Ridge-Adjusted Slack Variable Optimization for Supervised Classification

This paper presents an iterative classification algorithm called Ridge-adjusted Slack Variable Optimization (RiSVO). RiSVO is an iterative procedure with two steps: (1) A working subset of the training data is selected so as to reject "extreme" patterns. (2) the decision vector and threshold value are obtained by minimizing the energy function associated with the slack variables. From a computational perspective, we have established a sufficient condition for the "inclusion property" among successive working sets, which allows us to save computation time. Most importantly, under the inclusion property, the monotonic reduction of the energy function can be assured in both substeps at each iteration, thus assuring the convergence of the algorithm. Moreover, ridge regularization is incorporated to improve the robustness and better cope with over-fitting and ill-conditioned problems. To verify the proposed algorithm, we conducted simulations on three data sets from the UCI database: adult, shuttle and bank. Our simulation shows stability and convergence of the RiSVO method. The results also show improvement of performance over the SVM classifier

Blind separation of reflections using the image mixtures ratio

A new method for the blind separation of linear image mix-tures is presented in this paper. Such mixtures often oc-cur, when, for example, we photograph a scene through a semireflecting medium (windshield or glass). The proposed method requires two mixtures of two scenes captured under different illumination conditions. We show that the bound-ary values of the ratio of the two mixtures can lead to an accurate estimation of the separation matrix. The technique is very simple, fast, and reliable, as it does not depend on iterative procedures. The method effectiveness is tested on both artificially mixed images and real images. 1

Experimental User-Centered Evaluation of an Open Hypermedia System and Web Information Seeking Environments

This paper presents an experimental user-centered evaluation of two hypermedia system architectures, each representing a different interaction model and information-seeking environment. The first system is a hypermedia digital library based on the World Wide Web. This system represents an interaction model in which information seekers consistently use a single interface (i.e. a Web browser) to access different information seeking strategies (ISSs). The second system is a similar library (in terms of content and organisation) that is based on an agent-based Open Hypermedia System (OHS). This library encourages an interaction model in which multiple user interfaces and information seeking strategies may be used in a more parallel fashion. Several researchers have suggested that information seeking may be more effective in systems that allow the parallel use of multiple information seeking strategies. On the other hand, the ease of use of the simple click-and-go-to interaction model introduced by the Web and the consistency of its interface appears to be more attractive for most information seekers. The aim of this paper is to examine and discuss these hypotheses critically. Although general conclusions cannot be drawn from the experiment, the results present some useful indications. A first indication is that information seeking environments that support multiple seeking strategies through multiple interfaces may be more effective and efficient for some information seeking tasks. Also, results taken from a questionnaire given to users of the OHS indicate that complex interaction models may not be prohibitively difficult to use, even for inexperienced information seekers

Blind Equalization Of Multiuser CDMA Channels: A Frequency-Domain Approach

The blind estimation of mixing channels resulting from frequency selective fading and multipath in a multi-user CDMA system is an important problem in wireless communications. We present a novel frequency-domain approach using second order spectral statistics for recovering the unknown channels. Unlike other methods which are based on timedomain analysis we make no particular assumption about the support of the mixing channels except that they have finite length (FIR). The method is based on the fact that the source sequences obtain a known spectral color derived from the corresponding spreading code used in CDMA. 1. INTRODUCTION Code Division Mulitple Access (CDMA) communication systems have attracted a lot of attention recently due to their efficient utilization of the available bandwidth and their flexibility in accommodating variable traffic patterns. In a CDMA channel all users share the same frequency band and different orthogonal spreading codes are designed and assigned to diff..

Blind Equalization Of Multiuser CDMA Channels: A Frequency-Domain Approach

We address the problem of blind equalization of mixing channels, resulting from frequency selective fading and multipath in a multi-user CDMA system. We present a novel frequency-domain approach that employs second order spectral statistics of the observations and the users signatures. Unlike other methods, which are based on time-domain analysis, no particular assumptions are made about the support of the mixing channels, except that they have finite length. Since signatures correlations, rather that signatures themselves, are used, the proposed estimation is independent of users delays. Although performance does depend on the users signatures, signatures orthogonality is not required. 1. INTRODUCTION Code Division Multiple Access (CDMA) communication systems have attracted a lot of attention recently due to their efficient utilization of the available bandwidth and their flexibility in accommodating variable traffic patterns. In CDMA each user is assigned a unique code sequence, whi..