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Drag reduction in flows with clay mineral particles was experimentally studied. Experiments with clay suspensions flowing over smooth, gravel, and stone beds proved that resistance of the flow may be considerably reduced if the flow boundary is rough. The friction factor of flows of high clay concentrations over the gravel bed was less than half the clear-water flow at the same discharge and and energy slope. At low concentrations, a floc of clay particles having a long-chain structure may damp turbulence and result in drag reduction. At high concentrations, all flocs in clay suspension connect together and form a three-dimensional net structure, which affects the resistance in two ways: (1) By damping turbulence; (2) by increasing the viscous resistance. For flows over rough boundaries, turbulent shear dominates the resistance, and high clay concentrations cause drag reduction. For flows over a smooth bed, the effect of damping turbulence was counterbalanced by the effect of increasing viscous resistance; therefore, no drag reduction occurred.

Today's businesses rely ever more on dependable service provision deployed on information and communications technology (ICT) infrastructures. Service dependability is highly influenced by the properties of individual infrastructure components. Combining these properties for consistent dependability analysis is challenging as every service requester might use a different set of components during service usage, constituting the user-perceived view on a service. This paper presents a methodology to evaluate user-perceived instantaneous service availability. It uses three input models: (1) The ICT infrastructure, with failure rates, repair rates and deployment times of all components, (2) an abstract description of complex hierarchical services, (3) a mapping that contains concrete ICT components for the service pair requester and provider, as well as existing replicas, and a duration of usage. The presented methodology sets up the basis for automatic generation of availability models from those parts of the ICT infrastructure needed during provision for the specified pair. To calculate instantaneous availability, the age of the ICT components, the order and time of their usage during service provision are taken into account. The methodology supports generation of different availability models, exemplarily providing reliability block diagrams and fault-trees. We demonstrate the feasibility of the proposed approach by applying it to parts of the network infrastructure of University of Lugano, Switzerland.

An ever-increasing number of both functional and non-functional requirements has resulted in growing system complexity which demands for new solutions in system modeling and evaluation. As a remedy, service-oriented architecture (SOA) proposes services as basic building elements of system design. Service dependability is highly dependent on the properties of the underlying information and communications technology (ICT) infrastructure. This is especially true for the user-perceived dependability of a specific pair service client and provider as every pair can utilize different ICT components. We provide a model for the description of ICT components and their non-functional properties based on the Unified Modeling Language (UML). Given a service description, a network topology model and a pair service client and provider, we propose a methodology to automatically identify relevant ICT components and generate a user-perceived service infrastructure model (UPSIM). We demonstrate the feasibility of the methodology by applying it to parts of the service network infrastructure at University of Lugano (USI), Switzerland. We then show how this methodology can be used to facilitate user-perceived service dependability analysis.

SUMMARY 1. In order to quantify the effects of substratum roughness on shear stress and Fliesswasserstammtisch-(FST)-hemisphere movement, hemispheres were calibrated against shear stress in a laboratory flume with fully developed turbulent flow. In five different runs, substratum roughness, water depth and location of hemispheres in relation to the surrounding particles, were varied. 2. FST-hemisphere results were strongly influenced by bottom topography. In the case of hydraulically rough flow a linear relationship exists between shear stress (χc) and hemisphere density (ρh), whereas in the case of quasi-smooth flow a power law was obtained for the χc/ρh, relationship. Shear stress for a given hemisphere and relative roughness h/k > 4 (h= water depth; k= height of the roughness elements) deviated up to one order of magnitude between roughnesses. In water depths, where h/k 4, the χc/ρh relationships are dependent on the ratio h/k, due to water surface effects on hemisphere movement. In the case of k = d90=rh (d90= characteristic diameter of the largest particles of the bottom substratum; rh= radius of the hemispheres), the location of the hemispheres in respect to the roughness elements is of secondary importance. 3. In the case of hydraulically rough flow and wake interference between the roughness elements, the turbulent flow field close to the substratum is three-layered, each layer being characterized by its own velocity distribution laws (Dittrich & Hammann de Salazar, 1993). Depending on the height of the roughness elements, FST-hemispheres will be subjected mainly to flow forces of the near-bed layer (in rough substrata) or to flow forces distant from the near-bed zone (in fine substrata). The dominant flow forces acting on bottom particles, organisms, or FST-hemispheres are shear force and lift force. 4. The Local Shear Stress Model (Lamouroux et al., 1992) leads to a correct prediction of hemisphere distribution in a stream with a cobble size substratum, but to an overestimation of hemisphere numbers in a sandy-bottom stream. The substratum-dependent shear stress values therefore need to be entered into the model and a measure of substratum roughness included. 5. Macroinvertebrate abundance correlates well with the movement of FST-hemispheres. Samples from points with very high or very low roughness did not contribute to scatter in the data, indicating that the sum of the near-bed flow forces is relevant to macroinvertebrate distribution, not shear stress alone. We conclude, that FST-hemispheres are well suited to characterize near-bottom hydraulics and therefore the microhabitat of the benthos.

