Untersuchungen zur Wiederverwendung von Spundwänden

Insbesondere in den letzten Jahren wird das Thema Nachhaltigkeit und ressourcenschonender Umgang mit der Umwelt immer stärker in Politik und Gesellschaft diskutiert. Auch in der Geotechnik ist viel Potential vorhanden, nachhaltig mit den Rohstoffen umzugehen. In diesem Beitrag wird hierzu auf die Möglichkeiten der Wiederverwendung von Stahlspundwänden eingegangen. Dabei wird ein wesentliches Augenmerk auf die Möglichkeiten des Recyclings des Spundwandstahls gelegt. Weiterhin erfolgt eine ausführliche Diskussion bezüglich des Ziehens von Spundwänden und den hierbei auftretenden Problemen. So ist häufig ein Anstieg des Herausziehwiderstands über die Zeit feststellbar. Anhand verschiedener Finite‐Elemente‐Untersuchungen wird dieser Zuwachs des Herausziehwiderstands numerisch untersucht, und es können verschiedene Faktoren herausgearbeitet werden, die dem zugrunde liegen. Investigations regarding the re‐use of sheet‐piles. Especially in recent years the topic sustainability and careful handling of environment are discussed more and more in politics and society. In geotechnical engineering there is great potential to deal more sustainable with the used resources. In this contribution, the possibilities of re‐using steel sheet‐piles are discussed. A main scope is set on the possibilities of recycling of the steel. Furthermore, the pull‐out process of sheet‐piles is discussed and problems during the pull‐out process are described. In‐situ often an increase of pull‐out forces over time can be noticed. Several numerical investigations using finite element method are presented to investigate the possible factors which influence the increase in pull‐out forces.     

Optimising energy use in an existing commercial building: a case study of Australia’s Reef HQ Aquarium

Reef HQ Aquarium is a major tourism attraction in tropical North Queensland, Australia. In 8 years, a 50% reduction in grid electricity was achieved through targeted infrastructure investment, whilst growing the business. Initially, grid energy consumption was 2438 MWh per annum, with 490-kW peak demand and energy intensity of 1625 MJ m^?2 year^?1 used on typical equipment such as HVAC (heating, ventilation and air conditioning), machinery, lighting and catering equipment. Savings of 13% were achieved in the first year by increasing indoor air temperature set-points by 1.5 °C with no significant costs or impacts on occupant thermal comfort or worker productivity. Peak demand was decreased by 46% by upgrading the computerised building management system (BMS), HVAC, machinery and lighting; and by installing a 206-kW photovoltaic (PV) solar power system. This case study illustrates that (a) significant energy use reductions are possible at low cost; (b) capital investment in energy-efficient infrastructure can have short payback times and high direct and indirect benefits, particularly where equipment is ending its life. This study is unique as it examines how a commercial building with integrated chilled water thermal energy storage (TES) and a 3.2-ML chilled seawater aquarium system can be controlled by a BMS to optimise solar power to manage peak energy demand and also increase the utilisation of generated PV power in the absence of electrical battery storage. An interesting building is used to demonstrate efficiency methods with elements such as HVAC and lighting which usually consume over half commercial buildings’ energy use.     

A novel approach to determine high temperature wettability and interfacial reactions in liquid metal/solid interface

In many technical processes, high temperature wetting of a liquid metal phase on a solid substrate occurs via an extensive chemical reaction and the formation of a new solid compound at the interface. For instance, good adhesion of the zinc coating to the steel surface is one of the most important requirements that the hot-dip galvanizing process has to fulfill. Good adhesion directly depends on the formation of a defect-free Fe₂Al₅ inhibition layer at the interface. The complex surface chemistry of oxides on the steel surface which is a result of segregation and selective oxidation upon recrystallization annealing significantly influences the kinetics of the correlated reactive wetting. This article presents the development of a novel advanced technique for the investigation of high temperature wetting process up to a temperature of 1100 K and provides first new insights in the mechanisms of the reactive wetting process in presence of oxides on the surface. The method is based on the sessile drop method with an additional spinning technique to get rid off the liquid metal phase at any chosen wetting time, thusly opening the way to access the interfacial reaction layer directly. The presented work focuses on model alloys of interest which are mainly relevant to the industrial steel grades. Emphasis is put both on the wettability of liquid Zn and on the interfacial reactions during reactive wetting process. Insights into such reactive phenomena are fundamental demand to improve the hot-dip galvanizability of advanced high strength steel grades.     

Resonant column experiments with fine-grained model material – evidence of particle surface forces

Resonant column experiments were conducted with an extremely fine-grained material, viz. an -aluminum oxide (Al₂O₃), which serves as a model material for cohesive soils with particle diameters in the range of m. With this particle size interparticle forces from van der Waals and Coulombic interaction have an influence on the behavior of the material in dynamic shear tests. By adjusting the surface charge, and hence the Coulombic repulsion, we obtain repulsive or attractive particles, which influences sample fabric and shear stiffness. From the increase of shear stiffness at small strain (10^–6) with effective pressure we have estimated the net interparticle pressure from surface forces in the range of some kPa for a mean particle diameter of 0.8 m. Our results show that the behavior of fine-grained granular materials at small shear strains cannot only be described by their density and stress state. Particle surface forces have to be taken into account. The study described in this paper was sponsored by the German Research Council (DFG), Research Group FOR 371-2. The support is gratefully appreciated.We would like to thank Professor Gudehus for his valuable advice and many stimulating discussions.The KSEM micrograph and the grain size distribution data have been provided by the Institute of Ceramics in Mechanical Engineering, University of Karlsruhe (Research Group FOR 371, German Research Council, DFG). We would like to thank for cooperation and support.We thank the Institute for Technical Chemistry, Research Center Karlsruhe for providing the ESEM micrograph.     

