Wolfram Schiffmann

FernUniversität in Hagen · Computer Science

Most methods that compute trajectories for un- or low-powered flight operate under simplifying assumptions such as constant curve radii and wind conditions. Likewise, changes of air density with altitude that lead to significant differences between equivalent airspeed (EAS) und true airspeed (TAS) are often not considered. Some approaches are based...

The fatality rate for flights involving light, fixed-wing aircraft is relatively high, and most accidents occur after a loss of thrust in the lower airspace. In these emergency situations, with a lack of potential energy, an assistance or automated system could lead the aircraft safely to an appropriate landing field. Some solutions for path planni...

The interest in Deep Neural Networks has dramatically increased, especially e. g. in Computer Vision or Neural Language Processing tasks. Due to the heavy influence of the Neural Networks architecture on its predictive accuracy, Neural Architecture Search has gained much attention in recent years. Neural Architecture Search typically comes along wi...

The full loss of thrust of an aircraft requires fast and reliable decisions of the pilot. If no published landing field is within reach, an emergency landing field must be selected. The choice of a suitable emergency landing field denotes a crucial task to avoid unnecessary damage of the aircraft, risk for the civil population as well as the crew a...

The interest in developing smart cities has increased dramatically in recent years. In this context an intelligent transportation system depicts a major topic. The forecast of traffic flow is indispensable for an efficient intelligent transportation system. The traffic flow forecast is a difficult task, due to its stochastic and non linear nature....

Ein Motorausfall während des Flugs erfordert einen Notlandeanflug auf ein geeignetes Landefeld. Während des Anflugs auf das Notlandefeld wird die Flughöhe abgebaut und soll idealerweise am Landepunkt Null betragen. Aufgrund von Unsicherheiten (bspw. Windgeschwindigkeit und -Richtung) bei der Kalkulation des Anflugs, wird häufig ein überhöhter Anflu...

If the pilot of an aircraft is forced to perform an emergency landing, quick and reliable decisions regarding the flight path are necessary. Besides, it is not guaranteed that a published landing field is located within reach. In such a situation the selection of an appropriate emergency landing field denotes a crucial task for the pilot. The choic...

A neural network’s topology greatly influences its generalization ability. Many approaches to topology optimization employ heuristics, for example genetic algorithms, oftentimes consuming immense computational resources. In this contribution, we present a genetic algorithm for network topology optimization which can be deployed effectively in low-r...

A total loss of thrust poses a major hazard to passengers and aircrafts. In such situations, the pilot is forced to perform an emergency landing by fast and intuitive decisions. During the manoeuvre, the potential energy of the aircrafts altitude is converted into the kinetic energy to move a certain distance over ground. This may enable the aircra...

The demand for energy is rising despite the fact that more and more efficient electronics are available. One cause for this is the increasing need for computing power. More and more data centers providing computing power, e.g. for ubiquitous computing. In former years, with decreasing transistor sizes, energy demand could be reduced while performan...

Rising energy costs and negative environmental impact resulting from the generation of electricity, particularly when relying on fossil fuels, increase the need for energy-efficient computing. In addition to the optimization of hardware devices, the use of sophisticated software solutions for reducing energy consumption is an important area of curr...

The energy consumption of server farms is steadily increasing. This is mainly due to an increasing number of servers which are often underutilized most of the time. In this paper we discuss various strategies to improve the energy e ciency of a datacenter measured by the average number of operations executed per Joule. We assume a collection of het...

These years energy consumption has become the main constraint for the further improvement of computing ability of data centers. In this work, the energy efficient resource management strategies for web servers (one typical class of data centers) are discussed. We firstly introduce the daily pattern of requests sent to web servers which indicates th...

Modern server farms consume large amounts of energy by computing devices and cooling equipment. During the course of the day the load of these servers usually varies significantly. Especially, in times when they are under-utilized and work in an power-inefficient range, load distribution should be optimized to minimize total power consumption. This...

High performance servers of heterogeneous computing environments, as can be found in data centers for cloud computing, consume immense amounts of energy even though they are usually underutilized. In times when not all computing capabilities are needed the task to be solved is how to distribute the computational load in a power-efficient manner. Th...

High performance servers of data centers for cloud computing consume immense amounts of energy even though they are usually underutilized because they provide huge computing capabilities. In times when not all of those computing capabilities are needed the task to be solved is how to distribute the load in a power-efficient manner. The research que...

ArchC is an architecture description language that provides instruction set level simulation and binary tool chain generation. It is based on SystemC and can communicate with other SystemC components using transaction level modeling (TLM). In this article we present an upgrade of ArchC that allows TLM-2.0 usage and makes it available in timed simul...

