Accelerated Shift-and-Add Algorithms

The problem addressed in this paper is the computation of elementary functions (exponential, logarithm, trigonometric functions, hyperbolic functions and their reciprocals) in fixed precision, typically the computer single or double precision. The method proposed here combines Shift-and-Add algorithms and classical methods for the numerical integration of ODEs: it consists in performing the Shift-and-Add iteration until a point close enough to the argument is reached, thus only one step of Euler method or Runge-Kutta method is performed. This speeds up the computation while ensuring the desired accuracy is preserved. Time estimations on various processors are presented which illustrate the advantage of this hybrid method.     

Migration strategy towards Q3 interfaces of switching systems : a look at France Telecom switches

Future telecommunication management network (TMN) will be based upon object-oriented modelling of interfaces. Nevertheless, in case of public switched telephone network, this process will be long and difficult. However, as current interfaces are not completely satisfactory, some evolution steps from today’s interfaces towards tomorrow’sTMN ones are planned. This paper presents the different steps chosen by France Telecom. At first, introduction of a new protocol as close as possible to the target Q3 is detailed. Unification of the different heterogeneous commands is then shown through creation of standard commands, last, integration toTMN through Q-adaptor is presented.     

A model-driven traceability framework for software product lines

Software product line (SPL) engineering is a recent approach to software development where a set of software products are derived for a well defined target application domain, from a common set of core assets using analogous means of production (for instance, through Model Driven Engineering). Therefore, such family of products are built from reuse, instead of developed individually from scratch. SPL promise to lower the costs of development, increase the quality of software, give clients more flexibility and reduce time to market. These benefits come with a set of new problems and turn some older problems possibly more complex. One of these problems is traceability management. In the European AMPLE project we are creating a common traceability framework across the various activities of the SPL development. We identified four orthogonal traceability dimensions in SPL development, one of which is an extension of what is often considered as “traceability of variability”. This constitutes one of the two contributions of this paper. The second contribution is the specification of a metamodel for a repository of traceability links in the context of SPL and the implementation of a respective traceability framework. This framework enables fundamental traceability management operations, such as trace import and export, modification, query and visualization. The power of our framework is highlighted with an example scenario.     

Anisotropie des proprietes electriques de l'oxyde de fer Fe2O3α

The electrical conductivity and the thermoelectric power of trivalent iron oxide α-Fe₂O₃, studied in the crystallographic plane (001) and along the [001] axis, have shown typical anisotropic behaviour.In the same material, the existence of two electronic transitions at 2.14 and 2.50 eV respectively has been found after optical absorption measurements.At high temperature (T > 1020 K) the electrical conductivity has an essentially intrinsic origin, and is practically independent of the oxygen pressure, while the extrinsic contribution predominates below 720 K.According to the model developped for the interpretation of the above experimental results, the peculiar behaviour of the electrical conductivity results from variations in the mobility of the carriers, depending on the electronic levels they are likely to occupy. These levels were identified as the results of a split in the t_2g orbitals of iron under the influence of the rhombohedral. distortion of the crystal field.Furthermore, the anisotropy of mobility is strongly dependent on the magnetic order below Néel temperature.

Résumé

L'étude de la conductivité électrique et du pouvoir thermoélectrique de l'oxyde de fer Fe₂O₃α, effectuée selon la direction cristallographique [001] et dans le plan (001), a révélé une grande anisotropie de comportement. Sur le même matériau des mesures d'absorption optique ont montré l'existence de deux transitions électroniques, à 2,14 et 2,50 eV respectivement.Prenant en compte l'ensemble de ces résultats un modèle a été proposé pour expliquer les propriétés du matériau à diverses températures et sous différentes pressions partielles d'oxygène.A température élevée (T > 1020 K) la conductivité électrique, pratiquement indépendante de la pression d'oxygène, est à forte dominante intrinsèque. En revanche, à basse température (T < 720 K), la conductivité est d'origine extrinsèque.La diversité des mécanismes de conduction observés peut s'expliquer par l'existence de porteurs dont la mobilité varie suivant les niveaux d'énergie qu'ils occupent. Ces niveaux résultent de l'éclatement des orbitales t_2g du fer dû à la distorsion rhomboédrique du champ cristallin.Les mobilités anisotropes sont fortement affectées par l'ordre magnétique au-dessous de la température de Néel.     

