Search

OA Förderung 2022 Synthetic aperture radar (SAR) at the terahertz (THz) spectrum has emerging short-range applications. In comparison to the microwave spectrum, the THz spectrum is limited in propagation range but benefits from high spatial resolution. The THz SAR is of significant interest for several applications which necessitate the mapping of indoor environments to support various endeavors such as rescue missions, map-assisted wireless communications, and household robotics. This paper addresses the augmentation of the high-resolution indoor mapped environment for object recognition, which includes detection, localization, and classification. Indoor object recognition is currently dominated by the usage of optical and infrared (IR) systems. However, it is not widely explored by radar technologies due to the limited spatial resolution at the most commonly used microwave frequencies. However, the THz spectrum provides a new paradigm of possible adaptation of object recognition in the radar domain by providing image quality in good compliance to optical/IR systems. In this paper, a multi-object indoor environment is foremost mapped at the THz spectrum ranging from 325 to 500 GHz in order to investigate the imaging in highly scattered environments and accordingly create a foundation for detection, localization, and classification. Furthermore, the extraction and clustering of features of the mapped environment are conducted for object detection and localization. Finally, the classification of detected objects is addressed with a supervised machine learning-based support vector machine (SVM) model.

In recent years terahertz (THz) technology has attracted great interest in biosensing applications. Due to the interaction between analyte and electromagnetic (EM) field, a THz resonator is sensitive to changes in the refractive index of the analyte and can be used as a thin-film sensor for rapid pathogen diagnosis. To achieve high sensitivity and reliability, the sensor should have a high Q factor, a high field concentration at the site of the analyte, and the ability to compensate for temperature effects. However, conventional metamaterial methods have a low Q factor, which may lead to ambiguous detection and no attention has been paid to address the temperature effects. Here, we present a photonic crystal (PhC) based chip consisting of a reference channel and a sensing channel with two identical PhC slot resonators. The resonance difference between the resonators is temperature invariant and can be used for analyte detection. The dual-channel PhC chip has a Q factor of 5063 and a figure of merit of 3.1 /RIU/μm (RIU is refractive index unit), which are higher than that of metamaterial sensors. The chip is designed and simulated for the W band by 3D field simulations and is verified by measurements. Our results suggest that THz PhC resonators can provide high sensitivity and high resistance to environmental effects. We anticipate our work to be a starting point for future biosensing applications. OA Förderung 2022

Material characterization in the 0.1 - 10 THz range has been a major topic of research since its first demonstration 30 years ago. Advances in terahertz generation, detection, and data acquisition have contributed to improved bandwidth, signal power and signal-to-noise ratio. However, material characterization is still performed using conventional spectroscopic measurement schemes which require detailed information about the test object's shape, location, orientation relative to the measurement system, and a reference measurement. Here, we present a method for reference-free material characterization of dielectric objects using a terahertz time-domain spectroscopy system without a priori knowledge about the object and its position. The proposed method is based on ellipsometry combined with lensless imaging for the estimation of the refractive index. The method is a multistage procedure designed for small test objects in reflection mode. The diffracted terahertz radiation is separated from the specular reflected radiation in a post-processing step to enable a valid material parameter estimation. In this way, small dielectric objects can be located, imaged with a sub-mm resolution, and their material parameters extracted.

Distributed Antenna Systems (DAS) promise to deliver solutions for the future wireless challenges using multiple remote radio heads (RRHs) in a distributed architecture, thereby supporting high frequency re-use, increased coverage, decreasing interference and latency. DAS architecture consists of multiple RRHs connected to a centralized base station via an optical fiber network. This work explains different DAS deployment techniques on a real-time LTE system. It focuses on the implementation details of LTE PHY on a TI (Texas Instruments) DSP and corresponding processing blocks that need to be adapted to support the functionality of DAS. Different DAS use case scenarios of deployment, their advantages and key performance indicators, are analyzed. This work also includes the measurement results of deploying antenna selection scenario to investigate and validate DAS on a real-time LTE system

Wären wir in der Lage, die Energie des Sonnenlichtes vollständig in einer lagerbaren Form zu speichern, dann könnten wir in nur einer Stunde genug Ressourcen ansammeln, um den weltweiten Energiebedarf eines ganzen Jahres zu decken. Das Problem dabei ist aber, dass sich Licht nicht so einfach speichern lässt., Recycling of carbon dioxide to fuels or splitting of water for the generation of hydrogen are highly desirable solutions aiming to establish a sustainable energy supply and to reduce carbon emissions. Ideally, only the energy of the sun would be required for such a process. This is already possible using photocatalysts, in which the energy of light is converted into chemical energy by photogeneration of charge carriers. However, in spite of decades of research, no system has yet been developed that would function efficiently on the industrial scale. One challenge is the development of materials that can also absorb the large visible portion of the sun light, and not only the few percent of UV light that can be used, for example, by the widely established material TiO₂. This article highlights a new approach for the tailor-made development of photoactive oxide nanoparticles able to function under irradiation with visible light. Since the energy needed to photoexcite a certain material increases with a decrease in particle size, the excitation energy can be tuned by a variation of the size of the photoactive species. In the project described here, the whole size range, starting from large particles with typical properties of extended semiconductors over various sizes of clusters and agglomerates down to isolated photoactive species is studied for vanadium oxide. The synthesis of those different structures is possible using suitable inert supports with acidic or basic surface properties, in which a higher basicity of the surface will favor formation of more and more isolated vanadyl species. While the crystalline oxide V₂O₅ in the form of nanoparticles absorbs in the visible range, the excitation energy shifts more and more to the UV region when going to small oligomers and finally to isolated vanadyl species. It can clearly be shown that the photocatalytic activity of the different vanadium oxide species is a function of their size, in which only the isolated species show activity in organic dye degradation as photocatalytic model reaction. Our study highlighted here is a first showcase to generally establish the use of the quantum size effect for the development of photocatalysts with carefully designed light absorption properties and suitable positions of the energy levels., UNIKATE: Berichte aus Forschung und Lehre, no. 48Materials Chain: Forschung aus dem UA Ruhr-Profilschwerpunkt, p. 32