Influence of loading and heating processes on elastic and geomechanical properties of eclogites and granulites

Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(V_p) and S-wave(V_s) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in V_p and V_s are estimated to be 1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson's ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.     

NMR Spectroscopy: Determination of Peroxide Value in Vegetable and Krill Oil by Using Triphenylphosphine as Tagging Reagent

Hydroperoxides are formed as the primary product during lipid oxidation, being analyzed as the peroxide value to detect the degradation level of oils and fats. As an alternative to the classical titration method according to Wheeler, a ¹H‐{³¹P} decoupled NMR method is developed using triphenylphosphine (TPP) as a tagging agent. TPP reacts with peroxides to form TPP oxides. The quantification of the peroxide value is performed by comparing the amount of reacted TPP oxide and non‐reacted TPP. This approach eliminates the requirement for an additional internal standard. Low‐oxidized oils (peroxide value < 3 meq/kg) and high‐oxidized oils with peroxide values of 150 meq/kg are precisely quantified with an relative standard deviation (RSD) of 4.90% and 0.16%, respectively. A total number of 108 oil samples are examined using the newly‐developed ¹H‐{³¹P} decoupled NMR method, indicating the applicability for vegetable oils and krill oils. Practical Applications: The developed NMR method is applicable for the determination of the peroxide value in vegetable, marine and krill oils presenting a powerful alternative for the Wheeler titration method.     

Effect of Chemically Modified Carbon-Coated Iron Nanoparticles on the Structure of Human Atherosclerotic Plaques Ex Vivo and on Adipose Tissue in Chronic Experiment In Vivo

The high mortality rate caused by atherosclerosis makes it necessary to constantly search for new and better treatments. In previous reports, chemically modified carbon-coated iron nanoparticles (Fe@C NPs) have been demonstrated a high biocompatibility and promising anti-plaque properties. To further investigate these effects, the interaction of these nanoparticles with the adipose tissue of Wistar rats (in vivo) and human atherosclerotic plaques (ex vivo) was studied. For the in vivo study, cobalt–chromium (CoCr) alloy tubes, which are used for coronary stent manufacturing, were prepared with a coating of polylactic acid (PLA) which contained either modified or non-modified Fe@C NPs in a 5% by weight concentration. The tubes were implanted into an area of subcutaneous fat in Wistar rats, where changes in the histological structure and functional properties of the surrounding tissue were observed in the case of coatings modified with Fe@C NPs. For the ex vivo study, freshly explanted human atherosclerotic plaques were treated in the physiological solution with doses of modified Fe@C NPs, with mass equal to 5% or 25% relative to the plaques. This treatment resulted in the release of cholesterol-like compounds from the surface of the plaques into the solution, thus proving a pronounced destructive effect on the plaque structure. Chemically modified Fe@C NPs, when used as an anti-atherosclerosis agent, were able to activate the activity of macrophages, which could lead to the destruction of atherosclerotic plaques structures. These findings could prove the fabrication of next-generation vascular stents with built-in anti-atherosclerotic agents.     

An FFT-Based Approach for Fast Acquisition in Spread Spectrum Communication Systems

This paper describes a non-coherent technique forfast acquisition of direct sequence spread spectrum(DS/SS) signals in low earth orbit (LEO) satellitecommunication scenarios. Large Doppler offsets areinherent to such environments and are likely to causemajor problems during the code acquisition phase dueto the introduced frequency ambiguity. In the presentpaper we discuss the use of a set of partialcorrelators for code phase acquisition, combined witha fast Fourier transform (FFT) for the purpose of simultaneous Doppler estimation. We will show that theuse of this architecture largely accelerates thesynchronisation process compared to conventionaltechniques over a wide range of Doppler offsets.Furthermore we discuss the implementation of azero-padded FFT that increases the frequencyresolution to such an extent, that acquisition timesidentical to scenarios without existing Doppler offsetcan be achieved.     

Chemoenzymatic Preparation of Functional Click-Labeled Messenger RNA

Synthetic mRNAs are promising candidates for a new class of transformative drugs that provide genetic information for patients’ cells to develop their own cure. One key advancement to develop so-called druggable mRNAs was the preparation of chemically modified mRNAs, by replacing standard bases with modified bases, such as uridine with pseudouridine, which can ameliorate the immunogenic profile and translation efficiency of the mRNA. Thus the introduction of modified nucleobases was the foundation for the clinical use of such mRNAs. Herein we describe modular and simple methods to chemoenzymatically modify mRNA. Alkyne- and/or azide-modified nucleotides are enzymatically incorporated into mRNA and subsequently conjugated to fluorescent dyes using click chemistry. This allows visualization of the labeled mRNA inside cells. mRNA coding for the enhanced green fluorescent protein (eGFP) was chosen as a model system and the successful expression of eGFP demonstrated that our modified mRNA is accepted by the translation machinery.