method introduces the notion of the complicated air gap field, calculated from the Schwarz–Christoffel transformation of the air gap geometry, to take into account the effect of slot fringing and leakage. As a result, accurate solutions of the flux distribution and the bearing force can be obtained, which shows good agreement with the results of the finite-element method (FEM). The prototype of the HMTB is designed, analyzed, and tested. The results of the analytical model are compared with experimental data.

Published
2021

33. UAV Image Stitching With Transformer and Small Grid Reformation.

Author

Cui, Zhiyuan, Tang, Rongxin, and Wei, Jingbo

Abstract

Due to parallax and inadequate key points, it is difficult to stitch unmanned aerial vehicle (UAV) images that are not rich in structure, which is addressed in this letter. Global matching is judged along with local similarity by a trained transformer, which provides the possibility of finding plenty of key points in low-feature regions. A new point matching constraint is designed based on the scores from the transformer. Line protection and distortion resistance are also used in local correction to alleviate global aberrations. The experiment shows that our method outperforms four state-of-the-art algorithms significantly, which reduces the position error by half in stitching inconspicuous features, such as woodland, bare land, and river. [ABSTRACT FROM AUTHOR]

Published
2023
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39. Analysis and Comparison of Armature Fields and Inductances in Various Topologies of Compulsators

Author

Haoze Wang, Wei Jingbo, Kun Liu, and Zhigang Wu

Subjects
Alternator (automotive), Nuclear and High Energy Physics, business.industry, Computer science, Electrical engineering, Compensated pulsed alternator, Pulsed power, Condensed Matter Physics, Network topology, 01 natural sciences, Energy storage, 010305 fluids & plasmas, law.invention, Inductance, law, Electromagnetic coil, 0103 physical sciences, business, Armature (electrical engineering)
Abstract

Compulsator provides an excellent approach to achieve compact energy storage and pulsed power generation for several multi-MJ, multi-GW applications, including electromagnetic launchers, directed energy systems, and fusion reactors. There is a continuous research effort toward increasing the power capability and compactness of this machine since its invention. In general, specific machine designs aim to maximize the output current and power by minimizing the transient inductance of the armature winding. The field and the inductance of the armature winding are some of the most important parameters in the compulsator design. This article presents the development of a generic method to analyze the magnetic fields and inductances of the armature windings in compulsators based on fundamental principles. It derives analytical models for inductance calculation in various types of alternators as unified terms of simplified formulas. These are used for the design, analysis, and optimization of all air-core, iron-core, compensated, and uncompensated pulsed alternators (PAs). By comparing the distribution of armature reaction fields and the self-inductances in compulsators having different configurations, this article investigates the basic relationships between the topology of the alternator and the fields and inductances. This is not limited only to the study of PAs but it can also be used in both slotless and air-core conventional machines.

Published
2020

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