Probability-dependent gain-scheduled filtering for stochastic systems with missing measurements

Copyright @ 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.This brief addresses the gain-scheduled filtering problem for a class of discrete-time systems with missing measurements, nonlinear disturbances, and external stochastic noise. The missing-measurement phenomenon is assumed to occur in a random way, and the missing probability is time-varying with securable upper and lower bounds that can be measured in real time. The multiplicative noise is a state-dependent scalar Gaussian white-noise sequence with known variance. The addressed gain-scheduled filtering problem is concerned with the design of a filter such that, for the admissible random missing measurements, nonlinear parameters, and external noise disturbances, the error dynamics is exponentially mean-square stable. The desired filter is equipped with time-varying gains based primarily on the time-varying missing probability and is therefore less conservative than the traditional filter with fixed gains. It is shown that the filter parameters can be derived in terms of the measurable probability via the semidefinite program method.This work was supported in part by the Leverhulme Trust of the U.K., the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant GR/S27658/01, the National Natural Science Foundation of China under Grants 61028008, 61074016 and 60974030, the Shanghai Natural Science Foundation of China under Grant 10ZR1421200, and the Alexander von Humboldt Foundation of Germany

A text-based approach to the ImageCLEF 2010 photo annotation task

The challenges of searching the increasingly large collections of digital images which are appearing in many places mean that automated annotation of images is becoming an important task. We describe our participation in the ImageCLEF 2010 Visual Concept Detection and Annotation Task. Our approach used only the textual features (Flickr user tags and EXIF information) to perform the automatic annotation. Our approach was to explore the use of different techniques to improve the results of textual annotation. We identify the drawbacks of our approach and how these might be addressed and optimized in further work

Enhanced information retrieval using domain-specific recommender models

The objective of an information retrieval (IR) system is to retrieve relevant items which meet a user information need. There is currently significant interest in personalized IR which seeks to improve IR effectiveness by incorporating a model of the user’s interests. However, in some situations there may be no opportunity to learn about the interests of a specific user on a certain topic. In our work, we propose an IR approach which combines a recommender algorithm with IR methods to improve retrieval for domains where the system has no opportunity to learn prior information about the user’s knowledge of a domain for which they have not previously entered a query. We use search data from other previous users interested in the same topic to build a recommender model for this topic. When a user enters a query on a topic, new to this user, an appropriate recommender model is selected and used to predict a ranking which the user may find interesting based on the behaviour of previous users with similar queries. The recommender output is integrated with a standard IR method in a weighted linear combination to provide a final result for the user. Experiments using the INEX 2009 data collection with a simulated recommender training set show that our approach can improve on a baseline IR system

Isospin dependence of nucleon emission and radial flow in heavy-ion collisions induced by high energy radioactive beams

Using an isospin- and momentum-dependent transport model we study the emission of free nucleons and the nuclear radial flow in central heavy-ion collisions induced by high energy radioactive beams. The midrapidity neutron/proton ratio and its transverse momentum dependence are found very sensitive to the high density behavior of nuclear symmetry energy. The nuclear radial flow, however, depends only weakly on the symmetry energy.Comment: 13 pages including 6 figures, submitted to Phys. Rev.

Adjusting to Really Big Changes: The Labor Market in China, 1989-2009

China’s emerging labor market was buffeted by changes in demand and supply and institutional changes in the last two decades. Using the Chinese Urban Household Survey data from 1989 to 2009, our study shows that the market responded with substantial changes in the structure of wages and in employment and types of jobs that workers obtained that mirrors the adjustments found in labor markets in advanced economies. However, the one place where the Chinese labor market appears to diverge from the labor markets in advanced countries is the rapid convergence in earnings and occupational positions of cohorts who entered the job market under more or less favorable conditions. On this dimension, China’s labor market seems more flexible than those in other countries. Three related factors may explain this pattern: (1) the rapid growth of China’s economy; (2) the high rate of employee turnover; (3) the relative weakness of internal labor markets in China. Bottom line, the Chinese labor market has responded about as well as one could expect to the changes in the demand and supply factors and institutional shocks in this critical period in Chinese economic history.

