The utilization bound of non-preemptive rate-monotonic scheduling in controller area networks is 25%

Consider a distributed computer system comprising many computer nodes, each interconnected with a controller area network (CAN) bus. We prove that if priorities to message streams are assigned using rate-monotonic (RM) and if the requested capacity of the CAN bus does not exceed 25% then all deadlines are met.

Runtime CRPD management for rate-based scheduling

Temporal isolation is an increasingly relevant con- cern in particular for ARINC-351 and virtualisation- based systems. Traditional approaches like the rate- based scheduling framework RBED do not take into account the impact of preemptions in terms of loss of working set in the acceleration hardware (e.g. caches). While some improvements have been suggested in the literature, they are overly heavy in the presence of small high-priority tasks such as interrupt service routines. Within this paper we propose an approach enabling adaptive assessment of this preemption delay in a tem- poral isolation framework with special consideration of capabilities and limitations of the approach.

Modeling of the lung impedance using a fractional order ladder network with constant phase elements

The self similar branching arrangement of the airways makes the respiratory system an ideal candidate for the application of fractional calculus theory. The fractal geometry is typically characterized by a recurrent structure. This study investigates the identification of a model for the respiratory tree by means of its electrical equivalent based on intrinsic morphology. Measurements were obtained from seven volunteers, in terms of their respiratory impedance by means of its complex representation for frequencies below 5 Hz. A parametric modeling is then applied to the complex valued data points. Since at low-frequency range the inertance is negligible, each airway branch is modeled by using gamma cell resistance and capacitance, the latter having a fractional-order constant phase element (CPE), which is identified from measurements. In addition, the complex impedance is also approximated by means of a model consisting of a lumped series resistance and a lumped fractional-order capacitance. The results reveal that both models characterize the data well, whereas the averaged CPE values are supraunitary and subunitary for the ladder network and the lumped model, respectively.

Microstructure, mechanical properties and chemical degradation of brazed AISI 316 stainless steel/alumina systems

The main aims of the present study are simultaneously to relate the brazing parameters with: (i) the correspondent interfacial microstructure, (ii) the resultant mechanical properties and (iii) the electrochemical degradation behaviour of AISI 316 stainless steel/alumina brazed joints. Filler metals on such as Ag–26.5Cu–3Ti and Ag–34.5Cu–1.5Ti were used to produce the joints. Three different brazing temperatures (850, 900 and 950 °C), keeping a constant holding time of 20 min, were tested. The objective was to understand the influence of the brazing temperature on the final microstructure and properties of the joints. The mechanical properties of the metal/ceramic (M/C) joints were assessed from bond strength tests carried out using a shear solicitation loading scheme. The fracture surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The degradation behaviour of the M/C joints was assessed by means of electrochemical techniques. It was found that using a Ag–26.5Cu–3Ti brazing alloy and a brazing temperature of 850 °C, produces the best results in terms of bond strength, 234 ± 18 MPa. The mechanical properties obtained could be explained on the basis of the different compounds identified on the fracture surfaces by XRD. On the other hand, the use of the Ag–34.5Cu–1.5Ti brazing alloy and a brazing temperature of 850 °C produces the best results in terms of corrosion rates (lower corrosion current density), 0.76 ± 0.21 μA cm−2. Nevertheless, the joints produced at 850 °C using a Ag–26.5Cu–3Ti brazing alloy present the best compromise between mechanical properties and degradation behaviour, 234 ± 18 MPa and 1.26 ± 0.58 μA cm−2, respectively. The role of Ti diffusion is fundamental in terms of the final value achieved for the M/C bond strength. On the contrary, the Ag and Cu distribution along the brazed interface seem to play the most relevant role in the metal/ceramic joints electrochemical performance.

