42287277
A Divide-and-Conquer Approach to Acquire Syntactic Categories
In this paper we propose an unsupervised strategy for learning syntactic information that proceeds in several steps. First, we identify, cluster, and classify function words from unannotated corpora. Then, the acquired information is used in two different learning processes. On the one hand, it is used to learn morpho-syntactic categories of nouns and, on the other, it turns out to be useful to also induce syntactic/semantic relationships between content words. Experiments performed on Portuguese and English corpora are reported.
15739638
Identification of Document Language is Not yet a Completely Solved Problem
Existing Language Identification (LID) approaches do reach 100% precision, in most common situations, when dealing with documents written in just one language, and when those documents are large enough. However, LID approaches do not provide a reliable solution for some situations: when there is need to discriminate the correct variant of the language used in a text, for example, European or Brazilian variants of Portuguese, UK or USA English variants, or any other language variants. Another hard context occur with small touristic advertisements on the web, addressing foreigners but using local language to name most local entities. In this paper, we present a fully statistics- based LID approach which learns the most discriminant information according to each context, and identifies the correct language or language variant a text is written in. This methodology is shown to be correct for normal texts and maintains its robustness in hard LID contexts.
37459114
Cluster Analysis of Named Entities
This paper presents a statistics-based and language independent unsupervised approach for clustering possible named entities. We describe and motivate the features and statistical filters used by our clustering process. Using the Model-Based Clustering Analysis software we obtained different clusters of named entities. The method was applied to Bulgarian and English. For some clusters, precision is close to 100%; this helps human validation and saves time. Other clusters still need further refinement.
33482514
A study of failure models in feedback control systems
Feedback control systems have a peculiar behavior that allows them to compensate for disturbances in the controlled application. This paper investigates whether this resilience also extends to disturbances originating from faults in the controller itself. The question of what kind of failure model is more effective in this type of system is addressed, with three different models being studied: arbitrary failure, fail-silent, and fail-bounded. The study is conducted essentially by experimental fault injection in the controller of one of the best known and most demanding of the benchmarks used in the control systems area: an inverted pendulum. The considered failure models are compared according to criteria based on the quality of the control action. Other insights gained from the experiments made are described, for instance on how to significantly increase dependability at a very low cost in the feedback controllers, and on the need for a different kind of real-time scheduling algorithm.
32609589
Avoiding checkpoint contamination in parallel systems
Checkpointing and rollback recovery is a very effective technique to tolerate faults, provided the application is able to recover from a previous checkpoint and proceed with a failure-free computation. However, this technique may fall short if the checkpoint files are somehow contaminated by errors. This paper presents two mechanisms that may be used to determine if a committed checkpoint is error-free or not. These techniques can be used simultaneously for error detection and failure recovery. Both of them are based on checkpoint duplication: one makes use of spatial redundancy while the other is based on temporal redundancy. We discuss the main problems and trade-offs that have to be dealt with to implement these techniques. We then present a performance study that clearly shows the pros and cons of each one. As far as we know, this paper presents the first implementation of these mechanisms in a standard parallel computing system.
37612228
An approach to testability improvement of mixed-signal boards
The increasing complexity of mixed-signal boards makes an integrated analogue/digital testability approach an attractive proposition. This paper investigates one such approach based on the use of mixed-signal test support ICs together with standard board level test infrastructures. The architecture of a test support IC and preliminary experimental results are also presented.<<ETX>>
11507520
Web-based Metacomputing with JET
540709
The performance of coordinated and independent checkpointing
Checkpointing is a very effective technique to tolerate the occurrence of failures in distributed and parallel applications. The existing algorithms in the literature are basically divided into two main classes: coordinated and independent checkpointing. This paper presents an experimental study that compares the performance of these two classes of algorithms. The main conclusion of our study is that coordinated checkpointing is more efficient than independent checkpointing and all the arguments against the performance of coordinated algorithms were not verified in practice.