Gebraucht man das Wort Technik (η τεχνη) in seiner ursprünglichen Bedeutung als Kunst oder Kunstfertigkeit, so sind die Computer unserer Tage in ihr er Anwendung und Konstruktion wahre Kunstwerke der Elektrotechnik. Es war ein weiter Weg von der ersten Beobachtung (Griechenland im 6. Jh. v. Chr) des eigenart igen Verhaltens von Bernstein, das zum B...

In this paper, we propose a new framework for a resource broker that aims to find a good compromise between users' objectives and resource providers while executing workflows in Grid environments. Thus, resource brokers need to be aware of the interaction between local batch schedulers on multiple sites. A primary challenge for resource brokers is...

In diesem Kapitel werden wir in den Aufbau und die Funktion eines Personal Computers (PCs) einführen. Der Kern eines PCs besteht aus der Hauptplatine, auch Motherboard genannt, auf dem der Prozessor, Speicher, Ein–/Ausgabebausteine und –schnittstellen untergebracht sind. Wir beschäftigen uns ausführlich mit der Hauptplatine und den wichtigsten Komp...

The shifting bottleneck heuristic (SBH) for complex job shops decomposes the overall scheduling problem into a series of scheduling problems related to machine groups. These smaller, more tractable, scheduling problems are called subproblems. The heuristic is based on a disjunctive graph that is used to model the relationship between the subproblem...

Tuning the performance of grid applications is cumbersome because it is very difficult to decide which code to look at. In our previous work we proposed a tool to recommend tasks in a task graph that look most promising for improvement. In the present work we first show how to extract task graphs from real grid applications with the help of SCALASC...

Grid jobs often consist of a large number of tasks. If the performance of a statically scheduled grid job is unsat- isfactory, one must decide which code of which task should be improved. We propose a novel method to guide grid users as to which tasks of their grid job they should accelerate in order to reduce the makespan of the complete job. The...

Die modernen Informationstechnologien haben in allen Lebensbereichen starke Veränderungen bewirkt. Besonders stark beeinflusst sind die Wissenschaften, die auch eine treibende Kraft dieser Entwicklungen sind und immer größere Anforderungen an Rechner, Speicher und IT-Werkzeuge stellen. In neuen Experimenten der Teilchenphysik werden kaum bewältigba...

Modern science requires a close collaboration of scientists who are possibly scattered all over the world. The ongoing spreading of the internet and the emergence of grid and cloud techniques in recent years have caused intensified efforts in the development of infrastructures that are suitable to enhance a world-wide collaboration of researchers....

While fault-tolerance is desirable for grid applications because of the distributed and dynamic nature of grid resources, it has seldom been considered in static scheduling. We present a fault-tolerant static scheduler for grid applications that uses task duplication and combines the advantages of static scheduling, namely no overhead for the fault...

In the past several years, many scientific applications from various domains have taken advantage of e-science infrastructures that share storage or computational resources such as supercomputers, clusters or PC server farms across multiple organizations. Especially within e-science infrastructures driven by high-performance computing (HPC) such as...

In engineering applications often real-valued performance functions must be optimized. If the performance function is discontinuous, there exist no derivations with respect to the parameters that should be optimized. Thus, we can only use undirected search methods. In contrast to simple trial-and-error approaches, evolutionary strategies can extrac...

Today's large-scale scientific research often relies on the collaborative use of a Grid or c-Science infrastructure (e.g. DEISA, EGEE, TeraGrid, OSG) with computational, storage, or other types of physical resources. One of the goals of these emerging infrastructures is to support the work of scientists with advanced problem-solving tools. Many e-S...

A Task Graph (TG) is a model of a parallel program that consists of many subtasks that can be executed simultaneously on differ- ent processing elements. Subtasks exchange data via an interconnection network. The dependencies between subtasks are described by means of a Directed Acyclic Graph. Unfortunately, due to their characteris- tics, scheduli...

We present a lab-in-a-box, a metal case needing only power supply and network access, to provide a complete infrastructure to establish a microprocessor laboratory for embedded applications in computer engineering. The labo- ratory is used in distance teaching and thus all instruments and devices are controlled and observed via the net. Our fo- cus...

By means of a comprehensive test bench of 36000 test cases we evaluated the efficiency of functional parallel programs. For all the test cases schedules have been computed by various well known heuristics. We assumed a homogeneous target system (e.g. a compute cluster of equally powerful interconnected nodes) that can be part of a grid computing en...

