Real Propagation Research Articles

Coronal Mass Ejections modelling simulation

A violent solar eruption has the potential to disrupt the normal functioning of radio and cell phone technology, impeding communication and navigation. In addition, it could cause direct damage to artificial vehicles, resulting in non-structrual effects on the current human environment. In this paper, a solar eruption event was selected to represent typical occurrences, encompassing both solar flares and a coronal mass ejection. According to multiband observations, the flare is triggered by the magnetic flow emerging and disturbing the quadrupole magnetic field structure. The far-UV band observations found that the flare burst caused significant far-UV waves. We analyze the temporality of flare and coronal mass ejections to determine coronal mass ejections and flare are two manifestations of the same eruption event. This research adopted an improved cone model according to the multi-angle observation to simulate the real propagation direction, velocity and morphological evolution after the eruption, aimed to give an early warning to the earth’s space environment.

Source inference for misinformation spreading on hypergraphs

Source inference aims at revealing the seed of the misinformation spreading on social networks, and attracted great attention in the field of network science and cybersecurity. Extensive real-world data analyses have certificated that individual interactions exist pairwise and higher-order interactions, and thus should be described using the hypergraph. Previous studies about the source inference algorithms are mainly focused on simple graphs (i.e., a graph only has pairwise interactions) while neglecting the higher-order interactions. In this article, we propose a dynamical message-passing (DMP) algorithm to infer the misinformation spreading on hypergraphs. As a comparison, we also extend jordan centrality (JC), betweenness centrality (BC), closeness centrality (CC), and eigenvector centrality (EIG) algorithm to hypergraphs. The results show that our proposed DMP algorithm can accurately and effectively infer the propagation source on both artificial and real-world hypergraphs compared to the centrality algorithms. Even if the increase in propagation scale renders the other centrality algorithms completely ineffective, the DMP algorithm can still distinguish the real propagation sources in the form of a rank smaller than 10% of the network size. In general, our DMP algorithm provides an effective solution for inferring the misinformation source on high-order networks.

DISLPSI: A framework for source localization in signed social networks with structural balance

The theory of structural balance in signed networks plays an important role in information dissemination. Source localization is crucial for suppressing the spread of negative information, however, existing research on source localization has overlooked the theory of network structural balance. In this paper, we leverage the theory of structural balance in signed networks to develop a framework for source localization. This framework, called Direction Induced Search and Source Identification based Label Propagation (DISLPSI), consists of two main components: the Direction Induced Search (DIS) algorithm constructs a relaxed-induced search tree, and the Source Identification based Label Propagation (LPSI) algorithm validates the propagation source within the search tree. Meanwhile, in order to improve the proximity between the relaxed direction-induced search tree and the real propagation path, we propose the Adaptive Observation Node Selection (AONS) algorithm. Extensive simulation experiments demonstrate that the original LPSI algorithm performs very poorly in signed networks, proving that LPSI cannot be directly applied to signed networks. Conversely, the DISLPSI framework is effective in accurately localizing the source and robustness against the structural balance. Furthermore, the observer nodes selected by the AONS algorithm significantly enhance the source localization. We also find that the source localization framework is more advantageous in homogeneous networks than in heterogeneous networks.

Optical flow vector of elastic waves in transversely isotropic media

The propagation direction of the wavefield is particularly important for migration imaging in the reverse-time migration (RTM) of elastic waves in transversely isotropic (TI) media. However, due to the problem of the computational instability of the Poynting vector, the wave field propagation direction estimated based on the Poynting vector method has errors and cannot accurately indicate the real propagation direction of the elastic wavefield. To solve this problem, a method for calculating the optical flow vector of elastic waves in TI media is developed to obtain the propagation direction. The optical flow vector of elastic waves in TI media is determined by applying the spatial and temporal derivatives of the wavefield at each time step under the assumption that the wavefields are almost the same at subsequent time steps and are smooth in the spatial direction. As the additional smoothing item is added and the multiple iterative algorithm is introduced in calculating the optical flow vector, the direction is calculated more accurately than the Poynting vector. Based on the optical flow vectors, we can separate the source wavefield and receiver wavefield into four directions: up-going, down-going, left-going, and right-going wavefields, respectively, and finally perform elastic reverse-time migration (ERTM) imaging based on the optical flow vector traveling-wave separation. We use a layered model and the BP model to test our method. The testing results demonstrate that the optical flow vector can overcome the Poynting vector limitations and obtain more accurate and reliable information regarding the direction of elastic wave propagation in TI media, as well as precisely separate the wavefields. The separated wavefields for migration effectively improve the quality of the ERTM.