Cutting forces and wear analysis of Si3N4 diamond coated tools in high speed machining

Si3N4 tools were coated with a thin diamond film using a Hot-Filament Chemical Vapour Deposition (HFCVD) reactor, in order to machining a grey cast iron. Wear behaviour of these tools in high speed machining was the main subject of this work. Turning tests were performed with a combination of cutting speeds of 500, 700 and 900 m min−1, and feed rates of 0.1, 0.25 and 0.4 mm rot−1, remaining constant the depth of cut of 1 mm. In order to evaluate the tool behaviour during the turning tests, cutting forces were analyzed being verified a significant increase with feed rate. Diamond film removal occurred for the most severe set of cutting parameters. It was also observed the adhesion of iron and manganese from the workpiece to the tool. Tests were performed on a CNC lathe provided with a 3-axis dynamometer. Results were collected and registered by homemade software. Tool wear analysis was achieved by a Scanning Electron Microscope (SEM) provided with an X-ray Energy Dispersive Spectroscopy (EDS) system. Surface analysis was performed by a profilometer.

Adhesion and wear behaviour of NCD coatings on Si3N4 by micro-abrasion tests

Nanocrystalline diamond (NCD) coatings offer an excellent alternative for tribological applications, preserving most of the intrinsic mechanical properties of polycrystalline CVD diamond and adding to it an extreme surface smoothness. Silicon nitride (Si3N4) ceramics are reported to guarantee high adhesion levels to CVD microcrystalline diamond coatings, but the NCD adhesion to Si3N4 is not yet well established. Micro-abrasion tests are appropriate for evaluating the abrasive wear resistance of a given surface, but they also provide information on thin film/substrate interfacial resistance, i.e., film adhesion. In this study, a comparison is made between the behaviour of NCD films deposited by hot-filament chemical vapour deposition (HFCVD) and microwave plasma assisted chemical vapour deposition (MPCVD) techniques. Silicon nitride (Si3N4) ceramic discs were selected as substrates. The NCD depositions by HFCVD and MPCVD were carried out using H2–CH4 and H2–CH4–N2 gas mixtures, respectively. An adequate set of growth parameters was chosen for each CVD technique, resulting in NCD films having a final thickness of 5 m. A micro-abrasion tribometer was used, with 3 m diamond grit as the abrasive slurry element. Experiments were carried out at a constant rotational speed (80 r.p.m.) and by varying the applied load in the range of 0.25–0.75 N. The wear rate for MPCVD NCD (3.7±0.8 × 10−5 m3N−1m−1) is compatible with those reported for microcrystalline CVD diamond. The HFCVD films displayed poorer adhesion to the Si3N4 ceramic substrates than the MPCVD ones. However, the HFCVD films show better wear resistance as a result of their higher crystallinity according to the UV Raman data, despite evidencing premature adhesion failure.

A physical packing sequence algorithm for the container loading problem with static mechanical equilibrium conditions

The container loading problem (CLP) is a combinatorial optimization problem for the spatial arrangement of cargo inside containers so as to maximize the usage of space. The algorithms for this problem are of limited practical applicability if real-world constraints are not considered, one of the most important of which is deemed to be stability. This paper addresses static stability, as opposed to dynamic stability, looking at the stability of the cargo during container loading. This paper proposes two algorithms. The first is a static stability algorithm based on static mechanical equilibrium conditions that can be used as a stability evaluation function embedded in CLP algorithms (e.g. constructive heuristics, metaheuristics). The second proposed algorithm is a physical packing sequence algorithm that, given a container loading arrangement, generates the actual sequence by which each box is placed inside the container, considering static stability and loading operation efficiency constraints.