Drag forces exerted by single cylinders in an in-line and staggered multicylinder array were measured in a laboratory flume. The measurements were used to investigate the spatial variability of the drag forces, spatially averaged drag forces, and drag coefficients. The results showed that both individual drag forces and drag coefficients varied between ±30% from the spatially averaged mean. The data are also used to test a computational approach for the determination of the mean drag coefficient of multicylinder arrays taking into account the wake flow structure.

Service discovery is a fundamental concept in service networks. It provides networks with the capability to publish, browse and locate service instances. Service discovery is thus the precondition for a service network to operate correctly and for the services to be available. In the last decade, decentralized service discovery mechanisms have become increasingly popular. Especially in ad-hoc scenarios - such as ad-hoc wireless networks - they are an integral part of auto-configuring service networks. Albeit the fact that auto-configuring networks are increasingly used in application domains where dependability is a major issue, these environments are inherently unreliable. In this paper, we examine the dependability of decentralized service discovery. We simulate service networks that are automatically configured by Zeroconf technologies. Since discovery is a time-critical operation, we evaluate responsiveness - the probability to perform some action on time even in the presence of faults - of domain name system (DNS) based service discovery under influence of packet loss. We show that responsiveness decreases significantly already with moderate packet loss and becomes practicably unacceptable with higher packet loss.

Figure 2.1 shows the principle circuit of an inverter fed 3-phase AC motor with three phase windings u, v and w. The three phase voltages are applied by three pairs of semiconductor switches v u+/v u−, v v+/v v- and v w+/v w− with amplitude, frequency and phase angle defined by microcontroller calculated pulse patterns. The inverter is fed by the DC link voltage U DC . In our example, a transistor inverter is used, which is today realized preferably with IGBTs.

The current control loop plays a decisive role in a 3-phase drive system operated with field orientation. The design of the superimposed mechanical systems (speed and position control) wishes for an inner current control loop with ideal behaviour: With undelayed impression of the stator current.

For the clear specification of the electromagnetic processes in 3-phase AC machines and as a starting point for control design, equivalent circuits which are based on the representation of the physical quantities as complex space vectors in a stator-fixed coordinate system will be a very useful tool. A first starting-point and also a base for start values of a more exact estimation will be provided by the name plate or by the rated data of the motor. For a more exact parameter setting off-line identification methods which provide estimated values of motor parameters during a test run in standstill are discussed.

Due to the mechanical wear at the slip-rings wound rotor induction machines are only rarely used as motors today. Regardless, they gain increasing importance for generator applications in wind and water power plants. Their main advantage in this area is that the inverter in the rotor circuit can be designed to a smaller capacity with regard to the maximum generator output. Furthermore, the DFIM can be ran in a comparatively large slip range which allows for better utilization of the available wind energy.

A typical problem of the field-orientated control consists of the system having to evaluate the actual value of the rotor flux without flux sensors through a model from the measurable terminal quantities of the motor and the speed (cf. Sect. 4.4). The often used current-speed model contains the rotor time constant of the motor as an essential parameter whose exact knowledge influences decisively the quality of the control. This fact and the working point dependence of this parameter motivate the introduction of special measures to primarily compensate the temperature dependence of the rotor resistance. To achieve this, two approaches are in principle conceivable: Either the rotor flux model can be completed by an on-line adaptation method which corrects the rotor resistance permanently, or the rotor flux is estimated by an observer which is insensitive against variations of the rotor resistance. The first approach is subject of this chapter.

This chapter aims to explain principles of the actual-value measurement to highlight its problems to answer some related questions of the field orientation.

