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Aharonov-Bohm oscillations in phosphorene quantum rings: Mass anisotropy compensation by confinement potential

Physical Review B 2022年第16期105卷 165309-165309页

作者： Tanmay Thakur Bartłomiej Szafran Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Kraków Poland

We consider the Aharonov-Bohm (AB) effect on a confined electron ground state in a quantum ring defined electrostatically within the phosphorene monolayer. The strong anisotropy of effective masses in phosphorene quenches ground-state oscillations for a circular ring because of interrupted persistent current circulation around the ring. An elliptic deformation of the confinement potential can compensate for the anisotropy of the effective masses and produce ground-state parity transformations with the AB periodicity. Moreover, a specific ratio of the semiaxes is determined for which the spectrum becomes identical to that of a circular quantum ring and an isotropic effective mass. We identify a generalized angular momentum operator which commutes with the continuum Hamiltonian for the chosen ratio of the semiaxes that closes the avoided crossings of energy levels for states of the same parity and spin. Ground-state oscillations for the two-electron ground state are also discussed.

关键词： Aharonov-Bohm effect 2-dimensional systems Phosphorene Quantum dots Quantum rings

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Perfect cycles in the synchronous Heider dynamics in complete network

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Physical Review E 2022年第5期105卷 054312-054312页

作者： Zdzislaw Burda Malgorzata J. Krawczyk Krzysztof Kułakowski AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland

We discuss a cellular automaton simulating the process of reaching Heider balance in a fully connected network. The dynamics of the automaton is defined by a deterministic, synchronous, and global update rule. The dynamics has a very rich spectrum of attractors including fixed points and limit cycles, the length and number of which change with the size of the system. In this paper we concentrate on a class of limit cycles that preserve energy spectrum of the consecutive states. We call such limit cycles perfect. Consecutive states in a perfect cycle are separated from each other by the same Hamming distance. Also the Hamming distance between any two states separated by k steps in a perfect cycle is the same for all such pairs of states. The states of a perfect cycle form a very symmetric trajectory in the configuration space. We argue that the symmetry of the trajectories is rooted in the permutation symmetry of vertices of the network and a local symmetry of a certain energy function measuring the level of balance and frustration of triads.

关键词： Dynamics of networks

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Clean-Up Laser System for the Remote Terminal of an Optical Clock

Clean-Up Laser System for the Remote Terminal of an Optical ...

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European Frequency and Time Forum (EFTF)

作者： Przemysław Krehlik Łukasz Śliwczyński Łukasz Buczek Tomasz Kawalec Adam Wojciechowski Antoni Węglarz Jakub Dobosz Faculty of Computer Science Electronics and Telecommunications AGH University of Krakow Poland Faculty of Physics Astronomy and Computer Science Jagiellonian University in Krakow Poland Faculty of Physics University of Warsaw Poland

ISBN: (数字)9798350354270

ISBN: (纸本)9798350354287

In this work we present the concept and verification of the ULE cavity based clean-up system for a remote terminal of an optical atomic clock. Thanks to this solution the short-term stability of the signal provided by a long-haul optical fiber link is be significantly improved, to the level guaranteed by the high-finesse cavity, incorporated in the clean-up setup.

关键词： Optical fibers Time-frequency analysis Atom optics Europe Laser stability Optical fiber communication Fiber lasers Atomic clocks

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A comprehensive study on the microstructure of plasma spraying coatings after electron beam remelting 14

A comprehensive study on the microstructure of plasma sprayi...

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14th International Conference on Electron Beam Technologies, EBT 2022

作者： Wȩglowski, M.St. Śliwiński, P. Dymek, S. Kalemba-Rec, I. Kapuściński, M. Wrona, A. Kustra, K. Lukasiewicz - Institute of Welding Gliwice Poland Lukasiewicz - Institute of Non-Ferrous Metals Gliwice Poland AGH University of Science and Technology Faculty of Metals Engineering and Industrial Computer Science Krakow Poland

One of the most popular thermal spraying technology is atmospheric plasma spraying (APS). However, it should be noted, that numerous imperfections in the APS surface layers can be occurred. The porosity, microcracks as well as lamellar microstructure occurred. Moreover, the adhesion of the coating is limited. However, the reduction of porosity and other imperfections by remelting process can be eliminated. The laser or electron beams for remelting are the most popular technologies. Mainly, power of the beam and travelling speed influence on the thickness and the final properties of the remelted coatings. In the paper, the electron beam (EB) process for remelting of plasma spraying surface layers in relation to microstructure is presented. The Ni20%Cr + 30%Re APS coating on stainless steel substrate 316Ti grade by electron beam was remelted. The effect of remelting process on microstructure was presented. The light microscopy (LM) as well as scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) for microstructure analysis of APS coatings after EB remelting were used. The results show that the APS coatings subjected EB remelted becomes much denser. Moreover, the porosity was reduced and the chemical composition of the coatings after remelting became homogeneous. © Published under licence by IOP Publishing Ltd.

