Non-uniformity issues and workarounds in bounded-size sampling

A variety of schemes have been proposed in the literature to speed up query processing and analytics by incrementally maintaining a bounded-size uniform sample from a dataset in the presence of a sequence of insertion, deletion, and update transactions. These algorithms vary according to whether the dataset is an ordinary set or a multiset and whether the transaction sequence consists only of insertions or can include deletions and updates. We report on subtle non-uniformity issues that we found in a number of these prior bounded-size sampling schemes, including some of our own. We provide workarounds that can avoid the non-uniformity problem; these workarounds are easy to implement and incur negligible additional cost. We also consider the impact of non-uniformity in practice and describe simple statistical tests that can help detect non-uniformity in new algorithms.     

Mikrostrukturielle Charakterisierung von ultra-hochfesten Schweißgütern

Welded steel structures are a crucial part of lightweight constructions in several industrial segments. The filler metal plays a vital role in optimizing the properties of welded joints. In this study different methods were used to characterize the microstructure of ultra-high strength all-weld metal samples with different chemical compositions. It was evaluated which method can be used to link the grain size of a sample to its toughness.     

Enhancement of limited water supply network data for deterioration modelling and determination of rehabilitation rate

In the past decades, the main focus of water supply management has moved from construction of new water supply networks to rehabilitation and adaptation of the existing infrastructure. The decision-making process for the rehabilitation management relies heavily on the quality of the applied deterioration model. A recurring problem in the application of such models relates to the quality and availability of network data. These data are often incomplete or unreliable because building measures and damages are only documented properly recently and the recovery of older data is difficult and expensive. A key point in rehabilitation planning is therefore data collection and data reconstruction. Consequently, the aim of this paper is to present a methodology for the enhancement of the available data of water supply networks and the prognosis of the necessary rehabilitation rates under limited data availability. Results indicate that the presented data reconstruction technique has advantages as compared to traditional data extrapolation. It also allows the reconstruction of fragmentary data about existing water supply and wastewater collection systems for the operating utilities. However, it cannot be used for reconstructing failure types as well as the whole information on pipes (e.g. more than two missing information).     

Damage phenomena in lubricated rolling-sliding wear of a gas carburised 0.85%Mo low-alloyed sintered steel: theoretical analysis and experimental verification

The resistance to surface and subsurface damage during lubricated rolling-sliding wear of a carburised low-alloy sintered steel and the effect of shot peening were investigated. The formation of both contact fatigue cracks and of brittle tensile cracks may be predicted by a theoretical model that was experimentally validated. Carburising is effective in increasing the resistance to contact fatigue, but pores in a hard and brittle matrix may act as pre-existing cracks. Shot peening increases the contact fatigue resistance since compressive residual stresses oppose the nucleation of surface cracks.     

The Drop Weight Test Revisited: Characterization of the Crushability of Hot Sinter and Validation of the Approach with Natural Rocks

The crushing behaviour of sinter from blast furnace operations is known to depend on its temperature. In order to characterize it, hot sinter was subject to single particle tests in a very basic drop weight tester. Additionally, a laboratory jaw crusher was sacrificed to work the same feed material. As the results regarding net energy input were not consistent, two common rocks were tested in comparison with both the drop weight and the jaw crusher. Although some discrepancies remained, the results with the rocks can basically be considered as consistent. This investigation illustrates some of the difficulties that can arise when established test methods are applied on material with deviant properties.     

Increase in Generation of Poly-Crystalline Silicon by Atmospheric Pressure Plasma-Assisted Excimer Laser Annealing

In this work, a novel atmospheric pressure plasma-assisted excimer laser annealing method for increasing the generation efficiency of poly-crystalline silicon from amorphous silicon layers is presented. Here, both the plasma and the laser propagate coaxially in order to generate energetic synergies. The influence of different process gases and plasma discharge modes as well as the working distance were investigated. Depending on the particularly applied plasma, the crystalline area was increased by a factor of approx. 1.1 to 1.9, where the highest efficiency was observed when introducing an argon plasma beam to the annealing process.     

Fouling Detection in an Optically Accessible Microstructured Heat Exchanger

The application of highly effective microstructured devices in continuous production and industrial environments is frequently prone to fouling. A new method is presented to characterize fouling in these microstructures. Thermal fouling of aqueous solutions containing whey protein were used as a test system. Different fouling effects could be observed and distinguished. Integral fouling indicators, such as thermal fouling resistance and pressure drop, as conventional criteria for the occurrence of fouling were compared with direct local optical observation. Low thermal fouling resistances could be detected.     

Prozesskette zum stofflichen Recycling von Kunststoffabfällen

The material recycling rate for post-consumer plastic in Austria currently ranges around 25?%, because only post-consumer plastic fractions which are disposed as clean mono-materials are available for material recycling. A significant enhancement of the material recycling rate can be achieved with a process chain consisting of wet mechanical processing and thermochemical conversion. The wet mechanical process step enriches polyolefin and polystyrene from different waste sources, which are used as feedstock for a solvent-based, thermal depolymerisation. Via thermal cracking petrochemical intermediates (i.e. short- and long-chained, aromatic and paraffinic hydrocarbons) are produced, which can be appropriately fed into a conventional crude oil refinery and processed to marketable products. In this way, the material cycle can be closed economically feasible. Both the wet mechanical processing and the thermochemical conversion have been proofed in laboratory scale and are currently transferred to pilot scale.     

Liquid Organic Hydrogen Carriers as an efficient vector for the transport and storage of renewable energy

This contribution proposes the usage of Liquid Organic Hydrogen Carriers (LOHC) for the storage and subsequently the transport of renewable energy. It is expected that a significant share of future energy consumption will be satisfied with the import of energy coming from regions with high potential for renewable generation, e.g. the import of solar power from Northern Africa to Europe. In this context the transport of energy in form of chemical carriers is proposed supplementary to electrical transmission. Because of their high storage density and good manageability under ambient conditions Diesel-like LOHC substances could be transported within the infrastructure that already exists for the handling of liquid fossil fuels (e.g. oil tankers, tank trucks, pipelines, etc.). A detailed assessment of energy consumption as well as of transport costs is conducted that confirms the feasibility of the concept.