2019
Autores
Carvalho, MI; Facao, M;
Publicação
PHYSICAL REVIEW E
Abstract
We found stable soliton solutions for two generalizations of the cubic complex Ginzburg-Landau equation, namely, one that includes the term that, in optics, represents a delayed response of the nonlinear gain and the other including the self-steepening term, also in the optical context. These solutions do not require the presence of the delayed response of the nonlinear refractive index, such that, they exist regardless of the term previously considered essential for stabilization. The existence of these solitons was predicted by a perturbation approach, and then confirmed by solving the ordinary differential equations, resulting from a similarity reduction, and also by applying a linear stability analysis. We found that these solitons exist for a large region of the parameter space and possess very asymmetric amplitude profiles as well as a complicated chirp characteristic.
2019
Autores
Teixeira, D; Assuncao, L; Pereira, T; Malta, S; Pinto, P;
Publicação
JOURNAL OF SENSOR AND ACTUATOR NETWORKS
Abstract
Intrusion Detection Systems (IDS) are used to prevent attacks by detecting potential harmful intrusion attempts. Currently, there are a set of available Open Source IDS with different characteristics. The Open Source Host-based Intrusion Detection System (OSSEC) supports multiple features and its implementation consists of Agents that collect and send event logs to a Manager that analyzes and tests them against specific rules. In the Manager, if certain events match a specific rule, predefined actions are triggered in the Agents such as to block or unblock a particular IP address. However, once an action is triggered, the systems administrator is not able to centrally check and obtain detailed information of the past event logs. In addition, OSSEC may assume false positive or negative detections and their triggered actions: previously harmless but blocked IP addresses by OSSEC have to be unblocked in order to reestablish normal operation or potential harmful IP addresses not previously blocked by OSSEC should be blocked in order to increase protection levels. These operations to override OSSEC actions must be manually performed in every Agent, thus requiring time and human resources. Both these limitations have a higher impact on large scale OSSEC deployments assuming tens or hundreds of Agents. This paper proposes an extension to OSSEC that improves the administrator analysis capability by maintaining, organizing and presenting Agent logs in a central point, and it allows for blocking or unblocking IP addresses in order to override actions triggered by false detections. The proposed extension aims to increase efficiency of time and human resources management, mainly considering large scale OSSEC deployments.
2019
Autores
Costa, P; Montenegro, R; Pereira, T; Pinto, P;
Publicação
MOBILE NETWORKS & APPLICATIONS
Abstract
An increase number of cyberattacks on public and private organizations have been performed by exploiting their social and technological vulnerabilities. Mainly, these attacks aim to obtain illegal profits by extorting organizations, affecting their reputation and normal operation. In order to minimize the impact of these attacks, it is essential that these organizations not only implement preventive actions and efficient security mechanisms, but also continually evaluate the security risks their staff are exposed to when performing their job tasks. This paper presents a case study to assess the private and public Portuguese organizations security related practices followed by their staff. The results obtained by a conducted survey allow the analysis of behaviours and practices followed by the staff of these organizations and also allow to draw conclusions about their security procedures and risk awareness.
2019
Autores
Fontes, H;
Publicação
Abstract
2019
Autores
Clemente, M; Mendes, J; Moreira, A; Bernardes, G; Van Twillert, H; Ferreira, A; Amarante, JM;
Publicação
Journal of Oral Biology and Craniofacial Research
Abstract
Background/objective: Playing a wind instrument implies rhythmic jaw movements where the embouchure applies forces with different directions and intensities towards the orofacial structures. These features are relevant when comparing the differences between a clarinettist and a saxophone player embouchure, independently to the fact that both belong to the single-reed instrument group, making therefore necessary to update the actual classification. Methods: Lateral cephalograms were taken to single-reed, double-reed and brass instrumentalists with the purpose of analyzing the relationship of the mouthpiece and the orofacial structures. Results: The comparison of the different wind instruments showed substantial differences. Therefore the authors purpose a new classification of wind instruments: Class 1 single-reed mouthpiece, division 1– clarinet, division 2 –saxophone; Class 2 double-reed instruments, division 1– oboe, division 2– bassoon; Class 3 cup-shaped mouthpiece, division 1– trumpet and French horn, division 2- trombone and tuba; Class 4 aperture mouthpieces, division 1– flute, division 2 – transversal flute and piccolo. Conclusions: Elements such as dental arches, teeth and lips, assume vital importance at a new nomenclature and classification of woodwind instruments that were in the past mainly classified by the type of mouthpiece and not taking into consideration its relationship with their neighboring structures. © 2019 Craniofacial Research Foundation
2019
Autores
Bernardes, G; Aly, L; Davies, MEP;
Publicação
SMC 2016 - 13th Sound and Music Computing Conference, Proceedings
Abstract
In this paper we present SEED, a generative system capable of arbitrarily extending recorded environmental sounds while preserving their inherent structure. The system architecture is grounded in concepts from concatenative sound synthesis and includes three top-level modules for segmentation, analysis, and generation. An input audio signal is first temporally segmented into a collection of audio segments, which are then reduced into a dictionary of audio classes by means of an agglomerative clustering algorithm. This representation, together with a concatenation cost between audio segment boundaries, is finally used to generate sequences of audio segments with arbitrarily long duration. The system output can be varied in the generation process by the simple and yet effective parametric control over the creation of the natural, temporally coherent, and varied audio renderings of environmental sounds. Copyright: © 2016 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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