arXiv subjects

Yining Zhang

Publications and source records attributed to Yining Zhang.

At least 37 records · Page 2Linked to original sources

arXiv2025

Quasiperiodic Slow-Propagating EUV "Wave" Trains After the Filament Eruption

The eruption of the filament/flux rope generates the coronal perturbations, which further form EUV waves. There are two types of EUV waves, including fast-mode magnetosonic waves and slow waves. In this paper, we first report an event showing the Quasiperiodic Slow-Propagating (QSP) EUV "wave" trains during an M6.4-class flare (SOL2023-02-25T18:40), using multiple observations from SDO/AIA, CHASE/HIS, ASO-S/FMG, SUTRI, and LASCO/C2. The QSP "wave" trains occurred as the filament showed a rapid rise. The QSP "wave" trains have the projected speeds of 50-130 km s$^{-1}$ on the plane of the sky, which is slower than the fast-mode magnetosonic speed in the solar corona. And the calculated period of the QSP wave trains is 117.9 s, which is in good agreement with the associated flare Quasi-Periodic Pulsation (140.3 s). The QSP wave trains could be observed during the entire impulsive phase of the flare and lasted about 30 minutes in the field of view (FOV) of SDO/AIA. About 30 minutes later, they appeared in the FOV of LASCO/C2 and propagated to the northwest. We suggest that the QSP wave trains are probably apparent waves that are caused by the successive stretching of the inclined field lines overlying the eruptive filament. The periodic pattern of the QSP wave trains may be related to the intermittent energy release during the flare.

astro-ph.SR↗

arXiv2025

Observation of edge and bulk states in a three-site Kitaev chain

A chain of quantum dots (QDs) in semiconductor-superconductor hybrid systems can form an artificial Kitaev chain hosting Majorana bound states (MBSs). These zero-energy states are expected to be localised on the edges of the chain, at the outermost QDs. The remaining QDs, comprising the bulk, are predicted to host an excitation gap that protects the MBSs at the edges from local on-site perturbations. Here we demonstrate this connection between the bulk and edges in a minimal system, by engineering a three-site Kitaev chain in a two-dimensional electron gas. Through direct tunneling spectroscopy on each site, we show that the appearance of stable zero-bias conductance peaks at the outer QDs is correlated with the presence of an excitation gap in the middle QD. Furthermore, we show that this gap can be controlled by applying a superconducting phase difference between the two hybrid segments and that the MBSs are robust only when the excitation gap is present. We find a close agreement between experiments and the original Kitaev model, thus confirming key predictions for MBSs in a three-site chain.

cond-mat.mes-hall↗

arXiv2025

Quasiperiodic Super-Alfvenic Slippage Along Flare Ribbons Observed by the Interface Region Imaging Spectrograph

The apparent slipping motion of flare loops is regarded as a key feature of the 3D magnetic reconnection in the solar flares. The slippage with a super-Alfvénic speed could be defined as slipping-running reconnection while the slippage with a sub-Alfvénic speed is called slipping reconnection. Due to the limitation of the observational instrument temporal resolution, the apparent slippage of the flare loop footpoints along the flare ribbons with super-Alfvénic speed is quite rare to our knowledge. In this paper, we report a unique event that exhibits not only the sub-Alfvénic slippage, but also the quasiperiodic super-Alfvénic slippage of ribbon substructures during a C3.4-class flare (SOL2023-01-18-T15:23), using the high temporal resolution observations of the Interface Region Imaging Spectrograph ($\sim$2 s). The super-Alfvénic slippage with a speed of up to $\sim$ 1688 km s$^{-1}$ is directly observed in this study. The calculated period of the apparent super-Alfvénic slippage in both ribbons is between 8.4 and 11.9 seconds. This work provides the first observational evidence of the periodicity for the slipping-running magnetic reconnection.

astro-ph.SR↗

arXiv2025

A flux-controlled two-site Kitaev chain

In semiconducting-superconducting hybrid devices, Andreev bound states (ABSs) can mediate the coupling between quantum dots (QDs), allowing for the realisation of artificial Kitaev chains. In order to engineer Majorana bound states (MBSs) in these systems, one must control the energy of the ABSs. In this work, we show how extended ABSs in a flux tunable Josephson junction can be used to control the coupling between distant quantum dots separated by $\approx$ 1 $\mathrmμ$m. In particular, we demonstrate that the combination of electrostatic control and phase control over the ABSs significantly increases the parameter space in which MBSs are observed. Finally, by employing an additional spectroscopic probe in the hybrid region between the QDs, we gain information about the spatial distribution of the Majorana wave function in a two-site Kitaev chain.