This paper is motivated by the poor efficiency of static DAG scheduling algorithms applied on large-sized target systems. We analyze the efficiency of different static scheduling heuristics with respect to a large test bench that comprises different graph categories. The poor efficiency can be essentially explained by the lack of sufficient paralle...

In this paper we introduce a new algorithm for computing near optimal schedules for task graph scheduling problems. In contrast to conventional approaches for solving those scheduling problems, our algorithm is based on the same principles that ants use to find shortest paths between their nest and food sources. Like their natural counterparts, art...

This paper describes an algorithm, which calculates the approximate head pose of partially occluded faces without training or manual initialization. The presented approach works on low-resolution Webcam images. The algorithm is based on the observation that for small depth rotations of a head the rotation angles can be approximated linearly. It use...

We report about a performance evaluation of nature inspired stochastic vs. conventional deterministic scheduling algorithms. By means of a comprehensive test bench, that comprises task graphs with diverse properties, we determined the absolute performance of those algorithms with respect to the optimal solutions. Surprisingly, the nature inspired s...

We present a microprocessor lab that is accessible remotely, i.e. students can control the hardware in the lab from their computer at home. At the same time the lab also provides the features of a virtual lab, i.e. students conduct experiments on simulators. Both modes of the lab are run under a common user interface. This lab is suited especially...

Zusammenfassung Wir stellen ein Web-basiertes System zur Abwicklung des Übungsbetriebs im Grundstudium Technische Informatik an der FernUniversität vor. Das System umfasst drei Komponenten: ein Entwurfswerkzeug zur leichten Eingabe von Digitalschaltungen und der Möglichkeit der Selbstkontrolle ihrer Korrektheit, ein Web-gestütztes System zur Einrei...

Computational problems can usually be divided into a number of (sub)tasks. The data dependencies between these tasks can be described by a so called task graph. Since the task graph scheduling problem is known to be NP-hard, researchers devised an innumerable number of heuristic algorithms to solve this problem best. Up to now, these heuristics wer...

Die mehrbändige Technische Informatik bietet einen verständlichen Einstieg in dieses wichtige Teilgebiet der Informatik. Leser mit unterschiedlichen Vorkenntnissen gewinnen schrittweise einen Überblick über die in Studium und Beruf benötigten elektrotechnischen und elektronischen Grundlagen. Auf dieser Basis werden Komponenten und Strukturen von he...

In order to harness the power of parallel computing we must firstly find appropriate algorithms that consist of a collection of (sub)tasks and secondly schedule these tasks to processing elements that communicate data between each other by means of a network. In this paper, we consider task graphs that take into account both, computation and commun...

Der Fachbereich Informatik der FernUniversität/GH Hagen betreut zur Zeit ca. 7500 Studierende, die durch schriftliche Kurse und Präsenzkurse erreicht werden. Daneben ergänzen audio-visuelle Medien und die virtuelle Universität das Lehrangebot. Es gibt 8 Lehrstühle für praktische Informatik, 2 Lehrstühle für theoretische Informatik und 2 Lehrstühle...

This paper demonstrates how the backpropagation algorithm (BP) and its variants can be accelerated significantly while the quality of the trained nets will increase. Two modifications were proposed: First, instead of the usual quadratic error we use the cross entropy as an error function and second, we normalize the input patterns. The first modifi...

: The ZUSE Parallel PentiumPro Cluster (PPC) is a low cost but high performance parallel machine that consists of 32 LINUX controlled computing nodes with 200 MHz PentiumPro processors. The computing nodes are connected by the FastEthernet communication network with 100 MBit/s links. The outline of the paper is as follows. First, we explain when an...

While in the past years enhanced training algorithms for multilayer networks were devised, the construction of application specific network topologies, by comparison, remains something like a black art. Construction rules for determining an application specific network topology, e.g. the number of hidden units, the number of layers and the intercon...

While in the past years enhanced training algorithms for multilayer networks were devised, the construction of application specific network topologies, by comparison, remains something like a black art. Construction rules for determining an application specific network topology, e.g. the number of hidden units, the number of layers and the intercon...

The application of programmable devices to implement neural networks requires efficient training algorithms that cope with limited precision of the network components. These components comprise the weights, the sigmoid transfer function of the processing units and the weight-updates during the training process. In this paper we develop two integer...

this paper we present various approaches for automatic topology--optimization of backpropagation networks. First of all, we review the basics of genetic algorithms which are our essential tool for a topology search. Then we give a survey of backprop and the topological properties of feedforward networks. We report on pioneer work in the filed of to...

