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Heping Li

Publications and source records attributed to Heping Li.

8 recordsLinked to original sources

WILD-SAM: Phase-Aware Expert Adaptation of SAM for Landslide Detection in Wrapped InSAR Interferograms

Detecting slow-moving landslides directly from wrapped Interferometric Synthetic Aperture Radar (InSAR) interferograms is crucial for efficient geohazard monitoring, yet it remains fundamentally challenged by severe phase ambiguity and complex coherence noise. While the Segment Anything Model (SAM) offers a powerful foundation for segmentation, its direct transfer to wrapped phase data is hindered by a profound spectral domain shift, which suppresses the high-frequency fringes essential for boundary delineation. To bridge this gap, we propose WILD-SAM, a novel parameter-efficient fine-tuning framework specifically designed to adapt SAM for high-precision landslide detection on wrapped interferograms. Specifically, the architecture integrates a Phase-Aware Mixture-of-Experts (PA-MoE) Adapter into the frozen encoder to align spectral distributions and introduces a Wavelet-Guided Subband Enhancement (WGSE) strategy to generate frequency-aware dense prompts. The PA-MoE Adapter exploits a dynamic routing mechanism across heterogeneous convolutional experts to adaptively aggregate multi-scale spectral-textural priors, effectively aligning the distribution discrepancy between natural images and interferometric phase data. Meanwhile, the WGSE strategy leverages discrete wavelet transforms to explicitly disentangle high-frequency subbands and refine directional phase textures, injecting these structural cues as dense prompts to ensure topological integrity along sharp landslide boundaries. Extensive experiments on the ISSLIDE and ISSLIDE+ benchmarks demonstrate that WILD-SAM achieves state-of-the-art performance, significantly outperforming existing methods in both target completeness and contour fidelity.

cs.CV

Two-Dimensional Altermagnetism in Epitaxial CrSb Ultrathin Films

Altermagnets constitute an emerging class of collinear magnets that exhibit zero net magnetization yet host spin-split electronic bands arising from non-relativistic spin-space-group symmetries. Realization of altermagnetism in the two-dimensional (2D) limit remains an outstanding challenge because dimensional reduction suppresses kZ dispersion and destabilizes the symmetry operations essential for spin compensation. Here, we investigate ultrathin CrSb films grown epitaxially on Bi2Te3 substrate and uncover the evolution of altermagnetism in the 2D limit. Scanning tunneling microscopy (STM), quasiparticle interference (QPI), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations show that interfacial symmetry breaking in the one-unit-cell (1 UC) limit gives rise to localized electronic states and uncompensated magnetic moments. These interfacial effects become weakened from 7/4 UC, accompanied by the recovery of a bulk-like coordination environment and the emergence of altermagnetic electronic characteristics. Our results show that the essential altermagnetic electronic structure of CrSb survives at a thickness of only ~1.05 nm, demonstrating the robustness of altermagnetism in the 2D limit and opening opportunities for integrating stray-field-free spin order into low dimensional spintronic architectures.

cond-mat.mtrl-sci

Training Self-Supervised Depth Completion Using Sparse Measurements and a Single Image

Depth completion is an important vision task, and many efforts have been made to enhance the quality of depth maps from sparse depth measurements. Despite significant advances, training these models to recover dense depth from sparse measurements remains a challenging problem. Supervised learning methods rely on dense depth labels to predict unobserved regions, while self-supervised approaches require image sequences to enforce geometric constraints and photometric consistency between frames. However, acquiring dense annotations is costly, and multi-frame dependencies limit the applicability of self-supervised methods in static or single-frame scenarios. To address these challenges, we propose a novel self-supervised depth completion paradigm that requires only sparse depth measurements and their corresponding image for training. Unlike existing methods, our approach eliminates the need for dense depth labels or additional images captured from neighboring viewpoints. By leveraging the characteristics of depth distribution, we design novel loss functions that effectively propagate depth information from observed points to unobserved regions. Additionally, we incorporate segmentation maps generated by vision foundation models to further enhance depth estimation. Extensive experiments demonstrate the effectiveness of our proposed method.

cs.CV

Absence of dehydration due to superionic transition at Earth's core-mantle boundary

