MT: A Mathematica package to compute convolutions

We introduce the Mathematica package MT which can be used to compute, both analytically and numerically, convolutions involving harmonic polylogarithms, polynomials or generalized functions. As applications contributions to next-to-next-to-next-to leading order Higgs boson production and the Drell–Yan process are discussed.     

Aluminum–germanium wafer bonding of (AlGaIn)N thin-film light-emitting diodes

Eutectic aluminum–germanium wafer bonding was used to fabricate (AlGaIn)N thin-film light-emitting diodes (LEDs). Wafer bonding was carried out on 2″ wafer level at a bond temperature of 470 °C using patterned Al bond pads on the GaN-on-sapphire LED epiwafer and plain Ge substrates. The microstructure of the joint formation was characterized via cross-section analysis using scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX). Scanning acoustic microscopy was used to investigate the bond interface. The shear strength was determined to be 1–2 kN/cm². The formation of a liquid Al–Ge phase is evident from cross-section analysis and optical microscopy. During solidification, Al and Ge are separated into distinct phases again, which is revealed by EDX. The obtained bond is not free of micro-voids, yet it is mechanically stable and suited for the fabrication of thin-film LEDs by removing the sapphire substrate via laser lift-off, which is also demonstrated.     

Influence of drying on the content of sugars in wet processed green Arabica coffees

When wet processed coffee beans are dried, the resulting decrease in the water potential induces various metabolic responses. This study was aimed at elucidating the impact of these reactions on the composition of sugars, representing potential aroma precursors. Wet processed green coffees were dried under defined conditions, and the relevant sugars were analysed. Special emphasis was put on the influence of the drying regime, i.e. continuous dryings and such interrupted by pauses in order to mimic sun dryings.     

Hybrid 3D-textile reinforced composites with tailored property profiles for crash and impact applications

Novel 3D-textile reinforced composites with a stretched fibre arrangement have very good specific mechanical properties and outstanding energy absorption capabilities. With respect to the specific technical requirements, 3D-textile preforms can be adjusted with regard to stiffness, strength and crash-worthiness by the intelligent combination of different fibre materials in the textile preform. Thus, hybrid 3D-textile preforms with tailored property profiles are excellent candidates for the use in impact and crash components of innovative lightweight structures for the aircraft and vehicle industry as well as for mechanical engineering applications.     

Opacity Optimization for Surfaces

In flow visualization, integral surfaces rapidly tend to expand, fold and produce vast amounts of occlusion. While silhouette enhancements and local transparency mappings proved useful for semi‐transparent depictions, they still introduce visual clutter when surfaces grow more complex. An effective visualization of the flow requires a balance between the presentation of interesting surface parts and the avoidance of occlusions that hinder the view. In this paper, we extend the concept of opacity optimization to surfaces to obtain a global approach to the occlusion problem. Starting with a partition of the surfaces into patches, we compute per‐patch opacity as minimizer of a bounded‐variable least‐squares problem. For the final rendering, opacity is interpolated on the surfaces. The resulting visualization technique is interactive, frame‐coherent, view‐dependent and driven by domain knowledge.     

Solvent effects on esterification equilibria

Solvents are known to have strong impacts on the yields of equilibrium reactions. This work focuses on the thermodynamic investigation of these solvent effects on esterification reactions of acetic acid and propionic acid with ethanol. Esterification of acetic acid was performed in the solvents acetone, acetonitrile (ACN), dimethylformamide (DMF), and tetrahydrofurane as well as in mixtures thereof. ACN promotes the esterification of acetic acid, whereas it is strongly suppressed by DMF. The esterification of propionic acid was investigated with various reactant concentrations in acetone. The experimental equilibrium data in pure solvents and solvent mixtures were modeled using the thermodynamic equilibrium constant K_a and the reactant/product activity coefficients predicted by the perturbed chain‐statistical associating fluid theory (PC‐SAFT). For a given K_a, PC‐SAFT is able to predict the influence of the solvent and even solvent mixtures on the equilibrium concentrations of esterification in almost quantitative agreement with the experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3000–3011, 2015     

Plasmonic Enhancement or Energy Transfer? On the Luminescence of Gold‐, Silver‐, and Lanthanide‐Doped Silicate Glasses and Its Potential for Light‐Emitting Devices

With the technique of synchrotron X‐ray activation, molecule‐like, non‐plasmonic gold and silver particles in soda‐lime silicate glasses can be generated. The luminescence energy transfer between these species and lanthanide(III) ions is studied. As a result, a significant lanthanide luminescence enhancement by a factor of up to 250 under non‐resonant UV excitation is observed. The absence of a distinct gold and silver plasmon resonance absorption, respectively, the missing nanoparticle signals in previous SAXS and TEM experiments, the unaltered luminescence lifetime of the lanthanide ions compared to the non‐enhanced case, and an excitation maximum at 300–350 nm (equivalent to the absorption range of small noble metal particles) indicate unambiguously that the observed enhancement is due to a classical energy transfer between small noble metal particles and lanthanide ions, and not to a plasmonic field enhancement effect. It is proposed that very small, molecule‐like noble metal particles (such as dimers, trimers, and tetramers) first absorb the excitation light, undergo a singlet‐triplet intersystem crossing, and finally transfer the energy to an excited multiplet state of adjacent lanthanide(III) ions. X‐ray lithographic microstructuring and excitation with a commercial UV LED show the potential of the activated glass samples as bright light‐emitting devices with tunable emission colors.     

