arXiv subjects

Xinzhi Liu

Publications and source records attributed to Xinzhi Liu.

9 recordsLinked to original sources

arXiv2026

Stability and Bifurcations of Planar Switched Linear and Homogeneous Systems

We prove new necessary and sufficient conditions for uniform asymptotic stability under arbitrary switching of two-dimensional switched homogeneous systems with a finite number of subsystems using a worst-case switching analysis. The novelty of our approach is in its explicit nature, which allows us to then study in detail the codimension-one bifurcations of stability of the origin in switched linear systems and further conclude new local and global stability results for certain classes of nonlinear switched systems. In particular, we formulate an analogue of Lyapunov's indirect method for $\mathcal{C}^{1}$ switched nonlinear systems and derive a new method for determining the existence of a bounded basin of attraction for a class of switched nonlinear systems.

math.DS↗

arXiv2026

Thermodynamic uncertainty relations for multi-terminal systems with broken time-reversal symmetry

We investigate the thermodynamic uncertainty relations (TURs) in steady-state transport for a multi-terminal system consisting of two conducting terminals and N-2 probe terminals, within the linear response regime under broken time-reversal symmetry. We independently derive exact bounds on the TURs for the steady-state particle and heat currents under a strong constraint on the Onsager coefficients. Based on our proposed exact bounds, the analysis reveals that the bounds differ for particle and heat currents and are dependent on the system parameters. Furthermore, we demonstrate that under specific parameter conditions, the TURs of the particle and heat currents have a unified minimum value that depends solely on the number of terminals.

cond-mat.stat-mech↗

arXiv2025

Resilient Neural-Variable-Structure Consensus Control for Nonlinear MASs with Singular Input Gain Under DoS Attacks

This paper proposes a reliable learning-based adaptive control framework for nonlinear multi-agent systems (MASs) subject to Denial-of-Service (DoS) attacks and singular control gains, two critical challenges in cyber-physical systems. A neural-variable-structure adaptive controller is developed to achieve leader-follower consensus while ensuring robustness to external disturbances and adaptability to unknown nonlinear dynamics. A reliability-assessment rule is introduced to detect communication loss during DoS attacks, upon which a switched control mechanism is activated to preserve closed-loop stability and performance. Unlike existing resilient MAS control methods, the proposed strategy explicitly accommodates singular control gains and does not rely on restrictive assumptions such as Lipschitz continuity or prior bounds on nonlinearities. To the authors' knowledge, this is the first work to integrate neural learning, variable-structure robustness, and reliability-based switching into a unified consensus-tracking control architecture for heterogeneous nonlinear MASs with singular input gains under DoS attacks. Lyapunov-based analysis establishes uniform ultimate boundedness of all closed-loop signals, and Matlab/Simulink simulations on a connected automated vehicle platoon demonstrate the method's effectiveness and resilience.

eess.SY↗

arXiv2022

Input-to-State Stability of Time-Delay Systems With Delay-Dependent Impulses

This paper studies input-to-state stability (ISS) of general nonlinear time-delay systems subject to delay-dependent impulse effects. Sufficient conditions for ISS are constructed by using the method of Lyapunov functionals. It is shown that, when the continuous dynamics are ISS but the discrete dynamics governing the delay-dependent impulses are not, the impulsive system as a whole is ISS provided the destabilizing impulses do not occur too frequently. On the contrary, when the discrete dynamics are ISS but the continuous dynamics are not, the delayed impulses must occur frequently enough to overcome the destabilizing effects of the continuous dynamics so that the ISS can be achieved for the impulsive system. Particularly, when the discrete dynamics are ISS and the continuous dynamics are also ISS or just stable for the zero input, the impulsive system is ISS for arbitrary impulse time sequences. Compared with the existing results on impulsive time-delay systems, the obtained ISS criteria are more general in the sense that these results are applicable to systems with delay dependent impulses while the existing ones are not. Moreover, when consider time-delay systems with delay-free impulses, our result for systems with unstable continuous dynamics and stabilizing impulses is less conservative than the existing ones, as a weaker condition on the upper bound of impulsive intervals is obtained. To demonstrate the theoretical results, we provide two examples with numerical simulations, in which distributed delays and discrete delays in the impulses are considered, respectively.

math.OC↗

arXiv2022

Nematic fluctuations in the non-superconducting iron pnictide BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$

