243 research outputs found
A general method to prove the normalization theorem for first and second order typed lambda-calculi
No full textIn this paper we describe a method to prove the normalization property for a large variety of typed lambda calculi of first and second order, based on a proof of equivalence of two deduction systems.
We first illustrate the method on the elementary example of simply typed lambda calculus and then we show how to extend it to a more expressive dependent type system.
Finally we use it to prove the normalization theorem for Girard's system F
Sedoanalgesia in paediatric intensive care: A survey of 19 Italian units
No full textAim: To analyse the methods used to manage and monitor sedoanalgesia at Italian paediatric intensive care units (ICUs). Methods: Data were collected by administering a questionnaire that aimed to investigate whether ICUs adopted a validated protocol to manage sedoanalgesia. Results: The results revealed that a majority of the ICUs adopt a protocol for dealing with sedation and analgesia, but this protocol is implemented with difficulty or not at all in routine clinical practice. The most often used pharmacological combination, is midazolam and fentanyl. Several weaknesses remain in terms of the methods used to assess sedoanalgesia, which are generally not standardized, but rather based on recording the patient's physiological parameters. Conclusion: Sedation and analgesia are priority issues in the management of critically ill children. None of the numerous drugs available is ideal and the protocols currently used in clinical practice involve the combined use of different drugs. There is currently no shared and validated approach as to which is the most effective and safest sedoanalgesic regimen in critically ill children
Common Knowledge as a Coinductive Modality
No full textContains fulltext :
35009.pdf (Publisher’s version ) (Open Access
Modelling General Recursion in Type Theory
No full textthis paper is also included. A tutorial on the method can also be found in Bove 2003. Since our method separates the computational part from the logical part of a de nition, formalising partial functions becomes possible (Bove & Capretta 2001, Bove 2003). Proving that a certain function is total amounts to proving that the corresponding special-purpose accessibility predicate (or domain predicate) is satis ed by every inpu
Realization of an adaptive voltage driver for Voltage Coil Motors
No full textIn this paper we describe a head servo-positioning system for hard disk drives (HDDs), in which the usual current command for the voice coil motor has been replaced by a simpler voltage command. This solution has proven advantages in terms of cost, since the voltage driver does not require any resistive shunt for current measurement and phase-shaping passive networks for the current controller. Also, it requires a lower pin count and can be easily implemented with a PWM power stage. The voltage driver consists of a voltage-controlled power stage, with a pre-filter placed at its input, plus a back e.m.f. feed-forward compensator. The role of the pre-filter is to provide a transfer function between input signal and VCM current as close as possible to that of a standard current loop, so providing a one-to-one replacement to standard current drivers. To achieve this, it can be shown that the filter must cancel out the low-frequency pole of the VCM, located in a position which depends on the electrical impedance of the VCM itself. This, however, may change by ±30% during HDD operations, due to self-heating and consequent variation of the VCM resistance. Such variation may lead to an unsatisfactory performance of the voltage driver, so an adaptation mechanism, capable of tracking variations of VCM coil resistance, must be set up. This paper presents an on-line estimation procedure, based on an extended Kalman filter (EKF), capable of estimating the VCM coil resistance with a high degree of accuracy. EKF, however, usually brings a high computational load, making it unsuitable for real-time, low-cost embedded applications. The paper presents two reduced-order model of the VCM, for which the EKF can be implemented with 30 and 50% less computational effort, respectively, while maintaining a good estimate of the VCM coil resistance. The paper reports experimental results of VCM resistance estimation, obtained with the proposed algorithm, running in 30 S on a 25 MHz, fixed-point DSP. Also, the on-line estimation is used to adapt the pre-filter. Experimental results show that the servo performance with adaptive voltage driver is not affected by resistance variation and equivalent to that of the standard current driver
Realization of a Hard Disk Drive Head Servo-Positioning System with a Voltage-driven Voice-Coil Motor
No full textIn this paper we describe a head servo-positioning system for hard disk drives (HDDs), in which the usual current command for the voice coil motor has been replaced by a simpler voltage command. Current command of the voice coil motor (VCM) has been preferred so far, due to its good performance in terms of robustness. with this solution, in fact, the characteristics of the system to be controlled by the servo-controller are rather independent from all possible variations of electrical impedance of the VCM and power supply voltage. However, this solution has some drawbacks. In fact, in order to realize the current command, a current loop uses a shunt resistor as a current sensor and a linear high power operational amplifier with some phase-shaping network as a current driver. Both shunt resistor and linear amplifier are major sources of power dissipation. Moreover, linear amplifiers need a large area on the silicon chip, increasing the cost of the power device. On the other hand, a fully digital current loop would require a costly A/D converter, and this is one of the reasons why the current controller is still implemented in analog way, thus impeding the implementation of smart control strategies at this level. All the above considerations have led to the realization of a servo system with a voltage-driven VCM. We developed a solution in which current measurement is no longer needed in order to guarantee the correct behavior of the servo controller. The solution is based on a digital, multi-rate pre-filter, driving a voltage amplifier. The filter is designed in such a way that the transfer function between input signal and VCM current is close to that of a standard current loop, so providing a one-to-one replacement to standard current drivers. With the proposed solution, no measurement on the VCM current or voltage is required. It can be shown that with a proper tuning of the pre-filter, the proposed solution exhibits a good robustness against variations of VCM parameters. Since the proposed solution is fully digital, digitally driven switching power stages can be used. Experimental results, including those related to robustness issues, show that the HDD servo-positioning performance obtained with the new voltage-driven system matches that obtained with a standard current loop, in both seek and track following operations. Finally, in order to adapt the pre-filter to operating conditions, an on-line parameter estimation procedure, capable of determining VCM windings resistance, is presented
