Deposition and characterization of low-loss epitaxial non-linear dielectric thin films for microwave devices

Abstract

Oxide ferroelectric thin films for frequency-tunable microwave devices, in which the dielectric constant of the non-linear dielectric is varied by application of electric fields, have been deposited using PLD. We have fabricated single phase epitaxial Ba_0.6Sr_0.4TiO₃ and KTaO₃ thin film capacitors for applications at 300K and 77K, respectively. Single phase KTaO₃ films were obtained only with excess potassium source in the target along with KTaO₃ perovskite phase. The films have been characterized for structure and morphology by X-ray diffraction and AFM. The dielectric properties were measured in the low frequency range from 100 kHz to 10 MHz, using interdigitated capacitors. Low loss tangents (0.002 at 300K) were observed for highly oriented Ba_0.6Sr_0.4TiO₃ films. The importance of low losses for various devices is discussed and the dielectric constants, loss tangents and tunability of these films are reported in this paper.     

Broadening the Scope of Hypermedia Principles

Hypermedia systems have been implemented for such a wide range of applications that one must wonder whether their principles should not be included among the building blocks of computer environments themselves. In this paper, we argue that this would indeed be desirable and present a model on which such extension could be based.

After a brief review of hypermedia principles and the terminology used in this paper, we give examples of several computer applications in which hypermedia already are or could advantageously be used. We then suggest that most computer applications would greatly benefit if hypermedia were extended from isolated applications to a system-wide facility and that this could substantially simplify implementation of new hypermedia applications. This claim is then generalized and it is shown that extending hypermedia concepts to the organization of the computer environment itself --- the file system --- and to the user interface would make computer environments more flexible and easier to use.

We then list the main characteristics of such a ‘hyperenvironment’ and conclude the paper with an outline of its implementation model and an example.     

The TTA's Approach to Resilience after Transient Upsets

The Time-Triggered Architecture, as architecture for safety-critical real-time applications, incorporates fault-tolerance mechanisms to ensure correct system operation despite failures. The primary fault hypothesis of the TTA claims to tolerate either the arbitrary failure of any one of its nodes or the passively arbitrary failure of any one of its communication channels. To cover these failure modes, active redundancy techniques are used, which basically means that nodes and channels are physically replicated. The primary fault hypothesis, is, however, not strong enough for certain applications that have to tolerate transient upsets of multiple, possibly all, components in the system. Such a transient upset of the system may break up the synchrony of the nodes and leave disjoined sets of nodes synchronized to each other while the overall synchronization is lost. Although the TTA provides a clique avoidance algorithm that is able to correct a wide class of such multiple transient failures, a stronger algorithm is needed for full coverage. In this paper we discuss a secondary fault hypothesis for the TTA that addresses the transient upset of multiple components and present a new clique resolving algorithm based on the TTA's integrated diagnosis and startup service. This paper is a revised version of Steiner et al. (2003). This work has been funded by the European Project DECOS (Project number: IST-511764). Michael Paulitsch is currently affiliated with Honeywell International.     

Das MPEG-21 Multimedia-Framework

Zusammenfassung  Der MPEG-21-Standard wird seit Anfang 2000 innerhalb der Moving Picture Experts Group (MPEG) [8] entwickelt und stellt im Wesentlichen Beschreibungsformate, in MPEG-21 als Werkzeuge bezeichnet, zum transparenten, interoperablen Austausch von digitalen Multimediainhalten zur Verfügung.     

Conjugate heat transfer through nano scale porous media to optimize vacuum insulation panels with lattice Boltzmann methods

