208,760 research outputs found
Recent Advances in Real-Time Load-Pull Systems
No full textIn this paper, some of the latest advances in real-time load-pull technologies will be described. A recently introduced ultralow-loss directional coupler, which has been designed and realized by the authors, provides a number of advantages when used in load-pull test sets. This device has been called the load-pull head. The new ultralow-loss load-pull head can transform any passive precalibrated load-pull system into an easily calibrated and accurate real-time load-pull test set, without losing highreflection- coefficient capabilities. Moreover, if used to realize an active loop, the load-pull head reduces the risks of oscillations and the amount of the loop amplifier output power. As an example application, measurements with a passive real-time load-pull setup of a 30-W laterally diffused MOS (LDMOS) transistor are presented. Furthermore, some advice to bypass the remaining unavoidable losses due to probes and cables is given.We will show, with measurements and with very simple calculations, that the combined use of load-pull heads, a passive tuner, and an active loop not only boosts the available ΓL but also decreases the loop amplifier output power, with a sensible reduction in the overall cost of the syste
A Web-Based Distributed Virtual Educational Laboratory
No full textEvolution and cost of measurement equipment, continuous training, and distance learning make it difficult to provide a complete set of updated workbenches to every student. For a preliminary familiarization and experimentation with instrumentation and measurement procedures, the use of virtual equipment is often considered more than sufficient from the didactic point of view, while the hands-on approach with real instrumentation and measurement systems still remains necessary to complete and refine the student's practical expertise. Creation and distribution of workbenches in networked computer laboratories therefore becomes attractive and convenient. This paper describes specification and design of a geographically distributed system based on commercially standard components
Novel hardware and software solutions for a complete linear and non-linear microwave device characterization
No full textSurface Modification of Cotton and Polyester Fibers by Methacrylate Silane and Fluorinated Alkoxysilane via Sol-gel and UV-curing Coupled Process
No full textThe aim of the work was the surface modification of cotton and polyester fibers to confer hydro and oil repellency to the fabrics. Sol-gel, previously investigated by the same authors as textile finishing [1-3], was here chosen as surface treatment not involving the bulk of the fibers, so fabrics can keep unvaried comfort characteristics. Moreover, it was coupled to post UV-curing to enhance the
finishing adhesion to the fibers, with a consequent improvement of treatment fastness. Process optimization was in fact focused on an economical and ecofriendly process to obtain an effective finishing with good fastness to washing.
3-(Trimethoxysilyl)propyl methacrylate (MEMO) was used as sol-gel precursor both alone and with Fluorolink® S10, a commercial product from Solvey Solexis (Italy), to obtain an UV-curable modified nanosol to be applied to fabrics with weight-ons ranging from 5% to 30% o.w.f. Treated samples were tested by means of contact angle measurements with water and oil while fastness to washing was tested according ISO standard (till 5 washing cycles). Moreover the modifications occurred on fibers surface were investigated by FTIR-ATR and XPS while the influence on thermal properties were revealed by DSC measurements.
Promising results were obtained in terms of conferred water and oil repellency and treatment fastness, enhanced in particular on UV post-cured samples, as expected.
[1] F. Ferrero and M. Periolatto, Appl. Surf. Sci., 257, 201 (2013).
[2] M. Periolatto, F. Ferrero, A. Montarsolo, R.Mossotti, Cellulose, 20(1), 355 (2013). [3]
A.Montarsolo, M. Periolatto, M. Zerbola, F. Ferrero, R. Mossotti, Text. Res. J. , 83(11), 1190 (2013)
Real space and Q space analysis of local disorder induced by Al doping in the SmBa2Cu3O6+d superconductor
No full textThe cation substitutions for copper in RBa2Cu3O6+d (R = Y, Ln; 0 < d < 1) high Tc superconductors are widely studied in order to understand their physical properties [1]. In particular Al seems to be a suitable dopant because: i) it is a non-magnetic ion; ii) it substitutes for copper only on Cu1 (0,0,0) site, far from the superconducting planes; iii) its valence state is fixed, making simple the calculation of the total hole concentration; iiii) it is possible to vary the medium range structure of the superconductor throughout an aluminium-clustering process [2]. However, Aluminium doping introduces local disorder in the structure because of its different valence (+3 instead of +1/+2) and local environment (tetrahedric instead of square planar) in respect to copper. In order to fully understand the effect of Al doping on the physical properties of RBa2Cu3O6+d superconductors the nature of this disorder has to be defined. To do so we have investigated some SmBa2Cu3-xAlxO6+d samples with different Al concentration (x=0, 0.15, 0.33), annealed either in oxidising or in reducing conditions. The long and short range structure of the samples have been determined through the parallel real pace (PDF) and Q space (Rietveld) analysis of XRPD patterns obtained at the ID31 beamline of ESRF facility. References
[1] See, for instance, M.S. Skakle, Mater. Sci. Eng., R23, 1 (1998) and references therein
[2] M. Scavini, M. Daldosso, S. Cappelli, C. Oliva, M. Brunelli, C. Ferrero, A. Lascialfari, Europhys. Lett., 76(3), (2006) 443-44
Hydro and Oil Repellent Finishing of Textiles by UV-curing: Influence of Scaled-up Process Parameters
No full textThe topic of the present study was the semi-industrial scale-up of the hydro and oil repellent finishing of textile fabrics by ultraviolet (UV) curing of silica based or fluorocarbon resins on fiber surface. The method applied at laboratory scale to cotton, polyester and polyamide fibers was already studied in previous works [1-3]: the optimization of process parameters, followed by a deep
characterization of treated samples, revealed the effectiveness of the treatment. In the present
study, a great number of larger fabric samples were impregnated by padding with commercial
finishing agents and then were irradiated with an high power, semi industrial UV lamp, in air.
Samples add-on was significantly reduced in order to hold down the finishing cost. White and dyed samples of different textile composition were treated and evaluated in terms of conferred repellency, yellowing or color changes.
Most relevant process parameters were investigated, considering the thermal process normally adopted at industrial level as reference. Results were so statistically evaluated by Six Sigma method with Minitab 16 software, to point out the most influencing parameters and the real possibility to replace the thermal treatment with UV-curing.
[1] F. Ferrero, M. Periolatto, C. Udrescu, Fibers Polym, 13(2), 191 (2012).
[2] F. Ferrero, M. Periolatto, J of Nanosci Nanotechnol, 11, 8663 (2011).
[3] F. Ferrero, M. Periolatto, M. Sangermano, M. Bianchetto Songia, J App Polym Sci, 107, 810
(2008)
Three port network analyzer: an original implementation with a simplified calibration procedure
No full text
Generalized mixed-mode S-parameters
No full textThis paper presents an innovative approach to extend the S-parameter definition to multiport networks having conventional single-ended and differential ports, as is the case for operational amplifiers, transformers and baluns. To give maximum generality to this technique, for example, allowing for complex -parameter reference impedances, the mathematical derivation will be carried out with the most general definition of the -parameters. The presented approach gives the same results already published for circuits with differential ports only when the required simplifications are applied
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