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In this paper the generalized model of contact of two plan bodies that roll and slide or just roll is presented. The analytical solution of the correct distribution of pressure in the contact is realized in the presence of the normal compressive force, which realizes the contact, as well as of the force pair or of a tangential force. This model can be used on sprocket teeth due to sliding rolling or rolling itself on the gear pole. The results obtained have been experimentally confirmed by many researchers as well as by the damage that the wheels actually suffer from the teeth.

<p><strong>Background:</strong> Over the last decade have seen a drastically increase of interest in the Single photon avalanche diode (SPAD) detectors applications at many variety of quantum experiments where the detection efficiency at single-photon level is required. The calibration of such detectors involves predominantly the determination of the detection efficiency.</p><p><strong>Methods:</strong> The present study was carried out at Department of Photometry and Applied Radiometry, Physikalisch-Technische Bundesanstalt (PTB), National Metrology Institute of Germany. This work is focused in a reproducible and close-to-ideal alignment position method of the SPAD detectors to the incident beam for achieving low measurement uncertainty.</p><p><strong>Results:</strong> A dominantly Gaussian profile is obtained when the diameter of the detector is smaller than the beam diameter, whereas in case then the detector is larger than the beam, a dominantly rectangular scan is obtained. The optimal position (X/Y/Z) for setting the SPAD detector correspond to X_center = 235.11 mm, Y_center<em> </em>= 6.28 mm and Z_position = 14.6 mm. Homogeneity of the detection efficiency depends on the beam size and evaluated regions.</p><p><strong>Conclusions:</strong> The experimental set-up and experimental results needed for optimization of the SPAD detector position were described. This analysis gives important information in how to carry out the optimization of the detector position for the calibration of the SPAD and analysis of quantum detection homogeneity.</p>

BackgroundSilicon single-photon avalanche diodes (Si-SPADs) are the most used devices for measuring ultra-weak optical radiant fluxes in many quantum technology fields, such as quantum optics, quantum communication, quantum computing, etc. In all these fields, the detection efficiency is the main parameter, which has to be accurately known for achieving reliable measurements. In this paper we present the improvements performed on the setup described in López et al. (J Mod Opt 62:S21–S27, 2015) for determining the detection efficiency of Si-SPAD detectors with a low measurement uncertainty. The improvement arises from the precise alignment of the Si-SPAD detector and the low deviation reached between the total calculated filter transmission and the individual filter transmission measurements (≤0.05%) performed with an integrating sphere with attached Si-photodiode as standard detector.Results The relative standard uncertainty of the Si-SPAD detection efficiency measurement achieved is now as low as ~0.16%. Furthermore, the investigation of the detection efficiency homogeneity of two commercial Si-SPAD detectors from different manufacturers and with different sensor diameters is also presented. The obtained homogeneity is ≤2.2% within a region of diameter of 40 μm.ConclusionsThe detailed analysis presented in this paper shows the potential for achieving low measurement uncertainties for Si-SPAD detector calibration even in the low photon flux range. The low uncertainties are only to be realized for reproducible measurement conditions, i.e. in specific for equal beam sizes and beam shapes and well as for an irradiation of equal active areas of the detector. This, however, will be difficult to obtain when measurements are performed at different national metrology institutes.

The technology of severe plastic deformation (SPD) is the process on forming metals of large plastic strain that is used for mass production in order to make ultrafine-grained (UFG). Through research on the characterization of aluminium-based composite materials with several SPD methods, the ideal variable will be obtained in producing high-strength materials. The development of a new SPD method driven by requirements simplifies the process, so that it can be applied for mass production, some of the development of SPD technology is able to produce high plastic strain. The market for nanostructured materials produced by SPD technology is in sectors where superior traits such as specific strength is needed. This research is focused on a comparison of several SPD methods; APB, MAF, ECAP-PC and RPRF, in the scope of mechanical characterization on aluminium based composites. Result of mechanical properties obtained, the RPRF method is the best that is able to produce higher mechanical characteristics than other methods. That produces 75.9 VH10 hardness on RPRF, while APB 45.82 VH10, ECAP-PC 66.12 and MAF of 42.9 VH10