ZnO is a promising n-type oxide thermoelectric material, which is stable in air at elevated temperatures. In the present study, we report the bottom-up approach to create Al-doped ZnO nanocomposites from nanopowders, which are prepared by chemical vapour synthesis. With our synthesis route, we are able to create highly doped Al-containing ZnO nanocomposites that exhibit bulk-like electrical conductivity. Moreover, the impact of the microstructure of the nanocomposites on their thermal conductivity is enormous, with a value of 1.0 W m^(−1) K^(−1) for 1% Al–ZnO at room temperature, which is one of the lowest values reported, to date, on ZnO nanocomposites. The optimization of the Al-doping and microstructure with respect to the transport properties of bulk Al–ZnO nanocomposites leads to a zT value of about 0.24 at 950 K, underlining the potential of our technique.

Natural diamond is known for its outstanding thermal conductivity and electrical insulation. However, synthetic production allows for doping and tailoring microstructural and transport properties. Despite some motivation in the literature and the ongoing search for abundant and non-toxic thermoelectric materials, the first experimental study on a set of eight substrate-free boron-doped nanocrystalline diamond foils is presented herein. All transport coefficients were determined in the same direction within the same foils over a broad temperature range up to 900 °C. It is found that nanostructuring reduces the thermal conductivity by two orders of magnitude, but the mobility decreases significantly to around 1 cm 2 V −1 s −1 , too. Although degenerate transport can be concluded from the temperature dependence of the Seebeck coefficient, charge carriers notably scatter at grain boundaries where sp 2 -carbon modifications and amorphous boron-rich phases form during synthesis. A detailed analysis of doping efficiency yields an acceptor fraction of only 8–18 at%, meaning that during synthesis excess boron thermodynamically prefers electrically inactive sites. Decent power factors above 10 −4 W m −1 K −2 at 900 °C are found despite the low mobility, and a Jonker-type analysis grants a deeper insight into this issue. Together with the high thermal conductivity, the thermoelectric figure of merit zT does not exceed 0.01 at 900 °C.

Habilitation, Universität Duisburg-Essen, 2013 The focus of this work is to theoretically study and develop specific photonic-based hybrid or/and monolithic integrated functions operating in the microwave (300 MHz - 300 GHz) frequency band in order to respond to the always growing demand for higher data rate transmission. Next generation fixed wireless technology using radio over fiber technologies for high data rate applications with world record transmission capacities will be demonstrated. For the first time, the presented technologies enable the construction of wireless links operating at transmission speeds previously only known from fiber-optic communications. This capability will be of great value for future mobile backhauling, disaster recovery and temporary high capacity wireless links. At the same time, the proposed photonic-based microwave technologies will be shown, to be also of great value to a number of other generic application fields including sensing, instrumentation, health-care, medical applications and radio-astronomy.

Die Nano-Sicherheitsforschung hat in den letzten Jahren viel erreicht. Dazu zählen beispielsweise die Identifizierung von Orten mit möglicherweise hoher Exposition, von Nanomaterialien mit hohem toxikologischen Gefährdungspotenzial oder erste Untersuchungen zu Veränderungen und zum Verhalten von Nanomaterialien in der Umwelt. Nichtsdestotrotz gibt es noch wichtige offene Fragestellungen, die weiterer Forschung bedürfen, um einen sicheren und nachhaltigen Umgang mit Nanomaterialien zu gewährleisten. Hierzu zählen Fragen zu ihrem Lebenszyklus, zu ihrer Mobilität oder Akkumulation in der Umwelt sowie zu möglichen Auswirkungen auf Fauna und Flora. Auch hier sind Wissenschaftlerinnen und Wissenschaftler des IUTA und der Universität Duisburg-Essen aktiv., UNIKATE: Berichte aus Forschung und Lehre, no. 43NanoEnergie: Materialentwicklung für eine nachhaltige Energieversorgung, p. 110

Die Sicherheit elektrisch betriebener Fahrzeuge ist ein wichtiger Aspekt im Rahmen ihrer Markteinführung. Besonders die Batterie und die Hochspannungskabel bergen hohe Gefahrenpotenziale. Holger Hirsch beschäftigt sich mit dem Thema der elektrischen Sicherheit von Elektrofahrzeugen und dem sicheren Umgang mit diesen Fahrzeugen durch Einsatz- und Rettungskräfte im Falle eines Unfalls. Er analysiert die gängigen Sicherheitsstandards und Zulassungsverordnungen und erarbeitet technische sowie organisatorische Konzepte zur Sicherheit der elektrischen Fahrzeuge., The safety of electrically propelled vehicles is a sensitive issue, impacting on their full introduction to the market. All groups of people coming into contact with such vehicles, such as the fire brigade, workshop personnel and the driver must be protected against injuries caused by an electric shock and fault arcs. The propulsion battery and the High Volt wiring harness in particular represent new safety hazards in electric vehicles compared to commercial vehicles with combustion engines. The current standards and type approval regulations for the new types of electrically propelled vehicles are currently insufficient for vehicles licensed for public streets. Therefore, as requested in the current German standardisation roadmap, these standards must be adapt-ed to these new fields of application. In addition to the normative requirements, vehicle manufacturers have introduced several safety systems for the maintenance of electrical safety. The insulation resistance as well as the consistence of the whole electric propulsion circuit can be monitored by suitable measurement devices. Thus insulation faults, caused by an accident for example, can be detected reliably and a disconnection of the propulsion battery can be initialized. With regard to safety systems implemented in electric vehicles there is actually an urgent need for development. We are currently developing a test setup for experimental studies concerning safety systems which can be implemented in electric vehicles for improving electrical safety., UNIKATE: Berichte aus Forschung und Lehre, no. 39Ingenieurwissenschaften: Herausforderung Elektromobilität, p. 42

