arXiv subjects

Lin Han

Publications and source records attributed to Lin Han.

At least 19 recordsLinked to original sources

arXiv2025

SN 2022acko: a low-luminosity SNe IIP with signs of early circumstellar interaction

We present optical-ultraviolet photometry and optical spectra for the type II supernova (SN) 2022acko. The spectroscopic observations span phases from $\sim$ 1.5 to $\sim$ 60 days after the explosion, while the light curve was observed up to $\sim$ 300 days. The V-band peak is $-15.5 \pm 0.3$ mag, suggesting that SN 2022acko is a low-luminosity SN II (LLSN). The overall observed properties of SN 2022acko are consistent with those produced by a lower mass progenitor ($\rm M_{ZAMS} \sim $9-10M$_{\odot}$). The spectra at $t=1.5$d and $t=2.5$d exhibit a broad emission feature peaking near 4600 \AA (the ``ledge'' feature), which we interpret as blueshifted He II 4686 \AA lines arising from the ionized ejecta. Moreover, a possible flash-ionized (FI) emission line of H$\alpha$ (FWHM $\sim 1100\ \rm km \ s^{-1}$) was superposed on the broad emission component of H$\alpha$ P-Cgyni profile in the $t=1.5$d spectrum. Assuming an ejecta velocity of $\rm 12000\ km\ s^{-1}$, the rapid disappearance of this narrow H$\alpha$ emission line within two days suggests highly confined CSM within $\sim \rm 2\times10^{14}\, cm$. Assuming a spherically symmetric CSM, the mass loss rate within this radius is estimated to be $\rm \sim 5 \times 10^{-4} M_{\odot} \ year^{-1}$ based on our hybrid light curve model. The early ``ledge'' feature observed in SN 2022acko have also been observed in other SNe II, suggesting that early-phase circumstellar interaction (CSI) is more common than previously thought.

astro-ph.HE↗

arXiv2025

Forecasting Australian Electricity Generation by Fuel Mix

Electricity demand and generation have become increasingly unpredictable with the growing share of variable renewable energy sources in the power system. Forecasting electricity supply by fuel mix is crucial for market operation, ensuring grid stability, optimizing costs, integrating renewable energy sources, and supporting sustainable energy planning. We introduce two statistical methods, centering on forecast reconciliation and compositional data analysis, to forecast short-term electricity supply by different types of fuel mix. Using data for five electricity markets in Australia, we study the forecast accuracy of these techniques. The bottom-up hierarchical forecasting method consistently outperforms the other approaches. Moreover, fuel mix forecasting is most accurate in power systems with a higher share of stable fossil fuel generation.

stat.AP↗

arXiv2024

Ferroelectricity in oxygen-terminated 2D carbides of lanthanide elements

We investigate the properties of oxygen-functionalized carbides of lanthanide elements with the composition M2CO2 (M=Gd, Tb,Dy) that form two-dimensional (2D) structures. Our ab initio calculations reveal that oxygen termination turns M2C monolayers into semiconductors with two dynamically stable phases. Of these, the energetically favored alpha-phase becomes ferroelectric, whereas the beta-phase turns anti-ferroelectric. Applying in-plane biaxial strain may transform one phase into the other, changes the ferroelectric polarization of the alpha-phase in a linear fashion, and modifies the size and nature of the fundamental band gap from direct to indirect. The structure with a direct band gap exhibits in-plane isotropic electronic and optical properties. This previously unexplored class of systems also exhibits excellent photon absorption in the ultraviolet range.

cond-mat.mtrl-sci↗

arXiv2023

LEO Satellite Networking Relaunched: Survey and Current Research Challenges

This document surveys recent and current developments in LEO satellite networking. It presents a brief overview of satellite networking in order to contextualize the issue. It then focuses on current research work in emerging domains, such as Machine Learning, SDN, low latency networking, green networking, Information-Centric Networks, etc. For each, it presents recent works and a direction of the research community within that emerging domain. The paper also describes the current state of standardization efforts in 3GPP and in IETF for LEO satellite networking. In particular, we present in some detail the direction these standards body are pointing towards for LEO networking with inter-satellites links. Finally, some future challenges and interesting research directions are described and motivated. This is an overview of the current state of the LEO satellite research in both academic and industrial standardization environments which we believe will be helpful to understand the current state of the art.

