Effective Bandwidth Estimation in Data Networks: An Analysis for Two Traffic Characterizations

The Generalized Markov Fluid Model(GMFM)is assumed for modeling sources in the network because it is versatile to describe the traffic fluctuations.In order to estimate resources allocations or in other words the channel occupation of each source,the concept of effective bandwidth(EB)proposed by Kelly is used.In this paper we use an expression to determine the EB for this model which is of particular interest because it allows expressing said magnitude depending on the parameters of the model.This paper provides EB estimates for this model applying Kernel Estimation techniques in data networking.In particular we will study two differentiated cases:dispatches following a Gaussian and Exponential distribution.The performance of the proposed method is analyzed using simulated traffic traces generated by Monte Carlo Markov Chain algorithms.The estimation process worked much better in the Gaussian distribution case than in the Exponential one.

Initiating Binary Metal Oxides Microcubes Electromagnetic Wave Absorber Toward Ultrabroad Absorption Bandwidth Through Interfacial and Defects Modulation

Cobalt nickel bimetallic oxides(NiCo_(2)O_(4))have received numerous attentions in terms of their controllable morphology,high temperature,corrosion resistance and strong electromagnetic wave(EMW)absorption capability.However,broadening the absorption bandwidth is still a huge challenge for NiCo_(2)O_(4)-based absorbers.Herein,the unique NiCo_(2)O_(4)@C core-shell microcubes with hollow structures were fabricated via a facile sacrificial template strategy.The concentration of oxygen vacancies and morphologies of the three-dimensional(3D)cubic hollow core-shell NiCo_(2)O_(4)@C framework were effectively optimized by adjusting the calcination temperature.The specially designed 3D framework structure facilitated the multiple reflections of incident electromagnetic waves and provided rich interfaces between multiple components,generating significant interfacial polarization losses.Dipole polarizations induced by oxygen vacancies could further enhance the attenuation ability for the incident EM waves.The optimized NiCo_(2)O_(4)@C hollow microcubes exhibit superior EMW absorption capability with minimum RL(RLmin)of-84.45 dB at 8.4 GHz for the thickness of 3.0 mm.Moreover,ultrabroad effective absorption bandwidth(EAB)as large as 12.48 GHz(5.52-18 GHz)is obtained.This work is believed to illuminate the path to synthesis of high-performance cobalt nickel bimetallic oxides for EMW absorbers with excellent EMW absorption capability,especially in broadening effective absorption bandwidth.

Microwave absorption and bandwidth study of Y_(2)Co_(17)rare earth soft magnetic alloy with easy-plane anisotropy

The easy-plane anisotropy of the Y_(2)Co_(17)rare earth soft magnetic alloy has high saturation magnetization and operating frequency,and good impedance matching.Therefore,it is expected to become a kind of high-performance microwave absorbing material.In this paper,Y_(2)Co_(17)alloy was prepared by a reduction-diffusion method,and its micropowder was prepared as polyurethane(PU)based composite absorbing materials(Y_(2)Co_(17)/PU composites).The microwave properties of composites with different volume fractions were calculated.The composites showed outstanding absorption characteristics in the range of 20-30 vol%,and the minimum reflection loss(RL)was less than-50 d B.When the volume fraction was25%,the effective absorption bandwidth could cover the X-band at a thickness of 1.5 mm,and the Ku-band at a thickness of1.08 mm.The absorption mechanism was analyzed by the interface reflection model.The RL absorption peak bandwidth mechanism was discussed by using the amplitude relation and calculating the effective absorption bandwidth at different thicknesses.The effective absorption bandwidth values were in good agreement with the theoretical expectation.

