Full-field birefringence imaging by thermal-light polarization-sensitive optical coherence tomography. I. Theory

A method for measuring birefringence by use of thermal-light polarization-sensitive optical coherence tomography is presented. The use of thermal light brings to polarization-sensitive optical coherence tomography a resolution in the micrometer range in three dimensions. The instrument is based on a Linnik interference microscope and makes use of achromatic quarter-wave plates. A mathematical representation of the instrument is presented here, and the detection scheme is described, together with a discussion of the validity domain of the equations used to evaluate the birefringence in the presence of white-light illumination.     

On the designing of densely dispersion-managed optical fiber systems for ultrafast optical communication

We present some theoretical and experimental results which suggest the possibility of constructing a non-empirical methodology of designing optical transmission systems with ultra high bit-rate per channel. Theoretically, we present an average dispersion decreasing densely dispersion-managed (A4dm) fiber system, which exhibits many advantages over the densely dispersion-managed fiber system, such as the possibility of transmitting chirp-free Gaussian pulses at 160 Gbit/s per channel over transoceanic distances, with a reduced energy and minimal intra-channel interaction. Experimentally we present generation of a 160-GHz picosecond pulse train at 1550 nm using multiple four-wave mixing temporal compression of an initial dual frequency beat signal in the anomalous-dispersion regime of a non-zero dispersion shifted fiber. A complete intensity and phase characterization of the pulse train by means of a frequency-resolved optical gating technique is achieved, showing generation of transform-limited pedestal-free Gaussian pulses.     

Performance Measurement in the Belgian Document Ordering and Delivery System Impala

This paper deals with performance measures and performance indicators in the Impala electronic document ordering and delivery system for research libraries in Belgium and compares these with some international standards as, e.g., the ProLib/PI study commissioned by the European Commission.Performance measures: Costs (clearinghouse principle) Number of ILL requests made to other libraries Number of ILL requests made to other libraries without success Number of ILL requests made to other libraries with success Number of ILL requests received from other libraries Number of ILL requests received from other libraries and not satisfied Number of ILL requests received from other libraries that were satisfied Frequency asked titlesPerformance indicators: Success rate Borrowing-lending ratio per library Response times, split into several segments of the ILL-procedureThe article concludes with some indications for quality measurement in electronic document delivery where Impala will be able to measure the real supply times as perceived by the end user.     

Stability of feature selection algorithms: a study on high-dimensional spaces

With the proliferation of extremely high-dimensional data, feature selection algorithms have become indispensable components of the learning process. Strangely, despite extensive work on the stability of learning algorithms, the stability of feature selection algorithms has been relatively neglected. This study is an attempt to fill that gap by quantifying the sensitivity of feature selection algorithms to variations in the training set. We assess the stability of feature selection algorithms based on the stability of the feature preferences that they express in the form of weights-scores, ranks, or a selected feature subset. We examine a number of measures to quantify the stability of feature preferences and propose an empirical way to estimate them. We perform a series of experiments with several feature selection algorithms on a set of proteomics datasets. The experiments allow us to explore the merits of each stability measure and create stability profiles of the feature selection algorithms. Finally, we show how stability profiles can support the choice of a feature selection algorithm. Alexandros Kalousis received the B.Sc. degree in computer science, in 1994, and the M.Sc. degree in advanced information systems, in 1997, both from the University of Athens, Greece. He received the Ph.D. degree in meta-learning for classification algorithm selection from the University of Geneva, Department of Computer Science, Geneva, in 2002. Since then he is a Senior Researcher in the same university. His research interests include relational learning with kernels and distances, stability of feature selection algorithms, and feature extraction from spectral data. Julien Prados is a Ph.D. student at the University of Geneva, Switzerland. In 1999 and 2001, he received the B.Sc. and M.Sc. degrees in computer science from the University Joseph Fourier (Grenoble, France). After a year of work in industry, he joined the Geneva Artificial Intelligence Laboratory, where he is working on bioinformatics and datamining tools for mass spectrometry data analysis. Melanie Hilario has a Ph.D. in computer science from the University of Paris VI and currently works at the University of Geneva’s Artificial Intelligence Laboratory. She has initiated and participated in several European research projects on neuro-symbolic integration, meta-learning, and biological text mining. She has served on the program committees of many conferences and workshops in machine learning, data mining, and artificial intelligence. She is currently an Associate Editor of theInternational Journal on Artificial Intelligence Toolsand a member of the Editorial Board of theIntelligent Data Analysis journal.     