Finding influential nodes in complex networks based on Kullback–Leibler model within the neighborhood

As a research hot topic in the field of network security, the implementation of machine learning, such as federated learning, involves information interactions among a large number of distributed network devices. If we regard these distributed network devices and connection relationships as a complex network, we can identify the influential nodes to find the crucial points for optimizing the imbalance of the reliability of devices in federated learning system. This paper will analyze the advantages and disadvantages of existing algorithms for identifying influential nodes in complex networks, and propose a method from the perspective of information dissemination for finding influential nodes based on Kullback–Leibler divergence model within the neighborhood (KLN). Firstly, the KLN algorithm removes a node to simulate the scenario of node failure in the information dissemination process. Secondly, KLN evaluates the loss of information entropy within the neighborhood after node removal by establishing the KL divergence model. Finally, it assesses the damage influence of the removed node by integrating the network attributes and KL divergence model, thus achieving the evaluation of node importance. To validate the performance of KLN, this paper conducts an analysis and comparison of its results with those of 11 other algorithms on 10 networks, using SIR model as a reference. Additionally, a case study was undertaken on a real epidemic propagation network, leading to the proposal of management and control strategies for daily protection based on the influential nodes. The experimental results indicate that KLN effectively evaluates the importance of the removed node using KL model within the neighborhood, and demonstrate better accuracy and applicability across networks of different scales.

Considering individual game behavior and time delay in the multi-channel rumor propagation model

The rapid development of the Internet has accelerated the spread of rumors, posing challenges to social cohesion and stability. To address this, a multi-channel rumor propagation model incorporating individual game behavior and time delay is proposed. It depicts individuals strategically choosing propagation channels in the rumor spread process, capturing real-world intricacies more faithfully. Specifically, the model allowing spreaders to choose between text and video information base channels. Strategy adoption hinges on benefits versus costs, with payoffs dictating strategy and the propagation process determining an individual’s state. By theoretical analysis of the model, the propagation threshold and equilibrium points are obtained. Then the stability of the model is further demonstrated based on Routh–Hurwitz judgment and Descartes’ Rule of Signs. Numerical simulations are conducted to verify the correctness of the theoretical results and the sensitivity of the model to key parameters. The outcomes reveal that increasing the propagation cost of spreaders can significantly curb the spread of rumors. In contrast to the classical ISR model, rumors spread faster and more widely in the improved multi-channel rumor propagation model in this paper, which is a feature more aligned with real-world scenarios. Finally, the validity and predictive ability of the model are verified by using real rumor propagation data sets, indicating that the improved multi-channel rumor propagation model has good practical application and predictive value.

Numtrical Evaluation of Optimal Precoding Algorithm and Zero Forcing Precoding in MU-MISO Channel with Channel Aging

In paper the numerical investigation of the impact of delayed channel state information (CSI) due to user movement and caused channel aging on the performance of multiuser precoder in downlink MISO system. The time variant CSI is obtained by the least squares channel estimation. We consider Zero Forcing algorithm and numerical optimization based solution of calculating precoder vectors maximizimg sum rate of multiuser system. For numerical simulation the QuaDRiGa channel model reflecting the real propagation conditions for moving users is used. The obtained performance of multiuser Zero Forcing and optimization based beamforming in spatially correlated channel are compared based on the empirical cumulative density function of the sum rate of multiple users.

226 Advancing Neurovascular Diagnostics for Abnormal Hemodynamic Conditions Through AI-Driven Physics-informed Neural Networks

