Showing papers by "École Polytechnique de Montréal published in 1995"

Pattern Recognition and Neural Networks

Abstract: Title Type pattern recognition with neural networks in c++ PDF pattern recognition and neural networks PDF neural networks for pattern recognition advanced texts in econometrics PDF neural networks for applied sciences and engineering from fundamentals to complex pattern recognition PDF an introduction to biological and artificial neural networks for pattern recognition spie tutorial text vol tt04 tutorial texts in optical engineering PDF

A kinematic theory of rapid human movements. Part I. Movement representation and generation.

Abstract: This paper proposes a kinematic theory that can be used to study and analyze rapid human movements. It describes a synergy in terms of the agonist and antagonist neuromuscular systems involved in the production of these movements. It is shown that these systems have a log-normal impulse response that results from the limiting behavior of a large number of interdependent neuromuscular networks, as predicted by the central limit theorem. The delta log-normal law that follows from this model is very general and can reproduce almost perfectly the complete velocity patterns of an end-effector. The theory accounts for the invariance and rescalability of these patterns, as well as for the various observations that have been reported concerning the change in maximum and mean velocities, time to maximum velocity, etc., under different experimental conditions. Movement time, load effects, and control strategies are discussed in a companion paper.

Chapter 2 Time constrained routing and scheduling

Abstract: Publisher Summary Time constrained routing and scheduling problems are encountered in a variety of industrial and service sector applications, ranging from logistics and transportation systems to material handling systems in manufacturing. The traveling salesman problem with time windows has applications in single and multiple vehicle problems. The vehicle routing problem with time windows has many industrial applications including those where dock availability is a bottleneck such as for distribution centers. This chapter describes the significant advances made in time constrained routing and scheduling. In terms of solution methodology capable of solving realistic size problems, this field has seen a natural progression from ad-hoc methods to simple heuristics, to optimization-based heuristics and recently optimal algorithms. The chapter discusses fixed schedule problems and develops in detail the Dantzig-Wolfe decomposition/column generation approach which will then be applied to many of the other problem types. The vehicle routing problem with time windows and several important problem variants including the multiple traveling salesman problems is explored. The chapter examines a unified framework for fleet and crew scheduling problems.

A kinematic theory of rapid human movements

Abstract: This paper describes how a synergy made up of a pair of agonist and antagonist systems involved in the production of a rapid movement can control movement time A quadratic law is derived to predict the movement time as a function of the various parameters describing the neuromuscular synergy Conditions for a simplified description of the process, using a power law, are also presented It is predicted that movement time can be controlled at the input level by the ratio of the agonist to antagonist commands or at the system level by modifying the total log-time delay or the log-response time of the agonist or antagonist neuromuscular networks Adapting this approach to the specific case of movements executed under different spatial accuracy demands, it is found that movement time is linked to the inverse of the relative spatial error by similar laws The whole approach is used to explain within a single framework all the observations that have been reported concerning speed/accuracy trade-offs Strategies for controlling movement amplitude and duration are analyzed, and other predictions dealing with EMG, acceleration patterns, load effects and changes in the asymmetry of the velocity profile are also discussed

Surface characterization of cellulose fibres by XPS and inverse gas chromatography

Abstract: Inverse gas chromatography (IGC) was used to determine the dispersive component of the free energy as well as the acid-base properties of cellulose fibre surfaces, before and after modification by corona treatment. It was found that the corona treatment increases both the dispersive contribution to surface energy and its acidic character, whereas only a slight increase in its basicity was observed. It was also found that some chemical degradation of the surface occurs at high corona currents. The extent of modification of the surface properties, as revealed by IGC, was correlated to the surface chemical composition deduced from XPS analysis as well as with the electrical conductance and the pH of the water suspensions of the cellulose fibres.

Hydrodynamics of circulating fluidized bed risers: A review

Abstract: Any vessel in which solids are transported upward by a gas stream and then recycled to the bottom may be classified as a Circulating Fluidized Bed (CFB). We describe possible CFB operating regimes in the context of this broad classification and highlight commercial processes that employ CFB technology and potential applications. Process design and development require a fundamental understanding of gas and solids hydrodynamics — solids hold-up, mixing and velocity distribution. We discuss techniques used to measure solids mass flux, which is a critical parameter for both design and control. In the last decade, significant research efforts have been devoted to new experimental techniques to measure both gas and solids spatial and temporal distribution. We list these techniques and detail the different modelling approaches that have emerged based on the new data. Characterization of the data is still incomplete and the available models require further refinement to reliably predict the effect of scale, operating conditions and particle characteristics on hydrodynamics.

