arXiv subjects

Hu Jiang

Publications and source records attributed to Hu Jiang.

5 recordsLinked to original sources

arXiv2025

The Solar Close Observations and Proximity Experiments (SCOPE) mission

The Solar Close Observations and Proximity Experiments (SCOPE) mission will send a spacecraft into the solar atmosphere at a low altitude of just 5 R_sun from the solar center. It aims to elucidate the mechanisms behind solar eruptions and coronal heating, and to directly measure the coronal magnetic field. The mission will perform in situ measurements of the current sheet between coronal mass ejections and their associated solar flares, and energetic particles produced by either reconnection or fast-mode shocks driven by coronal mass ejections. This will help to resolve the nature of reconnections in current sheets, and energetic particle acceleration regions. To investigate coronal heating, the mission will observe nano-flares on scales smaller than 70 km in the solar corona and regions smaller than 40 km in the photosphere, where magnetohydrodynamic waves originate. To study solar wind acceleration mechanisms, the mission will also track the process of ion charge-state freezing in the solar wind. A key achievement will be the observation of the coronal magnetic field at unprecedented proximity to the solar photosphere. The polar regions will also be observed at close range, and the inner edge of the solar system dust disk may be identified for the first time. This work presents the detailed background, science, and mission concept of SCOPE and discusses how we aim to address the questions mentioned above.

astro-ph.SR↗

arXiv2023

MindOpt Tuner: Boost the Performance of Numerical Software by Automatic Parameter Tuning

Numerical software is usually shipped with built-in hyperparameters. By carefully tuning those hyperparameters, significant performance enhancements can be achieved for specific applications. We developed MindOpt Tuner, a new automatic tuning tool that supports a wide range of numerical software, including optimization and other solvers. MindOpt Tuner uses elastic cloud resources, features a web-based task management panel and integration with ipython notebook with both command-line tools and Python APIs. Our experiments with COIN-OR Cbc, an open-source mixed-integer optimization solver, demonstrate remarkable improvements with the tuned parameters compared to the default ones on the MIPLIB2017 test set, resulting in over 100x acceleration on several problem instances. Additionally, the results demonstrate that Tuner has a higher tuning efficiency compared to the state-of-the-art automatic tuning tool SMAC3.

cs.MS↗

arXiv2021

CLT for LSS of sample covariance matrices with unbounded dispersions

Under the high-dimensional setting that data dimension and sample size tend to infinity proportionally, we derive the central limit theorem (CLT) for linear spectral statistics (LSS) of large-dimensional sample covariance matrix. Different from existing literature, our results do not require the assumption that the population covariance matrices are bounded. Moreover, many common kernel functions in the real data such as logarithmic functions and polynomial functions are allowed in this paper. In our model, the number of spiked eigenvalues can be fixed or tend to infinity. One salient feature of the asymptotic mean and covariance in our proposed central limit theorem is that it is related to the divergence order of the population spectral norm.

math.ST↗

arXiv2019

Anisotropic Charge Carrier and Coherent Acoustic Phonon Dynamics of Black Phosphorus Studied by Transient Absorption Microscopy

Due to its corrugated hexagonal lattice structure, Black phosphorus (BP) has unique anisotropic physical properties, which provides an additional freedom for designing devices. Many body interactions, including interactions with phonon, is crucial for heat dissipation and charge carrier mobility in device. However, the rich properties of the coherent acoustic phonon, including anisotropy, propagation and generation were not fully interrogated. In this paper, the polarization-resolved transient absorption microscopy was conducted on BP flakes to study the dynamics of photoexcited charge carriers and coherent acoustic phonon. Polarization-resolved transient absorption images and traces were recorded and showed anisotropic and thickness-dependent charge carriers decay dynamics. The damping of the coherent acoustic phonon oscillation was found to be anisotropic, which was attributed to the polarization-dependent absorption length of the probe pulse. From the analysis of initial oscillation amplitude and phase of coherent acoustic phonon oscillation, we proposed that the direct deformation potential mechanism dominated the generation of coherent acoustic phonons in our experiment. Besides, we obtained the sound velocity of the coherent acoustic phonon from the oscillation frequency and the acoustic echo, respectively, which agreed well with each other. These findings provide significant insights into the rich acoustic phonon properties of BP, and promise important application for BP in polarization-sensitive optical and optoelectronic devices.

physics.chem-ph↗

arXiv2019

A Facile Method for Precise Layer Number Identification of Two-Dimensional Materials through Optical Images

Optical microscopy is believed to be an efficient method for identifying layer number of two-dimensional 2D materials. However, since illuminants, cameras and their parameters are different from lab to lab, it is impossible to identify layer numbers just by comparing a given optical image with standard or calculated images under standard conditions. Here we reported an image reconstruction method, converting raw optical images acquired by arbitrary illuminants and cameras into reconstructed images at specified illuminant and specified camera. After image reconstruction, the color differences of each layer number roughly equaled those calculated under specified condition. By comparing the color differences in reconstructed image with those calculated under specified condition, the layer numbers of 2D materials in our lab and published papers, including MoS2, WS2 and WSe2, were ambiguously identified. This study makes optical microscopy a precise method for identifying layer numbers of 2D materials on known substrate.

cond-mat.mtrl-sci↗