INTRODUCTION: Many studies have explored the application of machine learning and neural networks in extracting critical diagnostic information from structural and functional medical imaging. While these methods show potential for improving efficiency, concerns arise when interpreting subtle imaging features, especially when training data is limited. Physics-informed neural networks (PINNs) address these issues by incorporating governing equations from physical and mechanical models into the analysis. METHODS: We examined the use of a PINN that enforces the convection equation, relating contrast media propagation to blood velocity, the Navier-Stokes equations for velocity and pressure distributions, and the conservation of mass requirement to calculate velocity and pressure distributions within patient-specific blood vessels. We also implemented a boundary condition that accounts for real contrast-media propagation from 1000 fps high-speed angiographic (HSA) image sequences, allowing for an assumption-free problem space within a medical imaging framework. Velocity fields and pressure gradients were calculated for flow in aneurysms and carotid bifurcations. RESULTS: Our method demonstrates comparable results to computational fluid dynamics (CFD) without requiring manual data processing, significantly improving the efficiency of calculating high-resolution velocity and pressure fields. By integrating AI with physics modeling, this novel approach holds the potential for advancing neurovascular diagnostics and providing more accurate, personalized treatment plans for patients with neurovascular pathologies. CONCLUSIONS: This innovative approach, integrating physics modeling and artificial intelligence, offers more accurate and personalized diagnostics for patients with neurovascular pathologies. The PINN method not only achieves results comparable to computational fluid dynamics without the need for manual data processing but also greatly enhances the efficiency of calculating high-resolution velocity and pressure fields.

The popular gene of hot event: A hot event propagation mechanism based on information coupling and information energy interaction

Recently, the research on the propagation of hot events has received widespread attention. By analyzing the data of hot events and the data of the common events in the same period on the network, we found that hot events usually break out quickly and opinion leaders and cluster behaviors exist in their propagation process. At the same time, the media public opinion fields of reporting hot events overlap and promote each other. Based on the common factors that drive an event to become a hot event, we used the heat calculation formula and entropy method to put forward the propagation model of hot events based on information coupling and information energy interaction. In the model, the coupling values of different event information are quantified based on the information fragment coupling effect. The heat calculation formula is used to dynamically adjust the propagation probability of different individuals in the propagation process of hot event, and the sensational effect threshold is introduced based on the overall energy value of the event. Finally, we used the real social relationship networks to simulate the evolution propagation process of the hot events, and compared it with the crawling real propagation curve of the events. The proposed model provides a good supplement for the study of the hot events.

The influence of supersonic spatial-temporal coupling disturbance on detonation in an expanded chamber

At present, the most researches on perturbed detonation only considers single factor effects, and there are few studies on the impact of multi-factor coupled perturbations on detonation. In order to match the complex inflow conditions in real situation, the initiation and propagation process of detonation disturbed by spatial-temporal coupling have been studied. This study adopts an adaptive mesh refinement program. It can dynamically capture the structure change of detonation and reduce the total calculation amount. The N-S (Navier-Stokes) equation and single-step reaction model was used in this study. The calculation model is the classic expansion channel that can enhance thrust. After analyze the effects of disturbance amplitudes and disturbance stratification, the results indicates that the stratification phenomenon of disturbance has different effects on the characteristics of flow field. The expansion wall can weaken the disturbance intensity, but its effect is limited. It can only achieve good results when the disturbance on the straight wall side is weak, but the weakening effect of expansion wall also exacerbates the instability of wave. On the other hand, the stability of detonation waves under spatial stratification is stronger, which helps to maintain the intensity of detonation wave.

Rayleigh waves in isotropic elastic materials with micro-voids

In this paper, we show that a general method introduced by Fu and Mielke allows to give a complete answer on the existence and uniqueness of a subsonic solution describing the propagation of surface waves in an isotropic half space modelled with the linear theory of isotropic elastic materials with micro-voids. Our result is valid for the entire class of materials admitting real wave propagation which include auxetic materials (negative Poisson’s ratio) and composite materials with negative-stiffness inclusions (negative Young’s modulus). Moreover, the used method allows to formulate a simple and complete numerical strategy for the computation of the solution.

Numerical Evaluation of the MU-MIMO Beamforming Performance with Channel Estimation

This paper presents the numerical evaluation of the ZF beamforming algorithm and DFT precoding using the LS channel estimation in the multiuser multiantenna (MU-MIMO) downlink system. The sum rate performance depending on a number of users are presented. The arising inter user correlation degrades the sum rate (spectral efficiency) performance of multiuser MIMO system especially in scenarios where the number of users is larger than the number of antennas at the BS. For MIMO channel simulation the QuaDRiGa channel model reflecting the real propagation conditions is used. The obtained performance of MU-MIMO ZF precoding in spatially correlated channel are compared with DFT precoding based on the empirical cumulative density function of the sum rate of multiple users. Numerical results show that the ZF precoder outperforms the DFT precoder in channel with less spatial correlation. The DFT precoder in spatially more correlated channel has advantage over ZF precoder.