A Self-Similar Call Admission Control Algorithm in WiMAX

Modelling WiMAX network traffic based on the self-similarity character is better than the traditional model based on the Poisson process, because the former can provide more accurate calculation for effective bandwidth. In this paper we propose a WiMAX network traffic model based on M/Pareto model to describe its self-similarity character. Then we deduce the average transmission rate and the variance coefficient for the FBM traffic model by the M/Pareto model, and get the Hurst parameter of the FBM traffic model by statistical analysis method. By the FBM traffic model we get a formula for calculating the effective bandwidth. Accordingly, we propose a modified self-similar call admission control algorithm (SS-CAC). SS-CAC can avoid measuring the parameter values of FBM traffic flow to do call admission control. Simulation results show that SS-CAC greatly reduces the call blocking rate and improves the bandwidth utilization.

A Review on Metal-Organic Framework-Derived Porous Carbon-Based Novel Microwave Absorption Materials

The development of microwave absorption materials(MAMs) is a considerable important topic because our living space is crowed with electromagnetic wave which threatens human’s health.And MAMs are also used in radar stealth for protecting the weapons from being detected.Many nanomaterials were studied as MAMs,but not all of them have the satisfactory performance.Recently,metal-organic frameworks(MOFs) have attracted tremendous attention owing to their tunable chemical structures,diverse properties,large specific surface area and uniform pore distribution.MOF can transform to porous carbon(PC) which is decorated with metal species at appropriate pyrolysis temperature.However,the loss mechanism of pure MOF-derived PC is often relatively simple.In order to further improve the MA performance,the MOFs coupled with other loss materials are a widely studied method.In this review,we summarize the theories of MA,the progress of different MOF-derived PC-based MAMs,tunable chemical structures incorporated with dielectric loss or magnetic loss materials.The different MA performance and mechanisms are discussed in detail.Finally,the shortcomings,challenges and perspectives of MOF-derived PC-based MAMs are also presented.We hope this review could provide a new insight to design and fabricate MOF-derived PC-based MAMs with better fundamental understanding and practical application.

The effect of conductor loss on half-wave voltage and modulation bandwidth of electro-optic modulators

In this paper, we theoretically deduce the expressions of half-wave voltage and 3-dB modulation bandwidth in which conductor loss is taken into account. The results suggest that it will affect the theoretical values of half-wave voltage and bandwidth as well as the optimized electrode's dimension whether considering the conductor loss or not. As an example, we present a Mach-Zehnder (MZ) type polymer waveguide amplitude modulator. The half-wave voltage increases by 1 V and the 3-dB bandwidth decreases by 30% when the conductor loss is taken into account. Besides, the effects of impedance mismatching and velocity mismatching between microwave and light wave on the half-wave voltage, and 3-dB bandwidth are discussed.

Effects of Signal Spectrum Bandwidth on Different PMD Compensation Feedback Methods

We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth, including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal.

Simulation of quantum-well slipping effect on optical bandwidth in transistor laser

An optical bandwidth analysis of a quantum-well （16 nm） transistor laser with 150-μm cavity length using a charge control model is reported in order to modify the quantum-well location through the base region. At constant bias current, the simulation shows significant enhancement in optical bandwidth due to moving the quantum well in the direction of collector-base junction. No remarkable resonance peak, limiting factor in laser diodes, is observed during this modification in transistor laser structure. The method can be utilized for transistor laser structure design.

Construction of Co_(2)NiO_(4)@MnCo_(2)O_(4.5)nanoparticles with multiple hetero-interfaces for enhanced electromagnetic wave absorption

Nanocomposites with heterogeneous structures and magneto-electric synergistic losses have broad prospects for improving electromagnetic wave(EMW)absorption performance.In this study,we synthesized Co_(2)NiO_(4)@MnCo_(2)O_(4.5)nanoparticles with abundant hetero-interfaces and multiple magnetoelectric loss mechanisms by a facile hydrothermal method.The excess 0.5 oxygen atoms in MnCo_(2)O_(4.5) produce more vacancies and contribute to the enhancement of electrical conductivity.Sequential nanoneedle clusters facilitate multiple reflections and absorption of EMW in the materials,which are accompanied by an abundance of heterogeneous interfaces to improve the dielectric loss.The Co_(2)NiO_(4)@MnCo_(2)O_(4.5)composites showed a minimum reflection loss(RLmin)of30.01 dB and a superior effective absorption bandwidth(EAB)of 6.12 GHz(11.88 GHze18 GHz)at a thickness of 2.00 mm.Computer Simulation Technology(CST)revealed that the obtained particles show very low radar crosssection(RCS)values and almost full coverage angles.The maximum reduction of RCS at vertical incidence reaches 19.98 dB m2.The Co_(2)NiO_(4)@MnCo_(2)O_(4.5)nanoparticles exhibit outstanding radar attenuation properties,which can effectively inhibit the reflection and scattering of EMW.Therefore,the prepared Co_(2)NiO_(4)@MnCo_(2)O_(4.5)absorbers have great application potential in the field of EMW absorption.

