Lower limb contribution in kayak performance: modelling,simulation and analysis

Lower limb contribution in flatwater kayaking is difficult to quantify experimentally because lower-limbs and pelvis are hidden in the kayak. A computer simulation model was developed to assess the lower limb contribution to kayak performance. Three simulated movements were compared in terms of paddle tip velocity, force impulse, and mechanical work. The pelvis motion increased the paddle tip velocity by 0.15 m s⁻¹ at the stroke beginning and 0.34 m s⁻¹ afterward. The propulsive impulse was also modified by pelvis rotation with a 3.5 N s increase per stroke. For a set performance, the co-ordination involving the lower limbs decreased the mechanical work by 20 J. The above results were obtained by modelling the Ergometer-Athlete-Paddle {EAP} system using 18 bodies and 31 degrees of freedom. The motion capture data were transformed in generalized coordinate time histories by solving an inverse kinematics problem with optimization in order to assess both lower limb and upper limb positions and produce a cyclic motion. Then the {EAP} was simulated based on Lagrangian dynamics with Lagrange multipliers to introduce the paddle forces. Finally, the joint torques were calculated by solving an inverse dynamics problem with optimization in order to ensure a good distribution of lower limbs actuating torques.     

The effect of lubrication conditions on belt finishing

The belt finishing process is a recent manufacturing technique in the field of superfinishing of hard material. Belt finishing leads to an homogenous surface with a very smooth surface roughness and good bearing curve parameters. In this way, belt finishing can complement effectively hard turning, whose disability is the shifting of the surface quality due to tool flank wear. In order to study the effect and the interaction of lubrications conditions on belt finishing after hard turning, an experimental study is proposed. The interaction between lubrications conditions and belt feed and the effect on roughness parameters has been investigated. It was shown that minimum quantity lubrication with low belt feed is the best way to have the optimal roughness characteristics. Under these conditions, the process is not a basic belt finishing operation but a combination of belt finishing and lapping due to the presence of a slurry made of free abrasive grains, microchips and oil, in the contact. Additionally, it has been revealed that dry belt finishing is not suitable because of the rapid destruction of abrasive grains.     

High density hydrophilic and hydrophobic brush coatings using a polymeric primer layer

Polymer brush coatings, consisting of polymer chains covalently attached to a surface and being less than a hundred nanometer thick, allow the creation of functional surfaces without altering the inherent bulk properties or appearance of a product. Surface properties depend on the type and length of the polymer used, as well as on the grafting density of the polymer brush. By making use of a polymeric primer layer that is covalently linked to the substrate and creates a uniform and highly functionalized surface, polymer brush coatings with high grafting densities can be created. In this paper we report the preparation of hydrophilic as well as hydrophobic brush coatings on different substrates through the use of a poly(acrylic acid) primer layer. In addition, hydrophilic poly(ethylene glycol) brush coatings thus produced were shown to decrease adhesion of marine bacteria.     

Overview of the MPEG Reconfigurable Video Coding Framework

Video coding technology in the last 20 years has evolved producing a variety of different and complex algorithms and coding standards. So far the specification of such standards, and of the algorithms that build them, has been done case by case providing monolithic textual and reference software specifications in different forms and programming languages. However, very little attention has been given to provide a specification formalism that explicitly presents common components between standards, and the incremental modifications of such monolithic standards. The MPEG Reconfigurable Video Coding (RVC) framework is a new ISO standard currently under its final stage of standardization, aiming at providing video codec specifications at the level of library components instead of monolithic algorithms. The new concept is to be able to specify a decoder of an existing standard or a completely new configuration that may better satisfy application-specific constraints by selecting standard components from a library of standard coding algorithms. The possibility of dynamic configuration and reconfiguration of codecs also requires new methodologies and new tools for describing the new bitstream syntaxes and the parsers of such new codecs. The RVC framework is based on the usage of a new actor/ dataflow oriented language called CAL for the specification of the standard library and instantiation of the RVC decoder model. This language has been specifically designed for modeling complex signal processing systems. CAL dataflow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. The paper gives an overview of the concepts and technologies building the standard RVC framework and the non standard tools supporting the RVC model from the instantiation and simulation of the CAL model to software and/or hardware code synthesis.     

