Polytechnic Institute of Porto
Repositório Científico do Instituto Politécnico do PortoNot a member yet
26471 research outputs found
Sort by
Impact of Platoon Size on the Performance of TDMA-Based MAC Protocols
No full textVehicular networks are a core component in Intelligent Transportation Systems (ITS) enabling communication among vehicles for collaborative applications. One example of such an application that may bring benefits in reducing travel time, fuel consumption and improving safety is platooning. This application coordinates a group of vehicles that travel together, doing automatic control of inter-distances and speeds [1]. A critical part of this application is the vehicle-to-vehicle (V2V) communication highlighting the importance of improving the channel quality. Existing ITS standards, namely WAVE (USA) and ITS-G5 (Europe), use IEEE 802.11p DSRC (Dedicated Short-Range Communication) [2] that relies on CSMA/CA distributed access arbitration. Despite the Collision Avoidance attribute collisions can still occur and the channel quality can degrade significantly in dense traffic environments.info:eu-repo/semantics/publishedVersio
Context-aware tourism technologies
No full textNowadays travellers can benefit from the computing capabilities, collection of on board sensors and ubiquitous
Internet access provided by mobile devices. These are the three pillars of any tourist support
system since they provide the power, means and data to establish the local user context, to access
remote services and to provide value-added user-centred context-aware applications. However, making
sense of the user context data is not straightforward, as it requires dedicated knowledge acquisition and
knowledge representation solutions. Besides, the range and diversity of available data sources is huge,
requiring appropriate knowledge processing techniques to provide addequated tourism services. This
article presents an updated review, and a comparison of recent context-aware tourism applications
(CATA), including supporting technologies; and considering four possible dimensions: knowledge
acquisition, knowledge representation, knowledge processing and knowledge-based services. We propose
and apply a CATA analysis framework, contemplating these four dimensions to the applications
found in the literature. This survey constitutes, not only, a state of the art review on tourism mobile
applications, but, also, anticipates the latest development trends in tourism-related applications.info:eu-repo/semantics/publishedVersio
Time-Triggered Co-Scheduling of Computation and Communication with Jitter Requirements
No full textThe complexity of embedded application design is increasing with growing user demands. In particular, automotive embedded systems are highly complex in nature, and their functionality is realized by a set of periodic tasks. These tasks may have hard real-time requirements and communicate over an interconnect. The problem is to efficiently co-schedule task execution on cores and message transmission on the interconnect so that timing constraints are satisfied. Contemporary works typically deal with zero-jitter scheduling, which results in lower resource utilization, but has lower memory requirements. This article focuses on jitter-constrained scheduling that puts constraints on the tasks jitter, increasing schedulability over zero-jitter scheduling. The contributions of this article are: 1) Integer Linear Programming and Satisfiability Modulo Theory model exploiting problem-specific information to reduce the formulations complexity to schedule small applications. 2) A heuristic approach, employing three levels of scheduling scaling to real-world use-cases with 10,000 tasks and messages. 3) An experimental evaluation of the proposed approaches on a case-study and on synthetic data sets showing the efficiency of both zero-jitter and jitter-constrained scheduling. It shows that up to 28 percent higher resource utilization can be achieved by having up to 10 times longer computation time with relaxed jitter requirements.info:eu-repo/semantics/publishedVersio
Electricity consumption forecasting in office buildings: an artificial intelligence approach
