Beeping a maximal independent set

We consider the problem of computing a maximal independent set (MIS) in an extremely harsh broadcast model that relies only on carrier sensing. The model consists of an anonymous broadcast network in which nodes have no knowledge about the topology of the network or even an upper bound on its size. Furthermore, it is assumed that an adversary chooses at which time slot each node wakes up. At each time slot a node can either beep, that is, emit a signal, or be silent. At a particular time slot, beeping nodes receive no feedback, while silent nodes can only differentiate between none of its neighbors beeping, or at least one of its neighbors beeping. We start by proving a lower bound that shows that in this model, it is not possible to locally converge to an MIS in sub-polynomial time. We then study four different relaxations of the model which allow us to circumvent the lower bound and find an MIS in polylogarithmic time. First, we show that if a polynomial upper bound on the network size is known, it is possible to find an MIS in $\mathcal O (\log ^3 n)$ time. Second, if we assume sleeping nodes are awoken by neighboring beeps, then we can also find an MIS in $\mathcal O (\log ^3 n)$ time. Third, if in addition to this wakeup assumption we allow sender-side collision detection, that is, beeping nodes can distinguish whether at least one neighboring node is beeping concurrently or not, we can find an MIS in $\mathcal O (\log ^2 n)$ time. Finally, if instead we endow nodes with synchronous clocks, it is also possible to find an MIS in $\mathcal O (\log ^2 n)$ time.     

DEVELOPMENT OF AN EXPERT SYSTEM FOR CHRONIC OBSTRUCTIVE LUNG DISEASE

The long-term health care of patients suffering from chronic obstructive lung disease or high-risk persons entails time-consuming medical measures taken on the occasion of frequent return visits. It is tedious for the physician to execute this health-care program in a conventional manner. An expert system could effectively assist him in performing this challenging task. This article describes the technical concept of an expert system for this purpose based on the medical foundations outlined in a companion article (Jahn, 1990). The known expert systems for pulmonary diseases cannot sufficiently support the physician involved in this type of health care, since they are, among other things, limited to a “snapshot” approach to patient assessment. In contrast, the expert system now being developed handles temporal changes, gives advice on scheduling appropriate time intervals for return visits, and compares the actual response to therapy with the expected response.     

Convergence of an implicit–explicit midpoint scheme for computational micromagnetics

Based on lowest-order finite elements in space, we consider the numerical integration of the Landau–Lifschitz–Gilbert equation (LLG). The dynamics of LLG is driven by the so-called effective field which usually consists of the exchange field, the external field, and lower-order contributions such as the stray field. The latter requires the solution of an additional partial differential equation in full space. Following Bartels and Prohl (2006), we employ the implicit midpoint rule to treat the exchange field. However, in order to treat the lower-order terms effectively, we combine the midpoint rule with an explicit Adams–Bashforth scheme. The resulting integrator is formally of second-order in time, and we prove unconditional convergence towards a weak solution of LLG. Numerical experiments underpin the theoretical findings.     

Magnetic films for electromagnetic actuation in MEMS switches

Microsystem Technologies - This paper investigates the fabrication of magnetic films via electroplating to be applied into electromagnetic actuated micro electro-mechanical systems (MEMS) switches....     

CINCO: a simplicity-driven approach to full generation of domain-specific graphical modeling tools

International Journal on Software Tools for Technology Transfer - Even with the help of powerful metamodeling frameworks, the development of domain-specific graphical modeling tools is usually a...     

Assuring property conformance of code generators via model checking

Automatic code generation is an essential cornerstone of today’s model-driven approaches to software engineering. Thus a key requirement for the success of this technique is the reliability and correctness of code generators. This article describes how we employ standard model checking-based verification to check that code generator models developed within our code generation framework Genesys conform to (temporal) properties. Genesys is a graphical framework for the high-level construction of code generators on the basis of an extensible library of well-defined building blocks along the lines of the Extreme Model-Driven Development paradigm. We will illustrate our verification approach by examining complex constraints for code generators, which even span entire model hierarchies. We also show how this leads to a knowledge base of rules for code generators, which we constantly extend by e.g. combining constraints to bigger constraints, or by deriving common patterns from structurally similar constraints. In our experience, the development of code generators with Genesys boils down to re-instantiating patterns or slightly modifying the graphical process model, activities which are strongly supported by verification facilities presented in this article.     

Effect of initial microstructure on high velocity and hypervelocity impact cratering and crater-related microstructures in thick copper targets: Part II Stainless steel projectiles

Three different, thick copper targets (an as-received, 98 m grain size containing 1010 dislocations/cm2 (Vickers hardness of 0.89 GPa); an annealed, 124 m grain size containing 109 dislocations/cm2 (Vicker's hardness of 0.69 GPa); and a 763 m grain size containing 109 dislocations/cm2 (Vickers hardness of 0.67 GPa) were impacted with 3.18 mm diameter ferritic stainless steel projectiles at nominal velocities of 0.7, 2 and 5 km s-1. Like companion experiments utilizing soda-lime glass projectiles (Part I), absolute grain size of the target was observed to be less important than the dislocation density in the cratering process. At low impact velocity, depth/diameter ratios were observed to increase dramatically in contrast to less dense soda-lime glass impactors, and the impactor behaviours were also very different. The ferritic stainless steel impactors spalled into small fragments at or above 2 km s-1 impact velocity and a significant fraction of these fragments remained in the craters. No significant melt phenomena were observed either in connection with projectile fragmentation or in the crater-related, residual microstructures. Dynamic recrystallization, dislocation cell structures and microbands were significant microstructural features in the targets. They extended from the crater walls and contributed to hardness profiles within the cratered targets. These hardness profiles and actual hardness zones generally increased in extent from the crater wall with both impact velocity and projectile density.     

Hamiltonian discretization of boundary control systems

A fundamental problem in the simulation and control of complex physical systems containing distributed-parameter components concerns finite-dimensional approximation. Numerical methods for partial differential equations (PDEs) usually assume the boundary conditions to be given, while more often than not the interaction of the distributed-parameter components with the other components takes place precisely via the boundary. On the other hand, finite-dimensional approximation methods for infinite-dimensional input-output systems (e.g., in semi-group format) are not easily relatable to numerical techniques for solving PDEs, and are mainly confined to linear PDEs. In this paper we take a new view on this problem by proposing a method for spatial discretization of boundary control systems based on a particular type of mixed finite elements, resulting in a finite-dimensional input-output system. The approach is based on formulating the distributed-parameter component as an infinite-dimensional port-Hamiltonian system, and exploiting the geometric structure of this representation for the choice of appropriate mixed finite elements. The spatially discretized system is again a port-Hamiltonian system, which can be treated as an approximating lumped-parameter physical system of the same type. In the current paper this program is carried out for the case of an ideal transmission line described by the telegrapher's equations, and for the two-dimensional wave equation.