cs.NI↗

arXiv2023

Two-orbital spin-fermion model study of ferromagnetism in honeycomb lattice

The spin-fermion model was previously successful to describe the complex phase diagrams of colossal magnetoresistive manganites and iron-based superconductors. In recent years, two-dimensional magnets have rapidly raised up as a new attractive branch of quantum materials, which are theoretically described based on classical spin models in most studies. Alternatively, here the two-orbital spin-fermion model is established as a uniform scenario to describe the ferromagnetism in a two-dimensional honeycomb lattice. This model connects the magnetic interactions with the electronic structures. Then the continuous tuning of magnetism in these honeycomb lattices can be predicted, based on a general phase diagram. The electron/hole doping, from the empty $e_{g}$ to half-filled $e_{g}$ limit, is studied as a benchmark. Our Monte Carlo result finds that the ferromagnetic $T_{C}$ reaches the maximum at the quarter-filled case. In other regions, the linear relationship between $T_{C}$ and doping concentration provides a theoretical guideline for the experimental modulations of two-dimensional ferromagnetism tuned by ionic liquid or electrical gating.

cond-mat.str-el↗

arXiv2023

The Multi-modality Cell Segmentation Challenge: Towards Universal Solutions

Cell segmentation is a critical step for quantitative single-cell analysis in microscopy images. Existing cell segmentation methods are often tailored to specific modalities or require manual interventions to specify hyper-parameters in different experimental settings. Here, we present a multi-modality cell segmentation benchmark, comprising over 1500 labeled images derived from more than 50 diverse biological experiments. The top participants developed a Transformer-based deep-learning algorithm that not only exceeds existing methods but can also be applied to diverse microscopy images across imaging platforms and tissue types without manual parameter adjustments. This benchmark and the improved algorithm offer promising avenues for more accurate and versatile cell analysis in microscopy imaging.

eess.IV↗

arXiv2023

Segment Anything in Medical Images

Medical image segmentation is a critical component in clinical practice, facilitating accurate diagnosis, treatment planning, and disease monitoring. However, existing methods, often tailored to specific modalities or disease types, lack generalizability across the diverse spectrum of medical image segmentation tasks. Here we present MedSAM, a foundation model designed for bridging this gap by enabling universal medical image segmentation. The model is developed on a large-scale medical image dataset with 1,570,263 image-mask pairs, covering 10 imaging modalities and over 30 cancer types. We conduct a comprehensive evaluation on 86 internal validation tasks and 60 external validation tasks, demonstrating better accuracy and robustness than modality-wise specialist models. By delivering accurate and efficient segmentation across a wide spectrum of tasks, MedSAM holds significant potential to expedite the evolution of diagnostic tools and the personalization of treatment plans.

eess.IV↗

arXiv2023

Flux-Tunable Hybridization in a Double Quantum Dot Interferometer

A single electron shared between two levels threaded by a magnetic flux is an irreducibly simple quantum system in which interference is predicted to occur. We demonstrate tuning of the tunnel coupling between two such electronic levels with flux, implemented in a loop comprising two quantum dots. Using radio-frequency reflectometry of the dots' gate electrodes we extract the inter-dot coupling, which exhibits oscillations with a periodicity of one flux quantum. In different tunneling regimes we benchmark the oscillations' contrast, and find that their amplitude varies with the levels involved, while tunneling is generically not suppressed at oscillation minima. These results establish the feasibility and limitations of parity readout of qubits with tunnel couplings tuned by flux.

cond-mat.mes-hall↗

arXiv2023

Search for the singlet vector-like top quark in the $T\to tZ$ channel with $Z\to \nu\bar{\nu}$ at hadron colliders

Based on a simplified model including a singlet vector-like top quark $T$ with charge $|Q|=2/3$, we analyze the prospects of observing $T$ via the single $T$ production in the $tZ$ channel with $Z$ decaying to neutrinos at the hadron-hadron colliders. This simplified model only includes two free parameters, the coupling constant $g^*$ and the $T$ quark mass $m_T$. To investigate the observability of the single $T$ production, we perform a detailed background analysis and detector simulation for the collision energies 14~TeV, 27~TeV, and 100~TeV. We scan the $g^*-m_T$ parameter space and show the exclusion and discovery capabilities on the $T$ quark with the highest integrated luminosity designed at these colliders. Moreover, the limits from the narrow-width approximation and electroweak precision observables are considered.

hep-ph↗

arXiv2022

EISeg: An Efficient Interactive Segmentation Tool based on PaddlePaddle

In recent years, the rapid development of deep learning has brought great advancements to image and video segmentation methods based on neural networks. However, to unleash the full potential of such models, large numbers of high-quality annotated images are necessary for model training. Currently, many widely used open-source image segmentation software relies heavily on manual annotation which is tedious and time-consuming. In this work, we introduce EISeg, an Efficient Interactive SEGmentation annotation tool that can drastically improve image segmentation annotation efficiency, generating highly accurate segmentation masks with only a few clicks. We also provide various domain-specific models for remote sensing, medical imaging, industrial quality inspections, human segmentation, and temporal aware models for video segmentation. The source code for our algorithm and user interface are available at: https://github.com/PaddlePaddle/PaddleSeg.