The main driven force of the electronic nematic phase in iron-based superconductors is still under debate. Here, we report a comprehensive study on the nematic fluctuations in a non-superconducting iron pnictide system BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$ by electronic transport, angle-resolved photoemission spectroscopy (ARPES) and inelastic neutron scattering (INS) measurements. Previous neutron diffraction and transport measurements suggested that the collinear antiferromagnetism persists to $x=0.8$, with similar Néel temperature $T_N$ and structural transition temperature $T_s$ around 32 K, but the charge carriers change from electron type to hole type around $x=$ 0.5. In this study, we have found that the in-plane resistivity anisotropy also highly depends on the Cr dopings and the type of charge carriers. While ARPES measurements suggest possibly weak orbital anisotropy onset near $T_s$ for both $x=0.05$ and $x=0.5$ compounds, INS experiments reveal clearly different onset temperatures of low-energy spin excitation anisotropy, which is likely related to the energy scale of spin nematicity. These results suggest that the interplay between the local spins on Fe atoms and the itinerant electrons on Fermi surfaces is crucial to the nematic fluctuations of iron pnictides, where the orbital degree of freedom may behave differently from the spin degree of freedom, and the transport properties are intimately related to the spin dynamics.

cond-mat.supr-con↗

arXiv2021

ReCFA: Resilient Control-Flow Attestation

Recent IoT applications gradually adapt more complicated end systems with commodity software. Ensuring the runtime integrity of these software is a challenging task for the remote controller or cloud services. Popular enforcement is the runtime remote attestation which requires the end system (prover) to generate evidence for its runtime behavior and a remote trusted verifier to attest the evidence. Control-flow attestation is a kind of runtime attestation that provides diagnoses towards the remote control-flow hijacking at the prover. Most of these attestation approaches focus on small or embedded software. The recent advance to attesting complicated software depends on the source code and CFG traversing to measure the checkpoint-separated subpaths, which may be unavailable for commodity software and cause possible context missing between consecutive subpaths in the measurements. In this work, we propose a resilient control-flow attestation (ReCFA), which does not need the offline measurement of all legitimate control-flow paths, thus scalable to be used on complicated commodity software. Our main contribution is a multi-phase approach to condensing the runtime control-flow events; as a result, the vast amount of control-flow events are abstracted into a deliverable size. The condensing approach consists of filtering skippable call sites, folding program-structure related control-flow events, and a greedy compression. Our approach is implemented with binary-level static analysis and instrumentation. We employ a shadow stack mechanism at the verifier to enforce context-sensitive control-flow integrity and diagnose the compromised control-flow events violating the security policy. The experimental results on real-world benchmarks show both the efficiency of the control-flow condensing and the effectiveness of security enforcement.

cs.CR↗

arXiv2013

Magnetization Characteristic of Ferromagnetic Thin Strip by Measuring Anisotropic Magnetoresistance and Ferromagnetic Resonance

The magnetization characteristic in a permalloy thin strip is investigated by electrically measuring the anisotropic magnetoresistance and ferromagnetic resonance in in-plane and out-of-plane configurations. Our results indicate that the magnetization vector can rotate in the film plane as well as out of the film plane by changing the intensity of external magnetic field of certain direction. The magnetization characteristic can be explained by considering demagnetization and magnetic anisotropy. Our method can be used to obtain the demagnetization factor, saturated magnetic moment and the magnetic anisotropy.

cond-mat.mtrl-sci↗

arXiv2010

Weak antilocalization effect of high-mobility two-dimensional electron gas in inversion layer on p-type HgCdTe

Magnetoconductance of a gated two-dimensional electron gas (2DEG) in the inversion layer on p-type HgCdTe crystal is investigated. At strong magnetic fields, characteristic features such as quantum Hall effect of a 2DEG with single subband occupation are observed. At weak magnetic fields, weak antilocalization effect in ballistic regime is observed. Phase coherence time and zero-field spin-splitting are extracted according to Golub's model. The temperature dependence of dephasing rate is consistent with Nyquist mechanism including both singlet and triplet channel interactions.

cond-mat.mes-hall↗

arXiv2010

Gate-controlled weak antilocalization effect in inversion layer on p-type HgCdTe

We discover weak antilocalization effect of two-dimensional electron gas with one electric subband occupied in the inversion layer on p-type HgCdTe crystal. By fitting the model of Iordanskii, Lyanda-Geller and Pikus to data at varies temperatures and gate voltages, we extract phase coherence and spin-orbit scattering times as functions of temperature and carrier density. We find that Elliot-Yafet mechanism and Nyquist mechanism are the dominating spin decoherence and dephasing mechanisms, respectively. We also find that the Rashba parameter is relatively large and the dependence of Rashba parameter upon carrier density is not monotonic and an optimal carrier density exists for the maximization of spin-orbit coupling.

cond-mat.dis-nn↗