Entwurf und Herstellung von dünnwandigen Faltwerken aus zementbasierten Verbundwerkstoffen

Der in den Ingenieurwissenschaften zunehmend populäre Einsatz der Origami-Technik eröffnet neue Möglichkeiten zur Herstellung von effizienten Tragkonstruktionen [1]–[5]. In Verbindung mit leistungsfähigen, zementbasierten Verbundwerkstoffen bietet die Origami-Technik einen innovativen Ansatz für Entwurf und Realisierung von leichten tragenden Strukturen nach dem Prinzip form follows force – dem Grundgedanken des SPP 1542. [Aus: Motivation und Zielsetzung]The increasingly popular use of origami technology in the engineering sciences opens up new possibilities for the manufacture of efficient load-bearing structures [1]–[5]. In combination with high-performance, cement-based composite materials, origami technology of ers an innovative approach to the design and realisation of lightweight load-bearing structures based on the principle form follows force –the basic idea of SPP 1542. [Off: Motivation and objectives

A model of isotope transport in the unsaturated zone, case study

This work deals with a groundwater flow and solute transport model in the near-surface (predominantly unsaturated) zone. The model is implemented so that it allows simulations of contamination transport from a source located in a geological environment of a rock massif. The groundwater flow model is based on Richards’ equation. Evaporation is computed using the Hamon model. The transport model is able to simulate advection, diffusion, sorption and radioactive decay. Besides the basic model concept, the article also discusses potential cases that could lead to non-physical solutions. On three selected examples, which include, for example, rapidly changing boundary conditions, the article shows the solvability of such cases with the proposed model without unwanted effects, such as negative concentrations or oscillations of solution, that do not correspond to inputs

Modellierung und Bemessung von dünnwandigen Platten- und Schalentragwerken aus textilbewehrtem Beton

Als Großdemonstrator des Sonderforschungsbereichs 532 soll auf dem Gelände der Fakultät für Bauingenieurwesen der RWTH Aachen ein Ausstellungspavillon mit einer Dachkonstruktion aus Textilbeton errichtet werden. Der Beitrag zeigt die automatisierte Bemessung dieser komplexen Tragstruktur mit Hilfe eines hierfür entwickelten numerischen Bemessungsstools. Die Auswertung erfolgt für alle Lastfallkombinationen nach DIN 1055-100 und unter Berücksichtigung der Reduktion der Tragfähigkeit der textilen Bewehrung infolge einer Umlenkung im Riss sowie einer Erhöhung der aufnehmbaren Textilspannungen infolge Biegebeanspruchung. Zur Ermittlung der Tragfähigkeit der Textilbetonschale wurden am Institut für Massivbau Dehnkörper- und Biegeversuche durchgeführt, die in Bewehrungsgrad und Dicke dem realen Bauwerk am Schalenrand entsprachen.Within the collaborate research center 532 at RWTH Aachen University the construction of an exposition hall with a double-curved roof structure consisting of textile reinforced concrete is currently planned. A numerical tool has been developed to calculate the necessary number of reinforcement layers. Further, the tool evaluates the characteristic stresses of the load case combinations in the ultimate limit state taking into account a reduction of the load-bearing capacity of the textile reinforcement due to alignment of the rovings in the crack bridge and a better activation of the inner filaments for bending induced tension. The resistance of the material has been determined in experimental investigations of tensile and bending specimens of the same thickness and reinforcement ratio as the planned shell structure

Treaty over the teacups : an exploration of teacher educators’ understandings and application of the provisions of the Treaty of Waitangi at the University of Canterbury, College of Education.A thesis submitted in partial fulfilment of the requirements for the Degreeof Master of Education in the University of Canterbury

Teacher educators at the University of Canterbury, College of Education, like all teacher educators in Aotearoa New Zealand, have ethical, legal, and moral obligations in relation to Te Tiriti o Waitangi/the Treaty of Waitangi. The Treaty is an agreement that was signed in 1840 by representatives of the British Crown and representatives of independent Māori hapū (sub-tribe). The failure of the Crown to uphold the Treaty plus the colonisation of New Zealand has held wide-ranging ramifications for Māori, including a negative impact on Māori education. Policy guidelines both at a national level and locally at the University of Canterbury provide requirements and guidelines for teachers and teacher educators in relation to the Treaty. The aim of many of these guidelines is to address equity issues in education and to support Māori ākonga (students) to achieve success as Māori. This thesis draws upon data from interviews with five teacher educators from the University of Canterbury, College of Education to explore their understandings of the Treaty and how these understandings inform their practice. A qualitative research approach was applied to this study. Semi-structured interviews were used and a grounded theory approach to the data analysis was applied. Three key themes arose from the data and these provided insights into the teacher educator participants’ understandings of the Treaty, how they acquired Treaty knowledge and their curriculum decision making. Bronfenbrenner’s (1979) ecological systems theory approach was used as a framework to situate how the teacher educators’ understandings of the Treaty have developed. Critical theory and concepts associated with critical pedagogy underpin this research. Critical pedagogy highlights the importance for teacher educators in New Zealand to have an understanding of the historical and contemporary complexities of educational issues related to the Treaty

