Time filter

Source Type

Wheat Ridge, CO, United States

Alessandri A.,Genova Engineering, LLC. | Baglietto M.,niversity of Genoa | Battistelli G.,University of Florence
Automatica | Year: 2010

State estimation is addressed for a class of discrete-time systems that may switch among different modes taken from a finite set. The system and measurement equations of each mode are assumed to be linear and perfectly known, but the current mode of the system is unknown. Moreover, additive, independent, normally distributed noises are assumed to affect the dynamics and the measurements. First, relying on a well-established notion of mode observability developed "ad hoc" for switching systems, an approach to system mode estimation based on a maximum-likelihood criterion is proposed. Second, such a mode estimator is embedded in a Kalman filtering framework to estimate the continuous state. Under the unique assumption of mode observability, stability properties in terms of boundedness of the mean square estimation error are proved for the resulting filter. Simulation results showing the effectiveness of the proposed filter are reported. © 2010 Elsevier Ltd. All rights reserved.

Reverberi A.P.,DCCI | Fabiano B.,Genova Engineering, LLC. | Dovi V.G.,DCCI
International Communications in Heat and Mass Transfer | Year: 2013

We propose a method for the estimation of the overall heat transfer coefficient to/from a fluid in a cylindrical pipe at high Peclet numbers from/to a medium with unknown temperature profile in the axial direction. The method uses an analytical solution of the heat equation in cylindrical coordinates subject to a Robin boundary condition and a parametrised, piecewise linear approximation of the external temperature profile. The velocity profiles of both viscous and turbulent flows are considered and compact solutions of the temperature profile of the fluid are evaluated in both cases as functions of the heat transfer coefficient and of the unknown external temperature profile.It is shown that these solutions provide an efficient method for the estimation of the heat transfer coefficient from fluid temperature data based on separable least squares. The overall procedure is illustrated by a numerical example using simulated data. © 2012 Elsevier Ltd.

Storace M.,Genova Engineering, LLC. | Poggi T.,Genova Engineering, LLC.
International Journal of Circuit Theory and Applications | Year: 2011

Digital architectures for the circuit realization of multivariate piecewise-linear (PWL) functions are reviewed and compared. The output of the circuits is a digital word representing the value of the PWL function at the n-dimensional input. In particular, we propose two architectures with different levels of parallelism/complexity. PWL functions with n = 3 inputs are implemented on an FPGA and experimental results are shown. The accuracy in the representation of PWL functions is tested through three benchmark examples, two concerning three-variate static functions and one concerning a dynamical control system defined by a bi-variate PWL function. © 2009 John Wiley & Sons, Ltd.

Tagliafico G.,Genova Engineering, LLC. | Scarpa F.,Genova Engineering, LLC. | Canepa F.,University of Genoa
International Journal of Refrigeration | Year: 2010

Active Magnetic Regeneration (AMR) is a configuration that allows magnetic refrigeration to be suitable also for room temperature applications. This work is intended to detect, by means of a 1-D numerical model, the influence on the regenerator performances of the working condition ambient temperature (TCURIE ± 20 K) and of the operating parameters fluid mass flow rate (utilization factor 0.5÷3.5) and cycle frequency (0.1÷0.6 Hz). Simulations show that, tuning the fluid mass flow rate, a gadolinium AMR (395 g, f = 0.25 Hz, ΔB = 1.7 T) can reach a maximum cooling capacity of 130 W and a 40 W cooling power over a temperature span of 30 K. A COP of 5 can also be achieved with a temperature span of 30 K and a cooling power of 35 W. Frequency has a weak influence on the AMR's COP, while the ambient temperature is crucial. The system loses the 60% of cooling capacity if the ambient temperature is 20 K away from the material Curie temperature. © 2009 Elsevier Ltd and IIR.

Tagliafico A.,Italian National Cancer Institute | Tagliafico G.,Genova Engineering, LLC. | Martinoli C.,University of Genoa
Ultrasound in Medicine and Biology | Year: 2010

The possibility to realize a quantitative evaluation of nerve density on ultrasound is clinically important to enhance the evaluation of peripheral nerve disorders. We developed software that quantifies the ratio between the hypoechoic and hyperechoic areas of peripheral nerves on ultrasound. Nerve density was defined as (hypoechoic pixels)/(total pixels) and the purpose of our study was to asses if nerve density can be used to differentiate pathologic conditions affecting peripheral nerves. Ultrasound images of peripheral nerves were obtained with a high-frequency probe (17-5 MHz, 288 elements). Sixty-five different patients and (n = 65) controls (age range, 35-81 years; mean 55 years) were prospectively evaluated. Thirty-five patients had carpal tunnel syndrome and 30 patients had neurofibromas. Three radiologists performed a semiautomated evaluation with intra and interobserver agreement. A complete automatic evaluation was performed with no need of intra and interobserver evaluation. With the semiautomated evaluation, mean intraobserver agreement was good (K = 0.85). Interobserver agreements was good as well (reader 1 vs reader 2: k = 0.72; reader 2 vs reader 3: k = 0.80; reader 3 vs reader 1: k = 0.72). Differences among value of nerve density in normal nerves, CTS and neurofibromas were statistically significant (p < 0.0001). There were no statistically significant differences between the results obtained using the automatic or the semiautomatic method. Nerve density is capable of discriminating between normal and pathologic nerves of patients affected by carpal tunnel syndrome or neurofibromas. Moreover, nerve density measure is useful to discriminate between patients with mild and severe CTS. (E-mail: atagliafico@sirm.org). © 2010 World Federation for Ultrasound in Medicine & Biology.

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