No full textThe rising needs for increased energy efficiency and better use of renewable energy sources bring out the necessity for improved energy management and forecasting models. Electricity consumption, in particular, is subject to large variations due to the effect of multiple variables, such as the temperature, luminosity or humidity, and of course, consumers' habits. Current forecasting models are not able to deal adequately with the influence and correlation between the multiple involved variables. Hence, novel, adaptive forecasting models are needed. This paper presents a novel approach based on multiple artificial intelligence-based forecasting algorithms. The considered algorithms are artificial neural networks, support vector machines hybrid fuzzy inference systems, Wang and Mendel's fuzzy rule learning method and a genetic fuzzy system for fuzzy rule learning based on the MOGUL methodology. These algorithms are used to forecast the electricity consumption of a real office building, using multiple input variables and consumption disaggregation.This work has received funding from the European Union's Horizon 2020 research and innovation programme under project DOMINOES (grant agreement No 771066) and from FEDER Funds through COMPETE program and from National Funds through FCT under the project UID/EEA/00760/2019.info:eu-repo/semantics/publishedVersio
Biosensor for direct bioelectrocatalysis detection of nitric oxide using nitric oxide reductase incorporated in carboxylated single-walled carbon nanotubes / lipidic bilayer nanocomposite
No full textAn enzymatic biosensor based on nitric oxide reductase (NOR; purified from Marinobacter hydrocarbonoclasticus) was developed for nitric oxide (NO) detection. The biosensor was prepared by deposition onto a pyrolytic graphite electrode (PGE) of a nanocomposite constituted by carboxylated single-walled carbon nanotubes (SWCNTs), a lipidic bilayer [1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-di-(9Zoctadecenoyl)-3-trimethylammonium-propane (DOTAP), 1,2-distearoyl-sn-glycero-3-phosphoethanolaminepolyethylene glycol (DSPE-PEG)] and NOR. NOR direct electron transfer and NO bioelectrocatalysis were characterized by several electrochemical techniques. The biosensor development was also followed by scanning electron microscopy and Fourier transform infrared spectroscopy. Improved enzyme stability and electron transfer (1.96 × 10−4 cm.s−1 apparent rate constant) was obtained with the optimum SWCNTs/(DOPE:DOTAP:DSPEPEG)/NOR) ratio of 4/2.5/4 (v/v/v), which biomimicked the NOR environment. The PGE/[SWCNTs/(DOPE:DOTAP:DSPE-PEG)/NOR] biosensor exhibited a low Michaelis-Menten constant (4.3 μM), wide linear range (0.44–9.09 μM), low detection limit (0.13 μM), high repeatability (4.1% RSD), reproducibility (7.0% RSD), and stability (ca. 5weeks). Selectivity tests towards L-arginine, ascorbic acid, sodiumnitrate, sodiumnitrite and glucose showed that these compounds did not significantly interfere in NO biosensing (91.0 ± 9.3%–98.4 ± 5.3% recoveries).
The proposed biosensor, by incorporating the benefits of biomimetic features of the phospholipid bilayer
with SWCNT's inherent properties and NOR bioelectrocatalytic activity and selectivity, is a promising tool for NO.info:eu-repo/semantics/publishedVersio
Evaluating vehicle painting plans in an automobile assembly plant using an integrated AHP-PROMETHEE approach
No full textThe painting activity is one of the most complex and important activities in automobile manufacturing. The inherent complexity of the painting activity and the frequent need for repainting usually turn the painting process into a bottleneck in automobile assembly plants, which is reflected in higher operating costs and longer overall cycle times. One possible approach for optimizing the performance of the paint shop is to improve the efficiency of the color planning. This can be accomplished by evaluating the relative merits of a set of vehicle painting plans. Since this problem has a multicriteria nature, we resort to the multicriteria decision analysis (MCDA) methodology to tackle it. A recent trend in the MCDA field is the development of hybrid approaches that are used to achieve operational synergies between different methods. Here we apply, for the first time, an integrated approach that combines the strengths of the analytic hierarchy process (AHP) and the Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEE), aided by Geometrical Analysis for Interactive Aid (GAIA), to the problem of assessing alternative vehicle painting plans. The management of the assembly plant found the results of value and is currently using them in order to schedule the painting activities such that an enhancement of the operational efficiency of the paint shop is obtained. This efficiency gain has allowed the management to bid for a new automobile model to be assembled at this specific plant.info:eu-repo/semantics/publishedVersio
Characterization of hybrid pultruded structural products based on preforms
No full textPultrusion is a widely known technique for production of constant cross-section profiles, such as bars, L-shape or
T-shape profiles, as well as structural tubes in polymer matrix composite materials. In some applications, requirements are demanding for profiles able to provide better thermal or sound insulation or needing a slightly
higher moment of inertia without increasing the ratio between weight and strength. In such cases, hybrid
pultruded profiles with core based on preforms are a possible solution.
