Hyperstructures and memory evolutive systems

The aim of the paper is to compare two different approaches to the modeling of complex natural systems, in particular of their hierarchical organization with higher-order structures and their emergence processes. These approaches are, respectively, the hyperstructures (HS) of Baas and the memory evolutive systems (MES) of Ehresmann and Vanbremeersch. The HS are “structural” while MES, based on category theory, take dynamics more into account. It is shown how the dynamical organization and mechanisms developed for MES rely on simple ideas of a philosophical nature, that might be disengaged from the categorical setting and extended to the general frame of HS.     

An automatic keyphrase extraction system for scientific documents

Automatic keyphrase extraction techniques play an important role for many tasks including indexing, categorizing, summarizing, and searching. In this paper, we develop and evaluate an automatic keyphrase extraction system for scientific documents. Compared with previous work, our system concentrates on two important issues: (1) more precise location for potential keyphrases: a new candidate phrase generation method is proposed based on the core word expansion algorithm, which can reduce the size of the candidate set by about 75% without increasing the computational complexity; (2) overlap elimination for the output list: when a phrase and its sub-phrases coexist as candidates, an inverse document frequency feature is introduced for selecting the proper granularity. Additional new features are added for phrase weighting. Experiments based on real-world datasets were carried out to evaluate the proposed system. The results show the efficiency and effectiveness of the refined candidate set and demonstrate that the new features improve the accuracy of the system. The overall performance of our system compares favorably with other state-of-the-art keyphrase extraction systems.     

Influence of Ozonation of Humic and Fulvic Acids on Diuron Adsorption on Activated Carbon

The effect of ozonation on the competitor effect of humic and fulvic acids against diuron in adsorption on activated carbon in drinking water process has been studied. Ozonation treatment allows the removal of herbicides from drinking waters by modification of humic and fulvic acids structures. These latest are responsible for their adsorption variation on activated carbon. An ozone dose similar to that used in industrial pre-ozonation (1.3?mg ozone/l) does not cause significant transformations of humic and fulvic acids which could decrease their competitor effect and increase significantly the adsorption capacity of the activated carbon for a well-adsorbed pesticide like diuron.     

Available rotation capacity of composite bridge plate girders under negative moment and shear

This paper presents a study of the behaviour of slender composite plate girders under negative bending moment and shear. It is known that at composite bridge intermediate supports, the slender composite beams have very limited ductility, which has led to the adoption of elastic methods for the design of these members. However, this elastic design is time-consuming and does not correspond with real beam behaviour. In order to propose a simpler and more intuitive design method which corresponds better with real beam behaviour, the support region limited ductility must be quantified. In this study, slender composite beam ductility under shear and negative bending is investigated, using a numerical model developed specifically for this purpose. On the basis of the parametric analysis results, a simple analytical model for quantifying the slender composite beam support region ductility is proposed and verified.     

Electrical and mechanical percolation in graphene-latex nanocomposites

Conductive composites based on few layer graphene are of primary interests. In this work latex based composites were produced leading to a specific cellular morphology. Highly conductive graphene-based composite materials have been produced through a solvent-free procedure. Both the mechanical and conductivity behaviors were successfully described using a percolation approach that confirms the presence of a three dimensional filler network efficiently spread across the material. The influence of the aspect ratio between the conductive filler and the latex nanosphere drove the study. It was demonstrated experimentally that the tuning of the cell dimensions of the composite morphology influences the percolation threshold and the reachable maximum conductivity and reinforcement. These experimental results are consistent with phenomenological models based on the statistical percolation theory.     

On the Motion Planning Problem, Complexity, Entropy, and Nonholonomic Interpolation

We consider the sub-Riemannian motion planning problem defined by a sub-Riemannian metric (the robot and the cost to minimize) and a non-admissible curve to be ε-approximated in the sub-Riemannian sense by a trajectory of the robot. Several notions characterize the ε-optimality of the approximation: the “metric complexity” MC and the “entropy” E (Kolmogorov-Jean). In this paper, we extend our previous results. 1. For generic one-step bracketgenerating problems, when the corank is at most 3, the entropy is related to the complexity by E = 2πMC. 2. We compute the entropy in the special 2-step bracket-generating case, modelling the car plus a single trailer. The ε-minimizing trajectories (solutions of the “ε-nonholonomic interpolation problem”), in certain normal coordinates, are given by Euler's periodic inflexional elastica. 3. Finally, we show that the formula for entropy which is valid up to corank 3 changes in a wild case of corank 6: it has to be multiplied by a factor which is at most 3/2. 2000 Mathematics Subject Classification. 53C17, 49J15, 34H05. The second author is supported by grants RFBR 050100458 and UR 0401128.     

Reduction of tablet weight variability by optimizing paddle speed in the forced feeder of a high-speed rotary tablet press

Context: Tableting is a complex process due to the large number of process parameters that can be varied. Knowledge and understanding of the influence of these parameters on the final product quality is of great importance for the industry, allowing economic efficiency and parametric release.

Objective: The aim of this study was to investigate the influence of paddle speeds and fill depth at different tableting speeds on the weight and weight variability of tablets.

Materials and methods: Two excipients possessing different flow behavior, microcrystalline cellulose (MCC) and dibasic calcium phosphate dihydrate (DCP), were selected as model powders. Tablets were manufactured via a high-speed rotary tablet press using design of experiments (DoE). During each experiment also the volume of powder in the forced feeder was measured.

Results and discussion: Analysis of the DoE revealed that paddle speeds are of minor importance for tablet weight but significantly affect volume of powder inside the feeder in case of powders with excellent flowability (DCP). The opposite effect of paddle speed was observed for fairly flowing powders (MCC). Tableting speed played a role in weight and weight variability, whereas changing fill depth exclusively influenced tablet weight.

Conclusion: The DoE approach allowed predicting the optimum combination of process parameters leading to minimum tablet weight variability. Monte Carlo simulations allowed assessing the probability to exceed the acceptable response limits if factor settings were varied around their optimum. This multi-dimensional combination and interaction of input variables leading to response criteria with acceptable probability reflected the design space.     

On the performance of packet-switched cellular networks for wireless data communications

Cellular frequency reuse is known to be an efficient method to allow many wireless telephone subscribers to share the same frequency band. However, for wireless data and multi-media communications optimum cell layouts differ essentially from typical solutions for telephone systems. We argue that wireless radio systems for bursty message traffic preferably use the entire bandwidth in each cell. Packet queuing delays are derived for a network with multipath fading channels, shadowing, path loss and discontinuously transmitting base stations. Interference between cells can be reduced by appropriately scheduling transmissions or by spatial collision resolution.Portions of this paper have been presented at the IEEE International Conferences on Personal Indoor Mobile Radio Communications (PIMRC) of 1993 in Yokohama and 1994 in The Hague.