Realization of an adaptive voltage driver for voice coil motor
No full textIn this paper we describe a head servo-positioning system for hard disk drives (HDDs), in which the usual current command for the voice coil motor has been replaced by a simpler voltage command. This solution has proven advantages in terms of cost, since the voltage driver does not require any resistive shunt for current measurement and phase-shaping passive networks for the current controller. Also, it requires a lower pin count and can be easily implemented with a PWM power stage. The voltage driver consists of a voltage-controlled power stage, with a pre-filter placed at its input, plus a back e.m.f. feed-forward compensator. The role of the pre-filter is to provide a transfer function between input signal and VCM current as close as possible to that of a standard current loop, so providing a one-to-one replacement to standard current drivers. To achieve this, it can be shown that the filter must cancel out the low-frequency pole of the VCM, located in a position which depends on the electrical impedance of the VCM itself. This, however, may change by ±30% during HDD operations, due to self-heating and consequent variation of the VCM resistance. Such variation may lead to an unsatisfactory performance of the voltage driver, so an adaptation mechanism, capable of tracking variations of VCM coil resistance, must be set up. This paper presents an on-line estimation procedure, based on an extended Kalman filter (EKF), capable of estimating the VCM coil resistance with a high degree of accuracy. EKF, however, usually brings a high computational load, making it unsuitable for real-time, low-cost embedded applications. The paper presents two reduced-order model of the VCM, for which the EKF can be implemented with 30 and 50% less computational effort, respectively, while maintaining a good estimate of the VCM coil resistance. The paper reports experimental results of VCM resistance estimation, obtained with the proposed algorithm, running in 30 μS on a 25 MHz, fixed-point DSP. Also, the on-line estimation is used to adapt the pre-filter. Experimental results show that the servo performance with adaptive voltage driver is not affected by resistance variation and equivalent to that of the standard current driver. © Springer-Verlag 2005
A simulation and control design environment for single stage and dual stage hard disk drives
No full textWe describe an integrated tool for the design and evaluation of the performance of different control algorithms and strategies, applied to hard disk drives (HDDs) with single-stage actuators and dual-stage actuators. The tool is composed of a set of procedures for the computer-aided design of servocontrollers and a HDD simulator. In order to perform realistic simulations, each part of the HDD is described with high level of detail. As for the mechanics, the usual inertia plus resonance model of the voice coil motor (VCM) has been enriched with nonlinear friction modeling and, in case of DSAs, with the dynamic coupling between primary and secondary actuator. The nonlinear friction model has been tuned on experimental data, using an experimental system presented in the paper. As for the electronics, the VCM driver model is included and quantizations in the position error signal measurement and computation are explicitly considered. Also, in order to evaluate the tracking performance of different servocontrollers, repetitive run outs and nonrepetitive run outs are included. Such disturbances have been obtained from commercial HDDs, with a procedure that is detailed in the paper. The simulator is then validated by comparing simulation and experimental results, both in open-loop and closed-loop conditions, thus, confirming the effectiveness of the developed too
Epidemiologia degli incidenti domestici: analisi degli accessi presso il Pronto Soccorso dell'Ospedale Civile Maggiore (OCM) di Verona
No full textINTRODUZIONE: Gli incidenti domestici (ID) (avvenuti nella residenza abitativa
e nelle sue pertinenze: scale esterne, giardini, cantine, garage, etc.),
rappresentano un problema sociale e di sanità pubblica, in termini di vite
umane, invalidità e assistenza sanitaria. In Italia si stima che ogni anno ci
siano 1.300.000-1.700.000 accessi in PS per incidente domestico e 130.000
ricoveri, tuttavia i dati sono ancora incompleti e frammentari. Con uno studio
del fenomeno nella nostra area geografica si sono valutate: prevalenza,
caratteristiche ed eventuali interventi preventivi.
MATERIALI E METODI: Nel 2007 al PS dell’O.C.M. di Verona si sono registrati
3120 accessi per ID. La distribuzione è stata calcolata in relazione a: sesso,
età, mese, codice d’urgenza, tipo e sede del trauma.
RISULTATI: Emerge che i gruppi di popolazione più a rischio di ID sono i bambini
in età pre-scolare, gli uomini tra i 30 e i 40 anni e le donne sopra i 60 anni, con
un’incidenza annuale abbastanza omogenea. I due sessi hanno distribuzioni
simili fino ai 50 anni; in seguito vi è un aumento nelle femmine e una diminuzione
nei maschi. I traumi sono generalmente lievi (49,8% codici bianchi e 42,1%
codici verdi). La sede più colpita è rappresentata da mani e polsi (25,9%). Le
lesioni a più frequenti negli uomini sono: ferite alle mani (7,12%), corpi estranei
negli occhi (5,6%); nelle donne: fratture di mani e piedi (4,23% e 5,90% contro
l’1,76% e il 2,98% degli uomini). Il 5,7% degli ID viene ricoverato. Di questi il 5%
sono bambini e l’81,5% sono anziani (60,3% donne e 21,2% uomini).
CONCLUSIONI: La prevenzione deve basarsi su un approccio globale che
inizia con: la sorveglianza epidemiologica; programmi educativi a scuola; campagne
di informazione per tutta la popolazione; presenza di legislazione specifica;
corretto progetto architettonico e di arredamento degli ambienti di vita
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