1,720,987 research outputs found
Design of an efficient AC magnetohydrodynamic stirrer
No full textRapid mixing of two or more analytes in microchannel networks is essential in the design of most biochemical, immunoassays and DNA analysis microsystems. In this paper we report numerical simulations of a chaotic magneto-hydrodynamic (MHD) stirrer that exhibits fast mixing of steady pressure-driven flows in microchannels at medium-low Reynolds number. The proposed mixer is benchmarked against a MHD stirrer prototype recently reported in literature. Numerical results show that the proposed device has a higher and faster mixing efficiency with respect to recent literature
Wearable Instrument for Skin Potential Response Analysis in AAL applications
Full text linkA novel instrument able to acquire Skin Potential Response (SPR) signals is proposed; SPR is a branch of Electrodermal Activity (EDA) and consists of reading nervous electric pulses that arise when the sympathetic nervous system activates sweat glands as a reaction of an external stressing stimulus. Scientific literature shows that EDA is a good methodology to detect workload, increased stress level and many neurological diseases or addictions. In this paper, we present the design and characterization of a wearable, battery operated, wireless device which can acquire SPR data and can be integrated in a wireless sensor network for the AAL. The developed control panel is responsible of receiving the SPR data, plotting them in real time and, on a secondary screen, providing to the patient visual and auditory stimuli; as a further stimuli generator, an adaptive game controlled by the SPR signal has been developed. The synchronous plot of stimuli markers and SPR signal on the same graph can provide a very useful information for the SPR analysis
Investigating Mesa Structure Impact on C-V Measurements
No full textCapacitance-voltage (C-V) measurements play a crucial role in evaluating semiconductor device performance by revealing vital parameters such as doping levels and charge carrier behavior. This study specifically investigates the impact of mesa structures on C-V measurements in 4H-SiC PiN vertical diodes. Our analysis uncovers distinct capacitance values per unit area among diodes with varying diameters within the same diode family. These findings underscore the limitations of conventional capacitance equations formulated for planar devices when extended to mesa-structured devices. To separate the capacitance portion dependent solely on the PN junction's area from the overall depletion capacitance, which is influenced by the device's geometry, we applied a methodology involving multiple C-V measurements across diodes with differing diameters and validated the experimental outcomes through rigorous calculations. This enables the utilization of standard capacitance equations. Neglecting the impact of device geometry has the potential to introduce significant inaccuracies in critical device parameters. The proposed methodology addresses these limitations, offering valuable insights to enhance the accuracy of extracted quantities from C-V measurements. Furthermore, it provides guidance for interpreting experimental data obtained from devices incorporating mesa structures
Design and characterization of a real-time, wearable, endosomatic electrodermal system
Full text linkThis paper presents the design and characterization of a compact wearable system for long-term assessment of skin potential response, with the aim of monitoring mental stress in a variety of applications. Literature reports that the expected skin potential has peak-to-peak amplitudes of few millivolts in the frequency band [0.1, 10] Hz. The designed system is characterized by a slightly wider bandwidth of [0.08, 40] Hz, and it is based on a 12-bit ADC working with a sampling rate of 200 Sa/s, which can be increased up to 3.5 kSa/s. Data can be continuously acquired for up to 40 h with a battery of 3.7 V/1800 mAh. A Graphical User Interface was also developed for the host computer in.NET framework. The system, to our knowledge the first example of wearable endosomatic electrodermal activity sensor, joins to several skin conductance wearable measuring systems recently proposed in literature, and opens up opportunities for future comparisons of endosomatic and exosomatic responses in real life. The device is thoroughly characterized in accordance with the state-of-the-art of the metrological research in the field. © 2015 Elsevier Ltd. All rights reserved
OCVD Measurement of Ambipolar and Minority Carrier Lifetime in 4H-SiC Devices: Relevance of the Measurement Setup
Full text linkThe open-circuit voltage decay (OCVD) method is a well-known technique for conducting electrical measurements of carrier lifetime: the main advantages lie in the simple setup and the possibility of carrying out measurements in commercial devices without the need of removing the package, as for optical methods. Despite several researchers having reported carrier lifetimes measured by the OCVD method in different devices, there has been little discussion about the potential effect of the experimental setup on the obtained results. By comparing the outputs of the experimental measurements with those of numerical simulations, this study investigates the overlooked effect of the OCVD measurement setup on the former. Due to the growing importance of SiC-based devices, the analysis is applied to a 4H-SiC p-i-n diode. Two main points are addressed: 1) the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence; 2) the origin of the local minimum eventually appearing in the lifetime versus time curves is also investigated. It is found that the minimum can also be related to the time constant of the experimental setup, giving rise to doubts about the usual interpretation of this minimum as the minority carrier lifetime. A method is thus proposed to help discriminate between the two interpretations
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