Duisburg, Essen, Univ., Diss., 2009 The primary objective of this dissertation is to develop a black box optimization tool. The algorithm should be able to solve complex nonlinear, multimodal, discontinuous and mixed-integer power system optimization problems without any model reduction. Although there are many computational intelligence (CI) based algorithms which can handle these problems, they require intense human intervention in the form of parameter tuning, selection of a suitable algorithm for a given problem etc. The idea here is to develop an algorithm that works relatively well on a variety of problems with minimum human effort. An adaptive particle swarm optimization algorithm (PSO) is presented in this thesis. The algorithm has special features like adaptive swarm size, parameter free update strategies, progressive neighbourhood topologies, self learning parameter free penalty approach etc. The most significant optimization task in the power system operation is the scheduling of various generation resources (Unit Commitment, UC). The current practice used in UC modelling is the binary approach. This modelling results in a high dimension problem. This in turn leads to increased computational effort and decreased efficiency of the algorithm. A duty cycle based modelling proposed in this thesis results in 80 percent reduction in the problem dimension. The stern uptime and downtime requirements are also included in the modelling. Therefore, the search process mostly starts in a feasible solution space. From the investigations on a benchmark problem, it was found that the new modelling results in high quality solutions along with improved convergence. The final focus of this thesis is to investigate the impact of unpredictable nature of demand and renewable generation on the power system operation. These quantities should be treated as a stochastic processes evolving over time. A new PSO based uncertainty modelling technique is used to abolish the restrictions imposed by the conventional modelling algorithms. The stochastic models are able to incorporate the information regarding the uncertainties and generate day ahead UC schedule that are optimal to not just the forecasted scenario for the demand and renewable generation in feed but also to all possible set of scenarios. These models will assist the operator to plan the operation of the power system considering the stochastic nature of the uncertainties. The power system can therefore optimally handle huge penetration of renewable generation to provide economic operation maintaining the same reliability as it was before the introduction of uncertainty.

Duisburg, Essen, Univ., Diss., 2008 Optimierte Entfernungsmessung mit 3D-CMOS Bildsensor und Echtzeit-Verarbeitung der 3D-Daten für Anwendungen in der Automobil- und Sicherheitstechnik Diese Arbeit beschreibt und charakterisiert eine neu entwickelte Entfernungskamera für Reichweiten von 2 m bis 25 m und spezielle 3D-Echtzeit-Bildverarbeitungsalgorithmen zum Detektieren, Tracken und Klassifizieren von Objekten auf der Grundlage der dreidimensionalen Kameradaten. Die Technologie basiert auf einem 64x8 Pixel CMOS Bildsensor, welcher im Stande ist, dreidimensionale Szenen zu erfassen. Dies wird mittels indirekter Laufzeitmessung von NIR Laserpulsen, die von der Kamera ausgesandt und an Objekten im Blickfeld der Kamera reflektiert werden, realisiert. Eine analytische Beschreibung der Messsignale und eine darauf aufbauende Herleitung der verschiedenartigen Entfernungsmessungsalgorithmen wird in dieser Arbeit ebenso durchgefhrt, wie die vergleichende Betrachtung der Entfernungsmessungsalgorithmen durch Rechnung, Simulation und Experimente; dabei zeigt der MDSI3-Algorithmus die besten Ergebnisse über den gesamten Messbereich, und wird deshalb zum Standardalgorithmus des Entfernungsmesssystems. Ein Kameraprototyp mit Messgenauigkeiten im cm-Bereich bei einer Bildwiederholrate bis zu 100 Hz wurde entwickelt; eine detaillierte Evaluierung der Komponenten und des Systems ist hier beschrieben. Hauptaspekte sind dabei die Charakterisierung der zeitkritischen Messsignale, des Systemrauschens und der Entfernungsmesseigenschaften. Desweiteren wird in dieser Arbeit die neu entwickelte Echtzeit-Bildverarbeitung des Kameradatenstroms vorgestellt, die auf die Detektion von Objekten im Beobachtungsbereich und die verlässliche Ermittlung von Positions-,Geschwindigkeits- und Beschleunigungsschtzwerten abzielt. Der dabei verwendete Segmentierungsalgorithmus nutzt alle drei Dimensionen der Positionsmesswerte kombiniert mit den Intensitätswerten der Messsignale, und liefert so eine signifikante Verbesserung im Vergleich zur Segmentierung in konventionellen 2D Bildern. Position, Geschwindigkeit und Beschleunigung werden mit Hilfe eines Kalman-Filters im 3-dimensionalen Raum geschätzt. Das Filter passt sich dynamisch den Messbedingungen des jeweils gemessenen Objekts an, und berücksichtigt so Veränderungen der Dateneigenschaften. Die Leistungsfähigkeit der Bildverarbeitungsalgorithmen wird anhand von Beispielszenen demonstriert.