cond-mat.mes-hall↗

arXiv2024

Arti-PG: A Toolbox for Procedurally Synthesizing Large-Scale and Diverse Articulated Objects with Rich Annotations

The acquisition of substantial volumes of 3D articulated object data is expensive and time-consuming, and consequently the scarcity of 3D articulated object data becomes an obstacle for deep learning methods to achieve remarkable performance in various articulated object understanding tasks. Meanwhile, pairing these object data with detailed annotations to enable training for various tasks is also difficult and labor-intensive to achieve. In order to expeditiously gather a significant number of 3D articulated objects with comprehensive and detailed annotations for training, we propose Articulated Object Procedural Generation toolbox, a.k.a. Arti-PG toolbox. Arti-PG toolbox consists of i) descriptions of articulated objects by means of a generalized structure program along with their analytic correspondence to the objects' point cloud, ii) procedural rules about manipulations on the structure program to synthesize large-scale and diverse new articulated objects, and iii) mathematical descriptions of knowledge (e.g. affordance, semantics, etc.) to provide annotations to the synthesized object. Arti-PG has two appealing properties for providing training data for articulated object understanding tasks: i) objects are created with unlimited variations in shape through program-oriented structure manipulation, ii) Arti-PG is widely applicable to diverse tasks by easily providing comprehensive and detailed annotations. Arti-PG now supports the procedural generation of 26 categories of articulate objects and provides annotations across a wide range of both vision and manipulation tasks, and we provide exhaustive experiments which fully demonstrate its advantages. We will make Arti-PG toolbox publicly available for the community to use.

cs.CV↗

arXiv2024

ConceptFactory: Facilitate 3D Object Knowledge Annotation with Object Conceptualization

We present ConceptFactory, a novel scope to facilitate more efficient annotation of 3D object knowledge by recognizing 3D objects through generalized concepts (i.e. object conceptualization), aiming at promoting machine intelligence to learn comprehensive object knowledge from both vision and robotics aspects. This idea originates from the findings in human cognition research that the perceptual recognition of objects can be explained as a process of arranging generalized geometric components (e.g. cuboids and cylinders). ConceptFactory consists of two critical parts: i) ConceptFactory Suite, a unified toolbox that adopts Standard Concept Template Library (STL-C) to drive a web-based platform for object conceptualization, and ii) ConceptFactory Asset, a large collection of conceptualized objects acquired using ConceptFactory suite. Our approach enables researchers to effortlessly acquire or customize extensive varieties of object knowledge to comprehensively study different object understanding tasks. We validate our idea on a wide range of benchmark tasks from both vision and robotics aspects with state-of-the-art algorithms, demonstrating the high quality and versatility of annotations provided by our approach. Our website is available at https://apeirony.github.io/ConceptFactory.

cs.CV↗

arXiv2024

Quasi-periodic oscillations of flare loops and slipping motion of ribbon substructures during a C-class flare

Quasi-periodic oscillations in solar flaring emission have been observed over the past few decades. To date, the underpinning processes resulting in the quasi-periodic oscillations remain unknown. In this paper, we report a unique event that exhibits both the long-duration quasi-periodic intensity oscillations of flare loops and the quasi-periodic slipping motion of ribbon substructures during a C9.1-class flare (SOL2015-03-15-T01:15), using the observations from Solar Dynamics Observatory and Interface Region Imaging Spectrograph. The high-temperature flare loops rooted in the straight part of ribbons display a "bright-dim" intensity oscillation, with a period of about 4.5 minutes. The oscillation starts just after the flare onset and lasts over 3 hours. Meanwhile, the substructures within the ribbon tip display the quasi-periodic slipping motion along the ribbon at 1400 Åimages which has a similar periodicity to the stationary intensity oscillation of the flare loops in the straight part of the flare ribbons. We suggest that the quasi-periodic pattern is probably related to the loop-top dynamics caused by the reconnection outflow impinging on the flare loops.

astro-ph.SR↗

arXiv2024

Spatial dependence of local density of states in semiconductor-superconductor hybrids

