分数阶控制系统的仿真方法

该文对分数阶控制系统提出了一种数值仿真方法。该方法根据Riemann—Liouville定义的分数阶积分和微分，利用δ函数的过滤性质，得到分数阶积分和分数阶微分的近似计算，推导出了相应的分数阶微分方程的数值求解方法，从而得到了分数阶控制系统的一种仿真算法。利用“短记忆法则”对此仿真方法进行改进，可以减少计算量、提高运行速度。文中给出了一些仿真例子，仿真研究结果表明该方法是有效的，它可适用与不同的分数阶系统。对于分数阶控制系统的仿真研究具有一定的实际意义。     

网络带宽测量影响因素研究

详细讨论现有网络带宽的测量方法,从内因、外因两方面,分析总结带宽测量的影响因素,着重对其中的数据包大小、背景流量以及网络延迟进行了研究.     

一种IPv6网络可用带宽测量方法及分析

在分析IPv4网络带宽测量原理的基础上,结合下一代网络协议IPv6,提出了一种IPv6网络单程不等长包对减法可用带宽测量方法。利用IPv6报文的流标签字段控制测试报文序列的路径,设计并编程实现了IPv6网络可用带宽测量原型系统。试验结果表明,方法在IPv6网络下具有可行性,测量误差小于0.1M。测量结果符合实际,反映了网络可用带宽与时延的实时关联性,为网络监控和性能测量提供了有益的手段。     

DiffServ网络的拥塞控制和带宽保证

该文对DiffServ网络的拥塞控制和带宽保证的机制进行了分析和综述,包括TCP拥塞控制机制和路由器缓冲管理算法RED及RIO。研究表明DiffServ网络的拥塞控制和带宽保证的影响因素包括RTT、TCP/UDP相互作用等,解决方案包括对TCP拥塞控制机制的改进和对路由器流量调节器的改进。     

Fractional Rényi Entropy Image Enhancement for Deep Segmentation of Kidney MRI

Recently, many rapid developments in digital medical imaging have made further contributions to health care systems. The segmentation of regions of interest in medical images plays a vital role in assisting doctors with their medical diagnoses. Many factors like image contrast and quality affect the result of image segmentation. Due to that, image contrast remains a challenging problem for image segmentation. This study presents a new image enhancement model based on fractional Rényi entropy for the segmentation of kidney MRI scans. The proposed work consists of two stages: enhancement by fractional Rényi entropy, and MRI Kidney deep segmentation. The proposed enhancement model exploits the pixel’s probability representations for image enhancement. Since fractional Rényi entropy involves fractional calculus that has the ability to model the non-linear complexity problem to preserve the spatial relationship between pixels, yielding an overall better details of the kidney MRI scans. In the second stage, the deep learning kidney segmentation model is designed to segment kidney regions in MRI scans. The experimental results showed an average of 95.60% dice similarity index coefficient, which indicates best overlap between the segmented bodies with the ground truth. It is therefore concluded that the proposed enhancement model is suitable and effective for improving the kidney segmentation performance.     

Two-dimensional CFD simulation of chemical reactions in tapered-in and tapered-out fluidized bed reactors

This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results clearly indicate that an apt apex angle exists in tapered-in reactors in which the fractional conversion reaches a maximum value; while the variations of the apex angle slightly affect the fractional conversion in tapered-out fluidized beds. Increasing the residence time of the gas phase in the upper section of tapered-in beds has positive influences on the fractional conversion, while a further decrease in the gas phase velocity in the tapered-in reactors has a negative effect on the fractional conversion. Moreover, higher bed pressure drop was observed in tapered-in reactors than that in the columnar and tapered-out ones.     

A sampling theorem for fractional S-transform with error estimation

Fractional S-transform (FrST) is generalization of the S-transform (ST). Over the past few years, FrST plays an active role in optics, communication, and signal processing applications. This paper is focused on the sampling theorem of FrST, which is based on multiresolution subspace. It will provide an appropriate and reasonable model of sampling and reconstruction of the signal for real applications. Moreover, two kinds of reconstruction error, estimate truncation and aliasing error for sampling are also discussed. Efficacy of proposed work is validated with simulation results.     

Screening of Surfactant Foaming Properties Using the Gas-Sparging Method: Design of an Optimal Protocol

Foaming properties of five model surfactants, namely, sodium laureth sulfate (SLES), sodium dodecylsulfate (SDS), polyoxyethylene 23 lauryl ether (Brij L23), polysorbate 20 (Tween 20), and polysorbate 80 (Tween 80), have been compared as a function of experimental conditions using the gas-sparging method. The influence of surfactant concentration relative to the critical micelle concentration (CMC) and three process parameters—frit porosity, gas flow rate, and preset volume of foam (or bubbling time)—was studied by means of a 2^4–1 factorial design. Three foaming properties were considered: foam capacity, foam stability, and maximal foam density. At the CMC, SLES, SDS, Tween 20, and Brij L23 were indistinguishable, all having very high foaming capacity and stability, regardless of process conditions. At 0.1 CMC, differences among them were highlighted especially at the lowest frit porosity coupled to the highest gas flow rate. Those conditions are thus recommended when a rapid screening of surfactant foaming performances is needed.     

Global well-posedness of the incompressible fractional Navier–Stokes equations in Fourier–Besov spaces with variable exponents

We study the Cauchy problem of the fractional Navier–Stokes equations in critical variable exponent Fourier–Besov spaces $F{\stackrel{?}{B}}_{p\left(?\right),q}^{4?2\alpha ?\frac{3}{p\left(?\right)}}$. We discuss some properties of variable exponent Fourier–Besov spaces and prove a general global well-posedness result which covers some recent works about classical Navier–Stokes equations.     

Short-time Analysis of Magnetothermoelastic Wave Under Fractional Order Heat Conduction Law

This paper deals with the problem of magnetothermoelastic interactions in a perfectly conducting elastic medium in which the boundary is stress free and subjected to thermal loading in the context of the fractional-order, two-temperature generalized thermoelasticity theory (2TT). The two-temperature, three-phase-lag (2T3P) model and two-temperature Lord–Shulman (2TLS) model of thermoelasticity are combined into a unified formulation introducing unified parameters. The governing equations of generalized thermoelasticity of these models under the influence of a magnetic field are established. The basic equations have been written in the form of a vector-matrix differential equation in the Laplace-transform domain, which is then solved by the state-space approach. The numerical inversion of the transform is carried out by a method based on Fourier-series expansion techniques. Because of the short duration of the second sound effects, small time approximations of the solutions are studied. The numerical estimates of the quantities of physical interest are obtained and depicted graphically. The effect of the fractional-order parameter and the two-temperature and magnetic field parameters on the solutions has been studied and the comparisons among different thermoelastic models are made.