Determination of the modulus of elasticity of prestressing steel strands

RILEM Draft RecommendationsTC 80-TMS tension modulus of prestressing steel strands

Determination of the modulus of elasticity of prestressing steel strands     

DTT functionalization of Ag particles for conducting adhesives

We have studied the influence of the organic molecule DL-Dithiothreitol on the properties of isotropic conductive adhesives for application in microelectronics. The Ag fillers were prepared from commercial micro flakes or submicron particles from waste jewelry. The results show that coating of the Ag recycled fillers with thiol avoided the agglomeration of the particles improving the dispersion and the electrical and mechanical properties. By comparing the samples, the better properties were obtained from adhesives with recycled Ag particles relative to the ones formulated with commercial Ag flakes and improvement can be attributed to the absence of the lubricant layer and smaller size of the particles produced from recycled silver.     

How to Investigate the Setting Kinetics of Refractory Castables——A Review of Methods and Their Relevancy for Technical Use

This article contributes to a meaningful interpretation of results gathered by in-situ measurements of sonic velocity,electrical conductivity and the change of temperature during setting and curing of LC refractory castables. All said monitoring techniques are well known in the refractory community and are well documented in the literature. However,the time dependent changes of the said properties are not well correlated to mineralogical and in consequence technological changes of the material during setting and curing. The basic interest of refractory users of course is to define the time at which the installation or the pre-shape construction element can be demoulded. This is in principle possible with the methods listed above. However,after water addition the time dependent changes of sonic velocity,electrical conductivity and temperature are diverse as there are possible combinations of cements,microfines and surface-active additives. In further the ambient conditions,temperature and relative humidity have a strong influence on these properties and this does not only mean a simple time-shift. Up to now the results are more confusing than helpful to determine the best time for demoulding pre-shapes and refractory linings. Recent research at Koblenz University of Applied Science contributes to a deeper understanding of the setting behaviour,because besides the physical evolution of the said parameters the time dependent formation of hydrate phases is also investigated by means of gravi-metric method. The proposed presentation will show detailed insights in the evolution of refractory castables during setting and curing.Key words: refractory; setting kinetics; hydrate bond water     

Verifying OpenJDK’s LinkedList using KeY (extended paper)

As a particular case study of the formal verification of state-of-the-art, real software, we discuss the specification and verification of a corrected version of the implementation of a linked list as provided by the Java Collection Framework.

     

Optische Konstanten von Substraten im NIR/MIR‐Spektralbereich

Determination of the Optical Constants of Common Substrate Materials in the NIR/MIR‐Spectral Regions An approach is reported for determining the optical constants of substrates and single layer coatings in the near and mid‐infrared spectral regions. A combination of the algorithm from Nichelatti and a multi‐oscillator model has been used to determine the optical constants of the substrates. Thus, the approach even works when the sample transmittance is vanishing. We demonstrate the application of the approach to the evaluation of transmission and reflection spectra of common substrates (CaF₂, Q1, Sapphire) measured by a Fourier‐Transform‐Infrared spectrophotometer. The comparison of the calculated optical constants with values reported in literature confirms the validity of the used approach. We also demonstrate the IR characterisation of a tantalum oxide single layer deposited onto a Q1 substrate by means of the multi‐oscillator‐model. The results are again in good agreement with literature data.     

Preprocessor-based variability in open-source and industrial software systems: An empirical study

Almost every sufficiently complex software system today is configurable. Conditional compilation is a simple variability-implementation mechanism that is widely used in open-source projects and industry. Especially, the C preprocessor (CPP) is very popular in practice, but it is also gaining (again) interest in academia. Although there have been several attempts to understand and improve CPP, there is a lack of understanding of how it is used in open-source and industrial systems and whether different usage patterns have emerged. The background is that much research on configurable systems and product lines concentrates on open-source systems, simply because they are available for study in the first place. This leads to the potentially problematic situation that it is unclear whether the results obtained from these studies are transferable to industrial systems. We aim at lowering this gap by comparing the use of CPP in open-source projects and industry—especially from the embedded-systems domain—based on a substantial set of subject systems and well-known variability metrics, including size, scattering, and tangling metrics. A key result of our empirical study is that, regarding almost all aspects we studied, the analyzed open-source systems and the considered embedded systems from industry are similar regarding most metrics, including systems that have been developed in industry and made open source at some point. So, our study indicates that, regarding CPP as variability-implementation mechanism, insights, methods, and tools developed based on studies of open-source systems are transferable to industrial systems—at least, with respect to the metrics we considered.     

RILEM Draft Recommendation ‘Determination of the modulus of elasticity of prestressing steel strands’

RILEM Draft Recommendations

RILEM Draft Recommendation ‘Determination of the modulus of elasticity of prestressing steel strands’     

Surface texturing of Mo–V–Te–Nb–O x selective oxidation catalysts

The paper concentrates on the study of Mo–V–Te–Nb oxide mixtures by electron microscopy combined with catalytic investigation of these materials in the partial oxidation of propane. Surface texturing of catalyst particles composed of two phases referred to in the literature as M1 and M2 is revealed by high-resolution transmission electron microscopy of high performing catalysts. The chemical composition of the catalyst surface is modified by treatment in water to obtain a significant increment in yield of acrylic acid. A chemical realization of the site isolation concept recurring on a supramolecular arrangement of catalyst and reactant rather than on atomic site isolation is suggested. A complex Mo–V–Te–Nb–O _x precursor phase carries nanoparticles made from a network of oxoclusters active as catalyst for the conversion of propane to acrylic acid. The designed synthesis of the multi-element oxide bulk and of the surface structure with a different composition than the precursor phase improved the performance by a factor of 4.     

Growth of novel carbon phases by methane infiltration of free-standing single-walled carbon nanotube films

High-temperature methane infiltration of thin, free-standing films of acid-treated single-walled carbon nanotubes (SWCNT) has been studied by means of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. In the early stages of infiltration, carbon nuclei form predominantly at SWCNT bundle intersections. Further growth proceeds via the formation of graphite nanosheets - without further influence of the nanotube support. Both sheet edges and their structural imperfections act as reaction centers for subsequent deposition, likely giving rise to autocatalytic deposition kinetics. In contrast, infiltration with a H₂:CH₄ (24:1) mixture leads to the reductive activation of residual Ni/Co impurities embedded in the precursor SWCNT-felt. This is associated with a different predominant carbon deposition mode in which multiwalled carbon nanotubes grow out from the substrate.