End-to-End Available Bandwidth Estimation Tools, An Experimental Comparison

Abstract. The available bandwidth of a network path impacts the per-formance of many applications, such as VoIP calls, video streaming and P2P content distribution systems. Several tools for bandwidth estimation have been proposed in the last years but there is still uncertainty in their accuracy and efficiency under different network conditions. Although a number of experimental evaluations have been carried out in order to compare some of these methods, a comprehensive evaluation of all the existing active tools for available bandwidth estimation is still missing. This article introduces an empirical comparison of most of the active esti-mation tools actually implemented and freely available nowadays. Abing, ASSOLO, DietTopp, IGI, pathChirp, Pathload, PTR, Spruce and Yaz have been compared in a controlled environment and in presence of dif-ferent sources of cross-traffic. The performance of each tool has been investigated in terms of accuracy, time and traffic injected into the net-work to perform an estimation.

Extracting kinetic freeze-out temperature and radial flow velocity from an improved Tsallis distribution

We analyze the transverse momentum ($p_T$) spectra of identified particles ($\pi^{\pm}$, $K^{\pm}$, $p$, and $\bar p$) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a $\sqrt{s_{NN}}$ (center-of-mass energy per nucleon pair) range from 14.5 GeV [one of the Relativistic Heavy Ion Collider (RHIC) energies] to 2.76 TeV [one of the Large Hadron Collider (LHC) energies]. For the spectra with a narrow $p_T$ range, an improved Tsallis distribution which is in fact the Tsallis distribution with radial flow is used. For the spectra with a wide $p_T$ range, a superposition of the improved Tsallis distribution and an inverse power-law is used. Both the extracted kinetic freeze-out temperature ($T_0$) and radial flow velocity ($\beta_T$) increase with the increase of $\sqrt{s_{NN}}$, which indicates a higher excitation and larger expansion of the interesting system at the LHC. Both the values of $T_0$ and $\beta_T$ in central collisions are slightly larger than those in peripheral collisions, and they are independent of isospin and slightly dependent on mass.Comment: We have corrected the pseudorapidity ranges of the data quoted in this paper. The PHENIX data should be in the pseudorapidity range $|\eta|<0.35$, but not the rapidity range $|y|<0.5$; and the ALICE data should be in $|\eta|<0.8$ for high transverse momentum region and $|y|<0.5$ for low transverse momentum region, but not only $|y|<0.5$. These do not affect the results of the publicatio

Zinc oxide films prepared by sol–gel spin coating technique

Zinc oxide (ZnO) thin films and micro- and nanostructures are very promising candidates for novel applications in emerging thin-film transistors, solar cells, sensors and optoelectronic devices. In this paper, a low-cost sol-gel spin coating technique was used to fabricate ZnO films on glass substrates. The sol-gel fabrication process of the ZnO films is described. The influence of precursor concentration on the material properties of the ZnO films was investigated. Atomic force microscopy and X-ray diffractometry were employed to examine the structural properties of the ZnO films. The optical properties of the ZnO films were characterized with ultraviolet-visible spectroscopy. The experimental results reveal that the precursor concentration in the sol-gel spin coating process exerts a strong influence on the properties of the ZnO films. The effects of the precursor concentration are discussed. Document Type: Articl