1,721,198 research outputs found
A chaotic CMOS true-random analog/digital withe noise generator
No full textIn this work a discrete-time CMOS analog/digital white-noise generator is presented. The proposed circuit implements a discrete-time deterministic-chaos algorithm that can theoretically issue both delta-correlated analog-value sequences and delta-correlated 1-bit digitized sequences. SPICE simulations state a white-sequence generation maximum frequency above 10 MH
Plate laminae stacks: modelling and simulation of elastic guided propagation
No full textA model is presented describing the phenomenon of ultrasonic guided propagation in stacks of anisotropic laminae under a large variety of boundary conditions. This model can be effectively used in nondestructive testing (NDT) applications, the dispersive nature, of the propagation modes giving a signature of the actual material state
New method to bias CMOS cascode amplifiers
No full textThe authors present a new method for biasing AC-coupled cascode amplifiers. The proposed design allows the correct DC biasing with a single reference signal as well as a single power supply. A start-up circuit is added for correctly biasing the cascode amplifier at power on. SPICE simulations based on a 0.8 μm CMOS technology are include
Multielement ultrasonic system for robotic navigation
No full textIn this paper an ultrasonic multisensor acquisition and processing system with up to 32 air-ultrasound transducers in the frequency range of 40-200 kHz is presented. The system was developed for an obstacle avoidance applications in the robotics field. The acquisition and processing capability of the equipment (based on the digital signal processor TMS320C25 and can sample up to five parallel channels) allows the robot to perform tasks of different difficulty levels, from target-ranging to pattern recognition. As an example of application, a neural approach to a typical problem in the robotic navigation field is presented, which highlights the system-flexibility feature
Hidden Markov Models approach used for life parameters estimations
No full textIn modern electronics and in electrical applications design is very important to be able to predict the actual product life or, at least, to be able to provide the end user with a reasonable estimate of such parameter. It is important to be able to define the availability as a key parameter because, although other performance indicators (as the mean time before failures MTBF or mean time to failure MTTF) exist, they are often misused. To study the availability of an electrical, electronic or an electromechanical system, different methods can be used. The most common one relies on memory-less Markovian state space analysis due to the fact that a little information is needed, and under simple hypothesis, it is possible to gather some outcomes on the availability of steady state value. In this paper the authors, starting from classical approach of Markov models, introduce an extension known as Hidden Markov Models approach to overcome the limits of the previous one in estimating the system availability performance over time. Such a technique can be used to improve the logistic aspects connected with optimal maintenance planning. The provided dissertation in general can be used in different contexts without losing in generality
Very high-speed true random noise generator
No full textIn this work an original CMOS implementation of a discrete-time deterministic-chaos algorithm for random number generation is presented. The proposed circuit topology prevents the degradation of the generated-sequence statistical properties that can be caused by several factors, including the parameter spreading of the technological processes. Experimental results show that the circuit can issue delta-correlated 1-bit digital sequences with a generation maximum frequency above 12 MH
Modeling of the influence of H2O on metal oxide sensor responses to CO
No full textIn this work a model able to predict the dynamic response of conductimetric SnO2 sensors in presence
of humid mixtures of a reducing gas and oxygen is presented. Sensors consisting of large-grained porous
films are taken into account. For these sensors the conduction is given by the surface charge carriers,
whose density is exponentially related to the height of the potential barrier that establishes at the surface
of the grains. The barrier is due to the presence of some localized charge, trapped both on surface intrinsic
defects and on chemisorbed species. In this perspective the complete dynamic model of sensor response is
obtained by combining a set of differential equations describing the kinetics of surface species adsorption
and ionization, the relationship between the density of the charge trapped at the surface and the potential
barrier magnitude, and, finally, the relationship between film conductance and the potential barrier
height.
The presented work is a development of some previous studies that led to the development of a model
of the sensor behavior in dry mixtures of oxygen and CO. In the present study the influence of water
on sensor response, in the same operating conditions previously considered, is treated, and a simple
model of its effect is proposed. Water is accounted for as a further adsorbant interacting with the other
two chemical species. A dissociative adsorption is considered, where adsorbed OH− groups, by loosing
their electrons, behave as donors and inject a non-negligible (significant) amount of free electrons in
the conduction band. The experimental results obtained with a set of 8 Taguchi sensors prove that the
proposed model can predict the most important characteristics of the sensor behavior
Invariant Measures of Tunable Chaotic Sources: Robustness Analysis and Efficient Estimation
No full textIn this paper, a theoretical approach for studying the robustness of the chaotic statistics of piecewise affine maps with respect to parameter perturbations is discussed. The approach is oriented toward the study of the effects that the nonidealities derived from the circuit implementation of these chaotic systems have on their dynamics. The ergodic behavior of these systems is discussed in detail, adopting the approach developed by Boyarsky and Gora, with particular reference to the family of sawtooth maps, and the robustness of their invariant measures is studied. Although this paper is particularly focused on this specific family of maps, the proposed approach can be generalized to other piecewise affine maps considered in the literature for information and communications technology applications. Moreover, in this paper, an efficient method for estimating the unique invariant density for stochastically stable piecewise affine maps is proposed. The method is an alternative to Monte Carlo methods and to other methods based on the discretization of the Frobenius-Perron operator
A Hall-Effect Based Sensor for the Detection of Concentrations of Ferromagnetic Materials in Water
No full textIn this paper, the authors propose a novel sensing architecture for the detection of ferromagnetic materials suspended in water. These materials have a high magnetic permeability and are thus easily attracted by magnets and belong to the broader family of heavy metals. Their presence in water can be harmful for human health and for ecosystems as well: however, currently the only way to detect their presence is by means of laboratory analysis. The solution presented in this paper is based on the usage of a Hall effect sensor exploited to measure the magnetic field generated by a permanent magnet. Dispersed ferromagnetic particles in water are attracted by the permanent magnet, causing a change in the overall magnetic field strength which is detected by the Hall effect sensor. The sensor provides a voltage output with characteristic suitable to be easily acquired by a simple microcontroller. Laboratory tests were performed with different quantities of different types of ferromagnetic materials. The results of these tests suggest the feasibility of a measurement system able to detect small quantities of ferromagnetic contaminants in, laying the ground to the development of an integrated system to be employed for real-time field measurements
A variability-tolerant feedback technique for throughput maximization of TRBGs with predefined entropy
No full textIn this paper a probabilistic feedback technique to maximize the throughput of a generic True
Random Bit Generator (TRBG) circuit, under a given constraint on the entropy, is discussed. In
the proposed solution, the throughput of the device is dynamically and adaptively varied by an
on-line entropy detector, such to obtain, with an arbitrary confidence level, an entropy greater
than a given worst-case value. The approach, which has a general validity, introduces a method
for making maximum use of the TRBG random bit generation capabilities, maximizing the
generation throughput while preserving its entropy. It is different from the classical "open loop"
TRBG design approach, in which the circuit parameter variability determines an uncertainty
about the actual entropy of the device, with the proposed techniques the TRBG generation
speed is varied under a given constraint on the entropy. The method can be applied to all those
integrated TRBG circuits proposed in the literature and based on the uniform sampling of, e.g.,
random physical processes or chaotic dynamical systems
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