arXiv subjects

Nguyen Minh Quan

Publications and source records attributed to Nguyen Minh Quan.

5 recordsLinked to original sources

arXiv2026

Tunable Rashba Splitting in Janus InXPbP (X = S, Se, Te) Monolayers for Enhanced Photocatalytic Water Splitting

Janus two-dimensional (2D) materials exhibiting Rashba spin splitting have recently attracted considerable attention owing to their potential applications in spintronic devices and photocatalytic water splitting. In this work, we investigate, using first-principles calculations, the structural, mechanical, electronic, optical, and photocatalytic properties of Janus InXPbP (X = S, Se, Te) monolayers that exhibit significant Rashba effects. Our results demonstrate that all three monolayers are energetically, dynamically, and mechanically stable, as evidenced by cohesive energy calculations, phonon dispersion analysis, and elastic constants. By varying the chalcogen atom (X = S, Se, Te), the Rashba effect in InXPbP can be effectively tuned. Rashba parameters of 0.16 and 0.20 eVÅ are obtained near the conduction-band minimum (CBM) for InSPbP and InSePbP, respectively, whereas InTePbP exhibits giant Rashba spin splitting near both the CBM and valence-band maximum (VBM), with corresponding Rashba parameters of 0.90 and 0.87 eVÅ. Furthermore, the Janus InXPbP monolayers exhibit suitable band gaps of 1.21, 1.27, and 0.76 eV for InSPbP, InSePbP, and InTePbP, respectively, which are favorable for photocatalytic applications. All three monolayers possess suitable band-edge alignments for overall water splitting, yielding solar-to-hydrogen (STH) conversion efficiencies of 21.67%, 26.03%, and 29.83% for InSPbP, InSePbP, and InTePbP, respectively. Our findings not only enrich the family of Janus materials but also suggest that the Janus InXPbP monolayers are promising candidates for spintronic devices and high-performance photocatalytic water-splitting applications.

cond-mat.mtrl-sci↗

arXiv2026

Energy Efficiency Maximization for Integrated Sensing and Communications in Satellite-UAV MIMO Systems

This paper investigates energy efficiency maximization in an integrated sensing and communication framework for satellite-UAV MIMO systems, where a LEO satellite and a UAV simultaneously serve ground users and perform target sensing. Both the satellite and UAV are equipped with uniform planar arrays of transmit antennas, enabling a distributed multi-user and multi-target architecture. We derive the achievable downlink throughput by considering that the high-altitude satellite maintains a line-of-sight (LoS) link with users, while adopting a probabilistic model for the UAV that accounts for the likelihood of both LoS and non-line-of-sight conditions. The energy efficiency maximization problem is formulated as a complex non-convex optimization problem, subject to power constraints, quality of service (QoS) requirements, and beampattern gain constraints for accurate sensing. To tackle this challenge, we propose an efficient alternating optimization algorithm capable of handling the complex search space and QoS guarantees. Numerical results across diverse scenarios with multiple users demonstrate that the proposed method achieves high energy efficiency while meeting both communication and sensing performance targets.

cs.IT↗

arXiv2025

Clustering Strategies in Satellite-Aided Communications

With the rapid advancement of next-generation satellite networks, addressing clustering tasks, user grouping, and efficient link management has become increasingly critical to optimize network performance and reduce interference. In this paper, we provide a comprehensive overview of modern clustering approaches based on machine learning and heuristic algorithms. The experimental results indicate that improved machine learning techniques and graph theory-based methods deliver significantly better performance and scalability than conventional clustering methods, such as the pure clustering algorithm examined in previous research. These advantages are especially evident in large-scale satellite network scenarios. Furthermore, the paper outlines potential research directions and discusses integrated, multi-dimensional solutions to enhance adaptability and efficiency in future satellite communication.

cs.IT↗

arXiv2025

Metaheuristic Optimization of Trajectory and Dynamic Time Splitting for UAV Communication Systems

The integration of unmanned aerial vehicles (UAVs) into wireless communication systems has emerged as a transformative approach, promising cost-efficient connectivity. This paper addresses the optimization of the dynamic time-splitting ratio and flight trajectory for a communication system linking a ground base station to the UAV equipped with backscatter devices (referred to as UB), and from UB to an end user. Given the inherent non-convexity of the problem, we develop two meta-heuristic-based approaches inspired by genetic algorithm and particle swarm optimization to enhance the total achievable rate while reducing computational complexity. Numerical results demonstrate the effectiveness of these meta-heuristic solutions, showcasing significant improvements in the achievable rate and computation time compared to existing benchmarks.

cs.IT↗

arXiv2024

Fast Beam Placement for Ultra-Dense LEO Networks

Low Earth orbit (LEO) satellites has brought about significant improvements in wireless communications, characterized by low latency and reduced transmission loss compared to geostationary orbit (GSO) satellites. Ultra-dense LEO satellites can serve many users by generating active beams effective to their locations. The beam placement problem is challenging but important for efficiently allocating resources with a large number of users. This paper formulates and solves a fast beam placement optimization problem for ultra-dense satellite systems to enhance the link budget with a minimum number of active beams (NABs). To achieve this goal and balance load among beams within polynomial time, we propose two algorithms for large user groups exploiting the modified K-means clustering and the graph theory. Numerical results illustrate the effectiveness of the proposals in terms of the statistical channel gain-to-noise ratio and computation time over state-of-the-art benchmarks.

cs.IT↗