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Showing papers by "Polytechnic University of Turin published in 2004"


Reference EntryDOI
15 Nov 2004
TL;DR: The mathematical structure of the contact formulation for finite element methods is derived on the basis of a continuum description of contact, and several algorithms related to spatial contact search and fulfillment of the inequality constraints at the contact interface are discussed.
Abstract: This paper describes modern techniques used to solve contact problems within Computational Mechanics. On the basis of a continuum description of contact, the mathematical structure of the contact formulation for finite element methods is derived. Emphasis is also placed on the constitutive behavior at the contact interface for normal and tangential (frictional) contact. Furthermore, different discretization schemes currently applied to solve engineering problems are formulated for small and finite strain problems. These include isoparametric interpolations, node-to-segment discretizations and also mortar and Nitsche techniques. Furthermore, several algorithms related to spatial contact search and fulfillment of the inequality constraints at the contact interface are discussed. Here, especially the penalty and Lagrange multiplier schemes are considered and also SQP- and linear-programming methods are reviewed. Keywords: contact mechanics; friction; penalty method; Lagrange multiplier method; contact algorithms; finite element method; finite deformations; discretization methods

1,761 citations


Journal ArticleDOI
TL;DR: The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit ofMotor unit recruitment, the average discharge rate, and the degree of synchronization between motor units.
Abstract: This brief review examines some of the methods used to infer central control strategies from surface electromyogram (EMG) recordings. Among the many uses of the surface EMG in studying the neural control of movement, the review critically evaluates only some of the applications. The focus is on the relations between global features of the surface EMG and the underlying physiological processes. Because direct measurements of motor unit activation are not available and many factors can influence the signal, these relations are frequently misinterpreted. These errors are compounded by the counterintuitive effects that some system parameters can have on the EMG signal. The phenomenon of crosstalk is used as an example of these problems. The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit of motor unit recruitment, the average discharge rate, and the degree of synchronization between motor units. Although the global surface EMG is a useful measure of muscle activation and assessment, there are limits to the information that can be extracted from this signal.

1,376 citations


Proceedings ArticleDOI
27 Jun 2004
TL;DR: This is a full-rate 2times2 linear dispersion algebraic space-time code with unprecedented performance based on the Golden number 1+radic5/2.
Abstract: In this paper we present the Golden code for a 2times2 MIMO system. This is a full-rate 2times2 linear dispersion algebraic space-time code with unprecedented performance based on the Golden number 1+radic5/2

722 citations


Journal ArticleDOI
TL;DR: In this paper, a phenomenological model that describes the structure of turbulence within the canopy sublayer (CSL) is developed, which decomposes the space within the CSL intothree distinct zones: the deep zone is dominated by vortices connected with vonKarman vortex streets, butperiodically interrupted by strong sweep events whose features are influenced by canopy density.
Abstract: The canonical form of atmospheric flows near theland surface, in the absence of a canopy, resembles a rough-wallboundary layer. However, in the presence of an extensive and densecanopy, the flow within and just above the foliage behaves as aperturbed mixing layer. To date, no analogous formulation existsfor intermediate canopy densities. Using detailed laser Dopplervelocity measurements conducted in an open channel over a widerange of canopy densities, a phenomenological model that describesthe structure of turbulence within the canopy sublayer (CSL) isdeveloped. The model decomposes the space within the CSL intothree distinct zones: the deep zone in which the flow field isshown to be dominated by vortices connected with vonKarman vortex streets, butperiodically interrupted by strong sweep events whose features areinfluenced by canopy density. The second zone, which is near thecanopy top, is a superposition of attached eddies andKelvin–Helmholtz waves produced by inflectional instability in themean longitudinal velocity profile. Here, the relative importanceof the mixing layer and attached eddies are shown to vary withcanopy density through a coefficient α. We show that therelative enhancement of turbulent diffusivity over its surface-layer value near the canopy top depends on the magnitude ofα. In the uppermost zone, the flow follows the classicalsurface-layer similarity theory. Finally, we demonstrate that thecombination of this newly proposed length scale and first-orderclosure models can accurately reproduce measured mean velocity andReynolds stresses for a wide range of roughness densities. Withrecent advancement in remote sensing of canopy morphology, thismodel offers a promising physically based approach to connect theland surface and the atmosphere without resorting to empiricalmomentum roughness lengths.