Duisburg, Essen, Univ., Diss., 2008 Die drahtlose Übertragung von Daten nimmt in unserem Alltag einen immer größer werdenden Stellenwert ein, und es ist zu erwarten, dass der Trend zu drahtlosen Systemen auch in der Zukunft anhält und weitere Anwendungen hinzukommen. Dabei dürfen sich die unterschiedlichen Systeme und Dienste nicht gegenseitig stören, was sehr restriktive Vorgaben zur Nutzung der ein­zelnen Frequenzbänder erfordert und zu einer zunehmenden Frequenzknapp­heit führt. Dazu kommt, dass ein regelrechter Andrang auf lizenzfreie Fre­quenzbänder stattfindet, was den Effekt noch weiter verstärkt. Aus diesem Grund ist in jüngster Zeit die sogenannte Ultra Wideband-Technik (UWB) sehr populär geworden, die gegenüber herkömmlichen drahtlosen Systemen einige Vorteile aufweist. Die Nutzung des UWB-Frequenzbandes ist in den USA im Jahre 2002 sehr restriktiv durch die Federal Communications Commission (FCC) reglemen­tiert worden. Kern der Bestimmungen ist eine Frequenzmaske mit sehr gerin­ger spektraler Leistungsdichte. Dies stellt hohe Anforderungen an UWB-Sys­teme und eine konsequente Optimierung hinsichtlich der Systemempfindlich­keit, Effizienz und Reichweitenerhöhung. Eine Erhöhung des Gewinns (am Empfänger) wäre wünschenswert, führt bei Verwendung von aktiven Elemen­ten jedoch auch zu einer Erhöhung der Rauschleistung. Eine andere Möglich­keit ist die Verwendung von mehreren Empfangsantennen, auch Gruppenan­tenne genannt, da der Gewinn unter idealen Voraussetzungen mit der Anzahl der Elemente steigt, während die Rauschleistung gleich bleibt. In dieser Arbeit wird ein Konzept zur elektronischen Strahlformung ultrab­reitbandiger Signale vorgestellt. Ein FIR-Filter basiertes Strahlformungsnetz­werk wird dabei so erweitert, dass reale Einflüsse durch die Antennenelemen­te berücksichtigt werden können. Berechnungsgrundlagen werden für lineare und zirkulare Anordnungen der Antennenelemente vorgestellt. Ferner wird ein einfaches Konzept für ein analoges, elektronisch steuerbares FIR-Filter für den Mikrowellen-Frequenzbereich entwickelt und anhand eines vierstufi­gen Aufbaus in hybrider MIC-Technologie experimentell überprüft. Auf die­ser Basis wird ein Echtzeit-Demonstrator, bestehend aus einer zirkularen Gruppenantenne mit vier Elementen und fest eingestellten FIR-Filtern als Strahlformungsnetzwerk aufgebaut und für den Frequenzbereich von 1,5 GHz bis 2 GHz messtechnisch charakterisiert. Ein derartiges Experiment wurde im Rahmen dieser Arbeit erstmalig umgesetzt.

Duisburg, Essen, Univ., Diss., 2007 WIRELESS COMMUNICATIONS have undergone a drastic development in the past decade and have also been an important motivator for small antenna research. Introduction of new communications systems with wider system bands, evolution from single-band to multiband standard and a significant decrease in average of the terminal size are on the roadmap of the industry. All this combined with strict limitation due to the protection of mobile devices users from radiation exposure has created needs for adequate antenna solutions and better understanding of small antennas on small complex platforms. As answer to these great challenges, a purposeful investigation of a new concept for small antennas development on small platforms is proposed in this thesis. The performance of a small antenna mounted on a small conductive object, such as the chassis of a mobile phone is strongly affected by the size and shape of the object as well as the position of the small antenna on it. For a better understanding of the radiation properties of the radiating system constituted by a small antenna and the conductive chassis of a mobile phone device, this thesis conceptually considers the small antenna and the conductive chassis as two distinctive entities and separately investigates the radiation properties of the metal chassis. The idea here is that from the knowledge of the chassis radiation properties, one easily identifies the optimal location of the small antenna on the chassis and achieves a design of the small antenna to optimally meet some given requirements. Investigation of the conductive chassis radiation properties is based on the theory of characteristic modes. In fact, the theory of characteristic modes is a powerful analytical concept comparable to what modal analysis represents for waveguide circuits. At a frequency of interest this concept provides an insight on the contribution of different characteristic modes in the overall chassis radiation properties, which inexorably leads to the knowledge of the dominant characteristic mode. Resonant characteristic modes which dominates the radiation properties at their respective frequencies assign their radiation properties expressed in terms of resonance frequency and radiation quality factor to the conductive chassis. In the frame of this work, a numerical evaluation of characteristic modes on the surface of conductive chassis of mobile phones is proposed. This has been made possible through the solution of the resulting generalized eigenvalue problem representing the radiating system and leading to characteristic modes. For the resolution of the resulting generalized eigenvalue problem, an algorithm based on the QZ-decomposition is conceived and a corresponding software is developed. As application, results on the radiation properties as well as optimal location of the small antenna (considered as an exciter or coupler) to achieve an effective coupling with the chassis is presented for generic bar-type and folder-type phones. For the latter two cases of operation have been distinguished: the closed and open states. A simplified version of the theory of characteristic modes for the analysis of chassis radiation properties is presented in this thesis. It is based on the far-field radiation properties of a small radiator in free-space. The radiation vector is approximated by moments of different orders depending on the shape of the chassis. This practical approach operates by post-processing output data from standard commercial electromagnetic softwares. The purposeful utilization and the tuning of chassis modes for the design of multiband radiation characteristics on generic bar-type and folder-type geometries is demonstrated.

