Reversible suppression of the so-called fishtail effect in ultra pure single crystals of YBa2Cu3O7−δ achieved by proper oxygenation

We report on the absence of the so-called fishtail or peak effect in the magnetisation curves of properly oxygenated high purity (5N) single crystals of YBa₂Cu₃O_7–. As we recently reported [1] high pressure oxygenation procedures are suitable to produce a monotonous dependence of the critical current density with the magnetic field. In this article we report furthermore how to reversibly produce or remove this effect on the same crystal by proper oxygenation methods. Along with the high purity of the samples, — due to crystal growth in non reactive BaZrO₃ crucibles —, this proves that at least in pure samples the fishtail effect is due to different oxygenation states and/or oxygen distributions. In less pure samples, however, other sources for this anomaly like metallic impurities can act as an additional source for the fishtail anomaly.     

Perpendicular-incidence photometric ellipsometry of biaxial anisotropic thin films

A new measurement technique for the characterization of uniaxial as well as biaxial anisotropic surfaces and thin films is introduced. This technique is based on perpendicular-incidence photometric ellipsometry, in which a spectral-photometric dynamic ellipsometer with a rotating polarizer is used. This method is sensitive, contactless, nondestructive, and efficient for the estimation of anisotropic behavior. Furthermore, the spectroscopic measurement directly provides the anisotropy dispersion down to the UV wavelength range. Results on structurally anisotropic HfO(2) coatings are presented.     

Traversing step obstacles with manual wheelchairs

In the public transport system, there are sometimes step obstacles, such as curbs, steps, entrance steps of vehicles, edges of lifting platforms, internal steps in vehicles, etc. This paper describes research work carried out in Sweden to specify the heights of step obstacles possible to traverse with a manual wheelchair manoeuvred by an attendant. The work included trials with the subjects manoeuvring two different kinds of wheelchairs, with dummies as occupants, over a step obstacle with adjustable height. It also included trials with a person in the wheelchair. The subjects were 20 healthy persons in the age range of 23-60 years, with no or only little experience of manoeuvring wheelchairs, chosen to represent bus drivers or other helpers. They rated their perceived feeling of effort on a 10-level rating scale with ratio properties. The occupant rated the feeling of comfort and safety in three grades. All trials were recorded using a video-camera. From the video-film, the situations and series of actions of the subjects were analysed and the length of time for each task was measured. The forces needed when traversing step obstacles with a wheelchair were calculated according to the principles of mechanics and processed by a computer for the different principal traversing situations. The results show that for the planning of systems for public transportation, where the passenger can get assistance, a step height of 50 mm is acceptable, and a step height of 100 mm can be acceptable if there is enough room to manoeuvre the wheelchair, so that it is possible to choose the most convenient way to traverse the step. Higher heights should be avoided.     

Report of the Second Workshop on the Usage of NetFlow/IPFIX in Network Management

Following the success of the First Workshop on the Usage of NetFlow/IPFIX (Pras et al. in J Netw Syst Manag 17(4), 2009) in 2008, the European EMANICS Network of Excellence organized a second workshop in October 2009, held at Jacobs University Bremen. This report summarizes the workshop and presents its main conclusions.     

Distributed information service architecture for overlapping multiaccess networks

Multimedia delivery in mobile multiaccess network environments has emerged as a key area within the future Internet research domain. When network heterogeneity is coupled with the proliferation of multiaccess capabilities in mobile handheld devices, one can expect many new avenues for developing novel services and applications. New mechanisms for audio/video delivery over multiaccess networks will define the next generation of major distribution technologies, but will require significantly more information to operate according to their best potential. In this paper we present and evaluate a distributed information service, which can enhance media delivery over such multiaccess networks. We describe the proposed information service, which is built upon the new distributed control and management framework (DCMF) and the mobility management triggering functionality (TRG). We use a testbed which includes 3G/HSPA, WLAN and WiMAX network accesses to evaluate our proposed architecture and present results that demonstrate its value in enhancing video delivery and minimizing service disruption in an involved scenario.     

Tests and Proofs

This special issue collects current advances in the ongoing attempt to obtain synergies from the combination of Tests and Proofs.     

A Salience‐based Quality Metric for Visualization

Salience detection is a principle mechanism to facilitate visual attention. A good visualization guides the observer's attention to the relevant aspects of the representation. Hence, the distribution of salience over a visualization image is an essential measure of the quality of the visualization. We describe a method for computing such a metric for a visualization image in the context of a given dataset. We show how this technique can be used to analyze a visualization's salience, improve an existing visualization, and choose the best representation from a set of alternatives. The usefulness of this proposed metric is illustrated using examples from information visualization, volume visualization and flow visualization.     

SoundRiver: Semantically‐Rich Sound Illustration

Sound is an integral part of most movies and videos. In many situations, viewers of a video are unable to hear the sound track, for example, when watching it in a fast forward mode, viewing it by hearing‐impaired viewers or when the plot is given as a storyboard. In this paper, we present an automated visualization solution to such problems. The system first detects the common components (such as music, speech, rain, explosions, and so on) from a sound track, then maps them to a collection of programmable visual metaphors, and generates a composite visualization. This form of sound visualization, which is referred to as SoundRiver, can be also used to augment various forms of video abstraction and annotated key frames and to enhance graphical user interfaces for video handling software. The SoundRiver conveys more semantic information to the viewer than traditional graphical representations of sound illustration, such as phonoautographs, spectrograms or artistic audiovisual animations.