Cryptanalysis of the new TTS scheme in CHES 2004

We combine the method of searching for an invariant subspace of the unbalanced Oil and Vinegar signature scheme and the Minrank method to defeat the new TTS signature scheme, which was suggested for low-cost smart card applications at CHES 2004. We show that the attack complexity is less than 2⁵⁰.     

A visual digital library approach for time-oriented scientific primary data

Digital Library support for textual and certain types of non-textual documents has significantly advanced over the last years. While Digital Library support implies many aspects along the whole library workflow model, interactive and visual retrieval allowing effective query formulation and result presentation are important functions. Recently, new kinds of non-textual documents which merit Digital Library support, but yet cannot be fully accommodated by existing Digital Library technology, have come into focus. Scientific data, as produced for example, by scientific experimentation, simulation or observation, is such a document type. In this article we report on a concept and first implementation of Digital Library functionality for supporting visual retrieval and exploration in a specific important class of scientific primary data, namely, time-oriented research data. The approach is developed in an interdisciplinary effort by experts from the library, natural sciences, and visual analytics communities. In addition to presenting the concept and to discussing relevant challenges, we present results from a first implementation of our approach as applied on a real-world scientific primary data set. We also report from initial user feedback obtained during discussions with domain experts from the earth observation sciences, indicating the usefulness of our approach.     

Problem size scaling in the presence of parallel overhead

In this paper we study the performance of applications on multiprocessor systems. In particular we investigate the effect of synchronization and parallelization overhead where the fact that part of the application may be inherently sequential is taken into account. By relating our assumptions to an earlier work by Flatt and Kennedy we establish that the overhead function can be characterized using the concept of convex functions. In order to observe a satisfactory payoff for increased processing power it is essential to increase the problem size accordingly. We discuss linear and nonlinear scaling schemes and compare the corresponding asymptotic performance behaviour. Throughout this investigation we profit from the well developed mathematical apparatus of convex functions.     

Infinite horizon cancer treatment model with isoperimetrical constraint: existence of optimal solutions and numerical analysis

In this paper, a class of infinite horizon optimal control problems with a mixed control-state isoperimetrical constraint, also interpreted as a budget constraint, is considered. The underlying dynamics is assumed to be affine-linear in control. The crucial idea which is followed in this paper is the choice of a weighted Sobolev space as the state space. For this class of problems, we establish an existence result and apply it to a bilinear model of optimal cancer treatment with an isoperimetrical constraint including the overall amount of drugs used during the whole therapy horizon. A numerical analysis of this model is provided by means of open source software package OCMat, which implements a continuation method for solving discounted infinite horizon optimal control problems.     

Magnetic resonances of helical textures in 3He-A

The NMR frequencies of the helical texture in ³He-A in the presence of a magnetic field parallel to the superflow are reexamined in the entire stability region. The effects of the anisotropic contribution to the spin susceptibility are explicitly included and are shown to leave previous results qualitatively unchanged. On the other hand, we find that the anisotropic contribution gives rise to quantitative corrections of maximally 20% at T/T _c = 0.95, while its contribution in the immediate vicinity of T _c is negligibly small.Work supported in part by the National Science Foundation under grant number DMR 76-21032.Guggenheim Fellow 1979–1980.     

Management of complex data flows in the ASDEX Upgrade plasma control system

Establishing adequate technical and physical boundary conditions for a sustained nuclear fusion reaction is a challenging task. Phased feedback control and monitoring for heating, fuelling and magnetic shaping is mandatory, especially for fusion devices aiming at high performance plasmas. Technical and physical interrelations require close collaboration of many components in sequential as well as in parallel processing flows. Moreover, handling of asynchronous, off-normal events has become a key element of modern plasma performance optimisation and machine protection recipes.The manifoldness of plasma states and events, the variety of plant system operation states and the diversity in diagnostic data sampling rates can hardly be mastered with a rigid control scheme. Rather, an adaptive system topology in combination with sophisticated synchronisation and process scheduling mechanisms is suited for such an environment. Moreover, the system is subject to real-time control constraints: response times must be deterministic and adequately short.Therefore, the experimental tokamak device ASDEX Upgrade employs a discharge control system DCS, whose core has been designed to meet these requirements. In the paper we will compare the scheduling schemes for the parallelised realisation of a control workflow and show the advantage of a data-driven workflow over a managed workflow. The data-driven workflow as used in DCS is based on signals connecting process outputs and inputs. These are implemented as real-time streams of data samples. Consequently, real-time signal management forms the foundation of DCS. The paper explains the principal features such as tagged samples, signal groups, algorithmic blocks and processes as well as scheduling schemes which allow DCS control applications to be defined as self-contained modular building blocks glued together by a software framework.By virtue of this sound foundation, DCS is a mature but still evolving system for reliable, distributed control of an entire tokamak device coordinating and monitoring 20 diagnostic systems, 14 magnetic power supplies, 5 heating systems with a total power of more than 25 MW, 8 gas fuelling channels, a pellet injector and a killer gas gun.     