Majorana bound states are expected to appear in one-dimensional semiconductor-superconductor hybrid systems, provided they are homogenous enough to host a global topological phase. In order to experimentally investigate the uniformity of the system, we study the spatial dependence of the local density of states in multiprobe devices where several local tunnelling probes are positioned along a gate-defined wire in a two-dimensional electron gas. Spectroscopy at each probe reveals a hard induced gap, and an absence of subgap states at zero magnetic field. However, subgap states emerging at finite magnetic field are not always correlated between different probes. Moreover, we find that the extracted critical field and effective $g$-factor of the lowest energy subgap state varies significantly across the length of the wire. Upon studying several such devices we do however find examples of striking correlations in the local density of states measured at different tunnel probes. We discuss possible sources of variations across devices.

cond-mat.mes-hall↗

arXiv2024

The Solar Origin of an Intense Geomagnetic Storm on 2023 December 1st: Successive Slipping and Eruption of Multiple Magnetic Flux Ropes

The solar eruption that occurred on 2023 November 28 (SOL2023-11-28) triggered an intense geomagnetic storm on Earth on 2023 December 1. The associated Earth's auroras manifested at the most southern latitudes in the northern hemisphere observed in the past two decades. In order to explore the profound geoeffectiveness of this event, we conducted a comprehensive analysis of its solar origin to offer potential factors contributing to its impact. Magnetic flux ropes (MFRs) are twisted magnetic structures recognized as significant contributors to coronal mass ejections (CMEs), thereby impacting space weather greatly. In this event, we identified multiple MFRs in the solar active region and observed distinct slipping processes of the three MFRs: MFR1, MFR2, and MFR3. All three MFRs exhibit slipping motions at a speed of 40--137 km s$^{-1}$, extending beyond their original locations. Notably, the slipping of MFR2 extends to $\sim$30 Mm and initiate the eruption of MFR3. Ultimately, MFR1's eruption results in an M3.4-class flare and a CME, while MFR2 and MFR3 collectively produce an M9.8-class flare and another halo CME. This study shows the slipping process in a multi-MFR system, showing how one MFR's slipping can trigger the eruption of another MFR. We propose that the CME--CME interactions caused by multiple MFR eruptions may contribute to the significant geoeffectiveness.

astro-ph.SR↗

arXiv2024

Many-body Localization Transition of Ising Spin-1 Chains

In this paper, we theoretically investigate the many-body localization properties of one-dimensional Ising spin-1 chains by using the methods of exact matrix diagonalization. We compare it with the MBL properties of the Ising spin-1/2 chains. The results indicate that the one-dimensional Ising spin-1 chains can also undergo MBL phase transition. There are various forms of disorder, and we compare the effects of different forms of quasi-disorder and random disorder on many-body localization in this paper. First, we calculate the exctied-state fidelity to study the MBL phase transtion. By changing the form of the quasi-disorder, we study the MBL transition of the system with different forms of quasi-disorder and compare them with those of the random disordered system. The results show that both random disorder and quasi-disorder can cause the MBL phase transition in the one-dimensional Ising spin-1 chains. In order to study the effect of spin interactions, we compare Ising spin-1 chains and spin-1/2 chains with the next-nearest-neighbour(N-N) two-body interactions and the next-next-nearest-neighbour (N-N-N)interactions. The results show that the critical point increases with the addition of the interaction. Then we study the dynamical properties of the model by the dynamical behavior of diagonal entropy (DE), local magnetization and the time evolution of fidelity to further prove the occurrence of MBL phase transition in the disordered Ising spin-1 chains with the (N-N) coupling term and distinguish the ergodic phase (thermal phase) and the many-body localized phase. Lastly, we delve into the impact of periodic driving on one-dimensional Ising spin-1 chains. And we compare it with the results obtained from the Ising spin-1/2 chains. It shows that periodic driving can cause Ising spin-1 chains and Ising spin-1/2 chains to occur the MBL transition.

cond-mat.dis-nn↗

arXiv2024

STAR-RIS Assisted Wireless-Powered and Backscattering Mobile Edge Computing Networks