Secure and Optimal LOADng Routing for IoT with Composite Routing Metric

Security is the one of the major challenges for routing the data between the source and destination in an Internet of Things (IoT) network. To overcome this challenge, a secure Lightweight On-demand Ad hoc Distance-vector—Next Generation (LOADng) Routing Protocol is proposed in this paper. As the LOADng protocol is the second version of Ad Hoc On-Demand Distance Vector (AODV) protocol, it retains most of the basic functionality and characteristics of AODV. During the route discovery process, the cyclic shift transposition algorithm (CSTA) is used to encrypt the control packets of the LOADng protocol to improve its security. CSTA approach only derives transposition and substitution without product cipher with respect to input data. Besides this, for choosing the best probable path between the source and destination, routing metrics such as link quality Indicator (LQI), hop count (HC) and queue length (QL) are included in the control packets. The data is then securely sent using CSTA using the optimal secure path selected. Experimental Results depict that the proposed secure and optimal LOADng (SO-LOADng) using CSTA encryption obtains better throughput, delivery ratio encryption time and decryption time than the existing state-of-art approaches.     

Textile reinforcement in the bed joint of basement masonry and infill walls subjected to high wind loads

The successful structural verification of basement walls under earth pressure loading with light vertical loading is often difficult. This situation is often encountered for external basement walls under terrace doors, stairs, masonry light wells, etc., where the vertical loading that is theoretically necessary is absent. This makes it impossible to resist the acting flexural forces from earth using a vertical arch model alone. In such cases the basement wall must also resist the earth pressure in a horizontal direction. However, due to the fact the bending moment capacity of unreinforced masonry parallel to the bed joint is low you have the option here of using a textile‐reinforced bed joint with longitudinal fibres of alkali‐resistant glass or carbon fibre. With an appropriately adapted textile reinforcement in the bed joints, the masonry can fulfil the requirements for load‐bearing capacity against earth pressure with a horizontal load transfer, even under a small vertical load. The same applies to infill walls subjected to high wind loads the bending moment capacities of which are also slightly parallel to and vertically to the bed joint and cannot be provably demonstrated on large infill surfaces and strong wind loads. The load‐bearing can also be increased by improving the flexural strength parallel to the bed joint. The Chair of Structural Design in the Faculty of Architecture of the Technical University (TU) Dresden was carrying out extensive numerical and experimental studies for this purpose. In the journal Mauerwerk 01/2018 [1] first findings from small trial series have already been presented. In the meantime, a series of large‐scale tests have additionally been performed to check the promising results of the small‐scale tests with respect to their real applicability. This report should provide a combined insight into the work of the concluded research project.     

Dry laying of masonry to build demountable,highly energy‐efficient prototype houses – First findings from a currently running research project

In recent decades, energy efficiency has been the priority for masonry buildings in order to keep up with ever more stringent requirements. For the evaluation of the sustainability of building solutions, however, the embodied energy to produce a building and finally to dispose of it at the end of its lifecycle are also important. The energy used for the disposal of a building and the processing of the residues are also important for the overall energy balance since the handling of natural resources is increasingly the centre point of thought and action. A research team at the Chair of Structural Design of TU Dresden has thus been working since 2012 on demountable solutions in masonry, which can be dismantled at the end of a building lifetime and sorted for recycling, which fully complies with the requirement for the reduction of rubbish and waste products. The high precision of block production today permits us to omit the levelling effect of mortar and to build dry buildings in the future, i.e. to do without the bonding principle. The associated strength reductions can be suffered without problems. The appropriate basics of such a dry building method have been researched in a collaboration between the ILEK in Stuttgart and the Xella Technologie‐ und Forschungsgesellschaft mbH in Emstal. In this research project with the abbreviation ”REMOMAB“, the basics of an energy‐efficient dry building method suitable for recycling were collected and made available for practical application. In a follow‐up project, these basics are being implemented and tested on an experimental building. Cost aspects are also to be taken into account and if possible, construction solutions available on the market will be used – modified if necessary. Another aim is for the first time to dismantle such a building and to rebuild it at another location. This is intended to demonstrate that a reuse is possible after dismantling and such a building method can react to changing demands in the housing market.