: The ZUSE Parallel PentiumPro Cluster (PPC) is a low cost but high performance parallel machine that consists of 32 LINUX controlled computing nodes with 200 MHz PentiumPro processors. The computing nodes are connected by the FastEthernet communication network with 100 MBit/s links. The outline of the paper is as follows. First, we explain when an...

pirical Studies on the Speed of Convergence of Neural Network Training Using Genetic Algorithms, Proc. of the National Conf. of th American Association of Artificial Intelligence (AAAI), pp. 789--795 Heistermann J., 1990 : Learning in Neural Nets by Genetic Algorithms, Proc. of Parallel Processing in Neural Systems and Computers (ICNC), Eckmiller R...

Backpropagation is one of the most famous training algorithms for multilayer perceptrons. Unfortunately it can be very slow for practical applications. Over the last years many improvement strategies have been developed to speed up backpropagation. It's very difficult to compare these different techniques, because most of them have been tested on v...

In this paper we present a new approach for automatic topology optimization of backpropagation networks. It is based on a genetic algorithm. In contrast to other approaches it allows that two networks with different number of units can be crossed to a new valid "child" network. We applied this algorithm to a medical classification task, which is ex...

Artificial neural networks --- especially those using the error backpropagation algorithm --- are capable of learning to control an unknown plant by autonomously extracting the necessary information from the plant. Following the approach of Psaltis et al. and Saerens et al. a control architecture based on error backpropagation has been developed an...

this report also have been published on ESANN '93 [Schiffmann et al., 1993]. The dataset used in this comparision is available by anonymous ftp (FTP server: ics.uci.edu, files: pub/machine-learningdatabases /thyroid-disease/ann). Backpropagation is one of the most popular training algorithms for multilayer perceptrons. Unfortunately it can be very...

Artificial neural networks—especially those using the error back propagation algorithm—are capable of learning to control an unknown plant by autonomously extracting the necessary information from the plant. Following the approach of Psaltis, Sideris, and Yamamura, and Saerens and Soquet, a control architecture based on error back propagation has b...

Aufbau und Eigenschaften mehrschichtiger Perceptrons werden beschrieben. Theoretische Arbeiten bestätigen, daß die Architektur eines Netzes das erreichbare Ge-neralisierungsvermögen bestimmt. Ein biologisch motivierter Ansatz zur Topologie-Optimierung wird vorgestellt. Mit Hilfe genetischer Algorithmen werden die Netzgraphen einer Population mitein...

Dieser Beitrag berichtet über den Einsatz neuronaler Netzwerke als adaptive Regler. An einem linearen System dritter Ordnung mit Totzeit wird demonstriert, daß ein neuronales Netzwerk in der Lage ist, eine Regelstrecke, über die nur minimales qualitatives Wissen vorliegt, selbständig zu identifizieren und zu regeln. Das Training wird mit dem weit v...

The paper presents a method for building-up application adapted topologies for Backpropagation-trained neural networks. We investigate the influence of topology on classification performance and speed by comparing fixed and evolutionary created networks which were trained to recognize handwritten digits.

For many applications the classification of structural similar sections within waveforms raises a lot of difficulties. Such sections, called ‘structur-units’, could represent typical signal shapes (e.g. the PQRST sequence in normal ECG) or some transient events (e.g. the K-complex in EEG during sleep). To recognize such structur-units one often use...

Learning about Computer Engineering is a highly constructive process. At our depart-ment, computer engineering encompasses three courses and a laboratory session. In order to suc-cessfully learn the subject, the students should have hands-on experience with tools. While tools to program (compilers, interpreters, development environments) are widely...

Many production e-Science infrastructures (e.g. DEISA, D-Grid) have begun to offer a wide variety of services for end-users during the past several years. Many e-Scientists solve their scientific problems by us-ing parallel computing applications on clusters and collaborative on-line visualization and steering (COVS) is known as a tool for analyz-i...

We report from our recent practise of conducting web-based exercises with CAD tools at FernUniversitat, Germany's distance teaching university. The course "Computer Engineering I" introduces boolean func- tions, digital circuits, sequential circuits, memories, and their design. The assignments include design tasks of different digital circuits. Pap...

Virtual labs are excellent means to provide students with access to advanced microprocessor hardware. Running the lab, a remote server relieves students from complex installation of simulation software. With the long execution times of microprocessor simulations, a lab server provides results faster than the stu-dents' local machines. We report res...

Saarbrücken, Univ., Diss., 1986 (Nicht f.d. Austausch).

Zugl.: Koblenz, Universiẗat, Habil.-Schr., 1999.