No abstract is provided for this article.
A new resident virus propagation model with graded infection rate is established based on the properties of two important stages undergoing by resident virus,which are the latent phase,in which resident virus cannot infect other hosts because it has not yet been loaded into memory and the active phase,in which resident virus resides in memory and infects any suitable program that is executed on the computer.Two computer compartments with different infection rate are established.Furthermore,the dynamic behaviors of this model are investigated by stability theory and numerical simulations.It is found that the dynamical properties of this model are determined by basic reproductive rate.Specifically,virus-free equilibrium is globally asymptotically stable if basic reproductive rate is less than or equal to one,whereas the local asymptotical stability of the viral equilibrium is guaranteed if basic reproductive rate is bigger than one,followed by a conjecture on its global stability.Then the sensitivity analysis of basic reproductive rate to the system parameters is investigated and a collection of policies is advised to control the spread of computer virus over the Internet.
The small-world networks recently introduced by Watts and Strogatz [Nature 393 (1998) 440–442] have attracted much interest in studying the interesting properties of the networks without time-delay. However, a signal or influence travelling on the small-world networks often associated with time-delay features which are very common in biological and physical networks. We develop an analytical approach as well as numerical simulations to try to characterise the effect of time-delay on the properties of small-world networks. An analytical expression of the fractal dimension of the small-world networks is given and thus compared with the results from numerical simulations. Analysis shows that small-world networks with time-delay generally have the multifractals property.
No abstract is provided for this article.
In many design applications, designers often have to find the best geometrical configurations so as to achieve certain objectives with the minimum amount of materials used. Such shape or topology optimization problems are usually much harder to solve than nonlinear optimization problems in a fixed domain. In this paper, we use the recently developed bat algorithm to solve topology optimization problems. Results show that the distribution of different topological characteristics such as materials can be achieved efficiently. We have also tested the bat algorithm by solving nonlinear design benchmarks. Results suggest that bat algorithm is very efficient for solving nonlinear global optimization problems as well as topology optimization.
In modelling sediment compaction and mineral reactions, the rheological behaviour of sediments is typically considered as poroelastic or purely viscous. In fact, compaction due to pressure solution and mechanical processes in porous media is far more complicated. A generalised model of viscoelastic compaction and the smectite to illite mineral reaction in hydrocarbon basins is presented. A one-step dehydration model of the mineral reaction is assumed. The obtained non-linear governing equations are solved numerically and different combinations of physical parameters are used to simulate realistic situations in typical sedimentary basins. Comparison of numerical simulations with real data has shown very good agreement with respect to both the porosity profile and the mineral reaction.
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No abstract is provided for this article.
No abstract is provided for this article.
Compactional flow and temperature evolution in porous media is modelled as a two-phase deformation process. The mathematical model leads to a pair of nonlinear diffusion equations with a moving boundary. Two distinguished features of density-driven compaction and temperature profile are then analysed and different styles of behaviour are compared and shown in this paper.
The cross-ambiguity function (CAF) is commonly used to analyze the delay-Doppler characteristics of signals in radar, sonar, and communication systems. Accordingly, a CAF relates to the correlation processing of signals in the presence of delays and Doppler shifts. In this paper, we use a metaheuristic approach to address the CAF synthesis problem by jointly designing a pair of waveforms. The CAF ofwaveforms designed in this way, approximates a desired pre-defined CAF. It turns out that the waveforms designed by this approach have the benefit of low peak-to-average power ratios. Numerical examples are presented to show that nature-inspired metaheuristic algorithms can be used as an effective tool to synthesize different types of CAFs.
No abstract is provided for this article.
Background: Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic tumor and one of the most malignant tumors worldwide. Circulating tumor DNA (ctDNA) has significant diagnostic and prognostic value for cancer patients.
No abstract is provided for this article.
This paper proposes a generalized Firefly Algorithm (FA) to solve an optimization framework having objective function and constraints as multivariate functions of independent optimization variables. Four representative examples of how the proposed generalized FA can be adopted to solve downlink beamforming problems are shown for a classic transmit beamforming, cognitive beamforming, reconfigurable-intelligent-surfaces-aided (RIS-aided) transmit beamforming, and RIS-aided wireless power transfer (WPT). Complexity analyzes indicate that in large-antenna regimes the proposed FA approaches require less computational complexity than their corresponding interior point methods (IPMs) do, yet demand a higher complexity than the iterative and the successive convex approximation (SCA) approaches do. Simulation results reveal that the proposed FA attains the same global optimal solution as that of the IPM for an optimization problem in cognitive beamforming. On the other hand, the proposed FA approaches outperform the iterative, IPM and SCA in terms of obtaining better solution for optimization problems, respectively, for a classic transmit beamforming, RIS-aided transmit beamforming and RIS-aided WPT.