Biomechanics of the human knee joint in compression: reconstruction, mesh generation and finite element analysis

Abstract: Computer-assisted tomography with direct digitization and measurements were used to reconstruct the detailed geometry of an entire human knee joint specimen. These data were then merged with a mesh generation algorithm and material properties reported in the literature to develop a three dimensional non-linear finite element model of the knee joint. This model consists of three bony structures (tibia, femur and patella), their articular cartilage layers, medial and lateral menisci, and five principal ligaments (collaterals, cruciates and patellar tendon). The menisci are represented as a non-homogeneous composite of a solid matrix reinforced by radial and circumferential collagen fibres. The articulation of cartilage layers with each other as well as with intervening menisci and the wrapping of the medial collateral ligament with tibia are treated as general large displacement frictionless contact problems. The incremental response of the tibiofemoral joint in full extension is determined under axial forces of up to 1000 N applied on the femur. Analyses are carried out with the tibia fixed while the femur is set free to translate in medial-lateral, anterior-posterior, and proximal-distal directions; the internal-external rotation is either left free or fixed. Cases simulating total meniscectomy are also considered. The joint exhibits a non-linear stiffening response in the axial direction with large coupled displacements. At 1000 N, the load transferred through the joint is found to be greater for the lateral compartment than for the medial compartment and at the cartilage-cartilage contact than at the meniscus-cartilage contact. The menisci, firmly attached by their horns to the tibia, are radially extruded under the axial compression and cause greater contact areas and smaller, more uniform, contact pressures. Removal of menisci markedly increases the primary and coupled laxities of the joint, reduces total contact areas, and increases contact stresses. The predictions are in general agreement with measurements reported in the literature.

Archaean cratonic roots, mantle shear zones and deep electrical anisotropy

Abstract: THE extent to which the mantle participated in the growth and stabilization of ancient cratons is central to our understanding of the evolution of the continents1. The detection of seismic anisotropy beneath Precambrian North America, for example, has been interpreted as showing that strain-induced orientation of mantle minerals in subcontinental lithospheric mantle can preserve a record of ancient episodes of deformation2. Here we present mag-netotelluric measurements from the Superior Province of the Canadian shield, which reveal pronounced electrical anisotropy in the upper 100 km of the underlying mantle. We argue that this anisotropy is best explained by conducting graphite films, oriented within fractures or on grain boundaries, and associated with metasomatism of the mantle roots of major Archaean shear zones which transect the entire Superior Province. The uppermost mantle beneath the Canadian shield has therefore remained fixed to the crust and isolated from significant tectonic reworking since the late Archaean.

A new branching strategy for time constrained routing problems with application to backhauling

Abstract: In this paper, we explore a new branching strategy for branch-and-bound approaches based on column generation for the vehicle routing problems with time windows. This strategy involves branching on resource variables (time or capacity) rather than on network flow variables. We also examine criteria for selecting network nodes for branching. To test the effectiveness of the branching strategy, we conduct computational experiments on time window constrained vehicle routing problems where backhauling is permitted only after all the shipments to clients have been made. The branching method proved very effective. In cases where time was the more binding constraint, time-based branching succeeded in decreasing the number of nodes explored by two thirds and the total computation time by more than half when compared to flow-based branching. The computational results also show that the overall algorithm was successful in optimally solving problems with up to 100 customers. It produced an average cost decrease of almost 7% when backhauling was permitted as compared to the cost involved when the client and the distributor routes were distinct.

Weldlines in injection-molded parts: A review

Abstract: It is a well-known fact that weldlines are unavoidable in most injection-molded products of even moderate complexity. While there are many situations where they are barely perceptible, weldlines represent a potential source of weakness in molded parts. In injection molding weldlines are generated when two separate melt streams join either in multigated molds or as a consequence of flow around obstacles. The development of many interesting materials has been hampered by poor weldline strength. Among such materials are plastics reinforced with fibers or platelets, liquid crystal polymers, and a number of multiphase polymer blends. Weldlines have ever been called the “Achilles' heel” of these multiphase materials. This article is a review of the literature published on weldlines in injected parts. It deals primarily with the aspects related to the mechanical behavior of weldline-containing parts. It begins with a brief description of the phenomena important for the part formation in the mold, including those leading to weldlines, in addition to the techniques used to characterize weldline-containing parts. The following three sections consider the structure and properties of weldlines in neat amorphous and semicrystalline polymers, filled and reinforced plastics, and finally in polymer blends and alloys. In the last section methods developed for increasing the weldline strength are discussed. © 1994 John Wiley & Sons, Inc.