cs.CV↗

arXiv2022

Quantum capacitance of a superconducting subgap state in an electrostatically floating dot-island

We study a hybrid device defined in an InAs nanowire with an epitaxial Al shell that consists of a quantum dot in contact with a superconducting island. The device is electrically floating, prohibiting transport measurements, but providing access to states that would otherwise be highly excited and unstable. Radio-frequency reflectometry with lumped-element resonators couples capacitatively to the quantum dot, and detects the presence of discrete subgap states. We perform a detailed study of the case with no island states, but with quantum-dot-induced subgap states controlled by the tunnel coupling. When the gap to the quasi-continuum of the excited states is small, the capacitance loading the resonator is strongly suppressed by thermal excitations, an effect we dub "thermal screening". The resonance frequency shift and changes in the quality factor at charge transitions can be accounted for using a single-level Anderson impurity model. The established measurement method, as well as the analysis and simulation framework, are applicable to more complex hybrid devices such as Andreev molecules or Kitaev chains.

cond-mat.mes-hall↗

arXiv2022

Unusual electric polarization behavior in elemental quasi-2D allotropes of selenium

We investigate tunable electric polarization and electronic structure of quasi-two-dimensional (quasi-2D) allotropes of selenium, which are formed from their constituent one-dimensional (1D) structures through an inter-chain interaction facilitated by the multi-valence nature of Se. Our em ab initio calculations reveal that different quasi-2D Se allotropes display different types of electric polarization, including ferroelectric (FE) polarization normal to the chain direction in alpha and delta allotropes, non-collinear ferrielectric (FiE) polarization along the chain axis in tau-Se, and anti-ferroelectric (AFE) polarization in eta-Se. The magnitude and direction of the polarization can be changed by a previously unexplored rotation of the constituent chains. In that case, an in-plane polarization direction may change to out-of-plane in alpha-Se and delta-Se, flip its direction, and even disappear in tau-Se. Also, the band gap may be reduced and changed from indirect to direct by rotating the constituent chains about their axes in these quasi-2D Se allotropes.

cond-mat.mtrl-sci↗

arXiv2022

Ferroelectricity induced by the absorption of water molecules on double helix SnIP

We study the ferroelectricity in a one-dimensional system composed of a double helix SnIP with absorbing water molecules. Our ab initio calculations reveal two factors that are critical to the electrical polarization. The first one is the orientation of polarized water molecules staying in the R2 region of SnIP. The second one is the displacement of I atom which roots from subtle interaction with absorbed water molecules. A reasonable scenario of polarization flipping is proposed in this study. In the scenario, the water molecule is rolling-up with keeping the magnitude of its electrical dipole and changing its direction, meanwhile, the displacement of I atoms is also reversed. Highly tunable polarization can be achieved by applying strain, with 26.5% of polarization enhancement by applying tensile strain, with only 4% degradation is observed with 4% compressive strain. Finally, the direct band gap is also found to be correlated with strain.

cond-mat.mtrl-sci↗

arXiv2022

Controllable Single Cooper Pair Splitting in Hybrid Quantum Dot Systems

Cooper pair splitters hold utility as a platform for investigating the entanglement of electrons in Cooper pairs, but probing splitters with voltage-biased Ohmic contacts prevents the retention of electrons from split pairs since they can escape to the drain reservoirs. We report the ability to controllably split and retain single Cooper pairs in a multi-quantum-dot device isolated from lead reservoirs, and separately demonstrate a technique for detecting the electrons emerging from a split pair. First, we identify a coherent Cooper pair splitting charge transition using dispersive gate sensing at GHz frequencies. Second, we utilize a double quantum dot as an electron parity sensor to detect parity changes resulting from electrons emerging from a superconducting island.

cond-mat.mes-hall↗

arXiv2022

Single production of vector-like $T$ quark at future high-energy linear $e^{+}e^{-}$ collider