Der Texttyp der literarischen Utopie lässt sich im modallogischen Sinne als Entwurf einer denkbaren möglichen Welt charakterisieren. Anhand paradigmatischer Fallstudien zu Louis-Sébastien Merciers (1740-1814) L’An 2440 (1770/1771) und Christoph Martin Wielands (1733-1813) Der goldne Spiegel (1772) soll versucht werden, systematische Bausteine für ein textanalytisches Utopie-Modell zu gewinnen. In einem dreistufigen textanalytischen Zugriff werden (i) alethische (auf Weltstrukturen relativierte) und epistemische (auf Wissensstände relativierte) Modalitäten, (ii) deontische (auf Werte-/ Normensysteme relativierte) Modalitäten sowie (iii) temporale (auf Zeitintervalle relativierte) Aspekte in den Texten rekonstruiert und innerhalb eines logischen Rahmens für die Textanalyse fruchtbar gemacht. Im Zentrum steht der Versuch, Utopie als textintern semantisch zweigeteiltes semiotisches Strukturschema zu definieren und damit systematische Konvergenzen zwischen pro- und retrospektiven Zeitutopien („Ucrhonien“) herauszuarbeiten. Es zeigt sich dabei, dass die innovativen utopischen Texttypen der Spätaufklärung elementare Unverträglichkeiten in ihren innertextlichen Aussagekomplexen und ihren Modalisierungen aufweisen. Da gerade Texttypen der Utopie als eminenter Indikator für denkgeschichtlichen Wandel aufgefasst werden kann, ergeben sich hieraus Folgerungen für die Analyse der Denk-, Wissens- und Diskurssystems dieser Subepoche., Les utopies comme mondes possibles concevables. Éléments en vue d'un modèle de l'utopie propre à l'analyse textuelle à partir des cas paradigmatiques L'An 2440 (1770/1771) de Mercier et Der goldne Spiegel (1772) de Wieland. La forme textuelle que constitue l’utopie littéraire peut être caractérisée, dans le sens de la logique modale, comme l’esquisse d’un monde possible concevable. À partir de l’étude des cas paradigmatiques que constituent L'An 2440 (1770/1771) de Louis- Sébastien Mercier (1740-1814) et Der goldne Spiegel (1772) de Christoph Martin Wieland (1733-1813), il s’agit ici de dégager des éléments systématiques en vue d’un modèle de l’utopie propre à l’analyse textuelle. Dans une approche analytique en trois temps, les modalités (i) alétiques (relatives aux structures propres au monde) et épistémiques (relatives aux savoirs), les modalités (ii) déontiques (relatives aux systèmes de normes et de valeurs) ainsi que les aspects (iii) temporels (relatifs aux intervalles temporels) seront reconstruits dans les textes et rendus exploitables dans un cadre logique pour l’analyse textuelle. Au centre du propos se trouve la tentative de définir l’utopie comme un schéma structurel sémiotique sémantiquement divisé, afin de mettre en évidence des convergences systématiques entre des utopies temporelles («uchronies») pro- et rétrospectives. Ce faisant, il apparaît que les formes textuelles utopiques innovatives de l'Aufklärung tardive sont porteuses d’incompatibilités fondamentales dans les complexes discursifs intratextuels qui leur sont propres ainsi que dans leurs modalisations. La forme textuelle de l’utopie pouvant être appréhendée comme l’indicateur probant d’une évolution dans l’histoire de la pensée, il en résulte un certain nombre de conclusions pour l’analyse des systèmes de pensée, de savoirs et de discours propres à cette phase., Dittrich Andreas. Utopien als denkbare mögliche Welten. Bausteine für ein textanalytisches Utopie-Modell anhand paradigmatischer Fallstudien zu Mercier : L'An 2440 (1770/71) und Wieland Der goldne Spiegel (1772). In: Recherches germaniques, N°34, 2004. pp. 31-80.

The evolving liberalisation of the European telecommunication markets will result in a growing competition among service and network providers. In such an environment the rapid development and deployment of new telecommunication services take on increasing significance. The use of distributed object-oriented platforms that provide a set of common and generic building blocks for applications helps to reduce the efforts required to implement new telecommunication services. Therefore, there is a strong trend towards object-orientation in modelling and realisation of telecommunication services, especially in the employment of industry platform standards such as OMG/CORBA. Another key to the success of a service or network provider in this future environment is the comprehensive, flexible and integrated management of its telecommunication services. Traditionally, the state of the art in management-oriented applications is characterised by the OSI management and Internet management standards. However, specifically in the telecommunications world the Telecommunications Management Network (TMN) standard is becoming more and more important. This paper describes how a specific TMN-based management platform, i.e., the ANDROMEDA platform, is integrated within a CORBA-based environment. It outlines the required changes to the existing management platform and identifies the problems which are encountered during such a migration.

An experimental investigation of wind-induced flow and mixing processes in a two-layered system influenced by a thin film persisting on the water surface is reported in this study. Detailed documentation and description of the wind-induced flow and mixing processes are given. The entrainment rates and flow pattern depend on two dimensionless numbers, one characterizing the influence of surface films, the other characterizing the response of stratified basins to wind stress in the absence of surface films. The differences between the flow and mixing processes of a two-layered system influenced and not influenced by a surface film are pointed out and discussed.

There are many driving forces which have compelled telecommunication operators and vendors to seek new solutions in telecommunications management. Increased competition has led to an increased focus on how traditional operators can do their business better through the use of integrated service and network management systems. Moreover, there is a need to integrate legacy applications and new applications, all of which could be written in different languages, perhaps running on different platforms, and almost certainly distributed over a network. CORBA has been recognised as a key technology solution. Based on the case studies performed for the ACTS project PROSPECT, this paper discusses the advantages and disadvantages of TMN (Telecommunications Management Network) and CORBA regarding network and service management, and proposes a phased approach for TMN-CORBA co-existence in the telecommunications management arena based on the Management Systems Framework of the Network Management Forum. Moreover, it presents some initial ideas concerning required basic management functionality that serve as a background for the CORBA/TMN gateway functionality to be implemented within the PROSPECT trial network.