Anti-patterns for rule-based languages

Negation is intrinsic to human thinking and most of the time when searching for something, we base our patterns on both positive and negative conditions. This should be naturally reflected in software that provide pattern-based searches. We would like for example to specify that we search for white cars that are not station wagons, or that we search for a list of objects that does not contain two identical elements.     

Spatial Networks of Hybrid I/O Automata for Modeling Excitable Tissue

We propose a new biological framework, spatial networks of hybrid input/output automata (SNHIOA), for the efficient modeling and simulation of excitable-cell tissue. Within this framework, we view an excitable tissue as a network of interacting cells disposed according to a 2D spatial lattice, with the electrical behavior of a single cell modeled as a hybrid input/ouput automaton. To capture the phenomenon that the strength of communication between automata depends on their relative positions within the lattice, we introduce a new, weighted parallel composition operator to specify the influence of one automata over another.The purpose of the SNHIOA model is to efficiently capture the spatiotemporal behavior of wave propagation in 2D excitable media. To validate this claim, we show how SNHIOA can be used to model and capture different spatiotemporal behavior of wave propagation in 2D isotropic cardiac tissue, including normal planar wave propagation, spiral creation, the breakup of spirals into more complex (potentially lethal) spatiotemporal patterns, and the recovery of the tissue to the rest via defibrillation.     

Negotiation-Based Scheduling of Scientific Grid Workflows Through Advance Reservations

In its broadest sense, scheduling of Grid applications can be viewed as a negotiation process between a scheduling service optimising user-centric objectives such as execution time, and a resource manager optimising provider-centric metrics such as resource utilisation or fairness. In this paper we enhance an existing list scheduling algorithm designed for minimising the workflow makespan with advance reservation-based negotiation functionality. As an instantiation of the new negotiation phase, we investigate two advance reservation functionality from the resource provider perspective: attentive and progressive. We illustrate through real-world experiments a two-fold benefit of our approach: improved execution predictability from the user’s perspective, and higher resource utilisation fairness through a new progressive allocation strategy from the provider’s perspective.     

Distributed On-the-Fly Equivalence Checking

On-the-fly equivalence checking consists in comparing two Labeled Transition Systems (Ltss) modulo a given equivalence relation by exploring them in a demand-driven way. Since it avoids the explicit construction of Ltss, this method is able to detect errors even in systems that are too large to fit in the memory of a computer. In this paper, we aim at further improving the performance of on-the-fly equivalence checking using several machines connected by a network. We propose DSolve, a new algorithm for distributed on-the-fly resolution of Boolean Equation Systems (Bess), which enables equivalence checking modulo various relations characterized in terms of Bess. DSolve serves as verification engine for the distributed version of Bisimulator, an on-the-fly equivalence checker developed within the Cadp verification toolbox using the Open/Cæsar environment. Our experimental measures show quasi-linear speedups and a good scalability of the distributed version of Bisimulator w.r.t. its sequential version.     

Kinetics of polyesterification of adipic acid with 1,3-butanediol

The kinetics of non-catalyzed, acid catalyzed and alkyltin catalyzed polyesterification of adipic acid with 1, 3-butanediol as a model for polymeric ester synthesis was followed at 180°C and 215°C by monitoring of carboxyl, hydroxyl, and water content of the reaction system. The rate constants of the three processes were calculated using a simulation method. The process is kinetically controlled during the first 4–10 h (down to AV ? 20 mg KOH/g, conversion 95%) and then thermodynamically controlled by elimination of water from the system. Methyltin derivatives, especially trichloride, are more active catalysts but dibutyltin oxide can be used with good results. The model study suggests that addition of the catalyst at the beginning of the process and applying a vacuum (pressure 60 Torr) will reduce the reaction time in half, compared with adding catalyst at AV ? 20 mg KOH/g and using no vacuum.     

Spectroscopic characterisation of a cross-flow plasma jet

The aim of this work is to study the thermal characteristics and electron density based on atomic and molecular emission of a new plasma jet at atmospheric pressure. The novelty of our jet is its generation with a single electrode, the plasma gas flowing perpendicularly to the RF powered electrode (13.56 MHz, 10³ V). Optical emission of the plasma was collected in two ways: the normal viewing mode and the axial viewing mode. The plasma characteristic parameters as function of helium flow-rate, plasma power and position of the investigated zone were studied. The excitation, vibrational and rotational temperatures are in the range of 1500-2350 K, 3500-4400 K and 450-1100 K, respectively. The electron number densities are in the range of 10¹³-10¹⁴ cm⁻³. For qualitative observations regarding the atomic and molecular processes in the plasma we used the relative intensities of the most representative lines of He, N₂, O, H and .     

