Musiktauschbörsen

Im Informatik-Spektrum 1/2004 haben Steinmetz und Wehrle Peer-to-Peer-Systeme vorgestellt. Ein wichtiges Anwendungsfeld derartiger Systeme sind Tauschbörsen für Musik. Die Musikindustrie erleidet seit einigen Jahren massive Umsatzrückgänge und führt dies insbesondere auf die Tauschbörsen zurück. Nachfolgend werden konventionelle und innovative Ansätze zur Lösung dieses Problems skizziert.     

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Eignet sich Cloud-Computing als Instrument zur Förderung ökologischer Ziele?

Cloud computing has been introduced as a promising information technology (IT) that embodies not only economic advantages in terms of increased efficiency but also ecological gains through saving energy. The latter has become particularly important in view of the rising energy costs of IT. The present study analyzes whether necessary preconditions for accepting cloud computing as a new infrastructure, such as awareness and perceived net value, exist on the part of the users. The analysis is based on a combined research framework of the theory of reasoned action (TRA) and the technology acceptance model (TAM) in a cloud computing setting. Two consumer surveys, the one to elicit beliefs and the second to gain insight into the ranking of the variables, are employed. This study uses structural equation modeling (SEM) to evaluate the hypotheses. The results indicate support for the proposed research framework. Surprisingly however, the ecological factor does not play a role in forming cloud computing intentions, regardless of prior knowledge or experience. Empirical evidence of this study suggests increasing efforts for informing actual and potential users, particularly in respect to possible ecological advantages through applying the new IT infrastructure.     

Regular Gröbner Bases

In this paper we introduce the concept of bi-automaton algebras, generalizing the automaton algebras previously defined by Ufnarovski. A bi-automaton algebra is a quotient of the free algebra, defined by a binomial ideal admitting a Gröbner basis which can be encoded as a regular set; we call such a Gröbner basis regular. We give several examples of bi-automaton algebras, and show how automata connected to regular Gröbner bases can be used to perform reduction.     

Numerische Lösung von Anfangswertaufgaben gewöhnlicher Differentialgleichungen n-ter Ordnung mittels Einschrittverfahren

In the present paper a new exponentially fitted one-step method is given for the numerical treatment of the initial value problemy ⁽ⁿ⁾=f(x, y, y′, ..., y ^(n?1)),y ^(j) (x ₀)=y ₀ ^(j) j=0, 1, ...n?1. The method is given by a local linearisation off(x, y, y′, ..., y ^(n?1)). Using new functions the solution of a special linear differential equation of then-th order with constant coefficients is transformed in such a way so that it no longer contains numerical singularities. The efficiency of the method is demonstrated by several numerical stiff-examples.     

Multiplicative Bases,Gröbner Bases,and Right Gröbner Bases

In this paper, we study conditions on algebras with multiplicative bases so that there is a Gröbner basis theory. We introduce right Gröbner bases for a class of modules. We give an elimination theory and intersection theory for right submodules of projective modules in path algebras. Solutions to homogeneous systems of linear equations with coefficients in a quotient of a path algebra are studied via right Gröbner basis theory.     

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Datenschutzgerechte Smartphone-Nutzung erm?glichen! Düsseldorfer Kreis — Beschluss vom 04./05. Mai 2011     

Counting and Gröbner Bases

We show how the complexity of counting relates to the well known phenomenon that computing Gröbner bases under a lexicographic order is generally harder than total degree orders. We give simple examples of polynomials for which it is very easy to compute their Gröbner basis using a total degree order but for which exponential time is required for a lexicographic order. It follows that conversion algorithms do not help in such cases.     

Möbius–deBruijn: The product of Möbius cube and deBruijn digraph

Möbius cube and deBruijn digraph have been proved to be two of the most popular interconnection architectures, due to their desirable properties. Some of the attractive properties of one, however, are not found in the other. The Möbius–deBruijn architecture, proposed in this paper, is the product of Möbius cube and deBruijn digraph, which is a combination of the two architectures. It employs the Möbius cube as a unit cluster and connects many such clusters by means of given number of parallel deBruijn digraphs. Consequently, the Möbius–deBruijn provides some of the desirable properties of both the architectures, such as the flexibility in terms of embedding of parallel algorithms, the high level of fault-tolerant, and the efficient inter-cluster communication. The proposed architecture also possesses the logarithmic diameter, the optimal connectivity, and the simple routing mechanism amenable to network faults. The methodology to construct the Möbius–deBruijn can apply to the product of deBruijn digraph and other hypercube-like networks, and also applies to the product of Kautz digraph and hypercube-like networks.     

PACS in Töölö hospital

A 3-year PACS project was started in 1997 and completed in 1999 with filmless radiology and surgery. An efficient network for transferring images provides the infrastructure for integration of different distributed imaging systems and enables efficient handling of all patient-related information on one display station. Because of the need for high-speed communications and the massive amount of image data transferred in radiology, ATM (25, 155 Mbit/s) was chosen to be the main technology used. Both hardware and software redundancy of the system have been carefully planned. The size of the Dicom image library utilizing MO discs is currently 1.2 TB with 300 GB RAID capacity. For the increasing amount of teleradiologic consultations, a special Dicom gateway is planned. It allows a centralized and resilient handling and routing of received images around the hospital. Hospital-wide PACS has already improved the speed and quality of patient care by providing instant access to diagnostic information at multiple locations simultaneously. The benefits of PACS are considered from the viewpoint of the entire hospital: PACS offers a method for efficiently transporting patient-related images and reports to the referring physicians.     

Reduced Gröbner Bases Under Composition

In this paper we contribute with one main result to the interesting problem initiated by Hong (1998, J. Symb. Comput.25, 643–663) on the behaviour of Gröbner bases under composition of polynomials. Polynomial composition is the operation of replacing the variables of a polynomial with other polynomials. The main question of this paper is:When does composition commute with reduced Gröbner bases computation under the same term ordering?We give a complete answer for this question: let Θ be a polynomial map, then for every reduced Gröbner basisG,G ○ Θ is a reduced Gröbner basis if and only if the composition by Θ is compatible with the term ordering and Θ is a list of permuted univariate and monic polynomials. Besides, we also include other minor results concerned with this problem; in particular, we provide a sufficient condition to determine when composition commutes with reduced Gröbner bases computation (possibly) under different term ordering.     

Spectral grouping using the Nyström method

Spectral graph theoretic methods have recently shown great promise for the problem of image segmentation. However, due to the computational demands of these approaches, applications to large problems such as spatiotemporal data and high resolution imagery have been slow to appear. The contribution of this paper is a method that substantially reduces the computational requirements of grouping algorithms based on spectral partitioning making it feasible to apply them to very large grouping problems. Our approach is based on a technique for the numerical solution of eigenfunction problems known as the Nystrom method. This method allows one to extrapolate the complete grouping solution using only a small number of samples. In doing so, we leverage the fact that there are far fewer coherent groups in a scene than pixels.     

Semi-discrete method for generalized Schrödinger-type equations

In this article, a semi-discrete method for solving a class of generalized Schrödinger-type equations is presented. By discretization of the spatial variables, the initial-boundary value problem for partial differential equations can be reduced to the initial value problem for ordinary differential systems. And it is very convenient for numerical analyses and computations.