关键词： Remelting

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Thermal properties of structurally balanced systems on diluted and densified triangulations

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Physical Review E 2022年第2期105卷 024301-024301页

作者： Maciej Wołoszyn Krzysztof Malarz AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland

The dynamics of social relations and the possibility of reaching the state of structural balance (Heider balance) are discussed for various networks of interacting actors under the influence of the temperature modeling the social noise level. For that purpose, two main types of lattices are considered. The first is created by removing some links from a regular triangular lattice to produce a diluted triangular lattice, and the second by adding more links to create an enhanced triangular lattice. In both those cases, the full range of possible graph densities is discussed, limited by the extreme cases of networks which consist of a small number of separated triads and fully connected networks. It is shown that the existence of the balanced state is not possible if the average node degree is too close to the value characterizing the regular triangular lattice. Otherwise, both balanced (or partially balanced) and imbalanced states are possible, depending on the temperature. However, only for graphs which are dense enough a phase transition of the first kind is observed, while less enhanced networks (and all diluted) indicate a smooth crossover between the two states. The crossover temperatures are size independent only for the diluted triangular lattices and depend on the size of the system for the enhanced triangular lattices, as is the case also for the critical temperatures of the phase transition observed in denser enhanced lattices.

关键词： Social systems Social dynamics Social networks

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Tip-enhanced Raman spectroscopy reveals the structural rearrangements of tau protein aggregates at the growth phase

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NANOSCALE 2024年第10期16卷 5294-5301页

作者： Sofinska, Kamila Seweryn, Sara Skirlinska-Nosek, Katarzyna Barbasz, Jakub Lipiec, Ewelina [a]Jagiellonian University Faculty of Physics Astronomy and Applied Computer Science M. Smoluchowski Institute of Physics Łojasiewicza 11 30-348 Krakow Poland [b]Jagiellonian University Doctoral School of Exact and Natural Sciences Krakow Poland [c]Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences Niezapominajek 8 30-239 Krakow Poland

Tau protein aggregates inside neurons in the course of Alzheimer's disease (AD). Because of the enormous number of people suffering from AD, this disease has become one of the world's major health and social problems. The presence of tau lesions clearly correlates with cognitive impairments in AD patients, thus, tau is the target of potential treatments for AD, next to amyloid-beta. The exact mechanism of tau aggregation has not been understood in detail so far;especially little is known about the structural rearrangements of tau aggregates at the growth phase. The research into tau conformation at each step of the aggregation pathway will contribute to the design of effective therapeutic approaches. To follow the secondary structure of individual tau aggregates at the growth phase, we applied tip-enhanced Raman spectroscopy (TERS). The nanospectroscopic approach enabled us to follow the structure of individual aggregates occurring in the subsequent phases of tau aggregation. We applied multivariate data analysis to extract the spectral differences for tau aggregates at different aggregation phases. Moreover, atomic force microscopy (AFM) allowed the tracking of the morphological alterations for species occurring with the progression of tau aggregation. Tip-enhanced Raman spectroscopy (TERS) enabled the structural differences between tau protein aggregates to be revealed, specifically tau protofibrils and young fibrils at the level of individual aggregates.

关键词： Aggregates

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Wigner molecules in phosphorene quantum dots

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Physical Review B 2022年第20期106卷 205304-205304页

作者： Tanmay Thakur Bartłomiej Szafran AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland

We study Wigner crystallization of electron systems in phosphorene quantum dots with the confinement of an electrostatic origin with both circular and elongated geometry. The large effective masses in phosphorene promote the separation of the electron charges already for quantum dots of relatively small size. The anisotropy of the effective mass allows for the formation of Wigner molecules in the laboratory frame with a confined charge density that has lower symmetry than the confinement potential. We find that in circular quantum dots separate single-electron islands are formed for two and four confined electrons but not for three trapped carriers. The spectral signatures of the Wigner crystallization to be resolved by transport spectroscopy are discussed. Systems with Wigner molecule states are characterized by a nearly degenerate ground state at B=0 and are easily spin-polarized by the external magnetic field. In electron systems for which the single-electron islands are not formed, a more even distribution of excited states at B=0 is observed, and the confined system undergoes ground-state symmetry transitions at magnetic fields of the order of 1 T. The system of five electrons in a circular quantum dot is indicated as a special case with two charge configurations that appear in the ground state as the magnetic field is changed: one with the single electron islands formed in the laboratory frame and the other where only the pair-correlation function in the inner coordinates of the system has a molecular form as for three electrons. The formation of Wigner molecules of quasi-1D form is easier for the orientation of elongated quantum dots along the zigzag direction with heavier electron mass. The smaller electron effective mass along the armchair direction allows for freezing out the transverse degree of freedom in the electron motion. Calculations are performed with a version of the configuration interaction approach that uses a single-electron basis that is preo