628 citations


Journal ArticleDOI
TL;DR: The subsequent analysis of the links among soil moisture dynamics, plant water stress, and carbon assimilation offers an interpretation of recent manipulative field experiments on ecosystem response to shifts in the rainfall regime, showing that plant carbon Assimilation crucially depends not only on the total rainfall during the growing season but also on the intermittency and magnitude of the rainfall events.
Abstract: Some essential features of the terrestrial hydrologic cycle and ecosystem response are singled out by confronting empirical observations of the soil water balance of different ecosystems with the results of a stochastic model of soil moisture dynamics. The simplified framework analytically describes how hydroclimatic variability (especially the frequency and amount of rainfall events) concurs with soil and plant characteristics in producing the soil moisture dynamics that in turn impact vegetation conditions. The results of the model extend and help interpret the classical curve of Budyko, which relates evapotranspiration losses to a dryness index, describing the partitioning of precipitation into evapotranspiration, runoff, and deep infiltration. They also provide a general classification of soil water balance of the world ecosystems based on two governing dimensionless groups summarizing the climate, soil, and vegetation conditions. The subsequent analysis of the links among soil moisture dyna...

623 citations


Book
27 Aug 2004
TL;DR: In this paper, a scenario approach for Probabilistic Robust Design is presented for LPV systems. But the approach is not suitable for linear systems and does not address the limitations of the robustness Paradigm.
Abstract: Overview.- Elements of Probability Theory.- Uncertain Linear Systems and Robustness.- Linear Robust Control Design.- Some Limits of the Robustness Paradigm.- Probabilistic Methods for Robustness.- Monte Carlo Methods.- Randomized Algorithms in Systems and Control.- Probability Inequalities.- Statistical Learning Theory and Control Design.- Sequential Algorithms for Probabilistic Robust Design.- Sequential Algorithms for LPV Systems.- Scenario Approach for Probabilistic Robust Design.- Random Number and Variate Generation.- Statistical Theory of Radial Random Vectors.- Vector Randomization Methods.- Statistical Theory of Radial Random Matrices.- Matrix Randomization Methods.- Applications of Randomized Algorithms.- Appendix.

393 citations


Journal ArticleDOI
TL;DR: In this article, the detrending moving average (DMA) scaling technique is used to calculate the Hurst exponent H( t ) of several time series by dynamical implementation of a recently proposed scaling technique.
Abstract: We calculate the Hurst exponent H ( t ) of several time series by dynamical implementation of a recently proposed scaling technique: the detrending moving average (DMA). In order to assess the accuracy of the technique, we calculate the exponent H ( t ) for artificial series, simulating monofractal Brownian paths, with assigned Hurst exponents H. We next calculate the exponent H ( t ) for the return of high-frequency (tick-by-tick sampled every minute) series of the German market. We find a much more pronounced time-variability in the local scaling exponent of financial series compared to the artificial ones. The DMA algorithm allows the calculation of the exponent H ( t ) , without any a priori assumption on the stochastic process and on the probability distribution function of the random variables, as happens, for example, in the case of the Kitagawa grid and the extended Kalmann filtering methods. The present technique examines the local scaling exponent H ( t ) around a given instant of time. This is a significant advance with respect to the standard wavelet transform or to the higher-order power spectrum technique, which instead operate on the global properties of the series by Legendre or Fourier transform of qth-order moments.

