Level‐of‐Detail Streaming and Rendering using Bidirectional Sparse Virtual Texture Functions

Bidirectional Texture Functions (BTFs) are among the highest quality material representations available today and thus well suited whenever an exact reproduction of the appearance of a material or complete object is required. In recent years, BTFs have started to find application in various industrial settings and there is also a growing interest in the cultural heritage domain. BTFs are usually measured from real‐world samples and easily consist of tens or hundreds of gigabytes. By using data‐driven compression schemes, such as matrix or tensor factorization, a more compact but still faithful representation can be derived. This way, BTFs can be employed for real‐time rendering of photo‐realistic materials on the GPU. However, scenes containing multiple BTFs or even single objects with high‐resolution BTFs easily exceed available GPU memory on today's consumer graphics cards unless quality is drastically reduced by the compression. In this paper, we propose the Bidirectional Sparse Virtual Texture Function, a hierarchical level‐of‐detail approach for the real‐time rendering of large BTFs that requires only a small amount of GPU memory. More importantly, for larger numbers or higher resolutions, the GPU and CPU memory demand grows only marginally and the GPU workload remains constant. For this, we extend the concept of sparse virtual textures by choosing an appropriate prioritization, finding a trade off between factorization components and spatial resolution. Besides GPU memory, the high demand on bandwidth poses a serious limitation for the deployment of conventional BTFs. We show that our proposed representation can be combined with an additional transmission compression and then be employed for streaming the BTF data to the GPU from from local storage media or over the Internet. In combination with the introduced prioritization this allows for the fast visualization of relevant content in the users field of view and a consecutive progressive refinement.     

Formalizing non-termination of recursive programs

In applicative theories the recursion theorem provides a term which solves recursive equations. However, it is not provable that a solution obtained by is minimal. In the present paper we introduce an applicative theory in which it is possible to define a least fixed point operator. Still, our theory has a standard recursion theoretic interpretation.     

Clinorotation Increases the Growth of Utricular Otoliths of Developing Cichlid Fish

It has been shown earlier that hypergravity slows down inner ear otolith growth in developing fish as an adaptation towards increased environmental gravity. Suggesting that otolith growth is regulated by the central nervous system, thus adjusting otolithic weight to produce a test mass, applying functional weightlessness should yield an opposite effect, i.e. larger than normal otoliths. Therefore, larval siblings of cichlid fish (Oreochromis mossambicus) were housed for 7 days in a submersed, two-dimensional clinostat, which provided a residual gravity of approximately 0.007g. After the experiment, otoliths were dissected and their size (area grown during the experiment) was determined. Maintenance in the clinostat resulted in significantly larger utricular otoliths (lapilli, involved in graviperception). There were no statistical significant differences regarding saccular otoliths obtained (sagittae, involved in transmitting linear acceleration and, especially, in the hearing process). These results indicated, that the animals had in fact received functional weightlessness. In line and contrasting results on the otoliths of other teleost species kept at actual microgravity (spaceflight) or within rotating wall vessels are discussed.     

Pathways and pitfalls of implementing the use of woodfuels in Germany's bioenergy sector

The paper presents an empirical study on the use of woody biomass for energy supply in Germany and the federal state of Brandenburg. It aims to explain the role forestry enterprises have for bioenergy provision in this area. The ‘Institutions of Sustainability’ framework is used as an analytical tool to investigate the role of private and public actors in these transactions, respectively, in the governance structures they are subject to. Empirical evidence was gathered by in-depth interviews with actors from forestry and bioenergy practice. Triggered by favorable governance structures, i.e. strong support by national and regional policies, rising prices for fossil energy sources, and co-operation of committed individuals and groups, a new bioenergy industry has been successfully established. However, the forestry sector has so far been just a marginal fuel supplier for this industry. The study identifies pitfalls impeding a broad implementation of wood-energy supply in forestry: not cost-covering prices offered by the bioenergy sector, lacking market transparency and security of supply, lacking mobilization of forest wood, and a preference among forest managers to sell products to the wood-processing industry. In terms of the Institutions of Sustainability the properties of transactions (asset specificities, uncertainties, separability), characteristics of actors (values, rationality) and governance structures (long-term contractual obligations elsewhere) are decisive in explaining the current form of transaction.     

Consideration of the mechanical behaviour of small fatigue cracks

The mechanical behaviour of small fatigue cracks is investigated for a low, medium and high strength material. At first an elastic consideration is performed which give a good impression how the stress fields change with crack size. In part 2 a full elastic-plastic analysis of short cracks is performed using a new numerical scheme to simulate the growth of shear bands emanating from the crack tip. The influence of material and loading paramters as well as of the crack size on the plastic crack tip opening displacement is discussed. It is also investigated how it is possible to get a conservative estimate of the crack tip deformation at small cracks.     

A new model of the effect of stirring intensity on the rate of secondary nucleation

Secondary nucleation in industrial crystallizers depends on both supersaturation and mechanical stress by stirring. Most models which consider mechanical stress assume that nucleation is proprotional to the energy transferred to the crystals during collisions. This is not based on any physical relationship and, in addition, the models do not satisfactorily reproduce the experimental results. Own model, based on the theory of Hertz/Huber, which accounts for the stress of the crystals caused by impact, gave better results. This well-known and proven theory allows the calculation of the volume abraded during collisions between crystals and stirrer or walls. Introducing a nucleate efficienncy, the effect of mechanical stress on the rate of secondary nucleation, due to stirring intensity and crystallizer size, can be determined.     

SOCIO-ECONOMIC ASPECTS OF THE AUSTRIAN 200 kWp-PHOTOVOLTAIC-ROOFTOP PROGRAMME

Between 1992 and 1994 a 200 kWp-rooftop programme to promote small grid-connected Photovoltaic (PV) systems was conducted in Austria. Within this programme about 100 PV systems with an average capacity of 2.28 kWp were installed. This paper investigates the socio-economic aspects of this programme and the prospects for a further dissemination of this technology. The major conclusions of this investigation are as follows: (1) The motives to invest in a PV system are: (i) environmental protection; (ii) an alternative to nuclear power; (iii) technical interest. Yet, it is also important that the public supports this purchase by means providing subsidies. (2) The purchase of a PV system leads to different changes in consumer behaviour. Consumers with low initial consumption increased their electricity demand slightly, while the majority of consumers with high initial electricity demand saved electricity. (3) The financial incentives in the programme were not optimally designed. With the same amount of total subsidies it would have been possible to promote more PV systems. (4) The key factors for a further dissemination of PV systems are: (i) financial incentives; (ii) a reduction of the investment costs; (iii) increase in reliability; (iv) distribution of information; (v) enhancement of environmental awareness.     

Influence of impurities and deformation temperature on the saturation microstructure and ductility of HPT-deformed nickel

Ni with different purities between 99.69 and 99.99 wt.% was deformed by high-pressure torsion (HPT) to high strains, where no further refinement of the microstructure is observed. The HPT deformation temperature varied between −196 and 400 °C. Both impurities and temperature significantly affect the lower limit of the grain size obtained by HPT. In the investigated samples, carbon was the most important impurity element in controlling the limit of grain refinement. The decrease in grain size due to an increase in the carbon content from 0.008 to 0.06 wt.% for HPT-deformed Ni samples at room temperature enhanced the ultimate tensile strength from 1000 to 1700 MPa. Surprisingly, the carbon content did not deteriorate the ductility, defined as the reduction in area, which is mainly limited by the total amount of impurities besides carbon. Furthermore, the deformation temperature dependency on ductility was not very pronounced and only visible for deformation temperatures above 200 °C.