C. Pacheco

Experimental Performance Study of a Very High Speed Free Space Optics Link at the University of Beira Interior Campus: a Case Study

A very high speed FSO (free space optics) link has been successfully implemented for purposes of high requirement applications, at the University Campus. An experimental performance evaluation of this link has been carried out at various OSI levels (1, 4, and 7). Several results are presented and discussed.

Laboratory performance of wi-fi point-to-point links: A case study

Experimental laboratory measurements are made about several performance aspects of IEEE 802.11a, b, g point-to-point links, using Enterasys Networks access points (RBTR2). Detailed results are presented and discussed at OSI levels 1, 3, 4 and 7: SNR, latency, ICMP packet loss, TCP throughput, jitter, percentage datagram loss, and FTP transfer rate.

A new performance assessment of 5 GHz IEEE 802.11n four-node point-to-multipoint links

The performance of wireless communications is an essential point, leading to more trusty and efficacious communications. Security is also important. Laboratory experiments were performed on various performance points of Wi-Fi 5 GHz IEEE 802.11 n Open four-node point-to-multipoint links. Our study contributes to the performance assessment of this technology, utilizing accessible equipments (V-M200 access points from HP and WPC600N adapters from Linksys). New elaborated results are given and discussed, essentially at OSI levels 4 and 7, from TCP and UDP experiments: TCP throughput versus TCP packet size; jitter and percentage datagram loss versus UDP datagram size. Comparisons are made to correspondent results from Open point-to-point links. Conclusions are taken about the comparative performance of the links.

Potentialities of low energy MeV nuclear techniques and computer simulation in surface analysis of materials

Surface analysis is made by nuclear, non-destructive, means and computer simulation for the energy method of analysis. The predicted energy spectra are compared to experimental data, giving target composition and concentration profile information. Mainly, target parameterization and available nuclear data are considered in the computations. The method is favourably applied to the determination of an 18O step concentration profile in a thick oxidized target. A uniform concentration profile of 12C is found for a thick target. Elastic scattering permits depth profiling of Al and O in a thick oxide target.

Laboratory performance measurements of IEEE 802.11 a WEP PTMP links

Wireless communications using microwaves are increasingly important, e.g. Wi-Fi. Performance is a very crucial issue, improving reliability and efficiency in communications. Security is also critically important. Laboratory performance measurements are presented for Wi-Fi IEEE 802.11 a WEP point-to-multipoint links. Our study contributes to performance evaluation of this technology under WEP encryption, using available equipments (HP V-M200 access points and Linksys WPC600N adapters). The paper gives new results from TCP, UDP and FTP experiments in terms of TCP throughput, jitter, percentage of datagram loss and the FTP transfer rate for OSI layers 4 and 7, which are compared with the data from WEP point-to-point, Open point-to-multipoint links and WPA. Conclusions are drawn about the comparative performance of the links.

Applications of MeV ion beams and microscopy to non-destructive surface analysis of materials

Man has been developing a wide range of surface analysis techniques, involving e.g. ion, electron and photon beams interacting with a solid target. The techniques are, generally, complementary and provide target information for near surface depths. Nuclear techniques, which are non-destructive, provide for analysis over a few microns close to the surface giving absolute values of concentrations of isotopes and elements. Applications have been given in areas such as scientific, technologic, industry, arts and medicine, using MeV ion beams [1-7]. Tracing of isotopes with high sensitivities is possible by nuclear reactions. We use ion-ion reactions and the energy analysis method. At a suitably chosen energy of the incident ion beam, an energy spectrum is acquired of ions from the reaction, coming from several depths in the target. Such spectra are computer simulated and compared with experimental data, giving target composition and concentration profile information [4-7]. Elastic scattering is a particular and important case. A computer program has been developed in this context, mainly for flat targets [4-6]. The non-flat target situation arises as an extension. Successful applications of the method are given using the O(p,α0) N reaction and elastic scattering of (He) ions for three types of samples. SEM is used as a useful complementary technique. One sample (S1) was obtained by sequential high temperature oxidation of austenitic steel in C O2 and C O2 gases. An O diffusion concentration profile was expected. SEM has shown a reasonably flat oxide (Fig. 1). S1 was analysed by the O(p,α0) N reaction at Ep=1.78 MeV, 165 . A complementary error function profile of O was found, due to diffusion, and the diffusion coefficient was determined. The second sample (S2) was a self-supported target of anodic aluminium oxide obtained by aluminium anodization at 200 V, with an expected thickness of 0,2740 μm. S2 was analysed by elastic scattering of α particles at Eα =2.0 MeV, 135. An oxide with excellent uniformity and thickness X1= 0.2460 μm was found. Sample S3, labelled Al/Ag/Au, consisted of two thin layers of Ag and Au obtained by sequential vacuum deposition of Ag and Au onto a thick flat Al substrate; film thicknesses of X1=0.0648 μm and X2=0.1333 μm were initially expected for Au and Ag, respectively. It was analysed at Eα =1.5 MeV, 165 . Uniform concentration profiles were used along X3=0.55 μm for Al, X2=0.125 μm for Ag and X1=0.061 μm for Au (Figs. 3 and 4). A further analysis at a higher bombarding energy, Eα=2.9 MeV, permitted to conclude that the sample is better described by a structure Al/Ag/(Au,Ag) where the surface film consists of a mixture of Au and Ag due to the sequential vacuum evaporation, with a relative atomic density CAg/CAu of 5.6%. The results of the present work are illustrated for samples S1 (Figs. 1 and 2) and S3 (Figs. 3 and 4). The combined use of nuclear techniques and SEM microscopy has shown to be a highly powerful analytical tool for surface analysis of materials. Supports from Universidade da Beira Interior and FCT (Fundação para a Ciência e a Tecnologia)/PEst-OEFIS/UUI0524/2011 (Projecto Estratégico-UI524-2011-2012) are acknowledged. 122 doi:10.1017/S1431927614014317 Microsc. Microanal. 21 (Suppl 6), 2015

Experimental performance studies of laboratory WPA IEEE 802.11b, g PTMP links

Wireless communications using microwaves are increasingly important, e.g. Wi-Fi. Performance is a very crucial issue, resulting in more reliable and efficient communications. Security is equally very important. Laboratory measurements are made about several performance aspects of Wi-Fi IEEE 802.11b, g WPA point-to-multipoint links. A contribution is given to performance evaluation of this technology under WPA encryption, using available equipments (DAP-1522 access points from D-Link and WPC600N adapters from Linksys). Detailed results are presented and discussed, namely at OSI levels 4 and 7, from TCP, UDP and FTP experiments, permitting measurements of TCP throughput, jitter, percentage datagram loss and FTP transfer rate. Comparisons are made to corresponding results obtained for point-to-point links. Further comparisons are made to corresponding results obtained for WEP links. Conclusions are drawn about the comparative performance of the links.

Comparative performance studies of laboratory WPA IEEE 802.11g point-to-point links

Wireless communications using microwaves are increasingly important, e.g. Wi-Fi. Performance is a very important issue, resulting in more reliable and efficient communications. Security is equally very important. Laboratory measurements are made about several performance aspects of Wi-Fi IEEE 802.11g WPA point-to-point links. A contribution is given to performance evaluation of this technology under WPA encryption, using available wireless routers from Linksys (WRT54GL). Detailed results are presented and discussed, namely at OSI levels 4 and 7, from TCP, UDP and FTP experiments, permitting measurements of TCP throughput, jitter, percentage datagram loss and FTP transfer rate. Comparisons are made to corresponding results obtained for, mainly, open links. Conclusions are drawn about the comparative performance of the links.