Wireless powered and backscattering mobile edge computing (WPB-MEC) network is a novel network paradigm to supply energy supplies and computing resource to wireless sensors (WSs). However, its performance is seriously affected by severe attenuations and inappropriate assumptions of infinite computing capability at the hybrid access point (HAP). To address the above issues, in this paper, we propose a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) aided scheme for boosting the performance of WPB-MEC network under the constraint of finite computing capability. Specifically, energy-constrained WSs are able to offload tasks actively or passively from them to the HAP. In this process, the STAR-RIS is utilized to improve the quantity of harvested energy and strengthen the offloading efficiency by adapting its operating protocols. We then maximize the sum computational bits (SCBs) under the finite computing capability constraint. To handle the solving challenges, we first present interesting results in closed-form and then design a block coordinate descent (BCD) based algorithm, ensuring a near-optimal solution. Finally, simulation results are provided to confirm that our proposed scheme can improve the SCBs by 9.9 times compared to the local computing only scheme.

eess.SP↗

arXiv2024

Survey of Magnetic Field Parameters Associated With Large Solar Flares

Until now, how the magnetic fields in M/X-class flaring active regions (ARs) differ from C-class flaring ARs remains unclear. Here, we calculate the key magnetic field parameters within the area of high photospheric free energy density (HED region) for 323 ARs (217 C- and 106 M$/$X-flaring ARs), including total photospheric free magnetic energy density E$_{free}$, total unsigned magnetic flux $Φ$$_{HED}$, mean unsigned current helicity h$_{c}$, length of the polarity inversion lines $L$$_{PIL}$ with a steep horizontal magnetic gradient, etc., and compare these with flare/coronal mass ejection (CME) properties. We first show the quantitative relations among the flare intensity, the eruptive character and $Φ$$_{HED}$. We reveal that $Φ$$_{HED}$ is a measure for the GOES flux upper limit of the flares in a given region. For a given $Φ$$_{HED}$, there exists the lower limit of F$_\mathrm{SXR}$ for eruptive flares. This means that only the relatively strong flares with the large fraction of energy release compared to the total free energy are likely to generate a CME. We also find that the combinations of E$_{free}$-$L$$_{PIL}$ and E$_{free}$-h$_{c}$ present a good ability to distinguish between C-class and M$/$X-class flaring ARs. Using determined critical values of E$_{free}$ and $L$$_{PIL}$, one predicts correctly 93 out of 106 M/X-class flaring ARs and 159/217 C-class flaring ARs. The large $L$$_{PIL}$ or h$_{c}$ for M$/$X-class flaring ARs probably implies the presence of a compact current with twisted magnetic fields winding about it.

astro-ph.SR↗

arXiv2024

Signatures of Majorana protection in a three-site Kitaev chain

Majorana zero modes (MZMs) are non-Abelian excitations predicted to emerge at the edges of topological superconductors. One proposal for realizing a topological superconductor in one dimension involves a chain of spinless fermions, coupled through $p$-wave superconducting pairing and electron hopping. This concept is also known as the Kitaev chain. A minimal two-site Kitaev chain has recently been experimentally realized using quantum dots (QDs) coupled through a superconductor. In such a minimal chain, MZMs are quadratically protected against global perturbations of the QD electrochemical potentials. However, they are not protected from perturbations of the inter-QD couplings. In this work, we demonstrate that extending the chain to three sites offers greater protection than the two-site configuration. The enhanced protection is evidenced by the stability of the zero-energy modes, which is robust against variations in both the coupling amplitudes and the electrochemical potential variations in the constituent QDs. While our device offers all the desired control of the couplings it does not allow for superconducting phase control. Our experimental observations are in good agreement with numerical simulated conductances with phase averaging. Our work pioneers the development of longer Kitaev chains, a milestone towards topological protection in QD-based chains.

cond-mat.supr-con↗

arXiv2024

Empowering CAM-Based Methods with Capability to Generate Fine-Grained and High-Faithfulness Explanations