Photocatalytic Oxidative [2+2] Cycloelimination Reactions with Flavinium Salts: Mechanistic Study and Influence of the Catalyst Structure

Flavinium salts are frequently used in organo‐catalysis but their application in photoredox catalysis has not been systematically investigated, yet. Here, we synthesize a series of 5‐ethyl‐3‐methylalloxazinium salts with different substituents in positions 7 and 8 and investigate their application in light‐dependent oxidative cycloelimination of cyclobutanes. Detailed mechanistic investigations with a coumarin dimer as a model substrate reveal that the reaction preferentially occurs via the triplet‐born radical pair after electron transfer from the substrate to the triplet state of an alloxazinium salt. The very photostable 7,8‐dimethoxyderivative turns out to be a superior catalyst with a sufficiently high oxidation power (E* = 2.26 V) allowing the conversion of various cyclobutanes (with Eox up to 2.05 V) in high yields. Even compounds can be converted whose opening requires overcoming a high activation barrier due to a missing pre‐activation caused by bulky adjacent substituents, that favour ring opening, e.g. all‐trans dimethyl 3,4‐bis(4‐methoxyphenyl)cyclobutane‐1,2‐dicarboxylate

Experimental and Numerical Analysis of Spalling Effect in TRC Specimens

The paper presents the study of spalling effect occurring under tensile loading in thin-walled TRC specimens. The experimentally observed failure patterns are first classified and the performed experiment design is explained and discussed. A parameter study of spalling effect with varied thickness of concrete cover and reinforcement configurations including both the textile fabrics and the yarns provided the basis for numerical analysis of the effect. The applied numerical model was designed in order to capture the initiation and propagation of longitudinal cracks leading to the separation of concrete blocks from the textile fabrics. A meso-scopic material resolution in a single crack bridge is used for the simulation exploiting the periodic structure of the crack bridges both in the lateral and in the longitudinal direction of the TRC specimens. The matrix was modeled using an anisotropic damage model falling in the microplane-category of material models. The bond between yarn and matrix follows a non-linear bond-law calibrated using pull-out tests. The epoxy-impregnated reinforcement is considered as a homogeneous bar

Highly Chemoselective Catalytic Photooxidations by Using Solvent as a Sacrificial Electron Acceptor

Catalyst recovery is an integral part of photoredox catalysis. It is often solved by adding another component-a sacrificial agent-whose role is to convert the catalyst back into its original oxidation state. However, an additive may cause a side reaction thus decreasing the selectivity and overall efficiency. Herein, we present a novel approach towards chemoselective photooxidation reactions based on suitable solvent-acetonitrile acting simultaneously as an electron acceptor for catalyst recovery, and on anaerobic conditions. This is allowed by the unique properties of the catalyst, 7,8-dimethoxy-3-methyl-5-phenyl-5-deazaflavinium chloride existing in both strongly oxidizing and reducing forms, whose strength is increased by excitation with visible light. Usefulness of this system is demonstrated in chemoselective dehydrogenations of 4-methoxy- and 4-chlorobenzyl alcohols to aldehydes without over-oxidation to benzoic acids achieving yields up to 70 %. 4-Substituted 1-phenylethanols were oxidized to ketones with yields 80–100 % and, moreover, with yields 31-98 % in the presence of benzylic methyl group, diphenylmethane or thioanisole which are readily oxidized in the presence of oxygen but these were untouched with our system. Mechanistic studies based on UV-Vis spectro-electrochemistry, EPR and time-resolved spectroscopy measurements showed that the process involving an electron release from an excited deazaflavin radical to acetonitrile under formation of solvated electron is crucial for the catalyst recovery

Experimental investigation and Monte Carlo simulations of radionuclide production inside the Uranium spallation target QUINTA irradiated with a 660-MeV proton beam

The accelerator-Driven-System (ADS) is very important to study the neutron field and radionuclide production inside simple-geometry uranium subcritical setups irradiated with high energy particle beams. A subcritical setup QUINTA was irradiated with the 660-MeV proton beam from Phasotron accelerator at the Joint Institute for Nuclear Research (JINR). The radionuclide production in the region along the beam axis was investigated by the activation technique. The aim was to compare (n,x) with (p,x) reactions using activation detectors of 59Co and natPb, and compare experimental results with the calculated results using Monte Carlo simulation code MCNPX 2.7