Duisburg, Essen, Univ., Diss., 2007 Aufgrund stetig kleiner werdender Strukturgrößen in integrierten Schaltungen werden die heutigen, meist optisch arbeitenden Standardverfahren der Fehleranalyse bald an ihre Auflösungsgrenzen stoßen. Eine Alternative kann die Rastersonden Strom/Spannungsmesstechnik darstellen. Diese, auf der Rasterkraftmikroskopie basierende Testtechnik, zeigte bereits gute Ergebnisse hinsichtlich ihrer Empfindlichkeit sowie Ortsauflösung auf dem Gebiet kontaktloser Spannungs- und Strommessungen. Um die Restriktionen von Hebelarmsystemen zu umgehen bietet sich der Einsatz eines Nadelsensors an, welcher vor allem hinsichtlich des Testzugriffs hebelarmbasierten Sensoren überlegen ist. Allerdings wurde dieser Sensor bezüglich seiner Einsetzbarkeit in der Fehleranalyse bis heute kaum erforscht. Ziel der vorliegenden Arbeit war daher die Entwicklung und Realisierung eines nadelsensorbasierten Testsystems für die Fehleranalyse an integrierten Schaltungen. Das im Rahmen dieser Arbeit entwickelte Testsystem wurde u.a. auf seine Strom- und Spannungsempfindlichkeit ebenso wie der erzielbaren Ortsauflösung hin untersucht. So konnte eine Stromempfindlichkeit von 100µA sowie eine Spannungsempfindlichkeit von 100µV demonstriert werden. Die Ortsauflösung konnte bei Strommessungen zu 4µm, bei Spannungsmessungen zu 70 nm bestimmt werden. Gerade auf dem Gebiet der Spannungsmessungen gelang es somit, die bis dahin mit herkömmlichen Messsonden erzielte Empfindlichkeit um zwei Größenordnungen zu verbessern. Abschließend konnten die in dieser Arbeit erzielten Ergebnisse anhand mehrerer Beispiele erfolgreich in die praktische Fehleranalyse übertragen werden. So gelang es zum Beispiel durch Strompfadverfolgung innerhalb einer integrierten Schaltung den Fehlerort zu lokalisieren. An einem weiteren integrierten Schaltkreis konnte aufgrund der hohen Spannungsempfindlichkeit der Spannungsabfall einer stromdurchflossenen Leiterbahn vermessen werden, welches es ermöglichte einen vorliegenden ESD Schaden zu lokalisieren und zu verifizieren.

Duisburg, Essen, Univ., Diss., 2007 Nowadays, more and more applications require systems that can interact with humans. Agents can be perceived as computing services that humans, or even other agents, can request in order to accomplish their tasks. Some services may be simple and others rather complex. A way to determine the best agents (services) to be implemented is to identify who the actors are in the object of study, which roles they play, and (if possible) what kind of knowledge they use. Socially Intelligent Agents (SIAs) are agent systems that are able to connect and interface with humans, i.e. robotic or computational systems that show aspects of human-style social intelligence. In addition to their relevance in application areas such as e-commerce and entertainment, building artefacts in software and hardware has been recognized as a powerful tool for establishing a science of social minds which is a constructive approach toward understanding social intelligence in humans and other animals. Social intelligence in humans and other animals has a number of fascinating facets and implications for the design of SIAs. Human beings are biological agents that are embodied members of a social environment and are autobiographic agents who have a unique personality. They are situated in time and space and interpret new experiences based on reconstructions of previous experiences. Due to their physical embodiment, they have a unique perspective on the world and a unique history: an autobiography. Also, humans are able to express and recognize emotions, that are important in regulating individual survival and problem-solving as well as social interactions. Like artificial intelligence research trend, SIA research trend can be pursued with different goals in mind. A deep AI approach seeks to simulate real social intelligence and processes. A shallow AI approach, which will be highlighted also within this thesis, aims to create artefacts that are not socially intelligent per se, but rather appear socially intelligent to a given user. The shallow approach does not seek to create social intelligence unless it is meaningful social intelligence vis-à-vis some user situation In order to develop believable SIAs we do not have to know how beliefs-desires and intentions actually relate to each other in the real minds of the people. If one wants to create the impression of an artificial social agent driven by beliefs and desires, it is enough to draw on investigations on how people with different cultural background, develop and use theories of mind to understand the behaviours of others. Therefore, SIA technology needs to model the folk-theory reasoning rather than the real thing. To a shallow AI approach, a model of mind based on folk-psychology is as valid as one based on cognitive theory. Distance education is understood as online learning that is technology-based training which encompasses both computer-assisted and Web-based training. These systems, which appear to offer something for everyone at any time, in any place, do not always live up to the great promise they offer. The usage of social intelligent agents in online learning environments can enable the design of “enhanced-learning environments” that allow for the development and the assessment of social competences as well as the common professional competences. Within this thesis it is shown how to corroborate affective theory with role theory with agent technology in a synchronous virtual environment in order to overcome several inconveniences of distance education systems. This research embraces also the shallow approach of SIA and aims to provide the first steps of a method for creating a believable life-like tutor agent which can partially replace human-teachers and assist the students in the process of learning. The starting point for this research came from the fact: anxious, angry or depressed students do not learn; people in these conditions do not absorb information efficiently, consequentially it is an illusion to think that learning environments that do not consider motivational and emotional factors are adequate.

