A gradient flow approach to robust pole assignment in second-order systems

Assignment for second-order systems is considered. It is shown that assignment can be achieved by solving a linear matrix equation or linear system. An objective function measuring the robustness of the closed-loop spectrum is minimized via gradient flow.published_or_final_versio

An analysis of the participation of an online educational discussion forum - the study of Hong Kong Cyber Campus Forum

Information technology is now widely used in the education sector, and online discussion forum has been regarded as a useful tool for education. A large number of online forums have been set up with an unexamined assumption that participants will learn through interacting with others in the forums. This paper reports a case study of the discussion forum of the Hong Kong Cyber Campus (www.hkcampus.net). It is the in one of the largest public educational discussion forums in Hong Kong set up jointly by local higher education institutions, to provide a venue for educators, teachers, students and parents to discuss about educational issues and the use of information technology for teaching and learning. The current study addresses the following issues: (1) What are the major objects of discussion in the forum? (2) How the structure of the forum may affect interactions between the different types of participants? (3) To what extent is online discussion conducive to conceptual learning of the participants? (4) What are the characteristics of the interactions of the participants in online forum? (5) How should the moderator act effectively to facilitate discussion? What kinds of moderator's messages will spark off more discussion? What kinds of messages tend to end the discussion? To address these research questions, we have conducted an analysis of the messages of the forum generated in its first twelve months from Feb.1999 to Feb.2000. Some of the findings are highlighted in this paper, namely: (1) The objects of discussion are mostly about everyday work and life of students and teachers; (2) The structure of the forum does affect the amount of interaction between different types of participants; (3) Online discussion affords gathering opinion, exchanging information and expressing feelings; (4) Online forum appears weak in resolving conflicting views. Participants seldom exhibit a change of their beliefs during the discussion. It also tends to polarize the discussion, lead the participants to extreme points of view. This is especially salient when the participants do not share a common experience of the issue. (5) The kind of moderator's messages that try to round up, make conclusion and provide authoritative information tend to terminate the discussion, while the expression of example/experience with open meaning tend to spark off more discussion.published_or_final_versio

Robust Logistic Principal Component Regression for classification of data in presence of outliers

The Logistic Principal Component Regression (LPCR) has found many applications in classification of high-dimensional data, such as tumor classification using microarray data. However, when the measurements are contaminated and/or the observations are mislabeled, the performance of the LPCR will be significantly degraded. In this paper, we propose a new robust LPCR based on M-estimation, which constitutes a versatile framework to reduce the sensitivity of the estimators to outliers. In particular, robust detection rules are used to first remove the contaminated measurements and then a modified Huber function is used to further remove the contributions of the mislabeled observations. Experimental results show that the proposed method generally outperforms the conventional LPCR under the presence of outliers, while maintaining a performance comparable to that obtained under normal condition. © 2012 IEEE.published_or_final_versionThe 2012 IEEE International Symposium on Circuits and Systems (ISCAS), Seoul, Korea, 20-23 May 2012. In IEEE International Symposium on Circuits and Systems Proceedings, 2012, p. 2809-281

Robust recursive eigendecomposition and subspace-based algorithms with application to fault detection in wireless sensor networks

The principal component analysis (PCA) is a valuable tool in multivariate statistics, and it is an effective method for fault detection in wireless sensor networks (WSNs) and other related applications. However, its online implementation requires the computation of eigendecomposition (ED) or singular value decomposition. To reduce the arithmetic complexity, we propose an efficient fault detection approach using the subspace tracking concept. In particular, two new robust subspace tracking algorithms are developed, namely, the robust orthonormal projection approximation subspace tracking (OPAST) with rank-1 modification and the robust OPAST with deflation. Both methods rely on robust M-estimate-based recursive covariance estimate to improve the robustness against the effect of faulty samples, and they offer different tradeoff between fault detection accuracy and arithmetic complexity. Since only the ED in the major subspace is computed, their arithmetic complexities are much lower than those of other conventional PCA-based algorithms. Furthermore, we propose new robust T 2 score and SPE detection criteria with recursive update formulas to improve the robustness over their conventional counterparts and to facilitate online implementation for the proposed robust subspace ED and tracking algorithms. Computer simulation and experimental results on WSN data show that the proposed fault detection approach, which combines the aforementioned robust subspace tracking algorithms with the robust detection criteria, is able to achieve better performance than other conventional approaches. Hence, it serves as an attractive alternative to other conventional approaches to fault detection in WSNs and other related applications because of its low complexity, efficient recursive implementation, and good performance. © 2012 IEEE.published_or_final_versio

A New Method for Preliminary Identification of Gene Regulatory Networks from Gene Microarray Cancer Data Using Ridge Partial Least Squares with Recursive Feature Elimination and Novel Brier and Occurrence Probability Measures

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A new recursive dynamic factor analysis for point and interval forecast of electricity price

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Musical Interfaces: Visualization and Reconstruction of Music with a Microfluidic Two-Phase Flow

Detection of sound wave in fluids can hardly be realized because of the lack of approaches to visualize the very minute sound-induced fluid motion. In this paper, we demonstrate the first direct visualization of music in the form of ripples at a microfluidic aqueous-aqueous interface with an ultra-low interfacial tension. The interfaces respond to sound of different frequency and amplitude robustly with sufficiently precise time resolution for the recording of musical notes and even subsequent reconstruction with high fidelity. Our work shows the possibility of sensing and transmitting vibrations as tiny as those induced by sound. This robust control of the interfacial dynamics enables a platform for investigating the mechanical properties of microstructures and for studying frequency-dependent phenomena, for example, in biological systems.published_or_final_versio

Droplet-based electro-coalescence for probing threshold disjoining pressure

In this work, we investigate the coalescence of emulsion droplets in a controlled electric field. Two contacting droplets stabilized by surfactants can be forced to coalesce into a combined one when the applied voltage is above a critical value. The critical voltages change with the types, concentrations of surfactants and temperature. By exploring the drainage of a thin oil film trapped between emulsions, we interpret that the coalescence occurs as the electric compression overcomes the disjoining pressure barrier and squeezes the film to a critical thickness. Based on this, we have devised an approach to probe the threshold disjoining pressure which can help predict the emulsion stability and surfactant efficacy quantitatively. We have confirmed the validity of our approach for measuring the threshold disjoining pressure by comparing the result with other proven tests that involve centrifugation and thermal heating. Our approach is simple, reliable and robust in predicting emulsion stability and will facilitate the design of emulsion-based formulations by accelerating the testing of emulsion stability.postprin

Weighing matrices and spherical codes

Mutually unbiased weighing matrices (MUWM) are closely related to an antipodal spherical code with 4 angles. In the present paper, we clarify the relationship between MUWM and the spherical sets, and give the complete solution about the maximum size of a set of MUWM of weight 4 for any order. Moreover we describe some natural generalization of a set of MUWM from the viewpoint of spherical codes, and determine several maximum sizes of the generalized sets. They include an affirmative answer of the problem of Best, Kharaghani, and Ramp.Comment: Title is changed from "Association schemes related to weighing matrices

Load/Price Forecasting and Management of Demand Response for Smart Grids: Methodologies and Challenges

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