Fabrication and efficient electromagnetic waves attenuation of three-dimensional porous reduced graphene oxide/boron nitride/silicon carbide hierarchical structures

In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.

The point defect and electronic structure of K doped LaCo_(0.9)Fe_(0.1)O_(3)perovskite with enhanced microwave absorbing ability

ABO_(3)perovskites,owning unique properties,have great research prospect in electromagnetic wave absorption field.Normally,doping can significantly regulate the dielectric loss,whereas the magnetic loss can be ignored.In this work,the crystal structure and electromagnetic properties can be regulated systematically by the K,Fe co-doping for LaCoO_(3)perovskites(LKCFO)under the condition of fixed F content.In addition,the obtained samples show the obvious interfacial polarization effect on accounting to the small size effect,which is conducive to the effective microwave absorption.By analyzing the evolution of the positron annihilation lifetime and the first-principles calculation of the oxygen density of states for the series of LKCFO perovskites,it is found that the charge transport characteristics will be controlled by the point defect generated by allelic doping.The point defect content decreases and then increases as the doping level rises.The prepared perovskite exhibits the lowest defect density and the largest dielectric loss capability,which indicates that the lower point defects promote electron migration and thus enhance the dielectric loss;thus,the electromagnetic wave absorption bandwidth up to 6.2 GHz is reached.In contrast,both insufficient and excessive K doping are detrimental to the enhancement of microwave absorption.Especially,the practical application value was investigated using Computer Simulation Technology(CST)simulations.The LKCFO-2 exhibits the smallest RCS value(below-10 dBm^(2))at almost-90°-90°with a thickness of 2 mm,providing an effective method for study excellent microwave absorption and scattering property.

Optimal capacity and buffer size estimation under generalized Markov Fluids models and QoS parameters

Quality of service(QoS)for internet trafic management requires good trafic models and good estimation of sharing network resource.A link of a network processes all trafic and it is designed with certain capacity C and buffer size B.A Generalized Markov Fluid model(GMFM),introduced by Marr6n(2012),is assumed for the sources because it describes in a versatile way the traffic,allows estimation based on traffic traces,and also consistent effective bandwidth(EB)estimation can be done.QoS,interpreted as buffer overflow probability,can be estimated for GMFM through the EB estimation and solving the optimization problem presented in Courcoubetis and Siris[Perform.Eval.48:5-23,2002],the so-called inf-sup formulas.In this work,we implement a code to solve the inf-sup problem and other optimization related with it,that allow us to do traffic engineering in links of data networks to calculate both,minimum capacity required w hen QoS and buffer size are given or minimum buffer size required when QoS and capacity are given.

One-step synthesis and electromagnetic absorption properties of high entropy rare earth hexaborides(HE REB6)and high entropy rare earth hexaborides/borates(HE REB6/HE REB03)composite powders