Low Tc growth transitions in isotactic polypropylene: β to α and α to smectic phases

Summary Two growth transitions are observed by optical microscopy in the low T_c range (105–80°C) of isotactic polypropylene (iPP): to and to (probably) smectic phases. These transitions (notably to ) may be the cause of the complicated annealing and recrystallization behaviour of iPP, which is known to depend on the initial crystallization and post-crystallization thermal history.     

Finding Narrow Passages with Probabilistic Roadmaps: The Small-Step Retraction Method

Probabilistic Roadmaps (PRM) have been successfully used to plan complex robot motions in configuration spaces of small and large dimensionalities. However, their efficiency decreases dramatically in spaces with narrow passages. This paper presents a new method—small-step retraction—that helps PRM planners find paths through such passages. This method consists of slightly “fattening” robot's free space, constructing a roadmap in fattened free space, and finally repairing portions of this roadmap by retracting them out of collision into actual free space. Fattened free space is not explicitly computed. Instead, the geometric models of workspace objects (robot links and/or obstacles) are “thinned” around their medial axis. A robot configuration lies in fattened free space if the thinned objects do not collide at this configuration. Two repair strategies are proposed. The “optimist” strategy waits until a complete path has been found in fattened free space before repairing it. Instead, the “pessimist” strategy repairs the roadmap as it is being built. The former is usually very fast, but may fail in some pathological cases. The latter is more reliable, but not as fast. A simple combination of the two strategies yields an integrated planner that is both fast and reliable. This planner was implemented as an extension of a pre-existing single-query PRM planner. Comparative tests show that it is significantly faster (sometimes by several orders of magnitude) than the pre-existing planner. Mitul Saha received the B.S. degree from the Indian Institute of Technology, Kanpur, India, in 2001 and the M.S. degree from the Computer Science Department at Stanford University, Stanford, CA, in 2005. He is currently pursuing the Ph.D. degree in mechanical engineering at Stanford University. His research interests include motion planning, computer vision, graphics, and structural biology. Jean-Claude Latombe graduated in electrical and computer engineering from the National Polytechnic Institute of Grenoble, France, in 1970. He received the M.S. degree in electrical engineering from the National Polytechnic Institute of Grenoble in 1972, and the PhD degree in computer science from the University of Grenoble in 1977. He joined the Department of Computer Science at Stanford University in 1987, where he currently is the Kumagai Professor in the School of Engineering. He does research in the general areas of artificial intelligence, robotics, and geometric computing. He is particularly interested in motion planning, computational biology, and computer-assisted surgery. Yu-Chi Chang is a Ph.D. candidate in the Mechanical Engineering at Stanford University. Yu-Chi received the B.Sc. in Mechanical Engineering and the M.Sc. in Material Science from National Taiwan University, Taiwan, and the M.Sc. in Mechanical Engineering from Stanford University, United States. His current research interests include robust design and statistical analysis for manufacturing system. Friedrich Prinz is the Rodney H. Adams Professor of Engineering and Professor of Mechanical Engineering and Materials Science and Engineering, Stanford University. Professor Prinz received his Ph.D. degree in Physics from the University of Vienna in 1975. He has been active in synergistic activities with organizations like the National Research Council Committees, the Japanese Technology Evaluation Center and World Technology Evaluation Center, as well as Portuguese Science and Technology Foundation. He was elected to the Austrian Academy of Science (foreign member), Vienna, Austria in 1996. Dr. Prinz's current research activities address a wide range of problems related to design and rapid prototyping of organic and inorganic devices. His current work focuses on the fabrication and physics of fuel cells as well as the creation of biological cell structures. His group uses atomic force microscopy and impedance spectroscopy to characterize the behavior of electrochemical systems with micro and nano-scale dimensions.     