关键词： Coulomb blockade Localization 1-dimensional systems Quantum dots Wigner crystal Exact diagonalization Transport techniques Variational wave functional methods

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Entanglement Detection with Trace Polynomials

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Physical Review Letters 2024年第7期132卷 070202-070202页

作者： Albert Rico Felix Huber Faculty of Physics Astronomy and Applied Computer Science Institute of Theoretical Physics Jagiellonian University 30-348 Kraków Poland

We provide a systematic method for nonlinear entanglement detection based on trace polynomial inequalities. In particular, this allows us to employ multipartite witnesses for the detection of bipartite states, and vice versa. We identify pairs of entangled states and witnesses for which linear detection fails, but for which nonlinear detection succeeds. With the trace polynomial formulation a great variety of witnesses arise from immanant inequalities, which can be implemented in the laboratory through the randomized measurements toolbox.

关键词： Quantum correlations, foundations & formalism

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Machine Learning Approaches in Cybersecurity to Enhance Security in Future Network Technologies

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SN computer science 2025年第4期6卷 1-18页

作者： Ahmad, Sultan Haque, Md. Alimul Abdeljaber, Hikmat A. M. Eljialy, A.E.M. Nazeer, Jabeen Mishra, B.K. Department of Computer Science College of Computer Engineering and Sciences Prince Sattam Bin Abdulaziz University Alkharj 11942 Saudi Arabia University Center for Research and Development (UCRD) Department of Computer Science and Engineering Chandigarh University Mohali Punjab Gharuan 140413 India Department of Computer Science Veer Kunwar Singh University Bihar Ara India Department of Computer Science Faculty of Information Technology Applied Science Private University Amman Jordan MEU Research Unit Middle East University Amman 11831 Jordan Department of Information Systems College of Computer Engineering and Sciences Prince Sattam Bin Abdulaziz University Alkharj 11942 Saudi Arabia Department of Physics Veer Kunwar Singh University Ara 802301 India

As technology continues to evolve rapidly, cybersecurity has become a critical global concern. The increasing sophistication of cyber threats poses significant risks to individuals, businesses, and governments. To combat these threats, cybersecurity tools play a crucial role in monitoring, detecting, and mitigating security risks in digital environments. These tools ensure data protection, prevent unauthorized access, and safeguard sensitive information. However, traditional cybersecurity approaches are struggling to keep pace with emerging cyber-attacks. In response, machine learning (ML) has emerged as a powerful solution for enhancing cybersecurity strategies. ML algorithms enable organizations to analyze large datasets, identify anomalies, and predict potential threats with greater accuracy. Cybersecurity tools, integrated with ML, act as the final line of defense against attacks such as data breaches, identity theft, and system intrusions. This research explores the application of ML in selecting and optimizing cybersecurity models for enterprise ICT systems. It also emphasizes the growing demand for skilled professionals who can develop and implement ML-based security solutions. By examining current trends and future possibilities, this study provides valuable insights into the role of ML in strengthening cybersecurity measures and enhancing overall digital protection for organizations worldwide. © The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2025.

关键词： Cyber security Cybercrime Data analysis ML algorithms Network security Threats

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Interpretable Multi-task Learning with Shared Variable Embeddings

arXiv

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arXiv 2024年

作者： Zelaszczyk, Maciej Mańdziuk, Jacek Faculty of Mathematics and Information Science Warsaw University of Technology Poland Faculty of Computer Science AGH University of Krakow Poland

This paper proposes a general interpretable predictive system with shared information. The system is able to perform predictions in a multi-task setting where distinct tasks are not bound to have the same input/output structure. Embeddings of input and output variables in a common space are obtained, where the input embeddings are produced through attending to a set of shared embeddings, reused across tasks. All the embeddings are treated as model parameters and learned. The approach is distinct from existing vector quantization methods. Specific restrictions on the space of shared embedings and the sparsity of the attention mechanism are considered. Experiments show that the introduction of shared embeddings does not deteriorate the results obtained from a vanilla variable embeddings method. We run a number of further ablations. Inducing sparsity in the attention mechanism leads to both an increase in accuracy and a significant decrease in the number of training steps required. Shared embeddings provide a measure of interpretability in terms of both a qualitative assessment and the ability to map specific shared embeddings to pre-defined concepts that are not tailored to the considered model. There seems to be a trade-off between accuracy and interpretability. The basic shared embeddings method favors interpretability, whereas the sparse attention method promotes accuracy. The results lead to the conclusion that variable embedding methods may be extended with shared information to provide increased interpretability and accuracy. © 2024, CC BY.

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