Increasing processor utilization in hard-real-time systems with checkpoints

Often hard real-time systems require results that are produced on time despite the occurrence of processor failures. This paper considers a distributed system where tasks are periodic and each task occurs in multiple copies which are periodically synchronized in order to handle failures. The problem of preemptively scheduling a set of such tasks is discussed where every occurrence of a task has to be completely executed before the next occurrence of the same task. First, a static scheduling algorithm is proposed which uses periodic checkpoints to tolerate processor failures. Then, the performance of the algorithm is substancially improved employing a mixed strategy which constructs a schedule where high frequency tasks are duplicated, and low frequency tasks are periodically checkpointed. The performance of the solution proposed is evaluated in terms of the minimum achievable processor utilization due to the useful computation of the tasks. Moreover, analytical and simulation studies are used to reveal interesting trade-offs associated with the scheduling algorithm. In particular, if high frequency tasks are less than 70 percent of the total number of tasks then the mixed strategy yields a higher processor utilization than the task duplication scheme.     

Dynamics modelling and control of the 3-RCC translational platform

The article presents the inverse dynamics model of a novel translating parallel machine and proposes the structure of a force controller for the execution of tasks characterised by interaction with the environment. The task space model of machine’s dynamics is obtained in an efficient and compact form by means of the principle of virtual work. A virtual prototyping environment has been set up to test by computer simulation the potential of such kinematic architecture: the resulting dynamics is rather poor, mainly due to the high moving masses, but it is shown that hybrid position/force control schemes should be able to provide good performances, including the case of rather difficult operations, such as the peg-in-hole assembly.     

A Mixed Signal Fuzzy Controller Using Current Mode Circuits

A mixed analog-digital fuzzy logic inference processor chip, designed in a 0.35-μm CMOS technology, is presented. The analog fuzzy engine is based on a novel current-mode CMOS circuit used for the implementation of fuzzy partition membership functions. The architecture consists of a 3 inputs—1 output analog fuzzy engine, internal digital registers to store the parameters of the fuzzy controller, and a digital subsystem that allows the programmability of the fuzzy controller via an I ² C interface. The architecture, circuits, and some Cadence Spectre simulations are presented.     

Zinc porphyrin with phenoxy-bridged pentacoordinate bis(8-hydroxyquinaldinate)gallium lateral pendants: synthesis and photophysical characterization

This communication reports the synthesis of polymetallic species formed by a zinc-tetraphenolporphyrinate core (ZnTPP(OH)₄, 1) and peripheral gallium-quinaldinate fragments. The photophysical analysis of 1 and of the model compound , R, shows an appreciable overlap between the absorption spectra of 1 and the emission spectra of R, suggesting the presence of a donor–acceptor energy-transfer process. Contrarily, the obtained results indicated that energy transfer does not occur, hence these polymetallic complexes work as double emitting species, for which the colour of luminescence depends on the excitation energy.     

On the Identification and Analysis of Saccadic Eye Movements?A Quantitative Study of the Processing Procedures

A set of quantitative data about signal processing effects on the evaluation of amplitude, duration, and peak-velocity of single saccadic eye movements, as well as on the evaluation of the coefficients of amplitude-peak velocity and amplitude-duration characteristics of a family of saccades, is given. The following aspects of signal processing are theoretically discussed, experimentally supported, and summarized by normative graphs: 1) the analog low-pass filtering applied to the recorded eye movement; 2) its sampling and digitization; 3) the low-pass filtering applied to the digitized signal; 4) the algorithm used to compute the eye velocity; 5) the criteria adopted to determine the beginning and the ending points of the saccades; and 6) the laws used to fit the saccadic characteristics. According to the theoretical and experimental results obtained, some general operating rules and optimal setups for each of the most common experimental situations are proposed, with the aim of standardizing saccade analysis for both researchers and clinicians.     

Correlating equations for free convection heat transfer from horizontal isothermal cylinders set in a vertical array

Steady laminar free convection from flat vertical arrays of equally-spaced, horizontal isothermal cylinders set in free air, is studied numerically. A specifically developed computer-code based on the SIMPLE-C algorithm is used for the solution of the mass, momentum and energy transfer governing equations. Simulations are performed for arrays of 2-6 circular cylinders, for center-to-center separation distances from 2 up to more than 50 cylinder-diameters, and for values of the Rayleigh number based on the cylinder-diameter in the range between 5 × 10² and 5 × 10⁵. It is found that the heat transfer rate at the bottom cylinder remains the same as a single cylinder. In contrast, the downstream cylinders may exhibit either enhanced or reduced Nusselt numbers depending on their location in the array and on the geometry of the array. Heat transfer dimensionless correlating equations are proposed both for any individual cylinder in the array and for the whole tube-array. New correlation-equations for the calculation of the heat transfer rate from a single cylinder to the surrounding air are also proposed and compared to those available in the open literature.     

Atomistic simulation of liquid lead and lead-bismuth eutectic

Lead and the Pb-Bi eutectic (Pb 55.9 at.%) have been modeled by a n-body potential derived from a second moment approximation of a tight binding Hamiltonian. The thermal behavior of the two systems in the liquid phase has been reproduced and relevant structural parameters have been evaluated and compared with experimental data. The diffusion coefficients and the activation energy for diffusion have been also evaluated.     

The influence of photon peak arrival in the timing of plastic scintillators by means of pulsed laser and optical fibers

The influence of photon peak arrival in the laser-optical fibers timing system of a large array of plastic scintillators has been studied for different types of photomultipliers. The obtained results, helpful in properly designing the system are presented and discussed.     

Isothermal diffusion—reaction in a slab catalyst with bimolecular Langmuir-Hinshelwood kinetics: Connections with negative first-order kinetics

The problem of isothermal diffusion-reaction in a slab catalyst with bimolecular Langmuir—Hinshelwood kinetics is studied. Analytic solutions for the concentration profile and the catalytic effectiveness factor are reported for the full range of Thiele modulus values, in the limit of large adsorption inhibition constant. In this limit, connections with negative first-order kinetics are shown, and rather good explicit estimates of the region of multiple steady states are provided. Comparisons with numerical calculations are also made.     

Hydrolysis of tannery wastes to protein meal for animal feedstuffs: A process and product evaluation

Hydrolysis of protein solid wastes from tanneries to yield protein meal for animal nutrition has been performed in a pilot assembly designed to process 400 kg h^?1 of disposal material under optimum energy consumption and product yield conditions. Evaluation of the significance of amino acid degradation caused by the process, in relation to the product cost and quality in animal nutrition, was the purpose. A nutrition bioassay was carried out to study the incidence of dietary substitution of the above protein meal for soybean meal on growth performance by early weaned piglets. The results show that degradation of serine, proline, arginine and threonine occurs during collagen hydrolysis, and that only the threonine concentration in the product falls below the dietary requirement. However, integration of protein meal diets with the necessary amino acid content may be accomplished cheaply. Compared with other vegetable and animal commercial protein meals, the cost of the product obtained from tanned hides appears competitive. Processing of other tannery disposal material is not recommended, due to the low protein content of the starting material.