Guaranteeing hard real-time traffic with legitimately short deadlines with the timed token protocol

Synchronous bandwidth, defined as the maximum time a node is allowed to send its synchronous messages while holding the token, is a sensitive parameter for deadline guarantees of synchronous messages in any timed token network. In order to offer such guarantees, synchronous bandwidth has to be allocated carefully to each individual node. This paper studies the synchronous bandwidth allocated to those synchronous message streams whose deadlines are less than twice the Target Token Rotation Time (TTRT). A new approach for allocating synchronous bandwidth to such streams, which can be used with any previously published local synchronous bandwidth allocation (SBA) for guaranteeing a general synchronous message set with its minimum deadline (D_min) no less than 2 · TTRT, is proposed. The proposed scheme can be applied efficiently in practice to any general synchronous message set with D_min > TTRT. Numerical examples are presented to demonstrate the enhanced performance of this new local scheme over any of the previously published local SBA schemes.     

Model checking action system refinements

Action systems provide a formal approach to modelling parallel and reactive systems. They have a well established theory of refinement supported by simulation-based proof rules. This paper introduces an automatic approach for verifying action system refinements utilising standard CTL model checking. To do this, we encode each of the simulation conditions as a simulation machine, a Kripke structure on which the proof obligation can be discharged by checking that an associated CTL property holds. This procedure transforms each simulation condition into a model checking problem. Each simulation condition can then be model checked in isolation, or, if desired, together with the other simulation conditions by combining the simulation machines and the CTL properties.     

A priori and a posteriori analysis for a locking-free low order quadrilateral hybrid finite element for Reissner–Mindlin plates

This paper proposes a quadrilateral finite element method of the lowest order for Reissner–Mindlin (R–M) plates on the basis of Hellinger–Reissner variational principle, which includes variables of displacements, shear stresses and bending moments. This method uses continuous piecewise isoparametric bilinear interpolation for the approximation of transverse displacement and rotation. The piecewise-independent shear stress/bending moment approximation is constructed by following a self-equilibrium criterion and a shear-stress-enhanced condition. A priori and reliable a posteriori error estimates are derived and shown to be uniform with respect to the plate thickness t. Numerical experiments confirm the theoretical results.     

Designing a Controller for a Multi-Train Multi-Track System

The use of formal methods for analyzing and synthesizing a controller for a multi-train multi-track railway system is discussed. The research was motivated by a case study involving the Bay Area Rapid Transit (BART) system. The overall goal is to design a train acceleration control function that enables trains to be safely placed but also increases system throughput. The use of a modeling language for specifying safety properties and a control function is illustrated. The program transformation methodology supported in the HATS system is employed to generate an efficient implementation from a high-level specification of a controller. This implementation can then be used to simulate the controller behavior, thus further enhancing confidence in the design. Properties of optimization transformations can be verified using an rewrite-rule based induction theorem prover Rewrite Rule Laboratory (RRL).     

Probabilistic fusion of stereo with color and contrast for bilayer segmentation

This paper describes models and algorithms for the real-time segmentation of foreground from background layers in stereo video sequences. Automatic separation of layers from color/contrast or from stereo alone is known to be error-prone. Here, color, contrast, and stereo matching information are fused to infer layers accurately and efficiently. The first algorithm, layered dynamic programming (LDP), solves stereo in an extended six-state space that represents both foreground/background layers and occluded regions. The stereo-match likelihood is then fused with a contrast-sensitive color model that is learned on-the-fly and stereo disparities are obtained by dynamic programming. The second algorithm, layered graph cut (LGC), does not directly solve stereo. Instead, the stereo match likelihood is marginalized over disparities to evaluate foreground and background hypotheses and then fused with a contrast-sensitive color model like the one used in LDP. Segmentation is solved efficiently by ternary graph cut. Both algorithms are evaluated with respect to ground truth data and found to have similar performance, substantially better than either stereo or color/contrast alone. However, their characteristics with respect to computational efficiency are rather different. The algorithms are demonstrated in the application of background substitution and shown to give good quality composite video output.     

Runtime analysis of the (mu+1) EA on simple Pseudo-Boolean functions

Although Evolutionary Algorithms (EAs) have been successfully applied to optimization in discrete search spaces, theoretical developments remain weak, in particular for population-based EAs. This paper presents a first rigorous analysis of the (mu+1) EA on pseudo-Boolean functions. Using three well-known example functions from the analysis of the (1+1) EA, we derive bounds on the expected runtime and success probability. For two of these functions, upper and lower bounds on the expected runtime are tight, and on all three functions, the (mu+1) EA is never more efficient than the (1+1) EA. Moreover, all lower bounds grow with mu. On a more complicated function, however, a small increase of mu probably decreases the expected runtime drastically.This paper develops a new proof technique that bounds the runtime of the (mu+1) EA. It investigates the stochastic process for creating family trees of individuals; the depth of these trees is bounded. Thereby, the progress of the population towards the optimum is captured. This new technique is general enough to be applied to other population-based EAs.     

Situative Managementunterstützungssysteme

Digital natives increasingly populate organizations?? management. These new-generation managers more naturally accept management support systems (MSS), but also have higher expectations about how they should accommodate their individual user preferences. As a result, managers question MSS that have been developed without configuration mechanisms to accommodate their working style, relevant MSS use cases, and different MSS access modes. The objective of this article is to reveal managers?? different MSS use situations and propose levers for tailoring (conceptual) MSS design to them. Use situations generalize classes of similar user-group preferences. We first apply findings from a literature review to cluster managers?? user-group preferences into 36 MSS use situations. Second, we propose that the selection of end-user devices can serve as a main lever for MSS configuration. Third, we complete the configuration with a MSS user-interface design. Finally, we demonstrate utility of our configuration model by presenting and evaluating a prototype.     

Electronic window dressing: impression management with Websites

Businesses have embraced the Internet to reap economic advantages through the use of Websites. Most Website design guidelines fail to address issues of branding and identity formation, focusing instead on concerns adapted from previous technologies. However, many firms are not getting their desired results from the Website investments they have made following design guidelines reflecting graphic layout and system usability issues. We suggest that Websites should be considered ‘electronic storefronts’ or public work areas providing frames of symbolic representations that create impressions of their sponsoring firms. Our exploratory study shows that Websites influence potential customers' impressions of firms' legitimacy, innovation and caring, and that these impressions vary significantly across firms and industries. Website visitors encounter symbols that are compared to mental models stored in memory and used to form impressions of the site and to draw inferences about the firm. These inferences have previously been found to influence purchasing behavior. Designers should be cognizant of these aspects of e-Business and executives should recognize the power of Web-based impression management. Identity management must take center stage in creating a Web presence.