Why web-based pseudo relevance feedback systems fail

 We review pseudo-relevance feedback as a mechanism for expanding short texts. Where short texts exhibit evolving concepts, topics and other characteristics, Web-based feedback systems were touted as the most ideal way of enriching the feature space of short texts. However, we note from a recent implementation of a Web-based pseudo-relevance feedback that it would only perform well under clinical situations. Further improvements to address fundamental noise in Web documents did not show significant improvements leading us to conclude that relevance feedback using Web documents directly are unsuitable for real-world conditions. In this paper, we present Eddi, which is a recent system that provides an exemplar of a typical pseudo-relevance feedback system. We first show the conditions in which Eddi will work and then discuss the situations where it would fail. We then present the variations to Eddi from our attempt to improve the robustness of Eddi's algorithm when dealing with complex Web documents. We then present the results from all variations to show the lack of robustness for pseudo-relevance feedback with Web documents.

DSP-based sliding-mode control for electromagnetic-levitation precise position system

This paper investigates the robust tracking control problem for a bipolar electromagnetic-levitation precise-position system. The dynamic model of the precise-position device is derived by conducting a thorough analysis on the nonlinear electromagnetic forces. Conventional sliding-mode control and terminal sliding-mode control strategies are developed to guarantee asymptotic and finite-time tracking capabilities of the closed-loop system. A lumped uncertainty estimator is proposed to estimate the system uncertainties. The estimated information is then used to construct a smooth uniformly ultimately bounded sliding-mode control. An exact estimator is also proposed to exactly estimate the unknown uncertainties in finite time. The output of the exact estimator is used to design a continuous chattering free terminal sliding-mode control. The time taken for the closed-loop system to reach zero tracking error is proven to be finite. Experiment results are presented, using a real time digital-signal-processor (DSP) based electromagnetic-levitation system to validate the analysis.

The conversational skills of school-aged children with cochlear implants

Children with cochlear implants have been shown to have language skills on a par with children with severe hearing losses who have hearing aids. Earlier implants, bilateral implantation, and focused intervention programmes may result in some children with cochlear implants displaying similar language skills to their hearing peers. The development of pragmatic skills is central to communication competence and underpins the development of friendships. Although some studies of pragmatic skills in children with cochlear implants have been reported, most have used a contrived referential communication task rather than free conversation.

Method: This study investigated the conversational skills of 20 children with cochlear implants, aged between 9 and 12 years, in free conversation with their hearing peers. The pragmatic skills of these 20 deaf/hearing pairs or dyads were compared with the pragmatic skills of 20 hearing/hearing dyads. Pragmatic skills were analysed in terms of conversational balance, conversational turn types, and conversational maintenance. The impact of the participants’ level of speech intelligibility was also investigated.

Results: Children with cochlear implants tend to dominate conversations with their hearing peers. They initiated more topics, took longer turns, asked more questions, and tended to make more personal comments while their hearing friends tended to use more conversational devices and minimal answers. In contrast, pairs of matched hearing children were very balanced in all of these aspects of conversation. Speech intelligibility did not appear to impact consistently on the pragmatic skills of the children with cochlear implants but all children had a relatively high level of speech intelligibility.

Discussion: Rather than being characterized by frequent conversational breakdown as in older studies, children with cochlear implants had a strong grasp of basic conversational rules. They conversed in a similar way to some deaf adults who also have been shown to take control of the conversation. Findings are discussed for their implications for intervention and future research.

Unsupervised DRG upcoding detection in healthcare databases

Diagnosis Related Group (DRG) upcoding is an anomaly in healthcare data that costs hundreds of millions of dollars in many developed countries. DRG upcoding is typically detected through resource intensive auditing. As supervised modeling of DRG upcoding is severely constrained by scope and timeliness of past audit data, we propose in this paper an unsupervised algorithm to filter data for potential identification of DRG upcoding. The algorithm has been applied to a hip replacement/revision dataset and a heart-attack dataset. The results are consistent with the assumptions held by domain experts.