Based on a model-independent framework including the vector-like top partner (VLQ-$T$), we investigate the prospect of discovering the singlet or doublet VLQ-$T$ via the single production process $e^{-}e^{+}\to T\bar{t}+t\bar{T}$ with the $T\to Zt$ decay channel at future high energy linear $e^{+}e^{-}$ collider with $\sqrt{s}=3$ TeV. We focus on the hadronic decay of the top quark and two types of decay channel for the $Z$ boson: $Z\to \ell^{+}\ell^{-}$ and $Z\to \nu\bar{\nu}$. By carrying out a full simulation for the signals and the relevant SM backgrounds, the $2\sigma$ exclusion limit and $5\sigma$ discovery prospects are, respectively, obtained on the VLQ-$T$ mass and the coupling strength $g^{\ast}$ with the integrated luminosity of 5 ab$^{-1}$. In addition, we considered the initial state radiation and beamstrahlung effects as well as the systematic uncertainty effects of backgrounds, which are found to reduce the excluding or discovery capability.

hep-ph↗

arXiv2022

Variable and orbital-dependent spin-orbit field orientations in a InSb double quantum dot characterized via dispersive gate sensing

Utilizing dispersive gate sensing (DGS), we investigate the spin-orbit field ($\textbf{B}_{SO}$) orientation in a many-electron double quantum dot (DQD) defined in an InSb nanowire. While characterizing the inter-dot tunnel couplings, the measured dispersive signal depends on the electron charge occupancy, as well as on the amplitude and orientation of the external magnetic field. The dispersive signal is mostly insensitive to the external field orientation when a DQD is occupied by a total odd number of electrons. For a DQD occupied by a total even number of electrons, the dispersive signal is reduced when the finite external magnetic field aligns with the effective $\textbf{B}_{SO}$ orientation. This fact enables the identification of $\textbf{B}_{SO}$ orientations for different DQD electron occupancies. The $\textbf{B}_{SO}$ orientation varies drastically between charge transitions, and is generally neither perpendicular to the nanowire nor in the chip plane. Moreover, $\textbf{B}_{SO}$ is similar for pairs of transitions involving the same valence orbital, and varies between such pairs. Our work demonstrates the practicality of DGS in characterizing spin-orbit interactions in quantum dot systems, without requiring any current flow through the device.

cond-mat.mes-hall↗

arXiv2022

Extremal Dependence in Australian Electricity Markets

Electricity markets are significantly more volatile than other comparable financial or commodity markets. Extreme price outcomes and their transmission between regions pose significant risks for market participants. We examine the dependence between extreme spot price outcomes in the Australian National Electricity Market (NEM). We investigate extremal dependence both in a univariate and multivariate setting, applying the extremogram developed by Davis and Mikosch (2009) and Davis et al. (2011, 2012). We measure the persistence of extreme prices within individual regional markets and the transmission of extreme prices across different regions. With both 5-minute and 30-minute price data, we find that extreme prices are more persistent in the market with a higher share of intermittent renewable energy. We also find that persistence of extreme prices is more prevalent in more concentrated markets. We also show significant extremal price dependence between different regions, which is typically stronger between physically interconnected markets. The dependence structure of extreme prices shows asymmetric and time-dependent patterns. Applying the extremograms, we further show the effectiveness of the Australian Energy Market Commission's 2016 rebidding rule with respect to reducing the share of isolated price spikes that are often considered as an indication of strategic bidding. Our results provide important information for hedging decisions of market participants and for policy makers who aim to reduce market volatility and extreme price outcomes through effective regulations which guide the trading behaviour of market participants as well as improved network interconnections.

q-fin.RM↗

arXiv2021

Radio-frequency C-V measurements with sub-attofarad sensitivity

We demonstrate the use of radio-frequency (rf) resonators to measure the capacitance of nano-scale semiconducting devices in field-effect transistor configurations. The rf resonator is attached to the gate or the lead of the device. Consequently, tuning the carrier density in the conducting channel of the device affects the resonance frequency, quantitatively reflecting its capacitance. We test the measurement method on InSb and InAs nanowires at dilution-refrigerator temperatures. The measured capacitances are consistent with those inferred from the periodicity of the Coulomb blockade of quantum dots realized in the same devices. In an implementation of the resonator using an off-chip superconducting spiral inductor we find sensitivity values reaching down to 75~zF/$\sqHz$ at 1~kHz measurement bandwidth, and noise down to 0.45~aF at 1~Hz bandwidth. We estimate the sensitivity of the method for a number of other implementations. In particular we predict typical sensitivity of about 40~zF/$\sqHz$ at room temperature with a resonator comprised of off-the-shelf components. Of several proposed applications, we demonstrate two: the capacitance measurement of several identical 80~nm-wide gates with a single resonator, and the field-effect mobility measurement of an individual nanowire with the gate capacitance measured in-situ.

cond-mat.mes-hall↗