Mostrando recursos 1 - 20 de 62

  1. A quantitative approach for measuring the degree of flexibility of business process models

    Mejri, Asma; Ayachi-Ghannouchi, Sonia; Martinho, Ricardo
    Purpose The purpose of this paper is to measure the flexibility of business process models. The authors give the notions of flexible process distance, which corresponds to the number of change operations needed for transforming one process model into another, considering the different perspectives (functional, operational, behavioral, informational, and organizational). Design/methodology/approach The proposed approach is a quantitative-based approach to measure the flexibility of business process models. In this context, the authors presented a method to compute the distance between two process models. The authors measured the distance between a process model and a process variant in terms of the number of high-level change...

  2. Screening of obstructive sleep apnea using Hilbert–Huang decomposition of oronasal airway pressure recordings

    Caseiro, P.; Fonseca-Pinto, Rui; Andrade, A.
    Polysomnographic signals are usually recorded from patients exhibiting symptoms related to sleep disorders such as obstructive sleep apnea (OSA). Analysis of polysomnographic data allows for the determination of the type and severity of sleep apnea or other sleep-related disorders by a specialist or technician. The usual procedure entails an overnight recording several hours long. This paper presents a methodology to help with the screening of OSA using a 5-min oronasal airway pressure signal emanating from a polysomnographic recording during the awake period, eschewing the need for an overnight recording. The clinical sample consisted of a total of 41 subjects, 20...

  3. On the influence of time-series length in EMD to extract frequency content : simulations and models in biomedical signals

    Fonseca-Pinto, Rui; Ducla-Soares, J. L.; Araújo, F.; Aguiar, P.; Andrade, A.
    In this paper, fractional Gaussian noise (fGn) was used to simulate a homogeneously spreading broadband signal without any dominant frequency band, and to perform a simulation study about the influence of time-series length in the number of intrinsic mode functions (IMFs) obtained after empirical mode decomposition (EMD). In this context three models are presented. The first two models depend on the Hurst exponent H, and the last one is designed for small data lengths, in which the number of IMFs after EMD is obtained based on the regularity of the signal, and depends on an index measure of regularity. These...

  4. Towards 5G : performance evaluation of 60 GHz UWB OFDM communications under both channel and RF impairments

    Gomes, Rodolfo; Hammoudeh, Akram; Caldeirinha, Rafael F. S.; Al-Daher, Zaid; Fernandes, Telmo R.; Reis, João
    Detailed analysis on the impact of RF and channel impairments on the performance of Ultra-Wideband (UWB) wireless Orthogonal Frequency Division Multiplexing (OFDM) systems based on the IEEE 802.15.3c standard, for high data-rate applications using the 60 GHz millimetre frequency band is presented in this paper. This frequency band, due to the large available bandwidth is very attractive for future and 5G wireless communication systems. The usage of OFDM at millimetre-wave (mmWaves) frequencies is severely affected by non-linearities of the Radio Frequency (RF) front-ends. The impact of impairments is evaluated, in terms of some of the most important key performance indicators,...

  5. A 2D ray-tracing based model for wave propagation through forests at micro-and millimeter wave frequencies

    Leonor, Nuno R.; Sanchez, Manuel Garcia; Fernandes, Telmo R.; Caldeirinha, Rafael F. S.
    This paper proposes the extension of a 2-D ray-tracing-based model for radiowave propagation in the presence of trees and vegetation areas to include real-sized trees and outdoor forest scenarios. The original propagation model proved to be suitable to characterize the electromagnetic behavior in the presence of indoor tree formation scenarios, despite some limitations found when applied to real-sized trees. In addition, the original propagation model requires the prior knowledge of the trees’ re-radiation function to extract the relevant propagation input parameters, which is not always possible to obtain in outdoor scenarios. Therefore, an empirical method to extract the relevant input...

  6. Cardiorespiratory physiotherapy as a career choice-perspective of students and physiotherapists in Portugal

    Marques, Alda; Oliveira, Ana; Machado, Ana; Jácome, Cristina; Cruz, Joana; Pinho, Tânia; Hall, Andreia; Alvelos, Helena; Brooks, Dina
    We investigated Portuguese physiotherapy students' and physiotherapists' (1) perceptions of cardiorespiratory physiotherapy (CRP); (2) factors that influenced their decision to pursue a career in CRP; and (3) suggestions to develop CRP. Online surveys were disseminated to final year students and physiotherapists. A number of 189 students (mean age 23 [SD 6] years; 78% ♀) and 375 physiotherapists (mean age 31 [SD 8] years; 78% ♀) participated. Students' opinions about CRP were positively influenced by lecturers (n = 112, 69%), clinical experiences (n = 110, 68%), and scientific evidence (n = 93, 57%). Only 13% of students were "extremely interested" in specializing in CRP. Interest in the area and...