Im Rahmen der Arbeit wurde ein Verfahren zur Bestimmung der Partikelgrößenverteilung unter Bedingungen entwickelt und realisiert, wie sie bei industriellen Syntheseprozessen von Pulvern vorherrschen. Die Partikelgrößen sind im submikronen Bereich. Die Prozessbedingungen, die das Messen von Partikelgrößenverteilungen behindern sind subatmospherische Drücke, hohe Partikelanzahlkonzentrationen, die Anwesenheit von Salzsäure sowie hohe Temperaturen und schwankende Drücke. Das zu Grunde liegende Messprinzip ist die differentielle Mobilitätsanalyse, die auf dem Bestimmen der Geschwindigkeit geladener Partikel in einem elektrischen Feld beruht. Das Prinzip ist für das Messen von Partikelgrößenverteilungen nanoskaliger gasgetragener Partikel (Aerosole) unter Laborbedingungen etabliert. Das Ziel der Arbeit war, das Verfahren so zu verändern, dass Messungen unter den oben genannten Bedingungen möglich sind. Die Tauglichkeit war an verschieden Prozessen zu zeigen. Alle hauptsächlichen Operationen des Messsystem sind von Veränderungen in Hinblick auf Prozesstauglichkeit betroffen: 1. Probenahme, 2. elektrische Aufladung der Partikel, 3. Fraktionierung im elektrischen Feld, 4. Konzentrationsmessung nach der Fraktionierung. Die dazu notwendigen Komponenten wurden mit Ausnahme der Aufladung neu entwickelt und im Labor untersucht. Zur elektrischen Aufladung wird eine UV Bestrahlungseinheit verwandt. Sie birgt gegenüber der Aufladung mit einem β-Strahler nicht die Gefahr radioaktiver Kontamination. Der Grad der Aufladung hängt jedoch vom Partikelmaterial, von der Partikelgröße, vom Trägergas, seiner Temperatur und seinem Druck ab. Die Aufladung wurde durch ein mathematisches Modell beschrieben, das für die jeweiligen Messbedingungen numerisch gelöst wurde. Die Komponenten wurden zu einem kompakten Gerät zusammengefügt, das durch neu entwickelte Software und Schnittstellen von einem PC gesteuert wird. Ein großes Augenmerk liegt auf der Überführung des rohen Messsignals in die Partikelgrößenverteilung, die unter Berücksichtigung der Messbedingungen insbesondere auf die Partikelaufladung erfolgt. Das Gerät wurde an Anlagen zur Synthese von SiO2 Nanopartikeln der Degussa AG angewandt. Ein Einfluss von Prozessgrößen auf die Partikelgrößenverteilung wurde beobachtet. Die Eignung des Verfahrens für industrielle Syntheseprozesse nanoskaliger Pulver wurde gezeigt.

A concept for wideband electronic steered array using analogue FIR-filters has been formulated. This paper focuses on microwave applications, e.g. wideband antenna radiation pattern, where we explain the design of a desired radiation pattern for bandwidth 2:1. Therefore we consider a linear narrowband radiation pattern and expand it to a wideband array synthesis. The requirements for higher bandwidth, e.g. 3:1 in ultra wideband (UWB) communication systems, w.r.t. different design parameters are obtained. Finally, we propose the requirements for practical realization at microwave signal level.

Dezentrale Energiesysteme erfreuen sich durch finanzielle Anreize, mit denen umweltpoltische Ziele unterstützt werden, immer größerer Beliebtheit. Im Fachgebiet „Elektrische Anlagen und Netze” wurde ein flexibles Simulationswerkzeug entwickelt, das die Eigenschaften der einzelnen installierten Komponenten sowie ihr Zusammenspiel beim Betrieb des Gesamtsystems detailliert simuliert. So wird zum Beispiel eine vergleichende Untersuchung unterschiedlicher Varianten einer Photovoltaik-basierten Elektrizitätsversorgung für ein einzelnes abgelegenes Wohngebäude möglich., A comprehensive simulation tool with high temporal resolution was developed, allowing to overcome the current practice of having the design and dimensioning of energy systems with dispersed generation rely only on global energy harvest considerations. The simulation system allows to investigate the characteristics of dispersed generation components to be installed, as well as their control and interaction within a complete supply system, under high temporal resolution and simulation fidelity, thus providing a reasonable basis for efficient plant design. Device rating and control parameters of design variants can be optimized suitably by use of a superimposed genetic algorithm based optimization approach. Example application for the sound investigation of various configurations of PV based home electricity supply proves the versatile usability of the tool. Even if in the study presented here the focus was purely on electrical supply, the simulation tool is also capable of modeling combined heat and power systems; of course, the interdependences in dimensioning and control are then much more complicated than in the cases shown here., UNIKATE: Berichte aus Forschung und Lehre, no. 31Ingenieurwissenschaften - Von Nano bis Giga: Computersimulationen, p. 8

Handys haben unseren Alltag erobert: Fast jede(r) Deutsche besitzt eins. Die Simulation von Mobilfunknetzen ist vor allem angesichts ihrer zunehmenden Komplexität der Systeme – Stichworte sind hier zum Beispiel Internationalisierung und Kompatibilität – sinnvoll. So ist es möglich, bei Plänen für Weiterentwicklungen und Ausbau alle zu berücksichtigenden Parameter mit einzubeziehen., Digital cellular networks have experienced a rapid growth since their introduction in the early nineties of the last century. Nowadays mobile phones belong to the personal belongings for the daily life of many people. However, digital cellular networks are very complex systems, and their development and deployment costs a lot of money. Due to their complexity it is not possible to overlook all parameters and their influence on system performance from scratch. The only feasible way of evaluating such complex systems in detail is by means of computer simulations. However, again because of the complexity a single simulation for the whole system, which takes every aspect of the system into account, is not possible. Instead, one splits the system in a link level simulator and a system level simulator. The link level simulator covers all details of a single link between one or more transmit antennas and one or more receive antennas. A core component of the link level simulator is the channel model, which models the properties of the mobile channel between the antennas. Because of the great variability of mobile channels only statistical channel models are promising. But also of the kind of statistical models there exist a large variety. In this paper simulations are shown which were performed at the Department of Communication Technologies at the University Duisburg- Essen. There are examples of channel impulse responses shown as they are experienced by the base stations and mobile stations. It is demonstrated that both types of stations typically experience very different channels. Furthermore, there are link level simulations. These show the influence of different algorithms on the bit error ratio in nonfading and fading channels. Finally, there are simulation results shown which demonstrate the behavior of a whole mobile network., UNIKATE: Berichte aus Forschung und Lehre, no. 31Ingenieurwissenschaften - Von Nano bis Giga: Computersimulationen, p. 74

