Verformung von Stoßwellen durch Längsinduktivitäten und Querkapazitäten

Zusammenfassung Die Messung der größten Stirnsteilheit einer Stoßwelle auf der Wanderwellenleitung und ihrer Absenkung durch kleine Querkapazitäten (bis etwa 50 pF) wurde mit dem Binderschen Steilheitsmesser durchgeführt. Es zeigte sich, daß sich der Übergang eines Funkens an der Meßfunkenstrecke des Steilheitsmessers hier infolge des lichtschwachen Funkens besser mit dem Ohr als mit dem Auge feststellen ließ. Die Meßergebnisse lassen gegenüber der Rechnung für kleine Querkapazitäten (bis etwa 35 pF) eine geringere Abnahme der Steilheit erkennen, die durch die innere Induktivität des Stoßkreises bedingt sein dürfte. Für größere Querkapazitäten zeigt die gemessene Kurve den gleichen Charakter wie die gerechnete. Die Absolutwerte der Rechnung enthalten jedoch noch die für den vorliegenden Fall nicht genügend genau bekannte Funkenkonstante.Die Untersuchungen sind im Hochspannungsinstitut der Technischen Hochschule in Hannover ausgeführt. Herrn Prof. Dr. H. Schering danke ich für die Förderung meiner Arbeit.Von der Techn. Hochschule Hannover genehmigte Dissertation.     

Opportunities and Challenges of Magnetic Seeded Filtration in Multidimensional Fractionation

This study examines the general applicability of magnetic seeded filtration (MFS) for the fractionation of complex particulate systems by multiple particle features. Experimental studies on a laboratory scale showed that especially the electrostatic interactions govern the separation process. Furthermore, a clear size dependency could be shown, as the separation efficiency decreases with increasing size of target particles. Since MSF is both surface- and size-dependent, it is generally applicable in a multidimensional fractionation. Finally, the challenges to be overcome are addressed as well.     

Complex RNA-DNA hybrid nanoshapes from iterative mix-and-match screening

Hybrid nucleic acid nanostructures partition architectural and functional roles between ribonucleic acid(RNA)joints and deoxyribonucleic acid(DNA)connectors.Nanoshapes self-assemble from nucleic acid modules through synergistic stabilization of marginally stable base pairing interactions within circularly closed polygons.Herein,we report the development of hybrid nanoshapes that include multiple different RNA modules such as internal loop and three-way junction(3WJ)motifs.An iterative mix-and-match screening approach was used to identify suitable DNA connectors that furnished stable nanoshapes for combinations of different RNA modules.The resulting complex multicomponent RNA-DNA hybrid nanoshapes were characterized by atomic force microscopy(AFM)imaging.Our research provides proof of concept for modular design,assembly and screening of RNA-DNA hybrid nanoshapes as building blocks for complex extended nucleic acid materials with features at the sub-10 nm scale.     

ATM‐based multimedia communication via NGSO‐satellites

Future broadband satellite networks for multimedia will be seamlessly integrated into terrestrial broadband networks which often use asynchronous transfer mode (ATM) and recently also the less complex multi protocol label switching (MPLS) technique as transmission and switching protocol. In light of this, future broadband satellite networks may adopt the ATM transmission scheme and implement ATM or ATM‐like switches on board the satellites. However, as compared to communication in fixed networks, satellite communication is characterized by special constraints (e.g. signal delay, channel quality, dynamic network topology) that require novel ATM‐based communication technology for satellite systems. This paper presents results from the ATM‐Sat project that aims to complete this technically challenging and important R&D task in the cooperation between DLR, Fraunhofer Gesellschaft and Tesat‐Spacecom. In brief the following aspects have been addressed in the ATM‐Sat project:

• development of the concept and communication technology for a multimedia satellite system with,
  • non‐geostationary orbit (NGSO) satellites;
  • inter satellite links (ISLs);
  • on‐board ATM switching;
  • fixed and mobile terminals;
• verification of the developed communication technology with a demonstrator.

In particular the ATM‐Sat R&D tasks cover the system and protocol architecture, on‐board processing, ISL routing, up/downlink and on board ATM resource management (including medium access control), error control, IP over satellite‐ATM, and active intelligent antennas. Copyright © 2005 John Wiley & Sons, Ltd.     

Performance of materials for aircraft fuselage windows

Quality of performance of all glazing materials is essential, none more so than in aircraft windows. Since the beginning of aviation, pilots have extensively relied on vision out of the aircraft, and it is recognised that a clear view is paramount in landing, taxiing and take-off. Naturally, the most important aspect in performing these tasks is safety. The same safety aspects should apply to passenger windows, although the visual efficiency may be different from that of the materials around the cockpit. In a series of three papers, the research results of the mechanical and physical properties of aircraft passenger windows are presented. The objective of the present paper is to explain in very general terms the material used in the production of the windows, their properties and performance.     

Direct Synthesis of Few‐Layer Graphene on NaCl Crystals

Chemical vapor deposition is used to synthesize few‐layer graphene on micro crystalline sodium chloride (NaCl) powder. The water‐soluble nature of NaCl makes it convenient to produce free standing graphene layers via a facile and low‐cost approach. Unlike traditional metal‐catalyzed or oxygen‐aided growth, the micron‐size NaCl crystal planes play an important role in the nucleation and growth of few‐layer graphene. Moreover, the possibility of synthesizing cuboidal graphene is also demonstrated in the present approach for the first time. Raman spectroscopy, optical microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy are used to evaluate the quality and structure of the few‐layer graphene along with cuboidal graphene obtained in this process. The few‐layer graphene synthesized using the present method has an adsorption ability for anionic and cationic dye molecules in water. The present synthesis method may pave a facile way for manufacturing few‐layer graphene on a large scale.     

An object-based approach for detecting small brain lesions: application to Virchow-Robin spaces

This paper is concerned with the detection of multiple small brain lesions from magnetic resonance imaging (MRI) data. A model based on the marked point process framework is designed to detect Virchow-Robin spaces (VRSs). These tubular shaped spaces are due to retraction of the brain parenchyma from its supplying arteries. VRS are described by simple geometrical objects that are introduced as small tubular structures. Their radiometric properties are embedded in a data term. A prior model includes interactions describing the clustering property of VRS. A Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC) optimizes the proposed model, obtained by multiplying the prior and the data model. Example results are shown on T1-weighted MRI datasets of elderly subjects.