  7. First and second fundamental solutions of the time-fractional telegraph equation with Laplace or Dirac operators

    Ferreira, Milton; Rodrigues, Manuela M.; Vieira, Nelson
    In this work we obtain the first and second fundamental solutions (FS) of the multidimensional time-fractional equation with Laplace or Dirac operators, where the two time-fractional derivatives of orders α ∈]0, 1] and β ∈]1, 2] are in the Caputo sense. We obtain representations of the FS in terms of Hankel transform, double Mellin- Barnes integrals, and H-functions of two variables. As an application, the FS are used to solve Cauchy problems of Laplace and Dirac type.

  8. Entrando no Interior da Escola: etnografia e entrevistas etnográficas

    Vieira, Ricardo; Vieira, Ana
    Neste texto, depois de procurarem desconstruir a falsa oposição binária qualitativo-quantitativo, propondo um politeísmo metodológico, os autores centram-se nos paradigmas hermenêuticos e fenomenológicos, onde inscrevem a etnografia como abordagem que pode recorrer a diversas técnicas no sentido de compreender os sentidos que os atores sociais atribuem às suas práticas. Num segundo momento, mostram como a etnografia e a particularidade das entrevistas etnográficas são uma forma de aceder compreensivamente à dimensão interior da escola, buscando e construindo com os sujeitos sentidos e significados que as abordagens sistémicas têm descurado e transformado na caixa negra da instituição escolar.

  9. Stress responses of the sea cucumber Holothuria forskali during aquaculture handling and transportation

    Tonn, Nina; Novais, Sara C.; Silva, Cátia S. E.; Morais, Hugo A.; Correia, João P. S.; Lemos, Marco F. L.
    Animal welfare during handling and transportation to aquaculture facilities or public aquaria is commonly estimated by addressing injury and mortality levels. Although these procedures have been optimized for different species, data on individual species’ cellular capabilities to tolerate stress are still scarce. In the present study, several biomarkers related with oxidative stress and energy metabolism were assessed in Holothuria forskali during animal acclimation, pre-transport, transport and quarantine. Combined analyses confirmed that sea cucumbers experienced high oxidative stress during transport, but had the capability to deal with it using a complex of cellular defence mechanisms, which enabled recovery from oxidative stress...

  10. Using biomarkers to address the impacts of pollution on limpets ( Patella depressa ) and their mechanisms to cope with stress

    Silva, Cátia S. E.; Novais, Sara C.; Simões, Tiago; Caramalho, Márcia; Gravato, Carlos; Rodrigues, Maria J.; Maranhão, Paulo; Lemos, Marco F. L.
    Contaminant discharges, derived from human activities, are major concerns as they exert a continuous ecological pressure on aquatic systems, causing in fact cascading community effects. Although with associated ecological and fitness costs, physiological and biochemical defense mechanisms may restore the organism’s internal balance. Several studies have pointed biomarkers as tools to assess contamination levels, and also to understand potential mechanisms to cope with stress. In the present study, the fitness costs of limpets Patella depressa located in two different contaminated sites and when transplanted into a different common environment – with no known historical contamination – were assessed through the...

  11. Reproductive trade-offs in a temperate reef fish under high pCO2 levels

    Faria, A. M.; Lopes, A. F.; Silva, C. S. E.; Novais, S. C.; Lemos, M. F. L.; Gonçalves, E. J.
    Fishes are currently facing novel types of anthropogenic stressors that have never experienced in their evolutionary history, such as ocean acidification. Under these stressful conditions, energetically costly processes, such as reproduction, may be sacrificed for increased chances of survival. This trade-off does not only affect the organism itself but may result in reduced offspring fitness. In the present study, the effects of exposure to high pCO2 levels were tested on the reproductive performance of a temperate species, the two-spotted goby, Gobiusculus flavescens. Breeding pairs were kept under control (∼600 μatm, pH∼ 8.05) and high pCO2 levels (∼2300 μatm, pH∼ 7.60) conditions for...

  12. Polyphenols for an increased ability to cope with environmental toxicants

    Lagoa, Ricardo; Marques-da-Silva, Dorinda; Ribeiro, Vânia

  13. Light field image Coding using high-order intrablock prediction

    Monteiro, Ricardo J. S.; Nunes, Paulo J. L.; Rodrigues, Nuno M. M.; Faria, Sergio M. M. de
    This paper proposes a two-stage high-order intrablock prediction method for light field image coding. This method exploits the spatial redundancy in lenslet light field images by predicting each image block, through a geometric transformation applied to a region of the causal encoded area. Light field images comprise an array of microimages that are related by complex geometric transformations that cannot be efficiently compensated by state-of-the-art image coding techniques, which are usually based on low-order translational prediction models. The two-stage nature of the proposed method allows us to choose the order of the prediction model most suitable for each block, ranging...