Duisburg, Essen, Univ., Diss., 2007 With the increasing demand for higher performance, safety and reliability of dynamic systems, fault diagnosis has received more and more attention. The observer-based strategy is one of the active research fields, which is widely used to construct model-based fault detection systems for technical processes which can be well modelled as linear time invariant systems. Fault diagnosis for nonlinear system is an active area of research. Observer-based fault detection includes two stages, residual generation and residual evaluation. The residual generation problems and residual evaluation problems for systems with only deterministic disturbances or stochastic disturbances have been widely separately studied. Recently some efforts have been made in the integrated design of fault detection systems for systems with deterministic disturbances and stochastic disturbances. Recently, successful results of applying Takagi-Sugeno (TS) fuzzy model-based technique to solve fault detection and isolation problems met in the nonlinear system have been achieved. With TS model, a nonlinear dynamic system can be linearised around a number of operating points. Each linear model represents the local system behaviour around the operating point. The global system behaviour is described by a fuzzy IF-THEN rules which represent local linear input/output relations of the nonlinear system. Applying the Takagi-Sugeno fuzzy model based technique to solve fault detection and isolation problems in the nonlinear systems is active area of research. The main contribution of this thesis is the design of robust fault detection systems based on Takagi-Sugeno fuzzy filters. There are a number of schemes to achieve robustness problem in fault detection. One of them is to introduce a performance index. It is function of unknown input signal and fault signal. For continuous time system, first, robust fault detection system will be designed for nonlinear system with only deterministic disturbance as unknown inputs. Second, robust fault detection system will be designed for nonlinear system with deterministic disturbance as unknown inputs and parameter uncertainties. Finally, robust fault detection system will be designed for nonlinear system with deterministic disturbance as unknown inputs and stated delay. Sufficient conditions for solving robustness problem are given in terms of Linear Matrix Inequalities (LMIs). For discrete time system, kalman filter design for nonlinear system is diffcult. In this thesis new fault detection approach will be presented for nonlinear system with only stochastic disturbance. Fault Detection (FD) system for each local subsystem is design by solving the corresponding Discrete-time Algebraic Riccati Equation (DARE). Optimisation algorithm based on minimizing the residual covariance matrix is used to obtain a robust FD system optimised for global system behaviour. The optimisation algorithm is established in terms of LMIs. The different robust fault diagnosis system are developed to detect sensor faults of vehicle lateral dynamic control systems.

Duisburg, Essen, Univ., Diss., 2004 Tin oxide is one of the most important semiconducting materials for gas-sensing applications. The use of nanocrystalline particle films in gas-sensing devices significantly enhances the sensitivity of the devices due to the larger specific surface area and changes in the electrical properties. To understand the gas-sensing mechanism and to determine the influence of nanocrystallinity on the gas-sensing behaviour, it is important to carry out detailed electrical characterisation of the semiconductor material having well defined nanoparticle film structures. For this investigation, tin oxide (SnOx) nanoparticles were prepared using a gas phase synthesis set-up with SnO powder as the initial material. This set-up allowed the deposition of size-selected nanoparticles in the range of 10 to 35 nm and having a geometric standard deviation of sigma < 1.1, to form a nanoparticle film. To obtain information about the morphology, crystallographic structure and stoichiometry of the nanoparticles and nanoparticle films the well-known characterisation methods TEM, AES, STM, XRD and RBS were used. An automated measurement set-up was designed and fabricated for the measurement of the gas sensor characteristics and electrical parameters of nanostructured SnOx thin layers in controlled gas environments in a temperature range from room temperature to 300 °C. The set-up consisted of a gas environment chamber, a specially designed microhotplate and microhotplate holder together with a control, supply and electrical measurement equipment. Sensitivity and dynamic behaviour measurements were carried out by observing changes in the electrical conductance on exposure of gases, such as CO, CH4, C2H5OH, H2 and NO diluted in synthetic air. A systematic study was made to examine the material characteristics (particle size and chemical composition) as influenced by the process parameters of the synthesis set-up and the gas-sensing properties of SnOx layers. For the first time, it has been demonstrated conclusively that a decreasing particle size leads to an increased sensitivity and decreased response time. The effect is especially evident in the case of layers with particle size smaller than 20 nm. In addition, in-situ oxidised and post-annealed tin oxide nanoparticle films have higher sensitivity values and the maximum sensitivity shifts to lower operating temperature. The results of this work lead to a better understanding and improvement of tailored tin oxide gas sensors using monodisperse nanoparticles.

Duisburg, Essen, Univ., Diss., 2004 In the field of radiological diagnostics, especially for the computed tomography a large number of photodetector elements (so called Pixels) is needed to assemble a large-area X-Ray-sensitive detector. These pixels should provide very high sensitivity, a very large dynamic range and a high signal-to-noise-ratio. Moreover, an in-pixel digitization of the signals is desired. To meet these specifications, a digital CMOS-Pixel comprising a special type of photodiode and a single-loop sigma-delta-modulator was developed, theoretically analyzed, fabricated and characterized. A matrix of 4x4 digital CMOS-pixels with each of them consuming an area of 1mm² has been fabricated. For further signal processing the concept of a multichannel decimation filter is presented.