Cationic polymerization of 1,3,5,7-tetramethylcyclotetrasiloxane in aqueous emulsion. Part I. Preliminary results

The synthesis of poly(methylhydrogeno)siloxane (PMHS) by cationic polymerization of 1,3,5,7-tetramethylcyclotetrasiloxane (D₄ ^H) was studied in aqueous emulsion using dodecylbenzenesulphonic acid (DBSA) as emulsifier/initiator. With pure DBSA, the rates of polymerization are very high and the PMHS formation is not well-controlled (cross-linking reactions, emulsion not very stable). The addition of the sodium salt of DBSA as coemulsifier does not give satisfactory results. In the presence of a neutral coemulsifier (Brij35), the process leads to the formation of linear PMHS of controlled molecular weight in the range 7000–70 000 g mol ⁻¹ with a yield of 90%. No cross-linking reaction was observed, showing the good stability of the Si H bond in these experimental conditions. Preliminary investigations lead to the conclusion that the polymer is probably formed by initiation, propagation and termination reactions taking place simultaneously at the surface of 200 nm diameter monomer particles. Nevertheless, the peculiar mechanism of these reactions seems more complicated than those previously found in the case of anionic polymerization of D₄ in aqueous emulsion. © 1999 Society of Chemical Industry     

Hydrolysis of Tropical Tuber Starches by Bacterial and Pancreatic α-Amylases

Action of porcine pancreatic and Bacillus subtilis α-amylases on native tuber starches of yam (Dioscorea alata), sweet potato (Ipomea batatas) and tannia (Xanthosoma sagittifolium) was studied in comparison with the well known potato and cassava starches. Large differences in enzymes susceptibilities were observed when studied on 24h. Yam starch was 3.5% hydrolysed with 2,8 μkat amylase/g starch, three times less than potato and tannia starches while sweet potato starch was 53% hydrolysed, two times less than cassava starch. Except yam, level of hydrolysis was higher with porcine pancreatic amylase than with the Bacillus subtilis amylase while initial hydrolysis rate was lesser. Microscopic observations and image analysis pointed out that the polyhedric shaped granules of tannia, sweet potato and cassava starches were much more damaged than the spherical ones. Pitting occured preferentially on the edges of the granules and the enzymes penetrated into the starch granule by pores and canals of corrosion. Conversely to other starches, hydrolysis of yam starches evidenced greater differences between action of Bacillus subtilis and pancreatic α-amylases. The enzymes acted by pitting some parts of the granules surface, the number of pores and their size being related to enzyme source.     

Identification of ACT4, a novel essential actin-related gene in the yeast Saccharomyces cerevisiae

Actin molecules are major cytoskeleton components of all eukaryotic cells. All conventional actins that have been identified so far are 374–376 amino acids in size and exhibit at least 70% amino acid sequence identity when compared with one another. In the yeast Saccharomyces cerevisiae, one conventional actin gene ACT1 and three so-called actin-related genes, ACT2, ACT3 and ACT5, have been identified. We report here the discovery of a new actin-related gene in this organism, which we have named ACT4. The deduced protein, Act4, of 449 amino acids, exhibits only 33·4%, 26·7%, 23·4% and 29·2% identity to Act1, Act2, Act3 and Act5, respectively. In contrast, it is 68·4% identical to the product of the Schizosaccharomyces pombe Act2 gene and has a similar level of identity to other Sch. pombe Act2 homologues. This places Act4 in the Arp3 family of actin-related proteins. ACT4 gene disruption and tetrad analysis demonstrate that this gene is essential for the vegetative growth of yeast cells. The act4 mutants exhibit heterogenous morphological phenotypes. We hypothesize that Act4 may have multiple roles in the cell cycle. The sequence has been deposited in the Genome Sequence Data Base under Accession Number L37111.