Recently, the explanation of neural network models has garnered considerable research attention. In computer vision, CAM (Class Activation Map)-based methods and LRP (Layer-wise Relevance Propagation) method are two common explanation methods. However, since most CAM-based methods can only generate global weights, they can only generate coarse-grained explanations at a deep layer. LRP and its variants, on the other hand, can generate fine-grained explanations. But the faithfulness of the explanations is too low. To address these challenges, in this paper, we propose FG-CAM (Fine-Grained CAM), which extends CAM-based methods to enable generating fine-grained and high-faithfulness explanations. FG-CAM uses the relationship between two adjacent layers of feature maps with resolution differences to gradually increase the explanation resolution, while finding the contributing pixels and filtering out the pixels that do not contribute. Our method not only solves the shortcoming of CAM-based methods without changing their characteristics, but also generates fine-grained explanations that have higher faithfulness than LRP and its variants. We also present FG-CAM with denoising, which is a variant of FG-CAM and is able to generate less noisy explanations with almost no change in explanation faithfulness. Experimental results show that the performance of FG-CAM is almost unaffected by the explanation resolution. FG-CAM outperforms existing CAM-based methods significantly in both shallow and intermediate layers, and outperforms LRP and its variants significantly in the input layer. Our code is available at https://github.com/dongmo-qcq/FG-CAM.

cs.CV↗

arXiv2023

Zero-Shot Compositional Policy Learning via Language Grounding

Despite recent breakthroughs in reinforcement learning (RL) and imitation learning (IL), existing algorithms fail to generalize beyond the training environments. In reality, humans can adapt to new tasks quickly by leveraging prior knowledge about the world such as language descriptions. To facilitate the research on language-guided agents with domain adaption, we propose a novel zero-shot compositional policy learning task, where the environments are characterized as a composition of different attributes. Since there are no public environments supporting this study, we introduce a new research platform BabyAI++ in which the dynamics of environments are disentangled from visual appearance. At each episode, BabyAI++ provides varied vision-dynamics combinations along with corresponding descriptive texts. To evaluate the adaption capability of learned agents, a set of vision-dynamics pairings are held-out for testing on BabyAI++. Unsurprisingly, we find that current language-guided RL/IL techniques overfit to the training environments and suffer from a huge performance drop when facing unseen combinations. In response, we propose a multi-modal fusion method with an attention mechanism to perform visual language-grounding. Extensive experiments show strong evidence that language grounding is able to improve the generalization of agents across environments with varied dynamics.

cs.LG↗

arXiv2022

Two-dimensional modeling of the tearing-mode-governed magnetic reconnection in the large-scale current sheet above the two-ribbon flare

We attempt to model magnetic reconnection during the two-ribbon flare in the gravitationally stratified solar atmosphere with the Lundquist number of $S=10^6$ using 2D simulations. We found that the tearing mode instability leads to the inhomogeneous turbulence inside the reconnecting current sheet (CS) and invokes the fast phase of reconnection. Fast reconnection brings an extra dissipation of magnetic field which enhances the reconnection rate in an apparent way. The energy spectrum in the CS shows the power-law pattern and the dynamics of plasmoids governs the associated spectral index. We noticed that the energy dissipation occurs at a scale $l_{ko}$ of 100-200~km, and the associated CS thickness ranges from 1500 to 2500~km, which follows the Taylor scale $l_T=l_{ko} S^{1/6}$. The termination shock(TS) appears in the turbulent region above flare loops, which is an important contributor to heating flare loops. Substantial magnetic energy is converted into both kinetic and thermal energies via TS, and the cumulative heating rate is greater than the rate of the kinetic energy transfer. In addition, the turbulence is somehow amplified by TS, of which the amplitude is related to the local geometry of the TS.

astro-ph.SR↗

arXiv2021

Curved Koszul duality and cyclic (co)homology

We study the curved Koszul duality theory for associative algebras presented by quadratic-linear-constant (QLC) relations. As an application, we investigate the cyclic (co)homology of a QLC algebra and its Koszul dual curved DG algebra, and extend a result due to Feigin and Tsygan. We also study a commutative/Lie analog of this curved Koszul duality theory.

math.RA↗

arXiv2021

Stock index futures trading impact on spot price volatility. The CSI 300 studied with a TGARCH model

A TGARCH modeling is argued to be the optimal basis for investigating the impact of index futures trading on spot price variability. We discuss the CSI-300 index (China-Shanghai-Shenzhen-300-Stock Index) as a test case. The results prove that the introduction of CSI-300 index futures (CSI-300-IF) trading significantly reduces the volatility in the corresponding spot market. It is also found that there is a stationary equilibrium relationship between the CSI-300 spot and CCSI-300-IF markets. A bidirectional Granger causality is also detected. ''Finally'', it is deduced that spot prices are predicted with greater accuracy over a 3 or 4 lag day time span.

q-fin.ST↗