Characterisation of noisy speech channels in 2G and 3G mobile networks

As the wireless cellular market reaches competitive levels never seen before, network operators need to focus on maintaining Quality of Service (QoS) a main priority if they wish to attract new subscribers while keeping existing customers satisfied. Speech Quality as perceived by the end user is one major example of a characteristic in constant need of maintenance and improvement. It is in this topic that this Master Thesis project fits in. Making use of an intrusive method of speech quality evaluation, as a means to further study and characterize the performance of speech codecs in second-generation (2G) and third-generation (3G) technologies. Trying to find further correlation between codecs with similar bit rates, along with the exploration of certain transmission parameters which may aid in the assessment of speech quality. Due to some limitations concerning the audio analyzer equipment that was to be employed, a different system for recording the test samples was sought out. Although the new designed system is not standard, after extensive testing and optimization of the system's parameters, final results were found reliable and satisfactory. Tests include a set of high and low bit rate codecs for both 2G and 3G, where values were compared and analysed, leading to the outcome that 3G speech codecs perform better, under the approximately same conditions, when compared with 2G. Reinforcing the idea that 3G is, with no doubt, the best choice if the costumer looks for the best possible listening speech quality. Regarding the transmission parameters chosen for the experiment, the Receiver Quality (RxQual) and Received Energy per Chip to the Power Density Ratio (Ec/N0), these were subject to speech quality correlation tests. Final results of RxQual were compared to those of prior studies from different researchers and, are considered to be of important relevance. Leading to the confirmation of RxQual as a reliable indicator of speech quality. As for Ec/N0, it is not possible to state it as a speech quality indicator however, it shows clear thresholds for which the MOS values decrease significantly. The studied transmission parameters show that they can be used not only for network management purposes but, at the same time, give an expected idea to the communications engineer (or technician) of the end-to-end speech quality consequences. With the conclusion of the work new ideas for future studies come to mind. Considering that the fourth-generation (4G) cellular technologies are now beginning to take an important place in the global market, as the first all-IP network structure, it seems of great relevance that 4G speech quality should be subject of evaluation. Comparing it to 3G, not only in narrowband but also adding wideband scenarios with the most recent standard objective method of speech quality assessment, POLQA. Also, new data found on Ec/N0 tests, justifies further research studies with the intention of validating the assumptions made in this work.

Elaboração de um projeto de uma central fotovoltaica de miniprodução e estudo de viabilidade técnica, económica e financeira

Desde o final do século XVIII, quando se iniciou a revolução industrial, o crescimento económico tem sido assente num consumo elevado de combustíveis fósseis que libertam gases com efeito de estufa. A emissão destes gases e a escassez dos combustíveis fósseis são temas que, desde as últimas duas décadas do século XX, ocupam um lugar de destaque nas agendas de política mundial. A produção de energia através de fontes renováveis surge como alternativa e poderá ser a solução para países com escassos recursos de origem fóssil, como é o caso de Portugal, minimizando também a sua dependência energética do exterior. Uma das medidas de incentivo lançada pelo Governo Português em 2007, foi a criação de um regime simplificado aplicável à microprodução descentralizada de eletricidade através de fontes de energia renováveis e de cogeração. À semelhança da maioria dos países europeus, o principal meio de promoção destes sistemas em Portugal foram as Feed-in-Tariffs, que consistem numa tarifa de venda de energia elétrica de origem renovável acima da tarifa de mercado. Estas tarifas permitiram, sobretudo, o crescimento do setor fotovoltaico em Portugal. Atualmente, o amadurecimento da tecnologia fotovoltaica, associado ao constante aumento das tarifas de energia elétrica, permite que se torne vantajosa a instalação de sistemas fotovoltaicos para autoconsumo. Neste contexto, o atual Governo Português, criou recentemente um regime jurídico aplicável à produção de eletricidade para autoconsumo. O objetivo deste trabalho é demonstrar, com base na minha experiência profissional, a metodologia de dimensionamento de uma central fotovoltaica ligada à Rede Elétrica de Serviço Público. Será utilizado como objeto de estudo um projeto constituído por 28 centrais fotovoltaicas de Miniprodução de 100 kW, dispersas por Portugal Continental, para o qual será efetuada a análise financeira do investimento. Pretende-se ainda apresentar o novo enquadramento legislativo para o Autoconsumo e Pequena Produção distribuída, detalhar as suas principais caraterísticas e efetuar um estudo económico para cada um destes regimes.