368 citations


Journal ArticleDOI
20 Jun 2004
TL;DR: In this paper, a proportional-integral regulator using sinusoidal signal integrators (SSIs) is proposed for shunt type power conditioners to compensate current harmonics.
Abstract: In this paper, a current control scheme, based on proportional-integral regulators using sinusoidal signal integrators (SSIs), is proposed for shunt type power conditioners. The aim is to simplify the implementation of SSI-based current harmonic compensation for industrial implementations where strict limitations on the harmonic distortion of the mains' currents are required. To compensate current harmonics, the SSIs are implemented to operate both on positive and negative sequence signals. One regulator, for the fundamental current component, is implemented in the stationary reference frame. The other regulators, for the current harmonics, are all implemented in a synchronous reference frame rotating at the fundamental frequency. This allows the simultaneous compensation of two current harmonics with just one regulator, yielding a significant reduction of the computational effort compared with other current control methods employing sinusoidal signal integrators implemented in stationary reference frame. A simple and robust voltage filter is also proposed by the authors to obtain a smooth and accurate position estimation of the voltage vector at the point of common coupling (PCC) under distorted mains' voltages. The whole control algorithm has been implemented on a 16-b, fixed-point digital signal processor (DSP) platform controlling a 20-kVA power conditioner prototype. The experimental results presented in this paper for inductive and capacitive loads show the validity of the proposed solutions.

351 citations


Journal ArticleDOI
TL;DR: In this article, the predictive skills of single and two-equation models to compute pro- files of mean velocity (U), turbulent kinetic energy (K), and Reynolds stresses are compared against datasets collected in eight vegetation types and in a flume experiment.
Abstract: The predictive skills of single- and two-equation (or K-e) models to compute pro- files of mean velocity (U), turbulent kinetic energy (K), and Reynolds stresses ðu 0 w 0 Þ are compared against datasets collected in eight vegetation types and in a flume experiment. These datasets range in canopy height h from 0.12 to 23 m, and range in leaf area index (LAI) from 2 to 10 m 2 m � 2 . We found that for all datasets and for both closure models, measured and modelled U, K, and u 0 w 0 agree well when the mixing length (lm )i sa priori specified. In fact, the root-mean squared error between measured and modelled U, K, and u 0 w 0 is no worse than published values for second- and third-order closure approaches. Within the context of one- dimensional modelling, there is no clear advantage to including a turbulent kinetic dissipation rate (e) budget when lm can be specified instead. The broader implication is that the added complexity introduced by the e budget in K-e models need not translate into improved pre- dictive skills of U, K, and u0w0 profiles when compared to single-equation models.

331 citations


Journal ArticleDOI
TL;DR: In this paper, the analysis of the dispersion characteristics of surface wave data is presented, with particular attention to reliability and resolution, and different approaches that are used to estimate and interpret dispersion properties are considered.
Abstract: Surface-wave methods (SWMs) are very powerful tools for the near-surface characterization of sites. They can be used to determine the shear-wave velocity and the damping ratio overcoming, in some cases, the limitations of other shallow seismic techniques. The different steps of SWM have to be optimized, taking into consideration the conditions imposed by the small scale of engineering problems. This only allows the acquisition of apparent dispersion characteristics: i.e. the high frequencies and short distances involved make robust modelling algorithms necessary in order to take modal superposition into account. The acquisition has to be properly planned to obtain quality data over an adequate frequency range. Processing and inversion should enable the interpretation of the apparent dispersion characteristics, i.e. evaluating the local quality of the data, filtering coherent noise due to other seismic events and determining energy distribution, higher modes and attenuation. The different approaches that are used to estimate and interpret the dispersion characteristics are considered. Their potential and limits with regard to sensitivity to noise, reliability and capability of extracting significant information present in surface waves are discussed. The theory and modelling algorithms, and the acquisition, processing and inversion procedures suitable for providing stiffness and damping ratio profiles are illustrated, with particular attention to reliability and resolution.

