Vol. 7, No. 2 (2023): Regular Issue

Russian Internet Trolls use fake personas to spread disinformation through multiple social media streams. Given the increased frequency of this threat across social media platforms, understanding those operations is paramount in combating their influence. Building on existing scholarship on the inner functions within influence networks on social media, we suggest a new approach to map those types of operations. Using Twitter content identified as part of the Russian influence network, we created a predictive model to map the network operations. We classify accounts type based on their authenticity function for a sub-sample of accounts by introducing logical categories and training a predictive model to identify similar behavior patterns across the network. Our model attains 88% prediction accuracy for the test set. Validation is done by comparing the similarities with the 3 million Russian troll tweets dataset. The result indicates a 90.7% similarity between the two datasets. Furthermore, we compare our model predictions' on a Russian tweets dataset, and the results state that there is 90.5% correspondence between the predictions and the actual categories. The prediction and validation results suggest that our predictive model can assist with mapping the actors in such networks.

A new class of exact solutions of the non-linear two-dimensional Boussinesq model for internal gravity waves is derived in this paper. The most general forms of invariant solutions, which can not be guessed from the anisotropic property and correspondingly were not reported in previous studies, are presented in this paper by infinite-dimensional Lie algebra spanned by the infinitesimal symmetries. As a particular example, it is shown here that the nonlinear two-dimensional boussinesq model for internal gravity waves is invariant with respect to the dilations and rotation symmetries that provide the class of exact solutions that has not been reported in previous studies. The new remarkable property of spinning phenomena is observed for internal waves, which has not been reported in the previous studies. The effect of nonlinearity and the earth rotation on the spinining phenomena has been studied both numerically and analytically.

The critical speed of aeroengine can be adjusted by designing the support stiffness of elastic support structure. Squirrel cage elastic support structure is a common elastic support structure, so it is very important to optimize its design steps and calculate its stiffness accurately. The static characteristics of the squirrel cage elastic support structure such as stiffness and strength characteristics are analyzed, and the stiffness value, deformation and stress clouds of the structure are obtained, which are based on the finite element method. Then, the static stiffness test platform of the squirrel cage elastic support structure is built to verify the validity of the experiment from the perspective of simulation. Experimental verification shows that the experimental test values have good agreement with the simulation values, which proves the correctness of the simulation results. Finally, in order to achieve the maximum strength of the structure under the condition of specified installation space and specified stiffness value. The genetic algorithm is used to optimize the structure. The rule of the optimization result is summarized, which is verified by the theoretical analysis and simulation.

So far machine learning (ML) has become increasingly significant in spectrum sensing (SS) for future intelligent wireless communications. In order to obtain an effective SS performance in fading channel, this paper proposes a GMM (Gaussian Mixture Model) based cooperative SS under the conditions of AWGN (Additive White Gaussian Noise) channel and Rayleigh flat fading channel. For evaluating the SS performance, numerous NB (Naive Bayes) and SVM (Support Vector Machine), MLP (Multi-Layer Perceptron) based ML method, as well as the traditional cooperative SS technologies (AND criterion, OR criterion, and Maximum Ration Combining (MRC)) are also investigated for performance comparison. The ROC (receiver operating characteristics) and AUC (area under the curve) performance index is used to compare performance. Simulation results and analysis show that the proposed GMM-based cooperative SS enable acquire the best performance under the Rayleigh channel.

This paper investigates the impulse response of a longitudinally vibrating rod with a mass-damper-spring termination. The equations of motion of the system are derived using Lagrange's method. The vibration of the rod consists of rigid-body and elastic motions. The impulse response is predicted with a particular solution method which constructs the response as the summation of the solution satisfying homogeneous boundary conditions and a particular solution dealing with non-homogeneous boundary conditions. The particular solution method transforms the original partial differential equation to discrete dynamic systems represented in a state-space form. The transient and total impulse responses at selected locations on the rod are studied in detail. The vibration reduction of the rod by tuning the mass-damper-spring system is discussed with the help of root locus with respect to the mass, damping and stiffness parameters. The tuning of the mass-damper-spring system can change coupling between the rigid-body and elastic motions, which in turn can significantly affect the response of the rod. The method of particular solution is validated through the error analysis and response comparison of a rod with free-free boundary conditions.

This paper presents a theory for nonlinear dynamics of dynamical systems with two variable-crossing univariate vector fields. Dynamical systems with a variable-crossing univariate linear and quadratic vector fields are discussed, and the corresponding bifurcation and global dynamics are presented. The saddle-center bifurcations are presented through parabola-saddle bifurcations. Dynamical systems with two crossing-variable univariate quadratic vector fields are discussed, and the switching and appearing bifurcations for saddles and centers are discussed through the first integral manifolds, and the homoclinic networks will be first presented. Double-inflection bifurcations are for appearance of the saddle-center network, and the homoclinic networks with centers are constructed. The saddle-center networks with limit cycles are presented from the first integral manifolds.