Duisburg, Essen, Univ., Diss., 2004 Within the scope of this work, the possibilities of implantable microelectronic systems for giving back a certain vision to blind people are demonstrated. With respect to recent developments in ophthalmologic implants, two examples are presented in particular. The Intraocular Vision Aid (IoVA) has been developed for blind people whose cornea of the eye is opaque due to illness or accident. The Retina Implant (RI) has been developed for blind people whose photoreceptors in the human retina are degenerating. In both of the presented ophthalmologic implants, microelectronic circuits are applied in optical free space links, whose concepts and technical feasibility is the main objective of this work. Furthermore, the structural-design technologies developed for the application in eye implants are demonstrated by means of the Intraocular Vision Aid. In the broader sense, this includes the pilot development of a miniature LED-array, connected to a CMOS driver circuit by using a hybrid packaging of integrated circuits

Duisburg, Essen, Univ., Diss., 2003 This thesis analyzes in what respect human biosignals are suitable for communication among man and machine. An exemplary communication system is presented which provides the operation of a computer mouse by electro-oculographical signals (EOG) and head movements of the user. Special eyeglasses with integrated electrodes, amplifiers and acceleration sensors measure the biosignals and transfer them to computer-aided signal processing. In order to discuss here the relationship between 'biosignals' and 'information' it is necessary to define precisely these central quantities of man-machine communication. The applied information model with its five hierarchical levels statistics, syntax, semantics, pragmatics, and apobetics*, and empirically derived laws about information achieves this goal. Therefore, only under certain conditions the energetic-material biosignals of the individual are information carriers concurrently. It is compellingly concluded from the model that information can only be transmitted if the user of the man-machine system has voluntarily influenceable biosignals. Individually dependent, many bioelectric signals (among other biosignals) fulfil this condition: EOG, EMG and EEG signals, e. g.. Therefore, they are potentially suitable for communication in various man-machine systems. The operational man-machine system is based on the principles of the above information model and so exemplarily confirms the general statements. Obviously, biological signals for realistic man-machine communication must generally correspond to this information model. Keywords: biosignal, communication, man-machine System, information, EOG signal, head movement, computer mouse (* Derived from Greek 'apobeinon' = result, success, conclusion).

Duisburg, Essen, Univ., Diss., 2003 Field programmable logic devices provide a cost and time efficient way to create new microcontroller designs. These qualities are particular useful and desirable for high temperature applications in hostile environments above 250 °C. Starting from summarizing the present state-of-the-art in SIMOX high temperature developement the presented work introduces HTPAL devices as an example of a new class of programmable logic devices. These class is characterized by a range of features that were not available in am similar combination before: a wide temperature range from -50 °C up to 250 °C and above, high resistance against ionizing radiation, flexible and permanent field programmability by the end user. The wide temperature range results from an avantageous circuit structure combined with the SIMOX technology. Permanent field programmability is achieved by using a new One-time-programmable (OTP) MOSFET device, called a TOXFET. The new device consists of a high voltage NMOS transistor combined with a thin tunnel oxide to initially insulate the drain lead from the transistor structure.

Duisburg, Essen, Univ., Diss., 2003 Heterogeneous systems consist of a multitude of system components, which are derived from different physical and technical domains. The complexity of this components constantly increases thereby. For the functionality of the heterogeneous overall system the faultless interaction of these system components and frequently also the interaction with the physical influences of the environment are of crucial importance. In this thesis computer-aided design methods are examined, which support the validation of the system functionality, the verification of the separate design steps and the optimization of the heterogeneous system during a model-based top-down design. In particular for the range of microsystems and the range of mechatronic systems with hardware/software coupling simulation-based methods are presented, which facilitate a continuous model-based design of such systems.

Zugl.: Duisburg, Essen, Univ., Diss., 2003 Bei der PLC 'Powerline Communication' werden auf bestehenden Energieleitungssystemen, deren Eigenschaften nicht für hochfrequente Vorgänge optimiert sind, Daten im Frequenzbereich von 9kHz bis 30MHz übertragen. Aufgrund der Energieleitungseigenschaften wird die hochfrequente Signalenergie zum Teil abgestrahlt, so das aus informationstechnischer Sicht eine zusätzliche Signaldämpfung auftritt. Aus Sicht der EMV bedeutet das u.U. eine Beeinträchtigung der vorhandenen Funkdienste. In dieser Arbeit wird systematisch untersucht, mit welchen Abstrahlungen in PLC-Systemen zu rechnen ist und inwieweit diese tatsächlich problematisch hinsichtlich der EMV werden können. Ziel ist es, den Entwicklungsprozess für PLC-Systeme ausgehend von den strikten Randbedingungen der leitungsgeführten und abgestrahlten Störgrößen voranzutreiben. ... In dieser Arbeit wird eine Versuchsinstallation aufgebaut, mit der die Fernauslesung eines Energiezählers via PLC demonstriert wird. Prinzipiell werden aus den Daten nachher Lastprofil-Informationen entsprechend dem Verbraucherzustand (Lastmanagement auch mittels PLC) gewonnen. Dadurch kann eine dynamische Tarifumschaltung zur Optimierung der Tageslast erstellt werden. (Aus der Einleitung)

This paper introduces several feature extraction and selection techniques.Previous studies showed good results when neural networks are applied to the small-signal stability assessment. However the use of reduction techniques can decrease the number of features and thus the number of quantities, which need to be observed, measured and transmitted, respectively.

This paper deals with suitable approaches for fast assessment of oscillatory stability of large interconnected power systems within power system operation. Beside voltage stability and transient stability, oscillatory stability has to be assessed, too. It can be shown, that parallel eigenvalue computation using a parallel variant of Arnoldi method can reduce the time necessary for eigenvalue computation of large power systems.

This habilitation thesis has to primary goals. First, the often mentioned prejudice against higher order statistics, that a great number of data is necessary for accurate parameter estimation, should be proven. In fact, we show by theoretical analysis of different applications for higher order statistics that this prejudice is not true in general. The main conclusion is that the use of higher order statistics has to be proven case-by-case. The second goal is to present a new concept - so-called modulated cumulants - for identification of linear time invariant system. We show by simulations that these concept leads to very accurate estimates compared to known methods.