322 citations


Journal ArticleDOI
TL;DR: In this article, the use of the Murakami zig-zag function (MZZF) in the two-dimensional modeling of multilayered plates and shells is discussed.

Journal ArticleDOI
TL;DR: An optimal interval estimate of the regression function is obtained, providing its uncertainty range for any assigned regressor values, and the set estimate allows to derive an optimal identification algorithm, giving estimates with minimal guaranteed L"p error on the assigned domain of the regressors.

Journal ArticleDOI
TL;DR: In this article, the power loss in soft magnetic laminations for generic time dependence of the periodic magnetic polarization J(t) was quantitatively assessed within the theoretical framework of the statistical loss model.
Abstract: We have studied ways of predicting power losses in soft magnetic laminations for generic time dependence of the periodic magnetic polarization J(t). We found that, whatever the frequency and the induction waveform, the loss behavior can be quantitatively assessed within the theoretical framework of the statistical loss model. The prediction requires a limited set of preemptive experimental data, depending on whether or not the arbitrary J(t) waveform is endowed with local slope inversions (i.e., minor hysteresis loops) in its periodic time behavior. In the absence of minor loops, such data reduce, for any peak polarization value J/sub p/, to the loss figures obtained under sinusoidal J(t) at two different frequency values. In the presence of minor loops of semiamplitude J/sub m/, the two-frequency loss experiment should be carried out for both peak polarization values J/sub p/ and J/sub m/. Additional knowledge of the quasi-static major loop, to be used for modeling hysteresis loss, does improve the accuracy of the prediction method. A more general approach to loss in soft magnetic laminations is obtained in this way, the only limitation apparently being the onset of skin effect at high frequencies.

Journal ArticleDOI
TL;DR: The computational results show the effectiveness of this approach in terms of trading-off solution quality and computational times, the latter measure being especially important in large-scale systems where numerous daily requests need to be processed.
Abstract: In this paper we present a parallel regret insertion heuristic to solve a dial-a-ride problem with time windows. A new route initialization procedure is implemented, that keeps into account both the spatial and the temporal aspects of the problem, and a regret insertion is then performed to serve the remaining requests. The considered operating scenario is representative of a large-scale dial-a-ride program in Los Angeles County. The proposed algorithm was tested on data sets of 500 and 1000 requests built from data of paratransit service in this area. The computational results show the effectiveness of this approach in terms of trading-off solution quality and computational times. The latter measure being especially important in large-scale systems where numerous daily requests need to be processed.

Journal ArticleDOI
TL;DR: The resultant model is based on analytical derivations and constitutes a step forward in surface EMG signal modeling, including features not described in any other analytical approach.
Abstract: We propose a model for surface electromyography (EMG) signal generation with cylindrical description of the volume conductor. The model is more general and complete with respect to previous approaches. The volume conductor is described as a multilayered cylinder in which the source can be located either along the longitudinal or the angular direction, in any of the layers. The source is represented as a spatio-temporal function which describes the generation, propagation, and extinction of the intracellular action potential at the end-plate, along the fiber, and at the tendons, respectively. The layers are anisotropic. The volume conductor effect is described as a two-dimensional spatial filtering. Electrodes of any shape or dimension are simulated, forming structures which are described as spatial filters. The analytical derivation which leads to the signal in the temporal domain is performed in the spatial and temporal frequency domains. Numerical issues related to the frequency-based approach are discussed. The descriptions of the volume conductor and of the source are applied to the cases of signal generation from a limb and a sphincter muscle. Representative simulations of both cases are provided. The resultant model is based on analytical derivations and constitutes a step forward in surface EMG signal modeling, including features not described in any other analytical approach.

