Non-exclusion effects in g.p.c.: a review

Steric exclusion is generally the predominant separation mechanism in gel chromatography. However, adsorption on the gel and dissolution inside the gel also occur, greatly disturbing solute retention and especially hindering universal calibration for polymers. Some typical examples of such effects are given. The corresponding mechanisms are discussed and the bases of methods to present non-exclusion effects are given.     

Calculation of microstresses in a thick non-symmetric heterogeneous plate

We consider the thermoelastic behaviour of a thick non-symmetric heterogeneous plate and containing in its interior a large number of periodically distributed transverse holes or inclusions. We use theReissner-Mindlin thermoelastic linear model of thick plates with a known temperature and we distinguish displacements in the upper and lower part of the plate with respect to the middle plane. Due to the structure of the plate, thermal and elastic coefficients are non-uniformly and rapidly oscillating functions of the space variable.Two-Scale Convergence, which is the state of the art in the technique of mathematical homogenization, is used to obtain convergence results and formulas allowing one to calculate the distribution ofMicrostrains andMicrostresses inside the plate when a macroscopic behaviour is given. We give an example illustrating the computation of theseMicrostresses in the case of a symmetric plate.     

vSocial: a cloud-based system for social virtual reality learning environment applications in special education

Virtual Learning Environments (VLEs) are spaces designed to educate student groups remotely via online platforms. Although traditional VLEs have shown promise in educating students, they offer limited immersion that overall diminishes learning effectiveness. In this paper, we describe vSocial, a cloud-based virtual reality learning environment (VRLE) system that can be deployed over high-speed networks using the High Fidelity “social VR” platform. vSocial provides flexible control of group learning content and compliance with established VLE standards with improved immersive user experience for both instructor(s) and students. For our vSocial development, we build upon the use case of an existing special education VLE viz., iSocial that trains youth with Autism Spectrum Disorder by implementing the Social Competence Intervention (SCI) curriculum. The vSocial can be used to: (a) implement multiple learning modules using wearable VR technologies, (b) integrate cognitive state sensing devices, and (c) organize learning session data securely using web applications hosted on cloud resources. Our experiment results show that the VR mode of content delivery in vSocial better stimulates the generalization of lessons to the real world than non-VR lessons, and provides improved immersion when compared to an equivalent desktop version. Further, usability study results show that users can successfully use the web application features in vSocial for group learning activities with ease-of-use and consistency.

     

Fast prototyping of parallel-vision applications using functional skeletons

We present a design methodology for real-time vision applications aiming at significantly reducing the design-implement-validate cycle time on dedicated parallel platforms. This methodology is based upon the concept of algorithmic skeletons, i.e., higher order program constructs encapsulating recurring forms of parallel computations and hiding their low-level implementation details. Parallel programs are built by simply selecting and composing instances of skeletons chosen in a predefined basis. A complete parallel programming environment was built to support the presented methodology. It comprises a library of vision-specific skeletons and a chain of tools capable of turning an architecture-independent skeletal specification of an application into an optimized, deadlock-free distributive executive for a wide range of parallel platforms. This skeleton basis was defined after a careful analysis of a large corpus of existing parallel vision applications. The source program is a purely functional specification of the algorithm in which the structure of a parallel application is expressed only as combination of a limited number of skeletons. This specification is compiled down to a parametric process graph, which is subsequently mapped onto the actual physical topology using a third-party CAD software. It can also be executed on any sequential platform to check the correctness of the parallel algorithm. The applicability of the proposed methodology and associated tools has been demonstrated by parallelizing several realistic real-time vision applications both on a multi-processor platform and a network of workstations. It is here illustrated with a complete road-tracking algorithm based upon white-line detection. This experiment showed a dramatic reduction in development times (hence the term fast prototyping), while keeping performances on par with those obtained with the handcrafted parallel version. Received: 22 July 1999 / Accepted: 9 November 2000     

Interconnection between Trait,Structure, and Composition of Grain Boundaries in Cu(In,Ga)Se2 Thin‐Film Solar Cells

Grain boundaries (GBs) are crucial for solar cells incorporating polycrystalline absorbers and particularly for those characterized by small grain sizes (≈2 µm). For example, random GBs in Si solar cells are found to have a detrimental effect on the cell performance being characterized by an increased recombination activity relative to grains. Yet, their role in Cu(In,Ga)Se₂ (CIGS) solar cells still remains controversial. The recent electron‐beam‐induced current (EBIC) study shows that 58% of the GBs in CIGS exhibit enhanced electrical properties considered to be benign (for the device performance). Yet, they coexist with 16% detrimental GBs (reduced electrical properties) and 27% neutral ones (no change in electrical property when compared with the bulk). In the present study, these different GBs are investigated by combining EBIC with electron backscattered diffraction and atom probe tomography techniques on identical GBs. For the first time, a successful correlation is shown (for any device) that interconnects the GB characteristics to its composition. Sufficient statistics demonstrate that the collective fluctuations of all elements at GBs determine its trait. In general, benign (detrimental) GBs are characterized by Cu depletion (enrichment) that favored the formation of donor (acceptor) defects.     

Effects of the viewing context on target detection. Implications for road lighting design

The Small Target Visibility (STV) model is the main model used to assess the quality of road lighting installations (IESNA, 2000). However, this model is based on a simple detection task in foveal vision using psychophysical data from laboratory conditions. The purpose of this study was to evaluate the impact of a complex background and apparent motion on target detection performance in mesopic vision, for three luminance contrasts, with reference to the STV scenario. To do so, participants were invited to detect standard square targets varying in terms of contrast presented in three Conditions: a uniform background, still images, and a video. Luminance levels were chosen in the mesopic domain relevant for road lighting at night. Images and video were chosen in relation to a driving task at night. The results showed that both the spatial context and the apparent motion had a negative impact on peripheral target detection performance: contrasts which are easy to detect in conditions close to the STV reference data may lead to poor performance if one adds context variables. These results give evidence that the STV model used for road lighting design based on laboratory data is limited, which strengthens previous results (Mayeur et al., 2008). The results are discussed in relation to the field factor used by practitioners to compensate for the differences between the STV reference scenario (detection of a small square target on a lit road while driving) and the STV psychophysical reference data.