The properties and stability of hydrous phases are key to unraveling the mysteries of the water cycle in Earth's interior. Under the deep lower mantle conditions, hydrous phases transition into a superionic state. However, the influence of the superionic effect on their stability and dehydration processes remains poorly understood. Using ab initio calculations and deep-learning potential molecular dynamics simulations, we discovered a doubly superionic transition in delta-AlOOH, characterized by the highly diffusive behavior of ionic hydrogen and aluminum within the oxygen sub-lattice. These highly diffusive elements contribute significant external entropy into the system, resulting in exceptional thermostability. Free energy calculations indicate that dehydration is energetically and kinetically unfavorable when water exists in a superionic state under core-mantle boundary (CMB) conditions. Consequently, water can accumulate in the deep lower mantle over Earth's history. This deep water reservoir plays a crucial role in the global deep water and hydrogen cycles.

physics.geo-ph

Broadband microwave waveform generation with programmable chirp shapes via recirculating phase-modulated optical fiber loop controlled by low-speed electronics

Broadband microwave waveforms with programmable chirp shapes are captivating in numerous practical applications. Compared with electronic technology, photonic-assisted solutions exhibit excellent performance in bandwidth and flexibility, but still suffer from complex architecture and requirement of high-speed electronics. Besides, rapid manipulation of chirp shape is still a challenge in the scientific community. In this paper, we propose and demonstrate a novel concept for generating broadband microwave waveforms with programmable chirp shapes. This concept is realized on a simple fiber-optic platform involving a continuous-wave laser source, a recirculating phase-modulated optical fiber loop, and low-speed electronics with a sampling rate at the level of MS/s. Based on this method, chirped microwave waveforms with a bandwidth up to tens of GHz can be generated, where the chirp shape is identical to the low-frequency driving waveform of the recirculating phase-modulated optical fiber loop. In addition, all the parameters of the generated chirped microwave waveforms can be easily reconfigured in real time, including the bandwidth, the central frequency, and the temporal duration. In the experiment, broadband microwave waveforms with customized chirp shapes are generated, where the center frequency and bandwidth tuning ranges exceed 21 GHz, the temporal duration is tuned in the range of 9 ns to 180 ns, and the coherent time of the generated microwave waveform is larger than 100 {\mu}s. This simple fiber-optic platform paves a way to generate broadband microwave waveforms with user-definable chirp shapes, which can find applications in broadband radar systems, electronic warfare and wireless communications.

physics.optics

Image Based Camera Localization: an Overview

Recently, virtual reality, augmented reality, robotics, autonomous driving et al attract much attention of both academic and industrial community, in which image based camera localization is a key task. However, there has not been a complete review on image-based camera localization. It is urgent to map this topic to help people enter the field quickly. In this paper, an overview of image based camera localization is presented. A new and complete kind of classifications for image based camera localization is provided and the related techniques are introduced. Trends for the future development are also discussed. It will be useful to not only researchers but also engineers and other people interested.

cs.CV

Three photon absorption in ZnO and ZnS crystals

We report a systematic investigation of both three-photon absorption (3PA)spectra and wavelength dispersions of Kerr-type nonlinear refraction in wide-gap semiconductors. The Z-scan measurements are recorded for both ZnO and ZnS with femtosecond laser pulses. While the wavelength dispersions of the Kerr nonlinearity are in agreement with a two-band model, the wavelength dependences of the 3PA are found to be given by (3Ephoton/Eg-1)5/2(3Ephoton/Eg)-9. We also evaluate higher-order nonlinear optical effects including the fifth-order instantaneous nonlinear refraction associated with virtual three-photon transitions, and effectively seventh-order nonlinear processes induced by three-photon-excited free charge carriers. These higher-order nonlinear effects are insignificant with laser excitation irradiances up to 40 GW/cm2. Both pump-probe measurements and three-photon figures of merits demonstrate that ZnO and ZnS should be a promising candidate for optical switching applications at telecommunication wavelengths.

cond-mat.mtrl-sci

Observation of Interband Two-Photon Absorption Saturation in CdS Nanocrystals

We report the observation of interband two-photon absorption (TPA) saturation in cadmium sulfide nanocrystals (CdS NCs) under intense femtosecond laser excitation with 1.6-eV photon energy. The observation has been compared to interband TPA saturation in bulk CdS under the same experimental conditions. By using both Z-scan technique and transient absorption measurement, the saturation intensity has been determined to be 190 GW/cm^2 for CdS NCs of 4-nm diameter, which shows two orders of magnitude greater than that for CdS bulk crystal. The results are in agreement with an inhomogeneously-broadened, saturated TPA model.

cond-mat.mtrl-sci