Stable approximation of Helmholtz solutions in the disk by evanescent plane waves

Superpositions of plane waves are known to approximate well the solutions of the Helmholtz equation. Their use in discretizations is typical of Trefftz methods for Helmholtz problems, aiming to achieve high accuracy with a small number of degrees of freedom. However, Trefftz methods lead to ill-conditioned linear systems, and it is often impossible to obtain the desired accuracy in floating-point arithmetic. In this paper we show that a judicious choice of plane waves can ensure high-accuracy solutions in a numerically stable way, in spite of having to solve such ill-conditioned systems. Numerical accuracy of plane wave methods is linked not only to the approximation space, but also to the size of the coefficients in the plane wave expansion. We show that the use of plane waves can lead to exponentially large coefficients, regardless of the orientations and the number of plane waves, and this causes numerical instability. We prove that all Helmholtz fields are continuous superposition of evanescent plane waves, i.e., plane waves with complex propagation vectors associated with exponential decay, and show that this leads to bounded representations. We provide a constructive scheme to select a set of real and complex-valued propagation vectors numerically. This results in an explicit selection of plane waves and an associated Trefftz method that achieves accuracy and stability. The theoretical analysis is provided for a two-dimensional domain with circular shape. However, the principles are general and we conclude the paper with a numerical experiment demonstrating practical applicability also for polygonal domains.

Measuring Received Signal Strength of UWB Chaotic Radio Pulses for Ranging and Positioning

The use of ultra-wideband (UWB) signals for local positioning is very attractive for practice, because such signals have the potential to provide centimeter precision. In this paper, we consider wireless ranging (distance measurement) and positioning, using one of the kinds of UWB signals, i.e., chaotic radio pulses, which are noise-like signals with no constant shape. The distance measurement is based on an assessment in the receiver of the power of UWB chaotic radio pulses emitted by the transmitter. A new method for estimating their power and its experimental implementation is proposed and described. Experimental layouts of the transmitter and receiver and the principles of their operation are described. To determine the main features of this method under real signal propagation conditions, full-scale indoor measurements were carried out, and statistical estimates of the accuracy were made. We present the results of experimental testing of the proposed approach for positioning the emitter relative to a system of anchors in an office space 6 × 6.5 m2 in the mode of measuring object coordinates on a line and on a plane. The mean absolute error (MAE) of distance measurement (1D) was 25 cm, and the root mean squared error (RMSE) was 39 cm. When positioning on a plane (2D), the MAE of coordinate estimation was 34 cm and the RMSE was 42 cm. The proposed distance measurement method is intended for use in wireless UWB transceivers used in wireless sensor networks.

STUDY ON METHODS FOR ESTIMATING AND COMPENSATING FREQUENCY OFFSET IN 6G COMMUNICATION SYSTEMS WITH DFT-S-OFDM TECHNOLOGY UNDER CONDITIONS OF RICE AND RAYLEIGH PROPAGATION CHANNELS

The article investigates effectiveness of methods for estimating and compensating for carrier frequency offset (CFO) for signal processing technology based on orthogonal frequency distribution using discrete Fourier transform (DFT-s-OFDM) in terms of use of Rice and Rayleigh channels close to real propagation channels. Also, the possibility to increase the efficiency of estimating and compensating for frequency mismatch by introducing the Kronecker product operation into original algorithms of signal processing methods is considered. The article investigates the effectiveness of methods for estimating and compensating for carrier frequency offset (CFO) for signal processing technology based on orthogonal frequency distribution using discrete Fourier transform (DFT-s-OFDM) in conditions of using Rice and Rayleigh channels close to real propagation channels. Also, the possibility of increasing the efficiency of estimating and compensating for frequency mismatch by introducing the Kronecker product operation into the original algorithms of signal processing methods is considered. The effectiveness of using shorter guard intervals in noisy channels and high levels of frequency mismatch is confirmed.

