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Zur Erreichung des Sachziels Vertraulichkeit werden Daten (Dokumente, Dateien, E-Mails etc.) bei der Speicherung und Übertragung in lokalen Netzen, Intranets und im Internet häufig vom Endanwender verschlüsselt. Die dazu benutzten Schlüssel müssen bei Bedarf für den Endanwender genauso verfügbar sein wie für das Unternehmen bei Nicht-Verfügbarkeit des Endanwenders. Unternehmensinterne Schlüssel-Archive speichern die benutzten Schlüssel oder speichern die Adressen benutzter Schlüssel oder stellen auf andere Weise die benutzten Schlüssel auf Anforderung Berechtigten wieder bereit. Schlüssel-Archive sind aus der auf dem Escrowed Encryption Standard (EES) basierenden Clipper-Initiative der Vereinigten Staaten entstanden und werden dort als Key Recovery Center bezeichnet.
In verteilten und offenen Systemen wollen Kommunikationspartner beim Electronic Commerce Dokumente vertraulich, integer und rechtsverbindlich sowie zuordnungsbar authentisch und nachweisbar senden und empfangen. Für die an der Kommunikation beteiligten Kommunikationspartner muß dazu nachvollziehbar sein, wer wann mit wem welche Dokumente ausgetauscht hat. Zur Erreichung des Sachziels 'Vertraulichkeit' werden Dokumente bei der Speicherung auf einem Server und bei der Übertragung (über lokale Netzte, Intranets, Extranets und im Internet) vom Endanwender verschlüsselt. Dazu müssen die benutzten Schlüssel gegen unberechtigte Kenntnisnahme geschützt werden. Gleichzeitig muß auch die Verfügbarkeit der Schlüssel sichergestellt werden: Verschlüsselte Dokumente können nämlich nur dann wieder benutzbar gemacht werden, wenn sie bei berechtigtem Bedarf wieder entschlüsselt werden können. Im Unternehmen ist es deshalb erforderlich, Verfahren einzuführen, die die Verfügbarkeit gespeicherter Dokumente sicherstellen - auch wenn der originäre Inhaber dieser Dokumente nicht verfügbar ist (Reise, Urlaub, Krankheit, Ausscheiden). Schlüssel-Archive - sog. Enterprise Key Recovery Server - bieten die Möglichkeit, verschlüsselt gespeicherte Konzelationsschlüssel Berechtigten wieder zu Verfügung zu stellen. Damit können verschlüsselt gespeicherte Dokumente gespeichert werden. Enterprise Key Recovery Server werden im Rahmen des Projekts SECFORS - Secure Electronic Commerce an der Fachhochschule Rhein-Sieg zusammen mit Studierenden installiert und unter einer Reihe von Aspekten im Rahmen des vom Bundeswirtschaftsministerium geförderten Kompetenzzentrums Electronic Commerce Bonn Rhein-Sieg (KompEC) evaluiert; dazu werden Anforderungen an vertrauenswürdige Enterprise Key Recovery Server formuliert. Der Einsatz von Enterprise Key Recovery Servern ist in den USA Stand der Technik; in deutschen Unternehmen wird der Bedarf insbesondere deswegen differenziert gesehen, weil eine Verschlüsselung gespeicherter und übertragener Daten noch nicht flächendeckend durchgeführt wird.
Virtuelle Umgebungen
(2000)
In this paper we present a new storytelling approach, called Hypermedia Novel (HYMN), that extends the classical narration concept of a story. We develop an underlying modular concept – the narration module – that facilitates a new manner of reception as well as creation of a story. The HYMN focuses on the recipient and his role of consuming a story and a heterogeneous group of creative authors by providing narration modules and their interfaces without defining the granularity of the modules. Using several kinds ofmultimedia elements and a hyperlink structure, we present a first demonstrator that implements this new concept. We also discuss improvements, e.g. MPEG-4/7, that support both reception by the audience, and the process of creating the story by a dispersed team of authors.