Hierarchical Rasterization of Curved Primitives for Vector Graphics Rendering on the GPU

In this paper, we introduce the CPatch, a curved primitive that can be used to construct arbitrary vector graphics. A CPatch is a generalization of a 2D polygon: Any number of curves up to a cubic degree bound a primitive. We show that a CPatch can be rasterized efficiently in a hierarchical manner on the GPU, locally discarding irrelevant portions of the curves. Our rasterizer is fast and scalable, works on all patches in parallel, and does not require any approximations. We show a parallel implementation of our rasterizer, which naturally supports all kinds of color spaces, blending and super‐sampling. Additionally, we show how vector graphics input can efficiently be converted to a CPatch representation, solving challenges like patch self intersections and false inside‐outside classification. Results indicate that our approach is faster than the state‐of‐the‐art, more flexible and could potentially be implemented in hardware.     

Über die Altersbestimmung von Eichenholz in Norddeutschland mit Hilfe der Dendrochronologie

Zusammenfassung Die M?glichkeiten einer Alterbestimmung von Eichenholz in Norddeutschland mit Hilfe der dendrochronologischen Methode wurden an einigen Beispielen aufgezeigt und er?rtert. Daraus kann man folgern, da? eine dem Süden entsprechende Standardkurve für Norddeutschland nicht aufgebaut werden kann. Eine erfolgreiche Absolutdatierung ist meist nur mit Hilfe von gesicherten, streng standort-bezogenen Kurven durchführbar. Aber auch Relativdatierungen geben h?ufig genügend Aufschlu?. Die Altersbestimmungen der Klosteranlage Wienhausen/Celle bzw. der ausgegrabenen Siedlung Haithabu mit Hilfe norddeutscher Standortchronologien zeigen den Wert und die M?glichkeit der dendrochronologischen Datierung in Norddeutschland. Mitunter k?nnen Absolutdatierungen auch mit der süddeutschen Standardkurve erfolgen, wenn n?mlich Holz aus südlicheren Gegenden in Norddeutschland verbaut wurde. Auf diese Weise lie? sich die Bauzeit der mittelalterlichen Bremer Kogge ermitteln.

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On the dating of oakwood in Northern Germany by the dendrochronological method

Summary The possibilities of dating oakwood by the dendrochronological method have been demonstrated and discussed in relation to specimens from various sites in Northern Germany. It has been shown that a standard growth-ring series, such as that corresponding to the whole of Southern Germany, cannot be established for Northern Germany. In most cases a successful dating can be realized only by means of a definite growth-ring series related to a narrow site. However, the correlation between older and younger materials often procides sufficient information. The determination of the age of the monastry in Wienhausen/Celle and of the excavated settlement Haithabu illustrates the value and the possibilities of dendrochronology in Northern Germany. Absolute dating occasionally may be possible with the standard growth-ring series of Southern Germany; namely where wood from southern regions has been used in Northern Germany. In this way the date of construction of the Bremer Kogge was determined.

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Herrn Prof. Dr. Hans Mayer-Wegelin zur Vollendung des 70. Lebensjahres gewidmet.     

The planning of Berlin's city and historic centre

Since the fall of the Wall, there has been heavy international investment in building in East Berlin. On the whole, efforts have remained marginal. Only the western part of East Berlin with its baroque grid has been developed. The central and eastern parts remain as they were. The planning for City East follows four main criteria: to redefine the historic core by structural means without resort to architectural pastiche; to redesign the major roads which occupy much of the historic centre; to restructure the modernism of the GDR capital without demolishing the (mainly prefabricated) buildings; to form an idea of the third town which would be developed by merging existing features with our new plan.