Vergleich statischer und dynamischer Methoden zur Zustandsbewertung von Stahlbeton‐ und Spannbetontragwerken

Risse in Stahlbeton‐ und Spannbetontragwerken führen zu einem Steifigkeitsverlust, der die statischen und dynamischen Eigenschaften der jeweiligen Struktur beeinflusst. Eine klassische Methode zur Bestimmung statischer Kennwerte sind Probebelastungen, bei denen gemessene Verformungen mit rechnerischen Werten abgeglichen werden und somit einen Rückschluss auf die Tragfähigkeit der Struktur ermöglichen. Bei Bauwerken wie Brücken können derartige Tests sehr kosten‐, zeit‐ und materialaufwändig sein und erfordern häufig eine längerfristige Sperrung. Des Weiteren müssen die gemessenen Verformungen vor Ort durch erfahrene Ingenieure überwacht werden, um gegebenenfalls bei Überschreiten kritischer Werte den Test abzubrechen. Auch die dynamischen Eigenschaften von Strukturen werden maßgeblich durch die Steifigkeit beeinflusst und können in vielen Fällen schnell und mit wenig Aufwand bestimmt werden. Im Rahmen dieses Aufsatzes werden die Ergebnisse statischer und dynamischer Untersuchungen zur Zustandsbewertung, durchgeführt an Stahlbeton‐ und Spannbetonbauteilen im Labor und an einer schrittweise geschädigten Spannbetonbrücke, hinsichtlich ihrer Sensibilität auf Schäden und Handhabbarkeit in der praktischen Anwendung gegenübergestellt. Comparison of Static and Dynamic Methods to Assess the State of Reinforced and Prestressed Concrete Structures Cracks in reinforced and prestressed concrete structures lead to a reduction in stiffness and therefore to an influence on the static and dynamic properties. A conventional method to assess the static characteristics are static load tests which enable to correlate measured deformations with calculated values and to draw conclusions about the loading capacity. In case of bridges, these tests can be very cost‐intensive and time‐consuming and often require a closure of the bridge. Furthermore the measured deformations have to be examined in situ, in order to abort the test if the deformations exceed critical values. As well, the dynamic properties are affected by changes in stiffness and in many cases they can be quickly determined without large effort. Within this article the results of static and dynamic tests with laboratory reinforced and prestressed concrete structures and tests on a gradually damaged prestressed concrete bridge are presented. The results are compared with regard to the sensitivity of the different methods to damage.     

Power Dissipation of the Network-on-Chip in Multi-Processor System-on-Chip Dedicated for Video Coding Applications

In the near future, small electronic hand-held devices will be equipped with digital cameras capable of acquiring high resolution images (HDTV) at real-time rates, resulting in video streams of dozens of megabytes per second. The real-time video decoding and especially encoding of such streams with AVC/ H.264 or SVC standards require a huge amount of computing power that, in the case of a hand-held device, has to be delivered under the constraint of low power dissipation. In this paper we present a Multi-Processor System-on-Chip dedicated for high performance, low-power video coding applications using Network-on-Chip (NoC) as communication infrastructure. Extensive experiments have established the power dissipation models of individual NoC components, i.e. network interfaces, routers and wires. Based on these models and the NoC topology, we build the power model of the complete NoC. For three different implementation scenarios of the AVC/H.264 simple profile encoder we derive the power dissipation of the NoC for image resolutions up to HDTV at rate of 30 frames per second. The results obtained show that for the same application mapping scenario (worst case), moving from CIF to HDTV resolution will result in a 35% increase of the total power dissipation. Finally, for HDTV resolution, the difference in power dissipation between the worst (21 mW) and the best case application mapping scenario is 26%.

Engineering Disorder in Superdiffusive Lévy Glasses

Disorder is known to have a substantial impact on light transport in optical materials. In particular, when properly tuned, disorder can unveil optical properties that common, periodically patterned materials do not possess. In this paper, a method to realize disordered dielectric materials dubbed Lévy glasses, in which light transport is superdiffusive, is presented. The degree of superdiffusion is set by engineering the spatial inhomogeneity of the scatterer density in the material. A model that relates the microscopic parameters to the macroscopic transport properties of Lévy glasses is given and the signature of superdiffusion on the transmission profile in a slab configuration is shown experimentally.     

