Manifold surface reconstruction of an environment from sparse Structure-from-Motion data

The majority of methods for the automatic surface reconstruction of an environment from an image sequence have two steps: Structure-from-Motion and dense stereo. From the computational standpoint, it would be interesting to avoid dense stereo and to generate a surface directly from the sparse cloud of 3D points and their visibility information provided by Structure-from-Motion. The previous attempts to solve this problem are currently very limited: the surface is non-manifold or has zero genus, the experiments are done on small scenes or objects using a few dozens of images. Our solution does not have these limitations. Furthermore, we experiment with hand-held or helmet-held catadioptric cameras moving in a city and generate 3D models such that the camera trajectory can be longer than one kilometer.     

Statistical prioritization for software product line testing: an experience report

Software product lines (SPLs) are families of software systems sharing common assets and exhibiting variabilities specific to each product member of the family. Commonalities and variabilities are often represented as features organized in a feature model. Due to combinatorial explosion of the number of products induced by possible features combinations, exhaustive testing of SPLs is intractable. Therefore, sampling and prioritization techniques have been proposed to generate sorted lists of products based on coverage criteria or weights assigned to features. Solely based on the feature model, these techniques do not take into account behavioural usage of such products as a source of prioritization. In this paper, we assess the feasibility of integrating usage models into the testing process to derive statistical testing approaches for SPLs. Usage models are given as Markov chains, enabling prioritization of probable/rare behaviours. We used featured transition systems, compactly modelling variability and behaviour for SPLs, to determine which products are realizing prioritized behaviours. Statistical prioritization can achieve a significant reduction in the state space, and modelling efforts can be rewarded by better automation. In particular, we used MaTeLo, a statistical test cases generation suite developed at ALL4TEC. We assess feasibility criteria on two systems: Claroline, a configurable course management system, and Sferion?, an embedded system providing helicopter landing assistance.     

Fat crystal-stabilized water-in-oil emulsions as controlled release systems

Fat crystal-stabilized water-in-oil emulsions were developed as a controlled release matrix for the delivery of salt. Glycerol monostearate (GMS), glycerol monooleate (GMO) and polyglycerol polyricinoleate (PGPR) were used as emulsifiers and hydrogenated canola oil (HCO) was added as a solid fat. Salt release towards an external aqueous phase was measured via conductivity as a function of temperature. Following 2 h of release at room temperature, the GMS emulsion had the highest encapsulation efficiency followed by the PGPR-HCO, PGPR-only and GMO–HCO emulsions, respectively. The GMS crystals formed Pickering shells around the water droplets that effectively prevented salt transport whereas in the GMO–HCO emulsion, the presence of partial interfacial HCO crystal coverage resulted in lower retention. All crystal-stabilized emulsions showed rapid release of their salt load upon melting of the surrounding solid fat, while little temperature effect was observed with the PGPR-based emulsions. However, these emulsions were sensitive to the presence of a salt concentration gradient whereas the fat crystal-stabilized emulsions showed little response. Overall, this study demonstrated that the spatial distribution of the stabilizing fat crystals (i.e., interfacial vs. continuous phase) as well as the emulsifier type were critical factors controlling salt release patterns.     

Acknowledgement of Referees

The management of land resources, particularly the role of planning regulations, is critical in defining what land can be used in urban development – and this throws up certain key questions: How can one best manage land resources available? How can one address future urban development needs on the basis of existing land from a sustainable perspective? In this article we propose to question the extent of planning theories in the light of concrete urban development using land availability information. By using comprehensive national data we explore the case of Luxembourg, a small European country facing exacerbated pressures for metropolitanization. We use scenarios that go from a lesser to a greater degree of sustainability in order to project and articulate different configurations of land consumption based on a critical literature review (Smart Growth, New Urbanism, and transit oriented development (TOD)). We explore how modelling might be used to help inform spatial planning for urban growth. This framework is intended as an approach that would be applicable to other urban settings by using data that can be found in any typical municipal authority along with implementation in a geographical information system (GIS). The results create a tool which is useful for planning, monitoring or forecasting land consumption. The results also clearly show the limited impact of planning practices in terms of sustainability using land availability.     

Consolidation by spark plasma sintering of polyimide and polyetheretherketone

This article presents two high‐temperature thermoplastic powders which were sintered by spark plasma sintering in order to get homogeneous mechanical properties. Dense polyimide (PI) and polyetheretherketone (PEEK) specimens were obtained at temperatures as low as 320°C for PI and 200°C for PEEK, respectively. Relative densities higher than 99% were reached for both materials. In order to characterize their properties, in situ measurements with compression and hardness tests were carried out on sintered samples. This method allowed to obtain polymeric materials with improved mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40783.     

Experimental study of the stacking sequence effect on polymer/composite multi-layers submitted to thermomechanical cyclic loadings

Fast filling of hydrogen pressure tank leads to thermomechanical stresses in vessel structure. In this paper, the aim is to study the thermomechanical behaviour of the material used in the vessel structure. Flat coupons made of the same constituents as the hydrogen tank materials and with different stacking sequences have been tested under quasi-static tensile tests and fatigue. Three types of fatigue tests have been performed in order to understand damage mechanisms due to interactions between thermal and mechanical stresses: thermomechanical fatigue, 1 Hz mechanical fatigue and mechanical fatigue with a constant stress level stage. Damage development has been followed by acoustic emission and microscopic observations. Results show that, whatever the applied loading, there is a significant influence of the stacking sequence of the composite part. Moreover, the comparison of the material response to the different types of fatigue has revealed the harmful role of coupled temperature/mechanical cyclic stresses.     

TEM observations and finite element modelling of channel deformation in pre-irradiated austenitic stainless steels - Interactions with free surfaces and grain boundaries

Transmission electron microscopy (TEM) observations show that dislocation channel deformation occurs in pre-irradiated austenitic stainless steels, even at low stress levels (∼175 MPa, 290 °C) in low neutron dose (∼0.16 dpa, 185 °C) material. The TEM observations are utilized to design finite element (FE) meshes that include one or two “soft” channels (i.e. low critical resolved shear stress (CRSS)) of particular aspect ratio (length divided by thickness) embedded at the free surface of a “hard” matrix (i.e. high CRSS). The CRSS are adjusted using experimental data and physically based models from the literature. For doses leading to hardening saturation, the computed surface slips are as high as 100% for an applied stress close to the yield stress, when the observed channel aspect ratio is used. Surface slips are much higher than the grain boundary slips because of matrix constraint effect. The matrix CRSS and the channel aspect ratio are the most influential model parameters. Predictions based on an analytical formula are compared with surface slips computed by the FE method. Predicted slips, either in surface or bulk channels, agree reasonably well with either atomic force microscopy measures reported in the literature or measures based on our TEM observations. Finally, it is shown that the induced surface slip and grain boundary stress concentrations strongly enhance the kinetics of the damage mechanisms possibly involved in IASCC.     

Why low powdered activated carbon addition reduces membrane fouling in MBRs

Previous research had demonstrated that powdered activated carbon (PAC), when applied at very low dosages and long SRTs, reduces membrane fouling in membrane bioreactor (MBRs). In this contribution several mechanisms to explain this beneficial effect of PAC were investigated, including enhanced scouring of the membrane surface by PAC particles, adsorption of membrane foulants by PAC and subsequent biodegradation and a positive effect of PAC on the strength of the sludge flocs. It was concluded that the latter mechanism best explains why low dosages of PAC significantly reduce membrane fouling. Cheaper alternatives for PAC may have a similar effect.