Effect of nitrogen impurity on the stabilization of 3C–SiC polytype during heteroepitaxial growth by vapor–liquid–solid mechanism on 6H–SiC substrates

This work reports on the stabilization of 3C–SiC polytype during heteroepitaxial growth by vapor–liquid–solid (VLS) on on-axis and 2° off-axis 6H–SiC(0001) substrates using Si–Ge as liquid phase. It was found that, depending on growth conditions (mainly temperature or nitrogen amount in the reactor), the deposit could be either a complete 3C or 6H–SiC layer or even a mixture of both polytypes. The proportion of 3C inside the deposit increases when 1) nitrogen amount in the reactor increases or 2) temperature is decreased. Though the effect of temperature could be explained in terms of 3C–SiC initial island dissolution, the influence of nitrogen is less obvious but it is shown to be effective at the early stage of growth. Several hypotheses are proposed such as SiC lattice modification by N incorporation or surface effects during the early stage of growth.     

Designing exopolysaccharide-graft-poly(3-hydroxyalkanoate) copolymers for electrospun scaffolds

Poly(3-hydroxyalkanoate)s PHAs have been demonstrated to be a family of biopolyester with good biodegradability and biocompatibility. A glycosaminoglycan-like marine exopolysaccharide EPS HE800 was here incorporated to enhance cell adhesion. Novel graft copolymer HE800-g-PHA were prepared to improve the compatibility between hydrophobic PHA and hydrophilic HE800. The carboxylic end groups of PHA oligomers were activated with acyl chloride functions, allowing coupling to hydroxyl groups of HE800. Fibrous scaffolds were prepared by a modified electrospinning system which combined simultaneously PHA electrospinning and HE800-g-PHA copolymer electrospraying. Adhesion and growth of human mesenchymal stem cells on the HE800-g-PHA scaffolds showed a notable improvement over those on PHAs matrices.     

A Marine Propeller Aerodynamic Test Facility

Abstract:  Conventional propeller test facilities such as tow tanks, cavitation tunnels and the open sea have various limitations such as cost, accessibility, size and accuracy. An aerodynamic marine propeller test facility has been developed at the University of British Columbia to allow for performance evaluations of full-size marine propellers in the highly controlled environment of a wind tunnel. Thorough static and dynamic calibrations of the test rig confirmed that the sensors have a highly linear response with essentially zero crosstalk between the thrust and torque signals. Performance curves acquired from a commercial 24 × 24 propeller show that the repeatability error of the torque and thrust measurements is <1%. The uncertainties of the advance ratio, torque coefficient, thrust coefficient, and efficiency are 0.2%, 0.5%, 0.1%, and 1%, respectively. Performance curves measured over a range of the Reynolds numbers show that Reynolds number independence is achieved for Reynolds numbers above approximately 5 × 10⁵.     

Effect of a machining-induced defect on the tensile strength of a 3D composite material

This paper investigates the effect of finite specimen size upon the tensile failure of a tridirectional carbon-carbon composite along each reinforcement axis. Asymmetry in the position of load-bearing axial yarns across the cross-section is generated randomly by machining. This yields parasitic bending of the specimen, and thereby premature failure of the yarns subjected to the maximum bending stress. However, bending effects become negligible at final failure. Additionally, the composite failure strength _F is determined from the cross-sectional area of the actually load-bearing axial yarns, using both symmetrical and asymmetrical specimens. Results are in good agreement with previous work, and we show that the variability of _F is small.     

Policy-constrained bio-inspired processes for autonomic route management

Autonomic networking systems must be designed to achieve an appropriate balance between the operation of decentralized algorithms and processes that seek to maintain optimal or near-optimal behavior in terms of global stability, improved performance and adaptability, robustness and security, with the requirement for top-down control of the system by humans to ensure business goals are met. Taking a communications networking survivability case study, we show how the operation of decentralized algorithms, inspired by the operation of biological systems, can be controlled and constrained through the deployment of management policies authored by network administrators. We present survivability-related routing algorithms (inspired by chemotaxis, reaction-diffusion and quorum sensing biological processes) which work together to effectively reconfigure network resources when transient link failures occur and demonstrate how these algorithms can be re-parameterized via policies to improve performance given prevailing network conditions. Simulation results show how the combined operation of these algorithms, as controlled by policies, allows the network to react well to survive link failure events.     

Enabling context-aware multimedia annotation by a novel?generic semantic problem-solving platform

Automatic generation of metadata, facilitating the retrieval of multimedia items, potentially saves large amounts of manual work. However, the high specialization degree of feature extraction algorithms makes them unaware of the context they operate in, which contains valuable and often necessary information. In this paper, we show how Semantic Web technologies can provide a context that algorithms can interact with. We propose a generic problem-solving platform that uses Web services and various knowledge sources to find solutions to complex requests. The platform employs a reasoner-based composition algorithm, generating an execution plan that combines several algorithms as services. It then supervises the execution of this plan, intervening in case of errors or unexpected behavior. We illustrate our approach by a use case in which we annotate the names of people depicted in a photograph.     

Adapting the CBA algorithm by means of intensity of implication

In recent years, extensive research has been carried out by using association rules to build more accurate classifiers. The idea behind these integrated approaches is to focus on a limited subset of association rules. This paper aims to contribute to this integrated framework by adapting the Classification Based on Associations (CBA) algorithm. CBA was adapted by coupling it with another measurement of the quality of association rules: i.e. intensity of implication. The new algorithm has been implemented and empirically tested on an authentic financial dataset for purposes of bankruptcy prediction. We validated our results with an association ruleset, with C4.5, with original CBA and with CART by statistically comparing its performance via the area under the ROC-curve. The adapted CBA algorithm presented in this paper proved to generate significantly better results than the other classifiers at the 5% level of significance.     

Effect of tibial component position on patellar strain following total knee arthroplasty

Gliosarcomas are morphologically heterogeneous tumors of the central nervous system composed of gliomatous and sarcomatous components. The histogenesis of the latter is still a matter of debate. As mutations of the p53 tumor suppressor gene represent an early event in the development of gliomas, we attempted to determine whether both components of gliosarcomas share identical alterations of the p53 gene. Using single-strand conformation analysis (SSCA) and direct DNA sequencing of the p53 gene, we analyzed dissected gliomatous and sarcomatous parts of 12 formalin-fixed, paraffin-embedded gliosarcomas. The two tumors that contained a p53 alteration were found to carry the identical mutation (exon 5; codon 151, CCC-->TCC; codon 173, GTG-->GTA) in the gliomatous and the sarcomatous components. These findings suggest a common origin of the two cellular components from neoplastic glial cells.