Variability of geometric measurements from three-dimensional reconstructions of scoliotic spines and rib cages

Abstract: Three-dimensional (3-D) reconstructions of the spine are being used with increasing frequency to describe scoliotic deformities, but the reproducibility of most of these techniques and the implication for the reliability of measurements made on the reconstructions has not been reported. How reliable are these reconstructions, and can a clinician interpret with confidence the results of studies based on such mathematical models? A reproducibility study of various computerised measurements obtained from 3-D reconstructions of the spine and rib cage for five subjects with adolescent idiopathic scoliosis was done to evaluate the errors associated with repeated measurements and compare them with inter-and intraobserver errors reported for similar commonly used clinical measurements. The mean variation for the Cobb angle differed according to the plane of computation from 0.6° in the frontal plane to 6.7° in the sagittal plane; vertebral axial rotation varied from 2.3° to 5.9° according to the vertebral level, and rib hump measurements displayed an average variation of 1.4°. All these variations are below or within the error levels reported for equivalent 2-D measurements used by clinicians, which suggests that this 3-D model of idiopathic scoliosis may be used with confidence for clinical evaluations.

Gain characteristics of a high concentration Er3+-doped phosphate glass waveguide

Abstract: A channel waveguide on an erbium‐doped phosphate laser glass was fabricated by a dry silver‐film ion exchange technique, and its gain properties were studied experimentally. The propagation loss of the fabricated waveguide was 0.63 dB/cm at 1.3 μm. Er3+ concentration of 1×1020 ions/cm3 was chosen so that no concentration quenching occurred. This was confirmed by measuring a fluorescence lifetime of 8.4 ms at 1.54 μm. Gain of the fabricated waveguide was measured by using a Ti:sapphire laser at a wavelength of 980 nm and a laser diode of 1.532 μm producing pump and signal beams, respectively. The signal wavelength used for the experiments was shorter than the emission peak, and the measured gain of the 1.8 cm waveguide was comparable to the total loss. However, the model showed that lasing is expected at the emission peak with a 3.6 cm long waveguide fabricated in a similar manner. Calculation results showed that the potential gain of 8.8 dB can be realized with 250 mW pump power, and a 7.2 cm long waveguide provided that mode overlap can be increased by 20% and propagation loss can be reduced by 50%. No significant upconversion effect was observed up to 1.1×106 W/cm2 pump intensity.

Geometrical modeling of the spine and the thorax for the biomechanical analysis of scoliotic deformities using the finite element method

Abstract: Cet article presente les aspects geometriques d'un modele biomecanique d'une nouvelle generation qui a ete developpe afin d'etudier le comportement biomecanique du rachis et du thorax. Ce modele comporte une representation precise de la partie posterieure du rachis, tout en respectant les contraintes liees aux capacites informatiques et au calcul numerique. Une methode hybride a ete utilisee pour construire ce modele. Cette methode combine les reconstructions stereoradiographiques 3-D du rachis et du thorax de patients scoliotiques [1] a des donnees morphometriques des cotes [2, 3] ainsi qu'a des reconstructions 3-D de vertebres et du sternum provenant de specimens cadaveriques obtenues par empilement de coupes tomographiques [4]. Ces composantes anatomiques sont deformees a l'aide de transformations geometriques et de techniques d'interpolation, afin de les faire correspondre le plus adequatement possible a la geometrie reconstruite du patient scoliotique analyse. Dans la partie posterieure, les facettes articulaires sont modelisees et parametrisees par des surfaces elementaires simples (plans, cylindres, spheres). Les resultats obtenus pour un sujet normal indiquent que les facettes articulaires zygapophysaires sont mieux representees par des plans de T 1 a T 11 , et par des portions de surfaces cylindriques de T 12 a L 5 , ce qui est en accord avec la litterature [5, 6]. L'approche de modelisation a ete evaluee sur des segments vertebraux cadaveriques. Des parametres geometriques calcules a partir du modele ont ete compares aux mesures 3-D obtenues avec grande precision a l'aide d'un numerisateur 3-D, et une concordance entre les resultats a ete trouvee, particulierement pour les facettes articulaires. Un modele par elements finis a ensuite ete genere a partir du modele geometrique [7]. Ce modele est un outil clinique qui permet d'aborder de facon realiste l'etude des deformations scoliotiques et l'evaluation 3-D des traitements orthopediques.

