Vojkan Mihajlovi - Academia.edu (original) (raw)

Papers by Vojkan Mihajlovi

Research paper thumbnail of Exploiting Query Structure and Document Structure to Improve Document Retrieval Effectiveness ABSTRACT

In this paper we present a systematic analysis of document retrieval using unstructured and struc... more In this paper we present a systematic analysis of document retrieval using unstructured and structured queries within the score region algebra (SRA) structured retrieval framework. The behavior of different retrieval models, namely Boolean, tf.idf, GPX, language models, and Okapi, is tested using the transparent SRA framework in our three-level structured retrieval system called TIJAH. The retrieval models are implemented along four elementary retrieval aspects: element and term selection, element score computation, score combination, and score propagation.

Research paper thumbnail of An XML-IR-DB Sandwich: Is it Better with an Algebra in Between

Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to r... more Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to relational database expressions and exert the benefits of using an intermediate algebra. Adding an intermediate algebra on the logical level of a database enables a level of ...

Research paper thumbnail of Frontal EEG asymmetry based classification of emotional valence using common spatial patterns

In this work we evaluate the possibility of predicting the emotional state of a person based on t... more In this work we evaluate the possibility of predicting the emotional state of a person based on the EEG. We investigate the problem of classifying valence from EEG signals during the presentation of affective pictures, utilizing the "frontal EEG asymmetry" phenomenon. To distinguish positive and negative emotions, we applied the Common Spatial Patterns algorithm. In contrast to our expectations, the affective pictures did not reliably elicit changes in frontal asymmetry. The classifying task thereby becomes very hard as reflected by the poor classifier performance. We suspect that the masking of the source of the brain activity related to emotions, coming mostly from deeper structures in the brain, and the insufficient emotional engagement are among main reasons why it is difficult to predict the emotional state of a person.

Research paper thumbnail of Exploiting Query Structure and Document Structure to Improve Document Retrieval Effectiveness

In this paper we present a systematic analysis of document retrieval using unstructured and struc... more In this paper we present a systematic analysis of document retrieval using unstructured and structured queries within the score region algebra (SRA) structured retrieval frame- work. The behavior of difierent retrieval models, namely Boolean, tf.idf, GPX, language models, and Okapi, is tested using the transparent SRA framework in our three-level struc- tured retrieval system called TIJAH. The retrieval models are

Research paper thumbnail of An XML-IR-DB Sandwich: Is it Better With an Algebra in Between?

Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to r... more Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to relational database expressions and exert the benefits of using an intermediate algebra. Adding an intermediate algebra on the logical level of a database enables a level of ...

Research paper thumbnail of Framework for evaluating EEG signal quality of dry electrode recordings

2013 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2013

Dry electrodes provide the possibility of moving EEG usage from the research and clinical environ... more Dry electrodes provide the possibility of moving EEG usage from the research and clinical environment to real life applications. Having a framework for evaluating the performance of dry electrodes would facilitate this process and help EEG system developers to test their designs. This paper describes an evaluation method for dry electrode EEG recordings. The framework includes a setup for synchronous recordings with a parallel dry and gel electrode montage procedure. Several protocols are implemented to evaluate both the time and frequency content of the signal and to compute the setup and settling time. Signal quality was evaluated using signal correlations, SNR and P300 component characteristics. The preliminary data analysis and results show that a comparison between gel and dry electrodes is possible but improvements need to be made to the current evaluation framework.

Research paper thumbnail of Exploiting Query Structure and Document Structure to Improve Document Retrieval Effectiveness ABSTRACT

In this paper we present a systematic analysis of document retrieval using unstructured and struc... more In this paper we present a systematic analysis of document retrieval using unstructured and structured queries within the score region algebra (SRA) structured retrieval framework. The behavior of different retrieval models, namely Boolean, tf.idf, GPX, language models, and Okapi, is tested using the transparent SRA framework in our three-level structured retrieval system called TIJAH. The retrieval models are implemented along four elementary retrieval aspects: element and term selection, element score computation, score combination, and score propagation.

Research paper thumbnail of An XML-IR-DB Sandwich: Is it Better with an Algebra in Between

Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to r... more Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to relational database expressions and exert the benefits of using an intermediate algebra. Adding an intermediate algebra on the logical level of a database enables a level of ...

Research paper thumbnail of Frontal EEG asymmetry based classification of emotional valence using common spatial patterns

In this work we evaluate the possibility of predicting the emotional state of a person based on t... more In this work we evaluate the possibility of predicting the emotional state of a person based on the EEG. We investigate the problem of classifying valence from EEG signals during the presentation of affective pictures, utilizing the "frontal EEG asymmetry" phenomenon. To distinguish positive and negative emotions, we applied the Common Spatial Patterns algorithm. In contrast to our expectations, the affective pictures did not reliably elicit changes in frontal asymmetry. The classifying task thereby becomes very hard as reflected by the poor classifier performance. We suspect that the masking of the source of the brain activity related to emotions, coming mostly from deeper structures in the brain, and the insufficient emotional engagement are among main reasons why it is difficult to predict the emotional state of a person.

Research paper thumbnail of Exploiting Query Structure and Document Structure to Improve Document Retrieval Effectiveness

In this paper we present a systematic analysis of document retrieval using unstructured and struc... more In this paper we present a systematic analysis of document retrieval using unstructured and structured queries within the score region algebra (SRA) structured retrieval frame- work. The behavior of difierent retrieval models, namely Boolean, tf.idf, GPX, language models, and Okapi, is tested using the transparent SRA framework in our three-level struc- tured retrieval system called TIJAH. The retrieval models are

Research paper thumbnail of An XML-IR-DB Sandwich: Is it Better With an Algebra in Between?

Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to r... more Abstract: In this paper we address the problem of immediate translation of XPath+ IR queries to relational database expressions and exert the benefits of using an intermediate algebra. Adding an intermediate algebra on the logical level of a database enables a level of ...

Research paper thumbnail of Framework for evaluating EEG signal quality of dry electrode recordings

2013 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2013

Dry electrodes provide the possibility of moving EEG usage from the research and clinical environ... more Dry electrodes provide the possibility of moving EEG usage from the research and clinical environment to real life applications. Having a framework for evaluating the performance of dry electrodes would facilitate this process and help EEG system developers to test their designs. This paper describes an evaluation method for dry electrode EEG recordings. The framework includes a setup for synchronous recordings with a parallel dry and gel electrode montage procedure. Several protocols are implemented to evaluate both the time and frequency content of the signal and to compute the setup and settling time. Signal quality was evaluated using signal correlations, SNR and P300 component characteristics. The preliminary data analysis and results show that a comparison between gel and dry electrodes is possible but improvements need to be made to the current evaluation framework.