The 10 most recently published documents
IT-Governance
(2023)
Die digitale Transformation verstärkt den Einfluss der Informationstechnologie auf den Unternehmenserfolg erheblich. Damit erhöhen sich auch die Anforderungen an das Führungssystem der IT in den Unternehmen. Hier gilt die einfache Weisheit: Ein ungeeignetes Managementsystem bringt in der Regel schlechtere Entscheidungen mit sich.
Wie Sie zielorientiert bestimmen, wer im Unternehmen wie auf IT-relevante Entscheidungen einwirken soll, zeigt Ihnen Christopher Rentrop mit viel Übersicht:
- Grundlegende Ziele und Erfolgsfaktoren der IT-Governance
- Gestaltungselemente der IT-Governance: Strukturen und Prozesse, Entscheidungsrechte, relationale Mechanismen u.a.
- COBIT als Rahmenwerk der IT-Governance
- Spezifische Entscheidungsdomänen, Handlungsfelder und Verantwortlichkeiten
- Management, Weiterentwicklung und Erfolgsmessung der IT-Governance
Eine prägnante Orientierungshilfe, die Sie Schritt für Schritt zu einer organisationsgerechten Ausgestaltung des Führungssystems der IT leitet.
In 3D extended object tracking (EOT), well-established models exist for tracking the object extent using various shape priors. A single update, however, has to be performed for every measurement using these models leading to a high computational runtime for high-resolution sensors. In this paper, we address this problem by using various model-independent downsampling schemes based on distance heuristics and random sampling as pre-processing before the update. We investigate the methods in a simulated and real-world tracking scenario using two different measurement models with measurements gathered from a LiDAR sensor. We found that there is a huge potential for speeding up 3D EOT by dropping up to 95\% of the measurements in our investigated scenarios when using random sampling. Since random sampling, however, can also result in a subset that does not represent the total set very well, leading to a poor tracking performance, there is still a high demand for further research.
Public-key cryptographic algorithms are an essential part of todays cyber security, since those are required for key exchange protocols, digital signatures, and authentication. But large scale quantum computers threaten the security of the most widely used public-key cryptosystems. Hence, the National Institute of Standards and Technology ( NIST ) is currently in a standardization process for post-quantum secure public-key cryptography. One type of such systems is based on the NP-complete problem of decoding random linear codes and therefore called code-based cryptography. The best-known code-based cryptographic system is the McEliece system proposed in 1978 by Robert McEliece. It uses a scrambled generator matrix as a public key and the original generator matrix as well as the scrambling as private key. When encrypting a message it is encoded in the public code and a random but correctable error vector is added. Only the legitimate receiver can correct the errors and decrypt the message using the knowledge of the private key generator matrix. The original proposal of the McEliece system was based on binary Goppa codes, which are also considered for standardization. While those codes seem to be a secure choice, the public keys are extremely large, limiting the practicality of those systems. Many different code families were proposed for the McEliece system, but many of them are considered insecure since attacks exist, which use the known code structure to recover the private key. The security of code-based cryptosystems mainly depends on the number of errors added by the sender, which is limited by the error correction capability of the code. Hence, in order to obtain a high security for relatively short codes one needs a high error correction capability. Therefore maximum distance separable ( MDS ) codes were proposed for those systems, since those are optimal for the Hamming distance. In order to increase the error correction capability we propose q -ary codes over different metrics. There are many code families that have a higher minimum distance in some other metric than in the Hamming metric, leading to increased error correction capability over this metric. To make use of this one needs to restrict not only the number of errors but also their value. In this work, we propose the weight-one error channel, which restricts the error values to weight one and can be applied for different metrics. In addition we propose some concatenated code constructions, which make use of this restriction of error values. For each of these constructions we discuss the usability in code-based cryptography and compare them to other state-of-the-art code-based cryptosystems. The proposed code constructions show that restricting the error values allows for significantly lower public key sizes for code-based cryptographic systems. Furthermore, the use of concatenated code constructions allows for low complexity decoding and therefore an efficient cryptosystem.
This thesis presents the development of two different state-feedback controllers to solve the trajectory tracking problem, where the vessel needs to reach and follow a time-varying reference trajectory. This motion problem was addressed to a real-scaled fully actuated surface vessel, whose dynamic model had unknown hydrodynamic and propulsion parameters that were identified by applying an experimental maneuver-based identification process. This dynamic model was then used to develop the controllers. The first one was the backstepping controller, which was designed with a local exponential stability proof. For the NMPC, the controller was developed to minimize the tracking error, considering the thrusters’ constraints. Moreover, both controllers considered the thruster allocation problem and counteracted environmental disturbance forces such as current, waves and wind.The effectiveness of these approaches was verified in simulation using Matlab/Simulink and GRAMPC (in the case of the NMPC), and in experimental scenarios, where they were applied to the vessel, performing docking maneuvers at the Rhine River in Constance (Germany).
In spite of the amount of new tools and methodologies adopted in the road infrastructure sector, the performance of road infrastructure projects is not constantly improving. Considering that the volume of projects undertaken is forecasted to increase every year, this is a substantial issue for the road infrastructure sector. Hence this work focuses on the principles of Blockchain Technology, road infrastructure sector and the information exchange with the aim to use the advantages of the Blockchain Technology in supporting to overcome the various challenges along the life cycle of road infrastructure projects.