Design methodology for a multifunctional hand prosthesis

Abstract: The first part of this paper reviews different approaches to define the motion of the fingers and the thumb in order to obtain prehension. The last part presents the design of a hand prosthesis based on a new plane of action for the thumb and on proposed design specifications and functional characteristics. The design methodology consists of two steps: the morphology design of the hand prosthesis and the 4-bar mechanism design for each finger. A 3-D computer-aided design (CAD) interactive program was used as a design tool to obtain the hand morphology. This CAD technique was also used to check the geometry, the relative motions of the fingers, and the possibility of interference for the proposed model with two prehension patterns (tridigital and lateral). It is noted that identical flexion angles of the finger joints were obtained for these two prehension patterns, the difference being in the inclination angle of the thumb's plane of flexion. This finding greatly simplified the design of the internal mechanisms of the fingers. CAD was a powerful tool in the design process of this hand prosthesis and will be more and more useful in the future.

Droplet/fibre transitions in immiscible polymer blends generated during melt processing

Abstract: The modification of the morphology of immiscible binary blends in a co-rotating twin-screw extruder equipped with capillary dies of various lengths has been studied. Blends of polycarbonate and polypropylene were investigated using scanning electron microscopy. The size and shape of the dispersed phase were found to be significantly affected by the viscosity ratio. The morphology of the blends containing 5% minor phase varied with radial and axial positions in the die. Capillary instabilities were observed at the entrance of the die. The generation and disintegration of these capillary instabilities were found to occur rapidly. Fibre formation was favoured for all blends containing higher concentrations of minor phase (20%). To investigate the influence of the interface on deformation of the minor phase, blends of polyethylene and polyamide were compatibilized with a polyethylene copolymer ionomer. The compatibilizer was found to be effective in considerably reducing the size of the minor phase. The final state of deformation of the dispersed phase was reduced significantly with addition of the ionomer.

Interfacial reactions in Al-Mg (5083)/AI 2 O 3 p composites during fabrication and remelting

Abstract: The interface reactions between a-Al2O3 particles and 5083 Al-Mg alloys during fabrication by compocasting and subsequent remelting at 800 °C for 30 minutes have been studied using analytical transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Experimental results show that MgO is the main reaction compound produced by the reaction 3Mg (1) + A12O3 (s) = 3MgO (s) + 2A1 (1). The MgO crystals formed by interfacial reaction are very small (about 5 to 20 run in diameter), and the reaction zone is about 50 to 80-nm wide for as-cast materials and about 100 to 150 nm after remelting. The reaction kinetics is controlled by seepage of Mg and release of Al (1) along the newly formed MgAl2O4 or MgO grain boundaries. Because of the large volume expansion during the formation of MgO from the reaction between Mg (1) and A12O3 and because of the low diffusivity in MgO crystals, the reaction rate is very low.

Growth kinetics of vitis vinifera cell suspension cultures: I. Shake flask cultures.

Abstract: Vitis vinifera cell suspension cultures carried out in shake flasks were closely examined for biomass growth and cell division in relation to carbohydrate, NH4, NO3PO4, and dissolved oxygen (DO)consumption. After inoculation, the oxygen uptake rate of the cultures measured on-tine was observed to increase continuously to a maximum value of 3.8 mmol O2L−1h−1 at day 7 when cell division ceased and dissolved oxygen reached its lowest level of 17% air saturation. During this first phase of growth, the specific oxygen uptake rate remained constant at ∼0.6 mmol 02 O2 g−1 dw h−1or ∼2.2 μmol O2, (106 cells)−1 h−1 whereas dry biomass concentration increased exponentially from 1.5 to 6.0 g dw L−1. Thereafter, dry biomass concentration increased linearly to ∼14 g dw L−1 at day 14 following nitrate and carbohydrate uptake. During this second phase of growth, the biomass wet-to-dry weight ratio was found to increase in an inverse relationship with the estimated osmotic pressure of the culture medium. This corresponded to inflection points in the dry and wet biomass concentration and packed cell volume curves. Furthermore, growth and nutrient uptake results suggest that extracellular ammonium or phosphate ion availability may limit cell division. These findings indicate that cell division and biomass production of plant cell cultures may not always be completely associated, which suggests important new avenues to improve their productivity. © 1995 John Wiley & Sons, Inc.

Simultaneous optimization of thermochemical data for liquid iron alloys containing C, N, Ti, Si, Mn, S, and P

Abstract: A data base of thermochemical parameters for liquid iron-base alloys containing C, N, Ti, Si, Mn, S, and P is presented. A matrix of linear inequalities describing the experimental data among these elements was constructed. A set of internally consistent thermochemical data permitted by the uncertainties of the experiments was evaluated by means of a linear programming algorithm. Expressions for the interaction parameters of the solutes and the Gibbs energies of formation of the carbides, nitrides, carbonitrides, and sulfides of titanium were simultaneously optimized. It is shown that the resulting thermochemical data base reproduces the experimental data satisfactorily.