Considering the emergence of severe electromagnetic interference problems,it is vital to develop electromagnetic(EM)wave absorbing materials with high dielectric,magnetic loss and optimized impedance matching.However,realizing the synergistic dielectric and magnetic losses in a single phase material is still a challenge.Herein,high entropy(HE)rare earth hexaborides(REB6)powders with coupling of dielectric and magnetic losses were designed and successfully synthesized through a facial one-step boron carbide reduction method,and the effects of high entropy borates intermedia phases on the EM wave absorption properties were investigated.Five HE REB6 ceramics including(Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6,(Ce0.2Hu0.2Sm0.2Er0.2Yb0.2)B6,(Ce0.2Y0.2Eu0.2Er0.2Yb0.2)B6,(Ce0.2Ya2Sm0.2Eu0.2Yb0.2)B6,and(Nd0.2Y0.2Sm0.2Eu0.2Yb0.2)B6 possess CsCl-type cubic crystal structure,and their theoretical densities range from 4.84 to 5.25 g/cm^(3).(Ce02Y0.2Sm0.2Er0.2Yb02)B6 powders with the average particle size of 1.86 jim were found to possess the best EM wave absorption properties among these hexaborides.The RLmin value of(Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6 reaches-33.4 dB at 11.5 GHz at thickness of 2 mm;meanwhile,the optimized effective absorption bandwidth(EAB)is 3.9 GHz from 13.6 to 17.5 GHz with a thickness of 1.5 mm.The introduction of HE REB03(RE=Ce,Y,Sm,Eu,Er,Yb)as intermediate phase will give rise to the mismatching impedance,which will further lead to the reduction of reflection loss.Intriguingly,the HEREB6/HEREB03 still possess wide effective absorption bandwidth of 4.1 GHz with the relative low thickness of 1.7 mm.Considering the better stability,low density,and good EM wave absorption properties,HE REB6 ceramics are promising as a new type of EM wave absorbing materials.

Experimental study on broadband bistable energy harvester with L-shaped piezoelectric cantilever beam

This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.

Hierarchical composite of biomass derived magnetic carbon framework and phytic acid doped polyanilne with prominent electromagnetic wave absorption capacity

To solve the electromagnetic pollution,herein,a CoFe_(2)O_(4)/C/PANI composite was developed by a green route,which was constructed with spinel of metal oxide,graphitized carbon and conductive polymer composites.Benefiting from the designable interfaces and increased dipoles,the microwave dielectric response capability can be boosted significantly and resulted in the enhanced microwave absorbing performance.As revealed by the reflection loss curve,the minimum reflection loss(RLmin) reached-51.81 dB at 12.4 GHz under a matched thickness of 2.57 mm.At 2.5 mm,the effective absorbing band covered 8.88 GHz,suggesting the desirable wideband feature.In our case,the method of utilization of a novel green way to fabricate multiple-component EM absorber can be a promising candidate for high-performance EM absorber.

Electromagnetic wave absorption properties of cobalt-zinc ferrite nanoparticles doped with rare earth elements

Traditional ferrites are of poor electromagnetic wave(EMW) absorption while doping rare earth elements(REEs) can greatly enhance their permeability to improve the EMW loss performance.In this study,Co-Zn ferrite nanoparticles doped with various amounts of REEs(Gd^(3+),Nd^(3+)and Pr^(3+)) were synthesized by a hydrothermal method,and their particle morphology and an EMW absorption performance were characterized by using transmission electron microscopy(TEM) and a Vector network analyzer(VNA).The results show that the initial spherical Co-Zn ferrite nanoparticles present an irregular quadrilateral structure after Gd^(3+)doping,and the average particle size of Co_(0.5)Zn_(0.5-x)Gd_(x)Fe_(2) O_(4) increases from 26 to 50 nm with x increasing from 0 to 0.35.At x of 0.25,the reflectivity absorbance achieves-27.94 dB at 18 GHz with the effective absorption bandwidth(EAB) of 4.08 GHz at a sample thickness of 2.5 mm.When Nd^(3+)doping amount reaches x=0.3,the minimum reflection loss(RL)is-25.63 dB at 18 GHz and EAB is 3.91 GHz.Doping Pr^(3+)(x=0.25) in the sample broadens EAB,and the minimum RL is-16.1 dB at 16.81 GHz and EAB is 7.31 GHz.This study shows that the magnetic moment produced by doping REES can form magnetic domains,which affects the incident EMW and improves the magnetic loss.It is expected that REEs-doped Co-Zn ferrite nanoparticles can be used as efficient electromagnetic shielding materials in aerospace.