Morphology evolution induced by carbon nanotubes on thermal and mechanical characters of semi-crystalline aromatic polyimide

A series of nanocomposites based on a new semi-crystalline polyimide (PI) and multi-walled carbon nanotubes (MWCNTs) were prepared by in situ polymerization. The TEM measurement reveals the improved dispersion of carboxylic acid-functionalized MWCNTs (COOH-MWCNTs) in semi-crystalline PI compared with pristine MWCNTs. The TGA analysis show that the concentration of carboxylic acid groups on the surface of nanotubes is about 4.34 wt%. The FT-IR spectroscopy analysis indicate that the imide rings of the PI interact non-covalently with nanotubes. The Polarized optical microscopy observation reveals significant morphology evolution in semi-crystalline PI induced by MWCNTs. The SEM micrographs suggest the strong interfacial interaction between COOH-MWCNTs and PI main chains, and significant changes in the fracture surfaces morphology. The WAXRD measurements reveal that COOH-MWCNTs promote the semi-crystalline PI crystallinity and structure change. COOH-MWCNTs can more efficiently improve the mechanical and thermal properties of resulting nanocomposites than pristine MWCNTs. COOH-MWCNT/PI nanocomposites show increases of Young’s modulus and yield strength, as high as 20–30 %, without sacrificing the elongation at break at loadings of 0.5 wt% nanotubes. Furthermore, with increasing the loadings of COOH-MWCNTs to 1.0 wt%, Young’s modulus and yield strength decrease due to nanotube aggregation, but elongation at break increase about 46 %. An abrupt increase of elongation at break in pristine MWCNT/PI nanocomposites was also registered at nanotubes loadings increasing from 0.5 to 1 wt%. These results indicate that the properties of semi-crystalline PI nanocomposites reinforced with carbon nanotubes are not only determined by the dispersion of nanotubes in the PI matrix and their interfacial interactions, but also by the crystalline phase morphology evolution in the PI matrix.     

Guest Editors' Introduction: Tackling Key Problems in NoCs

This special issue highlights recent innovations in network on a chip (NoC) design. The four articles fall into two main thrusts: the first three focus on design methodology challenges in NoCs; the final article demonstrates a practical case study implementation of an NoC.     

Object Pose: The Link between Weak Perspective,Paraperspective, and Full Perspective

Recently, DeMenthon and Davis (1992, 1995) proposed a method for determining the pose of a 3-D object with respect to a camera from 3-D to 2-D point correspondences. The method consists of iteratively improving the pose computed with a weak perspective camera model to converge, at the limit, to a pose estimation computed with a perspective camera model. In this paper we give an algebraic derivation of DeMenthon and Davis' method and we show that it belongs to a larger class of methods where the perspective camera model is approximated either at zero order (weak perspective) or first order (paraperspective). We describe in detail an iterative paraperspective pose computation method for both non coplanar and coplanar object points. We analyse the convergence of these methods and we conclude that the iterative paraperspective method (proposed in this paper) has better convergence properties than the iterative weak perspective method. We introduce a simple way of taking into account the orthogonality constraint associated with the rotation matrix. We analyse the sensitivity to camera calibration errors and we define the optimal experimental setup with respect to imprecise camera calibration. We compare the results obtained with this method and with a non-linear optimization method.     

Formal verification of the NASA runway safety monitor

The runway safety monitor (RSM) designed by Lockheed Martin is part of NASA’s effort to reduce aviation accidents. We developed a Petri net model of the RSM protocol and used the model checking functions of our tool (stochastic and model checking analyzer for reliability and timing) SMART (Stochestic and model checking analyses for seliability and tunnig) to investigate a number of safety properties for the RSM. To mitigate the impact of state-space explosion, we built a highly discretized model of the system, obtained by partitioning the monitored runway zone into a grid of smaller volumes and by considering scenarios involving only two aircraft. The model also assumes that there are no communication failures, such as bad input from radar or lack of incoming data, thus it relies on a consistent view of reality by all participants. In spite of these simplifications, we were able to expose potential problems in the conceptual design of RSM. Our findings were forwarded to the design engineers, who undertook corrective action. Additionally, the results stress the efficiency attained by the new model checking algorithms implemented in SMART, and demonstrate their applicability to real-world systems. Attempts to verify RSM with similar NuSMV and SPIN models have failed due to excessive memory consumption. Work supported in part by the National Aeronautics and Space Administration under grant NAG-1-02095 and by the National Science Foundation under grants CCR-0219745 and ACI-0203971.