Journal ArticleDOI
TL;DR: In this article, a proper orthogonal decomposition based model is considered for two-dimensional vortex shedding past a confined square cylinder, and the controllability and observability of vortex shedding at a slightly supercritical Reynolds number is investigated relying on the accurate low-order models obtained.
Abstract: A proper orthogonal decomposition based model is considered for two-dimensional vortex shedding past a confined square cylinder. The aim is to study the validity of such a model for Reynolds numbers and blockage ratios that are different from those for which the model was derived. Using a calibration procedure it is shown that reliable results can be obtained in terms of short-term (one period) dynamics. Long-term dynamics are accurately captured with a variation of the Reynolds number, whereas the error becomes large when the blockage ratio changes. The controllability and observability of vortex shedding at a slightly supercritical Reynolds number is investigated relying on the accurate low-order models obtained.

Journal ArticleDOI
TL;DR: This study demonstrates a central inhibitory motor control mechanism with an efficacy correlated to the nociceptive activity and a significant decrease of the firing rates during the painful condition.
Abstract: The aim of this human study was to investigate the relationship between experimentally induced muscle pain intensity (i.e., amount of nociceptive activity) and motor unit (MU) firing decrease and M...

Journal ArticleDOI
TL;DR: The resulting algorithm is suitable for compression of data in band-interleaved-by-line format and outperforms 3-D-CALIC as well as other state-of-the-art compression algorithms.
Abstract: We propose a new lossless and near-lossless compression algorithm for hyperspectral images based on context-based adaptive lossless image coding (CALIC). Specifically, we propose a novel multiband spectral predictor, along with optimized model parameters and optimization thresholds. The resulting algorithm is suitable for compression of data in band-interleaved-by-line format; its performance evaluation on Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data shows that it outperforms 3-D-CALIC as well as other state-of-the-art compression algorithms.

Proceedings ArticleDOI
07 Mar 2004
TL;DR: A Markov model of a sensor network whose nodes may enter a sleep mode is developed and used to investigate the system performance in terms of energy consumption, network capacity, and data deliver delay and the trade-offs existing between these performance metrics and the sensor dynamics in sleep/active mode.
Abstract: A critical issue in wireless sensor networks is represented by the limited availability of energy within network nodes; therefore making good use of energy is a must. A widely employed energy-saving technique is to place nodes in sleep mode, corresponding to a low-power consumption as well as to reduced operational capabilities. In this work, we develop a Markov model of a sensor network whose nodes may enter a sleep mode, and we use this model to investigate the system performance in terms of energy consumption, network capacity, and data deliver delay. Furthermore, the proposed model enables us to investigate the trade-offs existing between these performance metrics and the sensor dynamics in sleep/active mode. Analytical results present an excellent matching with simulation results for a large variety of system scenarios showing the accuracy of our approach.

Journal ArticleDOI
TL;DR: In this article, the authors classify Ricci-flat structures on 6-dimensional nilmanifolds for which the fundamental 2-form is closed, a condition that is shown to depend only on the underlying complex structure J of M. The space of such structures is described when G is the complex Heisenberg group, and explicit solutions are obtained from a limacon-shaped curve in the complex plane.
Abstract: This paper classifies Hermitian structures on 6-dimensional nilmanifolds $M=\Ga\bs G$ for which the fundamental 2-form is $\pd\opd$-closed, a condition that is shown to depend only on the underlying complex structure J of M. The space of such J is described when G is the complex Heisenberg group, and explicit solutions are obtained from a limacon-shaped curve in the complex plane. Related theory is used to provide examples of various types of Ricci-flat structures.

Journal ArticleDOI
TL;DR: A modified follow-the-leader algorithm and the self-organizing maps for customer classification are focused on-an overview of basic theory for these methods is included and the performance of the customer classification on the real case of a set of customers supplied by a distribution company is discussed.
Abstract: Accurate knowledge of the customers' consumption patterns represents a worthwhile asset for electricity providers in competitive electricity markets. Various approaches can be used for grouping customers that exhibit similar electrical behavior into customer classes. In this paper, we focus on two approaches for customer classification-a modified follow-the-leader algorithm and the self-organizing maps. We include an overview of basic theory for these methods and discuss the performance of the customer classification on the real case of a set of customers supplied by a distribution company. We compare the results obtained from the two approaches by means of two suitably defined adequacy indicators and discuss the potential applications of the surveyed approaches.