Due to reduced thermal conductivity, vacuum insulation panels (VIPs) provide significant thermal insulation performance. Our novel vacuum panels operate at reduced pressure and are filled with a powder of precipitated silicic acid to further hinder convection and provide static stability against atmospheric pressure. To obtain an in depth understanding of heat transfer mechanisms, their interactions and their dependencies inside VIPs, detailed microscale simulations are conducted.Particle characteristics for silica are used with a discrete element method (DEM) simulation, using open source software Yade-DEM, to generate a periodic compressed packing of precipitated silicic acid particles. This aggregate packing is then imported into OpenLB (openlb.net) as a fully resolved geometry, and used to study the effects on heat transfer at the microscale. A three dimensional Lattice Boltzmann method (LBM) for conjugated heat transfer is implemented with open source software OpenLB, which is extended to include radiative heat transport. The infrared intensity distribution is solved and coupled with the temperature through the emissivity, absorption and scattering of the studied media using the radiative transfer equation by means of LBM. This new holistic approach provides a distinct advantage over similar porous media approaches by providing direct control and tuning of particle packing characteristics such as aggregate size, shape and pore size distributions and studying their influence directly on conduction and radiation independently. Our aim is to generate one holistic tool which can be used to generate silica geometry and then simulate automatically the thermal conductivity through the generated geometry.     

Impairment of long-term associative memory in aging snails (Lymnaea stagnalis).

Age-dependent impairment in learning and memory functions occurs in many animal species, including humans. Although cell death contributes to age-related cognitive impairment in pathological forms of aging, learning and memory deficiencies develop with age even without substantial cell death. The molecular and cellular basis of this biological aging process is not well understood but seems to involve a decline in the aging brain's capacity for experience-dependent plasticity. To aid in resolving this issue, we used a simple snail appetitive classical conditioning paradigm in which the underlying molecular, cellular, and neural network functions can be directly linked to age-associated learning and memory performance (i.e., the Lymnaea stagnalis feeding system). Our results indicate that age does not affect the acquisition of appetitive memory but that retention and/or consolidation of long-term memory become progressively impaired with advancing age. The latter phenomenon correlates with declining electrophysiological excitability in key neurons controlling the feeding behavior. Together, these results present the Lymnaea feeding system as a powerful paradigm for investigations of cellular and molecular foundations of biological aging in the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manufacturing and assembly of the plasma- and outer vessel of the cryostat for Wendelstein 7-X

Wendelstein 7-X is an advanced helical stellarator, which is presently under construction at the Greifswald branch of IPP. A set of 70 superconducting coils arranged in five modules provides a twisted shaped magnetic cage for the plasma and allows steady state operation. Operation of the magnet system at cryogenic temperatures requires a cryostat which provides thermal protection and gives access to the plasma. The main components of the cryostat are the plasma vessel, the outer vessel, the ports, and the thermal insulation. The German company, MAN Diesel & Turbo SE Deggendorf (former MAN DWE GmbH Deggendorf), is responsible for the manufacture and assembly of the plasma vessel, the outer vessel and the thermal insulation. This paper describes the manufacturing and assembly technology of the plasma and outer vessel of the cryostat for Wendelstein 7-X.     

Virtualisierung im Future Internet Virtualisierungsmethoden und Anwendungen

Das Future Internet stellt sich der Herausforderung, die Verkn?cherung und die Unzul?nglichkeiten des heutigen Internets zu überwinden. Es soll beispielsweise robust, zuverl?ssig und fehlertolerant sein und dabei Dienste auf energieeffiziente Weise erbringen. Zus?tzlich müssen auch neue Anforderungen antizipiert werden, die zukünftige Dienste und Netze stellen, um der Entwicklung von neuen Diensten und Protokollen nicht im Wege zu stehen. Erforderlich ist hierbei die Entwicklung einer ?u?erst variablen und rekonfigurierbaren Netzwerkarchitektur, die eine m?glichst einfache und autonome Netzwerkverwaltung mit einschlie?t. Die Virtualisierung von Host- und Netzwerkressourcen stellt in diesem Zusammenhang eine der Schlüsseltechnologien dar, mit der diese notwendige Flexibilit?t erreicht werden kann. Virtualisierung verbirgt die Komplexit?t von physikalischen Netzwerkinfrastrukturen und stellt homogene, flexible und dynamisch rekonfigurierbare virtuelle Ressourcen zur Verfügung. Dieser Artikel gibt einen überblick über verschiedene Host- und Netzwerkvirtualisierungsmethoden. An mehreren Beispielen wird aufgezeigt, wie verschiedene Herausforderungen angegangen werden k?nnen, die sowohl im heutigen Internet als auch im Internet der Zukunft eine Rolle spielen.