Identification of design motifs with pattern matching algorithms

Design patterns are important in software maintenance because they help in understanding and re-engineering systems. They propose design motifs, solutions to recurring design problems. The identification of occurrences of design motifs in large systems consists of identifying classes whose structure and organization match exactly or approximately the structure and organization of classes as suggested by the motif. We adapt two classical approximate string matching algorithms based on automata simulation and bit-vector processing to efficiently identify exact and approximate occurrences of motifs. We then carry out two case studies to show the performance, precision, and recall of our algorithms. In the first case study, we assess the performance of our algorithms on seven medium-to-large systems. In the second case study, we compare our approach with three existing approaches (an explanation-based constraint approach, a metric-enhanced explanation-based constraint approach, and a similarity scoring approach) by applying the algorithms on three small-to-medium size systems, JHotDraw, Juzzle, and QuickUML. Our studies show that approximate string matching based on bit-vector processing provides efficient algorithms to identify design motifs.     

Towards textile-based fiber-reinforced thermoplastic nanocomposites: Melt spun polypropylene-montmorillonite nanocomposite fibers

The present work is aimed at assessing the feasibility of integrating thermoplastic polypropylene nanocomposite matrices into conventional fiber-reinforced composites based on hybrid textiles that incorporate both the matrix and glass-fiber yarns, in order to reduce impregnation times. The focus is on the preparation and properties of the polypropylene nanocomposite fiber precursors and the implications for composite processing in general. However, preliminary results are also given that demonstrate satisfactory impregnation and consolidation of simple textiles produced byco-weaving the nanocomposite yarns with glass-fibers, given suitable processing conditions. POLYM. ENG. SCI., 47:1122–1132, 2007. © 2007 Society of Plastics Engineers     

Analyse de “microantennes” par une méthode temporelle

In this paper, a time domain analysis based on the resolutions of integral equations by the method of moments, is applied to the study of microstrip antennas. At first, the theory will be recalled with the different methods of calculation of antennas characteristics: input impedance, radiation pattern, as well as given approximations. Then, results will be presented and compared to those obtained with frequency methods.     

A comparison analysis of prefiltering methods in space-time trellis-based reduced-state turbo-detection

In this paper, we investigate two different prefiltering strategies, i.e., multiple input multiple output (MIMO) channel shortening and MIMO whitened matched filtering, to decode iteratively a space time bit interleaved coded modulation transmitted over MIMO block fading intersymbol interference channels using a trellis-based post-detector. Indeed, resorting to such front-ends allows significant complexity gain when compared to the optimal maximum a posteriori-based turbo-receiver. While those two approaches have been exhaustively visited in the past, their fair comparison in terms of trade-off between complexity and performance has – to our knowledge – never been tackled before. This paper aims at giving some valuable insights about the respective benefits of these two prefiltering methods with respect to the channel characteristics and overall receiver complexity.     

Comparison of glycemic index of spelt and wheat bread in human volunteers

The assessment of the glycemic index (GI) seems to be an important parameter to take into account in order to better understand the physiologic effects of foods with high carbohydrate levels. Among cereals, which are major sources of carbohydrates, spelt (Triticum spelta L.) has been considered as particularly interesting from a nutritional point of view. The aim of this study was to evaluate in vivo the GI of white spelt bread in healthy subjects. The wheat (Triticum aestivum L.) white bread was used as reference food. To avoid differences in the production of both breads, spelt and wheat breads were baked under the same controlled conditions. Results showed that the glycemic profile of spelt white bread was not different from that of wheat white bread (GI of 93 ± 9). The area under the glycemic curve significantly and negatively correlated to fasting glycemia and carbohydrate intake during evening meals preceding the test. In conclusion, the glycemic response to spelt bread was similar to that of wheat bread. However, in order to avoid more inter-individual variability, our data supports the importance to propose standardised carbohydrate content for the last meal before evaluating the GI of food.