Journal ArticleDOI
TL;DR: An urban network of signalized intersections can be suitably modeled as a hybrid system, in which the vehicle flow behavior is described by means of a time-driven model and the traffic light dynamics are represented by a discrete event model.
Abstract: An urban network of signalized intersections can be suitably modeled as a hybrid system, in which the vehicle flow behavior is described by means of a time-driven model and the traffic light dynamics are represented by a discrete event model. In this paper, a model of such a network via hybrid Petri nets is used to state and solve the problem of coordinating several traffic lights with the aim of improving the performance of some classes of special vehicles, i.e., public and emergency vehicles. The proposed model has been validated using real traffic data relevant to the city of Torino, Italy. Some relevant experimental results are reported and discussed.

Journal ArticleDOI
TL;DR: In this paper, the problem of finding a quadratic common Lyapunov function for a large family of stable linear systems has been studied and gradient iteration algorithms have been proposed to give deterministic convergence for finite system families and probabilistic convergence for infinite families.
Abstract: This note is concerned with the problem of finding a quadratic common Lyapunov function for a large family of stable linear systems. We present gradient iteration algorithms which give deterministic convergence for finite system families and probabilistic convergence for infinite families.

Journal ArticleDOI
TL;DR: In this paper, the goodness of fit tests based on Cramer-von Mises and Anderson-Darling statistics are discussed, with reference to the composite hypothesis that a sample of observations comes from a distribution, FH, whose parameters are unspecified.
Abstract: [1] The use of goodness of fit tests based on Cramer–von Mises and Anderson-Darling statistics is discussed, with reference to the composite hypothesis that a sample of observations comes from a distribution, FH, whose parameters are unspecified. When this is the case, the critical region of the test has to be redetermined for each hypothetical distribution FH. To avoid this difficulty, a transformation is proposed that produces a new test statistic which is independent of FH. This transformation involves three coefficients that are determined using the asymptotic theory of tests based on the empirical distribution function. A single table of coefficients is thus sufficient for carrying out the test with different hypothetical distributions; a set of probability models of common use in extreme value analysis is considered here, including the following: extreme value 1 and 2, normal and lognormal, generalized extreme value, three-parameter gamma, and log-Pearson type 3, in all cases with parameters estimated using maximum likelihood. Monte Carlo simulations are used to determine small sample corrections and to assess the power of the tests compared to alternative approaches.

Journal ArticleDOI
TL;DR: In this correspondence, various families of full diversity rotated Z/sup n/-lattice constellations based on algebraic number theory constructions are presented and closed-form expressions of their minimum product distance are given using the corresponding algebraic properties.
Abstract: In this correspondence, we present various families of full diversity rotated Z/sup n/-lattice constellations based on algebraic number theory constructions. We are able to give closed-form expressions of their minimum product distance using the corresponding algebraic properties.

Journal ArticleDOI
TL;DR: An automatic system for the detection and classification of MU action potentials from multi-channel surface EMG signals that was validated on simulated signals, at different levels of force, generated by a structure based surface EMg model and able to identify a MU sample representative of the muscle.

Journal ArticleDOI
TL;DR: In this paper, the results obtained considering a model of a stand-alone energy system supplied just with renewable sources of energy (RES) composed by an electrolyzer, a hydrogen tank and a proton exchange membrane fuel cell are exposed.