Warum beeinträchtigen bestimmte Kratzer auf einer CD nicht die Wiedergabequalität? Wie können Datenübertragungen gegen Informationsverlust gesichert werden? Warum und wie funktionieren öffentliche Verschlüsselungssysteme? Worin ist deren Sicherheit begründet? Auf welcher Grundlage werden Routing-Tabellen in Netzwerkknoten erstellt? Wie wird eine optimale Kompression von Daten erreicht?
Diese und viele andere Fragen müssen zufriedenstellend beantwortet werden können, um bestimmte Qualitäten von Informations- und Kommunikationstechnologien zu erreichen. Informatikerinnen und Informatiker aller Studienrichtungen müssen in der Lage sein, diese Technologien erfolgreich einzusetzen und weiterzuentwickeln. Dazu müssen sie die Grundlagen kennen, auf denen diese Technologien basieren.
Clusters of commodity PCs are widely considered as the way to go to improve rendering performance and quality in many real-time rendering applications. We describe the design and implementation of our parallel rendering system for real-time rendering applications. Major design objectives for our system are: usage of commodity hardware for all system components, ease of integration into existing Virtual Environments software, and flexibility in applying different rendering techniques, e.g. using ray tracing to render distinct objects with a particularly high quality.
Bond graph modelling was devised by Professor Paynter at the Massachusetts Institute of Technology in 1959 and subsequently developed into a methodology for modelling multidisciplinary systems at a time when nobody was speaking of object-oriented modelling. On the other hand, so-called object-oriented modelling has become increasingly popular during the last few years. By relating the characteristics of both approaches, it is shown that bond graph modelling, although much older, may be viewed as a special form of object-oriented modelling. For that purpose the new object-oriented modelling language Modelica is used as a working language which aims at supporting multiple formalisms. Although it turns out that bond graph models can be described rather easily, it is obvious that Modelica started from generalized networks and was not designed to support bond graphs. The description of bond graph models in Modelica is illustrated by means of a hydraulic drive. Since VHDL-AMS as an important language standardized and supported by IEEE has been extended to support also modelling of non-electrical systems, it is briefly investigated as to whether it can be used for description of bond graphs. It turns out that currently it does not seem to be suitable.
Multidisciplinary systems are described most suitably by bond graphs. In order to determine unnormalized frequency domain sensitivities in symbolic form, this paper proposes to construct in a systematic manner a bond graph from another bond graph, which is called the associated incremental bond graph in this paper. Contrary to other approaches reported in the literature the variables at the bonds of the incremental bond graph are not sensitivities but variations (incremental changes) in the power variables from their nominal values due to parameter changes. Thus their product is power. For linear elements their corresponding model in the incremental bond graph also has a linear characteristic. By deriving the system equations in symbolic state space form from the incremental bond graph in the same way as they are derived from the initial bond graph, the sensitivity matrix of the system can be set up in symbolic form. Its entries are transfer functions depending on the nominal parameter values and on the nominal states and the inputs of the original model. The sensitivities can be determined automatically by the bond graph preprocessor CAMP-G and the widely used program MATLAB together with the Symbolic Toolbox for symbolic mathematical calculation. No particular program is needed for the approach proposed. The initial bond graph model may be non-linear and may contain controlled sources and multiport elements. In that case the sensitivity model is linear time variant and must be solved in the time domain. The rationale and the generality of the proposed approach are presented. For illustration purposes a mechatronic example system, a load positioned by a constant-excitation d.c. motor, is presented and sensitivities are determined in symbolic form by means of CAMP-G/MATLAB.