After obtaining prototypes according to the methodologies described in a previous work, and as a complement
to that work, it is necessary to verify if the properties of these hybrid profiles correspond to the initial
expectations, by performing destructive and non-destructive tests. Thus, tensile, compression and bending tests
were performed, in order to verify the mechanical benefits achieved through the core introduction into the
hollow profile and to analyse the added value brought by these new products. These values, once properly
validated, can be added to existing databases related to structural calculation programs, enabling to get the
adequate values for calculations regarding this kind of profiles. In addition, thermal and acoustic insulation tests
were performed, in order to quantify the physical improvements achieved regarding these properties, which are
extremely important in specific applications linked to the civil construction and public works, among many
others. The cored profiles showed a strong adhesion between the profile and any kind of core tested as well as
improved properties in terms of thermal insulation and moment of inertia. However, the sound insulation did not
present significant improvements, probably due to GFRP profile external rigidity and consequent reflection.info:eu-repo/semantics/publishedVersio
Study of nanostructural bismuth oxide films prepared by radio frequency reactive magnetron sputtering
No full textBismuth oxide films were deposited onto quartz substrates by radio frequency reactive magnetron sputtering using a bismuth metal target. The substrate temperature was varied from room temperature to 500 oC. The state of Bi ions in the deposited films was characterized by XPS and the results showed that Bi ions existed as Bi3+ ions. The film structure was characterized by XRD and Raman scattering. The film deposited at room temperature shown a δ-phase predominant amorphous structure. As the substrate temperature was higher than 300 ºC, polycrystalline structure was formed. The film optical properties were studied by measuring the transmittance. The optical band gap was estimated by the Tauc plot, showing a red shift with the increase of the substrate temperature which gives it a potential application as a photocatalytic material for visible light.info:eu-repo/semantics/acceptedVersio
Simple multimodal optical technique for evaluation of free/bound water and dispersion of human liver tissue
No full textThe optical dispersion and water content of human liver were experimentally studied to estimate the optical dispersions of tissue scatterers and dry matter. Using temporal measurements of collimated transmittance [Tcðt Þ] of liver samples under treatment at different glycerol concentrations, free water and diffusion coefficient (Dgl) of glycerol in liver were found as 60.0% and 8.2 × 10−7 cm2∕s, respectively. Bound water was
calculated as the difference between the reported total water of 74.5% and found free water. The optical
dispersion of liver was calculated from the measurements of refractive index (RI) of tissue samples made
for different wavelengths between 400 and 1000 nm. Using liver and water optical dispersions at 20°C and
the free and total water, the dispersions for liver scatterers and dry matter were calculated. The estimated
dispersions present a decreasing behavior with wavelength. The dry matter dispersion shows higher RI values than liver scatterers, as expected. Considering 600 nm, dry matter has an RI of 1.508, whereas scatterers have an RI of 1.444. These dispersions are useful to characterize the RI matching mechanism in optical clearing treatments, provided that [Tcðt Þ] and thickness measurements are performed during treatment. The knowledge of Dgl is also important for living tissue cryoprotection applications.info:eu-repo/semantics/publishedVersio
Kinetics of Optical Properties of Colorectal Muscle During Optical Clearing
No full textIn this paper, we describe a simple and indirect method to evaluate the kinetics of the optical properties for biological tissues under optical clearing treatments.We use the theoretical formalism in this method to process experimental data obtained from colorectal muscle samples to evaluate and characterize the
dehydration and refractive index matching mechanisms.info:eu-repo/semantics/publishedVersio