Journal ArticleDOI
TL;DR: It is argued that C(n)(i) generates a stationary sequence of self-affine clusters C with length l, lifetime tau, and area s with power law distributed with exponents depending on H.
Abstract: We analyze the stochastic function ${C}_{n}(i)\ensuremath{\equiv}y(i)\ensuremath{-}{y}_{n}(i),$ where $y(i)$ is a long-range correlated time series of length ${N}_{\mathrm{max}}$ and ${y}_{n}(i)\ensuremath{\equiv}(1/n){\ensuremath{\sum}}_{k=0}^{n\ensuremath{-}1}y(i\ensuremath{-}k)$ is the moving average with window n. We argue that ${C}_{n}(i)$ generates a stationary sequence of self-affine clusters $\mathcal{C}$ with length $\mathcal{l},$ lifetime $\ensuremath{\tau},$ and area s. The length and the area are related to the lifetime by the relationships $\mathcal{l}\ensuremath{\sim}{\ensuremath{\tau}}^{{\ensuremath{\psi}}_{\mathcal{l}}}$ and $s\ensuremath{\sim}{\ensuremath{\tau}}^{{\ensuremath{\psi}}_{s}},$ where ${\ensuremath{\psi}}_{\mathcal{l}}=1$ and ${\ensuremath{\psi}}_{s}=1+H.$ We also find that $\mathcal{l},$ $\ensuremath{\tau},$ and s are power law distributed with exponents depending on H: $P(\mathcal{l})\ensuremath{\sim}{\mathcal{l}}^{\ensuremath{-}\ensuremath{\alpha}},$ $P(\ensuremath{\tau})\ensuremath{\sim}{\ensuremath{\tau}}^{\ensuremath{-}\ensuremath{\beta}},$ and $P(s)\ensuremath{\sim}{s}^{\ensuremath{-}\ensuremath{\gamma}},$ with $\ensuremath{\alpha}=\ensuremath{\beta}=2\ensuremath{-}H$ and $\ensuremath{\gamma}=2/(1+H).$ These predictions are tested by extensive simulations on series generated by the midpoint displacement algorithm of assigned Hurst exponent H (ranging from 0.05 to 0.95) of length up to ${N}_{\mathrm{max}}{=2}^{21}$ and n up to ${2}^{13}.$

Journal ArticleDOI
TL;DR: It is proved in this paper that there is no need for an ad hoc code design to meet the parallelism requirement, because, for any code and any choice of the scheduling of the reading/writing operations, there is a suitable mapping of the variables in the memory that grants a collision-free access.
Abstract: For high-data-rate applications, the implementation of iterative turbo-like decoders requires the use of parallel architectures posing some collision-free constraints to the reading/writing process from/into the memory. This consideration applies to the two main classes of turbo-like codes, i.e., turbo codes and low-density parity-check (LDPC) codes. Contrary to the literature belief, we prove in this paper that there is no need for an ad hoc code design to meet the parallelism requirement, because, for any code and any choice of the scheduling of the reading/writing operations, there is a suitable mapping of the variables in the memory that grants a collision-free access. The proof is constructive, i.e., it gives an algorithm that obtains the desired collision-free mapping. The algorithm is applied to two simple examples, one for turbo codes and one for LDPC codes, to illustrate how the algorithm works.

Journal ArticleDOI
01 Nov 2004
TL;DR: In this article, thermal sensitivity analysis of total enclosed fan cooled (TEFC) induction motors is presented, and the results are useful for identifying the most important thermal parameters and enabling robust designs to be developed that are insensitive to manufacturing tolerances.
Abstract: With the increasing pressures on electric motor manufactures to develop smaller and more efficient electric motors, there is a trend to carry out more thermal analysis in parallel with the traditional electromagnetic design. It has been found that attention to thermal design can be rewarded by major improvements in the overall performance. Thus, there is a requirement for accurate and reliable thermal analysis models that can be easily incorporated into motor design software. In the paper emphasis is given to thermal sensitivity analysis of total enclosed fan cooled (TEFC) induction motors. In particular, thermal parameters are modified and their effects on the temperature rise shown. The results are useful for identifying the most important thermal parameters and enables robust designs to be developed that are insensitive to manufacturing tolerances.