An Analog Circuit for Accurate OCVD Measurements
An electronic circuit for making accurate open-circuit voltage decay measurements is presented. The circuit overcomes the main limitations that occur in the standard method when used for carrier lifetime characterization because it realizes the ldquoopen-circuit conditionsrdquo of the device under test with an impedance higher than 100 MOmega and reduces the noise that is inherent in the differential operation of the method.
Sensitivity analysis of influence quantities on signal-to-noise ratio in face-based recognition systems
Nowadays, face recognition systems are going to widespread in many fields of application, from automatic user login for financial activities and access to restricted areas, to surveillance for improving security in airports and railway stations, to cite a few. In such scenarios, several architectures based on both 2D image analysis and 3D reconstruction are investigated and proposed in literature. The actual performance of such systems in terms of correct decision rate is affected by several quantities of influence mainly concerning the conditions of acquisition of the image to be processed. As an example, the image luminosity, the lens defocus and the movement of a subject during the image acquisition can be sources of uncertainty which propagate up to the final classification result, thus affecting the reliability of a subject identification. In previous papers, the authors proposed suitable uncertainty models for both 2D and 3D based architectures able to quantify on-line the level of confidence to assign to the output of such systems according to the ISO-GUM. The proposed models required, for each quantity of influence, to estimate separately their deviations with respect to the reference values achieved in ideal acquisition conditions during the training phase. On the other hand, the quality of an image may be linked to the more general concept of signal-to-noise ratio (SNR), because noise affects the pixel of the image, thus introducing uncertainty on the final image. Therefore, looking for the development of a more straight and simple to use uncertainty model, in this paper the relationships among the quantities of influence and the image SNR are investigated. This activity represents the first step toward the realization of face-based recognition systems able to assign a level of confidence to the output results starting only from the evaluation of SNR on the input image.
Theory of open circuit voltage decay in a p-n junction diode at high injection
Abstract A high injection theory of open circuit voltage decay in a p - n junction diode is given. The theory takes into account the saturation of junction voltage at high injections and coupling between emitter and base of the diode. The results are in qualitative agreement with the available experimental results. In particular the theory explains the plateau which has been observed in most experimental results on the open circuit voltage decay at high injections.