In der Informationsgesellschaft nehmen auch in Deutschland aggressive und kriminelle Handlungen (Computermißbrauch) ausweislich der jährlichen Kriminalstatistik [BMI02] zu. Weniger Bedeutung wird in Deutschland bisher politisch-motivierten Aktionen beigemessen. Weltweit werden klassische Verfahren wie ziviler Ungehorsam, innere Unruhen und Bürgerkrieg zunehmend durch IT-gestützte Verfahren ergänzt und ersetzt (Transformation). Durch die weltweite Verfügbarkeit der IT-gestützten Verfahren und des Internet muß der - auf einen Staat begrenzte - Begriff des zivilen Ungehorsams genauso wie der der inneren Unruhen und der des klassischen Bürgerkriegs transformiert werden in den ubiquitären Cyberspace. Angesichts zunehmender gewalttätiger Aktivitäten unterhalb der Kriegsschwelle im Cyberspace muß die Sensibilität für die Auswirkungen dieser Aktivitäten dringend geschaffen werden und angemessene Reaktionen müssen auf allen Ebenen (Private, Unternehmen und Behörden) erarbeitet werden.
As from the beginning of the late 70's an impressive number of innovative electronic payment systems have been developed and tested commercially. However, the resulting variety and complexity of the systems have turned out to be one of the obstacles for the broad acceptance of electronic payment. In this paper we propose a process and service oriented framework, which offers a structural and conceptual orientation in the field of electronic payment. It renders possible an integral view on electronic payment that goes beyond the frame of an individual system. To do this, we have generalized the systems-oriented approaches to a phase-oriented payment model. Using this model, requirements and supporting services for electronic payment can be sorted systematically and described from both the customers' and the merchants' viewpoint. Providing integrated payment processes and services is proving to be a difficult task. With this paper we would like to outline the necessity for a Payment Service Provider to act as a mediator for suppliers and users of electronic payment systems.
The MoMoSat service will enable mobile end-users to view, manage, annotate, and communicate mapbased information in the field. The handled information exists of a huge volume of raster (satellite or aerial images) and vector data (i.e. street networks, cadastral maps or points of interest), as well as text-specific geo-referenced textual notes (the so-called 'GeoNotes') and real-time voice.
Im vorliegenden Beitrag wird ein prozess- und serviceorientiertes Rahmenmodell vorgeschlagen, das eine strukturelle und begriffliche Orientierung für das Gebiet der elektronischen Bezahlung bietet. Das Rahmenmodell erlaubt eine ganzheitliche Betrachtung über die Merkmale eines einzelnen Zahlungssystems hinaus. Die systemspezifische Sicht auf die elektronische Zahlung wird zu einem prozessorientierten Phasenmodell verallgemeinert. Mit diesem lassen sich die unterstützenden Services für die elektronische Bezahlung aus Kunden- und Händlersicht systematisch zusammenstellen und beschreiben. Die organisatorische Umsetzung der Serviceprozesse führt zur Rolle des Payment Service Providers, der als Mittler zwischen Anbietern und Anwendern elektronischer Zahlungssysteme agiert.
A New Approach of Using Two Wireless Tracking Systems in Mobile Augmented Reality Applications
(2003)
Zur Schätzung der Exposition von Oberflächengewässern durch Pflanzenschutzmittel werden PEC-Werte mit Hilfe eines probabilistischen Verfahrens ermittelt. Hierfür werden zunächst verschiedene Regressionsanalysen zur Modellierung der Abdrift durchgeführt. Anschließend wird die ausgewählte Abdriftverteilung mit verschiedenen Verteilungsansätzen für die Aufwandmenge und das Gewässervolumen kombiniert.
Augmented Perception - AuPer
(2004)
Finding good Echo State Networks to control an underwater robot using evolutionary computations
(2004)
In interactive graphics it is often necessary to introduce large changes in the image in response to updated information about the state of the system. Updating the local state immediately would lead to a sudden transient change in the image, which could be perceptually disruptive. However, introducing the correction gradually using smoothing operations increases latency and degrades precision. It would be beneficial to be able to introduce graphic updates immediately if they were not perceptible. In the paper the use of saccade-contingent updates is exploited to hide graphic updates during the period of visual suppression that accompanies a rapid, or saccadic, eye movement. Sensitivity to many visual stimuli is known to be reduced during a change in fixation compared to when the eye is still. For example, motion of a small object is harder to detect during a rapid eye movement (saccade) than during a fixation. To evaluate if these findings generalize to large scene changes in a virtual environment, gaze behavior in a 180 degree hemispherical display was recorded and analyzed. This data was used to develop a saccade detection algorithm adapted to virtual environments. The detectability of trans-saccadic scene changes was evaluated using images of high resolution real world scenes. The images were translated by 0.4, 0.8 or 1.2 degrees of visual angle during horizontal saccades. The scene updates were rarely noticeable for saccades with a duration greater than 58 ms. The detection rate for the smallest translation was just 6.25%. Qualitatively, even when trans-saccadic scene changes were detectible, they were much less disturbing than equivalent changes in the absence of a saccade.