Modeling adaptive behaviors in Context UNITY

Context-aware computing refers to a paradigm in which applications sense aspects of the environment and use this information to adjust their behavior in response to changing circumstances. In this paper, we present a formal model and notation (Context UNITY) for expressing quintessential aspects of context-aware computations; existential quantification, for instance, proves to be highly effective in capturing the notion of discovery in open systems. Furthermore, Context UNITY treats context in a manner that is relative to the specific needs of an individual application and promotes an approach to context maintenance that is transparent to the application. In this paper, we construct the model from first principles, introduce its proof logic, and demonstrate how the model can be used as an effective abstraction tool for context-aware applications and middleware.     

Inserting virtual pedestrians into pedestrian groups video with behavior consistency

In this paper, we propose a novel approach to integrate virtual pedestrians into a scene of real pedestrian groups with behavior consistency, and this is achieved by dynamic path planning of virtual pedestrians. Rather than accounting for the local collision avoidance only, our approach is capable of finding an optimized path for each virtual pedestrian on his way based on the current global distribution of the real groups in the scene. The big challenge is due to the information of both position and velocity of real pedestrians in the video being unavailable; also the distribution of the groups in the scene may vary dynamically. We therefore need to detect and track real pedestrians on each frame of the video to acquire their distribution and motion information. We save this information by an efficient data structure, called environment grid. During the way of a virtual pedestrian, the respective agent frequently emits the detection rays through the environment cells to find the situation of the real pedestrians ahead of him and adjust the original path if necessary. Virtual pedestrians are merged into the video finally with the occlusion between virtual characters and the real pedestrians correctly presented. Experiment results on several scenarios demonstrate the effectiveness of the proposed approach.     

Using Task-Induced Pupil Diameter and Blink Rate to Infer Cognitive Load

Minimizing user cognitive load is suggested as an integral part of human-centered design, where a more intuitive, easy to learn, and adaptive interface is desired. In this context, it is difficult to develop optimal strategies to improve the design without first knowing how user cognitive load fluctuates during interaction. In this study, we investigate how cognitive load measurement is affected by different task types from the perspective of the load theory of attention, using pupil diameter and blink measures. We induced five levels of cognitive load during low and high perceptual load tasks and found that although pupil diameter showed significant effects on cognitive load when the perceptual load was low, neither blink rate nor pupil diameter showed significant effects on cognitive load when the perceptual load was high. The results indicate that pupil diameter can index cognitive load only in the situation of low perceptual load and are the first to provide empirical support for the cognitive control aspect of the load theory of attention, in the context of cognitive load measurement. Meanwhile, blink is a better indicator of perceptual load than cognitive load. This study also implies that perceptual load should be considered in cognitive load measurement using pupil diameter and blink measures. Automatic detection of the type and level of load in this manner helps pave the way for better reasoning about user internal processes for human-centered interface design.     

Sufficient LMI stability conditions for Lur’e type systems governed by a control law designed on their Euler approximate model

In this paper, the stability issue of Lur’e systems governed by a control law stabilising their forward Euler approximate model is investigated. More specifically, the considered control law is obtained by exploiting the advantages of a new Lur’e type Lyapunov function with disconnected level sets. This Lyapunov function is adapted to discrete-time Lur’e systems and to the structure of the forward Euler approximate model. The main result consists of linear matrix inequality conditions allowing to guarantee that the continuous-time Lur’e system associated with the proposed digital control law is globally asymptotically stable. The relevance of this approach is illustrated using a numerical example.