Plataforma de Dados de Saúde - Portal Institucional

O presente documento de dissertação retrata o desenvolvimento do projeto PDS-Portal Institucional cujo cerne é um sistema para recolha, armazenamento e análise de dados (plataforma de Business Intelligence). Este portal está enquadrado na área da saúde e é uma peça fundamental no sistema da Plataforma de dados da Saúde, que é constituído por quatro portais distintos. Esta plataforma tem como base um sistema totalmente centrado no utente, que agrega dados de saúde dos utentes e distribui pelos diversos intervenientes: utente, profissionais de saúde nacionais e internacionais e organizações de saúde. O objetivo principal deste projeto é o desenvolvimento do PDS-Portal Institucional, recorrendo a uma plataforma de Business Intelligence, com o intuito de potenciar os utilizadores de uma ferramenta analítica para análise de dados. Estando a informação armazenada em dois dos portais da Plataforma de dados da Saúde (PDS-Portal Utente e PDS-Portal Profissional), é necessário modular um armazém de dados que agregue a informação de ambos e, através do PDS-PI, distribua um conjunto de análises ao utilizador final. Para tal este sistema comtempla um mecanismo totalmente automatizado para extração, tratamento e carregamento de dados para o armazém central, assim como uma plataforma de BI que disponibiliza os dados armazenados sobre a forma de análises específicas. Esta plataforma permite uma evolução constante e é extremamente flexível, pois fornece um mecanismo de gestão de utilizadores e perfis, assim como capacita o utilizador de um ambiente Web para análise de dados, permitindo a partilha e acesso a partir de dispositivos móveis. Após a implementação deste sistema foi possível explorar os dados e tirar diversas conclusões que são de extrema importância tanto para a evolução da PDS como para os métodos de praticar os cuidados de saúde em Portugal. Por fim são identificados alguns pontos de melhoria do sistema atual e delineada uma perspetiva de evolução futura. É certo que a partir do momento que este projeto seja lançado para produção, novas oportunidades surgirão e o contributo dos utilizadores será útil para evoluir o sistema progressivamente.

Distribuição de Contaminantes Orgânicos em Solos Calcários – Influência dos minerais de Argila

O solo é um recurso multifuncional e vital para a humanidade, apresentando funções ecológicas, técnico-industriais, socioeconómicas e culturais, estabelecendo um vasto capital natural insubstituível. Face à sua taxa de degradação potencialmente rápida que, devido ao crescente desenvolvimento económico e incremento da população mundial, tem vindo a aumentar nas últimas décadas, o solo é, atualmente, um recurso finito e limitado. Devido a esta problemática, o presente documento visa abordar a progressiva preocupação sobre as questões geoambientais e toda a investigação que as envolvem, avaliando o modo como os contaminantes se dispersam pelo solo nas diferentes fases do mesmo (fases sólida, líquida e gasosa). A parte experimental centrou-se na análise da adsorção do benzeno, a partir da determinação das isotérmicas de adsorção. Para tal, foram previamente preparados reatores com calcário, sendo alguns deles previamente contaminados com um biocombustível, biodiesel, a uma concentração constante. Este processo foi monitorizado com base na evolução temporal da concentração na fase gasosa, através da cromatografia gasosa. De entre os objetivos, procurou-se analisar a distribuição dos contaminantes pelas fases constituintes do solo, ajustar os dados experimentais obtidos os modelos matemáticos de Langmuir, Freundlich e Polinomial, e verificar e discutir as soluções mais adequadas.

Dynamic stability metrics for the container loading problem

The Container Loading Problem (CLP) literature has traditionally evaluated the dynamic stability of cargo by applying two metrics to box arrangements: the mean number of boxes supporting the items excluding those placed directly on the floor (M1) and the percentage of boxes with insufficient lateral support (M2). However, these metrics, that aim to be proxies for cargo stability during transportation, fail to translate real-world cargo conditions of dynamic stability. In this paper two new performance indicators are proposed to evaluate the dynamic stability of cargo arrangements: the number of fallen boxes (NFB) and the number of boxes within the Damage Boundary Curve fragility test (NB_DBC). Using 1500 solutions for well-known problem instances found in the literature, these new performance indicators are evaluated using a physics simulation tool (StableCargo), replacing the real-world transportation by a truck with a simulation of the dynamic behaviour of container loading arrangements. Two new dynamic stability metrics that can be integrated within any container loading algorithm are also proposed. The metrics are analytical models of the proposed stability performance indicators, computed by multiple linear regression. Pearson’s r correlation coefficient was used as an evaluation parameter for the performance of the models. The extensive computational results show that the proposed metrics are better proxies for dynamic stability in the CLP than the previous widely used metrics.

Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extract

Context: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer. Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation. Materials and methods: Physical, microbiological and functional stability were evaluated during 6 months storage at 20 °C and 40 °C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed. Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20 °C for 6 months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610 ± 70 µgh−0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4 h after product’s application. Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.