N-dimensional versus (N–1)-dimensional connectivity testing of first-order queries to semi-algebraic sets

This paper addresses the question whether one can determine the connectivity of a semi-algebraic set in three dimensions by looking only at two-dimensional “samples” of the set, where these samples are defined by first-order queries. The question is answered negatively for two classes of first-order queries: cartesian-product-free, and positive one-pass. Floris Geerts is Post-doctoral researcher of the FWO-Vlaanderen. Hasselt University is a partner in the transnationale Universiteit Limburg; the authors belong to the School voor Informatietechnologie.     

Stabilization of Free Lime in BOF Slag by Melting and Solidification in Air

The present study reports on the mineralogy of BOF slag after melting and solidification under Ar and air atmosphere. Results indicate that free lime can be effectively stabilized in air without additional stabilizers like SiO₂. The stabilization mechanism was analyzed, and the role of the oxygen partial pressure was explored. Wustite is believed to be oxidized to hematite under high oxygen partial pressure and then stabilizes the free lime by forming brownmillerite.     

Forecasting broadband Internet adoption on trains in Belgium

Thanks to the massive success of mobile access devices such as netbooks or Apple’s iPhone 3G, Internet on the move has become one of the prominent features of today’s information society. With the emergence of wireless and mobile communication networks, the railroad industry is now catching up on this new technology in their battle with low-cost operators to bring more productivity and entertainment possibilities to its passengers. With millions of daily commuters as potential service users, this transport branch offers high business opportunities. However, while most field trials and research effort have mainly focused on the enabling technology, little research effort has been conducted to forecast the demand-side. This article tries to fill this gap by presenting original results gathered from a large-scale survey amongst 1324 regular train travellers. By means of the Product Specific Adoption Potential method, we predict the potential market penetration of wireless Internet services onboard trains and estimate the size and nature of five adopter segments in terms of socio-demographics, drivers and thresholds, willingness to pay, applications and quality of service. We will discuss the practical implications of these insights in order to develop viable business models, set up introduction strategies and build out user-driven infrastructure networks.     

Haematological status of wintering great tits (Parus major) along a metal pollution gradient

In the long-term biomonitoring of wild populations inhabiting polluted areas, the use of non-destructive biomarkers as markers of condition is very important. We examined the possible effects of metal pollution on the haematological status of adult great tits (Parus major) along a well-established pollution gradient near a non-ferrous smelter in Belgium. We measured blood and feather metal concentrations and assessed the haematological status (amount of red blood cells, haemoglobin concentration, haematocrit, mean corpuscular volume and mean corpuscular haemoglobin) of adult great tits during winter at four study sites. Metal concentrations in blood and feathers indicated that cadmium and lead were the most important metals in the pollution gradient under study. Measurements of haematological parameters revealed that haemoglobin concentration, haematocrit, mean corpuscular volume and mean corpuscular haemoglobin were lower in great tits from the more polluted sites. These parameters were significantly negatively correlated with blood lead concentration. The amount of red blood cells, however, did not significantly differ among study sites. Our results indicate that the haematological status of great tits is negatively affected by metal pollution and may therefore be used as a successful biomarker for monitoring the negative impact of metal exposure in the wild.     

Gate-defined confinement in bilayer graphene-hexagonal boron nitride hybrid devices

We report on the fabrication and measurement of nanoscale devices that permit electrostatic confinement in bilayer graphene on a substrate. The graphene bilayer is sandwiched between hexagonal boron nitride bottom and top gate dielectrics. Top gates are patterned such that constrictions and islands can be electrostatically induced. The high quality of the devices becomes apparent from the smooth pinch-off characteristics of the constrictions at low temperature with features indicative of conductance quantization. The islands exhibit clear Coulomb blockade and single-electron transport.     

Investigating the influence of QoS on personal evaluation behaviour in a mobile context

The efficiency of personal video suggestions generated by recommender systems is highly dependent on the quality of the obtained user feedback. This feedback has to reflect the personal interest in the content of the viewed video, to obtain accurate results. However, user feedback might undesirably be influenced by additional aspects such as the loading speed or the quality of the video. To date, this issue has received very little research attention. Therefore, this study investigates the direct influence of audio-visual quality parameters on explicit user feedback for the first time to our knowledge via a mobile, Living Lab experiment. This paper proposes a feedback model which takes the Quality of Service (QoS) parameters of the mobile network into account. This model can be used as an additional feedback filter for video recommendation systems that could help to eliminate the influences of QoS on explicit user feedback.     

Detailed analysis of exciton decay time change in organic light‐emitting devices caused by optical effects

Abstract— The exciton decay time in organic light‐emitting devices (OLEDs) depends on the optical environment, i.e., the thicknesses and refractive indices of all layers in a device. The decay of an exciton can occur through a radiative or a non‐radiative channel. Each of these channels has a probability, which is expressed by, respectively, the radiative and the non‐radiative decay rate. The radiative decay rate is influenced by the optical environment, i.e., the OLED's thin‐film layer structure. In this paper, a model for estimating the change of the exciton decay time (inverse of the decay rate) is presented. In addition, the decay time change in both top‐ and bottom‐emitting OLEDs as a function of the charge‐transport layer thicknesses has been investigated. Furthermore, the most important mechanism responsible for the exciton decay time change is outlined.     

A pragmatic model for selective laser melting with evaporation

Selective laser melting (SLM) is a Rapid Manufacturing technique in which parts of complex shape are produced by selectively melting layers of powder. A thorough understanding of the process is crucial for a good control of the properties of the produced parts. In this paper we present a pragmatic engineering model to study aspects of the SLM process using an enthalpy formulation and accounting for shrinkage and laser light penetration. We investigate the importance of evaporation for a set of process parameters relevant to production and find that evaporation is a phenomenon that cannot be neglected at realistic power inputs. However, phenomena such as Marangoni convection and wetting due to surface tension effects need to be considered in the future.     

Content and context for mobile television: Integrating trial,expert and user findings

Mobile television brings together two contemporary social developments: enhanced end-user mobility and new forms of access to media content. DVB-H trial activities worldwide reveal the industry’s belief in broadcast mobile television as ‘the next big thing’. To date however, these trials are mostly technology-driven and tend to overlook the user. As the past has innumerably proven, end-user acceptance and success of new media innovations are highly dependent on content, as the end-user can be considered as rather technology-agnostic. Evidently, content – suited to the consumer’s demands – is assumed to be a main key factor for the success of mobile television.