Within the scope of this paper, two studies were conducted. First, focus groups were used to explore where society (road infrastructure sector) stands in terms of industry 4.0 and to get a better understanding if and where the principles of Blockchain Technology can be used when managing projects in the road infrastructure sector. Second, semi-structured interviews were administrated with experts of the road infrastructure sector and experts of Blockchain Technology to better understand the interrelation between these two areas. Based on the outcome of the two studies, technology barriers and enablers were explored for the purpose of improved information exchange within the road infrastructure sector.
The two studies revealed that there are significant and strong interrelations between the principles of the Blockchain Technology, project management within the road infrastructure sector and information exchange. These interrelations are complex and diverse, but overall it can be concluded that the adoption of the principles of Blockchain Technology into the field of information exchange improves the management of road infrastructure projects. Based on the two studies a theoretical framework was developed.
In summary this research showed that trust is an important factor and builds the foundation for communication and to ensure a proper information exchange. Within the scope of this thesis, it was demonstrated that the principles of the Blockchain Technology can be used to increase transparency, traceability and immutability during the life cycle of road infrastructure projects in the area of information exchange.
Foil-air bearings (FABs) are predominantly used for high-speed, oil-free applications. Offering many advantages such as friction loss at high speeds, stability and price, they lack, however, load capacity as well as start-up and coast-down friction wear resistance.
The friction losses of FABs have been studied experimentally by many authors. In order to predict the friction and, consequently, the lifespan of a FAB, the start-up and coast-down regimes are modelled in such a way that allows for accurate, efficient simulation and later optimisation of lift-off speed and wear characteristics. The proposed simulation method applies the Kirchhoff-Love plate theory to the top foil mapping [20]. This system of differential equations is coupled with the underlying compliant foil to simulate the displacement due to the pressure buildup. Consequently, this coupled system allows for simulation from almost zero rounds per minute (rpm) to full speed. The underlying simulation model uses the finite difference method for spatial discretisation and a temporal explicit Runge-Kutta method.
Difficulties to overcome are the smooth combination of various friction regimes across the sliding surfaces as well as the synchronous coupling of Reynolds, deformation and kinematic equations with highly non-linear terms. Introducing an exponential pressure component based on Greenwood and Tripp’s theory avoids impingement between the rotor and foil.
Unter bestimmten Kontaktbedingungen zwischen Rad und Schiene können selbsterregte Schwingungen angeregt werden, die zu gegenphasigen Drehbewegungen der Radscheiben und hohen Torsionsmomenten in der Radsatzwelle führen. Zur Bestimmung des maximalen Torsionsmoments sind bislang aufwendige Testfahrten erforderlich, da keine Verfahren bekannt waren, die eine konservative Berechnung des Torsionsmoments ermöglichen [1]. In den vergangenen Jahren wurden die drei folgenden Berechnungsmethoden vertieft untersucht, um das maximale, dynamische Torsionsmoment zu berechnen:
- Simulationen von komplexen Mehrkörpersystemen (MKS)
- Differentialgleichungssysteme mit numerischer Berechnung
- Analytische Berechnung durch Reduktion auf ein Minimalmodell
In dieser Publikation sollen diese Berechnungsmethoden näher vorgestellt werden und durch eine Gegenüberstellung der jeweils berechneten und gemessenen Ergebnisse deren Möglichkeiten aber auch Limitationen aufgezeigt werden.
Ziel des Forschungsprojekts "Ekont" ist es, ein handgeführtes Gerät zum Betonabtrag an Innenkanten und Störstellen in Kernkraftwerken (KKW) zu entwickeln. Um die Reaktionskräfte zu reduzieren wird hierbei der neuartige Ansatz eines gegenläufigen Fräsprozesses untersucht. Ergebnis ist eine Getriebelösung, bei der eine mittlere Frässcheibe mit annähernd derselben Umfangsgeschwindigkeit in die entgegengesetzte Richtung von weiteren Frässcheiben rotiert.
In the past years, algorithms for 3D shape tracking using radial functions in spherical coordinates represented with different methods have been proposed. However, we have seen that mainly measurements from the lateral surface of the target can be expected in a lot of dynamic scenarios and only few measurements from the top and bottom parts leading to an error-prone shape estimate in the top and bottom regions when using a representation in spherical coordinates. We, therefore, propose to represent the shape of the target using a radial function in cylindrical coordinates, as these only represent regions of the lateral surface, and no information from the top or bottom parts is needed. In this paper, we use a Fourier-Chebyshev double series for 3D shape representation since a mixture of Fourier and Chebyshev series is a suitable basis for expanding a radial function in cylindrical coordinates. We investigate the method in a simulated and real-world maritime scenario with a CAD model of the target boat as a reference. We have found that shape representation in cylindrical coordinates has decisive advantages compared to a shape representation in spherical coordinates and should preferably be used if no prior knowledge of the measurement distribution on the surface of the target is available.
