Case study about the accuracy behavior of three different T-matrix methods

In this paper we discuss the influence of two different sets of weighting functions on the accuracy behavior of T-matrix calculations for scalar scattering problems. The first set of weighting functions is related to one of Waterman's original approaches. The other set results into a least-squares scheme for the transmission problem. It is shown that both sets of weighting functions produce results with a converse accuracy behavior in the near and far fields. Additional information, such as reciprocity and the fulfillment of the boundary condition, are needed to choose the set of weighting functions that is most appropriate for a certain application. The obtained criteria are applied afterward to an iterative T-matrix approach we developed to analyze scattering on regular particle geometries with an impressed but slight surface irregularity. However, its usefulness is demonstrated in this paper by analyzing the far-field scattering behavior of Chebyshev particles of higher orders.     

Schubtragfähigkeit von Mauerwerk aus Wärmedämmziegeln

Der Beitrag berichtet über zentrische und exzentrische Schubversuche an Mauerwerk aus Wärmedämmziegeln. Die Ergebnisse werden mit den aktuell gültigen Bemessungsansätzen in DIN 1053‐1 verglichen. Es wird gezeigt, dass die Versuchsergebnisse immer eine ausreichende Sicherheit gegenüber den Bemessungswerten nach DIN 1053‐1 aufweisen. Auch für Mauerwerk aus Wärmedämmziegeln mit allgemeiner bauaufsichtlicher Zulassung können somit die vereinfachten Bemessungsregeln der DIN 4149 ohne Abminderungen angewendet werden. In plane shear resistance of thermal insulating vertically perforated clay brick masonry. In plane shear tests on thermal insulating vertically perforated clay brick masonry are presented. The results are compared with the design rules from DIN 1053‐1. The test results exceeded the design predictions of DIN 1053‐1 by a significant safety margin. The simplified design rules from the German earthquake standard DIN 4149 can be applied to thermal insulating clay unit masonry with technical approvals without any reduction.     

The development and evaluation of microstructured reactors for the water gas shift and preferential oxidation reactions in the 5 kW range

5 kW_el One-Stage Water Gas Shift (WGS) and Preferential Oxidation (PROx) reactors were designed and evaluated for the clean-up of surrogate diesel reformate. For the WGS reactor, CO conversions of up to 95% were attained using typical surrogate synthetic diesel reformate. The PROx reactor was capable of converting a feed concentration of 1.0 mol% CO to 20 ppm. Load changes for both reactors could be carried out without significant overshoots of carbon monoxide.     

Die Erhebung von Brandlasten in 95 Industrie‐ und Gewerbebauten

Survey of fire loads in 95 industrial and commercial buildings. This article describes a survey of fire loads in 95 industrial and commercial Swiss companies from 40 sectors. The survey was carried out between July and December 2005 on behalf of the association of cantonal fire insurers (Vereinigung Kantonaler Feuerversicherungen – VKF). The survey results will be used as a basis for developing a simplified method for specifying technical measures for large fire zones in industrial buildings. The approach and results are briefly described below. The article concludes with an interpretation of the results and an outlook.     

Properties of high-temperature PEFC Celtec-P 1000 MEAs in start/stop operation mode

This paper aims at the comparison of two differently operated Celtec^®-P 1000 MEAs: one MEA is operated in a start/stop cycling mode (12 h operation at 160 °C followed by 12 h shutdown), the other MEA is continuously operated at 160 °C. We demonstrate more than 6000 h total operation time with more than 240 start/stop cycles, while the test is still ongoing. The degradation rate is 0.2 mV cycle⁻¹ or 11 μV h⁻¹ on a time basis. The continuously operated MEA is operated more than 6000 h with a degradation rate of approximately 5 μV h⁻¹. Through separation of the individual cathodic loss terms, a detailed insight into the doubled time-based degradation rate under start/stop cycling conditions could be given. Both Ohmic resistances and oxygen reduction overpotentials are basically identical in MEAs under continuous and start/stop cycling operation. In the start/stop cycled MEA, however, significantly increased cathodic mass transport overpotentials are observed as a result of enhanced corrosion of the cathode catalyst support, which confirms the generally discussed reverse-current mechanism under start/stop cycling conditions. Results from a newly developed MEA demonstrate that this mechanism can successfully be mitigated through improvement of the materials used in the MEA.     

Stability and antimicrobial efficiency of eugenol encapsulated in surfactant micelles as affected by temperature and pH

Growth inhibition of four strains of Escherichia coli O157:H7 (H1730, F4546, 932, and E0019) and Listeria monocytogenes (Scott A, 101, 108, and 310) by eugenol encapsulated in water soluble micellar nonionic surfactant solutions (Surfynol 485W) adjusted to pH 5, 6, and 7 and incubated at 10, 22, and 32 degrees C was determined. Concentrations of eugenol ranged from 0.2 to 0.9% at a surfactant concentration of 5%. Antimicrobial activity was assessed using a microbroth dilution assay. Eugenol encapsulated in surfactant micelles inhibited both microorganisms at pH 5, 6, and 7. At pH 5, some inhibition occurred in the absence of eugenol, i.e., by the surfactant itself (optical density at 24 h for L. monocytogenes = 0.07 and optical density at 24 h for E. coli O157:H7 = 0.09), but addition of >0.2% eugenol led to complete inhibition of both microorganisms. Inhibition of L. monocytogenes and E. coli O157:H7 decreased with increasing pH, that is, the minimum inhibitory concentration was 0.2, 0.5, and 0.5% of micellar encapsulated eugenol solutions at pH 5, 6, and 7, respectively. The encapsulated essential oil component in surfactant micelles was effective at all three temperatures tested (10, 22, and 32 degrees C), indicating that the activity of encapsulated eugenol was not affected by high or low (refrigeration) temperatures. Overall, strains of E. coli O157:H7 were more sensitive than strains of L. monocytogenes. Improved activity was attributed to increased solubility of eugenol in the aqueous phase due to the presence of surfactants and improved interactions of antimicrobials with microorganisms.     

Rapid elastic image registration for 3-D ultrasound

A Subvolume-based algorithm for elastic Ultrasound REgistration (SURE) was developed and evaluated. Designed primarily to improve spatial resolution in three-dimensional compound imaging, the algorithm registers individual image volumes nonlinearly before combination into compound volumes. SURE works in one or two stages, optionally using MIAMI Fuse software first to determine a global affine registration before iteratively dividing the volume into subvolumes and computing local rigid registrations in the second stage. Connectivity of the entire volume is ensured by global interpolation using thin-plate splines after each iteration. The performance of SURE was quantified in 20 synthetically deformed in vivo ultrasound volumes, and in two phantom scans, one of which was distorted at acquisition by placing an aberrating layer in the sound path. The aberrating layer was designed to induce beam aberrations reported for the female breast. Synthetic deformations of 1.5-2.5 mm were reduced by over 85% when SURE was applied to register the distorted image volumes with the original ones. Registration times were below 5 min on a 500-MHz CPU for an average data set size of 13 MB. In the aberrated phantom scans, SURE reduced the average deformation between the two volumes from 1.01 to 0.30 mm. This was a statistically significant (P = 0.01) improvement over rigid and affine registration transformations, which produced reductions to 0.59 and 0.50 mm, respectively.     

Improved Approximations for Tour and Tree Covers

A tree (tour) cover of an edge-weighted graph is a set of edges which forms a tree (closed walk) and covers every other edge in the graph. Arkin et al. give approximation algorithms with ratios 3.55 (tree cover) and 5.5 (tour cover). We present algorithms with a worst-case ratio of 3 for both problems.