Browsing by Issue Date, starting with "2022-08-15"
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- Signal quality monitoring aspects in GNSS signals affected by evil waveformsPublication . Sousa, Fernando; Nunes, Fernando; Negrinho, António; Fernandes, Pedro; Boto, PedroEvil waveforms (EWF) are anomalies in the GNSS transmitted signals that can degrade significantly the accuracy of the PVT solution. The cross-correlation function of the incoming signal disturbed by EWF distortion and the locally-generated code signal is obtained analytically for threat models TM-A, TM-B and TM-C. These results are useful to evaluate efficiently the performance of EWF detectors, namely the detectability and hazard regions.
- Performance of GNSS evil waveform detectors in the presence of multipathPublication . Nunes, Fernando; Sousa, FernandoThe detection of evil waveforms (EWF) in GNSS signals is crucial to refrain from using anomalous signals in the PVT solution, which could degrade significantly its accuracy. The EWF detectors are, in general, based on the computation of the distortion of the code autocorrelation function. Thus, the multipath effect, an independent mechanism that also distorts the autocorrelation shape, can be incorrectly assumed by the EWF detector as the presence of EWF, leading to a major increase of the probability of false alarm. In the paper we analyze the robustness of the main EWF detectors and modulations to the presence of multipath.
- Crosslinked bacterial cellulose hydrogels for biomedical applicationsPublication . Almeida, Ana; Saraiva, João N.; Cavaco, Gonçalo; Portela, Raquel; Leal, Catarina R.; Sobral, Rita; Almeida, Pedro L.The skin, fundamental barrier that protects internal tissues, prevents pathogen invasion, and maintains the body fluid equilibrium, may be compromised upon traumas, such as incisions and burns. The healing process of such wounds is costly and usually hindered by the patient’s physiological conditions, associated diseases, inflammation and external factors, namely bacterial infections. Recently, increasing attention has been given to bacterial cellulose-based membranes to be applied as dressings for healing purposes. Bacterial cellulose is an attractive biomaterial due to its unique structural characteristics such as high porosity, high water retention capacity, high mechanical strength, low density, and biodegradability. One drawback of bacterial cellulose hydrogels is that, after the first dehydration, the water retention capacity is hindered. In this work we produced, modified, and characterized hydrated and de-hydrated BC membranes. Two crosslinking methods were adopted (using citric acid and epichlorohydrin as crosslinking agents), and the results obtained from the characterizations such as water retention capacity, mechanical properties or contact angle were compared to those of unmodified bacterial cellulose. We demonstrate that the cross-linked bacterial cellulose membranes present physical properties suitable to be used as surgical and burn wound dressings when hydrated, or as exuding wound dressings, diapers dressing or sanitary pads when dehydrated.