Interactive rendering of complex models has many applications in the Virtual Reality Continuum. The oil&gas industry uses interactive visualizations of huge seismic data sets to evaluate and plan drilling operations. The automotive industry evaluates designs based on very detailed models. Unfortunately, many of these very complex geometric models cannot be displayed with interactive frame rates on graphics workstations. This is due to the limited scalability of their graphics performance. Recently there is a trend to use networked standard PCs to solve this problem. Care must be taken however, because of nonexistent shared memory with clustered PCs. All data and commands have to be sent across the network. It turns out that the removal of the network bottleneck is a challenging problem to solve in this context.In this article we present some approaches for network aware parallel rendering on commodity hardware. These strategies are technological as well as algorithmic solutions.
Most VE-frameworks try to support many different input and output devices. They do not concentrate so much on the rendering because this is tradi- tionally done by graphics workstation. In this short paper we present a modern VE framework that has a small kernel and is able to use different renderers. This includes sound renderers, physics renderers and software based graphics renderers. While our VE framework, named basho is still under development we have an alpha version running under Linux and MacOS X.
Motion parameters estimation of moving objects and ego motion applying an active camera system
(2004)
Honeypots und Honeynets
(2004)
RFID security
(2004)
The Render Cache [1,2] allows the interactive display of very large scenes, rendered with complex global illumination models, by decoupling camera movement from the costly scene sampling process. In this paper, the distributed execution of the individual components of the Render Cache on a PC cluster is shown to be a viable alternative to the shared memory implementation.As the processing power of an entire node can be dedicated to a single component, more advanced algorithms may be examined. Modular functional units also lead to increased flexibility, useful in research as well as industrial applications.We introduce a new strategy for view-driven scene sampling, as well as support for multiple camera viewpoints generated from the same cache. Stereo display and a CAVE multi-camera setup have been implemented.The use of the highly portable and inter-operable CORBA networking API simplifies the integration of most existing pixel-based renderers. So far, three renderers (C++ and Java) have been adapted to function within our framework.
This paper describes the work done at our Lab to improve visual and other quality of Virtual Environments. To be able to achieve better quality we built a new Virtual Environments framework called basho. basho is a renderer independent VE framework. Although renderers are not limited to graphics renderers we first concentrated on improving visual quality. Independence is gained from designing basho to have a small kernel and several plug-ins.
We present basho, a light weight and easily extendable virtual environment (VE) framework. Key benefits of this framework are independence of the scene element representation and the rendering API. The main goal was to make VE applications flexible without the need to change them, not only by being independent from input and output devices. As an example, with basho it is possible to switch from local illumination models to ray tracing by just replacing the renderer. Or to replace the graphical representation of the scene elements without the need to change the application. Furthermore it is possible to mix rendering technologies within a scene. This paper emphasises on the abstraction of the scene element representation.
Zur Zeit sind E-Government und E-Governance die Buzzwords in der Verwaltungsinformatik. In dieser Disziplin wechseln die Trends jedoch schnell, und es erscheinen am Horizont bereits die nachfolgenden Entwicklungen.
A generic approach to describing shape and topography of arbitrary objects is presented, using linguistic variables to combine different features in one fuzzy descriptor. Although the origin of the method lies in molecular visualization and drug design, it can be applied in principle to any surface represented by a polygon mesh. Two approaches to shape description are presented that both lead to linguistic variables that can be used for surface segmentation by means of shape: One approach is based on the calculation of canonical curvatures, the other describes the "embeddedness" of a surface area related to the overall geometry of a 3D object.
