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Yousef Azizi

Publications and source records attributed to Yousef Azizi.

5 recordsLinked to original sources

A Reliable Self-Organized Distributed Complex Network for Communication of Smart Agents

Collaboration among distributed agents is fundamental to many complex systems, particularly in communication networks where connectivity must be maintained under energy constraints. In this study, we utilize intelligent agents (nodes) trained through reinforcement learning techniques to establish connections with their neighbors, ultimately leading to the emergence of a large-scale communication cluster. Notably, there is no centralized administrator; instead, agents must adjust their connections based on information obtained from local observations. The connection strategy is formulated using a physical Hamiltonian, thereby categorizing this intelligent system under the paradigm of "Physics-Guided Machine Learning". Agents are trained via a Deep Q-Network using local observations to minimize changes in the Hamiltonian, enabling adaptive decision-making in dynamic environments. Simulation results demonstrate that the proposed collaborative strategy forms robust large-scale communication clusters while reducing transmission energy compared to baseline approaches. The network maintains high connectivity under agent mobility, density variations, node failures, and environmental obstacles, highlighting strong adaptability and resilience. These findings indicate that physics-guided reinforcement learning provides an effective mechanism for distributed topology optimization in emerging IoT and vehicular communication networks.

cs.MA

Energy-efficient antiferromagnetic skyrmion creation and its dynamics in structure-dependent magneto-elastic coupling

Existing skyrmion nucleation methods lead to increased Joule heating, limiting the applicability to metallic Antiferromagnetic (AFM) systems. In this study, we propose a novel, energy-efficient mechanical method for nucleating AFM skyrmions using Surface Acoustic Waves (SAWs). SAWs, which propagate along material surfaces with minimal attenuation, generate dynamic strain that induces a spatially varying torque on magnetic spins, offering a viable alternative to traditional current-based methods. Using the Thiele approach we investigate skyrmion dynamics in special AFMs, NiO-like or CoO-like, incorporating a magnetoelastic term that accounts for the unique spin arrangements, where spins align oppositely within parallel planes. Our findings reveal that the deformation induced by SAWs, influenced by the magnetostriction of materials like NiO and CoO, can modify the spin configuration, consequently, alters the skyrmion dynamics. This study not only demonstrates the potential of SAWs for efficient skyrmion nucleation in AFMs but also introduces new theoretical insights into specific magnetoelastic-induced skyrmion dynamics in AFM systems.

cond-mat.mtrl-sci

Simple Wideband RCS Reduction by Phase Gradient Modulated Surface

This paper presents the design and implementation of a simple, single-layer, broadband (97%, 11.3-32.3 GHz) Radar Cross Section Reduction (RCSR) Modulated Surface (MS). It uses modulation of the edge-length of the square patch (SP) radiators within adjacent unit cells. By using Sinusoidal Modulation (SM) of the edge length of the unit cells, the unit cells sequences with phase gradient, that plays an effective role in improving the RCSR, can be used for wideband RCSR achievement. The proposed structure with the dimension of 250*250mm2 that consists of 40 * 40 unit cells with period of 6mm printed on a RO4003 substrate of 1.6mm thickness and has been considered. Measurements on a prototype were conducted considering both mono- and bi-static arrangements for oblique incidences for both TM and TE polarization tests. A good agreement between simulation and measurement results proves the validity of the design criteria.

eess.SP

Bi-static Radar Cross Section Test Method by Using Historic Marconi Set-up and Time Gating

In this paper, a low-cost, simple and reliable bi-static Radar Cross Section (RCS) measurement method making use a historic Marconi set-up is presented. It uses a transmitting (Tx) antenna (located at a constant position, at a reference angle of θ = 0o) and a receiver (Rx) antenna (mounted on a moveable arm calibrated in the azimuthal direction with an accuracy of 0.1o). A time gating method is used to extract the information from the reflection in the time domain; applying time filter allows removing the antenna side lobe effects and other ambient noise. In this method, the Rx antenna (on the movable arm) is used to measure the reflected field in the angular range from 1o to 90o of reflection from the structure (printed PCB) and from the reference configuration represented by a ground (GND) plane of the same dimension. The time gating method is then applied to each pair of PCB / GND measurements to extract the bi-static RCS pattern of the structure at a given frequency. Here comparison of measurement results carried out at 18 GHz and 32 GHz with simulation indicates the successful performance of the proposed method. It can be used as a low-cost, reliable and available option in future measurement and scientific research.

eess.SP

Synchronization of oscillators through time-shifted common inputs

Shared upstream dynamical processes are frequently the source of common inputs in various physical and biological systems. However, due to finite signal transmission speeds and differences in the distance to the source, time shifts between otherwise common inputs are unavoidable. Since common inputs can be a source of correlation between the elements of multi-unit dynamical systems, regardless of whether these elements are directly connected with one another or not, it is of importance to understand their impact on synchronization. As a canonical model that is representative for a variety of different dynamical systems, we study limit-cycle oscillators that are driven by stochastic time-shifted common inputs. We show that if the oscillators are coupled, time shifts in stochastic common inputs do not simply shift the distribution of the phase differences, but rather the distribution actually changes as a result. The best synchronization is therefore achieved at a precise intermediate value of the time shift, which is due to a resonance-like effect with the most probable phase difference that is determined by the deterministic dynamics.

q-bio.NC