Electrophoretic deposition of carbon nanotubes

Electrophoretic deposition (EPD) has been gaining increasing interest as an economical and versatile processing technique for the production of novel coatings or films of carbon nanotubes (CNTs) on conductive substrates. The purpose of the paper is to present an up-to-date comprehensive overview of current research progress in the field of EPD of CNTs. The paper specifically reviews the preparation and characterisation of stable CNT suspensions, and the mechanism of the EPD process; it includes discussion of pure CNT coatings and CNT/nanoparticle composite films. A complete discussion of the EPD parameters is presented, including electrode materials, deposition time, electrode separation, deposition voltage and resultant electric field. The paper highlights potential applications of the resulting CNT and CNT/composite structures, in areas such as field emission devices, fuel cells, and supercapacitors.     

Increased hydropower production and hydropeaking mitigation along the Upper Inn River (Tyrol,Austria) with a combination of buffer reservoirs,diversion hydropower plants and retention basins

Research on hydropeaking in Austria started in the 1990s and the implementation of the WFD stipulated large research projects since the year 2009. The first research projects supported the process understanding and in a second investigation step, measures were evaluated. The mountains in the region of Tyrol create large heads and thus support the production of flexible energy. In this region, TIWAG is operating 9 large (>10 MW) and 27 small (<10 MW) hydropower plants, with an installed capacity of about 1,550 MW and a mean annual production of 3,000 GWh. As the governmental energy strategy foresees an extension of the hydropower production in Austria, suitable options were selected in 2004 by TIWAG and the water management framework plan for Western Tyrol was developed. This strategic planning instrument proposes five large power plants, with a generation of 1,800 GWh/year of renewable energy, which enables to reach the WFD targets, because the concept includes hydropeaking mitigation by combining buffer reservoirs (impoundments), diversion hydropower plants, and retention basins. We present our promising concept of hydropeaking mitigation and exemplify this based on the GKI, a hydropeaking diversion hydropower plants (HPP) at the Swiss/Austrian border as well as the Silz hydropeaking retention basin, with a volume of about 300,000 m³. As the presented case studies are the largest measures for hydropeaking mitigation being currently implemented in Central Europe, they have pilot-character. Thus, ongoing research and monitoring programs are expected to improve the knowledge about hydropeaking mitigation.     

Mobilising information systems scholarship for a circular economy: Review,synthesis, and directions for future research

One of today's grand societal challenges is to replace the current ‘take‐make‐waste’ economic model with a circular economic model that allows a gradual decoupling of economic activities from the consumption of finite virgin resources. While circular economy (CE) scholars have long lauded digital technologies such as sensors, distributed ledgers, or platforms as key enablers, our own community has not fully explored the potentials of information systems (IS) for a CE. Considering recent technological advances in software and hardware and our history of helping address wicked challenges, we believe the time is ripe to mobilise IS scholarship for a CE. Our findings from an interdisciplinary literature review show that research has primarily examined IS potentials for increasing efficiency of isolated intra‐organisational processes while neglecting the larger sustainability potential of IS to establish circular material flows—that is, slow down and close material loops across entire product lifecycles. In response, we propose directions for IS research that develop our knowledge of how IS can help understand and enact circular material flows to intensify and extend use of products and components and recycle waste materials. Our directions offer pathways to building and evaluating the problem‐solution pairing that could characterise a prolific CE‐IS relationship.     

Impact of sand and filler materials on the hydration behavior of calcium aluminate cement

In earlier work, we have observed discrepancies relating to the early hydration of calcium aluminate cement (CAC) when comparing data from heat flow calorimetry of CAC paste with results from mortar strength tests using the crushing method. Here, we investigated on this phenomenon and found that the sand which is used as a filler exerts a major influence on CAC hydration resulting in acceleration. Furthermore, in particular fine filler materials such as, for example, microsilica, fine limestone powder, and especially α- and γ-Al₂O₃ also produced a strong hydration accelerating effect which is dependent on their specific surface area. The mechanism underlying the acceleration is that under alkaline conditions their negative surface charge attracts calcium ions as was confirmed via inductively coupled plasma atomic emission measurements. Such a layer generates favourable conditions for the nucleation of CAC hydration products (C-A-H phases). The resulting crystalline hydrates which form on the surface of the filler particles submerged in CAC cement pore solution were visualized via SEM imaging. This way, specifically selected fillers can significantly accelerate CAC hydration and save precious lithium salts which are commonly used to boost the early strength of CAC.     

Three-dimensional simulation of sacrificial etching

Sacrificial etching is one of the most important process steps in micro-electro-mechanical systems technology, since it enables the generation of free-standing structures. These structures are often the main part of micro-mechanical devices, intended to sense or induce a mechanical movement. The etching process transforms an initial multi-segmented geometry and depends on material properties and several process conditions. One of the crucial issues for etching is the etching selectivity on different materials. The major task for the simulation is to give an answer, how sacrificial layer surfaces regress in time under the influence of process parameters and to which magnitude surrounding material segments are affected by the etching process. For this purpose we have developed a fully three-dimensional topography simulation tool, Etcher-Topo3D, which is capable to deal with realistic process conditions. The main concept is demonstrated in this work. During simulation the topography of the initial multi-segment geometry is changed which is handled by a level-set algorithm. After a simulation is finished, the level-set representation has usually to be converted back to a mesh representation to enable further analysis. To illustrate the main features of our simulation tool several examples of MEMS structures with a sacrificial layer are presented.     

A principled approach to programming with nested types in Haskell

Initial algebra semantics is one of the cornerstones of the theory of modern functional programming languages. For each inductive data type, it provides a Church encoding for that type, a build combinator which constructs data of that type, a fold combinator which encapsulates structured recursion over data of that type, and a fold/build rule which optimises modular programs by eliminating from them data constructed using the buildcombinator, and immediately consumed using the foldcombinator, for that type. It has long been thought that initial algebra semantics is not expressive enough to provide a similar foundation for programming with nested types in Haskell. Specifically, the standard folds derived from initial algebra semantics have been considered too weak to capture commonly occurring patterns of recursion over data of nested types in Haskell, and no build combinators or fold/build rules have until now been defined for nested types. This paper shows that standard folds are, in fact, sufficiently expressive for programming with nested types in Haskell. It also defines buildcombinators and fold/build fusion rules for nested types. It thus shows how initial algebra semantics provides a principled, expressive, and elegant foundation for programming with nested types in Haskell.     

Analyzing the metallurgical and cultural backgrounds of two Han-dynasty bronze-mirror fragments

Chinese TLV-bronze mirrors dating to the Han dynasty (206 B.C.-220 A.D.) were popular objects of everyday life as well as highly esteemed works of art. The decorated back of the mirror characterizes the culture of this period as well as the excellent early Chinese casting techniques.     

DuD Recht

DuD Recht

DuD Recht     

Formal testing for separation assurance

In order to address the rapidly increasing load of air traffic operations, innovative algorithms and software systems must be developed for the next generation air traffic control. Extensive verification of such novel algorithms is key for their adoption by industry. Separation assurance algorithms aim at predicting if two aircraft will get closer to each other than a minimum safe distance; if loss of separation is predicted, they also propose a change of course for the aircraft to resolve this potential conflict. In this paper, we report on our work towards developing an advanced testing framework for separation assurance. Our framework supports automated test case generation and testing, and defines test oracles that capture algorithm requirements. We discuss three different approaches to test-case generation, their application to a separation assurance prototype, and their respective strengths and weaknesses. We also present an approach for statistical analysis of the large numbers of test results obtained from our framework.