The objective of the presented approach is to develop a 3D-reconstruction method for micro organisms from sequences of microscopic images by varying the level-of-focus. The approach is limited to translucent silicatebased marine and freshwater organisms (e.g. radiolarians). The proposed 3D-reconstruction method exploits the connectivity of similarly oriented and spatially adjacent edge elements in consecutive image layers. This yields a 3D-mesh representing the global shape of the objects together with details of the inner structure. Possible applications can be found in comparative morphology or hydrobiology, where e.g. deficiencies in growth and structure during incubation in toxic water or gravity effects on metabolism have to be determined.
Zuverlässige Ad-Hoc Kommunikation mobiler Endgeräte mit satellitengestützter Internet-Anbindung
(2005)
Mobile Datenkommunikation basiert üblicherweise auf der drahtlosen Anbindung eines Endgerätes an eine Basisstation, die ihrerseits an eine feste Infrastruktur angebunden ist. In vielen Szenarien sind diese Voraussetzungen jedoch nicht gegeben. Beispiele hierfür sind Hochwasser, Erdbeben oder Flugzeugabstürze in dünn besiedelten Regionen. Einen Lösungsansatz für sich daraus ergebende Anforderungen bieten dynamisch aufgebaute Ad-Hoc Netze mit einer satellitengestützten Anbindung an eine Festnetz-Infrastruktur. In solchen Netzen stellen die mobilen Terminals die benötigte lokale Infrastruktur selbst dynamisch her. Ziel der hier vorgestellten Arbeiten ist es, die Zuverlässigkeit und Dienstqualität der verwendeten Technologien zu untersuchen und durch geeignete Mechanismen so anzupassen, dass die Anforderungen typischer Applikationen möglichst erfüllt werden. Zur Demonstration wurde ein Prototyp aufgebaut, der unter anderem die Anwendungen "Voice over IP" (VoIP), "Datenbankzugriff im Intranet" und Internetzugang (WWW) untersucht.
Im Rahmen eines Softwareentwicklungsprojekts wurde im Berufsgenossenschaftlichen Institut für Arbeitsschutz (BGIA) in enger Zusammenarbeit mit dem Fachbereich Informatik der Fachhochschule Bonn- Rhein-Sieg eine Anwendung zur Unterstützung von Softwareprüfungen implementiert. Basierend auf Softwaremetriken dient die Anwendung dem BGIA zur statischen Quellcodeanalyse sicherheitsrelevanter Software und unterstützt auf diese Weise Maschinenprüfer bei ihrer Arbeit. In diesem Projekt konnten bekannte Metriken, wie Halstead und McCabe, sowie neu entwickelte Kennzahlen und Qualitätskriterien an die Softwareanforderungen von Industriemaschinen angepasst und in einem Prototypen integriert werden.
The Virtual Memory Palace
(2006)
The intention of the Virtual Memory Palace is to help people memorize information by addressing their visual memory. The concept is based on the “Memory Palace” as an ancient Greek memorization technique, where symbols are placed in a certain way within an imaginative building in order to remember the original information whenever the mind goes through the vision of this building again. The goal of this work was to create such a Memory Palace in a virtual environment, so it requires less creative effort of the contemporary learner than was necessary in ancient Greece. The Virtual Memory Palace offers the possibility to freely explore a virtual 3d architectural model and to place icons at various locations within this model. Specific behaviors were assigned to these locations to make them more memorable. To test the benefit of this concept, an experiment with 15 subjects was conducted. The results show a higher remembrance rate of items learned in the Virtual Memory Palace compared to a wordlist. The observations made during the test showed that most of the subjects enjoyed the memorization environment and were astonished how well the Virtual Memory Palace worked for them.
BGML - a novel XML format for the exchange and the reuse of bond graph models of engineering systems
(2006)
The paper proposes a bond graph approach to model based fault detection and isolation (FDI) that uses residual sinks. These elements couple a reference model of a process engineering system to a bond graph model of the system that is subject to disturbances caused by faults. In this paper it is assumed that two faults do not appear simultaneously. The underlying mathematical model is a Differential Algebraic Equations (DAE) system. The approach is illustrated by means of the often used hydraulic two tanks system.