  14. Sand smelt ability to cope and recover from ocean's elevated CO 2 levels

    Silva, Cátia S. E.; Lemos, Marco F. L.; Faria, Ana M.; Lopes, Ana F.; Mendes, Susana; Gonçalves, Emanuel J.; Novais, Sara C.
    Considered a major environmental concern, ocean acidification has induced a recent research boost into effects on marine biodiversity and possible ecological, physiological, and behavioural impacts. Although the majority of literature indicate negative effects of future acidification scenarios, most studies are conducted for just a few days or weeks, which may be insufficient to detect the capacity of an organism to adjust to environmental changes through phenotypic plasticity. Here, the effects and the capacity of sand smelt larvae Atherina presbyter to cope and recover (through a treatment combination strategy) from short (15 days) and long-term exposure (45 days) to increasing pCO2...

  15. Effects of ocean acidification on the swimming ability, development and biochemical responses of sand smelt larvae

    Silva, Cátia S. E.; Novais, Sara C.; Lemos, Marco F. L.; Mendes, Susana; Oliveira, Ana P.; Gonçalves, Emanuel J.; Faria, Ana M.
    Ocean acidification, recognized as a major threat to marine ecosystems, has developed into one of the fastest growing fields of research in marine sciences. Several studies on fish larval stages point to abnormal behaviours, malformations and increased mortality rates as a result of exposure to increased levels of CO2. However, other studies fail to recognize any consequence, suggesting species-specific sensitivity to increased levels of CO2, highlighting the need of further research. In this study we investigated the effects of exposure to elevated pCO2 on behaviour, development, oxidative stress and energy metabolism of sand smelt larvae, Atherina presbyter. Larvae were caught...

  16. Ownership structure and performance: evidence from Portugal

    Lisboa, Inês; Esperança, José Paulo
    This paper provides new evidence on the impact of ownership over performance in small dimension markets. Analyzing the Portuguese firms we confirm the monitoring effect. Unlike previous studies, we also confirm the expropriation effect to low levels of ownership concentration. These results suggest that the free rider problem between the manager and the principal is significant in countries with small financial markets.

  17. Empresa familiar y bolsa: análisis de rentabilidad y estrategias de inversión

    Miralles-Marcelo, José Luís; Miralles-Quirós, Maria del Mar; Lisboa, Inês
    The objective of this study is to analyze return differences between family and non-family firms quoted on the Spanish stock market over the 1999-2008 period. Furthermore, we compare risk exposure for these kinds of firms; the abnormal profits that may be obtained with a zero cost trading strategy based on being long in family firms and short in non-family firms; and the founder and size effects on performance. Our main results indicate the possibility of gaining abnormal profits trading on small family firms and selling non-family firms. We also observe a significant higher beta risk for family businesses directly managed...

  18. The stock performance of family firms in the Portuguese market

    Miralles-Marcelo, José Luís; Miralles-Quirós, Maria del Mar; Lisboa, Inês
    The aim of this study is to analyse the stock performance of family firms from 1999 to 2008 in the Portuguese stock market, where these kinds of firms are frequently found. Consistent with previous research, we employ a methodology based on a portfolio formation approach. Furthermore, we study the performance of individual stocks using a panel data analysis. Our findings show that family firms outperform nonfamily ones, especially those family firms of smaller size. These results are relevant for investors, academics and the professional managers of these companies.

  19. The impact of family control on firm performance: evidence from Portugal and Spain

    Miralles-Marcelo, José Luís; Miralles-Quirós, Maria del Mar; Lisboa, Inês
    This study aims to assess performance differences between family and non-family firms, taking into account the Portuguese and the Spanish stock markets. We provide new evidence for this field since we take into account the heterogeneity among family firms. Our thesis is that the leadership of family firms, and the firm's size and age are moderators of the relationship between family control and firm performance. Using a panel data methodology, our main results show that family firms, especially the smaller and older, exhibit at least the same performance as non-family firms. Based on the results of the study, who manages...

  20. Family impact on capital structure: does financial crisis matter?

    Lisboa, Inês
    This study analyses whether family control impacts the firm’s capital structure and if results are influenced by financial turbulences. Using a sample of Portuguese listed firms during fourteen years, results show that family and-non family firms have different debt levels in periods of expansion. Moreover, the higher concentration of family ownership leads to reduction in the firm’s leverage, especially in recession periods. These results confirm the behavioural-agency theory: the family looks to socio-emotional wealth but assuring the firm presence for future generations.

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