Elastic parton scattering and non-statistical event-by-event mean-pt fluctuations in Au + Au collisions at RHIC

Non-statistical event-by-event mean-pt fluctuations in Au + Au collisions at sqrt(s_NN) = 130 and 200 GeV are analyzed in AMPT with string-melting, and the results are compared with STAR data. The analysis suggests that in-medium elastic parton scattering may contribute greatly to the mean-p_t fluctuations in relativistic heavy-ion collisions. Furthermore, it is demonstrated that non-statistical event-by-event mean-pt fluctuations can be used to probe the initial partonic dynamics in these collisions. The comparison shows that with an in-medium elastic parton scattering cross section sigma_p=10 mb, AMPT with string-melting can well reproduce sqrt(s_NN) = 130 GeV data on the centrality dependence of non-statistical event-by-event mean-pt fluctuations. The comparison also shows that the fluctuation data for sqrt(s_NN) = 200 GeV Au + Au collisions can be well reproduced with sigma_p between 6 and 10 mb.Comment: 6 pages, 3 figure

Effects of medium-induced ρ−ω\rho-\omega meson mixing on the equation of state in isospin-asymmetric nuclear matter

We reexamine effects of the $\rho-\omega$ meson mixing mediated by nucleon polarizations on the symmetry energy in isospin-asymmetric nuclear matter. Taking into account the rearrangement term neglected in previous studies by others, we evaluate the $\rho-\omega$ mixing angle in a novel way within the Relativistic Mean-Field Models with and without chiral limits. It is found that the symmetry energy is significantly softened at high densities contrary to the finding in earlier studies. As the first step of going beyond the lowest-order calculations, we also solve the RPA equation for the $\rho-\omega$ mixing. In this case, it is found that the symmetry energy is not only significantly softened by the $\rho-\omega$ mixing at supra-saturation densities, similar to the lowest-order $\rho-\omega$ mixing, but interestingly also softened at subsaturation densities. In addition, the softening of the symmetry energy at subsaturation densities can be partly suppressed by the nonlinear self-interaction of the $\sigma$ meson.Comment: Significant changes made. Accepted version to appear in PRC (2009

A proposal for the evaluation of adaptive information retrieval systems using simulated interaction

The Centre for Next Generation Localisation (CNGL) is involved in building interactive adaptive systems which combine Information Retrieval (IR), Adaptive Hypermedia (AH) and adaptive web techniques and technologies. The complex functionality of these systems coupled with the variety of potential users means that the experiments necessary to evaluate such systems are difficult to plan, implement and execute. This evaluation requires both component-level scientific evaluation and user-based evaluation. Automated replication of experiments and simulation of user interaction would be hugely beneficial in the evaluation of adaptive information retrieval systems (AIRS). This paper proposes a methodology for the evaluation of AIRS which leverages simulated interaction. The hybrid approach detailed combines: (i) user-centred methods for simulating interaction and personalisation; (ii) evaluation metrics that combine Human Computer Interaction (HCI), AH and IR techniques; and (iii) the use of qualitative and quantitative evaluations. The benefits and limitations of evaluations based on user simulations are also discussed

Detection of Majorana Kramers pairs using a quantum point contact

We propose a setup that integrates a quantum point contact (QPC) and a Josephson junction on a quantum spin Hall sample, experimentally realizable in InAs/GaSb quantum wells. The confinement due to both the QPC and the superconductor results in a Kramers pair of Majorana zero-energy bound states when the superconducting phases in the two arms differ by an odd multiple of $\pi$ across the Josephson junction. We investigate the detection of these Majorana pairs with the integrated QPC, and find a robust switching from normal to Andreev scattering across the edges due to the presence of Majorana Kramers pairs. This transport signature is expected to be exhibited in measurements of differential conductance and/or current cross-correlation at low bias

Towards evaluation of personalized and collaborative information retrieval

We propose to extend standard information retrieval (IR) ad-hoc test collection design to facilitate research on personalized and collaborative IR by gathering additional meta-information during the topic (query) development process. We propose a controlled query generation process with activity logging for each topic developer. The standard ad-hoc collection will thus be accompanied by a new set of thematically related topics and the associated log information, and has the potential to simulate a real-world search scenario to encourage retrieval systems to mine user information from the logs to improve IR effectiveness. The proposed methodology described in this paper will be applied in a pilot task which is scheduled to run in the FIRE 2011 evaluation campaign. The task aims at investigating the research question of whether personalized and collaborative IR retrieval experiments and evaluation can be pursued by enriching a standard ad-hoc collection with such meta-information