The 2006 European Conference on Modelling and Simulation (ECMS 2006) is a particularly significant event. Organised by the European Council on Modelling and Simulation (ECMS) and co-sponsored by the Society for Modelling and Simulation International (SCSI), it is the 20th conference in its well established series. Bonn-Rhein-Sieg University of Applied Sciences is pleased to host this conference one year after the 10th anniversary of the University’s foundation.
Bond graph modelling
(2006)
Bond Graph Modelling and Simulation of Mechatronic Systems: An Introduction into the Methodology
(2006)
This paper introduces into a graphical, computer aided modelling methodology that is particularly suited for the concurrent design of mechatronic systems, viz. of engineering systems with mechanical, electrical, hydraulic or pneumatic components including interactions of physical effects from various energy domains. Beyond the introduction, bond graph modelling of multibody systems, as an example of an advanced topic, is briefly addressed in order to demonstrate the potential of this powerful approach to modelling mechatronic systems. It is outlined how models of multibody systems including flexible bodies can be build in a systematic manner.
The development of mobile robotic systems is a demanding task regarding its complexity, required resources and skills in multiple fields such as software development, artificial intelligence, mechanical design, electrical engineering, signal processing, sensor technology or control theory. This holds true particularly for soccer playing robots, where additional aspects like high dynamics, cooperation and high physical stress have to be dealt with. In robot competitions such as RoboCup, additional skills in the domains of team, project and knowledge management are of importance.
Swedish wheeled mobile robots have remarkable mobility properties allowing them to rotate and translate at the same time. Being holonomic systems, their kinematics model results in the possibility of designing separate and independent position and heading trajectory tracking control laws. Nevertheless, if these control laws should be implemented in the presence of unaccounted actuator saturation, the resulting saturated linear and angular velocity commands could interfere with each other thus dramatically affecting the overall expected performance. Based on Lyapunov’s direct method, a position and heading trajectory tracking control law for Swedish wheeled robots is developed. It explicitly accounts for actuator saturation by using ideas from a prioritized task based control framework.
The prototype of a workflow system for the submission of content to a digital object repository is here presented. It is based entirely on open-source standard components and features a service-oriented architecture. The front-end consists of Java Business Process Management (jBPM), Java Server Faces (JSF), and Java Server Pages (JSP). A Fedora Repository and a mySQL data base management system serve as a back-end. The communication between front-end and back-end uses a SOAP minimal binding stub. We describe the design principles and the construction of the prototype and discuss the possibilities and limitations of work ow creation by administrators. The code of the prototype is open-source and can be retrieved in the project escipub at http://sourceforge.net/ .
In this paper, we describe an approach to academic teaching in computer science using storytelling as a means for background research to hypermedia and virtual reality topics. It is shown that narrative activity within the context of a Hypermedia Novel related to educational content can enhance motivation for self-conducted learning and in parallel lead to an edutainment system of its own. The narrative practice and background research as well as the resulting product can supplement lecture material with comparable success to traditional academic teaching approaches.
In this contribution a machine vision inspection system is presented which is designed as a length measuring sensor. It is developed to be applied to a range of heat shrink tubes, varying in length, diameter and color. The challenges of this task were the precision and accuracy demands as well as the real-time applicability of the entire approach since it should be realized in regular industrial line production. In production, heat shrink tubes are cut to specific sizes from a continuous tube. A multi-measurement strategy has been developed, which measures each individual tube segment several times with sub pixel accuracy while being in the visual field. The developed approach allows for a contact-free and fully automatic control of 100% of produced heat shrink tubes according to the given requirements with a measuring precision of 0.1mm. Depending on the color, length and diameter of the tubes considered, a true positive rate of 99.99% to 100% has been reached at a true negative rate of > 99.7.
Phase Space Rendering
(2007)