Pseudo-Linear Scale-Space Theory

It has been observed that linear, Gaussian scale-space, and nonlinear, morphological erosion and dilation scale-spaces generated by a quadratic structuring function have a lot in common. Indeed, far-reaching analogies have been reported, which seems to suggest the existence of an underlying isomorphism. However, an actual mapping appears to be missing.In the present work a one-parameter isomorphism is constructed in closed-form, which encompasses linear and both types of morphological scale-spaces as (non-uniform) limiting cases. The unfolding of the one-parameter family provides a means to transfer known results from one domain to the other. Moreover, for any fixed and non-degenerate parameter value one obtains a novel type of pseudo-linear multiscale representation that is, in a precise way, in-between the familiar ones. This is of interest in its own right, as it enables one to balance pros and cons of linear versus morphological scale-space representations in any particular situation.     

Design rules for autofrettage of an aluminium valve body

The following paper is intended to improve the fatigue behaviour of a complex aluminium valve geometry under high internal cyclic pressure loading. The autofrettage process helps to increase the fatigue durability and a simple, but efficient design method for this process is deployed. Based on non‐linear material's behaviour, finite element simulations of the crack‐free geometry help to determine the minimum and maximum autofrettage pressure to be used, without iterative crack simulations, which would require higher computational effort. Material tests under inverse plastifications were performed in order to determine the correct material model. The derived design method was validated with simplified specimens subjected to different autofrettage pressure levels and subsequent cyclic fatigue tests.     

Influence of gold thin-film interlayers on anodic bonding of copper microstructures produced by LIGA

 Neither pure copper nor solid gold can be anodically bonded to glass. It is only the gold coating on the copper which allows a joint to be built up as a result of the copper ions diffusing into the gold layer, but not many of them being able to migrate into the glass. To encapsulate microstructures produced by the LIGA technique, anodic bonding of gold-coated copper to Corning 0211-type glass was studied. For demonstration purposes, a glass platelet made of Corning 0211 was anodically bonded to a LIGA linear actuator consisting of electroplated copper coated with 1 μm of gold. A better understanding about the decisive parameters in anodic bonding was obtained by varying the bonding temperature and the thickness of the gold layer. Glass can be bonded on to the entire surface of gold layers 0.5–1 μm thick at temperatures as low as 300 °C; however, when the systems cool to room temperature, stress-induced cracks arise in the glass. On the other hand, thicker gold layers of 2.5 to 10 μm thickness require higher bonding temperatures for the same period of heating, but prevent the occurrence of such cracks because of their higher ductility. Received: 11 December 1997/Accepted: 11 March 1998     

Stereoisomeric flavour compounds

The enantiomeric distribution of 3-mercaptohexanol (1) and 3-methylthiohexanol (2) in yellow and purple passion fruits was determined by capillary gas chromatography (GC) using two different chiral stationary phases and a flame photometric detector. The results were confirmed by enantioselective capillary GC combined with mass spectrometric detection.1 shows an enrichment of the (S)-enantiomer, but the enantiomeric purity varies in a wide range. Irrespective from the enantiomeric distribution of1, 2 was detected with high enantiomeric purity in favour of the (S)-enantiomer. Using the method presented the addition of synthetic, racemic2 is easily detected.     

From Seeing to Being: Subliminal Social Comparisons Affect Implicit and Explicit Self-Evaluations.

The authors hypothesize that social comparisons can have automatic influences on self-perceptions. This was tested by determining whether subliminal exposure to comparison information influences implicit and explicit self-evaluation. Study 1 showed that subliminal exposure to social comparison information increased the accessibility of the self. Study 2 revealed that subliminal exposure to social comparison information resulted in a contrast effect on explicit self-evaluation. Study 3 showed that subliminal exposure to social comparison information affects self-evaluations more easily than it affects mood or evaluations of other people. Studies 4 and 5 replicated these self-evaluation effects and extended them to implicit measures. Study 6 showed that automatic comparisons are responsive to a person's perceptual needs, such that they only occur when people are uncertain about themselves. Implications for theories of social cognition, judgment, and comparison are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)