Stability of discrete-time linear systems with Markovian jumping parameters

Abstract: This paper deals with the robustness of a class of discrete-time linear systems with Markovian jumping parameters and unknown but bounded uncertainties. Assuming that the Markovian jump process (disturbance) has finite state space and that there is complete access to the system's state and its mode, we establish necessary and sufficient conditions for stochastic stability of the autonomous nominal model. We also establish sufficient conditions for robust stability for this class of uncertain systems under matching conditions and with bounded uncertainties.

The Hyogo-ken Nanbu earthquake (The great Hanshin earthquake) of 17 January 1995

Abstract: This report describes the observations and preliminary assessments of the members of the Reconnaissance Team of the New Zealand National Society for Earthquake Engineering which visited Kobe, Japan and the surrounding areas following the Hyogo-ken Nanbu earthquake of 17 January 1995. The report covers aspects of the effects of the earthquake on the ground, lifelines, buildings, bridges and other structures, and the community. Lessons for New Zealand are discussed.

A model for global symmetry detection in dense images

Abstract: —In this paper, a model is proposed for bilateral symmetry detection in images consisting of dense arrangements of local features. The model is elaborated on the basis of a psychophysical experiment showing that grouping precedes and facilitates symmetry detection. The proposed computational model consists of three stages: a grouping stage, a symmetry-detection stage, and a symmetry-subsumption stage. Reliance upon a preliminary grouping stage enables a significant reduction of the computational load for detecting symmetry. An implementation of the model is described, and results are presented, showing a good agreement of the model performance with human symmetry perception.

Comparison of approaches to spatial estimation in a bivariate context

Abstract: The problem of estimating a regionalized variable in the presence of other secondary variables is encountered in spatial investigations. Given a context in which the secondary variable is known everywhere (or can be estimated with great precision), different estimation methods are compared: regression, regression with residual simple kriging, kriging, simple kriging with a mean obtained by regression, kriging with an external drift, and cokriging. The study focuses on 19 pairs of regionalized variables from five different datasets representing different domains (geochemical, environmental, geotechnical). The methods are compared by cross-validation using the mean absolute error as criterion. For correlations between the principal and secondary variable under 0.4, similar results are obtained using kriging and cokriging, and these methods are superior slightly to the other approaches in terms of minimizing estimation error. For correlations greater than 0.4, cokriging generally performs better than other methods, with a reduction in mean absolute errors that can reach 46% when there is a high degree of correlation between the variables. Kriging with an external drift or kriging the residuals of a regression (SKR) are almost as precise as cokriging.

Dynamic mechanical analysis of prestrained Al2O3/Al metal-matrix composite

Abstract: The effect of prestraining on the elastic modulus,E, and damping capacity, tanφ, of 10 and 20 vol% Al2O3 particle-reinforced composites has been investigated as function of temperature using dynamic mechanical analysis. Both elastic modulus and damping capacity were found to increase with volume fraction. At 10 vol% the modulus and damping were relatively insensitive to prestrain. However, at 20 vol% it was observed that the modulus decreased with increasing prestrain while damping increased significantly. These results are discussed in terms of fraction of broken particles, particle size, and differential in thermal expansion between the matrix and Al2O3 particulate.

Angle‐resolved XPS study of plasma‐treated teflon PFA surfaces

Abstract: Teflon PFA (polytetrafluoroethylene-co-perfluoroalkoxy vinyl ether) was treated by a low-pressure microwave (2.45 GHz) plasma in O2, N2, H2, He and their mixtures. X-ray photoelectron spectroscopy measurements showed ablation of fluorine and incorporation of new O- and N-containing groups into the surface. Among the different gases, H2 is the most efficient for defluorination, N2 + H2 for surface functionalization, while O2 showed the least performance for both effects. Plasma treatments using N2 + H2 and O2 + H2 resulted in intermediate defluorination, i.e. between those in the pure gases, and sequential treatment by He/(N2 + H2) showed an additive effect of He and N2 + H2 alone. Angle-resolved XPS measurements revealed a pronounced gradient in the near-surface composition following H2, N2 + H2 and He/(N2 + H2) plasma treatments, in contrast to a more uniform depth distribution upon O2, N2 and He exposures. The surface modification of Teflon PFA leads to an enhanced adhesion of metals such as Cu, Ag and Au.