Reconstructions of time-evolving sound-speed fields perturbed by deformed and dispersive internal solitary waves in shallow water

The high-fidelity reconstruction of sound speeds is crucial for predicting acoustic propagation in shallow water where internal solitary waves (ISWs) are prevalent. Mapping temperatures from time series to spatial fields is an approach widely used to reproduce the sound speed perturbed by deformed internal waves. However, wave-shape distortions are inherent in the modeling results. This paper analyzes the formation mechanism and dynamic behavior of the distorted waveform that is shown to arise from the mismatch between the modeled and real propagation speeds of individual solitons within an ISW packet. To mitigate distortions, a reconstruction method incorporating the dispersion property of an ISW train is proposed here. The principle is to assign each soliton a real speed observed in the experiment. Then, the modeled solitons propagate at their intrinsic speeds, and the packet disperses naturally with time. The method is applied to reconstruct the sound speed perturbed by ISWs in the South China Sea. The mean and median of the root-mean-square error between the reconstructed and measured sound speeds are below 2 m/s. The modeled shape deformations and packet dispersion agree well with observations, and the waveform distortion is reduced compared with the original method. This work ensures the high fidelity of waveguide-environment reconstructions and facilitates the investigation of sound propagation in the future.

Continuous families of non-Hermitian surface solitons.

We show that surface solitons form continuous families in one-dimensional complex optical potentials of a certain shape. This result is illustrated by non-Hermitian gap-surface solitons at the interface between a uniform conservative medium and a complex periodic potential. Surface soliton families are parameterized by a real propagation constant. The range of possible propagation constants is constrained by the relation between the continuous spectrum of the uniform medium and the bandgap structure of the periodic potential.

A Dual-CP Quad-Port MIMO Antenna With Reduced Mutual Coupling for X-Band Application

A compact quad-port MIMO antenna with dual-polarization is proposed. Each of the four antenna elements features a modified rectangular radiator (MRR) backed by a partial ground plane and fed by a T-shaped microstrip line. The four antenna elements are interconnected by an X-shaped strip and isolated by a modified plus-shaped (MPS) structure, resulting in over -18 dB of isolation. With a small footprint of only 36 mm × 27 mm, the antenna exhibits a 10-dB impedance bandwidth with a completely overlapping 3-dB axial-ratio bandwidth (ARBW) of 19.32% (7.90–9.59 GHz). Additionally, it can provide a gain of over 3.5 dBi, an efficiency of over 70%, and an envelope correlation coefficient (ECC) of less than 0.01 in both isotropic and real propagation scenarios.

Uncertainty analysis of gamma-ray densitometry applied for gas flow modulation technique in bubble columns

The gas flow modulation technique is a recently proposed approach for measuring the axial gas dispersion coefficient in bubble columns. This study presents a quantitative analysis of the experimental uncertainty associated with gamma-ray densitometry and ensemble-averaging of the data. The considered uncertainty sources are the statistics of the photon counting process, a mismatch between the modelled and the real radiation propagation due to the spatial extent of the detector, and a potential mismatch between modulation and sampling frequencies. The analysis is based on a numerical gamma-ray propagation model and a Monte Carlo approach to account for statistical uncertainty. The proposed algorithm supports the selection of an optimal total scanning time based on detector size, modulation parameters, involved fluids and column and source parameters. The analysis reveals that a mismatch between the modulation and sampling frequencies is most critical while the impact of the other considered uncertainty sources is rather marginal.

Crack propagation and induced vibration characteristics of cracked cantilever plates under resonance state: Experiment and simulation

Cracks in aero-engine blades have caused great economic losses and safety hazards in the past decades. High cycle fatigue, as one of the main causes of blade crack propagation, has been of increasing interest in recent years. In this paper, the cantilever plate specimens are selected as the research object to analyze the real crack propagation path and the change of resonance frequencies under the resonance state. First, a joint simulation analysis method based on FRANC3D and ANSYS software is proposed for the analysis of the crack propagation path. The proposed method is verified through crack propagation experiments. Second, a dynamic model for cantilever plates with a real crack propagation path is proposed based on the shell element theory. Finally, the associations between crack propagation lengths and resonance frequencies are studied. Some interesting phenomena are found: the resonance frequency decreases as the crack propagation length increases and the resonance frequencies show a slow decrease, then a constant decrease, and finally a rapid decrease; the nearer the initial crack location is to the root of the cantilever plate, the greater the curvature of the crack propagation path. This study can provide a better understanding of blade fatigue and the reference for analysis of blade crack propagation paths.